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Sample records for screw joint stability

  1. Influence of Prosthetic Screw Material on Joint Stability in Passive and Non-Passive Implant-Supported Dentures

    PubMed Central

    Spazzin, Aloísio Oro; Henriques, Guilherme Elias Pessanha; de Arruda Nóbilo, Mauro Antônio; Consani, Rafael Leonardo Xediek; Correr-Sobrinho, Lourenço; Mesquita, Marcelo Ferraz

    2009-01-01

    Objectives: This study evaluated the influence of prosthetic screw material on joint stability in implantsupported dentures at two levels of fit. Methods: Ten mandibular implant-supported dentures were fabricated. Twenty cast models were fabricated using these dentures. Four groups (n=10) were tested, according to the vertical fit of the dentures [passive and non-passive] and prosthetic screw materials [titanium (Ti) or gold (Au) alloy]. The one-screw test was performed to quantify the vertical misfits using an optic microscope. The loosening torque for the prosthetic screws was measured 24 hours after the tightening torque (10 Ncm) using a digital torque meter. Data were analyzed by two-way ANOVA and Tukey’s test (α=0.05). Results: Overall, dentures with passive fit and Ti screws resulted in significantly higher loosening torque of the prosthetic screws (p<0.05). No significant interaction was found between fit level and screw material (p=0.199). The prosthetic screw material and fit of implant-supported dentures have an influence on screw joint stability. Ti screws presented higher joint stability than Au screws and minimum of misfit should be found clinically to improve the mechanical behavior of the screw joint. PMID:20148135

  2. Influence of the implant-abutment connection design and diameter on the screw joint stability

    PubMed Central

    Shin, Hyon-Mo; Huh, Jung-Bo; Yun, Mi-Jeong; Jeon, Young-Chan; Chang, Brian Myung

    2014-01-01

    PURPOSE This study was conducted to evaluate the influence of the implant-abutment connection design and diameter on the screw joint stability. MATERIALS AND METHODS Regular and wide-diameter implant systems with three different joint connection designs: an external butt joint, a one-stage internal cone, and a two-stage internal cone were divided into seven groups (n=5, in each group). The initial removal torque values of the abutment screw were measured with a digital torque gauge. The postload removal torque values were measured after 100,000 cycles of a 150 N and a 10 Hz cyclic load had been applied. Subsequently, the rates of the initial and postload removal torque losses were calculated to evaluate the effect of the joint connection design and diameter on the screw joint stability. Each group was compared using Kruskal-Wallis test and Mann-Whitney U test as post-hoc test (α=0.05). RESULTS The postload removal torque value was high in the following order with regard to magnitude: two-stage internal cone, one-stage internal cone, and external butt joint systems. In the regular-diameter group, the external butt joint and one-stage internal cone systems showed lower postload removal torque loss rates than the two-stage internal cone system. In the wide-diameter group, the external butt joint system showed a lower loss rate than the one-stage internal cone and two-stage internal cone systems. In the two-stage internal cone system, the wide-diameter group showed a significantly lower loss rate than the regular-diameter group (P<.05). CONCLUSION The results of this study showed that the external butt joint was more advantageous than the internal cone in terms of the postload removal torque loss. For the difference in the implant diameter, a wide diameter was more advantageous in terms of the torque loss rate. PMID:24843398

  3. Effect of Vertical Misfit on Screw Joint Stability of Implant-Supported Crowns

    NASA Astrophysics Data System (ADS)

    Assunção, Wirley Gonçalves; Delben, Juliana Aparecida; Tabata, Lucas Fernando; Barão, Valentim Adelino Ricardo; Gomes, Érica Alves

    2011-08-01

    The passive fit between prosthesis and implant is a relevant factor for screw joint stability and treatment success. The aim of this study was to evaluate the influence of vertical misfit in abutment-implant interface on preload maintenance of retention screw of implant-supported crowns. The crowns were fabricated with different abutments and veneering materials and divided into 5 groups ( n = 12): Gold UCLA abutments cast in gold alloy veneered with ceramic (Group I) and resin (Group II), UCLA abutments cast in titanium veneered with ceramic (Group III) and resin (Group IV), and zirconia abutments with ceramic veneering (Group V). The crowns were attached to implants by gold retention screws with 35-N cm insertion torque. Specimens were submitted to mechanical cycling up to 106 cycles. Measurements of detorque and vertical misfit in abutment-implant interface were performed before and after mechanical cycling. ANOVA revealed statistically significant difference ( P < 0.05) among groups for vertical misfit measured before and after mechanical cycling. The abutments cast in titanium exhibited the highest misfit values. Pearson correlation test did not demonstrate significant correlation ( P > 0.05) between vertical misfit and detorque value. It was concluded that vertical misfit did not influence torque maintenance and the abutments cast in titanium exhibited the highest misfit values.

  4. The effect of different implant-abutment connections on screw joint stability.

    PubMed

    Michalakis, Konstantinos X; Calvani, Pasquale Lino; Muftu, Sinan; Pissiotis, Argiris; Hirayama, Hiroshi

    2014-04-01

    Dental implants with an internal connection have been designed to establish a better stress distribution when lateral external forces act on the prosthesis and minimize the forces transmitted to the fastening screw. In the present study, 10 externally and 10 internally hexed implants were tested with a compressive force applied with an Instron Universal machine. Four cycles of loading-unloading were applied to each specimen to achieve displacements of 0.5, 1, 2, and 2.5 mm. The mean loads for the first cycle were 256.70 N for the external connection and 256 N for the internal connection implants. The independent t test did not reveal any significant differences among the 2 tested groups (P = .780). For the second cycle, the mean loads needed for a displacement of 1 mm were 818.19 N and 780.20 N for the external connection and the internal connection implants, respectively. The independent t test revealed significant differences among the 2 tested groups (P < .001). In the third cycle, the mean load values for a 2-mm displacement were 1394.10 N and 1225.00 N. The independent t test revealed significant differences among the 2 tested groups (P < .001). The mean loads for the fourth cycle were 1488.00 N for the external connection and 1029.00 N for the internal connection implants. These loads were required for a displacement of 2.5 mm. The independent t test revealed significant differences among the 2 tested groups (P < .001). The results of this in vitro study suggest that the internal connection design of the examined implant system could not prevent screw loosening during overloading. No implant or prosthesis failure was noticed in either group. PMID:24779947

  5. Prediction at long-term condyle screw fixation of temporomandibular joint implant: A numerical study.

    PubMed

    Ramos, A; Duarte, R J; Mesnard, M

    2015-05-01

    The fixation of commercial temporomandibular joint (TMJ) implant is accomplished by using screws, which, in some cases, can lead to loosening of the implant. The aim of this study was to predict the evolution of fixation success of a TMJ. Numerical models using a Christensen TMJ implant were developed to analyze strain distributions in the adjacent mandibular bone. The geometry of a human mandible was developed based on computed tomography (CT) scans from a cadaveric mandible on which a TMJ implant was subsequently placed. In this study, the five most important muscle forces acting were applied and the anatomical conditions replicated. The evolution of fixation was defined according to bone response methodology focused in strain distribution around the screws. Strain and micromotions were analyzed to evaluate implant stability, and the evolution process conduct at three different stages: start with all nine screws in place (initial stage); middle stage, with three screws removed (middle stage), and end stage, with only three screws in place (final stage). With regard to loosening, the implant success fixation changed the strains in the bone between 21% and 30%, when considering the last stage. The most important screw positions were #1, #7, and #9. It was observed that, despite the commercial Christensen TMJ implant providing nine screw positions for fixation, only three screws were necessary to ensure implant stability and fixation success. PMID:25819477

  6. Screw-Home Movement of the Tibiofemoral Joint during Normal Gait: Three-Dimensional Analysis

    PubMed Central

    Kim, Ha Yong; Yang, Dae Suk; Jeung, Sang Wook; Choi, Han Gyeol; Choy, Won Sik

    2015-01-01

    Background The purpose of this study was to evaluate the screw-home movement at the tibiofemoral joint during normal gait by utilizing the 3-dimensional motion capture technique. Methods Fifteen young males and fifteen young females (total 60 knee joints) who had no history of musculoskeletal disease or a particular gait problem were included in this study. Two more markers were attached to the subject in addition to the Helen-Hayes marker set. Thus, two virtual planes, femoral coronal plane (Pf) and tibial coronal plane (Pt), were created by Skeletal Builder software. This study measured the 3-dimensional knee joint movement in the sagittal, coronal, and transverse planes of these two virtual planes (Pf and Pt) during normal gait. Results With respect to kinematics and kinetics, both males and females showed normal adult gait patterns, and the mean difference in the temporal gait parameters was not statistically significant (p > 0.05). In the transverse plane, the screw-home movement occurred as expected during the pre-swing phase and the late-swing phase at an angle of about 17°. However, the tibia rotated externally with respect to the femur, rather than internally, while the knee joint started to flex during the loading response (paradoxical screw-home movement), and the angle was 6°. Conclusions Paradoxical screw-home movement may be an important mechanism that provides stability to the knee joint during the remaining stance phase. Obtaining the kinematic values of the knee joint during gait can be useful in diagnosing and treating the pathological knee joints. PMID:26330951

  7. The pedicle screw-rod system is an acceptable method of reconstructive surgery after resection of sacroiliac joint tumours

    PubMed Central

    Zhou, Yi-Jun; Yunus, Akbar; Tian, Zheng; Chen, Jiang-Tao; Wang, Chong; Xu, Lei-Lei

    2016-01-01

    Hemipelvic resections for primary bone tumours require reconstruction to restore weight bearing along anatomic axes. However, reconstruction of the pelvic arch remains a major surgical challenge because of the high rate of associated complications. We used the pedicle screw-rod system to reconstruct the pelvis, and the purpose of this investigation was to assess the oncology, functional outcome and complication rate following this procedure. The purpose of this study was to investigate the operative indications and technique of the pedicle screw-rod system in reconstruction of the stability of the sacroiliac joint after resection of sacroiliac joint tumours. The average MSTS (Musculoskeletal Tumour Society) score was 26.5 at either three months after surgery or at the latest follow-up. Seven patients had surgery-related complications, including wound dehiscence in one, infection in two, local necrosis in four (including infection in two), sciatic nerve palsy in one and pubic symphysis subluxation in one. There was no screw loosening or deep vein thrombosis occurring in this series. Using a pedicle screw-rod after resection of a sacroiliac joint tumour is an acceptable method of pelvic reconstruction because of its reduced risk of complications and satisfactory functional outcome, as well as its feasibility of reconstruction for type IV pelvis tumour resection without elaborate preoperative customisation. Level of evidence: Level IV, therapeutic study. PMID:27095944

  8. Analysis of screw pullout strength: a function of screw orientation in subtalar joint arthrodesis.

    PubMed

    McGlamry, Michael C; Robitaille, Melissa F

    2004-01-01

    The purpose of this cadaveric study was to compare the pullout strength and failure load of 2 different screw orientations for subtalar arthrodesis. Twenty-six specimens from 13 cadaver donors (1 left and 1 right each) were used. A 7.3- x 65-mm long-thread profile (32-mm length) cannulated screw inserted into the calcaneus from dorsal to plantar (calcaneal specimens) was compared with a 7.3- x 65-mm short-thread profile (16-mm length) cannulated screw inserted into the talus from plantar to dorsal (talar specimens). A torque screwdriver with a calibrated electronic vernier scale measured the torque of screw insertion. Screw pullout strength and load failure were measured by using a servohydraulic materials testing machine. Distraction was applied along the axis of the screw at a displacement rate of 25 mm/min. The peak torque of insertion in all calcaneal specimens was reached on initial insertion through the dorsal subchondral bone plate of the calcaneus; in talar specimens, it was reached as the screw threads were completely buried into the talus. A significant difference (P = .00647) was found between the mean torque of insertion for the calcaneal (1.50 Nm) and talar specimens (1.30 Nm). A comparison of pullout forces showed a significantly stronger mean failure load for calcaneal specimens (P = .000085). The mean failure load for paired calcaneal specimens was 1782 N compared with a mean 1245 N for talar specimens. Although the pullout force was clearly greater in the dorsal-to-plantar screw application, the pullout force in the plantar-to-dorsal orientation was also considerable. PMID:15480401

  9. Screw Placement and Osteoplasty Under Computed Tomographic-Fluoroscopic Guidance in a Case of Advanced Metastatic Destruction of the Iliosacral Joint

    SciTech Connect

    Trumm, Christoph Gregor; Rubenbauer, Bianca; Piltz, Stefan; Reiser, Maximilian F.; Hoffmann, Ralf-Thorsten

    2011-02-15

    We present a case of combined surgical screw placement and osteoplasty guided by computed tomography-fluoroscopy (CTF) in a 68-year-old man with unilateral osteolytic destruction and a pathological fracture of the iliosacral joint due to a metastasis from renal cell carcinoma. The patient experienced intractable lower back pain that was refractory to analgesia. After transarterial particle and coil embolization of the tumor-feeding vessels in the angiography unit, the procedure was performed under general anesthesia by an interdisciplinary team of interventional radiologists and trauma surgeons. Under intermittent single-shot CTF, two K wires were inserted into the left iliosacral joint from a lateral transiliac approach at the S1 level followed by two self-tapping surgical screws. Continuous CTF was used for monitoring of the subsequent polymethylmethacrylate injection through two vertebroplasty cannulas for further stabilization of the screw threads within the osteolytic sacral ala. Both the screw placement and cement injection were successful, with no complications occurring during or after the procedure. With additional nonsteroidal anti-inflammatory and opioid medication, the patient reported a marked decrease in his lower back pain and was able to move independently again at the 3-month follow-up assessment. In our patient with intolerable back pain due to tumor destruction and consequent pathological fracture of the iliosacral joint, CTF-guided iliosacral screw placement combined with osteoplasty was successful with respect to joint stabilization and a reduction in the need for analgesic therapy.

  10. Rotational Stability of Scaphoid Osteosyntheses: An In Vitro Comparison of Small Fragment Cannulated Screws to Novel Bone Screw Sets

    PubMed Central

    Erhart, Jochen; Unger, Ewald; Schefzig, Philip; Varga, Peter; Trulson, Inga; Gormasz, Anna; Trulson, Alexander; Reschl, Martin; Hagmann, Michael; Vecsei, Vilmos; Mayr, Winfried

    2016-01-01

    Background The current standard of care for operative repair of scaphoid fractures involves reduction and internal fixation with a single headless compression screw. However, a compression screw in isolation does not necessarily control rotational stability at a fracture or nonunion site. The single screw provides rotational control through friction and bone interdigitation from compression at the fracture site. We hypothesize that osteosyntheses with novel bone screw sets (BSS) equipped with anti-rotational elements provide improved rotational stability. Methods Stability of osteosynthesis under increasing cyclic torsional loading was investigated on osteotomized cadaveric scaphoids. Two novel prototype BSS, oblique type (BSS-obl.) and longitudinal type (BSS-long.) were compared to three conventional screws: Acutrak2®mini, HCS®3.0 and Twinfix®. Biomechanical tests were performed on scaphoids from single donors in paired comparison and analyzed by balanced incomplete random block design. Loading was increased by 50 mNm increments with 1,000 cycles per torque level and repeated until a rotational clearance of 10°. Primary outcome measure was the number of cycles to 10° clearance, secondary outcome measure was the maximum rotational clearance for each torque level. Findings BSS-obl. performed significantly better than Acutrak2®mini and HCS® (p = 0.015, p<0.0001). BSS-long. performed significantly better than HCS® (p = 0.010). No significant difference in performance between BSS-obl. and BSS-long. (p = 0.361), between BSS obl. and Twinfix® (p = 0.50) and BSS long. and Twinfix® (p = 0.667) was detected. Within the torque range up to 200 mNm, four of 21 (19%) BSS-long. and four of 21 (19%) BSS-obl. preparations showed early failure. The same loading led to early failure in four (29%) Twinfix®, seven (50%) Acutrak2®mini and 10 (71%) HCS® of 14 screw samples, respectively. Conclusions For both BSS and to a lesser extent for Twinfix® (as dual-component screw

  11. Simultaneous Use of Both Bilateral Intralaminar and Pedicle Screws for C2 Stabilization.

    PubMed

    Tarukado, Kiyoshi; Tono, Osamu; Doi, Toshio

    2015-10-01

    Four patients underwent stabilization surgery using both bilateral C2 pedicle screw (PS) and intralaminar screw (LS). Neural and vascular injury resulting from incorrect screw placement was assessed using computed tomography (CT). The evaluation of bone union was assessed by lateral flexion-extension X-ray films and CT. The symptoms were improved in all patients. There were no intraoperative complications. Furthermore, there were no cases of neurological worsening or vascular injury from incorrect screw placement. Failure of instrumentation or screw loosening during the follow-up period did not occur in any of the patients. All cases had accomplished bone union at the final follow-up. Theoretically, the stabilization technique using both bilateral C2 PS and LS at the same time can provide more stability than any other single technique. Simultaneous use of both bilateral C2 PS and LS is potentially a good choice for surgical repair. PMID:26435800

  12. Increase of stability in external fracture fixation by hydroxyapatite-coated bone screws.

    PubMed

    Augat, P; Claes, L; Hanselmann, K F; Suger, G; Fleischmann, W

    1995-01-01

    A major problem in fracture treatment by external fixation is screw loosening, which often results in reduced stability and can lead to prolonged treatment. A load-carrying experiment was conducted to determine whether coating implants with bioactive hydroxyapatite (HA) increases screw stability. Twelve HA-coated ASIF screws with 3 different macroporosities were inserted in 12 sheep that had already been fitted with a 6-pin external fixator for the treatment of a tibial osteotomy. The same number of uncoated polished steel screws served as controls. Although initial stability was not different for HA-coated screws, average removal torque after a 9-week implantation period increased with increasing macroporosity of the HA coating (p < .002). Instability of some screws was accompanied by histologic findings of cartilagenous tissue and proliferation of periosteal callus. Near the threads in the tibial cortex and in the shaft area of the screw were seen large numbers of HA particles that had been sheared off during implantation as well as during screw removal because of high contact forces between the HA coating and bone. Particulate debris of HA particles as well as the release of small bone fragments during explanation is likely to be unavoidable since HA adherence to bone is greater than adherence to steel after several weeks of implantation. PMID:7640445

  13. Study of Bone-screw Surface Fixation in Lumbar Dynamic Stabilization

    PubMed Central

    Luo, Yun-Gang; Yu, Tao; Liu, Guo-Min; Yang, Nan

    2015-01-01

    Background: We aimed to use the animal model of dynamic fixation to examine the interaction of the pedicle screw surface with surrounding bone, and determine whether pedicle screws achieve good mechanical stability in the vertebrae. Methods: Twenty-four goats aged 2–3 years had Cosmic® pedicle screws implanted into both sides of the L2-L5 pedicles. Twelve goats in the bilateral dynamic fixation group had fixation rods implanted in L2-L3 and L4-L5. Twelve goats in the unilateral dynamic fixation group had fixation rods randomly fixed on one side of the lumbar spine. The side that was not implanted with fixation rods was used as a static control group. Results: In the static control group, new bone was formed around the pedicle screw and on the screw surface. In the unilateral and bilateral dynamic fixation groups, large amounts of connective tissue formed between and around the screw threads, with no new bone formation on the screw surface; the pedicle screws were loose after the fixed rods were removed. The bone mineral density and morphological parameters of the region of interest (ROI) in the unilateral and bilateral dynamic fixation group were not significantly different (P > 0.05), but were lower in the fixed groups than the static control group (P < 0.05). This showed the description bone of the ROI in the static control group was greater than in the fixation groups. Under loading conditions, the pedicle screw maximum pull force was not significantly different between the bilateral and unilateral dynamic fixation groups (P > 0.05); however the maximum pull force of the fixation groups was significantly less than the static control group (P < 0.01). Conclusions: Fibrous connective tissue formed at the bone-screw interface under unilateral and bilateral pedicle dynamic fixation, and the pedicle screws lost mechanical stability in the vertebrae. PMID:25635433

  14. Optimization and Innovation of Screw Joints of Micron-Wood-Fiber Molded Products

    NASA Astrophysics Data System (ADS)

    Pan, Chengyi; Zhang, Jianyi

    Micron-wood-fiber molded products are new kinds of high strength man-made wooden products. They are innovative products among molded fiber products nowadays. This paper studied a new method to design their screw joints using optimal design. It has combined the optimal design with reliability design ingeniously. The CAD programming method was put forward, which can optimize the structural parameters of micron-wood-fiber molded products, and may be used on the strength design and the check of innovation for new products. The new calculating method and software had provided effective design method for screw joints of micron-wood-fiber molded products. It would increase the calculating efficiency and precision greatly.

  15. A biomechanical study on fixation stability with twin hook or lag screw in artificial cancellous bone.

    PubMed

    Olsson, O; Tanner, K E; Ceder, L; Ryd, L

    2002-01-01

    The twin hook has been developed as an alternative to the conventional lag screw to be combined with a barrelled side-plate in the treatment of trochanteric hip fractures. With two oppositely directed apical hooks introduced into the subchondral bone of the femoral head, the twin hook provides different stabilising properties to the lag screw. The femoral head purchase of the twin hook and the lag screw were compared in a biomechanical study using artificial cancellous bone, and responses to axial and torsional loading was determined. A distinct yield point in load and torque was noted for the lag screw, representing failure of the laminas supporting the threads. For the twin hook, gradual increase of load and torque occurred during impaction of the bone supporting the hooks. The peak loads and torques were higher for the lag screw, but were similar for both devices after 8 mm deformation. The stiffness was higher for the lag screw, but in counter-clockwise rotation the stiffness for the lag screw was negligible. The twin hook appeared to provide fixation stability comparable to that offered by the lag screw, but with conceivable advantages in terms of a deformation response involving bone impaction and gradually increasing stability. PMID:12466867

  16. Preload Analysis of Screw Bolt Joints on the First Wall Graphite Tiles in EAST

    NASA Astrophysics Data System (ADS)

    Cao, Lei; Song, Yuntao

    2012-09-01

    The first wall in the Experimental Advanced Superconducting Tokamak (EAST) used graphite tiles to withstand high thermal energy. The graphite tiles are mounted on the heat sink using screw bolts which have been preloaded to produce a clamp force. The clamp force is very important to keep the graphite tiles tightly on the surface of the heat sink so that the heat flux crosses this contacting surface in a small thermal resistor. Without the clamp force, the small gap between the graphite tiles and the heat sink will make it impossible for thermal power to be carried away by cooling water. Some bolts may even fall off with the loss of clamp force. From the mathematical models, the loss process of the clamp force has been studied. Research results explain how the different thermal expansions of three members of the screw joint makes the clamp force decrease to zero under temperature rise and external force, and how the stiffness affects the relation between the clamp force and temperature. The research also gives the critical temperature at which the clamp force can remain above zero. Analysis results indicate that the current screw joints are almost destined to lose their clamp force during the running time of EAST, so the bolt joints should be redesigned in order to improve its reliability.

  17. Facet joint changes after application of lumbar nonfusion dynamic stabilization.

    PubMed

    Lee, Soo Eon; Jahng, Tae-Ahn; Kim, Hyun Jib

    2016-01-01

    OBJECTIVE The long-term effects on adjacent-segment pathology after nonfusion dynamic stabilization is unclear, and, in particular, changes at the adjacent facet joints have not been reported in a clinical study. This study aims to compare changes in the adjacent facet joints after lumbar spinal surgery. METHODS Patients who underwent monosegmental surgery at L4-5 with nonfusion dynamic stabilization using the Dynesys system (Dynesys group) or transforaminal lumbar interbody fusion with pedicle screw fixation (fusion group) were retrospectively compared. Facet joint degeneration was evaluated at each segment using the CT grading system. RESULTS The Dynesys group included 15 patients, while the fusion group included 22 patients. The preoperative facet joint degeneration CT grades were not different between the 2 groups. Compared with the preoperative CT grades, 1 side of the facet joints at L3-4 and L4-5 had significantly more degeneration in the Dynesys group. In the fusion group, significant facet joint degeneration developed on both sides at L2-3, L3-4, and L5-S1. The subjective back and leg pain scores were not different between the 2 groups during follow-up, but functional outcome based on the Oswestry Disability Index improved less in the fusion group than in the Dynesys group. CONCLUSIONS Nonfusion dynamic stabilization using the Dynesys system had a greater preventative effect on facet joint degeneration in comparison with that obtained using fusion surgery. The Dynesys system, however, resulted in facet joint degeneration at the instrumented segments and above. An improved physiological nonfusion dynamic stabilization system for lumbar spinal surgery should be developed. PMID:26721580

  18. Polymethylmethacrylate-augmented screw fixation for stabilization in metastatic spinal tumors. Technical note.

    PubMed

    Jang, Jee Soo; Lee, Sang Ho; Rhee, Chang Hun; Lee, Seung Hoon

    2002-01-01

    Screw fixation augmented with polymethylmethacrylate (PMMA) or some other biocompatible bone cement has been used in patients with osteoporosis requiring spinal fusion. No clinical studies have been conducted on PMMA-augmented screw fixation for stabilization of the vertebral column in patients with metastatic spinal tumors. The purpose of this study was to determine whether screw fixation augmented with PMMA might be suitable in patients treated for multilevel metastatic spinal tumors. Ten patients with metastatic spinal tumors involving multiple vertebral levels underwent stabilization procedures in which PMMA was used to augment screw fixation after decompression of the spinal cord. Within 15 days, partial or complete relief from pain was obtained in all patients postoperatively. Two of four patients in whom neurological deficits caused them to be nonambulatory before surgery were able to ambulate postoperatively. Neither collapse of the injected vertebral bodies nor failure of the screw fixation was observed during the mean follow-up period of 6.7 months. Screw fixation augmented with PMMA may offer stronger stabilization and facilitate the instrumentation across short segments in the treatment of multilevel metastatic spinal tumors. PMID:11795702

  19. Stability of two-fold screw axis structures for cellulose

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Diffraction crystallography indicates that most forms of crystalline cellulose have two-fold screw axis symmetry. Even if exact symmetry is absent, the degree of pseudo symmetry is very high. On the other hand, this symmetry leads to short contacts between H4 and H1' across the glycosidic linkage....

  20. Morphometric analysis of distal interphalangeal joint and implications for arthrodesis with a headless compression screw.

    PubMed

    Braun, Benjamin; Bogle, Andrew; Wiesler, Ethan

    2015-01-01

    Using radiographs of a cross section of patients, measurements of phalanges were done to aid in surgical planning for distal interphalangeal joint (DIPJ) arthrodesis using a headless compression screw. Measurements were performed of the distal and middle phalanx of all fingers and the proximal and distal phalanx of the thumb. Three independent reviewers measured 50 patients. The average measurements (in mm) of anteroposterior (AP) dimensions were as follows: for the thumb P1 and P2: 5.7 and 5.5, lateral 4.2 and 3.5; for the index P2 and P3 AP: 4.2 and 3.3, lateral 2.1 and 1.8; for the long P2 and P3 AP: 4.5 and 3.5, lateral 2.2 and 1.8; for the ring P2 and P3 AP: 4.3 and 3.1, lateral 1.8 and 1.7; and for the small P2 and P3 AP: 3.7 and 2.2, lateral 1.8 and 1.5. Careful surgical planning by measuring the involved digit and knowledge of screw size is paramount to avoid complications from DIPJ arthrodesis with a compression screw. PMID:25830256

  1. Enhancement of pedicle screw stability using calcium phosphate cement in osteoporotic vertebrae: in vivo biomechanical study.

    PubMed

    Taniwaki, Yoshimichi; Takemasa, Ryuichi; Tani, Toshikazu; Mizobuchi, Hiroo; Yamamoto, Hiroshi

    2003-01-01

    We conducted an experimental study using female beagles with and without ovariectomy-induced osteoporosis to determine the effect of calcium phosphate cement (CPC) on the mechanical stability of inserted pedicle screws. A drill hole was created from the base of the transverse process to the vertebral body; CPC was injected into the hole, and then a screw was inserted into the same hole. In the presence of osteoporosis evidenced by dual X-ray absorptiometry, the stability of the inserted screw augmented by CPC against pull-out and cephalocaudal forces were significantly greater by 28% and 54% at 1 week after operation, 48% and 71% at 2 weeks, and 56% and 68% at 4 weeks compared with those without CPC. The pull-out strength increased progressively with time after surgery, probably reflecting new-bone growth from the surrounding cancellous bone, which was in direct contact with the CPC, as shown in the histologic study. At each time point the cephalocaudal rigidity was similar and the pull-out strength greater than that for the screws inserted without CPC in nonporotic dogs. These findings suggest that CPC augments the stability of the inserted pedicle screws and increases the stiffness of fixed osteoporotic motion segments using instrumentation. PMID:12768486

  2. CT-Guided Transfacet Pedicle Screw Fixation in Facet Joint Syndrome: A Novel Approach

    PubMed Central

    Manfré, Luigi

    2014-01-01

    Summary Axial microinstability secondary to disc degeneration and consequent chronic facet joint syndrome (CFJS) is a well-known pathological entity, usually responsible for low back pain (LBP). Although posterior lumbar fixation (PIF) has been widely used for lumbar spine instability and LBP, complications related to wrong screw introduction, perineural scars and extensive muscle dissection leading to muscle dysfunction have been described. Radiofrequency ablation (RFA) of facet joints zygapophyseal nerves conventionally used for pain treatment fails in approximately 21% of patients. We investigated a “covert-surgery” minimal invasive technique to treat local spinal instability and LBP, using a novel fully CT-guided approach in patients with axial instability complicated by CFJS resistant to radioablation, by introducing direct fully or partially threaded transfacet screws (transfacet fixation - TFF), to acquire solid arthrodesis, reducing instability and LBP. The CT-guided procedure was well tolerated by all patients in simple analogue sedation, and mean operative time was approximately 45 minutes. All eight patients treated underwent clinical and CT study follow-up at two months, revealing LBP disappearance in six patients, and a significant reduction of lumbar pain in two. In conclusion, CT-guided TFF is a fast and safe technique when facet posterior fixation is needed. PMID:25363265

  3. Strain induced in the condyle by self-tapping screws in the Biomet alloplastic temporomandibular joint: a preliminary experimental study.

