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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. Electrical resistance of screw-fastened thermal joints for ultra-low temperatures

    NASA Astrophysics Data System (ADS)

    Okamoto, Tohru; Fukuyama, Hiroshi; Ishimoto, Hidehiko; Ogawa, Shinji

    1990-04-01

    Electrical resistance measurements at 4.2 K have been made for various screw-fastened thermal joints used at ultra-low temperatures below 100 μK. The measured contact resistance for a gold-plated joint varied in inverse proportion to a tightening torque of the screw. With a maximum tightening torque for a 4-mm stainless-steel screw, several types of the joints revealed to have contact resistances below 10 nΩ. A current-decay method used to measure a small variation of contact resistance of less than 0.1 nΩ is also described.

  8. Selected Methods for Locking Screw Joints, Including the Use of Adhesives, Used in the Helicopter Construction

    NASA Astrophysics Data System (ADS)

    Rudawska, Anna; Cisz, Sławomir; Warda, Tomasz

    2014-12-01

    The paper presents the problems of preventing screw joints from self-loosening on one of helicopter. The research examines selected locking methods used in aircraft produced by different manufacturers. Experimental tests were performed to investigate the loosening torque of screw joints locked by various devices: cotter pin, locknut, centre punching, self-locking nut and adhesive. A comparative analysis of the investigated locking methods is made with respect to their locking strength and efficiency.

  9. 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

  10. Screw placement and osteoplasty under computed tomographic-fluoroscopic guidance in a case of advanced metastatic destruction of the iliosacral joint.

    PubMed

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

    2011-02-01

    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. PMID:19795167

  11. 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.

  12. 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

  13. Acrylic cement stabilized joint replacements.

    PubMed

    Urist, M R

    1975-11-01

    Surgical management of osteoarthritis, aseptic necrosis and rheumatoid arthritis has been revolutionized by the introduction of acrylic cement-stabilized joint surface replacement. Although single joint surface replacements have been employed extensively for more than half a century, total surface replacement operations with a wear-resistant high-density polyethylene and noncorrosive stainless steel stabilized by acrylic cement were introduced only a little more than 12 years ago. This evolved with Charnley's discovery of the high level of bone tolerance for acrylic cement. Acrylic cement made it possible mechanically to bond artificial joint surfaces to the bone ends and produce an insensitive Charcot-like functioning joint. A barium sulfate additive makes the cement radiopaque for visualizing the bone-cement interface. Barium sulfate additive also lowers the polymerization temperature and opens the polymer for influx of interstitial fluids. Antibiotics have also been added to the cement for prevention and treatment of infection of the surrounding tissues. In aged individuals with cardiovascular disease, the absorption of the acrylic monomer depresses cardiac output and produces hypotension for 2-5 minutes after impaction of acrylic cement into spongy bone. The hypotension has been minimized by cautious fluid replacement and maintenance of adequate blood volume before, during and after the operation. Approximately 30,000 total hip arthroplasties are performed in the United States annually in patients older than 50 years of age with fractured femoral head replacements, bilateral rheumatoid arthritis, old neglected congenital dislocations of the hip or osteonecrosis with and without osteoarthritis. The pain relief is more complete and the functional improvement more predictable than in any other previously recommended surgical operation for the purpose. For this reason, total hip arthroplasty has almost completely supplanted mold-arthroplasty, osteotomy, capsulotomy (hanging hip) and resection of the femoral head. Hemiarthroplasty in the form of femoral head replacement still is the procedure of choice in patients with fractures of the neck of the femur and a normal acetabular articular cartilage, irrespective of age. As a countermeasure against loosening of the prosthesis in patients with osteoporosis and a hollow proximal end of the femur, the stem can be stabilized with acrylic cement. A standard replaceable femoral head for subsequent conversion of femoral head replacement to total hip arthroplasty is an important consideration and presently is under investigation in several medical centers.(ABSTRACT TRUNCATED AT 400 WORDS) PMID:803182

  14. 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

  15. 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....

  16. Stabilization of the sacroiliac joint.

    PubMed

    Shaffrey, Christopher I; Smith, Justin S

    2013-07-01

    Lower back pain and pain involving the area of the posterior iliac spine are extremely common. Degeneration of the sacroiliac joint (SIJ) is one potential cause for lower back pain and pain radiating into the groin or buttocks. Degenerative changes to the lumbar spine and sacroiliac joints are common. A recent study evaluating SIJ abnormalities in a primary low back pain population demonstrated 31.7% of patients demonstrated SI joint abnormalities. (4) As is the case for the evaluation and management of isolated lower back pain, the evaluation, management, and role for surgical intervention in SIJ pain is very controversial. Many patients have degenerative changes of the disc, facet joints, and SIJs. A recent systematic review performed to determine the diagnostic accuracy of tests available to clinicians to identify the disc, facet joint, or SIJ as the source of low back pain concluded that tests do exist that change the probability of the disc or SIJ (but not the facet joint) as the source of low back pain. (3) It was also concluded that the usefulness of these tests in clinical practice, particularly for guiding treatment selection, remains unclear. (3) Although there is general agreement that SIJ pathological changes are a potential cause of pain, there is far less agreement about the optimal management of these conditions. A variety of conditions can cause SIJ dysfunction including degenerative and inflammatory arthritis, trauma, prior lumbosacral fusion, hip arthritis, limb length inequality, infections, and neoplasia. (8) There is increasing evidence that image intensifier-guided single periarticular injection can correctly localize pain to the SIJ but the optimal management strategy remains controversial. Recent publications have compared surgical versus injection treatments and fusion versus denervation procedures. (1 , 8) A systematic review found improvement regardless of the treatment, with most studies reporting over 40% improvement in pain as measured by VAS or NRS scores. (8) It cautioned that one of the studies reported 17.6% of patients experiencing mild/no pain compared with 82.4% experiencing marked/severe pain at 39 months after SIJ fusion procedures. (6 , 8) This systematic review also noted that despite improvements in reported pain, less than half of patients who had work status reported as returning to work. (8) Because of the functional and socioeconomic consequences of chronic lower back pain, numerous surgical treatments to improve this condition have been attempted by spinal surgeons through the years. Arthrodesis of the SIJ is a surgical procedure with a long history dating to the beginnings of spinal surgery. (7) Poor results, high complication rates and the need for additional surgical procedures have generally diminished the enthusiasm for this procedure until recently. (6) A variety of "minimally invasive" procedures have been recently introduced that have rekindled enthusiasm for the surgical management of SIJ pathology. The technique demonstrated in the "Stabilization of the SIJ with SI-Bone" is one of these new techniques. There has been a recent publication detailing the very short term clinical outcomes with this technique that reported encouraging results. (5) In this series of 50 patients, quality of life questionnaires were available for 49 patients preoperatively, 41 patients at 3 months, 40 at 6 months and only 27 at 12 months, complicating the ability to accurately assess true outcomes. Although the focus of this video by Geisler is on the surgical technique, there should have been more information provided on the expected surgical outcomes and potential complications of SIJ fusion. (2) The video only gives minimal information on how to appropriately select patients with potential SIJ pathology for surgical intervention. There are insufficient recommendations on the clinical and radiographic follow-up needed for this procedure. A concern with this implant is whether the porous plasma spray coating on the implant actually results in bone growth across the SIJ or only serves as a stabilizer. If true fusion does not result, deterioration in the clinical result could occur over time. This video nicely demonstrates the surgical technique of stabilization of the SIJ with SI-Bone product. There are numerous unanswered questions regarding patient selection for SIJ fusion or stabilization. There are an increasing number of surgical techniques for treating SIJ pathology and it is not clear which method may provide the best outcomes. Without prospective trials with nonconflicted surgeons and standardized selection criteria, the true role for SIJ fusion procedures in the management of chronic lower back pain will remain murky. The consequences of the unsupported enthusiasm for the surgical management of discogenic back pain still negatively impacts the public perception of spinal surgeons. Much more high quality information is needed regarding the surgical management of SIJ pathology before widespread use of this technique should be adopted. PMID:23829837

  17. 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

  18. 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

  19. 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.

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

    PubMed

    Roussel, Jean-Marc; Gailhanou, Marc

    2015-08-14

    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. PMID:26317731

  1. 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

  2. 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.

  3. Anterior cervical discectomy, fusion and stabilization by plate and screw--early experience.

    PubMed

    Islam, M A; Islam, M A; Habib, M A; Sakeb, N

    2012-08-01

    Anterior cervical plating is commonly performed to stabilize anterior cervical fusion. The aim of the study was to evaluate the clinical and functional outcome, radiological fusion and operative complications in cases of cervical spondylotic myelopathy and radiculopathy who underwent Anterior Cervical Discectomy and Fusion (ACDF) by autograft and stabilized with plate and screw. We evaluated 16 consecutive patients (M: F = 10:6) from January 2008 to December 2010 in Bangabandhu Sheikh Mujib Medical University (BSMMU) and different private hospitals in Dhaka, in cases where adequate conservative treatment failed. Single level ACDF by autograft and stabilization by plate and screw was done in 10 patients and 06 patients had two levels fusion. The mean follow up period was 18 months. The patients improved significantly (p < 0.05) and the recovery rate was 87.50%. All patients showed radiological fusion (p < 0.001). There was no hardware failure, graft extrusion or plate breakage. ACDF with plate and screw is fairly safe and effective therapy for cervical disc degeneration leading to myelo-radiculopathy where major post operative complications are uncommon. PMID:23227630

  4. 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

  5. Screw-Joints and Symmetries: Designing Nucleic Acid Nanotubes as Nano-Machines

    NASA Astrophysics Data System (ADS)

    Sherman, William

    2005-03-01

    In 2001, Mathieu et al.^1 presented the first nanotube constructed from DNA. Similar experimental techniques can be used to build a variety of other DNA nanotubes, but finding solutions to the structural constraint equations can be difficult. We show how symmetry based analysis can be used not only to find viable tube structures, but also to identify tube based devices. Such devices can pass through several states with varying tube profiles, inner and outer radii, and lengths. The theoretical basis for actuation of the devices is the screw-joint -- two double-helical domains joined by two or more symmetric Holliday junctions and one (or more) immobile Holliday junction(s). Two of the strands in the immobile junction can be pulled out of the system and replaced with different strands. This process changes the state of the device in a controlled and reversible manner. These devices are promising as gated pores, as well as stiff mechanical manipulators. This research supported by NIGMS, ONR, and NSF. ^1 F. Mathieu, C. Mao, N. C. Seeman, Journal of Biomolecular Structure & Dynamics, 18, p.907 (2001).

  6. 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

  7. 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 screwbone contact area. Low-level laser therapy may be a supplementary treatment method to increase the stability of the orthodontic mini screw. PMID:25594769

  8. Arthrodesis of the talocalcaneal joint for the treatment of two horses with talocalcaneal osteoarthritis.

    PubMed

    Pauwels, F E; Adams, S B; Blevins, W B

    2005-01-01

    Two horses with lameness due to tolocalcaneal osteoarthritis that failed to respond to conservative management were treated by tolocalcaneal arthrodesis using cortex screws placed in lag fashion. The affected joint of one horse was arthrodesed by compressing and stabilizing the medial facet of the joint with three screws. In the second horse, the medial and lateral facets of the affected tolocalcaneal joint were each compressed and stabilized with two screws. The lameness of both horses improved markedly following surgery. PMID:16594210

  9. 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

  10. 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

  11. Stability and repeatability of a continuous twin screw granulation and drying system.

    PubMed

    Vercruysse, J; Delaet, U; Van Assche, I; Cappuyns, P; Arata, F; Caporicci, G; De Beer, T; Remon, J P; Vervaet, C

    2013-11-01

    The aim of this study was to investigate the process transfer of a commercially available product from the current batch fluid bed granulation and drying production method to an innovative continuously operating "from powder to tablet" production line using twin screw granulation as an intermediate granulation step. By monitoring process outcomes (torque, water temperature at the granulator jacket inlet, differential pressure over the dryer filters, and temperature mill screen) and granule and tablet quality in function of process time, the stability and repeatability during long production runs were determined. Three consecutive 5h "from powder to tablet" production runs were performed using the ConsiGma™-25 system (GEA Pharma Systems, Collette™, Wommelgem, Belgium). A premix of two active ingredients, powdered cellulose, maize starch, pregelatinized starch, and sodium starch glycolate was granulated with distilled water. After drying and milling (1000 μm and 800 rpm), granules were in-line blended with magnesium stearate and directly compressed using a Modul™ P tablet press (tablet weight: 430 mg, main compression force: 12 kN). Granule (loss on drying, particle size distribution, friability, flow) and tablet (weight uniformity, hardness, thickness, friability, content uniformity, disintegration time, and dissolution) quality was evaluated in function of process time. For each of the logged process outcomes, a stabilization period was needed to reach steady-state conditions. Slightly deviating particle size distribution and friability results for milled granules were observed during start-up due to initial layering of the mill screen. However, no deviating tablet quality was detected in function of process time. For multiple hours, granule and tablet quality was constant in function of process time. Furthermore, process data trends were highly repeatable. Consequently, the ConsiGma™-25 system can be considered as a stable and repeatable system for the continuous production of tablets via wet granulation. PMID:23702273

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

    PubMed

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

    2011-01-01

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

  13. 46 CFR 154.524 - Piping joints: Welded and screwed couplings.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... penetration at the weld root except that for design temperatures colder than −10 °C (14 °F) the butt weld must... 979 kPa gauge (142 psig) must be removed after the weld is completed; (2) A consumable insert; or (3) An inert gas back-up on the first weld pass. (b) A slip-on welded joint with sleeves and...

  14. 46 CFR 154.524 - Piping joints: Welded and screwed couplings.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... penetration at the weld root except that for design temperatures colder than −10 °C (14 °F) the butt weld must... 979 kPa gauge (142 psig) must be removed after the weld is completed; (2) A consumable insert; or (3) An inert gas back-up on the first weld pass. (b) A slip-on welded joint with sleeves and...

  15. 46 CFR 154.524 - Piping joints: Welded and screwed couplings.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... penetration at the weld root except that for design temperatures colder than −10 °C (14 °F) the butt weld must... 979 kPa gauge (142 psig) must be removed after the weld is completed; (2) A consumable insert; or (3) An inert gas back-up on the first weld pass. (b) A slip-on welded joint with sleeves and...

  16. 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

  17. 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

  18. Biomechanical In Vitro - Stability Testing on Human Specimens of a Locking Plate System Against Conventional Screw Fixation of a Proximal First Metatarsal Lateral Displacement Osteotomy

    PubMed Central

    Arnold, Heino; Stukenborg-Colsman, Christina; Hurschler, Christof; Seehaus, Frank; Bobrowitsch, Evgenij; Waizy, Hazibullah

    2012-01-01

    Introduction: The aim of this study was to examine resistance to angulation and displacement of the internal fixation of a proximal first metatarsal lateral displacement osteotomy, using a locking plate system compared with a conventional crossed screw fixation. Materials and Methodology: Seven anatomical human specimens were tested. Each specimen was tested with a locking screw plate as well as a crossed cancellous srew fixation. The statistical analysis was performed by the Friedman test. The level of significance was p = 0.05. Results: We found larger stability about all three axes of movement analyzed for the PLATE than the crossed screws osteosynthesis (CSO). The Friedman test showed statistical significance at a level of p = 0.05 for all groups and both translational and rotational movements. Conclusion: The results of our study confirm that the fixation of the lateral proximal first metatarsal displacement osteotomy with a locking plate fixation is a technically simple procedure of superior stability. PMID:22675409

  19. 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

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

    PubMed Central

    2012-01-01

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

  1. 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

  2. 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

  3. 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

  4. Benefit and accuracy of intraoperative 3D-imaging after pedicle screw placement: a prospective study in stabilizing thoracolumbar fractures

    PubMed Central

    Mittlmeier, Thomas; Gierer, Philip; Harms, Christoph; Gradl, Georg

    2009-01-01

    Internal fixation is the established dorsal standard procedure for the treatment of thoracolumbar fractures. The main problem of the procedure is the false positioning of the pedicle screws. The exact determination of pedicle screws has up to now only been possible through postoperative computed tomography. This study was intended to clarify the diagnostic value of intraoperative 3D scans after pedicle screw implantation in thoracolumbar spine surgery. The direct intraoperative consequences of the 3D scans are reported and the results of the 3D scans are compared with the postoperative computed tomography images. Intraoperative 3D scans were prospectively carried out from June 2006 to October 2008 on 95 patients with fractures of the thoracolumbar spine that have been treated with internal fixation. Screws positions were categorised intraoperatively, screws in relevant malposition were repositioned immediately. A computed tomography of the involved spinal section was carried out postoperatively for all patients. The positions of the pedicle screws were determined and compared in the axial reconstructions of both procedures. Four hundred and fourteen pedicles with enclosed screws were evaluated by the 3D scans. The time needed for carrying out the 3D scan amounts to an average of 8.2min. Eleven screws (2.7%) in ten patients were primarily intraoperatively repositioned on the basis of the 3D scan evaluation. Two of 95 patients had to have false positions of the screws revised secondarily following evaluation of the computed tomographies. The secondary postoperative revision rate of the patients amounts to 2.1%. In relation to the number of screws, this is a revision rate of 0.5%. The postoperative computed tomographies showed 323 pedicles without cortical penetration by the screws (78.0%). Ninety-one screws penetrated the pedicle wall (22%). It was possible to postoperatively compare the position classifications of 406 pedicle screws. The CT showed 378 correct screw positions, while 28 screws were positioned falsely. On the basis of the 3D scans, 376 of 378 correct positions were correctly assessed. Twenty-one of 28 false positions could be correctly classified. The sensitivity of all 3D scans reached 91.3% and the specificity 98.2%. The position of 97.8% of the pedicle screws was correctly recognised by the intraoperative 3D scan. Nine screws were classified falsely (2.2%). The comparison of the classification results showed significantly higher error findings by the 3D scan in the spinal section T110 (P=0.014). The image quality of the 3D scan correlates significantly with the width of the scanned pedicle, with the body mass index, the scanned spinal section and the extent of the fixation assembly. 3D scans showed a high accuracy in predicting pedicle screw position. Primary false placement of screws and primary neurovascular damage cannot be avoided. But intraoperative evaluation of the 3D scans resulted in a primary revision rate of 2.7% of the pedicle screws and we could lower the secondary revision rate to 0.5%. PMID:19513764

  5. 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

  6. Immediate Weightbearing of First Metatarsophalangeal Joint Fusion Comparing Buried Crossed Kirschner Wires Versus Crossing Screws: Does Incorporating the Sesamoids Into the Fusion Contribute to Higher Incidence of Bony Union?

    PubMed

    Storts, Eric C; Camasta, Craig A

    2016-01-01

    First metatarsophalangeal joint (MTPJ) arthrodesis remains a commonly used and reliable procedure for a variety of pathologies of the first MTPJ. Many costly fixation constructions have been described to achieve union with first MTPJ arthrodesis. We hypothesized that the incidence of union would be the same for both buried Kirchner (K)-wire and solid crossed screw fixation with immediate weightbearing. To test this hypothesis, we retrospectively reviewed first MTPJ fusions performed by the senior author (C.A.C.) during a 6-year period and compared the incidence of union. Only patients who were immediately weightbearing in a surgical shoe and had undergone first MTPJ arthrodesis using K-wires or crossed screws were included. All patients had undergone incorporation of their sesamoids into the fusion. A total of 97 feet in 89 patients met the inclusion criteria. Of the 97 first MTPJ fusions, 48 (49.5%) had buried K-wire fixation and 49 (50.5%) crossed screw fixation. The mean age was 62 (range 41 to 75) years in the K-wire group and 60 (range 22 to 73) years in the crossed screw group. The mean follow-up period was 12.4 months in the K-wire group and 12.9 months in the crossed screw group. The rate of union in the K-wire group was 98% (1 nonunion) and the rate of union in the crossed screw group was 96% (2 nonunions). The 2 groups demonstrated similar high rates of fusion with immediate weightbearing, suggesting that less costly fixation is acceptable and effective for uncomplicated first MTPJ fusion. PMID:26905254

  7. 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 no revision surgeries performed for proximal junctional failure. Retrospective clinical questionnaires revealed that surgical expectations were met in 15 of 19 patients surveyed, 79%. One patient was not reachable for a postoperative phone interview. In patients who were not satisfied with their overall experience, the change in Cobb angle ranged from -0.92 to 9.13 degrees with an average change of 3.90 degrees. Whereas patients reporting an overall positive experience had a change in Cobb angle range from -0.12 to 8.07 degrees with an average change of 4.05 degrees. Conclusion: PJK and failure are well-recognized suboptimal outcomes of long-segmental fusions of the thoracolumbar spine that can lead to significant neurological morbidity and costly revision surgeries. With no known proximal junction failures to date, the MLSS technique has shown promising results in preventing adverse proximal junctional conditions and can be safely performed under fluoroscopy guidance. Future direction includes a comparative study establishing the relative risk of developing PJK with this novel technique versus a traditional long-segmental thoracolumbar fusion. PMID:26167364

  8. 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.

  9. 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

  10. 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.

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

    PubMed

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

    1993-02-01

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

  12. Biomechanical Analysis of Differing Pedicle Screw Insertion Angles

    PubMed Central

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

    2007-01-01

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

  13. 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.

  14. 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

  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. 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

  17. 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

  18. Ultra Long Construct Minimally Invasive Spinal Stabilization Using Percutaneous Pedicle Screws in the Treatment of Symptomatic Multicentric Spinal Metastasis

    PubMed Central

    Chan, Chris Yin Wei; Kwan, Mun Keong

    2015-01-01

    Managing multiple level spinal metastases is challenging. We report the case of a 58-year-old female with advanced lung cancer who presented with multiple pathological fractures of the thoracic spine (T5, T6, T7, and T8 vertebrae). She was treated with palliative radiotherapy. Her resting pain improved, but the instability pain persisted. One month later, she had a trivial fall leading to a pathological fracture of the L2 vertebra with cauda equine syndrome. The patient was treated surgically with minimally invasive decompression of the L2 and with percutaneous instrumented stabilization using an ultra-long construct from T3 to L5 (15 spinal levels), spanning the previously radiated zone and the decompression site. Postoperatively, she had significant improvements in pain and neurology. There were no surgical complications. Ultra long construct minimally invasive spinal stabilization is the ideal approach for symptomatic multicentric spinal metastasis with poor prognostic scores. Using this technique, the goals of spinal stabilization and direct neural decompression can be achieved with minimal morbidity. PMID:26713131

  19. Ultra Long Construct Minimally Invasive Spinal Stabilization Using Percutaneous Pedicle Screws in the Treatment of Symptomatic Multicentric Spinal Metastasis.

    PubMed

    Lee, Chee Kean; Chan, Chris Yin Wei; Kwan, Mun Keong

    2015-12-01

    Managing multiple level spinal metastases is challenging. We report the case of a 58-year-old female with advanced lung cancer who presented with multiple pathological fractures of the thoracic spine (T5, T6, T7, and T8 vertebrae). She was treated with palliative radiotherapy. Her resting pain improved, but the instability pain persisted. One month later, she had a trivial fall leading to a pathological fracture of the L2 vertebra with cauda equine syndrome. The patient was treated surgically with minimally invasive decompression of the L2 and with percutaneous instrumented stabilization using an ultra-long construct from T3 to L5 (15 spinal levels), spanning the previously radiated zone and the decompression site. Postoperatively, she had significant improvements in pain and neurology. There were no surgical complications. Ultra long construct minimally invasive spinal stabilization is the ideal approach for symptomatic multicentric spinal metastasis with poor prognostic scores. Using this technique, the goals of spinal stabilization and direct neural decompression can be achieved with minimal morbidity. PMID:26713131

  20. Ball screw inspection setup

    NASA Astrophysics Data System (ADS)

    Janusz, Rzepka; Sambor, Slawomir; Pienkowski, Janusz; Bielenin, Marcin

    2003-05-01

    In the following paper we describe arrangements of laser interferometer for investigation of screws and for inspection of ball screws. We have constructed two of them, namely: the technological setup for investigations of screw in process of production and the ball screw inspection setup. The former one is used to measure the pitch of screws. The data gathered during measurement is used to calculate the parameters for grinding machine. The later setup is used for testing parameters of complete ball screws. The software supporting this setup makes calculation of parameters of tested ball screw and creation of reports possible. Additionally, the inspection setup is the one that the torque measuring arrangements have been integrated on. Both the arrangements and the software allow for measurements of all parameters during movement of nut in full travel length of the ball screw and make charts and reports.

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

    PubMed Central

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

    2015-01-01

    A rigid spino-pelvic fixation to anchor long constructs is crucial to maintain the stability of long fusion in spinal deformity surgery. Besides obtaining immediate stability and proper biomechanical strength of constructs, the S2 alar-iliac (S2AI) screws have some more advantages. Four Korean fresh-frozen human cadavers were procured. Free hand S2AI screw placement is performed using anatomic landmarks. The starting point of the S2AI screw is located at the midpoint between the S1 and S2 foramen and 2 mm medial to the lateral sacral crest. Gearshift was advanced from the desired starting point toward the sacro-iliac joint directing approximately 20° angulation caudally in sagittal plane and 30° angulation horizontally in the coronal plane connecting the posterior superior iliac spine (PSIS). We made a S2AI screw trajectory through the cancellous channel using the gearshift. We measured caudal angle in the sagittal plane and horizontal angle in the coronal plane. A total of eight S2AI screws were inserted in four cadavers. All screws inserted into the iliac crest were evaluated by C-arm and naked eye examination by two spine surgeons. Among 8 S2AI screws, all screws were accurately placed (100%). The average caudal angle in the sagittal plane was 17.3±5.4°. The average horizontal angle in the coronal plane connecting the PSIS was 32.0±1.8°. The placement of S2AI screws using the free hand technique without any radiographic guidance appears to an acceptable method of insertion without more radiation or time consuming. PMID:26819698

  2. 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.

  3. 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

  4. Effect of Off-Axis Screw Insertion, Insertion Torque, and Plate Contouring on Locked Screw Strength

    PubMed Central

    Gallagher, Bethany; Silva, Matthew J.; Ricci, William M.

    2015-01-01

    Objectives This study quantifies the effects of insertion torque, off-axis screw angulation, and plate contouring on the strength of locking plate constructs. Methods Groups of locking screws (n = 6–11 screws) were inserted at 50%, 100%, 150%, and 200% of the manufacturer-recommended torque (3.2 Nm) into locking compression plates at various angles: orthogonal (control), 5-degree angle off-axis, and 10-degree angle off-axis. Screws were loaded to failure by a transverse force (parallel to the plate) either in the same (“+”) or opposite direction (“−”) of the initial screw angulation. Separately, locking plates were bent to 5 and 10-degree angles, with the bend apex at a screw hole. Locking screws inserted orthogonally into the apex hole at 100% torque were loaded to failure. Results Orthogonal insertion resulted in the highest average load to failure, 2577 ± 141 N (range, 2413–2778 N), whereas any off-axis insertion significantly weakened constructs (165–1285 N, at 100% torque) (P < 0.05). For “+” loading, torque beyond 100% did not increase strength, but 50% torque reduced screw strength (P < 0.05). Loading in the “−” direction consistently resulted in higher strengths than “+” loading (P < 0.05). Plate contouring of 5-degree angle did not significantly change screw strength compared with straight plates but contouring of 10-degree angle significantly reduced load to failure (P < 0.05). Conclusions To maximize the screw plate interface strength, locking screws should be inserted without cross-threading. The mechanical stability of locked screws is significantly compromised by loose insertion, off-axis insertion, or severe distortion of the locking mechanism. PMID:24343255

  5. 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

  6. 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

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

    PubMed Central

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

    2015-01-01

    [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

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

    PubMed

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

    2015-01-01

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

  9. Biomechanical measurements on scaphoid bone screws in an experimental model.

    PubMed

    Kaulesar Sukul, D M; Johannes, E J; Marti, R K; Klopper, P J

    1990-01-01

    A number of screws commonly used for internal fixation in scaphoid bone fractures and nonunions are compared regarding biomechanical properties and clinical applicability. The experiments were carried out on models made of ash-wood, representing a reconstruction and fixation as is performed in a cortico-cancellous inlay bone graft for scaphoid non-union. For fixation use was made of 2.7 and 3.5 AO/ASIF cortical screws respectively, 4.0 AO/ASIF cancellous screws, Herbert screws, and a newly designed screw called the three components screw (D.K.S.). The models with implanted screws were tested for bending strength, tensile strength and torsion stability. No large differences between the various screws were found regarding the measured parameters, so that a small intra-osteal implant such as the Herbert screw and the D.K.S., which can be inserted easily and which gives a certain amount of interfragmentary compression, will be sufficient for osteosynthesis of the scaphoid bone. In case an intra-osteal implant is not available a single 3.5 AO/ASIF cortical screw, inserted following lag-screw principles, is recommended. PMID:2277046

  10. Role of individual lower limb joints in reactive stability control following a novel slip in gait

    PubMed Central

    Yang, Feng; Pai, Yi-Chung

    2010-01-01

    Instability after slip onset is a key precursor leading to subsequent falls during gait. The purpose of this study was to determine the impact of reactive muscular response from individual lower limb joints on regaining stability control and impeding a novel, unannounced slip during the ensuing single-stance phase. Ten young adults resultant moments at three lower limb joints of both limbs, initially derived by an inverse-dynamics approach from empirical data, were optimized to accurately reproduce the original motion before being applied as input to the control variables of their individualized forward-dynamics model. Systematic alteration of the moments of each joint caused corresponding changes in the displacement and velocity of the center of mass (COM) and base of support (BOS) (i.e., their state variables, xCOM, ?COM, xBOS, ?BOS), and in the COM stability. The model simulation revealed that these joints had little influence on ?COM, but had substantial impact on ?BOS reduction, leading to improving the COM stability, mostly from knee flexors, followed by hip extensors, of the slipping limb. Per unit reactive increase in normalized knee flexor or hip extensor moments and per unit reactive reduction in commonly observed plantar-flexor moments could lead to as much as 57.72 10.46 or 22.33 5.55 and 13.09 2.27 units of reduction in normalized ?BOS, respectively. In contrast, such influence was negligible from the swing limb during this period, irrespective of individual variability. PMID:19896133

  11. 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.

  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 justification" of intraoperative neuromonitoring"... is the perception that the safety and efficacy of pedicle screw fixation are enhanced..." (Resnick et al. 2005b). However in summarizing a massive (over 1000 papers taken from the National Library of Medicine), contemporary, literature review spanning nearly a decade (1996 to 2003), this invited panel (Resnick et al. 2005b) recognized that the evidence-based documents contributing to the parts related to pedicle screw fixation and neuromonitoring were "... full of potential sources of error ..." and lacked appropriate, randomized, prospective studies for formulating rigid standards and guidelines. Nevertheless, current trends support the routine use and clinical utility of these neuromonitoring techniques. In particular free-run and triggered EMG have been well recognized in numerous publications for improving both the accuracy and safety of pedicle screw implantation. Currently, treatment with pedicle screw instrumentation routinely involves all levels of the spine - lumbosacral, thoracic, and cervical. Significant historical events, various neuromonitoring modalities, intraoperative alarm criteria, clinical efficacy, current trends, and caveats related to pedicle screw stimulation along the entire vertebral column will be reviewed. PMID:22808751

  13. 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.

  14. Immediate effects of bilateral manipulation of talocrural joints on standing stability in healthy subjects.

    PubMed

    Alburquerque-Sendín, Francisco; Fernández-de-las-Peñas, César; Santos-del-Rey, Miguel; Martín-Vallejo, Francisco Javier

    2009-02-01

    The purpose of this study was to investigate the immediate effects of bilateral talocrural joint manipulation on standing stability in healthy subjects. Sixty-two healthy subjects, 16 males and 46 females, aged from 18 to 32 years old (mean: 21+/-3 years old) participated in the study. Subjects were randomly divided into two groups: an intervention group (n=32), who received manipulation of bilateral talocrural joints and a control group (n=30) which did not receive any intervention. Baropodometric and stabilometric evaluations were assessed pre- and 5 min post-intervention by an assessor blinded to the treatment allocation. Intra-group and inter-group comparisons were analysed using appropriate parametric tests. The results indicated that changes on the X coordinate range, length of motion, and mean speed approximated to statistical significance (P=0.06), and changes on the Y coordinate range reached statistical significance (P=0.02). Average X and Y motions, and anterior-posterior or lateral velocities did not show significant differences. Our results showed that bilateral thrust manipulation of the talocrural joint did not modify standing stability, that is, the behavioural pattern of the projection of the centre of pressure, in healthy subjects. PMID:18280767

  15. The biomechanical influence of tibio-talar containment on stability of the ankle joint.

    PubMed

    Frigg, Arno; Frigg, Roman; Hintermann, Beat; Barg, Alexey; Valderrabano, Victor

    2007-11-01

    Chronic ankle instability (CAI) is a frequent sport orthopaedic entity. Although many risk factors have been studied extensively, little is known how it is influenced by the osseous joint configuration. Based on lateral X-rays, the radius of the talar surface and the tibial coverage of the talus (sector alpha) were measured on a DICOM/PACS system in 52 patients with CAI and an age- and sex-matched control group. The talar radius was found to be larger in patients with CAI (21.2 +/- 2.4 mm) than in the control group (17.7 +/- 1.9 mm; P < 0.0001). The tibio-talar sector was smaller in patients with CAI (80 degrees +/- 5.1 degrees ) than in the control group (88.4 degrees +/- 7.2 degrees ; P < 0.0001). The aim of this study is to analyse the biomechanical influence of the clinical data on stability of the ankle joint. A two-dimensional model of the tibio-talar joint in the sagittal plane was developed. The joint configuration was described by the tibio-talar sector (alpha) and the radius (r) of the talus. The force (F = F (BW) tan alpha/2) and energy (E = F (BW) r [1 - cos alpha/2]) to dislocate the talus out of the tibial plafond were deduced. Ankle stability is a function of the tibio-talar sector: the force necessary to dislocate the joint is decreasing with a smaller sector. The clinical data show that the force needed to dislocate the ankle of CAI patients was 14% weaker than the one needed in the case of healthy subjects (P < 0.0001). The energy to dislocate the ankle depends both on the sector and the radius. The clinical data do not show a significant difference between the energy needed to dislocate the joint of CAI patients and the one of healthy subjects. This is because there is a correlation of a small sector and a large radius for CAI ankles. CAI is associated with an unstable osseous joint configuration, which is characterized by a larger radius of the talus and a smaller tibio-talar sector. The findings of the biomechanical model explain the clinical observations and demonstrate how stability of the ankle joint is influenced by the osseous configuration. Surgical ankle ligament stabilization might be more recommended in patients with an unstable osseous configuration as such patients have a disposition for recurrent sprains. Removing anterior osteophytes for anterior impingement should be done carefully in CAI patients because this would decrease the tibial coverage of the talus and thus dispose the talus to dislocate anteriorly. People who have an unstable ankle configuration and who nevertheless engage in activities with high risk of ankle sprains could be asked to wear ankle protecting sports equipment. PMID:17628787

  16. 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

  17. Clinical application of C2 laminar screw technique

    PubMed Central

    Feng, Leling; Xu, Rongming; Liu, Xiaochen; Lee, Alan H.; Sun, Shaohua; Zhao, Liujun; Hu, Yong; Liu, Guanyi

    2010-01-01

    C2 laminar screws have become an increasingly used alternative method to C2 pedicle screw fixation. However, the outcome of this technique has not been thoroughly investigated. A total of 35 cases with upper cervical spinal instability undergoing C2 laminar screw fixation were reviewed. All cases had symptoms of atlantoaxial instability, such as craniocervical junction pain, and were fixed with the Vertex cervical internal fixation system. A total of 68 screws were placed and hybrid constructs (a C2 translaminar screw combined with a C2 pars screw) were incorporated in two patients. In this series, there were no intraoperative complications and no cases of neurological worsening or vascular injury from hardware placement. Computed tomographic scans demonstrated a partial dorsal laminar breach in ten patients. None of these resulted in neurological symptoms. None of the patients was found to have a breach of the ventral laminar cortex. All the C2 laminar screws fixations were performed successfully. There was no instability seen on the films with no evidence of hardware failure or screw loosening during the follow-up period in all patients. In conclusion, C2 laminar screw technique is straightforward and easily adopted; it can efficiently and reliably restore upper cervical stability. It is an alternative method to C2 pedicle screw fixation, especially in patients with unilateral occlusion of vertebral artery and pedicle deformity of C2. PMID:20524135

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

    PubMed

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

    1985-10-01

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

  19. Bilateral Pedicle and Crossed Translaminar Screws in C2.

    PubMed

    Mendelsohn, Daniel; Dea, Nicolas; Lee, Robert; Boyd, Michael C

    2015-10-01

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

  20. Bilateral Pedicle and Crossed Translaminar Screws in C2

    PubMed Central

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

    2015-01-01

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

  1. Stochastic stability analysis for joint process driven and networked hybrid systems

    NASA Astrophysics Data System (ADS)

    Yao, Jing; Lin, Feng; Wang, Hua O.

    2014-05-01

    The stochastic stability and impulsive noise disturbance attenuation in a class of joint process driven and networked hybrid systems with coupling delays (JPDNHSwD) has been investigated. In particular, there are two separable processes monitoring the networked hybrid systems. One drives inherent network structures and properties, the other induces random variations in the control law. Continuous dynamics and control laws in networked subsystems and couplings among subsystems change as events occur stochastically in a spatio-temporal fashion. When an event occurs, the continuous state variables may jump from one value to another. Using the stochastic Lyapunov functional approach, sufficient conditions on the existence of a remote time-delay feedback controller which ensures stochastic stability for this class of JPDNHSwD are obtained. The derived conditions are expressed in terms of solutions of LMIs. An illustrative example of a dynamical network driven by two Markovian processes is used to demonstrate the satisfactory control performance.

  2. Joint cavity injection combined with manual reduction and stabilization splint treatment of anterior disc displacement

    PubMed Central

    Liu, Junjie; Mu, Hong; Wang, Zhifeng; Lan, Jing; Zhang, Shizhou; Long, Xing; Zhang, Dongsheng

    2015-01-01

    Aim: This study aimed to compare the clinical efficacy of upper and lower joint cavity treatment (UJCT vs. LJCT) in patients with anterior disc displacement without reduction (ADDw/oR) of temporomandibular joint (TMJ). Material and methods: A total of 56 patients with unilateral ADDw/oR were randomly divided into two groups: UJCT group and LJCT group. Manual reduction was done in all the patients after joint cavity rejection of sodium hyaluronate. Then, they were treated with stabilization splint for one or two months. At last, Friction index was calculated to evaluate the therapeutic efficacy at 6 to 12 months follow-up. Results: The maximal mouth-opening degrees in the both groups increased significantly when compared with pre-treatment group (P < 0.01), and the Friction index decreased significantly when compared with pre-treatment group (P < 0.01); In LJCT group, the degrees of maximal mouth-opening increased significantly as compared to UJCT group (P < 0.05), and Friction index were also markedly lower than that in UJCT group (P < 0.05). Conclusion: In the patients with ADDw/oR of TMJ, the clinical efficacy of LJCT is superior to that of UJCT, especially in the TMJ pain relief, mouth-opening degree and mandibular movement improvement. PMID:26131189

  3. 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.

