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Sample records for additional screw fixation

  1. Axial loading cross screw fixation for the Austin bunionectomy.

    PubMed

    Rigby, Ryan B; Fallat, Lawrence M; Kish, John P

    2011-01-01

    The Austin procedure has become a common method of osteotomy for the correction of hallux abductovalgus when indicated. The V-type configuration is intrinsically stable but not without complications. One complication encountered is rotation and/or displacement of the capital fragment. We present the use of an axial loading screw in conjunction with a dorsally placed compression screw. The benefit to this technique lies in the orientation of the axial loading screw, because it is directed to resist the ground reactive forces while also providing a second point of fixation in a crossing screw design. In a head-to-head biomechanical comparison, we tested single dorsal screw fixation versus double screw fixation, including both the dorsal and the axial loading screws in 10 metatarsal Sawbones() (Pacific Research Laboratories Inc, Vashon, WA). Five metatarsals received single dorsal screw fixation and five received the dorsal screw and the additional axial loading screw. The metatarsals were analyzed on an Instron compression device for comparison; 100% of the single screw fixation osteotomies failed with compression at an average peak load of 205 N. Four of five axial loading double screw fixation osteotomies did not fail. This finding suggests that the addition of an axial loading screw providing cross screw orientation significantly increases the stability of the Austin osteotomy, ultimately decreasing the likelihood of displacement encountered in the surgical repair of hallux abductovalgus. PMID:21621434

  2. 21 CFR 872.4880 - Intraosseous fixation screw or wire.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Intraosseous fixation screw or wire. 872.4880... (CONTINUED) MEDICAL DEVICES DENTAL DEVICES Surgical Devices 872.4880 Intraosseous fixation screw or wire. (a) Identification. An intraosseous fixation screw or wire is a metal device intended to be...

  3. [Screw fracture after sliding hip screw fixation of an intertrochanteric fracture].

    PubMed

    Manicom, O; Karoubi, M; Mseddi, M; Demoura, A; Hernigou, P

    2006-10-01

    Although no cases have been reported to date, fracture of a sliding hip screw on a screw-plate fixation is a real entity since material watch registries have revealed two non-published cases. We report an illustrative case. A 67-year-old man was hospitalized for a right intertrochanteric fracture. The patient was treated with a sliding hip screw plate fixation (short cannon, 105 mm screw). On the eighth postoperative day, fracture impaction was present with complete loss of impaction reserve associated with secondary discrete divergence in the cannon-screw alignment. Weight-bearing was postponed until the 45th postoperative day. At three months, bone healing had not been achieved. A clear image was also visible at the plate end of the cannon. The patient complained of persistent pain but there were no signs of infection. At the fifth month, the patient fell from the standing position and standard x-rays visualized the nonunion of the intertrochanteric fracture plus a infratrochanteric diaphyseal fracture line in addition to a fracture of the sliding hip screw. The plate screws were intact. The patient underwent revision osteosynthesis with a Medoff plate. Fracture of a sliding hip screw is a rare event. In the present case, the mechanism involved an insufficient impaction reserve and use of a short cannon. Treatment requires extraction of the distal fragment of the screw and a new cemented osteosynthesis. PMID:17088758

  4. Strength comparison of allogenic bone screws, bioabsorbable screws, and stainless steel screw fixation.

    PubMed

    Rano, James A; Savoy-Moore, Ruth T; Fallat, Lawrence M

    2002-01-01

    Allogenic bone screws are new to the fixation market and have yet to be tested against current fixation materials. An in vitro comparison of the same sizes of stainless steel, bioabsorbable, and allogenic bone screws was undertaken to assess screw resistance to the forces of bending, pullout, and shear. Using aluminum plates to support the screws, forces up to 1000 Newtons were applied to six to eight samples of each type of screw. During each test, stainless steel screws withstood the maximum force that could be exerted by the testing apparatus without failing (bending, 113.9 +/- 11.8 N mean +/- SE; pullout 999.1 +/- 33.7 N; and shear, 997.5 +/- 108.8 N). In each test, compared to bioabsorbable screws, allogenic bone screws failed faster (pullout, allogenic: 12.4 +/- 1.1 seconds vs. bioabsorbable, 120.6 +/- 13.8 seconds; p = .001; bending, allogenic: 53.4 +/- 4.8 seconds vs. bioabsorbable, 201.9 +/- 11.1 seconds; p = .001; shear, allogenic 13.5 +/- 1.4 seconds vs. bioabsorbable, 43.8 +/- 0.9 seconds; p = .001) under equivalent (pullout: bioabsorbable, 385.0 +/- 18.4 N vs. allogenic, 401.0 +/- 35.9 N; p = .001) or lower (bending, allogenic: 4.7 +/- 0.2 N vs. bioabsorbable, 11.0 +/- 0.9 N; p = .675; shear, allogenic: 312.1 +/- 15.5 N vs. bioabsorbable 680.9 +/- 8.5 N; p = .001) loads, and in a highly variable fashion. Overall, the bioabsorbable screws withstood the forces of bending, pullout, and shear better than the allogenic screws, and stainless steel screws outperformed both bioabsorbable and allogenic screws. Despite these results, allogenic screws could still be useful in compliant patients who would benefit from their osteoconductive properties. PMID:11858609

  5. Pedicle Screw Fixation Study in Immature Porcine Spines to Improve Pullout Resistance during Animal Testing

    PubMed Central

    Le Cann, Sophie; Cachon, Thibaut; Viguier, Eric; Miladi, Lotfi; Odent, Thierry; Rossi, Jean-Marie; Chabrand, Patrick

    2015-01-01

    The porcine model is frequently used during development and validation of new spinal devices, because of its likeness to the human spine. These spinal devices are frequently composed of pedicle screws with a reputation for stable fixation but which can suffer pullouts during preclinical implantation on young animals, leading to high morbidity. With a view to identifying the best choices to optimize pedicle screw fixation in the porcine model, this study evaluates ex vivo the impact of weight (age) of the animal, the level of the vertebrae (lumbar or thoracic) and the type of screw anchorage (mono- or bi-cortical) on pedicle screw pullouts. Among the 80 pig vertebrae (90- and 140-day-old) tested in this study, the average screw pullout forces ranged between 419.9N and 1341.2N. In addition, statistical differences were found between test groups, pointing out the influence of the three parameters stated above. We found that the the more caudally the screws are positioned (lumbar level), the greater their pullout resistance is, moreover, screw stability increases with the age, and finally, the screws implanted with a mono-cortical anchorage sustained lower pullout forces than those implanted with a bi-cortical anchorage. We conclude that the best anchorage can be obtained with older animals, using a lumbar fixation and long screws traversing the vertebra and inducing bi-cortical anchorage. In very young animals, pedicle screw fixations need to be bi-cortical and more numerous to prevent pullout. PMID:26451947

  6. Pedicle Screw Fixation Study in Immature Porcine Spines to Improve Pullout Resistance during Animal Testing.

    PubMed

    Le Cann, Sophie; Cachon, Thibaut; Viguier, Eric; Miladi, Lotfi; Odent, Thierry; Rossi, Jean-Marie; Chabrand, Patrick

    2015-01-01

    The porcine model is frequently used during development and validation of new spinal devices, because of its likeness to the human spine. These spinal devices are frequently composed of pedicle screws with a reputation for stable fixation but which can suffer pullouts during preclinical implantation on young animals, leading to high morbidity. With a view to identifying the best choices to optimize pedicle screw fixation in the porcine model, this study evaluates ex vivo the impact of weight (age) of the animal, the level of the vertebrae (lumbar or thoracic) and the type of screw anchorage (mono- or bi-cortical) on pedicle screw pullouts. Among the 80 pig vertebrae (90- and 140-day-old) tested in this study, the average screw pullout forces ranged between 419.9N and 1341.2N. In addition, statistical differences were found between test groups, pointing out the influence of the three parameters stated above. We found that the the more caudally the screws are positioned (lumbar level), the greater their pullout resistance is, moreover, screw stability increases with the age, and finally, the screws implanted with a mono-cortical anchorage sustained lower pullout forces than those implanted with a bi-cortical anchorage. We conclude that the best anchorage can be obtained with older animals, using a lumbar fixation and long screws traversing the vertebra and inducing bi-cortical anchorage. In very young animals, pedicle screw fixations need to be bi-cortical and more numerous to prevent pullout. PMID:26451947

  7. Screw Versus Plate Fixation for Chevron Osteotomy: A Retrospective Study.

    PubMed

    Andrews, Boyd J; Fallat, Lawrence M; Kish, John P

    2016-01-01

    The chevron osteotomy is a popular procedure used for the correction of moderate hallux abducto valgus deformity. Fixation is typically accomplished with Kirschner wires or bone screws; however, in cystic or osteoporotic bone, these could be inadequate, resulting in displacement of the capital fragment. We propose using a locking plate and interfragmental screw for fixation of the chevron osteotomy that could reduce the healing time and decrease the incidence of displacement. We performed a retrospective cohort study for chevron osteotomies on 75 feet (73 patients). The control groups underwent fixation with 1 screw in 30 feet (40%) and 2 screws in 30 feet (40%). A total of 15 feet (20%) were included in the locking plate and interfragmental screw group. The patients were followed up until bone healing was achieved at a median of 7 (range 6 to 14) weeks. Our hypothesis was that those treated with the locking plate and interfragmental screw would have a faster healing time and fewer incidents of capital fragment displacement compared with the 1- or 2-screw groups. The corresponding mean intervals to healing for the 1-screw group was 7.711.28 (range 6 to 10) weeks, for the 2-screw group was 7.271.57 (range 6 to 14) weeks, and for the locking plate and interfragmental screw group was 7.011.00 (range 6 to 9) weeks. One case of capital fragment displacement occurred in the single screw group and one in the 2-screw group. No displacement occurred in the locking plate and interfragmental screw group. Neither finding was statistically significant. However, we believe the locking plate and interfragmental screw could be a viable option in patients with osteoporotic and cystic bone changes for correction of hallux abducto valgus. PMID:26277241

  8. Fracture risk and initial fixation of a cementless glenoid implant: the effect of numbers and types of screws.

    PubMed

    Suarez, Daniel R; Valstar, Edward R; Rozing, Piet M; van Keulen, Fred

    2013-10-01

    The initial fixation of an anatomical cementless glenoid component, provided by different numbers and types of screws, and the risk of bone fracture were evaluated by estimating the bone-implant interface micromotions and the principal strains around the prosthesis. Four different fixation configurations using locking or compression screws were tested. Estimation of the micromotions at the bone-implant interface was performed both experimentally, using an in vitro model, and computationally, using a numerical model. Principal bone strains were estimated using the numerical model. Subject variability was included by modelling two different bone qualities (healthy and rheumatoid bone). For the fixation configurations that used two screws, experimental and modelling results found that the micromotions at the bone-implant interface did not change with screw type. However, screw type had a significant effect on fixation when only one screw was used; in this case, a locking screw resulted in less micromotion at the bone-implant interface compared with the compression screw. Bone strains were predicted by the numerical model, and strains were found to be independent of the screw type; however, the predicted strain levels calculated in rheumatoid bone were larger than the strain levels that may cause bone damage for most considered arm positions. Predicted bone strain in healthy bone did not reach this level. While proper initial component fixation that allows biological fixation can be achieved by using additional screws, the risk of bone failure around the screws must be considered, especially in cases of weak bone. PMID:23804951

  9. Screw fixation of the syndesmosis: a cadaver model comparing stainless steel and titanium screws and three and four cortical fixation.

    PubMed

    Beumer, Annechien; Campo, Martin M; Niesing, Ruud; Day, Judd; Kleinrensink, Gert-Jan; Swierstra, Bart A

    2005-01-01

    We assessed syndesmotic set screw strength and fixation capacity during cyclical testing in a cadaver model simulating protected weight bearing. Sixteen fresh frozen legs with artificial syndesmotic injuries and a syndesmotic set screw made of stainless steel or titanium, inserted through three or four cortices, were axially loaded with 800 N for 225,000 cycles in a materials testing machine. The 225,000 cycles equals the number of paces taken by a person walking in a below knee plaster during 9 weeks. Syndesmotic fixation failure was defined as: bone fracture, screw fatigue failure, screw pullout, and/or excessive syndesmotic widening. None of the 14 out of 16 successfully tested legs or screws failed. No difference was found in fixation of the syndesmosis when stainless steel screws were compared to titanium screws through three or four cortices. Mean lateral displacement found after testing was 1.05 mm (S.D. = 0.42). This increase in tibiofibular width exceeds values described in literature for the intact syndesmosis loaded with body weight. Based on this laboratory study it is concluded that the syndesmotic set screw cannot prevent excessive syndesmotic widening when loaded with a load comparable with body weight. Therefore, we advise that patients with a syndesmotic set screw in situ should not bear weight. PMID:15589915

  10. Sacroiliac screw fixation: A mini review of surgical technique

    PubMed Central

    Alvis-Miranda, Hernando Raphael; Farid-Escorcia, Hector; Alcal-Cerra, Gabriel; Castellar-Leones, Sandra Milena; Moscote-Salazar, Luis Rafael

    2014-01-01

    The sacral percutaneous fixation has many advantages but can be associated with a significant exposure to X-ray radiation. Currently, sacroiliac screw fixation represents the only minimally invasive technique to stabilize the posterior pelvic ring. It is a technique that should be used by experienced surgeons. We present a practical review of important aspects of this technique. PMID:25336831

  11. Scaphoid Proximal Pole Fracture Following Headless Screw Fixation.

    PubMed

    Rancy, Schneider K; Zelken, Jonathan A; Lipman, Joseph D; Wolfe, Scott W

    2016-03-01

    Background?Headless screw fixation of scaphoid fractures and nonunions yields predictably excellent outcomes with a relatively low complication profile. However, intramedullary implants affect the load to failure and stress distribution within bone and may be implicated in subsequent fracture. Case Description?We describe a posttraumatic fracture pattern of the scaphoid proximal pole originating at the previous headless screw insertion site in three young male patients with healed scaphoid nonunions. Each fracture was remarkably similar in shape and size, comprised the volar proximal pole, and was contiguous with the screw entry point. Treatment was challenging but successful in all cases. Literature Review?Previous reports have posited that stress-raisers secondary to screw orientation may be implicated in subsequent peri-implant fracture of the femoral neck. Repeat scaphoid fracture after screw fixation has also been reported. However, the shape and locality of secondary fracture have not been described, nor has the potential role of screw fixation in the production of distinct fracture patterns. Clinical Relevance?Hand surgeons must be aware of this difficult complication that may follow antegrade headless screw fixation of scaphoid fracture nonunion, and of available treatment strategies. PMID:26855840

  12. Posterior lumbar interbody fusion with facet-screw fixation.

    PubMed

    Stonecipher, T; Wright, S

    1989-04-01

    The optimal surgical construct for lumbar fusion remains controversial. The posterior lumbar interbody fusion (PLIF) operation offers advantages including total nuclear disc excision, restoration of disc-space height, root decompression, limited muscle retraction and injury, and solid mechanical arthrodesis. Major disadvantages have included graft displacement, neurologic injury and nonunion. The use of posterior fixation as an adjunct to PLIF reduces the probability of these complications and increases the chances of fusion. This study examines 35 patients who underwent PLIF and facet-screw fixation. Indications for surgery included disabling low-back pain with discographic/MRI-demonstrated disc derrangement, recurrent disc herniation, and failed inter-transverse process fusions. Follow-up ranged from 6 to 18 months. There were no patients with significant neurologic injury or functional root loss. One patient developed graft displacement and failure of fixation (laminar fracture in markedly obese patient). Three patients had subcutaneous hematomas (no surgical treatment required). None of the cases required blood replacement. The authors have concluded that the addition of facet fixation/fusion to the PLIF operation substantially reduces the complication rate of the procedure. PMID:2718053

  13. The sustentaculum tali screw fixation for the treatment of Sanders type II calcaneal fracture: A finite element analysis

    PubMed Central

    Pang, Qing-Jiang; Yu, Xiao; Guo, Zong-Hui

    2014-01-01

    Objective: In the surgery of calcaneal fracture, whether the sustentaculum tali screw should always be placed is widely controversial. The aim of this study was to explore the necessity and function of the sustentaculum tali screw placement for the treatment of Sanders type II calcaneal fracture. Methods: The finite element analysis was used in this study. After the establishment of the finite element model of Sanders type II calcaneal fracture, the two internal fixation simulations were designed. In one model, the AO calcaneal plate was simulated on the lateral side of the calcanues with 7 screws being fixated at different position of the plate. In the other model, the calcaneus was fixated with the same AO calcaneal plate together with an additional screw being infiltrated into the sustentaculum tali. The two models were simulated under the same loading and the displacement of the fracture line and the stress distribution in the two models were calculated respectively. Results: The maximum principal stress focused on the cortical bone of sustentaculum tali in both the models under the same loading. The displacement of the fracture line, the maximum principal stress of calcaneus and internal fixation system in the model with sustentaculum screw fixation were smaller than that in the model without sustentaculum screw fixation. The stress in the model with sustentaculum screw fixation was more dispersed. Conclusions: The placement of sustentaculum tali screw is essential for fixation of type II calcaneal fracture to achieve the biomechanical stability. PMID:25225534

  14. Biomechanical evaluation of posterior screw fixation in cadaveric cervical spines.

    PubMed

    Papagelopoulos, Panayiotis J; Currier, Bradford L; Neale, Patricia G; Hokari, Yukitaka; Berglund, Lawrence J; Larson, Dirk R; Fisher, Dean R; An, Kai-Nan

    2003-06-01

    Sixteen fresh-frozen spines from cadavers (C4-T1) were randomized on the basis of dual energy xray absorptiometry analysis of bone mineral density. The specimens were subjected to physiologic loads (screws in C5 and pedicle screws in C7. The constructs differed only in the presence or absence of a transverse connector between the rods, presence or absence of lateral mass screws in C6, and unicortical or bicortical lateral mass screws. Insertional screw torque was higher in specimens with greater bone mineral density. Pedicle screws had greater torque than lateral mass screws. Posterior cervical spine rod fixation provided an equivalent stability by use of either unicortical or bicortical lateral mass screws. A transverse stabilizer between the rods reduces the number of lateral mass screws needed in posterior cervical spinal rod systems. Repeated stability tests, even when done with physiologic loads, may compromise the screw-bone interface. This effect is most pronounced in specimens that have low bone mineral density. PMID:12782855

  15. [Dyamic screw fixation for slipped capital femoral epiphysis. Treatment results].

    PubMed

    Hackenbroch, M H; Kumm, D A; Rtt, J

    2002-09-01

    Slipped capital femoral epiphysis always requires surgical treatment. The operative technique depends on the degree of dislocation and the type of the slip. The goal of treatment is to achieve physeal stability until the epiphyseal plate closes without harming the further femoral growth. In situ fixation is generally recommended for slipped capital femoral epiphyses of a mild degree. For this purpose the technique of dynamic screw fixation (DSF) is applicable using a long cannulated screw with a short thread.DSF is easy to handle, provides sufficient long-term fixation of the epiphysis, does not promote premature closure of the epiphysis, and engenders few complications. Therefore, this technique is also applicable for the prophylactic treatment of the contralateral unaffected hip, which we always perform. Moreover, DSF can be used following gentle reduction of acute epiphysiolysis, if the amount of eventual residual dislocation does not exceed 30 degrees. We report our results with dynamic screw fixation of 29 slipped capital femoral epiphyses of a mild degree, and the prophylactic dynamic screw fixation of 34 unaffected hips. The fixation technique achieved a reliable stabilization with no visible growth disturbance of the femoral neck in all cases. PMID:12232705

  16. Association between screw prominence and vascular complications after clavicle fixation

    PubMed Central

    Clitherow, Harry D. S.; Bain, Gregory I.

    2014-01-01

    Context: Fixation of clavicle fractures has become more common to prevent symptomatic malunion and nonunion. The subclavian and axillary vessels are in close proximity to the medial two-thirds of the clavicle, placing them at risk from prominent metalware. Injury to these major vessels has the potential to be life or limb-threatening. Despite this anatomical risk, iatrogenic vascular injury associated with clavicle fixation is rare. Aims: The aim of this study was to identify risk factors associated with modern fixation techniques in reported cases of vascular injury after clavicle fixation. Materials and Methods: A literature search was performed, and all identified cases of iatrogenic vascular injury associated with prominent clavicle fixation were analyzed. Clinical details, the total length of the prominent screws and the distance that they protruded from the far cortex were recorded. Results: Five cases were identified; there were four pseudoaneurysms and one arteriovenous fistula. The total length of the offending screw was identifiable in two cases, measuring 26 and 30 mm. The length of screw prominence was identifiable in 3 cases (8, 10 and 10 mm). The pseudoaneurysms presented at 2-10 years following clavicle fixation. Three of these cases developed limb-threatening ischemia. Conclusions: Vascular complications associated with clavicle fixation are uncommon but potentially limb-threatening. Several associated factors are identified. The authors provide a number of detailed recommendations aimed at preventing these complications. PMID:25538431

  17. Intra-operative screw trimming in direct screw fixation of the odontoid process fracture--technical note.

    PubMed

    Hasegawa, T; Yamano, K; Hamada, Y; Miyamori, T

    1992-01-01

    For a satisfactory direct screw fixation of fractures of the odontoid process it is necessary to use a screw of the proper total length and thread length, but such an optimal ready-made screw is not always available. The authors describe a technique of intra-operative screw trimming using a high-speed diamond drill. This adjustment is easily and quickly performed. It enables the screw to act as a compression screw, which facilitates fusion of the fractured surfaces. PMID:1595397

  18. Strength of initial mechanical fixation of screw ring acetabular components.

    PubMed

    Kody, M H; Kabo, J M; Markolf, K L; Dorey, F J; Amstutz, H C

    1990-08-01

    This study was conducted to determine the effects of design on the initial fixation of several types of screw-ring acetabular components. The components were tested in polyurethane foam to assess relative screw fixation strengths with a consistent material. Embalmed pelves from anatomic specimens were used to conduct paired tests between designs that showed large differences in insertional torque to failure in foam. The quality of the initial fixation in foam was found to be dependent on the design features of the components. Components with widely spaced, deep threads, and minimal thread interruptions offered the strongest initial fixation in foam. Tests in bone revealed a wide range of fixation strengths reflecting the variability in bone quality. No differences in fixation strength attributable to component design were observed in bone. When the insertional failure torque was greater than 60 N.m, one-half of the pelves fractured, and these fractures occurred with all designs. At failure torques less than 60 N.m, failure was predominantly due to thread strippage of the screw, with only two of 20 specimens experiencing pelvic fracture. PMID:2379353

  19. Evaluation of the Effect of Fixation Angle between Polyaxial Pedicle Screw Head and Rod on the Failure of Screw-Rod Connection

    PubMed Central

    Çetin, Engin; Özkaya, Mustafa; Güler, Ümit Özgür; Acaroğlu, Emre

    2015-01-01

    Introduction. Polyaxial screws had been only tested according to the ASTM standards (when they were perpendicularly positioned to the rod). In this study, effects of the pedicle screws angled fixation to the rod on the mechanical properties of fixation were investigated. Materials and Method. 30 vertically fixed screws and 30 screws fixed with angle were used in the study. Screws were used in three different diameters which were 6.5 mm, 7.0 mm, and 7.5 mm, in equal numbers. Axial pull-out and flexion moment tests were performed. Test results compared with each other using appropriate statistical methods. Results. In pull-out test, vertically fixed screws, in 6.5 mm and 7.0 mm diameter, had significantly higher maximum load values than angled fixed screws with the same diameters (P < 0.01). Additionally, vertically fixed screws, in all diameters, had significantly greater stiffness according to corresponding size fixed with angle (P < 0.005). Conclusion. Fixing the pedicle screw to the rod with angle significantly decreased the pull-out stiffness in all diameters. Similarly, pedicle screw instrumentation fixed with angle decreased the minimum sagittal angle between the rod and the screw in all diameters for flexion moment test but the differences were not significant.

  20. Unilateral Augmented Pedicle Screw Fixation for Foraminal Stenosis

    PubMed Central

    Kim, Jeong-Gyun; Jin, Yong-Jun; Kim, Ki-Jeong; Kim, Hyun-Jib

    2009-01-01

    Objective The purpose of this study is to evaluate the effectiveness of unilateral decompression and pedicle screw fixation for the unilateral symptomatic foraminal stenosis. Methods The study group comprises consecutive 16 patients who underwent unilateral decompression and bone cement augmented pedicle screw fixation from May 2003 to January 2006. The patients were evaluated by visual analog scale (VAS) for pain and the scoring system of the Japanese Orthopedic Association (JOA) for low back pain. The result of surgery was also evaluated with McNab's classification. Excellent or good outcome was considered as successful. The patients were followed at postoperative 1 month, 3 month, 6 month, and 1 year with standing AP and lateral films. Results The average VAS and JOA score of the 16 patients were 7.8 (range, 6-9) and 5.8 (range, 3 - 10) before surgery and 2.2 (range, 0 - 5) and 12.3 (range, 9 - 15) at the time of last follow up. Both VAS and JOA score improved significantly after the surgery (p < 0.05, t-test). All patients improved after the operation and no revision surgery was required. No metal failure or pseudoarthrosis was observed during the follow-up. The success rate was 87.5%. Conclusion Our data suggest that unilateral decompression and pedicle screw fixation for the unilateral symptomatic foraminal stenosis is an effect method for obtaining satisfactory clinical outcome. Its possible advantage is shorter operation time and reduced surgical extent. We believe that the reduced stiffness of unilateral fixation was compensated by pedicle screw augmentation and interbody fusion. PMID:19707487

  1. Coracoclavicular screw fixation for unstable distal clavicle fractures.

    PubMed

    Macheras, George; Kateros, Konstantinos T; Savvidou, Olga D; Sofianos, John; Fawzy, Ernest A; Papagelopoulos, Panayiotis J

    2005-07-01

    Fifteen patients with Neer type II distal clavicle fracture were treated surgically. Operative treatment included open reduction and fixation of the proximal clavicular fragment to the coracoid process using a 6.5-mm cancellous screw and repair of the coracoclavicular ligaments. Fracture union occurred at a mean of 7 weeks postoperatively without any serious complications. All patients returned to the pre-injury level of activity with no residual pain or dysfunction. PMID:16119284

  2. Additional Drive Circuitry for Piezoelectric Screw Motors

    NASA Technical Reports Server (NTRS)

    Smythe, Robert; Palmer, Dean; Gursel, Yekta; Reder, Leonard; Savedra, Raymond

    2004-01-01

    Modules of additional drive circuitry have been developed to enhance the functionality of a family of commercially available positioning motors (Picomotor . or equivalent) that provide linear motion controllable, in principle, to within increments .30 nm. A motor of this type includes a piezoelectric actuator that turns a screw. Unlike traditional piezoelectrically actuated mechanisms, a motor of this type does not rely on the piezoelectric transducer to hold position: the screw does not turn except when the drive signal is applied to the actuator.

  3. Biomechanical study of expandable pedicle screw fixation in severe osteoporotic bone comparing with conventional and cement-augmented pedicle screws.

    PubMed

    Chen, Yi-Long; Chen, Wen-Chuan; Chou, Chi-Wei; Chen, Jou-Wen; Chang, Chia-Ming; Lai, Yu-Shu; Cheng, Cheng-Kung; Wang, Shih-Tien

    2014-11-01

    Pedicle screws are widely utilized to treat the unstable thoracolumbar spine. The superior biomechanical strength of pedicle screws could increase fusion rates and provide accurate corrections of complex deformities. However, osteoporosis and revision cases of pedicle screw substantially reduce screw holding strength and cause loosening. Pedicle screw fixation becomes a challenge for spine surgeons in those scenarios. The purpose of this study was to determine if an expandable pedicle screw design could be used to improve biomechanical fixation in osteoporotic bone. Axial mechanical pull-out test was performed on the expandable, conventional and augmented pedicle screws placed in a commercial synthetic bone block which mimicked a human bone with severe osteoporosis. Results revealed that the pull-out strength and failure energy of expandable pedicle screws were similar with conventional pedicle screws augmented with bone cement by 2 ml. The pull-out strength was 5-fold greater than conventional pedicle screws and the failure energy was about 2-fold greater. Besides, the pull-out strength of expandable screw was reinforced by the expandable mechanism without cement augmentation, indicated that the risks of cement leakage from vertebral body would potentially be avoided. Comparing with the biomechanical performances of conventional screw with or without cement augmentation, the expandable screws are recommended to be applied for the osteoporotic vertebrae. PMID:24907127

  4. Screw fixation of dermal regeneration template for scalp reconstruction.

    PubMed

    Orseck, Michael J; Trujillo, Manny G; Ritter, Edmond F

    2012-05-01

    Despite many advances in reconstructive techniques, the full-thickness scalp defect remains a difficult problem for the reconstructive surgeon. Patient and disease-specific factors occasionally make reconstruction with a dermal regeneration template (DRT) an attractive option when other methods are less advised. Although the applicability of dermal regeneration templates has been well elucidated, the method of DRT immobilization has not been standardized. Given the difficulty of adherence and subsequent infiltration of host cells into the DRT from the underlying bone due to seroma, hematoma, or shearing forces, we propose a screw and bolster system for DRT immobilization. We present a series of 13 patients with full-thickness scalp loss who underwent reconstruction with DRT and a subsequent split-thickness skin graft. All 13 patients were treated with the screw-bolster method of DRT fixation before a vacuum-assisted closure dressing. The average surface area of the defect was 96 cm. The mean time interval between the application of DRT and skin graft was 28 days. At a mean of 9-month follow-up, all patients achieved a well-vascularized neodermis, and progressed to complete, stable wound healing following application of a split-thickness skin graft. We propose that a screw-bolster system of fixation is a safe and effective method of immobilizing DRT in full-thickness scalp defects. PMID:22531400

  5. Comparison of Pedicle Screw Loosening Mechanisms and the Effect on Fixation Strength.

    PubMed

    Mehmanparast, Hedayeh; Petit, Yvan; Mac-Thiong, Jean-Marc

    2015-12-01

    Screw loosening is a common complication in spinal fixation using pedicle screws which may lead to loss of correction and revision surgery. The mechanisms of pedicle screw loosening are not well understood. The purpose of this study was to compare the pedicle screw pullout force and stiffness subsequent or not to multidirectional cyclic bending load (toggling). Pedicle screws inserted into porcine lumbar vertebrae underwent toggling in craniocaudal (CC), mediolateral (ML) directions, and no toggling (NT) before pullout. This study suggests that toggling and in particular CC toggling should be included in biomechanical evaluation of pedicle screw fixation strength. PMID:26502116

  6. Biomechanical efficacy of monoaxial or polyaxial pedicle screw and additional screw insertion at the level of fracture, in lumbar burst fracture: An experimental study

    PubMed Central

    Wang, Hongwei; Li, Changqing; Liu, Tao; Zhao, Wei-dong; Zhou, Yue

    2012-01-01

    Background: Use of a pedicle screw at the level of fracture, also known as an intermediate screw, has been shown to improve clinical results in managing lumbar fracture, but there is a paucity of biomechanical studies to support the claim. The aim of this study was to evaluate the effect of adding intermediate pedicle screws at the level of a fracture on the stiffness of a short-segment pedicle fixation using monoaxial or polyaxial screws and to compare the strength of monoaxial and polyaxial screws in the calf spine fracture model. Materials and Methods: Flexibility of 12 fresh-frozen calf lumbar spine specimens was evaluated in all planes. An unstable burst fracture model was created at the level of L3 by the pre-injury and dropped-mass technique. The specimens were randomly divided into monoaxial pedicle screw (MPS) and polyaxial pedicle screw (PPS) groups. Flexibility was retested without and with intermediate screws (MPSi and PPSi) placed at the level of fracture in addition to standard screws placed at L2 and L4. Results: The addition of intermediate screws significantly increased the stability of the constructs, as measured by a decreased range of motion (ROM) in flexion, extension, and lateral bending in both MPS and PPS groups (P < 0.05). There was neither any significant difference in the ROM in the spines of the two groups before injury, nor a difference in the ROM between the MPSi and PPSi groups (P > 0.05), but there was a significant difference between MPS and PPS in flexion and extension in the short-segment fixation group (P < 0.05). Conclusions: The addition of intermediate screws at the level of a burst fracture significantly increased the stability of short-segment pedicle screw fixation in both the MPS and PPS groups. However, in short-segment fixation group, monoaxial pedicle screw exhibited more stability in flexion and extension than the polyaxial pedicle screw. PMID:22912513

  7. Multiple cannulated screw fixation of young femoral neck fractures

    PubMed Central

    Kim, Joo Yong; Kong, Gyu Min; Park, Dae Hyun; Kim, Dae Yoo

    2015-01-01

    Objective: We wanted to analyze the factors affecting the results of multiple cannulated screws fixation in patients less than 60 years old with femoral neck fracture (FNF). Methods: We reviewed 52 patients (30 males, 22 females) who were treated with multiple cannulated screws fixation for FNFs. They were followed up for more than one year during January 2002 to December 2012. They were classified by Gardens classification. The anatomic reduction was evaluated by Gardens alignment index on hip both anteroposterior and lateral images. Postoperative complications were analyzed during follow up periods. Results: By Gardens classification, 6 cases were in stage I, 13 cases in stage II, 30 cases in stage III and 3 cases in stage IV. During follow up periods, avascular necrosis of the femoral head was observed in 12 cases (23%) and nonunion was observed in 5 cases (9%). The 16 patients who had complications underwent total hip arthroplasty (31%). In non-displaced fracture groups (Garde I, II) did not have AVN nor nonunion. The incidence of complications in displaced fracture group was 51.5%. The complicated cases showed tendency for increased apex anterior angulation of femoral neck on hip lateral images and the result was statistically significant. (p=0.0260). Conclusion: The patients less than 60 years old who were treated with multiple cannulated screws fixation for displaced FNFs showed the incidence of complications was more than 50%. It needs a cautious approach for anatomical reduction, especially related to anterior angulation on hip lateral image. PMID:26870127

  8. The effect of screw type on the fixation of depressed fragments in tibial plateau fractures.

    PubMed

    Cooper, H J; Kummer, F J; Egol, K A; Koval, K J

    The ability of various screw types to stabilize depressed tibial plateau fractures was determined in a biomechanical study using a Sawbones model. Two sizes of both cancellous and cortical screws were evaluated for both supportfrom below and through the depressed fragment. As a general trend, cancellous bone screws provided a greater resistance to fragment displacement than cortical bone screws, and screws with a smaller thread diameter provided greater resistance to displacement than screws of the same thread type with a larger diameter. These results agree with the accepted standard that cancellous screws provide better fixation for tibial plateau fractures, but also are counterintuitive in that smaller screws provided greater fixation than larger screws of the same type. PMID:12003357

  9. Effectiveness of interference screw fixation in ulnar collateral ligament reconstruction.

    PubMed

    Nissen, Carl W

    2008-07-01

    Ulnar collateral ligament disruptions of the elbow are increasingly common for athletes involved in overhead sports. One newer reconstructive technique combines the use of a biotenodesis screw for ulnar fixation with the docking procedure for humeral fixation referred to as the DANE procedure. Biomechanical evaluations have determined that the combined procedure has properties similar to previous methods, but few comparative clinical studies have been performed. The current study compares the DANE procedure to a traditional method of ulnar collateral ligament reconstruction with a medium range follow-up. Twelve ulnar collateral ligament reconstructions were observed for a minimum of 21 months. Six reconstructions were performed using bone tunnels on the ulna. The other 6 used a biotenodesis interference screw on the ulna. Both groups used the docking procedure on the humerus. Identical rehabilitation phases were followed by both groups. Attention was paid not only to the time to return to play and the level able to be returned to but also to interoperative differences, including tourniquet time. We concluded that the DANE reconstruction is an appropriate and effective method. Results are similar to those achieved with a traditional reconstructive method. The study also demonstrates that tourniquet time and, therefore, operative time is less for the DANE procedure. PMID:19292392

  10. Biomechanical Evaluation of Plate Versus Lag Screw Only Fixation of Distal Fibula Fractures.

    PubMed

    Misaghi, Amirhossein; Doan, Josh; Bastrom, Tracey; Pennock, Andrew T

    2015-01-01

    Traditional fixation of unstable Orthopaedic Trauma Association type B/C ankle fractures consists of a lag screw and a lateral or posterolateral neutralization plate. Several studies have demonstrated the clinical success of lag screw only fixation; however, to date no biomechanical comparison of the different constructs has been performed. The purpose of the present study was to evaluate the biomechanical strength of these different constructs. Osteotomies were created in 40 Sawbones() distal fibulas and reduced using 1 bicortical 3.5-mm stainless steel lag screw, 2 bicortical 3.5-mm lag screws, 3 bicortical 3.5-mm lag screws, or a single 3.5-mm lag screw coupled with a stainless steel neutralization plate with 3 proximal cortical and 3 distal cancellous screws. The constructs were tested to determine the stiffness in lateral bending and rotation and failure torque. No significant differences in lateral bending or rotational stiffness were detected between the osteotomies fixed with 3 lag screws and a plate. Constructs fixed with 1 lag screw were weaker for both lateral bending and rotational stiffness. Osteotomies fixed with 2 lag screws were weaker in lateral bending only. No significant differences were found in the failure torque. Compared with lag screw only fixation, plate fixation requires larger incisions and increased costs and is more likely to require follow-up surgery. Despite the published clinical success of treating simple Orthopaedic Trauma Association B/C fractures with lag screw only fixation, many surgeons still have concerns about stability. For noncomminuted, long oblique distal fibula fractures, lag screw only fixation techniques offer construct stiffness similar to that of traditional plate and lag screw fixation. PMID:25990534

  11. Finite Element Analysis of Osteosynthesis Screw Fixation in the Bone Stock: An Appropriate Method for Automatic Screw Modelling

    PubMed Central

    Wieding, Jan; Souffrant, Robert; Fritsche, Andreas; Mittelmeier, Wolfram; Bader, Rainer

    2012-01-01

    The use of finite element analysis (FEA) has grown to a more and more important method in the field of biomedical engineering and biomechanics. Although increased computational performance allows new ways to generate more complex biomechanical models, in the area of orthopaedic surgery, solid modelling of screws and drill holes represent a limitation of their use for individual cases and an increase of computational costs. To cope with these requirements, different methods for numerical screw modelling have therefore been investigated to improve its application diversity. Exemplarily, fixation was performed for stabilization of a large segmental femoral bone defect by an osteosynthesis plate. Three different numerical modelling techniques for implant fixation were used in this study, i.e. without screw modelling, screws as solid elements as well as screws as structural elements. The latter one offers the possibility to implement automatically generated screws with variable geometry on arbitrary FE models. Structural screws were parametrically generated by a Python script for the automatic generation in the FE-software Abaqus/CAE on both a tetrahedral and a hexahedral meshed femur. Accuracy of the FE models was confirmed by experimental testing using a composite femur with a segmental defect and an identical osteosynthesis plate for primary stabilisation with titanium screws. Both deflection of the femoral head and the gap alteration were measured with an optical measuring system with an accuracy of approximately 3 m. For both screw modelling techniques a sufficient correlation of approximately 95% between numerical and experimental analysis was found. Furthermore, using structural elements for screw modelling the computational time could be reduced by 85% using hexahedral elements instead of tetrahedral elements for femur meshing. The automatically generated screw modelling offers a realistic simulation of the osteosynthesis fixation with screws in the adjacent bone stock and can be used for further investigations. PMID:22470474

  12. Finite element analysis of osteosynthesis screw fixation in the bone stock: an appropriate method for automatic screw modelling.

    PubMed

    Wieding, Jan; Souffrant, Robert; Fritsche, Andreas; Mittelmeier, Wolfram; Bader, Rainer

    2012-01-01

    The use of finite element analysis (FEA) has grown to a more and more important method in the field of biomedical engineering and biomechanics. Although increased computational performance allows new ways to generate more complex biomechanical models, in the area of orthopaedic surgery, solid modelling of screws and drill holes represent a limitation of their use for individual cases and an increase of computational costs. To cope with these requirements, different methods for numerical screw modelling have therefore been investigated to improve its application diversity. Exemplarily, fixation was performed for stabilization of a large segmental femoral bone defect by an osteosynthesis plate. Three different numerical modelling techniques for implant fixation were used in this study, i.e. without screw modelling, screws as solid elements as well as screws as structural elements. The latter one offers the possibility to implement automatically generated screws with variable geometry on arbitrary FE models. Structural screws were parametrically generated by a Python script for the automatic generation in the FE-software Abaqus/CAE on both a tetrahedral and a hexahedral meshed femur. Accuracy of the FE models was confirmed by experimental testing using a composite femur with a segmental defect and an identical osteosynthesis plate for primary stabilisation with titanium screws. Both deflection of the femoral head and the gap alteration were measured with an optical measuring system with an accuracy of approximately 3 m. For both screw modelling techniques a sufficient correlation of approximately 95% between numerical and experimental analysis was found. Furthermore, using structural elements for screw modelling the computational time could be reduced by 85% using hexahedral elements instead of tetrahedral elements for femur meshing. The automatically generated screw modelling offers a realistic simulation of the osteosynthesis fixation with screws in the adjacent bone stock and can be used for further investigations. PMID:22470474

  13. Four quadrant parallel peripheral screw fixation for displaced femoral neck fractures in elderly patients

    PubMed Central

    Satish, Bhava RJ; Ranganadham, Atmakuri V; Ramalingam, Karruppasamy; Tripathy, Sujit Kumar

    2013-01-01

    Background: The treatment options for displaced femoral neck fracture in elderly are screw fixation, hemiarthroplasty and total hip arthroplasty based primarily on age of the patient. The issues in screw fixation are ideal patient selection, optimal number of screws, optimal screw configuration and positioning inside the head and neck of femur. The problems of screw fixation may be loss of fixation, joint penetration, avascular necrosis of femoral head, nonunion, prolonged rehabilitation period and the need for second surgery in failed cases. We hereby present results of a modified screw fixation technique in femoral neck fractures in patients ?50 years of age. Materials and Methods: Patients ?50 years of age (range 50-73 years) who sustained displaced femoral neck fracture and fulfilled the inclusion criteria were enrolled in this prospective study. They were treated with closed reduction under image intensifier control and cannulated cancellous screw fixation. Accurate anatomical reduction was not aimed and a cross sectional contact area of >75% without varus was accepted as good reduction. Four screws were positioned in four quadrants of femoral head and neck, as parallel and as peripheral as possible. Radiological and functional results were evaluated periodically. Sixty four patients who could complete a minimum followup of two years were analyzed. Results: Radiologically, all fractures healed after mean duration of 10 weeks (range 8-12 weeks). There was no avascular necrosis. Nonanatomical healing was observed in 45 cases (70%). All patients except one had excellent functional outcome and could do cross-legged sitting and squatting. Chondrolysis with progressive head resorption was seen in one case, which was converted to total hip arthroplasty. Conclusion: Closed reduction and cannulated cancellous screw fixation gives satisfactory functional results in large group of elderly patients. The four quadrant parallel peripheral (FQPP) screw fixation technique gives good stability, allows controlled collapse, avoids fixation failure and achieves predictable bone healing in displaced femoral neck fracture in patients ?50 years of age. PMID:23682180

  14. Use of templates and self-tapping metal screws for temporary fixation of a resorbable plate system

    PubMed Central

    Sukegawa, Shintaro; Kanno, Takahiro; Shibata, Akane; Takahashi, Yuka; Furuki, Yoshihiko

    2015-01-01

    Resorbable plate systems combine the benefits of rigid internal fixation with the convenience of biodegradation; thus, precluding the need for removal and reducing their interference with craniofacial growth. However, in surgeries involving maxillofacial bone, when reduction or repositioning of the bone segment is inaccurate, refixation and rebending of the plate may be necessary. Here, we report using a temporary plate with self-tapping metal screws to avoid repeated rebending of the resorbable plate and using additional screws following inaccurate fixation in maxillofacial surgeries.

  15. Delayed subarachnoid hemorrhage following failed odontoid screw fixation.

    PubMed

    Wilson, David A; Fusco, David J; Theodore, Nicholas

    2011-06-01

    Iatrogenic vascular injury is a rare but potentially devastating complication of cervical spine instrumentation. The authors report on a patient who developed an anterior spinal artery pseudoaneurysm associated with delayed subarachnoid hemorrhage after undergoing odontoid screw placement 14 months earlier. This 86-year-old man presented with spontaneous subarachnoid hemorrhage (Fisher Grade 4) and full motor strength on neurological examination. Imaging demonstrated pseudarthrosis of the odontoid process, extension of the odontoid screw beyond the posterior cortex of the dens, and a pseudoaneurysm arising from an adjacent branch of the anterior spinal artery. Due to the aneurysm's location and lack of active extravasation, endovascular treatment was not attempted. Posterior C1-2 fusion was performed to treat radiographic and clinical instability of the C1-2 joint. Postoperatively, the patient's motor function remained intact. Almost all cases of vascular injury related to cervical spine instrumentation are recognized at surgery. To the authors' knowledge, this is the first report of delayed vascular injury following an uncomplicated cervical fixation. This case further suggests that the risk of this phenomenon may be elevated in cases of failed fusion. PMID:21395399

  16. Screw versus pin fixation with open reduction of pediatric lateral condyle fractures.

    PubMed

    Gilbert, Shawn R; MacLennan, Paul A; Schlitz, Ryne S; Estes, Ashley R

    2016-03-01

    Good results have been described for lateral condyle fractures treated by open reduction and fixation using Kirschner wires or screws. We, in our level III retrospective comparison clinical research study, retrospectively reviewed 84 patients (43 K-wire, 41 screw fixation; average age 5.6 years, average follow-up 6.8 months). With K-wires there were three nonunions (average time to union 9.6 weeks). With screws, all fractures healed (average of 7.8 weeks). Screw fixation patients spent fewer days in a cast and had a greater range of motion at the last follow-up. Screw fixation is associated with fewer nonunions and faster time to union, but a secondary procedure for removal is required. PMID:26583930

  17. Safety Eevaluation of Free-Hand Lateral Mass Screw Fixation in the Subaxial Cervical Spine; Evaluation of 1256 Screws.

    PubMed

    Kim, Hak-Suk; Suk, Kyung-Soo; Moon, Seong-Hwan; Lee, Hwan-Mo; Kang, Kyung-Chung; Lee, Sang-Hun; Kim, Jin-Soo

    2014-11-01

    Study Design. Prospective studyObjective. To evaluate the safety of the lateral mass screw (LMS) fixation.Summary of Background Data. LMS fixation has been known to have risk of injury to vertebral artery, nerve root, or facet joints.Methods. A consecutive series of 178 patients undergoing planned LMS fixation were studied. Screw fixation was performed by free hand technique. Entry point of screws was 2mm medial from the center of the lateral mass. Planned divergent angle of the screw was 30 degrees. Bicortical fixation was tried in all cases. After the surgery, 3 dimensional CT scan of the cervical spine was performed in all patients. We checked number of screws in each level, divergent angle of the screws, and violation of foramen transversarium (FT), intervertebral foramen or facet joint by screws. Reliability test was performed.Results. Total 1256 screws were fixed with 269 at C3, 318 at C4, 331 at C5, and 338 screws at C6. Mean divergent angle of the screws were 34.7/33.1 degrees at C3, 33.9/32.1 at C4, 34.7/32.7 at C5, and 33.6/30.7 at C6. Incidence of FT violation was 0.876%. FT violation was most common at C6 (6/11 violations). Mean divergent angle in cases of FT violation was 15.0 degrees and was significantly smaller than that of safe cases. There was no injury to vertebral artery. There was no violation of intervertebral foramen. Incidence of facet violation was 1.433%. 17 facet violations were within fusion segment. Only one screw violated healthy facet. Facet violation was most common at C3 (12/18 violations).Conclusion. LMS fixation was safe stabilizing technique with very low incidence of violation of FT, intervertebral foramen, and facet. There is a possibility of FT violation if the divergent angle was small. FT violation was most common at C6. Facet violation was most common at C3. PMID:25341994

  18. Comparison of two-transsacral-screw fixation versus triangular osteosynthesis for transforaminal sacral fractures.

    PubMed

    Min, Kyong S; Zamorano, David P; Wahba, George M; Garcia, Ivan; Bhatia, Nitin; Lee, Thay Q

    2014-09-01

    Transforaminal pelvic fractures are high-energy injuries that are translationally and rotationally unstable. This study compared the biomechanical stability of triangular osteosynthesis vs 2-transsacral-screw fixation in the repair of a transforaminal pelvic fracture model. A transforaminal fracture model was created in 10 cadaveric lumbopelvic specimens. Five of the specimens were stabilized with triangular osteosynthesis, which consisted of unilateral L5-to-ilium lumbopelvic fixation and ipsilateral iliosacral screw fixation. The remaining 5 were stabilized with a 2-transsacral-screw fixation technique that consisted of 2 transsacral screws inserted across S1. All specimens were loaded cyclically and then loaded to failure. Translation and rotation were measured using the MicroScribe 3D digitizing system (Revware Inc, Raleigh, North Carolina). The 2-transsacral-screw group showed significantly greater stiffness than the triangular osteosynthesis group (2-transsacral-screw group, 248.7 N/mm [standard deviation, 73.9]; triangular osteosynthesis group, 125.0 N/mm [standard deviation, 66.9]; P=.02); however, ultimate load and rotational stiffness were not statistically significant. Compared with triangular osteosynthesis fixation, the use of 2 transsacral screws provides a comparable biomechanical stability profile in both translation and rotation. This newly revised 2-transsacral-screw construct offers the traumatologist an alternative method of repair for vertical shear fractures that provides biplanar stability. It also offers the advantage of percutaneous placement in either the prone or supine position. PMID:25350616

  19. A new technique of bone cement augmentation via the disc space for percutaneous pedicle screw fixation.

    PubMed

    Park, Chang Kyu; Park, Choon Keun; Lee, Dong Chan; Lee, Dong Geun

    2016-01-01

    OBJECT In elderly patients with severe osteoporosis, instrumented lumbar interbody fusion may result in fixation failure or nonunion because of decreased pedicle screw pullout strength or increased interbody graft subsidence risk. Thus, given its many advantages, percutaneous pedicle screw fixation with cement augmentation can be an effective method to use in elderly patients. The authors report on an easy, safe, and economical technique for bone cement augmentation using a bone biopsy needle inserted into the disc space in 2 osteoporotic patients who were treated with posterior interbody fusion and percutaneous pedicle screw fixation. METHODS Two elderly patients who complained of back pain and intermittent neurological claudication underwent posterior interbody fusion with percutaneous pedicle screw fixation. After routinely assembling rods on the screws, a bone biopsy needle was inserted into the disc space via the operative field; the needle was then placed around the tips of the screws using fluoroscopic radiography for guidance. Bone cement was injected through the bone biopsy needle, also under fluoroscopic radiography guidance. RESULTS Both patients' symptoms improved after the operation, and there was no evidence of cage subsidence or screw loosening at the 4-month follow-up. CONCLUSIONS The indirect technique of bone cement augmentation via the disc space for percutaneous screw fixation could be an easy, safe, and economical method. PMID:26360145

  20. Percutaneous Cement-Augmented Screws Fixation in the Fractures of the Aging Spine: Is It the Solution?

    PubMed Central

    Pesenti, Sbastien; Peltier, Emilie; Adetchessi, Tarek; Dufour, Henry; Fuentes, Stphane

    2014-01-01

    Introduction. Management of elderly patients with thoracolumbar fractures is still challenging due to frequent osteoporosis and risk of screws pull-out. The aim of this study was to evaluate results of a percutaneous-only procedure to treat these fragile patients using cement-augmented screws. Methods. 12 patients diagnosed with a thoracolumbar fracture associated with an important loss of bone stock were included in this prospective study. Surgical procedure included systematically a percutaneous osteosynthesis using cemented fenestrated screws. When necessary, additional anterior support was performed using a kyphoplasty procedure. Clinical and radiographic evaluations were performed using CT scan. Results. On the whole series, 15 fractures were diagnosed and 96 cemented screws were inserted. The difference between the pre- and postoperative vertebral kyphosis was statistically significant (12.9 versus 4.4, P = 0.0006). No extrapedicular screw was reported and one patient was diagnosed with a cement-related pulmonary embolism. During follow-up period, no infectious complications, implant failures, or pull-out screws were noticed. Discussion. Aging spine is becoming an increasing public health issue. Management of these patients requires specific attention due to the augmented risk of complications. Using percutaneous-only screws fixation with cemented screw provides satisfactory results. A rigorous technique is mandatory in order to achieve best outcomes. PMID:24696858

  1. Endosseous Fixation Device for Lapidus Arthrodesis: Technique, Early Experience, and Comparison With Crossed Screw Fixation.

    PubMed

    Zelent, Marek E; Neese, David J; Peterson, Paul H

    2015-01-01

    First metatarsal cuneiform joint arthrodesis has been commonly used since the early 1900s for definitive treatment of a variety of conditions involving the medial column of the foot. Early applications of this procedure resulted in a relatively high rate of complications, including malunion and nonunion. We retrospectively examined a novel method of fixation involving an endosseous implant with a nonporous, rough exterior surface and compared it with the traditional crossed screw fixation, considered the standard of care for the procedure. Twenty-one feet in 19 patients served as the control group with crossed screws, and 18 feet in 17 patients served as the trial group using the study device. Null hypothesis testing was used to compare the outcomes parameters between the comparative groups. Postoperatively, the patients were allowed to walk in a prefabricated, removable, below-the-knee cast boot at a mean of 48.3 8.2 days in the control group and 24.4 9.7 days in the trial group. These differences were highly significant (p<.0001). Postoperatively, the patients were allowed to walk in a stiff-soled shoe at a mean of 65.2 8.4 days in the control group and 49.7 19.2 days in the trial group. These differences were also statistically significant (p=.0020). The patients in the control group required revision surgery in 7 of 21 procedures (33%), with 2 patients developing nonunion (9.5%). Only 1 patient in the trial group required revision surgery (5.8%), and no patient developed nonunion. From these results, we believe that the endosseous trial implant is a reliable option for fixation of the first metatarsal cuneiform arthrodesis procedure and might allow for earlier weightbearing with fewer postoperative complications. PMID:26364702

  2. Monoaxial pedicle screws are superior to polyaxial pedicle screws and the two pin external fixator for subcutaneous anterior pelvic fixation in a biomechanical analysis.

    PubMed

    Vaidya, Rahul; Onwudiwe, Ndidi; Roth, Matthew; Sethi, Anil

    2013-01-01

    Purpose. Comparison of monoaxial and polyaxial screws with the use of subcutaneous anterior pelvic fixation. Methods. Four different groups each having 5 constructs were tested in distraction within the elastic range. Once that was completed, 3 components were tested in torsion within the elastic range, 2 to torsional failure and 3 in distraction until failure. Results. The pedicle screw systems showed higher stiffness (4.008 0.113?Nmm monoaxial, 3.638 0.108?Nmm Click-x; 3.634 0.147?Nmm Pangea) than the exfix system (2.882 0.054?Nmm) in distraction. In failure testing, monoaxial pedicle screw system was stronger (360?N) than exfixes (160?N) and polyaxial devices which failed if distracted greater than 4?cm (157?N Click-x or 138?N Pangea). The exfix had higher peak torque and torsional stiffness than all pedicle systems. In torsion, the yield strengths were the same for all constructs. Conclusion. The infix device constructed with polyaxial or monoaxial pedicle screws is stiffer than the 2 pin external fixator in distraction testing. In extreme cases, the use of reinforcement or monoaxial systems which do not fail even at 360?N is a better option. In torsional testing, the 2 pin external fixator is stiffer than the pedicle screw systems. PMID:24368943

  3. Monoaxial Pedicle Screws Are Superior to Polyaxial Pedicle Screws and the Two Pin External Fixator for Subcutaneous Anterior Pelvic Fixation in a Biomechanical Analysis

    PubMed Central

    Vaidya, Rahul; Onwudiwe, Ndidi; Roth, Matthew; Sethi, Anil

    2013-01-01

    Purpose. Comparison of monoaxial and polyaxial screws with the use of subcutaneous anterior pelvic fixation. Methods. Four different groups each having 5 constructs were tested in distraction within the elastic range. Once that was completed, 3 components were tested in torsion within the elastic range, 2 to torsional failure and 3 in distraction until failure. Results. The pedicle screw systems showed higher stiffness (4.008 0.113?Nmm monoaxial, 3.638 0.108?Nmm Click-x; 3.634 0.147?Nmm Pangea) than the exfix system (2.882 0.054?Nmm) in distraction. In failure testing, monoaxial pedicle screw system was stronger (360?N) than exfixes (160?N) and polyaxial devices which failed if distracted greater than 4?cm (157?N Click-x or 138?N Pangea). The exfix had higher peak torque and torsional stiffness than all pedicle systems. In torsion, the yield strengths were the same for all constructs. Conclusion. The infix device constructed with polyaxial or monoaxial pedicle screws is stiffer than the 2 pin external fixator in distraction testing. In extreme cases, the use of reinforcement or monoaxial systems which do not fail even at 360?N is a better option. In torsional testing, the 2 pin external fixator is stiffer than the pedicle screw systems. PMID:24368943

  4. Surgical Strategies to Improve Fixation in the Osteoporotic Spine: The Effects of Tapping, Cement Augmentation, and Screw Trajectory

    PubMed Central

    Kuhns, Craig A.; Reiter, Michael; Pfeiffer, Ferris; Choma, Theodore J.

    2013-01-01

    Study Design Biomechanical study of pedicle screw fixation in osteoporotic bone. Objective To investigate whether it is better to tap or not tap osteoporotic bone prior to placing a cement-augmented pedicle screw. Methods Initially, we evaluated load to failure of screws placed in cancellous bone blocks with or without prior tapping as well as after varying the depths of tapping prior to screw insertion. Then we evaluated load to failure of screws placed in bone block models with a straight-ahead screw trajectory as well as with screws having a 23-degree cephalad trajectory (toward the end plate). These techniques were tested with nonaugmented (NA) screws as well as with bioactive cement (BioC) augmentation prior to screw insertion. Results In the NA group, pretapping decreased fixation strength in a dose-dependent fashion. In the BioC group, the tapped screws had significantly greater loads to failure (p < 0.01). Comparing only the screw orientation, the screws oriented at 23 degrees cephalad had a significantly higher failure force than their respective counterparts at 0 degrees (p < 0.01). Conclusions Standard pedicle screw fixation is often inadequate in the osteoporotic spine, but this study suggests tapping prior to cement augmentation will substantially improve fixation when compared with not tapping. Angulating screws more cephalad also seems to enhance aging spine fixation. PMID:24494181

  5. Fixation strength of biocomposite wedge interference screw in ACL reconstruction: effect of screw length and tunnel/screw ratio. A controlled laboratory study

    PubMed Central

    2010-01-01

    Background Primary stability of the graft is essential in anterior cruciate ligament surgery. An optimal method of fixation should be easy to insert and provide great resistance against pull-out forces. A controlled laboratory study was designed to test the primary stability of ACL tendinous grafts in the tibial tunnel. The correlation between resistance to traction forces and the cross-section and length of the screw was studied. Methods The tibial phase of ACL reconstruction was performed in forty porcine tibias using digital flexor tendons of the same animal. An 8 mm tunnel was drilled in each specimen and two looped tendons placed as graft. Specimens were divided in five groups according to the diameter and length of the screw used for fixation. Wedge interference screws were used. Longitudinal traction was applied to the graft with a Servohydraulic Fatigue System. Load and displacement were controlled and analyzed. Results The mean loads to failure for each group were 295,44 N (Group 1; 9 23 screw), 564,05 N (Group 2; 9 28), 614,95 N (Group 3; 9 35), 651,14 N (Group 4; 10 28) and 664,99 (Group 5; 10 35). No slippage of the graft was observed in groups 3, 4 and 5. There were significant differences in the load to failure among groups (ANOVA/P < 0.001). Conclusions Longer and wider interference screws provide better fixation in tibial ACL graft fixation. Short screws (23 mm) do not achieve optimal fixation and should be implanted only with special requirements. PMID:20591177

  6. Screw fixation in bone of guinea pigs sensitized to nickel and cobalt.

    PubMed

    Lewin, J; Lindgren, U; Wahlberg, J E

    1982-08-01

    A screw was inserted transversely through the distal femora and proximal tibiae of guinea pigs sensitized to either Ni or Co. An equal number of nonsensitized animals were treated in the same way. The animals with Ni allergy received an ASIF stainless steel screw and the animals with Co allergy a Howmedica Vitallium screw. After 6 weeks no obvious differences were observed in the histological picture around the femur screws that could be ascribed to metal sensitivity. The mechanical strength of the bone adjacent to the tibial screws was tested by measuring maximum torque during continuous tightening of the screws at a rate of 2 revolution/second. No significant differences in maximum torque resistance were found between sensitized and nonsensitized animals. The results indicate that sensitivity to Ni or Co does not compromise the mechanical fixation between metal and bone during the early period after the implantation. PMID:7102287

  7. Clinical Use of 3D Printing Guide Plate in Posterior Lumbar Pedicle Screw Fixation.

    PubMed

    Chen, Hongliang; Wu, Dongying; Yang, Huilin; Guo, Kaijin

    2015-01-01

    BACKGROUND This study aimed to evaluate the clinical efficacy of use of a 3D printing guide plate in posterior lumbar pedicle screw fixation. MATERIAL AND METHODS We enrolled 43 patients receiving posterior lumbar pedicle screw fixation. The experimental group underwent 3D printing guide plate-assisted posterior lumbar pedicle screw fixation, while the control group underwent traditional x-ray-assisted posterior lumbar pedicle screw fixation. After surgery, CT scanning was done to evaluate the accuracy of screw placement according to the Richter standard. RESULTS All patients were followed up for 1 month. The mean time of placement for each screw and the amount of hemorrhage was 4.92.1 min and 8.011.1 mL in the experimental group while 6.52.2 min and 59.913.0 mL in the control group, respectively, with significant differences (p<0.05). The fluoroscopy times of each screw placement was 0.50.4 in the experimental group, which was significantly lower than that in the control group 1.20.7 (p<0.05). The excellent and good screw placement rate was 100% in the experimental group and 98.4% in the control group, without any statistical difference (P>0.05). No obvious complications were reported in either group. CONCLUSIONS Compared with the traditional treatment methods, the intra-operative application of 3D printing guide plate can shorten the operation time and reduce the amount of hemorrhage. It can also reduce the fluoroscopy times compared with the traditional fluoroscopy, which cannot improve the accuracy rate of screw placement. PMID:26681388

  8. Clinical Use of 3D Printing Guide Plate in Posterior Lumbar Pedicle Screw Fixation

    PubMed Central

    Chen, Hongliang; Wu, Dongying; Yang, Huilin; Guo, Kaijin

    2015-01-01

    Background This study aimed to evaluate the clinical efficacy of use of a 3D printing guide plate in posterior lumbar pedicle screw fixation. Material/Methods We enrolled 43 patients receiving posterior lumbar pedicle screw fixation. The experimental group underwent 3D printing guide plate-assisted posterior lumbar pedicle screw fixation, while the control group underwent traditional x-ray-assisted posterior lumbar pedicle screw fixation. After surgery, CT scanning was done to evaluate the accuracy of screw placement according to the Richter standard. Results All patients were followed up for 1 month. The mean time of placement for each screw and the amount of hemorrhage was 4.9±2.1 min and 8.0±11.1 mL in the experimental group while 6.5±2.2 min and 59.9±13.0 mL in the control group, respectively, with significant differences (p<0.05). The fluoroscopy times of each screw placement was 0.5±0.4 in the experimental group, which was significantly lower than that in the control group 1.2±0.7 (p<0.05). The excellent and good screw placement rate was 100% in the experimental group and 98.4% in the control group, without any statistical difference (P>0.05). No obvious complications were reported in either group. Conclusions Compared with the traditional treatment methods, the intra-operative application of 3D printing guide plate can shorten the operation time and reduce the amount of hemorrhage. It can also reduce the fluoroscopy times compared with the traditional fluoroscopy, which cannot improve the accuracy rate of screw placement. PMID:26681388

  9. Evaluation of Occipitocervical Arthrodesis Rates with Screw-based Fixation and Osteoinductive Fusion Adjuncts.

    PubMed

    Stone, Jeremy G; Panczykowski, David M; Tempel, Zachary J; Tormenti, Matthew; Kanter, Adam S; Okonkwo, David O

    2015-09-01

    Occipitocervical (OC) instability may be associated with neurologic impairment and even death. There is a paucity of research on the rate of arthrodesis utilizing modern screw-based constructs coupled with adjuvant osteoinductive agents. We reviewed our experience with OC constructs and compared the fusion rate, functional outcome, and rate of adverse events between recombinant human bone morphogenetic protein (BMP)-2, autologous iliac crest bone graft (ICBG), a combination of BMP and ICBG, and local bone autograft alone. We performed a retrospective cohort analysis of all adult admissions for operative treatment of OC instability utilizing segmental screw-based constructs for OC arthrodesis between January 2003 and September 2012. Data concerning demographic characteristics, diagnostic and procedural details, radiographic pathology, and clinical course were abstracted from medical records. The primary end point was evidence of stable fixation and osseous union on either dynamic lateral radiographs or computed tomography (CT) imaging at most recent follow-up. Secondary end points included functional outcome as determined by Nurick scale and Neck disability index (NDI) at???1year postoperation, as well as perioperative morbidity and mortality at 30 days and 3 months. During the study period, 94 patients (mean age: 62??18 years) underwent OC fixation with segmental screw-based constructs. The four fusion adjunct cohorts analyzed included local autograft alone (32%), ICBG (41%), BMP (14%), or a combination of ICBG and BMP (14%). Notably, demineralized bone matrix was also used in 61% of cases overall, but its use did not differ significantly among the four cohorts (p?=?0.28). Median radiographic follow-up was 6 months postoperatively (range: 1.5-54 months). Clinical outcomes were assessed at a median postoperative follow-up of 45 months (range: 12-87 months). Overall, radiographic evidence of arthrodesis was present in 83% of patients assessed and was not significantly different between adjunct cohorts (local autograft 92%, ICBG 77%, BMP 88%, and combination of ICBG and BMP 83%; p?=?0.79). This finding persisted despite adjustment for age, pathology, number of levels instrumented, and attendant procedures. Importantly, neither the presence of arthrodesis nor fusion adjunct was significantly associated with functional outcome in both univariate and adjusted regression models. Additionally, perioperative adverse events occurred in 23% of cases and did not vary significantly in incidence or severity between fusion adjunct cohorts. We present a large series of patients treated for OC instability with rigid fixation utilizing modern segmental screw-based constructs. The use of adjuvant osteoinductive agents (BMP, ICBG, or a combination) produced equivalent rates of arthrodesis, functional outcome, and adverse events compared with use of local autograft alone. PMID:26171793

  10. Intraoperative Computed Tomography Navigation for Transpedicular Screw Fixation to Treat Unstable Thoracic and Lumbar Spine Fractures

    PubMed Central

    Lee, Ching-Yu; Wu, Meng-Huang; Li, Yen-Yao; Cheng, Chin-Chang; Hsu, Chu-Hsiang; Huang, Tsung-Jen; Hsu, Robert Wen-Wei

    2015-01-01

    Abstract Transpedicular screw (TPS) fixation in unstable thoracic and lumbar (TL) spine fractures remains technically difficult because of destroyed anatomical landmarks, unstable gross segments, and discrepancies in anatomic orientation using conventional anatomic landmarks, fluoroscopic guidance, or computed tomography (CT)-based navigation. In this study, we evaluated the safety and accuracy of TPS placement under intraoperative computed tomography (iCT) navigation in managing unstable TL spine fractures. From 2010 to 2013, we retrospectively reviewed the Spine Operation Registry records of patients who underwent posterior instrumented fusion to treat unstable TL spine fractures via the iCT navigation system. An unstable spine fracture was identified as AO/Magerl classification type B or type C. In all, 316 screws in 37 patients with unstable TL spine fractures were evaluated and involved 7 thoracic, 23 thoracolumbar junctional, and 7 lumbar fractures. The accuracy of TPS positioning in the pedicle without breach was 98% (310/316). The average number of iCT scans per patient was 2.1 (range 2–3). The average total radiation dose to patients was 15.8 mSv; the dose per single level exposure was 2.7 mSv. The TPS intraoperative revision rate was 0.6% (2/316) and no neurovascular sequela was observed. TPS fixation using the iCT navigation system obtained a 98% accuracy in stabilizing unstable TL spine fractures. A malplaced TPS could be revised during real-time confirmation of the TPS position, and no secondary operation was required to revise malplaced screws. The iCT navigation system provides accurate and safe management of unstable TL spine fractures. In addition, operating room personnel, including surgeons and nurses, did not need to wear heavy lead aprons as they were not exposed to radiation. PMID:25997042

  11. COMPLICATIONS OF THE SCREW/WASHER TIBIAL FIXATION TECHNIQUE FOR KNEE LIGAMENT RECONSTRUCTION

    PubMed Central

    Almeida, Alexandre; Roveda, Gilberto; Valin, Márcio Rangel; Almeida, Nayvaldo Couto de; Sartor, Vanderlei; Alves, Soraya Melina

    2015-01-01

    To evaluate the presence of pain at the site of the surgical incision and the need to remove the tibial fixation screw in anterior cruciate ligament (ACL) reconstruction, in relation to sex and body mass index (BMI). Methods: A group of 265 patients who underwent ACL reconstruction with ipsilateral flexor tendon grafts from the thigh in which the tibial fixation technique consisted of using a cortical screw and metal washer, between July 2000 and November 2007, were evaluated. Results: 176 patients were evaluated for an average of 33.3 ± 19.5 months; median of 29.5 months; IIQ: 17-45 months; minimum of 8 and maximum of 87 months. There was no statistical difference regarding complaints of pain at the site of the screw (p = 0.272) and the need to remove the tibial screw (p = 0.633) between sexes. There was no statistical difference regarding complaints of pain at the site of the screw (p = 0.08) and the need to remove the tibial screw (p = 0.379) according to BMI. Conclusion: The pain complaint rate at the screw site from the screw and metal washer method used for tibial fixation in ACL reconstruction was of the order of 25%, and the screw had to be removed in 10.8% of the cases. There was no predominance of pain complaints at the surgical wound between the sexes. There was a greater tendency to complain about pain among patients with BMI < 25. There was no predominance of screw and washer removal between the sexes or between individuals with different BMIs.