    PubMed

    Ramos, A; Duarte, R J; Mesnard, M

    2015-11-01

    The main aim of this study was to analyze how screws affect the strain concentration induced on the mandibular condyle during implantation, screwing, and drilling, as well as after condylar loading. A clean cadaveric mandible was analyzed experimentally in the intact state and was then implanted with a Biomet/Lorenz Microfixation temporomandibular joint (TMJ) implant with seven bicortical self-tapping screws. The external surface of the mandible was instrumented with three strain gauges. A load of 500N on the TMJ was applied to the condyle before and after implantation. The results showed a strain concentration of -1500μɛ near the screws due to their implantation on the external surface of the mandible. The drilling process induced up to 80μɛ near the hole. The strain concentration did not change when there were more than six screws. Loading on the TMJ before and after implantation presented only a 10% difference in maximum principal strain. This study demonstrates the importance of the strain concentration induced by the screws. The process of implanting screws shows the importance of lateral surface preparation for a good fit in the condyle. Strain distribution after implantation and loading of the Biomet implant was found to be similar to that in the intact condyle. PMID:26194773

  4. 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

  5. Stability of a Screw Dislocation in a ⟨011 ⟩ Copper Nanowire

    NASA Astrophysics Data System (ADS)

    Roussel, Jean-Marc; Gailhanou, Marc

    2015-08-01

    The stability of a screw dislocation in a free ⟨011 ⟩ copper nanowire is investigated using atomistic calculations. This study reveals a strong anisotropy of the Eshelby potential well (EPW) that traps the dislocation. Moreover the depth of the EPW is found to vanish when the radius of the nanowire decreases. It is demonstrated that this behavior is due to the dissociated state of the dislocation.

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

    PubMed Central

    İnceoğlu, 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

  7. The importance of trochanteric lag screws to achieve primary stability in cementless fixation of the RM hip prosthesis.

    PubMed

    Heitemeyer, U; Hierholzer, G; Haines, J

    1987-01-01

    To allow the bony incorporation of a cementless prosthesis it is important to achieve stability at the time of operation. To neutralize tension and torsional stresses the RM-shaft prosthesis is fixed with two lag screws in the trochanteric part of the femur. By measuring the applied torque intraoperatively we could demonstrate that the threads of the screws found a better grip when inserted from the bone to the prosthesis. Thus, the stronger fixation of the screws enhanced the primary stability of the cementless prosthesis. PMID:3566504

  8. 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.

  9. Locking Plate in Proximal Tibial Fracture: A Correlation between the Coronal Alignment of Tibia and Joint Screw Angle

    PubMed Central

    Oh, Jong-Keon; Varte, Lalrinliana; Ko, Jae-Han; Oh, Chang-Wug; Jung, Duk-Young; An, Hyonggin; Cho, Jae-Woo

    2013-01-01

    Purpose The purpose of this study is to evaluate the relationship between the angle formed between the proximal most screw through the locking compression plate-proximal lateral tibia (LCP PLT) and the joint line, and to evaluate if this angle can be used intraoperatively as an assessment tool to determine normal alignment of the tibia in the coronal plane. Materials and Methods There are two parts to this study: in the first part, LCP PLT was applied to 30 cadaveric adult tibia. The angle between the joint line and the proximal most screw was measured and termed as the 'joint screw angle' (JSA). In the second part, 56 proximal tibial fractures treated with LCP PLT were retrospectively studied. Two angles were measured on the radiographs, the medial proximal tibial angle (MPTA) and the JSA. Their relationship was analyzed statistically. Results The average JSA was 1.16 degrees in the anatomical study. Statistical analysis of the clinical study showed that the normal MPTA had a direct correlation with an acceptable JSA. Conclusion We therefore conclude that the JSA can be used intraoperatively to assess the achievement of a normal coronal axis. PMID:23549821

  10. Percutaneous Screw Fixation of Crescent Fracture-Dislocation of the Sacroiliac Joint.

    PubMed

    Shui, Xiaolong; Ying, Xiaozhou; Mao, Chuanwan; Feng, Yongzeng; Chen, Linwei; Kong, Jianzhong; Guo, Xiaoshan; Wang, Gang

    2015-11-01

    Crescent fracture-dislocation of the sacroiliac joint (CFDSIJ) is a type of lateral compression pelvic injury associated with instability. Open reduction and internal fixation is a traditional treatment of CFDSIJ. However, a minimally invasive method has never been reported. The purpose of this study was to assess the outcome of closed reduction and percutaneous fixation for different types of CFDSIJ and present their clinical outcome. The authors reviewed 117 patients diagnosed with CFDSIJ between July 2003 and July 2013. Closed reduction and percutaneous fixation was performed in 73 patients. Treatment selection was based on Day's fracture classification. For type I fractures, fixation perpendicular to the fracture line were performed. For type II fractures, crossed fixation was performed. For type III fractures, fixation was performed with iliosacral screws. Forty-four patients were treated by open reduction and plate fixation. Demographics, fracture pattern distribution, blood loss, incision lengths, revision surgeries, radiological results, and functional scores were compared. All 117 patients were followed for more than 6 months (mean, 14 months [range, 6-24 months]). Blood loss, extensive exposure, duration of posterior ring surgery, duration of hospital stay, and infection rates were lower in the closed group (P<.01). Patients in the closed group achieved better functional performance (P<.01). There were no significant differences in reduction quality (P=.32), revision surgery rates (P=.27), and iatrogenic neurologic injuries (P=.2) between the 2 groups. The authors' results indicate that closed reduction and percutaneous fixation is a safe and effective surgical method for CFDSIJ. PMID:26558677

  11. Percutaneous Transpedicular Interbody Fusion Technique in Percutaneous Pedicle Screw Stabilization for Pseudoarthrosis Following Pyogenic Spondylitis.

    PubMed

    Ikuta, Ko; Masuda, Keigo; Yonekura, Yutaka; Kitamura, Takahiro; Senba, Hideyuki; Shidahara, Satoshi

    2016-04-01

    This report introduces a percutaneous transpedicular interbody fusion (PTPIF) technique in posterior stabilization using percutaneous pedicle screws (PPSs). An 81-year-old man presented with pseudoarthrosis following pyogenic spondylitis 15 months before. Although no relapse of infection was found, he complained of obstinate low back pain and mild neurological symptoms. Radiological evaluations showed a pseudoarthrosis following pyogenic spondylitis at T11-12. Posterior stabilization using PPSs from Th9 to L2 and concomitant PTPIF using autologous iliac bone graft at T11-12 were performed. Low back pain and neurological symptoms were immediately improved after surgery. A solid interbody fusion at T11-12 was completed 9 months after surgery. The patient had no restriction of daily activity and could play golf at one year after surgery. PTPIF might be a useful option for perform segmental fusion in posterior stabilization using PPSs. PMID:27114777

  12. Percutaneous Transpedicular Interbody Fusion Technique in Percutaneous Pedicle Screw Stabilization for Pseudoarthrosis Following Pyogenic Spondylitis

    PubMed Central

    Masuda, Keigo; Yonekura, Yutaka; Kitamura, Takahiro; Senba, Hideyuki; Shidahara, Satoshi

    2016-01-01

    This report introduces a percutaneous transpedicular interbody fusion (PTPIF) technique in posterior stabilization using percutaneous pedicle screws (PPSs). An 81-year-old man presented with pseudoarthrosis following pyogenic spondylitis 15 months before. Although no relapse of infection was found, he complained of obstinate low back pain and mild neurological symptoms. Radiological evaluations showed a pseudoarthrosis following pyogenic spondylitis at T11–12. Posterior stabilization using PPSs from Th9 to L2 and concomitant PTPIF using autologous iliac bone graft at T11–12 were performed. Low back pain and neurological symptoms were immediately improved after surgery. A solid interbody fusion at T11–12 was completed 9 months after surgery. The patient had no restriction of daily activity and could play golf at one year after surgery. PTPIF might be a useful option for perform segmental fusion in posterior stabilization using PPSs. PMID:27114777

  13. The effect of screws and pegs on the initial fixation stability of an uncemented unicondylar knee replacement.

    PubMed

    Kaiser, A D; Whiteside, L A

    1990-10-01

    Two uncemented unicompartmental tibial components were examined for initial fixation stability. A conventional design that employed a single posteriorly angled peg was compared with a new design that was held in place by cancellous bone screws. The components were implanted into the medial condyles of 12 preserved human tibiae, and a cyclic load was first applied anteromedially and then posteromedially. The screwed implants failed at significantly higher loads (1634.8 +/- 121.6 N, mean +/- standard error of the mean) than the pegged implants (1103.3 +/- 152.0 N). On application of a 19.6-N preload, the screwed implants moved significantly less than the pegged implants. Although the differences in micromotion and subsidence were not always significant, there were definite trends. The screwed implants had much lower levels of temporary and permanent displacement compared with the pegged implants for all load levels from the initial load of 245.2 N up to and including the failure load. When the motion that resulted from moving the load from the anterior position to the posterior position was examined, the screwed implant's average total motion was less than 10 microns compared with almost 135 microns for the pegged implant after the 245.2-N load cycle. For the cycle before failure, the screwed implant's average motion increased to less than 29 microns, whereas the pegged implant's average total motion was almost 354 microns. From this information it appears clear that screws provide better initial fixation stability than angled pegs for uncemented unicondylar tibial components. PMID:2208852

  14. Muscle contribution to elbow joint valgus stability.

    PubMed

    Lin, Fang; Kohli, Navjot; Perlmutter, Sam; Lim, Dohyung; Nuber, Gordon W; Makhsous, Mohsen

    2007-01-01

    FCR may function as dynamic stabilizers, with the FCU being the primary stabilizer for elbow valgus stability, incorporating with the MUCL for all tested joint configurations. Our findings also suggest that the ECU and EDC increased MUCL strain and elbow valgus movement at both 45 degrees and 90 degrees . PMID:17936028

  15. Stability of Uncemented Cups - Long-Term Effect of Screws, Pegs and HA Coating: A 14-Year RSA Follow-Up of Total Hip Arthroplasty.

    PubMed

    Otten, Volker T C; Crnalic, Sead; Röhrl, Stephan M; Nivbrant, Bo; Nilsson, Kjell G

    2016-01-01

    Screws, pegs and hydroxyapatite-coating are used to enhance the primary stability of uncemented cups. We present a 14-year follow-up of 48 hips randomized to four groups: press-fit only, press-fit plus screws, press-fit plus pegs and hydroxyapatite-coated cups. Radiostereometric migration measurements showed equally good stability regardless cup augmentation. The mean wear rate was high, 0.21 mm/year, with no differences between the groups. Seven hips had radiographical osteolysis but only in hips with augmented cups. Cups without screw-holes compared with cups with screw-holes resulted in better clinical outcome at the 14-year follow-up. Thus, augmentation of uncemented cups with screws, pegs, or hydroxyapatite did not appear to improve the long-term stability compared with press-fit only. PMID:26260783

  16. Hybrid Stabilization of Thoracic Spine Fractures with Sublaminar Bands and Transpedicular Screws: Description of a Surgical Alternative and Review of the Literature

    PubMed Central

    Unterweger, Marie-Therese; Kandziora, Frank; Schnake, Klaus J.

    2015-01-01

    Stabilization of unstable thoracic fractures with transpedicular screws is widely accepted. However, placement of transpedicular screws can cause complications, particularly in the thoracic spine with physiologically small pedicles. Hybrid stabilization, a combination of sublaminar bands and pedicle screws, might reduce the rate of misplaced screws and can be helpful in special anatomic circumstances, such as preexisting scoliosis and osteoporosis. We report about two patients suffering from unstable thoracic fractures, of T5 in one case and T3, T4, and T5 in the other case, with preexisting scoliosis and extremely small pedicles. Additionally, one patient had osteoporosis. Patients received hybrid stabilization with pedicle screws adjacent to the fractured vertebral bodies and sublaminar bands at the level above and below the pedicle screws. No complications occurred. Follow-up was 12 months with clinically uneventful postoperative courses. No signs of implant failure or loss of reduction could be detected. In patients with very small thoracic pedicles, scoliosis, and/or osteoporosis, hybrid stabilization with sublaminar bands and pedicle screws can be a viable alternative to long pedicle screw constructs. PMID:26649214

  17. Histomorphometric Evaluation of the Effects of Various Diode Lasers and Force Levels on Orthodontic Mini Screw Stability

    PubMed Central

    Isman, Eren; Taner, Lale; Kurkcu, Mehmet

    2015-01-01

    Abstract Objective The purpose of this study was to evaluate the effects of different laser dose and force levels on the stability of orthodontic mini screws used for anchorage, by histomorphometric analyses. Background data Low-level laser therapy speeds up blood flow, improves the mechanism of the revitalization processes, reduces the risk of infection, boosts metabolic activities, and accelerates the healing of the damaged tissue. Although there are many research studies about low-level laser therapy applications in a variety of areas, no investigations were found concerning mini screw stability using various laser dose levels with different force level applications. Methods Seventeen New Zealand white rabbits were used. A total of 68 cylindrical, self-drilling orthodontic mini screws were threaded at the fibula. Experimental subjects were divided into six groups; force application was not performed in the first three groups, whereas 150g of force was applied via nickel-titanium closed-coil springs placed between two mini screws in the other three groups. Measurements of the initial torque values (10 Ncm) were manipulated by a digital portable torque gauge. Various low-level laser doses were applied to the groups during the postoperative 10 days. After 4 weeks, bone-to-implant contact and cortical bone thickness were histomorphometrically analyzed. Results In the 150g force plus 20 J/cm2 dosage group, the highest bone-to-implant contact values were observed. (p<0.05) There were no statistically significant correlations between cortical bone thickness and bone-to-implant contact values; on the other hand, no significant difference was found among the same groups in terms of cortical bone thickness values (p>0.05). Conclusions Low-level laser therapy was noticed to induce the mini screw–bone contact area. Low-level laser therapy may be a supplementary treatment method to increase the stability of the orthodontic mini screw. PMID:25594769

  18. Posterior cervical arthrodesis and stabilization: an early report using a novel lateral mass screw and rod technique

    PubMed

    Horgan; Kellogg; Chesnut

    1999-06-01

    OBJECTIVE: Posterior cervical arthrodesis and stabilization with lateral mass plates is a biomechanically sound construct in multiple planes of motion. It is reproducible and especially useful when the posterior elements are missing or fractured. Unfortunately, it is difficult to use in patients with severe degenerative spondylosis because the plate is malleable only in the sagittal plane and the screw positions are dictated by the plate's entry holes. METHODS: A novel system of lateral mass screws that can be positioned before placement of a lateral construct was used in nine patients. Their outcomes as well as the technical applications of this system were reviewed. RESULTS: A total of 52 screws were placed in nine patients who underwent posterior cervical arthrodesis with the Cervifix system (Synthes USA, Paoli, PA). Diagnoses included trauma in four patients, degenerative spondylosis in three, and tumor in two. Rods were molded individually according to the patient's anatomy. Compression, distraction, and lateral rotation, if indicated, were performed. Follow-up averaged 36 weeks. Lateral and anteroposterior radiographs, obtained at progressive intervals, revealed excellent fixation and screw purchase without pull-out. There were no cases of spinal cord, nerve root, or vertebral artery injury. CONCLUSION: The Cervifix system accommodates variation in anatomic size and spacing of the lateral masses, potentiating precise screw placement. The rods can be molded in multiple planes, and selective application of compressive, distractive, or lateral rotatory forces is allowed. The system is very straightforward and simple to use, and we have had good success without pseudarthrosis or complications from screw placement in our series. PMID:10371626

  19. Computer tomography assessment of pedicle screw insertion in percutaneous posterior transpedicular stabilization.

    PubMed

    Schizas, Constantin; Michel, Jacky; Kosmopoulos, Victor; Theumann, Nicolas

    2007-05-01

    Percutaneous insertion of cannulated pedicle screws has been recently developed as a minimally invasive alternative to the open technique during instrumented fusion procedures. Given the reported rate of screw misplacement using open techniques (up to 40%), we considered it important to analyze possible side effects of this new technique. Placement of 60 pedicle screws in 15 consecutive patients undergoing lumbar or lumbosacral fusion, mainly for spondylolisthesis, were analyzed. Axial, coronal, and sagittal reformatted computer tomography images were examined by three observers. Individual and consensus interpretation was obtained for each screw position. Along with frank penetration, we also looked at cortical encroachment of the pedicular wall by the screw. Thirteen percent of the patients (2/15) had severe frank penetration from the screws, while 80% of them (12/15) had some perforation. On axial images the incidence of severe frank pedicle penetration was 3.3% while the overall rate of screw perforation was 23%. In coronal images the overall screw perforation rate rose to 30% while the rate of severe frank pedicle penetration remained unchanged. One patient (6.6%) suffered S1 root symptoms due to a frankly medially misplaced screw, requiring re-operation. This study has shown that percutaneous insertion of cannulated pedicle screws in the lumbar spine is an acceptable procedure. The overall rate of perforation in axial images is below the higher rates reported in the literature but does remain important. Frank penetration of the pedicle was nevertheless low. It remains a demanding technique and has to be performed with extreme care to detail. PMID:16967297

  20. Biomechanical Evaluation of Pedicle Screw-Based Dynamic Stabilization Devices for the Lumbar Spine: A Systematic Review

    PubMed Central

    Ponnappan, Ravi K.; Song, Jason; Vaccaro, Alexander R.

    2008-01-01

    Study Design This study is a systematic review of published biomechanical studies involving pedicle screw-based posterior dynamic stabilization devices (PDS) with a special focus on kinematics and load transmission through the functional spine unit (FSU). Methods A literature search was performed via the PubMed online database from 1990 to 2008 using the following key words: “biomechanics,” “lumbar dynamic stabilization,” “Graf system,” “Dynesys,” and “posterior dynamic implant.” Citations were limited to papers describing biomechanics of pedicle screw-based PDS devices currently available for clinical use. Studies describing clinical experience, radiology, and in vivo testing were excluded from the review. Parameters measured included kinematics of the FSU (range of motion (ROM), neutral zone (NZ), and location of the center of rotation) and load transmission through the disk, facets, and instrumentation. Results A total of 27 publications were found that concerned the biomechanical evaluation of lumbar pedicle screw-based dynamic stabilization instrumentation. Nine in vitro experimental studies and 4 finite element analyses satisfied the inclusion criteria. The Dynesys implant was the most investigated pedicle screw-based PDS system. In vitro cadaveric studies mainly focused on kinematics comparing ROM of intact versus instrumented spines whereas finite element analyses allowed analysis of load transmission at the instrumented and adjacent levels. Conclusion Biomechanical studies demonstrate that pedicle screw-based PDS devices limit intervertebral motion while unloading the intervertebral disk. The implant design and the surgical technique have a significant impact on the biomechanical behavior of the instrumented spinal segment. The posterior placement of such devices results in non-physiologic intervertebral kinematics with a posterior shift of the axis of rotation. Biomechanical studies suggest that the difference at the adjacent level

  1. Electrical noise to a knee joint stabilizes quiet bipedal stance.

    PubMed

    Kimura, Tetsuya; Kouzaki, Motoki

    2013-04-01

    Studies have shown that a minute, noise-like electrical stimulation (ES) of a lower limb joint stabilizes one-legged standing (OS), possibly due to the noise-enhanced joint proprioception. To demonstrate the practical utility of this finding, we assessed whether the bipedal stance (BS), relatively stable and generally employed in daily activities, is also stabilized by the same ES method. Twelve volunteers maintained quiet BS with or without an unperceivable, noise-like ES of a knee joint. The results showed that the average amplitude, peak-to-peak amplitude, and standard deviation of the foot center of pressure in the anteroposterior direction were significantly attenuated by the ES (P<0.05). These results indicate that the BS also can be stabilized by an unperceivable, noise-like ES of a knee joint. PMID:23044409

  2. Migration pattern of cementless press fit cups in the presence of stabilizing screws in total hip arthroplasty.

    PubMed

    Zilkens, C; Djalali, S; Bittersohl, B; Kälicke, T; Kraft, C N; Krauspe, R; Jäger, Marcus

    2011-03-28

    The aim of this study was to evaluate the initial acetabular implant stability and late acetabular implant migration in press fit cups combined with screw fixation of the acetabular component in order to answer the question whether screws are necessary for the fixation of the acetabular component in cementless primary total hip arthroplasty. One hundred and seven hips were available for follow-up after primary THA using a cementless, porous-coated acetabular component. A total of 631 standardized radiographs were analyzed digitally by the "single-film-x-ray-analysis" method (EBRA). One hundred and one (94.4 %) acetabular components did not show significant migration of more than 1 mm. Six (5.6%) implants showed migration of more than 1 mm. Statistical analysis did not reveal preoperative patterns that would identify predictors for future migration. Our findings suggest that the use of screw fixation for cementless porous-coated acetabular components for primary THA does not prevent cup migration. PMID:21486725

  3. Massive osteochondritis of the lateral femoral condyle associated with discoid meniscus: management with meniscoplasty, rim stabilization and bioabsorbable screw fixation.

    PubMed

    Camathias, Carlo; Rutz, Erich; Gaston, Mark S

    2012-09-01

    Discoid menisci without tears and before surgical intervention may be an aetiological factor in the development of osteochondritis dissecans (OCD). We present the case of a massive OCD lesion in the lateral femoral condyle of a 12-year-old boy who presented with relatively few symptoms despite the size of the lesion. This was treated with meniscoplasty and rim stabilization, which has become established as the gold standard treatment for symptomatic discoid menisci. This was combined with bioabsorbable screw fixation of the OCD lesion, resulting in rapid resolution of symptoms and a return to normal magnetic resonance image appearances after 6 months. It is likely that instability of discoid menisci is a key causal component when present concurrently with OCD lesions. Therefore, stabilization of this is required as well as saucerization of the meniscus. OCD lesions which are of a sufficient size such that if they became unstable or dislocated would result in a significant defect should also be stabilized. We believe that bioabsorbable screw fixation presents a good solution for fixation in these cases and this combination of treatment should result in a satisfactory outcome. PMID:21817923

  4. The Effect of Lumbar Lordosis on Screw Loosening in Dynesys Dynamic Stabilization: Four-Year Follow-Up with Computed Tomography

    PubMed Central

    Kuo, Chao-Hung; Chang, Peng-Yuan; Tu, Tsung-Hsi; Fay, Li-Yu; Chang, Hsuan-Kan; Wu, Jau-Ching; Huang, Wen-Cheng; Cheng, Henrich

    2015-01-01

    Introduction. This study aimed to evaluate the effects of Dynesys dynamic stabilization (DDS) on clinical and radiographic outcomes, including spinal pelvic alignment. Method. Consecutive patients who underwent 1- or 2-level DDS for lumbar spondylosis, mild degenerative spondylolisthesis, or degenerative disc disease were included. Clinical outcomes were evaluated by Visual Analogue Scale for back and leg pain, Oswestry Disability Index, and the Japanese Orthopedic Association scores. Radiographic outcomes were assessed by radiographs and computed tomography. Pelvic incidence and lumbar lordosis (LL) were also compared. Results. In 206 patients with an average follow-up of 51.1 ± 20.8 months, there were 87 screws (8.2%) in 42 patients (20.4%) that were loose. All clinical outcomes improved at each time point after operation. Patients with loosened screws were 45 years older. Furthermore, there was a higher risk of screw loosening in DDS involving S1, and these patients were more likely to have loosened screws if the LL failed to increase after the operation. Conclusions. The DDS screw loosening rate was overall 8.2% per screw and 20.4% per patient at more than 4 years of follow-up. Older patients, S1 involvement, and those patients who failed to gain LL postoperatively were at higher risk of screw loosening. PMID:26779532

  5. The Effect of Polymethyl Methacrylate Augmentation on the Primary Stability of Cannulated Bone Screws in an Anterolateral Plate in Osteoporotic Vertebrae: A Human Cadaver Study.

    PubMed

    Rüger, Matthias; Sellei, Richard M; Stoffel, Marcus; von Rüden, Christian

    2016-02-01

    Study Design Cohort study. Objective Expandable anterolateral plates facilitate the reduction of posttraumatic deformities of thoracolumbar spine injuries and are commonly used in cases of unstable injuries or compromised bone quality. In this in vitro study, the craniocaudal yield load of the osseous fixation of an anterior angular stable plate fixation system and the effect of polymethyl methacrylate (PMMA) screw augmentation on the primary stability of the screw-bone interface during kyphosis reduction was evaluated in 12 osteoporotic human thoracolumbar vertebrae. Methods The anterolateral stabilization device used for this study is comprised of two swiveling flanges and an expandable midsection. It facilitates the controlled reduction of kyphotic deformities in situ with a geared distractor. Single flanges were attached to 12 thoracolumbar vertebrae. Six specimens were augmented with PMMA by means of cannulated bone screws. The constructs were subjected to static, displacement-controlled craniocaudal loading to failure in a servohydraulic testing machine. Results The uncemented screws cut out at a mean 393 ± 66 N, whereas the cemented screws showed significantly higher yield load of 966 ± 166 N (p < 0.02). We detected no significant correlation between bone mineral density and yield load in this setting. Conclusion Our results indicate that PMMA augmentation is an effective method to increase two- to threefold the primary stability of the screw-bone interface of an anterolateral spine stabilization system in osteoporotic bone. We recommend it in cases of severely compromised bone quality to reduce the risk of screw loosening during initial kyphosis correction and to increase long-term construct stability. PMID:26835201

  6. Effects of different mandibular fracture patterns on the stability of miniplate screw fixation in angle mandibular fractures.

    PubMed

    Pektas, Z O; Bayram, B; Balcik, C; Develi, T; Uckan, S

    2012-03-01

    The aim of the present study was to evaluate the effects of horizontally favourable and unfavourable mandibular fracture patterns on the fixation stability of titanium plates and screws by simulating chewing forces. Favourable and unfavourable mandibular fractures on 22 sheep hemimandibles were fixed with 4-hole straight titanium plates and 2.0mm×7mm titanium screws according to the Champy technique. Hemimandibles were mounted with a fixation device in a servohydraulic testing unit for compressive testing. Displacement values under 20, 60, 100, 120, 150, 200N, maximum displacements, and maximum forces the model could resist before breakage were recorded and compared. The authors found no statistically significant differences between the groups for the displacement values in the force range 60-200N (60, 100, 120, 150 and 200N). Statistically significant differences for maximum displacement values (displacement values at the breaking forces) between the groups were found (P<0.05). There was no evidence for the need to apply different treatment modalities to mandibular fractures regardless of whether the factures are favourable or not. PMID:22178275

  7. 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

  8. Decompressive cervical laminectomy and lateral mass screw-rod arthrodesis. Surgical analysis and outcome

    PubMed Central

    2011-01-01

    Background This study evaluates the outcome and complications of decompressive cervical Laminectomy and lateral mass screw fixation in 110 cases treated for variable cervical spine pathologies that included; degenerative disease, trauma, neoplasms, metabolic-inflammatory disorders and congenital anomalies. Methods A retrospective review of total 785 lateral mass screws were placed in patients ages 16-68 years (40 females and 70 males). All cases were performed with a polyaxial screw-rod construct and screws were placed by using Anderson-Sekhon trajectory. Most patients had 12-14-mm length and 3.5 mm diameter screws placed for subaxial and 28-30 for C1 lateral mass. Screw location was assessed by post operative plain x-ray and computed tomography can (CT), besides that; the facet joint, nerve root foramen and foramen transversarium violation were also appraised. Results No patients experienced neural or vascular injury as a result of screw position. Only one patient needed screw repositioning. Six patients experienced superficial wound infection. Fifteen patients had pain around the shoulder of C5 distribution that subsided over the time. No patients developed screw pullouts or symptomatic adjacent segment disease within the period of follow up. Conclusion decompressive cervical spine laminectomy and Lateral mass screw stabilization is a technique that can be used for a variety of cervical spine pathologies with safety and efficiency. PMID:21595968

  9. Abutment screw loosening of endosseous dental implant body/abutment joint by cyclic torsional loading test at the initial stage.

    PubMed

    Katsuta, Yasuhiro; Watanabe, Fumihiko

    2015-01-01

    Cyclic torsional loading tests were carried out in the laboratory using various implant systems, in order to clarify differences between the systems in loosening of abutment screws. Six samples from six commercially available abutment systems were used, giving a total of 36 samples. Four of the systems used internal connections, and two used external connections. The abutment screw for each system was tightened to a torque value specified by the manufacturer, and after 5 min, the loosening torque was measured using a digital torque meter. Measurements were taken twice, and a second measurement was taken as a reference value. A cyclic torsional loading test with 100,000 cycles was performed on the sample, and the loosening torque was again measured after the test. In conclusion, loosening of the abutment screw occurred as a result of cyclic torsional loading, and the degree of loosening varied with each implant system. PMID:26632240

  10. The Effect of Polymethyl Methacrylate Augmentation on the Primary Stability of Cannulated Bone Screws in an Anterolateral Plate in Osteoporotic Vertebrae: A Human Cadaver Study

    PubMed Central

    Rüger, Matthias; Sellei, Richard M.; Stoffel, Marcus; von Rüden, Christian

    2015-01-01

    Study Design Cohort study. Objective Expandable anterolateral plates facilitate the reduction of posttraumatic deformities of thoracolumbar spine injuries and are commonly used in cases of unstable injuries or compromised bone quality. In this in vitro study, the craniocaudal yield load of the osseous fixation of an anterior angular stable plate fixation system and the effect of polymethyl methacrylate (PMMA) screw augmentation on the primary stability of the screw–bone interface during kyphosis reduction was evaluated in 12 osteoporotic human thoracolumbar vertebrae. Methods The anterolateral stabilization device used for this study is comprised of two swiveling flanges and an expandable midsection. It facilitates the controlled reduction of kyphotic deformities in situ with a geared distractor. Single flanges were attached to 12 thoracolumbar vertebrae. Six specimens were augmented with PMMA by means of cannulated bone screws. The constructs were subjected to static, displacement-controlled craniocaudal loading to failure in a servohydraulic testing machine. Results The uncemented screws cut out at a mean 393 ± 66 N, whereas the cemented screws showed significantly higher yield load of 966 ± 166 N (p < 0.02). We detected no significant correlation between bone mineral density and yield load in this setting. Conclusion Our results indicate that PMMA augmentation is an effective method to increase two- to threefold the primary stability of the screw–bone interface of an anterolateral spine stabilization system in osteoporotic bone. We recommend it in cases of severely compromised bone quality to reduce the risk of screw loosening during initial kyphosis correction and to increase long-term construct stability. PMID:26835201

  11. 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

  12. Effect of number and geometry of resorbable screws on biomechanical stability of in vitro model with sagittal split ramus osteotomy.