  4. Stabilization of the sacroiliac joint with the SI-bone surgical technique.

    PubMed

    Geisler, Fred

    2013-07-01

    Although the motion of the sacroiliac joints (SIJ) is minimal, pain can originate from the SIJ on mechanical loading and affect walking, sitting and sleep patterns. The SIJ refers to the pair of joints inferior to the L5-S1 joint, and functions as the inferior adjacent level after a L5-S1 fusion. SIJ pain has a clinical overlay of symptoms often similar to low back pain (LBP) generated by the lumbar spine. The differential diagnosis in any patient with LBP should include the triad of low back, SIJ, and hip. SIJ pain is also a known cause of residual LBP after successful lumbar fusion. Relief of the patient's pain with a diagnostic SIJ block verifies the SIJ as the site of the pain generator. The SI-bone technique of stabilization of the SIJ is a true minimally invasive surgical technique performed through an initial small skin incision and then over pins, with the aid of fluoroscopy in three orthogonal axes with one axis parallel to the posterior sacral cortical line at the S1 to S2 region. The fluoroscopy procedure includes the following steps: 1) pre-op plan of the desired 3 implant trajectories to account for the anatomic variations; 2) placement of 3 Steinman pins at these trajectories across the SIJ starting in a small skin incision; 3) drill, broach and then implant placement as a cannulated system. All these steps are performed with the assistance of fluoroscopy in all three imaging planes - lateral, inlet and outlet views. The SI-Bone implants are triangular shaped titanium and have a rough surface for immediate stability. This rough surface is believed to aid in the osteo-fixation of the implants to the ilium and sacrum, as well as to long term fusion of the SIJ after its prolonged immobilization. The video can be found here: http://youtu.be/2YtFddohZRk. PMID:23829857

  5. 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

  6. 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.

  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. Bone properties of the humeral head and resistance to screw cutout

    PubMed Central

    Frich, Lars Henrik; Jensen, Niels Christian

    2014-01-01

    Surgical treatment of fractures involving the proximal humeral head is hampered by complications. Screw cutout is the major pitfall seen in connection with rigid plating. We have exploited a bony explanation for this phenomenon. Materials and Methods: We examined the convex surface of the humeral head looking at the density and the topographical strength of the subchondral bone using mechanical testing of bone cylinders harvested from the humeral head. We also studied the osseous architecture of the subchondral bone and thickness of the boneplate of the humeral head using a 3-dimensional serial sectioning technique. Results: The bone strength and bone density correlated well and revealed large regional variations across the humeral head. Bone strength and stiffness of the trabecular bone came to a maximum in the most medial anterior and central parts of the humeral head, where strong textural anisotropy was also found. We found in particular a lower bone strength and density in the posterior and inferior regions of the humeral head. A rapid decline in bone strength within a few mm below a relatively thin subchondral plate was also reported. Clinical Relevance: We have in this paper explored some of the most important factors connected with screw stability at the cancellous bone level. We discovered large variations in bone density and bone strength across the joint surface rendering certain areas of the humeral head less suitable for screw placement. The use of rigid plate constructs with divergent screw directions will predictably place screws in areas of the humeral head comprising low density and low strength cancellous bone. New concepts of plates and plating techniques for the surgical treatment of complex fractures of the proximal humerus should take bone distribution, strength, and architecture into account. PMID:24926160

  9. 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.

  10. 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.

  11. 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.

  12. 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 bone stock and can be used for further investigations. PMID:22470474

  13. 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 who did not have advanced DRUJ arthritis. PMID:25275473

  14. Maxillary sinus perforation by orthodontic anchor screws.

    PubMed

    Motoyoshi, Mitsuru; Sanuki-Suzuki, Rina; Uchida, Yasuki; Saiki, Akari; Shimizu, Noriyoshi

    2015-06-01

    To facilitate safe placement of orthodontic anchor screws (miniscrews), we investigated the frequency of maxillary sinus perforation after screw placement and the effect of sinus perforation on screw stability. Maxillary sinus perforations involving 82 miniscrews (diameter, 1.6 mm; length, 8 mm) were evaluated using cone-beam computed tomography. All miniscrews were placed in maxillary alveolar bone between the second premolar and first molar for anchorage for anterior retraction in patients undergoing first premolar extraction. The placement torque and screw mobility of each implant were determined using a torque tester and a Periotest device, and variability in these values in relation to sinus perforation was evaluated. Eight of the 82 miniscrews perforated the maxillary sinus. There was no case of sinusitis in patients with miniscrew perforation and no significant difference in screw mobility or placement torque between perforating and non-perforating miniscrews. The sinus floor was significantly thinner in perforated cases than in non-perforated cases. A sinus floor thickness of 6.0 mm or more is recommended in order to avoid miniscrew perforation of the maxillary sinus. PMID:26062857

  15. 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

  16. 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

  17. Effect of filler metal composition on the strength of yttria stabilized zirconia joints brazed with Pd-Ag-CuOx

    SciTech Connect

    Darsell, Jens T.; Weil, K. Scott

    2008-09-08

    The Ag-CuOx system is of interest to be used to be used as an air braze filler metal for joining high temperature electrochemical devices. Previous work has shown that the melting temperatures can be increased by adding palladium to Ag-CuOx and it is expected that this may aid high temperature stability. This work compares the room temperature bend strength of joints made between yttria-stabilized zirconia (YSZ) air brazed using Ag-CuOx without palladium and with 5 and 15mol% palladium additions. It has been found that in general palladium decreases joint strength, especially in low copper oxide compositions filler metals. At high copper oxide contents, brittle fracture through both copper oxide rich phases and the YSZ limits joint strength.

  18. Joint Adaptive Mean-Variance Regularization and Variance Stabilization of High Dimensional Data

    PubMed Central

    Dazard, Jean-Eudes; Rao, J. Sunil

    2012-01-01

    The paper addresses a common problem in the analysis of high-dimensional high-throughput “omics” data, which is parameter estimation across multiple variables in a set of data where the number of variables is much larger than the sample size. Among the problems posed by this type of data are that variable-specific estimators of variances are not reliable and variable-wise tests statistics have low power, both due to a lack of degrees of freedom. In addition, it has been observed in this type of data that the variance increases as a function of the mean. We introduce a non-parametric adaptive regularization procedure that is innovative in that : (i) it employs a novel “similarity statistic”-based clustering technique to generate local-pooled or regularized shrinkage estimators of population parameters, (ii) the regularization is done jointly on population moments, benefiting from C. Stein's result on inadmissibility, which implies that usual sample variance estimator is improved by a shrinkage estimator using information contained in the sample mean. From these joint regularized shrinkage estimators, we derived regularized t-like statistics and show in simulation studies that they offer more statistical power in hypothesis testing than their standard sample counterparts, or regular common value-shrinkage estimators, or when the information contained in the sample mean is simply ignored. Finally, we show that these estimators feature interesting properties of variance stabilization and normalization that can be used for preprocessing high-dimensional multivariate data. The method is available as an R package, called ‘MVR’ (‘Mean-Variance Regularization’), downloadable from the CRAN website. PMID:22711950

  19. 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.

  20. 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.

  1. Bioabsorbable Versus Metallic Screw Fixation for Tibiofibular Syndesmotic Ruptures: A Meta-Analysis.

    PubMed

    van der Eng, Dorien M; Schep, Niels W L; Schepers, Tim

    2015-01-01

    Ankle fractures with syndesmotic rupture require operative treatment. In most cases, this consists of fixation of the tibiofibular joint with 1 or more screws. Bioabsorbable screws are used for the same purpose but have the advantage that screw removal is unnecessary. The aim of the present study was to compare the results of bioabsorbable and metallic syndesmotic screws. A systematic search was performed in the Ovid MEDLINE electronic database and Google Scholar. Three randomized controlled trials and one comparison study, with 260 patients, were included. The experimental group consisted of patients with syndesmotic injuries treated with bioabsorbable screws versus the control group (patients treated with metallic screws). The primary outcomes were complications and wound infections. No statistically significant difference was demonstrable in the overall number of complications between the 2 groups. In the group of patients with a bioabsorbable screw, 32 of 137 (23.4%) experienced a complication versus 7 of 123 patients (5.7%) with a metallic screw. Data on wound-related complications showed no statistically significant difference, 19.7% versus 5.7%. The average maximum range of motion in both groups was comparable. Bioabsorbable syndesmotic screws and metallic syndesmotic screws were comparable with respect to the incidence of complications and range of motion. However, the absolute number of complications was greater with bioabsorbable screws. PMID:25960058

  2. 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

  3. 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.

  4. Comparison of arthroscopic anterior cruciate ligament reconstruction by bone-patellar tendon-bone graft with or without using interferential screw in general population.

    PubMed

    Arifeen, K N; Chowdhury, A Z; Sakeb, N; Joarder, A I; Salek, A K; Selimullah, A M

    2015-01-01

    Rupture of the Anterior Cruciate Ligament (ACL) is common, resulting reduced quality of life, increasing the meniscal injury risk, knee instability and early degenerative joint disease. Bone-Patellar Tendon-Bone (BPTB) became the gold standard surgery where conservative management failed. Adding interferential screw provides rigid fixation which is important for early accelerated rehabilitation program in athletes but we have carried out this prospective interventional study in Bangabandhu Sheikh Mujib Medical University (BSMMU) and our private settings from January 2007 to December 2011 to assess whether interferential screws provide any clinical and functional advantage in general population. Sixty six male patients of 21-40 years age, with ACL deficient knees were reconstructed with BPTB graft where 40 cases were augmented by interferential screws and 26 cases without and followed up for minimum 2 years. The clinical and functional outcome (by Lysholm Knee Scoring), post-operative knee stability (by clinical tests) and complications were assessed and recorded. There was significant (p<0.05, paired 't' test) improvement of knee function (limp, walking, stair climbing, squatting, thigh atrophy) in both groups but no significant difference between them (p>0.05, chi squared test) regarding clinical, functional outcome and knee stability. The complications were insignificant (p>0.05, chi squared test) in both groups but there were few cases of screw related complications with augmentation and pronounced anterior knee laxity without it. So, ACL reconstruction by BPTB grafts with or without augmentation results consistent and comparable outcome in general population. PMID:25725669

  5. 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

  6. 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.

  7. 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.

  8. Floating metatarsal: concomitant Lisfranc fracture-dislocation and complex dislocation of the first metatarsophalangeal joint.

    PubMed

    Leibner, E D; Mattan, Y; Shaoul, J; Nyska, M

    1997-03-01

    We describe a unique composite injury of the foot, with concomitant Lisfranc fracture-dislocation, and complex dislocation of the first metatarsophalangeal joint. When examining patients with Lisfranc joint injuries, one must keep in mind that the axial compression forces causing the injury may also damage the metatarsophalangeal joints, and direct attention to these structures. The reduction and stabilization of a "floating" first metatarsal should begin at the distal (metatarsophalangeal) end. The reduction of the distal dislocation will release tension on the plantar fascia, enabling the subsequent reduction of the proximal (Lisfranc) dislocation. A medial approach is convenient, affords easy access to the plantar and dorsal aspects of the joint, and repair of the medial joint structures when damaged. The use of screws for fixation of Lisfranc's fracture-dislocation, is well justified by the stability achieved. PMID:9095128

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

    PubMed

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

    1998-06-01

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

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

    PubMed

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

    2015-12-01

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

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

    PubMed

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

    2014-09-01

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

  12. Generating and stabilizing the Greenberger-Horne-Zeilinger state in circuit QED: Joint measurement, Zeno effect, and feedback

    SciTech Connect

    Feng Wei; Wang Peiyue; Ding Xinmei; Xu Luting; Li Xinqi

    2011-04-15

    In a solid-state circuit QED system, we extend the previous study of generating and stabilizing a two-qubit Bell state [Phys. Rev. A 82, 032335 (2010)] to a three-qubit GHZ state. In a dispersive regime, we employ the homodyne joint readout for multiple qubits to infer the state for further processing, and in particular we use it to stabilize the state directly by means of an alternate-flip-interrupted Zeno (AFIZ) scheme. Moreover, the state-of-the-art feedback action based on the filtered current enables not only a deterministic generation of the pre-GHZ state in the initial stage, but also a fast recovery from occasional error in the later stabilization process. We show that the proposed scheme can maintain the state with high fidelity if the efficient quantum measurement and rapid single-qubit rotations are available.

  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. 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.

  15. 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.

  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. 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.

  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. 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

  20. 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

  1. The pronator quadratus in motions and in stabilization of the radius and ulna at the distal radioulnar joint.

    PubMed

    Johnson, R K; Shrewsbury, M M

    1976-11-01

    Based upon the findings of dissections of 15 forearms and clinical observations in patients with disturbed architecture of the distal radioulnar joint, the pronator quadratus was found to be composed of two heads. A superficial head originated from the ulna and passed transversely to its insertion into the radius. It averaged 5.1 cm. in length, 4.5 cm. in width, 0.2 cm. in thickness, with a cross-sectional area of 0.95 cm.2 and a contractile volume of 2.6 cm.3. The deep head ran obliquely from a more proximal origin on the ulna to a distal insertion on the radius, with an average length of 4.0 cm., average width of 3.2 cm., and a thickness of 0.4 cm. Its average cross-sectional area was 1.64 cm.2 and its contractile volume 2.5 cm.3. A group of fibers occasionally was noted deep to both heads, running at right angles to them and paralleling the direction of the fibers of the interosseous membrane. The superficial head initiates pronation while the deep head coapts the joint surfaces and stabilizes the joint. PMID:1018088

  2. Comparison of Outcomes after Atlantoaxial Fusion with Transarticular Screws and Screw-Rod Constructs

    PubMed Central

    Kim, Ji Yong; Oh, Chang Hyun; Park, Hyeong-Chun; Seo, Hyun Sung

    2014-01-01

    Objective The purpose of this study was to compare the radiological and neurological outcomes between two atlantoaxial fusion method for atlantoaxial stabilization; C1 lateral mass-C2 pedicle screws (screw-rod constructs, SRC) versus C1-2 transarticular screws (TAS). Methods Forty-one patients in whom atlantoaxial instability was treated with atlantoaxial fixation by SRC group (27 patients, from March 2005 to May 2011) or TAS group (14 patients, from May 2000 to December 2005) were retrospectively reviewed. Numeric rating scale (NRS) for pain assessment, Oswestry disability index (ODI), and Frankel grade were also checked for neurological outcome. In radiologic outcome assessment, proper screw position and fusion rate were checked. Perioperative parameters such as blood loss during operation, operation time, and radiation exposure time were also reviewed. Results The improvement of NRS and ODI were not different between both groups significantly. Good to excellent response in Frankel grade is shown similarly in both groups. Proper screw position and fusion rate were also observed similarly between two groups. Total bleeding amount during operation is lesser in SRC group than TAS group, but not significantly (p=0.06). Operation time and X-ray exposure time were shorter in SRC group than in TAS group (all p<0.001). Conclusion Both TAS and SRC could be selected as safe and effective treatment options for C1-2 instability. But the perioperative result, which is technical demanding and X-ray exposure might be expected better in SRC group compared to TAS group. PMID:25132931

  3. 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

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

    PubMed

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

    2015-12-01

    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

  5. Carbon nanotube Archimedes screws.

    PubMed

    Oroszlány, László; Zólyomi, Viktor; Lambert, Colin J

    2010-12-28

    Recently, nanomechanical devices composed of a long stationary inner carbon nanotube and a shorter, slowly rotating outer tube have been fabricated. In this paper, we study the possibility of using such devices as nanoscale transducers of motion into electricity. When the outer tube is chiral, we show that such devices act like quantum Archimedes screws, which utilize mechanical energy to pump electrons between reservoirs. We calculate the pumped charge from one end of the inner tube to the other, driven by the rotation of a chiral outer nanotube. We show that the pumped charge can be greater than one electron per 360° rotation, and consequently, such a device operating with a rotational frequency of 10 MHz, for example, would deliver a current of ≈1 pAmp. PMID:21126086

  6. 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.

  7. Spline screw autochanger

    NASA Astrophysics Data System (ADS)

    Vranish, John M.

    1993-06-01

    A captured nut member is located within a tool interface assembly and being actuated by a spline screw member driven by a robot end effector. The nut member lowers and rises depending upon the directional rotation of the coupling assembly. The captured nut member further includes two winged segments which project outwardly in diametrically opposite directions so as to engage and disengage a clamping surface in the form of a chamfered notch respectively provided on the upper surface of a pair of parallel forwardly extending arm members of a bifurcated tool stowage holster which is adapted to hold and store a robotic tool including its end effector interface when not in use. A forward and backward motion of the robot end effector operates to insert and remove the tool from the holster.

  8. Split spline screw

    NASA Astrophysics Data System (ADS)

    Vranish, John M.

    1993-11-01

    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.

  9. Technique using interference fixation repair for plantar plate ligament disruption of lesser metatarsophalangeal joints.

    PubMed

    Sung, Wenjay

    2015-01-01

    Lesser metatarsophalangeal joint instability is a challenging disorder for the foot and ankle surgeon to repair. We believe that disruption of the plantar plate is common, and its repair should be carefully considered. However, we believe that most current techniques inadequately address repair of the complete plantar plate ligament tear, and, thus, instability and pain commonly persist after disruption of the plantar plate. In the present report, we present a technique we have found useful for repair of a complete plantar plate ligament rupture. The method we have described uses interference screw fixation through a dorsal incision to stabilize the lesser metatarsophalangeal joint. PMID:24973038

  10. 21 CFR 888.3070 - Pedicle screw spinal system.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 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....

  11. 21 CFR 888.3070 - Pedicle screw spinal system.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 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....

  12. 21 CFR 888.3070 - Pedicle screw spinal system.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 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....

  13. 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....

  14. Stability of Boolean networks: the joint effects of topology and update rules.

    PubMed

    Squires, Shane; Pomerance, Andrew; Girvan, Michelle; Ott, Edward

    2014-08-01

    We study the stability of orbits in large Boolean networks. We treat the case in which the network has a given complex topology, and we do not assume a specific form for the update rules, which may be correlated with local topological properties of the network. While recent past work has addressed the separate effects of complex network topology and certain classes of update rules on stability, only crude results exist about how these effects interact. We present a widely applicable solution to this problem. Numerical simulations confirm our theory and show that local correlations between topology and update rules can have profound effects on the qualitative behavior of these systems. PMID:25215788

  15. 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 translational motion at the joint compared with the IAR. An IAR resulted in the most translational motion at the glenohumeral joint. This demonstrates the biomechanical importance of performing an osteoallograft repair in which the allograft closely matches the Hill-Sachs defect and fully restores the preinjury state of the humeral head. Clinical Relevance: This study demonstrates the importance of performing an osteoallograft repair of a Hill-Sachs defect that closely matches the preinjury state and restores normal humeral head anatomy. PMID:27231698

  16. 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.

  17. A finite element analysis of two novel screw designs for scaphoid waist fractures.

    PubMed

    Varga, Peter; Zysset, Philippe K; Schefzig, Philip; Unger, Ewald; Mayr, Winfried; Erhart, Jochen

    2016-02-01

    The scaphoid is the most often fractured carpal bone. Scaphoid fracture repair with a headless compression screw allows for early functional recovery. The rotational stability of a single screw may be limited, having a potential negative impact on the healing process. Two novel screws have been designed to provide improved rotational stability compared to the existing ones. Using a computational finite element model of a scaphoid osteotomy, we compared the efficacy of one simple screw and the two new screws in restricting inter-fragmentary motion (IFM) in three functional positions of the wrist and as a function of inter-fragmentary compression force. The in-plane IFM was primary rotational and was better restricted by the new screws compared to the conventional one when the inter-fragmentary compression force was below 15-20 N, but provided no clear benefit in total flexion independently of the compression force. To better understand the differences in the non-compressed case, we analyzed the acting moments and investigated the effects of the bending and torsional screw stiffness on IFM. By efficiently restricting the inter-fragmentary shear, the new screws may be clinically advantageous when the inter-fragmentary compression force is partially or completely lost and may provide further benefits toward earlier and better healing of transverse waist fractures of the scaphoid. PMID:26654577

  18. 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

  19. Intramedullary screw fixation for midshaft fractures of the clavicle

    PubMed Central

    2009-01-01

    Open intramedullary fixation of 37 fresh midshaft clavicular fractures in 35 patients was performed using a 6.5 partially threaded cancellous screw. Mean age was 38 years (range 18–65). The screw was inserted from the medial fragment after retrograde drilling of that fragment. Average follow-up period was 21 months (range 9–36). Radiological evidence of union was apparent in all cases within six to eight weeks after surgery (mean 7.8). Two cases had intraoperative failure of fixation, nine complained of subcutaneous prominence of the screw head, five experienced decreased sensation over the site of incision, and three had symptoms of frozen shoulder. In conclusion, the technique is simple, affordable and it does not require special instrumentation or implants. It allows intramedullary compression, stability, stress sharing, minimal periosteal stripping, and early recovery after surgery. PMID:19225778

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

    PubMed

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

    2016-03-01

    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. [Orthopedics. 2016; 39(2):e253-e258.]. PMID:26840700

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

    PubMed

    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 a common physiological repertoire used to improve motor performance. PMID:27014116

  2. 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 a common physiological repertoire used to improve motor performance. PMID:27014116

  3. 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

  4. The long-term stability of metallic materials for use in joint endoprostheses.

    PubMed

    Thull, R

    1977-09-29

    In orthopedic implants, metals are permanently incorporated into bones and tissue. Usually the metals are not in the electrochemical equilibrium state immediately after implantation. The metal oxide forms itself only after hours up to weeks. In the meantime the metal releases ions into the tissue, much more than in the equilibrium state. On the other hand a passive layer can interchange mechanically with bones and implanted components. The resulting destruction of the surface leads equally to an increasing release of ions. As a consequence of these facts, perfect metals for application in implants must have a short repassivation period and mechanically indestructible surface oxides. To what extent the applied metals perform these conditions is tested for the stainless steel type 316 L, the multiphase alloy MP-35 N and TiAIV. A comparison of the rates of corrosion resulting from damage to, or destruction of, the passivating oxide layers, with the rates that can occur in connection with local forms of corrosion, shows that in joint implants, it is merely the repassivation properties of the metals employed that determine the concentration of ions in the tissue. PMID:927392

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

    PubMed

    de Almeida, V L; de S Vitorino, N; de O Nascimento, A L; 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

  6. 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

  7. 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.

  8. 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

  9. 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

  10. Transverse lag screw fixation in midline mandibulotomy. A case series.

    PubMed

    Serletti, J M; Pacella, S J; Coniglio, J U; Norante, J D

    2000-03-01

    Vertical midline mandibulotomy has provided a relatively simple and efficient means of obtaining access to intraoral tumors that are too large or too posterior to be removed transorally. Midline mandibulotomy has had the advantage of nerve and muscle preservation and places the osteotomy outside the typical field of radiotherapy, in contrast to lateral and paramedian osteotomies. Plate and screw fixation has been the usual means of osteosynthesis for these mandibulotomies; however, plate contouring over the symphyseal surface has been a time-consuming process. Unless the plate was contoured exactly, mandibular malalignment and malocclusion in dentulous patients has occurred. Use of parallel transverse lag screws has become a popular method of osteosynthesis for parasymphyseal fractures, and we have extended their use for mandibulotomy fixation. This paper reports our clinical experience with transverse lag screw fixation of midline mandibulotomies in 9 patients from 1994 to 1997. There were 7 men and 2 women with a mean age of 56 (range 35 to 71 years). The pathological diagnosis in all patients was squamous cell carcinoma; 8 cases were primary, and 1 patient presented with recurrent tumor. No tumors involved the mandibular periosteum. One patient had had previous radiotherapy, and 3 patients underwent postoperative radiotherapy. The mean follow-up has been 17 months (range 9 to 27). There was 1 minor complication and 1 major complication related to our technique. The major complication was a delayed nonunion of the mandibulotomy. This occurred because the 2 parallel screws were placed too close to one another, and this placement resulted in a delayed sagittal fracture of the anterior cortex and subsequent nonunion. Transverse lag screw fixation has not affected occlusion in our dentulous patients. Speech and diet were normal in the majority of our patients. Transverse lag screw fixation of the midline mandibulotomy has been a relatively safe, rapid, and reliable method for tumor access and postextirpation mandibular stabilization and has significant advantages over other current methods of mandibulotomy and fixation. PMID:10737321

  11. 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

  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. 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

  14. 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.

  15. 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

  16. Influence of micro- and nano-hydroxyapatite coatings on the osteointegration of metallic (Ti6Al4 V) and bioabsorbable interference screws: an in vivo study.

    PubMed

    Aksakal, B; Kom, M; Tosun, H B; Demirel, M

    2014-07-01

    The purpose of this study is to show and compare the fixation and osteointegration capability of metallic and bioabsorbable interference screws. For this, 8×20-mm interference screws were implanted into the bone tunnel in the proximal tibial metaphysis of sheep. The nano- (25 nm±0.8) and microscale (25 μm±0.5) hydroxyapatite were both dip-coated on Ti6Al4 V interference screws via an in vivo study. After the initial 12 weeks of postoperative, the pullout test, histopathology, X-ray diffraction and scanning electron microscopy examinations were performed. This multidisiplined work showed that the coated screws particularly those with nano-sized-HA coating and the bioabsorbable screws enhanced fixation and provided better stabilization, bone ingrowth and osteointegration than that of uncoated and microscale HA-coated screws. The bioabsorbable screws showed better histopathologic results. PMID:23689912

  17. 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.

  18. 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

  19. 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

  20. 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

  1. The Function of the Distal Interosseous Membrane and its Relevance to the Stability of the Distal Radioulnar Joint: An Anatomical and Biomechanical Review.

    PubMed

    Moritomo, H

    2015-10-01

    The purpose of this article is to review functional anatomy and biomechanics of the distal interosseous membrane (DIOM) and its relevance to the stability of the distal radioulnar joint. The intact DIOM constrained dorsal dislocation of the radius, but it seldom constrained palmar dislocation. A residual ulnar translation deformity of the radial shaft in distal radius fractures has the potential to cause the distal radioulnar joint instability when the triangular fibrocartilage complex injury is also present, because it may result in detensioning of DIOM. Ulnar shortening with the osteotomy performed proximal to the attachment of the DIOM had a more favorable effect on stability of the DRUJ compared with the effect of distal osteotomy, especially in the presence of the distal oblique bundle (DOB). The longitudinal resistance to ulnar shortening was significantly greater in proximal shortening than in distal shortening. PMID:25938817

  2. An anterior high cervical retropharyngeal approach for C1-C2 intrafacetal fusion and transarticular screw insertion.

    PubMed

    Kansal, Ritesh; Sharma, Alok; Kukreja, Sanjay

    2011-12-01

    Craniovertebral instability is a significant challenge to neurosurgeons. We describe an alternative anterior high cervical retropharyngeal approach for C1-C2 intrafacetal fusion and transarticular screw insertion. We dissected 10 cadaveric specimens and fixed the atlantoaxial joint with C1-C2 intrafacetal fusion and transarticular screw insertion. We achieved good surgical exposure and fixation in all cadavers with this technique. The anterior high cervical retropharyngeal approach for C1-C2 intrafacetal fusion and transarticular screw insertion may provide an alternative fusion technique for craniovertebral fusion. PMID:22015103

  3. 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

  4. 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.

  5. 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.

  6. 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.

  7. 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

  8. 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

  9. 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.

  10. Automated surgical screwdriver: automated screw placement.

    PubMed

    Thomas, R L; Bouazza-Marouf, K; Taylor, G J S

    2008-07-01

    The use of power screwdrivers and drills for tapping and screw insertion in surgery is becoming more common. It has been established from clinical observations that the use of a small air drill for inserting self-tapping screws provides improved coaxial alignment and precision, and that the drill should be stopped before the screw head is completely seated on the plate, presumably to reduce the risk of over-tightening. The risk of overrun and over-tightening during tapping and screw insertion is increased with the use of power tools. Prevention of over-tightening is dependent upon when the surgeon detects the onset of tightening, both visually and from the feel of the rapid increase in torque. If detection is too late, then over-tightening or stripping can occur. This study is concerned with using a mechatronic screwdriver to control the tapping depth and to prevent the over-tightening of screws. The effects of various parameters upon the torque profile during tapping and screw insertion have been investigated in synthetic bone and sheep tibia. An automated system is proposed for preventing over-tightening of pre-tapped and self-tapping screws when attaching a surgical plate to a sheep tibia in vitro. The system was used to attach a plate to a sheep tibia using self-tapping screws. The mean torque of the screws inserted using the automated system was 35 per cent of the stripping torque. PMID:18756698

  11. Technical factors related to the incidence of adjacent superior segment facet joint violation after transpedicular instrumentation in the lumbar spine.

    PubMed

    Chen, Zhiming; Zhao, Jie; Xu, Hao; Liu, Aigang; Yuan, Jiandong; Wang, Cong

    2008-11-01

    Segmental pedicle screw fixation is rapidly becoming a popular method of spinal instrumentation. Few studies have investigated the rates of adjacent superior segment facet joint violation. The purpose of our study were to investigate the incidence of superior segment facet joint violation after pedicle screw instrumentation in the lumbar spine and to evaluate technical factors related to the incidence. A prospective study including 96 patients who underwent lumbar and lumbosacral fusion was conducted between March 2006 and December 2007. All patients had bilateral or unilateral posterior pedicle screw-rod instrumentation with either CD-Horizon (top-loading screw) or TSRH (side-connecting screw) implants. Pedicle screws were instrumented according to the methods advocated by Roy-Camille (Group 1, 20 cases) or Weinstein (Group 2, 76 cases). All patients had computed tomography scan at 1 week post operation. CT scans were reviewed blind by an experienced spine research fellow and a consultant radiologist to determine violation of the adjacent superior segment facet joint. Superior segment facet joint violation occurred in all of the 20 patients (100%) and all of the top-level screws (100%) in Group 1. The spinal research fellow noted the incidence of facet joint violation to be present in 23.8% of the screws and 32.9% of the patients in Group 2, whereas the consultant radiologist noted this to be the case in 25.2 and 35.5%, respectively. The incidence of facet joint violation in patients with CD-Horizon screws was far lower than patients with TSRH screws (P < 0.001). In conclusion, it seems that meticulous surgical dissection without injuring the top-level facet joints, proper instrumentation of pedicle screws with the appropriate entry site (Weinstein's method), trajectory, and use of top-loading screw heads are some ways that surgeons could minimize the risk of top-level facet joint violation. PMID:18795343

  12. Screw insertion in trabecular bone causes peri-implant bone damage.

    PubMed

    Steiner, Juri A; Ferguson, Stephen J; van Lenthe, G Harry

    2016-04-01

    Secure fracture fixation is still a major challenge in orthopedic surgery, especially in osteoporotic bone. While numerous studies have investigated the effect of implant loading on the peri-implant bone after screw insertion, less focus has been put on bone damage that may occur due to the screw insertion process itself. Therefore, the aim of this study was to localize and quantify peri-implant bone damage caused by screw insertion. We used non-invasive three-dimensional micro-computed tomography to scan twenty human femoral bone cores before and after screw insertion. After image registration of the pre- and post-insertion scans, changes in the bone micro-architecture were identified and quantified. This procedure was performed for screws with a small thread size of 0.3mm (STS, N=10) and large thread size of 0.6mm (LTS, N=10). Most bone damage occurred within a 0.3mm radial distance of the screws. Further bone damage was observed up to 0.6mm and 0.9mm radial distance from the screw, for the STS and LTS groups, respectively. While a similar amount of bone damage was found within a 0.3mm radial distance for the two screw groups, there was significantly more bone damage for the LTS group than the STS group in volumes of interest between 0.3-0.6mm and 0.6-0.9mm. In conclusion, this is the first study to localize and quantify peri-implant bone damage caused by screw insertion based on a non-invasive, three-dimensional, micro-CT imaging technique. We demonstrated that peri-implant bone damage already occurs during screw insertion. This should be taken into consideration to further improve primary implant stability, especially in low quality osteoporotic bone. We believe that this technique could be a promising method to assess more systematically the effect of peri-implant bone damage on primary implant stability. Furthermore, including peri-implant bone damage due to screw insertion into patient-specific in silico models of implant-bone systems could improve the accuracy of these models. PMID:26920074

  13. 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

  14. 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

  15. 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

  16. 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

  17. Twin-Screw Extruders in Ceramic Extrusion

    NASA Astrophysics Data System (ADS)

    Wiedmann, Werner; Hölzel, Maria

    The machines mainly used for compounding plastics, chemicals and food are co-rotating, closely intermeshing twin-screw extruders. Some 30 000 such extruders are in use worldwide, about 1/3 are ZSKs from Coperion Werner & Pfleiderer, Stuttgart. In the chemical industry more and more batch mixers are being replaced by continuous twin-screw kneaders.

  18. Antegrade-retrograde opposing lag screws for internal fixation of simple displaced talar neck fractures.

    PubMed

    Abdelkafy, Ashraf; Imam, Mohamed Abdelnabi; Sokkar, Sherif; Hirschmann, Michael

    2015-01-01

    The talar neck is deviated medially with reference to the long axis of the body of the talus. In addition, it deviates plantarward. The talar neck fracture line is sometimes observed to be oriented obliquely (not perpendicular to the long axis of the talar neck). This occurs when the medially deviated talar neck strikes the horizontally oriented anterior lower tibial edge. Internal fixation of a simple displaced talar neck fracture usually requires 2 lag screws. Because the fracture line is obliquely oriented, a better method for positioning the screws perpendicular to the fracture line is to place them in a reversed direction to provide maximum interfragmentary compression at the fracture site, which could increase the likelihood of absolute stability with subsequent improvement in the incidence of fracture union and a reduction of complications, such as avascular necrosis of the body of the talus. Two lag screws are used, with the first inserted from posteriorly to anteriorly (perpendicular to the fracture line) using a medial approach after medial malleolar chevron osteotomy. The second screw is inserted from anteriorly to posteriorly (perpendicular to the fracture line) using an anterolateral approach. Both screw heads should be countersunk. A series of 8 patients underwent this form of internal fixation for talar neck fracture repair, with satisfactory functional outcomes. In conclusion, the use of antegrade-retrograde opposing lag screws is a reasonable method of internal fixation for simple displaced talar neck fractures. PMID:25459087

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

    PubMed

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

    2016-03-01

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

  20. 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

  1. [Total joint arthroplasty].

    PubMed

    Mibe, Junya; Yamamoto, Kengo

    2013-07-01

    Control of the disease activity is enabled due to the progress of drug therapy for rheumatoid arthritis. However, surgical treatments are necessary for unresponsive cases to the drug or for achieving higher QOL, and we can attain more tight control or cure by combination of drug therapy and surgical treatments. Total joint arthroplasty provides indolence, mobility, stability and is an useful joint reconstruction method. Shoulder and elbow joint work as a reach function together, and total joint arthroplasty become adaptation when extensive joint destruction or severe pain occurrs. With the usage of biologic agents joint repair is possible in small joints, but if the joint destruction progress in weight-bearing joints, repair is impossible and total joint arthroplasty can be required. PMID:23961679

  2. Techniques and accuracy of thoracolumbar pedicle screw placement

    PubMed Central

    Puvanesarajah, Varun; Liauw, Jason A; Lo, Sheng-fu; Lina, Ioan A; Witham, Timothy F

    2014-01-01

    Pedicle screw instrumentation has been used to stabilize the thoracolumbar spine for several decades. Although pedicle screws were originally placed via a free-hand technique, there has been a movement in favor of pedicle screw placement with the aid of imaging. Such assistive techniques include fluoroscopy guidance and stereotactic navigation. Imaging has the benefit of increased visualization of a pedicle’s trajectory, but can result in increased morbidity associated with radiation exposure, increased time expenditure, and possible workflow interruption. Many institutions have reported high accuracies with each of these three core techniques. However, due to differing definitions of accuracy and varying radiographic analyses, it is extremely difficult to compare studies side-by-side to determine which techniques are superior. From the literature, it can be concluded that pedicles of vertebrae within the mid-thoracic spine and vertebrae that have altered morphology due to scoliosis or other deformities are the most difficult to cannulate. Thus, spine surgeons would benefit the most from using assistive technologies in these circumstances. All other pedicles in the thoracolumbar spine should theoretically be cannulated with ease via a free-hand technique, given appropriate training and experience. Despite these global recommendations, appropriate techniques must be chosen at the surgeon’s discretion. Such determinations should be based on the surgeon’s experience and the specific pathology that will be treated. PMID:24829874

  3. 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

  4. Biomechanical Comparison of Osteoporotic Distal Radius Fractures Fixed by Distal Locking Screws with Different Length

    PubMed Central

    Liu, Xiong; Wu, Wei-dong; Fang, Ya-feng; Zhang, Mei-chao; Huang, Wen-hua

    2014-01-01

    Objectives To evaluate the postoperative stability of osteoporotic distal radius fractures fixed with distal locking screws with different length. Methods A comminuted extra-articular dorsally unstable distal radius fracture, treated with volar locking plate system, was created. The 18 specimens were randomized into 3 groups based on distal locked screws with different length: Group A had unicortical screws with 50% length to the dorsal cortex. Group B had unicortical screws with 75% length to the dorsal cortex. Group C had bicortical screws. Axial compression and bending loads were imposed on the models before and after cycling testing as well as load to clinical and catastrophic failure. Results Minimum change in stiffness was observed before and after fatigue for all groups. The final stiffness to bending forces was statistically similar in all groups, but stiffness to axial compression was statistically significant different: Group A approached significance with respect to groups B and C (P = 0.017, 0.009), whereas stiffness in group B and C was statistically similar (P = 0.93). Load to clinical failure was significantly less for group A (456.54±78.59 N) compared with groups B (580.24±73.85 N) and C (591.07±38.40 N). Load to catastrophic failure was statistically similar between groups, but mean values for Group A were 18% less than means for Group C. Conclusions The volar locking plate system fixed with unicortical locking screws with at least 75% length not only produced early stability for osteoporotic distal radius fractures, but also avoided extensor tendon complications due to dorsal screw protrusion. PMID:25080094

  5. Clinical and radiological comparison of treatment of atlantoaxial instability by posterior C1-C2 transarticular screw fixation or C1 lateral mass-C2 pedicle screw fixation.