  12. Lumbosacral fixation using sacroiliac buttress screws: a modification to the Jackson technique with intrasacral rods

    PubMed Central

    2014-01-01

    Background The use of intrasacral rods has been previously reported for posterior lumbosacral fixation. However, problems associated with this technique include poor stability of the rod in the sacrum, difficulty in contouring the rod to fit the lateral sacral mass, and the complicated assembly procedure for the rod and pedicle screws in the thoracolumbar segments after insertion of the rod into the sacrum. Methods We used a screw with a polyaxial head instead of an intrasacral rod, which was inserted into the lateral sacral mass and assembled to the rod connected cephalad to pedicle screws. The dorsal side of the screw was stabilized by the sacral subchondral bone at the sacroiliac joint with iliac buttress coverage, and the tip of the screw was anchored by the sacral cortex. Results Three different cases were used to illustrate lumbosacral fixation using intrasacral screws as an anchor for the spinal instrumentation. Effective resistance of flexural bending moment and fusion were achieved in these patients at the lumbosacral level. Conclusions An intrasacral screw can be stabilized by subchondral bone with iliac buttress coverage at the dorsal and ventral sacral cortex. Posterior spinal fusion with this screw technique enables easier assembly of the instrumentation and presents better stabilization than that provided by the previously reported intrasacral rod technique for correction and fusion of thoracolumbar kyphoscoliosis. PMID:25050132

  13. Cervical pedicle screw fixation at C6 and C7: A cadaveric study

    PubMed Central

    Li, Ye; Liu, Jingchen; Liu, Yulong; Wu, Yuntao; Zhu, Qingsan

    2015-01-01

    Background: Cervical pedicle screw fixation is an effective method for treating traumatic and non traumatic injuries. But many studies have reported higher incidence of cervical pedicle penetration, so many research efforts have aimed at improving the accuracy of cervical screw fixation. Most of the anatomical studies on cervical pedicle screw placement previously published focused on the measurements of anatomical parameters, the entry point of pedicle screw is vague. We preliminarily designed a C3, C4 and C5 pedicle screw fixation method that had clear entry point and clinical cases confirmed that this method is feasible and safe. So we did this study of cervical pedicle screw fixation for C6 and C7 vertebrae. Materials and Methods: Fifteen cervical vertebrae specimens were prepared and bilateral pedicle screws were manually inserted into C6 and C7. The intersection of the horizontal line through the midpoint of the transverse process root and the vertical line through the intersection of the posterolateral and posterior planes of the isthmus was the entry point. The screws were inserted along the axis of the pedicle, with the screw axis coinciding with the pedicle. The pedicle was truncated axially and sagittally along the trajectory and the narrowest pedicular height (PH), pedicular width (PW), overall length of the screw channel (LSC), transverse angle (E) and vertical angle (F) were measured. Results: In C6, the PW and PH were 6.12 0.78 and 7.48 0.81 mm, respectively. In C7, the PW and PH were 6.85 0.73 and 8.03 0.38 mm, respectively. The LSC was 30.83 0.91 mm. Two E angles were identified, namely E1 and E2 and their values were 89.61 1.24 and 59.71 1.10, respectively. Meanwhile, F averaged 75.86 1.12. Conclusion: The intersection of the horizontal line through the midpoint of the transverse process root and vertical line through the intersection of the posterolateral and posterior planes of the isthmus can be used as an entry point for C6 and C7 pedicle screw fixation. The screws should be inserted at 60 or 90 with the posterolateral isthmus in the horizontal plane and at 75 with the posterior isthmus in the sagittal plane. The LSC should not exceed 30 mm. PMID:26229170

  14. Less is more: lag screw only fixation of lateral malleolar fractures

    PubMed Central

    O’Shea, Kieran; Burke, Tom

    2006-01-01

    Displaced fractures of the lateral malleolus are typically treated with plate osteosynthesis with or without the use of lag screws, and immobilisation in a plaster cast for up to 6 weeks. Fixation through a smaller incision with less metal, such as lag screw only fixation, would theoretically lead to decreased infection rates and less irritation caused by hardware. The purpose of this study was to evaluate the benefits and success of lag screw only fixation of the lateral malleolus in non-comminuted oblique fractures of the lateral malleolus. A total of 25 patients who had non-comminuted unstable oblique fractures of their lateral malleolus that had been surgically fixed with lag screws only were retrospectively evaluated. All patients were younger than 60 years of age. Evaluation of the success of fixation, complications, resultant mobility and patient satisfaction was based on information gathered from chart reviews, X-ray findings and a standardised questionnaire based on the AOFAS Foot and Ankle Outcomes Questionnaire. These results were compared to an age-matched group of 25 consecutive patients treated with plate osteosynthesis. Of the 25 patients fixed with lag screws, nine had an unstable fracture of the lateral malleolus only, ten were bimalleolar fractures and six were trimalleolar. Eighteen patients were treated with two lag screws, and seven were treated with three lag screws. The bi- and trimalleolar fractures were treated with standard partially threaded cancellous screws. None of the lag screw-only group lost reduction. There were no documented wound infections in the lag screw group as compared to three deep infections in the plate group. Lag screw-only patients reported no palpable hardware as compared to 50% of the plate group. AOFAS scores at a mean of 12 months post-operative were similar in both groups. Lag screw only fixation of the lateral malleolus is a safe and effective method that has a number of advantages over plate osteosynthesis, in particular less soft tissue dissection, less prominent, symptomatic and palpable hardware and a reduced requirement for secondary surgical removal. PMID:16947052

  15. Crossed-screw fixation of the unstable thoracic and lumbar spine.

    PubMed

    Benzel, E C; Baldwin, N G

    1995-01-01

    An ideal spinal construct should immobilize only the unstable spinal segments, and thus only the segments fused. Pedicle fixation techniques have provided operative stabilization with the instrumentation of a minimal number of spinal segments; however, some failures have been observed with pedicle instrumentation. These failures are primarily related to excessive preload forces and limitations caused by the size and orientation of the pedicles. To circumvent these problems, a new technique, the crossed-screw fixation method, was developed and is described in this report. This technique facilitates short-segment spinal fixation and uses a lateral extracavitary approach, which provides generous exposure for spinal decompression and interbody fusion. The technique employs two large transverse vertebral body screws (6.5 to 8.5 mm in diameter) to bear axial loads, and two unilateral pedicle screws (placed on the side of the exposure) to restrict flexion and extension deformation around the transverse screws and to provide three-dimensional deformity correction. The horizontal vertebral body and the pedicle screws are connected to rods and then to each other via rigid crosslinking. The transverse vertebral body screws are unloaded during insertion by placing the construct in a compression mode after the interbody bone graft is placed, thus optimizing the advantage gained by the significant "toe-in" configuration provided and further decreasing the chance for instrumentation failure. The initial results of this technique are reported in a series of 10 consecutively treated patients, in whom correction of the deformity was facilitated. Follow-up examination (average 10.1 months after surgery) demonstrated negligible angulation. Chronic pain was minimal. The crossed-screw fixation technique is biomechanically sound and offers a rapid and safe form of short-segment three-dimensional deformity correction and solid fixation when utilized in conjunction with the lateral extracavitary approach to the unstable thoracic and lumbar spine. This approach also facilitates the secure placement of an interbody bone graft. PMID:7815111

  16. Cortical and Standard Trajectory Pedicle Screw Fixation Techniques in Stabilizing Multisegment Lumbar Spine with Low Grade Spondylolisthesis

    PubMed Central

    ?nceo?lu, Serkan

    2015-01-01

    Background Cortical screw (CS) fixation has been recently proposed as an alternative to the standard pedicle screw (PS) fixation technique. Biomechanical studies involving individual screw pullout and single level motion segment stabilization showed comparable performance of both techniques. However, whether this new fixation technique can be applied to the stabilization of multilevel lumbar segments with significant destabilization has been unclear. Purpose To compare stability of CS fixation to the traditional PS fixation in an unstable 3 level spondylolisthesis model. Study Design This is a biomechanical study comparing cortical trajectory pedicle screw fixation to traditional trajectory pedicle screw fixation in an unstable cadaveric model using nondestructive flexibility test. Methods Eight fresh frozen cadaveric lumbar spines (T12- S1) were obtained. After intact baseline testing, a 3-level lowgrade spondylolisthesis was simulated at the L1-4. Each specimen was instrumented with the PS and CS fixation systems. Standard nondestructive flexibility test was performed. Range of motion at each level was compared between the constructs during flexion-extension, lateral bending, and axial rotation. Results The destabilization model significantly increased the ROM in all planes (P<0.05). Both fixation techniques provided significant reduction in the ROM (P<0.05). There was no significant difference in ROM between the PS and CS groups in any of planes (P>0.05). Conclusions Cortical trajectory pedicle screw fixation provided stabilization to multilevel lumbar segment with low-grade spondylolisthesis comparable to the standard trajectory pedicle screw construct. PMID:26484009

  17. Proximal screws placement in intertrochanteric fractures treated with external fixation: comparison of two different techniques

    PubMed Central

    2011-01-01

    Background To compare two different techniques of proximal pin placement for the treatment of intertrochanteric fractures in elderly patients utilizing the Orthofix Pertrochanteric Fixator. Methods Seventy elderly high-risk patients with an average age of 81 years were treated surgically for intertrochanteric fracture, resulting from a low energy trauma. Patients were randomly divided in two groups regarding to the proximal pin placement technique. In Group A the proximal pins were inserted in a convergent way, while in Group B were inserted in parallel. Results All fractures healed uneventfully after a mean time of 98 days. The fixator was well accepted and no patient had significant difficulties while sitting or lying. The mean VAS score was 5.4 in group A and 5.7 in group B. At 12 months after surgery, in group A the average Harris Hip Score and the Palmer and Parker mobility score was 67 and 5.8, respectively. In group B, the average Harris Hip Score and the Palmer and Parker mobility score was 62 and 5.6, respectively. No statistically significant difference was found regarding the functional outcome. The mean radiographic exposure during pin insertion in Group A and Group B was 15 and 6 seconds, respectively. The difference between the two groups, regarding the radiographic exposure, was found to be significant. Conclusion Proximal screw placement in a parallel way is simple, with significant less radiation exposure and shorter intraoperative duration. In addition, fixation stability is equal compared to convergent pin placement. PMID:21939534

  18. Fully Threaded Versus Partially Threaded Screws: Determining Shear inCancellous Bone Fixation.

    PubMed

    Downey, Michael W; Kosmopoulos, Victor; Carpenter, Brian B

    2015-01-01

    Many researchers have studied and compared various forms of intraosseous fixation. No studies have examined the effects of shear through stiffness and failure strength of a fully threaded versus a partially threaded screw. Our hypothesis was that the fully threaded lag screw technique would provide greater shear strength and resistance. Thirty-six synthetic sawbone blocks were used to test screw fixation. In group 1 (n=9), 2 blocks were fixed together using a fully threaded 4.0-mm stainless steel cancellous bone screw and the lag technique. In group 2 (n=8), 2 blocks were fixed together using the standard manufacturer-recommended method for inserting 4.0-mm partially threaded stainless steel cancellous bone screws. The constructs were then mechanically tested. Shear was applied by compressing each construct at an axial displacement rate of 0.5 mm/s until failure. The fully threaded screw had a significantly greater (p=.026) initial stiffness (106.415.8N/mm) than the partially threaded screw (80.127.5N/mm). The yield load and displacement for the fully threaded group (429.411.7N and 7.20.35mm) were 64% and 67% greater than those for the partially threaded screw group (261.426.1N and 4.31.03mm), respectively. The results of the present study have demonstrated the importance of a full-thread construct to prevent shear and to decrease strain at the fracture. The confirmation of our hypothesis questions the future need and use of partially threaded screws for cancellous bone fixation. PMID:26210079

  19. Comparison of migration behavior between single and dual lag screw implants for intertrochanteric fracture fixation

    PubMed Central

    Kouvidis, George K; Sommers, Mark B; Giannoudis, Peter V; Katonis, Pavlos G; Bottlang, Michael

    2009-01-01

    Background Lag screw cut-out failure following fixation of unstable intertrochanteric fractures in osteoporotic bone remains an unsolved challenge. This study tested if resistance to cut-out failure can be improved by using a dual lag screw implant in place of a single lag screw implant. Migration behavior and cut-out resistance of a single and a dual lag screw implant were comparatively evaluated in surrogate specimens using an established laboratory model of hip screw cut-out failure. Methods Five dual lag screw implants (Endovis, Citieffe) and five single lag screw implants (DHS, Synthes) were tested in the Hip Implant Performance Simulator (HIPS) of the Legacy Biomechanics Laboratory. This model simulated osteoporotic bone, an unstable fracture, and biaxial rocking motion representative of hip loading during normal gait. All constructs were loaded up to 20,000 cycles of 1.45 kN peak magnitude under biaxial rocking motion. The migration kinematics was continuously monitored with 6-degrees of freedom motion tracking system and the number of cycles to implant cut-out was recorded. Results The dual lag screw implant exhibited significantly less migration and sustained more loading cycles in comparison to the DHS single lag screw. All DHS constructs failed before 20,000 cycles, on average at 6,638 ± 2,837 cycles either by cut-out or permanent screw bending. At failure, DHS constructs exhibited 10.8 ± 2.3° varus collapse and 15.5 ± 9.5° rotation around the lag screw axis. Four out of five dual screws constructs sustained 20,000 loading cycles. One dual screw specimens sustained cut-out by medial migration of the distal screw after 10,054 cycles. At test end, varus collapse and neck rotation in dual screws implants advanced to 3.7 ± 1.7° and 1.6 ± 1.0°, respectively. Conclusion The single and double lag screw implants demonstrated a significantly different migration resistance in surrogate specimens under gait loading simulation with the HIPS model. In this model, the double screw construct provided significantly greater resistance against varus collapse and neck rotation in comparison to a standard DHS lag screw implant. PMID:19450283

  20. Cannulated screw and hexapodal fixator reconstruction for compound upper tibial fractures

    PubMed Central

    Uzun, Metin; Bilen, Fikri Erkal; Eralp, Levent

    2014-01-01

    Objectives: The aim of the treatment of tibial plateau fractures is to obtain a pain-free and fully functional knee with closed reduction, percutaneous cannulated screw fixation and hexapodal external fixator reconstruction for high energy compound upper tibial fractures. Methods: Patients with comminuted tibial plateau fractures underwent closed reduction, percutaneous fixation with cannulated screws, and reconstruction with hexapodal external fixator. The follow-up period was 24 months. Results: The clinical and radiological results were good or excellent. The average knee flexion was 125. Conclusion: Our results are successful in the initial stage, however, it should be pointed out that during the long term follow-up osteoarthritis may develop leading to worsening of the condition. Level of Evidence IV, Case Series. PMID:24644420

  1. Percutaneous pedicle screw fixation for an unstable thoracic spine fracture after a traumatic degloving injury.

    PubMed

    Celano, Emma Christine; Baum, Griffin R; Gelbard, Rondi B; Ahmad, Faiz U

    2015-01-01

    Unstable spinal fractures require urgent surgical intervention to relieve compression of the spinal cord, correct spinal deformity, stabilise the spine and prevent further neurological injury. We report the case of a young man with a thoracic chance fracture in the setting of a devastating degloving injury, whose fracture was stabilised using minimally invasive, percutaneous pedicle screw fixation. We discuss the advantages of using a minimally invasive technique for spinal fixation and its role in the treatment of complicated, multisystem trauma patients. PMID:26646146

  2. Efficacy of novel-concept pedicle screw fixation augmented with calcium phosphate cement in the osteoporotic spine.

    PubMed

    Yazu, Masaya; Kin, Akihiro; Kosaka, Riya; Kinoshita, Mitsuo; Abe, Muneaki

    2005-01-01

    Pedicle screw instrumentation has become increasingly popular for rigid internal stabilization of the thoracolumbar spine. However, when pedicle screws are used in elderly osteoporotic patients, the screw-bone interface is stripped easily. Therefore, the risk of screw loosening and backing-out after surgery has increased. The purpose of this study was to evaluate the efficacy of the novel-concept pedicle screw fixation augmented with calcium phosphate cement (CPC) in the osteoporotic spine. The novel-concept screw has the same shape as the ordinary screw, but it is hollow and fabricated with 20 small holes (1.3 mm in diameter) leading to the hollow part on the bottom of the thread. Fifteen embalmed cadaveric lumbar vertebrae were instrumented with two types of pedicle screw (the ordinary screw and the novel-concept screw) in each pedicle. Only the novel-concept screws were augmented with CPC after insertion. Seven days later, axial pull-out testing was performed at a crosshead speed of 10 mm/min. The mean maximal pull-out strength of the ordinary screws was 258 N, and that of the novel concept screws was 637 N. These results suggest that the novel-concept screw augmented with CPC can be useful for pedicle screw fixation of the osteoporotic spine. PMID:15666124

  3. Biomechanical evaluation of four different posterior screw and rod fixation techniques for the treatment of the odontoid fractures.

    PubMed

    Li, Lei; Liu, Wen-Fei; Jiang, Hong-Kun; Li, Yun-Peng

    2015-01-01

    Problems that screw cannot be inserted may occur in screw-rod fixation techniques such as Harms technique. We compared the biomechanical stability imparted to the C-2 vertebrae by four designed posterior screw and rod fixation techniques for the management of odontoid fractures. A three-dimensional finite element model of the odontoid fracture was established by subtracting several unit structures from the normal model from a healthy male volunteer. 4 different fixation techniques, shown as follows: ? C-1 lateral mass and C-2 pedicle screw fixation (Harms technique); ? C-1 lateral mass and unilateral C-2 pedicle screw fixation combined with ipsilateral laminar screw fixation; ? Unilateral C-1lateral mass combined with ipsilateral C-1 posterior arch, and C-2 pedicle screw fixation; and ? Unilateral C1 lateral mass screw connected with bilateral C2 pedicle screw fixation was performed on the odontoid fracture model. The model was validated for axial rotation, flexion, extension, lateral bending, and tension for 1.5 Nm. Changes in motion in flexion-extension, lateral bending, and axial rotation were calculated. The finite element model of the odontoid fracture was established in this paper. All of the four screw-rod techniques significantly decreased motion in flexion-extension, lateral bending, and axial rotation, as compared with the destabilized odontoid fracture complex (P<0.05). There was no statistically significant difference in stability among the four screw techniques. We concluded that the first three fixation techniques are recommended to be used as surgical intervention for odontoid fracture, while the last can be used as supplementary for the former three methods. PMID:26309508

  4. Biomechanical evaluation of four different posterior screw and rod fixation techniques for the treatment of the odontoid fractures

    PubMed Central

    Li, Lei; Liu, Wen-Fei; Jiang, Hong-Kun; Li, Yun-Peng

    2015-01-01

    Problems that screw cannot be inserted may occur in screw-rod fixation techniques such as Harms technique. We compared the biomechanical stability imparted to the C-2 vertebrae by four designed posterior screw and rod fixation techniques for the management of odontoid fractures. A three-dimensional finite element model of the odontoid fracture was established by subtracting several unit structures from the normal model from a healthy male volunteer. 4 different fixation techniques, shown as follows: ? C-1 lateral mass and C-2 pedicle screw fixation (Harms technique); ? C-1 lateral mass and unilateral C-2 pedicle screw fixation combined with ipsilateral laminar screw fixation; ? Unilateral C-1lateral mass combined with ipsilateral C-1 posterior arch, and C-2 pedicle screw fixation; and ? Unilateral C1 lateral mass screw connected with bilateral C2 pedicle screw fixation was performed on the odontoid fracture model. The model was validated for axial rotation, flexion, extension, lateral bending, and tension for 1.5 Nm. Changes in motion in flexion-extension, lateral bending, and axial rotation were calculated. The finite element model of the odontoid fracture was established in this paper. All of the four screw-rod techniques significantly decreased motion in flexion-extension, lateral bending, and axial rotation, as compared with the destabilized odontoid fracture complex (P<0.05). There was no statistically significant difference in stability among the four screw techniques. We concluded that the first three fixation techniques are recommended to be used as surgical intervention for odontoid fracture, while the last can be used as supplementary for the former three methods. PMID:26309508

  5. Biomechanical Comparison of Spinal Fusion Methods Using Interspinous Process Compressor and Pedicle Screw Fixation System Based on Finite Element Method

    PubMed Central

    Choi, Jisoo; Kim, Sohee

    2016-01-01

    Objective To investigate the biomechanical effects of a newly proposed Interspinous Process Compressor (IPC) and compare with pedicle screw fixation at surgical and adjacent levels of lumbar spine. Methods A three dimensional finite element model of intact lumbar spine was constructed and two spinal fusion models using pedicle screw fixation system and a new type of interspinous devices, IPC, were developed. The biomechanical effects such as range of motion (ROM) and facet contact force were analyzed at surgical level (L3/4) and adjacent levels (L2/3, L4/5). In addition, the stress in adjacent intervertebral discs (D2, D4) was investigated. Results The entire results show biomechanical parameters such as ROM, facet contact force, and stress in adjacent intervertebral discs were similar between PLIF and IPC models in all motions based on the assumption that the implants were perfectly fused with the spine. Conclusion The newly proposed fusion device, IPC, had similar fusion effect at surgical level, and biomechanical effects at adjacent levels were also similar with those of pedicle screw fixation system. However, for clinical applications, real fusion effect between spinous process and hooks, duration of fusion, and influence on spinous process need to be investigated through clinical study. PMID:26962413

  6. A video guided solution for screw insertion in orthopedic plate fixation

    NASA Astrophysics Data System (ADS)

    Magaraggia, J.; Kleinszig, G.; Graumann, R.; Angelopoulou, E.; Hornegger, J.

    2013-03-01

    In orthopedic and trauma surgery, metallic plates are used for reduction and fixation of bone fractures. In clinical practice, the intra-operative planning for screw fixation is usually based on fluoroscopic images. Screw fixation is then performed on a free-hand basis. As such, multiple attempts may be required in order to achieve an optimal positioning of the fixing screws. To help the physician insert the screws in accordance to the planned position, we propose a method for screw insertion guidance. Our approach uses a small video camera, rigidly placed on the drill, and a set of small markers that are rigidly fixed on a variable angle drill sleeve. In order to investigate the achievable accuracy of our setup, we simulate the estimation of the drill bit position under two different marker arrangements, planar and 3D, and different noise levels. Furthermore, we motivate our choices for marker design and position given the limited space available for marker positioning, the requirement for accurate position estimation of the drill bit and the illumination changes that could affect the surgical site. We also describe our proposed marker detection and tracking pipeline. Our simulation results let us conclude that we can achieve an accuracy of 1° and 1mm in the estimation of angular orientation and tip position of the drill bit respectively, provided that we have accurate marker detection.

  7. Biomechanical advantages of dual over single iliac screws in lumbo-iliac fixation construct

    PubMed Central

    Zhuang, Xin-Ming; Zheng, Zhao-Min; Li, Ze-Min; Wang, Tai-Ping

    2010-01-01

    The development of iliac screws has provided a markedly easier way for spino-pelvic instrumentation than the classical Galveston technique. However, high rates of iliac screw loosening and breakage are usually reported, especially in cases where bilateral single iliac screws are used. Therefore, there is a need for exploring more stable iliac fixation techniques. Thus, the objective of this study was to compare the biomechanical effects of bilateral single and dual iliac screws on the stability of L3-iliac fixation construct under total sacrectomy condition. In this study, L2-pelvic specimens were harvested from seven fresh human cadavers. After biomechanically testing the intact state simulated by L3-L5 pedicle screw fixation, destabilization was introduced by total sacrectomy. Upon destabilization, L3-iliac screw-rod reconstructions were performed by four different techniques as follows: (1) bilateral single short iliac screws (Single-Short); (2) bilateral single long iliac screws (Single-Long); (3) bilateral dual short iliac screws, placed in the upper and lower iliac columns (Dual-UL); and (4) bilateral dual short iliac screws, all placed in the lower iliac column (Dual-Lower). These four iliac screw fixation techniques were sequentially preformed in the same specimen, and the lengths of the short and long iliac screws were 70 and 130mm, respectively. Biomechanical testing was performed on a material testing machine under 800N compression and 7Nm torsion loading modes to evaluate the construct stiffness. In compression, the stiffness of the L3-iliac fixation constructs of Single-Short, Single-Long, Dual-UL, and Dual-Lower techniques were 73, 76, 98, and 108% of the intact state, respectively. No significant differences were detected between Single-Short and Single-Long (P=0.589) techniques. However, the compressive stiffness of these two techniques was significantly lower than the intact state, and the Dual-UL and Dual-Lower techniques (P<0.05). There was no statistical difference between the intact condition and the Dual-Lower technique (P=0.109). Interestingly, Dual-Lower exhibited notably higher compressive stiffness than Dual-UL (+10.3%, P=0.049). In torsion, the stiffness of Single-Short, Single-Long, Dual-UL, and Dual-Lower techniques were 72, 79, 105, and 109% of the intact condition, respectively. No significant differences were detected between Single-Short and Single-Long techniques (P=0.338), and also among Dual-UL, Dual-lower techniques, and the intact state (P>0.05). However, Single-Short and Single-Long techniques provided markedly lower construct torsional stiffness than the other three groups (P<0.05). For lumbo-illiac reconstruction after total sacrectomy, even the use of bilateral single, long iliac screws do not help in restoring the local stability to the intact condition. However, dual iliac screws provide much higher construct stability than single iliac screw techniques. Therefore, dual iliac screw technique should be preferred for treating the unstable situation caused by total sacrectomy. PMID:20195650

  8. Biomechanical advantages of dual over single iliac screws in lumbo-iliac fixation construct.

    PubMed

    Yu, Bin-Sheng; Zhuang, Xin-Ming; Zheng, Zhao-Min; Li, Ze-Min; Wang, Tai-Ping; Lu, William W

    2010-07-01

    The development of iliac screws has provided a markedly easier way for spino-pelvic instrumentation than the classical Galveston technique. However, high rates of iliac screw loosening and breakage are usually reported, especially in cases where bilateral single iliac screws are used. Therefore, there is a need for exploring more stable iliac fixation techniques. Thus, the objective of this study was to compare the biomechanical effects of bilateral single and dual iliac screws on the stability of L3-iliac fixation construct under total sacrectomy condition. In this study, L2-pelvic specimens were harvested from seven fresh human cadavers. After biomechanically testing the intact state simulated by L3-L5 pedicle screw fixation, destabilization was introduced by total sacrectomy. Upon destabilization, L3-iliac screw-rod reconstructions were performed by four different techniques as follows: (1) bilateral single short iliac screws (Single-Short); (2) bilateral single long iliac screws (Single-Long); (3) bilateral dual short iliac screws, placed in the upper and lower iliac columns (Dual-UL); and (4) bilateral dual short iliac screws, all placed in the lower iliac column (Dual-Lower). These four iliac screw fixation techniques were sequentially preformed in the same specimen, and the lengths of the short and long iliac screws were 70 and 130 mm, respectively. Biomechanical testing was performed on a material testing machine under 800 N compression and 7 Nm torsion loading modes to evaluate the construct stiffness. In compression, the stiffness of the L3-iliac fixation constructs of Single-Short, Single-Long, Dual-UL, and Dual-Lower techniques were 73, 76, 98, and 108% of the intact state, respectively. No significant differences were detected between Single-Short and Single-Long (P = 0.589) techniques. However, the compressive stiffness of these two techniques was significantly lower than the intact state, and the Dual-UL and Dual-Lower techniques (P < 0.05). There was no statistical difference between the intact condition and the Dual-Lower technique (P = 0.109). Interestingly, Dual-Lower exhibited notably higher compressive stiffness than Dual-UL (+10.3%, P = 0.049). In torsion, the stiffness of Single-Short, Single-Long, Dual-UL, and Dual-Lower techniques were 72, 79, 105, and 109% of the intact condition, respectively. No significant differences were detected between Single-Short and Single-Long techniques (P = 0.338), and also among Dual-UL, Dual-lower techniques, and the intact state (P > 0.05). However, Single-Short and Single-Long techniques provided markedly lower construct torsional stiffness than the other three groups (P < 0.05). For lumbo-illiac reconstruction after total sacrectomy, even the use of bilateral single, long iliac screws do not help in restoring the local stability to the intact condition. However, dual iliac screws provide much higher construct stability than single iliac screw techniques. Therefore, dual iliac screw technique should be preferred for treating the unstable situation caused by total sacrectomy. PMID:20195650

  9. Chitosan-coated Stainless Steel Screws for Fixation in Contaminated Fractures

    PubMed Central

    Greene, Alex H.; Bumgardner, Joel D.; Yang, Yunzhi; Moseley, Jon

    2008-01-01

    Stainless steel screws and other internal fixation devices are used routinely to stabilize bacteria-contaminated bone fractures from multiple injury mechanisms. In this preliminary study, we hypothesize that a chitosan coating either unloaded or loaded with an antibiotic, gentamicin, could lessen or prevent these devices from becoming an initial nidus for infection. The questions investigated for this hypothesis were: (1) how much of the sterilized coating remains on the screw with simulated functional use; (2) is the unloaded or loaded chitosan coating bacteriostatic and biocompatible; and (3) what amount and rate does an antibiotic elute from the coating? In this study, the gentamicin eluted from the coating at a detectable level during 72 to 96hours. The coating was retained at the 90% level in simulated bone screw fixation and the unloaded and loaded chitosan coatings had encouraging invitro biocompatibility with fibroblasts and stem cells and were bacteriostatic against at least one strain of Staphylococcus aureus. The use of an antibiotic-loaded chitosan coating on stainless steel bone screws and internal fixation devices in contaminated bone fracture fixation may be considered after optimization of antibiotic loading and elution and more expanded invitro and invivo investigations with other organisms and antibiotics. PMID:18443893

  10. [Fresh fracture of the odontoid process treated with direct screw fixation; a case report].

    PubMed

    Hasegawa, T; Hamada, Y; Miyamori, T; Yamano, K

    1992-08-01

    A case of a fresh type II fracture (Anderson & D'Alonzo) of the odontoid process treated with direct screw fixation is reported. A 52-year-old man complained of severe neck pain following a hit on his forehead incurred in a falling accident. Neurological examination was normal. Cervical spine x-ray films and axial CT scans revealed a fracture at the base of the dens. It was slightly oblique leftup and rightdown, and the dens fragment was displaced 3mm lateral to the right. One week after the injury, this odontoid fracture was directly fixed with a compression screw by an anterior cervical approach. Immediately after the operation, his neck pain disappeared. He had only 4 days of bed rest and 2 months of external immobilization with a simple neck collar. He returned to his previous job 2 months after surgery without any limitation of his neck movement. At follow-up examination 16.5 months after the operation, x-ray films demonstrated complete fusion of the fracture and no problem about the screw such as displacement or breakage. Direct screw fixation of an odontoid fracture via a transcervical approach was thought to be a reasonable method of treatment. For proper assembly of this method, the following two points are particularly recommended: a screw insertion perpendicular to the fracture plane and the use of an optimal screw with both the desired total and thread lengths. PMID:1508315

  11. Hybrid lateral mass screw sublaminar wire construct: A salvage technique for posterior cervical fixation in pediatric spine surgery.

    PubMed

    Quinn, John C; Patel, Nitesh V; Tyagi, Rachana

    2016-03-01

    We present a novel salvage technique for pediatric subaxial cervical spine fusion in which lateral mass screw fixation was not possible due to anatomic constraints. The case presentation details a 4-year-old patient with C5-C6 flexion/distraction injury with bilateral jumped facets. Posterior cervical fixation was attempted; however, lateral mass fracture occurred during placement of screws. Using a wire-screw construct, an attempt was made to provide stable fixation. The patient was followed post-operatively for assessment of outcomes. After the patient had progressive kyphosis following initial closed reduction and external orthosis, internal reduction with fusion/fixation was performed. Lateral mass fracture occurred during placement of lateral mass screws. After placement of a sub-laminar wire-lateral mass screw construct, intra-operative evaluation determined stability. Post-operatively, the procedure resulted in stable fixation with evidence of bony fusion on follow-up. Pediatric subaxial cervical spine instrumentation provides rigid fixation however is technically difficult due to anatomic and instrumentation related constraints. In the presented patient, the wire-screw construct resulted in stable fixation and bony fusion on follow-up. A modified sublaminar wire-lateral mass screw construct is an example of a salvage technique that provides immediate stability in the event of instrumentation related lateral mass fracture. PMID:26541322

  12. Biomechanical study of the sacroiliac fracture fixation with titanium rods and pedicle screws

    PubMed Central

    Ueno, Fabrcio Hidetoshi; Pisani, Marina Justi; Machado, Andr Nunes; Rodrigues, Fbio Lucas; Fujiki, Edison Noburo; Rodrigues, Luciano Miller Reis

    2015-01-01

    OBJECTIVES: To assess biomechanically different fixations means of the sacroiliac joint with pedicle screws and to compare the traditional head height with reduced ones. METHODS: We used a polyethylene model representing the pelvic ring and simulated a unilateral sacroiliac dislocation. We set up three different constructions: 1) two screws attached to a rod; 2) two rods connected to two small head screws each; and 3) two rods connected to two average headed screws each. We conducted tests in a biomechanical testing and a mechanized processing laboratory. RESULTS: Group 1 supported an average maximum load of 99.70 N. Group 2 supported an average maximum load of 362.46 N. Group 3 endured an average maximum load of 404.15 N. In the assembly with one rod, the resistance decreased as compared with the one with two bars: 72.5 % compared to small-headed screws and 75.3 % to the traditional screw. CONCLUSION: The assembly with a single bar presented inferior results when compared to the double bar assembly. There was no statistical difference in the results between the screws used. Experimental Study. PMID:26207094

  13. Significantly lower femoral neck growth in screw fixation of the asymptomatic contralateral hip in unilateral slipped capital femoral epiphysis.

    PubMed

    Wölfle-Roos, Julia V; Urlaub, Stefanie; Reichel, Heiko; Taurman, Rita

    2016-05-01

    There is an ongoing debate on which fixation technique should be preferred for the prophylactic fixation of the asymptomatic contralateral hip in slipped capital femoral epiphysis (SCFE). In the case of Kirschner-wire (K-wire) fixation, there is a possibility of secondary loss of fixation because of longitudinal growth of the physis, whereas in screw fixation, physeal growth of the femoral neck might be impaired. The aim of this matched-pair study was to compare the longitudinal growth of the femoral neck in screw fixation versus K-wire fixation of the asymptomatic contralateral hip in SCFE. All 18 patients (female : male=3 : 15), who had undergone screw fixation of the asymptomatic contralateral hip between 9/2001 and 9/2011, were matched according to age, bone age, sex, and time to follow-up to another 18 patients with K-wire fixation. The length of the femoral neck of the contralateral hip was measured in parallel to either screw or K-wire from the apex of the femoral head to the opposite cortical bone. The ratio of the femoral neck length measured directly after surgery and on follow-up was defined as femoral neck growth. There was no significant difference between groups with respect to age, modified Oxford Bone age score, and time to follow-up. We found a significant difference in femoral neck growth between patients with screw fixation (5.5±4.3%) compared with K-wire fixation (8.9±5.7%, P=0.048 matched Wilcoxon test). The difference in femoral neck growth of patients with K-wire or screw fixation of the contralateral asymptomatic hip in SCFE was small, but statistically significant. Thus, despite high rates of secondary loss of fixation, K-wire fixation should still be considered, especially in very young patients. PMID:26919622

  14. [Animal experiment study of tensile strength of hydroxylapatite-coated AO/ASIF Schanz screws for external fixators].

    PubMed

    Dvid, A; Pommer, A; Eitenmller, J; Muhr, G; Hahn, M P

    1994-08-01

    The removal torque and the loosening and infection rates of AO/ASIF 4.5 mm Schanz screws (MS) have been compared with those of hydroxyapatite-coated (HA) and hydroxyapatite/silver phosphate-coated (HA/P) AO/ASIF Schanz screws in vivo. In sheep, the left tibia was fixed after a midshaft osteotomy by means of unilateral fixator with 6 Schanz screws in an antero-lateral position. The osteotomy gap was filled with bone wax to avoid bony overgrowth. After operation, the animals were allowed to walk around immediately. The loosening rate was 2.8% at the site of the two HA-coated screws and 36% at the site of the metal screws. The removal torque after 2, 4 and 6 months was 6.2 +/- 2.8 MPa for HA/P, 4.7 +/- 2.7 MPa for HA screws and 1.2 +/- 1.1 MPa for metal screws. Histological and fluoroscopic evaluation revealed intimate bone-HA contact at the cortex near to the fixator, whereas at the site of the metal screws a fibrous tissue layer was constantly found. Only in the cortex opposite to the external fixator a direct bone-metal interface was observed. Fluoroscopic analyses confirmed new bone formation next to the HA surface especially in the cortex adjacent to the fixator, whereas such phenomena were not detected adjacent to the surface of the metal screws. Furthermore, bony resorption around the metal screws (21%) was significantly greater than around the two coated screws (2%). These experimental data suggest that pin loosening can be reduced in external fixators by coating the screws with hydroxyapatite, especially if a long-term fixation is indicated. PMID:7973737

  15. Evaluation of a new approach for modelling the screw-bone interface in a locking plate fixation: a corroboration study.

    PubMed

    Moazen, Mehran; Mak, Jonathan H; Jones, Alison C; Jin, Zhongmin; Wilcox, Ruth K; Tsiridis, Eleftherios

    2013-07-01

    Computational modelling of the screw-bone interface in fracture fixation constructs is challenging. While incorporating screw threads would be a more realistic representation of the physics, this approach can be computationally expensive. Several studies have instead suppressed the threads and modelled the screw shaft with fixed conditions assumed at the screw-bone interface. This study assessed the sensitivity of the computational results to modelling approaches at the screw-bone interface. A new approach for modelling this interface was proposed, and it was tested on two locking screw designs in a diaphyseal bridge plating configuration. Computational models of locked plating and far cortical locking constructs were generated and compared to in vitro models described in prior literature to corroborate the outcomes. The new approach led to closer agreement between the computational and the experimental stiffness data, while the fixed approach led to overestimation of the stiffness predictions. Using the new approach, the pattern of load distribution and the magnitude of the axial forces, experienced by each screw, were compared between the locked plating and far cortical locking constructs. The computational models suggested that under more severe loading conditions, far cortical locking screws might be under higher risk of screw pull-out than the locking screws. The proposed approach for modelling the screw-bone interface can be applied to any fixation involved application of screws. PMID:23636756

  16. Assessment of penetration of dorsal screws after fixation of the distal radius using ultrasound: cadaveric study.

    PubMed

    Williams, D; Singh, J; Heidari, N; Ahmad, M; Noorani, A; Di Mascio, L

    2016-02-01

    Introduction Volar locking plates are used to treat unstable and displaced fractures of the distal radius. Potential advantages of stable anatomical reduction (eg early mobilisation) can be limited by penetration of dorsal screws, leading to synovitis and potential rupture of extensor tendons. Despite intraoperative imaging, penetration of dorsal screws continues to be a problem in volar plating of the distal radius. Ultrasound is a well recognised, readily available, diagnostic tool used to assess soft-tissue impingement by orthopaedic hardware. In this cadaveric study, we wished to ascertain the sensitivity and specificity of ultrasound for identification of protrusion of dorsal screws after volar plating of the distal radius. Methods Four adult, unpaired phenol-embalmed cadaveric distal radii were used. A VariAx™ Distal Radius Volar Locking Plate system (Stryker, Kalamazoo, MI, USA) was employed for instrumented fixation. A portable SIUI CTS 900 ultrasound machine (Providian Medical, Eastlake, OH, USA) was used to image the dorsal cortex to ascertain screw penetration. Results Specificity and sensitivity of ultrasound for detection of screw protrusion through the dorsal cortex was 100%. Conclusions Ultrasound was found to be a safe and accurate method for assessment of dorsal-screw penetration through the dorsal cortex of the radius after volar plating of the distal radius. It also aids diagnosis of associated tendon disorders (eg tenosynovitis) that might cause pain and limit wrist function. PMID:26829667

  17. Volar approach and screw fixation technique for fractures and non-unions of the carpal scaphoid.

    PubMed

    Breit, R; Segelov, P M; Caspary, E J

    1985-10-01

    Delayed or non-union of the carpal scaphoid may be treated in a variety of ways. This article describes the operative technique and clinical results of a volar approach and screw fixation technique, which offers distinct advantages over other approaches. The volar approach to the scaphoid is simple, safe and rapid. It allows access to the fracture for fixation, the radioscaphoid joint for assessment and the distal radius for the procurement of a bone graft where necessary. Access to the volar aspect of the scaphoid is also biomechanically sound as it allows insertion of a wedge-shaped bone graft into the 'collapsed' area of the scaphoid in established non-unions. Compression screwing of the fracture site has the same advantages of stability and early mobilization that applies in other sites. Our clinical experience in 32 fractures has involved a low complication rate with early return of mobility and activity. PMID:3868415

  18. Outcomes of percutaneous pedicle screw fixation for spinal trauma and tumours.

    PubMed

    Mobbs, Ralph J; Park, Ashley; Maharaj, Monish; Phan, Kevin

    2016-01-01

    We investigated the clinical and radiological results of percutaneous pedicle screw fixation in the management of spinal trauma and metastatic tumours. A retrospective analysis was performed on a series of 14 patients who were operated on from March 2009 to November 2011 by a single surgeon (RJM). Following a radiological review (CT scan/MRI), six patients underwent short segment fixation, while the remaining underwent long segment fixation. All patients had routine follow-ups at 4, 6, 12months, and annually thereafter. Clinical examinations were conducted preoperatively and postoperatively, and the length of operation, blood loss, and postoperative pain relief were recorded. There was a single patient with an incision site complication. The mean blood loss was 269mL. All of the parameters demonstrated no significant differences between the trauma and the tumour groups (p=0.10). The neurological power scores improved for all patients, with the largest increase being from a score of 2 to 4. At follow-up, the majority of patients had returned to their previous activities and had reduced pain scores. One patient suffered high pain levels from other medical conditions that were not related to the operation. Minimally invasive pedicle screw fixation is a suitable option for patients with spinal tumours and fractures, with acceptable safety and efficacy in this small retrospective patient series. We have seen favourable results in our patients, who have experienced an increased quality of life following their surgery. PMID:26422600

  19. Application of IMF screws to assist internal rigid fixation of jaw fractures: our experiences of 168 cases

    PubMed Central

    Bai, Zhenxi; Gao, Zhibiao; Xiao, Xia; Zhang, Wenjuan; Fan, Xing; Wang, Zhaoling

    2015-01-01

    Intermaxillary fixation (IMF) screws were first introduced to achieve IMF as a kind of bone borne appliance for jaw fractures in 1989. Because this method can overcome many disadvantages associated with tooth borne appliance, IMF screws have been popularly used for jaw fractures since then. From March 2011 to February 2014, we treated 168 cases with single or multiple jaw fractures by open reduction and a total of 705 IMF screws were intraoperatively applied in all the cases to achieve IMF and maintain dental occlusion as an adjuvant to open reduction. The numbers, implantation sites and complications of IMF screws were retrospectively analyzed. In our experience, we found that IMF screws were important to assist open reduction of jaw fractures but their roles should be objectively assessed and the reliability of open reduction and internal rigid fixation must be emphasized. Much attention should be paid when implanting. PMID:26617892

  20. Effects of Lateral Mass Screw Rod Fixation to the Stability of Cervical Spine after Laminectomy

    NASA Astrophysics Data System (ADS)

    Rosli, Ruwaida; Kashani, Jamal; Kadir, Mohammed Rafiq Abdul

    There are many cases of injury in the cervical spine due to degenerative disorder, trauma or instability. This condition may produce pressure on the spinal cord or on the nerve coming from the spine. The aim of this study was, to analyze the stabilization of the cervical spine after undergoing laminectomy via computational simulation. For that purpose, a three-dimensional finite element (FE) model for the multilevel cervical spine segment (C1-C7) was developed using computed tomography (CT) data. There are various decompression techniques that can be applied to overcome the injury. Usually, decompression procedures will create an unstable spine. Therefore, in these situations, the spine is often surgically restabilized by using fusion and instrumentation. In this study, a lateral mass screw-rod fixation was created to stabilize the cervical spine after laminectomy. Material properties of the titanium alloy were assigned on the implants. The requirements moments and boundary conditions were applied on simulated implanted bone. Result showed that the bone without implant has a higher flexion and extension angle in comparison to the bone with implant under applied 1Nm moment. The bone without implant has maximum stress distribution at the vertebrae and ligaments. However, the bone with implant has maximum stress distribution at the screws and rods. Overall, the lateral mass screw-rod fixation provides stability to the cervical spine after undergoing laminectomy.

  1. Radiostrontium clearance and bone formation in response to simulated internal screw fixation

    SciTech Connect

    Daum, W.J.; Simmons, D.J.; Fenster, R.; Shively, R.A.

    1987-06-01

    Changes in radiostrontium clearance (SrC) and bone formation (tetracycline labeling) were observed in the femurs of skeletally mature dogs following the various operative steps involved in bone screw fixation. Drilling, but not periosteal stripping, produced a small but statistically significant increase in SrC and endosteal bone formation in the distal third of the bone. Strontium clearance values equivalent to those produced by drilling alone were recorded after screw fixation at low or high torque (5 versus 20 inch pounds), as well as by the insertion of loosely fitting stainless steel implants. Bone formation (equals the percentage tetracycline-labeled trabecular bone surfaces) was increased by 30% when SrC values exceeded 3.5 ml/100 g bone/min, and the relationship was linear when SrC values ranged between 1.0 and 7.0 ml/100 g bone/min. The changes in SrC and bone formation one-week after bone screw application are primarily those associated with a response to local trauma caused by drilling.

  2. Minimally invasive mini open split-muscular percutaneous pedicle screw fixation of the thoracolumbar spine.

    PubMed

    Uluta?, Murat; Seer, Mehmet; elik, Suat Erol

    2015-03-01

    We prospectively assessed the feasibility and safety of a new percutaneous pedicle screw (PPS) fixation technique for instrumentation of the thoracic and lumbar spine in this study. All patients were operated in the prone position under general anesthesia. A 6 to 8 cm midline skin incision was made and wide subcutaneous dissection was performed. The paravertebral muscles were first dissected subperiosteally into the midline incision of the fascia for lumbar microdiscectomy with transforaminal lumbar interbody fusion cage implantation. After the secondary paramedian incisions on the fascia, the PPSs were inserted via cleavage of the multifidus muscles directly into the pedicles under fluoroscopy visualization. A total of 35 patients underwent surgery with this new surgical technique. The control group for operative time, blood loss and analgesic usage consisted of 35 randomly selected cases from our department. The control group underwent surgery via conventional pedicle screw instrumentation with paramedian fusion. All patients in the minimal invasive surgery series were ambulatory with minimal pain on the first postoperative day. The operation time and blood loss and the postoperative analgesic consumption were significantly less with this new technique. In conclusion, the minimal invasive mini open split-muscular percutaneous pedicle screw fixation technique is safe and feasible. It can be performed via a short midline skin incision and can also be combined with interbody fusion, causing minimal pain without severe muscle damage. PMID:25874062

  3. Minimally Invasive Mini Open Split-Muscular Percutaneous Pedicle Screw Fixation of the Thoracolumbar Spine

    PubMed Central

    Ulutaş, Murat; Seçer, Mehmet; Çelik, Suat Erol

    2015-01-01

    We prospectively assessed the feasibility and safety of a new percutaneous pedicle screw (PPS) fixation technique for instrumentation of the thoracic and lumbar spine in this study. All patients were operated in the prone position under general anesthesia. A 6 to 8 cm midline skin incision was made and wide subcutaneous dissection was performed. The paravertebral muscles were first dissected subperiosteally into the midline incision of the fascia for lumbar microdiscectomy with transforaminal lumbar interbody fusion cage implantation. After the secondary paramedian incisions on the fascia, the PPSs were inserted via cleavage of the multifidus muscles directly into the pedicles under fluoroscopy visualization. A total of 35 patients underwent surgery with this new surgical technique. The control group for operative time, blood loss and analgesic usage consisted of 35 randomly selected cases from our department. The control group underwent surgery via conventional pedicle screw instrumentation with paramedian fusion. All patients in the minimal invasive surgery series were ambulatory with minimal pain on the first postoperative day. The operation time and blood loss and the postoperative analgesic consumption were significantly less with this new technique. In conclusion, the minimal invasive mini open split-muscular percutaneous pedicle screw fixation technique is safe and feasible. It can be performed via a short midline skin incision and can also be combined with interbody fusion, causing minimal pain without severe muscle damage. PMID:25874062

  4. Rate of nonunion after first metatarsal-cuneiform arthrodesis using joint curettage and two crossed compression screw fixation: a systematic review.

    PubMed

    Donnenwerth, Michael P; Borkosky, Sara L; Abicht, Bradley P; Plovanich, Elizabeth J; Roukis, Thomas S

    2011-01-01

    First metatarsal-cuneiform joint arthrodesis is a commonly performed procedure to correct first ray pathology. The most widely accepted approach is curettage and 2 crossed compression screw fixation followed by a period of non-weight-bearing. Despite adequate joint preparation and stable internal fixation, nonunion has been cited as a known complication. This can lead to the need for revision surgery, which is undesirable and drives healthcare costs. To further investigate this topic, we conducted a systematic review to determine the rate of nonunion after the first metatarsal-cuneiform joint arthrodesis using curettage and 2 crossed compression screw fixation. Studies were eligible for inclusion only if they involved the following: arthrodesis of the first metatarsal-cuneiform joint with curettage and 2 crossed compression screw fixation, a minimum of 25 feet, with a mean follow-up of at least 6 months, and a period of postoperative non-weight-bearing. After considering all the potentially eligible references, 1 (1.8%) evidence-based medicine level I and 4 (7.3%) evidence-based medicine level IV studies met our inclusion criteria. A total of 537 patients (599 feet), 54 (10%) males and 483 (90%) females, with a weighted mean age of 49.4 years, were included. For those studies that specified the exact follow-up, the weighted mean was 30.9 months. A total of 30 nonunions (5%) were reported, with 17 (56.7%) symptomatic. The results of our systematic review revealed a relatively high rate of nonunion for first metatarsal-cuneiform joint arthrodesis with curettage and 2 crossed compression screw fixation, even when performed by experienced surgeons. Therefore, given the available data, additional prospective investigations are warranted, especially in the evaluation and comparison of fixation constructs and postoperative management. PMID:21908206

  5. Pedicle Morphometry for Thoracic Screw Fixation in Ethnic Koreans : Radiological Assessment Using Computed Tomographic Myelography

    PubMed Central

    Choi, Yong Soo; Yi, Hyeong-Joong; Kim, Young-Joon

    2009-01-01

    Objective In the thoracic spine, insertion of a pedicle screw is annoying due to small pedicle size and wide morphological variation between different levels of the spine and between individuals. The aim of our study was to analyze radiologic parameters of the pedicle morphometry from T1 to T8 using computed tomographic myelography (CTM) in Korean population. Methods For evaluation of the thoracic pedicle morphometry, the authors prospectively analyzed a consecutive series of 26 patients with stable thoracic spines. With the consent of patients, thoracic CTM were performed, from T1 to T8. We calculated the transverse outer diameters and the transverse angles of the pedicle, distance from the cord to the inner cortical wall of the pedicle, and distance from the cord to the dura. Results Transverse outer pedicle diameter was widest at T1 (7.66 2.14 mm) and narrowest at T4 (4.38 1.55 mm). Transverse pedicle angle was widest at T1 (30.2 12.0) and it became less than 9.0 below T6 level. Theoretical safety zone of the medial perforation of the pedicle screw, namely, distance from the cord to inner cortical wall of the pedicle was more than 4.5 mm. Conclusion Based on this study, we suggest that the current pedicle screw system is not always suitable for Korean patients. Computed tomography is required before performing a transpedicular screw fixation at the thoracic levels. PMID:19893719

  6. Is cross-screw fixation superior to plate for radial neck fractures?

    PubMed

    Li, S L; Lu, Y; Wang, M Y

    2015-06-01

    This study compares the outcomes of two methods of fixation of displaced fractures of the radial neck. The 58 patients with a mean age of 38.5 years (18 to 56), were treated in a non randomised study with screws (n = 29) or a plate and screws (n = 29) according to the surgeon's preference. The patients were reviewed at one year. Radiographs and functional evaluations were carried out up to one year post-operatively, using the Broberg and Morrey functional evaluation score, range of movement, and assessment of complications. The mean functional scores did not differ significantly between groups (90 (55 to 100) vs 84; 50 to 100, p = 0.09), but the mean range of forearm rotation in screw group was significantly better than in the plate group (152; 110 to 170 vs 134; 80 to 170, p = 0.001). Although not statistically significant, the screw group had a lower incidence of heterotopic ossification than the plate group (n = 1) than the plated group (n = 3) and the pathology was graded as less severe. PMID:26033065

  7. Morphometry of the cervical vertebral pedicles as a guide for transpedicular screw fixation.

    PubMed

    Kayalioglu, Gulgun; Erturk, Mete; Varol, Tuncay; Cezayirli, Enis

    2007-03-01

    Anatomical measurements of the cervical pedicle in a large series of human cervical vertebrae from 48 individuals were obtained to reduce the incidence and severity of complications caused by transpedicular screw placement. The greatest pedicle length was at C-3 and the greatest pedicle width was at C-6. Pedicle width and lateral mass thickness gradually increased from C-3 to C-6. Pedicle height and interpedicular distance increased from C-3 to C-5, and decreased slightly at C-6. The lateral mass-pedicle length was greatest at C-4. The present study found right-left differences for the pedicle-spinous process distance at C-6 (p < 0.05). Pedicle width and height were smaller than those reported in earlier studies, especially at C-3 and C-4, whereas the increasing pedicle widths at C-5 and C-6 were appropriate for pedicle screw fixation. PMID:17384491

  8. Experimental and Numerical Analysis of Screw Fixation in Anterior Cruciate Ligament Reconstruction

    NASA Astrophysics Data System (ADS)

    Chizari, Mahmoud; Wang, Bin; Snow, Martyn; Barrett, Mel

    2008-09-01

    This paper reports the results of an experimental and finite element analysis of tibial screw fixation in anterior cruciate ligament (ACL) reconstruction. The mechanical properties of the bone and tendon graft are obtained from experiments using porcine bone and bovine tendon. The results of the numerical study are compared with those from mechanical testing. Analysis shows that the model may be used to establish the optimum placement of the tunnel in anterior cruciate ligament reconstruction by predicting mechanical parameters such as stress, strain and displacement at regions in the tunnel wall.

  9. Biomechanical stability of a supra-acetabular pedicle screw Internal Fixation device (INFIX) vs External Fixation and plates for vertically unstable pelvic fractures

    PubMed Central

    2012-01-01

    Background We have recently developed a subcutaneous anterior pelvic fixation technique (INFIX). This internal fixator permits patients to sit, roll over in bed and lie on their sides without the cumbersome external appliances or their complications. The purpose of this study was to evaluate the biomechanical stability of this novel supraacetabular pedicle screw internal fixation construct (INFIX) and compare it to standard internal fixation and external fixation techniques in a single stance pelvic fracture model. Methods Nine synthetic pelves with a simulated anterior posterior compression type III injury were placed into three groups (External Fixator, INFIX and Internal Fixation). Displacement, total axial stiffness, and the stiffness at the pubic symphysis and SI joint were calculated. Displacement and stiffness were compared by ANOVA with a Bonferroni adjustment for multiple comparisons Results The mean displacement at the pubic symphysis was 20, 9 and 0.8?mm for external fixation, INFIX and internal fixation, respectively. Plate fixation was significantly stiffer than the INFIX and external Fixator (P?=?0.01) at the symphysis pubis. The INFIX device was significantly stiffer than external fixation (P?=?0.017) at the symphysis pubis. There was no significant difference in SI joint displacement between any of the groups. Conclusions Anterior plate fixation is stiffer than both the INFIX and external fixation in single stance pelvic fracture model. The INFIX was stiffer than external fixation for both overall axial stiffness, and stiffness at the pubic symphysis. Combined with the presumed benefit of minimizing the complications associated with external fixation, the INFIX may be a more preferable option for temporary anterior pelvic fixation in situations where external fixation may have otherwise been used. PMID:23017093

  10. Balancing Rigidity and Safety of Pedicle Screw Fixation via a Novel Expansion Mechanism in a Severely Osteoporotic Model

    PubMed Central

    Shea, Thomas M.; Doulgeris, James J.; Gonzalez-Blohm, Sabrina A.; Lee, William E.; Vrionis, Frank D.

    2015-01-01

    Many successful attempts to increase pullout strength of pedicle screws in osteoporotic bone have been accompanied with an increased risk of catastrophic damage to the patient. To avoid this, a single-armed expansive pedicle screw was designed to increase fixation strength while controlling postfailure damage away from the nerves surrounding the pedicle. The screw was then subsequently tested in two severely osteoporotic models: one representing trabecular bone (with and without the presence of polymethylmethacrylate) and the other representing a combination of trabecular and cortical bone. Maximum pullout strength, stiffness, energy to failure, energy to removal, and size of the resulting block damage were statistically compared among conditions. While expandable pedicle screws produced maximum pullout forces less than or comparable to standard screws, they required a higher amount of energy to be fully removed from both models. Furthermore, damage to the cortical layer in the composite test blocks was smaller in all measured directions for tests involving expandable pedicle screws than those involving standard pedicle screws. This indicates that while initial fixation may not differ in the presence of cortical bone, the expandable pedicle screw offers an increased level of postfailure stability and safety to patients awaiting revision surgery. PMID:25705655

  11. Changes in the computed tomography (pixel) value of mandibular ramus bone and fixation screws after sagittal split ramus osteotomy.

    PubMed

    Ueki, K; Moroi, A; Iguchi, R; Kosaka, A; Ikawa, H; Yoshizawa, K

    2015-11-01

    The purpose of this retrospective study was to evaluate the changes in computed tomography (CT) values of ramus bone and screws after sagittal split ramus osteotomy (SSRO) setback surgery. The subjects were 64 patients (128 sides) who underwent bilateral SSRO setback surgery. They were divided into six groups according to the fixation plate type used and the use or not of self-setting ?-tricalcium phosphate (Biopex): group 1: titanium plate and screws; group 2: titanium plate and screws with Biopex; group 3: poly-l-lactic acid (PLLA) plate and screws; group 4: PLLA plate and screws with Biopex; group 5: uncalcined and unsintered hydroxyapatite particles and poly-l-lactic acid (uHA/PLLA) plate and screws; group 6: PLLA/uHA plate and screws with Biopex. CT values (pixel values) of the lateral cortex, medial cortex, osteotomy site, and screws were measured preoperatively, immediately after surgery, and 1 year postoperatively using horizontal CT images at the mandibular foramen taken parallel to the Frankfort horizontal plane. There were significant differences in the time-course change of pixel values for the lateral cortex (P<0.0001) and the osteotomy site (P<0.0001) among the six groups. This study suggests that the fixation plate type and use of bone alternative material may affect bone quality during the process of bone healing after SSRO. PMID:26139563

  12. Strontium ranelate treatment enhances hydroxyapatite-coated titanium screws fixation in osteoporotic rats.

    PubMed

    Li, Yunfeng; Feng, Ge; Gao, Yuan; Luo, En; Liu, Xiaoguang; Hu, Jing

    2010-05-01

    Increased bone turnover with excessive bone resorption and decreased bone formation is known to impair implant fixation. Strontium ranelate is well known as an effective antiosteoporotic agent by its dual effect of antiresorbing and bone-forming activity. This study was designed to evaluate the effect of systemic strontium ranelate (SR) treatment on fixation of hydroxyapatite (HA)-coated titanium screws in ovariectomized (OVX) rats. Twelve weeks after being OVX (n=30) or sham (n=10) operated, 40 female Sprague-Dawley rats received unilateral implants in the proximal tibiae. The OVX rats were randomly divided into the following groups: OVX, OVX+SRL ("L" refers to low SR dose of 500 mg/kg/day), OVX+SRH ("H" refers to high SR dose of 1000 mg/kg/day).Twelve weeks after treatment, bone blocks with implants were evaluated with micro-CT and biomechanical push-out tests. Compared to OVX animals, SR treatment increased the bone volume ratio by 51.5% and 1.1-fold, the percentage osteointegration by 1.0-fold and 1.9-fold in micro-CT evaluation, and the maximal force by 1.9-fold and 3.3-fold in biomechanical push-out test, for the low and high dose of SR, respectively. Significant correlation between micro-CT and biomechanical properties demonstrated that trabecular parameters played an important role in predicting the biomechanical properties of implant fixation. Our findings suggest that SR treatment can dose-dependently improve HA-coated screw fixation in OVX rats and facilitate the stability of the implant in the osteoporotic bone. PMID:20014319

  13. Lateral fixation of AO type-B2 ankle fractures: the Acutrak plus compression screw technique.

    PubMed

    Lee, Yih-Shiunn; Hsu, Tzu-Liang; Huang, Chien-Rae; Chen, Shih-Hao

    2010-08-01

    The Acutrak plus compression screw (APCS) (Acumed Inc., Beaverton, OR, USA) is an intramedullary implant which can achieve stable fixation with minimum soft tissue dissection. The characteristics of the APCS include fully-threaded length, headless, cannulated, and variable thread pitch. Twenty-three patients with AO type-B2 ankle fractures treated with lateral fixation by an APCS were retrospectively reviewed. Evaluation of postoperative roentgenograms for adequacy of reduction revealed a good reduction in 22 of 23 (95.7%) patients. The average wound incision was 4.1 cm. The operative time was 25.3 minutes. All the ankle fractures showed radiographic evidence of healing within four months. At the final follow-up, the ankle scores of the patients were evaluated for functional outcomes. Good to excellent results were obtained in 21 (91.3%) patients. No patient complained of symptomatic hardware. In conclusion, lateral fixation of AO type-B2 ankle fractures by APCS offers several advantages including stable fixation, a small surgical wound, less dissection of soft tissue, no palpable hardware, and easy application with a short operating time. PMID:20177893

  14. A novel computed method to reconstruct the bilateral digital interarticular channel of atlas and its use on the anterior upper cervical screw fixation

    PubMed Central

    Wu, Ai-Min; Wang, Wenhai; Xu, Hui; Lin, Zhong-Ke; Yang, Xin-Dong; Wang, Xiang-Yang; Xu, Hua-Zi

    2016-01-01

    Purpose. To investigate a novel computed method to reconstruct the bilateral digital interarticular channel of atlas and its potential use on the anterior upper cervical screw fixation. Methods. We have used the reverse engineering software (image-processing software and computer-aided design software) to create the approximate and optimal digital interarticular channel of atlas for 60 participants. Angles of channels, diameters of inscribed circles, long and short axes of ellipses were measured and recorded, and gender-specific analysis was also performed. Results. The channels provided sufficient space for one or two screws, and the parameters of channels are described. While the channels of females were smaller than that of males, no significant difference of angles between males and females were observed. Conclusion. Our study demonstrates the radiological features of approximate digital interarticular channels, optimal digital interarticular channels of atlas, and provides the reference trajectory of anterior transarticular screws and anterior occiput-to-axis screws. Additionally, we provide a protocol that can help make a pre-operative plan for accurate placement of anterior transarticular screws and anterior occiput-to-axis screws. PMID:26925345

  15. Quadrupled semitendinosus-gracilis autograft fixation in the femoral tunnel: a comparison between a metal and a bioabsorbable interference screw.

    PubMed

    Caborn, D N; Coen, M; Neef, R; Hamilton, D; Nyland, J; Johnson, D L

    1998-04-01

    Although semitendinosus-gracilis (SG) grafts for anterior cruciate ligament reconstruction have many potential benefits, effective fixation remains a challenge. This study assessed differences between the maximum pullout forces needed to detach a quadrupled SG graft from a femoral tunnel when secured by either a metal or a bioabsorbable interference screw. Sixteen paired fresh frozen quadrupled SG autografts (x, 8.4 mm; range, 7-10 mm) from 8 donors were anchored into cadaveric femoral tunnels by either a 7-mm metal or a 7-mm bioabsorbable screw after bone mineral density (BMD) assessment and before undergoing a longitudinal 20 mm/min traction force. Statistical analysis compared BMD (gm/cm2), insertional torque (N-m), and maximum load at pullout (N) between screw types. Insertional torques (.28-1.21, N-m range) did not correlate (P>.05) to BMD or maximum load at pullout (x +/- S.D.) 242 +/- 90.7 N (metal screw) and 341.1 +/- 162.9 N (bioabsorbable screw). Differences did not exist between the maximum load at pullout for bioabsorbable or metal screw fixation (P = .16). Careful graft preparation, sizing, and matched tunnel placement enables interference fit and fixation capable of reliably withstanding the low-level rehabilitation loads to which the graft is exposed until bony ingrowth occurs. PMID:9586968

  16. Arthroscopic Fixation of Comminuted Glenoid Fractures Using Cannulated Screws and Suture Anchors.

    PubMed

    Qu, Feng; Yuan, Bangtuo; Qi, Wei; Li, Chunbao; Shen, Xuezhen; Guo, Qi; Zhao, Gang; Wang, Jiangtao; Li, Hongliang; Lu, Xi; Liu, Yujie

    2015-12-01

    We investigate the feasibility of arthroscopic fixation of comminuted glenoid fractures using cannulated screws and suture anchors.We retrospectively review 11 cases of closed comminuted glenoid fractures treated at our institution from August 2010 to May 2013. The 11 patients, 8 males and 3 females, had a mean age of 41 years (range: 27-55 years). The mechanisms of injury were traffic accidents in 9 cases and falls from height in 2 cases. The mean time from injury to surgery was 12 days (range: 3-28 days). All glenoid fractures were confirmed on x-ray and computed tomography. The major fracture fragments were fixed with cannulated screws and the small fragments were fixed with suture anchors.All surgical wounds healed with primary closure and no complications including infection and neurovascular damage were observed. All 11 patients were followed up for a mean of 21 months (range: 14-29 months). Bone union was achieved in all patients with a mean time of 10 months. At the last follow-up, range of motion of the shoulder joint was significantly improved (P < 0.05). Both ASES scores (41.4 ± 24.9, 87.3 ± 13.8) and Rowe scores (28.2 ± 18.6, 93.2 ± 11.2) were significantly increased after the surgery (P < 0.01), indicating significantly improved function and stability of the shoulder joint.Arthroscopic fixation using cannulated screws and suture anchors is feasible for the treatment of comminuted glenoid fractures. This method is minimally invasive and provides good functional recovery with a lower risk of complications. PMID:26656324

  17. Odontoid balloon kyphoplasty associated with screw fixation for Type II fracture in 2 elderly patients.

    PubMed

    Terreaux, Luc; Loubersac, Thomas; Hamel, Olivier; Bord, Eric; Robert, Roger; Buffenoir, Kevin

    2015-03-01

    Anterior screw fixation is a well-recognized technique that is used to stabilize Type IIB fractures of the odontoid process in the elderly. However, advanced age and osteoporosis are 2 risk factors for pseudarthrosis. Kyphoplasty has been described in the treatment of lytic lesions in C-2. The authors decided to combine these 2 techniques in the treatment of unstable fractures of the odontoid. Two approximately 90-year-old patients were treated for this type of fracture. Instability was demonstrated on dynamic radiography in one patient, and the fracture was seen on static radiography in the other. Clinical parameters, pain, range of motion, 36-Item Short Form Health Survey (SF-36) score (for the first patient), and radiological examinations (CT scans and dynamic radiographs) were studied both before and after surgery. After inflating the balloon both above and below the fracture line, the authors applied a high-viscosity polymethylmethacrylate cement. Some minor leakage of cement was noted in both cases but proved to be harmless. The screws were correctly positioned. The clinical result was excellent, both in terms of pain relief and in the fact that there was no reduction in the SF-36 score. The range of motion remained the same. A follow-up CT scan obtained 1 year later in one of the patients showed no evidence of change in the materials used, and the dynamic radiographs showed no instability. This combination of kyphoplasty and anterior screw fixation of the odontoid seems to be an interesting technique in osteoporotic Type IIB fractures of the odontoid process in the elderly, with good results both clinically and radiologically. PMID:25555053

  18. Management of Unstable Thoracolumbar Spinal Fractures by Pedicle Screws and Rods Fixation

    PubMed Central

    B.M., Muralidhar; Hegde, Durgaprasad; Hussain, P.S.B.

    2014-01-01

    Background: The thoracolumbar junction is the most common area of injury to the axial skeleton. Forces along the long stiff kyphotic thoracic spine switch abruptly into the mobile lordotic lumbar spine at the thoracolumbar junction. Goals of treatment are to obtain a painless, balanced, stable spine with optimum neurological function and maximum spine mobility. The present prospective study has evaluated the effectiveness of pedicle screw instrumentation in various fractures around the TL spine to overcome the complications encountered in the conservative line of management of these fractures. Materials & Methods: Thirty cases of fractures around the TL spine were operated with posterior pedicle screw fixation one or two level above and below the fracture. The cases were followed up for a mean of 9.5 months with radiological and neurological evaluation. Results: The average age groups of the patients studied were 21 to 53 years majority were males, fall from height being the predominant mode of injury involving the T12 and L1 vertebral body. The unstable burst fractures the most common type of fracture, radiological parameters sagittal angle and index were recorded pre and post-operatively. The neurological grading was done using the ASIA score. Follow-up was done for a minimum of 5 months where sagittal angle reduction achieved was 10.75 at final follow-up from 23.5 pre-operative. The sagittal index achieved at final follow-up was 72% compared to the pre-operative mean of 53%. The neurological improvement was regarded to be fair enough for the type of injury sustained and fixation achieved. Conclusion: We found that the application of posterior instrumentation using pedicle screw and rod resulted in a reasonable correction of the deformity with a significant reduction in recumbency-associated complications; the limiting factor being the small study group and short follow-up period. PMID:24701500

  19. Retrograde percutaneous screw fixation for scaphoid type II non-union in Schernberg zones 2 to 4: a series of 38 cases.

    PubMed

    Taleb, C; Bodin, F; Collon, S; Gay, A; Facca, S; Liverneaux, P

    2015-02-01

    Regardless of the treatment used, 25 to 45% of scaphoid fractures do not heal. Open surgery compromises vascularization and destabilizes ligament attachments. The aim of this retrospective study was to assess the value of retrograde percutaneous screw fixation of Alnot stage IIA and IIB scaphoid non-union in Schernberg zones 2 to 4. This series included 38 patients with a mean age of 31 years. Based on the Alnot classification, there were 16 stage IIA non-unions (12 in zone 3 and 4 in zone 2 according to the Schernberg classification) and 22 stage IIB non-unions (9 in zone 3 and 13 in zone 2). The time elapsed between the initial trauma and the surgical treatment was 10 months on average. Percutaneous retrograde fixation was performed with a cannulated 2.7mm compression screw. At 25 months follow-up, 31 of the non-union cases had healed (81.6%), of which 14 were stage IIA (87.5%) and 17 were stage IIB (77.3%), after an average 6.3 months. Average pain was 1.6. The average Quick DASH was 17.3/100. Compared to the opposite side, the average range of motion was 84.8% in flexion, 84.7% in extension, 98.9% in pronation, 96.5% in supination, 96.8% in ulnar deviation and 86.4% in radial deviation. The grip strength was 80.4% of the contralateral side. Seven patients did not heal after screw fixation; four of them healed after additional electromagnetic stimulation and three after addition of a vascularized bone graft. Based on this study's results, stage IIA non-unions can heal with simple retrograde percutaneous screw fixation. The same procedure could be enough for stage IIB non-union cases, however we recommend adding a cancellous bone graft by arthroscopy. Open surgery procedures are preferred when percutaneous procedures have failed. PMID:25579829

  20. Superior fixation of pegged trabecular metal over screw-fixed pegged porous titanium fiber mesh

    PubMed Central

    2011-01-01

    Background and purpose Lasting stability of cementless implants depends on osseointegration into the implant surface, and long-term implant fixation can be predicted using radiostereometric analysis (RSA) with short-term follow-up. We hypothesized that there would be improved fixation of high-porosity trabecular metal (TM) tibial components compared to low-porosity titanium pegged porous fiber-metal (Ti) polyethylene metal backings. Methods In a prospective, parallel-group, randomized unblinded clinical trial, we compared cementless tibial components in patients aged 70 years and younger with osteoarthritis. The pre-study sample size calculation was 22 patients per group. 25 TM tibial components were fixed press-fit by 2 hexagonal pegs (TM group) and 25 Ti tibial components were fixed press-fit and by 4 supplemental screws (Ti group). Stereo radiographs for evaluation of absolute component migration (primary effect size) and single-direction absolute component migration (secondary effect size) were obtained within the first postoperative week and at 6 weeks, 6 months, 1 year, and 2 years. American Knee Society score was used for clinical assessment preoperatively, and at 1 and 2 years. Results There were no intraoperative complications, and no postoperative infections or revisions. All patients had improved function and regained full extension. All tibial components migrated initially. Most migration of the TM components (n = 24) occurred within the first 3 months after surgery whereas migration of the Ti components (n = 22) appeared to stabilize first after 1 year. The TM components migrated less than the Ti components at 1 year (p = 0.01) and 2 years (p = 0.004). Interpretation We conclude that the mechanical fixation of TM tibial components is superior to that of screw-fixed Ti tibial components. We expect long-term implant survival to be better with the TM tibial component. PMID:21434781

  1. Enhanced Lapidus arthrodesis: crossed screw technique with middle cuneiform fixation further reduces sagittal mobility.

    PubMed

    Galli, Melissa M; McAlister, Jeffrey E; Berlet, Gregory C; Hyer, Christopher F

    2015-01-01

    Persistent medial column sagittal mobility can be encountered despite successful first tarsometatarsal stabilization if fixation has been limited to the first tarsometatarsal joint. The purpose of the present cadaveric research was to quantify the effect of a third point of fixation from the base of the first metatarsal to the middle cuneiform compared with the traditional isolated first tarsometatarsal fixation. Ten matched pairs of below-the-knee specimens, with a known cause of death, sex, ethnicity, and age, height, weight, and body mass index at death, were used for our examination. Portable fluoroscopy aided with the accurate placement of all points of fixation. Measurements of movement were obtained using the validated Klaue device. The 20 matched below-the-knee specimens were from 10 cadavers (2 female and 8 male donors, aged 72.8 ± 9.3 years, body mass index 21.1 ± 4.2 kg/m(2)). The sagittal plane motion of the first ray was 7.45 ± 1.82 mm before fixation. With isolated first tarsometatarsal fixation, the sagittal motion decreased to 4.41 ± 1.51 mm and decreased further to 3.12 ± 1.06 mm, with the addition of middle cuneiform fixation. Statistically significant enhancement of the stability of sagittal first ray motion was noted with the addition of the first metatarsal to middle cuneiform pin, even after simulated Lapidus fixation. Our findings suggest that first metatarsal to middle cuneiform fixation can be beneficial if excessive sagittal motion is present after standard 2-point fixation and can play a role in the prevention of recurrence and complications. PMID:25456344

  2. Time course of bone screw fixation following a local delivery of Zoledronate in a rat femoral model - a micro-finite element analysis.

    PubMed

    Kettenberger, Ulrike; Latypova, Adeliya; Terrier, Alexandre; Pioletti, Dominique P

    2015-05-01

    A good fixation of osteosynthesis implants is crucial for a successful bone healing but often difficult to achieve in osteoporotic patients. One possible solution to this issue is the local delivery of bisphosphonates in direct proximity to the implants, A critical aspect of this method, that has not yet been well investigated, is the time course of the implant fixation following the drug release. Usual destructive mechanical tests require large numbers of animals to produce meaningful results. Therefore, a micro-finite element (microFE) approach was chosen to analyze implant fixation. In vivo micro computed tomography (microCT) scans were obtained, first weekly and later bi-weekly, after implantation of polymeric screws in the femoral condyles of ovariectomized rats. In one half of the animals, Zoledronate was released from a hydrogel matrix directly in the peri-implant bone stock, the other animals were implanted only with screws as control. The time course of the implant fixation was investigated with linear elastic microFE models that were created based on in vivo microCT scans. The numerical models were validated against experimental pullout-tests measurements in an additional cadaver study. The microFE analysis revealed a significant increase in force at yield of the Zoledronate treated group compared to the control group. The force of the treated group was 28% higher after 17 days of screw implantation, 42% higher after 31 days. The significant difference persisted until the end of the in vivo study at day 58 (p<0.01). The early onset and prolonged duration of the implant anchorage improvement that was found in this study indicates the great potential of Zoledronate-loaded hydrogel for an enhancement of osteosynthesis implant fixation in impaired bone. PMID:25679481

  3. Pyoderma Gangrenosum Mimicking an Infected Wound following Dynamic Hip Screw Fixation

    PubMed Central

    Nizamoglu, Metin

    2015-01-01

    Pyoderma gangrenosum (PG) is an inflammatory ulcerative neutrophilic dermatosis that can occur following skin trauma. The correct diagnosis is not often made immediately as the condition can mimic an infective appearance. This leads to delays in the appropriate management of high dose steroids. Although debridement can offer aid in resolving lesions, this is contraindicated in the acute phase as this can cause acceleration of the pathogenic process. Biopsy of the lesion does not offer a definitive diagnosis; therefore suspicion must be maintained as the diagnosis is ultimately a clinical one. Any postoperative pustular ulcerative lesion not improving despite antibiotic therapy that also yields negative bacteriological and fungal studies should lead to consideration of this diagnosis. We document the first case of PG developing following intertrochanteric femur fracture fixation using dynamic hip screw. PMID:26380139

  4. Biomechanical effects of polyaxial pedicle screw fixation on the lumbosacral segments with an anterior interbody cage support

    PubMed Central

    Chen, Shih-Hao; Mo Lin, Ruey; Chen, Hsiang-Ho; Tsai, Kai-Jow

    2007-01-01

    Background Lumbosacral fusion is a relatively common procedure that is used in the management of an unstable spine. The anterior interbody cage has been involved to enhance the stability of a pedicle screw construct used at the lumbosacral junction. Biomechanical differences between polyaxial and monoaxial pedicle screws linked with various rod contours were investigated to analyze the respective effects on overall construct stiffness, cage strain, rod strain, and contact ratios at the vertebra-cage junction. Methods A synthetic model composed of two ultrahigh molecular weight polyethylene blocks was used with four titanium pedicle screws (two in each block) and two rods fixation to build the spinal construct along with an anterior interbody cage support. For each pair of the construct fixed with polyaxial or monoaxial screws, the linked rods were set at four configurations to simulate 0, 7, 14, and 21 lordosis on the sagittal plane, and a compressive load of 300 N was applied. Strain gauges were attached to the posterior surface of the cage and to the central area of the left connecting rod. Also, the contact area between the block and the cage was measured using prescale Fuji super low pressure film for compression, flexion, lateral bending and torsion tests. Results Our main findings in the experiments with an anterior interbody cage support are as follows: 1) large segmental lordosis can decrease the stiffness of monoaxial pedicle screws constructs; 2) polyaxial screws rather than monoaxial screws combined with the cage fixation provide higher compression and flexion stiffness in 21 segmental lordosis; 3) polyaxial screws enhance the contact surface of the cage in 21 segmental lordosis. Conclusion Polyaxial screws system used in conjunction with anterior cage support yields higher contact ratio, compression and flexion stiffness of spinal constructs than monoaxial screws system does in the same model when the spinal segment is set at large lordotic angles. Polyaxial pedicle screw fixation performs nearly equal percentages of vertebra-cage contact among all constructs with different sagittal alignments, therefore enhances the stabilization effect of interbody cages in the lumbosacral area. PMID:17349057

  5. A method for the fatigue testing of pedicle screw fixation devices.

    PubMed

    Goel, V K; Winterbottom, J M; Weinstein, J N

    1994-11-01

    Spinal devices/instrumentation are used to augment the stability of a decompressed spinal segment during surgery. Like any other mechanical component, the device can fail. A standard in vitro test protocol, was developed to determine load vs number of cycles to failure curve for a pedicle screw-plate/rod type spinal device. The protocol based on the use of an 'artificial spine' model, is clinically relevant. The protocol was used to characterize the load-carrying capacities and failure modes of a specific pedicle screw-rod type fixation device to demonstrate its appropriateness. The devices (Kaneda) were tested in the quasi-static as well as fatigue bending modes. In the bending fatigue mode, the devices failed at loads significantly smaller than the corresponding quasi-static failure load magnitude (806 N). The device exhibited an endurance limit in the fatigue bending mode. The device is not likely to exhibit failure if subjected to cyclic loads which cause less than 380 N axial compression (and an accompanying bending moment relative to the device of less than 13.57 Nm). The failures observed in specimens subjected to the fatigue tests ranged from complete to partial breakage of the paraspinal rods as opposed to failure due to permanent deformation (yielding) of the rods in the quasi-static bending test specimens. The protocol developed can be used for any other screw-plate/rod type spinal instrumentation. The use of a standard protocol by researchers would enable a comparison of various devices currently available in the market. Such comparative data would be useful for the scientific community, and agencies such as the FDA and ASTM.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7798289

  6. Use of a Percutaneous Pointed Reduction Clamp Before Screw Fixation to Prevent Gapping of a Fifth Metatarsal Base Fracture: A Technique Tip.