    PubMed

    Hwang, Jong-Min; Baek, Seung-Hak; Choi, Jin-Young

    2012-03-01

    The purpose of this study was to investigate the effect of the number and the geometry of resorbable screws (RSs; Inion CPS System; Inion Ltd, Tampere, Finland) on the biomechanical stability of the in vitro model with sagittal split ramus osteotomy. The sagittal split ramus osteotomy polyurethane hemimandible (Synbone, Malans, Switzerland) was fixed by 7 osteosynthesis methods after 5 mm advancement of the distal segment (n = 5 for each method): 1TP (1 titanium miniplate and 4 screws), 3RL (3 RSs with linear configuration at the retromolar area [RMA]), 2R1B (2 RSs at RMA and 1 RS at the mandibular body [MB]), 2R1A (2 RSs at the RMA and 1 RS at the mandibular angle [MA]), 3R1B (3 RSs at RMA and 1 RS at the MB), 3R1A (3 RSs at RMA and 1 RS at the MA), and 3R1A1B (3 RSs at the RMA, 1 RS at the MA, and 1 RS at the MB). Values of linear compressive load were measured at 1- to 5-mm displacement of the lower first molar with a 1-mm interval and were statistically analyzed. From 1- to 5-mm displacement, there were significant differences in load values among groups (P < 0.05, P < 0.01, P < 0.01, P < 0.001, and P < 0.001, respectively). When the amount of displacement was increased, the difference in load values between 1TP, 3RL, and 2R1B became significantly prominent. There was a significant difference in total load values according to number and geometry of RSs (P < 0.001). All kinds of geometry with more than 3 RSs were more rigid than 1TP. The 3R1A1B method showed better biomechanical stability than 1TP, 3RL, and 2R1B. In 3 RS and 4 RS groups, fixation in MA (2R1A, 3R1A) exhibited a tendency of better stability than fixation in MB (2R1B, 3R1B). Fixation with 2R1A could provide better biomechanical stability than 1TP and similar rigidity with 3R1A1B. PMID:22421826

  13. 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

  14. The Effects of Screw Length on Stability of Simulated Osteoporotic Distal Radius Fractures Fixed with Volar Locking Plates

    PubMed Central

    Wall, Lindley B.; Brodt, Michael D.; Silva, Matthew J.; Boyer, Martin I.; Calfee, Ryan P.

    2013-01-01

    Purpose Volar plating for distal radius fractures has caused extensor tendon ruptures secondary to dorsal screw prominence. This study was designed to determine the biomechanical impact of placing unicortical distal locking screws and pegs in an extra-articular fracture model. Methods Volar-locking distal radius plates were applied to 30 osteoporotic distal radius models. Radii were divided into 5 groups based on distal locking fixation: bicortical locked screws, 3 lengths of unicortical locked screws (abutting the dorsal cortex [full length], 75% length, and 50% length to dorsal cortex), and unicortical locked pegs. Distal radius osteotomy simulated a dorsally comminuted, extra-articular, fracture. Each constructs stiffness was determined under physiologic loads (axial compression, dorsal bending volar bending) before and after 1000 cycles of axial conditioning and prior to axial loading to failure (2mm of displacement) and subsequent catastrophic failure. Results Cyclic conditioning did not alter constructs stiffness. Stiffness to volar bending and dorsal bending forces were similar between groups. Final stiffness(N/mm) under axial load was statistically equivalent for all groups: bicortical screws(230), full-length unicortical screws(227), 75% length unicortical screws(226), 50% length unicortical screws(187), unicortical pegs(226). Force(N) at 2 mm displacement was significantly less for 50% length unicortical screws(311) compared to bicortical screws(460), full-length unicortical screws(464), 75% length unicortical screws(400), and unicortical pegs(356). Force(N) to catastrophic fracture was statistically equivalent between groups but mean values for pegs(749) and 50% length unicortical(702) screws were 16-21% less than means for bicortical(892), full-length unicortical(860), and 75% length(894) unicortical constructs. Discussion Locked unicortical distal screws of at least 75% length produce construct stiffness similar to bicortical fixation. Unicortical

  15. Improving the long-term stability of Ti6Al4V abutment screw by coating micro/nano-crystalline diamond films.

    PubMed

    Xie, Youneng; Zhou, Jing; Wei, Qiuping; Yu, Z M; Luo, Hao; Zhou, Bo; Tang, Z G

    2016-10-01

    Abutment screw loosening is the most common complication of implanting teeth. Aimed at improving the long-term stability of them, well-adherent and homogeneous micro-crystalline diamond (MCD) and nano-crystalline diamond (NCD) were deposited on DIO(®) (Dong Seo, Korea) abutment screws using a hot filament chemical vapor deposition (HFCVD) system. Compared with bare DIO(®) screws, diamond coated ones showed higher post reverse toque values than the bare ones (p<0.05) after cyclic loading one million times under 100N, and no obvious flaking happened after loading test. Diamond coated disks showed lower friction coefficients of 0.15 and 0.18 in artificial saliva when countered with ZrO2 than that of bare Ti6Al4V disks of 0.40. Though higher cell apoptosis rate was observed on film coated disks, but no significant difference between MCD group and NCD group. And the cytotoxicity of diamond films was acceptable for the fact that the cell viability of them was still higher than 70% after cultured for 72h. It can be inferred that coating diamond films might be a promising modification method for Ti6Al4V abutment screws. PMID:27393893

  16. Removal torque of nail interlocking screws is related to screw proximity to the fracture and screw breakage.

    PubMed

    White, Alexander A; Kubacki, Meghan R; Samona, Jason; Telehowski, Paul; Atkinson, Patrick J

    2016-06-01

    Studies have shown that titanium implants can be challenging to explant due to the material's excellent biocompatibility and resulting osseointegration. Clinically, titanium alloy nail interlocking screws may require removal to dynamize a construct or revise the nail due to nonunion, infection, pain, or periprosthetic fracture. This study was designed to determine what variables influence the removal torque for titanium alloy interlocking screws. An intramedullary nail with four interlocking screws was used to stabilize a 1-cm segmental femoral defect in a canine model for 16 weeks. The animals were observed to be active following a several-day recovery after surgery. In six animals, the femora and implanted nail/screws were first tested to failure in torsion to simulate periprosthetic fracture of an implant after which the screws were then removed. In four additional animals, the screws were removed without mechanical testing. Both intraoperative insertional and extraction torques were recorded for all screws. Mechanical testing to failure broke 10/24 screws. On average, the intact screws required 70% of the insertional torque during removal while broken screws only required 16% of the insertional torque (p < 0.001). In addition, intact screws closer to the fracture required 2.8 times more removal torque than the outboard distal screw (p < 0.005). On average, the angle of rotation to peak torque was ∼80°. The peak axial load did not significantly correlate with the torque required to remove the screws. On average, the removal torque was lower than at the time of insertion, and less torque was required to remove broken screws and screws remote to the fracture. However, broken screws will require additional time to retrieve the remaining screw fragment. This study suggests that broken screws and screws in prematurely active patients will require less torque to remove. PMID:27129382

  17. Inferolateral Entry Point for C2 Pedicle Screw Fixation in High Cervical Lesions

    PubMed Central

    Lee, Kwang Ho; Lee, Chul Hee; Hwang, Soo Hyun; Park, In Sung; Jung, Jin Myung

    2011-01-01

    Objective The purpose of this retrospective study was to evaluate the efficacy and safety of atlantoaxial stabilization using a new entry point for C2 pedicle screw fixation. Methods Data were collected from 44 patients undergoing posterior C1 lateral mass screw and C2 screw fixation. The 20 cases were approached by the Harms entry point, 21 by the inferolateral point, and three by pars screw. The new inferolateral entry point of the C2 pedicle was located about 3-5 mm medial to the lateral border of the C2 lateral mass and 5-7 mm superior to the inferior border of the C2-3 facet joint. The screw was inserted at an angle 30° to 45° toward the midline in the transverse plane and 40° to 50° cephalad in the sagittal plane. Patients received followed-up with clinical examinations, radiographs and/or CT scans. Results There were 28 males and 16 females. No neurological deterioration or vertebral artery injuries were observed. Five cases showed malpositioned screws (2.84%), with four of the screws showing cortical breaches of the transverse foramen. There were no clinical consequences for these five patients. One screw in the C1 lateral mass had a medial cortical breach. None of the screws were malpositioned in patients treated using the new entry point. There was a significant relationship between two group (p=0.036). Conclusion Posterior C1-2 screw fixation can be performed safely using the new inferolateral entry point for C2 pedicle screw fixation for the treatment of high cervical lesions. PMID:22200017

  18. Influence of abutment materials on the implant-abutment joint stability in internal conical connection type implant systems

    PubMed Central

    Jo, Jae-Young; Yang, Dong-Seok; Huh, Jung-Bo; Heo, Jae-Chan; Yun, Mi-Jung

    2014-01-01

    PURPOSE This study evaluated the influence of abutment materials on the stability of the implant-abutment joint in internal conical connection type implant systems. MATERIALS AND METHODS Internal conical connection type implants, cement-retained abutments, and tungsten carbide-coated abutment screws were used. The abutments were fabricated with commercially pure grade 3 titanium (group T3), commercially pure grade 4 titanium (group T4), or Ti-6Al-4V (group TA) (n=5, each). In order to assess the amount of settlement after abutment fixation, a 30-Ncm tightening torque was applied, then the change in length before and after tightening the abutment screw was measured, and the preload exerted was recorded. The compressive bending strength was measured under the ISO14801 conditions. In order to determine whether there were significant changes in settlement, preload, and compressive bending strength before and after abutment fixation depending on abutment materials, one-way ANOVA and Tukey's HSD post-hoc test was performed. RESULTS Group TA exhibited the smallest mean change in the combined length of the implant and abutment before and after fixation, and no difference was observed between groups T3 and T4 (P>.05). Group TA exhibited the highest preload and compressive bending strength values, followed by T4, then T3 (P<.001). CONCLUSION The abutment material can influence the stability of the interface in internal conical connection type implant systems. The strength of the abutment material was inversely correlated with settlement, and positively correlated with compressive bending strength. Preload was inversely proportional to the frictional coefficient of the abutment material. PMID:25551010

  19. Evolutionary Stability of Jointly Evolving Traits in Subdivided Populations.

    PubMed

    Mullon, Charles; Keller, Laurent; Lehmann, Laurent

    2016-08-01

    The evolutionary stability of quantitative traits depends on whether a population can resist invasion by any mutant. While uninvadability is well understood in well-mixed populations, it is much less so in subdivided populations when multiple traits evolve jointly. Here, we investigate whether a spatially subdivided population at a monomorphic equilibrium for multiple traits can withstand invasion by any mutant or is subject to diversifying selection. Our model also explores the correlations among traits arising from diversifying selection and how they depend on relatedness due to limited dispersal. We find that selection tends to favor a positive (negative) correlation between two traits when the selective effects of one trait on relatedness is positively (negatively) correlated to the indirect fitness effects of the other trait. We study the evolution of traits for which this matters: dispersal that decreases relatedness and helping that has positive indirect fitness effects. We find that when dispersal cost is low and the benefits of helping accelerate faster than its costs, selection leads to the coexistence of mobile defectors and sessile helpers. Otherwise, the population evolves to a monomorphic state with intermediate helping and dispersal. Overall, our results highlight the effects of population subdivision for evolutionary stability and correlations among traits. PMID:27420783

  20. Orientation of the "Lisfranc screw".

    PubMed

    Panchbhavi, Vinod K

    2012-11-01

    The reduction and stabilization of diastases between the medial cuneiform and the base of second metatarsal after a Lisfranc ligament injury is a crucial objective in the open reduction and internal fixation of these injuries. To achieve this objective, a single screw is used. The present practice is to insert the screw directed from the medial cuneiform bone into the base of the second metatarsal. This technique trick describes an easier method of insertion of the screw and one that possibly provides a better fixation. PMID:22549028

  1. 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

  2. The mast cell stabilizer ketotifen reduces joint capsule fibrosis in a rabbit model of post-traumatic joint contractures

    PubMed Central

    Hart, David A.; Befus, A. Dean; Salo, Paul T.; Zhang, Mei; Hildebrand, Kevin A.

    2013-01-01

    Objectives Using a rabbit model of post-traumatic joint contractures, we investigated whether treatment with a mast cell stabilizer after joint injury would lessen the molecular manifestations of joint capsule fibrosis. Methods Surgical joint injury was used to create stable post-traumatic contractures of the knee in skeletally mature New Zealand white rabbits. Four groups of animals were studied: a non-operated control group (n = 8), an operated contracture group (n = 13) and two operated groups treated with the mast cell stabilizer, ketotifen, at doses of 0.5 mg/kg (n = 9) and 1.0 mg/kg (n = 9) twice daily. Joint capsule fibrosis was assessed by quantifying the mRNA and protein levels of α-SMA, tryptase, TGF-β1, collagen I and collagen III. Significance was tested using an ANOVA analysis of variance. Results The protein and mRNA levels of α-SMA, TGF-β1, tryptase and collagen I and III were significantly elevated in the operated contracture group compared to control (p < 0.01). In both ketotifen-treated groups, protein and mRNA levels of α-SMA, TGF-β1 and collagen I were significantly reduced compared to the operated contracture group (p < 0.01). Conclusions These data suggest an inflammatory pathway mediated by mast cell activation is involved in joint capsule fibrosis after traumatic injury. PMID:22173279

  3. Influence of screw length and diameter on tibial strain energy density distribution after anterior cruciate ligament reconstruction

    NASA Astrophysics Data System (ADS)

    Yao, Jie; Kuang, Guan-Ming; Wong, Duo Wai-Chi; Niu, Wen-Xin; Zhang, Ming; Fan, Yu-Bo

    2014-04-01

    Postoperative tunnel enlargement has been frequently reported after anterior cruciate ligament (ACL) reconstruction. Interference screw, as a surgical implant in ACL reconstruction, may influence natural loading transmission and contribute to tunnel enlargement. The aims of this study are (1) to quantify the alteration of strain energy den sity (SED) distribution after the anatomic single-bundle ACL reconstruction; and (2) to characterize the influence of screw length and diameter on the degree of the SED alteration. A validated finite element model of human knee joint was used. The screw length ranging from 20 to 30mm with screw diameter ranging from 7 to 9 mm were investigated. In the post-operative knee, the SED increased steeply at the extra-articular tunnel aperture under compressive and complex loadings, whereas the SED decreased beneath the screw shaft and nearby the intra-articular tunnel aperture. Increasing the screw length could lower the SED deprivation in the proximal part of the bone tunnel; whereas increasing either screw length or diameter could aggravate the SED deprivation in the distal part of the bone tunnel. Decreasing the elastic modulus of the screw could lower the bone SED deprivation around the screw. In consideration of both graft stability and SED alteration, a biodegradable interference screw with a long length is recommended, which could provide a beneficial mechanical environment at the distal part of the tunnel, and meanwhile decrease the bone-graft motion and synovial fluid propagation at the proximal part of the tunnel. These findings together with the clinical and histological factors could help to improve surgical outcome, and serve as a preliminary knowledge for the following study of biodegradable interference screw. [Figure not available: see fulltext.

  4. Finite element model creation and stability considerations of complex biological articulation: The human wrist joint.

    PubMed

    Gíslason, Magnús K; Stansfield, Benedict; Nash, David H

    2010-06-01

    The finite element method has been used with considerable success to simulate the behaviour of various joints such as the hip, knee and shoulder. It has had less impact on more complicated joints such as the wrist and the ankle. Previously published finite element studies on these multi-bone joints have needed to introduce un-physiological boundary conditions in order to establish numerical convergence of the model simulation. That is necessary since the stabilizing soft tissue mechanism of these joints is usually too elaborate in order to be fully included both anatomically and with regard to material properties. This paper looks at the methodology of creating a finite element model of such a joint focussing on the wrist and the effects additional constraining has on the solution of the model. The study shows that by investigating the effects each of the constraints, a better understanding on the nature of the stabilizing mechanisms of these joints can be achieved. PMID:20303315

  5. Preventing proximal junctional failure in long segmental instrumented cases of adult degenerative scoliosis using a multilevel stabilization screw technique

    PubMed Central

    Sandquist, Lee; Carr, Daniel; Tong, Doris; Gonda, Roger; Soo, Teck M.

    2015-01-01

    Background: The authors sought to demonstrate the safety and effectiveness of the multilevel stabilization screw (MLSS) technique in decreasing the incidence of proximal junctional failure in long segmental instrumented fusions for adult degenerative scoliosis. Methods: Institutional review board approval was obtained and all patients with adult spinal deformity who underwent the MLSS technique were analyzed. A neuro-radiologist and spine-focused neurosurgeon not involved with the surgical treatment performed radiographic analysis. Proximal junctional angle was defined as the caudal endplate of the upper instrumented vertebra (UIV) to the cephalad endplate of two supradjacent vertebrae above the UIV. The UIV is defined as the most cephalad vertebra completed captured by the instrumentation. Abnormal proximal junctional kyphosis (PJK) was defined as proximal junctional sagittal Cobb angle >10 degrees and proximal junction sagittal Cobb angle at least 10 degrees greater than the preoperative measurement. The presence of both is criteria necessary to be considered abnormal. Results: Twenty patients with degenerative scoliosis underwent the MLSS technique with the upper-instrumented vertebrae in the proximal thoracic spine. Fifteen patients met inclusion criteria with greater than 12 months radiographic and clinical follow up. Three patients were excluded due to lack of follow up imaging and two patients were excluded due to the inability to measure the UIV. Age range was 44–84 years with a mean of 66. Eleven of the 15 patients were over the age of 60 at the time of surgery. The male-to-female ratio was 4:11. Body mass index (BMI) range was 24–44 with a mean of 31.5 units. The follow up period ranged from 14 to 58 months with an average follow up of 30 months. The mean change in Cobb angle at the proximal junction was 4.00 degrees with a range from -0.92 to 9.13 degrees. There were no fractures or instrumentation failures at or near the proximal junction. There was

  6. A rare case of floating clavicle and a novel technique for stabilizing the sternoclavicular joint

    PubMed Central

    Webb, Mark; Wallace, Angus

    2014-01-01

    We present the first ever case report of a floating clavicle with a unique combination of a posterior sternoclavicular joint dislocation and an associated grade III acromioclavicular joint dislocation. We treated this injury surgically by stabilizing both ends of clavicle using a polyester surgical mesh device (LockDown™; Mandaco 569 Limited, Redditch, UK; previously called the Nottingham Surgilig).

  7. Understanding stability of the distal radioulnar joint through an understanding of its anatomy.

    PubMed

    Hagert, Elisabet; Hagert, Carl-Göran

    2010-11-01

    The authors describe the anatomy of the distal radioulnar joint (DRUJ) and delineate the importance of viewing this joint as part of the whole forearm. The osseous congruity and ligamentous integrity is of essence for the stability of the DRUJ, according to the principles of tensegrity. The neuromuscular control and possible proprioceptive function of the DRUJ are also outlined. PMID:20951895

  8. 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. PMID:27022526

  9. Characterization of the torque limits and clamping force relationships for small stainless steel screws in tensile loaded joints of various metals

    SciTech Connect

    Bernardin, John D; Flores, Eugene M

    2009-01-01

    This study originated during the design of ChemCam, a Laser Induced Breakdown Spectroscopy (LIBS) and imaging instrument being developed for NASA's Mars Science Lab Rover. The mission needs for miniaturization, reduced weight, high reliability, minimal use of thread locking compounds, and the ability to handle harsh environmental conditions dictated the use of small, high strength screws to be threaded into a variety of metal alloys including Be-S200f, Al-6061-T6, Mg-ZK60A-T5, and Ti-6Al-4V The lack of a credible fastener torque database for small (No.0 through No.8) high strength stainless steel screws in various parent materials, led to the development of an experimental program to characterize the following: (A) The screw torque value versus angular rotation (which indicates yielding in the screw or parent material) as a function of screw diameter, screw head configuration, depth of thread engagement, type of parent material, type of surface treatment on parent material, presence of thread locking compound, repeatable threaded hole use, and degree of screw pedigree. (B) The relationship between fastener torque and clamping force for a subset of the above mentioned variables. The database generated from this study will serve as a design reference for utilizing small stainless steel fasteners and provide trending information for other researchers who may be interested in broadening its range of parameters. This paper reviews the related fastener torque and clamping force information from the literature, describes the experimental screw torque and clamping force monitoring equipment, presents the test matrix and experimental procedures, and discusses the empirical results.

  10. Clinical joint inactivity predicts structural stability in patients with established rheumatoid arthritis

    PubMed Central

    Gärtner, M; Sigmund, I K; Alasti, F; Supp, G; Radner, H; Machold, K; Smolen, J S; Aletaha, D

    2016-01-01

    Objectives Clinical joint activity is a strong predictor of joint damage in rheumatoid arthritis (RA), but progression of damage might increase despite clinical inactivity of the respective joint (silent progression). The aim of this study was to evaluate the prevalence of silent joint progression, but particularly on the patient level and to investigate the duration of clinical inactivity as a marker for non-progression on the joint level. Methods 279 patients with RA with any radiographic progression over an observational period of 3–5 years were included. We obtained radiographic and clinical data of 22 hand/finger joints over a period of at least 3 years. Prevalence of silent progression and associations of clinical joint activity and radiographic progression were evaluated. Results 120 (43.0%) of the patients showed radiographic progression in at least one of their joints without any signs of clinical activity in that respective joint. In only 7 (5.8%) patients, such silent joint progression would go undetected, as the remainder had other joints with clinical activity, either with (n=84; 70.0%) or without (n=29; 24.2%) accompanying radiographic progression. Also, the risk of silent progression decreases with duration of clinical activity. Conclusions Silent progression of a joint without accompanying apparent clinical activity in any other joint of a patient was very rare, and would therefore be most likely detected by the assessment of the patient. Thus, full clinical remission is an excellent marker of structural stability in patients with RA, and the maintenance of this state reduces the risk of progression even further. PMID:27110386

  11. Biomechanical analysis of expansion screws and cortical screws used for ventral plate fixation on the cervical spine

    PubMed Central

    Ullrich, Bernhard; Huber, Gerd; Morlock, Michael M.

    2009-01-01

    Compared to bicortical screws, the surgical risk of injuring intraspinal structures can be minimized with the use of monocortical screws. However, this reduction should not be achieved at the expense of the stability of the fixation. With monocortical stabilization, the expansion screws have the potential of absorbing high loads. Therefore, they are expected to be a suitable alternative to bicortical screws for revision surgeries and in osteoporotic bone. The purpose of this in vitro study was to investigate the stiffness of the two screw-plate systems used for ventral stabilization of the cervical spine, by focusing on the suitability of expansion screws as tools for revision treatments. The study was conducted in ten functional units of human cervical spines. The device sample stiffness was determined for four conditions using a turning moment of 2.25 N m each around one of the three principle axes. The conditions were native, destabilized, primarily stabilized with one of the screw-plate systems, followed by secondary stabilization using the expansion screw implant. The stabilized samples achieved a comparable, in most cases higher stiffness than the native samples. The samples undergoing secondary stabilization using expansion screws tend to display greater stiffness for all three axes compared to the primarily stabilized samples. The achieved tightening moment of the screws was higher than the one achieved with primary fixation. Both plates revealed similar primary stability. Revision surgeries with secondary instrumentation achieve a high stiffness of the screwed up segments. Monocortical expansion screws combined with a trapezoidal plate allow ventral stabilization of the cervical spine that is comparable to the plate fixation using bicortical screws. PMID:19588171

  12. Reduced knee joint moment in ACL deficient patients at a cost of dynamic stability during landing.

    PubMed

    Oberländer, Kai Daniel; Brüggemann, Gert-Peter; Höher, Jürgen; Karamanidis, Kiros

    2012-05-11

    The current study aimed to examine the effect of anterior cruciate ligament deficiency (ACLd) on joint kinetics and dynamic stability control after a single leg hop test (SLHT). Twelve unilateral ACLd patients and a control subject group (n=13) performed a SLHT over a given distance with both legs. The calculation of joint kinetics was done by means of a soft-tissue artifact optimized rigid full-body model. Margin of stability (MoS) was quantified by the difference between the base of support and the extrapolated center of mass. During landing, the ACLd leg showed lower external knee flexion moments but demonstrated higher moments at the ankle and hip compared to controls (p<0.05). The main reason for the joint moment redistribution in the ACLd leg was a more anterior position of the ground reaction force (GRF) vector, which affected the moment arms of the GRF acting about the joints (p<0.05). For the ACLd leg, trunk angle was more flexed over the entire landing phase compared to controls (p<0.05) and we found a significant correlation between moment arms at the knee joint and trunk angle (r² = 0.48;p<0.01). The consequence of this altered landing strategy in ACLd legs was a more anterior position of the center of mass reducing the MoS (p<0.05). The results illustrate the interaction between trunk angle, joint kinetics and dynamic stability during landing maneuvers and provide evidence of a feedforward adaptive adjustment in ACLd patients (i.e. more flexed trunk angle) aimed at reducing knee joint moments at the cost of dynamic stability control. PMID:22440611

  13. The effect of an active vibration stimulus according to different shoulder joint angles on functional reach and stability of the shoulder joint

    PubMed Central

    Kim, Eun-Kyung; Kim, Seong-Gil

    2016-01-01

    [Purpose] The purpose of this study was to analyze the effect of an active vibration stimulus exercise according to shoulder joint angles on functional reach and stability of the shoulder joint. [Subjects and Methods] Thirty healthy male students participated in this study. Upper limb length of each subject was measured to obtain normalized measurement values. The exercise groups were as follows: group I (n=10, shoulder joint angle of 90°), group II (n=10, shoulder joint angle of 130°), and group III (n=10, shoulder joint angle of 180°). After warm-up, an active vibration stimulus was applied to the subjects with a Flexi-Bar. The Functional Reach Test and Y-balance test were conducted for measurement of shoulder stability. [Results] Analysis of covariance was conducted with values before the intervention as covariates to analyze the differences among the groups in the two tests. There were significant differences among the groups. According to Bonferroni post hoc comparison, group I showed greater improvement than group III in the Functional Reach Test, and group II showed greater improvement than group I and group III in the Y-balance test. [Conclusion] The effect of the exercise with different shoulder joint angles revealed that the shoulder joint has a certain effective joint angle for its functionality and stability. In addition, application of an active vibration stimulus with a Flexi-Bar can be a very effective tool for improvement of functionality and stability of the shoulder joint. PMID:27134352

  14. The influence of joint line position on knee stability after condylar knee arthroplasty.

    PubMed

    Martin, J W; Whiteside, L A

    1990-10-01

    Using a special knee-testing device, ten knees obtained at autopsy were subjected to varus-valgus, anterior-posterior, and flexion-rotation analysis in the intact state and after total knee arthroplasty. The ten knees showed no significant change in stability after knee replacement when the joint line was maintained in its natural position. When the femoral component was repositioned 5 mm proximally and 5 mm anteriorly, a significant increase in laxity occurred during midflexion. When the joint line was shifted 5 mm distal and 5 mm posterior to its anatomic location, significant tightening occurred in midrange of motion. Coupled rotation of the tibia with knee flexion was decreased after surgery in all knees with no specific relationship to joint line position. Coupled rotation with varus-valgus testing, however, remained within the normal range through the first 30 degrees of flexion only when the joint line was restored to its normal anatomic position. Stability in condylar knee arthroplasty is in part dependent on position of the joint line. Surgical techniques that rely on restoring the flexion and extension gap without regard to joint line position may result in alteration of varus-valgus or anterior-posterior displacement in midrange flexion. PMID:2208849

  15. Minimally Invasive Spinal Stabilization Using Fluoroscopic-Guided Percutaneous Screws as a Form of Palliative Surgery in Patients with Spinal Metastasis

    PubMed Central

    Kwan, Mun Keong; Chan, Chris Yin Wei

    2016-01-01

    Study Design Prospective cohort study. Purpose To report the outcome of 50 patients with spinal metastases treated with minimally invasive stabilization (MISt) using fluoroscopic guided percutaneous pedicle screws with/without minimally invasive decompression. Overview of Literature The advent of minimally invasive percutaneous pedicle screw stabilization system has revolutionized the treatment of spinal metastasis. Methods Between 2008 and 2013, 50 cases of spinal metastasis with pathological fracture(s) with/without neurology deficit were treated by MISt at our institution. The patients were assessed by Tomita score, pain score, operation time, blood loss, neurological recovery, time to ambulation and survival. Results The mean Tomita score was 6.3±2.4. Thirty seven patients (74.0%) required minimally invasive decompression in addition to MISt. The mean operating time was 2.3±0.5 hours for MISt alone and 3.4±1.2 hours for MISt with decompression. Mean blood loss for MISt alone and MISt with decompression was 0.4±0.2 L and 1.7±0.9 L, respectively. MISt provided a statistically significant reduction in visual analog scale pain score with mean preoperative score of 7.9±1.4 that was significantly decreased to 2.5±1.2 postoperatively (p=0.000). For patients with neurological deficit, 70% displayed improvement of one Frankel grade and 5% had an improvement of 2 Frankel grades. No patient was bed-ridden postoperatively, with the average time to ambulation of 3.4±1.8 days. The mean overall survival time was 11.3 months (range, 2–51 months). Those with a Tomita score <8 survived significantly longer than those a Tomita score ≥8 with a mean survival of 14.1±12.5 months and 6.8±4.9 months, respectively (p=0.019). There were no surgical complications, except one case of implant failure. Conclusions MISt is an acceptable treatment option for spinal metastatic patients, providing good relief of instability back pain with no major complications. PMID:26949465

  16. Arthroscopic treatment of acute and chronic acromioclavicular joint dislocation.

    PubMed

    Lafosse, Laurent; Baier, Gloria P; Leuzinger, Jan

    2005-08-01

    This article presents an all-arthroscopic technique for coracoclavicular ligament reconstruction by ligamentoplasty after acute or chronic acromioclavicular joint dislocation. A coracoacromial ligament transfer is done to reconstruct the torn coracoclavicular ligaments, similar to open surgery. The coracoacromial ligament is dissected from the undersurface of the acromion and is reinserted on the inferior clavicle by transosseous suture fixation. Additional wire or screw stabilization may be used. With this method, we achieve a very satisfactory reduction of the dislocated acromioclavicular joint. PMID:16086572

  17. Minifragment screw fixation of oblique metacarpal fractures: a biomechanical analysis of screw types and techniques.

    PubMed

    Liporace, Frank A; Kinchelow, Tosca; Gupta, Salil; Kubiak, Erik N; McDonnell, Matthew