    PubMed

    Lee, Sun-Ho; Kim, Eun Sang; Sung, Joo-Kyung; Park, Yeun-Mook; Eoh, Whan

    2010-07-01

    We compared the clinical and radiological results of posterior atlantoaxial fixation surgery using transarticular screws to those using a polyaxial screw-rod system in 55 patients with symptomatic atlantoaxial instability. Patients underwent posterior C1-C2 fixation: 28 patients (group 1) underwent C1-C2 transarticular screw fixation and 27 patients (group 2) underwent C1 lateral mass-C2 pedicle screw fixation. Patients were followed-up for at least 24 months. The clinical and radiological results were evaluated in the early postoperative period and at 3, 6, 12 and 24 months after surgery. Long-term postoperative stability and bone fusion were examined. After surgery, 93% of patients in group 1 and 96% of patients in group 2 were free of neck pain. The solid fusion rates were 82% for group 1 patients and 96% for group 2 patients at 12 months (p<0.092). In group 1, three patients showed fibrous union. Four patients had hardware failure due to a screw malposition (one in group 1) and pseudoarthrodesis (two in group 1 and one in group 2). One patient in group 1 had cerebrospinal fluid leakage. One patient in group 2 had occipital neuralgia. One vertebral artery injury occurred during the screw placement in group 1 and another in group 2 during the muscle dissection. C1-C2 transarticular screw fixation and C1 lateral mass-C2 pedicle screw fixation both produced excellent results for stabilization of the atlantoaxial complex, but the radiological outcome tended to be superior in C1 lateral mass-C2 pedicle screw fixation. PMID:20399666

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

    PubMed Central

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

    2015-01-01

    Objective Pedicle screw fixation for spine arthrodesis is a useful procedure for the treatment of spinal disorders. However, instrument failure often occurs, and pedicle screw loosening is the initial step of a range of complications. The authors recently used a modified transpedicular polymethylmethacrylate (PMMA) screw augmentation technique to overcome pedicle screw loosening. Here, they report on the laboratory testing of pedicle screws inserted using this modified technique. Methods To evaluate pullout strengths three cadaveric spinal columns were used. Three pedicle screw insertion methods were utilized to compare pullout strength; the three methods used were; control (C), traditional transpedicular PMMA augmentation technique (T), and the modified transpedicular augmentation technique (M). After control screws had been pulled out, loosening with instrument was made. Screw augmentations were executed and screw pullout strength was rechecked. Results Pedicle screws augmented using the modified technique for pedicle screw loosening had higher pullout strengths than the control (1106.2±458.0 N vs. 741.2±269.5 N; p=0.001). Traditional transpedicular augmentation achieved a mean pullout strength similar to that of the control group (657.5±172.3 N vs. 724.5±234.4 N; p=0.537). The modified technique had higher strength than the traditional PMMA augmentation technique (1070.8±358.6 N vs. 652.2±185.5 N; p=0.023). Conclusion The modified PMMA transpedicular screw augmentation technique is a straightforward, effective surgical procedure for treating pedicle screw loosening, and exhibits greater pullout strength than traditional PMMA transpedicular augmentation. However, long-term clinical evaluation is required. PMID:25932288

  7. Effect of Filler Metal Composition on the Strength of Yttria Stabilized Zirconia Joints Brazed with Pd-Ag-CuO x

    NASA Astrophysics Data System (ADS)

    Darsell, Jens T.; Weil, K. Scott

    2008-09-01

    Various compositions in the Ag-CuO x system are being investigated as potential filler metals for use in air brazing high-temperature electrochemical devices such as solid oxide fuel cells and gas concentrators. Prior work has shown that the melting temperature, and therefore the potential operational temperature, of these materials can be increased by alloying with palladium. The current study examines the effects of palladium addition on the joint strength of specimens prepared from yttria stabilized zirconia (YSZ) bars brazed with three different families of filler metals: Ag-CuO, 5Pd-Ag-CuO, and 15Pd-Ag-CuO. In general, it was found that palladium leads to a small-to-moderate decrease in joint strength, particularly in low copper oxide containing filler metals. However, the declination in strength is likely an acceptable trade-off for increased use temperature. In addition, a critical composition was observed for each filler metal series at which the mechanism for joint failure underwent a transition, typically from ductile to brittle failure. In each case, this composition corresponds approximately to the silver-rich boundary composition of the liquid miscibility gap in each system at the temperature of brazing.

  8. 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.

  9. New permanent magnet couplings for screwing devices

    NASA Astrophysics Data System (ADS)

    Quellec, L.; Lemarquand, V.; Lemarquand, G.

    1998-06-01

    The use of permanent magnet coaxial synchronous couplings in screwing devices allows one to adjust the screwing torque very precisely, but the symmetrical behavior of classical systems always leads to a partial unscrewing. This article shows that the dissymmetry of this behavior can be enhanced only by the modification of the shape of the magnets stuck on the rotors. The consideration of some basic geometrical parameters (number and length of poles) and the application of rules to reach the dissymmetry lead to improved couplings for screwing devices.

  10. Joint Stability Characteristics of the Ankle Complex After Lateral Ligamentous Injury, Part I: A Laboratory Comparison Using Arthrometric Measurement

    PubMed Central

    Kovaleski, John E.; Heitman, Robert J.; Gurchiek, Larry R.; Hollis, J. M.; Liu, Wei; IV, Albert W. Pearsall

    2014-01-01

    Context: The mechanical property of stiffness may be important to investigating how lateral ankle ligament injury affects the behavior of the viscoelastic properties of the ankle complex. A better understanding of injury effects on tissue elastic characteristics in relation to joint laxity could be obtained from cadaveric study. Objective: To biomechanically determine the laxity and stiffness characteristics of the cadaver ankle complex before and after simulated injury to the anterior talofibular ligament (ATFL) and calcaneofibular ligament (CFL) during anterior drawer and inversion loading. Design: Cross-sectional study. Setting: University research laboratory. Patients or Other Participants: Seven fresh-frozen cadaver ankle specimens. Intervention(s): All ankles underwent loading before and after simulated lateral ankle injury using an ankle arthrometer. Main Outcome Measure(s): The dependent variables were anterior displacement, anterior end-range stiffness, inversion rotation, and inversion end-range stiffness. Results: Isolated ATFL and combined ATFL and CFL sectioning resulted in increased anterior displacement but not end-range stiffness when compared with the intact ankle. With inversion loading, combined ATFL and CFL sectioning resulted in increased range of motion and decreased end-range stiffness when compared with the intact and ATFL-sectioned ankles. Conclusions: The absence of change in anterior end-range stiffness between the intact and ligament-deficient ankles indicated bony and other soft tissues functioned to maintain stiffness after pathologic joint displacement, whereas inversion loading of the CFL-deficient ankle after pathologic joint displacement indicated the ankle complex was less stiff when supported only by the secondary joint structures. PMID:24568232

  11. Comparison of pullout strength of the thoracic pedicle screw between intrapedicular and extrapedicular technique: a meta-analysis and literature review

    PubMed Central

    Wang, Hua; Wang, Huafeng; Sribastav, Shilabant Sen; Ye, Fubiao; Liang, Chunxiang; Li, Zemin; Wang, Jianru; Liu, Hui; Wang, Xin; Zheng, Zhaomin

    2015-01-01

    Background: Intrapedicular fixation in thoracic spine is often limited, because of high risk of complication, especially in scoliosis patients. Extrapedicular screws fixation techniques provide an alternate solution for extremely small or abnormal thoracic pedicles deformity. However, the pullout resistance of extrapedicular screws has not been clearly defined. The aim of our study was to systematically review the existing evidence regarding the pullout resistance of thoracic extrapedicular screws compared with intrapedicular screws. Methods: A systematic search of all studies published through Nov 2014 was performed using Medline, EMBASE, OVID and other databases. All studies that compared the pullout resistance of thoracic extrapedicular screws with intrapedicular screws were selected. The data from the included studies were extracted and analyzed regarding pullout resistance force. Forest plots were constructed to summarize the data and compare the biomechanical stability achieved. Results: Five studies were included, with a total of 27 cadaveric specimens and 313 screws. The vertebral levels of the cadavers potted were T1-T8, T2-T12, T7-T9, T6-T11 and T4-T12 respectively. Overall, the results demonstrated that there was no significant difference in ultimate pullout strength between intrapedicular screws and extrapedicular screws (95% CI=-63.73 to 27.74; P=0.44); extrapedicular screws significantly increased the length of placements by a mean of 6.24 mm (95% CI=5.38 to 7.10; P<0.001); while the stiffness in intrapedicular screws was significantly stronger by a mean of 45.82 N/mm compared with extrapedicular screws (95% CI=-70.09 to -21.56; P<0.001). Conclusions: Meta-analysis of the existing literature showed that thoracic extrapedicular screws provided comparable but slightly lower pullout strength compared with intrapedicular screws, extrapedicular screws placement is much safer than intrapedicular screws. So thoracic extrapedicular screws offer a good alternative when it is hard to insert by intrapedicular approach, especially in scoliosis patients with severe vertebral deformities. PMID:26885199

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

    PubMed

    Cornelius, Carl-Peter; Ehrenfeld, Michael

    2010-06-01

    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

  13. 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

  14. Comparison between Bilateral C2 Pedicle Screwing and Unilateral C2 Pedicle Screwing, Combined with Contralateral C2 Laminar Screwing, for Atlantoaxial Posterior Fixation

    PubMed Central

    Hongo, Michio; Kobayashi, Takashi; Suzuki, Tetsuya; Abe, Eiji; Shimada, Yoichi

    2014-01-01

    Study Design A retrospective study. Purpose To compare clinical and radiological outcomes between bilateral C2 pedicle screwing (C2PS) and unilateral C2PS, combined with contralateral C2 laminar screwing (LS), for posterior atlantoaxial fixation. Overview of Literature Posterior fixation with C1 lateral mass screwing (C1LMS) and C2PS (C1LMS-C2PS method) is an accepted procedure for rigid atlantoaxial stabilization. However, conventional bilateral C2PS is not always allowed in this method due to anatomical variations of C2 pedicles and/or asymmetry of the vertebral artery. Although unilateral C2PS plus contralateral LS (C2PS+LS) is an alternative in such cases, the efficacy of this procedure has not been evaluated in controlled studies (i.e., with bilateral C2PS as a control). Methods Clinical and radiological records of patients who underwent the C1LMS-C2PS method, using unilateral C2PS+LS (n=9), and those treated using conventional bilateral C2PS (n=10) were compared, with a minimum two years follow-up. Results Postoperative complications related to the unilateral C2PS+LS technique included one case of spontaneous spinous process fracture of C2. A C1 anterior arch fracture occurred after a fall in one patient, who underwent bilateral C2PS and C1 laminectomy. No significant differences were seen between the groups in reduction of neck pain after surgery or improvement of neurological status, as evaluated using the Japanese Orthopaedic Association score. A delayed union occurred in one patient each of the groups, with the final fusion rate being 100% in both groups. Conclusions Clinical and radiological outcomes of unilateral C2PS+LS were comparable with those of the bilateral C2PS fixation technique for the C1LMS-C2PS method. PMID:25558320

  15. 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.

  16. Transarticular screw fixation for osteoarthritis of the atlanto axial segment.

    PubMed

    Grob, Dieter; Bremerich, Friedrich H; Dvorak, Jiri; Mannion, Anne F

    2006-03-01

    Atlantoaxial (C1-C2) facet joint osteoarthitis is a distinct clinical syndrome that often goes unrecognized. Severe pain resistant to conservative treatment that is corroborated by the radiographic findings represents the indication for surgery. The aim of this study was to retrospectively examine the long-term outcome [after an average 6.5 years (SD 4.0)] of C1-2 fusion for osteoarthritis of the atlantoaxial segment in 35 consecutive patients [25 male, 10 female; aged 62 (SD 15) years]. At follow-up, clinical outcome and radiological status was examined in 27/35 (77%) patients, and self-rated pain and disability (Neck Pain and Disability Scale; NPDS) in 29/35 (83%) patients. In 27/35 patients (77%), 2 screws were inserted; in 7 patients (20%), only 1 screw; and in 1 patient (3%), no screws. 11% of the patients had late complications requiring revision surgery. All patients showed solid fusion at the long-term follow-up. 26% patients showed an improvement in sensory disturbances, 63% no change, and 11% a worsening. 89% were pain-free or had markedly reduced pain. The average score on the NPDS (0-100) was 34 (SD 27), representing 'mild' neck problems, and the average pain intensity (0-5 VAS) was 1.5 (SD 1.5). Eighty-five percent of the patients declared that they would make the same decision again to undergo surgery. In conclusion, in a group of patients with a painful and debilitating degenerative disorder of C1-2, posterior transarticular atlantoaxial fusion proved to be an effective treatment with a low rate of serious complications. PMID:15968527

  17. 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.

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

    PubMed

    Benzel, E C; Baldwin, N G

    1995-01-01

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

  19. 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 ...

  20. 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.

  1. 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.

  2. Mechanical and thermomechanical stability issues of 96.5SN-3.5AG solder joints in microelectronic packages

    NASA Astrophysics Data System (ADS)

    Yang, Hong

    Flip chip technology is the ultimate solution for high performance and high density chip level interconnection. This thesis describes the investigation of using eutectic 96.5Sn-3.5Ag solder for flip chip applications. The principal components of the research include mechanical characterization, bumping process development, and finite element simulation for solder joint reliability. A novel solder bumping process was developed for wafer level fabrication of 96.5Sn-3.5Ag solder bumps. As a baseline process, an electroplating method was applied to fabricate the micro-scale solder bumps with 125-mum diameter, 250-mum pitch and approximately 80-mum height. Pre-deposition of solder bumps was carried out by electroplating over a fine-pattern photoresist mask. Rapid dissolution of Ag into Sn was accomplished during reflow and chip joining process. Nickel was selected as the diffusion barrier and wetting layer in the under-the-bump metallurgy (UBM). Microstructural and compositional analyses were performed using SEM and EDS. Three different mechanical testing techniques including tensile creep, lap shear creep, and automated ball indentation tests were used to characterize the mechanical deformation behavior of 96.5Sn-3.5Ag solder and solder joints. Constant-load creep tests on bulk specimens revealed a dislocation climb mechanism with a relatively large stress exponent of n = 10 for creep strain rates ranging from 10sp{-9} to 10sp{-3} and at temperatures ranging from 298K to 453K. The apparent activation energy for creep was found to be 0.57 ev. Lap shear creep tests on 96.5Sn-7.5Ag solder bumps also revealed a dislocation climb mechanism with a stress exponent of n = 10 for creep strain rates ranging from 10sp{-7} to 10sp{-4} at room temperature. In general, the solder joints are more creep resistant than the bulk specimen due to the inclusion of solder/base metal intermetallics. The intermetallic compounds may form precipitates or dispersoids in the solder matrix and thus hamper the creep deformation rate. The aspect ratio may also influence the creep deformation rate. A constitutive model is established which describes the mechanical deformation behavior of 96.5Sn-3.5Ag as a function of stress, time, and temperature. The constitutive equation was implemented in a two dimensional finite element model to study the solder joint reliability under a typical thermal cycling condition. The strain range values can be used in the Coffin-Manson equation for estimating the accelerating factors and thus to predict the life of a flip chip package. The methodology used in this investigation can be applied in the areas of solder mechanics, solder processing, and electronic packaging technologies.

  3. Prevalence of shoulder pain in Swedish flatwater kayakers and its relation to range of motion and scapula stability of the shoulder joint.

    PubMed

    Johansson, Anette; Svantesson, Ulla; Tannerstedt, Jörgen; Alricsson, Marie

    2016-05-01

    Few studies have investigated the incidence of injuries in kayakers. The aim was to study the prevalence of shoulder pain in competitive flatwater kayakers and to evaluate any differences in range of motion or scapula stability of the shoulder joint among kayakers with or without the history of shoulder pain. Thirty-one kayakers were participated in the study, and a questionnaire including background data was used. Shoulder range of motion was measured with a goniometer, and the participants were observed for scapula dyskinesis in flexion and abduction. Of the participating kayakers, 54.8% (n = 17) had experienced shoulder pain. Kayakers who had experienced shoulder pain showed a significantly lower degree of internal rotational range of motion versus kayakers with no reported shoulder pain, with a mean degree of internal rotation in the right shoulder 49.3 vs 60.0 (P = 0.017) and the left shoulder 51.9 vs 66.0 (P = 0.000). Kayakers who had experienced shoulder pain were also observed with a scapular dyskinesis (n = 15 of 17 kayakers) to a significantly higher degree (P = 0.001) than kayakers with no reported shoulder pain. Findings suggest that screening for scapular dyskinesis and testing for rotational range of motion in the shoulder joint is essential in order to treat and maybe prevent shoulder pain in kayakers. PMID:26301322

  4. 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

  5. Selective contribution of each hamstring muscle to anterior cruciate ligament protection and tibiofemoral joint stability in leg-extension exercise: a simulation study.

    PubMed

    Biscarini, Andrea; Botti, Fabio Massimo; Pettorossi, Vito Enrico

    2013-09-01

    A biomechanical model was developed to simulate the selective effect of the co-contraction force provided by each hamstring muscle on the shear and compressive tibiofemoral joint reaction forces, during open kinetic-chain knee-extension exercises. This model accounts for instantaneous values of knee flexion angle [Formula: see text], angular velocity and acceleration, and for changes in magnitude, orientation, and application point of external resistance. The tibiofemoral shear force (TFSF) largely determines the tensile force on anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL). Biceps femoris is the most effective hamstring muscle in decreasing the ACL-loading TFSF developed by quadriceps contractions for [Formula: see text]. In this range, the semimembranosus generates the dominant tibiofemoral compressive force, which enhances joint stability, opposes anterior/posterior tibial translations, and protects cruciate ligaments. The semitendinosus force provides the greatest decreasing gradient of ACL-loading TFSF for [Formula: see text], and the greatest increasing gradient of tibiofemoral compressive force for [Formula: see text]. However, semitendinosus efficacy is strongly limited by its small physiological section. Hamstring muscles behave as a unique muscle in enhancing the PCL-loading TFSF produced by quadriceps contractions for [Formula: see text]. The levels of hamstrings co-activation that suppress the ACL-loading TFSF considerably shift when the knee angular acceleration is changed while maintaining the same level of knee extensor torque by a concurrent adjustment in the magnitude of external resistance. The knowledge of the specific role and the optimal activation level of each hamstring muscle in ACL protection and tibiofemoral stability are fundamental for planning safe and effective rehabilitative knee-extension exercises. PMID:23670482

  6. Prosthesis loading after temporomandibular joint replacement surgery: a musculoskeletal modeling study.

    PubMed

    Ackland, David C; Moskaljuk, Adrian; Hart, Chris; Vee Sin Lee, Peter; Dimitroulis, George

    2015-04-01

    One of the most widely reported complications associated with temporomandibular joint (TMJ) prosthetic total joint replacement (TJR) surgery is condylar component screw loosening and instability. The objective of this study was to develop a musculoskeletal model of the human jaw to assess the influence of prosthetic condylar component orientation and screw placement on condylar component loading during mastication. A three-dimensional model of the jaw comprising the maxilla, mandible, masticatory muscles, articular cartilage, and articular disks was developed. Simulations of mastication and a maximum force bite were performed for the natural TMJ and the TMJ after prosthetic TJR surgery, including cases for mastication where the condylar component was rotated anteriorly by 0 deg, 5 deg, 10 deg, and 15 deg. Three clinically significant screw configurations were investigated: a complete, posterior, and minimal-posterior screw (MPS) configuration. Increases in condylar anterior rotation led to an increase in prosthetic condylar component contact stresses and substantial increases in condylar component screw stresses. The use of more screws in condylar fixation reduced screw stress magnitudes and maximum condylar component stresses. Screws placed superiorly experienced higher stresses than those of all other condylar fixation screws. The results of the present study have important implication for the way in which prosthetic components are placed during TMJ prosthetic TJR surgery. PMID:25565306

  7. Temperature calculation for extruder screws with internal heat pipes

    NASA Astrophysics Data System (ADS)

    Lakemeyer, C.; Schöppner, V.

    2014-05-01

    One possibility of directly influencing the temperature profile in an extruder is by tempering the screw. This method is currently used in double-screw extrusion and in certain specialized applications in the field of single-screw extrusion. Significant possibilities of influencing the temperature have been shown, for example, while processing PVC on counterrotating double-screw extruders [1]. However, until now, it has not been possible to theoretically model this effect. This paper will thus introduce a mathematical model which describes the effect of internal screw tempering on the temperature gradient of the material in the extruder, allowing processes using tempered screws to be better designed and dimensioned.

  8. The use of CT in the development and implementation of a preoperative protocol to aid in pedicle screw placement during scoliosis surgery.

    PubMed

    Jamieson, Douglas; Perdios, Angeliki; Varghese, Renjit; Reilly, Christopher W

    2008-04-01

    Scoliosis surgical constructs, using pedicle screws, provide increased fixed penetrable points for rod attachment. This allows improved curve correction and increases hardware stability. We have implemented a multidetector CT evaluation of the spine with post-process image manipulation to aid pedicle screw placement for deformity correction. Preoperative scanning was done with a Philips Brilliance 16 multislice CT scanner. The created image dataset provided valuable preoperative information regarding pedicle morphology, suitability for screw placement and preoperative screw planning. Projected intraoperatively, the images increased the surgeon's confidence during screw placement, especially in large deformities with severe rotation. Improving pre- and intraoperative pedicle information is a valuable tool in operative management of children with spinal deformity. PMID:18265967

  9. 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

  10. 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

  11. 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

  12. 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:24921709

  13. Low energy high pressure miniature screw valve

    DOEpatents

    Fischer, Gary J.; Spletzer, Barry L.

    2006-12-12

    A low energy high pressure screw valve having a valve body having an upper portion and a lower portion, said lower portion of said valve body defining an inlet flow passage and an outlet flow passage traversing said valve body to a valve seat, said upper portion of said valve body defining a cavity at said valve seat, a diaphragm restricting flow between said upper portion of said valve body and said lower portion, said diaphragm capable of engaging said valve seat to restrict fluid communication between said inlet passage and said outlet passage, a plunger within said cavity supporting said diaphragm, said plunger being capable of engaging said diaphragm with said valve seat at said inlet and outlet fluid passages, said plunger being in point contact with a drive screw having threads engaged with opposing threads within said upper portion of said valve body such engagement allowing motion of said drive screw within said valve body.

  14. Screw expander for light duty diesel engines

    NASA Technical Reports Server (NTRS)

    1983-01-01

    Preliminary selection and sizing of a positive displacement screw compressor-expander subsystem for a light-duty adiabatic diesel engine; development of a mathematical model to describe overall efficiencies for the screw compressor and expander; simulation of operation to establish overall efficiency for a range of design parameters and at given engine operating points; simulation to establish potential net power output at light-duty diesel operating points; analytical determination of mass moments of inertia for the rotors and inertia of the compressor-expander subsystem; and preparation of engineering layout drawings of the compressor and expander are discussed. As a result of this work, it was concluded that the screw compressor and expander designed for light-duty diesel engine applications are viable alternatives to turbo-compound systems, with acceptable efficiencies for both units, and only a moderate effect on the transient response.

  15. Pedicle screw-based posterior dynamic stabilisation of the lumbar spine: in vitro cadaver investigation and a finite element study.

    PubMed

    Oktenoglu, T; Erbulut, D U; Kiapour, A; Ozer, A F; Lazoglu, I; Kaner, T; Sasani, M; Goel, V K

    2015-08-01

    Pedicle screw-based dynamic constructs either benefit from a dynamic (flexible) interconnecting rod or a dynamic (hinged) screw. Both types of systems have been reported in the literature. However, reports where the dynamic system is composed of two dynamic components, i.e. a dynamic (hinged) screw and a dynamic rod, are sparse. In this study, the biomechanical characteristics of a novel pedicle screw-based dynamic stabilisation system were investigated and compared with equivalent rigid and semi-rigid systems using in vitro testing and finite element modelling analysis. All stabilisation systems restored stability after decompression. A significant decrease in the range of motion was observed for the rigid system in all loadings. In the semi-rigid construct the range of motion was significantly less than the intact in extension, lateral bending and axial rotation loadings. There were no significant differences in motion between the intact spine and the spine treated with the dynamic system (P>0.05). The peak stress in screws was decreased when the stabilisation construct was equipped with dynamic rod and/or dynamic screws. PMID:24708377

  16. Spline-Screw Multiple-Rotation Mechanism

    NASA Technical Reports Server (NTRS)

    Vranish, John M.

    1994-01-01

    Mechanism functions like combined robotic gripper and nut runner. Spline-screw multiple-rotation mechanism related to spline-screw payload-fastening system described in (GSC-13454). Incorporated as subsystem in alternative version of system. Mechanism functions like combination of robotic gripper and nut runner; provides both secure grip and rotary actuation of other parts of system. Used in system in which no need to make or break electrical connections to payload during robotic installation or removal of payload. More complicated version needed to make and break electrical connections. Mechanism mounted in payload.

  17. Screw Placement Accuracy and Outcomes Following O-Arm-Navigated Atlantoaxial Fusion: A Feasibility Study.

    PubMed

    Smith, Jacob D; Jack, Megan M; Harn, Nicholas R; Bertsch, Judson R; Arnold, Paul M

    2016-06-01

    Study Design Case series of seven patients. Objective C2 stabilization can be challenging due to the complex anatomy of the upper cervical vertebrae. We describe seven cases of C1-C2 fusion using intraoperative navigation to aid in the screw placement at the atlantoaxial (C1-C2) junction. Methods Between 2011 and 2014, seven patients underwent posterior atlantoaxial fusion using intraoperative frameless stereotactic O-arm Surgical Imaging and StealthStation Surgical Navigation System (Medtronic, Inc., Minneapolis, Minnesota, United States). Outcome measures included screw accuracy, neurologic status, radiation dosing, and surgical complications. Results Four patients had fusion at C1-C2 only, and in the remaining three, fixation extended down to C3 due to anatomical considerations for screw placement recognized on intraoperative imaging. Out of 30 screws placed, all demonstrated minimal divergence from desired placement in either C1 lateral mass, C2 pedicle, or C3 lateral mass. No neurovascular compromise was seen following the use of intraoperative guided screw placement. The average radiation dosing due to intraoperative imaging was 39.0 mGy. All patients were followed for a minimum of 12 months. All patients went on to solid fusion. Conclusion C1-C2 fusion using computed tomography-guided navigation is a safe and effective way to treat atlantoaxial instability. Intraoperative neuronavigation allows for high accuracy of screw placement, limits complications by sparing injury to the critical structures in the upper cervical spine, and can help surgeons make intraoperative decisions regarding complex pathology. PMID:27190736

  18. 21 CFR 888.3070 - Pedicle screw spinal system.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Pedicle screw spinal system. 888.3070 Section 888...) MEDICAL DEVICES ORTHOPEDIC DEVICES Prosthetic Devices § 888.3070 Pedicle screw spinal system. (a) Identification. Pedicle screw spinal systems are multiple component devices, made from a variety of...

  19. 21 CFR 872.4880 - Intraosseous fixation screw or wire.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

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

  20. Reciprocal screw theory based singularity analysis of a novel 3-DOF parallel manipulator

    NASA Astrophysics Data System (ADS)

    Fang, Hairong; Fang, Yuefa; Zhang, Ketao

    2012-07-01

    Singularity analysis is an essential issue for the development and application of parallel manipulators. Most of the existing researches focus on the singularity of parallel manipulators are carried out based on the study of Jacobian matrices. A 3-DOF parallel manipulator with symmetrical structure is presented. The novel parallel manipulator employs only revolute joints and consists of four closed-loop subchains connecting to both base and platform via revolute joints. The closed-loop subchain in each chain-leg is a spherical 6R linkage. The motion characteristics of the output link in the spherical 6R linkage with symmetrical structure are analyzed based on the interrelationships between screw systems. The constraints that are exerted on the platform by each chain-leg are investigated applying the concept of generalized kinematic pair in terms of equivalent screw system. Considering the geometric characteristics of the parallel manipulator, the singularity criteria of the parallel manipulator corresponding to different configurations are revealed based on the dependency of screw system and line geometry. The existing conditions of certain configuration that a singularity must occur are determined. This paper presents a new way of singularity analysis based on disposition of constraint forces on the geometrically identified constraint plane and the proposed approach is capable of avoiding the complexity in solving the Jacobian matrices.

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

    PubMed

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

    2015-05-01

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

  2. Computer simulation of screw dislocation in aluminum

    NASA Technical Reports Server (NTRS)

    Esterling, D. M.

    1976-01-01

    The atomic structure in a 110 screw dislocation core for aluminum is obtained by computer simulation. The lattice statics technique is employed since it entails no artificially imposed elastic boundary around the defect. The interatomic potential has no adjustable parameters and was derived from pseudopotential theory. The resulting atomic displacements were allowed to relax in all three dimensions.

  3. Nylon screws make inexpensive coil forms

    NASA Technical Reports Server (NTRS)

    Aucoin, G.; Rosenthal, C.

    1978-01-01

    Standard nylon screws act as coil form copper wire laid down in spiral thread. Completed coil may be bonded to printed-circuit board. However, it is impossible to tune coil by adjusting spacing between windings, technique sometimes used with air-core coils.

  4. Improvements to the single screw extruder

    NASA Technical Reports Server (NTRS)

    Hiemenz, C.; Ziegmann, G.; Franzkoch, B.; Hoffmanns, W.; Michaeli, W.

    1977-01-01

    The extrusion on a single screw extruder is examined. The process is divided into several steps: the dosage of the materials to be conveyed; the modification of the shape of the feeding opening which influences the feeding process and consequently the throughput of the extruder; optimizing the shape of the feeding zone to meet the specific material requirements; and plasticizing and homogenizing.

  5. Improvements In Ball-Screw Linear Actuators

    NASA Technical Reports Server (NTRS)

    Iskenderian, Theodore; Joffe, Benjamin; Summers, Robert

    1996-01-01

    Report describes modifications of design of type of ball-screw linear actuator driven by dc motor, with linear-displacement feedback via linear variable-differential transformer (LVDT). Actuators used to position spacecraft engines to direct thrust. Modifications directed toward ensuring reliable and predictable operation during planned 12-year cruise and interval of hard use at end of cruise.

  6. Computation of Flow in Screw Compressors

    NASA Astrophysics Data System (ADS)

    Kalitzin, Georgi; Cai, Xiaodan; Reba, Ramons; Medic, Gorazd

    2015-08-01

    A CFD model enabling accurate and computationally affordable simulation of unsteady flow in screw compressors has been developed. This paper focuses on computational aspects, including real-gas CFD using hybrid structured/unstructured moving grids, and specifics of grid generation for moving rotors and their communication with the discharge plenum.

  7. Treatment strategies for early neurological deficits related to malpositioned pedicle screws in the lumbosacral canal

    PubMed Central

    Du, J-Y.; Wu, J-S.; Wen, Z-Q.

    2016-01-01

    Objectives To employ a simple and fast method to evaluate those patients with neurological deficits and misplaced screws in relatively safe lumbosacral spine, and to determine if it is necessary to undertake revision surgery. Methods A total of 316 patients were treated by fixation of lumbar and lumbosacral transpedicle screws at our institution from January 2011 to December 2012. We designed the criteria for post-operative revision scores of pedicle screw malpositioning (PRSPSM) in the lumbosacral canal. We recommend the revision of the misplaced pedicle screw in patients with PRSPSM = 5′ as early as possible. However, patients with PRSPSM < 5′ need to follow the next consecutive assessment procedures. A total of 15 patients were included according to at least three-stage follow-up. Results Five patients with neurological complications (PRSPSM = 5′) underwent revision surgery at an early stage. The other ten patients with PRSPSM < 5′ were treated by conservative methods for seven days. At three-month follow-up, only one patient showed delayed onset of neurological complications (PRSPSM 7′) while refusing revision. Seven months later, PRSPSM decreased to 3′ with complete rehabilitation. Conclusions This study highlights the significance of consecutively dynamic assessments of PRSPSMs, which are unlike previous implementations based on purely anatomical assessment or early onset of neurological deficits.and also confirms our hypothesis that patients with early neurological complications may not need revision procedures in the relatively broad margin of the lumbosacral canal. Cite this article: X-J. Lin. Treatment strategies for early neurological deficits related to malpositioned pedicle screws in the lumbosacral canal: A pilot study. Bone Joint Res 2016;5:46–51. DOI: 10.1302/2046-3758.52.2000477. PMID:26868892

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

    PubMed Central

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

    2009-01-01

    Background Premature failure of either the nail and/or locking screws with unstable fracture patterns may lead to angulation, shortening, malunion, and IM nail migration. Up to thirty percent of all unreamed nail locking screws can break after initial weight bearing is allowed at 8–10 weeks if union has not occurred. The primary problem this presents is hardware removal during revision surgery. The purposes of our study was to evaluate the relative fatigue resistance of distal locking screws and bolts from representative manufacturers of tibial IM nail systems, and develop a relative risk assessment of screws and materials used. Evaluations included quantitative and qualitative measures of the relative performance of these screws. Methods Fatigue tests were conducted to simulate a comminuted fracture that was treated by IM nailing assuming that all load was carried by the screws. Each screw type was tested ten times in a single screw configuration. One screw type was tested an additional ten times in a two-screw parallel configuration. Fatigue tests were performed using a servohydraulic materials testing system and custom fixturing that simulated screws placed in the distal region of an appropriately sized tibial IM nail. Fatigue loads were estimated based on a seventy-five kilogram individual at full weight bearing. The test duration was one million cycles (roughly one year), or screw fracture, whichever occurred first. Failure analysis of a representative sample of titanium alloy and stainless steel screws included scanning electron microscopy (SEM) and quantitative metallography. Results The average fatigue life of a single screw with a diameter of 4.0 mm was 1200 cycles, which would correspond roughly to half a day of full weight bearing. Single screws with a diameter of 4.5 mm or larger have approximately a 50 percent probability of withstanding a week of weight bearing, whereas a single 5.0 mm diameter screw has greater than 90 percent probability of withstanding more than a week of weight bearing. If two small diameter screws are used, our tests showed that the probability of withstanding a week of weight bearing increases from zero to about 20 percent, which is similar to having a single 4.5 mm diameter screw providing fixation. Conclusion Our results show that selecting the system that uses the largest distal locking screws would offer the best fatigue resistance for an unstable fracture pattern subjected to full weight bearing. Furthermore, using multiple screws will substantially reduce the risk of premature hardware failure. PMID:19371438

  9. A joint electromagnetic and seismic study of an active pockmark within the hydrate stability field at the Vestnesa Ridge, West Svalbard margin

    NASA Astrophysics Data System (ADS)

    Goswami, Bedanta K.; Weitemeyer, Karen A.; Minshull, Timothy A.; Sinha, Martin C.; Westbrook, Graham K.; Chabert, Anne; Henstock, Timothy J.; Ker, Stephan

    2015-10-01

    We acquired coincident marine controlled source electromagnetic (CSEM), high-resolution seismic reflection and ocean-bottom seismometer (OBS) data over an active pockmark in the crest of the southern part of the Vestnesa Ridge, to estimate fluid composition within an underlying fluid-migration chimney. Synthetic model studies suggest resistivity obtained from CSEM data can resolve gas or hydrate saturation greater than 5% within the chimney. Acoustic chimneys imaged by seismic reflection data beneath the pockmark and on the ridge flanks were found to be associated with high-resistivity anomalies (+2-4 Ωm). High-velocity anomalies (+0.3 km/s), within the gas-hydrate stability zone (GHSZ) and low-velocity anomalies (-0.2 km/s) underlying the GHSZ, were also observed. Joint analysis of the resistivity and velocity anomaly indicates pore saturation of up to 52% hydrate with 28% free gas, or up to 73% hydrate with 4% free gas, within the chimney beneath the pockmark assuming a nonuniform and uniform fluid distribution, respectively. Similarly, we estimate up to 30% hydrate with 4% free gas or 30% hydrate with 2% free gas within the pore space of the GHSZ outside the central chimney assuming a nonuniform and uniform fluid distribution, respectively. High levels of free-gas saturation in the top part of the chimney are consistent with episodic gas venting from the pockmark.

  10. OSTEOSYNTHESIS OF FEMORAL NECK FRACTURES: TWO OR THREE SCREWS?

    PubMed Central

    Basile, Ricardo; Pepicelli, Gustavo Roberto; Takata, Edmilson Takehiro

    2015-01-01

    Objectives: To evaluate the efficacy of osteosynthesis on femoral neck fractures using two instead of three screws. Methods: Thirty-nine fractures were retrospectively evaluated, divided into groups in which two screws were used in parallel (n = 28) or three screws (n =11) in an inverted triangle configuration (in accordance with the AO technique). The patients were then followed up until reaching the outcome of either consolidation or failure. Results: In the group in which two screws were used, consolidation was observed in 23 of the 28 fractures (82%). In the group in which three screws were used, consolidation was observed in 6 of the 11 fractures (55%). There was no statistically significant difference between these percentages. Conclusion: There was no difference in the prognosis for these fractures when treated using two screws in parallel or three screws in an inverted triangle in accordance with the AO technique. Further studies are needed in order to establish a definitive conclusion.

  11. Chitosan-coated stainless steel screws for fixation in contaminated fractures.

    PubMed

    Greene, Alex H; Bumgardner, Joel D; Yang, Yunzhi; Moseley, Jon; Haggard, Warren O

    2008-07-01

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

  12. Foam granulation: new developments in pharmaceutical solid oral dosage forms using twin screw extrusion machinery.

    PubMed

    Thompson, M R; Weatherley, S; Pukadyil, R N; Sheskey, P J

    2012-07-01

    This paper investigates foam granulation in a twin screw extruder as a new continuous wet granulation technique for pharmaceutical powder drug formulations. Foamed aqueous binder has a reportedly lower soak-to-spread ratio than drop or spray liquid addition in batch granulation. This work demonstrates a twin screw extruder configuration for foam granulation and subsequently compares the new approach against liquid injection in the granulation of α-lactose monohydrate with a methylcellulose binder. Trials were conducted at high powder output rates (20-40 kg/h) and high screw speeds (220-320 RPM) with two screw configurations. Process stability improved with the new technique allowing granulation with less binder. The extruded mass maintained a low exit temperature, being insensitive to operating conditions unlike the liquid injection approach, where temperatures rose significantly as flow rate increased. The particle size distribution by foam granulation reflected a more uniformly wetted mass with larger granule growth noted even for conditions where dry powder exited by liquid injection. Other factors were found similar between the two binder delivery methods such as consumed mechanical energy, as well as fracture strength and compressibility of produced granules. PMID:22085462

  13. Radiographic evaluation of HDPE cemented and cementless Lord and An.C.A. screwed acetabular models.

    PubMed

    Toni, A; Sudanese, A; Viceconti, M; Montina, P P; Ciaroni, D; Calista, F; Terzi, S; Giunti, A

    1992-01-01

    A total of 187 alumina screwed porous-ceramic coated sockets (An.C.A.), 48 screwed smooth-surfaced Lord sockets, and 251 cemented polyethylene sockets were radiographically evaluated at an average follow-up of 30, 51 and 96 months respectively. After 6 years the Lord prostheses revealed a 38% incidence of loosening, similar to that observed for cemented sockets 10-12 years after surgery. The An.C.A. prostheses revealed radiographic loosening equal to 12% (6 cases) in the first 50 implants, and only 0.7% in the remaining 137 cases: overall, the An.C.A. acetabular prosthesis revealed an index of radiographic loosening equal to 3.3% (7/187). To guarantee "osteointegration" of the porous coating of An.C.A. sockets optimal stability must be obtained when the prosthesis is screwed in. Because the mid-term follow-up for this clinical experience is relatively short (30 months), an opinion on the reliability of the screwed "porous" sockets must await confirmation. PMID:1297574

  14. Is There an Optimal Proximal Locking Screw Length in Retrograde Intramedullary Femoral Nailing? Can We Stop Measuring for These Screws?

    PubMed

    Collinge, Cory A; Koerner, John D; Yoon, Richard S; Beltran, Michael J; Liporace, Frank A

    2015-10-01

    Insertion of locking screws through the proximal thigh while locking retrograde femoral nails is arguably more difficult and traumatic to local tissues than locking at other intramedullary nail sites. The purpose of this study was to evaluate whether a "standard" screw length for proximal interlocking of retrograde nails is possible, therefore assessing whether the act of measuring for these screws can be omitted. This article retrospective evaluates screw position and estimated proximal locking screw length in patients undergoing retrograde nailing using a large radiographically measured computed tomography cohort, with validation through a smaller clinical cohort. According to these data, it seems reasonable to skip depth gauge measurement during anteroposterior interlocking of retrograde femoral nails and insert a standard length screw based on location relative to the lesser trochanter. This should decrease the amount of local trauma to the patient at the locking screw site while increasing operating room efficiency by avoiding what can often become a difficult step during the procedure. PMID:25946415

  15. Novel flexible suture fixation for the distal tibiofibular syndesmotic joint injury: a cadaveric biomechanical model.