    PubMed

    Tan, Eric W; Cata, Ezequiel; Schon, Lew C

    2016-01-01

    Intramedullary screw fixation has become widely accepted as the standard of care for operative treatment of Jones fractures, allowing not only accelerated rehabilitation but also reduction of the risk of repeat fracture. The unique anatomy of the fifth metatarsal-mainly its inherent lateral curvature-makes fixation technically challenging. In general, surgical fixation should be performed with the largest screw possible, in both diameter and length, which will provide the strongest possible construct. However, an increased screw length and width have been associated with complications, including lateral gapping and distraction of the fracture site and malreduction of the fracture. The use of a pointed reduction clamp is a simple, yet effective, method of preventing iatrogenic displacement and gapping at the fracture site during placement of an intramedullary screw. Percutaneous reduction and stabilization of the fracture using this technique could help limit the complications associated with large screw fixation of Jones fractures. PMID:26188626

  7. Analysis of the Stress and Displacement Distribution of Inferior Tibiofibular Syndesmosis Injuries Repaired with Screw Fixation: A Finite Element Study

    PubMed Central

    Liu, Qinghua; Zhang, Kun; Zhuang, Yan; Li, Zhong; Yu, Bin; Pei, Guoxian

    2013-01-01

    Background Studies of syndesmosis injuries have concentrated on cadaver models. However, they are unable to obtain exact data regarding the stress and displacement distribution of various tissues, and it is difficult to compare models. We investigated the biomechanical effects of inferior tibiofibular syndesmosis injuries (ITSIs) and screw fixation on the ankle using the finite element (FE) method. Methodology/Principal Findings A three-dimensional model of a healthy ankle complex was developed using computed tomography (CT) images. We established models of an ITSI and of screw fixation at the plane 2.5 cm above and parallel to the tibiotalar joint surface of the injured syndesmosis. Simulated loads were applied under three conditions: neutral position with single-foot standing and internal and external rotation of the ankle. ITSI reduced contact forces between the talus and fibula, helped periarticular ankle ligaments withstand more load-resisting movement, and increased the magnitude of displacement at the lower extreme of the tibia and fibula. ITSI fixation with a syndesmotic screw reduced contact forces in all joints, decreased the magnitude of displacement at the lower extreme of the tibia and fibula, and increased crural interosseous membrane stress. Conclusions/significance Severe syndesmosis injuries cause stress and displacement distribution of the ankle to change multidirectional ankle instability and should be treated by internal fixation. Though the transverse syndesmotic screw effectively stabilizes syndesmotic diastasis, it also changes stress distribution around the ankle and decreases the joint's range of motion (ROM). Therefore, fixation should not be performed for a long period of time because it is not physiologically suitable for the ankle joint. PMID:24312464

  8. A Meta-Analysis of Unilateral versus Bilateral Pedicle Screw Fixation in Minimally Invasive Lumbar Interbody Fusion

    PubMed Central

    Liu, Zheng; Fei, Qi; Wang, Bingqiang; Lv, Pengfei; Chi, Cheng; Yang, Yong; Zhao, Fan; Lin, Jisheng; Ma, Zhao

    2014-01-01

    Study Design Meta-analysis. Background Bilateral pedicle screw fixation (PS) after lumbar interbody fusion is a widely accepted method of managing various spinal diseases. Recently, unilateral PS fixation has been reported as effective as bilateral PS fixation. This meta-analysis aimed to comparatively assess the efficacy and safety of unilateral PS fixation and bilateral PS fixation in the minimally invasive (MIS) lumbar interbody fusion for one-level degenerative lumbar spine disease. Methods MEDLINE/PubMed, EMBASE, BIOSIS Previews, and Cochrane Library were searched through March 30, 2014. Randomized controlled trials (RCTs) and controlled clinical trials (CCTs) on unilateral versus bilateral PS fixation in MIS lumbar interbody fusion that met the inclusion criteria and the methodological quality standard were retrieved and reviewed. Data on participant characteristics, interventions, follow-up period, and outcomes were extracted from the included studies and analyzed by Review Manager 5.2. Results Six studies (5 RCTs and 1 CCT) involving 298 patients were selected. There were no significant differences between unilateral and bilateral PS fixation procedures in fusion rate, complications, visual analogue score (VAS) for leg pain, VAS for back pain, Oswestry disability index (ODI). Both fixation procedures had similar length of hospital stay (MD = 0.38, 95% CI = −0.83 to 1.58; P = 0.54). In contrast, bilateral PS fixation was associated with significantly more intra-operative blood loss (P = 0.002) and significantly longer operation time (P = 0.02) as compared with unilateral PS fixation. Conclusions Unilateral PS fixation appears as effective and safe as bilateral PS fixation in MIS lumbar interbody fusion but requires less operative time and causes less blood loss, thus offering a simple alternative approach for one-level lumbar degenerative disease. PMID:25375315

  9. Treatment of neuromuscular scoliosis with posterior-only pedicle screw fixation

    PubMed Central

    Modi, Hitesh N; Suh, Seung-Woo; Song, Hae-Ryong; Fernandez, Harry M; Yang, Jae-Hyuk

    2008-01-01

    Background To determine whether posterior-only approach using pedicle screws in neuromuscular scoliosis population adequately addresses the correction of scoliosis and maintains the correction over time. Methods Between 2003 and 2006, 26 consecutive patients (7 cerebral palsy, 10 Duchenne muscular dystrophy, 5 spinal muscular atrophy and 4 others) with neuromuscular scoliosis underwent posterior pedicle screw fixation for the deformity. Preoperative, immediate postoperative and final follow-up Cobb's angle and pelvic obliquity were analyzed on radiographs. The average age of the patients was 17.5 years (range, 8–44 years) and the average follow-up was 25 months (18–52 months). Results Average Cobb's angle was 78.53° before surgery, 30.70° after surgery (60.9% correction), and 33.06° at final follow-up (57.9% correction) showing significant correction (p < 0.0001). There were 9 patients with curves more than 90° showed an average pre-operative, post operative and final follow up Cobb's angle 105.67°, 52.33° (50.47% correction) and 53.33° (49.53% correction) respectively and 17 patients with curve less than 90° showed average per operative, post operative and final follow up Cobb's angle 64.18, 19.24(70% correction) and 21.41(66.64 correction); which suggests statistically no significant difference in both groups (p = 0.1284). 7 patients underwent Posterior vertebral column resection due to the presence of a rigid curve. The average spinal-pelvic obliquity was 16.27° before surgery, 8.96° after surgery, and 9.27° at final follow-up exhibited significant correction (p < 0.0001). There was 1 poliomyelitis patient who had power grade 3 in lower limbs pre-operatively, developed grade 2 power post-operatively and gradually improved to the pre-operative stage. There was 1 case of deep wound infection and no case of pseud-arthrosis, instrument failures or mortality. Conclusion Results indicate that in patients with neuromuscular scoliosis, acceptable amounts of curve correction can be achieved and maintained with posterior-only pedicle screw instrumentation without anterior release procedure. PMID:18544164

  10. Percutaneous Facet Screw Fixation in the Treatment of Symptomatic Recurrent Lumbar Facet Joint Cyst: A New Technique.

    PubMed

    Amoretti, Nicolas; Gallo, Giacomo; Bertrand, Anne-Sophie; Bard, Robert L; Kelekis, Alexis

    2016-01-01

    We present a case of percutaneous treatment of symptomatic recurrent lumbar facet joint cyst resistant to all medical treatments including facet joint steroid injection. Percutaneous transfacet fixation was then performed at L4-L5 level with a cannulated screw using CT and fluoroscopy guidance. The procedure time was 30min. Using the visual analog scale (VAS), pain decreased from 9.5, preoperatively, to 0 after the procedure. At 6-month follow-up, an asymptomatic cystic recurrence was observed, which further reduced at the 1-year follow-up. Pain remained stable (VAS at 0) during all follow-ups. CT- and fluoroscopy-guided percutaneous cyst rupture associated with facet screw fixation could be an alternative to surgery in patients suffering from a symptomatic recurrent lumbar facet joint cyst. PMID:25944146

  11. Assessment of compression and strength of divergent screws mounted on miniplates for fixation of mandibular fractures: an in vitro experimental study.

    PubMed

    Jafarian, M; Pourdanesh, F; Esmaeelinejad, M; Dehghani, N; Aghdashi, F; Tabrizi, R

    2015-09-01

    An efficient band of tension is critical for the adequate fixation of mandibular fractures, so fixation devices that compress are helpful. We aimed to evaluate the possibility of creating compression using screws inserted divergently into miniplates placed in the tension zone of mandibular fractures and record the effects on the strength of fixation. For this in vitro experimental study we prepared 20 sheep hemimandibles. After angle fractures had been created, the specimens were divided into standard and study groups (n=10 in each). In the standard group the tension zones were fixed in the standard manner with 4-hole miniplates and 4 parallel screws. Those in the study group were fixed as for the standard group but with 445 divergent screws. The differences in the gap in the fracture line before and after fixation were measured as indicators of compression. The strength of fixation was also assessed with a universal testing machine in vitro. The amount of compression was significant only in the study group (p<0.001), and there was no difference in the strength of fixation between the two groups (p=0.7). We conclude that divergent drilling and insertion of screws creates more horizontal force when miniplates are used, and results in reduction in the size of the probable gap in the fracture line. Insertion of divergent screws in miniplates may create compression between fractured segments without jeopardising the strength of fixation. PMID:25921364

  12. Impact of Different Screw Designs on Durability of Fracture Fixation: In Vitro Study with Cyclic Loading of Scaphoid Bones

    PubMed Central

    Gruszka, Dominik; Herr, Robert; Hely, Hans; Hofmann, Peer; Klitscher, Daniela; Hofmann, Alexander; Rommens, Pol Maria

    2016-01-01

    Purpose The use of new headless compression screws (HCSs) for scaphoid fixation is growing, but the nonunion rate has remained constant. The aim of this study was to compare the stability of fixation resulting from four modern HCSs using a simulated fracture model to determine the optimal screw design(s). Methods We tested 40 fresh-frozen cadaver scaphoids treated with the Acumed Acutrak 2 mini (AA), the KLS Martin HBS2 midi (MH), the Stryker TwinFix (ST) and the Synthes HCS 3.0 with a long thread (SH). The bones with simulated fractures and implanted screws were loaded uniaxially into flexion for 2000 cycles with a constant bending moment of 800 Nmm. The angulation of the fracture fragments was measured continuously. Data were assessed statistically using the univariate ANOVA test and linear regression analysis, and the significance level was set at p < 0.05. Results The median angulation of bone fragments φ allowed by each screw was 0.89° for AA, 1.12° for ST, 1.44° for SH and 2.36° for MH. With regards to linear regression, the most reliable curve was achieved by MH, with a coefficient of determination of R2 = 0.827. This was followed by AA (R2 = 0.354), SH (R2 = 0.247) and ST (R2 = 0.019). Data assessed using an adapted ANOVA model showed no statistically significant difference (p = 0.291) between the screws. Conclusions The continuous development of HCSs has resulted in very comparable implants, and thus, at this time, other factors, such as surgeons’ experience, ease of handling and price, should be taken into consideration. PMID:26741807

  13. Minimally Invasive Transforaminal Lumbar Interbody Fusion with Unilateral Pedicle Screw Fixation: Comparison between Primary and Revision Surgery

    PubMed Central

    Kang, Moo Sung; Kim, Kyung Hyun; Kuh, Sung Uk; Chin, Dong Kyu; Kim, Keun Su; Cho, Yong Eun

    2014-01-01

    Minimally invasive surgery with a transforaminal lumbar interbody fusion (MIS TLIF) is an important minimally invasive fusion technique for the lumbar spine. Lumbar spine reoperation is challenging and is thought to have greater complication risks. The purpose of this study was to compare MIS TLIF with unilateral screw fixation perioperative results between primary and revision surgeries. This was a prospective study that included 46 patients who underwent MIS TLIF with unilateral pedicle screw. The patients were divided into two groups, primary and revision MIS TLIF, to compare perioperative results and complications. The two groups were similar in age, sex, and level of operation, and were not significantly different in the length of follow-up or clinical results. Although dural tears were more common with the revision group (primary 1; revision 4), operation time, blood loss, total perioperative complication, and fusion rates were not significantly different between the two groups. Both groups showed substantial improvements in VAS and ODI scores one year after surgical treatment. Revision MIS TLIF performed by an experienced surgeon does not necessarily increase the risk of perioperative complication compared with primary surgery. MIS TLIF with unilateral pedicle screw fixation is a valuable option for revision lumbar surgery. PMID:24949483

  14. Stability of bicortical screw versus plate fixation after mandibular setback with the bilateral sagittal split osteotomy: a systematic review and meta-analysis.

    PubMed

    Al-Moraissi, E A M; Ellis, E

    2016-01-01

    The purpose of this study was to test the hypothesis that there is no difference in skeletal stability between bicortical screw and miniplate fixation after mandibular setback surgery with the bilateral sagittal split osteotomy (BSSO). A systematic and electronic search of several databases with specific key words, a reference search, and a manual search through September 2014 was performed. The inclusion criteria encompassed clinical human studies, including randomized controlled trials (RCTs), controlled clinical trials (CCTs), and retrospective studies, with the aim of comparing bicortical screw fixation to miniplate fixation after mandibular setback with the BSSO. Changes in both linear (horizontal and vertical) and angular measurements (SNB and mandibular plane) were analyzed. The initial PubMed search identified 317 studies, of which seven met the inclusion criteria-one RCT, four CCTs, and two retrospective studies. Bicortical screw fixation was found to provide slightly better skeletal stability than miniplate fixation after setback with the BSSO, but the difference was not statistically significant. The results of this meta-analysis support the hypothesis that there is no statistically significant difference in skeletal stability between bicortical screw fixation and plate fixation of the BSSO when used for mandibular setback. PMID:26474933

  15. Failure of intertrochanteric fracture fixation with a dynamic hip screw in relation to pre-operative fracture stability and osteoporosis.

    PubMed

    Kim, W Y; Han, C H; Park, J I; Kim, J Y

    2001-01-01

    We have reviewed 178 intertrochanteric fractures treated by dynamic hip screw (DHS) fixation between March 1995 and December 1999 and followed for a minimum of 1 year. We used Singh's classification of the trabecular bone structure in the proximal femur as a measure of osteoporosis and also classified the fractures according to three different systems (Boyd-Griffin, Evans, AO). The postoperative radiographs were examined for loss of reduction, i.e. varus angulation >100, perforation of the femoral head, more than 20-mm extrusion of a lag screw or metal failure. We found 49 cases which showed radiographic failures. Two were stable fractures and 47 unstable fractures (Evans' classification). Unstable fractures with osteoporosis had a failure rate of more than 50%. In such cases DHS should not be the first choice for treatment. PMID:11820441

  16. DARTHROSCOPIC DOUBLE- BUNDLE RECONSTRUCTION OF ANTERIOR CRUCIATE LIGAMENT USING HAMSTRING TENDON GRAFTS - FIXATION WITH TWO INTERFERENCE SCREWS

    PubMed Central

    Carneiro, Mario; Navarro, Ricardo Dizioli; Nakama, Gilberto Yoshinobu; Barretto, João Mauricio; Bessa de Queiroz, Antonio Altenor; Malheiro Luzo, Marcus Vinicius

    2015-01-01

    Surgical procedures for double-bundle reconstruction of anterior cruciate ligament, which currently use semitendinous and gracilis tendon grafts, have been described in the last decade. Most of the techniques utilize twice the hardware used in single-bundle reconstructions. We report an original anterior cruciate ligament double-bundle reconstruction technique using semitendinous and gracilis tendon grafts, maintaining their tibial bone insertions with two tibial and two femoral tunnels. A simplified and precise outside-in femoral drilling technique is utilized, and the graft fixation is made utilizing only two interference screws.

  17. Analysis of stress induced by screws in the vertebral fixation system

    PubMed Central

    Fakhouri, Sarah Fakher; Shimano, Marcos Massao; de Araújo, Cleudmar Amaral; Defino, Helton Luiz Aparecido; Shimano, Antônio Carlos

    2014-01-01

    Objective: To compare, using photoelasticity, internal stress produced by USS II type screw with 5.2 and 6.2 mm external diameters, when submitted to three different pullout strengths. Methods: Two photoelastic models were especially made. The simulation was performed using loads of 1.8, 2.4 e 3.3 kgf.The fringe orders were evaluated around the screws. In all the models analyzed the shear stress were calculated. Results: Independently of the applied load, the smaller screw showed higher values of shear stress. Conclusion: According to the analysis performed, we observed that the place of highest stress was in the first thread of the lead, close to the head of the screws. Experimental study. PMID:24644414

  18. Atlantoaxial arthrodesis using C1-C2 transarticular screw fixation in a case of Morquio syndrome.

    PubMed

    Kulkarni, Arvind G; Shah, Siddharth M

    2011-09-01

    Prophylactic or therapeutic arthrodesis is recommended for atlantoaxial instability in Morquio syndrome. Occipitocervical fusion, the common approach for upper cervical fusion in Morquio syndrome sacrifices the movements at the occipitoatlantal joints. The use of C1-C2 transarticular screws for achieving C1-C2 arthrodesis, without compromising mobility at the occipitoatlantal joint in Morquio syndrome has not been reported. We report a case of Morquio syndrome with atlantoaxial instability and odontoid hypoplasia, where we successfully achieved C1-C2 arthrodesis using transarticular screws and bone graft. The advantages of this method over other methods of atlantoaxial arthrodesis in Morquio syndrome have also been discussed. PMID:21886932

  19. A Computed Tomography-Based Anatomic Comparison of Three Different Types of C7 Posterior Fixation Techniques : Pedicle, Intralaminar, and Lateral Mass Screws

    PubMed Central

    Jang, Woo Young; Kim, Il Sup; Lee, Ho Jin; Sung, Jae Hoon; Lee, Sang Won

    2011-01-01

    Objective The intralaminar screw (ILS) fixation technique offers an alternative to pedicle screw (PS) and lateral mass screw (LMS) fixation in the C7 spine. Although cadaveric studies have described the anatomy of the pedicles, laminae, and lateral masses at C7, 3-dimensional computed tomography (CT) imaging is the modality of choice for pre-surgical planning. In this study, the goal was to determine the anatomical parameter and optimal screw trajectory for ILS placement at C7, and to compare this information to PS and LMS placement in the C7 spine as determined by CT evaluation. Methods A total of 120 patients (60 men and 60 women) with an average age of 51.713.6 years were selected by retrospective review of a trauma registry database over a 2-year period. Patients were included in the study if they were older than 15 years of age, had standardized axial bone-window CT imaging at C7, and had no evidence of spinal trauma. For each lamina and pedicle, width (outer cortical and inner cancellous), maximal screw length, and optimal screw trajectory were measured, and the maximal screw length of the lateral mass were measured using m-view 5.4 software. Statistical analysis was performed using Student's t-test. Results At C7, the maximal PS length was significantly greater than the ILS and LMS length (PS, 33.93.1 mm; ILS, 30.83.1 mm; LMS, 10.61.3; p<0.01). When the outer cortical and inner cancellous width was compared between the pedicle and lamina, the mean pedicle outer cortical width at C7 was wider than the lamina by an average of 0.6 mm (pedicle, 6.81.2 mm; lamina, 6.21.2 mm; p<0.01). At C7, 95.8% of the laminae measured accepted a 4.0-mm screw with a 1.0 mm of clearance, compared with 99.2% of pedicle. Of the laminae measured, 99.2% accepted a 3.5-mm screw with a 1.0 mm clearance, compared with 100% of the pedicle. When the outer cortical and inner cancellous height was compared between pedicle and lamina, the mean lamina outer cortical height at C7 was wider than the pedicle by an average of 9.9 mm (lamina, 18.62.0 mm; pedicle, 8.71.3 mm; p<0.01). The ideal screw trajectory at C7 was also measured (47.84.8 for ILS and 35.18.1 for PS). Conclusion Although pedicle screw fixation is the most ideal instrumentation method for C7 fixation with respect to length and cortical diameter, anatomical aspect of C7 lamina is affordable to place screw. Therefore, the C7 intralaminar screw could be an alternative fixation technique with few anatomic limitations in the cases when C7 pedicle screw fixation is not favorable. However, anatomical variations in the length and width must be considered when placing an intralaminar or pedicle screw at C7. PMID:22102943

  20. Unstable Intertrochanteric Fracture Fixation – Is Proximal Femoral Locked Compression Plate Better Than Dynamic Hip Screw

    PubMed Central

    Asif, Naiyer; Qureshi, Owais Ahmad; Jilani, Latif Zafar; Hamesh, Tajdar; Jameel, Tariq

    2016-01-01

    Background Intertrochanteric fractures are one of the most common fractures encountered in our practice. Most of them need operative intervention and union is achieved. As per the literature dynamic hip screw (DHS) is the gold standard for the treatment of these fractures, however problem arises with maintenance of neck shaft angle and proper reduction in unstable intertrochanteric fractures. The situation gets more complex when “cut out” of femoral head screw occurs either alone or in combination with varus collapse when they are treated with DHS. Here we are giving results of unstable intertrochanteric fractures treated with Proximal Femoral Locked Compression Plate (PFLCP) as compared with similar patients treated with Dynamic Hip Screw (DHS). Materials and Methods The study included a total of 27 patients (17 males, 10 females) with unstable intertrochanteric fractures who were subjected to PFLCP treatment from March 2011 to November 2012 in one group. Another was a similar group of 35 patients treated with DHS from March 2008 to February 2010. Results of group 1 were compared with group 2. Detailed clinical conditions of all patients, duration of surgery, blood loss, length of incision and duration of image intensifier use were recorded. Patients were revisited at 6 weeks, 3 months, 6 months and 1 year after operation. Results were evaluated clinically by Harris hip Score and radiologically for fracture union. Progress of union and complications (limb shortening, varus collapse, cut out of femoral head screw and medialization of distal fragment) were recorded. Results Among 27 patients treated with PFLCP, one patient expired 6 week postoperatively and one patient lost to follow up, so 25 patients were evaluated for final outcome of which 23 (92%) showed union at follow up of 12 months. One patient developed bending of proximal screws and three developed varus collapse. Among the group treated with DHS, eight patients developed varus collapse, seven developed medialization and three had femoral head screw cut out. According to Harris hip Score 88% cases had good to excellent result in PFLCP group whereas only 60% cases in the DHS group had good to excellent result. Conclusion Treatment of unstable intertrochanteric fractures with proximal femoral locked plate (PFLCP) can give good healing, with a limited occurrence of complication. PMID:26894134

  1. Feasibility study of patient-specific surgical templates for the fixation of pedicle screws.

    PubMed

    Salako, F; Aubin, C-E; Fortin, C; Labelle, H

    2002-01-01

    Surgery for scoliosis, as well as other posterior spinal surgeries, frequently uses pedicle screws to fix an instrumentation on the spine. Misplacement of a screw can lead to intra- and post-operative complications. The objective of this study is to design patient-specific surgical templates to guide the drilling operation. From the CT-scan of a vertebra, the optimal drilling direction and limit angles are computed from an inverse projection of the pedicle limits. The first template design uses a surface-to-surface registration method and was constructed in a CAD system by subtracting the vertebra from a rectangular prism and a cylinder with the optimal orientation. This template and the vertebra were built using rapid prototyping. The second design uses a point-to-surface registration method and has 6 adjustable screws to adjust the orientation and length of the drilling support device. A mechanism was designed to hold it in place on the spinal process. A virtual prototype was build with CATIA software. During the operation, the surgeon places either template on patient's vertebra until a perfect match is obtained before drilling. The second design seems better than the first one because it can be reused on different vertebra and is less sensible to registration errors. The next step is to build the second design and make experimental and simulations tests to evaluate the benefits of this template during a scoliosis operation. PMID:15456075

  2. A prospective, randomised trial comparing the use of absorbable and metallic screws in the fixation of distal tibiofibular syndesmosis injuries: mid-term follow-up.

    PubMed

    Sun, H; Luo, C F; Zhong, B; Shi, H P; Zhang, C Q; Zeng, B F

    2014-04-01

    Our aim was to compare polylevolactic acid screws with titanium screws when used for fixation of the distal tibiofibular syndesmosis at mid-term follow-up. A total of 168 patients, with a mean age of 38.5 years (18 to 72) who were randomly allocated to receive either polylevolactic acid (n = 86) or metallic (n = 82) screws were included. The Baird scoring system was used to assess the overall satisfaction and functional recovery post-operatively. The demographic details and characteristics of the injury were similar in the two groups. The mean follow-up was 55.8 months (48 to 66). The Baird scores were similar in the two groups at the final follow-up. Patients in the polylevolactic acid group had a greater mean dorsiflexion (p = 0.011) and plantar-flexion of the injured ankles (p < 0.001). In the same group, 18 patients had a mild and eight patients had a moderate foreign body reaction. In the metallic groups eight had mild and none had a moderate foreign body reaction (p < 0.001). In total, three patients in the polylevolactic acid group and none in the metallic group had heterotopic ossification (p = 0.246). We conclude that both screws provide adequate fixation and functional recovery, but polylevolactic acid screws are associated with a higher incidence of foreign body reactions. PMID:24692626

  3. Free Hand Insertion Technique of S2 Sacral Alar-Iliac Screws for Spino-Pelvic Fixation: Technical Note, Acadaveric Study

    PubMed Central

    Park, Jong-Hwa; Kim, Ki-Jeong; Jahng, Tae-Ahn

    2015-01-01

    A rigid spino-pelvic fixation to anchor long constructs is crucial to maintain the stability of long fusion in spinal deformity surgery. Besides obtaining immediate stability and proper biomechanical strength of constructs, the S2 alar-iliac (S2AI) screws have some more advantages. Four Korean fresh-frozen human cadavers were procured. Free hand S2AI screw placement is performed using anatomic landmarks. The starting point of the S2AI screw is located at the midpoint between the S1 and S2 foramen and 2 mm medial to the lateral sacral crest. Gearshift was advanced from the desired starting point toward the sacro-iliac joint directing approximately 20 angulation caudally in sagittal plane and 30 angulation horizontally in the coronal plane connecting the posterior superior iliac spine (PSIS). We made a S2AI screw trajectory through the cancellous channel using the gearshift. We measured caudal angle in the sagittal plane and horizontal angle in the coronal plane. A total of eight S2AI screws were inserted in four cadavers. All screws inserted into the iliac crest were evaluated by C-arm and naked eye examination by two spine surgeons. Among 8 S2AI screws, all screws were accurately placed (100%). The average caudal angle in the sagittal plane was 17.35.4. The average horizontal angle in the coronal plane connecting the PSIS was 32.01.8. The placement of S2AI screws using the free hand technique without any radiographic guidance appears to an acceptable method of insertion without more radiation or time consuming. PMID:26819698

  4. Biomechanical comparison of dynamic condylar screw and locking compression plate fixation in unstable distal femoral fractures: An in vitro study

    PubMed Central

    Singh, Ashutosh Kumar; Rastogi, Amit; Singh, Vakil

    2013-01-01

    Background: Distal femur fractures are difficult to manage and the selection of implant for internal fixation remains controversial. The objective of this study is to establish the relative strength of fixation of a distal femoral locking plate (DFLP) compared with the dynamic condylar screw (DCS) in the distal femur fractures. Materials and Methods: Study was conducted on 16 freshly harvested cadaveric distal femoral specimens, eight implanted with DCS and other eight with DFLP. The construct was made unstable by removing a standard sized medial wedge of 1 cm base (gap-osteotomy) beginning 6 cm proximal to the lateral joint line in distal metaphyseal region with the loss of medial buttress. Fatigue test was conducted under load control mode at the frequency of I Hz. Specimens were subjected to cyclic loading of 2 kN, under observation for 50,000 cycles or until failure/cutout, which ever occurred earlier. Results: In DFLP group, there was no implant failure and the average number of cycles sustained was 50,000. Six out of eight specimens completed 50,000 cycles and two failed in DCS group. The average number of cycles sustained by DCS was 46150. Though the bone quality as assessed by dual energy X-ray absorptiometry DEXA was comparable in both DFLP and DCS group (P = 0.06), none failed in DFLP group and subsidence was 1.02 0.34 mm (range: 0.60-1.32 mm), which was significantly 43% lower (P = 0.006) than subsidence in DCS group (1.82 0.58; range: 1.20-3.08 mm). The average stiffness of DCS group was 52.8 4.2 N/mm, which was significantly lower than average stiffness of locked condylar plate group (71.2 5.1 N/mm) (P = 0.02). Conclusions: DFLP fixation of the distal femur fractures resulted in stronger construct than the DCS fixation in both cyclic loading and ultimate strength in biomechanical testing of a simulated A3 distal femur fracture. PMID:24379469

  5. Allograft anterior tibialis tendon with bioabsorbable interference screw fixation in anterior cruciate ligament reconstruction.

    PubMed

    Caborn, David N M; Selby, Jeffrey B

    2002-01-01

    For a variety of reasons, bone-patellar tendon-bone and Achilles tendon allografts have been used more commonly in anterior cruciate ligament reconstruction. Soft-tissue allografts used mainly are the semitendinosus, gracilis, and occasionally the quadriceps tendons. The anterior tibialis tendon is a thick, strong tendon that can be prepared with one doubling of the graft, has a large cross-sectional area, and has been shown to be stronger than semitendinosus, gracilis, patellar tendon, and native anterior cruciate ligament. Use of allograft shortens surgical time, eliminates graft harvest-site morbidity, and allows for a large supply of grafts for repeat or multiple ligament procedures. This graft can be fixed to the femoral and tibial bone tunnels with bioabsorbable interference screws for a hardware-free, completely endoscopic procedure. Two- to 4-year results of allograft procedures are comparable to autograft procedures, and there have been no early failures with this described technique using anterior tibialis tendon. PMID:11774151

  6. Allograft anterior tibialis tendon with bioabsorbable interference screw fixation in anterior cruciate ligament reconstruction.

    TOXLINE Toxicology Bibliographic Information

    Caborn DN; Selby JB

    2002-01-01

    For a variety of reasons, bone-patellar tendon-bone and Achilles tendon allografts have been used more commonly in anterior cruciate ligament reconstruction. Soft-tissue allografts used mainly are the semitendinosus, gracilis, and occasionally the quadriceps tendons. The anterior tibialis tendon is a thick, strong tendon that can be prepared with one doubling of the graft, has a large cross-sectional area, and has been shown to be stronger than semitendinosus, gracilis, patellar tendon, and native anterior cruciate ligament. Use of allograft shortens surgical time, eliminates graft harvest-site morbidity, and allows for a large supply of grafts for repeat or multiple ligament procedures. This graft can be fixed to the femoral and tibial bone tunnels with bioabsorbable interference screws for a hardware-free, completely endoscopic procedure. Two- to 4-year results of allograft procedures are comparable to autograft procedures, and there have been no early failures with this described technique using anterior tibialis tendon.

  7. Evaluation of implant loosening following segmental pedicle screw fixation in adolescent idiopathic scoliosis: a 2 year follow-up with low-dose CT

    PubMed Central

    2014-01-01

    Background The long term radiological status of screw fixation following scoliosis surgery with all pedicle screw construct is not previously studied. Aim To evaluate the incidence of loosening (implant failure) evaluated with low-dose CT two years following scoliosis surgery. Study design Retrospective study. Methods 81 consecutive patients with adolescent idiopathic scoliosis (AIS), aged 18??3years at 2years follow-up (83% were female), subjected for scoliosis corrective surgery with all pedicle screw construct (total of 1666 screws) has been examined with plain radiography and with low dose CT 6weeks and 2years postoperatively. Results In 26 out of 81 (32%) patients there were signs of loosening of one or more screws, a maximum 3 screws. 47 out of 1666 (2.8%) screws showed evidence of loosening. Preoperative Cobb angle was 56 among patients with loosening compared with 53 among patients with no evidence of loosening (P?=?0.288). In males there were signs of loosening in 8 out of 14 (57%) and in females 18 out of 67 (27%), (P?=?0.027). Among cases with loosening, 14% had suboptimal screw placement at the first postoperative CT compared with 11% among patients with no evidence of loosening (P?=?0.254). One patient with a loosened L4 screw had neurological deficit and subjected for revision of the construct. Out of 26 patients with evidence of loosening, 5 patients reported minor pain or discomfort, 1 patient had a minor proximal junctional kyphosis of about 15 and 3 patients showed evidence of pull-out of 35mm at the upper end of the construct but no clinical complaint. With plain radiography loosening could be observed only in 11 out of 26 cases, 5 were in the lumbar region. Conclusions In a consecutive series of 81 cases with AIS who had underwent scoliosis surgery, one third showed, 2years after the intervention, minor screw loosening. Males were more prone to develop screw loosening. In CT system that enables low-dose protocol, CT is recommended for the evaluation of evidence of screw loosening. PMID:25177357

  8. Sudden cerebral infarction after interventional vertebral artery embolism for vertebral artery injury during removal of C1-C2 pedicle screw fixation: a case report

    PubMed Central

    Yang, Yi; Liu, Hao; Ma, Litai; Zeng, Jiancheng; Song, Yueming; Xie, Xiaodong

    2015-01-01

    Vertebral artery injury (VAI) is a rare but serious complication of cervical spine surgery. Instrumented posterior surgery of the upper cervical spine places the vertebral artery at the highest risk of injury. However, VAI during removal of cervical internal fixation is really rare and unexpected. We present a case of 52-year-old male patient who suffered VAI during removal of C1-C2 pedicle screw fixation. An interventional vertebral artery embolism was performed and the patient suffered a sudden cerebral infarction one day after interventional vertebral artery embolism. From this case, removal of upper cervical pedicle screws of malposition is not recommended if it is not really necessary for some other reasons. Interventional vertebral artery embolism is an effective and less invasive procedure than open ligation surgery in the treatment of haemorrhage resulted from VAI but potential risk of cerebral infarction should not be ignored. PMID:26629224

  9. Posterior decompression and short segmental pedicle screw fixation combined with vertebroplasty for Kmmells disease with neurological deficits

    PubMed Central

    ZHANG, GUANG-QUAN; GAO, YAN-ZHENG; ZHENG, JIA; LUO, JIAN-PING; TANG, CHAO; CHEN, SHU-LIAN; WANG, HONG-QIANG; LIU, KE; XIE, RUI-GANG

    2013-01-01

    The aim of this study was to investigate the treatment of Kmmells disease with neurological deficits and to determine whether intravertebral clefts are a pathognomonic sign of Kmmells disease. A total of 17 patients who had initially been diagnosed with Kmmells disease were admitted, one patient was excluded from this study. Posterior decompression and vertebroplasty for the affected vertebrae were conducted. Pedicle screw fixation and posterolateral bone grafts were performed one level above and one level below the affected vertebrae. Vertebral tissue was extracted for histopathological examination. The mean time of follow-up was 22 months (range, 18 to 42 months). The anterior and middle vertebral heights were measured on standing lateral radiographs prior to surgery, one day postoperatively and at final follow-up. The Cobb angle, the visual analog scale (VAS) and the Frankel classification were used to evaluate the effects of the surgery. The VAS, anterior and middle vertebral heights and the Cobb angle were improved significantly one day postoperatively and at the final follow-up compared with the preoperative examinations (P<0.05). No significant differences were observed between the one-day postoperative results and those at final follow-up (P>0.05). The neurological function of all patients was improved by at least one Frankel grade. All patients in this study exhibited intravertebral clefts, and postoperative pathology revealed bone necrosis. One patient (not included in this study) showed an intravertebral cleft, but the pathology report indicated a non-Hodgkins lymphoma. The intravertebral cleft sign is not pathognomonic of Kmmells disease. Posterior decompression with short-segment fixation and fusion combined with vertebroplasty is an effective treatment for Kmmells disease with neurological deficits. PMID:23403724

  10. Novel Pedicle Screw and Plate System Provides Superior Stability in Unilateral Fixation for Minimally Invasive Transforaminal Lumbar Interbody Fusion: An In Vitro Biomechanical Study

    PubMed Central

    Zhu, Qingan; Zhou, Yue; Li, Changqing; Liu, Huan; Huang, Zhiping; Shang, Jin

    2015-01-01

    Purpose This study aims to compare the biomechanical properties of the novel pedicle screw and plate system with the traditional rod system in asymmetrical posterior stabilization for minimally invasive transforaminal lumbar interbody fusion (MI-TLIF). We compared the immediate stabilizing effects of fusion segment and the strain distribution on the vertebral body. Methods Seven fresh calf lumbar spines (L3-L6) were tested. Flexion/extension, lateral bending, and axial rotation were induced by pure moments of 5.0 Nm and the range of motion (ROM) was recorded. Strain gauges were instrumented at L4 and L5 vertebral body to record the strain distribution under flexion and lateral bending (LB). After intact kinematic analysis, a right sided TLIF was performed at L4-L5. Then each specimen was tested for the following constructs: unilateral pedicle screw and rod (UR); unilateral pedicle screw and plate (UP); UR and transfacet pedicle screw (TFS); UP and TFS; UP and UR. Results All instrumented constructs significantly reduced ROM in all motion compared with the intact specimen, except the UR construct in axial rotation. Unilateral fixation (UR or UP) reduced ROM less compared with the bilateral fixation (UP/UR+TFS, UP+UR). The plate system resulted in more reduction in ROM compared with the rod system, especially in axial rotation. UP construct provided more stability in axial rotation compared with UR construct. The strain distribution on the left and right side of L4 vertebral body was significantly different from UR and UR+TFS construct under flexion motion. The strain distribution on L4 vertebral body was significantly influenced by different fixation constructs. Conclusions The novel plate could provide sufficient segmental stability in axial rotation. The UR construct exhibits weak stability and asymmetrical strain distribution in fusion segment, while the UP construct is a good alternative choice for unilateral posterior fixation of MI-TLIF. PMID:25807513

  11. Comparison of Intertrochanteric Fracture Fixation with Dynamic Hip Screw and Bipolar Hemiarthroplasty Techniques

    PubMed Central

    Emami, Mohamad; Manafi, Alireza; Hashemi, Behrooz; Nemati, Ali; Safari, Saeed

    2013-01-01

    Background: At present, there is no consensus on an appropriate treatment modality for intertrochanteric fractures in the elderly with background diseases. The aim of the present study was to compare treatment outcomes of intertrochanteric fractures reduced with dynamic hip screws (DHS) and bipolar hemiarthroplasty in elderly patients with background medical conditions. Methods: In this randomized clinical trial, 60 patients with intertrochanteric fractures, who were 45-60 years old, were randomly divided into DHS and bipolar groups. After treatment, the two groups were compared in relation to complications and mortality rates, functional status using the Harris Hip Score (HHS), range of movement and severity of pain using the visual analogue score (VAS). Results: HHS (869 vs. 757.6), range of flexion (10511 degrees vs. 9017 degrees) and external rotation (357 degrees vs. 207 degrees) were significantly higher in the bipolar group compared to the DHS group (P<0.05). However, there were no significant differences in pain severity between the two groups. Conclusion: Reduction of intertrochanteric fractures in elderly patients with background medical conditions is more effective and less problematic with the bipolar technique compared to DHS and is better tolerated by patients, because this technique is associated with improvements in functional status and hip joint movement range. PMID:25207277

  12. CT Morphometric Analysis to Determine the Anatomical Basis for the Use of Transpedicular Screws during Reconstruction and Fixations of Anterior Cervical Vertebrae

    PubMed Central

    Chen, Chun; Ruan, Dike; Wu, Changfu; Wu, Weidong; Sun, Peidong; Zhang, Yuanzhi; Wu, Jigong; Lu, Sheng; Ouyang, Jun

    2013-01-01

    Background Accurate placement of pedicle screw during Anterior Transpedicular Screw fixation (ATPS) in cervical spine depends on accurate anatomical knowledge of the vertebrae. However, little is known of the morphometric characteristics of cervical vertebrae in Chinese population. Methods Three-dimensional reconstructions of CT images were performed for 80 cases. The anatomic data and screw fixation parameters for ATPS fixation were measured using the Mimics software. Findings The overall mean OPW, OPH and PAL ranged from 5.81 to 7.49 mm, 7.77 to 8.69 mm, and 33.40 to 31.13 mm separately, and SPA was 93.54 to 109.36 degrees from C3 to C6, 104.99 degrees at C7, whereas, 49.00 to 32.26 degrees from C4 to C7, 46.79 degrees at C3 (TPA). Dl/rSIP had an increasing trend away from upper endplate with mean value from 1.87 to 5.83 mm. Dl/rTIP was located at the lateral portion of the anterior cortex of vertebrae for C3 to C5 and ipsilateral for C6 to C7 with mean value from −2.70 to −3.00 mm, and 0.17 to 3.18 mm. The entrance points for pedicular screw insertion for C3 to C5 and C6 to C7 were recommended −2∼−3 mm and 0–4 mm from the median sagittal plane, respectively, 1–4 mm and 5–6 mm from the upper endplate, with TPA being 46.79–49.00 degrees and 40.89–32.26 degrees, respectively, and SPA being 93.54–106.69 degrees and 109.36–104.99 degrees, respectively. The pedicle screw insertion diameter was recommended 3.5 mm (C3 and C4), 4.0 mm (C5 to C7), and the pedicle axial length was 21–24 mm for C3 to C7 for both genders. However, the ATPS insertion in C3 should be individualized given its relatively small anatomical dimensions. Conclusions The data provided a morphometric basis for the ATPS fixation technique in lower cervical fixation. It will help in preoperative planning and execution of this surgery. PMID:24349038

  13. A cementless, elastic press-fit socket with and without screws

    PubMed Central

    2012-01-01

    Background The acetabular component has remained the weakest link in hip arthroplasty regarding achievement of long-term survival. Primary fixation is a prerequisite for long-term performance. For this reason, we investigated the stability of a unique cementless titanium-coated elastic monoblock socket and the influence of supplementary screw fixation. Patient and methods During 2006–2008, we performed a randomized controlled trial on 37 patients (mean age 63 years (SD 7), 22 females) in whom we implanted a cementless press-fit socket. The socket was implanted with additional screw fixation (group A, n = 19) and without additional screw fixation (group B, n = 18). Using radiostereometric analysis with a 2-year follow-up, we determined the stability of the socket. Clinically relevant migration was defined as > 1 mm translation and > 2º rotation. Clinical scores were determined. Results The sockets without screw fixation showed a statistically significantly higher proximal translation compared to the socket with additional screw fixation. However, this higher migration was below the clinically relevant threshold. The numbers of migratory sockets were not significantly different between groups. After the 2-year follow-up, there were no clinically relevant differences between groups A and B regarding the clinical scores. 1 patient dropped out of the study. In the others, no sockets were revised. Interpretation We found that additional screw fixation is not necessary to achieve stability of the cementless press-fit elastic RM socket. We saw no postoperative benefit or clinical effect of additional screw fixation. PMID:23083434

  14. New Technique for C1 Double-Door Laminoplasty Using Allograft Spacers and Titanium Miniplate Screw Fixation: Technical Report.

    PubMed

    Kim, Seok Woo; Lee, Jae-Hoo; Lee, Ho-Won; Oh, Jae-Keun; Kwak, Yoon-Hae

    2016-03-01

    Although conventional C1 laminectomy is the gold standard for decompression at the atlas, it provides little space for the bone graft to fuse. The fusion area can be extended cranially up to the occipital bone, but it requires sacrificing the function of the craniocervical junction. To date, no reports have focused on surgical techniques for successful decompression and fusion without disruption of the posterior C1 arch while providing enough room for the bone graft to fuse. This study introduces a new technique for C1-C2 fusion and C1 double-door laminoplasty in patients with C1-C2 instability, canal stenosis, and cervical spondylotic myelopathy. A 66-year-old man who had undergone C1-C2 fusion at a local clinic 2 years earlier visited our hospital due to progressive myelopathy. A preoperative computed tomography (CT) scan showed the tip of the odontoid process, extending into the spinal canal. On the axial view of T2-weighted magnetic resonance images, the tip of the odontoid process significantly compressed the spinal cord on the left side. The atlantodental interval was 7?mm on radiography; however, C1-C2 instability was not evident on flexion-extension X-rays due to the previous screw fixation. The patient underwent C1-C2 decompression and fusion surgery with our new surgical technique. The segmental screws were repositioned at C1 and C2, and we performed C1 double-door laminoplasty augmented with an allograft spacer and a titanium miniplate. A marked reduction was seen at postoperative radiograph and CT scan. Neurologic symptoms were relieved dramatically after surgery without any discomfort. No complications were noted. We introduced a new surgical technique that allows bone grafting, decompression, and fusion to be performed without disruption of the posterior C1 arch in the event of C1-C2 canal stenosis combined with instability. This technique may be indicated for other conditions that cause instability and stenosis at the C1-C2 area. PMID:26689563

  15. Segmental correction of adolescent idiopathic scoliosis by all-screw fixation method in adolescents and young adults. minimum 5 years follow-up with SF-36 questionnaire

    PubMed Central

    2012-01-01

    Background In our institution, the fixation technique in treating idiopathic scoliosis was shifted from hybrid fixation to the all-screw method beginning in 2000. We conducted this study to assess the intermediate -term outcome of all-screw method in treating adolescent idiopathic scoliosis (AIS). Methods Forty-nine consecutive patients were retrospectively included with minimum of 5-year follow-up (mean, 6.1; range, 5.1-7.3 years). The average age of surgery was 18.5 5.0 years. We assessed radiographic measurements at preoperative (Preop), postoperative (PO) and final follow-up (FFU) period. Curve correction rate, correction loss rate, complications, accuracy of pedicle screws and SF-36 scores were analyzed. Results The average major curve was corrected from 58.0 13.0 Preop to 16.0 9.0 PO(p < 0.0001), and increased to 18.4 8.6(p = 0.12) FFU. This revealed a 72.7% correction rate and a correction loss of 2.4 (3.92%). The thoracic kyphosis decreased little at FFU (22 12 to 20 6, (p = 0.25)). Apical vertebral rotation decreased from 2.1 0.8 PreOP to 0.8 0.8 at FFU (Nash-Moe grading, p < 0.01). Among total 831 pedicle screws, 56 (6.7%) were found to be malpositioned. Compared with 2069 age-matched Taiwanese, SF-36 scores showed inferior result in 2 variables: physical function and role physical. Conclusion Follow-up more than 5 years, the authors suggest that all-screw method is an efficient and safe method. PMID:22340624

  16. Biomechanical comparison of supplemental posterior fixations for two-level anterior lumbar interbody fusion.

    PubMed

    Wang, Mei; Tang, Shu-Jie; McGrady, Linda M; Rao, Raj D

    2013-03-01

    Posterior instrumentations have been used to supplement anterior lumbar interbody fusion with cages. Biomechanical studies on single-level anterior lumbar interbody fusion show that stand-alone cages supplemented with posterior translaminar facet or transfacet screw fixation exhibit comparable stability to those supplemented with pedicle screw/rod fixation, while stability of multilevel anterior lumbar interbody fusion remains mostly unknown. The objectives of this study are to compare the stabilization of three supplemental posterior fixations to two-level anterior lumbar interbody fusion, including translaminar facet fixation, transfacet screw fixation, and pedicle screw/rod fixation. Flexibility tests were conducted on fresh-frozen calf spines with moment up to 8.5 N m in flexion, extension, lateral bending, and axial rotation. Each specimen was tested at three stages: intact, anterior lumbar interbody fusion using Polyetheretherketone (PEEK) interbody cage at L3-L4 and L4-L5, and the same anterior lumbar interbody fusion plus one of the three supplemental posterior fixations. The addition of the supplemental posterior fixation increased stiffness at the fusion levels significantly in flexion (9.9 times), extension (5.4 times), and lateral bending (4.1 times). The pedicle screw/rod and translaminar screw fixations provide approximately 40% higher stiffness than the transfacet screw in lateral bending. The pedicle screw/rod fixation also displayed a trend of superior fixation in extension. Supplemental posterior fixation significantly improved stability of two-level anterior lumbar interbody fusion when compared to the stand-alone cages. Pedicle screw/rod system is still the "gold standard" in providing supplemental stability. However, both translaminar facet screws and transfacet screws are good alternatives to provide adequate fixation. PMID:23662340

  17. Arthroscopic Bioabsorbable Screw Fixation of Unstable Osteochondritis Dissecans in Adolescents: Clinical Results, Magnetic Resonance Imaging, and Second-Look Arthroscopic Findings

    PubMed Central

    Chun, Keun Churl; Kim, Kwang Mee; Jeong, Ki Joon; Lee, Yong Chan; Kim, Jeong Woo

    2016-01-01

    Background This study aimed to evaluate the clinical and radiological outcomes of arthroscopic bioabsorbable screw fixation in osteochondritis dissecans (OCD) in adolescent patients with unstable lesions causing pain. Methods The study included 11 patients (10 males and 1 female) with OCD who underwent arthroscopic bioabsorbable screw fixation between July 2007 and February 2014 and were available for follow-up for more than 12 months. The mean age at diagnosis was 16.3 years (range, 11 to 19 years), and the average follow-up period was 51 months (range, 12 to 91 months). Clinical results were evaluated using the Knee Injury and Osteoarthritis Outcome Score (KOOS), Lysholm knee score, and International Knee Documentation Committee (IKDC) score measured before surgery and at follow-up. Functional evaluation was made using the Tegner activity scale. Magnetic resonance imaging (MRI) and second-look arthroscopy were performed at the 12-month follow-up. Results Between the preoperative assessment and follow-up, improvements were seen in the KOOS (range, 44.9 to 88.1), Lysholm knee score (range, 32.6 to 82.8), and IKDC score (range, 40.8 to 85.6). The Tegner activity scale also improved from 2.8 to 6.1. Based on postoperative MRI, there were eight Dipaola grade I cases and three grade II cases. No complications due to fixation failure developed in any case. Second-look arthroscopy at 12 months postoperatively revealed that the lesion was covered with cartilage in all cases. Conclusions For unstable OCD lesions causing pain in adolescents, arthroscopic bioabsorbable screw fixation provided favorable outcomes with reduced pain and restoration of movement. Therefore, it should be considered as an effective treatment for OCD. PMID:26929800

  18. Limited Unilateral Decompression and Pedicle Screw Fixation with Fusion for Lumbar Spinal Stenosis with Unilateral Radiculopathy: A Retrospective Analysis of 25 Cases

    PubMed Central

    Zhang, Li; Miao, Hai-xiong; Wang, Yong; Chen, An-fu; Zhang, Tao

    2015-01-01

    Objective Lumbar spinal stenosis is conventionally treated with surgical decompression. However, bilateral decompression and laminectomy is more invasive and may not be necessary for lumbar stenosis patients with unilateral radiculopathy. We aimed to report the outcomes of unilateral laminectomy and bilateral pedicle screw fixation with fusion for patients with lumbar spinal stenosis and unilateral radiculopathy. Methods Patients with lumbar spinal stenosis with unilateral lower extremity radiculopathy who received limited unilateral decompression and bilateral pedicle screw fixation were included and evaluated using visual analog scale (VAS) pain and the Oswestry Disability Index (ODI) scores preoperatively and at follow-up visits. Ligamentum flavum thickness of the involved segments was measured on axial magnetic resonance images. Results Twenty-five patients were included. The mean preoperative VAS score was 6.6±1.6 and 4.6±3.1 for leg and back pain, respectively. Ligamentum flavum thickness was comparable between the symptomatic and asymptomatic side (p=0.554). The mean follow-up duration was 29.2 months. The pain in the symptomatic side lower extremity (VAS score, 1.32±1.2) and the back (VAS score, 1.75±1.73) significantly improved (p=0.000 vs. baseline for both). The ODI improved significantly postoperatively (6.60±6.5; p=0.000 vs. baseline). Significant improvement in VAS pain and ODI scores were observed in patients receiving single or multi-segment decompression fusion with fixation (p<0.01). Conclusion Limited laminectomy and unilateral spinal decompression followed by bilateral pedicle screw fixation with fusion achieves satisfactory outcomes in patients with spinal stenosis and unilateral radiculopathy. This procedure is less damaging to structures that are important for maintaining posterior stability of the spine. PMID:26279816

  19. Minimally Invasive Sinus Tarsi Approach With Cannulated Screw Fixation Combined With Vacuum-Assisted Closure for Treatment of Severe Open Calcaneal Fractures With Medial Wounds.

    PubMed

    Zhang, Taiyuan; Yan, Yan; Xie, Xinmin; Mu, Weidong

    2016-01-01

    The aim of our prospective study was to investigate the clinical results and advantages of a minimally invasive sinus tarsi approach with cannulated screw fixation combined with vacuum-assisted closure for the treatment of severe open calcaneal fractures with medial wounds. A total of 31 patients (32 feet) with open calcaneal fractures who were admitted to our hospital from January 2008 to May 2013 were selected for the study and randomly divided into 2 groups: the cannulated screw group (n = 16 patients, 16 feet) and the plate group (n = 15 patients, 16 feet). The Böhler and Gissane angles were compared before and after surgery. The clinical results were evaluated using according to the American Orthopaedic Foot and Ankle Society ankle-hindfoot scale and the rate of infection. The follow-up duration for all patients ranged from 10 to 36 (mean 24) months. No statistically significant differences were found in the radiologic indicators, incidence of early postoperative complications, or American Orthopaedic Foot and Ankle Society ankle-hindfoot scores (p > .05) between the 2 groups. However, a statistically significant difference was seen in the duration of hospitalization (p < .05) between the 2 groups. A minimally invasive sinus tarsi approach with cannulated screw fixation combined with vacuum-assisted closure is an effective method for the treatment of severe open calcaneal fractures with medial wounds. It provides good reduction and requires fewer days of hospitalization. PMID:26372552

  20. Pedicular and Extrapedicular Morphometric Analysis in the Korean Population : Computed Tomographic Assessment Relevance to Pedicle and Extrapedicle Screw Fixation in the Thoracic Spine

    PubMed Central

    Kim, Jun-Hak; Choi, Gyeong-Mi; Chang, In-Bok; Ahn, Sung-Ki; Song, Joon-Ho

    2009-01-01

    Objective To evaluate the anatomical parameters that must be considered when performing thoracic transpedicular or extrapedicular screw fixation. Methods We selected 958 vertebrae (1,916 pedicles) from 98 patients for analysis. Eight parameters were measured from CT scans : the transverse outer pedicular diameter, transverse inner pedicular diameter, length, angle, chord length of the pedicles and the transverse width, angle, and chord length of the pedicle-rib units. Results The age of the patients ranged from 21 to 82 years (mean : 48.2 years) and there were 57 men and 41 women. The narrowest transverse outer pedicular diameter was at T5 (4.4 mm). The narrowest pedicle length was at T1 (15.9 mm). For pedicle angle, T1 was 31.6 degrees, which was the most convergent angle, and it showed the tendency of the lower the level, the lesser the convergent angle. The chord length showed a horizontal pattern with similar values at all levels. For the PRU width, T5 showed a similar pattern to the pedicle width at 13.4 mm. For the PRU angle, T1 was the largest angle at 46.2 degrees and the tendency was the lower the level, the narrower the angle. For chord length, T1 was the shortest at 46.9 mm and T8 was the longest at 60.1 mm. Conclusion When transpedicular screw fixations carried out at the mid-thoracic level, special care must be taken because there is a high chance of danger of medial wall violation. In these circumstances, extrapedicular screw fixation may be considered as an alternative treatment. PMID:19844615

  1. Pedicle Screw Configuration for Thoracolumbar Burst Fracture Treatment: Short versus Long Posterior Fixation Constructs with and without Anterior Column Augmentation

    PubMed Central

    Peters, Todd; Hussain, Mir; Khalil, Saif

    2014-01-01

    Study Design An in-vitro study. Purpose The current study is aimed at investigating the differences in stability between short posterior fixation (SPF), hybrid posterior fixation (HPF), and long posterior fixation (LPF) with and without anterior column augmentation using calcium phosphate bone cement (CaP) for treating burst fractures (BFs). Overview of Literature The ideal treatment for thoracolumbar BF is controversial regarding the use of short or LPF constructs. Methods Seven human thoracolumbar spines (T9-L4) were tested on a six degree of freedom spine simulator in three physiologic planes, flexion-extension (FE), lateral bending (LB), and axial rotation (AR). Tested surgical constructs included the following: intact, injury (BF), SPF (T12-L2), HPF (T11-L2), LPF (T11-L3), SPF+CaP, HPF+CaP, LPF+CaP, and CaP alone (CaP). Range of motion (ROM) was recorded at T12-L2 in FE, LB, and AR. Results The reduction in mean ROM trended as follows: LPF>HPF>SPF. Only LPF constructs and HPF with anterior column augmentation significantly reduced mean ROM in FE and LB compared to the intact state. All instrumented constructs (SPF, HPF, and LPF) significantly reduced ROM in FE and LB compared to the injured condition. Furthermore, the instrumented constructs did not provide significant rotational stability. Injecting CaP provided minimal additional stability. Conclusions For the injury created, LPF and HPF provided better stability than SPF with and without anterior column augmentation. Therefore, highly unstable fractures may require extended, long or hybrid fusion constructs for optimum stability. PMID:24596603

  2. [A new design of internal fixation for scoliosis-multi-screw fixed distractor-compressor via the vertebral pedicle and its clinical application].

    PubMed

    Chi, Y L

    1991-08-01

    A new scoliotone, which is made up of screws, sockets, clamps, distraction rod and compression rod, was used stabilize immobilization of the spine in 10 cases. This scoliotone can produce free motion in three different levels, and has a strong power of fixation, distraction, compression and antitraction. In 10 cases when the patient's spinal curvature (cobb's angle) was less than 50 degrees, the average range of correction was 78.2% and the correction rate of kyphosis peak was 90%. When the spinal curvature was between 50 to 100 degrees, the average range of correction was 68.2%, and the correction rate of kyphosis peak was 87.7%. If the spinal curvature was more than 100 degrees, the average range of correction rate of kyphosis peak was 82%. After the operation, the patient might not be immobilized. In this paper, the biomechanical features of the vertebral arch, internal fixation and correction of kyphosis peak were discussed. PMID:1813237

  3. Definition of a safe zone for antegrade lag screw fixation of fracture of posterior column of the acetabulum by 3D technology.

    PubMed

    Feng, Xiaoreng; Zhang, Sheng; Luo, Qiang; Fang, Jintao; Lin, Chaowen; Leung, Frankie; Chen, Bin

    2016-03-01

    The objective of this study was to define a safe zone for antegrade lag screw fixation of fracture of posterior column of the acetabulum using a novel 3D technology. Pelvic CT data of 59 human subjects were obtained to reconstruct three-dimensional (3D) models. The transparency of 3D models was then downgraded along the axial perspective (the view perpendicular to the cross section of the posterior column axis) to find the largest translucent area. The outline of the largest translucent area was drawn on the iliac fossa. The line segments of OA, AB, OC, CD, the angles of OAB and OCD that delineate the safe zone (ABDC) were precisely measured. The resultant line segments OA, AB, OC, CD, and angles OAB and OCD were 28.46mm(13.15-44.97mm), 45.89mm (34.21-62.85mm), 36.34mm (18.68-55.56mm), 53.08mm (38.72-75.79mm), 37.44° (24.32-54.96°) and 55.78° (43.97-79.35°) respectively. This study demonstrates that computer-assisted 3D modelling techniques can aid in the precise definition of the safe zone for antegrade insertion of posterior column lag screws. A full-length lag screw can be inserted into the zone (ABDC), permitting a larger operational error. PMID:26867979

  4. Unilateral C1 Lateral Mass and C2 Pedicle Screw Fixation for Atlantoaxial Instability in Rheumatoid Arthritis Patients: Comparison with the Bilateral Method

    PubMed Central

    Paik, Seung-Chull; Bak, Koang Hum; Ryu, Jeil; Choi, Kyu-Sun

    2015-01-01

    Objective Bilateral C1 lateral mass and C2 pedicle screw fixation (C1LM-C2P) is an ideal technique for correcting atlantoaxial instability (AAI). However, the inevitable situation of vertebral artery injury or unfavorable bone structure may necessitate the use of unilateral C1LM-C2P. This study compares the fusion rates of the C1 lateral mass and C2 pedicle screw in the unilateral and bilateral methods. Methods Over five years, C1LM-C2P was performed in 25 patients with AAI in our institute. Preoperative studies including cervical X-ray, three-dimensional computed tomography (CT), CT angiogram, and magnetic resonance imaging were performed. To evaluate bony fusion, measurements of the atlanto-dental interval (ADI) and CT scans were performed in the preoperative period, immediate postoperative period, and postoperatively at 1, 3, 6, and 12 months. Results Unilateral C1LM-C2P was performed in 11 patients (44%). The need to perform unilateral C1LM-C2P was due to anomalous course of the vertebral artery in eight patients (73%) and severe degenerative arthritis in three patients (27%). The mean ADI in the bilateral group was 2.09 mm in the immediate postoperative period and 1.75 mm in 12-months postoperatively. The mean ADI in the unilateral group was 1.82 mm in the immediate postoperative period and 1.91 mm in 12-months postoperatively. Comparison of ADI measurements showed no significant differences in either group (p=0.893), and the fusion rate was 100% in both groups. Conclusion Although bilateral C1LM-C2P is effective for AAI from a biomechanical perspective, unilateral screw fixation is a useful alternative in patients with anatomical variations. PMID:26180616

  5. Bilateral C1C2 Transarticular Screw and C1 Laminar Hook Fixation and Bone Graft Fusion for Reducible Atlantoaxial Dislocation: A Seven-Year Analysis of Outcome

    PubMed Central

    Guo, Xiang; Ni, Bin; Xie, Ning; Lu, Xuhua; Guo, Qunfeng; Lu, Ming

    2014-01-01

    Background Bilateral C1-2 transarticular screw and C1 laminar hook fixation was developed on the basis of transarticular screws fixation. The modified technique has showed a better biomechanical stability than established techniques in previous study. However, long-term (minimum follow-up 7 years) outcomes of patients with reducible atlantoaxial dislocation who underwent this modified fixation technique have not still been reported. Methods A retrospective study was conducted to evaluate the outcome of 36 patients who underwent this modified technique. Myelopathy was assessed using the Ranawat myelopathy score and Myelopathy Disability Index. Pain scores were assessed using Visual Analogue Scale. Radiological imaging was assessed and the following data were extracted: the atlantodental intervals, the space available for cord, presence of spinal cord signal change on T2 weighted image, C1C2 angle, C2C7 angle and fusion rates. Findings All patients achieved a minimum seven-year follow up. 95% patients with neck and suboccipital pain improved after surgery; in their Visual Analogue pain scores, there was a greater than 50% improvement in their VAS scores with a drop of 5 points on the VAS (P<0.05). 92% of patients improved in the Ranawat myelopathy grade; the Myelopathy Disability Index assessment showed a preoperative mean score of 35.62 with postoperative mean 12.75(P<0.05). There was not any significant atlantoaxial instability at each follow-up time. The space available for cord increased in all patients. Postoperative sagittal kyphosis of the subaxial spine was not observed. After six months after surgery, bone grafts of all patients were fused. No complications related to surgery were found in the period of follow-up. Conclusions The long-term outcomes of this case series demonstrate that under the condition of thorough preoperative preparations, bilateral C1C2 transarticular screw and C1 laminar hook fixation and bone graft fusion is a reliable posterior atlantoaxial fusion technique for reducible atlantoaxial dislocation. PMID:24498163

  6. Hybrid Fixation of Tibial Eminence Fractures in Skeletally Immature Patients

    PubMed Central

    Gans, Itai; Babatunde, Oladapo M.; Ganley, Theodore J.

    2013-01-01

    Tibial eminence fractures most commonly occur in children and adolescents. When treating displaced fractures of the tibial eminence, some surgeons prefer screw fixation whereas others prefer suture fixation. The ultimate goal is to limit morbidity through early return to range of motion and activity. In this technical note, we describe 2 hybrid fixation techniques for fixing tibial eminence fractures, one for type III and the other for type IV fractures. The first technique (variation A) is used to treat type III fractures and combines use of both a bioabsorbable compression screw and suture for fixation. The second technique (variation B) is used to treat type IV fractures and combines use of both a bioabsorbable compression screw and shoulder anchor fixation. We have found that these methods provide efficient, secure, and reliable fixation using standard techniques common to arthroscopic surgery. In addition, the growth plates are spared in children and adolescents, and the need for reoperation to remove hardware is eliminated. PMID:24265991

  7. Comparison of Head Center Position and Screw Fixation Options Between a Jumbo Cup and an Offset Center of Rotation Cup in Revision Total Hip Arthroplasty: A Computer Simulation Study.

    PubMed

    Faizan, Ahmad; Black, Brandon J; Fay, Brian D; Heffernan, Christopher D; Ries, Michael D

    2016-01-01

    Jumbo acetabular cups are commonly used in revision total hip arthroplasty (THA). A straightforward reaming technique is used which is similar to primary THA. However, jumbo cups may also be associated with hip center elevation, limited screw fixation options, and anterior soft tissue impingement. A partially truncated hemispherical shell was designed with an offset center of rotation, thick superior rim, and beveled anterior and superior rims as an alternative to a conventional jumbo cup. A three dimensional computer simulation was used to assess head center position and safe screw trajectories. Results of this in vitro study indicate that a modified hemispherical implant geometry can reduce head center elevation while permitting favorable screw fixation trajectories into the pelvis in comparison to a conventional jumbo cup. PMID:26253481

  8. Optimizing Stability in Femoral Neck Fracture Fixation.

    PubMed

    Ye, Ye; Hao, Jiandong; Mauffrey, Cyril; Hammerberg, E Mark; Stahel, Philip F; Hak, David J

    2015-10-01

    Optimizing stability of femoral neck fracture fixation is important in obtaining a successful outcome. The mechanical problems and strategies for achieving optimal stability differ depending on patients' age and degree of osteoporosis. Femoral neck fractures in younger adults usually result from high-energy trauma and have a vertical fracture pattern. Strategies for optimizing fixation stability in this group include placing additional screws at right angles to the fracture plane and medial buttress plate augmentation. In elderly patients, screw position relative to the intact cortical femoral neck bone is of critical importance. Additional strategies for optimizing fixation stability in this group include the concept of length stable fixation, use of adjunctive calcium phosphate cement, and use of novel fixed angle fixation implants. PMID:26488776

  9. Minimally Invasive Unilateral vs. Bilateral Pedicle Screw Fixation and Lumbar Interbody Fusion in Treatment of Multi-Segment Lumbar Degenerative Disorders

    PubMed Central

    Liu, Xiaoyang; Li, Guangrun; Wang, Jiefeng; Zhang, Heqing

    2015-01-01

    Background The choice for instrumentation with minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF) in treatment of degenerative lumbar disorders (DLD) remains controversial. The goal of this study was to investigate clinical outcomes in consecutive patients with multi-segment DLD treated with unilateral pedicle screw (UPS) vs. bilateral pedicle screw (BPS) instrumented TLIF. Material/Methods Eighty-four consecutive patients who had multi-level MIS-TLIF were retrospectively reviewed. All data were collected to compare the clinical outcomes between the 2 groups. Results Both groups showed similar clinical function scores in VAS and ODI. The two groups differed significantly in operative time (P<0.001), blood loss (P<0.001), and fusion rate (P=0.043), respectively. Conclusions This study demonstrated similar clinical outcomes between UPS fixation and BPS procedure after MIS-TLIF for multi-level DLD. Moreover, UPS technique was superior in operative time and blood loss, but represented lower fusion rate than the BPS construct did. PMID:26603050

  10. Midline Lumbar Fusion with Cortical Bone Trajectory Screw

    PubMed Central

    MIZUNO, Masaki; KURAISHI, Keita; UMEDA, Yasuyuki; SANO, Takanori; TSUJI, Masanori; SUZUKI, Hidenori

    2014-01-01

    A novel cortical bone trajectory (CBT) screw technique provides an alternative fixation technique for lumbar spine. Trajectory of CBT screw creates a caudo-cephalad path in sagittal plane and a medio-lateral path in axial plane, and engages cortical bone in the pedicle. The theoretical advantage is that it provides enhanced screw grip and interface strength. Midline lumbar fusion (MIDLF) is composed of posterior mid-line approach, microsurgical laminectomy, and CBT screw fixation. We adopted the MIDLF technique for lumbar spondylolisthesis. Advantages of this technique include that decompression and fusion are available in the same field, and it minimizes approach-related damages. To determine whether MIDLF with CBT screw is as effective as traditional approach and it is minimum invasive technique, we studied the clinical and radiological outcomes of MIDLF. Our results indicate that MIDLF is effective and minimum invasive technique. Evidence of effectiveness of MIDLF is that patients had good recovery score, and that CBT screw technique was safety in clinical and stable in radiological. MIDLF with CBT screw provides the surgeon with additional options for fixation. This technique is most likely to be useful for treating lumbar spondylolisthesis in combination with midline decompression and insertion of an interbody graft, such as the transforaminal lumbar interbody fusion or posterior lumbar interbody fusion techniques. PMID:25169139

  11. Bony Healing of Unstable Thoracolumbar Burst Fractures in the Elderly Using Percutaneously Applied Titanium Mesh Cages and a Transpedicular Fixation System with Expandable Screws

    PubMed Central

    Eschler, Anica; Ender, Stephan Albrecht; Schiml, Katharina; Mittlmeier, Thomas; Gradl, Georg

    2015-01-01

    Introduction There is a high incidence of vertebral burst fractures following low velocity trauma in the elderly. Treatment of unstable vertebral burst fractures using the same principles like in stable vertebral burst fractures may show less favourable results in terms of fracture reduction, maintenance of reduction and cement leakage. In order to address these shortcomings this study introduces cementless fixation of unstable vertebral burst fractures using internal fixators and expandable intravertebral titanium mesh cages in a one-stage procedure via minimum-invasive techniques. Material and Methods A total of 16 consecutive patients (median age 76 years, range 5894) with unstable thoracolumbar burst fractures and concomitant osteoporosis were treated by an internal fixator inserted via minimum invasive technique one level above and below the fractured vertebra. Fracture reduction was achieved and maintained by transpedicular placement of two titanium mesh cages into the fractured vertebral body during the same procedure. Intra- and postoperative safety of the procedure as well as analysis of reduction quality was analysed by 3D C-arm imaging or CT, respectively. Clinical and radiographic follow-up averaged 10.4 months (range 4.524.5). Results Stabilization of the collapsed vertebral body was achieved in all 16 cases without any intraoperative complication. Surgical time averaged 1026.6 minutes (71194). The postoperative kyphotic angle (KA) and Cobb angle revealed significant improvements (KA 13.7 to 7.4, p<0.001; Cobb 9.6 to 6.0, p<0.002) with partial loss of reduction at final follow-up (KA 8.3, Cobb 8.7). VAS (Visual Analogue Scale) improved from 7.6 to 2.6 (p<0.001). Adjacent fractures were not observed. One minor (malposition of pedicle screw) complication was encountered. Conclusion Cementless fixation of osteoporotic burst fractures revealed substantial pain relief, adequate maintenance of reduction and a low complication rate. Bony healing after unstable osteoporotic burst fractures is possible. Trial Registration www.germanctr.de DRKS00005657 PMID:25706642

  12. Fatigue strength of common tibial intramedullary nail distal locking screws

    PubMed Central

    Griffin, Lanny V; Harris, Robert M; Zubak, Joseph J

    2009-01-01

    Background Premature failure of either the nail and/or locking screws with unstable fracture patterns may lead to angulation, shortening, malunion, and IM nail migration. Up to thirty percent of all unreamed nail locking screws can break after initial weight bearing is allowed at 810 weeks if union has not occurred. The primary problem this presents is hardware removal during revision surgery. The purposes of our study was to evaluate the relative fatigue resistance of distal locking screws and bolts from representative manufacturers of tibial IM nail systems, and develop a relative risk assessment of screws and materials used. Evaluations included quantitative and qualitative measures of the relative performance of these screws. Methods Fatigue tests were conducted to simulate a comminuted fracture that was treated by IM nailing assuming that all load was carried by the screws. Each screw type was tested ten times in a single screw configuration. One screw type was tested an additional ten times in a two-screw parallel configuration. Fatigue tests were performed using a servohydraulic materials testing system and custom fixturing that simulated screws placed in the distal region of an appropriately sized tibial IM nail. Fatigue loads were estimated based on a seventy-five kilogram individual at full weight bearing. The test duration was one million cycles (roughly one year), or screw fracture, whichever occurred first. Failure analysis of a representative sample of titanium alloy and stainless steel screws included scanning electron microscopy (SEM) and quantitative metallography. Results The average fatigue life of a single screw with a diameter of 4.0 mm was 1200 cycles, which would correspond roughly to half a day of full weight bearing. Single screws with a diameter of 4.5 mm or larger have approximately a 50 percent probability of withstanding a week of weight bearing, whereas a single 5.0 mm diameter screw has greater than 90 percent probability of withstanding more than a week of weight bearing. If two small diameter screws are used, our tests showed that the probability of withstanding a week of weight bearing increases from zero to about 20 percent, which is similar to having a single 4.5 mm diameter screw providing fixation. Conclusion Our results show that selecting the system that uses the largest distal locking screws would offer the best fatigue resistance for an unstable fracture pattern subjected to full weight bearing. Furthermore, using multiple screws will substantially reduce the risk of premature hardware failure. PMID:19371438

  13. [Arthroscopic and percutaneous bone screw techniques with a new screw system].

    PubMed

    Resch, H; Kathrein, A; Golser, K; Sperner, G

    1992-02-01

    A new screwdriver is presented with which small titanium screws can be introduced into a joint under arthroscopic guidance. The screws are centrally cannulated, 2.7 mm thick (thread diameter), and available with and without a washer (5 mm in diameter, serrated and convex, flexible but not removable). The screwdriver has a special screw-holding device which allows the screw to be grasped and released making it possible to remove a screw already implanted in the joint at an earlier time. This arthroscopic screwing system has been used in 81 cases to date. In 59 patients with shoulder instability, arthroscopic refixation of the detached labrum-capsule complex was performed. In the first 32 of these cases an intra-articular screwing technique was used and in the following 27 cases an extra-articular screwing technique was applied. In addition, in 9 patients a fractured and displaced greater tuberosity was reduced and fixated percutaneously under the guidance of an image intensifier by means of this screwdriver. Other fields of application were the knee joint (type III fracture of the intercondylar eminence in 5 patients) and the ankle (displaced fracture of the talus in 2 patients and osteochondritis dissecans in 1). Complications were seen only in the patients with shoulder instability who were treated by the intra-articular screwing technique (screw loosening in 4 patients). This was the reason why the intra-articular technique was replaced by the extra-articular method. Since that time no further complications caused by the screws have been seen. Redislocation of the shoulder joint occurred in 1 case 7 months after operation.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:1570537

  14. FIXATION OF SUPRACONDYLAR FEMORAL FRACTURES: A BIOMECHANICAL ANALYSIS COMPARING 95° BLADE PLATES AND DYNAMIC CONDYLAR SCREWS (DCS)

    PubMed Central

    Percope Andrade, Marco Antônio; Rodrigues, André Soares; Mendonça, Celso Junio; Santos Portela, Luiz Gustavo

    2015-01-01

    Objective: To determine, by means of comparative biomechanical tests, whether greater compressive load resistance and flexion is presented by 95° angled blade plates or by dynamic condylar screws (DCS), and to correlate the failure type presented during the tests with each type of plate. Methods: Sixty-five porcine femurs were subjected to 1 cm medial wedge osteotomy, in the metaphysis, to simulate an unstable supracondylar femoral fracture. Osteosynthesis was performed on these pieces: 35 were fixed using 95° lateral blade plates and 30 with DCS plates. Another variable studied was the failure type presented in each group, in an attempt to correlate this with the type of plate. Results: There were no statistically significant differences in biomechanical resistance between the two types of plates, or between the failure type and the plate type used for the osteosynthesis. Conclusion: The two types of plate behaved in a similar fashion. However, the angled blade plate proved to be superior to the DCS in the flexion test. No statistical difference in failure type or type of plate used was observed.