    2008-12-01

    The lag screw technique has historically been a successful and accepted way to treat oblique metacarpal fractures. However, it does take additional time and involve multiple steps that can increase the risk of fracture propagation or comminution in the small hand bones of the hand. An alternate fixation technique uses bicortical interfragmentary screws. Other studies support the clinical effectiveness and ease of this technique. The purpose of this study is to biomechanically assess the strength of the bicortical interfragmentary screw versus that of the traditional lag screw. Using 48 cadaver metacarpals, oblique osteotomies were created and stabilized using one of four methods: 1.5 mm bicortical interfragmentary (IF) screw, 1.5 mm lag technique screw, 2.0 mm bicortical IF screw, or 2.0 mm lag technique screw. Biomechanical testing was performed to measure post cyclic displacement and load to failure. Data was analyzed using one-way analysis of variance (ANOVA). There was no significant difference among the fixation techniques with regard to both displacement and ultimate failure strength. There was a slight trend for a higher load to failure with the 2.0 mm IF screw and 2.0 mm lag screw compared to the 1.5 mm IF and 1.5 mm lag screws, but this was not significant. Our results support previously established clinical data that bicortical interfragmentary screw fixation is an effective treatment option for oblique metacarpal fractures. This technique has clinical importance because it is an option to appropriately stabilize the often small and difficult to control fracture fragments encountered in metacarpal fractures. PMID:18780019

  18. Tibiotalar joint arthrodesis for the treatment of severe ankle joint degeneration secondary to rheumatoid arthritis.

    PubMed

    Caron, M; Kron, E; Saltrick, K R

    1999-04-01

    The technical aspects of fusion of the rheumatoid ankle do not deviate from those in the post-traumatic or osteoarthritic ankle. Screw fixation can usually be achieved, and rarely is fixation failure a problem in rheumatoid ankle arthrodesis. If fixation is difficult because of deformity or bone quality, external fixation or locking intramedullary nails should be used. The placement of cannulated screws and adequacy of screw fixation has not been a problem (Fig. 13). Screw fixation provides compression and prevents rotation. The surgeon, however, needs to be assured that no screws invade the subtalar joint and that all threads are beyond the arthrodesis site. A washer may be necessary for further stability if this screw is not inserted at too great an angle. The authors have found that troughing out of the cortical surface of the tibia with a power bur aids in screw insertion. Not only does the trough act as a countersink, but it also provides a path for screw insertion and prevents palpable screw irritation. Malalignment is unforgiving. The foot must be placed neutral to dorsiflexion and plantarflexion. Equinus positioning places added stress on the tibia and a back-knee gait occurs. Approximately 5 degrees of valgus is recommended, and varus positioning is unforgiving. Internal and external rotation is determined by the position of the contralateral extremity. Nonunion does not seem to be a problem with rigid internal fixation to any greater degree in patients with RA. Despite this, patients may continue to have pain despite solid fusion, which can be caused by incomplete correction of deformity, painful internal fixation, or adjacent joint pathology. Additionally, patients may experience supramalleolar pain above the fusion site consistent with tibial stress fracture, which is more common if the subtalar or midtarsal joint is rigid or if the patient is obese. A rocker sole shoe with impact-absorbing soles used after brief periods of guarded mobilization in a

  19. All arthroscopic stabilization of acute acromioclavicular joint dislocation with fiberwire and endobutton system

    PubMed Central

    Spoliti, Marco; De Cupis, Mauro; Via, Alessio Giai; Oliva, Francesco

    2014-01-01

    Summary Introduction: acromioclavicular (AC) joint dislocation is common in athletes and in contact sports and about 9% of shoulder injuries involves this joint. The majority of these AC lesions can be successfully treated conservatively but high grade dislocation and some cases of type III dislocation need a surgical treatment. Many different operative techniques have been described over the years. The purpose of this study is to evaluate the results of arthroscopic stabilization of AC joint dislocation with TightRope® system. Materials and methods: nineteen patients with acute AC dislocation were treated by arthroscopic fixation with TightRope® system. Any associated lesions were repaired. All patients were assessed before surgery (T0), at 3 months (T1), at 6 months (T2) and at 1 year after the surgery (T3) using a visual analogic scale (VAS) and Constant-Murley Score (CMS). All patients were evaluated with X-ray. Results: six AC-joint dislocations involved the right shoulder and thirteen the left shoulder. Ten were type III dislocation, three were type IV and six were type V dislocation. We found a statistically significant reduction of pain (p< 0.01) at T1 compared to the pretreatment scores. The CMS measures showed an improvement between T1, T2 and T3, but the difference was statistically significant only between T1 and T3 (p= 0.017). The postoperative X-Ray of the shoulder showed a good reduction of the AC joint dislocation. We had 1 case of recurrence and 2 cases of loss of intraoperative reduction. Conclusion: arthroscopic technique for acute AC joint dislocations with the use of the TightRope® device is minimally invasive and it allows an anatomic restoration of the joint. It is a safe and effective procedure ensuring stable AC joint reconstruction and good cosmetic results. PMID:25767774

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

    NASA Astrophysics Data System (ADS)

    Görres, Joseph; Brehler, Michael; Franke, Jochen; Wolf, Ivo; Vetter, Sven Y.; Grützner, 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.

  1. 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

  2. Effects of neuromuscular training on knee joint stability after anterior cruciate ligament reconstruction.

    PubMed

    Shim, Jae-Kwang; Choi, Ho-Suk; Shin, Jun-Ho

    2015-12-01

    [Purpose] This study examined the effects of neuromuscular training on knee joint stability after anterior cruciate ligament reconstruction. [Subjects and Methods] The subjects were 16 adults who underwent arthroscopic anterior cruciate reconstruction and neuromuscular training. The Lysholm scale was used to assess functional disorders on the affected knee joint. A KT-2000 arthrometer was used to measure anterior displacement of the tibia against the femur. Surface electromyography was used to detect the muscle activation of the vastus medialis oblique, vastus lateralis, biceps femoris, and semitendinosus before and after neuromuscular training. [Results] There was significant relaxation in tibial anterior displacement of the affected and sound sides in the supine position before neuromuscular training. Furthermore, the difference in the tibial anterior displacement of the affected knee joints in the standing position was reduced after neuromuscular training. Moreover, the variation of the muscle activation evoked higher muscle activation of the vastus medialis oblique, vastus lateralis, biceps femoris, and semitendinosus. [Conclusion] Neuromuscular training may improve functional joint stability in patients with orthopedic musculoskeletal injuries in the postoperative period. PMID:26834316

  3. Treatment of Displaced Sacroiliac Fracture Using the Lateral Window for Short Plate Buttress Reduction and Percutaneous Sacroiliac Screw Fixation.

    PubMed

    Murphy, Colin G; Gill, James R; Carrothers, Andrew D; Hull, Peter D

    2016-04-01

    Fractures through the sacroiliac joint are very challenging to treat, technically difficult to reduce through closed methods on account of the multiaxial displacement of fractures fragments, frequently occur in very unwell patients, and have poor outcomes if malreduction is present. We describe a technique utilising the lateral window and a short buttress plate to reduce and stabilize the fragments prior to percutaneous fixation with sacroiliac screws. PMID:27200398

  4. Treatment of Displaced Sacroiliac Fracture Using the Lateral Window for Short Plate Buttress Reduction and Percutaneous Sacroiliac Screw Fixation

    PubMed Central

    Murphy, Colin G.; Gill, James R.; Carrothers, Andrew D.; Hull, Peter D.

    2016-01-01

    Fractures through the sacroiliac joint are very challenging to treat, technically difficult to reduce through closed methods on account of the multiaxial displacement of fractures fragments, frequently occur in very unwell patients, and have poor outcomes if malreduction is present. We describe a technique utilising the lateral window and a short buttress plate to reduce and stabilize the fragments prior to percutaneous fixation with sacroiliac screws. PMID:27200398

  5. Hip and knee joints are more stabilized than driven during the stance phase of gait: an analysis of the 3D angle between joint moment and joint angular velocity.

    PubMed

    Dumas, R; Cheze, L

    2008-08-01

    Joint power is commonly used in orthopaedics, ergonomics or sports analysis but its clinical interpretation remains controversial. Some basic principles on muscle actions and energy transfer have been proposed in 2D. The decomposition of power on 3 axes, although questionable, allows the same analysis in 3D. However, these basic principles have been widely criticized, mainly because bi-articular muscles must be considered. This requires a more complex computation in order to determine how the individual muscle force contributes to drive the joint. Conversely, with simple 3D inverse dynamics, the analysis of both joint moment and angular velocity directions is essential to clarify when the joint moment can contribute or not to drive the joint. The present study evaluates the 3D angle between the joint moment and the joint angular velocity and investigates when the hip, knee and ankle joints are predominantly driven (angle close to 0 degrees and 180 degrees ) or stabilized (angle close to 90 degrees ) during gait. The 3D angle curves show that the three joints are never fully but only partially driven and that the hip and knee joints are mainly stabilized during the stance phase. The notion of stabilization should be further investigated, especially for subjects with motion disorders or prostheses. PMID:18206375

  6. Muscle co-contraction modulates damping and joint stability in a three-link biomechanical limb.

    PubMed

    Heitmann, Stewart; Ferns, Norm; Breakspear, Michael

    2011-01-01

    Computational models of neuromotor control require forward models of limb movement that can replicate the natural relationships between muscle activation and joint dynamics without the burdens of excessive anatomical detail. We present a model of a three-link biomechanical limb that emphasizes the dynamics of limb movement within a simplified two-dimensional framework. Muscle co-contraction effects were incorporated into the model by flanking each joint with a pair of antagonist muscles that may be activated independently. Muscle co-contraction is known to alter the damping and stiffness of limb joints without altering net joint torque. Idealized muscle actuators were implemented using the Voigt muscle model which incorporates the parallel elasticity of muscle and tendon but omits series elasticity. The natural force-length-velocity relationships of contractile muscle tissue were incorporated into the actuators using ideal mathematical forms. Numerical stability analysis confirmed that co-contraction of these simplified actuators increased damping in the biomechanical limb consistent with observations of human motor control. Dynamic changes in joint stiffness were excluded by the omission of series elasticity. The analysis also revealed the unexpected finding that distinct stable (bistable) equilibrium positions can co-exist under identical levels of muscle co-contraction. We map the conditions under which bistability arises and prove analytically that monostability (equifinality) is guaranteed when the antagonist muscles are identical. Lastly we verify these analytic findings in the full biomechanical limb model. PMID:22275897

  7. Muscle Co-Contraction Modulates Damping and Joint Stability in a Three-Link Biomechanical Limb

    PubMed Central

    Heitmann, Stewart; Ferns, Norm; Breakspear, Michael

    2012-01-01

    Computational models of neuromotor control require forward models of limb movement that can replicate the natural relationships between muscle activation and joint dynamics without the burdens of excessive anatomical detail. We present a model of a three-link biomechanical limb that emphasizes the dynamics of limb movement within a simplified two-dimensional framework. Muscle co-contraction effects were incorporated into the model by flanking each joint with a pair of antagonist muscles that may be activated independently. Muscle co-contraction is known to alter the damping and stiffness of limb joints without altering net joint torque. Idealized muscle actuators were implemented using the Voigt muscle model which incorporates the parallel elasticity of muscle and tendon but omits series elasticity. The natural force-length-velocity relationships of contractile muscle tissue were incorporated into the actuators using ideal mathematical forms. Numerical stability analysis confirmed that co-contraction of these simplified actuators increased damping in the biomechanical limb consistent with observations of human motor control. Dynamic changes in joint stiffness were excluded by the omission of series elasticity. The analysis also revealed the unexpected finding that distinct stable (bistable) equilibrium positions can co-exist under identical levels of muscle co-contraction. We map the conditions under which bistability arises and prove analytically that monostability (equifinality) is guaranteed when the antagonist muscles are identical. Lastly we verify these analytic findings in the full biomechanical limb model. PMID:22275897

  8. Running stability is enhanced by a proximo-distal gradient in joint neuromechanical control

    PubMed Central

    Daley, M. A.; Felix, G.; Biewener, A. A.

    2008-01-01

    Summary We currently know little about how animals achieve dynamic stability when running over uneven and unpredictable terrain, often characteristic of their natural environment. Here we investigate how limb and joint mechanics of an avian biped, the helmeted guinea fowl Numida meleagris, respond to an unexpected drop in terrain during running. In particular, we address how joint mechanics are coordinated to achieve whole limb dynamics. Based on muscle–tendon architecture and previous studies of steady and incline locomotion, we hypothesize a proximo-distal gradient in joint neuromechanical control. In this motor control strategy, (1) proximal muscles at the hip and knee joints are controlled primarily in a feedforward manner and exhibit load-insensitive mechanical performance, and (2) distal muscles at the ankle and tarsometatarso-phalangeal (TMP) joints are highly load-sensitive, due to intrinsic mechanical effects and rapid, higher gain proprioceptive feedback. Limb kinematics and kinetics during the unexpected perturbation reveal that limb retraction, controlled largely by the hip, remains similar to level running throughout the perturbed step, despite altered limb loading. Individual joints produce or absorb energy during both level and perturbed running steps, such that the net limb work depends on the balance of energy among the joints. The hip maintains the same mechanical role regardless of limb loading, whereas the ankle and TMP switch between spring-like or damping function depending on limb posture at ground contact. Initial knee angle sets limb posture and alters the balance of work among the joints, although the knee contributes little work itself. This distribution of joint function results in posture-dependent changes in work performance of the limb, which allow guinea fowl to rapidly produce or absorb energy in response to the perturbation. The results support the hypothesis that a proximo-distal gradient exists in limb neuromuscular performance

  9. Running stability is enhanced by a proximo-distal gradient in joint neuromechanical control.

    PubMed

    Daley, M A; Felix, G; Biewener, A A

    2007-02-01

    We currently know little about how animals achieve dynamic stability when running over uneven and unpredictable terrain, often characteristic of their natural environment. Here we investigate how limb and joint mechanics of an avian biped, the helmeted guinea fowl Numida meleagris, respond to an unexpected drop in terrain during running. In particular, we address how joint mechanics are coordinated to achieve whole limb dynamics. Based on muscle-tendon architecture and previous studies of steady and incline locomotion, we hypothesize a proximo-distal gradient in joint neuromechanical control. In this motor control strategy, (1) proximal muscles at the hip and knee joints are controlled primarily in a feedforward manner and exhibit load-insensitive mechanical performance, and (2) distal muscles at the ankle and tarsometatarso-phalangeal (TMP) joints are highly load-sensitive, due to intrinsic mechanical effects and rapid, higher gain proprioceptive feedback. Limb kinematics and kinetics during the unexpected perturbation reveal that limb retraction, controlled largely by the hip, remains similar to level running throughout the perturbed step, despite altered limb loading. Individual joints produce or absorb energy during both level and perturbed running steps, such that the net limb work depends on the balance of energy among the joints. The hip maintains the same mechanical role regardless of limb loading, whereas the ankle and TMP switch between spring-like or damping function depending on limb posture at ground contact. Initial knee angle sets limb posture and alters the balance of work among the joints, although the knee contributes little work itself. This distribution of joint function results in posture-dependent changes in work performance of the limb, which allow guinea fowl to rapidly produce or absorb energy in response to the perturbation. The results support the hypothesis that a proximo-distal gradient exists in limb neuromuscular performance and motor

  10. JOINT UNITED STATES/IAEA PROPOSED APPROACH FOR SAFEGUARDS DURING PLUTONIUM STABILIZATION, PACKAGING, AND SHIPMENT

    SciTech Connect

    L. KWEI; B. SMITH; ET AL

    2001-02-01

    For safety reasons, the U.S. Department of Energy (DOE) is preparing to stabilize and package plutonium oxide currently subject to International Atomic Energy Agency safeguards at the Rocky Flats Environmental Technology Site (RFETS) beginning in the year 2001. The Hanford Site will also stabilize and package plutonium materials under IAEA safeguards. The U.S. and the IAEA began consultations in late 1996 to develop an approach to the application of safeguards during stabilization and packaging. With the plans to ship RFETS plutonium to Savannah River for interim storage prior to final disposition, this work has been extended to include safeguards during shipment. This paper will discuss the elements of a joint U.S./IAEA proposal for this task.

  11. Stabilization of the fast modes of a flexible-joint robot

    SciTech Connect

    Readman, M.C.; Belanger, P.R. )

    1992-04-01

    In this work the robot is assumed to be an open kinematic chain with only revolute joints. Each joint is modeled as a linear torsional spring. The model equations consist of two coupled dynamic systems, one representing the usual rigid body or slow dynamics and the other the fast dynamics introduced by the joint flexibility. The model presented in this article is in a form that brings out the influence on the fast subsystem dynamics of the rigid body parameters and the robot geometry. The model clearly shows the effect that link and drive parameters have on the dynamics of the fast subsystem. It is shown that under certain assumptions there exists a decentralized velocity control law that asymptotically stabilizes the fast subsystem dynamics. In general this control law is gain scheduled. For sufficiently small drive inertias there always exists a fixed decentralized control law that will asymptotically stabilize the fast dynamics. This is true even for large drive ratios. For sufficiently large drive inertias it may not be possible to use a fixed decentralized control law. Under certain conditions a gain-scheduled velocity feedback law can be designed to give attractive pole damping factors. Some examples are given to illustrate these ideas.

  12. 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

  13. 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

  14. 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.

  15. Simple coating with fibronectin fragment enhances stainless steel screw osseointegration in healthy and osteoporotic rats.

    PubMed

    Agarwal, Rachit; González-García, Cristina; Torstrick, Brennan; Guldberg, Robert E; Salmerón-Sánchez, Manuel; García, Andrés 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 α5β1 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

  16. Screw-matrix method in dynamics of multibody systems

    NASA Astrophysics Data System (ADS)

    Yanzhu, Liu

    1988-05-01

    In the present paper the concept of screw in classical mechanics is expressed in matrix form, in order to formulate the dynamical equations of the multibody systems. The mentioned method can retain the advantages of the screw theory and avoid the shortcomings of the dual number notation. Combining the screw-matrix method with the tool of graph theory in Roberson/Wittenberg formalism. We can expand the application of the screw theory to the general case of multibody systems. For a tree system, the dynamical equations for each j-th subsystem, composed of all the outboard bodies connected by j-th joint can be formulated without the constraint reaction forces in the joints. For a nontree system, the dynamical equations of subsystems and the kinematical consistency conditions of the joints can be derived using the loop matrix. The whole process of calculation is unified in matrix form. A three-segment manipulator is discussed as an example.

  17. High Temperature Stability of Dissimilar Metal Joints in Fission Surface Power Systems

    SciTech Connect

    Locci, Ivan E.; Nesbitt, James A.; Ritzert, Frank J.; Bowman, Cheryl L.

    2007-01-30

    Future generations of power systems for spacecraft and lunar surface systems will likely require a strong dependence on nuclear power. The design of a space nuclear power plant involves integrating together major subsystems with varying material requirements. Refractory alloys are repeatedly considered for major structural components in space power reactor designs because refractory alloys retain their strength at higher temperatures than other classes of metals. The relatively higher mass and lower ductility of the refractory alloys make them less attractive for lower temperature subsystems in the power plant such as the power conversion system. The power conversion system would consist more likely of intermediate temperature Ni-based superalloys. One of many unanswered questions about the use of refractory alloys in a space power plant is how to transition from the use of the structural refractory alloy to more traditional structural alloys. Because deleterious phases can form when complex alloys are joined and operated at elevated temperatures, dissimilar material diffusion analyses of refractory alloys and superalloys are needed to inform designers about options of joint temperature and operational lifetime. Combinations of four superalloys and six refractory alloys were bonded and annealed at 1150 K and 1300 K to examine diffusional interactions in this study. Joints formed through hot pressing and hot isostatic pressing were compared. Results on newer alloys compared favorably to historical data. Diffusional stability is promising for some combinations of Mo-Re alloys and superalloys at 1150 K, but it appears that lower joint temperatures would be required for other refractory alloy couples.

  18. Long-term stability of conservative orthodontic treatment in a patient with temporomandibular joint disorder

    PubMed Central

    Mitsui, Silvia Naomi; Yasue, Akihiro; Kuroda, Shingo; Tanaka, Eiji

    2016-01-01

    This article reports the orthodontic treatment of a 20-year-old patient with dental crowding and temporomandibular joint disorders (TMDs). The patient presented moderate anterior crowding with a Class I molar relationship and masticatory disturbance in the mandibular position induced by previous splint therapy. Orthodontic treatment with multi-bracket appliance was initiated to correct the anterior crowding in both dental arches, after the extraction of first premolars and third molars, and also to maintain the splint-induced position of the condyles. After 26 months of treatment, an acceptable occlusion was achieved without any TMD symptoms. After 18-month retention, flattening on the right condyle was observed, possibly as an adaptative remodeling. After 16-year retention period, the occlusion was maintained without recurrence of any TMD symptoms, indicating a long-term stability of occlusion and temporomandibular joint (TMJ) components. Our results suggest the possibility of compromised treatment in patients with TMD to achieve a long-term stability in occlusion and TMJ function. PMID:27556023

  19. Long-term stability of conservative orthodontic treatment in a patient with temporomandibular joint disorder.

    PubMed

    Mitsui, Silvia Naomi; Yasue, Akihiro; Kuroda, Shingo; Tanaka, Eiji

    2016-01-01

    This article reports the orthodontic treatment of a 20-year-old patient with dental crowding and temporomandibular joint disorders (TMDs). The patient presented moderate anterior crowding with a Class I molar relationship and masticatory disturbance in the mandibular position induced by previous splint therapy. Orthodontic treatment with multi-bracket appliance was initiated to correct the anterior crowding in both dental arches, after the extraction of first premolars and third molars, and also to maintain the splint-induced position of the condyles. After 26 months of treatment, an acceptable occlusion was achieved without any TMD symptoms. After 18-month retention, flattening on the right condyle was observed, possibly as an adaptative remodeling. After 16-year retention period, the occlusion was maintained without recurrence of any TMD symptoms, indicating a long-term stability of occlusion and temporomandibular joint (TMJ) components. Our results suggest the possibility of compromised treatment in patients with TMD to achieve a long-term stability in occlusion and TMJ function. PMID:27556023

  20. The effect of co-stabilizer muscle activation on knee joint position sense: a single group pre-post test

    PubMed Central

    Nam, Yeongyo; Lee, Ho Jun; Choi, Myongryol; Chung, Sangmi; Park, Junhyung; Yu, Jaeho

    2016-01-01

    [Purpose] The purpose of this study was to investigate the effect of co-stabilizer muscle activation on knee joint position sense. [Subjects and Methods] This study was a pre-post, single-blinded randomly controlled trial (angle sequence randomly selected) design. Seven healthy adults with no orthopaedic or neurological problems participated in this study. Knee joint position sense was measured by a target matching test at target angles of 30°, 45° and 80° of knee flexion a using digital inclinometer under two conditions: erect sitting, which is known to highly activate co-stabilizer muscle and slump sitting, which is known to little activate the co-stabilizer muscle. [Results] A significant difference in joint position matching error at the knee flexion angle of 45° was founded between two conditions erect sitting: (3.83 ± 1.47) and slump sitting: (1.00 ± 0.63). There were no significant differences in joint position matching error at the other target angles. [Conclusion] Knee joint position sense at 45° is likely to be affected by activation of co-stabilizer muscle, and this value is suitable for facilitation of joint position sense with skilled movement. PMID:27512279

  1. New Screw Design for Securing Buried Distractors Usefulness and Ease of Removal.

    PubMed

    Fariña, Rodrigo; Hinojosa, Andrés; Sánchez, Martín; Olate, Sergio

    2015-07-01

    There are 2 types of distraction devices for mandibular distraction: buried and external. The advantage of buried devices is the stability, but the difficulty in removing the screws is the greatest disadvantage. To resolve this problem, an osteosynthesis screw (Fariña Screw) has been designed, which greatly facilitates its removal when buried distractors are used. PMID:26102540

  2. CT- and fluoroscopy-guided percutaneous screw fixation of a "carrot-stick" spinal fracture in an elderly man with ankylosing spondylitis.

    PubMed

    Huwart, Laurent; Amoretti, Nicolas

    2013-12-01

    We present a case of percutaneous fixation of a "carrot-stick" spinal fracture in an elderly patient with ankylosing spondylitis (AS). A surgical stabilization was not possible in this 83-year-old man with comorbidities. Under local anesthesia, percutaneous screw fixation of a transdiscal shear fracture at the level T10-T11 was performed using computed tomography (CT) and fluoroscopy guidance. Two 4.0-mm Asnis III cannulated screws were placed to fix facet joints using transfacet pedicle pathway. The procedure time was 30 min. Using the visual analog scale (VAS), pain decreased from 10, preoperatively, to 1 after the procedure. Radiographic fusion was observed at a 3-month post-procedural CT scan. CT- and fluoroscopy-guided percutaneous screw fixation of spinal fractures could potentially be an alternative to surgery in elderly AS patients with poor performance status. PMID:23842576

  3. Cement as a locking mechanism for screw heads in acetabular revision shells - a biomechanical analysis.

    PubMed

    Laflamme, G Y; Alami, G B; Zhim, F

    2008-01-01

    In acetabular revisions, polyethylene (PE) liners are often cemented into metal shells on top of acetabular screw heads. This study investigates the possibility of using this technique to obtain fixed-angle acetabular screws Eth a concept that has not yet been reported in the literature. Two groups of screws (n=8) were inserted into Trabecular Metal revision shells (Zimmer), into which PE liners were then cemented. Screws in Group 1, inserted in the shell's pre-fabricated holes, were countersunk, whereas screws in Group 2 were inserted in custom-drilled holes that make their heads protrude into, and interdigitate with, the overlying cement mantle. Perpendicular loading was then applied to the screw shafts both statically to failure and cyclically. A greater stiffness was observed for the protruding screws upon static loading; and while the countersunk screws all failed at the screw-cement junction (53.44 + or - 8.33 N), the protruding screws all failed at the screw shaft (1049.79 + or - 32.12 N) a 20-fold difference (p< 0.05). Under cyclic loading, only the protruding screw head specimen did not fail, undergoing an overall displacement within the limits of osseointegration.These results support the hypothesis that the protrusion of an acetabular screw head into an overlying cement mantle significantly increases its angular stability. Provided other variables are favorable, this locking effect may increase the initial stability of the whole implant, thus improving the ultimate success of complex acetabular revisions. PMID:18645971

  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. High Temperature Stability of Dissimilar Metal Joints in Fission Surface Power Systems

    NASA Technical Reports Server (NTRS)

    Locci, Ivan E.; Nesbitt, James A.; Ritzert, Frank J.; Bowman, Cheryl L.

    2007-01-01

    Future generations of power systems for spacecraft and lunar surface systems will likely require a strong dependence on nuclear power. The design of a space nuclear power plant involves integrating together major subsystems with varying materia1 requirements. Refractory alloys are repeatedly considered for major structural components in space power reactor designs because refractory alloys retain their strength at higher temperatures than other classes of metals. The relatively higher mass and lower ductility of the refractory alloys make them less attractive for lower temperature subsystems in the power plant such as the power conversion system. The power conversion system would consist more likely of intermediate temperature Ni-based superalloys. One of many unanswered questions about the use of refractory alloys in a space power plant is how to transition from the use of the structural refractory alloy to more traditional structural alloys. Because deleterious phases can form when complex alloys are joined and operated at elevated temperatures, dissimilar material diffusion analyses of refractory alloys and superalloys are needed to inform designers about options of joint temperature and operational lifetime. Combinations of four superalloys and six refractory alloys were bonded and annealed at 1150 K and 1300 K to examine diffusional interactions in this study. Joints formed through hot pressing and hot isostatic pressing were compared. Results on newer alloys compared favorably to historical data. Diffusional stability is promising for some combinations of Mo-Re alloys and superalloys at 1150 K, but it appears that lower joint temperatures would be required for other refractory alloy couples.

  6. Volar Stabilization of the Distal Radioulnar Joint for Chronic Instability Using the Pronator Quadratus.

    PubMed

    Lee, Sang Ki; Lee, Jae Won; Choy, Won Sik

    2016-04-01

    In cases of chronic distal radioulnar joint (DRUJ) instability without DRUJ arthritis, reconstruction of the mechanical integrity of the radioulnar ligaments of the triangular fibrocartilage complex has been considered an ideal surgical treatment. However, reconstructive methods have several disadvantages.We evaluated volar stabilization of the DRUJ for chronic instability using the pronator quadratus (PQ) to determine whether it provided (1) proper stability, (2) restored wrist function, (3) was relatively convenient, and (4) was associated with a low complication rate. Altogether, 21 patients with chronic DRUJ instability (12 men, 9 women) with a mean age of 34 years (range, 17-65 years) were enrolled in the study. The diagnostic criteria were as follows: 3 months after the injury, greater than 8 mm of palmar-dorsal translation of the ulna relative to the radius, there was a lack of clear end point resistance compared with the contralateral side, and nonstressed computed tomographic scans provided supporting evidence. Follow-up was at least 12 months (range, 12-38 months). Palmar-dorsal translation of the ulna relative to the radius was decreased significantly from 10 to 4 mm (P = 0.028) and epicenter was increased significantly at the last follow-up [P = 0.015/0.026 (70 degrees of supination/neutral, respectively)]. Wrist range of motion was not significantly different, but grip strength had increased from 72% to 91%. Disabilities of the arm, shoulder, and hand and patient-rated wrist evaluation were also decreased compared with preoperative measurements [34.4 to 12.5/42.7 to 14.7 (disabilities of the arm, shoulder, and hand/patient-rated wrist evaluation, respectively)]. Pronator quadratus advancement volar stabilization provided proper stability, restored wrist function, was relatively convenient, and was associated with few complications. Our experience indicates that it is an acceptable, effective treatment option to reverse DRUJ instability in patients

  7. Biomechanical and Histological Evaluation of Roughened Surface Titanium Screws Fabricated by Electron Beam Melting

    PubMed Central

    Yang, Jun; Cai, Hong; Lv, Jia; Zhang, Ke; Leng, Huijie; Wang, Zhiguo; Liu, Zhongjun

    2014-01-01

    Background Various fabrication methods are used to improve the stability and osseointegration of screws within the host bone. The aim of this study was to investigate whether roughened surface titanium screws fabricated by electron beam melting can provide better stability and osseointegration as compared with smooth titanium screws in sheep cervical vertebrae. Methods Roughened surface titanium screws, fabricated by electron beam melting, and conventional smooth surface titanium screws were implanted into sheep for 6 or 12 weeks (groups A and B, respectively). Bone ingrowth and implant stability were assessed with three-dimensional imaging and reconstruction, as well as histological and biomechanical tests. Results No screws in either group showed signs of loosening. Fibrous tissue formation could be seen around the screws at 6 weeks, which was replaced with bone at 12 weeks. Bone volume/total volume, bone surface area/bone volume, and the trabecular number were significantly higher for a define region of interest surrounding the roughened screws than that surrounding the smooth screws at 12 weeks. Indeed, for roughened screws, trabecular number was significantly higher at 12 weeks than at 6 weeks. On mechanical testing, the maximum pullout strength was significantly higher at 12 weeks than at 6 weeks, as expected; however, no significant differences were found between smooth and roughened screws at either time point. The maximum torque to extract the roughened screws was higher than that required for the smooth screws. Conclusions Electron beam melting is a simple and effective method for producing a roughened surface on titanium screws. After 12 weeks, roughened titanium screws demonstrated a high degree of osseointegration and increased torsional resistance to extraction over smooth titanium screws. PMID:24788866

  8. 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

  9. Analysis of Modeling Parameters on Threaded Screws.

    SciTech Connect

    Vigil, Miquela S.; Brake, Matthew Robert; Vangoethem, Douglas

    2015-06-01

    Assembled mechanical systems often contain a large number of bolted connections. These bolted connections (joints) are integral aspects of the load path for structural dynamics, and, consequently, are paramount for calculating a structure's stiffness and energy dissipation prop- erties. However, analysts have not found the optimal method to model appropriately these bolted joints. The complexity of the screw geometry cause issues when generating a mesh of the model. This paper will explore different approaches to model a screw-substrate connec- tion. Model parameters such as mesh continuity, node alignment, wedge angles, and thread to body element size ratios are examined. The results of this study will give analysts a better understanding of the influences of these parameters and will aide in finding the optimal method to model bolted connections.