    PubMed

    Gough, Brandon E; Chong, Alexander C M; Howell, Steven J; Galvin, Joseph W; Wooley, Paul H

    2014-01-01

    Syndesmotic injuries of the ankle commonly occur by an external rotation force applied to the ankle joint. Ten fresh-frozen lower extremities from cadavers were used. A specially designed apparatus was used to stabilize the specimen and rotate the ankle joint from internally rotated 25° to externally rotated 35° at a rate of 6°/s for 10 cycles. Two stages were tested (stage I, specimens intact; and stage II, simulated pronation external rotation type injury with fixation). Group 1 was fixed with a novel suture construct across the syndesmotic joint, and group 2 was fixed with a single metallic screw. The torque, rotational angle, and 3-dimensional syndesmotic diastasis readings were recorded. Three-dimensional tibiofibular diastasis was identified. The fibula of the intact specimens displaced an average of 8.6 ± 1.7, 2.4 ± 1.0, and 1.4 ± 1.0 mm in the anterior, lateral, and superior direction, respectively, when the foot was externally rotated 35°. The sectioning of the syndesmostic ligaments and deltoid ligament resulted in a significant decrease in syndesmotic diastasis and foot torsional force (p < .05). The ligament-sectioned specimen lost 57% (externally rotated) and 17% (internally rotated) torsional strength compared with the intact specimen. Groups 1 and 2 provided similar biomechanical stability in this cadaveric model of a syndesmosis deficiency. PMID:24846162

  16. Effect of a defect structure on the static and long-term strength of submicrocrystalline VT1-0 titanium fabricated by plastic deformation during screw and lengthwise rolling

    NASA Astrophysics Data System (ADS)

    Betekhtin, V. I.; Kolobov, Yu. R.; Sklenicka, V.; Kadomtsev, A. G.; Narykova, M. V.; Dvorak, J.; Golosov, E. V.; Kardashev, B. K.; Kuz'menko, I. N.

    2015-01-01

    The effect of nanoporosity and the highly dispersed carbide particles that form during screw and lengthwise rolling of VT1-0 titanium on its mechanical and, partly, thermal stability characteristics is revealed and analyzed.

  17. Joint Problems

    MedlinePlus

    ... Information Causes & Symptoms Diagnosis & Tests Care & Treatment Lifestyle & ... Facts & Information What are Joint Problems? Your musculoskeletal system is constructed of bones, muscles, and joints. The ...

  18. Translational mini-screw implant research.

    PubMed

    Rossouw, Emile

    2014-09-01

    It is important to thoroughly test new materials as well as techniques when these innovations are to be utilized in the human clinical situation. Translational research fills this important niche. The purpose of translational research is to establish the continuity of evidence from the laboratory to the clinic and in so-doing, provide evidence that the material is functioning appropriately and that the process in the human will be successful. This concept applies to the mini-screw implant; which, has been very successfully introduced into the orthodontic armamentarium over the last decade for application as a temporary anchorage device. The examples of translational research that will be illustrated in this paper have paved the way to ensure that clinicians have evidence to confidently utilize mini-screw implants in orthodontic practice. Needless to say, more studies are needed to ensure a safe, effective and efficient manner to practice orthodontics. PMID:25138369

  19. In vitro comparison of resistance to implant failure in unstable trochanteric fractures fixed with intramedullary single screw versus double screw device

    PubMed Central

    Rastogi, Amit; Arun, GR; Singh, Vakil; Singh, Anant; Singh, Ashutosh K; Kumaraswamy, Vinay

    2014-01-01

    Background: The purpose of this study was to compare the resistance of intramedullary single screw device (Gamma nail) and double screw device proximal femoral nail (PFN) in unstable trochanteric fractures in terms of the number of cycles sustained, subsidence and implant failure in an axial loading test in cadaveric femora. Materials and Methods: The study was conducted on 18 dry cadaveric femoral specimens, 9 of these were implanted with a Gamma nail and 9 with PFN. There was no significant difference found in average dual energy X-ray absorptiometry value between both groups. The construct was made unstable (AO type 31A3.3) by removing a standard sized posteromedial wedge. These were tested on a cyclic physiological loading machine at 1 cycle/s with a load of 200 kg. The test was observed for 50,000 loading cycles or until implant failure, whichever occurred earlier. Peak displacements were measured and analysis was done to determine construct stiffness and gap micromotion in axial loading. Result: It was observed that there was statistically significant difference in terms of displacement at the fracture gap and overall construct stiffness of specimens of both groups. PFN construct group showed a mean subsidence of 1.02 mm and Gamma nail construct group showed mean subsidence of 2.36 mm after cycling. The average stiffness of Gamma nail group was 62.8 ± 8.4 N/mm which was significantly lower than average stiffness of the PFN group (80.4 ± 5.9 N/mm) (P = 0.03). In fatigue testing, 1 out of 9 PFN bone construct failed, while 5 of 9 Gamma nail bone construct failed. Conclusion: When considering micromotion (subsidence) and incidence of implant/screw failure, double screw device (PFN) had statistically significant lower micromotion across the fracture gap with axial compression and lower incidence of implant failure. Hence, double screw device (PFN) construct had higher stability compared to single screw device (GN) in an unstable trochanteric fracture femur model. PMID:24932039

  20. Intraoperative 3-dimensional imaging (O-arm) for assessment of pedicle screw position: Does it prevent unacceptable screw placement?

    PubMed Central

    Sembrano, Jonathan N.; Polly, David W.; Ledonio, Charles Gerald T.; Santos, Edward Rainier G.

    2012-01-01

    Background Pedicle screws are biomechanically superior over other spinal fixation devices. When improperly positioned, they lose this advantage and put adjacent structures at risk. Accurate placement is therefore critical. Postoperative computed tomography (CT) scans are the imaging gold standard and have shown malposition rates ranging from 2% to 41%. The O-arm (Medtronic Navigation, Louisville, Colorado) is an intraoperative CT scanner that may allow intervention for malpositioned screws while patients are still in the operating room. However, this has not yet been shown in clinical studies. The primary objective of this study was to assess the usefulness of the O-arm for evaluating pedicle screw position by answering the following question: What is the rate of intraoperative pedicle screw revision brought about by O-arm imaging information? A secondary question was also addressed: What is the rate of unacceptable thoracic and lumbar pedicle screw placement as assessed by intraoperative O-arm imaging? Methods This is a case series of consecutive patients who have undergone spine surgery for which an intraoperative 3-dimensional (3D) CT scan was used to assess pedicle screw position. The study comprised 602 pedicle screws (235 thoracic and 367 lumbar/sacral) placed in 76 patients, and intraoperative 3D (O-arm) imaging was obtained to assess screw position. Action taken at the time of surgery based on imaging information was noted. An independent review of all scans was also conducted, and all screws were graded as either optimal (no breach), acceptable (breach ≤2 mm), or unacceptable (breach >2 mm). The rate of pedicle screw revision, as detected by intraoperative 3D CT scan, was determined. Results On the basis of 3D imaging information, 17 of 602 screws (2.8%) in 14 of 76 cases (18.4%) were revised at the time of surgery. On independent review of multiplanar images, 11 screws (1.8%) were found to be unacceptable, 32 (5.3%) were acceptable, and 559 (92.9%) were optimal. All unacceptable screws were revised to an optimal or acceptable position, and an additional 6 acceptable screws were revised to an optimal position. Thus, by the end of the cases, none of the 602 pedicle screws in the 76 surgical procedures was in an unacceptable position. Conclusion The new-generation intraoperative 3D imaging system (O-arm) is a useful tool that allows more accurate assessment of pedicle screw position than plain radiographs or fluoroscopy alone. It prompted intraoperative repositioning of 2.8% of pedicle screws in our series. Most importantly, it allowed identification and revision of all unacceptably placed pedicle screws without the need for reoperation. PMID:25694871

  1. Treatment of methicillin-resistant Staphylococcus epidermidis infection following repair of an ulnar fracture and humeroradial joint luxation in a horse.

    PubMed

    Trostle, S S; Peavey, C L; King, D S; Hartmann, F A

    2001-02-15

    A 27-month-old Rocky Mountain Horse was examined because of a fracture of the proximal portion of the ulna and luxation of the humeroradial joint (Monteggia fracture). Open reduction was performed, using a mechanical distractor, and the ulnar fracture was stabilized by application of a bone plate and screws. After surgery, the horse developed an infection of the surgical site, and bacterial culture of fluid from the surgical site yielded a pure growth of methicillin-resistant Staphylococcus epidermidis susceptible to oxytetracycline, erythromycin, rifampin, and vancomycin. Treatment with oxytetracycline did not result in a favorable clinical response. Therefore, the horse was treated systemically with vancomycin and rifampin, and vancomycin-impregnated polymethyl methacrylate beads were implanted at the surgical site. Six months after surgery, the horse was sound at a walk or trot, and bony union was evident on radiographs of the elbow joint. PMID:11229509

  2. Dual load path ball screw with rod end swivel

    NASA Technical Reports Server (NTRS)

    Wngett, Paul (Inventor)

    2002-01-01

    A dual drive ball has a ball screw shaft coupled at one end to a gear train and coupled at the other end to a ball screw nut. The ball screw shaft and ball screw nut are connected through complementary helical grooves filled with ball bearing balls. The outer surface of the ball screw nut is plined and can be driven by a second gear train. An output tube is coupled at one end to the ball screw nut and at its opposite end has a connector portion with a groove on its inner surface. A rod end has a coupling member for coupling to a surface to be actuated and a shaft portion with a groobe on its outer surface. This shaft portion is received with in the outputtube portion and the corresponding grooves are coupled through the use of a plurality of ball bearing balls.

  3. Modeling the Parker instability in a rotating plasma screw pinch

    NASA Astrophysics Data System (ADS)

    Khalzov, I. V.; Brown, B. P.; Katz, N.; Forest, C. B.

    2012-02-01

    We analytically and numerically study the analogue of the Parker (magnetic buoyancy) instability in a uniformly rotating plasma screw pinch confined in a cylinder. Uniform plasma rotation is imposed to create a centrifugal acceleration, which mimics the gravity required for the classical Parker instability. The goal of this study is to determine how the Parker instability could be unambiguously identified in a weakly magnetized, rapidly rotating screw pinch, in which the rotation provides an effective gravity and a radially varying azimuthal field is controlled to give conditions for which the plasma is magnetically buoyant to inward motion. We show that an axial magnetic field is also required to circumvent conventional current driven magnetohydrodynamic (MHD) instabilities such as the sausage and kink modes that would obscure the Parker instability. These conditions can be realized in the Madison plasma Couette experiment (MPCX). Simulations are performed using the extended MHD code NIMROD for an isothermal compressible plasma model. Both linear and nonlinear regimes of the instability are studied, and the results obtained for the linear regime are compared with analytical results from a slab geometry. Based on this comparison, it is found that in a cylindrical pinch, the magnetic buoyancy mechanism dominates at relatively large Mach numbers (M > 5), while at low Mach numbers (M < 1), the instability is due to the curvature of magnetic field lines. At intermediate values of Mach number (1 < M < 5), the Coriolis force has a strong stabilizing effect on the plasma. A possible scenario for experimental demonstration of the Parker instability in MPCX is discussed.

  4. Disorders of the sacroiliac joint.

    PubMed

    Sizer, Phillip S; Phelps, Valerie; Thompsen, Kirk

    2002-03-01

    Controversies have surrounded the sacroiliac joint. The sacroiliac joint (SIJ) is a considerably complex and strong joint with limited mobility, mechanically serving as a force transducer and a shock absorber. Anatomical changes are seen in the SIJ throughout an individual's lifetime. The ligamentous system associated with the SIJ serves to enhance stability and offer proprioceptive feedback in context with the rich plexus of articular receptors. Stability in the SIJ is related to form and force closure. Movement in the SIJ is 3-D about an axis outside of the joint. The functional examination of the SIJ is related to a clinical triad. PMID:17134467

  5. Screws, Propellers and Fans Based on a Mobius Strip

    NASA Technical Reports Server (NTRS)

    Seiner, John M.; Backley, Floyd D.; Gilinsky, Mikhail

    1998-01-01

    A Mobius strip concept is intended for improving the working efficiency of propellers and screws. Applications involve cooling, boat propellers, mixing in appliance, blenders, and helicopters. Several Mobius shaped screws for the average size kitchen mixers have been made and tested. The tests have shown that the mixer with the Mobius shaped screw pair is most efficient, and saves more than 30% of the electric power by comparison with the standard. The created video film about these tests illustrates efficiency of Mobius shaped screws.

  6. Minimally Invasive Technique for PMMA Augmentation of Fenestrated Screws

    PubMed Central

    Kogias, Evangelos; Sircar, Ronen; Krüger, Marie T.; Volz, Florian; Scheiwe, Christian; Hubbe, Ulrich

    2015-01-01

    Purpose. To describe the minimally invasive technique for cement augmentation of cannulated and fenestrated screws using an injection cannula as well as to report its safety and efficacy. Methods. A total of 157 cannulated and fenestrated pedicle screws had been cement-augmented during minimally invasive posterior screw-rod spondylodesis in 35 patients from January to December 2012. Retrospective evaluation of cement extravasation and screw loosening was carried out in postoperative plain radiographs and thin-sliced triplanar computed tomography scans. Results. Twenty-seven, largely prevertebral cement extravasations were detected in 157 screws (17.2%). None of the cement extravasations was causing a clinical sequela like a new neurological deficit. One screw loosening was noted (0.6%) after a mean follow-up of 12.8 months. We observed no cementation-associated complication like pulmonary embolism or hemodynamic insufficiency. Conclusions. The presented minimally invasive cement augmentation technique using an injection cannula facilitates convenient and safe cement delivery through polyaxial cannulated and fenestrated screws during minimally invasive screw-rod spondylodesis. Nevertheless, the optimal injection technique and design of fenestrated screws have yet to be identified. This trial is registered with German Clinical Trials DRKS00006726. PMID:26075297

  7. Extraforaminal lumbar interbody fusion for cage migration after screw removal: a case report.

    PubMed

    Kim, Myung Hoon; Kim, Seok Won; Kim, Sung Hoon; Kim, Hyeun Sung

    2013-06-01

    The use of titanium cages for posterior lumbar interbody fusion (PLIF) has gained popularity because it offers the advantages of anterior column support and stabilization. However, cage migration into the spinal canal may have severe or disastrous consequences. Here, the authors report an unexpected case of posterior migration of fusion cages after screw removal in a patient that underwent PLIF 12 months previously. Removal of the offending cages through revision extraforaminal lumbar interbody fusion (ELIF) with percutaneous screw fixation successfully managed this complication. As far as the authors' knowledge, this is the first case report to describe this sort of complication, and cautions that care must be taken to prevent cage migration. PMID:24757471

  8. Friction-induced noise of gear system with lead screw and nut: Mode-coupling instability

    NASA Astrophysics Data System (ADS)

    Kang, Jaeyoung

    2015-11-01

    The mode-coupling instability in the gear system with a lead screw and nut is investigated. The actual gear geometry and the contact kinematics are developed in analytical the model. The complete set of vibration modes including axial, torsion and transverse displacements is applied to seek the solution of the linearized gear system. From the linear stability analysis, the bending mode pair as well as the torsion and axial mode pair have the strong tendency towards the mode-coupling instability. It points out that squeak noise in the lead screw system can occur even for a constant friction coefficient without the negative-friction velocity slope. The closed-form solution and numerical calculation also show that the rotating direction can drastically change the onset of mode-coupling instability.

  9. Metatarsophalangeal Joint Fusion: Why and How?

    PubMed

    Rammelt, Stefan; Panzner, Ines; Mittlmeier, Thomas

    2015-09-01

    First metatarsophalangeal (MTP) joint fusion aims at elimination of pain resulting from end-stage arthritis and obtaining a stable, plantigrade first toe. Associated deformities are corrected and greater defects are filled with interposition autograft or allograft. Fusion is generally obtained with screws, staples, and/or low-profile plates. Complications include infection, osteonecrosis, implant protrusion or failure, nonunion, and malunion, the latter 2 each occurring in approximately 6% of cases. The medium-term results of first MTP joint fusion indicate mostly good functional results with success rates of approximately 90%. PMID:26320560

  10. Effect of Joint Line Elevation after Posterior-stabilized and Cruciate-retaining Total Knee Arthroplasty on Clinical Function and Kinematics

    PubMed Central

    Ji, Song-Jie; Zhou, Yi-Xin; Jiang, Xu; Cheng, Zhi-Yuan; Wang, Guang-Zhi; Ding, Hui; Yang, Ming-Lei; Zhu, Zhong-Lin

    2015-01-01

    Background: Joint line (JL) is a very important factor for total knee arthroplasty (TKA) to restore. The objective of this study was to evaluate the early clinical and kinematic results of TKAs with posterior-stabilized (PS) or cruciate retaining (CR) implants in which the JL was elevated postoperatively. Methods: Data were collected from patients who underwent TKA in our department between April 2011 and April 2014. The patients were divided into two groups based on the prosthesis they received (PS or CR). At 1-year postoperatively, clinical outcomes were evaluated by the American Knee Society (AKS) knee score, AKS function score, and patella score. In vivo kinematic analysis after TKA was performed on all patients and a previously validated three-dimensional to two-dimensional image registration technique was used to obtain the kinematic data. Anteroposterior (AP) translation of the medial and lateral femoral condyles, and axial rotation relative to the tibial plateau, were analyzed. The data were assessed using the Mann–Whitney test. Results: At time of follow-up, there were differences in the AKS knee scores (P = 0.005), AKS function scores (P = 0.025), patella scores (P = 0.015), and postoperative range of motions (P = 0.004) between the PS group and the CR group. In the PS group, the magnitude of AP translation for the medial and lateral condyle was 4.9 ± 3.0 mm and 12.8 ± 3.3 mm, respectively. Axial rotation of the tibial component relative to the femoral component was 12.9 ± 4.5°. In the CR group, the magnitude of AP translation for the medial and lateral condyle was 4.3 ± 3.5 mm and 7.9 ± 4.2 mm, respectively. The axial rotation was 6.7 ± 5.9°. There were statistically different between PS group and CR group in kinematics postoperatively. Conclusion: Our results demonstrate that postoperative JL elevation had more adverse effects on the clinical and kinematic outcomes of CR TKAs than PS TKAs. PMID:26521783

  11. Magnesium Alloys as a Biomaterial for Degradable Craniofacial Screws

    PubMed Central

    Henderson, Sarah E.; Verdelis, Konstantinos; Maiti, Spandan; Pal, Siladitya; Chung, William L.; Chou, Da-Tren; Kumta, Prashant N.; Almarza, Alejandro J.

    2014-01-01

    Recently, magnesium (Mg) alloys have received significant attention as a potential biomaterial for degradable implants, and this study was directed at evaluating the suitability of Mg for craniofacial bone screws. The objective was to implant screws fabricated from commercially available Mg-alloys (pure Mg and AZ31) in-vivo in a rabbit mandible. First, Mg-alloy screws were compared to stainless steel screws in an in-vitro pull-out test and determined to have a similar holding strength (~40N). A finite element model of the screw was created using the pull-out test data, and the model can be used for future Mg-alloy screw design. Then, Mg-alloy screws were implanted for 4, 8, and 12 weeks, with two controls of an osteotomy site (hole) with no implant and a stainless steel screw implanted for 12 weeks. MicroCT (computed tomography) was used to assess bone remodeling and Mg-alloy degradation, both visually and qualitatively through volume fraction measurements for all time points. Histologic analysis was also completed for the Mg-alloys at 12 weeks. The results showed that craniofacial bone remodeling occurred around both Mg-alloy screw types. Pure Mg had a different degradation profile than AZ31, however bone growth occurred around both screw types. The degradation rate of both Mg-alloy screw types in the bone marrow space and the muscle were faster than in the cortical bone space at 12 weeks. Furthermore, it was shown that by alloying Mg, the degradation profile could be changed. These results indicate the promise of using Mg-alloys for craniofacial applications. PMID:24384125

  12. Comparative clinical study of locking screws versus smooth locking pegs in volar plating of distal radius fractures.

    PubMed

    Boretto, J G; Pacher, N; Giunta, D; Gallucci, G L; Alfie, V; De Carli, P

    2014-09-01

    The present study was performed to test the null hypothesis on no difference in stability of fixation after volar plating of intra-articular distal radius fractures (AO C2-C3) with either locking smooth pegs or locking screws in a clinical setting. A retrospective evaluation included adult patients with C2-C3 AO fractures treated with a volar plate with locking smooth pegs or locking screws. Radiographic assessment was performed to evaluate extra- and intra-articular parameters in the early postoperative period and after bone union. Twenty-seven consecutive patients were included. Thirteen cases had fixation with locking screws and 14 had fixation with locking smooth pegs. Both groups had bone fragment displacement after fixation. However, there were no significant differences between the groups either in extra- or intra-articular parameters defined by Kreder et al. (1996). Our study shows that, in a clinical setting, there is no difference in stability fixation between locking screws or smooth locking pegs in C2-C3 distal radius fractures. PMID:24401740

  13. Injection of coal by screw feed

    NASA Technical Reports Server (NTRS)

    Fisher, R.

    1977-01-01

    The use of the screw feeder for injecting solids through a 20 to 30 psi barrier is common practice in the cement making industry. An analytical extrapolation of that design, accounting for pressure holding characteristics of a column of solids, shows that coal can be fed to zones at several hundred psi with minimal or no loss of gas. A series of curves showing the calculated pressure gradient through a moving column of solids is presented. Mean particle size, solids velocity, and column length are parameters. Further study of this system to evaluate practicality is recommended.

  14. Joint-sparing Corrections in Malunited Lisfranc Joint Injuries.

    PubMed

    Nery, Caio; Raduan, Fernando; Baumfeld, Daniel

    2016-03-01

    Lisfranc fracture-dislocations are very serious and potentially disabling injuries. Unfortunately, they are often misdiagnosed. Multiplanar midfoot deformities that result from these fracture-dislocations are precursors of joint degeneration and significant functional disabilities. Anatomic reduction with different types of internal fixation is an efficient method to reconstruct midfoot alignment and stability. Joint-preserving reconstruction techniques emerge as a viable alternative to corrective fusion as they achieve stable joint realignment with preserved motion. PMID:26915786

  15. Computer-Aided Surgery Does Not Increase the Accuracy of Dorsal Pedicle Screw Placement in the Thoracic and Lumbar Spine: A Retrospective Analysis of 2,003 Pedicle Screws in a Level I Trauma Center

    PubMed Central

    Kraus, Michael; Weiskopf, Julia; Dreyhaupt, Jens; Krischak, Gert; Gebhard, Florian

    2014-01-01

    Study Design A retrospective analysis of a prospective database. Objective Meta-analyses suggest that computer-assisted systems can increase the accuracy of pedicle screw placement for dorsal spinal fusion procedures. The results of further meta-analyses report that in the thoracic spine, both the methods have comparable placement accuracy. These studies are limited due to an abundance of screw classification systems. The aim of this study was to assess the placement accuracy and potentially influencing factors of three-dimensionally navigated versus conventionally inserted pedicle screws. Methods This was a retrospective analysis of a prospective database at a level I trauma center of pedicle screw placement (computer-navigated versus traditionally placed) for dorsal spinal stabilizations. The cases spanned a 5.5-year study period (January 1, 2005, to June 30, 2010). The perforations of the pedicle were differentiated in three grades based on the postoperative computed tomography. Results The overall placement accuracy was 86% in the conventional group versus 79% in the computer-navigated group (grade 0). The computer-navigated procedures were superior in the lumbar spine and the conventional procedures were superior in the thoracic spine, but both failed to be of statistical significance. The level of experience of the performing surgeon and the patient's body mass index did not influence the placement accuracy. The only significant influence was the spinal segment: the higher the spinal level where the fusion was performed, the more likely the screw was displaced. Conclusions The computer-navigated and conventional methods are both safe procedures to place transpedicular screws at the traumatized thoracic and lumbar spine. At the moment, three-dimensionally based navigation does not significantly increase the placement accuracy. PMID:25844281

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

    PubMed Central

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

    2015-01-01

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

  17. Periodic Stresses in Gyroscopic Bodies, with Applications to Air Screws

    NASA Technical Reports Server (NTRS)

    Zahm, A F

    1918-01-01

    Report discusses periodic stresses in gyroscopic bodies with applications to air screws caused by particle mass. Report concludes that all modern air screws obey the laws found for plane groups of particles. In particular the two-bladers exert on the shaft a rhythmic gyroscopic torque; the multibladers a steady one; both easily calculable for any given conditions of motion and mass distribution.

  18. Power-Tool Adapter For T-Handle Screws

    NASA Technical Reports Server (NTRS)

    Deloach, Stephen R.

    1992-01-01

    Proposed adapter enables use of pneumatic drill, electric drill, electric screwdriver, or similar power tool to tighten or loosen T-handled screws. Notched tube with perpendicular rod welded to it inserted in chuck of tool. Notched end of tube slipped over screw handle.

  19. Application studies of CFRTP hexagon socket head cap screws

    NASA Astrophysics Data System (ADS)

    Sano, Akihiko; Matsumoto, Masaru

    PPS thermoplastic CFRP is used to fabricate screws via injection molding; these samples were tested for tensile strength and torque vs axial tension. Attention was given to the effects of various lubricants. When MoS2 was applied to the screw's threading, its axial tension increased from 10 to 16 kN.

  20. The study on performance of twin screw conveyer

    SciTech Connect

    Qian Shude; Gu Fangzhen; Zhang Dongli

    1996-10-01

    The mechanism of oppositely rotating twin screw conveyer is analyzed and studied experimentally and theoretically formulating the semiempirical equation of output. Factors affecting the output of twin screw conveyer such as speed, properties of material, pitch, direction of rotation, the form of blade and of the openings, etc. are also studied.

  1. Joint Disorders

    MedlinePlus

    A joint is where two or more bones come together, like the knee, hip, elbow, or shoulder. Joints can be damaged by many types of injuries or diseases, including Arthritis - inflammation of a joint. It causes pain, stiffness, and swelling. Over time, ...

  2. Feasibility of C2 Vertebra Screws Placement in Patient With Occipitalization of Atlas: A Tomographic Study.

    PubMed

    Ji, Wei; Liu, Xiang; Huang, Wenhan; Huang, Zucheng; Li, Xueshi; Chen, Jianting; Wu, Zenghui; Zhu, Qingan

    2015-09-01

    Occipitalization of atlas (OA) is a congenital disease with the possibility of anomalous bony anatomies and the C2 pedicle screw insertion is technically challenging. However, there are no existing literatures clarified the dimensions and angulations of the C2 pedicles, lamina and lateral masses for screw insertion in patients with OA. Therefore, the aim of this study was to assess the morphometric features of C2 for screw placement in OA to guide the use of surgical screws. Measurements of the OA patients on the computer tomography (CT) images including lamina angle, length and thickness, pedicle angle, length and thickness, and lateral mass thickness and length of the axis vertebra. The OA patients data were compared with age and gender matched cohort of randomly selected patients in a control group without OA. The picture archiving and communication system was used for all patients who had received cervical CT scanning between January 2001 and January 2015. Measurements were performed independently by 2 experienced observers who reviewed the CT scans and recorded the patients with OA. Statistical analysis was performed at a level of significance P < 0.05. A total of 73 patients (29 males and 44 females) were eligible to be included in the OA group. In most of the measurements the pathological cohort had significantly smaller values compared to the control group (P < 0.05). In the OA group, only 45% of the pedicles and 88% of the lamina had thicknesses bigger than 3.5 mm. Both groups had all pedicle and lamina lengths bigger than 12 mm. Regarding the length of the lateral mass, no value was bigger than 12 mm in the OA group, whereas 40% of the values in the control group were bigger than 12 mm. The average pedicle and laminar angles were 37° and 49° in the patients with OA, respectively. The variable anatomy in patients with OA needs to be taken into account when performing spinal stabilization as the C2 bony architectures are significantly smaller than normal. Anatomically, translaminar screw is a more viable option in comparison with pedicle screw for C2 fixation in OA. Nevertheless, the suitability should be fully assessed prior to surgery. PMID:26376390

  3. Feasibility of C2 Vertebra Screws Placement in Patient With Occipitalization of Atlas

    PubMed Central

    Ji, Wei; Liu, Xiang; Huang, Wenhan; Huang, Zucheng; Li, Xueshi; Chen, Jianting; Wu, Zenghui; Zhu, Qingan

    2015-01-01

    Abstract Occipitalization of atlas (OA) is a congenital disease with the possibility of anomalous bony anatomies and the C2 pedicle screw insertion is technically challenging. However, there are no existing literatures clarified the dimensions and angulations of the C2 pedicles, lamina and lateral masses for screw insertion in patients with OA. Therefore, the aim of this study was to assess the morphometric features of C2 for screw placement in OA to guide the use of surgical screws. Measurements of the OA patients on the computer tomography (CT) images including lamina angle, length and thickness, pedicle angle, length and thickness, and lateral mass thickness and length of the axis vertebra. The OA patients data were compared with age and gender matched cohort of randomly selected patients in a control group without OA. The picture archiving and communication system was used for all patients who had received cervical CT scanning between January 2001 and January 2015. Measurements were performed independently by 2 experienced observers who reviewed the CT scans and recorded the patients with OA. Statistical analysis was performed at a level of significance P?stabilization as the C2 bony architectures are significantly smaller than normal. Anatomically, translaminar screw is a more viable option in comparison with pedicle screw for C2 fixation in OA. Nevertheless, the suitability should be fully assessed prior to surgery. PMID:26376390

  4. Ball Screw Actuator Including an Axial Soft Stop

    NASA Technical Reports Server (NTRS)

    Wingett, Paul T. (Inventor); Forrest, Steven Talbert (Inventor); Abel, Steve (Inventor); Woessner, George (Inventor); Hanlon, Casey (Inventor)

    2016-01-01

    An actuator includes an actuator housing, a ball screw, and an axial soft stop assembly. The ball screw extends through the actuator housing and has a first end and a second end. The ball screw is coupled to receive a drive force and is configured, upon receipt of the drive force, to selectively move in a retract direction and an extend direction. The axial soft stop assembly is disposed within the actuator housing. The axial soft stop assembly is configured to be selectively engaged by the ball screw and, upon being engaged thereby, to translate, with compliance, a predetermined distance in the extend direction, and to prevent further movement of the ball screw upon translating the predetermined distance.

  5. The Analysis of Soil Resistance During Screw Displacement Pile Installation

    NASA Astrophysics Data System (ADS)

    Krasinski, Adam

    2015-02-01

    The application of screw displacement piles (SDP) is still increasing due to their high efficiency and many advantages. However, one technological problem is a serious disadvantage of those piles. It relates to the generation of very high soil resistance during screw auger penetration, especially when piles are installed in non-cohesive soils. In many situations this problem causes difficulties in creating piles of designed length and diameter. It is necessary to find a proper method for prediction of soil resistance during screw pile installation. The analysis of screw resistances based on model and field tests is presented in the paper. The investigations were carried out as part of research project, financed by the Polish Ministry of Science and Higher Education. As a result of tests and analyses the empirical method for prediction of rotation resistance (torque) during screw auger penetration in non-cohesive subsoil based on CPT is proposed.

  6. A simple model of throughput calculation for single screw

    NASA Astrophysics Data System (ADS)

    Béreaux, Yves; Charmeau, Jean-Yves; Moguedet, Maël

    2007-04-01

    To be able to predict the throughput of a single-screw extruder or the metering time of an injection moulding machine for a given screw geometry, set of processing conditions and polymeric material is important both for practical and designing purposes. Our simple model show that the screw geometry is the most important parameter, followed by polymer rheology and processing conditions. Melting properties and length seem to intervene to a lesser extent. The calculations hinges on the idea of viewing the entire screw as a pump, conveying a solid and a molten fraction. The evolution of the solid fraction is the essence of the plastication process, but under particular circumstances, its influence on the throughput is nil. This allows us to get a very good estimate on the throughput and pressure development along the screw. Our calculations are compared to different sets of experiments available from the literature. We have consistent agreement both in throughput and pressure with published data.

  7. Effect of insertion torque on bone screw pullout strength.

    PubMed

    Lawson, K J; Brems, J

    2001-05-01

    The effect of insertion torque on the holding strength of 4.5-mm ASIF/AO cortical bone screws was studied in vitro. Screw holding strength was determined using an Instron materials testing machine (Bristol, United Kingdom) on 55 lamb femora and 30 human tibiocortical bone sections. Holding strength was defined as tensile stress at pullout with rapid loading to construct failure. Different insertion torques were tested, normalizing to the thickness of cortical bone specimen engaged. These represented low, intermediate, high, and thread-damaging insertion torque. All screws inserted with thread-damaging torque and single cortex engaging screws inserted to high torque tightening moments showed diminished holding strength. This loss of strength amounted to 40%-50% less than screws inserted with less torque. PMID:11379993

  8. Screw dislocations in GaN

    SciTech Connect

    Liliental-Weber, Zuzanna; Jasinski, Jacek B.; Washburn, Jack; O'Keefe, Michael A.

    2002-02-15

    GaN has received much attention over the past few years because of several new applications, including light emitting diodes, blue laser diodes and high-power microwave transistors. One of the biggest problems is a high density of structural defects, mostly dislocations, due to a lack of a suitable lattice-matched substrate since bulk GaN is difficult to grow in large sizes. Transmission Electron Microscopy (TEM) has been applied to study defects in plan-view and cross-sections on samples prepared by conventional techniques such as mechanical thinning and precision ion milling. The density of dislocations close to the sample surface of a 1 mm-thick HVPE sample was in the range of 3x109 cm-2. All three types of dislocations were present in these samples, and almost 50 percent were screw dislocations. Our studies suggest that the core structure of screw dislocations in the same material might differ when the material is grown by different methods.

  9. Percutaneous epiphysiodesis using transphyseal screws (PETS).

    PubMed

    Métaizeau, J P; Wong-Chung, J; Bertrand, H; Pasquier, P

    1998-01-01

    We describe a new technique of percutaneous epiphysiodesis using transphyseal screws (PETS) and our experience with it in 32 cases of limb-length inequality and nine angular knee deformities. A subgroup of 18 patients with postfracture limb overgrowth formed a clinical model for study of the real efficacy of PETS. It proved a reliable method with few complications and many advantages such as simplicity of technique, short operating time, rapid postoperative rehabilitation, and reversibility. Bone-length inequality decreased from a preepiphysiodesis average of 2.47 cm (range, 1.5-4.6) to 0.51 cm at skeletal maturity. The tibiofemoral angle reduced from a preoperative average of 7.66 degrees to 0.86 degrees at maturity. The screws began to exert significant growth inhibition within 6 months of insertion, slowing down the distal femoral and upper tibial physes by 68 and 56%, respectively. They achieved maximum growth retardation over the ensuing 12 months, slowing down the distal femoral physis by 89% and the proximal tibial physis by 95%. At skeletal maturity, total femoral growth was 45% and total tibial growth was 52% that of the normal side. Key PMID:9600565

  10. CT-based morphometric analysis of C1 laminar dimensions: C1 translaminar screw fixation is a feasible technique for salvage of atlantoaxial fusions

    PubMed Central

    Yew, Andrew; Lu, Derek; Lu, Daniel C.

    2015-01-01

    Background: Translaminar screw fixation has become an alternative in the fixation of the axial and subaxial cervical spine. We report utilization of this approach in the atlas as a salvage technique for atlantoaxial stabilization when C1 lateral mass screws are precluded. To assess the feasibility of translaminar fixation at the atlas, we have characterized the dimensions of the C1 lamina in the general adult population using computed tomography (CT)-based morphometry. Methods: A 46-year-old male with symptomatic atlantoaxial instability secondary to os odontoideum underwent bilateral C1 and C2 translaminar screw/rod fixation as C1 lateral mass fixation was precluded by an anomalous vertebral artery. The follow-up evaluation 2½ years postoperatively revealed an asymptomatic patient without recurrent neck/shoulder pain or clinical signs of instability. To better assess the feasibility of utilizing this approach in the general population, we retrospectively analyzed 502 consecutive cervical CT scans performed over a 3-month period in patients aged over 18 years at a single institution. Measurements of C1 bicortical diameter, bilateral laminar length, height, and angulation were performed. Laminar and screw dimensions were compared to assess instrumentation feasibility. Results: Review of CT imaging found that 75.9% of C1 lamina had a sufficient bicortical diameter, and 63.7% of C1 lamina had sufficient height to accept bilateral translaminar screw placement. Conclusions: CT-based measurement of atlas morphology in the general population revealed that a majority of C1 lamina had sufficient dimensions to accept translaminar screw placement. Although these screws appear to be a feasible alternative when lateral mass screws are precluded, further research is required to determine if they provide comparable fixation strength versus traditional instrumentation methods. PMID:26005585

  11. Exercise and the Knee Joint.

    ERIC Educational Resources Information Center

    Clarke, H. Harrison, Ed.

    1976-01-01

    This report by the President's Council on Physical Fitness and Sports examines the effects of various forms of physical exercise on the knee joint which, because of its vulnerability, is especially subject to injury. Discussion centers around the physical characteristics of the joint, commonly used measurements for determining knee stability,…

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

    PubMed Central

    Zhou, Yue; Li, Changqing; Liu, Huan

    2015-01-01

    Purpose Minimally invasive transforaminal lumbar interbody fusion (MI-TLIF) is increasingly popular for the surgical treatment of degenerative lumbar disc diseases. The constructs intended for segmental stability are varied in MI-TLIF. We adopted finite element (FE) analysis to compare the stability after different construct fixations using interbody cage with posterior pedicle screw-rod or pedicle screw-plate instrumentation system. Methods A L3–S1 FE model was modified to simulate decompression and fusion at L4–L5 segment. Fixation modes included unilateral plate (UP), unilateral rod (UR), bilateral plate (BP), bilateral rod (BR) and UP+UR fixation. The inferior surface of the S1 vertebra remained immobilized throughout the load simulation, and a bending moment of 7.5 Nm with 400N pre-load was applied on the L3 vertebra to recreate flexion, extension, lateral bending, and axial rotation. Range of motion (ROM) and Von Mises stress were evaluated for intact and instrumentation models in all loading planes. Results All reconstructive conditions displayed decreased motion at L4–L5. The pedicle screw-plate system offered equal ROM to pedicle screw-rod system in unilateral or bilateral fixation modes respectively. Pedicle screw stresses for plate system were 2.2 times greater than those for rod system in left lateral bending under unilateral fixation. Stresses for plate were 3.1 times greater than those for rod in right axial rotation under bilateral fixation. Stresses on intervertebral graft for plate system were similar to rod system in unilateral and bilateral fixation modes respectively. Increased ROM and posterior instrumentation stresses were observed in all loading modes with unilateral fixation compared with bilateral fixation in both systems. Conclusions Transforaminal lumbar interbody fusion augmentation with pedicle screw-plate system fixation increases fusion construct stability equally to the pedicle screw-rod system. Increased posterior instrumentation stresses are observed in all loading modes with plate fixation, and bilateral fixation could reduce stress concentration. PMID:26649749

  13. Lateral Movement of Screw Dislocations During Homoepitaxial Growth and Devices Yielded Therefrom Free of the Detrimental Effects of Screw Dislocations

    NASA Technical Reports Server (NTRS)

    Neudeck, Philip G. (Inventor); Powell, J. Anthony (Inventor)

    2004-01-01

    The present invention is related to a method that enables and improves wide bandgap homoepitaxial layers to be grown on axis single crystal substrates, particularly SiC. The lateral positions of the screw dislocations in epitaxial layers are predetermined instead of random, which allows devices to be reproducibly patterned to avoid performance degrading crystal defects normally created by screw dislocations.