  15. Fixation using alternative implants for the treatment of hip fractures (FAITH): design and rationale for a multi-centre randomized trial comparing sliding hip screws and cancellous screws on revision surgery rates and quality of life in the treatment of femoral neck fractures

    PubMed Central

    2014-01-01

    Background Hip fractures are a common type of fragility fracture that afflict 293,000 Americans (over 5,000 per week) and 35,000 Canadians (over 670 per week) annually. Despite the large population impact the optimal fixation technique for low energy femoral neck fractures remains controversial. The primary objective of the FAITH study is to assess the impact of cancellous screw fixation versus sliding hip screws on rates of revision surgery at 24 months in individuals with femoral neck fractures. The secondary objective is to determine the impact on health-related quality of life, functional outcomes, health state utilities, fracture healing, mortality and fracture-related adverse events. Methods/Design FAITH is a multi-centre, multi-national randomized controlled trial utilizing minimization to determine patient allocation. Surgeons in North America, Europe, Australia, and Asia will recruit a total of at least 1,000 patients with low-energy femoral neck fractures. Using central randomization, patients will be allocated to receive surgical treatment with cancellous screws or a sliding hip screw. Patient outcomes will be assessed at one week (baseline), 10 weeks, 6, 12, 18, and 24 months post initial fixation. We will independently adjudicate revision surgery and complications within 24 months of the initial fixation. Outcome analysis will be performed using a Cox proportional hazards model and likelihood ratio test. Discussion This study represents major international efforts to definitively resolve the treatment of low-energy femoral neck fractures. This trial will not only change current Orthopaedic practice, but will also set a benchmark for the conduct of future Orthopaedic trials. Trial registration The FAITH trial is registered at ClinicalTrials.gov (Identifier NCT00761813). PMID:24965132

  16. Responses of soil nitrogen fixation to Spartina alterniflora invasion and nitrogen addition in a Chinese salt marsh

    PubMed Central

    Huang, Jingxin; Xu, Xiao; Wang, Min; Nie, Ming; Qiu, Shiyun; Wang, Qing; Quan, Zhexue; Xiao, Ming; Li, Bo

    2016-01-01

    Biological nitrogen fixation (BNF) is the major natural process of nitrogen (N) input to ecosystems. To understand how plant invasion and N enrichment affect BNF, we compared soil N-fixation rates and N-fixing microbes (NFM) of an invasive Spartina alterniflora community and a native Phragmites australis community in the Yangtze River estuary, with and without N addition. Our results indicated that plant invasion relative to N enrichment had a greater influence on BNF. At each N level, the S. alterniflora community had a higher soil N-fixation rate but a lower diversity of the nifH gene in comparison with the native community. The S. alterniflora community with N addition had the highest soil N-fixation rate and the nifH gene abundance across all treatments. Our results suggest that S. alterniflora invasion can increase soil N fixation in the high N-loading estuarine ecosystem, and thus may further mediate soil N availability. PMID:26869197

  17. Responses of soil nitrogen fixation to Spartina alterniflora invasion and nitrogen addition in a Chinese salt marsh.

    PubMed

    Huang, Jingxin; Xu, Xiao; Wang, Min; Nie, Ming; Qiu, Shiyun; Wang, Qing; Quan, Zhexue; Xiao, Ming; Li, Bo

    2016-01-01

    Biological nitrogen fixation (BNF) is the major natural process of nitrogen (N) input to ecosystems. To understand how plant invasion and N enrichment affect BNF, we compared soil N-fixation rates and N-fixing microbes (NFM) of an invasive Spartina alterniflora community and a native Phragmites australis community in the Yangtze River estuary, with and without N addition. Our results indicated that plant invasion relative to N enrichment had a greater influence on BNF. At each N level, the S. alterniflora community had a higher soil N-fixation rate but a lower diversity of the nifH gene in comparison with the native community. The S. alterniflora community with N addition had the highest soil N-fixation rate and the nifH gene abundance across all treatments. Our results suggest that S. alterniflora invasion can increase soil N fixation in the high N-loading estuarine ecosystem, and thus may further mediate soil N availability. PMID:26869197

  18. Percutaneous fixation of scaphoid fractures.

    PubMed

    Slade, J F; Jaskwhich, D

    2001-11-01

    The scaphoid proximal pole and waist fractures presented here were treated by a novel dorsal percutaneous technique with arthroscopic assistance. All fractures healed, with good final functional results and no complications. The advantages of the dorsal percutaneous approach to scaphoid fixation are: (1) the proximal-to-distal placement of the guide pin and screw allow for more precise placement along the central axis of the scaphoid, which decreases healing time and reduces risk of screw thread exposure. (2) The dorsal approach avoids injuring the vulnerable volar ligament anatomy. And (3) the insertion of the screw from the proximal to distal direction allows the more rigid fixation of proximal scaphoid fractures. Arthroscopy allows confirmation of fracture reduction and screw implantation as well as evaluation of concurrent ligament injuries not detected with standard imaging. Percutaneous K-wires act as joysticks to reduce and compress fracture fragments prior to fixation. The presented technique allows for early, rigid internal fixation with minimal associated morbidity. Patients successfully treated with this technique include those with stable and unstable acute fractures of the scaphoid at all locations, including the proximal pole. Nondisplaced fractures that present with delayed or fibrous union without evidence of avascular necrosis, cyst formation, or bony sclerosis may also be treated with this technique. This technique allows for faster rehabilitation and an earlier return to work or avocation without restriction once CT scan confirms a solid union. Some articles document extraordinary rapid healing by standard radiographs; however, we caution that scaphoid bone healing cannot accurately be determined without CT scan. Percutaneous, arthroscopically assisted internal fixation by a dorsal approach may be considered in all acute scaphoid fractures selected for surgical fixation. The dorsal guidewire permits dorsal and volar implantation of a cannulated screw along the central axis of the scaphoid. This technique permits the reduction of displaced fractures and the stable repair of fractures of the proximal pole. In addition, selected scaphoid fibrous union or delayed union may also be repaired, with realistic expectations of healing. The proven benefits of the percutaneous technique include decreased soft tissue trauma; arthroscopic visualization of the fracture, ensuring anatomic reduction; and stable fixation, allowing early physical rehabilitation. The theoretical benefits of the technique include decreased risk of interruption of the tenuous scaphoid blood supply. Percutaneous internal fixation of scaphoid fractures provides faster rehabilitation, earlier return to work, and quicker bony union in most patients. PMID:11775468

  19. Predictive Factors for a Kyphosis Recurrence Following Short-Segment Pedicle Screw Fixation Including Fractured Vertebral Body in Unstable Thoracolumbar Burst Fractures

    PubMed Central

    Kim, Gun-Woo; Hur, Hyuk; Lee, Jung-Kil; Kim, Jae-Hyoo; Kim, Soo-Han

    2014-01-01

    Objective The technique of short segment pedicle screw fixation (SSPSF) has been widely used for stabilization in thoracolumbar burst fractures (TLBFs), but some studies reported high rate of kyphosis recurrence or hardware failure. This study was to evaluate the results of SSPSF including fractured level and to find the risk factors concerned with the kyphosis recurrence in TLBFs. Methods This study included 42 patients, including 25 males and 17 females, who underwent SSPSF for stabilization of TLBFs between January 2003 and December 2010. For radiologic assessments, Cobb angle (CA), vertebral wedge angle (VWA), vertebral body compression ratio (VBCR), and difference between VWA and Cobb angle (DbVC) were measured. The relationships between kyphosis recurrence and radiologic parameters or demographic features were investigated. Frankel classification and low back outcome score (LBOS) were used for assessment of clinical outcomes. Results The mean follow-up period was 38.6 months. CA, VWA, and VBCR were improved after SSPSF, and these parameters were well maintained at the final follow-up with minimal degree of correction loss. Kyphosis recurrence showed a significant increase in patients with Denis burst type A, load-sharing classification (LSC) score >6 or DbVC >6 (p<0.05). There were no patients who worsened to clinical outcome, and there was no significant correlation between kyphosis recurrence and clinical outcome in this series. Conclusion SSPSF including the fractured vertebra is an effective surgical method for restoration and maintenance of vertebral column stability in TLBFs. However, kyphosis recurrence was significantly associated with Denis burst type A fracture, LSC score >6, or DbVC >6. PMID:25368766

  20. EFFECT OF NITROGEN AND METAL ADDITIONS ON NITROGEN FIXATION ACTIVITY IN BIOLOGICAL SOIL CRUSTS

    NASA Astrophysics Data System (ADS)

    Alexander, K.; Lui, D.; Anbar, A. D.; Garcia-Pichel, F.; Hartnett, H. E.

    2009-12-01

    Biological soil crusts (BSCs) are diverse consortia of microorganisms that live in intimate association with soils in arid environments. Also called cryptogamic or microbiotic crusts, these communities can include cyanobacteria, algae, heterotrophic bacteria, fungi, lichens, and mosses. Together, these organisms provide many services to their surrounding ecosystems, including reduction of water runoff, promotion of water infiltration, and prevention of soil erosion. The cyanobacteria and algae also provide fixed carbon (C) to the soil through photosynthesis, and because atmospheric deposition of nitrogen (N) in arid environments is low, the major input of biologically available N comes from cyanobacteria capable of converting nitrogen gas (N2) to ammonium (NH4+). Biological soil crusts are easily destroyed by livestock grazing, motor vehicle travel, and many forms of recreational and agricultural land use. Loss of BSC cover can leave the soil vulnerable to intense erosion that can remove the nutrients necessary to sustain plant and animal life, thus accelerating the process of desertification. In order to preserve existing crusts and encourage the development of new crusts, it is crucial to understand the nutrient requirements of metabolism and growth in these microbial communities. This study investigated the affect of nitrogen and metal additions on N2-fixation activity in cyanobacterially-dominated crusts from the Colorado Plateau near Moab, Utah. Although N2-fixation has been studied in this system before, the affect of nutrient additions on N2-fixation activity has not been documented. The goal of this work was to understand how N and metal supplementation affects crust N metabolism. Three experiments were conducted to observe how N2-fixation activity changed with the addition of N, molybdenum (Mo), and vanadium (V). Molybdenum and vanadium were chosen because they are most commonly found at the active site of the enzyme nitrogenase, the molecule responsible for the biological conversion of N2 to NH4+. The Mo-dependent version of the enzyme is the most efficient, and it is used by the majority of N2-fixing organisms. Elements were added as aqueous solutions of NH4NO3, Na2MoO4, and Na3VO4 respectively. Nitrogen fixation potential was assayed using a modified acetylene reduction technique. Results from the N-addition experiment show that when N is provided, BSC organisms stop N2-fixation activity. This confirms that under natural conditions, the community is limited with respect to N. In general, crusts under Mo-addition fix at higher rates than crusts with no added Mo. This implies that crusts may also be limited with respect to Mo. However, contrary to our expectations, crusts fix at lower rates when V is added as compared to a no-V control. It is possible that this is the result of V-toxicity, or that V competes with the uptake and utilization of available Mo, thus exacerbating Mo-limitation. Experiments are currently underway to investigate how the geochemistry of the soil porewater changes as a result of these nutrient additions.

  1. Multilevel mini-open TLIFs and percutaneous pedicle screw fixation: description of a simple technical nuance used to increase intraoperative safety and improve workflow. Tips and tricks and review of the literature.

    PubMed

    Barbagallo, Giuseppe M V; Certo, Francesco; Visocchi, Massimiliano; Sciacca, Giovanni; Piccini, Mario; Albanese, Vincenzo

    2015-04-01

    We describe a technical variation used to enhance intraoperative safety and efficiency in multilevel percutaneous pedicle screw fixation (PPSFs) and mini-open transforaminal lumbar interbody fusion (m-TLIFs). A review of the literature on percutaneous screw insertion techniques and related pitfalls is presented. PPSFs and m-TLIFs are increasingly used techniques in multilevel lumbar degenerative disease. Facetectomy and TLIF are usually performed before inserting ipsilateral pedicle screws. Such techniques can cause unintended violation of the pedicle and injure the dura or neural structures, particularly in multilevel cases. A literature review revealed a lack of intraoperative and fluoroscopic images detailing the technique for multilevel PPSF and m-TLIF(s) performed through tubular, expandable retractors. Thirteen patients with two- to four-level disease underwent multilevel PPSF and m-TLIF (one to four levels). The Kirschner Cage Screw (KCS) technique, consisting of early insertion of K-wires in all pedicles followed by facetectomy and m-TLIF(s) and, finally, screw insertion, was used in order to minimize the risk of dural/neural injuries. Neither CSF (cerebrospinal fluid) leaks nor nerve root injuries nor technique-related complications were encountered with a follow-up ranging from 7 to 38 months (mean 23.6). In conclusion, the KCS technique allows safe identification of the pedicles without opening the canal during m-TLIF(s). Moreover, by visualizing the K-wires inside the retractor, the surgeon can check the pedicle position during facetectomy, and screws can be introduced with a minimal risk of neural or dural injuries. We believe that the proposed technique increases the safety and ease of the procedure, particularly in multilevel cases. PMID:25391632

  2. Removal of broken pedicle screws. Technical note.

    PubMed

    Miyamoto, K; Shimizu, K; Kouda, K; Hosoe, H

    2001-07-01

    The authors describe a simple, new method for removing broken pedicle screws. Under microscopic visualization a straight, narrow slot is etched in the broken surface of the pedicle screw by using a power drill with a 2-mm diamond burr. A minus screwdriver is then inserted into the slot, and the broken screw is rotated and removed. There is no need to enlarge the screw hole around the broken screw or to use any special devices. The authors succeeded in removing broken screws in two cases, and there were no complications. This method allows preservation of both the pedicle and the screw hole. Consequently, it is possible to insert new pedicle screws into the same hole without losing the strength and stability of pedicle screw fixation. The authors recommend this simple and new method for removal of broken pedicle screws. PMID:11453420

  3. Direct repair of defects in lumbar spondylolysis with a new pedicle screw hook fixation: clinical, functional and Ct-assessed study

    PubMed Central

    Troussel, Serge

    2007-01-01

    Spondylolysis is a common entity, a minority of people affected by this disease need medical care, and only a few require surgery. Reconstruction of the pars interarticularis is an interesting alternative to segmental fusion; this technique has the advantage of preserving segmental motion. Most authors report good results for young patients without intervertebral disk or facet degenerative changes. Moreover Louis also showed good to excellent results with his technique carried out among people who presented a satisfactory disk height (equal to two thirds of normal height). This could extend the number of patients for whom pars interarticularis repair could be proposed. In this study, the limit of reconstruction was set at grade 3of the Pfirrmanns classification. The fixation of the isthmus was done with a new kind of pedicle screw hook system. This stable and strong device is easy to use, allows an anatomic pars interarticularis reconstruction of spondylolysis and avoids a postoperative bracing. Twenty-three patients were assessed in this study, the mean age at operation was 34 (range 1652years) and the average follow-up was for 59months (range 6113months). Eight patients showed moderate degenerative disk disease before the surgery and 12 patients had a grade 1 spondylolisthesis. The visual analogical scale, the Oswestry disability index (ODI) and the modified Prolo score were used for assessment of pain and clinical outcome before and after surgery. The results were from excellent to good for twenty patients (87%) and fair for three of them (13%). The consolidation of the isthmus was assessed at the end of the study (CT-scan); the fusion rate was observed in 91%. Among patients aged less than 30years results are from good, to excellent in all cases and consolidation was always observed. All of them showed normal disc signal before the surgery. In the group aged more than 30years, the results varied from good to excellent in 73% and fusion of the defect was discovered in 82% of cases. Eight of them (73%) had moderate disk signal modification before the surgery. All people with fair results displayed moderate disk degeneration signs at MRI before surgery; but two of those three patients had a failure of defect consolidation too and it is also associated with poor results by several authors. No complication was found in this series. According to the good results reported by Louis and upto the current finding, the authors believe that pars interarticularis repair can be carried out on patients with moderate degenerative disk disease; the stage 3 of Pfirrmanns classification seems a good limit. The Bone and joint research (B.J.R. system) is readily usable by any surgeon using pedicle screw systems and having a short learning curve. No device failure has been observed in this series. PMID:17520298

  4. Percutaneous Transpedicular Fixation: Technical tips and Pitfalls of Sextant and Pathfinder Systems

    PubMed Central

    Hassan, Ahmed Salah Aldin

    2016-01-01

    Study Design The efficacy of the operative techniques, possible benefits as well as pitfalls and limitations of the techniques are discussed. Potential drawbacks are also detected. Purpose This study aims to report indications, techniques, and our experience with the use of the Sextant and PathFinder percutaneous transpedicular screw fixation systems. Overview of Literature Percutaneous pedicle screw insertion is a novel technique. Successful percutaneous placement of pedicle screws requires surgical skill and experience because of lack of anatomic surface landmarks. Fluoroscopy-guided percutaneous placement of pedicle screws is effective. Many systems are now available. Methods We conducted a prospective operative and postoperative analysis of 40 patients with absolute indication for thoracic or lumbar instability between January 2009 and June 2013. All procedures were performed with the Sextant (group A) and PathFinder (group B) systems under fluoroscopic guidance. Operative techniques are discussed and the results compared. Results Percutaneous transpedicular screw fixation minimizes the morbidity associated with open techniques without compromising the quality of fixation. A total of 190 screws were inserted. There was no additional morbidity. Postoperative computed tomography images and plain X-rays were analyzed. Reduction of visual analog scale scores of back pain was evident. Conclusions Fluoroscopy-guided percutaneous pedicular screws are feasible and can be safely done. Current systems allow multi-segmental fixation with significantly less difficulties. The described techniques have acceptable intra- and postoperative complication rates, and overall sufficient pain control with early mobilization of patients. PMID:26949466

  5. A Biomechanical Comparison of Expansive Pedicle Screws for Severe Osteoporosis: The Effects of Screw Design and Cement Augmentation

    PubMed Central

    Tai, Ching-Lung; Tsai, Tsung-Ting; Lai, Po-Liang; Chen, Yi-Lu; Liu, Mu-Yi; Chen, Lih-Huei

    2015-01-01

    Expansive pedicle screws significantly improve fixation strength in osteoporotic spines. However, the previous literature does not adequately address the effects of the number of lengthwise slits and the extent of screw expansion on the strength of the bone/screw interface when expansive screws are used with or without cement augmentation. Herein, four designs for expansive pedicle screws with different numbers of lengthwise slits and different screw expansion levels were evaluated. Synthetic bones simulating severe osteoporosis were used to provide a comparative platform for each screw design. The prepared specimens were then tested for axial pullout failure. Regardless of screw design, screws with cement augmentation demonstrated significantly higher pullout strength than pedicle screws without cement augmentation (p < 0.001). For screws without cement augmentation, solid screws exhibited the lowest pullout strength compared to the four expansive groups (p < 0.01). No significant differences in pullout strength were observed between the expansive screws with different designs (p > 0.05). Taken together, our results show that pedicle screws combined with cement augmentation may greatly increase screw fixation regardless of screws with or without expansion. An increase in both the number of slits and the extent of screw expansion had little impact on the screw-anchoring strength. Cement augmentation is the most influential factor for improving screw pullout strength. PMID:26720724

  6. Complications associated with thoracic pedicle screws in spinal deformity

    PubMed Central

    Li, Gang; Lv, Guohua; Passias, Peter; Kozanek, Michal; Metkar, Umesh S.; Liu, Zhongjun; Wood, Kirkham B.; Rehak, Lubos

    2010-01-01

    Thoracic pedicle screws have superior anchoring strength compared with other available fixation techniques. However, these are not universally accepted in many developing countries because of the concerns regarding safety and complications. In addition, there is evidence that pedicle morphology is unique in Chinese patients. The goal of this study was to analyze the complications seen at our institution, while using thoracic pedicle screws for the treatment of thoracic deformity, and to determine the safety of our techniques for the treatment of thoracic deformity in a Chinese population. From 1998 to 2005, there were 208 thoracic deformity patients treated at our institution, 70 of whom were male and 138 were female. Their age ranged from 11 to 55years (mean of 14.9years). All of them underwent corrective deformity surgery using posterior pedicle screw systems and follow-up was available for at least 3years. Etiologic diagnoses included adolescent idiopathic scoliosis in 119 patients, congenital kyphoscoliosis in 38, adult scoliosis in 37 and undetermined in 14. Screw positions were evaluated using intraoperative and postoperative radiographs and a CT scan was performed when a concern for screw malposition was present. All radiographic evaluations were carried out in a double-blinded fashion. A total of 1,123 thoracic pedicle screws were inserted (5.4 thoracic screws/patient). The deformity correction rate was 81, 65 and 62% for idiopathic, congenital and adult scoliosis patients, respectively. The overall complication rate was 16.5% at the final follow-up. Complication rates directly and indirectly related to pedicle screws were 7.2 and 9.3%, respectively. There were no significant screw-related neurologic or visceral complications that adversely affected long-term results. The complications seen with thoracic pedicle screws in a Chinese population were similar to other populations and could be utilized safely for the treatment of thoracic deformity in this population. PMID:20237943

  7. Surgical treatment of the osteoporotic spine with bone cement-injectable cannulated pedicle screw fixation: technical description and preliminary application in 43 patients

    PubMed Central

    Dai, Fei; Liu, Yaoyao; Zhang, Fei; Sun, Dong; Luo, Fei; Zhang, Zehua; Xu, Jianzhong

    2015-01-01

    OBJECTIVES: To describe a new approach for the application of polymethylmethacrylate augmentation of bone cement-injectable cannulated pedicle screws. METHODS: Between June 2010 and February 2013, 43 patients with degenerative spinal disease and osteoporosis (T-score <-2.5) underwent lumbar fusion using cement-injectable cannulated pedicle screws. Clinical outcomes were evaluated using a Visual Analog Scale and the Oswestry Disability Index. Patients were given radiographic follow-up examinations after 3, 6, and 12 months and once per year thereafter. RESULTS: All patients were followed for a mean of 15.7±5.6 months (range, 6 to 35 months). The Visual Analog Scale and Oswestry Disability Index scores showed a significant reduction in back pain (p = 0.018) and an improvement in lower extremity function (p = 0.025) in patients who underwent lumbar fusion using the novel screw. Intraoperative cement leakage occurred in four patients, but no neurological complications were observed. Radiological observation indicated no loosening or pulling out of the novel screw, and bone fusion was excellent. CONCLUSIONS: The described polymethylmethacrylate augmentation technique using bone cement-injectable cannulated pedicle screws can reduce pain and improve spinal dysfunction in osteoporotic patients undergoing osteoporotic spine surgery. PMID:25789520

  8. Strontium-impregnated bioabsorbable composite for osteoporotic fracture fixation.

    PubMed

    Wu, Chang-Chin; Kuo, Chih-Lin; Fan, Fang-Yu; Yang, Kai-Chiang

    2015-10-01

    Osteoporosis impairs the bone-healing process as well as bone fracture fixation. The intervention of osteoporosis is considered to be one part of bone fracture treatment. Thus, orthopedic fixators impregnated with antiosteoporosis regimens will improve fracture fixation in osteoporotic bone. In this study, the strontium (Sr) and calcium phosphate ceramic (CPC) were mixed first and then mixed with poly(?-caprolactone) (PCL) to fabricate a bioactive and bioabsorbable bone fixators. The prepared Sr-CPC/PCL screws were implanted into the distal femur of ovariectomized rabbits. The results showed that Sr-CPC/PCL composite had the appropriate mechanical properties, good biocompatibility, and radio-opacity. The Sr addition created a porous structure and accelerated the degradation of bone screws, but the degradation products did not acidify the surrounding environment. For osteoporotic animals, favorable osteointegration around the Sr-CPC/PCL screws was found, and the total porosity of trabecular bone was decreased under the inspections of micro-computerized tomography. Compared with PCL or CPC/PCL screw, animals which received Sr-CPC/PCL were found to have better results in terms of trabecular number, thickness, and separation. This study reveals that the Sr-impregnated bone fixator improves osseointegration in osteoporotic animals. Sr-CPC/PCL composite is a good candidate material for osteofixation in osteoporotic patients. PMID:25847487

  9. A new alternative to expandable pedicle screws: Expandable poly-ether-ether-ketone shell.

    PubMed

    Demir, Teyfik

    2015-05-01

    Screw pullout is a very common problem in the fixation of sacrum with pedicle screws. The principal cause of this problem is that the cyclic micro motions in the fixation of sacrum are higher than the other regions of the vertebrae that limit the osteo-integration between bone and screw. In addition to that, the bone quality is very poor at sacrum region. This study investigated a possible solution to the pullout problem without the expandable screws' handicaps. Newly designed poly-ether-ether-ketone expandable shell and classical pedicle screws were biomechanically compared. Torsion test, pullout tests, fatigue tests, flexion/extension moment test, axial gripping capacity tests and torsional gripping capacity tests were conducted in accordance with ASTM F543, F1798 and F1717. Standard polyurethane foam and calf vertebrae were used as embedding medium for pullout tests. Classical pedicle screw pullout load on polyurethane foam was 564.8?N compared to the failure load for calf vertebrae's 1264?N. Under the same test conditions, expandable poly-ether-ether-ketone shell system's pullout loads from polyurethane foam and calf vertebrae were 1196.3 and 1890?N, respectively. The pullout values for expandable poly-ether-ether-ketone shell were 33% and 53% higher than classical pedicle screw on polyurethane foam and calf vertebrae, respectively. The expandable poly-ether-ether-ketone shell exhibited endurance on its 90% of yield load. Contrary to poly-ether-ether-ketone shell, classical pedicle screw exhibited endurance on 70% of its yield load. Expandable poly-ether-ether-ketone shell exhibited much higher pullout performance than classical pedicle screw. Fatigue performance of expandable poly-ether-ether-ketone shell is also higher than classical pedicle screw due to damping the micro motion capacity of the poly-ether-ether-ketone. Expandable poly-ether-ether-ketone shell is a safe alternative to all other expandable pedicle screw systems on mechanical perspective. PMID:25991716

  10. A 10-year follow-up of transpedicular screw fixation and intervertebral autogenous posterior iliac crest bone graft or intervertebral B-Twin system in failed back surgery syndrome

    PubMed Central

    Cincu, Rafael; Lorente, Francisco de Asis; Gomez, Joaquin; Eiras, Jose; Agrawal, Amit

    2015-01-01

    Background: The spine surgeons have been combining anterior and posterolateral fusion (circumferential fusion) as the final solution to treat spinal disorders and many have been using it to treat failed back surgery syndrome (FBSS). In present study, we analyzed and compared the clinical and radiological outcomes in patients with transpedicular screw fixation and intervertebral autogenous posterior iliac crest bone graft or in patients with transpedicular screw fixation and intervertebral B-Twin system for FBSS with a follow-up period of 10 years after the surgery. Materials and Methods: This study was a retrospective case study performed on 55 patients with FBSS. Clinical and radiological changes were compared between the two groups of patients on the basis of improvement of back pain, radicular pain, and work capacity. Outcome was measured in terms of Oswestry Low Back Pain Disability Index, and the changes in pain and function were documented every year from before surgery until 2012. We analyzed the evolution of 55 cases of FBSS those underwent segmental circumferential posterior fusions from June 2001 to February 2003, operated by a single surgeon and followed up during 10 years until February 2012. The patients were divided into 2 groups: In 25 patients, posterolateral fusions with Legacy (Medtronic, Inc. NYSE: MDT) screws and intersomatic autogenous posterior iliac crest bone graft was performed, and, in 30 patients, posterolateral fusions with the same screws and intersomatic fusion B-Twin (Biomet Spain Orthopaedics, S.L.) system was performed. In all cases, we used posterior lumbar interbody fusion (PLIF)/transforaminal lumbar interbody fusion (TLIF) approach for intervertebral graft, and the artrodesis was supplemented at intertransverse level with Autologus Growth Factor (AGF-MBA INCORPORADO, S.A.). The outcome was measured in terms of Oswestry Low Back Pain Disability Index, and the changes in pain and function were documented every year and compared from before surgery to the final follow-up visit. Preoperative and postoperative scores were available for all patients. Results: The average age of these patients was comparable in both groups (mean age 42.6 versus 50.2 years). The average follow-up period was 200.6 months in the first group (screws and intersomatic bone) and 184.4 months in the second group (screws and B-Twin). In the autologus bone graft group, the CT scan and Rx study revealed loss of height of intervertebral space between 25% and 45% of 24 h postoperative height of intervertebral operated disc, and the patients continued to lose the height until 20 months after the surgery. In the B Twin group, the CT scan and Rx study revealed a loss of height of the intervertebral level of 8-12% over a period of 9 months follow-up, followed by stability. A total of 31 patients (55%) had improved Oswestry Low Back Pain Disability Index >40% of the total possible points, although this did not reflect in PSI or return to work rate. Conclusions: The patients with rigid fixation do well in terms of correction of lumbar lordosis, but they do not do well in terms of recurrence of pain. Furthermore, they need some kind of intervention to control pain after the first year after surgery. In patients in whom bone graft is used, although they do not maintain and sustain the lumbar lordosis in the long term, they have less recurrence of pain with less chances of intervention for pain control. PMID:25972934

  11. Vertical Bone Grafting and Periosteal Vertical Mattress Suture for the Fixation of Resorbable Membranes and Stabilization of Particulate Grafts in Horizontal Guided Bone Regeneration to Achieve More Predictable Results: A Technical Report.

    PubMed

    Urban, Istvan A; Lozada, Jaime L; Wessing, Bastian; Surez-Lpez Del Amo, Fernando; Wang, Hom-Lay

    2016-01-01

    Osteosynthesis screws and titanium or resorbable pins have been recommended for fixing guided bone regeneration (GBR) membranes and stabilizing the graft. However, the removal of fixation screws or pins often requires an additional surgical procedure. This article presents a periosteal suturing technique with resorbable sutures for the fixation of grafts and membranes in GBR in single implant sites. This technique avoids potential complications of using fixation screws or pins, such as perforation of the roots when inserting the pins, and eliminates the need for a second retrieval surgery. PMID:26901293

  12. Single column locking plate fixation is inadequate in two column acetabular fractures. A biomechanical analysis

    PubMed Central

    2010-01-01

    Background The objective of this study was to determine whether one can achieve stable fixation of a two column (transverse) acetabular fracture by only fixing a single column with a locking plate and unicortical locking screws. We hypothesized that a locking plate applied to the anterior column of a transverse acetabular fracture would create a construct that is more rigid than a non-locking plate, and that this construct would be biomechanically comparable to two column fixation. Methods Using urethane foam models of the pelvis, we simulated transverse acetabular fractures and stabilized them with 1) an anterior column plate with bicortical screws, 2) an anterior locking plate with unicortical screws, 3) an anterior plate and posterior column lag screw, and 4) a posterior plate with an anterior column lag screw. These constructs were mechanically loaded on a servohydraulic material testing machine. Construct stiffness and fracture displacement were measured. Result and Discussion We found that two column fixation is 54% stiffer than a single column fixation with a conventional plate with bicortical screws. There was no significant difference between fixation with an anterior column locking plate with unicortical screws and an anterior plate with posterior column lag screw. We detected a non-significant trend towards more stiffness for the anterior locking plate compared to the anterior non-locking plate. Conclusion In conclusion, a locking plate construct of the anterior column provides less stability than a traditional both column construct with posterior plate and anterior column lag screw. However, the locking construct offers greater strength than a non-locking, bicortical construct, which in addition often requires extensive contouring and its application is oftentimes accompanied by the risk of neurovascular damage. PMID:20459688

  13. Optimal placement of bicortical screws in sagittal split-ramus osteotomy of mandible.

    PubMed

    Obeid, G; Lindquist, C C

    1991-06-01

    When a bicortical screw is used for the rigid fixation of sagittal split-ramus osteotomy, by definition the threads of the screw should engage in the buccal plates as well as in the lingual plates. In a study of six dry mandibles we found that when 2 and 2.7 mm screws are used in noncountersunk holes, it is almost certain that a thread will engage the buccal cortical plate. With countersinking 55% of the 2.7 mm and 27% of the 2.0 mm screws had no threads engaged in the buccal cortical plate. This changes these screws from bicortical to compression type. An anatomic study of bone thickness demonstrated that the thickest buccal and lingual cortical plates were in the superior border of the ramus, just distal to the last molar. In addition, a change in the intercondylar distance before and after surgery was observed in every mandible. PMID:2062519

  14. Do Newer-Generation Bioabsorbable Screws Become Incorporated into Bone at Two Years After ACL Reconstruction with Patellar Tendon Graft?

    PubMed Central

    Cox, Charles L.; Spindler, Kurt P.; Leonard, James P.; Morris, Brent J.; Dunn, Warren R.; Reinke, Emily K.

    2014-01-01

    Background: Bioabsorbable interference screws are used frequently for graft fixation in ACL (anterior cruciate ligament) reconstruction. The resorption properties of many available screws that are marketed as bioabsorbable are not well defined. The CALAXO (Smith & Nephew Endoscopy) and MILAGRO (DePuy Synthes) bioabsorbable screws contain polymers of poly(lactic-co-glycolic acid) (PLGA) plus additives to encourage osseointegration over time. The purpose of this study was to evaluate radiographic and magnetic resonance imaging (MRI) properties and compare patient-reported outcomes at a minimum of two years of follow-up after ACL reconstruction using CALAXO or MILAGRO bioabsorbable interference screws. Methods: A cohort of patients who underwent ACL reconstruction in which the fixation used was either CALAXO or MILAGRO screws returned for repeat radiographs for evaluation of tunnel widening, repeat MRI for evaluation of graft integrity and screw breakdown, and completion of the pain and symptom items of the KOOS (Knee injury and Osteoarthritis Outcome Score) questionnaire. Results: At a mean of three years (range, 2.5 to 4.0 years) after surgery, thirty-one patients with sixty-two CALAXO screws and thirty-six patients with seventy-two MILAGRO screws returned for repeat evaluation. Two blinded, independent reviewers found no significant differences between the two screw types when comparing radiographs for tibial or femoral tunnel widening or MRIs for graft integrity, tibial and femoral foreign body reactions, or femoral screw degradation. Both reviewers found a significant difference between the two screw types when comparing tibial screw degradation properties (p < 0.01). All analyzed CALAXO screws were rated as partially intact or degraded; the MILAGRO screws were more likely to be rated as intact. No significant differences were noted between the two screw types when comparing the two KOOS subscales. Conclusions: CALAXO screws in the tibial tunnel were more likely to be rated as degraded or partially degraded compared with MILAGRO screws at a mean of three years after implantation for ACL reconstruction. Although these newer-generation bioabsorbable screws were designed to promote osseointegration, no tunnel narrowing was noted, and in the majority of cases the remains of the screws were present at approximately three years. Level of Evidence: Therapeutic Level II. See Instructions for Authors for a complete description of levels of evidence. Peer Review: This article was reviewed by the Editor-in-Chief and one Deputy Editor, and it underwent blinded review by two or more outside experts. The Deputy Editor reviewed each revision of the article, and it underwent a final review by the Editor-in-Chief prior to publication. Final corrections and clarifications occurred during one or more exchanges between the author(s) and copyeditors. PMID:24500587

  15. Segmental Stiffness Achieved by Three Types of Fixation for Unstable Lumbar Spondylolytic Motion Segments

    PubMed Central

    Choma, Theodore; Pfeiffer, Ferris; Vallurupalli, Santaram; Mannering, Irene; Pak, Youngju

    2012-01-01

    Objective?The objective of this study was to compare the relative stability in lumbar spondylolysis (SP) of a rigid anterior plate (with a novel compression slot) versus traditional posterior pedicle screw (PS) fixation. Summary of Background Data?Arthrodesis has been a mainstay of treatment for symptomatic isthmic spondylolisthesis in adults. Posterior PS fixation has become a commonly used adjunct. Some have advocated anterior lumbar interbody fixation (ALIF) plate as an alternative. The relative stability afforded by ALIF in SP has not been well characterized, nor has the contribution afforded by a compression screw slot in an ALIF plate. Methods?Calf spine segments were characterized in the normal state, after sectioning the pars (SP model), then after reconstruction with an interbody spacer and either PS/rods, or an ALIF plate, or both. Results?ALIF plate conferred stability on the spondylolytic segment only comparable to that of the normal functional spinal unit (FSU). Posterior fixation was more stable than anterior fixation in all testing modes. Addition of an ALIF plate conferred a significant additional stability in those that already had posterior fixation. The utilization of an anterior compression screw conferred additional stability in extension testing only. Conclusions?ALIF plate reconstruction in the setting of SP may not confer enough segmental stability to predictably encourage fusion beyond that of the uninstrumented intact FSU. The utilization of an integral compression screw in an ALIF plate may not confer clinically significant additional construct stability in SP. PMID:24353951

  16. Co-optimization of diesel fuel biodegradation and N{sub 2} fixation through the addition of particulate organic carbon

    SciTech Connect

    Piehler, M.; Swistak, J.; Paerl, H.

    1995-12-31

    Petroleum hydrocarbon pollution in the marine environment is widespread and current bioremedial techniques are often not cost effective for small spills. The formulation of simple and inexpensive bioremedial methods could help reduce the impacts of frequent low volume spills in areas like marinas and ports. Particulate organic carbon (POC) was added to diesel fuel amended samples from inshore marine waters in the form of corn-slash (post-harvest leaves and stems), with and without inorganic nutrients (nitrate and phosphate). Biodegradation of diesel fuel ({sup 14}C hexadecane mineralization) and N{sub 2} fixation were measured in response to the additions, The addition of POC was necessary for N{sub 2} fixation and diesel fuel biodegradation to co-occur. The effects of diesel fuel and inorganic nutrient additions on N{sub 2} fixation rates were not consistent, with both inhibitory and stimulatory responses to each addition observed. The highest observed diesel fuel biodegradation levels were in response to treatments that included inorganic nutrients. The addition of POC alone increased diesel fuel degradation levels above that observed in the control. In an attempt to determine the effect of the POC on the microbial community, the corn particles were observed microscopically using scanning electron microscopy and light microscopy with tetrazolium salt additions. The corn particles were found to have abundant attached bacterial communities and microscale oxygen concentration gradients occurring on individual particles. The formation of oxygen replete microzones may be essential for the co-occurrence of aerobic diesel fuel biodegradation and oxygen inhibited N2 fixation. Mesocosm experiments are currently underway to further examine the structure and function of this primarily heterotrophic system and to explore the potential contribution of N{sub 2} fixation to the N requirements of diesel fuel biodegradation.

  17. A New Mini-External Fixator for Treating Hallux Valgus: A Preclinical, Biomechanical Study.

    PubMed

    Erdil, Mehmet; Ceylan, Hasan Huseyin; Polat, Gokhan; Kara, Deniz; Bozdag, Ergun; Sunbuloglu, Emin

    2016-01-01

    Proximal metatarsal osteotomy is the most effective technique for correcting hallux valgus deformities, especially in metatarsus primus varus. However, these surgeries are technically demanding and prone to complications, such as nonunion, implant failure, and unexpected extension of the osteotomy to the tarsometatarsal joint. In a preclinical study, we evaluated the biomechanical properties of the fixator and compared it with compression screws for treating hallux valgus with a proximal metatarsal osteotomy. Of 18 metatarsal composite bone models proximally osteotomized, 9 were fixed with a headless compression screw and 9 with the mini-external fixator. A dorsal angulation of 10 and displacement of 10mm were defined as the failure threshold values. Construct stiffness and the amount of interfragmentary angulation were calculated at various load cycles. All screw models failed before completing 1000 load cycles. In the fixator group, only 2 of 9 models (22.2%) failed before 1000 cycles, both between the 600th and 700th load cycles. The stability of fixation differed significantly between the groups (p<.001). The stability provided by the mini-external fixator was superior to that of compression screw fixation. Additional testing of the fixator is indicated. PMID:26190777

  18. Early Results from Posterior Cervical Fusion with a Screw-Rod System

    PubMed Central

    Kim, Sang Hyun; Shin, Dong Ah; Yi, Seung; Yoon, Do Heum; Kim, Keung Nyun

    2007-01-01

    Purpose We performed 65 cases of posterior fusion surgery for cervical and/or high thoracic lesions using a polyaxial screw-rod system. Patients and Methods A total of 486 screws were implanted in 65 patients. Results Fixation of the screws was carried out over an average of 2.9 spinal segments. Upon evaluation by postoperative CT scans, twelve (2.5%) screws had suboptimal trajectories but two of these revealed radiculopathy in one patient and required screw repositioning. No vascular sequelae resulted. There has been no segmental motion in any of the cases to date. As for other complications, there was one case of dural tearing and two cases of lateral mass fractures. There were no infections or other wound healing problems or hardware failures. No patients had neurological deterioration after surgery. There were statistically significant improvements in the mean Neck Disability Index (NDI) scores and Visual Analogue Scale (VAS) scores in the preoperative and late postoperative follow-up evaluations. Although further studies are required to establish the long-term results of fusion rates and clinical outcomes. Conclusion We cautiously suggest that the posterior polyaxial screw-rod system can be safely used as a primary or additional fusion method in this risky region. The successful and safe use of this method is dependent on a precise preoperative surgical plan and tactics for ensuring safe screw fixation. PMID:17594152

  19. Poly(D,L-lactide) coating is capable of enhancing osseous integration of Schanz screws in the absence of infection.

    PubMed

    Partale, K; Klein, P; Schell, H; Schmidmaier, G; Wildemann, B; Bail, H; Schiller, R; Bragulla, H; Duda, G N

    2005-07-01

    Pin loosening is a major complication in external fixation. Biological and mechanical conditions play an important role in the maintenance and enhancement of the implant-bone interface in fracture fixation. It is thought that biodegradable coatings may be capable of preventing pin track infection and pin loosening. The goal of this study was therefore to analyze the influence of a biodegradeable coating on the osseous integration of Schanz' screws during fracture treatment. Standardized osteotomies (3-mm fracture gap) of the right tibiae were performed on 16 sheep and stabilized by an AO mono-lateral external fixator. Additional, mechanically less loaded Schanz' screws were also mounted. All screws were randomly coated with biodegradable poly(D,L-lactide). The sheep were sacrificed after 9 weeks. All screws were removed and rolled on blood agar plates for microbiological analysis. Histological sections of the pin tracks were histochemically and morphometrically analyzed. Clinically, no signs of severe infection were visible. Microbiological analysis revealed 14.8% colonization by Staphylococcus aureus in the coated and 29% in the uncoated screws. Histomorphometry of the bone surrounding the Schanz' screws revealed that significantly more osseous integration had occurred on poly(D,L-lactide)-coated screws in the absence of bacterial colonization. Significantly more bone remodeling and a higher osteoclastic activity was seen near the screw-bone interface in the uncoated screw group. Up to a threefold increase in new bone formation and more severe remodeling was observed around the screw entry compared to the pin exit in all groups. Loaded screws showed significantly more callus formation around the exit sites than their less loaded counterparts. In the present study, poly(D,L-lactide) coating of Schanz' screws was found to enhance osseous integration in the absence of bacterial colonization in sheep by causing less cortical remodeling and less osteoclastic activity in the cortices compared to uncoated screws. Additionally, the coating appeared to reduce the instances of pin track infections. Mechanical loading showed an adverse effect on bone formation and remodeling. It has been shown that both biological and mechanical factors play an important role in the maintenance of osseous integrity of the pin-bone interface. Poly(D,L-lactide) coating of Schanz' screws does not prevent osseous destruction and severe bacterial colonization along the pin tracts, but can improve osseous integration of Schanz' screws in the absence of infection. PMID:15909297

  20. Interactive effects of tunnel dilation on the mechanical properties of hamstring grafts fixed in the tibia with interference screws.

    PubMed

    Rittmeister, M E; Noble, P C; Bocell, J R; Alexander, J W; Conditt, M A; Kohl, H W

    2001-09-01

    The effect of dilation of the tibial tunnel on the strength of hamstring graft fixation using interference screws was evaluated. In all, 28 RCI screws were tested in male human tibia-hamstring constructs with tibial tunnels reamed or dilated to the respective size of the graft diameter. Dilation of the tibial tunnel failed to significantly enhance hamstring fixation. Grafts secured in dilated tunnels displayed an 11% greater resistance to the initiation of graft slippage (174+/-112 N) compared to their undilated controls (156+/-77 N, P=0.63). Dilation of the tibial tunnel increased the failure load by an average of 4%, independent of screw diameter (dilated specimens: 360+/-120 N, controls: 345+/-88 N, P=0.74). Biomechanical research on the effect of tibial tunnel dilation in hamstring fixation has not provided satisfactory evidence as to the benefits of this additional surgical step during anterior cruciate ligament (ACL) reconstruction. PMID:11685357

  1. Bilateral Pedicle and Crossed Translaminar Screws in C2

    PubMed Central

    Mendelsohn, Daniel; Lee, Robert; Boyd, Michael C.

    2015-01-01

    Multiple techniques exist for the fixation of C2, including axial pedicle screws and bilateral translaminar screws. We describe a novel method of incorporating both the translaminar and pedicle screws within C2 to improve fixation to the subaxial spine in patients requiring posterior cervical instrumentation for deformity correction or instability. We report three cases of patients with cervical spinal instability, who underwent cervical spine instrumentation for stabilization and/or deformity correction. Bilateral C2 pedicle screws were inserted, followed by bilateral crossed laminar screws. The instrumentation method successfully achieved fixation in all three patients. There were no immediate postoperative complications, and hardware positioning was satisfactory. Instrumenting C2 with translaminar and pedicle screws is technically feasible, and it may improve fixation to the subaxial spine in patients with poor bone quality or severe subaxial deformity, which require a stronger instrumentation construct. PMID:26435799

  2. Comparison of Hallux Interphalangeal Joint Arthrodesis Fixation Techniques: A Retrospective Multicenter Study.

    PubMed

    Thorud, Jakob C; Jolley, Tyler; Shibuya, Naohiro; Lew, Eric; Britt, Matthew; Butterfield, Ted; Boike, Alan; Hardy, Mark; Brancheau, Steven P; Motley, Travis; Jupiter, Daniel C

    2016-01-01

    Few studies have investigated the complications that occur after hallux interphalangeal joint arthrodesis. The present study evaluated complications in 152 patients aged 18 to 80 years from 2005 to 2012 from 4 different academic institutions after hallux interphalangeal joint arthrodesis. Overall, 65.8% of the patients had ≥1 complication. Infections occurred in 16.5%, dehiscence in 12.5%, and reoperations in 27.0%. The clinical nonunion rate was ≥17.8%, and the radiographic nonunion rate was ≥13.8%. After logistic regression analysis, only the study site and peripheral neuropathy were associated with having ≥1 complication (p < .01 and p < .05, respectively). Single screw fixation compared with other fixation did not have a statistically significant influence on the postoperative complications. However, when fixation was expanded to 4 categories, single screw fixation had lower infection and reoperation rates than either crossed Kirschner wires or other fixation category but not compared with crossed screws on multivariate logistic regression analysis. Although additional studies are warranted, the findings from the present study might aid in both the prognosis of complications and the support of the use of a single screw over crossed Kirchner wire fixation in hallux interphalangeal joint arthrodesis. PMID:25960055

  3. Intrapelvic migration of a gamma nail lag screw: review of the possible mechanisms.

    PubMed

    Flint, John H; Sanchez-Navarro, C Francisco; Buckwalter, Joseph A; Marsh, J Lawrence

    2010-04-01

    This article presents a case of intrapelvic migration of a Gamma nail lag screw (Stryker, Mahwah, New Jersey) in an 82-year-old woman 7 months after fixation of an unstable pertrochanteric fracture. Two of the most common complications associated with the use of the Gamma nail and other sliding intramedullary devices, as well as lag screw and side plate devices, relate to the lag screw: cut out and medial migration in the femoral head. As compared to lag screw migration in the femoral head, intrapelvic migration of the Gamma lag screw is a rare complication. To our knowledge, intra-pelvic migration after disengagement of the lag screw from the Gamma nail has been reported in the literature only 3 times. Several risk factors can be associated with Gamma nail failure, most importantly damage to femoral head leading to lag screw migration, plate/lag or nail/lag screw interface dysfunction, technical mistakes, and additional subsequent trauma. This article reviews the literature and the theories for such device failures. PMID:20415308

  4. Cyanoacrylate fixation of the craniofacial skeleton: an experimental study.

    PubMed

    Amarante, M T; Constantinescu, M A; O'Connor, D; Yaremchuk, M J

    1995-04-01

    This study examined the feasibility of achieving bone fixation of the upper facial skeleton using n-butyl-2-cyanoacrylate. We compared the fixation obtained with this adhesive to that obtained with plates and screws in an animal model. The stability of fixation of both osteotomies and onlay grafts was studied in six minipigs. Three osteotomies were performed on each side of the skull. Additionally, a parietal split-thickness autograft was fixated to the nasal bone as an onlay. Plates and screws were used on the right and adhesive on the left. The animals were killed at 6 weeks, and both sides were compared biomechanically and histologically. Clinical assessment showed stability of all fragments. No statistical difference was found in the comparison of the maximum torque to failure between analogous plated and glued sides. Radiographic cephalometry revealed no significant displacement of the fragments. Histologic analysis demonstrated bony union. In this study, n-butyl-2-cyanoacrylate was as effective as plates and screws in the fixation of surgically created osteotomies of the upper facial skeleton. PMID:7892307

  5. Screw positions in femoral neck fractures. Comparison of two different screw positions in cadavers.

    PubMed

    Lindequist, S; Wredmark, T; Eriksson, S A; Samnegård, E

    1993-02-01

    To evaluate the influence of different screw positions on the stability of fixation in femoral neck fractures, 30 cadaveric proximal femora were osteotomized and fixed with 2 cannulated screws. The proximal screw was placed either with a posterior cortical support in the femoral neck or centrally, supported only by cancellous bone. The distal screw rested on the femoral calcar. The specimens were tested in bending, using the force at 2 and 5 mm deflection at the osteotomy site and at fracture, as an expression of the stability of fixation. The test sequences were recorded on a x-y plotter and on videotape. Bone density measurements were made at the femoral neck, Ward's triangle, and the trochanter region. Our findings indicate that a posterior position with cortical support for the proximal screw, compared to a central screw position with only cancellous bone support, increases the stability of femoral neck fractures. PMID:8451951

  6. SCREW MIGRATION IN TOTAL KNEE ARTHROPLASTY: CLINICAL REPORT

    PubMed Central

    Fonseca, Fernando; Tomé, José; Barreto, Manuel

    2015-01-01

    Complications from total knee arthroplasty caused by the implanted material are rare, with the exception of polyethylene wear. Descriptions of screw migration into the knee joint cavity are very rare. The authors report intra-articular migration of a polyethylene safety screw in a case of total knee arthroplasty, with sacrifice of the posterior cruciate ligament (TKA Performance; Biomet, Warsaw, IN, USA), which necessitated new surgery to remove the screw, replace the polyethylene insert and emplace a new fixation screw.

  7. The Use of MMF Screws: Surgical Technique, Indications, Contraindications, and Common Problems in Review of the Literature

    PubMed Central

    Cornelius, Carl-Peter; Ehrenfeld, Michael

    2010-01-01

    Mandibulo-maxillary fixation (MMF) screws are inserted into the bony base of both jaws in the process of fracture realignment and immobilisation. The screw heads act as anchor points to fasten wire loops or rubber bands connecting the mandible to the maxilla. Traditional interdental chain-linked wiring or arch bar techniques provide the anchorage by attached cleats, hooks, or eyelets. In comparison to these tooth-borne appliances MMF screws facilitate and shorten the way to achieve intermaxillary fixation considerably. In addition, MMF screws help to reduce the hazards of glove perforation and wire stick injuries. On the downside, MMF screws are attributed with the risk of tooth root damage and a lack of versatility beyond the pure maintenance of occlusion such as stabilizing loose teeth or splinting fragments of the alveolar process. The surgical technique of MMF screws as well as the pros and cons of the clinical application are reviewed. The adequate screw placement to prevent serious tooth root injuries is still an issue to rethink and modify conceptual guidelines. PMID:22110819

  8. Pull-out strength comparison of a novel expanding fastener against an orthopaedic screw in an ovine vertebral body: an ex-vivo study.

    PubMed

    Oldakowski, Matthew; Oldakowska, Intan; Kirk, Thomas B; Ford, Chris T; Sercombe, Tim B; Hardcastle, Philip; Day, Robert E

    2016-02-01

    The purpose of this study was to mechanically test a novel Unthreaded Expandable Fastener (UEF), manufactured using Selective Laser Melting, which was designed for fixation in the cervical lateral mass. The pull-out strength and stiffness of the prototype UEFs was evaluated in a non-osteoporotic ovine bone model against equivalent screws. The prototype UEF demonstrated a 41% increase in failure force and a 60% reduction in failure force standard deviation compared to the screws. All bone samples were micro CT-scanned and no significant differences in bone microstructural properties was found between the screw and UEF sample sets, indicating that the UEFs may be less sensitive to bone quality variation. This increased performance can potentially translate into improved surgical outcome and reduced surgical risk for lateral mass fixation. With further design optimisation, additional improvement in performance over screws may be possible in future studies. PMID:26758778

  9. Treating forearm fractures using an internal fixator: a prospective study.

    PubMed

    Fernndez Dell'Oca, A A; Tepic, S; Frigg, R; Meisser, A; Haas, N; Perren, S M

    2001-08-01

    Some major complications of internal fixation with plates, such as infections and disturbance of healing, have been shown to be related to necrosis of bone and to the soft tissues immediately deep to the plate. This is attributable to plate contact. To deal with this phenomenon, an internal fixator, the Point Contact Fixator, was developed according to a new concept. The Point Contact Fixator resembles a plate but functions like a fixator, that is, the fracture is stabilized using a splint fixed to the bone by monocortical, angularly locked screws that are designed not to exert pressure between the splint and the bone, thereby minimizing implant-to-bone contact. Vascular damage to the osseous blood supply consequently is avoided. The new internal fixator is the first of a new family of implants in addition to nails, plates, and external fixators. To study the potential of the Point Contact Fixator in a prospective study, 79 forearm fractures in 55 patients were treated in a consecutive series by one surgeon using the same technique throughout. Followup to union is reported for 100% of the patients. Handling the fixator was simple; healing was uneventful; and the rate of complication was low. PMID:11501811

  10. Medial malleolar fractures: a biomechanical study of fixation techniques.

    PubMed

    Fowler, T Ty; Pugh, Kevin J; Litsky, Alan S; Taylor, Benjamin C; French, Bruce G

    2011-08-01

    Fracture fixation of the medial malleolus in rotationally unstable ankle fractures typically results in healing with current fixation methods. However, when failure occurs, pullout of the screws from tension, compression, and rotational forces is predictable. We sought to biomechanically test a relatively new technique of bicortical screw fixation for medial malleoli fractures. Also, the AO group recommends tension-band fixation of small avulsion type fractures of the medial malleolus that are unacceptable for screw fixation. A well-documented complication of this technique is prominent symptomatic implants and secondary surgery for implant removal. Replacing stainless steel 18-gauge wire with FiberWire suture could theoretically decrease symptomatic implants. Therefore, a second goal was to biomechanically compare these 2 tension-band constructs. Using a tibial Sawbones model, 2 bicortical screws were compared with 2 unicortical cancellous screws on a servohydraulic test frame in offset axial, transverse, and tension loading. Second, tension-band fixation using stainless steel wire was compared with FiberWire under tensile loads. Bicortical screw fixation was statistically the stiffest construct under tension loading conditions compared to unicortical screw fixation and tension-band techniques with FiberWire or stainless steel wire. In fact, unicortical screw fixation had only 10% of the stiffness as demonstrated in the bicortical technique. In a direct comparison, tension-band fixation using stainless steel wire was statistically stiffer than the FiberWire construct. PMID:21815575

  11. The Effects of Spinopelvic Parameters and Paraspinal Muscle Degeneration on S1 Screw Loosening

    PubMed Central

    Kim, Jin-Bum; Lee, Young-Seok; Nam, Taek-Kyun; Park, Yong-Sook; Kim, Young-Baeg

    2015-01-01

    Objective To investigate risk factors for S1 screw loosening after lumbosacral fusion, including spinopelvic parameters and paraspinal muscles. Methods We studied with 156 patients with degenerative lumbar disease who underwent lumbosacral interbody fusion and pedicle screw fixation including the level of L5-S1 between 2005 and 2012. The patients were divided into loosening and non-loosening groups. Screw loosening was defined as a halo sign larger than 1 mm around a screw. We checked cross sectional area of paraspinal muscles, mean signal intensity of the muscles on T2 weight MRI as a degree of fatty degeneration, spinopelvic parameters, bone mineral density, number of fusion level, and the characteristic of S1 screw. Results Twenty seven patients showed S1 screw loosening, which is 24.4% of total. The mean duration for S1 screw loosening was 7.3±4.1 months after surgery. Statistically significant risk factors were increased age, poor BMD, 3 or more fusion levels (p<0.05). Among spinopelvic parameters, a high pelvic incidence (p<0.01), a greater difference between pelvic incidence and lumbar lordotic angle preoperatively (p<0.01) and postoperatively (p<0.05). Smaller cross-sectional area and high T2 signal intensity in both multifidus and erector spinae muscles were also significant muscular risk factors (p<0.05). Small converging angle (p<0.001) and short intraosseous length (p<0.05) of S1 screw were significant screw related risk factors (p<0.05). Conclusion In addition to well known risk factors, spinopelvic parameters and the degeneration of paraspinal muscles also showed significant effects on the S1 screw loosening. PMID:26587190

  12. Clear Zone Formation around Screws in the Early Postoperative Stages after Posterior Lumbar Fusion Using the Cortical Bone Trajectory Technique

    PubMed Central

    Iwatsuki, Koichi; Ohnishi, Yu-Ichiro; Ohkawa, Toshika; Yoshimine, Toshiki

    2015-01-01

    Study Design Retrospective study. Purpose To evaluate the initial fixation using the cortical bone trajectory (CBT) technique for posterior lumbar fusion through assessment of the clear zones around the screws and the risk factors involved. Overview of Literature Postoperative radiolucent zones (clear zones) are an indicator of poor conventional pedicle screw fixation. Methods Between January 2013 and April 2014, 19 patients (8 men and 11 women) underwent posterior lumbar interbody fusion or posterior lumbar fusion using the CBT technique. A total of 109 screws were used for evaluation with measurement of the maximum insertional torque of last two screw rotations. Clear zone-positivity on plain radiographs was investigated 6 months after surgery. The relation between intraoperative insertional torque and clear zone-positivity was investigated by one-way analysis of variance. In addition, the correlation between clear zone-positivity and gender, age (<75 years old or >75 years old), or operative stabilization level (<2 or >3 vertebral levels) was evaluated using the chi-square test. Results Clear zones were observed around six screws (5.50%) in five patients (26.3%). The mean insertional torque (4.00±2.09 inlbs) of clear zone-positive screws was lower than that of clear zone-negative screws (8.12±0.50 in-lbs), but the difference was not significant. There was a significant correlation between clear zone-positivity and operative level of stabilization. Conclusions The low incidence of clear zone-positive screws indicates good initial fixation using the CBT technique. Multilevel fusions may be risk factors for clear zone generation. PMID:26713120

  13. Reverse oblique end screws in nonlocking plates decrease construct strength in synthetic osteoporotic bone medium.

    PubMed

    Charpentier, Paul M; Flanagan, Brian P; Srivastava, Ajay K; Atkinson, Patrick J

    2015-01-01

    Fracture stability can be challenging for osteoporotic individuals. The end screw of nonlocked plates is subjected to the greatest loading and is typically the site of construct failure. To enhance fixation, the end screw can be angled away from the fracture. The current study biomechanically evaluated screws angled the other direction: toward the fracture using 3.5-mm dynamic compression plates in an osteoporotic bone model. Three different plate lengths (6-, 8-, 12-hole) were tested in three-point bending with an oblique, perpendicular, or reverse oblique end screw. The peak load for loss of screw fixation for the reverse oblique end screw constructs was significantly less than the other screw orientations for all plate lengths. The 12-hole peak load, energy, and displacement magnitudes for all three screw orientations were significantly greater than all 6- and 8-hole constructs. The use of a reverse oblique end screw is inferior to both perpendicular and oblique end screws. PMID:25988696

  14. Biomechanical Analysis of Differing Pedicle Screw Insertion Angles

    PubMed Central

    Sterba, William; Kim, Do-Gyoon; Fyhrie, David P.; Yeni, Yener N.; Vaidya, Rahul

    2007-01-01

    Background Pedicle screw fixation to stabilize lumbar spinal fusion has become the gold standard for posterior stabilization. A significant percentage of surgical candidates are classified as obese or morbidly obese. For these patients, the depth of the incisions and soft tissue makes it extremely difficult to insert pedicle screws along the pedicle axis. As such, the pedicle screws could only be inserted in a much more sagittal axis. However, biomechanical stability of the angled screw insertion has been controversial. We hypothesized that the straight or parallel screw was a more stable construct compared to the angled or axially inserted screw when subjected to caudal cyclic loading. Methods We obtained 12 fresh frozen lumbar vertebrae from L3 to L5 from five cadavers. Schantz screws (6.0mm) were inserted into each pedicle, one angled and along the axis of the pedicle and the other parallel to the spinous process. Fluoroscopic imaging was used to guide insertion. Each screw was then subjected to caudal cyclic loads of 50N for 2000 cycles at 2Hz. Analysis of initial damage, initial rate, and total damage during cyclic loading was undertaken. Findings Average total fatigue damage for straight screws measured 0.3980.38 mm, and 0.6890.96 mm for angled screws. Statistical analysis for total fatigue damage ratio of angled to straight screws revealed that a significant stability was achieved in straight- screw construct (p<0.03). Interpretation This study showed that straight screw insertion results in a more stable pedicle-screw construct. The angled screw insertion technique resulted in more scattered values of damage indicating that the outcome from the angled screw fixation is less predictable. This validates the use of this technique to implant pedicle screws across the axis of the pedicle rather than along the axis, (parallel to the midline sagittal line), and has broad implications in instrumented posterior lumbar spinal surgery. PMID:17208340

  15. Loosening torque of Universal Abutment screws after cyclic loading: influence of tightening technique and screw coating

    PubMed Central

    Regalin, Alexandre; Bhering, Claudia Lopes Brilhante; Alessandretti, Rodrigo; Spazzin, Aloisio Oro

    2015-01-01

    PURPOSE The purpose of this study was to evaluate the influence of tightening technique and the screw coating on the loosening torque of screws used for Universal Abutment fixation after cyclic loading. MATERIALS AND METHODS Forty implants (Titamax Ti Cortical, HE, Neodent) (n=10) were submerged in acrylic resin and four tightening techniques for Universal Abutment fixation were evaluated: A - torque with 32 Ncm (control); B - torque with 32 Ncm holding the torque meter for 20 seconds; C - torque with 32 Ncm and retorque after 10 minutes; D - torque (32 Ncm) holding the torque meter for 20 seconds and retorque after 10 minutes as initially. Samples were divided into subgroups according to the screw used: conventional titanium screw or diamond like carbon-coated (DLC) screw. Metallic crowns were fabricated for each abutment. Samples were submitted to cyclic loading at 106 cycles and 130 N of force. Data were analyzed by two-way ANOVA and Tukey's test (5%). RESULTS The tightening technique did not show significant influence on the loosening torque of screws (P=.509). Conventional titanium screws showed significant higher loosening torque values than DLC (P=.000). CONCLUSION The use of conventional titanium screw is more important than the tightening techniques employed in this study to provide long-term stability to Universal Abutment screws. PMID:26576253

  16. The biomechanical aspects of reconstruction for segmental defects of the mandible: a finite element study to assess the optimisation of plate and screw factors.

    PubMed

    Bujtr, Pter; Simonovics, Jnos; Vradi, Kroly; Sndor, George K B; Avery, C M E

    2014-09-01

    A bone plate is required to restore the load-bearing capacity of the mandible following a segmental resection. A good understanding of the underlying principles is crucial for developing a reliable reconstruction. A finite element analysis (FEA) technique has been developed to study the biomechanics of the clinical scenarios managed after surgical resection of a tumour or severe trauma to assist in choosing the optimal hardware elements. A computer aided design (CAD) model of an edentulous human mandible was created. Then 4 common segmental defects were simulated. A single reconstruction plate was designed to span the defects. The hardware variations studied were: monocortical or bicortical screw fixation and non-locking or locking plate design. A standardized load was applied to mimic the human bite. The von Mises stress and strain, spatial changes at the screw-bone interfaces were analysed. In general, the locking plate and monocortical screw fixation systems were most effective. Non-locking plating systems produced larger screw "pull-out" displacements, especially at the hemimandible (up to 5% strain). Three screws on either side of the defect were adequate for all scenarios except extensive unilateral defects when additional screws and an increased screw diameter are recommended. The simplification of screw geometry may underestimate stress levels and factors such as poor adaptation of the plate or reduced bone quality are likely to be indications for bicortical locking screw fixation. The current model provides a good basis for understanding the complex biomechanics and developing future refinements in plate or scaffold design. PMID:24467871

  17. Medial malleolus screws: out in one view and out.

    PubMed

    Wera, Jeffrey C; Seligson, David; Riehl, John T

    2015-10-01

    Cartilage damage or mechanical blocking from screw penetration into intra-articular cartilage can reduce the chances of successful outcomes during medial malleolus fixation. There have been diverging opinions among surgeons concerning the reliability of radiographic assessment of fracture fixation and malleolus screw positioning. Therefore, this radiographic study examines the location of medial malleolus lag screws relative to the ankle mortise articular surface. In three Sawbones models, Kirschner wires were overdrilled with a 4.0-mm cannulated cortical screw simulating screws that would be intra- and extra-articular when performing open reduction and internal fixation of a medial malleolar fracture. Under fluoroscopy, images were evaluated to determine whether known intra-articular screws appeared extra-articular in any radiographic view. No image from models with known intra-articular penetration appeared extra-articular in any view or under "live" fluoroscopy. At 20 internal rotation, a screw with a known extra-articular position appeared to be within the cartilage. Intra-operative fluoroscopy is necessary to ensure proper extra-articular placement of screws. If a screw is pictured extra-articular in any radiograph, then it can be assumed that the screw is indeed out of the joint. PMID:26198780

  18. Systemic nickel allergy after internal fixation of a bunionectomy.

    PubMed

    Zhubrak, Michelle; Bar-David, Tzvi

    2014-01-01

    Allergic reactions to implanted metals have been estimated to occur in 1% to 5% of orthopedic cases. Stainless steel screws, which contain 14% nickel, are commonly used for internal fixation in an array of podiatric procedures. We present a rare case of a systemic allergic reaction to nickel secondary to stainless steel screw fixation in a bunionectomy procedure. PMID:24774988

  19. Polypyrrole coating on poly-(lactide/glycolide)-?-tricalcium phosphate screws enhances new bone formation in rabbits.

    PubMed

    Zhao, Ming-Dong; Bjrninen, Miina; Cao, Lu; Wang, Hui-Ren; Pelto, Jani; Li, Xiang-Qian; Hyttinen, Jari; Jiang, Yun-Qi; Kellomki, Minna; Miettinen, Susanna; Sndor, George K; Seppnen, Riitta; Haimi, Suvi; Dong, Jian

    2015-12-01

    Polypyrrole (PPy) has gained interest as an implant material due to its multifunctional properties and its high compatibility with several cell and tissue types. For the first time, the biocompatibility and osteointegration of PPy coating, incorporated with chondroitin sulfate (CS), were studied in vivo by implanting PPy-coated bioabsorbable bone fixation composite screws of poly-(lactide/glycolide) copolymer (PLGA) and ?-tricalcium phosphate (TCP) into New Zealand white rabbits. Uncoated bioabsorbable polymer composite screws and commercially available stainless steel cortical screws were used as reference implants. The rabbits were euthanized 12 and 26 weeks after the implantation. The systemic effects were evaluated from food and water consumption, body weight, body temperature, clinical signs, blood samples, internal organ weights, and histological examination. Local effects were studied from bone tissue and surrounding soft tissue histology. New bone formation was evaluated by micro-computed tomography, tetracycline labeling and torsion tests. Torsion tests were performed in order to capture the peak value of the torsion force during the course of the screw's loosening. The coated screws induced significantly more bone formation than the uncoated screws. In addition, none of the implants induced any systemic or local toxicity. The results suggest that PPy is biocompatible with bone tissue and is a potential coating for enhancing osteointegration in orthopedic implants. PMID:26610717

  20. Apparatus to test insertion and removal torque of bone screws.

    PubMed

    Koistinen, A; Santavirta, S; Lappalainen, R

    2003-01-01

    This paper describes affordable equipment for testing bone screw torque, corresponding to ASTM standard F543-00 for testing metallic medical bone screws. Correct testing of thin and long bone screws is essential due to screw failures during insertion and removal of the screws. Furthermore, insertion torque is an important factor in predicting fixation strength, screw pull-out force and effects of surface treatment of screws. The capability of the custom-built tester was determined using polytetrafluoroethylene and wood disc samples and bone screws. Bovine cortical bones allowed testing to the failure limit, i.e. the torque increased in long screws to the fracture limit. For 2.7 and 3.5 mm thick self-tapping cortical bone screws, the failure torques were 30-50 per cent higher than the minimum values required by the standard (1.0 and 2.3 N m respectively). The equipment provided reproducible results and fulfilled the ASTM standard very well. Preliminary testing with amorphous diamond coated bone screws showed good durability of the coating and on average 10-15 per cent lower torque values compared with uncoated screws. The equipment can be used to measure insertion and removal torques as described in the standard. Furthermore, it also allows testing of normal screws and bolts. PMID:14702987

  1. Flexible fixation and fracture healing: do locked plating 'internal fixators' resemble external fixators?

    PubMed

    Schmal, Hagen; Strohm, Peter C; Jaeger, Martin; Südkamp, Norbert P

    2011-02-01

    External and internal fixators use bone screws that are locked to a plate or bar to prevent periosteal compression and associated impairment of blood supply. Both osteosynthesis techniques rely on secondary bone healing with callus formation with the exception of compression plating of simple, noncomminuted fractures. External fixation uses external bars for stabilization, whereas internal fixation is realized by subcutaneous placement of locking plates. Both of these "biologic" osteosynthesis methods allow a minimally invasive approach and do not compromise fracture hematoma and periosteal blood supply. Despite these similarities, differences between the two fixation methods prevail. Locked plating "internal fixators" allow a combination of biomechanical principles such as buttressing and dynamic compression. Periarticular locking plates are anatomically contoured to facilitate fixation of articular fractures. They allow for subchondral stabilization using small-diameter angular stable screws as well as buttressing of the joint and the metaphyseal component of a fracture. Biomechanically, they can be far stiffer than external fixators, because subcutaneous plates are located much closer to the bone surface than external fixator bars. External fixators have the advantage of being less expensive, highly flexible, and technically less demanding. They remain an integral part of orthopaedic surgery for emergent stabilization, for pediatric fractures, for definitive osteosynthesis in certain indications such as distal radius fractures, and for callus distraction. PMID:21248555

  2. A biomechanical comparison of Schuhli nuts or cement augmented screws for plating of humeral fractures.

    PubMed

    Jazrawi, L M; Bai, B; Simon, J A; Kummer, F J; Birdzell, L T; Koval, K J

    2000-08-01

    Schuhli locking nuts can be used in poor quality cortical bone to enhance fixation stability as an alternative to cement augmented screws. This study compared the fixation strength and stability of plate constructs using Schuhli locking nuts with standard screws and cement augmented screws for fixation of simulated humeral shaft fractures in a test model with osteoporosis. The constructs were tested in axial compression, 4-point bending, and torsion to determine fixation stability. The humeri were cycled in torsion (4.5 Nm) for 1000 cycles to simulate upper extremity use during the early postoperative period and retested for stability. The Schuhli locking nuts and cement augmented screws had significantly greater fixation stability than the standard screws before (range, 6-14 times greater) and after cycling in torsional loading (range, 3-3.6 times greater). Although cement augmented screws and Schuhli augmentation showed increased fixation stability compared with the standard screws in axial and 4-point bending before cycling (range, 1.3-1.4 times greater), this was not significant. Compared with Schuhli fixation, cement augmented screws showed no significant difference in fixation stability in all loading modes before and after cycling. Schuhli locking nuts offer the stability of cement augmentation while avoiding its potential adverse effects on fracture healing with extravasation and thermal necrosis. PMID:10943207

  3. Pullout Strength after Expandable Polymethylmethacrylate Transpedicular Screw Augmentation for Pedicle Screw Loosening

    PubMed Central

    Cho, Yong Jun; Kim, Young-Baeg; Park, Seung Won

    2015-01-01

    Objective Pedicle screw fixation for spine arthrodesis is a useful procedure for the treatment of spinal disorders. However, instrument failure often occurs, and pedicle screw loosening is the initial step of a range of complications. The authors recently used a modified transpedicular polymethylmethacrylate (PMMA) screw augmentation technique to overcome pedicle screw loosening. Here, they report on the laboratory testing of pedicle screws inserted using this modified technique. Methods To evaluate pullout strengths three cadaveric spinal columns were used. Three pedicle screw insertion methods were utilized to compare pullout strength; the three methods used were; control (C), traditional transpedicular PMMA augmentation technique (T), and the modified transpedicular augmentation technique (M). After control screws had been pulled out, loosening with instrument was made. Screw augmentations were executed and screw pullout strength was rechecked. Results Pedicle screws augmented using the modified technique for pedicle screw loosening had higher pullout strengths than the control (1106.2458.0 N vs. 741.2269.5 N; p=0.001). Traditional transpedicular augmentation achieved a mean pullout strength similar to that of the control group (657.5172.3 N vs. 724.5234.4 N; p=0.537). The modified technique had higher strength than the traditional PMMA augmentation technique (1070.8358.6 N vs. 652.2185.5 N; p=0.023). Conclusion The modified PMMA transpedicular screw augmentation technique is a straightforward, effective surgical procedure for treating pedicle screw loosening, and exhibits greater pullout strength than traditional PMMA transpedicular augmentation. However, long-term clinical evaluation is required. PMID:25932288

  4. Solid and hollow pedicle screws affect the electrical resistance: A potential source of error with stimulus-evoked electromyography

    PubMed Central

    Wang, Hongwei; Liao, Xinhua; Ma, Xianguang; Li, Changqing; Han, Jianda; Zhou, Yue

    2013-01-01

    Background: Although stimulus evoked electromyography (EMG) is commonly used to confirm the accuracy of pedicle screw placement. There are no studies to differentiate between solid screws and hollow screws to the electrical resistance of pedicle screws. We speculate that the electrical resistance of the solid and hollow pedicle screws may be different and then a potential source of error with stimulus-evoked EMG may happen. Materials and Methods: Resistance measurements were obtained from 12 pedicle screw varieties (6 screws of each manufacturer) across the screw shank based on known constant current and measured voltage. The voltage was measured 5 times at each site. Results: Resistance of all solid screws ranged from 0.084 Ω to 0.151 Ω (mean =0.118 ± 0.024 Ω) and hollow screws ranged from 0.148 Ω to 0.402 Ω (mean = 0.285 ± 0.081 Ω). There was a significant difference of resistance between the solid screws and hollow screws (P < 0.05). The screw with the largest diameter no matter solid screws or hollow screws had lower resistance than screws with other diameters. No matter in solid screws group or hollow screws group, there were significant differences (P < 0.05) between the 5.0 mm screws and 6.0 mm screws, 6.0 mm screws and 7.0 mm screws, 5.0 mm screws and 7.0 mm screws, 4.5 mm screws and 5.5 mm screws, 5.5 mm screws and 6.5 mm screws, 4.5 mm screws and 6.5 mm screws. The resistance of hollow screws was much larger than the solid screws in the same diameter group (P < 0.05). Conclusions: Hollow pedicle screws have the potential for high electrical resistance compared to the solid pedicle screws and therefore may affect the EMG response during stimulus-evoked EMG testing in pedicle screw fixation especially in minimally invasive percutaneous pedical screw fixation surgery. PMID:23960278

  5. High speed fracture fixation: assessing resulting fixation stability and fastener withdrawal strength.

    PubMed

    Prygoski, Matthew Philip; Sanchez Caballero, Samuel; Schmid, Steven R; Lozier, Antony J; Selles, Miguel Angel

    2013-09-01

    A new method of bone fracture fixation has been developed in which fixation darts (small diameter nails/pins) are driven across a fracture site at high velocity with a pneumatically powered gun. When fixation darts are inserted oblique to one another, kinematic constraints prevent fragment motion and allow bone healing to progress. The primary aim of this study is to determine if fixation darts can provide reasonable fixation stability compared to bone screws, which were used as a benchmark since they represent a simple, yet well-established, surgical technique. The first objective was to evaluate macro-level stability using different numbers of darts inserted parallel and oblique to each other; experimental comparisons were undertaken in a bone analog model. Experimental results showed fixation darts could not be substituted for screws on a one-to-one basis, but that a plurality of fixation darts provided comparable fixation to two bone screws while allowing for faster insertion and damaging less bone. A second objective was to evaluate micro-level stability; a finite element model was created in order to provide a detailed look at the stress state surrounding the fixation darts and the evolution of the fracture gap. Even with relatively weak fixation dart configurations, the fracture gap was maintained below physiological thresholds for bone healing. Most failures of the fixed fractures were attributed to fixation dart pullout from the cancellous structure. The final objective of the study was to characterize this mode of failure with separate fixation dart and screw pullout tests conducted in Sawbones cancellous foam and fresh porcine cancellous bone. The results showed that the cancellous foam was an acceptable substitute for real bone and provided a conservative estimate of the fixation darts' performance relative to bone screws. A final comparison between experimental and numerically predicted pullout strengths provided confirmation that the model and experiments were consistent. PMID:23722627

  6. The holding power of orthopedic screws in vivo.

    PubMed

    Schatzker, J; Sanderson, R; Murnaghan, J P

    1975-05-01

    Great difficulty is encountered in choosing screws for internal fixation, for screws differ in material, geometry, dimension, and in insertion technique. Recently claims have been made that self-tapping screws cause necrosis of bone and result in fibrous tissue formation, with loss of holding power. This investigation was undertaken to study the healing of bone about screws inserted for a period of 3 months. Self tapping and non-self tapping screws were employed. The Vitallium screws not only differed in dimension, but also in configuration of the thread, with the smaller of the self-tapping screws exhibiting a "V" thread in distinction to the buttress thread of the larger screw. The histologic data were correlated with the holding power of the screws as obtained by means of a push out test, performed with the aid of an Instrom testing machine. The largest screw tested, the 4.5 mm non-self tapping stainless steel AO screw (Type 1), provided the greatest safety factor to push out loading over the period tested in the unloaded system. The self tapping and non-self tapping screws of similar material and size were found to maintain comparable holding power at all intervals tested in vivo in the unloaded system. No histological differentiation could be made with regard to both death or tissue reaction around the implant, between the stainless steel or cobalt chromium alloy materials, nor between the self tapping and non-self tapping insertion methods. PMID:1139814

  7. [External fixator: surgical technique, pinless fixator, change in procedure].