  10. 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 µm. 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

  11. 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 µm. 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

  12. R package MVR for Joint Adaptive Mean-Variance Regularization and Variance Stabilization

    PubMed Central

    Dazard, Jean-Eudes; Xu, Hua; Rao, J. Sunil

    2015-01-01

    We present an implementation in the R language for statistical computing of our recent non-parametric joint adaptive mean-variance regularization and variance stabilization procedure. The method is specifically suited for handling difficult problems posed by high-dimensional multivariate datasets (p ≫ n paradigm), such as in ‘omics’-type data, among which are that the variance is often a function of the mean, variable-specific estimators of variances are not reliable, and tests statistics have low powers due to a lack of degrees of freedom. The implementation offers a complete set of features including: (i) normalization and/or variance stabilization function, (ii) computation of mean-variance-regularized t and F statistics, (iii) generation of diverse diagnostic plots, (iv) synthetic and real ‘omics’ test datasets, (v) computationally efficient implementation, using C interfacing, and an option for parallel computing, (vi) manual and documentation on how to setup a cluster. To make each feature as user-friendly as possible, only one subroutine per functionality is to be handled by the end-user. It is available as an R package, called MVR (‘Mean-Variance Regularization’), downloadable from the CRAN. PMID:26819572

  13. 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.

  14. Acceleration-based joint stability parameters for total knee arthroplasty that correspond with patient-reported instability.

    PubMed

    Roberts, Dustyn; Khan, Humera; Kim, Joo H; Slover, James; Walker, Peter S

    2013-10-01

    There is no universally accepted definition of human joint stability, particularly in nonperiodic general activities of daily living. Instability has proven to be a difficult parameter to define and quantify, since both spatial and temporal measures need to be considered to fully characterize joint stability. In this preliminary study, acceleration-based parameters were proposed to characterize the joint stability. Several time-statistical parameters of acceleration and jerk were defined as potential stability measures, since anomalous acceleration or jerk could be a symptom of poor control or stability. An inertial measurement unit attached at the level of the tibial tubercle of controls and patients following total knee arthroplasty was used to determine linear acceleration of the knee joint during several activities of daily living. The resulting accelerations and jerks were compared with patient-reported instability as determined through a standard questionnaire. Several parameters based on accelerations and jerks in the anterior/posterior direction during the step-up/step-down activity were significantly different between patients and controls and correlated with patient reports of instability in that activity. The range of the positive to negative peak acceleration and infinity norm of acceleration, in the anterior/posterior direction during the step-up/step-down activity, proved to be the best indicators of instability. As time derivatives of displacement, these acceleration-based parameters represent spatial and temporal information and are an important step forward in developing a definition and objective quantification of human joint stability that can complement the subjective patient report. PMID:23886970

  15. 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

  16. Effect of cement washout on loosening of abutment screws and vice versa in screw- and cement- retained implant-supported dental prosthesis

    PubMed Central

    Kim, Seok-Gyu; Son, Mee-Kyoung

    2015-01-01

    PURPOSE The purpose of this study was to examine the abutment screw stability of screw- and cement-retained implant-supported dental prosthesis (SCP) after simulated cement washout as well as the stability of SCP cements after complete loosening of abutment screws. MATERIALS AND METHODS Thirty-six titanium CAD/CAM-made implant prostheses were fabricated on two implants placed in the resin models. Each prosthesis is a two-unit SCP: one screw-retained and the other cemented. After evaluating the passive fit of each prosthesis, all implant prostheses were randomly divided into 3 groups: screwed and cemented SCP (Control), screwed and noncemented SCP (Group 1), unscrewed and cemented SCP (Group 2). Each prosthesis in Control and Group 1 was screwed and/or cemented, and the preloading reverse torque value (RTV) was evaluated. SCP in Group 2 was screwed and cemented, and then unscrewed (RTV=0) after the cement was set. After cyclic loading was applied, the postloading RTV was measured. RTV loss and decementation ratios were calculated for statistical analysis. RESULTS There was no significant difference in RTV loss ratio between Control and Group 1 (P=.16). No decemented prosthesis was found among Control and Group 2. CONCLUSION Within the limits of this in vitro study, the stabilities of SCP abutment screws and cement were not significantly changed after simulated cement washout or screw loosening. PMID:26140172

  17. Biomechanical Analysis of Pedicle Screw Fixation for Thoracolumbar Burst Fractures.

    PubMed

    McDonnell, Matthew; Shah, Kalpit N; Paller, David J; Thakur, Nikhil A; Koruprolu, Sarath; Palumbo, Mark A; Daniels, Alan H

    2016-05-01

    Treatment of unstable thoracolumbar burst fractures remains controversial. Long-segment pedicle screw constructs may be stiffer and impart greater forces on adjacent segments compared with short-segment constructs, which may affect clinical performance and long-term out come. The purpose of this study was to biomechanically evaluate long-segment posterior pedicle screw fixation (LSPF) vs short-segment posterior pedicle screw fixation (SSPF) for unstable burst fractures. Six unembalmed human thoracolumbar spine specimens (T10-L4) were used. Following intact testing, a simulated L1 burst fracture was created and sequentially stabilized using 5.5-mm titanium polyaxial pedicle screws and rods for 4 different constructs: SSPF (1 level above and below), SSPF+L1 (pedicle screw at fractured level), LSPF (2 levels above and below), and LSPF+L1 (pedicle screw at fractured level). Each fixation construct was tested in flexion-extension, lateral bending, and axial rotation; range of motion was also recorded. Two-way repeated-measures analysis of variance was performed to identify differences between treatment groups and functional noninstrumented spine. Short-segment posterior pedicle screw fixation did not achieve stability seen in an intact spine (P<.01), whereas LSPF constructs were significantly stiffer than SSPF constructs and demonstrated more stiffness than an intact spine (P<.01). Pedicle screws at the fracture level did not improve either SSPF or LSPF construct stability (P>.1). Long-segment posterior pedicle screw fixation constructs were not associated with increased adjacent segment motion. Al though the sample size of 6 specimens was small, this study may help guide clinical decisions regarding burst fracture stabilization. [Orthopedics. 2016; 39(3):e514-e518.]. PMID:27135451

  18. Dynamic stability analysis of torsional vibrations of a shaft system connected by a Hooke's joint through a continuous system model

    NASA Astrophysics Data System (ADS)

    Bulut, Gökhan

    2014-08-01

    Stability of parametrically excited torsional vibrations of a shaft system composed of two torsionally elastic shafts interconnected through a Hooke's joint is studied. The shafts are considered to be continuous (distributed-parameter) systems and an approximate discrete model for the torsional vibrations of the shaft system is derived via a finite element scheme. The stability of the solutions of the linearized equations of motion, consisting of a set of Mathieu-Hill type equations, is examined by means of a monodromy matrix method and the results are presented in the form of a Strutt-Ince diagram visualizing the effects of the system parameters on the stability of the shaft system.

  19. Increase in joint stability at the expense of energy efficiency correlates with force variability during a fatiguing task.

    PubMed

    Cashaback, Joshua G A; Cluff, Tyler

    2015-02-26

    Empirical evidence suggests that our nervous system considers many objectives when performing various tasks. With the progression of fatigue, researchers have noted increase in both joint moment variability and muscular cocontraction during isometric force production tasks. Muscular cocontraction increases joint stability, but is metabolically costly. Thus, our nervous system must select a compromise between joint stability and energy efficiency. Interestingly, the continuous increase in cocontraction with fatigue suggests there may be a shift in the relative weighting of these objectives. Here we test the notion of dynamic objective weightings. Using multi-objective optimization, we found a shift in objective weighting that favoured joint stability at the expense of energy efficiency during fatigue. This shift was highly correlated with muscular cocontraction (R(2)=0.78, p<0.001) and elbow moment variability in the time (R(2)=0.56, p<0.01) and frequency (R(2)=0.57, p<0.01) domains. By considering a dynamic objective weighting we obtained strong correlations with predicted and collected muscle activity (R(2)=0.94, p<0.001). PMID:25597814

  20. Control strategy for stabilizing force with goal-equivalent joint torques is frequency-dependent during human hopping.

    PubMed

    Yen, Jasper T; Chang, Young-Hui

    2009-01-01

    Normal human locomotion requires the ability to control a complex, redundant neuromechanical system to repetitively cycle the legs in a stable manner. In a reduced paradigm of locomotion, hopping, we investigated the ability of human subjects to exploit motor redundancy in the legs to coordinate joint torques fluctuations to minimize force fluctuations generated against the ground. Although we saw invariant performance in terms of force stabilization across frequencies, we found that the role of joint torque coordination in stabilizing force was most important at slow hopping frequencies. Notably, the role of this coordinated variation strategy decreased as hopping frequency increased, giving way to an independent joint variation strategy. At high frequencies, the control strategy to stabilize force was more dependent on a direct reduction in ankle torque fluctuations. Through the systematic study of how joint-level variances affect task-level end-point function, we can gain insight into the underlying control strategies in place for automatically counteracting cycle-to-cycle deviations during normal human locomotion. PMID:19964783

  1. Sensitivity of the stability of a waste emplacement drift to variation in assumed rock joint parameters in welded tuff

    SciTech Connect

    Christianson, M.

    1989-04-01

    This report presents the results of a numerical analysis to determine the effects of variation of rock joint parameters on stability of waste disposal rooms for vertical emplacement. Conditions and parameters used were taken from the Nevada Nuclear Waste Storage Investigation (NNWSI) Project Site Characterization Plan Conceptual Design report (MacDougall et al., 1987). Mechanical results are presented which illustrate the predicted distribution of stress, joint slip, and room deformations for times of initial excavation and after 50 years heating. 82 refs., 93 figs.

  2. Hydroxyapatite composite resin cement augmentation of pedicle screw fixation.

    PubMed

    Turner, Alexander W L; Gillies, R Mark; Svehla, Martin J; Saito, Masanobu; Walsh, William R

    2003-01-01

    Pedicle screw stability is poor in osteopenic vertebrae attributable, in part, to low screw-bone interface strength. The current authors examined cement augmentation using a low curing temperature hydroxyapatite and bis-phenol-A glycidol methacrylate-based composite resin. This cement may stiffen the screw-bone interface and reduce the harmful effects associated with polymethylmethacrylate regarding temperature and toxic monomer. Thirty-five lumbar vertebrae from human cadavers were instrumented with pedicle screws, with one pedicle previously injected with cement and the other as the control. Caudocephalad toggling of +/- 1 mm for 1600 cycles was applied to the pedicle screws, and the resulting forces supported by the implant-bone interface were captured by a load cell. A curve was constructed from the peak caudal load for each cycle and three mechanical measures parameterized this curve: (1) initial load; (2) rate of load decay during the first 400 cycles; and (3) final load. The initial load increased by 16% as a result of cement augmentation, the final load increased by 65%, and the rate of load decay decreased by 59%. Cement augmentation of pedicle screws increased the stiffness and stability of the screw-bone interface. PMID:12579026

  3. 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.

  4. Percutaneous screw fixation of acetabular fractures: applicability of hip arthroscopy.

    PubMed

    Yang, Jae-Hyuk; Chouhan, Devendra Kumar; Oh, Kwang-Jun

    2010-11-01

    Percutaneous screw fixation of the anterior column of the acetabulum has been a challenging task because of its unique anatomy and a risk of intra-articular penetration. Evidence is lacking for any tools to provide visual scrutiny of fracture reduction and intra-articular screw penetration. We report 2 cases of fracture of the acetabulum that developed in young female athletes, in which the anterior column was fixed with a percutaneous screw by use of hip arthroscopy as an assisting tool for intra-articular observation. In our experience this method was found to be promising in terms of anatomic reduction of the fracture site, avoiding articular penetration during screw insertion, with additional advantages of joint debridement, lavage, and reduction in radiation exposure. PMID:20888169

  5. 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.

  6. Squeak noise in lead screw systems: Self-excited vibration of continuous model

    NASA Astrophysics Data System (ADS)

    Kang, Jaeyoung; Kim, Keysun

    2010-08-01

    The dynamic instability of a spinning lead screw in contact with a screw nut is investigated analytically. The lead screw is modeled as a circular beam vibrating in transverse and torsion direction. The contact kinematics between the lead screw and the nut is described on the contact threads in the lead screw. The onset of squeak noise is numerically predicted with a variety of system parameters. Stability analysis shows that the transverse vibration modes can generate squeak noise in the lead screw system. It is highlighted that squeak noise can be controlled by system design parameters in such a manner that the squeak propensity is dependent on rotation speed, screw radius, axial load, contact location, and so on.

  7. Dorsal multiple plating without routine transarticular screws for fixation of Lisfranc injury.

    PubMed

    Stern, Richard E; Assal, Mathieu

    2014-12-01

    Following a Lisfranc joint injury, stable fixation of the tarsometatarsal joints is crucial to avoid deformity and posttraumatic osteoarthritis, but the ideal method of fixation remains controversial. Kirschner wire (K-wire) fixation of all involved joints with cast immobilization resulted in loss of position, and was replaced by open reduction with improved fixation using transarticular screws. However, it seems intuitive that transarticular screws will result in further damage to already traumatized joints, and this has led to plate-spanning techniques. The objective of this study was to describe the method of dorsal multiple plating without the routine use of transarticular screws, and to report on the ability of plate fixation to maintain alignment comparable to that of transarticular screw fixation in 15 patients. PMID:25437072

  8. [Unilateral triangular lumbopelvic stabilization: indications and techniques].

    PubMed

    Hoffmann, M F; Dudda, M; Schildhauer, T A

    2013-11-01

    Operative fixation has become treatment of choice for unstable sacral fractures. Osteosynthesis for these fractures results in loss of reduction in up to 15%. Vertical sacral fractures involving the S1 facet joint (Isler 2 and 3) may lead to multidirectional instability. Multidirectional instability of the posterior pelvic ring and lumbopelvic junction may be stabilized and forces balanced by a so-called lumbopelvic triangular fixation. Lumbopelvic triangular fixation combines vertical fixation between the lumbar vertebral pedicle and the ilium, with horizontal fixation, as an iliosacral screw or a transiliacal plate osteosynthesis. The iliac screw is directed from the posterior superior iliac spine (PSIS) to the anterior inferior iliac spine (AIIS). Thereby, lumbopelvic fixation decreases the load to the sacrum and SI joint and transfers axial loads from the lumbar spine directly onto the ilium. Triangular lumbopelvic fixation allows early full weight bearing and therefore reduces prolonged immobilization. The placement of iliac screws may be a complex surgical procedure. Thus, the technique requires thorough surgical preparation and operative logistics. Wound-related complications may occur. Preexisting Morell-Lavalée lesions increase the risk for infection. Prominent implants cause local irritation and pain. Hardware prominence and pain are markedly reduced with screw head recession into the PSIS. PMID:24233083

  9. Unilateral lag-screw technique for an isolated anterior 1/4 atlas fracture

    PubMed Central

    Keskil, Semih; Göksel, Murat; Yüksel, Ulaş

    2016-01-01

    Study Design: Fractures of the atlas are classified based on the fracture location and associated ligamentous injury. Among patients with atlas fractures treated using external immobilization, nonunion of the fracture could be seen. Objective: Ideally, treatment strategy for an unstable atlas fracture would involve limited fixation to maintain the fracture fragments in a reduced position without restricting the range of motion (ROM) of the atlantoaxial and atlantooccipital joints. Summary of Background Data: Such a result can be established using either transoral limited internal fixation or limited posterior lateral mass fixation. However, due to high infection risk and technical difficulty, posterior approaches are preferred but none of these techniques can fully address anterior 1/4 atlas fractures such as in this case. Materials and Methods: A novel open and direct technique in which a unilateral lag screw was placed to reduce and stabilize a progressively widening isolated right-sided anterior 1/4 single fracture of C1 that was initially treated with a rigid cervical collar is described. Results: Radiological studies made after the surgery showed no implant failure, good cervical alignment, and good reduction with fusion of C1. Conclusions: It is suggested that isolated C1 fractures can be surgically reduced and immobilized using a lateral compression screw to allow union and maintain both C1-0 and C1-2 motions, and in our knowledge this is the first description of the use of a lag screw to achieve reduction of distracted anterior 1/4 fracture fragments of the C1 from a posterior approach. This technique has the potential to become a valuable adjunct to the surgeon's armamentarium, in our opinion, only for fractures with distracted or comminuted fragments whose alignment would not be expected to significantly change with classical lateral mass screw reduction. PMID:27041886

  10. A capillary Archimedes' screw

    NASA Astrophysics Data System (ADS)

    Darbois Texier, Baptiste; Dorbolo, Stephane

    2014-11-01

    As used by Egyptians for irrigation and reported by Archimedes, a screw turning inside a hollow pipe can pull out a fluid againt gravity. At a centimetric scale, an analagous system can be found with a drop pending on a rotating spiral which is tilted toward the horizontal. The ascent of the drop to the top of the spiral is considered and a theoretical model based on geometrical considerations is proposed. The climb of the drop is limited by the fluid deposition on the screw at high capillary number and by a centrifugation phenomenon. We find out the range of fluid proprities and spiral characteristics for which an ascending motion of the drop is possible. Finally we discuss the efficiency of such system to extract a fluid from a bath at a centrimetric scale.

  11. NUT SCREW MECHANISMS

    DOEpatents

    Glass, J.A.F.

    1958-07-01

    A reactor control mechanism is described wherein the control is achieved by the partial or total withdrawal of the fissile material which is in the form of a fuel rod. The fuel rod is designed to be raised and lowered from the reactor core area by means of two concentric ball nut and screw assemblies that may telescope one within the other. These screw mechanisms are connected through a magnetic clutch to a speed reduction gear and an accurately controllable prime motive source. With the clutch energized, the fuel rod may be moved into the reactor core area, and fine adjustments may be made through the reduction gearing. However, in the event of a power failure or an emergency signal, the magnetic clutch will become deenergized, and the fuel rod will drop out of the core area by the force of gravity, thus shutting down the operation of the reactor.

  12. Influence of Thickness and Contact Surface Geometry of Condylar Stem of TMJ Implant on Its Stability

    NASA Astrophysics Data System (ADS)

    Arabshahi, Zohreh; Kashani, Jamal; Kadir, Mohammed Rafiq Abdul; Azari, Abbas

    The aim of this study is to examine the effect thickness and contact surface geometry of condylar stem of TMJ implant on its stability in total reconstruction system and evaluate the micro strain resulted in bone at fixation screw holes in jaw bone embedded with eight different designs of temporomandibular joint implants. A three dimensional model of a lower mandible of an adult were developed from a Computed Tomography scan images. Eight different TMJ implant designs and fixation screws were modeled. Three dimensional finite element models of eight implanted mandibles were analyzed. The forces assigned to the masticatory muscles for incisal clenching were applied consisting of nine important muscular loads. In chosen loading condition, The results indicated that the anatomical curvature contact surface design of TMJ implant can moderately improve the stability and the strain resulted in fixation screw holes in thinner TMJ implant was diminished in comparison with other thicknesses.

  13. 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

  14. 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

  15. 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.

  16. 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

  17. Comparison of stability of 2.0 mm standard and 2.0 mm locking miniplate/screws for the fixation of sagittal split ramus osteotomy on sheep mandibles.

    PubMed

    Oguz, Yener; Saglam, Haci; Dolanmaz, Dogan; Uckan, Sina

    2011-03-01

    Ten unembalmed adult sheep mandibles were used. The mandibles were sectioned in the midline, followed by sagittal split ramus osteotomies to obtain 20 hemimandibles. Each distal segment was advanced 5mm on each hemimandible. Ten of the specimens were fixed with 4-hole extended 2.0 mm titanium miniplates and screws and the other 10 were fixed with 4-hole extended 2.0 mm locking miniplates/screws. Each fixed specimen was mounted on a servo-hydraulic testing unit with the fixation device, and was tested to a range of forces of 0-140 N. The displacement values (mm) under 20, 60, 120, and 140 N were compared with the help of the Mann-Whitney U-test, and there were no significant differences between them at any force tested. Locking miniplate/screws and standard miniplate/screws showed similar displacement values at the range of forces tested. PMID:20226575

  18. Can discrete joint action be synergistic? Studying the stabilization of interpersonal hand coordination.

    PubMed

    Romero, Veronica; Kallen, Rachel; Riley, Michael A; Richardson, Michael J

    2015-10-01

    The human perceptual-motor system is tightly coupled to the physical and informational dynamics of a task environment. These dynamics operate to constrain the high-dimensional order of the human movement system into low-dimensional, task-specific synergies-functional groupings of structural elements that are temporarily constrained to act as a single coordinated unit. The aim of the current study was to determine whether synergistic processes operate when coacting individuals coordinate to perform a discrete joint-action task. Pairs of participants sat next to each other and each used 1 arm to complete a pointer-to-target task. Using the uncontrolled manifold (UCM) analysis for the first time in a discrete joint action, the structure of joint-angle variance was examined to determine whether there was synergistic organization of the degrees of freedom employed at the interpersonal or intrapersonal levels. The results revealed that the motor actions performed by coactors were synergistically organized at both the interpersonal and intrapersonal levels. More importantly, however, the interpersonal synergy was found to be significantly stronger than the intrapersonal synergies. Accordingly, the results provide clear evidence that coacting individuals can become temporarily organized to form single synergistic 2-person systems during performance of a discrete joint action. PMID:26052696

  19. Can Discrete Joint Action Be Synergistic? Studying the Stabilization of Interpersonal Hand Coordination

    PubMed Central

    Romero, Veronica; Kallen, Rachel; Riley, Michael A.; Richardson, Michael J.

    2016-01-01

    The human perceptual-motor system is tightly coupled to the physical and informational dynamics of a task environment. These dynamics operate to constrain the high-dimensional order of the human movement system into low-dimensional, task-specific synergies—functional groupings of structural elements that are temporarily constrained to act as a single coordinated unit. The aim of the current study was to determine whether synergistic processes operate when coacting individuals coordinate to perform a discrete joint-action task. Pairs of participants sat next to each other and each used 1 arm to complete a pointer-to-target task. Using the uncontrolled manifold (UCM) analysis for the first time in a discrete joint action, the structure of joint-angle variance was examined to determine whether there was synergistic organization of the degrees of freedom employed at the interpersonal or intrapersonal levels. The results revealed that the motor actions performed by coactors were synergistically organized at both the interpersonal and intrapersonal levels. More importantly, however, the interpersonal synergy was found to be significantly stronger than the intrapersonal synergies. Accordingly, the results provide clear evidence that coacting individuals can become temporarily organized to form single synergistic 2-person systems during performance of a discrete joint action. PMID:26052696

  20. Thumb Carpometacarpal Joint Stabilization in Ehlers-Danlos Syndrome--Case Report.

    PubMed

    Breahna, Anca Nicoleta; Meads, Bryce Maurice

    2015-10-01

    We report the case of an 18-years-old patient with thumb carpometacarpal ligament laxity due to Ehlers-Danlos syndrome who was treated with trapezial opening wedge osteotomy combined with volar ligaments reconstruction. Two years postoperatively she is pain free and the thumb carpometacarpal joint is stable. PMID:26388011

  1. A study of the effects of water concentration on the stability of interfaces in adhesive joints

    SciTech Connect

    Jackson, R.S.; Kinloch, A.J.; Gardhan, L.M.; Bowditch, M.R.

    1996-12-31

    The effect of water concentration on steel-epoxide joints was assessed. The 90{degrees} peel test method has been used to obtain fracture energy, G{sub c} values for adhered joints which have been previously conditioned in a range of relative humidities. Firstly, a loss of peel strength has been seen with increased water content of the adhesive. Further, a critical water concentration marking the transition from slight to pronounced loss of joint strength has been observed. Secondly, a theory for G{sub c} has been used to account for elastic and plastic deformation in the peel arm. However, the theory has not been able to fully account for changes in peel arm thickness but has for changes in the peel angle. Thirdly, apparent interfacial failure has been observed under visual inspection. Auger and X-ray photoelectron spectroscopy will be employed to (i) identify the locus of joint failure and (ii) the site and mechanisms of environmental attack by water.

  2. A Novel Blasted and Grooved Low Profile Pedicle Screw Able to Resist High Compression Bending Loads

    PubMed Central

    Kim, Young-Sung; Choi, Hong-June; Kim, Kyung-Hyun; Park, Jeong-Yoon; Jeong, Hyun-Yong; Chin, Dong-Kyu; Kim, Keun-Su; Yoon, Young-Sul; Lee, Yoon-Chul; Cho, Yong-Eun

    2012-01-01

    Objective Polyaxial pedicle screws are a safe, useful adjunct to transpedicular fixation. However, the large screw head size can cause soft tissue irritation, high rod positioning, and facet joint injury. However, the mechanical resistance provided by small and low profile pedicle screws is very limited. We therefore developed a novel, low profile pedicle screw using grooving and blasting treatment that is able to resist a high compression bending load. Methods We evaluated the compression bending force to displacement and yield loads for seven different screw head types that differed with regard to their groove intervals and whether or not they had been blasted. Results The rank order of screw types that had the greatest compression bending force to displacement was as follows: (1) universal polyaxial, (2) low polyaxial with 0.1mm grooves and blasting, (3) low polyaxial with blasting, (4) low polyaxial with 0.15mm grooves and blasting, (5) low polyaxial with 0.05mm grooves and blasting, (6) low polyaxial with 0.05mm grooves, (7) and low polyaxial. Low polyaxial screws with 0.1mm grooves and blasting had the maximum yield load and highest compression bending force to displacement of all seven polyaxial screw head systems evaluated. Conclusion Blasting and grooving treatment of pedicle screw heads resulted in screw heads with a high yield load and compression bending force relative to displacement because of increased friction. Low polyaxial pedicle screws with 0.1 mm grooves treated by blasting have mechanical characteristics similar to those of universal polyaxial pedicle screws. PMID:25983790

  3. 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.

  4. An Innovative Universal Screw Removal Instrument

    PubMed Central

    Elmadağ, Mehmet; Uzer, Gökçer; Acar, Mehmet Ali

    2015-01-01

    Objective To present the clinical benefits of an instrument designed to facilitate removal of polyaxial screws during revision surgery. Methods All polyaxial screws can be removed without additional materials or a large amount of debridement using our newly designed instrument. Forty-two screws were removed from five patients without any complications using this instrument. Results We removed the cap screws and rods from the 42 polyaxial screws in five patients and made them monoaxial using the new screw removal apparatus. The screws and rods were removed quickly in a minimally invasive way with no complications. No damage to the pedicle or surrounding soft tissue occurred during screw removal. No neurogenic changes developed during revision surgery after changing the screws. Conclusion This newly designed screw removal instrument was used safely and effectively to remove all polyaxial and monoaxial pedicle screws. PMID:25883660

  5. Horizontal and Vertical Stabilization of Acute Unstable Acromioclavicular Joint Injuries Arthroscopy-Assisted

    PubMed Central

    Cisneros, Luis Natera; Sarasquete Reiriz, Juan; Besalduch, Marina; Petrica, Alexandru; Escolà, Ana; Rodriguez, Joaquim; Fallone, Jan Carlo

    2015-01-01

    We describe the technical aspects of an arthroscopy-assisted procedure indicated for the management of acute unstable acromioclavicular joint injuries, consisting of a synthetic augmentation of both the coracoclavicular and acromioclavicular ligaments, that anatomically reproduces the coracoclavicular biomechanics and offers fixation that keeps the torn ends of the ligaments facing one another, thus allowing healing of the native structures without the need for a second surgical procedure for metal hardware removal. PMID:26870653

  6. Slope Stability Problems and Back Analysis in Heavily Jointed Rock Mass: A Case Study from Manisa, Turkey

    NASA Astrophysics Data System (ADS)

    Akin, Mutluhan

    2013-03-01

    This paper presents a case study regarding slope stability problems and the remedial slope stabilization work executed during the construction of two reinforced concrete water storage tanks on a steep hill in Manisa, Turkey. Water storage tanks of different capacities were planned to be constructed, one under the other, on closely jointed and deformed shale and sandstone units. The tank on the upper elevation was constructed first and an approximately 20-m cut slope with two benches was excavated in front of this upper tank before the construction of the lower tank. The cut slope failed after a week and the failure threatened the stability of the upper water tank. In addition to re-sloping, a 15.6-m deep contiguous retaining pile wall without anchoring was built to support both the cut slope and the upper tank. Despite the construction of a retaining pile wall, a maximum of 10 mm of displacement was observed by inclinometer measurements due to the re-failure of the slope on the existing slip surface. Permanent stability was achieved after the placement of a granular fill buttress on the slope. Back analysis based on the non-linear (Hoek-Brown) failure criterion indicated that the geological strength index (GSI) value of the slope-forming material is around 21 and is compatible with the in situ-determined GSI value (24). The calculated normal-shear stress plots are also consistent with the Hoek-Brown failure envelope of the rock mass, indicating that the location of the sliding surface, GSI value estimated by back analysis, and the rock mass parameters are well defined. The long-term stability analysis illustrates a safe slope design after the placement of a permanent toe buttress.