  14. Effect of DDGS, Moisture Content, and Screw Speed on the Physical Properties of Extrudates in Single Screw Extrusion

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Three isocaloric (3.5 kcal/g) ingredient blends containing 20, 30, and 40% (wb) DDGS along with soy flour, corn flour, fish meal, mineral and vitamin mix, with the net protein adjusted to 28% (wb) for all blends, were extruded in a single screw laboratory-scale extruder at screw speeds of 100, 130, ...

  15. Experimental trial on surgical treatment for transverse fractures of the proximal phalanx: technique using intramedullary conical compression screw versus lateral compression plate☆

    PubMed Central

    Ibanez, Daniel Schneider; Rodrigues, Fabio Lucas; Salviani, Rafael Salmeron; Roberto, Fernando Augusto Reginatto; Pengo Junior, Jose Roberto; Aita, Marcio Aurelio

    2015-01-01

    Objective To compare the mechanical parameters between two methods for stabilization through compression: 1.5 mm axial compression plate versus conical compression screw used as an intramedullary tutor. Methods Polyurethane models (Sawbone®) that simulated transverse fractures of the proximal phalanx were used. The models were divided into three groups: lateral plate, conical screw and no implant. Results Greater force was needed to result in fatigue in the synthesis using an intramedullary plate. Thus, this model was proven to be mechanically superior to the model with the lateral plate. Conclusion Stabilization using the Acutrak® screw for treating fractures in the model used in this trial presents mechanical results that are statistically significantly superior to those from the axial compression technique using the lateral plate (Aptus Hand®). PMID:26535195

  16. Distal Tibial Metaphyseal Fractures: Does Blocking Screw Extend the Indication of Intramedullary Nailing?

    PubMed Central

    Moongilpatti Sengodan, Mugundhan; Vaidyanathan, Singaravadivelu; Karunanandaganapathy, Sankaralingam; Subbiah Subramanian, Sukumaran; Rajamani, Samuel Gnanam

    2014-01-01

    Aim. To evaluate the clinical use of blocking screws as a supplement to stability in distal tibial metaphyseal fractures treated with statically locked intramedullary nail. Main Outcome Measurement. Alignment and reduction preoperatively, postoperatively, and at healing were the main outcome measured with an emphasis on maintenance of initial reduction on followup. Patients and Methods. This was a prospective study of 20 consecutive cases of distal tibial metaphyseal fractures treated with statically locked intramedullary nailing with supplementary blocking screw between August 2006 and September 2007 with a maximum followup of 3 years. Medullary canal diameter was measured at the levels of fracture and isthmus. Results. The mean diameter of tibia at the level of isthmus was 11.9 mm and at the fracture site was 22.9 mm. Mean length of distal fracture segment was 4.6 cm. Mean varus/valgus alignment was 10.3 degrees preoperatively and 1.7 degrees immediatly postoperatively and was maintained till union. Using Karlstrom-Olerud score the outcome was excellent to good in 90%. Conclusion. We conclude that the use of blocking screw as a supplement will aid in achieving and maintaining the reduction of distal tibial metaphyseal fractures when treated with intramedullary nailing thereby extending the indication of intramedullary nailing. PMID:24967128

  17. Basic Study for Ultrasound-Based Navigation for Pedicle Screw Insertion Using Transmission and Backscattered Methods

    PubMed Central

    Chen, Ziqiang; Wu, Bing; Zhai, Xiao; Bai, Yushu; Zhu, Xiaodong; Luo, Beier; Chen, Xiao; Li, Chao; Yang, Mingyuan; Xu, Kailiang; Liu, Chengcheng; Wang, Chuanfeng; Zhao, Yingchuan; Wei, Xianzhao; Chen, Kai; Yang, Wu; Ta, Dean; Li, Ming

    2015-01-01

    The purpose of this study was to understand the acoustic properties of human vertebral cancellous bone and to study the feasibility of ultrasound-based navigation for posterior pedicle screw fixation in spinal fusion surgery. Fourteen human vertebral specimens were disarticulated from seven un-embalmed cadavers (four males, three females, 73.14 ± 9.87 years, two specimens from each cadaver). Seven specimens were used to measure the transmission, including tests of attenuation and phase velocity, while the other seven specimens were used for backscattered measurements to inspect the depth of penetration and A-Mode signals. Five pairs of unfocused broadband ultrasonic transducers were used for the detection, with center frequencies of 0.5 MHz, 1 MHz, 1.5 MHz, 2.25 MHz, and 3.5 MHz. As a result, good and stable results were documented. With increased frequency, the attenuation increased (P<0.05), stability of the speed of sound improved (P<0.05), and penetration distance decreased (P>0.05). At about 0.6 cm away from the cortical bone, warning signals were easily observed from the backscattered measurements. In conclusion, the ultrasonic system proved to be an effective, moveable, and real-time imaging navigation system. However, how ultrasonic navigation will benefit pedicle screw insertion in spinal surgery needs to be determined. Therefore, ultrasound-guided pedicle screw implantation is theoretically effective and promising. PMID:25861053

  18. Metal artifacts from titanium and steel screws in CT, 1.5T and 3T MR images of the tibial Pilon: a quantitative assessment in 3D

    PubMed Central

    Radzi, Shairah; Cowin, Gary; Robinson, Mark; Pratap, Jit; Volp, Andrew; Schuetz, Michael A.

    2014-01-01

    Radiographs are commonly used to assess articular reduction of the distal tibia (pilon) fractures postoperatively, but may reveal malreductions inaccurately. While magnetic resonance imaging (MRI) and computed tomography (CT) are potential three-dimensional (3D) alternatives they generate metal-related artifacts. This study aims to quantify the artifact size from orthopaedic screws using CT, 1.5T and 3T MRI data. Three screws were inserted into one intact human cadaver ankle specimen proximal to and along the distal articular surface, then CT, 1.5T and 3T MRI scanned. Four types of screws were investigated: titanium alloy (TA), stainless steel (SS) (Ø =3.5 mm), cannulated TA (CTA) and cannulated SS (CSS) (Ø =4.0 mm, Ø empty core =2.6 mm). 3D artifact models were reconstructed using adaptive thresholding. The artifact size was measured by calculating the perpendicular distance from the central screw axis to the boundary of the artifact in four anatomical directions with respect to the distal tibia. The artifact sizes (in the order of TA, SS, CTA and CSS) from CT were 2.0, 2.6, 1.6 and 2.0 mm; from 1.5T MRI they were 3.7, 10.9, 2.9, and 9 mm; and 3T MRI they were 4.4, 15.3, 3.8, and 11.6 mm respectively. Therefore, CT can be used as long as the screws are at a safe distance of about 2 mm from the articular surface. MRI can be used if the screws are at least 3 mm away from the articular surface except for SS and CSS. Artifacts from steel screws were too large thus obstructed the pilon from being visualised in MRI. Significant differences (P<0.05) were found in the size of artifacts between all imaging modalities, screw types and material types, except 1.5T versus 3T MRI for the SS screws (P=0.063). CTA screws near the joint surface can improve postoperative assessment in CT and MRI. MRI presents a favourable non-ionising alternative when using titanium hardware. Since these factors may influence the quality of postoperative assessment, potential improvements in operative techniques should be considered. PMID:24914417

  19. Endoscopic endonasal atlantoaxial transarticular screw fixation technique: an anatomical feasibility and biomechanical study.

    PubMed

    Mendes, George A C; Dickman, Curtis A; Rodriguez-Martinez, Nestor G; Kalb, Samuel; Crawford, Neil R; Sonntag, Volker K H; Preul, Mark C; Little, Andrew S

    2015-05-01

    OBJECT The primary disadvantage of the posterior cervical approach for atlantoaxial stabilization after odontoidectomy is that it is conducted as a second-stage procedure. The goal of the current study is to assess the surgical feasibility and biomechanical performance of an endoscopic endonasal surgical technique for C1-2 fixation that may eliminate the need for posterior fixation after odontoidectomy. METHODS The first step of the study was to perform endoscopic endonasal anatomical dissections of the craniovertebral junction in 10 silicone-injected fixed cadaveric heads to identify relevant anatomical landmarks. The second step was to perform a quantitative analysis using customized software in 10 reconstructed adult cervical spine CT scans to identify the optimal screw entry point and trajectory. The third step was biomechanical flexibility testing of the construct and comparison with the posterior C1-2 transarticular fixation in 14 human cadaveric specimens. RESULTS Adequate surgical exposure and identification of the key anatomical landmarks, such as C1-2 lateral masses, the C-1 anterior arch, and the odontoid process, were provided by the endonasal endoscopic approach in all specimens. Radiological analysis of anatomical detail suggested that the optimal screw entry point was on the anterior aspect of the C-1 lateral mass near the midpoint, and the screw trajectory was inferiorly and slightly laterally directed. The custommade angled instrumentation was crucial for screw placement. Biomechanical analysis suggested that anterior C1-2 fixation compared favorably to posterior fixation by limiting flexion-extension, axial rotation, and lateral bending (p > 0.3). CONCLUSIONS This is the first study that demonstrates the feasibility of an endoscopic endonasal technique for C1-2 fusion. This novel technique may have clinical utility by eliminating the need for a second-stage posterior fixation operation in certain patients undergoing odontoidectomy. PMID:25679235

  20. Influence of the implant abutment types and the dynamic loading on initial screw loosening

    PubMed Central

    Kim, Eun-Sook

    2013-01-01

    PURPOSE This study examined the effects of the abutment types and dynamic loading on the stability of implant prostheses with three types of implant abutments prepared using different fabrication methods by measuring removal torque both before and after dynamic loading. MATERIALS AND METHODS Three groups of abutments were produced using different types of fabrication methods; stock abutment, gold cast abutment, and CAD/CAM custom abutment. A customized jig was fabricated to apply the load at 30° to the long axis. The implant fixtures were fixed to the jig, and connected to the abutments with a 30 Ncm tightening torque. A sine curved dynamic load was applied for 105 cycles between 25 and 250 N at 14 Hz. Removal torque before loading and after loading were evaluated. The SPSS was used for statistical analysis of the results. A Kruskal-Wallis test was performed to compare screw loosening between the abutment systems. A Wilcoxon signed-rank test was performed to compare screw loosening between before and after loading in each group (α=0.05). RESULTS Removal torque value before loading and after loading was the highest in stock abutment, which was then followed by gold cast abutment and CAD/CAM custom abutment, but there were no significant differences. CONCLUSION The abutment types did not have a significant influence on short term screw loosening. On the other hand, after 105 cycles dynamic loading, CAD/CAM custom abutment affected the initial screw loosening, but stock abutment and gold cast abutment did not. PMID:23509006

  1. Feasibility Study of Free-Hand Technique for Pedicle Screw Insertion at C7 without Fluoroscopy-Guidance

    PubMed Central

    Lee, Gun Woo; Kim, Ho-Joong; Yeom, Jin S.; Uh, Jae-Hyung; Park, Jong-Ho; Lee, Ji-Hoon; Kim, Dong-Wook

    2016-01-01

    Study Design Retrospective interventional study. Purpose To introduce a free-hand pedicle screw (PS) insertion technique without fluoroscopic guidance in the C7 vertebra and evaluate the procedure's feasibility and radiologic outcomes. Overview of Literature Although PS insertion at C7 has been recognized as a critical procedure in posterior cervical fusion surgery, conventional techniques for C7 PS have several limitations. Methods Thirty two patients (64 screws) who underwent PS insertion in C7 with the novel technique were included in this study. Postoperative clinical and radiological outcomes were evaluated. Special attention was paid to the presence of any problems in the screw position including cortical breaches of the PS and encroachment of the PS into the spinal canal or the vertebral foramen. This novel technique for PS insertion in C7 without fluoroscopy guidance had three key elements. First, the ideal PS entry point was chosen near the C6–7 facet joint using preoperative images. Second, the convergent angle distance was measured at axial computed tomography (CT) imaging, which defined the distance between the tip of C7 spinous process and the extended line passing through the pedicle axis from the ideal entry point. Third, the cranial-caudal angle distance was measured in sagittal CT images, which defined the distance between the tip of the C7 spinous process and the extended line passing through the pedicle axis. Results Cortical breach on postoperative CT images was observed in three screws. All violated only the lateral wall of the affected pedicle. The breached screws occurred in the initial five cases. Postoperative neurologic deterioration was not observed in any patient, regardless of cortical breaching. Conclusions The novel technique successfully allows for C7 PS to be placed and is associated with a low rate of cortical breach. PMID:26949456

  2. Subcritical Onset of Plasma Fluctuations and Magnetic Self-Organization in a Line-Tied Screw Pinch

    NASA Astrophysics Data System (ADS)

    Brookhart, Matthew Irvin

    The line-tied screw pinch is an important model for solar plasma and has been studied theoretically and numerically for decades. Often these theoretical models used current profiles and equilibria that are difficult to make using inductive techniques conventionally used for creating pinch plasmas. This dissertation investigates the MHD stability of the line-tied screw pinch for a range of novel current profiles never before studied in a laboratory plasma. These studies used the Line-Tied Reconnection Experiment, a versatile line-tied screw pinch. The device was heavily modified to create more astrophysically relevant plasmas and provide increased diagnostic access. Multidimensional arrays of magnetic probes were built allow simultaneous measurements of dynamic plasma structures. Plasma is injected into the experiment at six discrete locations. Stability analysis of the line-tied screw pinch assumes one dimensional equilibria. Internal measurements suggest that the 1D assumption is approximately valid for experimental plasmas, but plasmas undergo complex, three dimensional dynamics and self-organization without the presence of linear instability. Screw pinch equilibria with zero-net-current and hollow current profiles are created for the first time in the laboratory. The zero-net-current equilibrium transitions to a sub-critical dynamic state that reorganizes the equilibrium and prevents the formation of linear instability. The hollow current equilibrium self-organizes into a relaxed state at a critical value of magnetic field, independent of plasma current. Plasmas with two and three distinct flux ropes do not have a 1D equilibrium and exhibit dynamic interactions. These interactions create an inverse cascade as flux ropes become unstable and merge.

  3. Scaphoid Proximal Pole Fracture Following Headless Screw Fixation.

    PubMed

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

    2016-03-01

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

  4. Midline Lumbar Fusion with Cortical Bone Trajectory Screw

    PubMed Central

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

    2014-01-01

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

  5. Economics of water injected air screw compressor systems

    NASA Astrophysics Data System (ADS)

    Venu Madhav, K.; Kovačević, A.

    2015-08-01

    There is a growing need for compressed air free of entrained oil to be used in industry. In many cases it can be supplied by oil flooded screw compressors with multi stage filtration systems, or by oil free screw compressors. However, if water injected screw compressors can be made to operate reliably, they could be more efficient and therefore cheaper to operate. Unfortunately, to date, such machines have proved to be insufficiently reliable and not cost effective. This paper describes an investigation carried out to determine the current limitations of water injected screw compressor systems and how these could be overcome in the 15-315 kW power range and delivery pressures of 6-10 bar. Modern rotor profiles and approach to sealing and cooling allow reasonably inexpensive air end design. The prototype of the water injected screw compressor air system was built and tested for performance and reliability. The water injected compressor system was compared with the oil injected and oil free compressor systems of the equivalent size including the economic analysis based on the lifecycle costs. Based on the obtained results, it was concluded that water injected screw compressor systems could be designed to deliver clean air free of oil contamination with a better user value proposition than the oil injected or oil free screw compressor systems over the considered range of operations.

  6. Management of a fractured implant abutment screw: a clinical report.

    PubMed

    Canpolat, Ceyhun; Ozkurt-Kayahan, Zeynep; Kazazoğlu, Ender

    2014-07-01

    In an abutment screw fracture, it is generally a challenge for the clinician to remove fractured fragments. In some cases, the screw cannot be removed, and alternative solutions should be considered. This clinical report describes the replacement of a ball attachment with a fractured screw, which was impossible to retrieve, with a cast dowel with ball attachment. The patient who presented to the Department of Prosthodontics, Yeditepe University, Faculty of Dentistry was a 65-year-old woman, wearing a mandibular complete denture supported by two implants for 4 years. She complained about the loss of retention of the denture because of the fractured abutment screw, and it was found that another dentist had previously tried to retrieve the fractured screw with no success. It was decided to construct a cast dowel with ball attachment to improve retention without sacrificing the implant. The interior of the implant and the fractured screw were machined with a rotating instrument. An impression was taken with a metal strip and silicone-based materials. In the laboratory, a stone die was generated from the impression, and a custom-made cast dowel with ball attachment was constructed. It was then cemented with glass ionomer cement and connected to the denture with the direct method. The alternative procedure described in this clinical report was successful for the removal of the fractured abutment screw and use of the existing denture. PMID:24393481

  7. Salvaging the pullout strength of stripped screws in osteoporotic bone.

    PubMed

    Pechon, Pierre H M; Mears, Simon C; Langdale, Evan R; Belkoff, Stephen M

    2013-06-01

    Our goal was to determine whether the pullout strength of stripped screw holes in osteoporotic bone could be increased with readily available materials from the operating room. We inserted 3.5-mm stainless steel nonlocking self-tapping cortical screws bicortically into 5 osteoporotic humeri. Each screw was first stripped by rotating it 1 full turn past maximum torque. In the control group, the screw was pulled out using an MTS machine (858; MTS Inc, Eden Prairie, Minnesota). In the treatment groups, the screw was removed, the hole was augmented with 1 of the 3 materials (stainless steel wire, polysorb suture, or polyethylene terephthalate glycol plastic sheet), and the screws were replaced and then pulled out. The effect of material on pullout strength was checked for significance (P < .05) using a general linearized latent and mixed model (Stata10; StataCorp, College Station, Texas). The mean (95% confidence interval) pullout strength for the unaugmented hole was 138 N (range 88-189), whereas the holes augmented with plastic, suture, or wire had mean pullout strengths of 255 N (range 177-333), 228 N (range 149-308), and 396 N (range 244-548), respectively. Although wire augmentation resulted in pullout strength that was significantly greater than that of the unaugmented screw, it was still below that of the intact construct. PMID:24093076

  8. Spline-locking screw fastening strategy

    NASA Technical Reports Server (NTRS)

    Vranish, John M.

    1992-01-01

    A fastener was developed by NASA Goddard for efficiently performing assembly, maintenance, and equipment replacement functions in space using either robotics or astronaut means. This fastener, the 'Spline Locking Screw' (SLS) would also have significant commercial value in advanced space manufacturing. Commercial (or DoD) products could be manufactured in such a way that their prime subassemblies would be assembled using SLS fasteners. This would permit machines and robots to disconnect and replace these modules/parts with ease, greatly reducing life cycle costs of the products and greatly enhancing the quality, timeliness, and consistency of repairs, upgrades, and remanufacturing. The operation of the basic SLS fastener is detailed, including hardware and test results. Its extension into a comprehensive fastening strategy for NASA use in space is also outlined. Following this, the discussion turns toward potential commercial and government applications and the potential market significance of same.

  9. Spline-Locking Screw Fastening Strategy (SLSFS)

    NASA Technical Reports Server (NTRS)

    Vranish, John M.

    1991-01-01

    A fastener was developed by NASA Goddard for efficiently performing assembly, maintenance, and equipment replacement functions in space using either robotic or astronaut means. This fastener, the 'Spline Locking Screw' (SLS) would also have significant commercial value in advanced manufacturing. Commercial (or DoD) products could be manufactured in such a way that their prime subassemblies would be assembled using SLS fasteners. This would permit machines and robots to disconnect and replace these modules/parts with ease, greatly reducing life cycle costs of the products and greatly enhancing the quality, timeliness, and consistency of repairs, upgrades, and remanufacturing. The operation of the basic SLS fastener is detailed, including hardware and test results. Its extension into a comprehensive fastening strategy for NASA use in space is also outlined. Following this, the discussion turns toward potential commercial and government applications and the potential market significance of same.

  10. Spline-Screw Payload-Fastening System

    NASA Technical Reports Server (NTRS)

    Vranish, John M.

    1994-01-01

    Payload handed off securely between robot and vehicle or structure. Spline-screw payload-fastening system includes mating female and male connector mechanisms. Clockwise (or counter-clockwise) rotation of splined male driver on robotic end effector causes connection between robot and payload to tighten (or loosen) and simultaneously causes connection between payload and structure to loosen (or tighten). Includes mechanisms like those described in "Tool-Changing Mechanism for Robot" (GSC-13435) and "Self-Aligning Mechanical and Electrical Coupling" (GSC-13430). Designed for use in outer space, also useful on Earth in applications needed for secure handling and secure mounting of equipment modules during storage, transport, and/or operation. Particularly useful in machine or robotic applications.

  11. SCREW COMPRESSOR CHARACTERISTICS FOR HELIUM REFRIGERATION SYSTEMS

    SciTech Connect

    Ganni, Venkatarao; Knudsen, Peter; Creel, Jonathan; Arenius, Dana; Casagrande, Fabio; Howell, Matt

    2008-03-01

    The oil injected screw compressors have practically replaced all other types of compressors in modern helium refrigeration systems due to their large displacement capacity, minimal vibration, reliability and capability of handling helium's high heat of compression.At the present state of compressor system designs for helium systems, typically two-thirds of the lost input power is due to the compression system. Therefore it is important to understand the isothermal and volumetric efficiencies of these machines to help properly design these compression systems to match the refrigeration process. This presentation summarizes separate tests that have been conducted on Sullair compressors at the Superconducting Super-Collider Laboratory (SSCL) in 1993, Howden compressors at Jefferson Lab (JLab) in 2006 and Howden compressors at the Spallation Neutron Source (SNS) in 2006. This work is part of an ongoing study at JLab to understand the theoretical basis for these efficiencies and their loss

  12. Use of traction screw to aid in fracture reduction in bilateral parasymphysis fracture of mandible.

    PubMed

    Jaisani, Mehul R; Pradhan, Leeza; Dongol, Ashok; Acharaya, Pradeep; Sagtani, Alok

    2016-06-01

    Treatment of bilateral parasymphysis fracture often requires special attention due to airway considerations and difficulty in achieving precise anatomic reduction. The central fracture fragment is often displaced posteriorly and inferiorly due to muscle pull, and this adds to difficulty in reduction and stabilization of the central fracture fragment during plate fixation. With this article, we advocate a technique using stainless steel screw and self-holding screwdriver to manipulate the central fragment and achieve an anatomic reduction. We have used this technique in 12 patients with bilateral parasymphysis fracture without any complications and have found it very effective. PMID:26404945

  13. Comparison of ender nails, dynamic hip screws, and Gamma nails in the treatment of peritrochanteric femoral fractures.

    PubMed

    Habernek, H; Wallner, T; Aschauer, E; Schmid, L

    2000-02-01

    Three hundred seventy-six patients with peritrochanteric fractures treated over a 10-year period were reviewed. In 85 patients treated with Ender nailing, the most frequent complications were leg shortening (34), external rotation failure (21), and postoperative distal gliding of the nails (7). In 183 patients treated with dynamic hip screws or a 95 degree condylar or a 130 degree blade plate, 3 presented with infection, 5 with instability, and 4 with femoral head necrosis. In 105 patients treated with Gamma nailing, the most serious complications were infections (3), inward rotation failure (2), postoperative bleeding at the insertion site (2), and shaft fracture (1). Because of its inherent instability, Ender nailing is no longer used. The implantation technique for the dynamic hip screw is safer and simpler than the various models of the ASIF blade plate. However, the dynamic hip screw has been superseded by the Gamma nail because of its absolute stability. In the beginning, Gamma nailing was technically more demanding with a higher number of intraoperative complications. In this study, the number of malalignments did not differ significantly between the dynamic hip screw (14) and the Gamma nail (11), but was high with Ender nailing (56). PMID:10688288

  14. Analysis of Material Flow in Screw Extrusion of Aluminum

    SciTech Connect

    Haugen, Bjoern; Oernskar, Magnus; Welo, Torgeir; Wideroee, Fredrik

    2010-06-15

    Screw extrusion of aluminum is a new process for production of aluminum profiles. The commercial potential could be large. Little experimental and numerical work has been done with respect to this process.The material flow of hot aluminum in a screw extruder has been analyzed using finite element formulations for the non-Newtonian Navier-Stokes equations. Aluminum material properties are modeled using the Zener-Holloman material model. Effects of stick-slip conditions are investigated with respect to pressure build up and mixing quality of the extrusion process.The numerical results are compared with physical experiments using an experimental screw extruder.

  15. Noninvasive method for retrieval of broken dental implant abutment screw.

    PubMed

    Gooty, Jagadish Reddy; Palakuru, Sunil Kumar; Guntakalla, Vikram Reddy; Nera, Mahipal

    2014-04-01

    Dental implants made of titanium for replacement of missing teeth are widely used because of ease of technical procedure and high success rate, but are not free of complications and may fail. Fracturing of the prosthetic screw continues to be a problem in restorative practice and great challenge to remove the fractured screw conservatively. This case report describes and demonstrates the technique of using an ultrasonic scaler in the removal of the fracture screw fragment as a noninvasive method without damaging the hex of implants. PMID:24963261

  16. Noninvasive method for retrieval of broken dental implant abutment screw

    PubMed Central

    Gooty, Jagadish Reddy; Palakuru, Sunil Kumar; Guntakalla, Vikram Reddy; Nera, Mahipal

    2014-01-01

    Dental implants made of titanium for replacement of missing teeth are widely used because of ease of technical procedure and high success rate, but are not free of complications and may fail. Fracturing of the prosthetic screw continues to be a problem in restorative practice and great challenge to remove the fractured screw conservatively. This case report describes and demonstrates the technique of using an ultrasonic scaler in the removal of the fracture screw fragment as a noninvasive method without damaging the hex of implants. PMID:24963261

  17. Helical screw rheometer: A new concept in rotational rheometry

    NASA Astrophysics Data System (ADS)

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

    1984-02-01

    The helical screw rheometer represents a new concept in viscometry: a rotational instrument that generates a pressure difference and therefore does not require torque measurement. The device is basically a metering screw that operates with no discharge. The results that are necessary to obtain the power-law constitutive parameters from pressure drop and rotation rate data are presented along with comparisons between theory and experiment for a prototype instrument operated at ambient conditions. The helical screw rheometer may offer advantages over conventional instruments for: (1) high-pressure measurements; (2) chemically-reacting fluids; (3) heterogeneous fluids; and (4) on-line measurements.

  18. Optically driven Archimedes micro-screws for micropump applications: multiple blade design

    NASA Astrophysics Data System (ADS)

    Baldeck, Patrice L.; Lin, Chih-Lang; Lin, Yu-Sheng; Lin, Chin-Te; Chung, Tien-Tung; Bouriau, Michel; Vitrant, Guy

    2011-10-01

    We study the rotation of photo-driven Archimedes screw with multiple blades. The micron-sized Archimedes screws are readily made by the two-photon polymerization technique. Free-floating screws that are trapped by optical tweezers align in the laser irradiation direction, and rotate spontaneously. In this study we demonstrate that the rotation speeds of two-blade-screws is twice the rotation speed of one-blade-screw. However, more complex 3-blade-screws rotate slower than 2-blade-screws due to their limited geometry resolution at this micron scale.

  19. Vibration analysis of three-screw pumps under pressure loads and rotor contact forces

    NASA Astrophysics Data System (ADS)

    Li, Wanyou; Lu, Hanfeng; Zhang, Yue; Zhu, Chuan; Lu, Xiqun; Shuai, Zhijun

    2016-01-01

    Two main vibration sources in three-screw pumps, the fluid exciting force and the screw contact force, are studied to provide the basis for vibration control in this paper. A fluid exciting force model and a screw contact model are proposed to calculate these forces. An experimental test is carried out to obtain the vibration response of a three-screw pump. A calibrated finite element model of the three-screw pump is used to verify the vibration response under the fluid exciting force and the screw contact force obtained from the proposed models. The results show that the screw contact force is more dominant than the fluid exciting force.

  20. Biomechanical Comparison of Pedicle Screw Augmented with Different Volumes of Polymethylmethacrylate in Osteoporotic and Severely Osteoporotic Synthetic Bone Blocks in Primary Implantation: An Experimental Study

    PubMed Central

    Liu, Da; Zhang, Xiao-jun; Liao, Dong-fa; Zhou, Jiang-jun; Li, Zhi-qiang; Zhang, Bo; Wang, Cai-ru; Lei, Wei; Kang, Xia; Zheng, Wei

    2016-01-01

    This study was designed to compare screw stabilities augmented with different volumes of PMMA and analyze relationship between screw stability and volume of PMMA and optimum volume of PMMA in different bone condition. Osteoporotic and severely osteoporotic synthetic bone blocks were divided into groups A0-A5 and B0-B5, respectively. Different volumes of PMMA were injected in groups A0 to A5 and B0 to B5. Axial pullout tests were performed and Fmax was measured. Fmax in groups A1-A5 were all significantly higher than group A0. Except between groups A1 and A2, A3 and A4, and A4 and A5, there were significant differences on Fmax between any other two groups. Fmax in groups B1-B5 were all significantly higher than group B0. Except between groups B1 and B2, B2 and B3, and B4 and B5, there were significant differences on Fmax between any other two groups. There was significantly positive correlation between Fmax and volume of PMMA in osteoporotic and severely osteoporotic blocks. PMMA can significantly enhance pedicle screw stability in osteoporosis and severe osteoporosis. There were positive correlations between screw stability and volume of PMMA. In this study, injection of 3 mL and 4 mL PMMA was preferred in osteoporotic and severely osteoporotic blocks, respectively. PMID:26885525

  1. Screw- vs cement-implant-retained restorations: an experimental study in the Beagle. Part 1. Screw and abutment loosening.

    PubMed

    Assenza, Bartolomeo; Scarano, Antonio; Leghissa, Giulio; Carusi, Giorgio; Thams, Ulf; Roman, Fidel San; Piattelli, Adriano

    2005-01-01

    The causes of implant failures can be biological or mechanical. The mechanical causes include fracture of the implant, fracture of the abutment, and loosening of the abutment. Numerous studies show that abutment loosening constitutes one of the marked implant postsurgery complications requiring clinical intervention. The aim of the present study was to evaluate the incidence of the screw loosening in screwed or cemented abutments. Six adult male Beagles were used. In each dog, the first molars and 2 premolars were extracted. The sutures were removed after 7 days. After 3 months, 10 implants were placed in each dog, 5 in the right mandible and 5 in the left mandible. The abutments either were screwed in (n=30) by applying a total strength of 30 N/cm or were cemented (n=30). After 12 months, 8 (27%) loosened screws were present in screwed abutments, whereas no abutment loosening was observed in cemented abutments (P = .0001). Screwed abutments are often submitted to nonaxial loads that determine screw and abutment loosening. PMID:16265854

  2. Ceramic joints

    DOEpatents

    Miller, Bradley J.; Patten, Jr., Donald O.

    1991-01-01

    Butt joints between materials having different coefficients of thermal expansion are prepared having a reduced probability of failure of stress facture. This is accomplished by narrowing/tapering the material having the lower coefficient of thermal expansion in a direction away from the joint interface and not joining the narrow-tapered surface to the material having the higher coefficient of thermal expansion.

  3. 21. NBS SUIT LAB. THREE GLOVES, HELMET, AND SCREW DRIVER ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    21. NBS SUIT LAB. THREE GLOVES, HELMET, AND SCREW DRIVER TORQUE WRENCH FOR ASSEMBLY AND REPAIR OF BOTH. - Marshall Space Flight Center, Neutral Buoyancy Simulator Facility, Rideout Road, Huntsville, Madison County, AL

  4. Screw anchors economically control pipeline buoyancy in muskeg

    SciTech Connect

    Robertson, R.; Curle, R.

    1995-04-24

    To control buoyancy of large-diameter pipelines that cross such wet areas as muskeg swamps in Alberta Province, Canada, NOVA Gas Transmission Ltd., Calgary, for more than 6 years investigated alternatives to traditional concrete weights. The company`s research indicated that helical screw anchors offer cost-effective buoyancy control for natural-gas pipelines 20-in. OD and larger. Muskegs are organic soils with high water tables, low shear strengths, and low densities (specific gravity of 1.04). NOVA`s experience demonstrated practical and cost benefits of screw anchors to resist uplift forces. And among other benefits, substitution of screw anchors for concrete weights significantly reduced the number of heavy trucks that must be moved across the muskeg. The paper discusses buoyancy control, pipeline adaptation, pipe stresses and corrosion, pipeline construction and screw-anchor installation, economics and other benefits.

  5. Adhesive-backed terminal board eliminates mounting screws

    NASA Technical Reports Server (NTRS)

    1965-01-01

    Low-profile terminal board is used in dense electronic circuits where mounting and working space is limited. The board has a thin layer of pressure-sensitive adhesive backing which eliminates the need for mounting screws.

  6. Biomechanical Evaluation of 6.5-mm Cannulated Screws.

    PubMed

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

    2016-01-01

    Although biomechanical and clinical evidence exists regarding smaller compression screws, biomechanical data regarding the larger headless screws are not currently available. Headed and headless 6.5-mm cannulated compression screws were examined, with analysis of interfragmentary compression, insertion torque, and resistance of the construct to a shear force. No significant differences were seen between the maximum insertion torque of the headless or headed screws. Maximum and steady-state compression forces were also not significantly different between groups. Countersinking the headless model 2 mm led to a 77.01% decrease in steady-state compression levels. Shear testing did not reveal any significant differences in peak load at ultimate failure, specimen stiffness, or final block displacement, although a trend to increased peak load and stiffness was seen with the headless specimens. PMID:27082882

  7. Experimental study of the subtalar joint axis: preliminary investigation.

    PubMed

    Zographos, S; Chaminade, B; Hobatho, M C; Utheza, G

    2000-01-01

    An experimental study of the subtalar joint has been conducted with the aim of establishing its axis of movement as well as analysing the associated movement. For description of the axis, CT data for five positions of a single foot were reconstructed using a 3D programme, the 3D data was processed by Patran software. Measures of angular displacements were made from three amputated feet placed in a specially constructed foot frame. Four instantaneous axes of movement could be defined. Calculation of displacements showed an important rolling of the calcaneus (45 degrees). Tacking was evident in inversion, with an opposite displacement between the front and rear part of the calcaneus, whereas during eversion tacking affected only the rear part of the bone: these results were confirmed by 3D reconstructions. Henke's axis was described as that for the talonavicular joint, but acceptable for the subtalar joint. Several authors investigating the coordinates of this axis have reported large differences and described screw-like movements, the latter being incompatible with a fixed axis: instantaneous axes, however are compatible with a screw-like movement. The subtalar joint appears to work as a pivot joint during inversion and as a plane joint during eversion. Although Henke's axis has pedagogical value the subtalar joint has a series of instantaneous axes. PMID:11236321

  8. Causes and treatments of lag screw's cut out after intramedullary nailing osteosinthesis for trochanteric fractures.

    PubMed

    Gazzotti, Gabriele; Matino, Giovanni; Tsatsis, Christos; Sacchetti, GianLuigi; Baudi, Paolo; Catani, Fabio

    2014-01-01

    Background. Superior cut-out of a lag screw remains a serious complication in the treatment of trochanteric or subtrochanteric fractures and it is related to many factors: the type of fracture, osteoporosis and the stability of fracture reduction. Little is known about the outcome after revision surgery for complications of the gamma nail. We assessed the outcome in patients who had revision surgery because of lag screw's cut out after gamma nailing for a trochanteric fracture.Material and Method. We present a study of 20 consecutive patients who underwent treatment after 20 cut-out of the lag screw fixation of a trochanteric fracture with Gamma Locking Nail from September 2004 to November 2010. In 16 patients hip prothesis was performed, in 1 the removal of the implant and in 3 the reosteosynthesis. We reviewed 13 patients: 10 total hip arthroplasty, 2 endoprothesis and 1 reosteosynthesis of nail and lag screw (mean follow up: 26 months, mean age: 73 years old), 7 patients died. Patients were reviewed retrospectively by an independent observer. Clinical evaluation was performed, Oxford score and Harris Hip score were measured. X-Ray examination was performed after a minimum of 12 months of follow up.Results. Mean Harris Hip Score mean was 67 and mean Oxford score was 32 in hip prothesis group (12 patients). We had several complications, Implant-related complications were: 2 ipometria > 2cm, 2 recurrent hip arthroplasty dislocations (1 reoperated), 4 persistent thigh pain. In only 4 patients none complications were observed. Another patient,  who had been subjected to reosteosinthesis, obtained better results (HHS:95, Oxford score:45) but with a 2 cm ipometria and occasional pain in the thigh.Conclusion. Cut out after gamma nail is consequent to biological or mechanical causes. Treatment of this complication is hip prosthesis (parzial or total hip arthroplasty), reosteosynthesis of the lag screw and/or the nail and the removal of the implant. Conversion to total/parzial hip arthroplasty may be a demanding operation with a higher complication rate respect to the standard, while reosteosynthesis is possible in selected patients and early cutting out. PMID:25245649

  9. Screw thread parameter measurement system based on image processing method

    NASA Astrophysics Data System (ADS)

    Rao, Zhimin; Huang, Kanggao; Mao, Jiandong; Zhang, Yaya; Zhang, Fan

    2013-08-01

    In the industrial production, as an important transmission part, the screw thread is applied extensively in many automation equipments. The traditional measurement methods of screw thread parameter, including integrated test methods of multiparameters and the single parameter measurement method, belong to contact measurement method. In practical the contact measurement exists some disadvantages, such as relatively high time cost, introducing easily human error and causing thread damage. In this paper, as a new kind of real-time and non-contact measurement method, a screw thread parameter measurement system based on image processing method is developed to accurately measure the outside diameter, inside diameter, pitch diameter, pitch, thread height and other parameters of screw thread. In the system the industrial camera is employed to acquire the image of screw thread, some image processing methods are used to obtain the image profile of screw thread and a mathematics model is established to compute the parameters. The C++Builder 6.0 is employed as the software development platform to realize the image process and computation of screw thread parameters. For verifying the feasibility of the measurement system, some experiments were carried out and the measurement errors were analyzed. The experiment results show the image measurement system satisfies the measurement requirements and suitable for real-time detection of screw thread parameters mentioned above. Comparing with the traditional methods the system based on image processing method has some advantages, such as, non-contact, easy operation, high measuring accuracy, no work piece damage, fast error analysis and so on. In the industrial production, this measurement system can provide an important reference value for development of similar parameter measurement system.

  10. Crystal geometry of screw dislocation glide in tungsten nanocrystals

    NASA Astrophysics Data System (ADS)

    Sadanov, E. V.

    2015-02-01

    A zigzag pattern of low-temperature dislocation glide occurring in tungsten nanocrystals in the intersecting planes {110} and {211}, which belong to the <111> crystallographic zone, has been revealed using field ion microscopy. It has been shown that cores of 1/2[111] screw dislocations are undissociated within the limits of the resolution of the field ion microscope. It has been found experimentally that surface atoms are displaced into metastable positions in the region of the trace of screw dislocation motion.