    PubMed

    Oberli, H; Frigg, R; Schenk, R

    1994-12-01

    External Fixation-Technique: The advantages of external over internal fixation are as follows: a) endosteal and periosteal blood supply is undisturbed, b) "low-tech" equipment may be used, c) secondary adjustments are possible and d) easy implant removal. These benefits however are outweighed by the main disadvantages of long term external fixation i.e. pin complications and delayed union of fractures. Better understanding of postoperative management and careful application of screws of improved design will lead to better results. Today's standard applications of external fixation for tibial fractures is a unilateral fixator, using Schanz screws. The pin-bone interface is the most critical site of all external fixation. By avoiding heat necrosis (low temperature drilling) and preventing micro motion at the pin-bone interface (by applying bending- or more recently radial-preload), pin complications such as infection and loosening can be reduced. Two Schanz screws are inserted into each main fragment and are connected with one short tube per fragment. The fracture is then reduced by using these tubes as handles. After reduction a third tube connects the first two by means of two tube-to-tube clamps. This type of fixation will easily allow for three dimensional secondary corrections of alignment. Approximately three weeks following the injury some motion at the fracture site will stimulate callus formation. This can be achieved by destabilisation, dynamisation or "active stimulation" of the fracture site [2]. Pinless fixator: The pinless external fixator holds the fragments firmly with pointed clamps that penetrate about one millimeter into cortical bone without entering and contaminating the medullary canal.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7875986

  8. Surgical Treatment of Calcaneal Avulsion Fracture in Elderly Patients Using Cannulated Cancellous Screws and Titanium Wire.

    PubMed

    Miyamura, Satoshi; Ota, Haruka; Okamoto, Michio; Namba, Jiro; Yamamoto, Koji

    2016-01-01

    Avulsion fractures of the calcaneus are relatively uncommon and are seen most frequently in elderly or osteoporotic patients. A surgical method that avoids displacement of the avulsed fragment after fixation has not been developed. We report the cases of 3 patients (a 73-year-old male, an 85-year-old male, and an 81-year-old female) treated by open reduction and internal fixation using titanium wire and cannulated cancellous screws. The posterior approach was used by way of a vertical midline incision. The fracture was fixed with 2 screws, and then a titanium wire was passed through the holes of the cannulated screws. A small incision on the lateral side of planter was added for the exit and return of the wire. The wire knot was bent inside the proximal Achilles tendon bursa in 2 patients and was directed to the plantar side in 1 to avoid irritation. Bony union was achieved without repeat displacement of the fragment in all 3 patients. Normal ankle function was restored, and the patients recovered the activities of daily living almost to the original level. Although an additional plantar incision is required, this surgical technique provides strong internal fixation. PMID:26440932

  9. Cell-specific CO2 fixation rates of two distinct groups of plastidic protists in the Atlantic Ocean remain unchanged after nutrient addition.

    PubMed

    Grob, Carolina; Jardillier, Ludwig; Hartmann, Manuela; Ostrowski, Martin; Zubkov, Mikhail V; Scanlan, David J

    2015-04-01

    To assess the role of open-ocean ecosystems in global CO2 fixation, we investigated how picophytoplankton, which dominate primary production, responded to episodic increases in nutrient availability. Previous experiments have shown nitrogen alone, or in combination with phosphorus or iron, to be the proximate limiting nutrient(s) for total phytoplankton grown over several days. Much less is known about how nutrient upshift affects picophytoplankton CO2 fixation over the duration of the light period. To address this issue, we performed a series of small volume (8-60 ml) - short term (10-11 h) nutrient addition experiments in different regions of the Atlantic Ocean using NH4 Cl, FeCl3 , K medium, dust and nutrient-rich water from 300 m depth. We found no significant nutrient stimulation of group-specific CO2 fixation rates of two taxonomically and size-distinct groups of plastidic protists. The above was true regardless of the region sampled or nutrient added, suggesting that this is a generic phenomenon. Our findings show that at least in the short term (i.e. daylight period), nutrient availability does not limit CO2 fixation by the smallest plastidic protists, while their taxonomic composition does not determine their response to nutrient addition. PMID:25345650

  10. Surgical screw segmentation for mobile C-arm CT devices

    NASA Astrophysics Data System (ADS)

    Grres, Joseph; Brehler, Michael; Franke, Jochen; Wolf, Ivo; Vetter, Sven Y.; Grtzner, Paul A.; Meinzer, Hans-Peter; Nabers, Diana

    2014-03-01

    Calcaneal fractures are commonly treated by open reduction and internal fixation. An anatomical reconstruction of involved joints is mandatory to prevent cartilage damage and premature arthritis. In order to avoid intraarticular screw placements, the use of mobile C-arm CT devices is required. However, for analyzing the screw placement in detail, a time-consuming human-computer interaction is necessary to navigate through 3D images and therefore to view a single screw in detail. Established interaction procedures of repeatedly positioning and rotating sectional planes are inconvenient and impede the intraoperative assessment of the screw positioning. To simplify the interaction with 3D images, we propose an automatic screw segmentation that allows for an immediate selection of relevant sectional planes. Our algorithm consists of three major steps. At first, cylindrical characteristics are determined from local gradient structures with the help of RANSAC. In a second step, a DBScan clustering algorithm is applied to group similar cylinder characteristics. Each detected cluster represents a screw, whose determined location is then refined by a cylinder-to-image registration in a third step. Our evaluation with 309 screws in 50 images shows robust and precise results. The algorithm detected 98% (303) of the screws correctly. Thirteen clusters led to falsely identified screws. The mean distance error for the screw tip was 0.8 +/- 0.8 mm and for the screw head 1.2 +/- 1 mm. The mean orientation error was 1.4 +/- 1.2 degrees.

  11. Pull-out strengths for a range of screws inserted into the calcaneus: a preliminary study.

    PubMed

    Muller, M; Abel, E W; McLeod, G; Rowley, D I

    1992-05-01

    The holding strengths of AO screws in the calcaneus were tested with a view to incorporating them into a new design of ankle prosthesis aimed at reducing the incidence of loosening. Comparative studies were performed to determine the optimal type and number of screws and their optimal location and thread length. Pull-out tests with 4.5-mm cortical and 6.5-mm cancellous screws were performed on screws inserted into the posterior and middle facets of the calcaneus, these being the two most suitable places for screw fixation. The cancellous screws showed much higher holding strength than the cortical screws. There is room for only a single screw in each facet. The results indicated that a screw of 16-mm thread length should be inserted into the middle facet and a screw of 60-mm thread length into and through the posterior facet. The high holding strengths suggest that screw fixation could be a viable alternative to commonly used methods for anchoring the lower prosthetic component. Further tests are to be conducted which simulate the different types of loads occurring during gait and other activities. These will allow decisions to be made about the benefits of the proposed screw fixation method. This work is part of a long-term project which aims to produce a new ankle prosthesis that does not suffer the problems of loosening associated with present current designs. A strong screw fixation of the talar component may help to improve stability. The results show that a good fixation into the calcaneus can be achieved, and suggest that further work based on this approach is worthwhile. PMID:23915690

  12. Bioabsorbable expansion bolt fixation in anterior cruciate ligament reconstruction.

    PubMed

    Piltz, S; Steinbauer, T; Meyer, L; Plitz, W; Andress, H J; Lob, G

    2004-01-01

    The current study evaluated initial fixation strength of a bioabsorbable expansion bolt compared with interference screw fixation in anterior cruciate ligament reconstruction using a bone-patellar tendon-bone graft. Thirty calf tibial plateaus with adjacent patella and extensor ligaments were used. Bioabsorbable poly-L-lactide interference screws were used for graft fixation in Group I, titanium screws in Group II, and bioabsorbable poly-DL-lactide expansion bolts were used in Group III. The mean force-to-failure (+/- standard deviation) in the three groups was 487 +/- 205 N, 713 +/- 218 N, and 594 +/- 224 N, respectively. The differences between Groups I and II were significant. No statistical differences were found regarding stiffness. Graft damage was significantly less in Group III compared with screw fixation. The fixation concept of an expansion bolt shows similar fixation strength and less graft damage compared with the established interference screw fixation. Because of the total absence of torque forces in contrast to bioabsorbable screws, the risk of implant breakage is minimized. PMID:15043122

  13. Pedicle screw placement in the lumbar spine: effect of trajectory and screw design on acute biomechanical purchase.

    PubMed

    Wray, Steven; Mimran, Ronnie; Vadapalli, Sasidhar; Shetye, Snehal S; McGilvray, Kirk C; Puttlitz, Christian M

    2015-05-01

    OBJECT Low bone mineral density in patients undergoing lumbar spinal surgery with screws is an especially difficult challenge because poor bone quality can severely compromise the maximum achievable purchase of the screws. A relatively new technique, the cortical bone screw trajectory, utilizes a medialized trajectory in the caudocephalad direction to engage a greater amount of cortical bone within the pars interarticularis and pedicle. The objectives of this cadaveric biomechanical study were to 1) evaluate a cortical screw system and compare its mechanical performance to the traditional pedicle screw system; 2) determine differences in bone quality associated with the cortical screw trajectory versus the normal pedicle screw insertion technique; 3) determine the cortical wall breach rate with both the cortical and traditional screw trajectories; and 4) determine the performance of the traditional screw in the cortical screw trajectory. METHODS Fourteen fresh frozen human lumbar spine sections (L1-5) were used in this study (mean age 57 19 years). The experimental plan involved drilling and tapping screw holes for 2 trajectories under navigation (a traditional pedicle screw and a cortical screw) in both high-and low-quality vertebrae, measuring the bone quality associated with these trajectories, placing screws in the trajectories, and evaluating the competence of the screw purchase via 2 mechanical tests (pullout and toggle). The 3 experimental variants were 1) traditional pedicle screws placed in the traditional pedicle screw trajectory, 2) traditional pedicle screws placed in the cortical screw trajectory, and 3) cortical screws placed in the cortical screw trajectory. RESULTS A statistically significant increase in bone quality was observed for the cortical trajectories with a cortical screw (42%; p < 0.001) and traditional pedicle screw (48%; p < 0.001) when compared to the traditional trajectory with a traditional pedicle screw within the high-quality bone group. These significant differences were also found in the lowquality bone cohort. All mechanical parameter comparisons (screw type and trajectory) between high-quality and lowquality samples were significant (p < 0.01), and these data were all linearly correlated (r ? 0.65) to bone mineral density. Not all mechanical parameters determined from pullout and toggle testing were statistically significant between the 3 screw/trajectory combinations. The incidence of cortical wall breach with the cortical or traditional pedicle screw trajectories was not significantly different. CONCLUSIONS The data demonstrated that the cortical trajectory provides denser bone that allows for utilization of smaller screws to obtain mechanical purchase that is equivalent to long pedicle screws placed in traditional pedicle screw trajectories for both normal- and low-quality bone. Overall, this biomechanical study in cadavers provides evidence that the cortical screw trajectory represents a good option to obtain fixation for the lumbar spine with low-quality bone. PMID:25679236

  14. Role of the compression screw in the dynamic hip-screw system: A finite-element study.

    PubMed

    Chang, Chih-Wei; Chen, Yen-Nien; Li, Chun-Ting; Peng, Yao-Te; Chang, Chih-Han

    2015-12-01

    The dynamic hip-screw (DHS) system is a common implant for fixation of proximal femur fractures. During assembly, it has been recommended to remove the compression screw after initial compression has been obtained; however, related complications had been reported. So far, the role of compression screw in the reconstructed stability of hip fractures as well as the mechanical strength of the DHS system has rarely been mentioned. This study investigated the function of this screw in the DHS system during fracture healing. Based on the FE method, six numerical models of proximal femur were employed to analyze the mechanical response of a DHS implant with various fracture types and different fixation strategies (with or without a compression screw). The displacement of the femur head and peak von Mises stress were selected as indices of the stability of a fractured femur stabilized by a DHS device and of the risk of implant failure, respectively. Our results showed that a retained compression screw increased reconstructed structural stiffness, reducing the displacement of the femur head. This screw also helped to lessen mechanical failure of side plate by reducing the peak von Mises stress around the connection between the barrel and side plate. Both findings were evident in the proximal femur fracture involving the intertrochanteric part, and even more obvious in the setting of bony defects. Thus, we recommend the maintenance of compression screw in the DHS system while treating the intertrochanteric fracture, particularly in cases with bony defects. PMID:26521645

  15. The effect of screw insertion angle and thread type on the pullout strength of bone screws in normal and osteoporotic cancellous bone models.

    PubMed

    Patel, Purvi S D; Shepherd, Duncan E T; Hukins, David W L

    2010-10-01

    Screw fixation can be extremely difficult to achieve in osteoporotic (OP) bone because of its low strength. This study determined how pullout strength is affected by placing different bone screws at varying angles in normal and OP bone models. Pullout tests of screws placed axially, and at angles to the pullout axis (ranging from 10 to 40), were performed in 0.09 g cm(-3), 0.16 g cm(-3) and 0.32 g cm(-3) polyurethane (PU) foam. Two different titanium alloy bone screws were used to test for any effect of thread type (i.e. cancellous or cortical) on the screw pullout strength. The cancellous screw required a significantly higher pullout force than the cortical screw (p<0.05). For both screws, pullout strength significantly increased with increasing PU foam density (p<0.05). For screws placed axially, and sometimes at 10, the observed mechanism of failure was stripping of the internal screw threads generated within the PU foam by screw insertion. For screws inserted at 10, 20, 30 and 40, the resistance to pullout force was observed to be by compression of the PU foam material above the angled screw; clinically, this suggests that compressed OP bone is stronger than unloaded OP bone. PMID:20558097

  16. Apparent absence of local response to bone screws in guinea pigs with contact sensitivity.

    PubMed

    Lewin, J; Lindgren, J U; Wahlberg, J E

    1987-01-01

    Guinea pigs sensitized to nickel, cobalt, or chromium were used to study if impaired fixation occurred as a result of allergy against metal implants in bone. Screws made from stainless-steel (ASTM F55, F138-139) or cobalt chromium (ASTM F75-76) were inserted in the right and left proximal tibiae, and the mechanical strength of the fixation to the bone was evaluated after 4 months. In addition, we studied the histology on decalcified sections of the implant bone interface from the distal femur where the same type of screws had been inserted. To see if changes in bone density occurred in the proximal tibia as a result of allergy, the amount of ash was determined. Although the animals maintained their contact sensitivity throughout the experimental period, there were no differences between allergic and control animals for any of the parameters studied. All screws were well fixed in the tibia at the end of the experiment, and histologically we did not find any significant differences between allergic and control animals by qualitative examination. The experiment supports our earlier results from a 6-week experiment and indicates that contact allergy may be unimportant for the fate of orthopedic implants. PMID:3681534

  17. [Bone-supported rapid maxillary expansion with an implant-borne Hyrax screw: the Dresden Distractor].

    PubMed

    Tausche, Eve; Hansen, Lars; Schneider, Matthias; Harzer, Winfried

    2008-06-01

    Rapid palatal expansion is indicated in the orthopedic treatment of transverse maxillary deficiency for correction of severe crossbite. The fixation of the appliance at the teeth crowns leads to more tipping at the two halves of the maxilla than bodily transverse movement. Additional resorptions at the buccal cortical bone with fenestrations and gingival retraction were observed. The aim of the present study was focused on the improvement of bodily movement and optimization of the surgical osteotomy (Glassman's technique) in adult patients with application of the Dresden Distractor (DD). In 15 patients, the new method involving minimized surgical intervention and direct fixation of the hyrax screw by one implant and one bone screw was tested. The implants were loaded directly by activation of the screw two times per day. CT scans were taken before and six month after insertion of the DD. In the horizontal and the vertical planes there was a V-shaped opening of the suture in anterior, respective cranial direction, corroborating previous studies. Dental arch showed this V-shape as well, indicating tooth protection. If forces are transferred via teeth the progressive increase of skeletal resistance in anterior to posterior direction lead to dental tipping. DD is a suitable minimal invasive tooth-independent bone-borne expansion method, protecting teeth and causing skeletal as well as dental effect with 10 degree less tipping and as a precondition for stable post surgical occlusion. PMID:18505675

  18. Factors affecting the pullout strength of cancellous bone screws.

    PubMed

    Chapman, J R; Harrington, R M; Lee, K M; Anderson, P A; Tencer, A F; Kowalski, D

    1996-08-01

    Screws placed into cancellous bone in orthopedic surgical applications, such as fixation of fractures of the femoral neck or the lumbar spine, can be subjected to high loads. Screw pullout is a possibility, especially if low density osteoporotic bone is encountered. The overall goal of this study was to determine how screw thread geometry, tapping, and cannulation affect the holding power of screws in cancellous bone and determine whether current designs achieve maximum purchase strength. Twelve types of commercially available cannulated and noncannulated cancellous bone screws were tested for pullout strength in rigid unicellular polyurethane foams of apparent densities and shear strengths within the range reported for human cancellous bone. The experimentally derived pullout strength was compared to a predicted shear failure force of the internal threads formed in the polyurethane foam. Screws embedded in porous materials pullout by shearing the internal threads in the porous material. Experimental pullout force was highly correlated to the predicted shear failure force (slope = 1.05, R2 = 0.947) demonstrating that it is controlled by the major diameter of the screw, the length of engagement of the thread, the shear strength of the material into which the screw is embedded, and a thread shape factor (TSF) which accounts for screw thread depth and pitch. The average TSF for cannulated screws was 17 percent lower than that of noncannulated cancellous screws, and the pullout force was correspondingly less. Increasing the TSF, a result of decreasing thread pitch or increasing thread depth, increases screw purchase strength in porous materials. Tapping was found to reduce pullout force by an average of 8 percent compared with nontapped holes (p = 0.0001). Tapping in porous materials decreases screw pullout strength because the removal of material by the tap enlarges hole volume by an average of 27 percent, in effect decreasing the depth and shear area of the internal threads in the porous material. PMID:8872262

  19. Pullout performance comparison of pedicle screws based on cement application and design parameters.

    PubMed

    Tolunay, Tolga; Başgül, Cemile; Demir, Teyfik; Yaman, Mesut E; Arslan, Arslan K

    2015-11-01

    Pedicle screws are the main fixation devices for certain surgeries. Pedicle screw loosening is a common problem especially for osteoporotic incidents. Cannulated screws with cement augmentation are widely used for that kind of cases. Dual lead dual cored pedicle screw has already given promising pullout values without augmentation. This study concentrates on the usage of dual lead dual core with cement augmentation as an alternative to cannulated and standard pedicle screws with cement augmentation. Five groups (dual lead dual core, normal pedicle screw and cannulated pedicle screw with augmentation, normal pedicle screw, dual lead dual cored pedicle screw) were designed for this study. Healthy bovine vertebrae and synthetic polyurethane foams (grade 20) were used as embedding test medium. Test samples were prepared in accordance with surgical guidelines and ASTM F543 standard testing protocols. Pullout tests were conducted with Instron 3300 testing frame. Load versus displacement values were recorded and maximum pullout loads were stated. The dual lead dual cored pedicle screw with poly-methyl methacrylate augmentation exhibited the highest pullout values, while dual lead dual cored pedicle screw demonstrated similar pullout strength as cannulated pedicle screw and normal pedicle screw with poly-methyl methacrylate augmentation. The dual lead dual cored pedicle screw with poly-methyl methacrylate augmentation can be used for osteoporotic and/or severe osteoporotic patients according to its promising results on animal cadaver and synthetic foams. PMID:26503840

  20. Treatment of scaphoid waist fractures with the HCS screw

    PubMed Central

    Gehrmann, Sebastian V.; Grassmann, Jan-Peter; Wild, Michael; Jungbluth, Pascal; Kaufmann, Robert A.; Windolf, Joachim; Hakimi, Mohssen

    2014-01-01

    The aim of the study was to evaluate the clinical results of the Headless Compression Screw (HCS, Synthes) when used for treatment of acute scaphoid waist fractures. The new screw design generates interfragmentary compression with use of a compression sleeve. Twenty-one patients were treated for acute scaphoid waist fractures type B2 with HCS screws. The average time to the final follow-up examination was 12.8 months. All 21 fractures united after a mean time of 7.2 weeks. The mean DASH score was 7.1. The average motion of the wrist in extension was 61, flexion was 46, radial abduction reached 25 and the ulnar abduction was 31. The maximally achieved grip strength was 86% compared to the uninjured side. Treatment of type B2 scaphoid fractures with the Headless Compression Screw showed good functional and radiographic results. The results are similar to those identified using other screw fixation systems. PMID:26504721

  1. Tangential View and Intraoperative Three-Dimensional Fluoroscopy for the Detection of Screw-Misplacements in Volar Plating of Distal Radius Fractures

    PubMed Central

    Rausch, Sascha; Marintschev, Ivan; Graul, Isabel; Wilharm, Arne; Klos, Kajetan; Hofmann, Gunther O.; Florian Gras, Marc

    2015-01-01

    Background: Volar locking plate fixation has become the gold standard in the treatment of unstable distal radius fractures. Juxta-articular screws should be placed as close as possible to the subchondral zone, in an optimized length to buttress the articular surface and address the contralateral cortical bone. On the other hand, intra-articular screw misplacements will promote osteoarthritis, while the penetration of the contralateral bone surface may result in tendon irritations and ruptures. The intraoperative control of fracture reduction and implant positioning is limited in the common postero-anterior and true lateral two-dimensional (2D)-fluoroscopic views. Therefore, additional 2D-fluoroscopic views in different projections and intraoperative three-dimensional (3D) fluoroscopy were recently reported. Nevertheless, their utility has issued controversies. Objectives: The following questions should be answered in this study; 1) Are the additional tangential view and the intraoperative 3D fluoroscopy useful in the clinical routine to detect persistent fracture dislocations and screw misplacements, to prevent revision surgery? 2) Which is the most dangerous plate hole for screw misplacement? Patients and Methods: A total of 48 patients (36 females and 13 males) with 49 unstable distal radius fractures (22 x 23 A; 2 x 23 B, and 25 x 23 C) were treated with a 2.4 mm variable angle LCP Two-Column volar distal radius plate (Synthes GmbH, Oberdorf, Switzerland) during a 10-month period. After final fixation, according to the manufactures' technique guide and control of implant placement in the two common perpendicular 2D-fluoroscopic images (postero-anterior and true lateral), an additional tangential view and intraoperative 3D fluoroscopic scan were performed to control the anatomic fracture reduction and screw placements. Intraoperative revision rates due to screw misplacements (intra-articular or overlength) were evaluated. Additionally, the number of surgeons, time and radiation-exposure, for each step of the operating procedure, were recorded. Results: In the standard 2D-fluoroscopic views (postero-anterior and true lateral projection), 22 screw misplacements of 232 inserted screws were not detected. Based on the additional tangential view, 12 screws were exchanged, followed by further 10 screws after performing the 3D fluoroscopic scan. The most lateral screw position had the highest risk for screw misplacement (accounting for 45.5% of all exchanged screws). The mean number of images for the tangential view was 3 2.5 images. The mean surgical time was extended by 10.02 3.82 minutes for the 3D fluoroscopic scan. An additional radiation exposure of 4.4 4.5seconds, with a dose area product of 39.2 14.5 cGy/cm2 were necessary for the tangential view and 54.4 20.9 seconds with a dose area product of 2.1 2.2 cGy/cm2, for the 3D fluoroscopic scan. Conclusions: We recommend the additional 2D-fluoroscopic tangential view for detection of screw misplacements caused by overlength, with penetration on the dorsal cortical surface of the distal radius, predominantly observed for the most lateral screw position. The use of intraoperative 3D fluoroscopy did not become accepted in our clinical routine, due to the technical demanding and time consuming procedure, with a limited image quality so far. PMID:26101762

  2. Treatment of fractures of the condylar head with resorbable pins or titanium screws: an experimental study.

    PubMed

    Schneider, Matthias; Loukota, Richard; Kuchta, Anne; Stadlinger, Bernd; Jung, Roland; Speckl, Katrin; Schmiedekampf, Robert; Eckelt, Uwe

    2013-07-01

    We aimed to compare in vivo the stability of fixation of condylar fractures in sheep using sonic bone welding and standard titanium screws. We assessed stability of the osteosynthesis and maintenance of the height of the mandibular ramus. Height decreased slightly in both groups compared with the opposite side. The volume of the condyle increased considerably in both groups mainly because callus had formed. The results showed no significant disadvantages for pin fixation compared with osteosynthesis using titanium screws. PMID:22901526

  3. Biomechanical Concepts for Fracture Fixation.

    PubMed

    Bottlang, Michael; Schemitsch, Christine E; Nauth, Aaron; Routt, Milton; Egol, Kenneth A; Cook, Gillian E; Schemitsch, Emil H

    2015-12-01

    Application of the correct fixation construct is critical for fracture healing and long-term stability; however, it is a complex issue with numerous significant factors. This review describes a number of common fracture types and evaluates their currently available fracture fixation constructs. In the setting of complex elbow instability, stable fixation or radial head replacement with an appropriately sized implant in conjunction with ligamentous repair is required to restore stability. For unstable sacral fractures with vertical or multiplanar instabilities, "standard" iliosacral screw fixation is not sufficient. Periprosthetic femur fractures, in particular Vancouver B1 fractures, have increased stability when using 90/90 fixation versus a single locking plate. Far cortical locking combines the concept of dynamization with locked plating to achieve superior healing of a distal femur fracture. Finally, there is no ideal construct for syndesmotic fracture stabilization; however, these fractures should be fixed using a device that allows for sufficient motion in the syndesmosis. In general, orthopaedic surgeons should select a fracture fixation construct that restores stability and promotes healing at the fracture site, while reducing the potential for fixation failure. PMID:26584263

  4. Lateral Mass Fixation in the Subaxial Cervical Spine.

    PubMed

    Kurd, Mark F; Millhouse, Paul W; Schroeder, Gregory D; Kepler, Christopher K; Vaccaro, Alexander R

    2015-08-01

    The use of lateral mass screws and rods in the subaxial spine has become the standard method of fixation for posterior cervical spine fusions. Multiple techniques have been described for the placement of lateral mass screws, including the Magerl, the Anderson, and the An techniques. While these techniques are all slightly different, the overall goal is to obtain solid bony fixation while avoiding the neurovascular structures. The use of lateral mass screws has been shown to be a safe and effective technique for achieving a posterior cervical fusion. PMID:26049972

  5. A Biomechanical Comparison of Three Different Posterior Fixation Constructs Used for C6C7 Cervical Spine Immobilization: A Finite Element Study

    PubMed Central

    HONG, Jae Taek; QASIM, Muhammad; ESPINOZA ORAS, Alejandro A.; NATARAJAN, Raghu N.; AN, Howard S.

    2014-01-01

    The intralaminar screw construct has been recently introduced in C6C7 fixation. The aim of the study is to compare the stability afforded by three different C7 posterior fixation techniques using a three-dimensional finite element model of a C6C7 cervical spine motion segment. Finite element models representing three different cervical anchor types (C7 intralaminar screw, C7 lateral mass screw, and C7 pedicle screw) were developed. Range of motion (ROM) and maximum von Mises stresses in the vertebra for the three screw techniques were compared under pure moments in flexion, extension, lateral bending, and axial rotation. ROM for pedicle screw construct was less than the lateral mass screw construct and intralaminar screw construct in the three principal directions. The maximum von Misses stress was observed in the C7 vertebra around the pedicle in all the three screw constructs. Maximum von Mises stress in pedicle screw construct was less than the lateral mass screw construct and intralaminar screw construct in all loading modes. This study demonstrated that the pedicle screw fixation is the strongest instrumentation method for C6C7 fixation. Pedicle screw fixation resulted in least stresses around the C7 pedicle-vertebral body complex. However, if pedicle fixation is not favorable, the laminar screw can be a better option compared to the lateral mass screw because the stress around the pedicle-vertebral body complex and ROM predicted for laminar screw construct was smaller than those of lateral mass screw construct. PMID:24418790

  6. A Biomechanical Comparison of Three 1.5-mm Plate and Screw Configurations and a Single 2.0-mm Plate for Internal Fixation of a Mandibular Condylar Fracture

    PubMed Central

    Aquilina, Peter; Parr, William C.H.; Chamoli, Uphar; Wroe, Stephen; Clausen, Philip

    2014-01-01

    The most stable pattern of internal fixation for mandibular condyle fractures is an area of ongoing discussion. This study investigates the stability of three patterns of plate fixation using readily available, commercially pure titanium implants. Finite element models of a simulated mandibular condyle fracture were constructed. The completed models were heterogeneous in bone material properties, contained approximately 1.2 million elements and incorporated simulated jaw adducting musculature. Models were run assuming linear elasticity and isotropic material properties for bone. No human subjects were involved in this investigation. The stability of the simulated condylar fracture reduced with the different implant configurations, and the von Mises stresses of a 1.5-mm X-shaped plate, a 1.5-mm rectangular plate, and a 1.5-mm square plate (all Synthes (Synthes GmbH, Zuchwil, Switzerland) were compared. The 1.5-mm X plate was the most stable of the three 1.5-mm profile plate configurations examined and had comparable mechanical performance to a single 2.0-mm straight four-hole plate. This study does not support the use of rectangular or square plate patterns in the open reduction and internal fixation of mandibular condyle fractures. It does provide some support for the use of a 1.5-mm X plate to reduce condylar fractures in selected clinical cases. PMID:25136411

  7. Extraction of sunflower oil by twin screw extruder: screw configuration and operating condition effects.

    PubMed

    Amalia Kartika, I; Pontalier, P Y; Rigal, L

    2006-12-01

    The objective of this study was to investigate the screw configuration allowing oil extraction from sunflower seeds with a twin-screw extruder. Experiments were conducted using a co-rotating twin-screw extruder. Five screw profiles were examined to define the best performance (oil extraction yield, specific mechanical energy and oil quality) by studying the influence of operating conditions, barrel temperature, screw speed and feed rate. Generally, the position and spacing between two reversed screw elements affected oil extraction yield. An increase of oil extraction yield was observed as the reversed screw elements were moved with increased spacing between two elements and with smaller pitch elements. In addition, oil extraction yield increased as barrel temperature, screw speed and feed rate were decreased. Highest oil extraction yield (85%) with best cake meal quality (residual oil content lower than 13%) was obtained under operating conditions of 120 degrees C, 75 rpm and 19 kg/h. Furthermore, the operating parameters influenced energy input. A decrease in barrel temperature and feed rate followed by an increase in screw speed increased energy input, particularly specific mechanical energy input. Effect of the operating parameters on oil quality was less important. In all experiments tested, the oil quality was very good. The acid value was below 2 mg of KOH/g of oil and total phosphorus content was low, below 100 mg/kg. PMID:16337375

  8. Screw-locking wrench

    NASA Technical Reports Server (NTRS)

    Vranish, John M. (Inventor)

    2007-01-01

    A tool comprises a first handle and a second handle, each handle extending from a gripping end portion to a working end portion, the first handle having first screw threads disposed circumferentially about an inner portion of a first through-hole at the working end portion thereof, the second handle having second screw threads disposed circumferentially about an inner portion of a second through-hole at the working end portion thereof, the first and second respective through-holes being disposed concentrically about a common axis of the working end portions. First and second screw locks preferably are disposed concentrically with the first and second respective through-holes, the first screw lock having a plurality of locking/unlocking screw threads for engaging the first screw threads of the first handle, the second screw lock having a plurality of locking/unlocking screw threads for engaging the second screw threads of the second handle. A locking clutch drive, disposed concentrically with the first and second respective through-holes, engages the first screw lock and the second screw lock. The first handle and the second handle are selectively operable at their gripping end portions by a user using a single hand to activate the first and second screw locks to lock the locking clutch drive for either clockwise rotation about the common axis, or counter-clockwise rotation about the common axis, or to release the locking clutch drive so that the handles can be rotated together about the common axis either the clockwise or counter-clockwise direction without rotation of the locking clutch drive.

  9. Medial patellofemoral ligament reconstruction: a new technique for graft fixation at the patella without implants.

    PubMed

    Shafizadeh, Sven; Balke, Maurice

    2014-02-01

    Patellofemoral instability is a complex disorder that is often accompanied by insufficiency or tearing of the medial patellofemoral ligament. Over the past few years, several techniques using free tendon grafts for medial patellofemoral ligament reconstruction have become popular because of their reproducible effect and good outcome. Whereas most surgeons prefer femoral fixation of the graft using an interference screw, the possibilities of patellar fixation are numerous. All of the different techniques have their own advantages and pitfalls. We describe a technique in which we drill 2 blind-ending tunnels (1 cm) at the medial aspect of the patella, where the doubled graft (not the free ends) is pulled in and fixed. By using a special technique for shuttling the sutures, there is no need for an additional skin incision and no need for implants, allowing very secure graft fixation without a relevant risk of fracture. PMID:24749029

  10. Bone impregnated hip screw in femoral neck fracture: Clinicoradiological results

    PubMed Central

    Sundar Raj, PK; Nuuman, Jiju A; Pattathil, Amish Sunder

    2015-01-01

    Background: Femoral neck fractures are treated either by internal fixation or arthroplasty. Usually, cannulated cancellous screws are used for osteosynthesis of fracture neck of femur. The bone impregnated hip screw (BIHS) is an alternative implant, where osteosyntehsis is required in femoral neck fracture. Materials and Methods: The BIHS is a hollow screw with thread diameter 8.3 mm, shank diameter 6.5 mm and wall thickness 2.2 mm and holes in the shaft of the screw with diameter 2 mm, placed in a staggered fashion. Biomechanical and animal experimental studies were done. Clinical study was done in two phases: Phase 1 in a group of volunteers, only with BIHS was used in a pilot study and phase 2 comparative study was done in a group with AO cannulated screws and the other group treated with BIHS. Results: In the phase 1 study, out of 15 patients, only one patient had delayed union. In phase 2, there were 78 patients, 44 patients in BIHS showed early union, compared to the rest 34 cases of AO cannulated screws Out of 44 patients with BIHS, 41 patients had an excellent outcome, 2 had nonunions and one implant breakage was noted. Conclusions: Bone impregnated hip screw has shown to provide early solid union since it incorporates the biomechanical principles and also increases the osteogenic potential and hence, found superior to conventional cannulated cancellous screw. PMID:26015608

  11. A Complication of Posterior Malleolar Fracture Fixation.

    PubMed

    Patel, Ankit; Charles, Loren; Ritchie, James

    2016-01-01

    We present a case of tibial nerve impingement by an anteroposterior screw inserted for stabilization of a posterior malleolar fracture. This specific complication has not previously been described in published studies, although numerous reports have described various forms of peripheral nerve entrapment. We discuss the merits of fixation of these fractures using a posterolateral approach. PMID:25907349

  12. Split spline screw

    NASA Technical Reports Server (NTRS)

    Vranish, John M. (inventor)

    1993-01-01

    A split spline screw type payload fastener assembly, including three identical male and female type split spline sections, is discussed. The male spline sections are formed on the head of a male type spline driver. Each of the split male type spline sections has an outwardly projecting load baring segment including a convex upper surface which is adapted to engage a complementary concave surface of a female spline receptor in the form of a hollow bolt head. Additionally, the male spline section also includes a horizontal spline releasing segment and a spline tightening segment below each load bearing segment. The spline tightening segment consists of a vertical web of constant thickness. The web has at least one flat vertical wall surface which is designed to contact a generally flat vertically extending wall surface tab of the bolt head. Mutual interlocking and unlocking of the male and female splines results upon clockwise and counter clockwise turning of the driver element.

  13. Fixation of Soft Tissue to Bone: Techniques and Fundamentals.

    PubMed

    Cole, Brian J; Sayegh, Eli T; Yanke, Adam B; Chalmers, Peter N; Frank, Rachel M

    2016-02-01

    A myriad of orthopaedic injuries require surgical fixation of torn connective tissue to an osseous insertion site with either direct repair or reconstruction with a soft-tissue graft. Numerous factors influence the strength of a soft-tissue-to-bone fixation construct, including tissue quality, implant strength, contact area and pressure, and tensioning. Each fixation technique differs with respect to biologic integration, biomechanical stability, and failure mechanism. Fixation methods may or may not require an implant, such as interference screws, staples, internal buttons, transfixion pins, or suture anchors. Understanding the optimal method of soft-tissue fixation for a given scenario is crucial for successful repair or reconstruction. PMID:26752738

  14. Vascularized bone grafting fixed by biodegradable magnesium screw for treating osteonecrosis of the femoral head.

    PubMed

    Zhao, Dewei; Huang, Shibo; Lu, Faqiang; Wang, Benjie; Yang, Lei; Qin, Ling; Yang, Ke; Li, Yangde; Li, Weirong; Wang, Wei; Tian, Simiao; Zhang, Xiuzhi; Gao, Wenbin; Wang, Zongpu; Zhang, Yu; Xie, Xinhui; Wang, Jiali; Li, Junlei

    2016-03-01

    Hip-preserving surgery with vascularized bone graft implantation has been widely practiced in treating osteonecrosis of the femoral head (ONFH). However, the current approach presents a drawback, in which the implanted bone graft without screw fixation may slip or exhibit a certain degree of displacement postoperatively. This study was designed to investigate the application potential of biodegradable magnesium (Mg) screws for the fixation of vascularized bone graft in ONFH patients. Forty-eight patients were randomly divided into two groups: the Mg screw group (vascularized bone grafting fixed by Mg screws) and the control group (vascularized bone grafting without fixation). During 12 month follow-up period after surgery, treatment outcomes in patients were assessed by multiple imaging techniques including x-ray and computed tomography (CT) scanning as well as functional recovery Harris hip score (HHS). The temporal changes in serum levels of Mg, Ca, and P as well as invivo degradation rate of Mg screws were determined. The absence of potential adverse effects induced by degradation products from Mg screws on surrounding bone tissue was validated via CT imaging analysis. HHS was significantly improved in the Mg screw group when compared to the control group. X-ray imaging analysis showed that the screw shape did not show significant alteration due to the diameter of Mg screws measured with approximate 25% reduction within 12 months post-surgically. The postoperative serum levels of Ca, Mg, and P, which are relevant for liver and kidney function, were all within normal physiological range in all patients of both groups. The use of biodegradable Mg screws may provide a promising bone graft-screw fixation route in treating ONFH and present considerable potential for orthopedic applications. PMID:26724456

  15. Effects of Elevated CO2 and N Addition on Growth and N2 Fixation of a Legume Subshrub (Caragana microphylla Lam.) in Temperate Grassland in China

    PubMed Central

    Zhang, Lin; Wu, Dongxiu; Shi, Huiqiu; Zhang, Canjuan; Zhan, Xiaoyun; Zhou, Shuangxi

    2011-01-01

    It is well demonstrated that the responses of plants to elevated atmospheric CO2 concentration are species-specific and dependent on environmental conditions. We investigated the responses of a subshrub legume species, Caragana microphylla Lam., to elevated CO2 and nitrogen (N) addition using open-top chambers in a semiarid temperate grassland in northern China for three years. Measured variables include leaf photosynthetic rate, shoot biomass, root biomass, symbiotic nitrogenase activity, and leaf N content. Symbiotic nitrogenase activity was determined by the C2H2 reduction method. Elevated CO2 enhanced photosynthesis and shoot biomass by 83% and 25%, respectively, and the enhancement of shoot biomass was significant only at a high N concentration. In addition, the photosynthetic capacity of C. microphylla did not show down-regulation under elevated CO2. Elevated CO2 had no significant effect on root biomass, symbiotic nitrogenase activity and leaf N content. Under elevated CO2, N addition stimulated photosynthesis and shoot biomass. By contrast, N addition strongly inhibited symbiotic nitrogenase activity and slightly increased leaf N content of C. microphylla under both CO2 levels, and had no significant effect on root biomass. The effect of elevated CO2 and N addition on C. microphylla did not show interannual variation, except for the effect of N addition on leaf N content. These results indicate that shoot growth of C. microphylla is more sensitive to elevated CO2 than is root growth. The stimulation of shoot growth of C. microphylla under elevated CO2 or N addition is not associated with changes in N2-fixation. Additionally, elevated CO2 and N addition interacted to affect shoot growth of C. microphylla with a stimulatory effect occurring only under combination of these two factors. PMID:22046376

  16. Preliminary experience with biodegradable implants for fracture fixation

    PubMed Central

    Dhillon, Mandeep S; Prabhakar, Sharad; Prasanna, Chandiralingam

    2008-01-01

    Background: Biodegradable implants were designed to overcome the disadvantages of metal-based internal fixation devices. Although they have been in use for four decades internationally, many surgeons in India continue to be skeptical about the mechanical strength of biodegradable implants, hence this study. Materials and Methods: A prospective study was done to assess the feasibility and surgeon confidence level with biodegradable implants over a 12-month period in an Indian hospital. Fifteen fractures (intra-articular, metaphyseal or small bone fractures) were fixed with biodegradable implants. The surgeries were randomly scheduled so that different surgeons with different levels of experience could use the implants for fixation. Results: Three fractures (one humeral condyle, two capitulum), were supplemented by additional K-wires fixation. Trans-articular fixator was applied in two distal radius and two pilon fractures where bio-pins alone were used. All fractures united, but in two cases the fracture displaced partially during the healing phase; one fibula due to early walking, and one radius was deemed unstable even after bio-pin and external fixator. Conclusions: Biodegradable -implants are excellent for carefully selected cases of intra-articular fractures and some small bone fractures. However, limitations for use in long bone fractures persist and no great advantage is gained if a “hybrid” composite is employed. The mechanical properties of biopins and screws in isolation are perceived to be inferior to those of conventional metal implants, leading to low confidence levels regarding the stability of reduced fractures; these implants should be used predominantly in fracture patterns in which internal fixation is subjected to minimal stress. PMID:19753159

  17. Biomechanical analysis on transverse tibial fixation in anterior cruciate ligament reconstructions☆

    PubMed Central

    Filho, Edmar Stieven; Mendes, Mariane Henseler Damaceno; Claudino, Stephanie; Baracho, Filipe; Borges, Paulo César; da Cunha, Luiz Antonio Munhoz

    2015-01-01

    Objective To verify whether the combination of tibial cross pin fixation and femoral screw fixation presents biomechanical advantages when compared to femoral cross pin fixation and tibial screw fixation for the reconstruction of the anterior cruciate ligament (ACL). Methods Thirty-eight porcine knees and bovine extensor digitorum tendons were used as the graft materials. The tests were performed in three groups: (1) standard, used fourteen knees, and the grafts were fixated with the combination of femoral cross pin and a tibial screw; (2) inverted, used fourteen knees with an inverted combination of tibial cross pin and a femoral screw; (3) control, ten control tests performed with intact ACL. After the grafts fixation, all the knees were subjected to tensile testing to determine yield strength and ultimate strength. Results There was no statistically significant difference in survival techniques in regard to strength, yield load and tension. There was a higher survival compared in the standard curves of yield stress (p < 0.05). Conclusion There is no biomechanical advantage, observed in animal models testing, in the combination of tibial cross pin fixation and femoral screw when compared to femoral cross pin fixation and tibial screw. PMID:26229913

  18. External fixator pin design.

    PubMed

    Halsey, D; Fleming, B; Pope, M H; Krag, M; Kristiansen, T

    1992-05-01

    The integrity of the bone-pin interface is the critical link in the stability of external fixation systems. External fixation pins placed in cancellous metaphyseal bone frequently loosen over time, resulting in fixation failure and an increased risk of infection. To design an external fixation pin with optimal bone-metal interface strength in cancellous bone, a systematic study of various thread design features was performed. Combinations of pitch, tooth profile, and minor diameter in 5 mm self-tapping half pins were evaluated in coaxial pullout testing using a fresh bovine cancellous bone. A significant increase in pullout strength was found with a decrease in minor diameter. No statistical differences were found in pullout strength attributable to thread profile and pitch. There were no significant interactions between minor diameter and tooth profile or minor diameter and pitch. The data obtained suggest significantly greater holding power in cancellous bone can be achieved by using an external fixation pin with a smaller minor diameter or a larger interference. Additional pullout testing of five commercially available external fixator pins was performed. Of these, the two pins with the largest interference demonstrated greater pullout strength. Therefore, within a range of acceptable major diameters and adequate minor diameters for the torsional strength requirements, an optimal interference for cancellous pin application may exist and it may well be larger than that present in currently available external fixation pins. PMID:1563166

  19. Functional load of plates in fracture fixation in vivo and its correlate in bone healing.

    PubMed

    Stoffel, K; Klaue, K; Perren, S M

    2000-05-01

    In clinical practice efforts are made to apply a fixation plate on the side opposite the strongest muscle pull. This achieves an optimal distribution of compression between the fragment ends (principle of tension band plating). This is however frequently impossible for anatomical or surgical reasons. In an 'in vivo' study lasting 8 weeks a standardized oblique osteotomy was performed on the tibia of 16 sheep in four different models of tension band plating (a contoured and an overbent plate with or without an interfragmentary lag screw) were assessed. Tension on the plate surface was recorded by strain gauges for different gait speeds on the treadmill. These measurements were performed throughout the experiment. Radiographs were taken at regular intervals in order to assess stability and polychrome sequential labelling and microradiographs served to investigate the healing process. Possible relationships and/or interactions between plate tension and bone healing were investigated. Implant loading under bending strain was reduced the most for the combination of plate overbending with a lag screw. The insertion of a lag screw reduces the surface strain on the plate whether it is contoured or overbent. The bending and torsional forces are greatest if a straight plate is used alone and the principle of tension band plating is not applied. Direct bone healing was only observed in the group with contoured plate and lag screw. Overbending combined with a lag screw provided only a relatively unstable fixation. A residual gap immediately beneath the plate permits "dynamic compression" since the screws slide towards the osteotomy when loaded producing bone resorption under the plate and signs of screw loosening. The models with contoured and overbent plates without a lag screw were histologically assessed as very unstable with signs of secondary fragment displacement, obvious callus formation, resorption at the fragment ends and under the plate, delayed and diminished Haversian remodelling and corrosion sites at the screw heads and at the adjacent site on the plate hole. In all groups, stripping of the periosteum under the plate was associated with porosis of the corresponding cortex as a sign of temporarily impaired blood supply. A relationship between implant loading and/or unloading (stress shielding) could not be demonstrated. Callus formation, measured quantitatively on the radiographs, is directly related to the strain on the plate. Direct bone healing is rapid and is seen histologically three weeks postoperatively, particularly for fixations with contoured plate and lag screw. The early appearance of fixation callus in the presence of an intact blood supply indicates a primary instability of the osteosynthesis. Later, it may be an indication of secondary instability. The time at which osteons appear, their number and location provides information on the stability of the osteosynthesis. At a time when indirect fracture reduction and stabilization using minimally invasive techniques and implants is being propagated, additional ways and means must be sought to assess clinically the load on the implants and the risk of implant failure. PMID:10853760

  20. Stability of unicortical locked fixation versus bicortical non-locked fixation for forearm fractures.

    PubMed

    Pater, Timothy J; Grindel, Steve I; Schmeling, Gregory J; Wang, Mei

    2014-01-01

    Locking plate fixation is being widely applied for fixation of forearm fractures and has many potential advantages, such as fixed angle fixation and improved construct stability, especially in osteoporotic bone. Biomechanical data comparing locking devices to commonly used Low Contact Dynamic Compression (LCDCP) plates for the fixation of forearm fractures has been lacking. The purpose of this study was to compare the fixation stability of a 3.5-mm unicortical locked plate with bicortical non-locked LCDCP plates. Six matched pairs of fresh frozen cadaveric forearms were randomly assigned to unicortical locked and bicortical unlocked groups. Non-destructive four-point bending and torsional test was performed on the ulna and radius separately, using a servohydraulic testing system to obtain construct stiffness of the intact specimens and specimens after osteotomy and plating. The specimens were then loaded to failure to test the fixation strength. The locked unicortical fixation showed significantly higher bending stiffness than the unlocked bicortical fixation, but with significantly lower stiffness and strength in torsion. Fixation strength was comparable between the two groups under bending, but significantly greater in the bicortical non-locked group under torsion. Findings from this study suggest that postoperative rehabilitation protocols may need modification to limit torsional loading in the early stage when using locked unicortical fixation. The study also points out the potential advantage of a hybrid fixation that combines locked unicortical and unlocked bicortical screws. PMID:26273524

  1. Absorbable Screws Versus Metallic Screws for Distal Tibiofibular Syndesmosis Injuries: A Meta-Analysis.

    PubMed

    Xie, Yuanlong; Cai, Lin; Deng, Zhouming; Ran, Bing; Hu, Chao

    2015-01-01

    A meta-analysis was performed to investigate the outcomes between absorbable screw (AS) and metallic screw (MS) fixation for distal tibiofibular syndesmosis injuries (DTSIs). Randomized controlled trials comparing AS versus MS fixation in DTSIs were searched systematically, and the outcomes were analyzed using Review Manager Software, version 5.2. The risk ratio (RR) or mean difference with the 95% confidence interval (CI) was calculated using the fixed effects or random effects model. A total of 16 studies were included in the meta-analysis. No statistically significant difference was found between AS and MS fixation in excellent and good functional recovery rate (RR 1.11, 95% CI 1.00 to 1.23, I(2) = 60%, p = .06), infection (RR 1.66, 95% CI 0.73 to 3.79, I(2) = 0%, p = .23), incidence of pain (RR 0.68, 95% CI 0.24 to 1.92, I(2) = 12%, p = .47), screw broken (RR 0.31, 95% CI 0.03 to 2.93, I(2) = %, p = .31), heterotopic ossification (RR 1.93, 95% CI 0.21 to 17.62, I(2) = 51%, p = .56; 472 cases in 4 studies), fracture healing time (mean difference -1.88, 95% CI -3.51 to -0.26, I(2) = 93%, p = .02,), duration of operation time (mean difference 7.64, 95% CI -3.80 to 19.09, I(2) = 98%, p = .19). The incidence of foreign body reaction was higher with AS fixation (RR 6.07, 95% CI 2.54 to 14.50, I(2) = 0%, p < .001). The reoperation rate was higher with MS fixation (RR 0.08, 95% CI 0.03 to 0.18, I(2) = 77%, p < .01). The functional outcomes of AS were as good as those with MS for DTSIs. Other than the foreign body reaction, the complications occurring after AS fixation were not as serious as those with MS fixation. AS fixation might be a preferable alternative for reconstruction of DTSIs. PMID:25956019

  2. Mechanical comparison of fixation techniques for the offset V osteotomy: a saw bone study.

    PubMed

    Jacobson, Keith; Gough, Adam; Mendicino, Samuel S; Rockett, Matthew S

    2003-01-01

    Four different techniques for the fixation of an offset V bunionectomy were tested on solid-foam saw-bone models for the purpose of determining the strongest form of fixation for the osteotomy. Twenty identical models were placed into 4 different groups. Groups varied as to the placement and caliber of fixation. Models were loaded with a servo-hydraulic testing machine until failure of fixation occurred. Video analysis was used to record the pattern of failure of the fixation. Failure occurred either distal to the first screw, through the first screw hole, between the 2 screws, through the second screw hole, or proximal to the second screw. The mean force to failure of the groups was group 1, 58.1 N; group 2, 59.3 N; group 3, 64.0 N; and group 4, 105.66 N. There was a statistical significant difference between group 4 and the other 3 groups (F(1) = 55.45, P < 0.05). There was no statistical difference between groups 1 to 3. In groups 1 to 3, 87% of the failures were through the distal screw hole, whereas the remaining 13% were through the proximal screw hole. In group 4, 60% of the failures were through the proximal screw hole and 40% were through the distal screw hole. It was concluded that, in this model, the strongest form of fixation for an offset V osteotomy was the 2.7-mm cortical screw placed distally with the proximal point of fixation being a threaded 0.062-inch Kirschner wire. PMID:14688775

  3. Factors affecting fixation of the glenoid component of a reverse total shoulder prothesis.

    PubMed

    Chebli, Caroline; Huber, Philippe; Watling, Jonathan; Bertelsen, Alexander; Bicknell, Ryan T; Matsen, Frederick

    2008-01-01

    The semiconstrained design of the reverse arthroplasty allows loads from the humerus to challenge the fixation of the glenoid component to the scapula. We examined some of the factors affecting the quality of glenoid screw fixation, including the density of the material into which the screws are placed, the purchase of individual screws, and the direction of loading in relation to screw placement. Loads were applied by the humeral component to glenoid components with different conditions of fixation. The load to failure for each set of conditions was measured and compared statistically. Load to failure was less when the glenoid component was fixed to material of lesser density. Each screw contributed to the quality of fixation; the screw nearest the point of load application made the largest contribution. Load to failure was less when the load was colinear with a line through the nonlocking holes in the base plate compared to colinear with a line through the locking holes. In performing a reverse total shoulder, surgeons should emphasize secure intraosseous placement of the fixation screws in the best quality bone available. The placement of the inferior screw appears to be the most critical. PMID:18249566

  4. Improved Screw-Thread Lock

    NASA Technical Reports Server (NTRS)

    Macmartin, Malcolm

    1995-01-01

    Improved screw-thread lock engaged after screw tightened in nut or other mating threaded part. Device does not release contaminating material during tightening of screw. Includes pellet of soft material encased in screw and retained by pin. Hammer blow on pin extrudes pellet into slot, engaging threads in threaded hole or in nut.

  5. Biomechanical testing of implant free wedge shaped bone block fixation for bone patellar tendon bone anterior cruciate ligament reconstruction in a bovine model

    PubMed Central

    2010-01-01

    Background The use of an interference fit wedged bone plug to provide fixation in the tibial tunnel when using bone-patellar tendon-bone autograft for anterior cruciate ligament reconstruction offers many theoretic advantages including the potential to offer a more economical and biological alternative to screw fixation. This technique has not been subjected to biomechanical testing. We hypothesised that a wedged bone plug fixation technique provides equivalent tensile load to failure as titanium interference screw fixation. Methods In a controlled laboratory setting, anterior cruciate ligament reconstruction was performed in 36 bovine knees using bone-patella-bone autograft. In 20 knees tibial fixation relied upon a standard cuboid bone block and interference screw. In eight knees a wedge shaped bone block with an 11 mm by 10 mm base without a screw was used. In a further eight knees a similar wedge with a 13 mm by 10 mm base was used. Each specimen used a standard 10 mm tibial tunnel. The reconstructions were tested biomechanically in a physiological environment using an Instron machine to compare ultimate failure loads and modes of failure. Results Statistical analysis revealed no significant difference between wedge fixation and screw fixation (p = 0.16), or between individual groups (interference screw versus 11 mm versus 13 mm wedge fixation) (P = 0.35). Conclusions Tibial tunnel fixation using an impacted wedge shaped bone block in anterior cruciate ligament reconstruction has comparable ultimate tensile strength to titanium interference screw fixation. PMID:20813059

  6. Cortical Bone Trajectory for Lumbar Pedicle Screw Placement: A Review of Published Reports.

    PubMed

    Phan, Kevin; Hogan, Jarred; Maharaj, Monish; Mobbs, Ralph J

    2015-08-01

    There have been a number of developments in screw design and implantation techniques over recent years, including proposal of an alternative trajectory for screw fixation aimed at increasing purchase of pedicle screws in higher density bone. Cortical bone trajectory (CBT) screw insertion follows a lateral path in the transverse plane and caudocephalad path in the sagittal plane. This technique has been advocated because it is reportedly less invasive, improves screw-bone purchase and reduces neurovascular injury; however, these claims have not been supported by robust clinical evidence. The available evidence was therefore reviewed to assess the relative merits of CBT and highlight areas for further research. To this end, a search of relevant published studies reporting biomechanical, morphometric or clinical outcomes after use of CBT screws in patients with spinal pathologies was performed via six electronic databases. PMID:26311095

  7. Ball Screw Actuator Including a Compliant Ball Screw Stop

    NASA Technical Reports Server (NTRS)

    Wingett, Paul T. (Inventor); Hanlon, Casey (Inventor)

    2015-01-01

    An actuator includes a ball nut, a ball screw, and a ball screw stop. The ball nut is adapted to receive an input torque and in response rotates and supplies a drive force. The ball screw extends through the ball nut and has a first end and a second end. The ball screw receives the drive force from the ball nut and in response selectively translates between a retract position and a extend position. The ball screw stop is mounted on the ball screw proximate the first end to translate therewith. The ball screw stop engages the ball nut when the ball screw is in the extend position, translates, with compliance, a predetermined distance toward the first end upon engaging the ball nut, and prevents further rotation of the ball screw upon translating the predetermined distance.

  8. A biomechanical study of conventional acetabular internal fracture fixation versus locking plate fixation

    PubMed Central

    Mehin, Ramin; Jones, Bryn; Zhu, Qingan; Broekhuyse, Henry

    2009-01-01

    Background Conventional internal fixation entails the use of an interfragmentary lag screw along with a plate. Not all acetabular fractures are amenable to the placement of an interfragmentary lag screw, and the fracture may be displaced during tightening of the interfragmentary lag screw. Locking plates are a possible solution. We sought to determine whether a locking plate construct can provide stability equivalent to that provided with a conventional construct for transverse acetabular fractures. Methods We used 5 paired fresh-frozen cadaveric acetabula. We fixed one side with the conventional technique and the other side with a locking plate. We subjected each fixation to a cyclic compressive force up to 500 cycles, followed by compressive force until failure. We monitored 3-dimensional motion of the fracture. Results The average fracture gap at 50 N compressive force after 500 loading cycles was 0.41 (standard deviation [SD] 0.49) mm for the conventional plate and lag screw construct compared with 0.76 (SD 0.62) mm for the locked plate construct (p = 0.46). The force to failure, as defined by 2 mm of fracture gap, was 848 (SD 805) N for the conventional plate and lag screw construct compared with 506 (SD 277) N for the locked plate fixation (p = 0.34). Conclusion The locking plate construct is as strong as the conventional plate plus interfragmentary lag screw construct for fixing transverse acetabular fractures. Locking plates may improve management of acetabular fractures by eliminating the need for placement of an interfragmentary lag screw. Furthermore, they may be helpful in revision hip arthroplasty in patients with pelvic discontinuity. PMID:19503667

  9. 21 CFR 888.3030 - Single/multiple component metallic bone fixation appliances and accessories.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ..., such as screws and nails, or bolts, nuts, and washers. These devices are used for fixation of fractures..., supracondylar, or condylar fractures of the femur; for fusion of a joint; or for surgical procedures...

  10. 21 CFR 888.3030 - Single/multiple component metallic bone fixation appliances and accessories.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ..., such as screws and nails, or bolts, nuts, and washers. These devices are used for fixation of fractures..., supracondylar, or condylar fractures of the femur; for fusion of a joint; or for surgical procedures...

  11. 21 CFR 888.3030 - Single/multiple component metallic bone fixation appliances and accessories.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ..., such as screws and nails, or bolts, nuts, and washers. These devices are used for fixation of fractures..., supracondylar, or condylar fractures of the femur; for fusion of a joint; or for surgical procedures...

  12. 21 CFR 888.3030 - Single/multiple component metallic bone fixation appliances and accessories.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ..., such as screws and nails, or bolts, nuts, and washers. These devices are used for fixation of fractures..., supracondylar, or condylar fractures of the femur; for fusion of a joint; or for surgical procedures...

  13. Screw osteosynthesis of displaced lateral humeral condyle fractures in children: a mid-term review.

    PubMed

    Loke, W P; Shukur, M H; Yeap, J K

    2006-02-01

    Displaced humeral condyle fractures in children are traditionally fixed with smooth Kirschner wire at the expense of a risk of secondary displacement following removal of wire. Screw fixation of such fractures has recently been advocated as it provides stable fixation. We have been using screw osteosynthesis for treatment of displaced lateral humeral condyle fractures in children in our institution since the turn of this century. This study provides a midterm review of treatment of such injuries with special regards to growth disturbances after screw osteosynthesis and to assess rate of union with a view to formulate guidelines for screw removal. We review the outcomes of screw osteosynthesis for displaced lateral condyle fracture of the humerus (19 Milch type-1 and 15 Milch type-II) in 34 children treated in our institution from January 2000 to March 2004. The average age of the patients was 6.1 years. The average follow up was 24.5 months. Screw osteosynthesis led to union (average 6.9 weeks) in all patients with excellent results in 28 patients. Growth disturbances in the form of lateral condyle overgrowth (2 patients), valgus deformity secondary to lateral condyle avascular necrosis (2 patients) and fishtail deformity ((3 patients) were recognized. The implants should not be removed until fracture union is established. Screw osteosynthesis of the lateral humeral condyle fracture prevents secondary fracture redisplacement and lateral condyle overgrowth is probably related to hyperemic response to metaphyseal fixation and early removal of implant before radiological union. PMID:17042228

  14. Impact of screw configuration on the particle size distribution of granules produced by twin screw granulation.

    PubMed

    Vercruysse, J; Burggraeve, A; Fonteyne, M; Cappuyns, P; Delaet, U; Van Assche, I; De Beer, T; Remon, J P; Vervaet, C

    2015-02-01

    Twin screw granulation (TSG) has been reported by different research groups as an attractive technology for continuous wet granulation. However, in contrast to fluidized bed granulation, granules produced via this technique typically have a wide and multimodal particle size distribution (PSD), resulting in suboptimal flow properties. The aim of the current study was to evaluate the impact of granulator screw configuration on the PSD of granules produced by TSG. Experiments were performed using a 25 mm co-rotating twin screw granulator, being part of the ConsiGma™-25 system (a fully continuous from-powder-to-tablet manufacturing line from GEA Pharma Systems). Besides the screw elements conventionally used for TSG (conveying and kneading elements), alternative designs of screw elements (tooth-mixing-elements (TME), screw mixing elements (SME) and cutters) were investigated using an α-lactose monohydrate formulation granulated with distilled water. Granulation with only conveying elements resulted in wide and multimodal PSD. Using kneading elements, the width of the PSD could be partially narrowed and the liquid distribution was more homogeneous. However, still a significant fraction of oversized agglomerates was obtained. Implementing additional kneading elements or cutters in the final section of the screw configuration was not beneficial. Furthermore, granulation with only TME or SME had limited impact on the width of the PSD. Promising results were obtained by combining kneading elements with SME, as for these configurations the PSD was narrower and shifted to the size fractions suitable for tableting. PMID:25562758

  15. Neuromuscular scoliosis and pelvic fixation in 2015: Where do we stand?

    PubMed Central

    Anari, Jason B; Spiegel, David A; Baldwin, Keith D

    2015-01-01

    Neuromuscular scoliosis is a challenging problem to treat in a heterogeneous patient population. When the decision is made for surgery the surgeon must select a technique employed to correct the curve and achieve the goals of surgery, namely a straight spine over a level pelvis. Pre-operatively the surgeon must ask if pelvic fixation is worth the extra complications and infection risk it introduces to an already compromised host. Since the advent of posterior spinal fusion the technology used for instrumentation has changed drastically. However, many of the common problems seen with the unit rod decades ago we are still dealing with today with pedicle screw technology. Screw cut out, pseudoarthrosis, non-union, prominent hardware, wound complications, and infection are all possible complications when extending a spinal fusion construct to the pelvis in a neuromuscular scoliosis patient. Additionally, placing pelvic fixation in a neuromuscular patient results in extra blood loss, greater surgical time, more extensive dissection with creation of a deep dead space, and an incision that extends close to the rectum in patients who are commonly incontinent. Balancing the risk of placing pelvic fixation when the benefit, some may argue, is limited in non-ambulating patients is difficult when the literature is so mottled. Despite frequent advancements in technology issues with neuromuscular scoliosis remain the same and in the next 10 years we must do what we can to make safe neuromuscular spine surgery a reality. PMID:26396932

  16. Prediction of Deformity Correction by Pedicle Screw Instrumentation in Thoracolumbar Scoliosis Surgery

    NASA Astrophysics Data System (ADS)

    Kiriyama, Yoshimori; Yamazaki, Nobutoshi; Nagura, Takeo; Matsumoto, Morio; Chiba, Kazuhiro; Toyama, Yoshiaki

    In segmental pedicle screw instrumentation, the relationship between the combinations of pedicle screw placements and the degree of deformity correction was investigated with a three-dimensional rigid body and spring model. The virtual thoracolumbar scoliosis (Cobb’s angle of 47 deg.) was corrected using six different combinations of pedicle-screw placements. As a result, better correction in the axial rotation was obtained with the pedicle screws placed at or close to the apical vertebra than with the screws placed close to the end vertebrae, while the correction in the frontal plane was better with the screws close to the end vertebrae than with those close to the apical vertebra. Additionally, two screws placed in the convex side above and below the apical vertebra provided better correction than two screws placed in the concave side. Effective deformity corrections of scoliosis were obtained with the proper combinations of pedicle screw placements.

  17. Biodegradable implant materials in fracture fixation.

    PubMed

    Illi, O E; Weigum, H; Misteli, F

    1992-01-01

    Based on our experiences in paediatric traumatology treated conservatively or with metallic implants, we looked for alternative fixation possibilities in the field of biodegradables. We designed a new driving system for screws consisting of an indwelling screw driver which transduces the torque force over the whole length of the thread. With this technical approach, the head and the neck of the screw as the most friable point for the fracture of the implant could be avoided. In 48 calves aged 6 weeks we performed a comparative study with either conservative treatment (repositioning and casting) or osteosynthesis with biodegradable screws made from polylactate acid or metallic screws (AO type) after an oblique osteotomy at a 45 degrees angle to the axis of the right metacarpal bone. Results from 1 to 6 weeks postoperatively were compared and good to excellent results obtained in equal amounts for PLA and steel screw osteosynthesis, whereas conservative treatment was only successful in one third of the cases. Clinical, radiological and histological follow-up proved the feasibility of biodegradable osteosynthesis in the growing skeleton. For clinical evaluation in children, the resorption time of biodegradable materials has to be lowered to 3 to 6 months. PMID:10149979

  18. Bicondylar tibial fractures: Internal or external fixation?

    PubMed Central

    Kumar, Gunasekaran; Peterson, Nicholas; Narayan, Badri

    2011-01-01

    Bicondylar fractures of the tibia, representing the Schatzker V and VI fractures represent a challenging problem. Any treatment protocol should aim at restoring articular congruity and the metaphyseo-diaphsyeal dissociation (MDD)both of these are equally important to long-term outcome. Both internal and external fixations have their proponents, and each method of treatment is associated with its unique features and complications. We review the initial and definitive management of these injuries, and the advantages and disadvantages of each method of definitive fixation. We suggest the use of a protocol for definitive management, using either internal or external fixation as deemed appropriate. This protocol is based on the fracture configuration, local soft tissue status and patient condition. In a nutshell, if the fracture pattern and soft tissue status are amenable plate fixation (single or double) is performed, otherwise limited open reduction and articular surface reconstruction with screws and circular frame is performed. PMID:21430865

  19. [Sacroiliac fixation: a new technique after pelvic trauma].

    PubMed

    Hoffmann, E; Levassor, N; Rillardon, L; Lavelle, G; Guigui, P

    2003-12-01

    We propose a new technique for sacroiliac fixation for the treatment of pelvic fracture with vertical and horizontal instability (Tile class C). This fixation technique allows control of vertical displacement while allowing, if needed, a certain degree of movement in the horizontal plane to facilitate reduction of anterior lesions. The technique involves insertion of two sacral screws, one in S1 and one in S2, and two iliac screws. The iliac screws are inserted in the posterior iliac crest through two sacroiliac connectors placed on a rod linking the two sacral screws. Vertical displacement is controlled by blocking the screw heads on the connecting rod. If needed, a certain degree of horizontal mobility of the half pelvis can be allowed by loosening the connectors on the rods. This technique was used for 4 patients. Anatomic reduction was achieved and no secondary movement of the osteosynthesis material nor secondary displacement were observed. The quality of the fixation allowed rapid weight bearing in the standing position and early walking without crutches. This type of fixation can only be used for type C12 fractures in the Tile classification. PMID:14726839

  20. A novel approach to navigated implantation of S-2 alar iliac screws using inertial measurement units.

    PubMed

    Jost, Gregory F; Walti, Jonas; Mariani, Luigi; Cattin, Philippe

    2016-03-01

    OBJECT The authors report on a novel method of intraoperative navigation with inertial measurement units (IMUs) for implantation of S-2 alar iliac (S2AI) screws in sacropelvic fixation of the human spine and its application in cadaveric specimens. METHODS Screw trajectories were planned on a multiplanar reconstruction of the preoperative CT scan. The pedicle finder and screwdriver were equipped with IMUs to guide the axial and sagittal tilt angles of the planned trajectory, and navigation software was developed. The entry points were chosen according to anatomical landmarks on the exposed spine. After referencing, the sagittal and axial orientation of the pedicle finder and screwdriver were wirelessly monitored on a computer screen and aligned with the preoperatively planned tilt angles to implant the S2AI screws. The technique was performed without any intraoperative imaging. Screw positions were analyzed on postoperative CT scans. RESULTS Seventeen of 18 screws showed a good S2AI screw trajectory. Compared with the postoperatively measured tilt angles of the S2AI screws, the IMU readings on the screwdriver were within an axial plane deviation of 0° to 5° in 15 (83%) and 6° to 10° in 2 (11%) of the screws and within a sagittal plane deviation of 0° to 5° in 15 (83%) and 6° to 10° in 3 (17%) of the screws. CONCLUSIONS IMU-based intraoperative navigation may facilitate accurate placement of S2AI screws. PMID:26565762

  1. BIOMECHANICAL EVALUATION OF THE INFLUENCE OF CERVICAL SCREWS TAPPING AND DESIGN

    PubMed Central

    Silva, Patricia; Rosa, Rodrigo César; Shimano, Antonio Carlos; Albuquerque de Paula, Francisco José; Volpon, José Batista; Aparecido Defino, Helton Luiz

    2015-01-01

    Objective: To assess if the screw design (self-drilling/self-tapping) and the pilot hole tapping could affect the insertion torque and screw pullout strength of the screw used in anterior fixation of the cervical spine. Methods: Forty self-tapping screws and 20 self-drilling screws were inserted into 10 models of artificial bone and 10 cervical vertebrae of sheep. The studied parameters were the insertion torque and pullout strength. The following groups were created: Group I-self-tapping screw insertion after pilot hole drilling and tapping; Group II-self-tapping screw insertion after pilot hole drilling without tapping; Group III-self-drilling screw insertion without drilling and tapping. In Groups I and II, the pilot hole had 14.0 mm in depth and was made with a 3mmn drill, while tapping was made with a 4mm tap. The insertion torque was measured and the pullout test was performed. The comparison between groups was made considering the mean insertion torque and the maximum mean pullout strength with the variance analysis (ANOVA; p≤ 0.05). Results: Previous drilling and tapping of pilot hole significantly decreased the insertion torque and the pullout strength. Conclusion: The insertion torque and pullout strength of self-drilling screws were significantly higher when compared to self-tapping screws inserted after pilot hole tapping.

  2. Complications of pedicle screws in lumbar and lumbosacral fusions in 105 consecutive primary operations.

    PubMed

    Jutte, P C; Castelein, R M

    2002-12-01

    Pedicle screw fixation is technically demanding and associated with high complication rates. The aim of this study was to identify and quantify the pedicle screw-related complications in 105 consecutive operations. We retrospectively analysed 105 consecutive primary operations. We found complications of varying severity in 54% of the patients. Deep infections were found in 4.7%, all successfully cured by debridement and antibiotics. There were no permanent neurological complications related to the screws. One serious neurological sequela, a T10 paraplegia, was unrelated to screw placement between L3 and S1. Screw misplacement was found in 6.5% of the screws. Screw breakage occurred in 12.4% of the patients, inevitably leading to loss of correction. Reduced spondylolisthesis L5-S1 without anterior support was found to be especially prone to screw breakage. The study confirmed that pedicle screw placement is a technically demanding procedure with a high complication rate. Fortunately, most complications are not severe. Infections can be dealt with by thorough debridement and parenteral antibiotics. Neurological sequelae can be minimised by careful tactile technique. To avoid screw breakage and subsequent loss of correction, anterior support should be provided, through either posterior or anterior lumbar interbody fusion (PLIF or ALIF) techniques, in reduced spondylolisthesis L5-S1. PMID:12522719

  3. Effect of different radial hole designs on pullout and structural strength of cannulated pedicle screws.

    PubMed

    Chen, Hsin-Chang; Lai, Yu-Shu; Chen, Wen-Chuan; Chen, Jou-Wen; Chang, Chia-Ming; Chen, Yi-Long; Wang, Shih-Tien; Cheng, Cheng-Kung

    2015-08-01

    Cannulated pedicle screws are designed for bone cement injection to enhance fixation strength in severely osteoporotic spines. However, the screws commonly fracture during insertion. This study aims to evaluate how different positions/designs of radial holes may affect the pullout and structural strength of cannulated pedicle screws using finite element analysis. Three different screw hole designs were evaluated under torsion and bending conditions. The pullout strength for each screw was determined by axial pullout failure testing. The results showed that when the Von Mises stress reached the yield stress of titanium alloy the screw with four radial holes required a greater torque or bending moment than the nine and twelve hole screws. In the pullout test, the strength and stiffness of each screw with cement augmentation showed no significant differences, but the screw with four radial holes had a greater average pullout strength, which probably resulted from the significantly greater mean maximum lengths of cement augmentation. Superior biomechanical responses, with lower stress around the radial holes and greater pullout strength, represented by cannulated pedicle screw with four radial holes may worth recommending for clinical application. PMID:26054806

  4. Comparative Analysis of Interval, Skipped, and Key-vertebral Pedicle Screw Strategies for Correction in Patients With Lenke Type 1 Adolescent Idiopathic Scoliosis.