  7. Tibiofibular screw fixation for syndesmotic ruptures: a biomechanical analysis.

    PubMed

    Stein, G; Eichler, C; Ettmann, L; Koebke, J; Müller, L P; Thelen, U; Skouras, E

    2012-09-01

    The mechanisms of injuries to the tibiofibular syndesmosis include isolated rupture and rupture in combination with ankle fractures. Current concepts of surgical treatment are fixation using bioabsorbable screws, syndesmotic stapling, syndesmotic hooks, and the widely used screw fixation. Postoperative care utilises passive motion of the ankle joint either with or without axial weight-bearing. The aim of our investigation was to quantify the motion of the mortise during axial load. Therefore, photoelastic tests, on the one hand, and biomechanical tests of cadaveric specimens, on the other, using axial loads of up to 2,000 N were used. Our photoelastic investigations showed force distribution through the screw into the cranial and caudal parts of the distal fibula. Biomechanical testing showed a progressive dehiscence in both ruptured and fixated specimens up to 2.89 (ruptured) and 2.42 mm (despite screw). Our findings strongly suggest a concept of partial weight-bearing at most to support regeneration of scar tissue and to prevent the appearance of instability in the ankle joint. PMID:22415030

  8. 21 CFR 888.3070 - Pedicle screw spinal system.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... immobilization and stabilization of spinal segments in skeletally mature patients as an adjunct to fusion in the...; spinal tumor; and failed previous fusion (pseudarthrosis). These pedicle screw spinal systems must comply... with significant mechanical instability or deformity requiring fusion with instrumentation....

  9. 21 CFR 888.3070 - Pedicle screw spinal system.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... immobilization and stabilization of spinal segments in skeletally mature patients as an adjunct to fusion in the...; spinal tumor; and failed previous fusion (pseudarthrosis). These pedicle screw spinal systems must comply... with significant mechanical instability or deformity requiring fusion with instrumentation....

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

    PubMed Central

    Alvis-Miranda, Hernando Raphael; Farid-Escorcia, Hector; Alcalá-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. Does Repair of a Hill-Sachs Defect Increase Stability at the Glenohumeral Joint?

    PubMed Central

    Bakshi, Neil K.; Jolly, John T.; Debski, Richard E.; Sekiya, Jon K.

    2016-01-01

    Background: The effect of osteoallograft repair of a Hill-Sachs lesion and the effect of allograft fit on glenohumeral translations in response to applied force are poorly understood. Purpose: To compare the impact of a 25% Hill-Sachs lesion, a perfect osteoallograft repair (PAR) of a 25% Hill-Sachs lesion, and an “imperfect” osteoallograft repair (IAR) of a 25% Hill-Sachs lesion on glenohumeral translations in response to a compressive load and either an anterior or posterior load in 3 clinically relevant arm positions. Study Design: Controlled laboratory study. Methods: A robotic/universal force-moment sensor testing system was used to apply joint compression (22 N) and an anterior or posterior load (44 N) to cadaveric shoulders (n = 9) with the skin and deltoid removed (intact) at 3 glenohumeral joint positions (abduction/external rotation): 0°/0°, 30°/30°, and 60°/60°. The 25% bony defect state, PAR state, and IAR state were created and the loading protocol was performed. Translational motion was measured in each position for each shoulder state. A nonparametric repeated-measures Friedman test with a Wilcoxon signed-rank post hoc test was performed to compare the biomechanical parameters (P < .05). Results: Compared with the defect shoulder, the PAR shoulder had significantly less anterior translation with an anterior load in the 0°/0° (15.3 ± 8.2 vs 16.6 ± 9.0 mm, P = .008) and 30°/30° (13.6 ± 7.1 vs 14.2 ± 7.0 mm, P = .021) positions. Compared with IAR, the PAR shoulder had significantly less anterior translation with an anterior load in the 0°/0° (15.3 ± 8.2 vs 16.6 ± 9.0 mm, P = .008) and 30°/30° (13.6 ± 7.1 vs 14.4 ± 7.1 mm, P = .011) positions, and the defect shoulder had significantly less anterior translation with an anterior load in the 30°/30° (14.2 ± 7.0 vs 14.4 ± 7.0 mm, P = .038) position. Conclusion: PAR resulted in the least translational motion at the glenohumeral joint. The defect shoulder had significantly less

  12. Does surgery for instability of the shoulder truly stabilize the glenohumeral joint?

    PubMed Central

    Lädermann, Alexandre; Denard, Patrick J.; Tirefort, Jérôme; Kolo, Frank C.; Chagué, Sylvain; Cunningham, Grégory; Charbonnier, Caecilia

    2016-01-01

    Abstract Despite the fact that surgery is commonly used to treat glenohumeral instability, there is no evidence that such treatment effectively corrects glenohumeral translation. The purpose of this prospective clinical study was to analyze the effect of surgical stabilization on glenohumeral translation. Glenohumeral translation was assessed in 11 patients preoperatively and 1 year postoperatively following surgical stabilization for anterior shoulder instability. Translation was measured using optical motion capture and computed tomography. Preoperatively, anterior translation of the affected shoulder was bigger in comparison to the normal contralateral side. Differences were significant for flexion and abduction movements (P < 0.001). Postoperatively, no patients demonstrated apprehension and all functional scores were improved. Despite absence of apprehension, postoperative anterior translation for the surgically stabilized shoulders was not significantly different from the preoperative values. While surgical treatment for anterior instability limits the chance of dislocation, it does not seem to restore glenohumeral translation during functional range of motion. Such persistent microinstability may explain residual pain, apprehension, inability to return to activity and even emergence of dislocation arthropathy that is seen in some patients. Further research is necessary to better understand the causes, effects, and treatment of residual microinstability following surgical stabilization of the shoulder. PMID:27495043

  13. Percutaneous Sacroiliac Screw Technique.

    PubMed

    Tidwell, John; Cho, Rosa; Reid, J Spence; Boateng, Henry; Copeland, Carol; Sirlin, Edward

    2016-08-01

    Remembering that preoperative planning, surgical indications, and fracture reduction are paramount for this procedure, presented here is our technique for performing percutaneous sacroiliac screws, both transiliac-transsacral and sacral style. A combination of video, still pictures, and fluoroscopy images will guide the viewer through the process we routinely use highlighting specific details. Patient positioning and intraoperative fluoroscopy imaging are critical to a successful procedure. Although inlet and outlet films remain important, we find the procedure best started on the lateral sacral view to reduce the need for start site, trajectory, and imaging position changes during the case. A cannulated pig sticker (drill guide) used with long drill tip guide wires provide improved manual control to both finding a good start site and directing the trajectory. For patient safety, sacral anatomy and safe zones are discussed as well. Using these technical points will help make this a successful procedure. PMID:27441927

  14. 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.

  15. Editorial Commentary: Are Larger Screws the Answer When Anatomic Reconstruction of an Acromioclavicular Separation Fails?

    PubMed

    Denard, Patrick J

    2016-08-01

    Although fixation methods have improved, failure after fixation of an acromioclavicular joint separation is not uncommon. This biomechanical study shows that in the setting of graft slippage through previously well-placed clavicular tunnels, a revision anatomic reconstruction is feasible with larger tenodesis screws. Although the risk of clavicular fracture increases with larger tunnels, anatomic revision with larger screws is an option in select cases. PMID:27495861

  16. Surgical technique: hemi-extensor carpi radialis brevis tenodesis for stabilizing the midcarpal joint in Ehlers-Danlos syndrome.

    PubMed

    Krijgh, David D; Harley, Oliver J; Hovius, Steven E; Coert, J Henk; Walbeehm, Erik T

    2014-10-01

    Patients with the hypermobility type of Ehlers-Danlos (EDS-HT) often complain of wrist pain, usually originating from subluxations. As a result of the laxity, wrist function in these patients can be highly limited. This paper presents a surgical technique that stabilizes the lunocapitate joint with the use of an extensor carpi radialis brevis strip. Five patients with confirmed EDS-HT were treated with an extensor carpi radialis brevis tenodesis for their midcarpal instability. Two patients presented with complications following surgery, one major and one minor. This paper presents a potentially satisfactory surgical solution to recurrent midcarpal instability in EDS-HT patients and demonstrates that the use of an autologous tendon might be feasible in spite of a background of abnormal collagen metabolism. PMID:25194773

  17. 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

  18. Effect of Jaw Clenching on Balance Recovery: Dynamic Stability and Lower Extremity Joint Kinematics after Forward Loss of Balance

    PubMed Central

    Ringhof, Steffen; Stein, Thorsten; Hellmann, Daniel; Schindler, Hans J.; Potthast, Wolfgang

    2016-01-01

    Postural control is crucial for most tasks of daily living, delineating postural orientation and balance, with its main goal of fall prevention. Nevertheless, falls are common events, and have been associated with deficits in muscle strength and dynamic postural stability. Recent studies reported on improvements in rate of force development and static postural control evoked by jaw clenching activities, potentially induced by facilitation of human motor system excitability. However, there are no studies describing the effects on dynamic stability. The present study, therefore, aimed to investigate the effects of submaximum jaw clenching on recovery behavior from forward loss of balance. Participants were 12 healthy young adults, who were instructed to recover balance from a simulated forward fall by taking a single step while either biting at a submaximum force or keeping the mandible at rest. Bite forces were measured by means of hydrostatic splints, whereas a 3D motion capture system was used to analyze spatiotemporal parameters and joint angles, respectively. Additionally, dynamic stability was quantified by the extrapolated CoM concept, designed to determine postural stability in dynamic situations. Paired t-tests revealed that submaximum biting did not significantly influence recovery behavior with respect to any variable under investigation. Therefore, reductions in postural sway evoked by submaximum biting are obviously not transferable to balance recovery as it was assessed in the present study. It is suggested that these contradictions are the result of different motor demands associated with the abovementioned tasks. Furthermore, floor effects and the sample size might be discussed as potential reasons for the absence of significances. Notwithstanding this, the present study also revealed that bite forces under both conditions significantly increased from subjects’ release to touchdown of the recovery limb. Clenching the jaw, hence, seems to be part of

  19. 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.

  20. Distal Locking Screws for Intramedullary Nailing of Tibial Fractures.

    PubMed

    Agathangelidis, Filon; Petsatodis, Georgios; Kirkos, John; Papadopoulos, Pericles; Karataglis, Dimitrios; Christodoulou, Anastasios

    2016-01-01

    Recently introduced tibial intramedullary nails allow a number of distal screws to be used to reduce the incidence of malalignment and loss of fixation of distal metaphyseal fractures. However, the number of screws and the type of screw configuration to be used remains obscure. This biomechanical study was performed to address this question. Thirty-six Expert tibial nails (Synthes, Oberdorf, Switzerland) were introduced in composite bone models. The models were divided into 4 groups with different distal locking configurations ranging from 2 to 4 screws. A 7-mm gap osteotomy was performed 72 mm from the tibial plafond to simulate a 42-C3 unstable distal tibial fracture. Each group was divided in 3 subgroups and underwent nondestructive biomechanical testing in axial compression, coronal bending, and axial torsion. The passive construct stiffness was measured and statistically analyzed with one-way analysis of variance. Although some differences were noted between the stiffness of each group, these were not statistically significant in compression (P=.105), bending (P=.801), external rotation (P=.246), and internal rotation (P=.370). This in vitro study showed that, when using the Expert tibial nail for unstable distal tibial fractures, the classic configuration of 2 parallel distal screws could provide the necessary stability under partial weight-bearing conditions. PMID:26840700

  1. Stability of treatments for recurrent temporomandibular joint luxation: a systematic review.

    PubMed

    de Almeida, V L; Vitorino, N de S; Nascimento, A L de O; da Silva Júnior, D C; de Freitas, P H L

    2016-03-01

    Temporomandibular joint luxation (TMJ) is the excessive anterior translation of the mandibular condyle out of its normal range of movement and away from the glenoid fossa. Once dislocation occurs, the abnormal condylar position generates reflex contractions of the masticatory muscles, which in turn hinder movement of the condyle back to its resting position. Frequent luxation episodes characterize a condition referred to as recurrent TMJ luxation. While there are several surgical and conservative therapeutic options available for recurrent TMJ luxation, a robust, evidence-based rationale for choosing one technique over another is missing. Thus, a systematic review based on the PRISMA statement was proposed in an attempt to determine which therapeutic option results in the longest time to relapse. There is no good quality evidence on which treatment options guarantee the long-term elimination of recurrent TMJ luxation. In cases of post-surgical relapse, eminectomy has often been used as a 'rescue procedure', which may mean that surgeons empirically consider this treatment to be the 'gold standard' for addressing recurrent TMJ luxation. PMID:26616027

  2. 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

  3. Effects of internal viscous damping on the stability of a rotating shaft driven through a universal joint

    NASA Astrophysics Data System (ADS)

    Mazzei, A. J.; Scott, R. A.

    2003-08-01

    A rotating flexible shaft, with both external and internal viscous damping, driven through a universal joint is considered. The mathematical model consists of a set of coupled, linear partial differential equations with time-dependent coefficients. Use of Galerkin's technique leads to a set of coupled linear differential equations with time-dependent coefficients. Using these differential equations some effects of internal viscous damping on parametric and flutter instability zones are investigated by the monodromy matrix technique. The flutter zones are also obtained on discarding the time-dependent coefficients in the differential equations which leads to an eigenvalue analysis. A one-term Galerkin approximation aided this analysis. Two different shafts ("automotive" and "lab") were considered. Increasing internal damping is always stabilizing as regards to parametric instabilities. For flutter type instabilities it was found that increasing internal damping is always stabilizing for rotational speeds v below the first critical speed, v1. For v> v1, there is a value of the internal viscous damping coefficient, Civ, which depends on the rotational speed and torque, above which destabilization occurs. The value of Civ ("critical value") at which the unstable zone first enters the practical range of operation was determined. The dependence of Civ critical on the external damping was investigated. It was found for the automotive case that a four-fold increase in external damping led to an increase of about 20% of the critical value. For the lab model an increase of two orders of magnitude of the external damping led to an increase of critical value of only 10%. For the automotive shaft it was found that this critical value also removed the parametric instabilities out of the practical range. For the lab model it is not always possible to completely stabilize the system by increasing the internal damping. For this model using Civ critical, parametric instabilities are

  4. Biomechanical impact of C2 pedicle screw length in an atlantoaxial fusion construct

    PubMed Central

    Xu, Risheng; Bydon, Mohamad; Macki, Mohamed; Belkoff, Stephen M.; Langdale, Evan R.; McGovern, Kelly; Wolinsky, Jean-Paul; Gokalsan, Ziya L.; Bydon, Ali

    2014-01-01

    Background: Posterior, atlantoaxial (AA) fusions of the cervical spine may include either standard (26 mm) or short (16 mm) C2 pedicle screws. This manuscript focused on an in vitro biomechanical comparison of standard versus short C2 pedicle screws to perform posterior C1-C2 AA fusions. Methods: Twelve human cadaveric spines underwent C1 lateral mass screw and standard C2 pedicle screw (n = 6) versus short C2 pedicle screw (n = 6) fixation. Six additional controls were not instrumented. The peak torque, peak rotational interval, and peak stiffness of the constructs were analyzed to failure levels. Results: The peak torque to construct failure was not statistically significantly different among the control spine (12.2 Nm), short pedicle fixation (15.5 Nm), or the standard pedicle fixation (11.6 Nm), P = 0.79. While the angle at the peak rotation statistically significantly differed between the control specimens (47.7° of relative motion) and the overall instrumented specimens (P < 0.001), the 20.7° of relative rotation in the short C2 pedicle screw specimens was not statistically significantly higher than the 13.7° of relative rotation in the standard C2 pedicle screw specimens (P = 0.39). Similarly, although the average stiffness was statistically significantly lower in control group (0.026 Nm/degree) versus the overall instrumented specimens (P = 0.001), the standard C2 pedicle screws (2.54 Nm/degree) did not differ from the short C2 pedicle screws Conclusions: Both standard and short C2 pedicle screws allow for equally rigid fixation of C1 lateral mass-C2 AA fusions. Usage of a short C2 pedicle screw may be an acceptable method of stabilization in carefully selected patient populations. PMID:25289157

  5. Multipoint joint time and frequency dissemination in delay-stabilized fiber optic links.

    PubMed

    Śliwczyński, Ł; Krehlik, P

    2015-03-01

    This paper presents the system for dissemination of both the RF frequency (e.g., 5, 10, or 100 MHz) and time (pulse per second) signals using an actively tapped fiber-optic link with electronic stabilization of the propagation delay. In principle several nodes for accessing the time/frequency signals may be added without the degradation of the dissemination in the main link. We are discussing the algorithm of determining the propagation delay from the local end of the link to the access node that is required for calibration of the time dissemination. Performed analysis shows that the uncertainty of the time calibration at the access node may in practice be dominated by the dependence of the propagation delay of the receivers on impinging optical powers and is only weakly affected by the distance between the local and access modules. The uncertainty is, however, still low, being only about two times higher compared with the calibration uncertainty of the main link. Experimental results performed on several spooled fibers show that the accuracy of described calibration procedures, expressed as a difference from the results of direct measurement, is not worse than 35 ps. PMID:25768810

  6. Use of the talon hip compression screw in intertrochanteric fractures of the hip.

    PubMed

    Bramlet, Dale G

    2004-08-01

    A retrospective analysis of a compression hip screw with four reversibly deployable talons was done. Fifty-four patients had sufficient radiographs to be included in this analysis. One-year mortality was 17% and increased to 41% by 2 years. No lag screws cut out, and postoperative slide was reduced compared with that in many published series. Three patients had revision of a failed alternate-type hip pin with the Talon hip compression screw. Previous studies showed the talons provide the definitive difference in allowing enhanced compression at the time of surgery, preventing cut-out by enhanced rotational stability, and allowing immediate postoperative weightbearing without excessive limb shortening. The failure mode of the Talon compression hip screw seems to be side-plate loosening rather than varus deformity and lag screw cut-out. The Talon compression hip screw especially is effective with weak, osteoporotic bone and in unstable, three-part and four-part fractures. A previous study showed that Talon deployment notably improved interfragment compression and torsional strength, and that engagement or penetration into or through the cortical bone at the base of the femoral head-neck junction in the inferior lag screw position was the critical technical step to maximize the talon lag screw purchase. PMID:15292793

  7. Effects of bone materials on the screw pull-out strength in human spine.

    PubMed

    Zhang, Qing Hang; Tan, Soon Huat; Chou, Siaw Meng

    2006-10-01

    A three-dimensional finite element model simulating the threaded connections including detailed helix curve for the bone and surgical screw was constructed. Validation of the FE model was conducted by comparing the predicted screw pull-out strength in different foam materials against experimental study. The FE model was then further analyzed to investigate the interaction of bone material and purchase length on the screw pull-out strength. The results show that failure of the connection was due to bone shearing which occurred along a cylindrical surface determined by the outer perimeter of the screw. The cortical shell resists around 50% of the pull-out strength for a screw of 4mm in major diameter and 22 mm in length. The effects of purchase length on the pull-out strength were different for different bone material. It is the bone material that determines the stability of the inserted surgical screw. The significance of the purchase length on the pull-out strength of cortical screw will be much lower than that in cancellous bone screw. PMID:16414303

  8. Joint Instability and Osteoarthritis

    PubMed Central

    Blalock, Darryl; Miller, Andrew; Tilley, Michael; Wang, Jinxi

    2015-01-01

    Joint instability creates a clinical and economic burden in the health care system. Injuries and disorders that directly damage the joint structure or lead to joint instability are highly associated with osteoarthritis (OA). Thus, understanding the physiology of joint stability and the mechanisms of joint instability-induced OA is of clinical significance. The first section of this review discusses the structure and function of major joint tissues, including periarticular muscles, which play a significant role in joint stability. Because the knee, ankle, and shoulder joints demonstrate a high incidence of ligament injury and joint instability, the second section summarizes the mechanisms of ligament injury-associated joint instability of these joints. The final section highlights the recent advances in the understanding of the mechanical and biological mechanisms of joint instability-induced OA. These advances may lead to new opportunities for clinical intervention in the prevention and early treatment of OA. PMID:25741184

  9. Joint instability and osteoarthritis.

    PubMed

    Blalock, Darryl; Miller, Andrew; Tilley, Michael; Wang, Jinxi

    2015-01-01

    Joint instability creates a clinical and economic burden in the health care system. Injuries and disorders that directly damage the joint structure or lead to joint instability are highly associated with osteoarthritis (OA). Thus, understanding the physiology of joint stability and the mechanisms of joint instability-induced OA is of clinical significance. The first section of this review discusses the structure and function of major joint tissues, including periarticular muscles, which play a significant role in joint stability. Because the knee, ankle, and shoulder joints demonstrate a high incidence of ligament injury and joint instability, the second section summarizes the mechanisms of ligament injury-associated joint instability of these joints. The final section highlights the recent advances in the understanding of the mechanical and biological mechanisms of joint instability-induced OA. These advances may lead to new opportunities for clinical intervention in the prevention and early treatment of OA. PMID:25741184

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

    PubMed Central

    Ueno, Fabrício Hidetoshi; Pisani, Marina Justi; Machado, André Nunes; Rodrigues, Fábio 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

  11. 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.

  12. Influence of abutment screw design and surface coating on the bending flexural strength of the implant set.

    PubMed

    Prado, Célio Jesus do; Neves, Flávio Domingues das; Soares, Carlos José; Dantas, Kelly Abadia; Dantas, Talita Souza; Naves, Lucas Zago

    2014-04-01

    The purpose of this study was to analyze the influence of the setting and the presence of solid lubricant on the abutment screw surface on the flexural strength of the joint implant/abutment/screw. Forty abutments were connected to external hex implants, divided into 4 groups (n = 10): FE (titanium alloy screw threaded in the extremity), LE (titanium alloy screw with solid lubricant and thread in the extremity), FT (titanium alloy screw with threaded in all its length), and LT (titanium alloy screw with solid lubricant and thread in all its length). Through the mechanical flexural test, the implant/abutment resistance was evaluated with load applied perpendicular to the long axis in a mechanical testing machine (EMIC) under a speed of 0.5 mm/min. Data were submitted to a statistics test, and results showed statistically significant differences between the FE group and the other groups, and the FE group showed the lowest values. The LE group showed greater values than the LT group, and the values were statistically significant. According to the methodology used, it can be concluded that within noncoated titanium screws, a screw threaded along its entire length provided greater rigidity to the implant set, while with the screw containing solid lubricant, the screw threaded in all its length provided less rigidity of the implant set than screws with the thread only on the end. Among screws with the same geometry, those with the solid lubricant are statistically higher than those which do not have threads just at the end, but those with threads along their entire length do not show statistically significant differences. PMID:22251283

  13. Pure Varus Injury to the Knee Joint.

    PubMed

    Yoo, Jae Ho; Lee, Jung Ha; Chang, Chong Bum

    2015-06-01

    A 30-year-old male was involved in a car accident. Radiographs revealed a depressed marginal fracture of the medial tibial plateau and an avulsion fracture of the fibular head. Magnetic resonance imaging showed avulsion fracture of Gerdy's tubercle, injury to the posterior cruciate ligament (PCL), posterior horn of the medial meniscus, and the attachments of the lateral collateral ligament and the biceps femoris tendon. The depressed fracture of the medial tibial plateau was elevated and stabilized using a cannulated screw and washer. The injured lateral and posterolateral corner (PLC) structures were repaired and augmented by PLC reconstruction. However, the avulsion fracture of Gerdy's tubercle was not fixed because it was minimally displaced and the torn PCL was also not repaired or reconstructed. We present a unique case of pure varus injury to the knee joint. This case contributes to our understanding of the mechanism of knee injury and provides insight regarding appropriate treatment plans for this type of injury. PMID:26217477

  14. The Mast Cell Stabilizer Ketotifen Fumarate Lessens Contracture Severity and Myofibroblast Hyperplasia: A Study of a Rabbit Model of Posttraumatic Joint Contractures

    PubMed Central

    Monument, Michael J.; Hart, David A.; Befus, A. Dean; Salo, Paul T.; Zhang, Mei; Hildebrand, Kevin A.

    2010-01-01

    Background The propensity of the elbow to become stiff after trauma is widely appreciated and in this setting, the joint capsule is commonly recognized as the major motion-limiting anatomical structure. Affected joint capsules become fibrotic, characterized by myofibroblast hyperplasia and excessive collagen deposition. Mast cell hyperplasia is common within fibrotic tissue and mast cells are known to synthesize many profibrotic mediators. We have hypothesized that mast cell inhibition after skeletal injury will lessen the degree of contracture severity and will reduce myofibroblast hyperplasia within the joint capsule. Methods Posttraumatic contractures of the knee were created using a combination of intra-articular injury coupled to internal immobilization in skeletally mature, New Zealand white rabbits. Four groups of animals were studied: a non-operative control group (CON), an operative contracture group (ORC) and two-operative groups treated with a mast cell stabilizer, Ketotifen fumarate at doses of 0.5mg/kg (KF0.5) and 1.0mg/kg (KF1.0) twice daily, respectively. After 8 weeks of immobilization, flexion contractures were measured biomechanically and the posterior joint capsule was harvested for quantification of myofibroblast and mast cell numbers. Results Flexion contractures developed in the ORC group (58 ± 14°) and the severity of contracture was significantly reduced in both groups treated with Ketotifen (KF0.5: 42 ± 17° and KF1.0: 45 ± 10°, p<0.02). Joint capsule myofibroblast and mast cell numbers were significantly increased within the operative contracture group (p<0.001). In both surgical groups treated with Ketotifen, myofibroblast and mast cell numbers were significantly reduced (p<0.001). Conclusions The use of a mast cell stabilizer, Ketotifen was effective in reducing the biomechanical and cellular manifestations of joint capsule fibrosis in a rabbit model of posttraumatic joint contracture. This is suggestive that an inflammatory pathway

  15. Absorbable scaphoid screw development: a comparative study on biomechanics

    PubMed Central

    Wang, Yi; Song, Muguo; Xu, Yongqing; He, Xiaoqing; Zhu, YueLiang

    2016-01-01

    Background The scaphoid is critical for maintaining the stability and movement of the wrist joints. This study aimed to develop a new internal fixator absorbable scaphoid screw (ASS) for fixation of the scaphoid waist after fracture and to test the biomechanical characteristics of ASS. Materials and methods An ASS was prepared using polylactic acids and designed based on scaphoid measurements and anatomic features. Twenty fractured scaphoid waist specimens were randomly divided into experimental and control groups (n=10/group). Reduction and internal fixation of the scaphoid were achieved with either Kirschner wires (K-wires) or ASS. A moving target simulator was used to test palmar flexion and dorsal extension, with the range of testing (waist movement) set from 5° of palmar flexion to 25° of dorsal extension. Flexion and extension were repeated 2,000 times for each specimen. Fracture gap displacements were measured with a computerized tomography scanning. Scaphoid tensile and bending strengths were measured by using a hydraulic pressure biomechanical system. Results Prior to biomechanical fatigue testing, fracture gap displacements were 0.16±0.02 mm and 0.22±0.02 mm in the ASS and K-wire groups, respectively. After fatigue testing, fracture gap displacements in the ASS and the K-wire groups were 0.21±0.03 mm and 1.52±0.07 mm, respectively. The tensile strengths for the ASS and K-wire groups were 0.95±0.02 MPa and 0.63±0.02 MPa, respectively. Conclusion Fixation using an ASS provided sufficient mechanical support for the scaphoid after fracture. PMID:27217756

  16. Assessment of Ankle and Hindfoot Stability and Joint Pressures Using a Human Cadaveric Model of a Large Lateral Talar Process Excision

    PubMed Central

    Sands, Andrew; White, Charles; Blankstein, Michael; Zderic, Ivan; Wahl, Dieter; Ernst, Manuela; Windolf, Markus; Hagen, Jennifer E.; Richards, R. Geoff; Stoffel, Karl; Gueorguiev, Boyko

    2015-01-01

    Abstract Lateral talar process fragment excision may be followed by hindfoot instability and altered biomechanics. There is controversy regarding the ideal fragment size for internal fixation versus excision and a concern that excision of a large fragment may lead to significant instability. The aim of this study was to assess the effect of a simulated large lateral talar process excision on ankle and subtalar joint stability. A custom-made seesaw rig was designed to apply inversion/eversion stress loading on 7 fresh-frozen human cadaveric lower legs and investigate them in pre-excision, 5 cm3 and 10 cm3 lateral talar process fragment excision states. Anteroposterior radiographs were taken to assess ankle and subtalar joint tilt and calculate angular change from neutral hindfoot alignment to 10-kg forced inversion/eversion. Ankle joint pressures and contact areas were measured under 30-kg axial load in neutral hindfoot alignment. In comparison to the pre-excision state, no significantly different mediolateral angular change was observed in the subtalar joint after 5 and 10 cm3 lateral talar process fragment excision in inversion and eversion. With respect to the ankle joint, 10-cm3 fragment excision produced significantly bigger inversion tibiotalar tilt compared with the pre-excision state, P = .04. No significant change of the ankle joint pressure and contact area was detected after 5 and 10-cm3 excision in comparison with the pre-excison state. An excision of up to 10 cm3 of the lateral talar process does not cause a significant instability at the level of the subtalar joint but might be a destabilizing factor at the ankle joint under inversion stress. The latter could be related to extensive soft tissue dissection required for resection. PMID:25789950

  17. 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.

  18. 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.

  19. Pursuing low joint resistivity in Cu-stabilized REBa2Cu3O δ coated conductor tapes by the ultrasonic weld-solder hybrid method

    NASA Astrophysics Data System (ADS)

    Shin, Hyung-Seop; Kim, Jong-min; Dedicatoria, Marlon J.

    2016-01-01

    Development of a coated conductor tape joint with good quality and low joint resistivity, R sj, in terms of transport and mechanical properties, was attempted by direct bonding at the interface of the Cu-Cu stabilizers in overlapped GdBCO CC tapes. In this study, we attempted to achieve a low R sj by introducing hybrid joining, soldering and ultrasonic welding (UW), and its mechanism was analyzed theoretically. Coated conductor tapes were experimentally joined using various methods of soldering, UW, and combinations of the two. As a result, a much lower R sj of about 57 nΩ · cm2 was obtained for RCE-DR-processed GdBCO CC tape joints using the hybrid joining method. The mechanical properties of the jointed CC tapes were also evaluated at room temperature and 77 K under self-field. Load-displacement curves of joined CC tapes followed the curve of the single CC tape. Critical current and joint resistance, R j, of hybrid-joined CC tape were retained after double bending at room temperature up to 20 mm bending diameter.