  11. Polyaxial Screws in Locked Plating of Tibial Pilon Fractures.

    PubMed

    Yenna, Zachary C; Bhadra, Arup K; Ojike, Nwakile I; Burden, Robert L; Voor, Michael J; Roberts, Craig S

    2015-08-01

    This study examined the axial and torsional stiffness of polyaxial locked plating techniques compared with fixed-angle locked plating techniques in a distal tibia pilon fracture model. The effect of using a polyaxial screw to cross the fracture site was examined to determine its ability to control relative fracture site motion. A laboratory experiment was performed to investigate the biomechanical stiffness of distal tibia fracture models repaired with 3.5-mm anterior polyaxial distal tibial plates and locking screws. Sawbones Fourth Generation Composite Tibia models (Pacific Research Laboratories, Inc, Vashon, Washington) were used to model an Orthopaedic Trauma Association 43-A1.3 distal tibia pilon fracture. The polyaxial plates were inserted with 2 central locking screws at a position perpendicular to the cortical surface of the tibia and tested for load as a function of axial displacement and torque as a function of angular displacement. The 2 screws were withdrawn and inserted at an angle 15° from perpendicular, allowing them to span the fracture and insert into the opposing fracture surface. Each tibia was tested again for axial and torsional stiffness. In medial and posterior loading, no statistically significant difference was found between tibiae plated with the polyaxial plate and the central screws placed in the neutral position compared with the central screws placed at a 15° position. In torsional loading, a statistically significant difference was noted, showing greater stiffness in tibiae plated with the polyaxial plate and the central screws placed at a 15° position compared with tibiae plated with the central screws placed at a 0° (or perpendicular) position. This study showed that variable angle constructs show similar stiffness properties between perpendicular and 15° angle insertions in axial loading. The 15° angle construct shows greater stiffness in torsional loading. PMID:26270750

  12. Effect of angular stability and other locking parameters on the mechanical performance of intramedullary nails.

    PubMed

    Hoffmann, Stefanie; Gerber, Claus; von Oldenburg, Geert; Kessler, Manuel; Stephan, Daniel; Augat, Peter

    2015-04-01

    To extend the indications of intramedullary nails for distal or proximal fractures, nails with angle stable locking options have been developed. Studies on the mechanical efficacy of these systems have been inconsistent likely due to confounding variables such as number, geometry, or orientation of the screws, as well as differences in the loading mode. Therefore, the aim of this study was to quantify the effect of angular stability on the mechanical performance of intramedullary nails. The results could then be compared with the effects of various locking screw parameters and loading modes. A generic model was developed consisting of artificial bone material and titanium intramedullary nail that provided the option to systematically modify the locking screw configuration. Using a base configuration, the following parameters were varied: number of screws, distance and orientation between screws, blocking of screws, and simulation of freehand locking. Tension/compression, torsional, and bending loads were applied. Stiffness and clearance around the zero loading point were determined. Angular stability had no effect on stiffness but completely blocked axial clearance (p=0.003). Simulation of freehand locking reduced clearance for all loading modes by at least 70% (p<0.003). The greatest increases in torsional and bending stiffness were obtained by increasing the number of locking screws (up to 80%, p<0.001) and by increasing the distance between them (up to 70%, p<0.001). In conclusion, our results demonstrate that the mechanical performance of IM nailing can be affected by various locking parameters of which angular stability is only one. While angular stability clearly reduces clearance of the screw within the nail, mechanical stiffness depends more on the number of screws and their relative distance. Thus, optimal mechanical performance in IM nailing could potentially be obtained by combining angular stability with optimal arrangement of locking screws. PMID:25581739

  13. Biomechanical Analysis of Fusion Segment Rigidity Upon Stress at Both the Fusion and Adjacent Segments: A Comparison between Unilateral and Bilateral Pedicle Screw Fixation

    PubMed Central

    Kim, Ho-Joong; Kang, Kyoung-Tak; Chang, Bong-Soon; Lee, Choon-Ki; Kim, Jang-Woo

    2014-01-01

    Purpose The purpose of this study was to investigate the effects of unilateral pedicle screw fixation on the fusion segment and the superior adjacent segment after one segment lumbar fusion using validated finite element models. Materials and Methods Four L3-4 fusion models were simulated according to the extent of decompression and the method of pedicle screws fixation in L3-4 lumbar fusion. These models included hemi-laminectomy with bilateral pedicle screw fixation in the L3-4 segment (BF-HL model), total laminectomy with bilateral pedicle screw fixation (BF-TL model), hemi-laminectomy with unilateral pedicle screw fixation (UF-HL model), and total laminectomy with unilateral pedicle screw fixation (UF-TL model). In each scenario, intradiscal pressures, annulus stress, and range of motion at the L2-3 and L3-4 segments were analyzed under flexion, extension, lateral bending, and torsional moments. Results Under four pure moments, the unilateral fixation leads to a reduction in increment of range of motion at the adjacent segment, but larger motions were noted at the fusion segment (L3-4) in the unilateral fixation (UF-HL and UF-TL) models when compared to bilateral fixation. The maximal von Mises stress showed similar patterns to range of motion at both superior adjacent L2-3 segments and fusion segment. Conclusion The current study suggests that unilateral pedicle screw fixation seems to be unable to afford sufficient biomechanical stability in case of bilateral total laminectomy. Conversely, in the case of hemi-laminectomy, unilateral fixation could be an alternative option, which also has potential benefit to reduce the stress of the adjacent segment. PMID:25048501

  14. Screw dislocation driven growth of nanomaterials.

    PubMed

    Meng, Fei; Morin, Stephen A; Forticaux, Audrey; Jin, Song

    2013-07-16

    Nanoscience and nanotechnology impact our lives in many ways, from electronic and photonic devices to biosensors. They also hold the promise of tackling the renewable energy challenges facing us. However, one limiting scientific challenge is the effective and efficient bottom-up synthesis of nanomaterials. We can approach this core challenge in nanoscience and nanotechnology from two perspectives: (a) how to controllably grow high-quality nanomaterials with desired dimensions, morphologies, and material compositions and (b) how to produce them in a large quantity at reasonable cost. Because many chemical and physical properties of nanomaterials are size- and shape-dependent, rational syntheses of nanomaterials to achieve desirable dimensionalities and morphologies are essential to exploit their utilities. In this Account, we show that the dislocation-driven growth mechanism, where screw dislocation defects provide self-perpetuating growth steps to enable the anisotropic growth of various nanomaterials at low supersaturation, can be a powerful and versatile synthetic method for a wide variety of nanomaterials. Despite significant progress in the last two decades, nanomaterial synthesis has often remained an "art", and except for a few well-studied model systems, the growth mechanisms of many anisotropic nanostructures remain poorly understood. We strive to go beyond the empirical science ("cook-and-look") and adopt a fundamental and mechanistic perspective to the anisotropic growth of nanomaterials by first understanding the kinetics of the crystal growth process. Since most functional nanomaterials are in single-crystal form, insights from the classical crystal growth theories are crucial. We pay attention to how screw dislocations impact the growth kinetics along different crystallographic directions and how the strain energy of defected crystals influences their equilibrium shapes. Furthermore, such inquiries are supported by detailed structural investigation to identify the evidence of dislocations. The dislocation-driven growth mechanism not only can unify the various explanations behind a wide variety of exotic nanoscale morphologies but also allows the rational design of catalyst-free solution-phase syntheses that could enable the scalable and low cost production of nanomaterials necessary for large scale applications, such as solar and thermoelectric energy conversions, energy storage, and nanocomposites. In this Account, we discuss the fundamental theories of the screw dislocation driven growth of various nanostructures including one-dimensional nanowires and nanotubes, two-dimensional nanoplates, and three-dimensional hierarchical tree-like nanostructures. We then introduce the transmission electron microscopy (TEM) techniques to structurally characterize the dislocation-driven nanomaterials for future searching and identifying purposes. We summarize the guidelines for rationally designing the dislocation-driven growth and discuss specific examples to illustrate how to implement the guidelines. By highlighting our recent discoveries in the last five years, we show that dislocation growth is a general and versatile mechanism that can be used to grow a variety of nanomaterials via distinct reaction chemistry and synthetic methods. These discoveries are complemented by selected examples of anisotropic crystal growth from other researchers. The fundamental investigation and development of dislocation-driven growth of nanomaterials will create a new dimension to the rational design and synthesis of increasingly complex nanomaterials. PMID:23738750

  15. Pullout strength of misplaced pedicle screws in the thoracic and lumbar vertebrae - A cadaveric study

    PubMed Central

    Saraf, Shyam K; Singh, Ravindra P; Singh, Vakil; Varma, Ashish

    2013-01-01

    Background: The objective of this cadaveric study was to analyze the effects of iatrogenic pedicle perforations from screw misplacement on the mean pullout strength of lower thoracic and lumbar pedicle screws. We also investigated the effect of bone mineral density (BMD), diameter of pedicle screws, and the region of spine on the pullout strength of pedicle screws. Materials and Methods: Sixty fresh human cadaveric vertebrae (D10–L2) were harvested. Dual-energy X-ray absorptiometry (DEXA) scan of vertebrae was done for BMD. Titanium pedicle screws of different diameters (5.2 and 6.2 mm) were inserted in the thoracic and lumbar segments after dividing the specimens into three groups: a) standard pedicle screw (no cortical perforation); b) screw with medial cortical perforation; and c) screw with lateral cortical perforation. Finally, pullout load of pedicle screws was recorded using INSTRON Universal Testing Machine. Results: Compared with standard placement, medially misplaced screws had 9.4% greater mean pullout strength and laterally misplaced screws had 47.3% lesser mean pullout strength. The pullout strength of the 6.2 mm pedicle screws was 33% greater than that of the 5.2 mm pedicle screws. The pullout load of pedicle screws in lumbar vertebra was 13.9% greater than that in the thoracic vertebra (P = 0.105), but it was not statistically significant. There was no significant difference between pullout loads of vertebra with different BMD (P = 0.901). Conclusion: The mean pullout strength was less with lateral misplaced pedicle screws while medial misplaced pedicle screw had more pullout strength. The pullout load of 6.2 mm screws was greater than that of 5.2 mm pedicle screws. No significant correlation was found between bone mineral densities and the pullout strength of vertebra. Similarly, the pullout load of screw placed in thoracic and lumbar vertebrae was not significantly different. PMID:23798753

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

    PubMed Central

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

    2013-01-01

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

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

    PubMed Central

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

    2016-01-01

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

  18. Testing the stability of the polyethylene acetabulum cemented on a frozen bone graft substrate on a model of an artificial hip joint.

    PubMed

    Plomi?ski, J; Watral, Z; Kwiatkowski, K

    2008-01-01

    The stability of the polyethylene acetabulum cemented on a substrate made of frozen bone grafts was investigated. The force was applied to the edge of the acetabulum and the magnitude of the force and resulting displacement were recorded. These tests were preceded by stress testing, during which the acetabulum was subjected to loading forces of 1 or 3 kN through 100,000 cycles. Additionally the influence of the thickness of grafts layer on the overall stability of an implant was also determined. The experiments proved that such factors as initial compacting of bone grafts, magnitude of the loading force and thickness of grafts layer greatly affect the stability of the artificial acetabulum. PMID:19152466

  19. Finger joint injuries.

    PubMed

    Prucz, Roni B; Friedrich, Jeffrey B

    2015-01-01

    Finger joint dislocations and collateral ligament tears are common athletic hand injuries. Treatment of the athlete requires a focus on safe return to play and maximizing function. Certain dislocations, such as proximal interphalangeal and distal interphalangeal volar dislocations, may be associated with tendon injuries and must be treated accordingly. Treatment of other dislocations is ultimately determined by postreduction stability, with many dislocations amenable to nonoperative treatment (ie, immobilization followed by rehabilitation). Protective splinting does not necessarily preclude athletic participation. Minor bone involvement typically does not affect the treatment plan, but significant articular surface involvement may necessitate surgical repair or stabilization. Percutaneous and internal fixation are the mainstays of surgical treatment. Treatment options that do not minimize recovery or allow the patient to return to protected play, such as external fixation, are generally avoided during the season of play. Undertreated joint injuries and unrecognized ligament injuries can result in long term disability. PMID:25455398

  20. Temporomandibular Joint, Closed

    MedlinePlus

    ... Gallery > Oral Health > The Temporomandibular Joint, Closed The Temporomandibular Joint, Closed Main Content Title: The Temporomandibular Joint, Closed Description: The temporomandibular joint connects the ...

  1. Safety and Efficacy of Pedicle Screws and Titanium Mesh Cage in the Treatments of Tuberculous Spondylitis of the Thoracolumbar Spine

    PubMed Central

    Lee, Jae Chul; Kim, Yon-Il

    2008-01-01

    Study Design This is a retrospective series. Purpose We wanted to analyze the safety and effectiveness of using the newer generation metallic implants (pedicle screws and/or titanium mesh) for the treatment of tuberculous spondylitis. Overview of the Literature There have been various efforts to prevent the development of a kyphotic deformity after the treatment of tuberculous spondylitis, including instrumentation of the spine. Pedicle screws and titanium mesh cages have become more and more popular for treating various spinal problems. Methods Twenty two patients who had tuberculous spondylitis were treated with anterior radical debridement and their anterior column of spine was supported with a tricortical iliac bone graft (12 patients) or by mesh (10 patients). Supplementary posterior pedicle screw instrumentation was performed in 17 of 22 patients. The combination of surgeries were anterior strut bone grafting and posterior pedicle screws in 12 patients, anterior titanium mesh and posterior pedicle screws in 5 patients and anterior mesh only without pedicle screws in 5 patients. The patients were followed up with assessing the laboratory inflammatory parameters, the serial plain radiographs and the neurological recovery. Results The erythrocyte sedimentation rate and C-reactive protein levels were eventually normalized and there was no case of persistent infection or failure to control infection in spite of a mettalic implant in situ. The overall correction of kyphotic deformity was initially 8.9 degrees, and the loss of correction was 6.2 degrees. In spite of some loss of correction, this technique effectively prevented clinically significant kyphotic deformity. The preoperative Frankel grades were B for 1 patient, C for 4, D for 4 and E for 13. At the final follow-up, 7 of 9 patients recovered completely to Frankel grade E and only two patients showed a Frankel grade of D. Conclusions Stabilizing the spine with pedicle screws and/or titanium mesh in patients with tubercuous spondylitis effectively prevents the development of kyphotic deformity and this did not prevent controlling infection when this technique was combined with radical debridement and anti-tuberculous chemotherapy. PMID:20404959

  2. The influence of screw configuration on the pretreatment performance of a continuous twin screw-driven reactor (CTSR).

    PubMed

    Choi, Chang Ho; Um, Byung-Hwan; Oh, Kyeong Keun

    2013-03-01

    A combination of a continuous twin screw-driven reactor (CTSR) and a dilute acid pretreatment was used for the pretreatment of biomass with a high cellulose content and high monomeric xylose hydrolyzate. With the newly modified CTSR screw configuration (Config. 3), the influences of the screw rotational speed (30-60 rpm), of the pretreatment conditions such as acid concentration (1-5%) and reaction temperature (160-175 °C) at the operating condition of biomass feeding rate (1.0 g/min) and acid feeding rate (13.4 mL/min) on the pretreatment performance were investigated. The cellulose content in the pretreated rape straw was 67.1% at the following optimal conditions: barrel temperature of 165 °C, acid concentration of 3.0% (w/v), and screw rotational speed of 30 rpm. According to the three screw configurations, the glucose yields from enzymatic hydrolysis were 70.1%, 72.9%, and 78.7% for screw Configs. 1, 2, and 3, respectively. PMID:23395738

  3. Investigation of an 11mm diameter twin screw granulator: Screw element performance and in-line monitoring via image analysis.

    PubMed

    Sayin, Ridade; Martinez-Marcos, Laura; Osorio, Juan G; Cruise, Paul; Jones, Ian; Halbert, Gavin W; Lamprou, Dimitrios A; Litster, James D

    2015-12-30

    As twin screw granulation (TSG) provides one with many screw element options, characterization of each screw element is crucial in optimizing the screw configuration in order to obtain desired granule attributes. In this study, the performance of two different screw elements - distributive feed screws and kneading elements - was studied in an 11 mm TSG at different liquid-to-solid (L/S) ratios. The kneading element configuration was found to break large granules more efficiently, leading to narrower granule size distributions. While pharmaceutical industry shifts toward continuous manufacturing, inline monitoring and process control are gaining importance. Granules from an 11 mm TSG were analysed using the Eyecon™, a real-time high speed direct imaging system, which has been used to capture accurate particle size distribution and particle count. The size parameters and particle count were then assessed in terms of their ability to be a suitable control measure using the Shewhart control charts. d10 and particle count were found to be good indicators of the change in L/S ratio. However, d50 and d90 did not reflect the change, due to their inherent variability even when the process is at steady state. PMID:26385406

  4. Virtual Passive Controller for Robot Systems Using Joint Torque Sensors

    NASA Technical Reports Server (NTRS)

    Aldridge, Hal A.; Juang, Jer-Nan

    1997-01-01

    This paper presents a control method based on virtual passive dynamic control that will stabilize a robot manipulator using joint torque sensors and a simple joint model. The method does not require joint position or velocity feedback for stabilization. The proposed control method is stable in the sense of Lyaponov. The control method was implemented on several joints of a laboratory robot. The controller showed good stability robustness to system parameter error and to the exclusion of nonlinear dynamic effects on the joints. The controller enhanced position tracking performance and, in the absence of position control, dissipated joint energy.

  5. Helical Screw Expander Evaluation Project. Final report

    SciTech Connect

    McKay, R.

    1982-03-01

    A functional 1-MW geothermal electric power plant that featured a helical screw expander was produced and then tested in Utah in 1978 to 1979 with a demonstrated average performance of approximately 45% machine efficiency over a wide range of test conditions in noncondensing operation on two-phase geothermal fluids. The Project also produced a computer-equipped data system, an instrumentation and control van, and a 1000-kW variable load bank, all integrated into a test array designed for operation at a variety of remote test sites. Additional testing was performed in Mexico in 1980 under a cooperative test program using the same test array, and machine efficiency was measured at 62% maximum with the rotors partially coated with scale, compared with approximately 54% maximum in Utah with uncoated rotors, confirming the importance of scale deposits within the machine on performance. Data are presented for the Utah testing and for the noncondensing phases of the testing in Mexico. Test time logged was 437 hours during the Utah tests and 1101 hours during the Mexico tests.

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

    NASA Astrophysics Data System (ADS)

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

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

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

    PubMed

    Chang, Wei-Jen; Pan, Yu-Hwa; Tzeng, Jy-Jiunn; Wu, Ting-Lin; Fong, Tsorng-Harn; Feng, Sheng-Wei; Huang, Haw-Ming

    2015-01-01

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

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

    PubMed

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

    2015-11-01

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

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

    PubMed Central

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

    2015-01-01

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

  10. Distal radioulnar joint injuries

    PubMed Central

    Thomas, Binu P; Sreekanth, Raveendran

    2012-01-01

    Distal radioulnar joint is a trochoid joint relatively new in evolution. Along with proximal radioulnar joint, forearm bones and interosseous membrane, it allows pronosupination and load transmission across the wrist. Injuries around distal radioulnar joint are not uncommon, and are usually associated with distal radius fractures,fractures of the ulnar styloid and with the eponymous Galeazzi or Essex_Lopresti fractures. The injury can be purely involving the soft tissue especially the triangular fibrocartilage or the radioulnar ligaments. The patients usually present with ulnar sided wrist pain, features of instability, or restriction of rotation. Difficulty in carrying loads in the hand is a major constraint for these patients. Thorough clinical examination to localize point of tenderness and appropriate provocative tests help in diagnosis. Radiology and MRI are extremely useful, while arthroscopy is the gold standard for evaluation. The treatment protocols are continuously evolving and range from conservative, arthroscopic to open surgical methods. Isolated dislocation are uncommon. Basal fractures of the ulnar styloid tend to make the joint unstable and may require operative intervention. Chronic instability requires reconstruction of the stabilizing ligaments to avoid onset of arthritis. Prosthetic replacement in arthritis is gaining acceptance in the management of arthritis. PMID:23162140

  11. Compliant joint

    NASA Technical Reports Server (NTRS)

    Eklund, Wayne D. (Inventor); Kerley, James J. (Inventor)

    1990-01-01

    A compliant joint is provided for prosthetic and robotic devices which permits rotation in three different planes. The joint provides for the controlled use of cable under motion. Perpendicular outer mounting frames are joined by swaged cables that interlock at a center block. Ball bearings allow for the free rotation of the second mounting frame relative to the first mounting frame within a predetermined angular rotation that is controlled by two stop devices. The cables allow for compliance at the stops and the cables allow for compliance in six degrees of freedom enabling the duplication or simulation of the rotational movement and flexibility of a natural hip or knee joint, as well as the simulation of a joint designed for a specific robotic component for predetermined design parameters.

  12. Joint pain

    MedlinePlus

    ... or conditions. It may be linked to arthritis , bursitis , and muscle pain . No matter what causes it, ... Autoimmune diseases such as rheumatoid arthritis and lupus Bursitis Chondromalacia patellae Crystals in the joint: gout (especially ...

  13. Placement of C1 Pedicle Screws Using Minimal Exposure: Radiographic, Clinical, and Literature Validation

    PubMed Central

    Storey, Christopher M.; Nixon, Menarvia K.C.; Haydel, Justin; Nanda, Anil; Sin, Anthony

    2015-01-01

    Background Traditional C1-2 fixation involves placement of C1 lateral mass screws. Evolving techniques have led to the placement of C1 pedicle screws to avoid exposure of the C1-C2 joint capsule. Our minimal dissection technique utilizes anatomical landmarks with isolated exposure of C2 and the inferior posterior arch of C1. We evaluate this procedure clinically and radiographically through a technical report. Methods Consecutive cases of cranial-vertebral junction surgery were reviewed for one fellowship trained spinal surgeon from 2008-2014. Information regarding sex, age, indication for surgery, private or public hospital, intra-operative complications, post-operative neurological deterioration, death, and failure of fusion was extracted. Measurement of pre-operative axial and sagittal CT scans were performed for C1 pedicle width and C1 posterior arch height respectively. Results 64 patients underwent posterior cranio-vertebral junction fixation surgery. 40 of these patients underwent occipital-cervical fusion procedures. 7/9 (77.8%) C1 instrumentation cases were from trauma with the remaining two (22.2%) from oncologic lesions. The average blood loss among isolated C1-C2 fixation was 160cc. 1/9 patients (11.1%) suffered pedicle breech requiring sub-laminar wiring at the C1 level. On radiographic measurement, the average height of the C1 posterior arch was noted at 4.3mm (range 3.8mm to 5.7mm). The average width of the C1 pedicle measured at 5.3mm (range 2.8 to 8.7mm). The patient with C1 pedicle screw failure had a pedicle width of 2.78mm on pre-operative axial CT imaging. Conclusion Our study directly adds to the literature with level four evidence supporting a minimal dissection of C1 arch in the placement of C1 pedicle screws with both radiographic and clinical validation. Clinical Relevance Justification of this technique avoids C2 nerve root manipulation or sacrifice, reduces bleeding associated with the venous plexus, and leaves the third segment of the vertebral artery unexplored. Pre-operative review of imaging is critical in the placement of C1-C2 instrumentation. PMID:26484006

  14. Proximal interphalangeal arthrodesis in the horse. A retrospective study and a modified screw technique.

    PubMed

    Caron, J P; Fretz, P B; Bailey, J V; Barber, S M

    1990-01-01

    Arthrodesis of the proximal interphalangeal joint was used to treat lameness resulting from osteoarthrosis and for closed subluxation in 35 horses. Six horses had bilateral arthrodeses. Several conventional internal fixation techniques and a three converging screw method were used. Criteria for success included the horse performing its previous or intended athletic activity and the owner being satisfied with the outcome. Using these criteria, a successful outcome was obtained in 65% of the 26 animals in which adequate follow-up was available. A successful outcome was observed in four of six horses with bilateral arthrodeses. The internal fixation technique used did not influence the success rate, and the duration of postoperative casting was similar in successful and unsuccessful cases. The success rate of proximal interphalangeal arthrodeses was 46% in the fore limbs and 83% in the hind limbs. Complications included infection, cast ulcers, bone or implant failure, implant loosening, and laminitis. PMID:2349775

  15. Adaptive backstepping sliding mode control of flexible ball screw drives with time-varying parametric uncertainties and disturbances.

    PubMed

    Dong, Liang; Tang, Wen Cheng

    2014-01-01

    This paper presents a method to model and design servo controllers for flexible ball screw drives with dynamic variations. A mathematical model describing the structural flexibility of the ball screw drive containing time-varying uncertainties and disturbances with unknown bounds is proposed. A mode-compensating adaptive backstepping sliding mode controller is designed to suppress the vibration. The time-varying uncertainties and disturbances represented in finite-term Fourier series can be estimated by updating the Fourier coefficients through function approximation technique. Adaptive laws are obtained from Lyapunov approach to guarantee the convergence and stability of the closed loop system. The simulation results indicate that the tracking accuracy is improved considerably with the proposed scheme when the time-varying parametric uncertainties and disturbances exist. PMID:24053935

  16. Use of the electro-mechanical impedance method for the assessment of dental implant stability

    NASA Astrophysics Data System (ADS)

    Rizzo, Piervincenzo; Boemio, Giovanni; de Nardo, Luigi

    2011-04-01

    The robustness and reliability of the Electro-Mechanical Impedance (EMI) method to assess dental prostheses stability is presented. The study aim at addressing an increasing need in the biomedical area where robust, reliable, and non-invasive methods to assess the bone-interface of dental and orthopedic implants are increasingly demanded for clinical diagnosis and direct prognosis. In this study two different dental screws were entrenched in polyurethane foams and immersed in a solution of nitric acid to allow material degradation, inversely simulating a bone-healing process. This process was monitored by bonding a Piezoceramic Transducer (PZT) to the implant and measuring the admittance of the PZT over time. To simulate healing, a second set of experiments was conducted. It consisted of placing four dental screws inside a joint compound specimen and observing the setting of the fresh compound allocated in the alveolus containing each implant. In all cases it was found that the PZT's conductance and the statistical features associated with the analysis of the admittance signatures were sensitive to the degradation or the setting process.

  17. Anterior Glenoid Rim Fracture Following Use of Resorbable Devices for Glenohumeral Stabilization

    PubMed Central

    Augusti, Carlo Alberto; Paladini, Paolo; Campi, Fabrizio; Merolla, Giovanni; Bigoni, Marco; Porcellini, Giuseppe

    2015-01-01

    Background Resorbable anchors are widely used in arthroscopic stabilization of the shoulder as a means of soft tissue fixation to bone. Their function is to ensure repair stability until they are replaced by host tissue. Complications include inflammatory soft tissue reactions, cyst formation, screw fragmentation in the joint, osteolytic reactions, and enhanced glenoid rim susceptibility to fracture. Purpose To evaluate resorption of biodegradable screws and determine whether they induce formation of areas with poor bone strength that may lead to glenoid rim fracture even with minor trauma. Study Design Case series; Level of evidence, 4. Methods This study evaluated 12 patients with anterior shoulder instability who had undergone arthroscopic stabilization with the Bankart technique and various resorbable anchors and subsequently experienced redislocation. The maximum interval between arthroscopic stabilization and the new dislocation was 52 months (mean, 22.16 months; range, 12-52 months). The mean patient age was 31.6 years (range, 17-61 years). The persistence or resorption of anchor holes; the number, area, and volume of osteolytic lesions; and glenoid erosion/fracture were assessed using computed tomography scans taken after redislocation occurred. Results Complete screw resorption was never documented. Osteolytic lesions were found at all sites (mean diameter, 5.64 mm; mean depth, 8.09 mm; mean area, 0.342 cm2; mean volume, 0.345 cm3), and all exceeded anchor size. Anterior glenoid rim fracture was seen in 9 patients, even without high-energy traumas (75% of all recurrences). Conclusion Arthroscopic stabilization with resorbable devices is a highly reliable procedure that is, however, not devoid of complications. In all 12 patients, none of the different implanted anchors had degraded completely, even in patients with longer follow-up, and all induced formation of osteolytic areas. Such reaction may lead to anterior glenoid rim fracture according to the literature and as found in 75% of the study patients with local osteolysis (9/12). Reducing anchor number and/or size may reduce the risk of osteolytic areas and anterior glenoid rim fracture. PMID:26665093

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

    PubMed Central

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

    2015-01-01

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

  19. Evaluation of the stress distribution change at the adjacent facet joints after lumbar fusion surgery: a biomechanical study.

    PubMed

    Ma, Jianxiong; Jia, Haobo; Ma, Xinlong; Xu, Weiguo; Yu, Jingtao; Feng, Rui; Wang, Jie; Xing, Dan; Wang, Ying; Zhu, Shaowen; Yang, Yang; Chen, Yang; Ma, Baoyi

    2014-07-01

    Spinal fusion surgery has been widely applied in clinical treatment, and the spinal fusion rate has improved markedly. However, its postoperative complications, especially adjacent segment degeneration, have increasingly attracted the attention of spinal surgeons. The most common pathological condition at adjacent segments is hypertrophic degenerative arthritis of the facet joint. To study the stress distribution changes at the adjacent facet joint after lumbar fusion with pedicle screw fixation, human cadaver lumbar spines were used in the present study, and electrical resistance strain gauges were attached on L1-L4 articular processes parallel or perpendicular to the articular surface of facet joints. Subsequently, electrical resistance strain gauge data were measured using anYJ-33 static resistance strain indicator with three types of models: the intact model, the laminectomy model, and the fusion model with pedicle screw fixation. The strain changes in the measurement sites indirectly reflect the stress changes. Significant differences in strain were observed between the normal and laminectomy state at all facet joints. Significant differences in strain were observed between the normal and the pedicle screw fixation fusion state at the L1/2 and L3/4 facet joints. The increased stress on the facet joints after lumbar fusion with pedicle screw fixation may be the cause of adjacent segment degeneration. PMID:24963037

  20. Osteoarthritis of the Manubriosternal Joint: An Uncommon Cause of Chest Pain.

    PubMed

    Vaishya, Raju; Vijay, Vipul; Rai, Bibek K

    2015-01-01

    Osteoarthritis of the manubriosternal joint is a rare cause of chest pain. The diagnosis is difficult, and other serious causes of chest pain have to be ruled out first. We report one case that was treated with fusion of the manubriosternal joint using an iliac crest bone graft with a cervical locking plate and screws with excellent results. Preoperative CT scan images were used to measure the screw length and the drill stop depth. In this case report, we have shown that arthrodesis can be an effective way of treating osteoarthritis of the manubriosternal joint when other measures fail. Furthermore, the use of a cervical locking plate with appropriate and careful preoperative planning affords a safe surgical technique, rapid pain relief, and ultimately, sound and asymptomatic union of the joint. PMID:26677420

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

    PubMed Central

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

    2015-01-01

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

  2. The Mechanical Benefit of Medial Support Screws in Locking Plating of Proximal Humerus Fractures

    PubMed Central

    Liu, Yanjie; Pan, Yao; Zhang, Wei; Zhang, Changqing; Zeng, Bingfang; Chen, Yunfeng

    2014-01-01

    Background The purpose of this study was to evaluate the biomechanical advantages of medial support screws (MSSs) in the locking proximal humeral plate for treating proximal humerus fractures. Methods Thirty synthetic left humeri were randomly divided into 3 subgroups to establish two-part surgical neck fracture models of proximal humerus. All fractures were fixed with a locking proximal humerus plate. Group A was fixed with medial cortical support and no MSSs; Group B was fixed with 3 MSSs but without medial cortical support; Group C was fixed with neither medial cortical support nor MSSs. Axial compression, torsional stiffness, shear stiffness, and failure tests were performed. Results Constructs with medial support from cortical bone showed statistically higher axial and shear stiffness than other subgroups examined (P<0.0001). When the proximal humerus was not supported by medial cortical bone, locking plating with medial support screws exhibited higher axial and torsional stiffness than locking plating without medial support screws (P?0.0207). Specimens with medial cortical bone failed primarily by fracture of the humeral shaft or humeral head. Specimens without medial cortical bone support failed primarily by significant plate bending at the fracture site followed by humeral head collapse or humeral head fracture. Conclusions Anatomic reduction with medial cortical support was the stiffest construct after a simulated two-part fracture. Significant biomechanical benefits of MSSs in locking plating of proximal humerus fractures were identified. The reconstruction of the medial column support for proximal humerus fractures helps to enhance mechanical stability of the humeral head and prevent implant failure. PMID:25084520

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

    PubMed

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

    1994-11-01

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

  4. Screw dislocations in GaN grown by different methods

    SciTech Connect

    Liliental-Weber, Z.; Zakharov, D.; Jasinski, J.; O'Keefe, M.A.; Morkoc, H.

    2003-05-27

    A study of screw dislocations in Hydride-Vapor-Phase-Epitaxy (HVPE) template and Molecular-Beam-Epitaxy (MBE) over-layers was performed using Transmission Electron Microscopy (TEM) in plan-view and in cross-section. It was observed that screw dislocations in the HVPE layers were decorated by small voids arranged along the screw axis. However, no voids were observed along screw dislocations in MBE overlayers. This was true both for MBE samples grown under Ga-lean and Ga-rich conditions. Dislocation core structures have been studied in these samples in the plan-view configuration. These experiments were supported by image simulation using the most recent models. A direct reconstruction of the phase and amplitude of the scattered electron wave from a focal series of high-resolution images was applied. It was shown that the core structures of screw dislocations in the studied materials were filled. The filed dislocation cores in an MBE samples were stoichiometric. However, in HVPE materials, single atomic columns show substantial differences in intensities and might indicate the possibility of higher Ga concentration in the core than in the matrix. A much lower intensity of the atomic column at the tip of the void was observed. This might suggest presence of lighter elements, such as oxygen, responsible for their formation.

  5. Numerical simulation of a twin screw expander for performance prediction

    NASA Astrophysics Data System (ADS)

    Papes, Iva; Degroote, Joris; Vierendeels, Jan

    2015-08-01

    With the increasing use of twin screw expanders in waste heat recovery applications, the performance prediction of these machines plays an important role. This paper presents a mathematical model for calculating the performance of a twin screw expander. From the mass and energy conservation laws, differential equations are derived which are then solved together with the appropriate Equation of State in the instantaneous control volumes. Different flow processes that occur inside the screw expander such as filling (accompanied by a substantial pressure loss) and leakage flows through the clearances are accounted for in the model. The mathematical model employs all geometrical parameters such as chamber volume, suction and leakage areas. With R245fa as working fluid, the Aungier Redlich-Kwong Equation of State has been used in order to include real gas effects. To calculate the mass flow rates through the leakage paths formed inside the screw expander, flow coefficients are considered as constant and they are derived from 3D Computational Fluid Dynamic calculations at given working conditions and applied to all other working conditions. The outcome of the mathematical model is the P-V indicator diagram which is compared to CFD results of the same twin screw expander. Since CFD calculations require significant computational time, developed mathematical model can be used for the faster performance prediction.

  6. The best location for proximal locking screw for femur interlocking nailing: A biomechanical study

    PubMed Central

    Karaarslan, Ahmet A; Karakaşli, Ahmet; Aycan, Hakan; Çeçen, Berivan; Yildiz, Didem Venüs; Sesli, Erhan

    2016-01-01

    Background: Proximal locking screw deformation and screw fracture is a frequently seen problem for femur interlocking nailing that affects fracture healing. We realized that there is lack of literature for the right level for the proximal locking screw. We investigated the difference of locking screw bending resistance between the application of screws on different proximal femoral levels. Materials and Methods: We used a total of 80 proximal locking screws for eight groups, 10 screws for each group. Three-point bending tests were performed on four types of screws in two different trochanteric levels (the lesser trochanter and 20 mm proximal). We determined the yield points at three-point bending tests that a permanent deformation started in the locking screws using an axial compression testing machine. Results: The mean yield point value of 5 mm threaded locking screws applied 20 mm proximal of lesser trochanter was 1022 ± 49 (range 986–1057) (mean ± standard deviation, 95% confidence interval). On the other hand, the mean yield point value of the same type of locking screws applied on the lesser trochanteric level was 2089 ± 249 (range 1911–2268). Which means 103% increase of screw resistance between two levels (P = 0.000). In all screw groups, on the lesser trochanter line we determined 98–174% higher than the yield point values of the same type of locking screws in comparison with 20 mm proximal to the lesser trochanter (P = 0.000). Conclusion: According to our findings, there is twice as much difference in locking screw bending resistance between these two application levels. To avoid proximal locking screw deformation, locking screws should be placed in the level of the lesser trochanter in nailing of 1/3 middle and distal femur fractures. PMID:26955183

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

    PubMed

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

    2015-01-01

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

  8. In vitro biomechanical study of pedicle screw pull-out strength based on different screw path preparation techniques

    PubMed Central

    Moldavsky, Mark; Salloum, Kanaan; Bucklen, Brandon; Khalil, Saif; Mehta, Jwalant S

    2016-01-01

    Background: Poor screw-to-bone fixation is a clinical problem that can lead to screw loosening. Under-tapping (UT) the pedicle screw has been evaluated biomechanically in the past. The objective of the study was to determine if pedicle preparation with a sequential tapping technique will alter the screw-to-bone fixation strength using a stress relaxation testing loading protocol. Materials and Methods: Three thoracolumbar calf spines were instrumented with pedicle screws that were either probed, UT, standard-tapped (ST), or sequential tapped to prepare the pedicle screw track and a stress relaxation protocol was used to determine pull-out strength. The maximum torque required for pedicle screw insertion and pull-out strength was reported. A one-way ANOVA and Tukeys post-hoc test were used to determine statistical significance. Results: The pedicle screw insertion torques for the probed, UT, ST and sequentially tapped (SQT) techniques were 5.09 (±1.08) Nm, 5.39 (±1.61) Nm, 2.93 (±0.43) Nm, and 3.54 (±0.67) Nm, respectively. There is a significant difference between probed compared to ST (P ≤ 0.05), as well as UT compared to both ST and SQT (P ≤ 0.05). The pull-out strength for pedicle screws for the probed, UT, ST and SQT techniques was 2443 (±782) N, 2353(±918) N, 2474 (±521) N, and 2146 (±582) N, respectively, with no significant difference (P ≥ 0.05) between techniques. Conclusions: The ST technique resulted in the highest pull-out strength while the SQT technique resulted in the lowest. However, there was no significant difference in the pull-out strength for the various preparation techniques and there was no correlation between insertion torque and pull-out strength. This suggests that other factors such as bone density may have a greater influence on pull-out strength. PMID:27053808

  9. An Atraumatic Symphysiolysis with a Unilateral Injured Sacroiliac Joint in a Patient with Cushing's Disease: A Loss of Pelvic Stability Related to Ligamentous Insufficiency?