    PubMed

    Wang, Fei; Xu, Xi-Ming; Lu, Yanghu; Wei, Xian-Zhao; Zhu, Xiao-Dong; Li, Ming

    2016-03-01

    Pedicle screw constructs have become the mainstay for surgical correction in patients with spinal deformities. To reduce or avoid the risk of pedicle screw-based complications and to decrease the costs associated with pedicle screw instrumentation, some authors have introduced interval, skipped, and key-vertebral pedicle screw strategies for correction. However, there have been no comparisons of outcomes among these 3 pedicle screw-placement strategies.The aim of this study was to compare the correlative clinical outcomes of posterior correction and fusion with pedicle screw fixation using these 3 surgical strategies.Fifty-six consecutive patients with Lenke type 1 adolescent idiopathic scoliosis were included in this study. Twenty patients were treated with the interval pedicle screw strategy (IPSS), 20 with the skipped pedicle screw strategy (SPSS), and 16 with the key-vertebral pedicle screw strategy (KVPSS). Coronal and sagittal radiographs were analyzed before surgery, at 1 week after surgery, and at the last follow-up after surgery.There were no significant differences among the 3 groups regarding preoperative radiographic parameters. No significant difference was found between the IPSS and SPSS groups in correction of the main thoracic curve (70.8% vs 70.0%; P = 0.524). However, there were statistically significant differences between the IPSS and KVPSS groups (70.8% vs 64.9%) and between the SPSS and KVPSS groups (70.0% vs 64.9%) in correction of the main thoracic curve (P < 0.001 for both). Additionally, there were no significant differences among the 3 strategies for sagittal parameters at the immediate postoperative and last postoperative follow-up periods, though there were significant differences in the Cobb angle between the preoperative and immediate postoperative periods among the 3 groups, but not between the immediate postoperative and last follow-up periods. The amount of hospital charges in the SPSS group was significantly higher than those in the IPSS (P < 0.001) and KVPSS groups (P < 0.001). There were also significant differences in operative time between the IPSS and KVPSS groups (P < 0.001) and between the SPSS and KVPSS groups (P < 0.001).Each of the 3 types of pedicle screw strategies for correction in patients with Lenke type 1 adolescent idiopathic scoliosis are effective, with satisfactory coronal and acceptable sagittal plane results. Although the KVPSS does not provide superior operative correction compared with the IPSS and SPSS, it can achieve a satisfactory clinical outcome and is more cost-effective. PMID:26962821

  5. Tibial Fixation Properties of a Continuous-Loop ACL Hamstring Graft Construct with Suspensory Fixation in Porcine Bone.

    PubMed

    Smith, Patrick A; DeBerardino, Thomas M

    2015-12-01

    The aim of this article is to compare tibial fixation strength of suspensory fixation for a quadrupled semitendinosus continuous loop all-inside anterior cruciate ligament (ACL) construct versus a doubled semitendinosus and gracilis graft fixated with an interference screw. Biomechanical testing was conducted using human hamstring allografts and porcine tibias. Constructs were cycled from 50 to 250 N for 500 cycles followed by a pull to failure. The average load to failure of tibial suspensory fixation of the all-inside continuous loop construct (1,012 N) was statistically different compared with the tibial interference screw group (612 N) (p < 0.001). The cyclic displacement of the continuous loop construct (2.5 mm) was not statistically different from the interference screw construct (1.9 mm). For both the groups, approximately half the overall cyclic displacement occurred with the first cycle. Tibial side suspensory fixation of a novel all-inside continuous loop hamstring graft provided suitable strength for tibial fixation for ACL reconstruction. The continuous loop construct had a significantly higher load to failure compared with the use of an interference screw, and cyclic loading was comparable. Use of hamstring soft tissue grafts is very common for ACL reconstruction. An all-inside ACL reconstruction is based on a continuous loop construct utilizing a single semitendinosus graft that is quadrupled employing suspensory fixation on both the femoral and tibial side. Suspensory fixation on the femoral side been previously reported, but this is the first report of strength of this method of suspensory fixation on the tibia. PMID:25347056

  6. Biomechanical Analysis of the Fixation System for T-Shaped Acetabular Fracture.

    PubMed

    Fan, Yanping; Lei, Jianyin; Zhu, Feng; Li, Zhiqiang; Chen, Weiyi; Liu, Ximing

    2015-01-01

    This study aims to evaluate the biomechanical mechanism of fixation systems in the most frequent T-shaped acetabular fracture using finite element method. The treatment of acetabular fractures was based on extensive clinical experience. Three commonly accepted rigid fixation methods (double column reconstruction plates (P 2), anterior column plate combined with posterior column screws (P + PS), and anterior column plate combined with quadrilateral area screws (P + QS)) were chosen for evaluation. On the basis of the finite element model, the biomechanics of these fixation systems were assessed through effective stiffness levels, stress distributions, force transfers, and displacements along the fracture lines. All three fixation systems can be used to obtain effective functional outcomes. The third fixation system (P + QS) was the optimal method for T-shaped acetabular fracture. This fixation system may reduce many of the risks and limitations associated with other fixation systems. PMID:26495030

  7. Biomechanical Analysis of the Fixation System for T-Shaped Acetabular Fracture

    PubMed Central

    Fan, Yanping; Lei, Jianyin; Zhu, Feng; Li, Zhiqiang; Chen, Weiyi; Liu, Ximing

    2015-01-01

    This study aims to evaluate the biomechanical mechanism of fixation systems in the most frequent T-shaped acetabular fracture using finite element method. The treatment of acetabular fractures was based on extensive clinical experience. Three commonly accepted rigid fixation methods (double column reconstruction plates (P 2), anterior column plate combined with posterior column screws (P + PS), and anterior column plate combined with quadrilateral area screws (P + QS)) were chosen for evaluation. On the basis of the finite element model, the biomechanics of these fixation systems were assessed through effective stiffness levels, stress distributions, force transfers, and displacements along the fracture lines. All three fixation systems can be used to obtain effective functional outcomes. The third fixation system (P + QS) was the optimal method for T-shaped acetabular fracture. This fixation system may reduce many of the risks and limitations associated with other fixation systems. PMID:26495030

  8. Development and Testing of X-Ray Imaging-Enhanced Poly-L-Lactide Bone Screws

    PubMed Central

    Tzeng, Jy-Jiunn; Wu, Ting-Lin; Fong, Tsorng-Harn; Feng, Sheng-Wei; Huang, Haw-Ming

    2015-01-01

    Nanosized iron oxide particles exhibit osteogenic and radiopaque properties. Thus, iron oxide (Fe3O4) nanoparticles were incorporated into a biodegradable polymer (poly-L-lactic acid, PLLA) to fabricate a composite bone screw. This multifunctional, 3D printable bone screw was detectable on X-ray examination. In this study, mechanical tests including three-point bending and ultimate tensile strength were conducted to evaluate the optimal ratio of iron oxide nanoparticles in the PLLA composite. Both injection molding and 3D printing techniques were used to fabricate the PLLA bone screws with and without the iron oxide nanoparticles. The fabricated screws were implanted into the femoral condyles of New Zealand White rabbits. Bone blocks containing the PLLA screws were resected 2 and 4 weeks after surgery. Histologic examination of the surrounding bone and the radiopacity of the iron-oxide-containing PLLA screws were evaluated. Our results indicated that addition of iron oxide nanoparticles at 30% significantly decreased the ultimate tensile stress properties of the PLLA screws. The screws with 20% iron oxide exhibited strong radiopacity compared to the screws fabricated without the iron oxide nanoparticles. Four weeks after surgery, the average bone volume of the iron oxide PLLA composite screws was significantly greater than that of PLLA screws without iron oxide. These findings suggested that biodegradable and X-ray detectable PLLA bone screws can be produced by incorporation of 20% iron oxide nanoparticles. Furthermore, these screws had significantly greater osteogenic capability than the PLLA screws without iron oxide. PMID:26466309

  9. Helical screw viscometer

    DOEpatents

    Aubert, J.H.; Chapman, R.N.; Kraynik, A.M.

    1983-06-30

    A helical screw viscometer for the measurement of the viscosity of Newtonian and non-Newtonian fluids comprising an elongated cylindrical container closed by end caps defining a circular cylindrical cavity within the container, a cylindrical rotor member having a helical screw or ribbon flight carried by the outer periphery thereof rotatably carried within the cavity whereby the fluid to be measured is confined in the cavity filling the space between the rotor and the container wall. The rotor member is supported by axle members journaled in the end caps, one axle extending through one end cap and connectable to a drive source. A pair of longitudinally spaced ports are provided through the wall of the container in communication with the cavity and a differential pressure meter is connected between the ports for measuring the pressure drop caused by the rotation of the helical screw rotor acting on the confined fluid for computing viscosity.

  10. Is Polymethyl Methacrylate a Viable Option for Salvaging Lateral Mass Screw Failure in the Subaxial Cervical Spine?

    PubMed Central

    Gallizzi, Michael A.; Kuhns, Craig A.; Jenkins, Tyler J.; Pfeiffer, Ferris M.

    2014-01-01

    Study Design?Biomechanical analysis of lateral mass screw pullout strength. Objective?We compare the pullout strength of our bone cementrevised lateral mass screw with the standard lateral mass screw. Methods?In cadaveric cervical spines, we simulated lateral mass screw cutouts unilaterally from C3 to C7. We salvaged fixation in the cutout side with polymethyl methacrylate (PMMA) or Cortoss cement (Orthovita, Malvern, Pennsylvania, United States), allowed the cement to harden, and then drilled and placed lateral mass screws back into the cement-augmented lateral masses. On the contralateral side, we placed standard lateral mass screws into the native, or normal lateral, masses and then compared pullout strength of the cement-augmented side to the standard lateral mass screw. For pullout testing, each augmentation group was fixed to a servohydraulic load frame and a specially designed pullout fixture was attached to each lateral mass screw head. Results?Quick-mix PMMA-salvaged lateral mass screws required greater force to fail when compared with native lateral mass screws. Cortoss cement and PMMA standard-mix cement-augmented screws demonstrated less strength of fixation when compared with control-side lateral mass screws. Attempts at a second round of cement salvage of the same lateral masses led to more variations in load to failure, but quick-mix PMMA again demonstrated greater load to failure when compared with the nonaugmented control lateral mass screws. Conclusion?Quick-mix PMMA cement revision equips the spinal surgeon with a much needed salvage option for a failed lateral mass screw in the subaxial cervical spine. PMID:25649421

  11. Is polymethyl methacrylate a viable option for salvaging lateral mass screw failure in the subaxial cervical spine?

    PubMed

    Gallizzi, Michael A; Kuhns, Craig A; Jenkins, Tyler J; Pfeiffer, Ferris M

    2015-02-01

    Study Design Biomechanical analysis of lateral mass screw pullout strength. Objective We compare the pullout strength of our bone cement-revised lateral mass screw with the standard lateral mass screw. Methods In cadaveric cervical spines, we simulated lateral mass screw "cutouts" unilaterally from C3 to C7. We salvaged fixation in the cutout side with polymethyl methacrylate (PMMA) or Cortoss cement (Orthovita, Malvern, Pennsylvania, United States), allowed the cement to harden, and then drilled and placed lateral mass screws back into the cement-augmented lateral masses. On the contralateral side, we placed standard lateral mass screws into the native, or normal lateral, masses and then compared pullout strength of the cement-augmented side to the standard lateral mass screw. For pullout testing, each augmentation group was fixed to a servohydraulic load frame and a specially designed pullout fixture was attached to each lateral mass screw head. Results Quick-mix PMMA-salvaged lateral mass screws required greater force to fail when compared with native lateral mass screws. Cortoss cement and PMMA standard-mix cement-augmented screws demonstrated less strength of fixation when compared with control-side lateral mass screws. Attempts at a second round of cement salvage of the same lateral masses led to more variations in load to failure, but quick-mix PMMA again demonstrated greater load to failure when compared with the nonaugmented control lateral mass screws. Conclusion Quick-mix PMMA cement revision equips the spinal surgeon with a much needed salvage option for a failed lateral mass screw in the subaxial cervical spine. PMID:25649421

  12. Surface polishing positively influences ease of plate and screw removal.

    PubMed

    Hayes, J S; Seidenglanz, U; Pearce, A I; Pearce, S G; Archer, C W; Richards, R G

    2010-01-01

    Difficulties removing temporary fracture fixation devices due to excessive bony on-growth results in extended surgical time leading to excessive blood loss, debris contamination and potentially refracture. Commercially available locking plates and screws are manufactured for clinics with a micro-rough surface, which contributes to the excessive bony on-growth reported. We have applied polishing technology to commercially pure titanium locking compression plates (LCP) and titanium-6%aluminium-7%niobium (TAN) plates and screws to assess if it can alleviate problems with strong bony overgrowth. Samples were implanted for 6, 12 and 18 months in a bilateral sheep tibia non fracture model and assessed for screw removal torque, percentage of bone contact and tissue-material response. Both electropolishing (p=0.001) and paste polishing (p=0.010) of TAN screws significantly reduced the mean torque required for removal compared to their micro-rough counterparts. This was accompanied by a trend for a lower percentage of bone contact for polished screws. This difference in bone contact was significant for paste polished TAN screws (p<0.001 parallel but not electropolished TAN screws (p=0.066). Ex vivo, soft tissue removal was much easier (approximately five minutes) for polished constructs, which was difficult and at least four times longer for standard micro-rough constructs. We suggest that polishing of locked plate/screw systems will improve ease of removal and reduce implant related removal complications encountered due to excessive strong bony on-growth while maintaining biocompatibility and implant stability. Future studies aim to assess the potential of this technology in the next level of complication, a fracture model. PMID:20186671

  13. Screw-Retaining Allen Wrench

    NASA Technical Reports Server (NTRS)

    Granett, D.

    1985-01-01

    Steadying screws with fingers unnecessary. Crimp in uncompressed spring wire slightly protrudes from one facet of Allen wrench. Compressed spring retains Allen screw. Tool used with Allen-head screws in cramped spaces with little or no room for fingers to hold fastener while turned by wrench.

  14. Weber C ankle fractures: a retrospective audit of screw number, size, complications, and retrieval rates.

    PubMed

    Walker, Logan; Willis, Nigel

    2015-01-01

    Tibiofibular transfixation of Weber C injuries using a diastasis screw is the current method of fixation. However, controversy remains regarding the screw size and number, number of cortices engaged, and the interval to screw removal. The present study reviewed the current practice in the Wellington Region. A retrospective audit of patients with documented Weber C injuries in the Capital & Coast District Health Board from June 2012 to December 2013 was performed. The clinical medical records and radiographs were reviewed, and the patient demographics, surgeon details, screw number, size, cortices engaged, screw removal period, and documented complications were recorded. A total of 36 operations were documented, of which 27 (75%) cases also required fibula plating. Of the 36 cases, 25 (69.44%) used a single diastasis screw, 33 (91.67%) used 4.5-mm screws, and 18 (50%) engaged 3 cortices. Surgical practice did not vary with the experience level. Of the 36 patients, 29 (80.56%) underwent routine screw removal at a median of 20 (25th to 75th quartile range 16 to 22) weeks. Also, 9 (25%) cases of screw fracture occurred, with a median documented interval to fracture of 18 (25th to 75th quartile range 15 to 20) weeks. The surgical management of Weber C injuries is consistent with current practice. The routine removal of diastasis screws by 20 weeks postoperatively was not different from the documented interval of screw removal when screw fractures had occurred. The timing of screw removal needs to be weighed against the fracture risk, patient symptoms, and the risk of secondary procedure complications. PMID:25619809

  15. Parallel analysis of finite element model controlled trial and retrospective case control study on percutaneous internal fixation for vertical sacral fractures

    PubMed Central

    2013-01-01

    Background Although percutaneous posterior-ring tension-band metallic plate and percutaneous iliosacral screws are used to fix unstable posterior pelvic ring fractures, the biomechanical stability and compatibility of both internal fixation techniques for the treatment of Denis I, II and III type vertical sacral fractures remain unclear. Methods Using CT and MR images of the second generation of Chinese Digitized Human male No. 23, two groups of finite element models were developed for Denis I, II and III type vertical sacral fractures with ipsilateral superior and inferior pubic ramus fractures treated with either a percutaneous metallic plate or a percutaneous screw. Accordingly, two groups of clinical cases that were fixed using the above-mentioned two internal fixation techniques were retrospectively evaluated to compare postoperative effect and function. Parallel analysis was performed with a finite element model controlled trial and a case control study. Results The difference of the postoperative Majeed standards and outcome rates between two case groups was no statistically significant (P?>?0.05). Accordingly, the high values of the maximum displacements/stresses of the plate-fixation model group approximated those of the screw-fixation model group. However, further simulation of Denis I, II and III type fractures in each group of models found that the biomechanics of the plate-fixation models became increasingly stable and compatible, whereas the biomechanics of the screw-fixation models maintained tiny fluctuations. When treating Denis III fractures, the biomechanical effects of the pelvic ring of the plate-fixation model were better than the screw-fixation model. Conclusions Percutaneous plate and screw fixations are both appropriate for the treatment of Denis I and II type vertical sacral fractures; whereas percutaneous plate fixation appears be superior to percutaneous screw fixation for Denis III type vertical sacral fracture. Biomechanical evidence of finite element evaluations combined with clinical evidence will contribute to our ability to distinguish between indications that require plate or screw fixation for vertical sacral fractures. PMID:23879618

  16. Rotary screw compressors in the gas patch

    SciTech Connect

    Jandjel, D.G.

    1996-01-01

    In 1959, Howden introduced the oil-injected rotary screw (OIS) compressor, which has, since then, methodically replaced the reciprocating (piston) compressor in applications such as air, refrigeration and fuel gas. Rotary screw compressors have been making inroads in gas recovery, a field once dominated by reciprocating compressors. Rotary screws do not require extensive maintenance, thus downtime is minimized throughout an operating year. Preventive maintenance is simple, since it consists of regular oil sample analysis which does not require system shut-down. As a result of the slide valve, OIS compressors can tune to field conditions with the greatest of ease, and without complicated process control. In addition, this method of capacity control is more efficient than unloading or use of a bypass-recirculation line. Both engineers and operators alike have found this flexibility to be a most redeeming feature. Finally, OIS compressors are capable of much larger flows then recips. 2 figs.

  17. Anterior subcutaneous internal fixation for treatment of unstable pelvic fractures

    PubMed Central

    2014-01-01

    Background Fractures of the pelvic ring including disruption of the posterior elements in high-energy trauma have both high morbidity and mortality rates. For some injury pattern part of the initial resuscitation includes either external fixation or plate fixation to close the pelvic ring and decrease blood loss. In certain situations especially when associated with abdominal trauma and the need to perform laparotomies both techniques may put the patient at risk of either pintract or deep plate infections. We describe an operative approach to percutaneously close and stabilize the pelvic ring using spinal implants as an internal fixator and report the results in a small series of patients treated with this technique during the resuscitation phase. Findings Four patients were treated by subcutaneous placement of an internal fixator. Screw fixation was carried out by minimally invasive placement of two supra-acetabular iliac screws. Afterwards, a subcutaneous transfixation rod was inserted and attached to the screws after reduction of the pelvic ring. All patients were allowed to fully weight-bear. No losses of reduction or deep infections occurred. Fracture healing was uneventful in all cases. Conclusion Minimally invasive fixation is an alternative technique to stabilize the pelvic ring. The clinical results illustrate that this technique is able to achieve good results in terms of maintenance of reduction the pelvic ring. Also, abdominal surgeries no longer put the patient at risk of infected pins or plates. PMID:24606833

  18. [Time saving and effective method of temporary intraoperative reposition in mandibular fractures. Realization with the FAMI screw].

    PubMed

    Fangmann, R; Mischkowski, R A; Hidding, J

    1999-01-01

    Open reduction and rigid fixation with maxillomandibular fixation at least intraoperatively is the method of choice for treatment of mandibular fractures. We report an effective method of internal temporary fixation which significantly facilitates fracture reduction and stabilization. The technique is used in combination with special FAMI screws and a monocortical miniplates system according to Champy, which eliminates in most cases the need for maxillomandibular fixation. Our results in 78 patients with mandibular fractures confirmed the reliability and the efficiency of the internal temporary fixation. PMID:10077962

  19. Tacks: a new technique for craniofacial fixation.

    PubMed

    Cohen, S R; Holmes, R E; Amis, P; Fitchner, H; Shusterman, E M

    2001-11-01

    Biodegradable fixation in craniofacial surgery provides secure fixation while eliminating much of the concern over intracranial migration of metallic plates and screws. One limitation of present biodegradable systems, however, is the need for tapping the drill hole before screw insertion. Herein, a new method of rigid, biodegradable fixation with tacks (Macrapore, Inc., San Diego, CA) is described. The tacks are made of a 70:30 ratio of the L and DL form of polylactic acid (L,DL-PLA). Degradation times range from 18 to 36 months. Newer prototypes are nearly developed for more rapid dissolution times. From April 1999 to February 2000, tack fixation has been applied in 100 patients (51 males, 49 females aged 3 months to 61 years). Indications for operation were craniosynostosis (n = 33); craniofacial trauma or post-traumatic deformities (n = 11); cleft lip and palate (n = 13); craniofacial syndromes (n = 18); other diagnoses (n = 11). Patients underwent fronto-orbital advancement with cranial reshaping; monobloc osteotomy, open reduction-internal fixation of fractures; hypertelorbitism repair; cranioplasty; stabilization of grafts; major cranial reconstruction; zygomatic advancement; alveolar cleft repair; and iliac bone graft donor site protection. Tacks were also used for temporalis muscle and lateral canthal suspension. Follow-up ranged from 16 to 28 months. Complications occurred in 7 patients, 4 of whom had infections and during debridement had biodegradable implants removed. None of the complications appeared to be related to the use of tacks. The tacks are carried in a specially designed holder and may be placed by hand or with the light tap of a mallet on the tack driver. An automatic driver has been developed. Overall, the performance of the tacks has been excellent. They are easily handled by the nursing personnel and rapidly inserted by the surgeon. Stability appears to be excellent. At this time, it is probably preferable to employ tap and screws for orthognathic surgery or other osteotomies with substantial load bearing. PMID:11711829

  20. The feasibility and radiological features of sacral alar iliac fixation in an adult population: a 3D imaging study

    PubMed Central

    Wu, Ai-Min; Chi, Yong-Long

    2016-01-01

    Background: Surgical treatments for adult spinal deformities often include pelvic fixation, and the feasibility of sacral-2 alar iliac (S2AI) screw fixation has been shown previously. However, sometimes S2AI screw fixation cannot be applied due to the presence of an osteolytic lesion or trauma or because the biomechanical properties of only an S2AI screw is insufficient. Therefore, we questioned the feasibility of using sacral AI screws in other segments and determined whether S3AI and S4AI screws have the potential to be used for sacral fractures. The aim of this study was to investigate the feasibility and radiological features of sacral AI fixation in S1S4 in an adult population using 3D imaging techniques. Methods: Computed tomography (CT) scans were taken of 45 patients and were imported into Mimics (Version 10.01, Materialise, Belgium) software to reconstruct the 3D digital images. Next, a cylinder (radius of 3.5 mm) was drawn to imitate the screw trajectory of a S14 AI screw, and every imitated screw in each segment was adjusted to a maximum upward and downward angle to acquire the feasible region. The parameters of the S14AI screw trajectories were measured. Results: Sacral AI screws could be successfully imitated using 3D digital imaging. The S4AI screw trajectory could be obtained in 19 of 45 patient images (42.2%), while the feasibility rates of S1AI, S2AI, and S3AI screw fixation were 100%, 100%, and 91.1% (41/45), respectively. The feasible regions of S1AI, S2AI, and S3AI screw trajectories were wide enough, while the adjustable angle of S4AI screws was very small. Conclusion: It is feasible to place S12AI screws in the entire adult population and S34AI screws in some of the adult population. Furthermore, our study suggested that 3D digital images are suitable to study the feasibility of new screw fixation. PMID:26855859

  1. Innovative approach in the development of computer assisted algorithm for spine pedicle screw placement.

    PubMed

    Solitro, Giovanni F; Amirouche, Farid

    2016-04-01

    Pedicle screws are typically used for fusion, percutaneous fixation, and means of gripping a spinal segment. The screws act as a rigid and stable anchor points to bridge and connect with a rod as part of a construct. The foundation of the fusion is directly related to the placement of these screws. Malposition of pedicle screws causes intraoperative complications such as pedicle fractures and dural lesions and is a contributing factor to fusion failure. Computer assisted spine surgery (CASS) and patient-specific drill templates were developed to reduce this failure rate, but the trajectory of the screws remains a decision driven by anatomical landmarks often not easily defined. Current data shows the need of a robust and reliable technique that prevents screw misplacement. Furthermore, there is a need to enhance screw insertion guides to overcome the distortion of anatomical landmarks, which is viewed as a limiting factor by current techniques. The objective of this study is to develop a method and mathematical lemmas that are fundamental to the development of computer algorithms for pedicle screw placement. Using the proposed methodology, we show how we can generate automated optimal safe screw insertion trajectories based on the identification of a set of intrinsic parameters. The results, obtained from the validation of the proposed method on two full thoracic segments, are similar to previous morphological studies. The simplicity of the method, being pedicle arch based, is applicable to vertebrae where landmarks are either not well defined, altered or distorted. PMID:26922675

  2. Nuts and bolts: dimensions of commonly utilized screws in upper extremity surgery.

    PubMed

    Douglass, Nathan; Yao, Jeffrey

    2015-02-01

    A plethora of screw designs and sizes are available from multiple companies for use in upper extremity surgery. Knowing the dimensions of screws is critical in the treatment of bone of varying dimensions for fractures, osteotomies, or arthrodeses. Although many screws are named by their major thread diameter, this is not always true. Because of this confusing nomenclature and vast number of options, we sought to review the most commonly used screws and codify their dimensions into a readily available article and reference chart. This article highlights the basic dimensions of commonly used headless screws, stand-alone lag screws, non-locking and locking screws for plating, and biocomposite screws. Commonly described treatments using these screws include fixation of elbow, wrist, carpal, metacarpal, and phalangeal fractures and osteotomies, as well as arthrodeses of upper extremity joints. This article and its tables are by no means exhaustive of all commercially available implants. The focus is on the most commonly used implants in the United States as of 2014. PMID:25617959

  3. SPECT-CT Assessment of Pseudarthrosis after Spinal Fusion: Diagnostic Pitfall due to a Broken Screw

    PubMed Central

    Rager, Olivier; Amzalag, Gaël; Varoquaux, Arthur; Schaller, Karl; Ratib, Osman; Tessitore, Enrico

    2013-01-01

    A 43-year-old drug addicted female was referred for a L5-S1 posterolateral in situ fixation with autologous graft because of an L5/S1 severe discopathy with listhesis. After six months, low back pain recurred. A Tc-99m HDP SPECT-CT diagnosed a pseudarthrosis with intense uptake of the L5-S1 endplates and a fracture of the right S1 screw just outside the metal-bone interface without any uptake or bone resorption around the screw. The absence of uptake around a broken screw is a pitfall that the physician should be aware of. PMID:24159394

  4. Missing nitrogen fixation in the Benguela region

    NASA Astrophysics Data System (ADS)

    Wasmund, Norbert; Struck, Ulrich; Hansen, Anja; Flohr, Anita; Nausch, Günther; Grüttmüller, Annett; Voss, Maren

    2015-12-01

    Opposing opinions on the importance of nitrogen fixation in the northern Benguela upwelling region provoked us to investigate the magnitude of nitrogen fixation in front of northern Namibia and southern Angola. Measurements of nitrogen fixation rates using the 15N method at 66 stations during seven cruises from 2008 to 2014 showed that, in general, the 15N content in the biomass did not increase after tracer incubation with 15N2, indicating that no nitrogen fixation occurred. Correspondingly, the filamentous nitrogen-fixing cyanobacterium Trichodesmium was almost not present. The abundant picocyanobacteria did obviously not perform nitrogen fixation to a significant degree. The artificial improvement of conditions for nitrogen fixation in mesocosm experiments, including phosphate and iron additions and a warmer temperature, failed to induce nitrogen fixation. A plausible explanation of these findings is a lack of conditioned cells for nitrogen fixation in the Benguela region.

  5. The Utility of the Fluoroscopic Skyline View During Volar Locking Plate Fixation of Distal Radius Fractures

    PubMed Central

    Vaiss, Lucile; Ichihara, Satoshi; Hendriks, Sarah; Taleb, Chihab; Liverneaux, Philippe; Facca, Sybille

    2014-01-01

    Background?Open reduction and internal fixation (ORIF) using a volar locking plate is a common method for treating displaced distal radius fractures. There is, however, the risk of extensor tendon rupture due to protrusion of the screw tips past the dorsal cortex, which cannot always be adequately seen on a lateral fluoroscopic view. We therefore wished to compare the sensitivity of an intraoperative fluoroscopic skyline view to a lateral fluorosocopic view in detecting past pointing of these screws. Material and Methods?Our series included 75 patients with an average age of 59 years who underwent volar locked plate fixation of a displaced distal radius fracture. Intraoperative anteroposterior (AP), lateral, and skyline fluoroscopic views were performed in each case. The number of screws that were seen to protrude past the dorsal cortex of the distal fracture fragment were recorded for both the lateral and skyline views. The number of screws that required exchange was also documented. Results?No screws were seen to protrude past the dorsal cortical bone on the lateral fluroscopic views. 15 of 300 screws (5%) were seen to protrude past the dorsal cortex by an average of 0.8?mm (range, 0.5 to 2 mm) and were exchanged for shorter screws in 11/75 patients. Conclusion?Our results demonstrate that the skyline is more sensitive than a lateral fluoroscopic view at demonstrating protrusion of the screws in the distal fracture fragment following volar locked plate fixation. Level of Evidence?IV PMID:25364637

  6. Additives

    NASA Technical Reports Server (NTRS)

    Smalheer, C. V.

    1973-01-01

    The chemistry of lubricant additives is discussed to show what the additives are chemically and what functions they perform in the lubrication of various kinds of equipment. Current theories regarding the mode of action of lubricant additives are presented. The additive groups discussed include the following: (1) detergents and dispersants, (2) corrosion inhibitors, (3) antioxidants, (4) viscosity index improvers, (5) pour point depressants, and (6) antifouling agents.

  7. Variation of plate fixation for mandibular advancement with intraoral vertical ramus osteotomy using endoscopically assisted intraoral rigid or semi-rigid internal fixation: Case series study: Postoperative condylar seating control for mandibular advancement.

    PubMed

    Hara, Shingo; Mitsugi, Masaharu; Tatemoto, Yukihiro

    2015-12-01

    The purpose of the present study was to evaluate the safety and efficacy associated with mandibular advancement by intraoral vertical ramus osteotomy (IVRO) with endoscopically assisted intraoral rigid or semi-rigid internal fixation. The study sample included all patients who had undergone an mandibular advancement by IVRO procedure with endoscopically assisted intraoral plate fixation from September 2008 to May 2012. An mandibular advancement by IVRO with endoscopically assisted intraoral rigid or semi-rigid internal fixation was used for mandibular advancement. The patients were analyzed prospectively, with more than 2 years of follow-up, and were evaluated in terms of functional results, postoperative complications, and skeletal stability. A total of 14 patients (bilateral, 7 patients with class II; unilateral, 7 patients with asymmetry) were included in the present study. The average degree of mandibular advancement was 5.51.9mm (range, 3-9mm). Both the occlusal relationship and facial appearance in all patients were significantly improved by the surgical-orthodontic treatment, with no major harmful clinical symptoms. In addition, one-screw semi-rigid fixation could control postoperative passive condylar seating. This study showed that mandibular advancement by IVRO with endoscopically assisted, intraoral semi-rigid internal fixation offers a promising treatment alternative for patients with skeletal class II malocclusion or facial asymmetry. PMID:26610634

  8. Screwed superconducting cosmic strings

    NASA Astrophysics Data System (ADS)

    Ferreira, C. N.

    2002-02-01

    We show that it is possible to build up a consistent model describing a superconducting cosmic string (SCS) endowed with torsion. A full string solution is obtained by matching the internal and external solutions. We derive the deficit angle, the geodesics of and the gravitational force on a test particle moving under the action of this screwed SCS. A couple of potential astrophysical phenomena are highlighted: the dynamics of compact objects orbiting torsioned SCS and the accretion of matter onto it.

  9. Preliminary study of the feasibility and accuracy of percutaneous peri-acetabular screw insertion in a porcine model.

    PubMed

    Cassar-Gheiti, A J; Dodds, M K; Byrne, D P; Mulhall, K J

    2013-02-01

    The aim of this pilot study was to assess a new method of training for peri-acetabular screw placement under indirect vision using standard C-arm fluoroscopy using a porcine model. Two novice orthopaedic residents placed 72 screws (36 each) about the acetabula of six porcine pelves under C-arm fluoroscopic guidance. Unsatisfactory screw position was noted in 22 of 72, with five instances of screw ingress into the hip joint. All of these cases occurred in the first half of each resident's series. Screw direction and final position improved over subsequent trials. This pilot study demonstrates that surgical simulation techniques are applicable in percutaneous screw fixation. Such an approach could be useful for both residents in training and more experienced surgeons who wish to perform this procedure in cases where it is appropriate. PMID:23000053

  10. Dynamic-locking-screw (DLS)leads to less secondary screw perforations in proximal humerus fractures

    PubMed Central

    2014-01-01

    Background Loss of reduction and screw perforation causes high failure rates in the treatment of proximal humerus fractures. The purpose of the present study was to evaluate the early postoperative complications using modern Dynamic Locking Screws (DLS 3.7) for plating of proximal humerus fractures. Methods Between 03/2009 and 12/2010, 64 patients with acute proximal humerus fractures were treated by angular stable plate fixation using DLSs in a limited multi-centre study. Follow-up examinations were performed three, six, twelve and twenty-four weeks postoperatively and any complications were carefully collected. Results 56 of 64 patients were examined at the six-month follow-up. Complications were observed in 12 patients (22%). In five cases (9%), a perforation of the DLS 3.7 occurred. Conclusions Despite the use of modern DLS 3.7, the early complications after plating of proximal humerus fractures remain high. The potential advantage of the DLS 3.7 regarding secondary screw perforation has to be confirmed by future randomized controlled trials. PMID:24894637

  11. Finite Element Analysis of a New Pedicle Screw-Plate System for Minimally Invasive Transforaminal Lumbar Interbody Fusion

    PubMed Central

    Zhou, Yue; Li, Changqing; Liu, Huan

    2015-01-01

    Purpose Minimally invasive transforaminal lumbar interbody fusion (MI-TLIF) is increasingly popular for the surgical treatment of degenerative lumbar disc diseases. The constructs intended for segmental stability are varied in MI-TLIF. We adopted finite element (FE) analysis to compare the stability after different construct fixations using interbody cage with posterior pedicle screw-rod or pedicle screw-plate instrumentation system. Methods A L3S1 FE model was modified to simulate decompression and fusion at L4L5 segment. Fixation modes included unilateral plate (UP), unilateral rod (UR), bilateral plate (BP), bilateral rod (BR) and UP+UR fixation. The inferior surface of the S1 vertebra remained immobilized throughout the load simulation, and a bending moment of 7.5 Nm with 400N pre-load was applied on the L3 vertebra to recreate flexion, extension, lateral bending, and axial rotation. Range of motion (ROM) and Von Mises stress were evaluated for intact and instrumentation models in all loading planes. Results All reconstructive conditions displayed decreased motion at L4L5. The pedicle screw-plate system offered equal ROM to pedicle screw-rod system in unilateral or bilateral fixation modes respectively. Pedicle screw stresses for plate system were 2.2 times greater than those for rod system in left lateral bending under unilateral fixation. Stresses for plate were 3.1 times greater than those for rod in right axial rotation under bilateral fixation. Stresses on intervertebral graft for plate system were similar to rod system in unilateral and bilateral fixation modes respectively. Increased ROM and posterior instrumentation stresses were observed in all loading modes with unilateral fixation compared with bilateral fixation in both systems. Conclusions Transforaminal lumbar interbody fusion augmentation with pedicle screw-plate system fixation increases fusion construct stability equally to the pedicle screw-rod system. Increased posterior instrumentation stresses are observed in all loading modes with plate fixation, and bilateral fixation could reduce stress concentration. PMID:26649749

  12. A novel patient-specific navigational template for cervical pedicle screw placement.

    PubMed

    Lu, Sheng; Xu, Yong Q; Lu, William W; Ni, Guo X; Li, Yan B; Shi, Ji H; Li, Dong P; Chen, Guo P; Chen, Yu B; Zhang, Yuan Z

    2009-12-15

    STUDY DESIGN.: Prospective trial. OBJECTIVE.: To develop and validate a novel, patient-specific navigational template for cervical pedicle placement. SUMMARY OF BACKGROUND DATA.: Owing to the narrow bony anatomy and the proximity to the vertebral artery and the spinal cord, cervical instrumentation procedures demand the need for a precise technique for screw placement. PATIENT.: Specific drill template with preplanned trajectory has been thought as a promising solution for cervical pedicle screw placement. METHODS.: Patients with cervical spinal pathology (n = 25) requiring instrumentation were recruited. Volumetric CT scan was performed on each desired cervical vertebra and a 3-dimensional reconstruction model was generated from the scan data. Using reverse engineering technique, the optimal screw size and orientation were determined and a drill template was designed with a surface that is the inverse of the posterior vertebral surface. The drill template and its corresponding vertebra were manufactured using rapid prototyping technique and tested for violations. The navigational template was sterilized and used intraoperatively to assist with the placement of cervical screws. In total, 88 screws were inserted into levels C2-C7 with 2 to 6 screw in each patient. After surgery, the positions of the pedicle screws were evaluated using CT scan and graded for validation. RESULTS.: This method showed its ability to customize the placement and the size of each screw based on the unique morphology of the cervical vertebra. In all the cases, it was relatively very easy to manually place the drill template on the lamina of the vertebral body during the surgery. The required time between fixation of the template to the lamina and insertion of the pedicle screws was about 80 seconds. Of the 88 screws, 71 screws had no deviation and 14 screws had deviation <2 mm, 1 screw had a deviation between 2 to 4 mm and there were no misplacements. Fluoroscopy was used only once for every patient after the insertion of all the pedicle screws. CONCLUSION.: The authors have developed a novel patient-specific navigational template for cervical pedicle screw placement with good applicability and high accuracy. This method significantly reduces the operation time and radiation exposure for the members of the surgical team. The potential use of such a navigational template to insert cervical pedicle screws is promising. This technique has been clinically validated to provide an accurate trajectory for pedicle screw placement in the cervical spine. PMID:20010385

  13. Drill Free Screws: a new form of osteosynthesis screw.

    PubMed

    Heidemann, W; Gerlach, K L; Grbel, K H; Kllner, H G

    1998-06-01

    Although the application of self-tapping and non self-tapping screws is virtually universal in cranio-maxillofacial surgery, the inevitable, time consuming procedure of drilling a pilot hole has some potential disadvantages, such as damage to nerves, tooth roots or tooth germs, thermal necrosis of the bone and drill bit breakage. Drill Free Screws (DFS) are a recently developed type of osteosynthesis screws, having a tip like a cork screw and specially formed cutting flutes which enable insertion of the screws without drilling. DFS 1.5 and 2 mm were inserted into discs of wood, polyvinylchloride (PVC) and porcine mandibular bone of varying thicknesses between 2 and 4 mm. The values of insertion torque and maximum torque were recorded using an electric torque tester. Thereafter, the screws were inserted with a fixed torque and uniaxial pull out tests were performed. In comparison with this, the same procedure was performed using 1.5 and 2 mm self-tapping titanium screws. Ten trials for each screw-material-combination were conducted to determine insertion torque, maximum torque and pull out analysis. The results showed that the holding power of DFS lay between 70 and 104% of the holding power of self-tapping titanium screws; only in PVC was the difference more than 15%. PMID:9702635

  14. In vitro and in vivo studies on the degradation of high-purity Mg (99.99wt.%) screw with femoral intracondylar fractured rabbit model.

    PubMed

    Han, Pei; Cheng, Pengfei; Zhang, Shaoxiang; Zhao, Changli; Ni, Jiahua; Zhang, Yuanzhuang; Zhong, Wanrun; Hou, Peng; Zhang, Xiaonong; Zheng, Yufeng; Chai, Yimin

    2015-09-01

    High-purity magnesium (HP Mg) takes advantage in no alloying toxic elements and slower degradation rate in lack of second phases and micro-galvanic corrosion. In this study, as rolled HP Mg was fabricated into screws and went through in vitro immersion tests, cytotoxicity test and bioactive analysis. The HP Mg screws performed uniform corrosion behavior in vitro, and its extraction promoted cell viability, bone alkaline phosphatase (ALP) activity, and mRNA expression of osteogenic differentiation related gene, i.e. ALP, osteopontin (OPN) and RUNX2 of human bone marrow mesenchymal stem cells (hBMSCs). Then HP Mg screws were implanted in vivo as load-bearing implant to fix bone fracture and subsequently gross observation, range of motion (ROM), X-ray scanning, qualitative micro-computed tomography (?CT) analysis, histological analysis, bending-force test and SEM morphology of retrieved screws were performed respectively at 4, 8, 16 and 24 weeks. As a result, the retrieved HP Mg screws in fixation of rabbit femoral intracondylar fracture showed uniform degradation morphology and enough bending force. However, part of PLLA screws was broken in bolt, although its screw thread was still intact. Good osseointegration was revealed surrounding HP Mg screws and increased bone volume and bone mineral density were detected at fracture gap, indicating the rigid fixation and enhanced fracture healing process provided by HP Mg screws. Consequently, the HP Mg showed great potential as internal fixation devices in intra-articular fracture operation. PMID:26117658

  15. A comparison of preload values in gold and titanium dental implant retaining screws.

    PubMed

    Doolabh, R; Dullabh, H D; Sykes, L M

    2014-08-01

    This in vitro investigation compared the effect of using either gold or titanium retaining screws on preload in the dental implant- abutment complex. Inadequate preload can result in screw loosening, whilst fracture may occur if preload is excessive. These are the most commonly reported complications in implant-retained prostheses, and result in unscheduled, costly and time-consuming visits for the patient and the clinician. This study investigated changes in preload generation after repeated torque applications to gold and titanium screws. The test set-up consisted of an implant body, a cylindrical transmucosa abutment, and the test samples of gold and of titanium retaining screws. The implant bodies were anchored using a load cell, and the transmucosal abutments were attached using either gold or titanium retaining screws. A torque gauge was used to apply torque of 20Ncm, 32Ncm, and 40Ncm to the retaining screws. The preloads generated in each screw type were compared at each torque setting, and after repeated tightening episodes. In addition, the effect of applying torque beyond the manufacturers' recommendations was also examined. Gold retaining screws were found to achieve consistently higher preload values than titanium retaining screws. Preload values were not significantly different from the first to the tenth torque cycle. Titanium screws showed more consistent preload values, albeit lower than those of the gold screws. However due to possible galling of the internal thread of the implant body by titanium screws, gold screws remain the retaining screw of choice. Based on the findings of this study, gold retaining screws generate better preload than titanium. Torque beyond the manufacturers' recommendations resulted in a more stable implant complex. However, further investigations, with torque applications repeated until screw breakage, are needed to advise on ideal maintenance protocols. PMID:26548212

  16. Analysis of the helical plate for bone fracture fixation.

    PubMed

    Krishna, Kotlanka Rama; Sridhar, Idapalapati; Ghista, Dhanjoo N

    2008-12-01

    The improvements in oblique fracture fixation by means of the hemi-helical plate (HHP) to provide the bone-plate-screw assembly with enhanced holding capacity are discussed. The HHP is designed to provide stable fixation for helical cracks caused by torsional loading, such that the bone interfaces at the crack are brought into apposition and compressive strains are applied at the cracked interfaces. The HHP wraps around the bone, and hence is also suited for fixation of comminuted fractures. This is because, instead of employing multiple screws across the cracks, the HHP holds the bone fragments together. First, we illustrate through experiments the special capabilities of the HHP with respect to its fracture-holding capability, in comparison with straight-plate fixation with different screw orientations (convergent, divergent, alternately convergent and divergent, and perpendicular). Second, the finite-element (FE) analysis of the HHP is described, to elucidate the efficacy of fracture-gap movement and closure, and the flexibility of the fixation under compressive, bending moment and torsional loads. PMID:18823624

  17. Lagged Syndesmotic Fixation: Our Clinical Experience.

    PubMed

    Kwaadu, Kwasi Yiadom; Fleming, Justin James; Salmon, Trudy

    2015-01-01

    Ankle fractures are very common, and although algorithms are in place for osseous management, consensus has not been reached regarding treatment of associated ligamentous injuries. Although tibiofibular syndesmotic stabilization can be done using different forms of fixation, the biomedical literature has long emphasized the risk of long-term restriction of ankle mobility with the use of lagged transfixation. However, when reduction cannot be maintained with positional fixation, we found that lagging the syndesmotic screw helped to maintain the reduction without causing functional restriction. In this report, we describe our experience with patients who had undergone lagged tibiofibular transfixation and were available for short- to intermediate-term follow-up to assess ankle function. A total of 31 patients (32.63% of 95 consecutive patients) were available at a mean of 34.87 (range 18 to 52) months to complete the American Orthopedic Foot and Ankle Society ankle-hindfoot questionnaire. The mean score was 88.38 (range 42 to 100) points at a mean follow-up interval of 34.87 (range 18 to 52) months. Of 31 patients, 19 had an AOFAS score of 90 points, 9 an AOFAS score of 80 to 89 points, 2 an AOFAS score of 60 to 69 points, and 1 an AOFAS score of <60 points. Because all syndesmotic screws were placed using the lag technique, unrestricted motion compared with the uninjured limb was used as the endpoint. All subjects had unrestricted motion compared with the uninjured limb, refuting the assertion that lagged syndesmotic screw fixation confers more restriction in ankle kinematics than positional syndesmotic fixation. PMID:25736445

  18. Low noise lead screw positioner

    NASA Technical Reports Server (NTRS)

    Perkins, Gerald S. (inventor)

    1986-01-01

    A very precise and low noise lead screw positioner, for positioning a retroreflector in an interferometer is described. A gas source supplies inert pressurized gas, that flows through narrow holes into the clearance space between a nut and the lead screw. The pressurized gas keeps the nut out of contact with the screw. The gas flows axially along the clearance space, into the environment. The small amount of inert gas flowing into the environment minimizes pollution. By allowing such flow into the environment, no seals are required between the end of the nut and the screw.

  19. Is there a mechanical difference between lag screws and double cerclage?

    PubMed

    Kanakis, T E; Cordey, J

    1991-05-01

    Comminuted fractures of the long bones present problems of mechanical instability. We therefore used a plate and six screws as the main osteosynthesis combined with supplementary lag screws or cerclage wire. These two supplementary methods were compared. As a model, we used 60 plastic tibias with standard midshaft butterfly fractures. These models, depending on the osteosynthesis applied for the fixation of the butterfly onto the main fracture, were split into three groups of 20 bones. Group A1 with two lag screws, group A2 with two lag screws and two double cerclages, and group A3 with two double cerclages with no lag screws. The models were tested in torque and axial load. The results were: 1. In torque, group A1 was the most unstable with significant statistical difference from group A2 (P less than 0.01) and from A3 (P less than 0.05). There was no significant statistical difference between groups A2 and A3. 2. In axial load, group A3 was stable with significant statistical difference from A2 (P less than 0.05). There was no difference between A1 and A3. The experiment showed that if the cerclage is used double, anchored at the end of the screws and tensioned, it acts like a spring and is mechanically more stable than lag screws in torque. In axial load, no mechanical difference exists between lag screws and double cerclage. PMID:2071198

  20. The use of silk-based devices for fracture fixation

    NASA Astrophysics Data System (ADS)

    Perrone, Gabriel S.; Leisk, Gary G.; Lo, Tim J.; Moreau, Jodie E.; Haas, Dylan S.; Papenburg, Bernke J.; Golden, Ethan B.; Partlow, Benjamin P.; Fox, Sharon E.; Ibrahim, Ahmed M. S.; Lin, Samuel J.; Kaplan, David L.

    2014-03-01

    Metallic fixation systems are currently the gold standard for fracture fixation but have problems including stress shielding, palpability and temperature sensitivity. Recently, resorbable systems have gained interest because they avoid removal and may improve bone remodelling due to the lack of stress shielding. However, their use is limited to paediatric craniofacial procedures mainly due to the laborious implantation requirements. Here we prepare and characterize a new family of resorbable screws prepared from silk fibroin for craniofacial fracture repair. In vivo assessment in rat femurs shows the screws to be self-tapping, remain fixed in the bone for 4 and 8 weeks, exhibit biocompatibility and promote bone remodelling. The silk-based devices compare favourably with current poly-lactic-co-glycolic acid fixation systems, however, silk-based devices offer numerous advantages including ease of implantation, conformal fit to the repair site, sterilization by autoclaving and minimal inflammatory response.

  1. Computer-assisted periacetabular screw placement: Comparison of different fluoroscopy-based navigation procedures with conventional technique.

    PubMed

    Ochs, Bjrn Gunnar; Gonser, Christoph; Shiozawa, Thomas; Badke, Andreas; Weise, Kuno; Rolauffs, Bernd; Stuby, Fabian Maria

    2010-12-01

    The current gold standard for operatively treated acetabular fractures is open reduction and internal fixation. Fractures with minimal displacement may be stabilised by minimally invasive methods such as percutaneous periacetabular screws. However, their placement is a demanding procedure due to the complex pelvic anatomy. The aim of this study was to evaluate the accuracy of periacetabular screw placement assessing pre-defined placement corridors and comparing different fluoroscopy-based navigation procedures and the conventional technique. For each screw an individual periacetabular placement corridor was preoperatively planned using the planning software iPlan CMF() 3.0 (BrainLAB). 210 screws (retrograde anterior column screws, retrograde posterior column screws, supraacetabular ilium screws) were placed in an artificial Synbone pelvis model (30 hemipelves) and in human cadaver specimen (30 hemipelves). 2D- and 3D-fluoroscopy-based navigation procedures were compared to the conventional technique. Insertion time and radiation exposure to specimen were also recorded. The achieved screw position was postoperatively assessed by an Iso-C(3D) scan. Perforations of bony cortices or articular surfaces were analysed and the screw deviation severity (difference of the operatively achieved screw position and the preoperatively planned screw position in reference to the pre-defined corridors) was determined using image fusion. Using 3D-fluoroscopy-based navigation, the screw perforation rate (7%) was significantly lower compared to 2D-fluoroscopy-based navigation (20%). For all screws, the deviation severity was significantly lower using a 3D- compared to a 2D-fluoroscopy-based navigation and the conventional technique. Analysing the posterior column screws, the screw deviation severity was significantly lower using 3D- compared to 2D-fluoroscopy-based navigation. However, for the anterior column screw, the screw deviation severity was similar regardless of the imaging method. Despite the advantages of the 3D-fluoroscopy-based navigation, this method led to significantly longer total procedure and fluoroscopic times, and the applied radiation dose was significantly higher. Percutaneous periacetabular screw placement is demanding. Especially for posterior column screws, due to a lower perforation rate and a higher accuracy in periacetabular screw placement, 3D-fluoroscopy-based navigation procedure appears to be the method of choice for image guidance in acetabular surgery. PMID:20728881

  2. A Novel Fixation System for Acetabular Quadrilateral Plate Fracture: A Comparative Biomechanical Study

    PubMed Central

    Zha, Guo-Chun; Sun, Jun-Ying; Dong, Sheng-Jie; Zhang, Wen; Luo, Zong-Ping

    2015-01-01

    This study aims to assess the biomechanical properties of a novel fixation system (named AFRIF) and to compare it with other five different fixation techniques for quadrilateral plate fractures. This in vitro biomechanical experiment has shown that the multidirectional titanium fixation (MTF) and pelvic brim long screws fixation (PBSF) provided the strongest fixation for quadrilateral plate fracture; the better biomechanical performance of the AFRIF compared with the T-shaped plate fixation (TPF), L-shaped plate fixation (LPF), and H-shaped plate fixation (HPF); AFRIF gives reasonable stability of treatment for quadrilateral plate fracture and may offer a better solution for comminuted quadrilateral plate fractures or free floating medial wall fracture and be reliable in preventing protrusion of femoral head. PMID:25802849

  3. A technique for medial canthal fixation using resorbable poly-L-lactic acid-polyglycolic acid fixation kit.

    PubMed

    Sharma, Vidushi; Nemet, Arik; Ghabrial, Raf; Martin, Peter A; Kourt, Gina; Danks, Jenny J; Marcells, George

    2006-08-01

    Achieving secure bony fixation of medial canthus is a challenge. We used a resorbable poly-L-lactic acid-polyglycolic acid screw (LactoSorb office fixation kit) in 5 cases: 2 with traumatic medial canthal dystopia, 1 with scleroderma and orbital fat atrophy causing malapposition of the medial canthus to globe, and 2 with invasive medial canthal tumors necessitating subtotal medial orbital exenteration. The resorbable screw with preplaced suture was drilled into the medial orbital wall, using a handheld self-drilling tap. The preplaced suture was used to anchor the medial canthus. We achieved satisfactory canthal position in all 5 cases. There were no complications in 4 cases during a mean +/- SD follow-up of 11.3 +/- 6 months; however, the scleroderma case developed wound dehiscence 6 weeks after surgery. The LactoSorb kit is a safe and effective technique to achieve bony medial canthal fixation in carefully selected cases. PMID:16908820

  4. Using Ultrasound to Prevent Screw Penetration.

    PubMed

    Balfour, George W

    2016-03-01

    Ultrasound is a readily available, inexpensive, easy-to-use, and rapid diagnostic tool. Physicians can use ultrasound to identify excessively long screws or screw penetration into joints. This article illustrates ultrasound identification of problem screws. PMID:26803568

  5. Reduction and Maintenance of Scapholunate Dissociation Using the TwinFix Screw

    PubMed Central

    Opreanu, Razvan C.; Baulch, Michelle; Katranji, Abdalmajid

    2009-01-01

    Objective: Closed reduction and internal fixation of the scapholunate dissociation are currently performed using K-wires or a headless bone screw. We present an alternative for this fixation by means of a cannulated screw with dynamic adjustable interfragmentary compression and discuss the advantages of using this type of technique. Methods: Closed reduction of the scapholunate interval was achieved using a K-wire centered through the scaphoid and lunate bones followed by delivery of a cannulated compression screw to maintain the scapholunate interval. Results: Nine months after the surgery, the hand active range of motion was significantly improved. Only minimal pain was experienced with high loadings of the wrist and the patient achieved much improvement in his wrist strength. Conclusions: The technique we present is simple to perform and represents an attractive alternative to the conventional procedures to achieve the reduction of the scapholunate diastasis and the maintenance of the scapholunate interval. PMID:19252680

  6. Tibial Tunnel Cyst Formation after Anterior Cruciate Ligament Reconstruction Using a Non-Bioabsorbable Interference Screw

    PubMed Central

    Joshi, Yogesh V.; Phaltankar, Padmanabh M.; Charalambous, Charalambos P.

    2015-01-01

    Tibial cyst formation following the use of bioabsorbable interference screws in anterior cruciate ligament (ACL) reconstruction is well-described; however, cyst formation after the use of metallic interference screws is not well-documented. We describe a case of osteolytic lesion of the proximal tibia presenting to us 20 years after ACL reconstruction using an autologous bone-tendon-bone graft. The original graft fixation technique was interference fixation with a metal screw in the tibial and femoral tunnels. A two-stage revision reconstruction of the ACL was undertaken with curettage and bone grafting of the tibial lesion in the first stage and reconstruction using a four-strand hamstring tendon in the second stage. The patient recovered satisfactorily with complete healing of the cyst and returned to pre-injury level of activities. We have reviewed case reports and case series that describe the aetiology of intra-osseous cyst formation following ACL reconstruction. PMID:26673117

  7. Tibial Tunnel Cyst Formation after Anterior Cruciate Ligament Reconstruction Using a Non-Bioabsorbable Interference Screw.

    PubMed

    Joshi, Yogesh V; Bhaskar, Deepu; Phaltankar, Padmanabh M; Charalambous, Charalambos P

    2015-12-01

    Tibial cyst formation following the use of bioabsorbable interference screws in anterior cruciate ligament (ACL) reconstruction is well-described; however, cyst formation after the use of metallic interference screws is not well-documented. We describe a case of osteolytic lesion of the proximal tibia presenting to us 20 years after ACL reconstruction using an autologous bone-tendon-bone graft. The original graft fixation technique was interference fixation with a metal screw in the tibial and femoral tunnels. A two-stage revision reconstruction of the ACL was undertaken with curettage and bone grafting of the tibial lesion in the first stage and reconstruction using a four-strand hamstring tendon in the second stage. The patient recovered satisfactorily with complete healing of the cyst and returned to pre-injury level of activities. We have reviewed case reports and case series that describe the aetiology of intra-osseous cyst formation following ACL reconstruction. PMID:26673117

  8. Different patterns of bone fixation with hydroxyapatite and resorbable CaP coatings in the rabbit tibia at 6, 12, and 52 weeks.

    PubMed

    Reigstad, Ole; Johansson, Carina; Stenport, Victoria; Wennerberg, Ann; Reigstad, Astor; Røkkum, Magne

    2011-10-01

    Applying bioactive coatings on orthopedic implants can increase the fixation and long-term implant survival. In our study, we compared a resorbable electrochemically deposited calcium phosphate coating (Bonit®) to a thin (40 μm) plasma-sprayed hydroxyapatite (HA) coating, applied on grit-blasted screw-shaped Ti-6Al-4V implants in the cortical region of rabbit tibia, implanted for 6, 12, and 52 weeks. The removal torque results demonstrated stronger bone-to-implant fixation for the HA than Bonit-coated screws at 6 and 12 weeks. After 52 weeks, the fixation was in favor of the Bonit-coated screws, but the difference was statistically insignificant. Coat flaking and delamination of the HA with multinucleated giant cell activity and bone resorption observed histologically seemed to preclude any significant increase in fixation comparing the HA implants at 6 versus 12 weeks and 12 versus 52 weeks. The Bonit-coated implants exhibited increasing fixation from 6 to 12 weeks and from 12 to 52 weeks, and the coat was resorbed within 6 weeks, with minimal activity of multinucleated giant cells or bone resorption. A different fixation pattern was observed for the two coatings with a sharper but time limited increase in fixation for the HA-coated screws, and a slower but more steadily increasing fixation pattern for the Bonit-coated screws. The side effects were more serious for the HA coating and limiting the expected increase in fixation with time. PMID:21648067

  9. A Pitfall in Fixation of Distal Humeral Fractures with Pre-Contoured Locking Compression Plate

    PubMed Central

    Jayakumar, Prakash; Ring, David

    2015-01-01

    Anatomically precontoured locking plates are intended to facilitate the fixation of articular fractures and particularly those associated with osteoporosis. Fractures of the distal humerus are relatively uncommon injuries where operative intervention can be exceptionally challenging. The distal humeral trochlea provides a very narrow anatomical window through which to pass a fixed-angle locking screw, which must also avoid the olecranon, coronoid, and radial fossae. We describe 3 patients (ages 27, 49, and 73 years) with a bicolumnar fracture of the distal humerus where very short distal locking screws were used. Intra-articular screw placement was avoided but loss of fixation occurred in two patients and a third was treated with a prolonged period of immobilization. We postulate that fixed-angle screw trajectories may make it difficult for the surgeon to place screws of adequate length in this anatomically confined region, and may lead to insufficient distal fixation. Surgical tactics should include placement of as many screws as possible into the distal fragment, as long as possible and that each screw passes through a plate without necessarily locking in. PMID:26110181

  10. Novel posterior fixation keratoprosthesis

    NASA Astrophysics Data System (ADS)

    Lacombe, Emmanuel

    1992-08-01

    The keratoprosthesis is the last solution for corneally blind patients that cannot benefit from corneal transplants. Keratoprostheses that have been designed to be affixed anteriorly usually necessitate multi-step surgical procedures and are continuously subjected to the extrusion forces generated by the positive intraocular pressure; therefore, clinical results in patients prove inconsistent. We proposed a novel keratoprosthesis concept that utilizes posterior corneal fixation which `a priori' minimizes the risk of aqueous leakage and expulsion. This prosthesis is implanted in a single procedure thereby reducing the number of surgical complications normally associated with anterior fixation devices. In addition, its novel design makes this keratoprosthesis implantable in phakic eyes. With an average follow-up of 13 months (range 3 to 25 months), our results on 21 cases are encouraging. Half of the keratoprostheses were implanted in severe burn cases, with the remainder in cases of pseudo- pemphigus. Good visual results and cosmetic appearance were obtained in 14 of 21 eyes.

  11. Screw/stud removal tool

    NASA Technical Reports Server (NTRS)

    Daniels, K.; Herrick, D. E.; Rothermel, L.

    1980-01-01

    Tool removes stubborn panheaded screws or studs where conventional tools would be either too weak or inconvenient to use. Screws with damaged heads or slots can also be removed this way. Tool can be worked with one hand and easily fits limited-access and blind areas. It can be made in various sizes to fit different screwheads.

  12. Fixation strength of a novel bioabsorbable expansion bolt for patellar tendon bone graft fixation: an experimental study in calf tibial bone.

    PubMed

    Piltz, Stefan; Strunk, Patrick; Meyer, Ludger; Plitz, Wolfgang; Lob, Guenter

    2004-09-01

    This biomechanical study compares the initial fixation strength of a novel bioabsorbable two-shell expansion bolt (EB) with that of a well-established interference-screw technique in bone-patellar tendon-bone (BPTB) reconstruction in a calf model. Thirty tibia plateaus (age 5-6 months) were assigned to three groups: In groups I and II, trapezoidal bone plugs of BPTB grafts were fixed with bioabsorbable poly-L-lactide interference screws (8 x 23 mm) or titanium interference screws (8 x 25 mm) respectively. In group III, semicircular grafts were fixed using bioabsorbable poly-D, L-lactide expansion bolts (5.8/8.7 x 10 x 35 mm). The tensile axis was parallel to the bone tunnel, and the construction was loaded until failure applying a displacement rate of 1 mm per second. In group II the mean ultimate loads to failure (713 N+/-218 N) were found to be significantly higher than those of groups I (487 N+/-205 N) and III (510 N+/-133 N). Measurement of stiffness showed 45 N/mm+/-13.3 in group I, 58 N/mm+/-17.4 in group II and 46 N/mm+/-6.9 in group III, and did not demonstrate significant differences. We found a correlation between insertion torque and wedge insertion force and ultimate loads to failure in all groups (r=0.53 in group I, r =0.54 in group II, and r =0.57 in group III). Cross-section planes of bone tunnel increased by 51%, 30% and 31% respectively, following insertion of screws or expansion of bolts (p<0.05). We conclude that ACL graft fixation by means of the presented expansion bolt demonstrates a fixation strength similar to the established bioabsorbable screw fixation, and is a reasonable alternative fixation method, especially since some of the specific pitfalls of screw fixation can be avoided. PMID:15042285

  13. Mini posterior lumbar interbody fusion with presacral screw stabilization in early lumbosacral instability

    PubMed Central

    Shetty, Arjun; Kini, Abhishek R; Chacko, A; Sunil, Upadhyaya; Vinod, K; Geover, Lobo

    2015-01-01

    Background: Surgical options for the management of early lumbosacral spondylolisthesis and degenerative disc disease with instability vary from open lumbar interbody fusion with transpedicular fixation to a variety of minimal access fusion and fixation procedures. We have used a combination of micro discectomy and axial lumbosacral interbody fusion with presacral screw fixation to treat symptomatic patients with lumbosacral spondylolisthesis or lumbosacral degenerative disc disease, which needed surgical stabilization. This study describes the above technique along with analysis of results. Materials and Methods: Twelve patients with symptomatic lumbosacral (L5-S1) instability and degenerative lumbosacral disc disease were treated by micro discectomy and interbody fusion using presacral screw stabilization. Patients with history of bowel, bladder dysfunction and local anorectal diseases were excluded from this study. Postoperatively all patients were evaluated neurologically and radiologically for screw position, fusion and stability. Oswestry disability index was used to evaluate results. Results: We had nine females and three males with a mean age of 47.33 years (range 26–68 years). Postoperative assessment revealed three patients to have screw placed in anterior 1/4th of the 1st sacral body, in rest nine the screws were placed in the posterior 3/4th of sacral body. At 2 years followup, eight patients (67%) showed evidence of bridging trabeculae at bone graft site and none of the patients showed evidence of instability or implant failure. Conclusion: Presacral screw fixation along with micro discectomy is an effective procedure to manage early symptomatic lumbosacral spondylolisthesis and degenerative disc disease with instability. PMID:26015626

  14. Anterior and posterior fixation for delayed treatment of posterior atlantoaxial dislocation without fracture.

    PubMed

    Yu, Hai Ming; Malhotra, Karan; Butler, Joseph S; Wu, Shi Qiang

    2015-01-01

    Posterior atlantoaxial dislocation (PAAD) without fracture of the odontoid process is a rare injury. Authors have variously reported closed or open reduction, followed by either anterior or posterior fixation, but there is no consensus on best treatment. We present a particularly unstable case of PAAD. Open reduction through a retropharyngeal approach with odontoidectomy was required for reduction. Anterior fixation with transarticular lag screws was required prior to posterior fixation with pedicle screws. Despite non-compliance with postoperative immobilisation, imaging at 20-month follow-up confirmed solid fusion. The patient is pain-free with a good range of movement of the neck and has returned to a manual job. Our case had a greater degree of instability than was previously reported, which necessitated 360 fixation. This is the first reported case of this treatment strategy, which provided a very stable fixation allowing fusion despite early movement and without causing undue stiffness. PMID:26516249

  15. Comparison of Expansive Pedicle Screw and Polymethylmethacrylate-Augmented Pedicle Screw in Osteoporotic Sheep Lumbar Vertebrae: Biomechanical and Interfacial Evaluations

    PubMed Central

    Zhang, Bo; Xie, Qing-yun; Wang, Cai-ru; Liu, Jin-biao; Liao, Dong-fa; Jiang, Kai; Lei, Wei; Pan, Xian-ming

    2013-01-01

    Background It was reported that expansive pedicle screw (EPS) and polymethylmethacrylate-augmented pedicle screw (PMMA-PS) could be used to increase screw stability in osteoporosis. However, there are no studies comparing the two kinds of screws in vivo. Thus, we aimed to compare biomechanical and interfacial performances of EPS and PMMA-PS in osteoporotic sheep spine. Methodology/Principal Findings After successful induction of osteoporotic sheep, lumbar vertebrae in each sheep were randomly divided into three groups. The conventional pedicle screw (CPS) was inserted directly into vertebrae in CPS group; PMMA was injected prior to insertion of CPS in PMMA-PS group; and the EPS was inserted in EPS group. Sheep were killed and biomechanical tests, micro-CT analysis and histological observation were performed at both 6 and 12 weeks post-operation. At 6-week and 12-week, screw stabilities in EPS and PMMA-PS groups were significantly higher than that in CPS group, but there were no significant differences between EPS and PMMA-PS groups at two study periods. The screw stability in EPS group at 12-week was significantly higher than that at 6-week. The bone trabeculae around the expanding anterior part of EPS were more and denser than that in CPS group at 6-week and 12-week. PMMA was found without any degradation and absorption forming non-biological screw-PMMA-bone interface in PMMA-PS group, however, more and more bone trabeculae surrounded anterior part of EPS improving local bone quality and formed biological screw-bone interface. Conclusions/Significance EPS can markedly enhance screw stability with a similar effect to the traditional method of screw augmentation with PMMA in initial surgery in osteoporosis. EPS can form better biological interface between screw and bone than PMMA-PS. In addition, EPS have no risk of thermal injury, leakage and compression caused by PMMA. We propose EPS has a great application potential in augmentation of screw stability in osteoporosis in clinic. PMID:24086381

  16. Concentric double cables fixation as an alternative suspension method for the endoscopic forehead lift.

    PubMed

    Massoud, Karim S; Aboelatta, Yasser Abdallah

    2015-06-01

    Fixation of the elevated eyebrow is an important final step in endoscopic forehead lifting. One of the most common methods of fixation includes temporal fasciae sutures for the tail of the eyebrow, and mini-screws for the body of the eyebrow. The concentric cables fixation is an alternative method for elevation of both the tail and the body of the eyebrow. This technique is compared to temporal fasciae suture and mini-screws fixation. Thirty-one patients were included in this study. They were divided into two groups; group I included patients who underwent fixation using fascia sutures and mini-screws, while group II patients underwent concentric cables suspension. Traditional screw and suture technique elevated the eyebrow tail by 7.2, 6.7, 6.3, and 6.0 mm, while the concentric cables resulted in 7.6, 6.8, 6.5, and 6.3 mm elevation at 1, 3, 6, and 12 months postoperatively, respectively. The mean values of brow body elevation were 6.8, 6.4, 6.2, and 5.9 mm for group I, while the mean values of group II were 6, 5.4, 4.8, and 4.7 mm. The concentric cables technique showed a fewer complications rate compared to traditional fixation. The concentric cables fixation offers an alternative inexpensive method to suspend the tail, and to a lesser extent the body, of both eyebrows simultaneously with long-term stability. A fewer complications rate was documented compared to traditional temporal fasciae sutures and mini-screws fixation. PMID:25272310

  17. Biomechanical and histological evaluation of an expandable pedicle screw in osteoporotic spine in sheep

    PubMed Central

    Wan, Shiyong; Wu, Zixiang; Liu, Da; Gao, Mingxuan; Fu, Suochao

    2010-01-01

    Transpedicular fixation can be challenging in the osteoporotic spine as reduced bone mineral density compromises the mechanical stability of the pedicle screw. Here, we sought to investigate the biomechanical and histological properties of stabilization of expandable pedicle screw (EPS) in the osteoporotic spine in sheep. EPSs and standard pedicle screws, SINO screws, were inserted on the vertebral bodies in four female ovariectomized sheep. Pull-out and cyclic bending resistance test were performed to compare the holding strength of these pedicle screws. High-resolution micro-computed tomography (CT) was performed for three-dimensional image reconstruction. We found that the EPSs provided a 59.6% increase in the pull-out strength over the SINO screws. Moreover, the EPSs withstood a greater number of cycles or load with less displacement before loosening. Micro-CT image reconstruction showed that the tissue mineral density, bone volume fraction, bone surface/bone volume ratio, trabecular thickness, and trabecular separation were significantly better in the expandable portion of the EPSs than those in the anterior portion of the SINO screws (P<0.05). Furthermore, the trabecular architecture in the screwbone interface was denser in the expandable portion of the EPS than that in the anterior portion of the SINO screw. Histologically, newly formed bone tissues grew into the center of EPS and were in close contact with the EPS. Our results show that the EPS demonstrates improved biomechanical and histological properties over the standard screw in the osteoporotic spine. The EPS may be of value in treating patients with osteoporosis and warrants further clinical studies. PMID:20577766

  18. Pedicle screw cement augmentation. A mechanical pullout study on different cement augmentation techniques.

    PubMed

    Costa, Francesco; Ortolina, Alessandro; Galbusera, Fabio; Cardia, Andrea; Sala, Giuseppe; Ronchi, Franco; Uccelli, Carlo; Grosso, Rossella; Fornari, Maurizio

    2016-02-01

    Pedicle screws with polymethyl methacrylate (PMMA) cement augmentation have been shown to significantly improve the fixation strength in a severely osteoporotic spine. However, the efficacy of screw fixation for different cement augmentation techniques remains unknown. This study aimed to determine the difference in pullout strength between different cement augmentation techniques. Uniform synthetic bones simulating severe osteoporosis were used to provide a platform for each augmentation technique. In all cases a polyaxial screw and acrylic cement (PMMA) at medium viscosity were used. Five groups were analyzed: I) only screw without PMMA (control group); II) retrograde cement pre-filling of the tapped area; III) cannulated and fenestrate screw with cement injection through perforation; IV) injection using a standard trocar of PMMA (vertebroplasty) and retrograde pre-filling of the tapped area; V) injection through a fenestrated trocar and retrograde pre-filling of the tapped area. Standard X-rays were taken in order to visualize cement distribution in each group. Pedicle screws at full insertion were then tested for axial pullout failure using a mechanical testing machine. A total of 30 screws were tested. The results of pullout analysis revealed better results of all groups with respect to the control group. In particular the statistical analysis showed a difference of Group V (p=0.001) with respect to all other groups. These results confirm that the cement augmentation grants better results in pullout axial forces. Moreover they suggest better load resistance to axial forces when the distribution of the PMMA is along all the screw combining fenestration and pre-filling augmentation technique. PMID:26762776

  19. In-vitro development of a temporal abutment screw to protect osseointegration in immediate loaded implants

    PubMed Central

    2015-01-01

    PURPOSE In this study, a temporal abutment fixation screw, designed to fracture in a controlled way upon application of an occlusal force sufficient to produce critical micromotion was developed. The purpose of the screw was to protect the osseointegration of immediate loaded single implants. MATERIALS AND METHODS Seven different screw prototypes were examined by fixing titanium abutments to 112 Mozo-Grau external hexagon implants (MG Osseous; Mozo-Grau, S.A., Valladolid, Spain). Fracture strength was tested at 30 in two subgroups per screw: one under dynamic loading and the other without prior dynamic loading. Dynamic loading was performed in a single-axis chewing simulator using 150,000 load cycles at 50 N. After normal distribution of obtained data was verified by Kolmogorov-Smirnov test, fracture resistance between samples submitted and not submitted to dynamic loading was compared by the use of Student's t-test. Comparison of fracture resistance among different screw designs was performed by the use of one-way analysis of variance. Confidence interval was set at 95%. RESULTS Fractures occurred in all screws, allowing easy retrieval. Screw Prototypes 2, 5 and 6 failed during dynamic loading and exhibited statistically significant differences from the other prototypes. CONCLUSION Prototypes 2, 5 and 6 may offer a useful protective mechanism during occlusal overload in immediate loaded implants. PMID:25932315

  20. Better Axial Stiffness of a Bicortical Screw Construct Compared to a Cable Construct for Comminuted Vancouver B1 Proximal Femoral Fractures.