  20. Is a Sliding Hip Screw or IM Nail the Preferred Implant for Intertrochanteric Fracture Fixation?

    PubMed Central

    Aros, Brian; Tosteson, Anna N. A.; Gottlieb, Daniel J.

    2008-01-01

    This study was performed to determine whether patients who sustain an intertrochanteric fracture have better outcomes when stabilized using a sliding hip screw or an intramedullary nail. A 20% sample of Part A and B entitled Medicare beneficiaries 65 years or older was used to generate a cohort of patients who sustained intertrochanteric femur fractures between 1999 and 2001. Two fracture implant groups, intramedullary nail and sliding hip screw, were identified using Current Procedural Terminology and International Classification of Diseases, 9th Revision codes. The cohort consisted of 43,659 patients. Patients treated with an intramedullary nail had higher rates of revision surgery during the first year than those treated with a sliding hip screw (7.2% intramedullary nail versus 5.5% sliding hip screw). Mortality rates at 30 days (14.2% intramedullary nail versus 15.8% sliding hip screw) and 1 year (30.7% intramedullary nail versus 32.5% sliding hip screw) were similar. Adjusted secondary outcome measures showed significant increases in the intramedullary nail group relative to the sliding hip screw group for index hospital length of stay, days of rehabilitation services in the first 6 months after discharge, and total expenditures for doctor and hospital services. Level of Evidence: Level III, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence. PMID:18465180

  1. Distal tibial physeal bridge: a complication from a tension band plate and screw construct. Report of a case.

    PubMed

    Oda, Jon E; Thacker, Mihir M

    2013-05-01

    We report on a case of a tension band plate and screw construct (Eight Plate) used over the anterior distal tibia in an 9-year-old girl in an attempt to induce recurvatum of the ankle joint to correct a recalcitrant equinus deformity. With growth of the distal tibial physis, the epiphyseal screw was drawn through the physis into the distal tibial metaphysis, resulting in the creation of a transphyseal bony bar. Caution should be exercised when attempting temporary hemiepiphyseodesis using a plate and screw construct in small epiphyses or in an osteopenic bone. PMID:22158054

  2. 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: ① C-1 lateral mass and C-2 pedicle screw fixation (Harms technique); ② C-1 lateral mass and unilateral C-2 pedicle screw fixation combined with ipsilateral laminar screw fixation; ③ Unilateral C-1lateral mass combined with ipsilateral C-1 posterior arch, and C-2 pedicle screw fixation; and ④ 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

  3. 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: ① C-1 lateral mass and C-2 pedicle screw fixation (Harms technique); ② C-1 lateral mass and unilateral C-2 pedicle screw fixation combined with ipsilateral laminar screw fixation; ③ Unilateral C-1lateral mass combined with ipsilateral C-1 posterior arch, and C-2 pedicle screw fixation; and ④ 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 competence of six different bone screws for reconstructive surgery in three different transplants: Fibular, iliac crest, scapular and artificial bone.

    PubMed

    Pietsch, Arnold P; Raith, Stefan; Ode, Jan-Eric; Teichmann, Jan; Lethaus, Bernd; Möhlhenrich, Stephan C; Hölzle, Frank; Duda, Georg N; Steiner, Timm

    2016-06-01

    The goal of this study was to determine a combination of screw and transplantation type that offers optimal primary stability for reconstructive surgery. Fibular, iliac crest, and scapular transplants were tested along with artificial bone substrate. Six different kinds of bone screws (Medartis(©)) were compared, each type utilized with one of six specimens from human transplants (n = 6). Controlled screw-in-tests were performed and the required torque was protocolled. Subsequently, pull-out-tests were executed to determine the retention forces. The artificial bone substitute material showed significantly higher retention forces than real bone samples. The self-drilling screws achieved the significantly highest retention values in the synthetic bone substitute material. Cancellous screws achieved the highest retention in the fibular transplants, while self-drilling and cancellous screws demonstrated better retention than cortical screws in the iliac crest. In the scapular graft, no significant differences were found between the screw types. In comparison to the human transplant types, the cortical screws showed the significantly highest values in the fibula and the lowest values in the iliac crest. The best retention was found in the combination of cancellous screws with fibular graft (514.8 N + -252.3 N). For the flat bones (i.e., scapular and illiac crest) we recommend the cancellous screws. PMID:27107477

  5. Arthroscopic Reduction and Transportal Screw Fixation of Acetabular Posterior Wall Fracture: Technical Note.

    PubMed

    Park, Jin Young; Chung, Woo Chull; Kim, Che Keun; Huh, Soon Ho; Kim, Se Jin; Jung, Bo Hyun

    2016-06-01

    Acetabular fractures can be treated with variable method. In this study, acetabular posterior wall fracture was treated with arthroscopic reduction and fixation using cannulated screw. The patient recovered immediately and had a satisfactory outcome. In some case of acetabular fracture could be good indication with additional advantages of joint debridement and loose body removal. So, we report our case with technical note. PMID:27536654

  6. Arthroscopic Reduction and Transportal Screw Fixation of Acetabular Posterior Wall Fracture: Technical Note

    PubMed Central

    Park, Jin young; Kim, Che Keun; Huh, Soon Ho; Kim, Se Jin; Jung, Bo Hyun

    2016-01-01

    Acetabular fractures can be treated with variable method. In this study, acetabular posterior wall fracture was treated with arthroscopic reduction and fixation using cannulated screw. The patient recovered immediately and had a satisfactory outcome. In some case of acetabular fracture could be good indication with additional advantages of joint debridement and loose body removal. So, we report our case with technical note. PMID:27536654

  7. Outcome comparison of Lisfranc injuries treated through dorsal plate fixation versus screw fixation

    PubMed Central

    Hu, Sun-jun; Chang, Shi-min; Li, Xiao-hua; Yu, Guang-rong

    2014-01-01

    OBJECTIVE: The objective of this prospective study was to test whether the treatment of Lisfranc injuries with open reduction and dorsal plate fixation would have the same or better functional outcomes as treatment with standard trans-articular screw fixation. METHODS: Sixty patients with primarily isolated Lisfranc joint injury were treated by open reduction and dorsal plate fixation or standard screw fixation. The patients were followed on average for 31 months. Evaluation was performed with patients' chief complaint, clinical examination, radiography, and AOFAS Midfoot Scale. RESULTS: Thirty two patients were treated with open reduction and dorsal plate fixation, and twenty eight patients were treated with open reduction and screw fixation. After two years follow-up, the mean AOFAS Midfoot score was 83.1 points in the dorsal plate fixation group and 78.5 points in the screw fixation group (p<0.01). Of the dorsal plate fixation group, radiographic analysis revealed anatomic reduction in twenty-nine patients (90.6%, 29/32) and nonanatomic reduction in three patients. Of the screw fixation group, radiographic analysis revealed anatomic reduction in twenty-three patients and nonanatomic reduction in five patients (82.1%, 23/28). CONCLUSIONS: Open reduction and dorsal plate fixation for a dislocated Lisfranc injury do have better short and median term outcome and a lower reoperation rate than standard screw ORIF. In our experience, we recommend using dorsal plate in ORIF on dislocated Lisfranc injuries. Level of Evidence II, Prospective Comparative Study. PMID:25538478

  8. Treatment of proximal phalangeal fractures with an antegrade intramedullary screw: a cadaver study.

    PubMed

    Borbas, P; Dreu, M; Poggetti, A; Calcagni, M; Giesen, T

    2016-09-01

    The aim of this study was to quantify the articular cartilage defect created with two different antegrade techniques of intramedullary osteosynthesis with a headless compression screw inserted through the metacarpophalangeal joint. In 12 out of 24 fingers from six cadaveric hands, a trans-articular technique with cannulated headless compression screws (2.2 and 3.0 mm diameter) was used; whereas in the other 12 fingers, an intra-articular fixation technique was used. The areas of the articular surface and the defects created were measured with a digital image software program. All measurements were made twice by two observers. In the intra-articular technique, the average defect in the base of the articular surface of the proximal phalanx was 4.6% with the 2.2 mm headless compression screw and 8.5% with the 3.0 mm screw. In the trans-articular technique, the defect size was slightly smaller; 4.2% with the 2.2 mm screw and 8% with the 3.0 mm screw, but the differences were not statistically significant. The main advantage of the intra-articular technique was that it avoided damage to the articular surface of the metacarpal head. PMID:27056278

  9. Implant failure in a proximal femoral fracture treated with dynamic hip screw fixation

    PubMed Central

    Dabis, John; Abdul-Jabar, Hani B.; Dabis, Hosam

    2015-01-01

    Dynamic hip screw fixation is a common orthopaedic procedure and to date, still can cause difficulties to the senior trauma surgeon. We present a case where an extra-capsular fracture of the proximal femur was managed with a dynamic hip screw (DHS) fixation. She proceeded to the operating theatre, where the fracture was stabilized with a 75-mm DHS and short-barrelled plate. The implant position was checked with intraoperative screening and the position accepted. Following attempted mobilization at 11 days post-operatively, the patient developed a recurrence of her preoperative pain. X-ray showed that the implant screw had separated from the barrel. Later scrutiny of the intraoperative screening films revealed that the barrel and screw were not engaged at the time of surgery. Intraoperative screening films should be carefully checked to ensure congruity of implant components. PMID:26136561

  10. Implant failure in a proximal femoral fracture treated with dynamic hip screw fixation.

    PubMed

    Dabis, John; Abdul-Jabar, Hani B; Dabis, Hosam

    2015-01-01

    Dynamic hip screw fixation is a common orthopaedic procedure and to date, still can cause difficulties to the senior trauma surgeon. We present a case where an extra-capsular fracture of the proximal femur was managed with a dynamic hip screw (DHS) fixation. She proceeded to the operating theatre, where the fracture was stabilized with a 75-mm DHS and short-barrelled plate. The implant position was checked with intraoperative screening and the position accepted. Following attempted mobilization at 11 days post-operatively, the patient developed a recurrence of her preoperative pain. X-ray showed that the implant screw had separated from the barrel. Later scrutiny of the intraoperative screening films revealed that the barrel and screw were not engaged at the time of surgery. Intraoperative screening films should be carefully checked to ensure congruity of implant components. PMID:26136561

  11. An analysis of screw fixation of the femoral component in cementless hip arthroplasty.

    PubMed

    Martin, J W; Sugiyama, H; Kaiser, A D; Van Hoech, J; Whiteside, L A

    1990-01-01

    A cementless hip stem that allows screw fixation of the collar to cortical bone in the calcar region was found to achieve enhanced rotational stability when implanted in preserved cadaveric human femora. Although the implants with screws showed less tendency for subsidence than the implants without screws, rotational micromotion was not found to be statistically different under light loading conditions. When implanted in composite bone, the addition of screws in the configuration tested was associated with significant metal-on-metal wear during combined compression and rotational cyclic loading. This finding is of concern due to potential wear particle toxicity and possible lowered fatigue life of the prosthesis. Therefore, specific design changes are recommended. PMID:2243211

  12. Helical screw expander evaluation project

    NASA Astrophysics Data System (ADS)

    McKay, R.

    1982-03-01

    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.

  13. Screw-fed pump system

    SciTech Connect

    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.

  14. 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.

  15. Minimally invasive dynamic hip screw for fixation of hip fractures

    PubMed Central

    Ho, Michael; Garau, Giorgio; Walley, Gayle; Oliva, Francesco; Panni, Alfredo Schiavone; Longo, Umile Giuseppe

    2008-01-01

    We compared a minimally invasive surgical technique to the conventional (open approach) surgical technique used in fixation of hip fractures with the dynamic hip screw (DHS) device. Using a case-control design (44 cases and 44 controls), we tested the null hypothesis that there is no difference between the two techniques in the following outcome measures: duration of surgery, time to mobilisation and weight bearing postoperatively, length of hospital stay, mean difference of pre- and postoperative haemoglobin levels, position of the lag screw of the DHS device in the femoral head, and the tip–apex distance. The minimally invasive DHS technique had significantly shorter duration of surgery and length of hospital stay. There was also less blood loss in the minimally invasive DHS technique. The minimally invasive DHS technique produces better outcome measures in the operating time, length of hospital stay, and blood loss compared to the conventional approach while maintaining equal fixation stability. PMID:18478227

  16. 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.

  17. 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

  18. Stabilization of coxo-femoral luxation using tenodesis of the deep gluteal muscle. Technique description and reluxation rate in 65 dogs and cats (1995-2008).

    PubMed

    Rochereau, P; Bernardé, A

    2012-01-01

    This retrospective study documents deep gluteal tenodesis (DGT) used to stabilize coxo- femoral luxation (CFL) in dogs and cats, and to report reluxation rate and clinical outcome after DGT. Medical records (1995-2008) of 65 dogs and cats with traumatic CFL treated by capsulorrhaphy and DGT were reviewed. Animals with radiographic evidence of pre-existing hip dysplasia or articular fractures had been excluded. Reluxation rate and outcome were assessed by clinical examination, performed two and ten weeks postoperatively. Surgical treatment was performed between one and 20 days after the initiating event. No perioperative complications occurred. All hip joints were correctly reduced and stabilized immediately after DGT completion. Except for five patients, placement of the screw was considered correct. In two of these patients, the screws were too long and were protruding into the pelvic canal. In two dogs, the screws were not tightened adequately, and in one dog the screw was too short. Twenty-six dogs and eight cats were re-examined between eight and 13 weeks postoperatively. Re- luxation did not occur in any of them. Outcomes were good in two cases and excellent in 32 cases; all but two had a normal range-of-motion of the reconstructed hip, and were free of lameness and did not show any signs of pain. Traumatic CFL can be stabilized safely and effectively by DGT in dogs and cats. This technique should be considered among other capsular reinforcement techniques in the presence of an intact deep gluteal muscle. PMID:22028015

  19. 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

  20. 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

  1. Assessing the Intraoperative Accuracy of Pedicle Screw Placement by Using a Bone-Mounted Miniature Robot System through Secondary Registration

    PubMed Central

    Wu, Chieh-Hsin; Tsai, Cheng-Yu; Chang, Chih-Hui; Lin, Chih-Lung; Tsai, Tai-Hsin

    2016-01-01

    Introduction Pedicle screws are commonly employed to restore spinal stability and correct deformities. The Renaissance robotic system was developed to improve the accuracy of pedicle screw placement. Purpose In this study, we developed an intraoperative classification system for evaluating the accuracy of pedicle screw placements through secondary registration. Furthermore, we evaluated the benefits of using the Renaissance robotic system in pedicle screw placement and postoperative evaluations. Finally, we examined the factors affecting the accuracy of pedicle screw implantation. Results Through use of the Renaissance robotic system, the accuracy of Kirschner-wire (K-wire) placements deviating <3 mm from the planned trajectory was determined to be 98.74%. According to our classification system, the robot-guided pedicle screw implantation attained an accuracy of 94.00% before repositioning and 98.74% after repositioning. However, the malposition rate before repositioning was 5.99%; among these placements, 4.73% were immediately repositioned using the robot system and 1.26% were manually repositioned after a failed robot repositioning attempt. Most K-wire entry points deviated caudally and laterally. Conclusion The Renaissance robotic system offers high accuracy in pedicle screw placement. Secondary registration improves the accuracy through increasing the precision of the positioning; moreover, intraoperative evaluation enables immediate repositioning. Furthermore, the K-wire tends to deviate caudally and laterally from the entry point because of skiving, which is characteristic of robot-assisted pedicle screw placement. PMID:27054360

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

    PubMed

    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

  3. 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

  4. A novel radiographic targeting guide for percutaneous placement of transfacet screws in the cervical spine with limited fluoroscopy: A cadaveric feasibility study

    PubMed Central

    Jackson, David M.; Karp, Jacqueline E.; O'Brien, Joseph R.; Anderson, D. Greg; Gelb, Daniel E.; Ludwig, Steven C.

    2012-01-01

    Background We describe a technique for percutaneous transfacet screw placement in the cervical spine without the need for lateral-view fluoroscopy. Methods Previously established articular pillar morphometry was used to define the ideal trajectory for transfacet screw placement in the subaxial cervical spine. A unique targeting guide was developed to allow placement of Kirschner wires across the facet joint at 90° without the guidance of lateral-view fluoroscopy. Kirschner wires and cannulated screws were placed percutaneously in 7 cadaveric specimens. Placement of instrumentation was performed entirely under modified anteroposterior-view fluoroscopy. All specimens were assessed for acceptable screw placement by 2 fellowship-trained orthopaedic spine surgeons using computed tomography. Open dissection was used to confirm radiographic interpretation. Acceptable placement was defined as a screw crossing the facet joint, achieving purchase in the inferior and superior articular processes, and not violating critical structures. Malposition was defined as a violation of the transverse foramen, spinal canal, or nerve root or inadequate fixation. Results A total of 48 screws were placed. Placement of 45 screws was acceptable. The 3 instances of screw malposition included a facet fracture, a facet distraction, and a C6-7 screw contacting the C7 nerve root in a specimen with a small C7 superior articular process. Conclusions Our data show that with the appropriate radiographic technique and a targeting guide, percutaneous transfacet screws can be safely placed at C3-7 without the need for lateral-view fluoroscopy during the targeting phase. Because of the variable morphometry of the C7 lateral mass, however, care must be taken when placing a transfacet screw at C6-7. Clinical Relevance This study describes a technique that has the potential to provide a less invasive strategy for posterior instrumentation of the cervical spine. Further investigation is needed before this

  5. Joint-Angle Coordination Patterns Ensure Stabilization of a Body-Plus-Tool System in Point-to-Point Movements with a Rod

    PubMed Central

    Valk, Tim A.; Mouton, Leonora J.; Bongers, Raoul M.

    2016-01-01

    When performing a goal-directed action with a tool, it is generally assumed that the point of control of the action system is displaced from the hand to the tool, implying that body and tool function as one system. Studies of how actions with tools are performed have been limited to studying either end-effector kinematics or joint-angle coordination patterns. Because joint-angle coordination patterns affect end-effector kinematics, the current study examined them together, with the aim of revealing how body and tool function as one system. Seated participants made point-to-point movements with their index finger, and with rods of 10, 20, and 30 cm attached to their index finger. Start point and target were presented on a table in front of them, and in half of the conditions a participant displacement compensated for rod length. Results revealed that the kinematics of the rod's tip showed higher peak velocity, longer deceleration time, and more curvature with longer rods. End-effector movements were more curved in the horizontal plane when participants were not displaced. Joint-angle trajectories were similar across rod lengths when participants were displaced, whereas more extreme joint-angles were used with longer rods when participants were not displaced. Furthermore, in every condition the end-effector was stabilized to a similar extent; both variability in joint-angle coordination patterns that affected end-effector position and variability that did not affect end-effector position increased in a similar way vis-à-vis rod length. Moreover, the increase was higher in those conditions, in which participants were not displaced. This suggests that during tool use, body and tool are united in a single system so as to stabilize the end-effector kinematics in a similar way that is independent of tool length. In addition, the properties of the actual trajectory of the end-effector, as well as the actual joint-angles used, depend on the length of the tool and the

  6. True anteroposterior view pedicle screw insertion technique

    PubMed Central

    Bai, Jia-yue; Zhang, Wei; An, Ji-long; Sun, Ya-peng; Ding, Wen-yuan; Shen, Yong

    2016-01-01

    Background The wide use of minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF) surgery in the treatment of degenerative disc disease of lumbar spine in spinal surgery highlights the gradual decrease in the use of traditional pedicle screw insertion technology. This study aims to analyze the accuracy of the true anteroposterior view pedicle screw insertion technique in MIS-TLIF surgery, compare it with conventional pedicle screw insertion technology, and discuss its clinical application value. Methods Fifty-two patients undergoing true anteroposterior view (group A) and 87 patients undergoing conventional pedicle screw insertion (group B) were diagnosed with lumbar disc herniation or lumbar spinal stenosis. Time for screw placement, intraoperative irradiation exposure, accuracy rate of pedicle screw insertion, and incidence of neurovascular injury were compared between the two groups. Results The time for screw placement and intraoperative irradiation exposure was significantly less in group A. Penetration rates of the paries lateralis of vertebral pedicle, medial wall of vertebral pedicle, and anterior vertebral wall were 1.44%, 0%, and 2.40%, respectively, all of which were significantly lower than that in group B. No additional serious complications caused by the placement of screw were observed during the follow-up period in patients in group A, but two patients with medial penetration underwent revision for unbearable radicular pain. Conclusion The application of true anteroposterior view pedicle screw insertion technique in MIS-TLIF surgery shortens time for screw placement and reduces the intraoperative irradiation exposure along with a higher accuracy rate of screw placement, which makes it a safe, accurate, and efficient technique. PMID:27418828

  7. When Planning Screw Fracture Fixation Why the 5.5 mm Screw is the Goldilocks Screw. An Observational Computer Tomographic Study of Fifth Metatarsal Bone Anatomy in a Sample of Patients

    PubMed Central

    Iselin, Lukas D.; Ramawat, Sunil; Hanratty, Brian; Klammer, Georg; Stavrou, Peter

    2015-01-01

    Abstract We wanted to verify our clinical experience that the 5.5 mm screw was ideal in the majority of fifth metatarsal fracture fixation. The size of a screw is important for the successful surgical treatment of these fractures in order to obtain the maximal stability while reducing the risk for iatrogenic fracture. A sample of patients undergoing computer tomographic imaging of the foot for investigation other than fifth metatarsal pathology were recruited. The parameters of the fifth metatarsal bone anatomy were measured. These parameters of the 5.5 mm screw were correlated with this data. The upper parameter (the diameter of the threads) was 5.5 and the lower parameter (the diameter of the shank) was 4.0 mm. Twenty seven patients were recruited. The proximal third internal diameter ranged from 3.6 to 7.0 mm with a mean of 5.0 mm. 93% of the metatarsals could easily accommodate the 5.5 mm screw. Two of the metatarsals had an internal diameter of < 4 mm (7%). It is our belief that the 5.5 mm screw may be used safely in the majority of patients with fifth metatarsal fractures. PMID:25950685

  8. Are allogenic or xenogenic screws and plates a reasonable alternative to alloplastic material for osteosynthesis--a histomorphological analysis in a dynamic system.

    PubMed

    Jacobsen, C; Obwegeser, J A

    2010-12-01

    Despite invention of titanium and resorbable screws and plates, still, one of the main challenges in bone fixation is the search for an ideal osteosynthetic material. Biomechanical properties, biocompatibility, and also cost effectiveness and clinical practicability are factors for the selection of a particular material. A promising alternative seems to be screws and plates made of bone. Recently, xenogenic bone pins and screws have been invented for use in joint surgery. In this study, screws made of allogenic sheep and xenogenic human bone were analyzed in a vital and dynamic sheep-model and compared to conventional titanium screws over a standard period of bone healing of 56 days with a constant applied extrusion force. Biomechanical analysis and histomorphological evaluation were performed. After 56 days of insertion xenogenic screws made of human bone showed significantly larger distance of extrusion of on average 173.8 μm compared to allogenic screws made of sheep bone of on average 27.8 and 29.95 μm of the titanium control group. Severe resorption processes with connective tissue interposition were found in the histomorphological analysis of the xenogenic screws in contrast to new bone formation and centripetal vascularization of the allogenic bone screw, as well as in processes of incorporation of the titanium control group. The study showed allogenic cortical bone screws as a substantial alternative to titanium screws with good biomechanical properties. In contrast to other reports a different result was shown for the xenogenic bone screws. They showed insufficient holding strength with confirmative histomorphological signs of degradation and insufficient osseointegration. Before common clinical use of xenogenic osteosynthetic material, further evaluation should be performed. PMID:20813368

  9. Implicit modeling of screw threads for efficient finite element analysis of complex bone-implant systems.

    PubMed

    Inzana, Jason A; Varga, Peter; Windolf, Markus

    2016-06-14

    Finite element analysis is commonly used to assist in the development and evaluation of orthopedic devices. The physics of these models are simplified through approximations that enable more efficient simulations, without compromising the accuracy of the relative comparisons between implant designs or configurations. This study developed and evaluated a technique to approximate the behavior of a finely threaded screw using a smooth cylinder with the threads implicitly represented through interfacial contact conditions. This pseudo-threaded model was calibrated by comparing to simulations that explicitly modeled the thread geometry with frictional contact. A parametric analysis was performed with a single screw-in-bone system, five loading directions, and three Young׳s moduli that span the range of cancellous bone (200, 600, and 1,000MPa). Considering that screw cut-out from cancellous bone is a critical clinical issue in the osteoporotic proximal humerus, the pseudo-threaded model was compared with a bonded interface to examine three different screw configurations in a 3-part proximal humerus fracture across 10 patients. In the single screw-in-bone system, the pseudo-threaded model predicted the screw displacement of the explicitly threaded model with 1-5% difference and estimated the strain distributions and magnitudes more accurately than a bonded interface. Yet, the relative comparisons of implant stability across the three different screw configurations in the proximal humerus were not affected by the modeling choice for the bone-screw interface. Therefore, the bonded interface could serve as a more efficient methodology for making relative comparisons between implants that utilize the same thread profile. PMID:27157243

  10. Influences of the biaxial strain and c-screw dislocation on the clustering in InGaN alloys

    NASA Astrophysics Data System (ADS)

    Lei, Huaping; Chen, Jun; Ruterana, Pierre

    2010-11-01

    Using the molecular dynamics simulation based on Stillinger-Weber potentials, the roles of lattice mismatch and threading dislocations (c-screw type) on phase segregation in InGaN alloys have been explored. The thermodynamic stability and structural deformation of the InGaN alloys with In-rich clusters are analyzed when biaxial stress and c-screw dislocations act on the systems. The results show that the formation of In-rich clusters is suppressed in the case of lattice mismatch, whereas it takes place in the presence of c-screw dislocations independent of the strain condition of InGaN alloys.

  11. Bioresorbable composite screws manufactured via forging process: pull-out, shear, flexural and degradation characteristics.

    PubMed

    Felfel, R M; Ahmed, I; Parsons, A J; Rudd, C D

    2013-02-01

    Bioresorbable screws have the potential to overcome some of the complications associated with metallic screws currently in use. Removal of metallic screws after bone has healed is a serious issue which can lead to refracture due to the presence of screw holes. Poly lactic acid (PLA), fully 40 mol% P(2)O(5) containing phosphate unidirectional (P40UD) and a mixture of UD and short chopped strand random fibre mats (P40 70%UD/30%RM) composite screws were prepared via forging composite bars. Water uptake and mass loss for the composite screws manufactured increased significantly to ∼1.25% (P=0.0002) and ∼1.1% (P<0.0001), respectively, after 42 days of immersion in PBS at 37 °C. The initial maximum flexural load for P40 UD/RM and P40 UD composite screws was ∼60% (P=0.0047) and ∼100% (P=0.0037) higher than for the PLA screws (∼190 N), whilst the shear load was slightly higher in comparison to PLA (∼2.2 kN). The initial pull-out strengths for the P40 UD/RM and PLA screws were similar whereas that for P40 UD screws was ∼75% higher (P=0.022). Mechanical properties for the composite screws decreased initially after 3 days of immersion and this reduction was ascribed to the degradation of the fibre/matrix interface. After 3 days interval the mechanical properties (flexural, shear and pull-out) maintained their integrity for the duration of the study (at 42 days). This property retention was attributed to the chemical durability of the fibres used and stability of the matrix properties during the degradation process. It was also deemed necessary to enhance the fibre/matrix interface via use of a coupling agent in order to maintain the initial mechanical properties acquired for the required period of time. Lastly, it is also suggested that the degrading reinforcement fibres may have the potential to buffer any acidic products released from the PLA matrix. PMID:23262309

  12. C2 nerve dysfunction associated with C1 lateral mass screw fixation.

    PubMed

    Huang, Da-geng; Hao, Ding-jun; Li, Guang-lin; Guo, Hao; Zhang, Yu-chen; He, Bao-rong

    2014-11-01

    The C1 lateral mass screw technique is widely used for atlantoaxial fixation. However, C2 nerve dysfunction may occur as a complication of this procedure, compromising the quality of life of affected patients. This is a review of the topic of C2 nerve dysfunction associated with C1 lateral mass screw fixation and related research developments. The C2 nerve root is located in the space bordered superiorly by the posterior arch of C1 , inferiorly by the C2 lamina, anteriorly by the lateral atlantoaxial joint capsule, and posteriorly by the anterior edge of the ligamentum flavum. Some surgeons suggest cutting the C2 nerve root during C1 lateral mass screw placement, whereas others prefer to preserve it. The incidence, clinical manifestations, causes, management, and prevention of C2 nerve dysfunction associated with C(1) lateral mass screw fixation are reviewed. Sacrifice of the C2 nerve root carries a high risk of postoperative numbness, whereas postoperative nerve dysfunction can occur when it has been preserved. Many surgeons have been working hard on minimizing the risk of postoperative C2 nerve dysfunction associated with C1 lateral mass screw fixation. PMID:25430709

  13. Recurrent laryngeal edema imitating angioedema caused by dislocated screw after anterior spine surgery.

    PubMed

    Wójtowicz, 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

  14. 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

  15. Limitation of total hip arthroplasty of the acetabular roof by press-fit without screw fixation: discussion of a biomechanical study.

    PubMed

    Kanda, Akio; Kaneko, Kazuo; Obayashi, Osamu; Mogami, Atsuhiko; Iwase, Hideaki

    2013-05-01

    In total hip arthroplasty of the acetabular roof fixed by press-fit without screw fixation, there is little possibility for loosening to occur, because it is difficult for wear debris to enter between the cup and the acetabular roof, as screw holes are not present. However, stability is provided only by contact. In the case of acetabular dysplasia, it is not well understood whether sufficient initial fixation power is provided. We performed a torsion test and a lever-out test. In the torsion test, in the case of a normal hip joint, as the cup grew bigger, the fixation power tended to increase in strength. In the acetabular dysplasia model, with cups of each size, as the protrusion angle increased, the fixation power of the cup tended to become weak. When the protrusion angle approaches 15 degrees, we must use a cup that is 4 mm larger than the original cup to achieve the same initial fixation power. Furthermore, when the protrusion angle is 15 degrees in cups that are over 48 mm in size, we obtain fixation power that is theoretically adequate, but when small cups, for example, 46 mm in size are set with protrusion, the initial fixation power decreases significantly, and we cannot obtain a fixation power that is theoretically adequate. PMID:23412291

  16. Scaphoid Fracture Fixation with an Acutrak(®) Screw.

    PubMed

    Loving, Vilert A; Richardson, Michael L

    2006-01-01

    We report a case of fixation of a scaphoid fracture using an Acutrak(®) screw. This screw is cannulated and headless, which allows it to be implanted below the surface of the bone. It uses the same concept of variable thread pitch as the Herbert screw, but unlike the Herbert screw, is fully threaded, with continuously varying pitch along its length. This variable pitch creates constant compression across a fracture as the screw is advanced, and gives the screw its unique appearance. This feature may improve internal holding power, as well as allow a fracture or osteotomy site to lie anywhere along the length of the screw. PMID:27298683

  17. 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.