    PubMed Central

    Höch, Andreas; Pieroh, Philipp; Dehghani, Faramarz; Josten, Christoph; Böhme, Jörg

    2016-01-01

    Glucocorticoids are well known for altering bone structure and elevating fracture risk. Nevertheless, there are very few reports on pelvic ring fractures, compared to other bones, especially with a predominantly ligamentous insufficiency, resulting in a rotationally unstable pelvic girdle. We report a 39-year-old premenopausal woman suffering from an atraumatic symphysiolysis and disruption of the left sacroiliac joint. She presented with external rotational pelvic instability and immobilization. Prior to the injury, she received high-dose glucocorticoids for a tentative diagnosis of rheumatoid arthritis over two months. This diagnosis was not confirmed. Other causes leading to the unstable pelvic girdle were excluded by several laboratory and radiological examinations. Elevated basal cortisol and adrenocorticotropic hormone levels were measured and subsequent corticotropin-releasing hormone stimulation, dexamethasone suppression test, and petrosal sinus sampling verified the diagnosis of adrenocorticotropic hormone-dependent Cushing's disease. The combination of adrenocorticotropic hormone-dependent Cushing's disease and the additional application of exogenous glucocorticoids is the most probable cause of a rare atraumatic rotational pelvic instability in a premenopausal patient. To the authors' knowledge, this case presents the first description of a rotationally unstable pelvic ring fracture involving a predominantly ligamentous insufficiency in the context of combined exogenous and endogenous glucocorticoid elevation. PMID:26904337

  10. Double-sided fiber laser beam welding process of T-joints for aluminum aircraft fuselage panels: Filler wire melting behavior, process stability, and their effects on porosity defects

    NASA Astrophysics Data System (ADS)

    Tao, Wang; Yang, Zhibin; Chen, Yanbin; Li, Liqun; Jiang, Zhenguo; Zhang, Yunlong

    2013-11-01

    Aluminum alloy T-joints for aircraft fuselage panels were fabricated by double-sided fiber laser beam welding with filler wire, and the influence of the wire feeding posture on the welding process stability was investigated. A CMOS high speed video system was used to observe the wire melting behavior and the weld pool dynamics in real time during the welding process by using a bandpass red laser with an emission wavelength of 808 nm as backlight source to illuminate the welding zone. The weld porosity defects were analyzed by X-ray radiography. The effects of wire feeding posture on the wire melting behavior, process stability, and porosity defects were investigated. The experimental results indicated that three distinct filler material transfer modes were identified under different wire feeding positions: liquid bridge transfer mode, droplet transfer mode, and spreading transfer mode. The liquid bridge transfer mode could guarantee a stable welding process, and result in the lowest porosity. Compared with wire feeding in the leading direction, the process was not stable and porosity increased when wire feeding in the trailing direction. Increased in the wire feeding angle was disadvantage for pores to escape from the weld molten pool, meanwhile, it made the welding process window smaller due to increasing the centering precision requirement for adjusting the filler wire.

  11. Instantaneous screws of weight-bearing knee: what can the screws tell us about the knee motion.

    PubMed

    Wolf, Alon

    2014-07-01

    There are several ways to represent a given object's motion in a 3D space having 6DOF i.e., three translations and three rotations. Some of the methods that are used are mathematical and do not provide any geometrical insight into the nature of the motion. Screw theory is a mathematical, while at the same time, geometrical method in which the 6DOF motion of an object can be represented. We describe the 6DOF motion of a weight-bearing knee by its screw parameters, that are extracted from 3D Optical Reflective motion capture data. The screw parameters which describe the transformation of the shank with respect to the thigh in each two successive frames, is represented as the instantaneous screw axis of the motion given in its Plücker line coordinate, along with its corresponding pitch and intensity values. Moreover, the Striction curve associated with the motion provides geometrical insight into the nature of the motion and its repeatability. We describe the theoretical background and demonstrate what the screw can tell us about the motion of healthy subjects' knee. PMID:24599550

  12. Efficiency study of oil cooling of a screw compressor

    SciTech Connect

    Tree, D.R.; McKellar, M.G.

    1989-04-01

    One of the major goals of all compressor manufacturers is to build as efficient a compressor as possible. Over the last several years improvements to the design of screw compressors has made them efficiently competitive with other types of compressors, especially at large loads. The primary purpose of this research is to investigate four different methods of cooling a 250 horsepower compressor and determine their effects on the efficiency of the compressor. Two conventional methods, liquid injection and thermosyphon cooling, and two new methods, V-PLUS and Fresco oil injection, are investigated. The screw compressor used in the tests was a VRS-500 screw compressor made by the Vilter Manufacturing Corporation. 6 figs.

  13. [Midcarpal fusion using break-away compression screw].

    PubMed

    Maire, N; Facca, S; Gouzou, S; Liverneaux, P

    2012-02-01

    Indication of midcarpal fusion is SNAC or SLAC wrist grade 3. The main complication of circular plate (most common technique) is non-union. In this context, the purpose of our work was to propose the use of break-away compression screws to decrease the rate of non-union. Our series included ten patients. The fusion was fixed using two break-away compression screws (2mm diameter). No bone graft was used. As assessment, subjective (pain, Quick-DASH) and objective (strength, mobility) criteria were reviewed at follow-up. All the criteria were significantly improved after operation except mobility. Among the complications, we noticed one delayed bone-healing with a good outcome and a radiological consolidation. Midcarpal fusion by dorsal approach using break-away compression screws appears to us a technique of interest, not requiring a bone graft, with good cost effectiveness. PMID:22245281

  14. Mild coal gasification screw pyrolyzer development and design

    SciTech Connect

    Camp, D.W.

    1990-08-01

    Our objective is to produce information and design recommendations needed for the development of an efficient continuous process for the mild gasification of caking bituminous coals. We have focused on the development of an externally heated pyrolyzer in which the sticky, reacting coal is conveyed by one or more screws. We have taken a multifaceted approach to forwarding the development of the externally-heated screw pyrolyzer. Small scale process experiments on a 38-mm single screw pyrolyzer have been a major part of our effort. Engineering analyses aimed at producing design and scaleup equations have also been important. Process design recommendations follow from these. We critically review our experimental data and experience, and information from the literature and equipment manufactures for the purpose of making qualitative recommendations for improving practical pyrolyzer design and operation. Benchscale experiments are used to supply needed data and test some preliminary concepts. 6 refs., 4 figs., 1 tab.

  15. Blast joint

    SciTech Connect

    Uherek, R.J.; Claycomb, J.R.

    1989-12-26

    This patent describes a blast joint. It comprises: at least two tubular members having threaded opposed ends; a plurality of erosion resistant rings encasing the tubular members; support means for supporting the erosion resistant rings about the tubular member; coupling shield means supported on at least one of the tubular members in telescoping relation about the erosion resistant rings; at least one tubular open ended slip sleeve mounted about the erosion resistant rings on the tubular members for providing a surface for engagement by pipe slips for suspending the tubular members in a well bore; and connector means for connecting the tubular members to form the blast joint.

  16. A technique for removal of a fractured implant abutment screw.

    PubMed

    Kurt, Murat; Güler, Ahmet Umut; Duran, İbrahim

    2013-12-01

    The aim of this technique report was to present a procedure for removal of a fractured implant abutment screw. Whatever the cause, when an abutment fracture has occurred, the fractured screw segment inside the implant must be removed. The methods used by the clinicians may include the use of an endo-explorer self-made screwdriver and the use of implant repair kit available for some implant systems. The advantage of the presented method is that it may be extended to other implant systems that do not have a special repair kit and also that the technique is simple and does not require special equipment. PMID:21905898

  17. Virtual estimates of fastening strength for pedicle screw implantation procedures

    NASA Astrophysics Data System (ADS)

    Linte, Cristian A.; Camp, Jon J.; Augustine, Kurt E.; Huddleston, Paul M.; Robb, Richard A.; Holmes, David R.

    2014-03-01

    Traditional 2D images provide limited use for accurate planning of spine interventions, mainly due to the complex 3D anatomy of the spine and close proximity of nerve bundles and vascular structures that must be avoided during the procedure. Our previously developed clinician-friendly platform for spine surgery planning takes advantage of 3D pre-operative images, to enable oblique reformatting and 3D rendering of individual or multiple vertebrae, interactive templating, and placement of virtual pedicle implants. Here we extend the capabilities of the planning platform and demonstrate how the virtual templating approach not only assists with the selection of the optimal implant size and trajectory, but can also be augmented to provide surrogate estimates of the fastening strength of the implanted pedicle screws based on implant dimension and bone mineral density of the displaced bone substrate. According to the failure theories, each screw withstands a maximum holding power that is directly proportional to the screw diameter (D), the length of the in-bone segm,ent of the screw (L), and the density (i.e., bone mineral density) of the pedicle body. In this application, voxel intensity is used as a surrogate measure of the bone mineral density (BMD) of the pedicle body segment displaced by the screw. We conducted an initial assessment of the developed platform using retrospective pre- and post-operative clinical 3D CT data from four patients who underwent spine surgery, consisting of a total of 26 pedicle screws implanted in the lumbar spine. The Fastening Strength of the planned implants was directly assessed by estimating the intensity - area product across the pedicle volume displaced by the virtually implanted screw. For post-operative assessment, each vertebra was registered to its homologous counterpart in the pre-operative image using an intensity-based rigid registration followed by manual adjustment. Following registration, the Fastening Strength was computed for each displaced bone segment. According to our preliminary clinical study, a comparison between Fastening Strength, displaced bone volume and mean voxel intensity showed similar results (p < 0.1) between the virtually templated plans and the post-operative outcome following the traditional clinical approach. This study has demonstrated the feasibility of the platform in providing estimates the pedicle screw fastening strength via virtual implantation, given the intrinsic vertebral geometry and bone mineral density, enabling the selection of the optimal implant dimension adn trajectory for improved strength.

  18. Single crystal alumina for dental implants and bone screws.

    PubMed

    Kawahara, H; Hirabayashi, M; Shikita, T

    1980-09-01

    When ground to a suitable form, flexural strength of single crystal alumina (Al2O3) decreases to as low as one third the strength of the intact crystal. This flexural strength decrease is, however, recovered by chemical etching at a high temperature to eliminate surface defects caused by grinding. By using this strength recovery treatment, various types of single crystal implants with fine structure were able to be designed. Four kinds of single crystal bone screws and single crystal dental implants of screw and anchor type were designed. Flexural strength and impact strength of the implants were measured. PMID:7349666

  19. Host-feeding sources and habitats jointly affect wing developmental stability depending on sex in the major Chagas disease vector Triatoma infestans.

    PubMed

    Nattero, Julieta; Dujardin, Jean-Pierre; del Pilar Fernández, María; Gürtler, Ricardo E

    2015-12-01

    Fluctuating asymmetry (FA), a slight and random departure from bilateral symmetry that is normally distributed around a 0 mean, has been widely used to infer developmental instability. We investigated whether habitats (ecotopes) and host-feeding sources influenced wing FA of the hematophagous bug Triatoma infestans. Because bug populations occupying distinct habitats differed substantially and consistently in various aspects such as feeding rates, engorgement status and the proportion of gravid females, we predicted that bugs from more open peridomestic habitats (i.e., goat corrals) were more likely to exhibit higher FA than bugs from domiciles. We examined patterns of asymmetry and the amount of wing size and shape FA in 196 adult T. infestans collected across a gradient of habitat suitability and stability that decreased from domiciles, storerooms, kitchens, chicken coops, pig corrals, to goat corrals in a well-defined area of Figueroa, northwestern Argentina. The bugs had unmixed blood meals on human, chicken, pig and goat depending on the bug collection ecotope. We documented the occurrence of FA in wing shape for bugs fed on all host-feeding sources and in all ecotopes except for females from domiciles or fed on humans. FA indices for wing shape differed significantly among host-feeding sources, ecotopes and sexes. The patterns of wing asymmetry in females from domiciles and from goat corrals were significantly different; differences in male FA were congruent with evidence showing that they had higher mobility than females across habitats. The host-feeding sources and habitats of T. infestans affected wing developmental stability depending on sex. PMID:26318543

  20. Joint lubrication.

    PubMed

    McCutchen, C W

    1983-01-01

    The fine-pored, easily compressed articular cartilage provides animal joints with self-pressurized hydrostatic (weeping) lubrication. The solid skeletons of the cartilages press against each other, but so lightly that their rubbing is lubricated successfully by synovial fluid--a boundary lubricant too weak to lubricate ordinary bearings. PMID:6317095

  1. Real-Time Estimation of Ball-Screw Thermal Elongation Based upon Temperature Distribution of Ball-Screw

    NASA Astrophysics Data System (ADS)

    Kodera, Takehiko; Yokoyama, Kazuhiro; Miyaguchi, Kazuo; Nagai, Yutaka; Suzuki, Takamasa; Masuda, Masami; Yazawa, Takanori

    The optical telemeter system has been developed, which converts the temperature of rotating spindle to the digital data and carries the digital data from LED on the rotating side toward PD on the stationary side by the optical data transmission. Based upon the temperature distribution of hollow ball-screw obtained by the telemeter system, the thermal elongation of the ball-screw is estimated as the one-dimensional thermal elongation. Estimation accuracy, which is the difference between the estimated thermal elongation and the measured thermal elongation, is -3.1∼+3.2µ m for the thermal elongation of 50-60µ m over the length of 935.5mm of the ball-screw.

  2. [How to choose and deliver orthodontic mini-screws: important notions].

    PubMed

    Steve, Marc; Racy, Emmanuel; Kerbrat, Jean-Baptiste

    2015-12-01

    Orthodontic mini-screws are developing more and more because they make orthodontics easier and broaden its applications. This exponential development has arrived at a well defined mini-screw and a codified installation procedure. The aim of this article is to provide the conceptual elements of mini-screws in order to allow their safe use in orthodontic offices. PMID:26655416

  3. Acrylic resin guide for locating the abutment screw access channel of cement-retained implant prostheses.

    PubMed

    Ahmed, Ayman; Maroulakos, Georgios; Garaicoa, Jorge

    2016-05-01

    Abutment screw loosening represents a common and challenging technical complication of cement-retained implant prostheses. This article describes the fabrication of a simple and accurate poly(methyl methacrylate) guide for identifying the location and angulation of the abutment screw access channel of a cement-retained implant prosthesis with a loosened abutment screw. PMID:26794698

  4. Angled Screw Channel: An Alternative to Cemented Single-Implant Restorations--Three Clinical Examples.

    PubMed

    Gjelvold, Björn; Sohrabi, Majid Melvin; Chrcanovic, Bruno Ramos

    2016-01-01

    This article presents three cases of single labially tilted implants restored with screw-retained single crowns. Individualized abutments with an angled screw channel were used to avoid an unesthetic vestibular access channel. This individualized abutment allows the dentist and dental technician to use the screw-retained restorations where a cemented reconstruction would otherwise have been needed. PMID:26757334

  5. Handbook on dynamics of jointed structures.

    SciTech Connect

    Ames, Nicoli M.; Lauffer, James P.; Jew, Michael D.; Segalman, Daniel Joseph; Gregory, Danny Lynn; Starr, Michael James; Resor, Brian Ray

    2009-07-01

    The problem of understanding and modeling the complicated physics underlying the action and response of the interfaces in typical structures under dynamic loading conditions has occupied researchers for many decades. This handbook presents an integrated approach to the goal of dynamic modeling of typical jointed structures, beginning with a mathematical assessment of experimental or simulation data, development of constitutive models to account for load histories to deformation, establishment of kinematic models coupling to the continuum models, and application of finite element analysis leading to dynamic structural simulation. In addition, formulations are discussed to mitigate the very short simulation time steps that appear to be required in numerical simulation for problems such as this. This handbook satisfies the commitment to DOE that Sandia will develop the technical content and write a Joints Handbook. The content will include: (1) Methods for characterizing the nonlinear stiffness and energy dissipation for typical joints used in mechanical systems and components. (2) The methodology will include practical guidance on experiments, and reduced order models that can be used to characterize joint behavior. (3) Examples for typical bolted and screw joints will be provided.

  6. [Endoprosthetic replacement of rheumatoid finger joints].

    PubMed

    Thabe, H

    2011-07-01

    Resection arthroplasty, arthrodesis and prosthetic reconstruction are able to guarantee the maintenance of good functional ability of finger joints even in late stages and with severe destruction. Destruction of soft tissues of the finger joints cannot be corrected by prosthetic measures alone. A stabile situation of the wrist joint is one of the most important prerequisites for a normal performance of daily life activities. Silastic endoprostheses are still the gold standard for finger replacement in rheumatoid arthritis. PMID:21695554

  7. Screw-in fluorescent bulbs brighten utility savings programs

    SciTech Connect

    Not Available

    1986-04-01

    A new line of fluorescent bulbs, designed to replace standard 50 or 60-watt incandescents, create a bright, equivalent lighting effect for 75% less energy. The bulbs are being used successfully in a variety of utility savings programs from California to Maine. The Marathon bulbs use a screw base that fits any conventional socket. 1 figure.

  8. INTERIOR VIEW OF JAMES HARRIS CUTTING SCREW THREADS INTO THE ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    INTERIOR VIEW OF JAMES HARRIS CUTTING SCREW THREADS INTO THE INTERIOR OF FITTINGS ON ONE IN A BANK OF TAPPING MACHINES, EACH OPERATED BY THE SAME WORKER SIMULTANEOUSLY BUT TIMED TO REQUIRE WORKER ACTION AT INTERVALS THAT DO NOT INTERFERE WITH THE OTHER MACHINES. - Stockham Pipe & Fittings Company, Tapping Room, 4000 Tenth Avenue North, Birmingham, Jefferson County, AL

  9. Cellulose and the twofold screw axis: Modeling and experimental arguments

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Crystallography indicates that molecules in crystalline cellulose either have 2-fold screw-axis (21) symmetry or closely approximate it, leading to short distances between H4 and H1' across the glycosidic linkage. Therefore, modeling studies of cellobiose often show elevated energies for 21 structur...

  10. Some refinements of the theory of the viscous screw pump.

    NASA Technical Reports Server (NTRS)

    Elrod, H. G.

    1972-01-01

    Recently performed analysis for herringbone thrust bearings has been incorporated into the theory of the viscous screw pump for Newtonian fluids. In addition, certain earlier corrections for sidewall and channel curvature effects have been simplified. The result is a single, refined formula for the prediction of the pressure-flow relation for these pumps.

  11. Installation/Removal Tool for Screw-Mounted Components

    NASA Technical Reports Server (NTRS)

    Ash, J. P.

    1984-01-01

    Tweezerlike tool simplifies installation of screws in places reached only through narrow openings. With changes in size and shape, basic tool concept applicable to mounting and dismounting of transformers, sockets, terminal strips and mechanical parts. Inexpensive tool fabricated as needed by bending two pieces of steel wire. Exact size and shape selected to suit part manipulated and nature of inaccessible mounting space.

  12. Two Turns of the Screw: Feminism and the Humanities.

    ERIC Educational Resources Information Center

    Heinzelman, Susan Sage

    1988-01-01

    Maintains that the humanities get "screwed" in the academy because they are feminized. Explores this process of "feminization," focusing on college English departments. Offers a different view of the relationship between "soft" humanities and "hard" disciplines, reconceived from a feminist perspective. (SR)

  13. Three-Point Gear/Lead Screw Positioning

    NASA Technical Reports Server (NTRS)

    Calco, Frank S.

    1993-01-01

    Triple-ganged-lead-screw positioning mechanism drives movable plate toward or away from fixed plate and keeps plates parallel to each other. Designed for use in tuning microwave resonant cavity. Other potential applications include adjustable bed plates and cantilever tail stocks in machine tools, adjustable platforms for optical equipment, and lifting platforms.

  14. Delayed Presentation of Aortic Injury by a Thoracic Pedicle Screw.

    PubMed

    Sevuk, Utkan; Mesut, Abdullah; Kiraz, Ilker; Kose, Kaan; Ayaz, Firat; Erkul, Aylin

    2016-04-01

    Delayed presentation of a thoracic aortic injury is an extremely rare complication after spine surgery. We report a case of delayed presentation of a thoracic aortic injury with a vertebral pedicle screw after posterior spinal surgery without periaortic hematoma, hemorrhage or pseudoaneurysm formation and review the relevant literature. doi: 10.1111/jocs.12718 (J Card Surg 2016;31:220-230). PMID:26864154

  15. Granulation of increasingly hydrophobic formulations using a twin screw granulator.

    PubMed

    Yu, Shen; Reynolds, Gavin K; Huang, Zhenyu; de Matas, Marcel; Salman, Agba D

    2014-11-20

    The application of twin screw granulation in the pharmaceutical industry has generated increasing interest due to its suitability for continuous processing. However, an understanding of the impact of formulation properties such as hydrophobicity on intermediate and finished product quality has not yet been established. Hence, the current work investigated the granulation behaviour of three formulations containing increasing amounts of hydrophobic components using a Consigma™-1 twin screw granulator. Process conditions including powder feed rate, liquid to solid ratio, granulation liquid composition and screw configuration were also evaluated. The size of the wet granules was measured in order to enable exploration of granulation behaviour in isolation without confounding effects from downstream processes such as drying. The experimental observations indicated that the granulation process was not sensitive to the powder feed rate. The hydrophobicity led to heterogeneous liquid distribution and hence a relatively large proportion of un-wetted particles. Increasing numbers of kneading elements led to high shear and prolonged residence time, which acted to enhance the distribution of liquid and feeding materials. The bimodal size distributions considered to be characteristic of twin screw granulation were primarily ascribed to the breakage of relatively large granules by the kneading elements. PMID:25124058

  16. Joint assembly

    NASA Technical Reports Server (NTRS)

    Wilson, Andrew (Inventor); Punnoose, Andrew (Inventor); Strausser, Katherine (Inventor); Parikh, Neil (Inventor)

    2010-01-01

    A joint assembly is provided which includes a drive assembly and a swivel mechanism. The drive assembly features a motor operatively associated with a plurality of drive shafts for driving auxiliary elements, and a plurality of swivel shafts for pivoting the drive assembly. The swivel mechanism engages the swivel shafts and has a fixable element that may be attached to a foundation. The swivel mechanism is adapted to cooperate with the swivel shafts to pivot the drive assembly with at least two degrees of freedom relative to the foundation. The joint assembly allows for all components to remain encased in a tight, compact, and sealed package, making it ideal for space, exploratory, and commercial applications.

  17. Joint Stability Characteristics of the Ankle Complex in Female Athletes With Histories of Lateral Ankle Sprain, Part II: Clinical Experience Using Arthrometric Measurement

    PubMed Central

    Kovaleski, John E.; Heitman, Robert J.; Gurchiek, Larry R.; Hollis, J. M.; Liu, Wei; IV, Albert W. Pearsall

    2014-01-01

    Context: This is part II of a 2-part series discussing stability characteristics of the ankle complex. In part I, we used a cadaver model to examine the effects of sectioning the lateral ankle ligaments on anterior and inversion motion and stiffness of the ankle complex. In part II, we wanted to build on and apply these findings to the clinical assessment of ankle-complex motion and stiffness in a group of athletes with a history of unilateral ankle sprain. Objective: To examine ankle-complex motion and stiffness in a group of athletes with reported history of lateral ankle sprain. Design: Cross-sectional study. Setting: University research laboratory. Patients or Other Participants: Twenty-five female college athletes (age = 19.4 ± 1.4 years, height = 170.2 ± 7.4 cm, mass = 67.3 ± 10.0 kg) with histories of unilateral ankle sprain. Intervention(s): All ankles underwent loading with an ankle arthrometer. Ankles were tested bilaterally. Main Outcome Measure(s): The dependent variables were anterior displacement, anterior end-range stiffness, inversion rotation, and inversion end-range stiffness. Results: Anterior displacement of the ankle complex did not differ between the uninjured and sprained ankles (P = .37), whereas ankle-complex rotation was greater for the sprained ankles (P = .03). The sprained ankles had less anterior and inversion end-range stiffness than the uninjured ankles (P < .01). Conclusions: Changes in ankle-complex laxity and end-range stiffness were detected in ankles with histories of sprain. These results indicate the presence of altered mechanical characteristics in the soft tissues of the sprained ankles. PMID:24568223

  18. PROXIMAL TIBIAL OSTEOTOMY: STABILIZATION OF THE MEDIAL OPENING WITH A TRICORTICAL ILIAC BONE GRAFT

    PubMed Central

    da Cunha Luciano, Roberto; de Moura Souza, Getúlio Danival; Rispoli, Juliano; Cardoso, Rodrigo Galvão; do Nascimento, Marcus Vinícius Martins; Domingos, Gustavo Gontijo; Luciano, Dyego Vilela

    2015-01-01

    Objective: Radiographic assessment of lower limb alignment, in the frontal and sagittal planes, after high tibial osteotomy. To stabilize the osteotomy, a tricortical iliac graft was used, along with a positioning screw. Methods: Prospective study on 46 patients with ages ranging from 17 to 61 years. Among them, 42 patients presented genu varum secondary to knee osteoarthritis and four from other causes. Teleradiography was performed for surgical planning, using the Frank Noyes method, as modified by Fugizawa. A conventional surgical access of 3 cm was made to harvest a tricortical iliac graft. Osteotomy was performed under radioscopic control, by means of an anteromedial incision of 3 cm with release of the superficial portion of the medial collateral ligament. The graft was placed in the posterior portion of the osteotomy, to maintain an unaltered tibial slope. The screw crossed the osteotomy orthogonally to protect the lateral cortex. Pre and postoperative radiographic criteria were established to assess the results. Results: There was consolidation in 100% of the cases and maintenance of the mechanical axis, obtained intraoperatively, in 94% of the cases. The posterior slope of the tibial plateau in the sagittal plane ranged from 7° to 12°. Joint mobility was restored in all the patients. Eleven patients presented temporary pain at the site of graft harvesting, but none had paresthesia. The incidence of complications was 8% (infection, loss of correction and joint fracture). Conclusion: The technique was shown to be reproducible, simple, biological, accurate and low-cost, and it may be an alternative to the existing techniques.

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

    PubMed

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

    2016-01-01

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

  20. Covering the screw-access holes of implant restorations in the esthetic zone: a clinical report.

    PubMed

    Saboury, Abolfazl; Gooya, Ali

    2014-11-01

    Screw-retained implant restorations have an advantage of predictable retention as well as retrievability, and obviate the risk of excessive sub-gingival cement commonly associated with cement retained implant restorations. Screw-retained restorations generally have screw access holes, which can compromise esthetics and weaken the porcelain around the holes. The purpose of this study is to describe the use of a separate overcasting crown design to cover the screw access hole of implant screw-retained prosthesis for improved esthetics. PMID:25628703

  1. Covering the Screw-Access Holes of Implant Restorations in the Esthetic Zone: A Clinical Report

    PubMed Central

    Saboury, Abolfazl; Gooya, Ali

    2014-01-01

    Screw-retained implant restorations have an advantage of predictable retention as well as retrievability, and obviate the risk of excessive sub-gingival cement commonly associated with cement retained implant restorations. Screw-retained restorations generally have screw access holes, which can compromise esthetics and weaken the porcelain around the holes. The purpose of this study is to describe the use of a separate overcasting crown design to cover the screw access hole of implant screw-retained prosthesis for improved esthetics. PMID:25628703

  2. The general theory of blade screws including propellers, fans, helicopter screws, helicoidal pumps, turbo-motors, and different kinds of helicoidal blades

    NASA Technical Reports Server (NTRS)

    De Bothezat, George

    1920-01-01

    Report presents a theory which gives a complete picture and an exact quantitative analysis of the whole phenomenon of the working of blade screws, but also unites in a continuous whole the entire scale of states of work conceivable for a blade screw. Chapter 1 is devoted to the establishment of the system of fundamental equations relating to the blade screw. Chapter 2 contains the general discussion of the 16 states of work which may establish themselves for a blade screw. The existence of the vortex ring state and the whirling phenomenon are established. All the fundamental functions which enter the blade-screw theory are submitted to a general analytical discussion. The general outline of the curve of the specific function is examined. Two limited cases of the work of the screw, the screw with a zero constructive pitch and the screw with an infinite constructive pitch, are pointed out. Chapter 3 is devoted to the study of the propulsive screw or propeller. (author)

  3. An Arthroscopic Technique for Long Head of Biceps Tenodesis With Double Knotless Screw

    PubMed Central

    Su, Wei-Ren; Ling, Florence Y.; Hong, Chih-Kai; Chang, Chih-Hsun; Chung, Kai-Chen; Jou, I-Ming

    2015-01-01

    Tenodesis of the long head of the biceps (LHB) is a frequently performed procedure during shoulder arthroscopy for the treatment of degenerative, traumatic, or inflammatory lesions of the LHB tendon. Arthroscopic techniques for LHB tenodesis using knotless screw techniques offer the advantage of circumventing the need for arthroscopic knot tying. In 2012 Song and Williams described a novel tenodesis technique that does not require any knot-tying procedures by using a knotless anchor. However, a single-anchor configuration may not offer adequate stabilization of the LHB tendon. Therefore we propose a modified method that uses a double knotless anchor that offers advantages over the single knotless anchor, such as an increase in the contact area between the tendon and bone to facilitate tendon-to-bone healing and strengthening of the tenodesis construct. PMID:26759780

  4. Interpolating gain-scheduled H∞ loop shaping design for high speed ball screw feed drives.

    PubMed

    Dong, Liang; Tang, WenCheng; Bao, DaFei

    2015-03-01

    This paper presents a method to design servo controllers for flexible ball screw drives with time-varying dynamics, which are mainly due to the time-varying table position and the workpiece mass. A gain-scheduled H∞ loop shaping controller is designed to achieve high tracking performance against the dynamic variations. H∞ loop shaping design procedure incorporates open loop shaping by a set of compensators to obtain performance/robust stability tradeoffs. The interpolating gain-scheduled controller is obtained by interpolating the state space model of the linear time-invariant (LTI) controllers estimated for fixed values of the scheduling parameters and a linear least squares problem can be solved. The proposed controller has been compared with P/PI with velocity and acceleration feedforward and adaptive backstepping sliding mode control experimentally. The experimental results indicate that the tracking performance has been improved and the robustness for time-varying dynamics has been achieved with the proposed scheme. PMID:25592980

  5. Comparison of the Mechanical Characteristics of a Universal Small Biplane Plating Technique Without Compression Screw and Single Anatomic Plate With Compression Screw.

    PubMed

    Dayton, Paul; Ferguson, Joe; Hatch, Daniel; Santrock, Robert; Scanlan, Sean; Smith, Bret

    2016-01-01

    To better understand the mechanical characteristics of biplane locked plating in small bone fixation, the present study compared the stability under cyclic cantilever loading of a 2-plate locked biplane (BPP) construct without interfragmentary compression with that of a single-plate locked construct with an additional interfragmentary screw (SPS) using surrogate bone models simulating Lapidus arthrodesis. In static ultimate plantar bending, the BPP construct failed at significantly greater load than did the SPS construct (556.2 ± 37.1 N versus 241.6 ± 6.3 N, p = .007). For cyclic failure testing in plantar bending at a 180-N starting load, the BPP construct failed at a significantly greater number of cycles (158,322 ± 50,609 versus 13,718 ± 10,471 cycles) and failure load (242.5 ± 25.0 N versus 180.0 ± 0.0 N) than the SPS construct (p = .002). For cyclic failure testing in plantar bending at a 120-N starting load, the results were not significantly different between the BPP and SPS constructs for the number of cycles (207,646 ± 45,253 versus 159,334 ± 69,430) or failure load (205.0 ± 22.4 N versus 185.0 ± 33.5 N; p = .300). For cyclic testing with 90° offset loading (i.e., medial to lateral bending) at a 120-N starting load, all 5 BPP constructs (tension side) and 2 of the 5 SPS constructs reached 250,000 cycles without failure. Overall, the present study found the BPP construct to have superior or equivalent stability in multiplanar orientations of force application in both static and fatigue testing. Thus, the concept of biplane locked plating, using 2 low profile plates and unicortical screw insertion, shows promise in small bone fixation, because it provides consistent stability in multiplanar orientations, making it universally adaptable to many clinical situations. PMID:26872521

  6. Clinical degradation and biocompatibility of different bioabsorbable interference screws: a report of six cases.

    PubMed

    Stähelin, A C; Weiler, A; Rüfenacht, H; Hoffmann, R; Geissmann, A; Feinstein, R

    1997-04-01

    The clinical biocompatibility and degradation of bioabsorbable interference screws of different polymer composition is described in this report for six patients who underwent repeat arthroscopy after anterior cruciate ligament (ACL) reconstruction. Bioabsorbable interference screws were used for bone plug fixation of bone--patellar tendon--bone (BPTB) autografts. Poly (L-lactide) (PLLA) interference screws were used in one case, poly (D,L-lactide-co-glycolide) (PDLLA-co-PGA) in two cases and poly (D,L-lactide) (PDLLA) in three cases. The patients either underwent removal of the femoral screw or had a biopsy taken from the screw site during re-arthroscopy. Large fragments of the PLLA screw were still present 20 months postoperatively. In one case, the PDLLA-co-PGA screw was extruded spontaneously from the tibial bone tunnel 3 weeks after the operation. In the second PDLLA-co-PGA screw case, there was no evidence left of the screw material on biopsy 12 months after implantation. The PDLLA screw in one patient was removed 6 weeks after implantation without any signs of degradation. No traces of the PDLLA screws were found in the two other patients, 10 or 14 months postoperatively. There were no clinical signs of foreign-body reactions in all cases. PMID:9127085

  7. Cervical Pedicle Screw Insertion Using the Technique with Direct Exposure of the Pedicle by Laminoforaminotomy

    PubMed Central

    Jo, Dae-Jean; Kim, Ki-Tack; Kim, Sung-Min; Lee, Sang-Hun

    2012-01-01

    Objective To present the accuracy and safety of cervical pedicle screw insertion using the technique with direct exposure of the pedicle by laminoforaminotomy. Methods We retrospectively reviewed 12 consecutive patients. A total of 104 subaxial cervical pedicle screws in 12 patients had been inserted. We also assessed the clinical and radiological outcomes and analyzed the direction and grade of pedicle perforation (grade 0: no perforation, 1: <25%, 2: 20% to 50%, 3: >50% of screw diameter) on the postoperative vascular-enhanced computed tomography scans. Grade 2 and 3 were considered as incorrect position. Results The correct position was found in 95 screws (91.3%); grade 0-75 screws, grade 1-20 screws and the incorrect position in 9 screws (8.7%); grade 2-6 screws, grade 3-3 screws. There was no neurovascular complication related with cervical pedicle screw insertion. Conclusion This technique (technique with direct exposure of the pedicle by laminoforaminotomy) could be considered relatively safe and easy method to insert cervical pedicle screw. PMID:23323166

  8. A rationale method for evaluating unscrewing torque values of prosthetic screws in dental implants

    PubMed Central

    SALIBA, Felipe Miguel; CARDOSO, Mayra; TORRES, Marcelo Ferreira; TEIXEIRA, Alexandre Carvalho; LOURENÇO, Eduardo José Veras; TELLES, Daniel de Moraes

    2011-01-01

    Objectives Previous studies that evaluated the torque needed for removing dental implant screws have not considered the manner of transfer of the occlusal loads in clinical settings. Instead, the torque used for removal was applied directly to the screw, and most of them omitted the possibility that the hexagon could limit the action of the occlusal load in the loosening of the screws. The present study proposes a method for evaluating the screw removal torque in an anti-rotational device independent way, creating an unscrewing load transfer to the entire assembly, not only to the screw. Material and methods Twenty hexagonal abutments without the hexagon in their bases were fixed with a screw to 20 dental implants. They were divided into two groups: Group 1 used titanium screws and Group 2 used titanium screws covered with a solid lubricant. A torque of 32 Ncm was applied to the screw and then a custom-made wrench was used for rotating the abutment counterclockwise, to loosen the screw. A digital torque meter recorded the torque required to loosen the abutment. Results There was a significant difference between the means of Group 1 (38.62±6.43 Ncm) and Group 2 (48.47±5.04 Ncm), with p=0.001. Conclusion This methodology was effective in comparing unscrewing torque values of the implant-abutment junction even with a limited sample size. It confirmed a previously shown significant difference between two types of screws. PMID:21437472

  9. Numerical simulation of bone screw induced pretension: the cases of under-tapping and conical profile.

    PubMed

    Chatzistergos, Panagiotis E; Magnissalis, Evangelos A; Kourkoulis, Stavros K

    2014-03-01

    Even though screw induced pretension impacts the holding strength of bone screws, its implementation into the numerical simulation of the pullout phenomenon remains a problem with no apparent solution. The present study aims at developing a new methodology to simulate screw induced pretension for the cases of: (a) cylindrical screws inserted with under-tapping and (b) conical screws. For this purpose pullout was studied experimentally using synthetic bone and then simulated numerically. Synthetic bone failure was simulated using a bilinear cohesive zone material model. Pretension generation was simulated by allowing the screw to expand inside a hole with smaller dimensions or different shape than the screw itself. The finite element models developed here were validated against experimental results and then utilized to investigate the impact of under-tapping and conical angle. The results indicated that pretension can indeed increase a screw's pullout force but only up to a certain degree. Under-tapping increased cylindrical screws' pullout force up to 12%, 15% and 17% for synthetic bones of density equal to 0.08 g cm(-3), 0.16 g cm(-3) and 0.28 g cm(-3), respectively. Inserting a conical screw into a cylindrical hole increased pullout force up to 11%. In any case an optimum level of screw induced pretension exists. PMID:24388102

  10. System for Image-Processing-Based Inspection of a Screw Hole on a Molded Plastic Frame

    NASA Astrophysics Data System (ADS)

    Satoh, Hironobu; Takeda, Fumiaki

    A screw hole is incorrectly molded if the pin on the mold is broken when the plastic is molded by injection molding. Sampling inspection is carried out manually to identify the incorrectly molded screw hole. In the sampling inspection, the incorrectly molded screw hole on the molded plastic frame is rarely overlooked. Therefore, the development of a system for the high-precision identification of the incorrectly molded screw hole is required. The purpose of this study is to develop a screw-hole inspection system that distinguishes between a correctly molded screw hole and an incorrectly molded one. In this paper, a screw-hole inspection system is proposed. There is a need to capture clearly the screw hole on an uneven plastic frame and therefore, a multi-camera system is used. The proposed system consists of several Web cameras with the individual adjustable focus. Moreover, the inspection of the screw holes is performed using an inspection algorithm that is developed for a multi-camera system. When 2548 correctly molded screw holes and 2940 incorrectly molded screw holes were inspected by the proposed system, the inspection success rate was 100.0%. Finally, we have verified its effectiveness by performing an experiment.

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

    PubMed

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

    1999-01-01

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

  12. Joint Replacement Surgery

    MedlinePlus

    ... Trial Journal Articles Arthritis July 2014 Joint Replacement Surgery: Health Information Basics for You and Your Family What Is Joint Replacement Surgery? Joint replacement surgery is removing a damaged joint ...

  13. Outcome of Pedicle Screw Fixation and Monosegmental Fusion in Patients with Fresh Thoracolumbar Fractures

    PubMed Central

    Rohilla, Rajesh Kumar; Kamboj, Kulbhushan; Magu, Narender Kumar; Kaur, Kiranpreet

    2014-01-01

    Study Design Prospective clinical study. Purpose The present prospective study aims to evaluate the clinical, radiological, and functional and quality of life outcomes in patients with fresh thoracolumbar fractures managed by posterior instrumentation of the spine, using pedicle screw fixation and monosegmental fusion. Overview of Literature The goals of treatment in thoracolumbar fractures are restoring vertebral column stability and obtaining spinal canal decompression, leading to early mobilization of the patient. Methods Sixty-six patients (46 males and 20 females) of thoracolumbar fractures with neurological deficit were stabilized with pedicle screw fixation and monosegmental fusion. Clinical, radiological and functional outcomes were evaluated. Results The mean preoperative values of Sagittal index, and compression percentage of the height of the fractured vertebra were 22.75° and 46.73, respectively, improved (statistically significant) to 12.39°, and 24.91, postoperatively. The loss of correction of these values at one year follow-up was not statistically significant. The mean preoperative canal compromise (%) improved from 65.22±17.61 to 10.06±5.31 at one year follow-up. There was a mean improvement in the grade of 1.03 in neurological status from the preoperative to final follow-up at one year. Average Denis work scale index was 4.1. Average Denis pain scale index was 2.5. Average WHOQOL-BREF showed reduced quality of life in these patients. Patients of early surgery group (operated within 7 days of injury) had a greater mean improvement of neurological grade, radiological and functional outcomes than those in the late surgery group, but it was not statistically significant. Conclusions Posterior surgical instrumentation using pedicle screws with posterolateral fusion is safe, reliable and effective method in the management of fresh thoracolumbar fractures. Fusion helps to decrease the postoperative correction loss of radiological parameters. There is no correlation between radiographic corrections achieved for deformities and functional outcome and quality of life post spinal cord injury. PMID:24967043

  14. L'espace articulaire de la Robotique Industrielle est un espace vectorielIndustrial Robotics joint space is a vector space

    NASA Astrophysics Data System (ADS)

    Tondu, Bertrand

    2003-05-01

    The mathematical modelling of industrial robots is based on the vectorial nature of the n-dimensional joint space of the robot, defined as a kinematic chain with n degrees of freedom. However, in our opinion, the vectorial nature of the joint space has been insufficiently discussed in the literature. We establish the vectorial nature of the joint space of an industrial robot from the fundamental studies of B. Roth on screws. To cite this article: B. Tondu, C. R. Mecanique 331 (2003).