    PubMed

    Griffiths, Jamie T; Taheri, Arash; Day, Robert E; Yates, Piers J

    2015-12-01

    The aim of this study was to biomechanically evaluate the Locking attachment plate (LAP) construct in comparison to a Cable plate construct, for the fixation of periprosthetic femoral fractures after cemented total hip arthroplasty. Each construct incorporated a locking compression plate with bi-cortical locking screws for distal fixation. In the Cable construct, 2 cables and 2 uni-cortical locking screws were used for proximal fixation. In the LAP construct, the cables were replaced by a LAP with 4 bi-cortical locking screws. The LAP construct was significantly stiffer than the cable construct under axial load with a bone gap (P=0.01). The LAP construct offers better axial stiffness compared to the cable construct in the fixation of comminuted Vancouver B1 proximal femoral fractures. PMID:26239233

  1. Material properties and composition of soft-tissue fixation.

    PubMed

    Suchenski, Maureen; McCarthy, Mary Beth; Chowaniec, David; Hansen, Derek; McKinnon, William; Apostolakos, John; Arciero, Robert; Mazzocca, Augustus D

    2010-06-01

    Surgical interference screws and suture anchors for attaching soft tissue, such as ligaments and tendons, to bone are routinely used in arthroscopic surgery and sports medicine. Interference screw fixation provides a press fit between bone, graft/tendon, and screw and is frequently used to attach replacement ligaments in tunnels drilled for anterior and posterior cruciate ligament reconstruction. Suture anchors are used in surgical procedures wherein it is necessary for a surgeon to attach (tie) tissue to the surface of the bone, for example, during joint reconstruction and ligament repair or replacement. The composition of these implants ranges from metals to polymers and composites. Typically, because of the relatively large amount of torque that must be applied during insertion, these screws are constructed from metal. However, interference screws and suture anchors have also been constructed from bioabsorbable polymers and composites. The ideal material would (1) provide adequate mechanical fixation, (2) completely degrade once no longer needed, and (3) be completely replaced by bone. Because no material has been shown to be superior for all applications, the surgeon must weigh the advantages and disadvantages of each to evaluate the optimum material for a given application and patient. The purpose of this article is to present a comprehensive review of the commercially available interference screws and suture anchors, with an emphasis on implant composition, interaction, and design. This article provides the orthopaedic surgeon with a background on biomaterials, specifically those used in interference screws and suture anchors. Because there is no material that is perfect for all surgical situations, this review can be used to make educated decisions on a case-by-case basis. PMID:20511042

  2. Hip screw lateral migration with no cut-out or non-union implication: a case report

    PubMed Central

    2009-01-01

    Hip screw migration of peritrochanteric fracture fixation devices is a described complication in English literature. Medial migration occupies the majority of these cases whereas lateral migration is rare. We report the case of an 85-year-old woman whose intramedullary osteosynthesis of a trochanteric fracture was complicated by hip screw lateral migration. Mobilization was not influenced and no cut-out or non-union was detected. The migrated hip screw was easily removed and the discomfort vanished. The need for adequate surgical technique and radiographic examination after re-injuries even if the patient remains ambulatory is emphasised. PMID:20181153

  3. A Technique of Superficial Medial Collateral Ligament Reconstruction Using an Adjustable-Loop Suspensory Fixation Device

    PubMed Central

    Deo, Shaneel; Getgood, Alan

    2015-01-01

    This report describes superficial medial collateral ligament reconstruction of the knee using a novel method of graft fixation with the ACL Tightrope RT (Arthrex, Naples, FL). After tibial fixation with either a standard interference screw or staple, femoral fixation of the semitendinosus tendon is performed with the adjustable-loop suspensory fixation device, which allows for both initial graft tensioning and re-tensioning after cyclical knee range of motion. This provides the ability for the graft to accommodate for resultant soft-tissue creep and stress relaxation, thereby allowing for optimal soft-tissue tension and reduction in laxity at the end of the procedure. PMID:26258041

  4. Robot assisted navigated drilling for percutaneous pedicle screw placement: A preliminary animal study

    PubMed Central

    Wang, Hongwei; Zhou, Yue; Liu, Jun; Han, Jianda; Xiang, Liangbi

    2015-01-01

    Background: There is much more radiation exposure to the surgeons during minimally invasive pedicle screws placement. In order to ease the surgeon's hand-eye coordination and to reduce the iatrogenic radiation injury to the surgeons, a robot assisted percutaneous pedicle screw placement is useful. This study assesses the feasibility and clinical value of robot assisted navigated drilling for pedicle screw placement and the results thus achieved formed the basis for the development of a new robot for pedicle screw fixation surgery. Materials and Methods: Preoperative computed tomography (CT) of eight bovine lumbar spines (L1L5) in axial plane were captured for each vertebra, the entry points and trajectories of the screws were preoperatively planned. On the basis of preoperative CT scans and intraoperative fluoroscopy, we aligned the robot drill to the desired entry point and trajectory, as dictated by the surgeon's preoperative plan. Eight bovine lumbar spines were inserted 80 K-wires using the spine robot system. The time for system registration and pedicle drilling, fluoroscopy times were measured and recorded. Postoperative CT scans were used to assess the position of the K-wires. Results: Assisted by spine robot system, the average time for system registration was (343.4 18.4) s, the average time for procedure of drilling one pedicle screw trajectory was (89.5 6.1) s, times of fluoroscopy for drilling one pedicle screw were (2.9 0.8) times. Overall, 12 (15.0%) of the 80 K-wires violated the pedicle wall. Four screws (5.0%) were medial to the pedicle and 8 (10.5%) were lateral. The number of K-wires wholly within the pedicle were 68 (85%). Conclusions: The preliminary study supports the view that computer assisted pedicle screw fixation using spinal robot is feasible and the robot can decrease the intraoperative fluoroscopy time during the minimally invasive pedicle screw fixation surgery. As spine robotic surgery is still in its infancy, further research in this field is worthwhile especially the accuracy of spine robot system should be improved. PMID:26229168

  5. Pseudarthrosis of femoral neck stress fracture treated with open reduction, sliding hip screw and bone morphogenic protein

    PubMed Central

    Dargan, D.; McCaffrey, D.; Kealey, W.D.C.

    2012-01-01

    INTRODUCTION Pseudarthrosis of femoral neck stress fractures in young adults are associated with a high incidence of complications and revision surgery. The majority are treated urgently with closed reduction and internal fixation. PRESENTATION OF CASE We describe a displaced tension-type femoral neck fatigue fracture presenting late. Pseudarthrosis formation prior to surgery resulted in resorption and shortening of the femoral neck. Open reduction and internal fixation was performed, with adjuvant recombinant human bone morphogenic protein-7 therapy. Radiological union was achieved by twelve weeks and by one year the patient was asymptomatic. DISCUSSION Reports of successful management of femoral neck fatigue fracture non-unions are rare. Meyer's muscle pedicle graft, valgus subtrochanteric osteotomy, and cannulated screw fixation with autologous iliac crest bone graftare alternative procedures. CONCLUSION This extremely rare fracture type merits open reduction to enable accurate fracture reduction. Supplementing sliding hip screw fixation with an orthobiological agent was successful in this challenging situation. PMID:22898259

  6. Simple coating with fibronectin fragment enhances stainless steel screw osseointegration in healthy and osteoporotic rats.

    PubMed

    Agarwal, Rachit; Gonzlez-Garca, Cristina; Torstrick, Brennan; Guldberg, Robert E; Salmern-Snchez, Manuel; Garca, Andrs J

    2015-09-01

    Metal implants are widely used to provide structural support and stability in current surgical treatments for bone fractures, spinal fusions, and joint arthroplasties as well as craniofacial and dental applications. Early implant-bone mechanical fixation is an important requirement for the successful performance of such implants. However, adequate osseointegration has been difficult to achieve especially in challenging disease states like osteoporosis due to reduced bone mass and strength. Here, we present a simple coating strategy based on passive adsorption of FN7-10, a recombinant fragment of human fibronectin encompassing the major cell adhesive, integrin-binding site, onto 316-grade stainless steel (SS). FN7-10 coating on SS surfaces promoted ?5?1 integrin-dependent adhesion and osteogenic differentiation of human mesenchymal stem cells. FN7-10-coated SS screws increased bone-implant mechanical fixation compared to uncoated screws by 30% and 45% at 1 and 3 months, respectively, in healthy rats. Importantly, FN7-10 coating significantly enhanced bone-screw fixation by 57% and 32% at 1 and 3 months, respectively, and bone-implant ingrowth by 30% at 3 months compared to uncoated screws in osteoporotic rats. These coatings are easy to apply intra-operatively, even to implants with complex geometries and structures, facilitating the potential for rapid translation to clinical settings. PMID:26100343

  7. Technical tips: dualplate fixation technique for comminuted proximal humerus fractures.

    PubMed

    Choi, Sungwook; Kang, Hyunseong; Bang, Hyeongsig

    2014-08-01

    The authors report dualplate fixation technique for providing stable fixation in comminuted proximal humerus fractures. This technique has been used for proximal humerus fractures with metaphyseal comminution and provides excellent anatomical reduction and neck shaft angle (NSA). The recently locking plate is clinically more widely used due to its small size, low rigidity, high elasticity, and biomechanical properties such as fixed initial angle and rotational stability. However, in severely comminuted complex type proximal metaphyseal humerus fractures, the use of locking plate alone does not provide stable fixation, leading to complications such as varus collapse, anterior-posterior angulation, screw cutout, nonunion, malunion, and metal failure. Therefore, a more robust and enhanced fixation method, the dual plating technique using the locking compression plate (Proximal Humeral Internal Locking System and Variable Angle Locking Compression Plate) was developed. PMID:24813097

  8. Pelvic Fixation in Adult and Pediatric Spine Surgery: Historical Perspective, Indications, and Techniques: AAOS Exhibit Selection.

    PubMed

    Jain, Amit; Hassanzadeh, Hamid; Strike, Sophia A; Menga, Emmanuel N; Sponseller, Paul D; Kebaish, Khaled M

    2015-09-16

    Achieving solid osseous fusion across the lumbosacral junction has historically been, and continues to be, a challenge in spine surgery. Robust pelvic fixation plays an integral role in achieving this goal. The goals of this review are to describe the history of and indications for spinopelvic fixation, examine conventional spinopelvic fixation techniques, and review the newer S2-alar-iliac technique and its outcomes in adult and pediatric patients with spinal deformity. Since the introduction of Harrington rods in the 1960s, spinal instrumentation has evolved substantially. Indications for spinopelvic fixation as a means to achieve lumbosacral arthrodesis include a long arthrodesis (five or more vertebral levels) or use of three-column osteotomies in the lower thoracic or lumbar spine, surgical treatment of high-grade spondylolisthesis, and correction of lumbar deformity and pelvic obliquity. A variety of techniques have been described over the years, including Galveston iliac rods, Jackson intrasacral rods, the Kostuik transiliac bar, iliac screws, and S2-alar-iliac screws. Modern iliac screws and S2-alar-iliac screws are associated with relatively low rates of pseudarthrosis. S2-alar-iliac screws have the advantages of less implant prominence and inline placement with proximal spinal anchors. Collectively, these techniques provide powerful methods for obtaining control of the pelvis in facilitating lumbosacral arthrodesis. PMID:26378268

  9. The flying buttress construct for posterior spinopelvic fixation: a technical note

    PubMed Central

    2011-01-01

    Background Posterior fusion of the spine to the pelvis in paediatric and adult spinal deformity is still challenging. Especially assembling of the posterior rod construct to the iliac screw is considered technically difficult. A variety of spinopelvic fixation techniques have been developed. However, extreme bending of the longitudinal rods or the use of 90-degree lateral offset connectors proved to be difficult, because the angle between the rod and the iliac screw varies from patient to patient. Methods We adopted a new spinopelvic fixation system, in which iliac screws are side-to-side connected to the posterior thoracolumbar rod construct, independent of the angle between the rod and the iliac screw. Open angled parallel connectors are used to connect short iliac rods from the posterior rod construct to the iliac screws at both sides. The construct resembles in form and function an architectural Flying Buttress, or lateral support arches, used in Gothic cathedrals. Results and discussion Three different cases that illustrate the Flying Buttress construct for spinopelvic fixation are reported here with the clinical details, radiographic findings and surgical technique used. Conclusion The Flying Buttress construct may offer an alternative surgical option for spinopelvic fixation in circumstances wherein coronal or sagittal balance cannot be achieved, for example in cases with significant residual pelvic obliquity, or in revision spinal surgery for failed lumbosacral fusion. PMID:21489256

  10. Self-energized screw coupling

    NASA Technical Reports Server (NTRS)

    Lefever, A. E.; Totah, R. S.

    1980-01-01

    Threaded coupling carries its own store of rotational energy. Originally developed to ease task of astronauts assembling structures in space, coupling offers same advantages in other hazardous operations, such as underwater and in and around nuclear reactors. Coupling consists of two parts: crew portion and receptacle. When screw portion is inserted into receptacle and given slight push by operator, trigger pins release ratchet, allowing energy stored in springs to rotate screw into nut in receptacle.

  11. Static and cyclical biomechanical analysis of pedicle screw spinal constructs.

    PubMed

    Cunningham, B W; Sefter, J C; Shono, Y; McAfee, P C

    1993-09-15

    Biomechanical evaluation of twelve different spinal devices in vitro employing pedicle screws was performed using static (n = 5) and cyclical testing (n = 3) parameters. In general, the rank order of implant failures was similar between static and cyclical tests, performed at 600 N compressive load, 5 Hz, and 1 million cycles. The mean number of cycles to failure was higher for spinal instrumentation systems employing longitudinal rods than those using plates (ANOVA F = 16.94, P < .001). At 600 N, the compact Cotrel-Dubousset, TSRH, and ISOLA rod systems demonstrated mean cycles to failure ranging from 200,000 to 800,000 cycles. The remaining devices including Dyna-lok, Kirschner plate, and VSP devices had failures ranging from 50,000 to 210,000 cycles. Polyethylene cylinders representing vertebral bodies were used to eliminate the problems of biologic deterioration encountered with cadaveric spines (a full cyclical test to 1 million cycles required 56 hours), and thus to provide analysis of the weak portion of each spinal system. The failure of eleven of the twelve spinal systems occurred by fracture of a pedicle screw, most commonly at the junction of the upper screw thread and the collar (Kirschner, AO fixator, standard CD, ISOLA, and TSRH). However, in Dynalok and VSP systems, fracture of the threaded portion of the screw just posterior to the integral nuts was the most common screw fracture location. The compact CD system was the only spinal implant that consistently failed by fracture of the longitudinal spinal member (rod). The fatigue life of rod based systems was longer than plate based systems. These studies confirm the importance of anterior column load sharing (vertebral body, corpectomy bone graft) as the mean bending strength demonstrated by these implant systems was not inordinately high using this "worst case scenario" model. PMID:8235849

  12. Planning screw insertion trajectory in lumbar spinal fusion using pre-operative CT images.

    PubMed

    Daemi, N; Ahmadian, A; Mirbagheri, A; Ahmadian, A H; Saberi, H; Amidi, F; Alirezaie, J

    2015-08-01

    Spinal fusion permanently connects two or more vertebrae in spine to improve stability, correct a deformity or reduce pain by immobilizing the vertebrae through pedicle screw fixation. Pedicle screws should be inserted very carefully to prevent possible irrecoverable damages to the spinal cord. Surgeons use CT/fluoroscopic images to find how to insert the screws safely. However, there is still human error, as determining precise trajectory in 3D space is difficult because of asymmetric structure of pedicle. In this study we attempt to propose a shape based method to help the surgeons to find the more accurate and safe path for screw insertion that minimizes the risk or invasiveness of the surgery using pre-operative CT images. We extracted two features for insertion paths from CT images, named "safety margin" and "pedicular screw fixation strength". By using weighted k-means different paths were clustered and compared with each other. Results of comparison between those paths obtained from surgeon's pre-operative planning, intra operative and the proposed method proves a great improvement on the rate of success in reaching a suitable insertion trajectory by using our method. It is observed that the risk of damage in intra operative stage can be potentially high and it can be reduced considerably by using the proposed planning approach. PMID:26737081

  13. A Simple and Reliable Method of Narrowing Genioplasty Using Biodegradable Screws.

    PubMed

    Lee, Tae Sung

    2016-01-01

    The T-osteotomy technique is widely performed to improve lower face aesthetics. During this narrowing genioplasty procedure, metal fixtures are required to rigidly fix the bone segments. Specifically, the use of biodegradable osteofixations has become a viable surgical option as more patients now have the desire to surreptitiously undergo aesthetic surgery. The present report describes a narrowing genioplasty procedure with the use of biodegradable screws only. When the T-osteotomy technique was performed to narrow the chin, the bone segments were first temporarily fixed with a 4-hole titanium plate and screws. Later during the operation, the plate and screws were replaced with 4 biodegradable screws with bicortical fixation. Completion of bone healing can be confirmed by follow-up radiographs taken 6 months after the surgery. Despite increasing demand for the use of absorbable materials in aesthetic surgeries, biodegradable fixation systems have not been widely used for aesthetic surgeries due to a perception of high cost, inconvenient manipulation, prolonged operative time, and suspicions on long-term stability. Our novel method of using only biodegradable screws allows such limitations to be easily overcome by surgeons. PMID:26716548

  14. In vivo study of magnesium plate and screw degradation and bone fracture healing.

    PubMed

    Chaya, Amy; Yoshizawa, Sayuri; Verdelis, Kostas; Myers, Nicole; Costello, Bernard J; Chou, Da-Tren; Pal, Siladitya; Maiti, Spandan; Kumta, Prashant N; Sfeir, Charles

    2015-05-01

    Each year, millions of Americans suffer bone fractures, often requiring internal fixation. Current devices, like plates and screws, are made with permanent metals or resorbable polymers. Permanent metals provide strength and biocompatibility, but cause long-term complications and may require removal. Resorbable polymers reduce long-term complications, but are unsuitable for many load-bearing applications. To mitigate complications, degradable magnesium (Mg) alloys are being developed for craniofacial and orthopedic applications. Their combination of strength and degradation make them ideal for bone fixation. Previously, we conducted a pilot study comparing Mg and titanium devices with a rabbit ulna fracture model. We observed Mg device degradation, with uninhibited healing. Interestingly, we observed bone formation around degrading Mg, but not titanium, devices. These results highlighted the potential for these fixation devices. To better assess their efficacy, we conducted a more thorough study assessing 99.9% Mg devices in a similar rabbit ulna fracture model. Device degradation, fracture healing, and bone formation were evaluated using microcomputed tomography, histology and biomechanical tests. We observed device degradation throughout, and calculated a corrosion rate of 0.400.04mm/year after 8 weeks. In addition, we observed fracture healing by 8 weeks, and maturation after 16 weeks. In accordance with our pilot study, we observed bone formation surrounding Mg devices, with complete overgrowth by 16 weeks. Bend tests revealed no difference in flexural load of healed ulnae with Mg devices compared to intact ulnae. These data suggest that Mg devices provide stabilization to facilitate healing, while degrading and stimulating new bone formation. PMID:25712384

  15. BIOMECHANICAL STUDY OF TRANSCORTICAL OR TRANSTRABECULAR BONE FIXATION OF PATELLAR TENDON GRAFT WITH BIOABSORBABLE PINS IN ACL RECONSTRUCTION IN SHEEP

    PubMed Central

    Albano, Mauro Batista; Borges, Paulo César; Namba, Mario Massatomo; da Silva, João Luiz Vieira; de Assis Pereira Filho, Francisco; Filho, Edmar Stieven; Matias, Jorge Eduardo Fouto

    2015-01-01

    Objective: To determine the initial resistance of fixation using the Rigid Fix® system, and compare it with traditional fixation methods using metal interference screws; and to evaluate the resistance of the fixation with the rigid fix system when the rotational position of the bone block is altered in the interior of the femoral tunnel. Methods: forty ovine knee specimens (stifle joints) were submitted to anterior cruciate ligament reconstruction (ACL) using a bone-tendon-bone graft. In twenty specimens, the Rigid Fix method was used; this group was subdivided into two groups: ten knees the pins transfixed only the spongious area of the bone block, and ten for fixation passing through the layer of cortical bone. In the twenty remaining specimens, the graft was fixed with 9mm metal interference screws. Results: comparison of the RIGIDFIX® method with the metal interference screw fixation method did not show any statistically significant differences in terms of maximum load and rigidity; also, there were no statistically significant differences when the rotational position of the bone block was altered inside the femoral tunnel. For these evaluations, a level of significance of p < 0.017 was considered. Conclusion: fixation of the bone-tendon-bone graft with 2 bioabsorbable pines, regardless of the rotational position inside the femoral tunnel, gave a comparable fixation in terms of initial resistance to the metal interference screw, in this experimental model.

  16. In vivo pedicle screw placement: image-guided virtual vision.

    PubMed

    Carl, A L; Khanuja, H S; Gatto, C A; Matsumoto, M; vomLehn, J; Schenck, J; Rohling, K; Lorensen, W; Vosburgh, K

    2000-06-01

    Near-real-time frameless stereotaxy registering intraoperative anatomy to a preoperative three-dimensional computer model has been developed for use with in vivo pedicle screw placement. Eight patients underwent thoracolumbar and lumbar spine stabilization surgery using this new technology, and 32 pedicle screws were placed. Three additional patients had 12 pedicle screws removed during revision surgery, and they allowed the authors to estimate the accuracy of this navigational system. Accuracy was determined by comparing pedicle screw position on postoperative computed tomographs for the first eight patients and on preoperative computed tomographs for the latter three patients, with the intraoperative computer trajectory data gathered during operation. In the group of eight patients, all screws were intrapedicular. In evaluating all 11 patients, the overall accuracy was +/- 2 mm, but the greatest error of 5.4 mm was noted in the sagittal plane measurement. During the development phase of this technology, time constraints prolong surgery, but this may be addressed once the tool's accuracy has been confirmed and intraoperative radiographic confirmation becomes unnecessary. In vivo real-time frameless stereotaxy for pedicle screw placement offers promise for the future. Refinements are needed to improve accuracy and address time constraints. PMID:10872760

  17. The hybrid ring tubular external fixator: a biomechanical study.

    PubMed

    Stein, H; Mosheiff, R; Baumgart, F; Frigg, R; Perren, S M; Cordey, J

    1997-06-01

    OBJECTIVE: To measure and compare the mechanical properties in bending of the four-ring, and three-ring/one-tube hybrid external fixation frames. DESIGN. IN VITRO: measurements of the mechanical behaviour of ring and ring-tubular external fixation frames. In the latter, one ring of the full circular frame was replaced by one tube and Schanz screws. BACKGROUND: The mechanical properties of the classical Ilizarov four-ring external fixation frames has been compared to those of other external fixation frames by various authors. However, in clinical practice the hybrid fixation frame is being used with increasing frequency. Therefore the mechanical properties of the latter are of immediate interest and clinical value. METHODS: On explanted sheep tibiae with single and double osteotomies, frame stiffness in the four-point bending mode was measured at different K-wire tensions, comparing the values obtained from four-ring frames, to those of three-ring-tubular hybrid frames. These measurements were made under conditions of (a) bone distraction (BD), and (b) segment transport (ST), both at the initial and final stages of this procedure. RESULTS: In circular frames, frame stiffness in bending for increasing K-wire tension showed a Gaussian distribution both in distraction and post-ST with an optimum at 1000 N. In ring tubular hybrid frames, however, frame stiffness showed a more linear relationship to K-wire tension. CONCLUSIONS: In the four-ring Ilizarov external fixation frame, the exchange of one ring with one tube and one Schanz screw both reduced frame stiffness in bending and converted to linear its relationship to K-wire tension. RELEVANCE: Under clinical conditions, the use of a similar ring tubular hybrid external fixator allows the adjustment of frame stiffness in a simple and practical way. This is not the case with the original ring fixation frame. PMID:11415731

  18. Evolving fixation methods in endoscopically assisted forehead rejuvenation: controversies and rationale.

    PubMed

    Rohrich, R J; Beran, S J

    1997-11-01

    The goals of surgical rejuvenation of the forehead include component brow manipulation, attenuation of transverse forehead rhytids, and reduction of glabellar frown lines. The endoscopic approach has proved successful in achieving these goals in selective patients while minimizing incisions and improving scalp sensation. Efficacy of endoscopic brow manipulation is dependent on (1) complete release of the brow at the supraorbital rim, (2) brow depressor muscle resection/release, and (3) tension-free fixation of the brow position until wound healing has occurred. Fixation of the brow using an endoscopic technique, unlike the open technique, is dependent on skin retraction and tension-free scalp fixation during the process of wound healing to maintain the desired brow position. Techniques for endoscopic fixation are arbitrarily divided into endogenous and exogenous. Endogenous methods include extensive galea-frontalis-occipitalis release, lateral spanning suspension sutures, external bolster fixation, anterior port skin excision, galea-frontalis advancement, cortical tunnels, and tissue adhesives. Exogenous techniques include internal screw or plate fixation, Mitek anchor fixation, external screw fixation, and absorbable K-wires. This article provides a goal-oriented review of these evolving techniques and a rationale for the use of fixation methods in endoscopically assisted forehead rejuvenation. PMID:9385975

  19. Current trends in pedicle screw stimulation techniques: lumbosacral, thoracic, and cervical levels.

    PubMed

    Isley, Michael R; Zhang, Xiao-Feng; Balzer, Jeffrey R; Leppanen, Ronald E

    2012-06-01

    Unequivocally, pedicle screw instrumentation has evolved as a primary construct for the treatment of both common and complex spinal disorders. However an inevitable and potentially major complication associated with this type of surgery is misplacement of a pedicle screw(s) which may result in neural and vascular complications, as well as impair the biomechanical stability of the spinal instrumentation resulting in loss of fixation. In light of these potential surgical complications, critical reviews of outcome data for treatment of chronic, low-back pain using pedicle screw instrumentation concluded that "pedicle screw fixation improves radiographically demonstrated fusion rates;" however the expense and complication rates for such constructs are considerable in light of the clinical benefit (Resnick et al. 2005a). Currently, neuromonitoring using free-run and evoked (triggered) electromyography (EMG) is widely used and advocated for safer and more accurate placement of pedicle screws during open instrumentation procedures, and more recently, guiding percutaneous placement (minimally invasive) where the pedicle cannot be easily inspected visually. The latter technique, evoked or triggered EMG when applied to pedicle screw instrumentation surgeries, has been referred to as the pedicle screw stimulation technique. As concluded in the Position Statement by the American Society of Neurophysiological Monitoring (ASNM), multimodality neuromonitoring using free-run EMG and the pedicle screw stimulation technique was considered a practice option and not yet a standard of care (Leppanen 2005). Subsequently, the American Association of Neurological Surgeons/Congress of Neurological Surgeons (AANS/CNS) Joint Section on Disorders of the Spine and Peripheral Nerves published their "Guidelines for the Performance of Fusion Procedures for Degenerative Disease of the Lumbar Spine" (Heary 2005, Resnick et al. 2005a, Resnick et al. 2005b). It was concluded that the "primary justification" of intraoperative neuromonitoring"... is the perception that the safety and efficacy of pedicle screw fixation are enhanced..." (Resnick et al. 2005b). However in summarizing a massive (over 1000 papers taken from the National Library of Medicine), contemporary, literature review spanning nearly a decade (1996 to 2003), this invited panel (Resnick et al. 2005b) recognized that the evidence-based documents contributing to the parts related to pedicle screw fixation and neuromonitoring were "... full of potential sources of error ..." and lacked appropriate, randomized, prospective studies for formulating rigid standards and guidelines. Nevertheless, current trends support the routine use and clinical utility of these neuromonitoring techniques. In particular free-run and triggered EMG have been well recognized in numerous publications for improving both the accuracy and safety of pedicle screw implantation. Currently, treatment with pedicle screw instrumentation routinely involves all levels of the spine - lumbosacral, thoracic, and cervical. Significant historical events, various neuromonitoring modalities, intraoperative alarm criteria, clinical efficacy, current trends, and caveats related to pedicle screw stimulation along the entire vertebral column will be reviewed. PMID:22808751

  20. Efficacy of 2-mm locking miniplates in the management of mandibular fractures without maxillomandibular fixation

    PubMed Central

    Prabhakar, Chandan; Shetty, Jayaprasad N.; Hemavathy, O. R.; Guruprasad, Yadavalli

    2011-01-01

    Background: The management of trauma has evolved greatly over the past many years. Various bone plating systems have been developed to provide stable fixation of mandibular fractures. The introduction of the locking plate/screw system has offered certain advantages over the conventional plating systems. This system does not require intimate adaptation of the miniplates to the underlying bone and has greater stability. This study evaluates the efficacy of locking miniplate/screw system in the treatment of mandibular fractures without maxillomandibular fixation. Materials and Methods: This was a prospective study analyzing 20 patients with undisplaced or minimally displaced mandibular fractures, who reported to Department of Oral and Maxillofacial Surgery, Government Dental College and Research Institute, Bangalore. The selected cases were treated by open reduction and internal fixation using the 2.0 mm locking plate/screw system. Results: Open reduction and internal fixation with the 2.0 mm locking plate/screw system were achieved in all the 20 cases with satisfactory stability of the fracture fragments. The system was found to be reliable and effective intraoperatively. Only two complications were noted in the study. Conclusion: The locking miniplate system was found to be reliable and effective in management of mandibular fractures without postoperative intermaxillary fixation, however further studies with more sample size is required. PMID:22442606

  1. Prevention of pin track infection in external fixation with silver coated pins: clinical and microbiological results.

    PubMed

    Mass, A; Bruno, A; Bosetti, M; Biasibetti, A; Cannas, M; Gallinaro, P

    2000-09-01

    Pin tract infection is a frequent complication of external fixation; according to literature its frequency ranges from 2-30%. The recent introduction of silver coating of polymeric materials was found to decrease bacterial adhesion; its clinical use with Foley catheters and central venous catheters led to significant results. To verify the ability of the same silver coating to decrease the bacterial colonization on external fixation screws, a prospective randomized study was carried out on 24 male patients; a total of 106 screws were implanted in the lower limb to fix femoral or tibial diaphyseal fractures: 50 were coated with silver and 56 were commercially available stainless steel screws. Although the coated screws resulted in a lower rate of positive cultures (30.0%) than the uncoated screws (42.9%), this difference was not statistically significant (p = 0.243). The clinical behavior of the coated screws did not differ from that of the uncoated ones. Furthermore, the implant of silver-coated screws resulted in a significant increase in the silver serum level. These results led us to consider it ethically unacceptable to continue this investigation. PMID:10984710

  2. Vertebral body compression fracture after percutaneous pedicle screw removal in a young man.

    PubMed

    Cappuccio, M; De Iure, F; Amendola, L; Martucci, A

    2015-12-01

    Hazards and potential complications associated with pedicle screw insertions have been reported. In contrast, complications due to implant removal are rarely described. An unreported case of acute vertebral body compression fracture following pedicle screw removal in a young man occurred during an episode of forceful coughing. Spinal implants need to be removed in cases of complications, pain or tissue irritation, and removal is mandatory when fixation involves L2 or the lower segments. Complications associated with spinal implant removal are rare but possible, and patients must be informed of this potential risk. PMID:25417175

  3. Benefit and accuracy of intraoperative 3D-imaging after pedicle screw placement: a prospective study in stabilizing thoracolumbar fractures

    PubMed Central

    Mittlmeier, Thomas; Gierer, Philip; Harms, Christoph; Gradl, Georg

    2009-01-01

    Internal fixation is the established dorsal standard procedure for the treatment of thoracolumbar fractures. The main problem of the procedure is the false positioning of the pedicle screws. The exact determination of pedicle screws has up to now only been possible through postoperative computed tomography. This study was intended to clarify the diagnostic value of intraoperative 3D scans after pedicle screw implantation in thoracolumbar spine surgery. The direct intraoperative consequences of the 3D scans are reported and the results of the 3D scans are compared with the postoperative computed tomography images. Intraoperative 3D scans were prospectively carried out from June 2006 to October 2008 on 95 patients with fractures of the thoracolumbar spine that have been treated with internal fixation. Screws positions were categorised intraoperatively, screws in relevant malposition were repositioned immediately. A computed tomography of the involved spinal section was carried out postoperatively for all patients. The positions of the pedicle screws were determined and compared in the axial reconstructions of both procedures. Four hundred and fourteen pedicles with enclosed screws were evaluated by the 3D scans. The time needed for carrying out the 3D scan amounts to an average of 8.2min. Eleven screws (2.7%) in ten patients were primarily intraoperatively repositioned on the basis of the 3D scan evaluation. Two of 95 patients had to have false positions of the screws revised secondarily following evaluation of the computed tomographies. The secondary postoperative revision rate of the patients amounts to 2.1%. In relation to the number of screws, this is a revision rate of 0.5%. The postoperative computed tomographies showed 323 pedicles without cortical penetration by the screws (78.0%). Ninety-one screws penetrated the pedicle wall (22%). It was possible to postoperatively compare the position classifications of 406 pedicle screws. The CT showed 378 correct screw positions, while 28 screws were positioned falsely. On the basis of the 3D scans, 376 of 378 correct positions were correctly assessed. Twenty-one of 28 false positions could be correctly classified. The sensitivity of all 3D scans reached 91.3% and the specificity 98.2%. The position of 97.8% of the pedicle screws was correctly recognised by the intraoperative 3D scan. Nine screws were classified falsely (2.2%). The comparison of the classification results showed significantly higher error findings by the 3D scan in the spinal section T110 (P=0.014). The image quality of the 3D scan correlates significantly with the width of the scanned pedicle, with the body mass index, the scanned spinal section and the extent of the fixation assembly. 3D scans showed a high accuracy in predicting pedicle screw position. Primary false placement of screws and primary neurovascular damage cannot be avoided. But intraoperative evaluation of the 3D scans resulted in a primary revision rate of 2.7% of the pedicle screws and we could lower the secondary revision rate to 0.5%. PMID:19513764

  4. Benefit and accuracy of intraoperative 3D-imaging after pedicle screw placement: a prospective study in stabilizing thoracolumbar fractures.

    PubMed

    Beck, Markus; Mittlmeier, Thomas; Gierer, Philip; Harms, Christoph; Gradl, Georg

    2009-10-01

    Internal fixation is the established dorsal standard procedure for the treatment of thoracolumbar fractures. The main problem of the procedure is the false positioning of the pedicle screws. The exact determination of pedicle screws has up to now only been possible through postoperative computed tomography. This study was intended to clarify the diagnostic value of intraoperative 3D scans after pedicle screw implantation in thoracolumbar spine surgery. The direct intraoperative consequences of the 3D scans are reported and the results of the 3D scans are compared with the postoperative computed tomography images. Intraoperative 3D scans were prospectively carried out from June 2006 to October 2008 on 95 patients with fractures of the thoracolumbar spine that have been treated with internal fixation. Screws positions were categorised intraoperatively, screws in relevant malposition were repositioned immediately. A computed tomography of the involved spinal section was carried out postoperatively for all patients. The positions of the pedicle screws were determined and compared in the axial reconstructions of both procedures. Four hundred and fourteen pedicles with enclosed screws were evaluated by the 3D scans. The time needed for carrying out the 3D scan amounts to an average of 8.2 min. Eleven screws (2.7%) in ten patients were primarily intraoperatively repositioned on the basis of the 3D scan evaluation. Two of 95 patients had to have false positions of the screws revised secondarily following evaluation of the computed tomographies. The secondary postoperative revision rate of the patients amounts to 2.1%. In relation to the number of screws, this is a revision rate of 0.5%. The postoperative computed tomographies showed 323 pedicles without cortical penetration by the screws (78.0%). Ninety-one screws penetrated the pedicle wall (22%). It was possible to postoperatively compare the position classifications of 406 pedicle screws. The CT showed 378 correct screw positions, while 28 screws were positioned falsely. On the basis of the 3D scans, 376 of 378 correct positions were correctly assessed. Twenty-one of 28 false positions could be correctly classified. The sensitivity of all 3D scans reached 91.3% and the specificity 98.2%. The position of 97.8% of the pedicle screws was correctly recognised by the intraoperative 3D scan. Nine screws were classified falsely (2.2%). The comparison of the classification results showed significantly higher error findings by the 3D scan in the spinal section T1-10 (P = 0.014). The image quality of the 3D scan correlates significantly with the width of the scanned pedicle, with the body mass index, the scanned spinal section and the extent of the fixation assembly. 3D scans showed a high accuracy in predicting pedicle screw position. Primary false placement of screws and primary neurovascular damage cannot be avoided. But intraoperative evaluation of the 3D scans resulted in a primary revision rate of 2.7% of the pedicle screws and we could lower the secondary revision rate to 0.5%. PMID:19513764

  5. Treatment of Palatal Fractures by Osteosynthesis with 2.0-mm Locking Plates as External Fixator

    PubMed Central

    Cienfuegos, Ricardo; Sierra, Eduardo; Ortiz, Benjamin; Fernández, Gerardo

    2010-01-01

    Treatment options for palatal fractures range from orthodontic braces, acrylic bars, and arch bars for maxillomandibular fixation to internal fixation, with plates and screws placed under the palate mucosa and periosteum, together with pyriform aperture or alveolar plating plus buttress reconstruction. Forty-five patients, ages 4 to 56, were treated using medium- or high-profile locking plates placed over the palatal mucosa as an external fixator for palatal fractures, together with treatment for other associated facial fractures. In open fractures, plates were placed after approximating the edges of the mucosal wounds. Plates and screws for palate fixation were removed at 12 weeks, when computed tomography scans provided evidence of fracture healing. All palatal fractures healed by 12 weeks, with no cases of mucosal necrosis, bone exposure, fistulae, or infections. This approach achieves adequate stability, reduces the risk of bone and mucosal necrosis, and promotes healing of mucosal wounds in case of open fractures. PMID:22132261

  6. Fixation of basicervical and related fractures

    PubMed Central

    2009-01-01

    We prospectively studied 42 patients in order to identify a group of proximal femoral fractures having liability for axial and rotational instability, and to present results of their fixation using the dynamic hip screw (DHS) with derotation screw (DRS). At 12months postoperatively, patients were functionally evaluated and the radiological outcome was analysed. All fractures united within an average period of 11.5weeks. The mean sliding distance was 5.5mm and mean shortening of the limbs was 2 mm. According to the criteria of Kyle et al. (J Bone Joint Surg [Am] 61-A:216221), 39 patients obtained excellent results, two good and one fair. We conclude that the AO types B2.1, A1.1, A2.1, A2.2 and A2.3 have a common instability denominator and therefore should be treated alike. The sliding component of the DHS allows solid fixation of the two major fragments in two planes and the DRS in the third plane. PMID:19475407

  7. Avulsion Fracture of the Calcaneus Treated With a Soft Anchor Bridge and Lag Screw Technique: A Report of Two Cases.

    PubMed

    Yoshida, Kazushige; Kasama, Kentaro; Akahane, Tsutomu

    2016-01-01

    The displaced extra-articular avulsion fracture of the calcaneus has been classified as a Böhler type 1c calcaneal fracture, and most cases will require surgical repair. In the present report, we describe 2 patients in whom we performed the soft anchor bridge technique using single loaded suture anchors with lag screws for the repair of Böhler type 1c avulsion fractures of the calcaneus. In one of these patients, clinically relevant osteoporosis complicated the injury. In both cases, bone union was achieved, and by 1.5 months after surgery satisfactory recovery was observed. To our knowledge, the soft anchor bridge technique was first used for the treatment of rotator cuff tears, and the greatest merit of this technique is the ability to generate vertical compression force to the pulled out rotator cuff through the use of knotting sutures. In recent years, the soft anchor bridge technique using 4 suture anchors has also been used for fractures of the greater tuberosity of the humerus, an injury that poses operative difficulties similar to those encountered with an avulsion fracture of the calcaneus owing to the traction force of the rotator cuff and relative weakness of adjacent bone. The outcomes of our patients suggest that the soft anchor bridge technique combined with adjunct lag screws is useful in the fixation of avulsion fractures of the calcaneus. In addition, the result in the elderly patient indicates the possibility of using this technique for patients with osteoporosis. PMID:25451203

  8. Comparison of Biomechanical Characteristics and Pelvic Ring Stability Using Different Fixation Methods to Treat Pubic Symphysis Diastasis: A Finite Element Study.

    PubMed

    Yao, Feng; He, Yu; Qian, Hebu; Zhou, Dongsheng; Li, Qinghu

    2015-12-01

    The intention of this study was to compare the biomechanical characteristics using 5 internal fixation methods used clinically to stabilize a pubic symphysis diastasis (PSD, Tile type B1).A 3-dimensional finite element model of PSD was simulated using 5 implants, including single superior plate (Single-Plate), superior and anterior plate (Dual-Plate), single cannulated screw (Single-Screw), crossed dual cannulated screws (Cross-Screw), and parallel dual cannulated screws (Para-Screw). Three loads were distributed in all models, including dual-leg standing, single-leg stance, and rotation. To evaluate the biomechanical properties, the construct stiffness, the stress distribution, and the von Misses stress were recorded and analyzed. To evaluate pelvic ring stability, the micromotion of the pubic symphysis and iliosacral joint was analyzed.Disruption of pubic symphysis dramatically decreased the pelvic ring stability. Cross-screw and Para-Screw showed higher stiffness than other methods. All implants endured the maximum von Misses stress under single-leg stance. For Plate-Screw system, the maximum stress occurred at a place where it strides over pubic symphysis and adjacent Plate-Screw interface. The single implant and Para-Screw had a tendency to fail. Para-Screw showed the best fixation effect under dual-leg conditions. Cross-screw showed superior antishearing force capacity under single-leg stance. Dual-Plate provided maximum antihorizontal rotation. Para-Screw provided the maximum stabilization for the posterior pelvic ring.This study showed the biomechanical advantages of dual-implant for PSD only from the finite element view. The Para-Screw provided high construct stiffness under 3 load conditions. The single implant and Para-Screw had a tendency to fail. The better anterior and posterior pelvic stabilization were obtained by the dual-implant fixation than other methods. Therefore, the Cross-Screw and Dual-Plate fixation methods should be preferred in the treatment of pubic symphysis from the finite element view. PMID:26656353

  9. Comparison of pullout strength of the thoracic pedicle screw between intrapedicular and extrapedicular technique: a meta-analysis and literature review

    PubMed Central

    Wang, Hua; Wang, Huafeng; Sribastav, Shilabant Sen; Ye, Fubiao; Liang, Chunxiang; Li, Zemin; Wang, Jianru; Liu, Hui; Wang, Xin; Zheng, Zhaomin

    2015-01-01

    Background: Intrapedicular fixation in thoracic spine is often limited, because of high risk of complication, especially in scoliosis patients. Extrapedicular screws fixation techniques provide an alternate solution for extremely small or abnormal thoracic pedicles deformity. However, the pullout resistance of extrapedicular screws has not been clearly defined. The aim of our study was to systematically review the existing evidence regarding the pullout resistance of thoracic extrapedicular screws compared with intrapedicular screws. Methods: A systematic search of all studies published through Nov 2014 was performed using Medline, EMBASE, OVID and other databases. All studies that compared the pullout resistance of thoracic extrapedicular screws with intrapedicular screws were selected. The data from the included studies were extracted and analyzed regarding pullout resistance force. Forest plots were constructed to summarize the data and compare the biomechanical stability achieved. Results: Five studies were included, with a total of 27 cadaveric specimens and 313 screws. The vertebral levels of the cadavers potted were T1-T8, T2-T12, T7-T9, T6-T11 and T4-T12 respectively. Overall, the results demonstrated that there was no significant difference in ultimate pullout strength between intrapedicular screws and extrapedicular screws (95% CI=-63.73 to 27.74; P=0.44); extrapedicular screws significantly increased the length of placements by a mean of 6.24 mm (95% CI=5.38 to 7.10; P<0.001); while the stiffness in intrapedicular screws was significantly stronger by a mean of 45.82 N/mm compared with extrapedicular screws (95% CI=-70.09 to -21.56; P<0.001). Conclusions: Meta-analysis of the existing literature showed that thoracic extrapedicular screws provided comparable but slightly lower pullout strength compared with intrapedicular screws, extrapedicular screws placement is much safer than intrapedicular screws. So thoracic extrapedicular screws offer a good alternative when it is hard to insert by intrapedicular approach, especially in scoliosis patients with severe vertebral deformities. PMID:26885199

  10. Mechanical testing of a device for subcutaneous internal anterior pelvic ring fixation versus external pelvic ring fixation

    PubMed Central

    2014-01-01

    Background Although useful in the emergency treatment of pelvic ring injuries, external fixation is associated with pin tract infections, the patients limited mobility and a restricted surgical accessibility to the lower abdomen. In this study, the mechanical stability of a subcutaneous internal anterior fixation (SIAF) system is investigated. Methods A standard external fixation and a SIAF system were tested on pairs of Polyoxymethylene testing cylinders using a universal testing machine. Each specimen was subjected to a total of 2000 consecutive cyclic loadings at 1Hz with sinusoidal lateral compression/distraction (+/?50N) and torque (+/? 0.5Nm) loading alternating every 200cycles. Translational and rotational stiffness were determined at 100, 300, 500, 700 and 900cycles. Results There was no significant difference in translational stiffness between the SIAF and the standard external fixation when compared at 500 (p?=?.089), 700 (p?=?.081), and 900 (p?=?.266) cycles. Rotational stiffness observed for the SIAF was about 50 percent higher than the standard external fixation at 300 (p?=?.005), 500 (p?=?.020), and 900 (p?=?.005) cycles. No loosening or failure of the rod-pin/rod-screw interfaces was seen. Conclusions In comparison with the standard external fixation system, the tested device for subcutaneous internal anterior fixation (SIAF) in vitro has similar translational and superior rotational stiffness. PMID:24684828

  11. Comparison of theoretical fixation stability of three devices employed in medial opening wedge high tibial osteotomy: a finite element analysis

    PubMed Central

    2014-01-01

    Background Medial open wedge high tibial osteotomy is a well-established procedure for the treatment of unicompartmental osteoarthritis and symptomatic varus malalignment. We hypothesized that different fixation devices generate different fixation stability profiles for the various wedge sizes in a finite element (FE) analysis. Methods Four types of fixation were compared: 1) first and 2) second generation Puddu plates, and 3) TomoFix plate with and 4) without bone graft. Cortical and cancellous bone was modelled and five different opening wedge sizes were studied for each model. Outcome measures included: 1) stresses in bone, 2) relative displacement of the proximal and distal tibial fragments, 3) stresses in the plates, 4) stresses on the upper and lower screw surfaces in the screw channels. Results The highest load for all fixation types occurred in the plate axis. For the vast majority of the wedge sizes and fixation types the shear stress (von Mises stress) was dominating in the bone independent of fixation type. The relative displacements of the tibial fragments were low (in ?m range). With an increasing wedge size this displacement tended to increase for both Puddu plates and the TomoFix plate with bone graft. For the TomoFix plate without bone graft a rather opposite trend was observed. For all fixation types the occurring stresses at the screw-bone contact areas pulled at the screws and exceeded the allowable threshold of 1.2MPa for at least one screw surface. Of the six screw surfaces that were studied, the TomoFix plate with bone graft showed a stress excess of one out of twelve and without bone graft, five out of twelve. With the Puddu plates, an excess stress occurred in the majority of screw surfaces. Conclusions The different fixation devices generate different fixation stability profiles for different opening wedge sizes. Based on the computational simulations, none of the studied osteosynthesis fixation types warranted an intransigent full weight bearing per se. The highest fixation stability was observed for the TomoFix plates and the lowest for the first generation Puddu plate. These findings were revealed in theoretical models and need to be validated in controlled clinical settings. PMID:25012591

  12. Lateral mass fixation in subaxial cervical spine: anatomic review.

    PubMed

    Mohamed, Elrahmany; Ihab, Zidan; Moaz, Anwar; Ayman, Nabawi; Haitham, Abo-Elw

    2012-03-01

    Introduction?The cervical spine is a highly mobile segment of the spinal column, liable to a variety of diseases and susceptible to trauma. It is a complex region where many vital structures lie in close proximity. Lateral mass screw fixation has become the method of choice in stabilizing subaxial cervical spine among other posterior cervical fixation techniques whenever the posterior elements are absent or compromised. Objective?This study examined cervical specimens of cadavers and cervical computed tomography (CT) scans to minimize as much as possible complications of cervical lateral mass screw placement such as vertebral artery or nerve root injuries, facet joint violations, or inadequate placement. Methods?Forty normal cervical CT scans, obtained from the emergency unit as part of the trauma workup, were included in this study plus 10 cervical cadaveric specimens obtained from the Alexandria Neuro-anatomy laboratory. There were three fixed parameters for screw insertion in this study. First, the point of screw insertion was the midpoint of the lateral mass; it was the crossing point between the sagittal and axial planes of the posterior cortex of the lateral mass. Second, the direction of the screw in the craniocaudal plane was 30 degrees cranially to avoid facet joint penetration. Third, the exit point of the screw was located on the ventral cortex of the lateral mass just lateral to the root of the transverse process in the midaxial cut of each lateral mass, to make a sound bicortical fixation without injuring the vertebral artery or the nerve root. The selected screw trajectory in this study was the line drawn between the inlet and exit points. The depth and width of the lateral mass of the cervical vertebrae from C3 to C7 were measured as well as the angle of screw trajectory from the sagittal plane. All these measures were applied on the cadaveric specimens to make sure that no injury to the vertebral artery, nerve root, or facet joint occurred. Results?As regards the collected measurements of the lateral mass of all subaxial cervical vertebrae, the study revealed that the average depth of the lateral mass was 12.83??1.28 mm. The average width of the lateral mass was 11.92??0.96 mm. The average divergent angle of bicortical screw insertion without injury to the vertebral artery or the nerve root was 19.51??1.83 degrees. As regard the cadaveric specimens, based on all the collected measurements taken from the CT scans, there was no reported injury to the vertebral arteries or nerve roots or penetration to the facet joints. Conclusion?Lateral mass fixation can be applied easily and safely for all levels of subaxial cervical spine from C3 to C6 with the following parameters: (1) the point of entry is the midpoint of the lateral mass; (2) the screw trajectory is directed 30 degrees cranially and 20 degrees laterally; (3) the screw length is 13 to 15 mm. PMID:24353945

  13. Lateral Mass Fixation in Subaxial Cervical Spine: Anatomic Review

    PubMed Central

    Mohamed, Elrahmany; Ihab, Zidan; Moaz, Anwar; Ayman, Nabawi; Haitham, Abo-elw

    2012-01-01

    Introduction?The cervical spine is a highly mobile segment of the spinal column, liable to a variety of diseases and susceptible to trauma. It is a complex region where many vital structures lie in close proximity. Lateral mass screw fixation has become the method of choice in stabilizing subaxial cervical spine among other posterior cervical fixation techniques whenever the posterior elements are absent or compromised. Objective?This study examined cervical specimens of cadavers and cervical computed tomography (CT) scans to minimize as much as possible complications of cervical lateral mass screw placement such as vertebral artery or nerve root injuries, facet joint violations, or inadequate placement. Methods?Forty normal cervical CT scans, obtained from the emergency unit as part of the trauma workup, were included in this study plus 10 cervical cadaveric specimens obtained from the Alexandria Neuro-anatomy laboratory. There were three fixed parameters for screw insertion in this study. First, the point of screw insertion was the midpoint of the lateral mass; it was the crossing point between the sagittal and axial planes of the posterior cortex of the lateral mass. Second, the direction of the screw in the craniocaudal plane was 30 degrees cranially to avoid facet joint penetration. Third, the exit point of the screw was located on the ventral cortex of the lateral mass just lateral to the root of the transverse process in the midaxial cut of each lateral mass, to make a sound bicortical fixation without injuring the vertebral artery or the nerve root. The selected screw trajectory in this study was the line drawn between the inlet and exit points. The depth and width of the lateral mass of the cervical vertebrae from C3 to C7 were measured as well as the angle of screw trajectory from the sagittal plane. All these measures were applied on the cadaveric specimens to make sure that no injury to the vertebral artery, nerve root, or facet joint occurred. Results?As regards the collected measurements of the lateral mass of all subaxial cervical vertebrae, the study revealed that the average depth of the lateral mass was 12.83??1.28 mm. The average width of the lateral mass was 11.92??0.96 mm. The average divergent angle of bicortical screw insertion without injury to the vertebral artery or the nerve root was 19.51??1.83 degrees. As regard the cadaveric specimens, based on all the collected measurements taken from the CT scans, there was no reported injury to the vertebral arteries or nerve roots or penetration to the facet joints. Conclusion?Lateral mass fixation can be applied easily and safely for all levels of subaxial cervical spine from C3 to C6 with the following parameters: (1) the point of entry is the midpoint of the lateral mass; (2) the screw trajectory is directed 30 degrees cranially and 20 degrees laterally; (3) the screw length is 13 to 15 mm. PMID:24353945

  14. Accuracy and safety of pedicle screw placement in neuromuscular scoliosis with free-hand technique

    PubMed Central

    Modi, Hitesh N.; Fernandez, Harry; Yang, Jae Hyuk; Song, Hae-Ryong

    2008-01-01

    It is a retrospective analytic study of 1,009 transpedicular screws (689 thoracic and 320 lumbosacral), inserted with free-hand technique in neuromuscular scoliosis using postoperative CT scan. The aim of paper was to determine the accuracy and safety of transpedicular screw placement with free-hand technique in neuromuscular scoliosis and to compare the accuracy at different levels in such population. All studies regarding accuracy and safety of pedicle screw in scoliosis represent idiopathic scoliosis using various techniques such as free-hand, navigation, image intensifier, etc., for screw insertion. Anatomies of vertebrae and pedicle are distorted in scoliosis, hence accurate and safe placement of pedicle screw is prerequisite for surgery. Between 2004 and 2006, 37 consecutive patients, average age 20years (944years), of neuromuscular scoliosis were operated with posterior pedicle screw fixation using free-hand technique. Accuracy of pedicle screws was studied on postoperative CT scan. Placement up to 2mm medial side and 4mm lateral side was considered within-safe zone. Of the 1,009 screws, 273 screws were displaced medially, laterally or on the anterior side showing that 73% screws (68% in thoracic and 82.5% in lumbar spine) were accurately placed within pedicle. Considering the safe zone, 93.3% (942/1009, 92.4% in thoracic and 95.3% in lumbar spine) of the screws were within the safe zone. Comparing accuracy according to severity of curve, accuracy was 75% in group 1 (curve <90) and 69% in group 2 (curve >90) with a safety of 94.8 and 91.2%, respectively (P=0.35). Comparing the accuracy at different thoracic levels, it showed 67, 64 and 72% accuracy in upper, middle and lower thoracic levels with safety of 96.6, 89.2 and 93.1%, respectively, exhibiting no statistical significant difference (P=0.17). Pedicle screw placement in neuromuscular scoliosis with free-hand technique is accurate and safe as other conditions. PMID:18830636

  15. Expandable insert serves as screw anchor

    NASA Technical Reports Server (NTRS)

    1966-01-01

    Expandable self-locking adapter secures components to panels having one accessible side. Mounting holes in the panels may not be threaded to accommodate screws, therefore, the adapter contains a female thread that will mate a mounting screw.

  16. Models of Fixation and Tissue Processing

    PubMed Central

    Grizzle, William E.

    2009-01-01

    Fixation and processing of tissue to paraffin blocks are used to permit tissues to be cut thinly (4 to 5 m); cutting thin sections of tissue and staining them histochemically or immunohistochemically are necessary to permit tissues to be viewed adequately as to their structures (e.g., subcellular components and surrounding stroma) using a bright field microscope. Over the last century, anatomists and pathologists have used fixation in 10% neutral buffered formalin (10% NBF) as the fixative of choice. Also, both human and veterinary pathologists have trained using fixation in 10% NBF so these professionals have been and are reluctant to change the microscopic appearance of diagnostic tissues by using a different type of fixation; in addition, the effects of tissue processing on the microscopic appearance of tissue has essentially been ignored in most studies. Because of the use of 10% NBF by pathologists, archives of paraffin blocks contain essentially paraffin blocks only fixed in 10% NBF. Thus, if retrospective studies use archival paraffin blocks to correlate the molecular features of diseases with the outcomes of diseases, the studies must be based upon using tissue fixed in 10% NBF. Studies of how fixation in 10% NBF interacts with histochemical and immunohistochemical staining are very limited in number and most are based upon relatively long times of fixation in 10% NBF (? 36 hours). Current times of fixation in 10% NBF have been reduced to < 24 hours. Actually, little is known about fixation in 10% NBF and its interaction with tissue processing at any time of fixation, especially short times of fixation. Even less is known about how fixation of tissues in 10% NBF interact with more modern assays using immunohistochemistry, real time quantitative PCR, and techniques which depend upon the analysis of proteins extracted from paraffin blocks such as analysis by multiplex immunoassays or by mass spectrometry. In general, multiple antibody-antigen combinations are reported not to work in tissues fixed in 10% NBF, i.e., immunorecognition is almost lost completely for such antibody-antigen combinations as Ki67/MIB, ER? and PR, and partially lost for Bcl-2. Several models have been developed to study the interactions of tissue fixation and immunorecognition, but most have viewed the problem in immunorecognition as being completely caused by fixation. Also, some of the models discussed in this special issue do not predict observations of the effects of fixation on frozen tissues fixed in 10% NBF, but not processed to paraffin blocks. This article is a brief review of issues with using 10% NBF combined with tissue processing as a combined process to study biomarkers as identified by immunohistochemistry. PMID:19886755

  17. Nitrogen fixation ability of exopolysaccharide synthesis mutants of Rhizobium sp. strain NGR234 and Rhizobium trifolii is restored by the addition of homologous exopolysaccharides.

    PubMed Central

    Djordjevic, S P; Chen, H; Batley, M; Redmond, J W; Rolfe, B G

    1987-01-01

    Several transposon Tn5-induced mutants of the broad-host-range Rhizobium sp. strain NGR234 produce little or no detectable acidic exopolysaccharide (EPS) and are unable to induce nitrogen-fixing nodules on Leucaena leucocephala var. Peru or siratro plants. The ability of these Exo- mutants to induce functioning nodules on Leucaena plants was restored by coinoculation with a Sym plasmid-cured (Nod- Exo+) derivative of parent strain NGR234, purified EPS from the parent strain, or the oligosaccharide from the EPS. Coinoculation with EPS or related oligosaccharide also resulted in formation of nitrogen-fixing nodules on siratro plants. In addition, an Exo- mutant (ANU437) of Rhizobium trifolii ANU794 was able to form nitrogen-fixing nodules on white clover in the presence of added EPS or related oligosaccharide from R. trifolii ANU843. These results demonstrate that the absence of Rhizobium EPSs can result in failure of effective symbiosis with both temperate and subtropical legumes. Images PMID:3025187

  18. PHYSIOLOGY OF NITROGEN FIXATION BY BACILLUS POLYMYXA

    PubMed Central

    Grau, F. H.; Wilson, P. W.

    1962-01-01

    Grau, F. H. (University of Wisconsin, Madison) and P. W. Wilson. Physiology of nitrogen fixation by Bacillus polymyxa. J. Bacteriol. 83:490496. 1962.Of 17 strains of Bacillus polymyxa tested for fixation of molecular nitrogen, 15 fixed considerable quantities (30 to 150 ?g N/ml). Two strains of the closely related B. macerans did not use N2, but possibly other members of this species may do so. Confirmation of fixation was obtained by showing incorporation of N15 into cell material. Both iron and molybdenum are specifically required for fixation; without the addition of these metals to the nitrogen-free medium, the growth rate and the total nitrogen fixed were reduced about 30 to 50%. No requirement for added molybdenum could be shown when ammonia was the nitrogen source, and the absence of iron caused only a slight decrease in growth. Washed-cell suspensions of B. polymyxa containing an active hydrogenase readily incorporated N15 into cell materials when provided with mannitol, glucose, or pyruvate but not when formate was the substrate. Hydrogen is a specific inhibitor of fixation, reducing both the rate and final amount of nitrogen fixed; it did not reduce growth on ammonia. Fixation was strictly anaerobic, 1% oxygen in the gas phase being sufficient to stop fixation. Arsenate is a powerful inhibitor of fixation of N2 by washed-cell suspensions of B. polymyxa, indicating that high-energy phosphate may be significant for this process. PMID:13901244

  19. Distal femur defects reconstructed with polymethylmethacrylate and internal fixation devices: a biomechanical study.

    PubMed

    Uglialoro, Anthony D; Maceroli, Michael; Beebe, Kathleen S; Benevenia, Joseph; Patterson, Francis R

    2009-08-01

    Benign aggressive distal femur tumors are treated with curettage, adjuvant phenol or argon, and polymethylmethacrylate (PMMA) packing. For large defects, an internal fixation device is added to reduce the fracture risk. The purpose of this study is to compare the strength of locking plates to other fixation devices for stabilization of these defects. Lateral condyle defects in young, fresh frozen femurs were packed with PMMA and augmented by internal fixation. Three groups of 4 matched pairs of femurs were organized for the following comparisons: (1) stacked Steinmann pins vs crossed screws; (2) stacked pins vs locking plates; and (3) crossed screws vs locking plates. Specimens were subjected to axial load-to-failure testing on an MTS machine. There was no difference in load-to-failure strength (P=.177) using Steinmann pins or crossed screws. Locking plate constructs were stronger (P=.028) than Steinmann pin constructs. Locking plate constructs were also stronger (P<.001) than crossed-screw constructs. Steinmann pin constructs failed with severe intra-articular fractures; crossed screw constructs failed with bulging of the defects, articular impaction, and minimal fracture propagation. Locking plate constructs failed with extra-articular spiral shaft fractures. PMID:19708631

  20. Computer-Assisted Percutaneous Scaphoid Fixation: Concepts and Evolution

    PubMed Central

    Smith, Erin J.; Ellis, Randy E.; Pichora, David R.

    2013-01-01

    Background The treatment for undisplaced scaphoid waist fractures has evolved from conventional cast immobilization to percutaneous screw insertion. Percutaneous fixation reduces some of the risks of open surgery, but can be technically demanding and carries the risk of radiation exposure. Recently, computer-assisted percutaneous scaphoid fixation (CAPSF) has been gaining interest. Materials and Methods Conventional percutaneous scaphoid fixation is performed under fluoroscopic guidance and involves insertion of a guide wire along the length of the scaphoid to facilitate placement of a cannulated screw. Adapting computer-assisted techniques for scaphoid fixation poses several unique challenges including patient tracking and registration. Results To date, five groups have successfully implemented systems for CAPSF. These systems have implemented wrist immobilization strategies to resolve the issue of patient tracking and have developed unique guidance techniques incorporating 2D fluoroscope, cone-beam CT, and ultrasound, to circumvent patient-based registration. Conclusions Computer-aided percutaneous pinning of scaphoid waist fractures can significantly reduce radiation exposure and has the potential to improve the accuracy of this procedure. This article reviews the rationale for, and the evolution of, CAPSF and describes the key principles of computer-assisted technology. PMID:24436833

  1. The use of intraosseous screw for upper molar distalization: a case report.

    PubMed

    Polat-Ozsoy, Omr

    2008-04-01

    The use of implants has made a major change in orthodontic treatment mechanics. They have replaced conventional unaesthetic and compliance dependent extraoral appliances with well accepted intraoral mechanics. Implants can be used in molar and canine distalization, intrusion and in extraoral force applications. In the present case report, treatment of a case using an intermaxillary fixation screw (IMF) will be presented. The treatment results will be evaluated using pretreatment, post distalization and post treatment cephalometric radiographs and dental casts. PMID:19212521

  2. Treatment of juvenile hallux valgus interphalangeus with a double compression headless bone screw.

    PubMed

    Gksel, Ferdi; Ermutlu, Cenk; Glge, Umut Hatay; Kaymaz, Burak

    2015-01-01

    A 14-year-old girl presented with idiopathic valgus deformity of her left great toe at the interphalangeal joint (IPJ). The deformity, which had been present but asymptomatic for the past 4 years, began to enlarge and cause discomfort. The measured IPJ angle on anteroposterior standing X-ray was 26. We treated the toe by medial closing wedge osteotomy and fixation with a double compression headless bone screw (DCHBS). Postoperative hallux valgus interphalangeus (HVI) angle was 14. PMID:26243744

  3. Biomechanical evaluation of a new cross-pin technique for the fixation of different sized bone-patellar tendon-bone grafts.

    PubMed

    Zantop, Thore; Welbers, Barbara; Weimann, Andre; Rmmler, Markus; Hedderich, Jrgen; Musahl, Volker; Petersen, Wolf

    2004-11-01

    To overcome the disadvantages of interference-screw fixation of bone-patellar tendon-bone (BPTB) grafts, new fixation techniques for anterior cruciate ligament (ACL) grafts using biodegradable pins have been developed. The hypothesis of the present study was that cross-pin fixation techniques provide a primary stability that is comparable to that of interference screws. A biomechanical in vitro study was discussed. Human BPTB grafts of 8, 9 and 10 mm diameter were fixed in bovine knees with biodegradable cross pins (diameter: 2.0, 2.7 or 3.2 mm) or biodegradable interference screws. Stiffness and ultimate load were evaluated. For 9 and 10 mm BPTB grafts, no statistically significant difference in maximum load and stiffness was found between the four fixation techniques tested. For 8 mm bone blocks the maximum load of the 3.2 mm pins (274.2 N) was significantly lower than for the 2.0 mm pins (479.8 N) and the interference screws (504.0 N). Predominant failure mode in this group was bone-block fracture. Thicker grafts (9 and 10 mm) fixed with the 2.0 mm pins predominantly failed by implant fracture. Femoral fixation of 8, 9 and 10 mm BPTB grafts using cross pins leads to biomechanical properties that are comparable to biodegradable interference screws when tested by a single-cycle load to failure. Cross pins provide a rigid fixation for 9 and 10 mm BPTB grafts. PMID:15221210

  4. Air-Lubricated Lead Screw

    NASA Technical Reports Server (NTRS)

    Perkins, G. S.

    1983-01-01

    Air lubricated lead screw and nut carefully machined to have closely matched closely fitting threads. Compressed air injected into two plenums encircle nut and flow through orifices to lubricate mating threads. Originally developed to position precisely interferometer retroreflector for airborne measurement of solar infrared radiation, device now has positioning accuracy of 0.25 micron.

  5. Comparing the Intramedullary Nailing Method Versus Dynamic Hip Screw in Treatment of Unstable Intertrochanteric Fractures

    PubMed Central

    Yeganeh, Ali; Taghavi, Roozbeh; Moghtadaei, Mehdi

    2016-01-01

    Introduction: Dynamic Hip Screw fixation is currently considered as a standard treatment for pre-trochanteric fractures; however, due to the long-term hospitalization and some other complications, some researchers have proposed intramedullary nailing as the alternative surgical treatment. The aim of this study was to compare and examine the consequences of the using intramedullary nailing method versus Dynamic Hip Screw. Methods: In this study 114 patients with unstable Intertrochanteric fracture refer to Rasoul Akram hospital during 2011 to 2013 has been selected. After reduction, fixation surgery with PFN nail (60 patients) and Dynamic Hip Screw (54 patients) has been performed. All patients were screen during surgery and six months after surgery and some parameters like, bleeding, union, as well as complications such as collapse, varus and medialization of the distal fragment were record and patients. Results: About some parameters like cutting length, surgery duration, bleeding there were significant differences between two groups. In six months follow up period 2 patinas from nail and 8 patients from DHS group had non-union. Also from the point of radiologic and clinical parameters, like anterior thigh pain, cut out, medialization of the distal fragment, collapse of the neck, walking recovery and daily activities were significant between two groups. Conclusion: Due to the reduced hospital stay in intramedullary nailing method and the necessity of doing repeated surgery and applying intramedullary nailing when the patients are not treated with external fixation, the researchers recommend intramedullary nailing as the first option in treating such patients. PMID:26980933

  6. Pediatric mandibular fractures treated by rigid internal fixation.

    PubMed

    Wong, G B

    1993-09-01

    Mandibular fractures in the pediatric patient population are relatively uncommon. These patients present with their own unique treatment requirements. Most fractures have been treated conservatively by dental splints. Closed reduction techniques with maxillomandibular fixation (MMF) in very young children can pose several concerns, including cooperation, compliance and adequate nutritional intake. Rigid internal fixation of unstable mandibular fractures using miniplates and screws circumvents the need for MMF and allows immediate jaw mobilization. At major pediatric trauma institutions, there has been an increasing trend toward the use of this treatment when open reduction is necessary. This article presents a report of a five-year-old child who presented with bilateral mandibular fractures and was treated by rigid internal fixation and immediate mandibular mobilization. PMID:8402340

  7. Comparative strength measurements of five different fixation systems applied on an in vitro model of femoral midshaft osteotomy.

    PubMed

    Korovessis, Panagiotis; Deligianni, Despina; Petsinis, Giorgos; Baikousis, Andreas

    2002-01-01

    Oblique midshaft fractures of long bones can be stabilized using either plates and screws, lag screws, wires, cerclages, or a combination of these methods. Fractures at the distal tip of a well-fixed femoral prosthesis are difficult to stabilize with plates and screws because of the underlying intramedullary stem, polymethylmetacrylate (PMMA) cement, and thin periprosthetic femoral cortex. In this study we compared in vitro the mechanical performance of five different osteosynthesis techniques applied on an oak femoral model obliquely oscillated to mimic a short oblique fracture: (a) Double stainless steel wiring; (b) two 4.5 mm lag screws; (c) combination of one 4.5 mm cortical screw and one stainless steel wire; (d) one titanium compression cerclage Gundolf (CCG) combined with one 4.5 mm screw; and (e) double CCG. The five fixation constructs were subjected to a noncyclic destructive axial compression and torsional loading. The highest torque stiffness proved to be the double CCG and the double screw constructs, followed by and combination of CCG-screw and double screw constructs. The mode of failure in torque was a longitudinal crack close to the screw tip and loosening of the CCG and wire. The double screw, double CCG, and screw-CCG constructs provided the highest stiffness in axial compressive forces. The mode of failure in compression was loosening of the CCG and wire and bending of the screw. This comparative study showed that double CCG can theoretically replace the conventional methods of "minimal" osteosynthesis in the midshaft of long bones, and thus shows promise in the treatment of difficult short-oblique type femoral fracture at the distal tip of a well-fixed femoral prosthesis. The advantages of using the CCG is simplicity of technique, biocompatibility of titanium, no interference in modern imaging techniques, and avoidance of stripping of muscles and degloving of bone surfaces, as often happens in platting. PMID:24570155

  8. In vitro biomechanical evaluation of four fixation techniques for distractiveflexion injury stage 3 of the cervical spine

    PubMed Central

    Henriques, Thomas; Cunningham, Bryan W.; Mcafee, Paul C.

    2015-01-01

    Purpose Anterior plate fixation has been reported to provide satisfactory results in cervical spine distractive flexion (DF) injuries stages 1 and 2, but will result in a substantial failure rate in more unstable stage 3 and above. The aim of this investigation was to determine the biomechanical properties of different fixation techniques in a DF-3 injury model where all structures responsible for the posterior tension band mechanism are torn. Methods The multidirectional three-dimensional stiffness of the subaxial cervical spine was measured in eight cadaveric specimens with a simulated DF-3 injury at C5C6, stabilized with four different fixation techniques: anterior plate alone, anterior plate combined with posterior wire, transarticular facet screws, and a pedicle screwrod construct, respectively. Results The anterior plate alone did not improve stability compared to the intact spine condition, thus allowing considerable range of motion around all three cardinal axes (p > 0.05). The anterior plate combined with posterior wire technique improved flexionextension stiffness (p = 0.023), but not in axial rotation and lateral bending. When the anterior plate was combined with transarticular facet screws or with a pedicle screwsrod instrumentation, the stability improved in flexionextension, lateral bending, and in axial rotation (p < 0.05). Conclusions These findings imply that the use of anterior fixation alone is insufficient for fixation of the highly unstable DF-3 injury. In these situations, the use of anterior fixation combined with a competent posterior tension band reconstruction (e.g. transarticular screws or a posterior pedicle screwsrod device) improves segmental stability. PMID:25742755

  9. Comparison of Isocentric C-Arm 3-Dimensional Navigation and Conventional Fluoroscopy for Percutaneous Retrograde Screwing for Anterior Column Fracture of Acetabulum

    PubMed Central

    He, Jiliang; Tan, Guoqing; Zhou, Dongsheng; Sun, Liang; Li, Qinghu; Yang, Yongliang; Liu, Ping

    2016-01-01

    Abstract Percutaneous screw insertion for minimally displaced or reducible acetabular fracture using x-ray fluoroscopy and computer-assisted navigation system has been advocated by some authors. The purpose of this study was to compare intraoperative conditions and clinical results between isocentric C-arm 3-dimensional (Iso-C 3D) fluoroscopy and conventional fluoroscopy for percutaneous retrograde screwing of acetabular anterior column fracture. A prospective cohort study was conducted. A total of 22 patients were assigned to 2 different groups: 10 patients in the Iso-C 3D navigation group and 12 patients in the conventional group. The operative time, fluoroscopic time, time of screw insertion, blood loss, and accuracy were analyzed between the 2 groups. There were significant differences in operative time, screw insertion time, fluoroscopy time, and mean blood loss between the 2 groups. Totally 2 of 12 (16.7%) screws were misplaced in the conventional fluoroscopy group, and all 10 screws were in safe zones in the navigation group. Percutaneous screw fixation using the Iso-C 3D computer-assisted navigation system significantly reduced the intraoperative fluoroscopy time and blood loss in percutaneous screwing for acetabular anterior column fracture. The Iso-C 3D computer-assisted navigation system provided a reliable and effective method for percutaneous screw insertion in acetabular anterior column fractures compared to conventional fluoroscopy. PMID:26765448

  10. CT-based 3-D visualisation of secure bone corridors and optimal trajectories for sacroiliac screws.

    PubMed

    Mendel, Thomas; Radetzki, Florian; Wohlrab, David; Stock, Karsten; Hofmann, Gunther Olaf; Noser, Hansrudi

    2013-07-01

    Sacroiliac screw (SI) fixation represents the only minimally invasive method to stabilise unstable injuries of the posterior pelvic ring. However, it is technically demanding. The narrow sacral proportions and a high inter-individual shape variability places adjacent neurovascular structures at potential risk. In this study a CT-based virtual analysis of the iliosacral anatomy in the human pelvis was performed to visualise and analyse 3-D bone corridors for the safe placement of SI-screws in the first sacral segment. Computer-aided calculation of 3-D transverse and general SI-corridors as a sum of all inner-bony 7.3-mm screw positions was done with custom-made software algorithms based on CT-scans of intact human pelvises. Radiomorphometric analysis of 11 CT-DICOM datasets using the software Amira 4.2. Optimal screw tracks allowing the greatest safety distance to the cortex were computed. Corridor geometry and optimal tracks were visualised; measurement data were calculated. A transverse corridor existed in 10 pelvises. In one dysmorphic pelvis, the pedicular height at the level of the 1st neural foramina came below the critical distance of 7.3mm defined by the outer screw diameter. The mean corridor volume was 45.2 cm3, with a length of 14.9cm. The oval cross-section measured 2.8 cm2. The diameter of the optimal screw pathway with the greatest safety distance was 14.2mm. A double cone-shaped general corridor for screw penetration up to the centre of the S1-body was calculated bilaterally for every pelvis. The mean volume was 120.6 cm3 for the left side and 115.8 cm3 for the right side. The iliac entry area measured 49.1 versus 46.0 cm2. Optimal screw tracks were calculated in terms of projected inlet and outlet angles. Multiple optimal screw positions existed for each pelvis. The described method allows an automated 3-D analysis with regard to secure SI-screw corridors even with a high number of CT-datasets. Corridor visualisation and calculation of optimal screw tracks trains the visual thinking of the surgeon and can improve pre-operative planning. Prospectively, the introduced method can be implemented in computer-assisted surgery applications involving pelvic trauma. PMID:23246561

  11. Biomechanical measurements of cortical screw purchase in five types of human and artificial humeri.

    PubMed

    Aziz, Mina S R; Nicayenzi, Bruce; Crookshank, Meghan C; Bougherara, Habiba; Schemitsch, Emil H; Zdero, Radovan

    2014-02-01

    Humerus shaft fracture fixation is largely dependent on cortical screw purchase in host bone. Only 2 prior studies assessed cortical screw purchase in human humeral shafts, but were of very limited scope and did not fully assess humerus material properties. Also, no studies evaluated the human dried or artificial humeri both commercially available from Sawbones. Vashon, WA, USA. Therefore, present authors measured cortical screw purchase in human fresh-frozen (FF) (n=19), human embalmed (EM) (n=18), human dried (DR) (n=14), artificial "normal" (AN) (n=13), and artificial "osteoporotic" (AO) (n=13) humeri. Each humerus had 2 bicortical screws of 3.5-mm diameter inserted 20mm apart through the shaft's anterior and posterior cortices. Absolute force, displacement, and energy for screw-bone interface failure were measured by screw pullout tests, afterwhich data were normalized by total surface area engaged at the screw-bone interface. For absolute force, AN humeri reached a higher load than EM (p=0.001) and AO (p<0.001) humeri, whilst AN humeri achieved lower normalized force than DR humeri (p=0.018). For absolute displacement, AO humeri achieved a lower level than FF humeri (p=0.013), whilst for normalized displacement AN humeri had lower levels than all other groups (p?0.005) and AO humeri had lower values than EM humeri (p=0.029). For absolute and normalized energy, there were no statistical differences (p?0.066). Human bone mineral density (BMD) ranged from 0.7 to 1.8g/cm(2) and was linearly correlated to screw pullout parameters in 14 of 18 cases (R=0.61 to 0.96), whilst humerus age was not. Consequently, it is recommended that human fresh-frozen, human embalmed, and human dried humeri can be used interchangeably for cortical screw purchase, since they were statistically equivalent for all comparisons. However, artificial humeri were involved in all statistical differences observed and, thus, may not replicate cortical screw purchase in human humeri. To date, this is the most comprehensive study on cortical screw purchase in human and artificial humeral shafts. PMID:24295967

  12. Screw insertion in trabecular bone causes peri-implant bone damage.

    PubMed

    Steiner, Juri A; Ferguson, Stephen J; van Lenthe, G Harry

    2016-04-01

    Secure fracture fixation is still a major challenge in orthopedic surgery, especially in osteoporotic bone. While numerous studies have investigated the effect of implant loading on the peri-implant bone after screw insertion, less focus has been put on bone damage that may occur due to the screw insertion process itself. Therefore, the aim of this study was to localize and quantify peri-implant bone damage caused by screw insertion. We used non-invasive three-dimensional micro-computed tomography to scan twenty human femoral bone cores before and after screw insertion. After image registration of the pre- and post-insertion scans, changes in the bone micro-architecture were identified and quantified. This procedure was performed for screws with a small thread size of 0.3mm (STS, N=10) and large thread size of 0.6mm (LTS, N=10). Most bone damage occurred within a 0.3mm radial distance of the screws. Further bone damage was observed up to 0.6mm and 0.9mm radial distance from the screw, for the STS and LTS groups, respectively. While a similar amount of bone damage was found within a 0.3mm radial distance for the two screw groups, there was significantly more bone damage for the LTS group than the STS group in volumes of interest between 0.3-0.6mm and 0.6-0.9mm. In conclusion, this is the first study to localize and quantify peri-implant bone damage caused by screw insertion based on a non-invasive, three-dimensional, micro-CT imaging technique. We demonstrated that peri-implant bone damage already occurs during screw insertion. This should be taken into consideration to further improve primary implant stability, especially in low quality osteoporotic bone. We believe that this technique could be a promising method to assess more systematically the effect of peri-implant bone damage on primary implant stability. Furthermore, including peri-implant bone damage due to screw insertion into patient-specific in silico models of implant-bone systems could improve the accuracy of these models. PMID:26920074

  13. Some refinements of the theory of the viscous screw pump.

    NASA Technical Reports Server (NTRS)

    Elrod, H. G.