  18. Vertical-Screw-Auger Conveyer Feeder

    NASA Technical Reports Server (NTRS)

    Walton, Otis (Inventor); Vollmer, Hubert J. (Inventor)

    2016-01-01

    A conical feeder is attached to a vertically conveying screw auger. The feeder is equipped with scoops and rotated from the surface to force-feed regolith the auger. Additional scoops are possible by adding a cylindrical section above the conical funnel section. Such then allows the unit to collect material from swaths larger in diameter than the enclosing casing pipe of the screw auger. A third element includes a flexible screw auger. All three can be used in combination in microgravity and zero atmosphere environments to drill and recover a wide area of subsurface regolith and entrained volatiles through a single access point on the surface.

  19. Reinforcement of osteosynthesis screws with brushite cement.

    PubMed

    Van Landuyt, P; Peter, B; Beluze, L; Lemaître, J

    1999-08-01

    The fixation of osteosynthesis screws remains a severe problem for fracture repair among osteoporotic patients. Polymethyl-methacrylate (PMMA) is routinely used to improve screw fixation, but this material has well-known drawbacks such as monomer toxicity, exothermic polymerization, and nonresorbability. Calcium phosphate cements have been developed for several years. Among these new bone substitution materials, brushite cements have the advantage of being injectable and resorbable. The aim of this study is to assess the reinforcement of osteosynthesis screws with brushite cement. Polyurethane foams, whose density is close to that of cancellous bone, were used as bone model. A hole was tapped in a foam sample, then brushite cement was injected. Trabecular osteosynthesis screws were inserted. After 24 h of aging in water, the stripping force was measured by a pull-out test. Screws (4.0 and 6.5 mm diameter) and two foam densities (0.14 and 0.28 g/cm3) were compared. Cements with varying solid/liquid ratios and xanthan contents were used in order to obtain the best screw reinforcement. During the pull-out test, the stripping force first increases to a maximum, then drops to a steady-state value until complete screw extraction. Both maximum force and plateau value increase drastically in the presence of cement. The highest stripping force is observed for 6.5-mm screws reinforced with cement in low-density foams. In this case, the stripping force is multiplied by 3.3 in the presence of cement. In a second experiment, cements with solid/liquid ratio ranging from 2.0 to 3.5 g/mL were used with 6.5-mm diameter screws. In some compositions, xanthan was added to improve injectability. The best results were obtained with 2.5 g/mL cement containing xanthan and with 3.0 g/mL cements without xanthan. A 0.9-kN maximal stripping force was observed with nonreinforced screws, while 1.9 kN was reached with reinforced screws. These first results are very promising regarding screw

  20. Navigation of Pedicle Screws in the Thoracic Spine with a New Electromagnetic Navigation System: A Human Cadaver Study

    PubMed Central

    Hahn, Patrick; Oezdemir, Semih; Komp, Martin; Giannakopoulos, Athanasios; Kasch, Richard; Merk, Harry; Liermann, Dieter; Godolias, Georgios; Ruetten, Sebastian

    2015-01-01

    Introduction. Posterior stabilization of the spine is a standard procedure in spinal surgery. In addition to the standard techniques, several new techniques have been developed. The objective of this cadaveric study was to examine the accuracy of a new electromagnetic navigation system for instrumentation of pedicle screws in the spine. Material and Method. Forty-eight pedicle screws were inserted in the thoracic spine of human cadavers using EMF navigation and instruments developed especially for electromagnetic navigation. The screw position was assessed postoperatively by a CT scan. Results. The screws were classified into 3 groups: grade 1 = ideal position; grade 2 = cortical penetration <2 mm; grade 3 = cortical penetration ≥2 mm. The initial evaluation of the system showed satisfied positioning for the thoracic spine; 37 of 48 screws (77.1%, 95% confidence interval [62.7%, 88%]) were classified as group 1 or 2. Discussion. The screw placement was satisfactory. The initial results show that there is room for improvement with some changes needed. The ease of use and short setup times should be pointed out. Instrumentation is achieved without restricting the operator's mobility during navigation. Conclusion. The results indicate a good placement technique for pedicle screws. Big advantages are the easy handling of the system. PMID:25759814

  1. 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

  2. Joint swelling

    MedlinePlus

    Swelling of a joint ... Joint swelling may occur along with joint pain . The swelling may cause the joint to appear larger or abnormally shaped. Joint swelling can cause pain or stiffness. After an ...

  3. Does surgery for instability of the shoulder truly stabilize the glenohumeral joint?: A prospective comparative cohort study.

    PubMed

    Lädermann, Alexandre; Denard, Patrick J; Tirefort, Jérôme; Kolo, Frank C; Chagué, Sylvain; Cunningham, Grégory; Charbonnier, Caecilia

    2016-08-01

    Despite the fact that surgery is commonly used to treat glenohumeral instability, there is no evidence that such treatment effectively corrects glenohumeral translation. The purpose of this prospective clinical study was to analyze the effect of surgical stabilization on glenohumeral translation.Glenohumeral translation was assessed in 11 patients preoperatively and 1 year postoperatively following surgical stabilization for anterior shoulder instability. Translation was measured using optical motion capture and computed tomography.Preoperatively, anterior translation of the affected shoulder was bigger in comparison to the normal contralateral side. Differences were significant for flexion and abduction movements (P < 0.001). Postoperatively, no patients demonstrated apprehension and all functional scores were improved. Despite absence of apprehension, postoperative anterior translation for the surgically stabilized shoulders was not significantly different from the preoperative values.While surgical treatment for anterior instability limits the chance of dislocation, it does not seem to restore glenohumeral translation during functional range of motion. Such persistent microinstability may explain residual pain, apprehension, inability to return to activity and even emergence of dislocation arthropathy that is seen in some patients. Further research is necessary to better understand the causes, effects, and treatment of residual microinstability following surgical stabilization of the shoulder. PMID:27495043

  4. S-1 and S-2-alar-iliac screw fixation via intraoperative navigation.

    PubMed

    Pham, Martin H; Jakoi, Andre M; Hsieh, Patrick C

    2016-07-01

    Adult deformity patients often require fixation to the sacrum and pelvis for construct stability and improved fusion rates. Although certain sacropelvic fixation techniques can be challenging, the availability of intraoperative navigation has made many of these techniques more feasible. In this video case presentation, the authors demonstrate the techniques of S-1 bicortical screw and S-2-alar-iliac screw fixation under intraoperative navigation in a 67-year-old female. This instrumentation placement was part of an overall T-10-pelvis construct for the correction of adult spinal deformity. The video can be found here: https://youtu.be/3HZo-80jQr8 . PMID:27364427

  5. 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.

  6. Deuterium beam acceleration with 3rd harmonic ion cyclotron resonance heating in Joint European Torus: Sawtooth stabilization and Alfvén eigenmodes

    NASA Astrophysics Data System (ADS)

    Gassner, T.; Schoepf, K.; Sharapov, S. E.; Kiptily, V. G.; Pinches, S. D.; Hellesen, C.; Eriksson, J.; JET-EFDA contributors

    2012-03-01

    Experiments on accelerating NBI-produced deuterium (D) beam ions from their injection energy of ˜110 keV up to the MeV energy range with 3rd harmonic ion cyclotron resonance heating were performed on the Joint European Torus [P. H. Rebut and B. E. Keen, Fusion Technol. 11, 13 (1987)]. A renewed set of nuclear diagnostics was used for analysing fast D ions during sawtooth stabilization, monster sawtooth crashes, and during excitation of Alfvén eigenmodes (AEs) residing inside the q = 1 radius. The measurements and modeling of the fast ions with the nonlinear HAGIS code [S. D. Pinches et al., Comput. Phys. Commun. 111, 133 (1998)] show that monster sawtooth crashes are strongly facilitated by the AE-induced re-distribution of the fast D ions from inside the q = 1 radius to the plasma edge.

  7. Maxillo-mandibular counter-clockwise rotation and mandibular advancement with TMJ Concepts total joint prostheses: part II--airway changes and stability.

    PubMed

    Coleta, K E D; Wolford, L M; Gonçalves, J R; Pinto, A dos Santos; Cassano, D S; Gonçalves, D A G

    2009-03-01

    The purpose of this study was to evaluate the anatomical changes and stability of the oropharyngeal airway and head posture following TMJ reconstruction and mandibular advancement with TMJ Concepts custom-made total joint prostheses and maxillary osteotomies with counter-clockwise rotation of the maxillo-mandibular complex. All patients were operated at Baylor University Medical Center, Dallas TX, USA, by one surgeon (Wolford). The lateral cephalograms of 47 patients were analyzed to determine surgical and post-surgical changes of the oropharyngeal airway, hyoid bone and head posture. Surgery increased the narrowest retroglossal airway space 4.9 mm. Head posture showed flexure immediately after surgery (-5.6+/-6.7 degrees) and extension long-term post surgery (1.8+/-6.7 degrees); cervical curvature showed no significant change. Surgery increased the distances between the third cervical vertebrae and the menton 11.7+/-9.1 mm and the third cervical vertebrae and hyoid 3.2+/-3.9 mm, and remained stable. The distance from the hyoid to the mandibular plane decreased during surgery (-3.8+/-5.8 mm) and after surgery (-2.5+/-5.2 mm). Maxillo-mandibular advancement with counter-clockwise rotation and TMJ reconstruction with total joint prostheses produced immediate increase in oropharyngeal airway dimension, which was influenced by long-term changes in head posture but remained stable over the follow-up period. PMID:19135866

  8. Helical rotary screw expander power system

    NASA Technical Reports Server (NTRS)

    Mckay, R. A.; Sprankle, R. S.

    1974-01-01

    An energy converter for the development of wet steam geothermal fields is described. A project to evaluate and characterize a helical rotary screw expander for geothermal applications is discussed. The helical screw expander is a positive displacement machine which can accept untreated corrosive mineralized water of any quality from a geothermal well. The subjects of corrosion, mineral deposition, the expansion process, and experience with prototype devices are reported.

  9. 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.

  10. Intramedullary fixation with screwed, conical stems--unsolicited results from animal experiments.

    PubMed

    van Loon, P J; Weinans, H; Huiskes, R; de Groot, K; Slooff, T J

    1992-01-01

    For the purpose of studying bone remodeling around prostheses, a segmental replacement for the goat tibia was designed, using a conical, screw-threaded, hydroxyapatite-coated stem for fixation. Eight goats were provided with the implant, seven of which loosened within 10 days post-operatively, displaying progressive radiolucency and gross rotational motion. The eighth one also loosened radiographically, but developed a stabilizing callus bridge to prevent motion. A second design of similar shape and coating, but lacking the screw threads, was designed and also applied in eight animals. In this case, no loosening occurred in the first 6 weeks post-operatively. It is concluded that the application of screwed intramedullary stems for prosthetic fixation is not a viable concept, because the threads prevent the stem from subsiding and restabilizing when minor initial interface stress-relaxation and remodeling has occurred. PMID:10149986

  11. The treatment of metastasis to the femoral neck using percutaneous hollow perforated screws with cement augmentation.

    PubMed

    Kang, H G; Roh, Y W; Kim, H S

    2009-08-01

    We have developed a hollow perforated cannulated screw. One or more of these was implanted percutaneously in 11 patients with an osteolytic metastasis in the femoral neck and multiple metastases elsewhere. They were supplemented by one or two additional standard 6.5 mm cannulated screws in nine patients. Polymethylmethacrylate bone cement was injected through the screw into the neck of the femur using small syringes, as in vertebroplasty. The mean amount of cement injected was 23.2 ml (17 to 30). Radiotherapy was started on the fourth post-operative day and chemotherapy, on average, was resumed a day later. Good structural stability and satisfactory relief from pain were achieved in all the patients. This technique may be useful in the palliation of metastases in the femoral neck. PMID:19651838

  12. Percutaneous Pedicle Screw Fixation Technique in the Thoracic and Lumbar Spine-Tips and Tricks.

    PubMed

    Gazzeri, Roberto

    2016-04-01

    The need for spinal fixation in patients who cannot tolerate classical open surgery has led in recent years to the development of minimally invasive approaches. The use of percutaneous pedicle screw fixation offers several advantages, such as less blood loss and postoperative pain due to blunt separation of the muscles with reduction of soft tissue dissection. Medical records and demographic information, diagnosis, and preoperative pain levels of 63 patients who underwent percutaneous minimally invasive thoracolumbar spine stabilization using the Illico® Fixation System (Alphatec Spine, Carlsbad, California) were analysed: a total of 344 screws were implanted. Preoperative and postoperative clinical assessment of the patients were based on a visual analogue scale. Because percutaneous techniques do not allow gross visualization of the vertebra and erroneous placement of the screw may be high in the initial cases, we discuss the techniques for a safe implantation of pedicle screws using a single or double intraoperative fluoroscopy. We report tips and tricks for technical challenges including fixation in osteoporotic patients, percutaneous insertion of long rods, compression/distraction using multiaxial screws turning into monoaxial, and use of minimally invasive retractror for interbody fusion. Recently, indications for minimally invasive percutaneous fixation have expanded and my results support that it may be considered a safe and effective option for the treatment of degenerative and traumatic thoracolumbar spinal diseases. PMID:27121407

  13. Plan to procedure: combining 3D templating with rapid prototyping to enhance pedicle screw placement

    NASA Astrophysics Data System (ADS)

    Augustine, Kurt E.; Stans, Anthony A.; Morris, Jonathan M.; Huddleston, Paul M.; Matsumoto, Jane M.; Holmes, David R., III; Robb, Richard A.

    2010-02-01

    Spinal fusion procedures involving the implantation of pedicle screws have steadily increased over the past decade because of demonstrated improvement in biomechanical stability of the spine. However, current methods of spinal fusion carries a risk of serious vascular, visceral, and neurological injury caused by inaccurate placement or inappropriately sized instrumentation, which may lead to patient paralysis or even fatality. 3D spine templating software developed by the Biomedical Imaging Resource (BIR) at Mayo Clinic allows the surgeon to virtually place pedicle screws using pre-operative 3D CT image data. With the template plan incorporated, a patient-specific 3D anatomic model is produced using a commercial rapid prototyping system. The pre-surgical plan and the patient-specific model then are used in the procedure room to provide real-time visualization and quantitative guidance for accurate placement of each pedicle screw, significantly reducing risk of injury. A pilot study was conducted at Mayo Clinic by the Department of Radiology, the Department of Orthopedics, and the BIR, involving seven complicated pediatric spine cases. In each case, pre-operative 3D templating was carried out and patient specific models were generated. The plans and the models were used intra-operatively, providing precise pedicle screw starting points and trajectories. Postoperative assessment by the surgeon confirmed all seven operations were successful. Results from the study suggest that patient-specific, 3D anatomic models successfully acquired from 3D templating tools are valuable for planning and conducting pedicle screw insertion procedures.

  14. Design and testing of external fixator bone screws.

    PubMed

    Evans, M; Spencer, M; Wang, Q; White, S H; Cunningham, J L

    1990-11-01

    In external fixation, bone screw loosening still presents a major clinical problem. For this study, the design factors influencing the mechanics of the bone-screw interface were analysed and various experimental screws designed with the intention of maximizing the strength and stiffness of the inserted screw. Push-in, pull-out and bending tests were then carried out on the three experimental screws, and on two commercially available screws in both a synthetic material and in cadaveric bone; photoelastic tests on different screw threadforms were also performed. The results of the push-in and pull-out tests indicate that both the screw threadform and cutting head have a significant effect on the holding strength of the screw. The photoelastic tests show that most of the applied load is distributed over the first few threads closest to the load, and that the area between the thread crests is subjected to high shear stresses. PMID:2266740

  15. Ball Screw Actuator Including a Stop with an Integral Guide

    NASA Technical Reports Server (NTRS)

    Wingett, Paul T. (Inventor); Perek, John (Inventor); Geck, Kellan (Inventor)

    2015-01-01

    An actuator includes a housing assembly, a ball nut, a ball screw, and a ball screw stop. The ball nut is rotationally mounted in the housing assembly, is adapted to receive an input torque, and is configured, upon receipt thereof, to rotate and supply a drive force. The ball screw is mounted within the housing assembly and extends through the ball nut. The ball screw has a first end and a second end, and is coupled to receive the drive force from the ball nut. The ball screw is configured, upon receipt of the drive force, to selectively translate between a stow position and a deploy position. The ball screw stop is mounted on the ball screw to translate therewith and is configured to at selectively engage the housing assembly while the ball screw is translating, and engage the ball nut when the ball screw is in the deploy position.

  16. 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

  17. Insertion Profiles of 4 Headless Compression Screws

    PubMed Central

    Hart, Adam; Harvey, Edward J.; Lefebvre, Louis-Philippe; Barthelat, Francois; Rabiei, Reza; Martineau, Paul A.

    2013-01-01

    Purpose In practice, the surgeon must rely on screw position (insertion depth) and tactile feedback from the screwdriver (insertion torque) to gauge compression. In this study, we identified the relationship between interfragmentary compression and these 2 factors. Methods The Acutrak Standard, Acutrak Mini, Synthes 3.0, and Herbert-Whipple implants were tested using a polyurethane foam scaphoid model. A specialized testing jig simultaneously measured compression force, insertion torque, and insertion depth at half-screw-turn intervals until failure occurred. Results The peak compression occurs at an insertion depth of −3.1 mm, −2.8 mm, 0.9 mm, and 1.5 mm for the Acutrak Mini, Acutrak Standard, Herbert-Whipple, and Synthes screws respectively (insertion depth is positive when the screw is proud above the bone and negative when buried). The compression and insertion torque at a depth of −2 mm were found to be 113 ± 18 N and 0.348 ± 0.052 Nm for the Acutrak Standard, 104 ± 15 N and 0.175 ± 0.008 Nm for the Acutrak Mini, 78 ± 9 N and 0.245 ± 0.006 Nm for the Herbert-Whipple, and 67 ± 2N, 0.233 ± 0.010 Nm for the Synthes headless compression screws. Conclusions All 4 screws generated a sizable amount of compression (> 60 N) over a wide range of insertion depths. The compression at the commonly recommended insertion depth of −2 mm was not significantly different between screws; thus, implant selection should not be based on compression profile alone. Conically shaped screws (Acutrak) generated their peak compression when they were fully buried in the foam whereas the shanked screws (Synthes and Herbert-Whipple) reached peak compression before they were fully inserted. Because insertion torque correlated poorly with compression, surgeons should avoid using tactile judgment of torque as a proxy for compression. Clinical relevance Knowledge of the insertion profile may improve our understanding of the implants, provide a better basis for comparing screws

  18. 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

  19. The anterolateral ligament (ALL) and its role in rotational extra-articular stability of the knee joint: a review of anatomy and surgical concepts.

    PubMed

    Roessler, Philip P; Schüttler, Karl F; Heyse, Thomas J; Wirtz, Dieter C; Efe, Turgay

    2016-03-01

    The anterolateral ligament of the knee (ALL) has caused a lot of rumors in orthopaedics these days. The structure that was first described by Segond back in 1879 has experienced a long history of anatomic descriptions and speculations until its rediscovery by Claes in 2013. Its biomechanical properties and function have been examined recently, but are not yet fully understood. While the structure seems to act as a limiter of internal rotation and lateral meniscal extrusion its possible proprioceptive effect remains questionable. Its contribution to the pivot shift phenomenon has been uncovered in parts, therefore it has been recognized that a concomitant anterolateral stabilization together with ACL reconstruction may aid in prevention of postoperative instability after severe ligamentous knee damages. However, there are a lot of different methods to perform this procedure and the clinical outcome has yet to be examined. This concise review will give an overview on the present literature to outline the long history of the ALL under its different names, its anatomic variances and topography as well as on histologic examinations, imaging modalities, arthroscopic aspects and methods for a possible anterolateral stabilization of the knee joint. PMID:26714471

  20. Pullout strength of pedicle screws with cement augmentation in severe osteoporosis: A comparative study between cannulated screws with cement injection and solid screws with cement pre-filling

    PubMed Central

    2011-01-01

    Background Pedicle screws with 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, namely solid screws with retrograde cement pre-filling versus cannulated screws with cement injection through perforation, remains unknown. This study aimed to determine the difference in pullout strength between conical and cylindrical screws based on the aforementioned cement augmentation techniques. The potential loss of fixation upon partial screw removal after screw insertion was also examined. Method The Taguchi method with an L8 array was employed to determine the significance of design factors. Conical and cylindrical pedicle screws with solid or cannulated designs were installed using two different screw augmentation techniques: solid screws with retrograde cement pre-filling and cannulated screws with cement injection through perforation. Uniform synthetic bones (test block) simulating severe osteoporosis were used to provide a platform for each screw design and cement augmentation technique. Pedicle screws at full insertion and after a 360-degree back-out from full insertion were then tested for axial pullout failure using a mechanical testing machine. Results The results revealed the following 1) Regardless of the screw outer geometry (conical or cylindrical), solid screws with retrograde cement pre-filling exhibited significantly higher pullout strength than did cannulated screws with cement injection through perforation (p = 0.0129 for conical screws; p = 0.005 for cylindrical screws). 2) For a given cement augmentation technique (screws without cement augmentation, cannulated screws with cement injection or solid screws with cement pre-filling), no significant difference in pullout strength was found between conical and cylindrical screws (p >0.05). 3) Cement infiltration into the open cell of the test block led to

  1. 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

  2. On Interlayer Stability and High-Cycle Simulator Performance of Diamond-Like Carbon Layers for Articulating Joint Replacements

    PubMed Central

    Thorwarth, Kerstin; Thorwarth, Götz; Figi, Renato; Weisse, Bernhard; Stiefel, Michael; Hauert, Roland

    2014-01-01

    Diamond like carbon (DLC) coatings have been proven to be an excellent choice for wear reduction in many technical applications. However, for successful adaption to the orthopaedic field, layer performance, stability and adhesion in physiologically relevant setups are crucial and not consistently investigated. In vitro wear testing as well as adequate corrosion tests of interfaces and interlayers are of great importance to verify the long term stability of DLC coated load bearing implants in the human body. DLC coatings were deposited on articulating lumbar spinal disks made of CoCr28Mo6 biomedical implant alloy using a plasma-activated chemical vapor deposition (PACVD) process. As an adhesion promoting interlayer, tantalum films were deposited by magnetron sputtering. Wear tests of coated and uncoated implants were performed in physiological solution up to a maximum of 101 million articulation cycles with an amplitude of ±2° and −3/+6° in successive intervals at a preload of 1200 N. The implants were characterized by gravimetry, inductively coupled plasma optical emission spectrometry (ICP-OES) and cross section scanning electron microscopy (SEM) analysis. It is shown that DLC coated surfaces with uncontaminated tantalum interlayers perform very well and no corrosive or mechanical failure could be observed. This also holds true in tests featuring overload and third-body wear by cortical bone chips present in the bearing pairs. Regarding the interlayer tolerance towards interlayer contamination (oxygen), limits for initiation of potential failure modes were established. It was found that mechanical failure is the most critical aspect and this mode is hypothetically linked to the α-β tantalum phase switch induced by increasing oxygen levels as observed by X-ray diffraction (XRD). It is concluded that DLC coatings are a feasible candidate for near zero wear articulations on implants, potentially even surpassing the performance of ceramic vs. ceramic. PMID

  3. On interlayer stability and high-cycle simulator performance of diamond-like carbon layers for articulating joint replacements.

    PubMed

    Thorwarth, Kerstin; Thorwarth, Götz; Figi, Renato; Weisse, Bernhard; Stiefel, Michael; Hauert, Roland

    2014-01-01

    Diamond like carbon (DLC) coatings have been proven to be an excellent choice for wear reduction in many technical applications. However, for successful adaption to the orthopaedic field, layer performance, stability and adhesion in physiologically relevant setups are crucial and not consistently investigated. In vitro wear testing as well as adequate corrosion tests of interfaces and interlayers are of great importance to verify the long term stability of DLC coated load bearing implants in the human body. DLC coatings were deposited on articulating lumbar spinal disks made of CoCr28Mo6 biomedical implant alloy using a plasma-activated chemical vapor deposition (PACVD) process. As an adhesion promoting interlayer, tantalum films were deposited by magnetron sputtering. Wear tests of coated and uncoated implants were performed in physiological solution up to a maximum of 101 million articulation cycles with an amplitude of ±2° and -3/+6° in successive intervals at a preload of 1200 N. The implants were characterized by gravimetry, inductively coupled plasma optical emission spectrometry (ICP-OES) and cross section scanning electron microscopy (SEM) analysis. It is shown that DLC coated surfaces with uncontaminated tantalum interlayers perform very well and no corrosive or mechanical failure could be observed. This also holds true in tests featuring overload and third-body wear by cortical bone chips present in the bearing pairs. Regarding the interlayer tolerance towards interlayer contamination (oxygen), limits for initiation of potential failure modes were established. It was found that mechanical failure is the most critical aspect and this mode is hypothetically linked to the α-β tantalum phase switch induced by increasing oxygen levels as observed by X-ray diffraction (XRD). It is concluded that DLC coatings are a feasible candidate for near zero wear articulations on implants, potentially even surpassing the performance of ceramic vs. ceramic. PMID

  4. Fixation Strength of Caudal Pedicle Screws after Posterior Lumbar Interbody Fusion with the Modified Cortical Bone Trajectory Screw Method

    PubMed Central

    Miwa, Toshitada; Yamashita, Tomoya; Kuroda, Yusuke; Ohwada, Tetsuo

    2016-01-01

    Study Design Clinical case series. Purpose In the posterior lumbar interbody fusion (PLIF) procedure in our institute, the cephalad screw trajectory follows a mediolateral and caudocephalad directed path according to the original cortical bone trajectory (CBT) method. However, the starting point of the caudal screw is at the medial border of the pedicle on an articular surface of the superior articular process, and the trajectory takes a mediolateral path parallel to the cephalad endplate. The incidence of caudal screw loosening after PLIF with this modified CBT screw method was investigated, and significant risk factors for caudal screw loosening were evaluated. Overview of Literature A biomechanical study of this modified caudal screw trajectory using the finite element method reported about a 20% increase in uniaxial yield pullout load compared with the traditional trajectory. However, there has been no clinical study concerning the fixation strength of this modified caudal screw trajectory. Methods The subjects were 193 consecutive patients who underwent single-level PLIF with modified CBT screw fixation. Caudal screw loosening was checked in computed tomography at 6 months after surgery, and screw loosening was defined as a radiolucency of 1 mm or more at the bone-screw interface. Results The incidence of caudal screw loosening after lumbosacral PLIF (46.2%) was significantly higher than that after floating PLIF (6.0%). No significant differences in sex, brand of the instruments, and diameter and length of the caudal screw were evident between patients with and without caudal screw loosening. Patients with caudal screw loosening were significantly older at the time of surgery than patients without caudal screw loosening. Conclusions Fixation strength of the caudal screw after floating PLIF with this modified CBT screw technique was sufficiently acceptable. Fixation strength after the lumbosacral procedure was not. PMID:27559442

  5. Biomechanical and finite element analyses of bone cement-Injectable cannulated pedicle screw fixation in osteoporotic bone.

    PubMed

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

    2016-07-01

    The objectives of this study were to investigate the safety and biomechanical stability of a polymethylmethacrylate (PMMA)-augmented bone cement-injectable cannulated pedicle screw (CICPS) in cancellous bone model, and to analyze the stress distribution at the screw-cement-bone interface. The OMEGA cannulated pedicle screw (OPS) and conventional pedicle screw (CPS) were used as control groups. Safety of the CICPS was evaluated by the static bending and bending fatigue tests. Biomechanical stability was analyzed by the maximum axial pullout strength and maximum torque tests. Stress distribution at the screw-cement-bone interface was analyzed by the finite element (FE) method. The CICPS and CPS produced statistically similar values for bending stiffness, bending structural stiffness, and bending yield moment. The maximum pullout force was 53.47 ± 8.65 N in CPS group, compared to 130.82 ± 7.32 N and 175.45 ± 43.01 N in the PMMA-augmented OPS and CICPS groups, respectively (p < 0.05). The CICPS had a significantly greater torque than the OPS and CPS. The FE model did not reveal excessive stress at the screw-cement-bone interface in the CICPS group. In conclusion, PMMA-augmentation with CICPS may be a potentially useful method to increase the stability of pedicle screws in patients with osteoporosis. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 104B: 960-967, 2016. PMID:25976272

  6. 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

  7. Twin screw wet granulation: Binder delivery.

    PubMed

    Saleh, Mohammed F; Dhenge, Ranjit M; Cartwright, James J; Hounslow, Michael J; Salman, Agba D

    2015-06-20

    The effects of three ways of binder delivery into the twin screw granulator (TSG) on the residence time, torque, properties of granules (size, shape, strength) and binder distribution were studied. The binder distribution was visualised through the transparent barrel using high speed imaging as well as quantified using offline technique. Furthermore, the effect of binder delivery and the change of screw configuration (conveying elements only and conveying elements with kneading elements) on the surface velocity of granules across the screw channel were investigated using particle image velocimetry (PIV). The binder was delivered in three ways; all solid binder incorporated with powder mixture, 50% of solid binder mixed with powder mixture and 50% mixed with water, all the solid binder dissolved in water. Incorporation of all solid binder with powder mixture resulted in the relatively longer residence time and higher torque, narrower granule size distribution, more spherical granules, weaker big-sized granules, stronger small-sized granules and better binder distribution compared to that in other two ways. The surface velocity of granules showed variation from one screw to another as a result of uneven liquid distribution as well as shown a reduction while introducing the kneading elements into the screw configuration. PMID:25869451

  8. The reaction of cortical bone to compression by screw threads.

    PubMed

    Schatzker, J; Horne, J G; Sumner-Smith, G

    1975-09-01

    Cortical bone subjected to compression by screw threads retains its integrity and is not resorbed. Screws which generate compression at the interface of their threads with bone can be expected to provide adequate fixation until bone union occurs. PMID:1157421

  9. [Cement augmentation of pedicle screws : Pros and cons].

    PubMed

    Schnake, K J; Blattert, T R; Liljenqvist, U

    2016-09-01

    Cement augmentation of pedicle screws biomechanically increases screw purchase in the bone. However, clinical complications may occur. The pros and cons of the technique are discussed from different clinical perspectives. PMID:27514827

  10. 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