    1972-01-01

    Recently performed analysis for herringbone thrust bearings has been incorporated into the theory of the viscous screw pump for Newtonian fluids. In addition, certain earlier corrections for sidewall and channel curvature effects have been simplified. The result is a single, refined formula for the prediction of the pressure-flow relation for these pumps.

  14. Metallurgical examination of gun barrel screws

    SciTech Connect

    Bird, E.L.; Clift, T.L.

    1996-06-01

    The examination was conducted to determine the extent of degradation that had occurred after a series of firings; these screws prevent live rounds of ammunition from being loaded into the firing chamber. One concern is that if the screw tip fails and a live round is accidentally loaded into the chamber, a live round could be fired. Another concern is that if the blunt end of the screw begins to degrade by cracking, pieces could become small projectiles during firing. All screws used in firing 100 rounds or more exhibited some degree degradation, which progressively worsened as the number of rounds fired increased. (SEM, metallography, x-ray analysis, and microhardness were used.) Presence of cracks in these screws after 100 fired rounds is a serious concern that warrants the discontinued use of these screws. The screw could be improved by selecting an alloy more resistant to thermal and chemical degradation.

  15. In vitro characteristics of a bioabsorbable suspension screw and suture system for endoscopic brow lift surgery.

    PubMed

    Pietrzak, William S; Eppley, Barry L

    2007-03-01

    The time requirement for endoscopic subperiosteal brow lift fixation is as little as 10-14 days. Many types of bioabsorbable fixation have been applied to this procedure, including bioabsorbable suture coupled with a bioabsorbable bone anchor, with excellent outcomes. Typically, the anchor and suture materials differ, each having their own hydrolytic strength loss profile. The dynamic relationship between the instantaneous state of degradation of the bone anchor and the suture components can affect fixation strength and failure mode, a poorly understood phenomenon. We examined the use of 2x5 mm PLLA-PGA (82:18) copolymer screws containing a suture eyelet in the head, paired with one of four types of bioabsorbable suture (2-0 and 3-0 Vicryl and 2-0 and 3-0 PDS-II), in a model system designed to mimic brow lift fixation. Constructs were inserted into a synthetic bone substrate and incubated in pH 7.4 buffer at 37 degrees C for up to 3 weeks, then loaded to failure. Initial failure loads were dependent upon suture size but not suture material, with 2-0 suture constructs (63-70N) failing at twice the load of the 3-0 suture constructs (30-35N). The following 3 week strength retentions were obtained: 40-55% for 2-0 and 3-0 Vicryl suture, 100% for 3-0 PDS-II suture, and 58% for 2-0 PDS-II suture constructs. The predominant failure mode was suture breakage at the knot, with the later intervals utilizing 2-0 PDS-II suture including some screw head failures. This suspension screw, when coupled with an appropriate suture, appears to have suitable mechanical properties for endoscopic brow lift fixation. PMID:17414297

  16. Fixation of zygomatic and mandibular fractures with biodegradable plates

    PubMed Central

    Degala, Saikrishna; Shetty, Sujeeth; Ramya, S

    2013-01-01

    Context: In this prospective study, 13 randomly selected patients underwent treatment for zygomaticcomplex fractures (2 site fractures) and mandibular fractures using 1.5 / 2 / 2.5-mm INION CPS biodegradable plates and screws. Aims: To assess the fixation of zygomatic-complex and mandibular fractures with biodegradable copolymer osteosynthesis system. Materials and Methods: In randomly selected 13 patients, zygomatic-complex and mandibular fractures were plated using resorbable plates and screws using Champy's principle. All the cases were evaluated clinically and radiologically for the type of fracture, need for the intermaxillary fixation (IMF) and its duration, duration of surgery, fixation at operation, state of reduction at operation, state of bone union after operation, anatomic reduction, paresthesia, occlusal discrepancies, soft tissue infection, immediate and late inflammatory reactions related to biodegradation process, and any need for the removal of the plates. Statistical Analysis Used: Descriptives, Frequencies, and Chi-square test were used. Results: In our study, the age group range was 5 to 55 years. Road traffic accidents accounted for the majority of patients six, (46.2%). Postoperative occlusal discrepancies were found in seven patients as mild to moderate, which resolved with IMF for 1-8 weeks. There were minimal complications seen and only as soft tissue infection. Conclusions: Use of biodegradable osteosynthesis system is a reliable alternative method for the fixation of zygomatic-complex and mandibular fractures. The biodegradable system still needs to be refined in material quality and handling to match the stability achieved with metal system. Biodegradable plates and screws is an ideal system for pediatric fractures with favorable outcome. PMID:23662255

  17. Fixation: A Bibliography.

    ERIC Educational Resources Information Center

    Pedrini, D. T.; Pedrini, Bonnie C.

    Fixation and regression were considered complementary by Freud. You tend to regress to a point of fixation. They are both opposed to progression. In the general area, Anna Freud has written (The Ego and the Mechanisms of Defence. London: Hogarth and the Psycho-Analytic Institute, 1937), Sears has evaluated (Survey of Objective Studies of…

  18. Screw Instability of the Magnetic Field Connecting a Rotating Black Hole with its Surrounding Disk

    NASA Astrophysics Data System (ADS)

    Wang, Ding-Xiong; Ma, Ren-Yi; Lei, Wei-Hua; Yao, Guo-Zheng

    2004-02-01

    We discuss the screw instability of the magnetic field connecting a rotating black hole (BH) with its surrounding disk based on the model of the coexistence of the Blandford-Znajek (BZ) process and the magnetic coupling (MC) process (CEBZMC). We derive criteria for the screw instability with the state of CEBZMC based on the calculations of the poloidal and toroidal components of the magnetic field on the disk. By these criteria the screw instability will occur if the BH spin and the power-law index for the variation of the magnetic field on the disk are greater than some critical values. It turns out that the instability occurs outside some critical radii on the disk. We argue that the state of CEBZMC always accompanies the screw instability. In addition, we show that the screw instability contributes only a small fraction of magnetic extraction of energy from a rotating BH.

  19. Recurrent Laryngeal Edema Imitating Angioedema Caused by Dislocated Screw after Anterior Spine Surgery

    PubMed Central

    Wjtowicz, Piotr; Szafarowski, Tomasz; Migacz, Ewa; Krzeski, Antoni

    2015-01-01

    The anterior cervical spine surgery is a common procedure to stabilize vertebrae damaged by various diseases. The plates and screws are usually used in the spine fixation. This kind of instrumentation may detach from the bones which is a rare but well-known complication. A 77-year-old male presented to the otorhinolaryngology department with throat pain, choking, and dysphagia. At first the angioedema was diagnosed and he was treated conservatively. The endoscopy revealed laryngeal edema, being more defined on the right side with right vocal fold paresis. CT scans showed the stabilizing plate with two screws attached tightly and the back-out of the third screw toward soft tissue of the neck. In the meantime, his condition deteriorated and he needed tracheotomy. In few days the surgical removal of the dislocated screw was performed successfully. Although two-month follow-up reported no obstruction of the larynx, the vocal folds paresis with gradual functional improvement was observed. Long-term complication of anterior spine surgery sometimes may suggest laryngeal angioedema at first. If the conservative treatment is ineffective and there is a history of anterior spine surgery, the clinicians should consider the displacement of the plate or screws in differential diagnosis. PMID:25755901

  20. Designs and Techniques That Improve the Pullout Strength of Pedicle Screws in Osteoporotic Vertebrae: Current Status

    PubMed Central

    Shea, Thomas M.; Laun, Jake; Gonzalez-Blohm, Sabrina A.; Doulgeris, James J.; Lee, William E.; Vrionis, Frank D.

    2014-01-01

    Osteoporosis is a medical condition affecting men and women of different age groups and populations. The compromised bone quality caused by this disease represents an important challenge when a surgical procedure (e.g., spinal fusion) is needed after failure of conservative treatments. Different pedicle screw designs and instrumentation techniques have been explored to enhance spinal device fixation in bone of compromised quality. These include alterations of screw thread design, optimization of pilot hole size for non-self-tapping screws, modification of the implant's trajectory, and bone cement augmentation. While the true benefits and limitations of any procedure may not be realized until they are observed in a clinical setting, axial pullout tests, due in large part to their reproducibility and ease of execution, are commonly used to estimate the device's effectiveness by quantifying the change in force required to remove the screw from the body. The objective of this investigation is to provide an overview of the different pedicle screw designs and the associated surgical techniques either currently utilized or proposed to improve pullout strength in osteoporotic patients. Mechanical comparisons as well as potential advantages and disadvantages of each consideration are provided herein. PMID:24724097

  1. Designs and techniques that improve the pullout strength of pedicle screws in osteoporotic vertebrae: current status.

    PubMed

    Shea, Thomas M; Laun, Jake; Gonzalez-Blohm, Sabrina A; Doulgeris, James J; Lee, William E; Aghayev, Kamran; Vrionis, Frank D

    2014-01-01

    Osteoporosis is a medical condition affecting men and women of different age groups and populations. The compromised bone quality caused by this disease represents an important challenge when a surgical procedure (e.g., spinal fusion) is needed after failure of conservative treatments. Different pedicle screw designs and instrumentation techniques have been explored to enhance spinal device fixation in bone of compromised quality. These include alterations of screw thread design, optimization of pilot hole size for non-self-tapping screws, modification of the implant's trajectory, and bone cement augmentation. While the true benefits and limitations of any procedure may not be realized until they are observed in a clinical setting, axial pullout tests, due in large part to their reproducibility and ease of execution, are commonly used to estimate the device's effectiveness by quantifying the change in force required to remove the screw from the body. The objective of this investigation is to provide an overview of the different pedicle screw designs and the associated surgical techniques either currently utilized or proposed to improve pullout strength in osteoporotic patients. Mechanical comparisons as well as potential advantages and disadvantages of each consideration are provided herein. PMID:24724097

  2. Helical screw expander evaluation project

    NASA Technical Reports Server (NTRS)

    Mckay, R.

    1982-01-01

    A one MW helical rotary screw expander power system for electric power generation from geothermal brine was evaluated. The technology explored in the testing is simple, potentially very efficient, and ideally suited to wellhead installations in moderate to high enthalpy, liquid dominated field. A functional one MW geothermal electric power plant that featured a helical screw expander was produced and then tested with a demonstrated average performance of approximately 45% machine efficiency over a wide range of test conditions in noncondensing, operation on two-phase geothermal fluids. The Project also produced a computer equipped data system, an instrumentation and control van, and a 1000 kW variable load bank, all integrated into a test array designed for operation at a variety of remote test sites. Data are presented for the Utah testing and for the noncondensing phases of the testing in Mexico. Test time logged was 437 hours during the Utah tests and 1101 hours during the Mexico tests.

  3. Screw-fed pump system

    DOEpatents

    Sprouse, Kenneth M

    2014-11-25

    A pump system includes a pump that includes a first belt and a second belt that are spaced apart from each other to provide generally straight sides of a passage there between. There is an inlet at one end of the passage and an outlet at an opposite end of the passage, with a passage length that extends between the inlet and the outlet. The passage defines a gap distance in a width direction between the straight sides at the passage inlet. A hopper includes an interior space that terminates at a mouth at the passage inlet. At least one screw is located within the interior space of the hopper and includes a screw diameter in the width direction that is less than or equal to the gap distance.

  4. A new adhesive technique for internal fixation in midfacial surgery

    PubMed Central

    Endres, Kira; Marx, Rudolf; Tinschert, Joachim; Wirtz, Dieter Christian; Stoll, Christian; Riediger, Dieter; Smeets, Ralf

    2008-01-01

    Background The current surgical therapy of midfacial fractures involves internal fixation in which bone fragments are fixed in their anatomical positions with osteosynthesis plates and corresponding screws until bone healing is complete. This often causes new fractures to fragile bones while drilling pilot holes or trying to insert screws. The adhesive fixation of osteosynthesis plates using PMMA bone cement could offer a viable alternative for fixing the plates without screws. In order to achieve the adhesive bonding of bone cement to cortical bone in the viscerocranium, an amphiphilic bone bonding agent was created, analogous to the dentin bonding agents currently on the market. Methods The adhesive bonding strengths were measured using tension tests. For this, metal plates with 2.0 mm diameter screw holes were cemented with PMMA bone cement to cortical bovine bone samples from the femur diaphysis. The bone was conditioned with an amphiphilic bone bonding agent prior to cementing. The samples were stored for 1 to 42 days at 37 degrees C, either moist or completely submerged in an isotonic NaCl-solution, and then subjected to the tension tests. Results Without the bone bonding agent, the bonding strength was close to zero (0.2 MPa). Primary stability with bone bonding agent is considered to be at ca. 8 MPa. Moist storage over 42 days resulted in decreased adhesion forces of ca. 6 MPa. Wet storage resulted in relatively constant bonding strengths of ca. 8 MPa. Conclusion A new amphiphilic bone bonding agent was developed, which builds an optimizied interlayer between the hydrophilic bone surface and the hydrophobic PMMA bone cement and thus leads to adhesive bonding between them. Our in vitro investigations demonstrated the adhesive bonding of PMMA bone cement to cortical bone, which was also stable against hydrolysis. The newly developed adhesive fixing technique could be applied clinically when the fixation of osteosynthesis plates with screws is impossible. With the detected adhesion forces of ca. 6 to 8 MPa, it is assumed that the adhesive fixation system is able to secure bone fragments from the non-load bearing midfacial regions in their orthotopic positions until fracture consolidation is complete. PMID:18489785

  5. Fixation Options for the Volar Lunate Facet Fracture: Thinking Outside the Box.

    PubMed

    Harness, Neil G

    2016-03-01

    Background?Fractures of the distal radius with small volar ulnar marginal fracture fragments are difficult to stabilize with standard volar locking plates. The purpose of this study is to describe alternative techniques available to stabilize these injuries. Materials and Methods?Five patients were identified retrospectively with unstable volar lunate facet fracture fragments treated with supplemental fixation techniques. The demographic data, pre- and postoperative radiographic parameters, and early outcomes data were analyzed. The AO classification, preoperative and final postoperative ulnar variance, articular step-off, volar tilt, radial inclination, and teardrop angle were measured. The lunate subsidence and length of the volar cortex available for fixation were measured from the initial injury films. Description of Technique?Lunate facet fixation was based on the morphology of the fragment, and stabilization was achieved with headless compression screws in three patients, a tension band wire construct in one, and two cortical screws in another. Results?Five patients with a mean age of 58 years (range: 41-82) were included. There were two AO C3.2 and three B3.3 fractures. Preoperative radiographic measurements including radial inclination, tilt, and ulnar variance all improved after surgery and were maintained within normal limits at 3-month follow-up. There was no change in the teardrop angle at final follow-up (70-64 degrees; p?=?0.14). None of the patients had loss of fixation or volar carpal subluxation. The mean visual analog scale pain score at 3 months was 1 (range: 0-2). Conclusions?The morphology of volar lunate facet fracture fragments is variable, and fixation must be customized to the particular pattern. Small fragments may preclude the use of plates and screws for fixation. These fractures can be managed successfully with tension band wire constructs and headless screws. These low-profile implants may decrease the risk of tendon irritation that might accompany distally placed plates. PMID:26855830

  6. 30 CFR 18.32 - Fastenings-additional requirements.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... and Design Requirements § 18.32 Fastenings—additional requirements. (a) Bolts, screws, or studs shall...) Lockwashers shall be provided for all bolts, screws, and studs that secure parts of explosion-proof enclosures... conduct explosion tests with standard bolts, nuts, cap screws, or studs substituted for any special...

  7. 30 CFR 18.32 - Fastenings-additional requirements.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... and Design Requirements § 18.32 Fastenings—additional requirements. (a) Bolts, screws, or studs shall...) Lockwashers shall be provided for all bolts, screws, and studs that secure parts of explosion-proof enclosures... conduct explosion tests with standard bolts, nuts, cap screws, or studs substituted for any special...

  8. 30 CFR 18.32 - Fastenings-additional requirements.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... and Design Requirements § 18.32 Fastenings—additional requirements. (a) Bolts, screws, or studs shall...) Lockwashers shall be provided for all bolts, screws, and studs that secure parts of explosion-proof enclosures... conduct explosion tests with standard bolts, nuts, cap screws, or studs substituted for any special...

  9. 30 CFR 18.32 - Fastenings-additional requirements.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... and Design Requirements § 18.32 Fastenings—additional requirements. (a) Bolts, screws, or studs shall...) Lockwashers shall be provided for all bolts, screws, and studs that secure parts of explosion-proof enclosures... conduct explosion tests with standard bolts, nuts, cap screws, or studs substituted for any special...

  10. 30 CFR 18.32 - Fastenings-additional requirements.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... and Design Requirements § 18.32 Fastenings—additional requirements. (a) Bolts, screws, or studs shall...) Lockwashers shall be provided for all bolts, screws, and studs that secure parts of explosion-proof enclosures... conduct explosion tests with standard bolts, nuts, cap screws, or studs substituted for any special...

  11. Posterior Spinal Reconstruction with Pedicle Screws, Multiple Iliac Screws and Wisconsin Spinal Wires in a Patient with Neurofibromatosis Scoliosis: A Case Report

    PubMed Central

    Kim, Woong-Beom; Park, Young-Seop; Park, Jong-Hwa

    2015-01-01

    A 54-year-old female with neurofibromatosis type 1 presented with progressing truncal shift owing to spinal deformity. On plain radiograph, the Cobb angle was 54 degree in coronal plane. Radiological examinations showed severe dystrophic change with dysplastic pedicles, bony scalloping, neural foraminal widening from dural ectasia. The patient underwent deformity correction and reconstruction surgery from the T9 to the pelvis using multiple iliac screws and Wisconsin interspinous segmental instrumentation by wiring due to maximize fixation points. The postoperative course was uneventful. One-year follow-up radiographs showed a successful curve correction with solid fusion. We report a case of pedicle dysplasia and dystrophic change treated by posterior segmental spinal instrumentation and fusion with help of multiple iliac screws and modified Wisconsin interspinous segmental wiring. PMID:26512279

  12. Early Experience with Biodegradable Fixation of Pediatric Mandibular Fractures.

    PubMed

    Mazeed, Ahmed Salah; Shoeib, Mohammed Abdel-Raheem; Saied, Samia Mohammed Ahmed; Elsherbiny, Ahmed

    2015-09-01

    This clinical study aims to evaluate the stability and efficiency of biodegradable self-reinforced poly-l/dl-lactide (SR-PLDLA) plates and screws for fixation of pediatric mandibular fractures. The study included 12 patients (3-12 years old) with 14 mandibular fractures. They were treated by open reduction and internal fixation by SR-PLDLA plates and screws. Maxillomandibular fixation was maintained for 1 week postoperatively. Clinical follow-up was performed at 1 week, 6 weeks, 3 months, and 12 months postoperatively. Radiographs were done at 1 week, 3 months, and 12 months postoperatively to observe any displacement and fracture healing. All fractures healed both clinically and radiologically. No serious complications were reported in the patients. Normal occlusion was achieved in all cases. Biodegradable osteofixation of mandibular fractures offers a valuable clinical solution for pediatric patients getting the benefit of avoiding secondary surgery to remove plates, decreasing the hospital stay, further painful procedures, and psychological impact. PMID:26269728

  13. Role of internal and external fixation in ankle fusion.

    PubMed

    Pfahler, M; Krodel, A; Tritschler, A; Zenta, S

    1996-01-01

    Between August 1980 and September 1993, 35 tibiotalar arthrodeses in 34 patients with primary and secondary osteoarthritis of the ankle were performed. Two different surgical techniques were employed. Internal screw fixation according to Wagner and Pock [20] and an external fixation method according to the resection compression arthrodesis by Charnley and Muller [14]. Twenty patients with 21 fusions could be investigated retrospectively. For evaluation we used self-assessment, clinical examination and radiographic analysis in combination with the score described by McGuire et al. [12]. In 80% the results were good and satisfactory with a median improvement of 23 score points on a scale of 100% 95 points, respectively. The most important advantages were pain relief and increase of walking distance. The fusion rate was 95%. We found osteoarthritis in the neighbouring joints did not have any influence on the surgical result. With respect to the two surgical techniques, the internal screw fixation method achieved fusion earlier with fewer complications and better improvement according to the McGuire score. Tibiotalar fusion is a safe therapy with reproducible good results involving pain relief, full weight-bearing and increase of walking distance. PMID:8861579

  14. Shock-Absorbent Ball-Screw Mechanism

    NASA Technical Reports Server (NTRS)

    Hirr, Otto A., Jr.; Meneely, R. W.

    1986-01-01

    Actuator containing two ball screws in series employs Belleville springs to reduce impact loads, thereby increasing life expectancy. New application of springs increases reliability of equipment in which ball screws commonly used. Set of three springs within lower screw of ball-screw mechanism absorbs impacts that result when parts reach their upper and lower limits of movement. Mechanism designed with Belleville springs as shock-absorbing elements because springs have good energy-to-volume ratio and easily stacked to attain any stiffness and travel.

  15. Automated surgical screwdriver: automated screw placement.

    PubMed

    Thomas, R L; Bouazza-Marouf, K; Taylor, G J S

    2008-07-01

    The use of power screwdrivers and drills for tapping and screw insertion in surgery is becoming more common. It has been established from clinical observations that the use of a small air drill for inserting self-tapping screws provides improved coaxial alignment and precision, and that the drill should be stopped before the screw head is completely seated on the plate, presumably to reduce the risk of over-tightening. The risk of overrun and over-tightening during tapping and screw insertion is increased with the use of power tools. Prevention of over-tightening is dependent upon when the surgeon detects the onset of tightening, both visually and from the feel of the rapid increase in torque. If detection is too late, then over-tightening or stripping can occur. This study is concerned with using a mechatronic screwdriver to control the tapping depth and to prevent the over-tightening of screws. The effects of various parameters upon the torque profile during tapping and screw insertion have been investigated in synthetic bone and sheep tibia. An automated system is proposed for preventing over-tightening of pre-tapped and self-tapping screws when attaching a surgical plate to a sheep tibia in vitro. The system was used to attach a plate to a sheep tibia using self-tapping screws. The mean torque of the screws inserted using the automated system was 35 per cent of the stripping torque. PMID:18756698

  16. Freehand Thoracic Pedicle Screw Placement: Review of Existing Strategies and a Step-by-Step Guide Using Uniform Landmarks for All Levels

    PubMed Central

    Baaj, Ali A

    2016-01-01

    Pedicle screw fixation in the thoracic spine presents certain challenges due to the critical regional neurovascular anatomy as well as the narrow pedicular corridor that typically exists. With increased awareness of the dangers of intraoperative radiation, the ability to place pedicle screws with anatomic landmarks alone is paramount. In this study, we reviewed the literature from 1990 to 2015 for studies that included freehand pedicle screw placement in the thoracic spine with special emphasis on entry points and the trajectories of the screws. We excluded studies that used fluoroscopy guidance, navigation techniques, cadaveric and biomechanical articles, case reports, and experimental studies on animals. The search retrieved 40 articles, and after careful selection, seven articles were analyzed. Over 8,000 screws were placed in the different studies. The mean accuracy for placement of the thoracic screws was 93.3%. However, there is little consensus between studies in entry points, sagittal, and axial trajectories of the screws. We complete this review by presenting our step-by-step technique for the placement of freehand pedicle screws in the thoracic spine. PMID:27014535

  17. Photographic fixative poisoning

    MedlinePLUS

    Photographic developer poisoning; Hydroquinone poisoning; Quinone poisoning; Sulfite poisoning ... Hydroquinones Quinones Sodium thiosulfate Sodium sulfite/bisulfite Boric acid Photographic fixative can also break down (decompose) to form sulfur ...

  18. Assessment of the RIVET fixation system for cranioplasty using the pull-out technique.

    PubMed

    Sakamoto, Yoshiaki; Minabe, Toshiharu; Kato, Tatsuya; Kishi, Kazuo

    2015-03-01

    Cranioplasty using custom-made hydroxyapatite (HAP) ceramic implants is a common procedure to repair skull defects. However, commercially available titanium screws are only minimally stabilized due to characteristic brittleness. We developed the RIVET technique which involves fixing a bioabsorbable plate atop a HAP block using bioabsorbable screws extending beyond both layers, and evaluated fixation strength using the pull-out test and microtomography. Three experimental conditions were compared: a non-RIVET group, RIVET group, and dry skull control group. Pull-out strength significantly differed across groups (non-RIVET group, 1.33 1.21 kgf; RIVET group, 4.46 0.84 kgf; and control group, 6.99 1.14 kgf, P < 0.01). Microtomography of the dry skull control group revealed thread grooves fitted to the screws. The non-RIVET and RIVET groups presented fewer thread grooves than the control group, and the screws did not fit perfectly to the HAP block. However, fixation in the RIVET group was more stable, as the rivet was firmly lodged into the implant. In conclusion, by melting and creating the rivet, pull-out strength can be increased and rigid stabilization of HAP can be obtained. This technique uses commercially available absorbable plate and screws, and thus can be used widely in clinical applications involving HAP blocks with different porosities and thicknesses. PMID:25555895

  19. Assessment of sagittal split ramus osteotomy rigid internal fixation techniques using a finite element method.

    PubMed

    Albougha, S; Darwich, K; Darwich, M A; Albogha, M H

    2015-07-01

    In this study, finite element analysis (FEA) was used to evaluate nine rigid internal fixation techniques for sagittal split ramus osteotomy. To achieve this, a computed tomography (CT) scan of a healthy patient was obtained and used to generate the geometry of a half-mandible. The geometries of bicortical screws, miniplates, and monocortical screws were designed and combined with the mandible in nine models simulating various techniques. Four models used bicortical screws in various arrangements and four used miniplates of various designs. One model represented a hybrid technique. A load of 500 N was applied to the posterior teeth and FEA was applied. The most stable techniques were the hybrid technique and a single straight miniplate, presenting the least displacement among all models. Bicortical screws, while presenting reasonable stability, showed high strain areas near the anterior ramus ridge, superoposterior to the screws, implying a risk of bone fracture in this area. On the other hand, the T-shaped and double Y-shaped miniplates were associated with high von Mises stresses that would impair their rigidity, especially where angles appeared in their designs. We recommend the use of a single straight miniplate because it provides sufficient stable fixation with minimal risks or disadvantages. PMID:25766461

  20. Analysis of the osseous/metal interface of drill free screws and self-tapping screws.

    PubMed

    Heidemann, Wolfgang; Terheyden, Hendrik; Louis Gerlach, Klaus

    2001-04-01

    Aim: A comparison of metal/osseous interface and bone remodelling after insertion of different types of titanium bone screws in vivo. Material: Samples of five of each of the following bone screw types were inserted into the anterior wall of the frontal sinus of five Gttingen minipigs: self-tapping micro- (1.5 mm) and miniscrews (2.0 mm) or drill free micro- (1.5 mm) and miniscrews (2.0 mm) (Martin Medizintechnik, Tuttlingen, Germany). Screw length was 7 mm. Methods: Sequential intraperitoneal injections of fluorochromes were performed between the second and ninth postoperative week. After 6 months the pigs were sacrificed, the screw-bone-blocks resected, and microradiographic, histological and fluorescence microscopical examinations were carried out. Results: Using drill free screws, mean screw/bone contact was 88.4% (miniscrews), or 93.8% (microscrews). With self-tapping miniscrews it was 54.9%, but in microscrews 81%; the differences were statistically significant (t -test: p<0.05). By fluorescence microscopy, the amount of bone remodelling (ratio of residual vs. newly formed bone) was measured. Significantly more of the residual bone was found in the region of the screw threads using drill free screws (miniscrews: mean 71.8%, microscrews: mean 67.9%) than in the region of screw threads with self-tapping screws (miniscrews: mean 33.1%, microscrews: mean 42.4%). Conclusion: The present data support the view that screw/bone contact with drill free screws was superior to that of self-tapping screws; the greater amount of original bone in the threads of drill free screws demonstrated that the insertion of drill free screws did not cause harm to the surrounding bone. Both results are important for osteosynthesis in regions where thin cortical bone is present, such as the central midface. Copyright 2001 European Association for Cranio-Maxillofacial Surgery. PMID:11308282

  1. Navigated pedicle screw placement using computed tomographic data in dorsolumbar fractures

    PubMed Central

    Kapoor, Saurabh; Sharma, Rajbahadur; Garg, Sudhir; Jindal, Rohit; Gupta, Ravi; Goe, Anshul

    2014-01-01

    Background: Computed tomographic (CT) based navigation is a technique to improve the accuracy of pedicle screw placement. It is believed to enhance accuracy of pedicle screw placement, potentially avoiding complications arising due to pedicle wall breach. This study aims to assess the results of dorsolumbar fractures operated by this technique. Materials and Methods: Thirty consecutive skeletally mature patients of fractures of dorsolumbar spine (T9L5) were subjected to an optoelectronic navigation system. All patients were thoroughly examined for neurological deficit. The criterion for instability were either a tricolumnar injury or presence of neurological deficit or both. Patients with multilevel fractures and distorted spine were excluded from study. Time taken for insertion of each pedicle screw was recorded and placement assessed with a postoperative CT scan using Laine's grading system. Results: Only one screw out of a total of 118 screws was misplaced with a Laine's Grade 5 placement, showing a misplacement rate of 0.847%. Average time for matching was 7.8 min (range 5-12 min). Average time taken for insertion of a single screw was 4.19 min (range 2-8 min) and total time for all screws after exposure was 34.23 min (range 24-45 min) for a four screw construct. No neurovascular complications were seen in any of the patients postoperatively and in subsequent followup of 1-year duration. Conclusion: CT-based navigation is effective in improving accuracy of pedicle screw placement in traumatic injuries of dorsolumbar spine (T9-L5), however additional cost of procuring CT scan to the patient and cost of equipment is of significant concern in developing countries. Reduced radiation exposure and lowered ergonomic constraints around the operation table are its additional benefits. PMID:25404766

  2. Negative pressure wound therapy and external fixation device: a simple way to seal the dressing.

    PubMed

    Bulla, Antonio; Farace, Francesco; Uzel, Andr-Pierre; Casoli, Vincent

    2014-07-01

    Negative pressure therapy is widely applied to treat lower limb trauma. However, sealing a negative pressure dressing in the presence of an external fixation device may be difficult and time consuming. Therefore, screws, pins, wires, etc, may preclude the vacuum, preventing the plastic drape to perfectly adhere to the foam. To maintain the vacuum, we tried to prevent air leaking around the screws putting bone wax at the junction between the pins and the plastic drape. This solution, in our hands, avoids air leakage and helps maintain vacuum in a fast and inexpensive way. PMID:24296597

  3. Minimally invasive rapid palatal expansion with an implant-supported hyrax screw.

    PubMed

    Harzer, Winfried; Reusser, Lars; Hansen, Lars; Richter, Rene; Nagel, Thomas; Tausche, Eve

    2010-02-01

    Rapid palatal expansion is indicated in the orthopedic treatment of transverse maxillary deficiency for correction of severe crossbite. The fixation of the appliance at the tooth crowns leads to more tipping connected with resorptions at the buccal cortical bone, fenestrations and gingival retraction. The aim of the present study was focused on the improvement of bodily movement and optimization of the surgical osteotomy (Glassman's technique) in adult patients with application of the Dresden Distractor (DD). In 18 patients, the new method with a special mechanism of adaptation involving minimized surgical intervention and direct fixation of the hyrax screw by one implant and one bone screw was tested. The implants were loaded directly by activation of the hyrax screw two times per day. CT scans were taken before and 6 months after insertion of the DD. In the horizontal and vertical planes there was a V-shaped opening of the suture in anterior and cranial direction, corroborating previous studies. Dental arch also showed this V-shape, indicating tooth protection. DD is a suitable minimally invasive tooth-independent bone-borne expansion method, protecting teeth and causing skeletal as well as dental effect with tipping reduced by 10 degrees. PMID:20128744

  4. Only fixation for lumbar canal stenosis: Report of an experience with seven cases

    PubMed Central

    Goel, Atul

    2014-01-01

    Study Design and Objective: The author reports experience with treatment of degenerative lumbar canal stenosis that involved fixation-arthrodesis of the affected spinal segment using double insurance transarticular screws for each joint. No direct bone, ligament or disc resection is done for decompression of the spinal dural tube or root canal. Methods and Summary of Background Data: During the period March 2011-September 2011, seven patients having lumbar canal stenosis were treated with a modification of transarticular method of screw fixation that involved insertion of two or double insurance screws at each articular joint. The operation involved section of the spinous process at its base, opening up of the facet joint, denuding of articular cartilage, insertion of intra-articular bone graft and insertion of two transarticular screws at each facet joint. The fixation was done in four levels in two patients, at three levels in four patients and at two levels in one patient. Oswestry disability index and visual analog scale were used to clinically assess the patients before and after the surgery and at follow-up. Results: During the average period of follow-up of 26.9 months (range 24-30 months), there was varying degree of recovery of symptoms. The procedure resulted in firm stabilization and fixation of the spinal segment and provided a ground for arthrodesis. During the period of follow-up, one patient underwent re-exploration and decompressive laminectomy as she continued to have significant pain symptom. Conclusions: Vertical instability and telescoping, listhesis or overriding of the facets on physical activity seems to be the defining phenomenon in the pathogenesis of lumbar canal stenosis. The clinical outcome in our patients suggest that fixation of the spinal segment can be a rationale form of treatment. Double insurance transarticular method of treatment is a simple, safe, and effective method of spinal stabilization. PMID:25013342

  5. Degradation behaviour of LAE442-based plate-screw-systems in an in vitro bone model.

    PubMed

    Wolters, Leonie; Besdo, Silke; Angrisani, Nina; Wriggers, Peter; Hering, Britta; Seitz, Jan-Marten; Reifenrath, Janin

    2015-04-01

    The use of absorbable implant materials for fixation after bone fracture helps to avoid a second surgery for implant removal and the risks and costs involved. Magnesium (Mg) is well known as a potential metallic material for degradable implants. The aim of the present in vitro study was to evaluate if degradable LAE442-based magnesium plate-screw-systems are suitable candidates for osteosynthesis implants in load-bearing bones. The corrosion behaviour was tested concerning the influence of different surface treatments, coatings and screw torques. Steel plates and screws of the same size served as control. Plates without special treatment screwed on up to a specified torque of 15cNm or 7cNm, NaOH treated plates (15cNm), magnesium fluoride coated plates (15cNm) and steel plates as control (15cNm) were examined in pH-buffered, temperature-controlled SBF solution for two weeks. The experimental results indicate that the LAE442 plates and screws coated with magnesium fluoride revealed a lower hydrogen evolution in SBF solution as well as a lower weight loss and volume decrease in ?-computed tomography (?CT). The nanoindentation and SEM/EDX measurements at several plate areas showed no significant differences. Summarized, the different screw torques did not affect the corrosion behaviour differently. Also the NaOH treatment seemed to have no essential influence on the degradation kinetics. The plates coated with magnesium fluoride showed a decreased corrosion rate. Hence, it is recommended to consider this coating for the next in vivo study. PMID:25686954

  6. Experimental results of single screw mechanical tests: a follow-up to SAND2005-6036.

    SciTech Connect

    Lee, Sandwook; Lee, Kenneth L.; Korellis, John S.; McFadden, Sam X.

    2006-08-01

    The work reported here was conducted to address issues raised regarding mechanical testing of attachment screws described in SAND2005-6036, as well as to increase the understanding of screw behavior through additional testing. Efforts were made to evaluate fixture modifications and address issues of interest, including: fabrication of 45{sup o} test fixtures, measurement of the frictional load from the angled fixture guide, employment of electromechanical displacement transducers, development of a single-shear test, and study the affect of thread start orientation on single-shear behavior. A286 and 302HQ, No.10-32 socket-head cap screws were tested having orientations with respect to the primary loading axis of 0{sup 0}, 45{sup o}, 60{sup o}, 75{sup o} and 90{sup o} at stroke speeds 0,001 and 10 in/sec. The frictional load resulting from the angled screw fixture guide was insignificant. Load-displacement curves of A286 screws did not show a minimum value in displacement to failure (DTF) for 60{sup o} shear tests. Tests of 302HQ screws did not produce a consistent trend in DTF with load angle. The effect of displacement rate on DTF became larger as shear angle increased for both A286 and 302HQ screws.

  7. Fibular fixation as an adjuvant to tibial intramedullary nailing in the treatment of combined distal third tibia and fibula fractures: a biomechanical investigation

    PubMed Central

    Morin, Paul M.; Reindl, Rudolf; Harvey, Edward J.; Beckman, Lorne; Steffen, Thomas

    2008-01-01

    Objective Distal third tibia fractures have classically been treated with standard plating, but intramedullary (IM) nailing has gained popularity. Owing to the lack of interference fit of the nail in the metaphyseal bone of the distal tibia, it may be beneficial to add rigid plating of the fibula to augment the overall stability of fracture fixation in this area. This study sought to assess the biomechanical effect of adding a fibular plate to standard IM nailing in the treatment of distal third tibia and fibula fractures. Methods Eight cadaveric tibia specimens were used. Tibial fixation consisted of a solid titanium nail locked with 3 screws distally and 2 proximally, and fibular fixation consisted of a 3.5 mm low-contact dynamic compression plate. A section of tibia and fibula was removed. Testing was accomplished with an MTS machine. Each leg was tested 3 times; with and without a fibular plate and with a repetition of the initial test condition. Vertical displacements were tested with an axial load up to 500 N, and angular rotation was tested with torques up to 5 Nm. Results The difference in axial rotation was the only statistically significant finding (p = 0.003), with fibular fixation resulting in 1.1 less rotation through the osteotomy site (17.96 v. 19.10). Over 35% of this rotational displacement occurred at the naillocking bolt interface with the application of small torsional forces. Conclusion Fibular plating in addition to tibial IM fixation of distal third tibia and fibula fractures leads to slightly increased resistance to torsional forces. This small improvement may not be clinically relevant. PMID:18248705

  8. Dynamic Hip Screw for the Treatment of Femoral Neck Fractures: A Prospective Study with 96 Patients

    PubMed Central

    Schwartsmann, Carlos Roberto; Jacobus, Lucas Senger; Spinelli, Leandro de Freitas; Boschin, Leonardo Carbonera; Gonalves, Ramiro Zilles; Ypez, Anthony Kerbes; Barreto, Rodrigo Py Gonalves; Silva, Marcelo Faria

    2014-01-01

    Objectives. To study the correlation between avascular necrosis and the demographics, time elapsed from fracture to surgery, quality of reduction, Garden classification, and the position of the screw following use of the dynamic hip screw (DHS) in the treatment of subcapital neck fractures. Methods. A prospective study of 96 patients with subcapital neck fractures was carried out in a faculty hospital. Patients underwent surgery with closed reduction and internal fixation with DHS. Results. There were 58% male and 42% female patients, with a mean age of 53 years (+/?14). In terms of Garden classification, 60% were Garden IV, 26% were Garden III, and 14% were Garden II. Nonunion was observed in three cases (3%) and was treated with valgus intertrochanteric osteotomy, in all cases leading to successful healing. Avascular necrosis was observed in 16% of patients. The positioning of the screw into the femoral head showed a significant correlation with necrosis. Conclusions. The incidence of necrosis in patients under the age of 50 years is twice as high as that in older patients. Displacement is a predictive factor regarding osteonecrosis and is associated with a high and anterior position of the screw in the femoral head. Level II of evidence. Study Type: therapeutic study. PMID:24967124

  9. The treatment of fractures with a dynamic axial fixator.

    PubMed

    De Bastiani, G; Aldegheri, R; Renzi Brivio, L

    1984-08-01

    The results obtained with a lightweight dynamic axial fixator in the treatment of fractures are reported. The apparatus comprises a single bar with articulating ends which clamp self-tapping screws and can be locked at an angle appropriate for axial alignment. A telescopic facility allows ready conversion from rigid to dynamic fixation once periosteal callus formation has commenced. Reduction and controlled distraction or compression are achieved by means of a detachable compressor unit. We treated 288 patients with fresh fractures and 50 with ununited fractures. The success rate for fresh fractures was 94%, with average healing times ranging from 3.4 to 6.5 months. In ununited fractures also, the success rate was 94% with average healing times ranging from 4.7 to 6.5 months. Complications were minimal. The device is versatile and can be applied in an average of 15 minutes. It permits ambulatory fracture care without sacrificing a sound anatomical result. PMID:6746689

  10. [Progress on treatment of transverse patella fractures with tension band fixation].

    PubMed

    Yu, Xiu-ling; Xu, Chao; Li, Shun-dong; Zhan, Jian-dong; Xu, Zai-qiang

    2015-11-01

    Transverse fracture is the most common in patella fracture and tension band fixation is one of the most effective methods. Surgical wire tension band technique is simple, the use of materials is also simple, but it is not strong and difficult to promote. Kirschner tension band technique can get satisfactory reduction with reliable fixation, but it is easy to complicate with steel wire breakage and Kirschner loosening. Screw tension band technique inherits the traditional advantages of simple manipulation and reliable fixation, also overcomes the disadvantages of early activity limitations caused soft tissue irritation of tension band around knee, the slippage and breakage of internal fixation, and the technique can be popularized generally. PMID:26757540

  11. [Internal fixation of radial shaft fractures: Anatomical and biomechanical principles].

    PubMed

    Barton?ek, J; Na?ka, O; Tu?ek, M

    2015-10-01

    Radius is a critical bone for functioning of the forearm and therefore its reconstruction following fracture of its shaft must be anatomical in all planes and along all axes. The method of choice is plate fixation. However, it is still associated with a number of unnecessary complications that were not resolved even by introduction of locking plates, but rather the opposite. All the more it is surprising that discussions about anatomical and biomechanical principles of plate fixation have been reduced to minimum or even neglected in the current literature. This applies primarily to the choice of the surgical approach, type of plate, site of its placement and contouring, its working length, number of screws and their distribution in the plate. At the same time it has to be taken into account that a plate used to fix radius is exposed to both bending and torsion stress. Based on our 30-year experience and analysis of literature we present our opinions on plate fixation of radial shaft fractures:We always prefer the volar Henry approach as it allows expose almost the whole of radius, with a minimal risk of injury to the deep branch of the radial nerve.The available studies have not so far found any substantial advantage of LCP plates as compared to 3.5mm DCP or 3.5mm LC DCP plates, quite the contrary. The reason is high rigidity of the locking plates, a determined trajectory of locking screws which is often unsuitable, mainly in plates placed on the anterior surface of the shaft, and failure to respect the physiological curvature of the radius. Therefore based on our experience we prefer "classical" 3.5mm DCP plates.Volar placement of the plate, LCP in particular, is associated with a number of problems. The volar surface covered almost entirely by muscles, must be fully exposed which negatively affects blood supply to the bone. A straight plate, if longer, either lies with its central part partially off the bone and overlaps the interosseous border, or its ends overhang the bone laterally. In a locking plate with a fixed determined trajectory of screws, the locking screws in the central holes of the plate pass off the shaft centre only through a thin interosseous border (medial position), or screws at the ends of the plate are inserted eccentrically (lateral position). Both these techniques reduce stability of internal fixation. Where the plate overlaps the interosseous border, it is difficult to control the mutual rotation of the two main fragments. A shorter LCP plate increases rigidity of fixation, suppresses bone healing and often leads to non-union.Placement of the plate on the lateral surface of the radius is more beneficial from the viewpoint of the bending and torsion stress. Lateral surface of the radius is a tension site, its distal half is not covered by muscles which eliminates the necessity to release them, the interosseous border is not obscured by plate and all this allows a safe control of rotational position of fragments. A properly pre-bent plate follows the physiological curvature of the lateral surface of the radius. Full tightening of standard screws will fix both main fragments firmly to the apex of plate concavity and increase stability of the internal fixation. Due to the shape of the cross-section of the radial shaft, the trajectory of screws is the longest in case of lateral placement of the plate, which increases rotational stability.We place the plate always in a minimal three-hole length on each main fragment. Transverse two-fragment fractures may be fixed with a 2+2 configuration, i.e. with two screws on each main fragment. Fractures with an inter-fragment or comminuted zone are fixed in the 3+3 mode. More extensive comminutions, defects or segmental fractures require 4 plate holes on each fragment, but not more. When drilling screw holes the drill must be directed into the interosseous border. As a result, the screw has the longest trajectory and the best fixation in the bone. Perforation of the anterior or posterior surface of the radius considerably shortens the trajectory of the

  12. Extraforaminal lumbar interbody fusion for cage migration after screw removal: a case report.

    PubMed

    Kim, Myung Hoon; Kim, Seok Won; Kim, Sung Hoon; Kim, Hyeun Sung

    2013-06-01

    The use of titanium cages for posterior lumbar interbody fusion (PLIF) has gained popularity because it offers the advantages of anterior column support and stabilization. However, cage migration into the spinal canal may have severe or disastrous consequences. Here, the authors report an unexpected case of posterior migration of fusion cages after screw removal in a patient that underwent PLIF 12 months previously. Removal of the offending cages through revision extraforaminal lumbar interbody fusion (ELIF) with percutaneous screw fixation successfully managed this complication. As far as the authors' knowledge, this is the first case report to describe this sort of complication, and cautions that care must be taken to prevent cage migration. PMID:24757471

  13. Improving Carbon Fixation Pathways

    PubMed Central

    Ducat, Daniel C.

    2012-01-01

    A recent resurgence in basic and applied research on photosynthesis has been driven in part by recognition that fulfilling future food and energy requirements will necessitate improvements in crop carbon-fixation efficiencies. Photosynthesis in traditional terrestrial crops is being reexamined in light of molecular strategies employed by photosynthetic microbes to enhance the activity of the Calvin cycle. Synthetic biology is well-situated to provide original approaches for compartmentalizing and enhancing photosynthetic reactions in a species independent manner. Furthermore, the elucidation of alternative carbon-fixation routes distinct from the Calvin cycle raises possibilities that alternative pathways and organisms can be utilized to fix atmospheric carbon dioxide into useful materials. PMID:22647231

  14. Improving carbon fixation pathways

    SciTech Connect

    Ducat, DC; Silver, PA

    2012-08-01

    A recent resurgence in basic and applied research on photosynthesis has been driven in part by recognition that fulfilling future food and energy requirements will necessitate improvements in crop carbon-fixation efficiencies. Photosynthesis in traditional terrestrial crops is being reexamined in light of molecular strategies employed by photosynthetic microbes to enhance the activity of the Calvin cycle. Synthetic biology is well-situated to provide original approaches for compartmentalizing and enhancing photosynthetic reactions in a species independent manner. Furthermore, the elucidation of alternative carbon-fixation routes distinct from the Calvin cycle raises possibilities that novel pathways and organisms can be utilized to fix atmospheric carbon dioxide into useful materials.

  15. The development and evaluation of individualized templates to assist transoral C2 articular mass or transpedicular screw placement in TARP-IV procedures: adult cadaver specimen study

    PubMed Central

    Li, Xue-Shi; Wu, Zeng-Hui; Xia, Hong; Ma, Xiang-Yang; Ai, Fu-Zhi; Zhang, Kai; Wang, Jian-Hua; Mai, Xiao-Hong; Yin, Qing-Shui

    2014-01-01

    OBJECTIVES: The transoral atlantoaxial reduction plate system treats irreducible atlantoaxial dislocation from transoral atlantoaxial reduction plate-I to transoral atlantoaxial reduction plate-III. However, this system has demonstrated problems associated with screw loosening, atlantoaxial fixation and concealed or manifest neurovascular injuries. This study sought to design a set of individualized templates to improve the accuracy of anterior C2 screw placement in the transoral atlantoaxial reduction plate-IV procedure. METHODS: A set of individualized templates was designed according to thin-slice computed tomography data obtained from 10 human cadavers. The templates contained cubic modules and drill guides to facilitate transoral atlantoaxial reduction plate positioning and anterior C2 screw placement. We performed 2 stages of cadaveric experiments with 2 cadavers in stage one and 8 in stage two. Finally, guided C2 screw placement was evaluated by reading postoperative computed tomography images and comparing the planned and inserted screw trajectories. RESULTS: There were two cortical breaching screws in stage one and three in stage two, but only the cortical breaching screws in stage one were ranked critical. In stage two, the planned entry points and the transverse angles of the anterior C2 screws could be simulated, whereas the declination angles could not be simulated due to intraoperative blockage of the drill bit and screwdriver by the upper teeth. CONCLUSIONS: It was feasible to use individualized templates to guide transoral C2 screw placement. Thus, these drill templates combined with transoral atlantoaxial reduction plate-IV, may improve the accuracy of transoral C2 screw placement and reduce related neurovascular complications. PMID:25518033

  16. Screw-released roller brake

    NASA Technical Reports Server (NTRS)

    Vranish, John M. (Inventor)

    1999-01-01

    A screw-released roller brake including an input drive assembly, an output drive assembly, a plurality of locking sprags, a mechanical tripper nut for unlocking the sprags, and a casing therefor. The sprags consist of three dimensional (3-D) sprag members having pairs of contact surface regions which engage respective pairs of contact surface regions included in angular grooves or slots formed in the casing and the output drive assembly. The sprags operate to lock the output drive assembly to the casing to prevent rotation thereof in an idle mode of operation. In a drive mode of operation, the tripper is either self actuated or motor driven and is translated linearly up and down against a spline and at the limit of its travel rotates the sprags which unlock while coupling the input drive assembly to the output drive assembly so as to impart a turning motion thereto in either a clockwise or counterclockwise direction.

  17. Visualization and understanding of the granulation liquid mixing and distribution during continuous twin screw granulation using NIR chemical imaging.

    PubMed

    Vercruysse, Jurgen; Toiviainen, Maunu; Fonteyne, Margot; Helkimo, Niko; Ketolainen, Jarkko; Juuti, Mikko; Delaet, Urbain; Van Assche, Ivo; Remon, Jean Paul; Vervaet, Chris; De Beer, Thomas

    2014-04-01

    Over the last decade, there has been increased interest in the application of twin screw granulation as a continuous wet granulation technique for pharmaceutical drug formulations. However, the mixing of granulation liquid and powder material during the short residence time inside the screw chamber and the atypical particle size distribution (PSD) of granules produced by twin screw granulation is not yet fully understood. Therefore, this study aims at visualizing the granulation liquid mixing and distribution during continuous twin screw granulation using NIR chemical imaging. In first instance, the residence time of material inside the barrel was investigated as function of screw speed and moisture content followed by the visualization of the granulation liquid distribution as function of different formulation and process parameters (liquid feed rate, liquid addition method, screw configuration, moisture content and barrel filling degree). The link between moisture uniformity and granule size distributions was also studied. For residence time analysis, increased screw speed and lower moisture content resulted to a shorter mean residence time and narrower residence time distribution. Besides, the distribution of granulation liquid was more homogenous at higher moisture content and with more kneading zones on the granulator screws. After optimization of the screw configuration, a two-level full factorial experimental design was performed to evaluate the influence of moisture content, screw speed and powder feed rate on the mixing efficiency of the powder and liquid phase. From these results, it was concluded that only increasing the moisture content significantly improved the granulation liquid distribution. This study demonstrates that NIR chemical imaging is a fast and adequate measurement tool for allowing process visualization and hence for providing better process understanding of a continuous twin screw granulation system. PMID:24211658

  18. The Fixation of Nitrogen.

    ERIC Educational Resources Information Center

    Andrew, S. P. S.

    1978-01-01

    Discusses the fixation of atmospheric nitrogen in the form of ammonia as one of the foundations of modern chemical industry. The article describes ammonia production and synthesis, purifying the hydrogen-nitrogen mix, nitric acid production, and its commericial plant. (HM)

  19. Update: Biological Nitrogen Fixation.

    ERIC Educational Resources Information Center

    Wiseman, Alan; And Others

    1985-01-01

    Updates knowledge on nitrogen fixation, indicating that investigation of free-living nitrogen-fixing organisms is proving useful in understanding bacterial partners and is expected to lead to development of more effective symbioses. Specific areas considered include biochemistry/genetics, synthesis control, proteins and enzymes, symbiotic systems,…

  20. Update: Biological Nitrogen Fixation.

    ERIC Educational Resources Information Center

    Wiseman, Alan; And Others

    1985-01-01

    Updates knowledge on nitrogen fixation, indicating that investigation of free-living nitrogen-fixing organisms is proving useful in understanding bacterial partners and is expected to lead to development of more effective symbioses. Specific areas considered include biochemistry/genetics, synthesis control, proteins and enzymes, symbiotic systems,

  1. Fixation produced by conflict.

    PubMed

    Karsh, E B

    1970-05-15

    All rats given a choice between a rewarded alternative and a conflict alternative (rewarded and punished) developed position fixations when the position of the alternatives was reversed. In contrast, all animals given one rewarded alternative and another nonrewarded (or punished and nonrewarded) alternative learned to choose the rewarded side during 25 successive reversals. PMID:5444066

  2. The biomechanics of guided growth: does screw size, plate size, or screw configuration matter?

    PubMed

    Schoenleber, Scott J; Iobst, Christopher A; Baitner, Avi; Standard, Shawn C

    2014-03-01

    Guided growth with the eight-plate is a commonly used technique to correct angular limb deformities in children. However, the optimal combination of plate size, screw size, and screw configuration has not been determined. Using osteotomized femoral sawbones and a rail frame, we developed a growth model to examine the effect of these variables at 6-month, 12-month, and 18-month growth increments. The mean annual coronal plane change was 11.3. Screw size and plate size were not associated with the rate of angular correction. Screw configuration was important, with parallel screws resulting in optimal correction at all time points compared with divergent screws (P<0.05). PMID:24322536

  3. [Tests for evaluating various methods of bone fixation in digital replantation].

    PubMed

    Jablecki, J; Kaczmarzyk, J; Kaczmarzyk, L; Orzechowski, P; Kocieba, R

    2000-01-01

    Clinical results comparing different methods of bony fixation in 50 replanted digits in a series of 41 patients over a 13 year period are presented. The analysis was restricted only to replantantions involving sharp amputations of the proximal phalanx in order to restrict this study to a relatively homogenous group of patients. Evaluated techniques included: single and crossed Kirschner wire, intraosseous wire with or without Kirschner wire support, intramedullary splintage and intramedullary screws. Angulation deformities and delayed union were most common in cases treated with Kirschner wire technique. Nonunion was noted in 1 case (2%) stabilized with a single Kirschner wire. Angulation deformities were noted in 6 cases (12%). No such complications were noted in cases treated with intramedullary splintage and intramedullary screws. The best stabilizing effect and the most rapid union was noted in cases treated with intramedullary screws. PMID:11388011

  4. Complications of Distal Radius Fixation.

    PubMed

    Lee, Dennis S; Weikert, Douglas R

    2016-04-01

    Complications following any form of distal radius fixation remain prevalent. With an armamentarium of fixation options available to practicing surgeons, familiarity with the risks of newer plate technology as it compares with other conventional methods is crucial to optimizing surgical outcome and managing patient expectations. This article presents an updated review on complications following various forms of distal radius fixation. PMID:26772950

  5. Rapid Two-Temperature Formalin Fixation

    PubMed Central

    Roberts, Esteban; Borlee, Grace; Otter, Michael; Baird, Geoffrey S.

    2013-01-01

    Formalin fixation is a mainstay of modern histopathologic analysis, yet the practice is poorly standardized and a significant potential source of preanalytical errors. Concerns of workflow and turnaround time drive interest in developing shorter fixation protocols, but rapid protocols can lead to poor histomorphology or inadequate downstream assay results. Additionally, assays such as immunohistochemistry for phosphorylated epitopes have historically been challenging in the context of formalin-fixed tissue, indicating that there may be room for improvement in this process that is fundamental to the practice of anatomic pathology. With these issues in mind, we studied basic formalin biochemistry to develop a novel formalin fixation protocol that involves a pre-incubation in subambient temperature formalin prior to a brief exposure to heated formalin. This new protocol is more rapid than standard protocols yet preserves histomorphology and yields tissue that is compatible with an expanded set of downstream clinical and research assays, including immunohistochemistry for phosphorylated epitopes. PMID:23349806

  6. Comparative endurance testing of the Biomet Matthews Nail and the Dynamic Compression Screw, in simulated condylar and supracondylar femoral fractures

    PubMed Central

    O'Connor-Read, Laurence M; Davidson, Jerome A; Davies, Benjamin M; Matthews, Michael G; Smirthwaite, Paul

    2008-01-01

    Background The dynamic compression screw is a plate and screws implant used to treat fractures of the distal femur. The Biomet Matthews Nail is a new retrograde intramedullary nail designed as an alternative surgical option to treat these fractures. The objective of this study was to assess the comparative endurance of both devices. Method The dynamic compression screw (DCS) and Biomet Matthews Nail (BMN) were implanted into composite femurs, which were subsequently cyclically loaded using a materials testing machine. Simulated fractures were applied to each femur prior to the application of load. Either a Y type fracture or a transverse osteotomy was prepared on each composite femur using a jig to enable consistent positioning of cuts. Results The Biomet Matthews Nail demonstrated a greater endurance limit load over the dynamic compression screw in both fracture configurations. Conclusion The distal locking screws pass through the Biomet Matthews Nail in a unique "cruciate" orientation. This allows for greater purchase in the bone of the femoral condyle and potentially improves the stability of the fracture fixation. As these fractures are usually in weak osteoporotic bone, the Biomet Matthews Nail represents a favourable surgical option in these patients. PMID:18208608

  7. The RIVET: a novel technique involving absorbable fixation for hydroxyapatite osteosynthesis.

    PubMed

    Shido, Hirokazu; Sakamoto, Yoshiaki; Miwa, Tomoru; Ohira, Takayuki; Yoshida, Kazunari; Kishi, Kazuo

    2013-05-01

    Cranioplasty using custom-made hydroxyapatite (HAP) ceramic implants is a common procedure for the repair of skull defects. The advantages of using HAP are that it is nonmetallic, unlike titanium; biocompatible; and osteoconductive. Furthermore, it can be molded to any complex shape that may be needed. A disadvantage is that titanium screws and plates are in development for its fixation. We developed a technique for implant fixation using bioabsorbable screws and plates, and named this technique RIVET: resorbable immobilization for vacuolar en bloc technique.Before each operation, the implant was customized for the patient in question on the basis of models prepared using computed tomography data. The bioabsorbable plates were attached to the implant by drilling, tapping, and screwing, as shown in the video (http://links.lww.com/SCS/A43). The interior portion of the screw was then melted to flatten it against the internal surface of the implant, forming a rivet to join the plate and HAP implant.We used this technique for cranial reconstruction in 2 patients, with satisfying and functional results. We did not encounter any complications.In conclusion, the technique described here allows surgeons to fix implants and plates together more rigidly, giving a better result than possible with previous methods. PMID:23714917

  8. Tool Preloads Screw and Applies Locknut

    NASA Technical Reports Server (NTRS)

    Wood, K. E.

    1982-01-01

    Special tool reaches through structural members inside Space Shuttle fasten nut on preloaded screw that holds thermal protection tile against outside skin of vehicle. Tool attaches tiles with accuratelycontrolled tensile loading.

  9. Can fixation instability improve text perception during eccentric fixation in patients with central scotomas?

    PubMed Central

    Druaz, A; Matter, M; Whatham, A R; Goldschmidt, M; Duret, F; Issenhuth, M; Safran, A B

    2004-01-01

    Background: Oculomotor behaviour was investigated in 14 patients with central scotomas from age related macular degeneration (AMD) or Stargardts disease. A scanning laser ophthalmoscope (SLO) was used to project letters and words onto the retina and to assess fixation behaviour. Five patients reported while deciphering letters that they needed to move their eye to prevent the image from vanishing. The observation of the SLO fundus images revealed that the gradual disappearance of the stimulus did not result from a transient projection of the word in the lesion. This prompted the authors to investigate, in an experimental setting, whether purposeful changes in fixation position could improve the perception of an eccentrically fixated text stimulus. Methods: Twenty normal subjects were asked to alternate fixation, every three to four seconds, between two vertically aligned dots, spaced 10 apart, and to report any changes in the perception of a laterally located letter, 1.5 in height, 7 apart and equidistant between the two fixation spots. Results: Nineteen subjects reported a transient refreshment of the letter image immediately after the realisation of a saccade. Improved perception lasted approximately a second. With persistent fixation, they noted a rapid fading effect that reduced letter recognition. Conclusion: These observations suggest that ocular instability during eccentric viewing can have a functional advantage, probably related to counteracting Troxlers phenomenon. In addition to alternating between PRLs, it appears that saccades related to fixation instability might be valuable and improve text perception in individuals with a central scotoma and eccentric fixation. This possibility should be taken into consideration when conducting visual rehabilitation procedures. PMID:15031154

  10. Extraction strength of cannulated cancellous bone screws.

    PubMed

    Hearn, T C; Schatzker, J; Wolfson, N

    1993-01-01

    The purpose of this study was to determine whether the alterations in the relative dimensions of thread and core diameter that accompany cannulation of cancellous bone screws affect their holding strength. The screws were inserted in bovine femoral cancellous bone and mounted in the load train of a materials testing system. They were then extracted under servo-hydraulic displacement control. The tests were repeated in synthetic cancellous material. From the corresponding load-displacement histories, the maximum force values attained were determined as the screws' holding strengths. The results of tests from 17 matched pairs of bovine femora, and of 15 tests of each screw in synthetic material, were recorded. No significant differences in extraction strength between 7.0-mm cannulated and 6.5-mm standard cancellous bone screws were found. Based on tests in the bovine femur and synthetic cancellous material, this study showed that the extraction strength of cancellous bone screws is not altered by the changes in thread-to-core ratio accommodating cannulation. PMID:8459298

  11. Optical and Exciton Dynamical Properties of a Screw-Dislocation-Driven ZnO:Sn Microstructure.

    PubMed

    Dai, Jun; Lu, Junfeng; Wang, Fang; Guo, Jiyuan; Gu, Ning; Xu, Chunxiang

    2015-06-17

    Screw dislocation plays a critical role in crystal growth and significantly affects the carrier dynamics process of luminescent semiconductor materials. In this paper, we report a novel screw-dislocation-induced ZnO:Sn hillock microstructure. The detailed growth process and possible formation mechanism of screw dislocation are demonstrated. The temperature-dependent photoluminescence reveals the free exciton recombination emission mechanism of the ZnO:Sn hillock microstructure. By comparing time-resolved photoluminescence spectra with those of two other samples without screw dislocations, it is found that the screw dislocation in the ZnO:Sn microstructures effectively decreases the carrier lifetime. In addition, UV Fabry-Perot lasing action is observed from the ZnO:Sn hillock microstructure, and the numerical simulation of the standing wave pattern and light intensity distribution further confirm the Fabry-Perot lasing mechanism. Therefore, ZnO:Sn can be utilized as a UV laser gain medium, and its optical properties can be modulated by screw dislocation. PMID:26011860

  12. External Fixation: Principles and Applications.

    PubMed

    Bible, Jesse E; Mir, Hassan R

    2015-11-01

    The modularity and ease of application of modern external fixation has expanded its potential use in the management of fractures and other musculoskeletal conditions. In fracture care, it can be used for provisional and definitive fixation. Short-term provisional applications include "damage control" and periarticular fracture fixation. The risk:benefit ratio of added stability needs to be assessed with each fixator. Soft-tissue management is critical during pin insertion to lessen the risk of loosening and infection. Although provisional fixation is safe for early conversion to definitive fixation, several factors affect the timing of definitive surgery, including the initial injury, external fixator stability, infection, and the physiologic state of the patient. PMID:26306568

  13. External Fixation combined with Limited Internal Fixation versus Open Reduction Internal Fixation for Treating Ruedi-Allgower Type III Pilon Fractures

    PubMed Central

    Guo, Yongzhi; Tong, Liangyong; Li, Shaoguang; Liu, Zhi

    2015-01-01

    Background The optimal treatment of type III pilon fractures remains controversial. Hence, we performed this study to investigate whether open reduction and internal fixation (ORIF) is superior to external fixations combined with limited internal fixations (EFLIF). Material/Methods From January 2012 to October 2013, a total of 78 patients were included. Twenty-six patients underwent EFLIF and 52 patients underwent ORIF. All subjects were followed up at 1, 3, 6, and 12 months postoperatively. All outcomes and complications were recorded. Results No statistical differences were observed in Mazur score or ROM between the 2 groups. There were significant differences between the 2 groups in hospital stay (P<0.001), reduction results (P=0.019), screw loosening (P=0.025), and traumatic arthritis (P=0.037). Conclusions Similar functional outcomes were achieved in EFLIF and ORIF groups. Due to several limitations of this study, a well-designed randomized controlled trial involving more patients and long-term follow-up is needed to find an optimal treatment protocol. PMID:26050786

  14. The Role of Minimally Invasive Plate Osteosynthesis in Rib Fixation: A Review.

    PubMed

    Bemelman, Michael; van Baal, Mark; Yuan, Jian Zhang; Leenen, Luke

    2016-02-01

    More than a century ago, the first scientific report was published about fracture fixation with plates. During the 1950's, open reduction and plate fixation for fractures were standardized by the founders of Arbeitsgemeinschaft für osteosynthesefragen/Association for the Study of Internal Fixation. Since the introduction of plate fixation for fractures, several plates and screws have been developed, all with their own characteristics. To accomplice more fracture stability, it was thought the bigger the plate, the better. The counter side was a compromised blood supply of the bone, often resulting in bone necrosis and ultimately delayed or non-union. With the search and development of new materials and techniques for fracture fixation, less invasive procedures have become increasingly popular. This resulted in the minimally invasive plate osteosynthesis (MIPO) technique for fracture fixation. With the MIPO technique, procedures could be performed with smaller incisions and thus with less soft tissue damage and a better preserved blood supply. The last 5 years rib fixation has become increasingly popular, rising evidence has become available suggesting that surgical rib fixation improves outcome of patients with a flail chest or isolated rib fractures. Many surgical approaches for rib fixation have been described in the old literature, however, most of these techniques are obscure nowadays. Currently mostly large incisions with considerable surgical insult are used to stabilize rib fractures. We think that MIPO deserves a place in the surgical treatment of rib fractures. We present the aspects of diagnosis, preoperative planning and operative techniques in regard to MIPO rib fixation. PMID:26889439

  15. The Role of Minimally Invasive Plate Osteosynthesis in Rib Fixation: A Review

    PubMed Central

    Bemelman, Michael; van Baal, Mark; Yuan, Jian Zhang; Leenen, Luke

    2016-01-01

    More than a century ago, the first scientific report was published about fracture fixation with plates. During the 1950’s, open reduction and plate fixation for fractures were standardized by the founders of Arbeitsgemeinschaft für osteosynthesefragen/Association for the Study of Internal Fixation. Since the introduction of plate fixation for fractures, several plates and screws have been developed, all with their own characteristics. To accomplice more fracture stability, it was thought the bigger the plate, the better. The counter side was a compromised blood supply of the bone, often resulting in bone necrosis and ultimately delayed or non-union. With the search and development of new materials and techniques for fracture fixation, less invasive procedures have become increasingly popular. This resulted in the minimally invasive plate osteosynthesis (MIPO) technique for fracture fixation. With the MIPO technique, procedures could be performed with smaller incisions and thus with less soft tissue damage and a better preserved blood supply. The last 5 years rib fixation has become increasingly popular, rising evidence has become available suggesting that surgical rib fixation improves outcome of patients with a flail chest or isolated rib fractures. Many surgical approaches for rib fixation have been described in the old literature, however, most of these techniques are obscure nowadays. Currently mostly large incisions with considerable surgical insult are used to stabilize rib fractures. We think that MIPO deserves a place in the surgical treatment of rib fractures. We present the aspects of diagnosis, preoperative planning and operative techniques in regard to MIPO rib fixation. PMID:26889439

  16. CARBON DIOXIDE FIXATION.

    SciTech Connect

    FUJITA,E.

    2000-01-12

    Solar carbon dioxide fixation offers the possibility of a renewable source of chemicals and fuels in the future. Its realization rests on future advances in the efficiency of solar energy collection and development of suitable catalysts for CO{sub 2} conversion. Recent achievements in the efficiency of solar energy conversion and in catalysis suggest that this approach holds a great deal of promise for contributing to future needs for fuels and chemicals.

  17. Biomechanical comparison of internal fixation techniques for the Akin osteotomy of the proximal phalanx.

    PubMed

    Chacon, Yolanda; Fallat, Lawrence M; Dau, Nathan; Bir, Cynthia

    2012-01-01

    The Akin osteotomy is performed at the proximal phalanx for correction of an abducted great toe in a hallux abducto valgus deformity. Several internal fixation techniques have been widely advocated; however, their respective stabilities have not been compared. A biomechanical analysis was performed comparing 5 commonly used fixation techniques for the Akin osteotomy to determine the strongest method in simulated weightbearing in sawbone models. An Akin osteotomy was uniformly performed on 25 sawbones and fixated with 5 different internal fixation types, including a 2-hole locking plate and locking screws, a heat-sensitive memory staple (8 mm 8 mm), a 28-gauge monofilament wire, 2.7-mm bicortical screws, and crossed 0.062-in. Kirschner wires. The results of simulated weightbearing load to failure rates with an Instron compression device demonstrated the following mean load to failures: crossed Kirschner wire, 57.05 N; 2-hole locking plate, 36.49 N; monofilament wire, 35.69 N; heat-sensitive memory staple, 34.32 N; and 2.7-mm bicortical screw, 13.66 N. Statistical analysis demonstrated the crossed Kirschner wire technique performed significantly better than the other fixation techniques (p < .007); the 4 other techniques were found not to be significantly different statistically (p = .041) from each another. Our study results suggest a crossing Kirschner wire construct significantly increases the stability of the Akin osteotomy in a sawbone model. This might be clinically extrapolated in an effort to improve patient outcomes because these osteotomies can undergo nonunion and malunion, resulting in postoperative pain and swelling. PMID:22819001

  18. Bone Cement Augmentation of Short Segment Fixation for Unstable Burst Fracture in Severe Osteoporosis

    PubMed Central

    Kim, Hyeun Sung; Park, Sung Keun; Joy, Hoon; Ryu, Jae Kwang; Ju, Chang Il

    2008-01-01

    Objective The purpose of this study was to determine the efficacy of short segment fixation following postural reduction for the re-expansion and stabilization of unstable burst fractures in patients with osteoporosis. Methods Twenty patients underwent short segment fixation following postural reduction using a soft roll at the involved vertebra in cases of severely collapsed vertebrae of more than half their original height. All patients had unstable burst fracture with canal compromise, but their motor power was intact. The surgical procedure included postural reduction for 2 days and bone cement-augmented pedicle screw fixations at one level above, one level below and the fractured level itself. Imaging and clinical findings, including the level of the vertebra involved, vertebral height restoration, injected cement volume, local kyphosis, clinical outcome and complications were analyzed. Results The mean follow-up period was 15 months. The mean pain score (visual analogue scale) prior to surgery was 8.1, which decreased to 2.8 at 7 days after surgery. The kyphotic angle improved significantly from 21.65.8 before surgery to 5.23.7 after surgery. The fraction of the height of the vertebra increased from 35% and 40% to 70% in the anterior and middle portion. There were no signs of hardware pull-out, cement leakage into the spinal canal or aggravation of kyphotic deformities. Conclusion In the management of unstable burst fracture in patients with severe osteoporosis, short segment pedicle screw fixation with bone cement augmentation following postural reduction can be used to reduce the total levels of pedicle screw fixation and to correct kyphotic deformities. PMID:19096650

  19. Helical Screw Expander Evaluation Project. Final report

    SciTech Connect

    McKay, R.

    1982-03-01

    A functional 1-MW geothermal electric power plant that featured a helical screw expander was produced and then tested in Utah in 1978 to 1979 with a demonstrated average performance of approximately 45% machine efficiency over a wide range of test conditions in noncondensing operation on two-phase geothermal fluids. The Project also produced a computer-equipped data system, an instrumentation and control van, and a 1000-kW variable load bank, all integrated into a test array designed for operation at a variety of remote test sites. Additional testing was performed in Mexico in 1980 under a cooperative test program using the same test array, and machine efficiency was measured at 62% maximum with the rotors partially coated with scale, compared with approximately 54% maximum in Utah with uncoated rotors, confirming the importance of scale deposits within the machine on performance. Data are presented for the Utah testing and for the noncondensing phases of the testing in Mexico. Test time logged was 437 hours during the Utah tests and 1101 hours during the Mexico tests.

  20. Management of acute displaced midshaft clavicular fractures using Herbert cannulated screw: Technique and results in 114 patients

    PubMed Central

    Richardson, Martin; Asadollahi, Saeed; Richardson, Louise

    2013-01-01

    Purpose: A new and simple operative technique has been developed to provide internal fixation for midshaft clavicle fractures. This involves the use of a large fragment Herbert Screw that is entirely embedded within the bone. Screw fixation is combined with bone grafting from intramedullary reamings of the fracture fragments. The purpose of this report is to assess the outcomes following treatment of midshaft clavicular fracture using this method. Materials and Methods: One hundred and fourteen patients with acute displaced midshaft fracture were identified between 2002 and 2007. All patients were followed until fracture union. Patients’ medical records were reviewed. Disability of the Arm, Shoulder, and Hand questionnaire (DASH), and American Shoulder and Elbow Surgeons Elbow form (ASES) were posted to all patients. Outcome measures included union rate, time to union, implant removal rate, DASH, and ASES scores. Results: Patients’ median age was 29.5 years (interquartile range, 19-44 years). The most common injury mechanism was sports injury (28%). The median time from injury to surgery was 5 days (interquartile range, 2-9 days). Union occurred in an average of 8.8 weeks. Non-union occurred in three cases (2.6%). The re-operation rate for symptomatic hardware prominence screw was 1.7%. The median DASH score was 0.83 and the median ASES was 100 (n = 35). Conclusions: Intramedullary fixation using cannulated Herbert screw can be used as an effective approach for operative management of midshaft clavicular fractures. Using this method, an appropriate outcome could be achieved and a second intervention for implant removal could be avoided in great majority of cases. Level of Evidence: Level III PMID:23960363

  1. DLS 5.0 - The Biomechanical Effects of Dynamic Locking Screws

    PubMed Central

    Dbele, Stefan; Gardner, Michael; Schrter, Steffen; Hntzsch, Dankward; Stckle, Ulrich; Freude, Thomas

    2014-01-01

    Introduction Indirect reduction of dia-/metaphyseal fractures with minimally invasive implant application bridges the fracture zone in order to protect the soft-tissue and blood supply. The goal of this fixation strategy is to allow stable motion at the fracture site to achieve indirect bone healing with callus formation. However, concerns have arisen that the high axial stiffness and eccentric position of locked plating constructs may suppress interfragmentary motion and callus formation, particularly under the plate. The reason for this is an asymmetric fracture movement. The biological need for sufficient callus formation and secondary bone healing is three-dimensional micro movement in the fracture zone. The DLS was designed to allow for increased fracture site motion. The purpose of the current study was to determine the biomechanical effect of the DLS_5.0. Methods Twelve surrogate bone models were used for analyzing the characteristics of the DLS_5.0. The axial stiffness and the interfragmentary motion of locked plating constructs with DLS were compared to conventional constructs with Locking Head Screws (L