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

    PubMed Central

    2011-01-01

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

  16. Accuracy of robot-assisted pedicle screw placement for adolescent idiopathic scoliosis in the pediatric population.

    PubMed

    Macke, Jeremy J; Woo, Raymund; Varich, Laura

    2016-06-01

    This is a retrospective review of pedicle screw placement in adolescent idiopathic scoliosis (AIS) patients under 18 years of age who underwent robot-assisted corrective surgery. Our primary objective was to characterize the accuracy of pedicle screw placement with evaluation by computed tomography (CT) after robot-assisted surgery in AIS patients. Screw malposition is the most frequent complication of pedicle screw placement and is more frequent in AIS. Given the potential for serious complications, the need for improved accuracy of screw placement has spurred multiple innovations including robot-assisted guidance devices. No studies to date have evaluated this robot-assisted technique using CT exclusively within the AIS population. Fifty patients were included in the study. All operative procedures were performed at a single institution by a single pediatric orthopedic surgeon. We evaluated the grade of screw breach, the direction of screw breach, and the positioning of the patient for preoperative scan (supine versus prone). Of 662 screws evaluated, 48 screws (7.2 %) demonstrated a breach of greater than 2 mm. With preoperative prone position CT scanning, only 2.4 % of screws were found to have this degree of breach. Medial malposition was found in 3 % of screws, a rate which decreased to 0 % with preoperative prone position scanning. Based on our results, we conclude that the proper use of image-guided robot-assisted surgery can improve the accuracy and safety of thoracic pedicle screw placement in patients with adolescent idiopathic scoliosis. This is the first study to evaluate the accuracy of pedicle screw placement using CT assessment in robot-assisted surgical correction of patients with AIS. In our study, the robot-assisted screw misplacement rate was lower than similarly constructed studies evaluating conventional (non-robot-assisted) procedures. If patients are preoperatively scanned in the prone position, the misplacement rate is further decreased. PMID:27072149

  17. Effect of pin location on stability of pelvic external fixation.

    PubMed

    Kim, W Y; Hearn, T C; Seleem, O; Mahalingam, E; Stephen, D; Tile, M

    1999-04-01

    Pelvic external fixators allow two locations of pin purchase: anterosuperior (into the iliac crest) and anteroinferior (into the supraacetabular dense bone, between the anterior superior and anterior inferior iliac spine). The purpose of this study was to compare the stability of these two methods of fixation on Tile Type B1 (open book) and C (unstable) pelvic injuries. Five unembalmed cadaveric pelves (mean age, 68 years; four males and one female) were loaded vertically in a servohydraulic testing machine in a standing posture. The AO tubular system and Orthofix were used. On each pelvis, a Type B1 injury was simulated. Each external fixator was applied in each location in random order. Cyclic loads were applied through the sacral body to a maximum of approximately 200 N while force and displacement of the pelvic ring were recorded digitally. Sacroiliac joint motion was quantified tridimensionally with displacement transducers, mounted on the sacrum and contacting a target fixed to the posterior superior iliac spine. A Type C injury was created and augmented with two iliosacral lag screws, and the tests were repeated. For the Type B1 injuries with anteroinferior pin purchase, the mean stiffness was 201.2 N/mm for the AO frame and 203.2 N/mm for the Orthofix. For the anterosuperior frames the mean stiffness was 143.9 N/mm for the AO frame and 163.3 N/mm for the Orthofix. For Type B1 and Type C injuries, the anteroinferior location of pin purchase resulted in significantly reduced sacroiliac joint separation. There were no significant differences between the frame types. Dissection of the preinserted anatomic specimen revealed no evidence of injury to the lateral femoral cutaneous nerve after blunt dissection and drilling with protective drill sleeves. It is concluded that the anteroinferior location of external fixation pins is a safe technique with the potential for increased stability of fixation. PMID:10212618

  18. 46 CFR 154.524 - Piping joints: Welded and screwed couplings.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... welds is allowed for an open ended pipe with an external diameter of 50 mm (2 in.) or less and a design... with an external diameter of 50 mm (2 in.) or less and a design temperature of −55 °C (−67 °F)...

  19. 46 CFR 154.524 - Piping joints: Welded and screwed couplings.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... welds is allowed for an open ended pipe with an external diameter of 50 mm (2 in.) or less and a design... with an external diameter of 50 mm (2 in.) or less and a design temperature of −55 °C (−67 °F)...

  20. Cervical anterior transpedicular screw fixation (ATPS)—Part II. Accuracy of manual insertion and pull-out strength of ATPS

    PubMed Central

    Acosta, Frank; Tauber, Mark; Fox, Michael; Martin, Hudelmaier; Forstner, Rosmarie; Augat, Peter; Penzkofer, Rainer; Pirich, Christian; Kässmann, H.; Resch, Herbert; Hitzl, Wolfgang

    2008-01-01

    Reconstruction after multilevel decompression of the cervical spine, especially in the weakened osteoporotic, neoplastic or infectious spine often requires circumferential stabilization and fusion. To avoid the additional posterior surgery in these cases while increasing rigidity of anterior-only screw-plate constructs, the authors introduce the concept of anterior transpedicular screw (ATPS) fixation. We demonstrated its morphological feasibility as well as its indications in a previous study in Part I of our project. Consequently, the objectives of the current study were to assess the ex vivo accuracy of placing ATPS into the cervical vertebra as well as the biomechanical performance of ATPS in comparison to traditional vertebral body screws (VBS) in terms of pull-out strength (POS). Twenty-three ATPS were inserted alternately to two screws into the pedicles and vertebral bodies, respectively, of six cadaveric specimens from C3–T1. For insertion of ATPS, a manual fluoroscopically assisted technique was used. Pre- and post insertional CT-scans were used to assess accuracy of ATPS insertion in the axial and sagittal planes. A newly designed grading system and accuracy score were used to delineate accuracy of ATPS insertion. Following insertion of screws, 23 ATPS and 22 VBS were subjected to pull-out testing (POT). The bone mineral density (BMD) of each specimen was assessed prior to POT. Statistical analysis showed that the incidence of correctly placed screws and non-critical pedicles breaches in axial plane was 78.3%, and 95.7% in sagittal plane. Hence, according to our definition of “critical” pedicle breach that exposes neurovascular structures at risk, 21.7% (n = 5) of all ATPS inserted showed a critical pedicle breach in axial plane. Notably, no critical pedicle perforation occurred at the C6 to T1 levels. Pull-out testing of ATPS and VBS revealed that pull-out resistance of ATPS was 2.5-fold that of VBS. Mean POS of 23 ATPS with a mean BMD of 0.566 g/cm2 and a mean osseus screw purchase of 27.2 mm was 467.8 N. In comparison, POS of 22 VBS screws with a mean BMD of 0.533 g/cm2 and a mean osseus screw purchase of 16.0 mm was 181.6 N. The difference in ultimate pull-out strength between the ATPS and VBS group was significant (p < 0.000001). Also, accuracy of ATPS placement in axial plane was shown to be significantly correlated with POS. In contrast, there was no correlation between screw-length, BMD, or level of insertion and the POS of ATPS or VBS. The study demonstrated that the use of ATPS might be a new technique worthy of further investigation. The use of ATPS shows the potential to increase construct rigidity in terms of screw-plate pull-out resistance. It might diminish construct failures during anterior-only reconstructions of the highly unstable decompressed cervical spine. Electronic supplementary material The online version of this article (doi:10.1007/s00586-007-0573-x) contains supplementary material, which is available to authorized users. PMID:18224357

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

    PubMed Central

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

    2009-01-01

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

  2. Alternative technique of cement augmentation of loosened pedicle screws -- technical note and presentation of two cases.

    PubMed

    Kocak, T; Däxle, M; Reichel, H; Lattig, F

    2013-01-01

    An alternative cement augmentation technique for pedicle screws is described, which was applied in two patients with mono- and bisegmental non-union after preceding multisegmental lumbar fusion. The correctly placed pedicle screws in S1 with diameters of 6 and 8.5 mm had severely enlarged the screw cavities due to segmental instability. Revision screws with 10 mm diameter demonstrated sufficient purchase only on the left side. Therefore, cement augmentation was performed for the right sided screws. After verification of intact pedicle borders, the cavity was filled up with PMMA bone cement. Afterwards, a Kirschner wire was positioned centrally, the hardening of the cement was awaited, the cement was gradually drilled and the screw was placed. In both patients, sufficient purchase of the cemented pedicle screws was documented. Screw insertion after awaiting the hardening of the bone cement in pedicles and vertebral bodies with huge defect situations seems to be an alternative to previous cement augmentation techniques of pedicle screws with the advantage, that the screws could be more easily unscrewed, if necessary. PMID:23452428

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

    PubMed

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

    2016-03-01

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

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

    PubMed

    Jutte, P C; Castelein, R M

    2002-12-01

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

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

    PubMed Central

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

    2015-01-01

    Objective: To assess if the screw design (self-drilling/self-tapping) and the pilot hole tapping could affect the insertion torque and screw pullout strength of the screw used in anterior fixation of the cervical spine. Methods: Forty self-tapping screws and 20 self-drilling screws were inserted into 10 models of artificial bone and 10 cervical vertebrae of sheep. The studied parameters were the insertion torque and pullout strength. The following groups were created: Group I-self-tapping screw insertion after pilot hole drilling and tapping; Group II-self-tapping screw insertion after pilot hole drilling without tapping; Group III-self-drilling screw insertion without drilling and tapping. In Groups I and II, the pilot hole had 14.0 mm in depth and was made with a 3mmn drill, while tapping was made with a 4mm tap. The insertion torque was measured and the pullout test was performed. The comparison between groups was made considering the mean insertion torque and the maximum mean pullout strength with the variance analysis (ANOVA; p≤ 0.05). Results: Previous drilling and tapping of pilot hole significantly decreased the insertion torque and the pullout strength. Conclusion: The insertion torque and pullout strength of self-drilling screws were significantly higher when compared to self-tapping screws inserted after pilot hole tapping. PMID:27004189

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

    PubMed

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

    2015-08-01

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

  7. A novel computer-assisted drill guide template for placement of C2 laminar screws.

    PubMed

    Lu, Sheng; Xu, Yong Q; Zhang, Yuan Z; Xie, Le; Guo, Hai; Li, Dong P

    2009-09-01

    The present method of C2 laminar screw placement relies on anatomical landmarks for screw placement. Placement of C2 laminar screws using drill template has not been described in the literature. The authors reported on their experience with placement of C2 laminar screws using a novel computer-assisted drill guide template in nine patients undergoing posterior occipito-cervical fusion. CT scan of C2 vertebrae was performed. 3D model of C2 vertebrae was reconstructed by software MIMICS 10.01. The 3D vertebral model was then exported in STL format, and opened in a workstation running software UG imageware12.0 for determining the optimal laminar screw size and orientation. A virtual navigational template was established according to the laminar anatomic trait. The physical vertebrae and navigational template were manufactured using rapid prototyping. The navigational template was sterilized and used intraoperative to assist the placement of laminar screw. Overall, 19 C2 laminar screws were placed and the accuracy of screw placement was confirmed with postoperative X-ray and CT scanning. There were not complications of related screws insertion. Average follow-up was 9 months (range 4-13 months), 77.8% of the patients exhibited improvement in their myelopathic symptoms; in 22.2% the symptoms were unchanged. Postoperative computed tomographic (CT) scanning was available for allowing the evaluation of placement of thirteen C2 laminar screws, all of which were in good position with no spinal canal violation. This study shows a patient-specific template technique that is easy to use, can simplify the surgical act and generates highly accurate C2 laminar screw placement. Advantages of this technology over traditional techniques include planning of the screw trajectory is done completely in the presurgical period as well as the ability to size the screw to the patient's anatomy. PMID:19517142

  8. Detecting thrust bearing failure within a screw compressor

    SciTech Connect

    Pallaver, C.

    1994-05-01

    A 3 1/2 mile ring of over 1000 superconducting magnets are needed to focus and drive the world`s highest energy particle smasher. 24 Refrigerators supply liquid helium to the magnets; 34 high pressure oil flooded screw compressors supply 285 psig helium gas to the refrigerators. The 400 h.p. screws are reliable machines that use 45 gallons of oil per minute to seal and lubricate the rotors, lubricate the bearings, and remove the heat of compression. These machines are spaced out in seven buildings over four miles. A minimum of 28 machines must be operating at all times. A contingent of operators start, stop, and monitor any machine from a distant control room. The 34 compressors have an average of 32,000 hours; 9 machines have over 40,000 hours; the highest is 55,000 hours.

  9. Efficiency study of oil cooling of a screw compressor

    SciTech Connect

    Tree, D.R.; McKellar, M.G. . Ray W. Herrick Labs.); Fresco, A. )

    1990-01-01

    One of the major goals of all compressor manufacturers is to design and build as efficient a compressor as possible. In a screw compressor it appears that the way the compressor is cooled can have an effect on the compressor's efficiency. This paper presents experimental data on three different screw compressor cooling methods: Liquid Refrigerant Injection Cooling System; Thermosyphon Cooling System; and Oil Injection System. All tests were conducted on a hot gas bypass system using refrigerant R-22. The data taken shows that the Oil Injection System is slightly better than the other two. These tests should be repeated with a higher oil flow rate and ammonia as the working fluid. 10 figs.

  10. Delayed perforation of the aorta by a thoracic pedicle screw.

    PubMed

    Wegener, Bernd; Birkenmaier, Christof; Fottner, Andreas; Jansson, Volkmar; Dürr, Hans Roland

    2008-09-01

    Pedicle screw instrumentation has become increasingly popular during the past 20 years and a vast selection of products is available on the market. With rising implantation rates, reports about specific complications also have increased. The main reason for these complications is the fact that the course of the pedicle and in turn the positioning of the pedicle screw cannot be adequately controlled visually. Based on the anatomy of the surrounding structures, complications caused by malpositioning can be divided into three main groups: mechanical, neurological and vascular. Beyond mechanical limitations of spinal motion, nerve injury can lead to neurological problems while injuries to vascular structures usually cause hemorrhage. These typical problems in general become apparent intraoperatively or in the immediate postoperative course. We report on a rare delayed complication and analyze the factors that led to it. In addition, we outline our treatment strategy. The goal has to be to avoid such problems in the future by using suitable navigational aids. PMID:18622634

  11. Analysis of Eyring-Powell Fluid in Helical Screw Rheometer

    PubMed Central

    Siddiqui, A. M.; Haroon, T.; Zeb, M.

    2014-01-01

    This paper aims to study the flow of an incompressible, isothermal Eyring-Powell fluid in a helical screw rheometer. The complicated geometry of the helical screw rheometer is simplified by “unwrapping or flattening” the channel, lands, and the outside rotating barrel, assuming the width of the channel is larger as compared to the depth. The developed second order nonlinear differential equations are solved by using Adomian decomposition method. Analytical expressions are obtained for the velocity profiles, shear stresses, shear at wall, force exerted on fluid, volume flow rates, and average velocity. The effect of non-Newtonian parameters, pressure gradients, and flight angle on the velocity profiles is noticed with the help of graphical representation. The observation confirmed the vital role of involved parameters during the extrusion process. PMID:24707194

  12. Coracoclavicular screw fixation for unstable distal clavicle fractures.

    PubMed

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

    2005-07-01

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

  13. Screw-Thread Inserts As Temporary Flow Restrictors

    NASA Technical Reports Server (NTRS)

    Trimarchi, Paul

    1992-01-01

    Coil-spring screw-thread inserts found useful as temporary flow restrictors. Inserts placed in holes through which flow restricted, effectively reducing cross sections available for flow. Friction alone holds inserts against moderate upstream pressures. Use of coil-spring thread inserts as flow restrictors conceived as inexpensive solution to problem of adjusting flow of oxygen through orifices in faceplate into hydrogen/oxygen combustion chamber. Installation and removal of threaded inserts gentle enough not to deform orifice tubes.

  14. Modelling of the Heating Process in a Thermal Screw

    NASA Astrophysics Data System (ADS)

    Zhang, Xuan; Veje, Christian T.; Lassen, Benny; Willatzen, Morten

    2012-11-01

    The procedure of separating efficiently dry-stuff (proteins), fat, and water is an important process in the handling of waste products from industrial and commercial meat manufactures. One of the sub-processes in a separation facility is a thermal screw where the raw material (after proper mincing) is heated in order to melt fat, coagulate protein, and free water. This process is very energy consuming and the efficiency of the product is highly dependent on accurate temperature control of the process. A key quality parameter is the time that the product is maintained at temperatures within a certain threshold. A detailed mathematical model for the heating process in the thermal screw is developed and analysed. The model is formulated as a set of partial differential equations including the latent heat for the melting process of the fat and the boiling of water, respectively. The product is modelled by three components; water, fat and dry-stuff (bones and proteins). The melting of the fat component is captured as a plateau in the product temperature. The model effectively captures the product outlet temperature and the energy consumed. Depending on raw material composition, "soft" or "dry", the model outlines the heat injection and screw speeds necessary to obtain optimal output quality.

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

    PubMed Central

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

    2014-01-01

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

  16. Continuous expression of slurry in a screw press

    SciTech Connect

    Shirato, M.; Hayashi, N.; Iwata, M.; Murase, T.; Ogawa, Y.

    1985-01-01

    An approximate method is described for predicting the steadystate performance of a screw press for the continuous expression of a slurry, with the worm channel being modified as the path between two flat plates. Screw expression of a slurry involves two mechanisms of dewatering which, for a batch operation, can be analyzed by the variable-pressure, variable-rate theory of filtration and by consolidation theory. By assuming that the expression consists of a succession of batch processes, basic equations are derived for the relationship between the dehydration rate, the feed rate, and the expression pressure distribution in a constant-pitch, straighttaper screw press. The thickness of the filter cake in the worm channel and the flow distribution in the consolidated cake are calculated for a given pressure distribution and feed rate, and the solids concentration and rate of discharge of the cake are estimated. The critical speed of rotation of the worm, at which the slurry becomes highly deliquored, is strongly influenced by the external diameter and helical angle of the worm. The theoretical results are in good agreement with experimental data for clay slurries with a concentration of 0.31-0.46 in the feed.

  17. Conservative Surgical Treatment of Infected Ulceration of the First Metatarsophalangeal Joint With Osteomyelitis in Diabetic Patients.

    PubMed

    Dalla Paola, Luca; Carone, Anna; Morisi, Claudio; Cardillo, Sara; Pattavina, Marco

    2015-01-01

    Ulceration of the plantar aspect of the first metatarsophalangeal joint is a common localization in the diabetic foot. Conservative treatment of this lesion is a challenging problem, performed through the soft tissues and osseous debridement. The present study included a cohort of 28 patients affected by diabetes mellitus and a first ray lesion penetrating the bone. After surgical debridement with removal of the infected bone, we positioned antibiotic-loaded bone cement and stabilized the treated area with an external fixator. All patients with critical limb ischemia had their vascular disease treated before the procedure. The mean follow-up was 12.2 ± 6.9 months. Four patients developed a relapse of the ulceration after the procedure. In the postoperative period, 1 patient (3.57%) developed dehiscence of the surgical site and underwent a second procedure. In the follow-up period, 2 patients (7.14%) experienced bone cement dislocation. In 1 of these patients, a new ulceration was observed dorsally to the surgical site. The approach was surgical revision with bone cement replacement and stabilization with a new external fixator. In the other patient, given the absence of ulcerations, the cement was removed, and arthrodesis with internal stabilization using 2 cannulated screws was performed. One patient (3.57%), who had developed a relapse of ulceration after recurrent critical ischemia, underwent a percutaneous revascularization procedure and transmetatarsal amputation. During the follow-up period, no ulceration recurrences, transfer ulcerations, shoe fit problems, or gait abnormalities were detected in the other 24 patients. Our study presents the results of a technique requiring a 1-stage surgical approach to a relatively common problem, which is often difficult to solve. PMID:25249400

  18. Use of a continuous twin screw granulation and drying system during formulation development and process optimization.

    PubMed

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

    2015-01-01

    Since small scale is key for successful introduction of continuous techniques in the pharmaceutical industry to allow its use during formulation development and process optimization, it is essential to determine whether the product quality is similar when small quantities of materials are processed compared to the continuous processing of larger quantities. Therefore, the aim of this study was to investigate whether material processed in a single cell of the six-segmented fluid bed dryer of the ConsiGma™-25 system (a continuous twin screw granulation and drying system introduced by GEA Pharma Systems, Collette™, Wommelgem, Belgium) is predictive of granule and tablet quality during full-scale manufacturing when all drying cells are filled. Furthermore, the performance of the ConsiGma™-1 system (a mobile laboratory unit) was evaluated and compared to the ConsiGma™-25 system. A premix of two active ingredients, powdered cellulose, maize starch, pregelatinized starch and sodium starch glycolate was granulated with distilled water. After drying and milling (1000 μm, 800 rpm), granules were blended with magnesium stearate and compressed using a Modul™ P tablet press (tablet weight: 430 mg, main compression force: 12 kN). Single cell experiments using the ConsiGma™-25 system and ConsiGma™-1 system were performed in triplicate. Additionally, a 1h continuous run using the ConsiGma™-25 system was executed. Process outcomes (torque, barrel wall temperature, product temperature during drying) and granule (residual moisture content, particle size distribution, bulk and tapped density, hausner ratio, friability) as well as tablet (hardness, friability, disintegration time and dissolution) quality attributes were evaluated. By performing a 1h continuous run, it was detected that a stabilization period was needed for torque and barrel wall temperature due to initial layering of the screws and the screw chamber walls with material. Consequently, slightly deviating granule and tablet quality attributes were obtained during the start-up phase of the 1h run. For the single cell runs, granule and tablet properties were comparable with results obtained during the second part of the 1h run (after start-up). Although deviating granule quality (particle size distribution and Hausner ratio) was observed due to the divergent design of the ConsiGma™-1 unit and the ConsiGma™-25 system (horizontal set-up) used in this study, tablet quality produced from granules processed with the ConsiGma™-1 system was predictive for tablet quality obtained during continuous production using the ConsiGma™-25 system. PMID:25528462

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

    PubMed

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

    2009-12-15

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

  20. Imaging screw dislocations at atomic resolution by aberration-corrected electron optical sectioning

    NASA Astrophysics Data System (ADS)

    Yang, H.; Lozano, J. G.; Pennycook, T. J.; Jones, L.; Hirsch, P. B.; Nellist, P. D.

    2015-06-01

    Screw dislocations play an important role in materials' mechanical, electrical and optical properties. However, imaging the atomic displacements in screw dislocations remains challenging. Although advanced electron microscopy techniques have allowed atomic-scale characterization of edge dislocations from the conventional end-on view, for screw dislocations, the atoms are predominantly displaced parallel to the dislocation line, and therefore the screw displacements are parallel to the electron beam and become invisible when viewed end-on. Here we show that screw displacements can be imaged directly with the dislocation lying in a plane transverse to the electron beam by optical sectioning using annular dark field imaging in a scanning transmission electron microscope. Applying this technique to a mixed [a+c] dislocation in GaN allows direct imaging of a screw dissociation with a 1.65-nm dissociation distance, thereby demonstrating a new method for characterizing dislocation core structures.

  1. Imaging screw dislocations at atomic resolution by aberration-corrected electron optical sectioning

    PubMed Central

    Yang, H.; Lozano, J. G.; Pennycook, T. J.; Jones, L.; Hirsch, P. B.; Nellist, P. D.

    2015-01-01

    Screw dislocations play an important role in materials' mechanical, electrical and optical properties. However, imaging the atomic displacements in screw dislocations remains challenging. Although advanced electron microscopy techniques have allowed atomic-scale characterization of edge dislocations from the conventional end-on view, for screw dislocations, the atoms are predominantly displaced parallel to the dislocation line, and therefore the screw displacements are parallel to the electron beam and become invisible when viewed end-on. Here we show that screw displacements can be imaged directly with the dislocation lying in a plane transverse to the electron beam by optical sectioning using annular dark field imaging in a scanning transmission electron microscope. Applying this technique to a mixed [a+c] dislocation in GaN allows direct imaging of a screw dissociation with a 1.65-nm dissociation distance, thereby demonstrating a new method for characterizing dislocation core structures. PMID:26041257

  2. Field simulation of axisymmetric plasma screw pinches by alternating-direction-implicit methods

    SciTech Connect

    Lambert, M.A.

    1996-06-01

    An axisymmetric plasma screw pinch is an axisymmetric column of ionized gaseous plasma radially confined by forces from axial and azimuthal currents driven in the plasma and its surroundings. This dissertation is a contribution to detailed, high resolution computer simulation of dynamic plasma screw pinches in 2-d {ital rz}-coordinates. The simulation algorithm combines electron fluid and particle-in-cell (PIC) ion models to represent the plasma in a hybrid fashion. The plasma is assumed to be quasineutral; along with the Darwin approximation to the Maxwell equations, this implies application of Ampere`s law without displacement current. Electron inertia is assumed negligible so that advective terms in the electron momentum equation are ignored. Electrons and ions have separate scalar temperatures, and a scalar plasma electrical resistivity is assumed. Altemating-direction-implicit (ADI) methods are used to advance the electron fluid drift velocity and the magnetic fields in the simulation. The ADI methods allow time steps larger than allowed by explicit methods. Spatial regions where vacuum field equations have validity are determined by a cutoff density that invokes the quasineutral vacuum Maxwell equations (Darwin approximation). In this dissertation, the algorithm was first checked against ideal MM stability theory, and agreement was nicely demonstrated. However, such agreement is not a new contribution to the research field. Contributions to the research field include new treatments of the fields in vacuum regions of the pinch simulation. The new treatments predict a level of magnetohydrodynamic turbulence near the bulk plasma surface that is higher than predicted by other methods.

  3. Knee joint replacement

    MedlinePlus

    Knee joint replacement is a surgery to replace a knee joint with a man-made joint. The artificial joint is called a prosthesis . ... cartilage and bone are removed from the knee joint. Man-made pieces are then placed in the ...

  4. Surgical strategies to improve fixation in the osteoporotic spine: the effects of tapping, cement augmentation, and screw trajectory.

    PubMed

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

    2014-02-01

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

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

    PubMed Central

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

    2013-01-01

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

  6. Hollow Mill for Extraction of Stripped Titanium Screws: An Easy, Quick, and Safe Technique

    PubMed Central

    Gupta, Ravi; Singh, Harpreet; Singh, Amit; Garg, Sudhir

    2014-01-01

    Removal of jammed titanium screws can be difficult due to the problem of stripping of the hexagonal heads of the screws. We present a technique of extraction of stripped screws with the use of a standard 4.5 mm stainless steel hollow mill in a patient of peri-implant fracture of the radius fixed with a titanium locking plate 2 years back. The technique is quick, safe, and cost effective. PMID:25013544

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

    PubMed

    Solitro, Giovanni F; Amirouche, Farid

    2016-04-01

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

  8. Screw placement relative to the calcaneal fracture constant fragment: an anatomic study.

    PubMed

    Bussewitz, Bradly W; Hyer, Christopher F

    2015-01-01

    Placement of a screw from the lateral wall of the calcaneus into the constant sustentaculum tali fragment can be difficult when surgically repairing a calcaneal fracture. This screw serves to compress the fracture fragments and support the posterior facet. This difficulty results from the small landing zone of the sustentaculum tali with its nearby vulnerable soft tissue structures. We present an anatomic study of 10 cadavers to determine a starting point and angle of screw advancement when placing a constant fragment screw. PMID:25441853

  9. An Unexpected Complication after Headless Compression Screw Fixation of an Osteochondral Fracture of Patella

    PubMed Central

    Aydoğmuş, Suavi; Keçeci, Tolga

    2016-01-01

    This study evaluated complications associated with implant depth in headless compression screw treatment of an osteochondral fracture associated with a traumatic patellar dislocation in a 21-year-old woman. Computed tomography and X-rays showed one lateral fracture fragment measuring 25 × 16 mm. Osteosynthesis was performed with two headless compression screws. Five months later, the screws were removed because of patella-femoral implant friction. We recommend that the screw heads be embedded to a depth of at least 3 mm below the cartilage surface. Further clinical studies need to examine the variation in cartilage thickness in the fracture fragment. PMID:27051547

  10. Access to Abutment Screw in Cement Retained Restorations: A Clinical Tip

    PubMed Central

    Harianawala, Husain; Kantharia, Nidhi; Sethi, Tania; Jambhekar, Shantanu

    2015-01-01

    Abutment screw loosening has been reported to be the most common prosthetic complications occurring in screw retained as well as cement retained implant restorations. Different methods to treat this issue have been reported in the literature so far; however these have their own short-comings. Retrievability of an implant restoration intact becomes a clinical challenge when the restoration is cement retained especially with an angulated abutment. This technique is aimed at accurately determining the position of the abutment screw in 3 dimensional relationships using a vacuum formed clear stent. This technique can be used as a viable protocol for management of screw loosening in cement retained implant restorations. PMID:25859535

  11. Joint x-ray

    MedlinePlus

    X-ray - joint; Arthrography; Arthrogram ... x-ray technologist will help you position the joint to be x-rayed on the table. Once in place, pictures are taken. The joint may be moved into other positions for more ...

  12. Arthroscopically assisted acromioclavicular joint reconstruction.

    PubMed

    Baumgarten, Keith M; Altchek, David W; Cordasco, Frank A

    2006-02-01

    Arthroscopically assisted acromioclavicular joint reconstruction avoids the large incisions necessary with open reconstructions. This acromioclavicular joint reconstruction technique via the subacromial space does not violate the rotator interval or require screw removal. The patient is placed in a modified beach-chair position. The arthroscope is placed into the subacromial space, and a bursectomy is performed through a lateral subacromial portal. The coracoacromial ligament is released from the acromion with an electrocautery and an arthroscopic elevator. A nonabsorbable suture is passed through the coracoacromial ligament with a suture passer, and an arthroscopic suture grasper is used to deliver both ends of the suture out through the lateral portal. The coracoid is identified and isolated using a radiofrequency ablator placed through the anterior portal while visualizing through the lateral portal. A percutaneous shuttle device is passed through the skin superomedial to the coracoid. The shuttle is visualized entering superior to the coracoid and is passed just medial to the coracoid. Once the tip of the shuttle can be visualized in the recess inferior to the coracoid, the shuttle loop is advanced. A suture grasper is used to deliver both ends of the shuttle out through the anterior portal. A semitendinosus allograft is used to reconstruct the coracoclavicular ligament. A nonabsorbable suture is passed through both ends of the allograft. Three strands of nonabsorbable suture are braided together. The tendon and the braided suture are shuttled around the coracoid. At this point, both the braided suture and the allograft tendon enter the anterior portal, wrap around the coracoid base, and exit the anterior portal. A 3-cm incision is made over the distal clavicle. A hole is drilled through the clavicle with a 5-mm drill. A loop of 22-gauge wire is passed through the hole in the clavicle, and a looped suture is shuttled through the hole. A curved clamp is used to create a tunnel from the acromioclavicular joint, under the deltoid, to the anterior portal. The ends of the braided suture and the tendon sutures are grasped by the clamp and pulled out the acromioclavicular joint incision. The limbs of the braided suture and the tendon suture that pass medial to the coracoid are shuttled through the hole in the clavicle using the looped suture that was previously passed through the clavicle. The acromioclavicular joint is reduced by pushing down on the distal clavicle with a bone tamp while simultaneously lifting the acromion upward by superiorly loading the humerus at the elbow. Once the acromioclavicular joint is reduced or slightly over-reduced, the braided suture is tied down securely. The acromioclavicular joint should remain reduced even after the manual reduction maneuver is released. The semitendinosus allograft is tensioned around the distal end of the clavicle and sutured to itself with a nonabsorbable suture. The released coracoacromial ligament is retrieved from the clavicular incision and sutured to the distal clavicle and semitendinosus allograft. The incision is closed in standard fashion, and a sling is applied. PMID:16458813

  13. Spacesuit mobility knee joints

    NASA Technical Reports Server (NTRS)

    Vykukal, H. C. (Inventor)

    1979-01-01

    Pressure suit mobility joints are for use in interconnecting adjacent segments of an hermetically sealed spacesuit in which low torques, low leakage and a high degree of reliability are required. Each of the joints is a special purpose joint characterized by substantially constant volume and low torque characteristics and includes linkages which restrain the joint from longitudinal distension and includes a flexible, substantially impermeable diaphragm of tubular configuration spanning the distance between pivotally supported annuli. The diaphragms of selected joints include rolling convolutions for balancing the joints, while various joints include wedge-shaped sections which enhance the range of motion for the joints.

  14. Spacesuit mobility joints

    NASA Technical Reports Server (NTRS)

    Vykukal, H. C. (Inventor)

    1978-01-01

    Joints for use in interconnecting adjacent segments of an hermetically sealed spacesuit which have low torques, low leakage and a high degree of reliability are described. Each of the joints is a special purpose joint characterized by substantially constant volume and low torque characteristics. Linkages which restrain the joint from longitudinal distension and a flexible, substantially impermeable diaphragm of tubular configuration spanning the distance between pivotally supported annuli are featured. The diaphragms of selected joints include rolling convolutions for balancing the joints, while various joints include wedge-shaped sections which enhance the range of motion for the joints.

  15. [Osteosynthesis after periprosthetic fractures of the knee joint].

    PubMed

    von Matthey, F; Ruchholtz, S; Biberthaler, P; Hanschen, M

    2016-04-01

    Periprosthetic fractures around the knee joint are of increasing relevance due to increasing numbers of total knee replacements and increasing life expectations. These fractures can be a real challenge due to an often limited patient compliance, reduced bone quality and impaired bone perfusion of potential intramedullary shafts resulting in poor healing and lack of fixation options for screws. These fractures necessitate special knowledge and approaches, which are systematically dealt with in this article, beginning with the correct diagnostics through to the most recent developments in the field of osteosynthetic techniques. The trends of minimally invasive techniques are presented and the options and limitations are described. PMID:26992714

  16. Feasibility of Intra-operative Computed Tomography Navigation System for Pedicle Screw Insertion of the Thoraco-lumbar Spine.

    PubMed

    Lee, Ming-Hsueh; Lin, Martin Hsiu-Chu; Weng, Hsu-Huei; Cheng, Wan-Chun; Tsai, Yuan-Hsiung; Wang, Ting-Chung; Yang, Jen-Tsung

    2012-12-01

    STUDY DESIGN:: A retrospective analysis of feasibility of intraoperative computed tomography (iCT) navigation for pedicle screw insertion of the thoraco-lumbar spine OBJECTIVES:: This study assessed the feasibility of an iCT navigation system by evaluating the screw insertion time, screw revision time, and learning curve of the iCT surgical team in patients who underwent thoraco-lumbar pedicle screw surgery using this navigation system. SUMMARY OF BACKGROUND DATA:: The iCT navigation system has been reported to improve the accuracy and safety of pedicle screw insertion. However, the assessment of the feasibility of spinal instrumentation guided by iCT navigation system is limited. METHODS:: From the time iCT navigation system was set-up to a period covering 16 months, consecutive patients who underwent thoracic or lumbar spinal pedicle screw surgery were enrolled. The screw insertion and screw revision times were estimated using the system's automatic time recording between the intra-operative CT scans. The insertion time per screw of the first 50 patients not requiring screw revision was also analyzed to evaluate the learning curve of the iCT surgical team. RESULTS:: There were 178 patients with a total of 932 pedicle screws. The cortical breach rate was 3.2% and the screw revision rate was 1.4%. The insertion time per screw was 10.2±6.3▒min and the screw revision time was 13.8±9.9▒min. The learning curve of the iCT surgical team for pedicle screw insertion guided by this navigation system was not steep and experience from less than 10 patients was adequate to provide familiarity with this system. CONCLUSION:: The iCT navigation system is clinically feasible for thoraco-lumbar pedicle screw surgery. It provides high-level safety and accuracy, as well as ease of screw revision when required. PMID:23222100

  17. Evaluation of mechanical properties of three different screws for rapid maxillary expansion

    PubMed Central

    2013-01-01

    Background The aim of this in vitro study was the evaluation of the mechanical properties the screws for rapid maxillary expansion (RME). Methods Three commercially available screws for RME were tested: Leone A2620; Dentaurum Hyrax; Forestadent Palatal Split Screw. All expansion screws were 10 mm in size. For the evaluation of mechanical properties, the screws for RME were adjusted using the same maxillary dental model. An Instron 3365 testing machine with a load cell of 5 kN recorded the forces released by the screws at different amounts of activation (1, 5, 10, 15 and 20 quarters of a turn). Each type of screw was tested 10 times. Comparisons between the forces released by the different types of screws at different amounts of activation were carried out by means of analysis of Kruskal-Wallis test with post-hoc test di Tukey (P < 0.05). Results The results of this study showed that all 3 expansion devices were able to develop forces that could produce a separation of the palatine processes. The Hyrax and A2620 expanders developed force values over 20 kg and the Palatal Split screws about 16 kg. Both the A2620 and Hyrax expanders showed significantly greater amounts of forces at all the different amounts of activations with respect to the Palatal Split screw. Conclusions All tested devices showed the capability of developing expansion forces (16-20 kg) adequate for RME. The A2620 and Hyrax expanders showed a greater level of rigidity than the Palatal Split screw. PMID:24330632

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

    PubMed

    Demir, Teyfik

    2015-05-01

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

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

    PubMed

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

    2016-03-01

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

  20. Comparison of success rates of orthodontic mini-screws by the insertion method

    PubMed Central

    Kim, Jung Suk; Choi, Seong Hwan; Cha, Sang Kwon; Kim, Jang Han; Lee, Hwa Jin; Yeom, Sang Seon

    2012-01-01

    Objective The aim of this study was to compare the success rates of the manual and motor-driven mini-screw insertion methods according to age, gender, length of mini-screws, and insertion sites. Methods We retrospectively reviewed 429 orthodontic mini-screw placements in 286 patients (102 in men and 327 in women) between 2005 and 2010 at private practice. Age, gender, mini-screw length, and insertion site were cross-tabulated against the insertion methods. The Cochran-Mantel-Haenszel test was performed to compare the success rates of the 2 insertion methods. Results The motor-driven method was used for 228 mini-screws and the manual method for the remaining 201 mini-screws. The success rates were similar in both men and women irrespective of the insertion method used. With respect to mini-screw length, no difference in success rates was found between motor and hand drivers for the 6-mm-long mini-screws (68.1% and 69.5% with the engine driver and hand driver, respectively). However, the 8-mm-long mini-screws exhibited significantly higher success rates (90.4%, p < 0.01) than did the 6-mm-long mini-screws when placed with the engine driver. The overall success rate was also significantly higher in the maxilla (p < 0.05) when the engine driver was used. Success rates were similar among all age groups regardless of the insertion method used. Conclusions Taken together, the motor-driven insertion method can be helpful to get a higher success rate of orthodontic mini-screw placement. PMID:23173117

  1. [Intermaxillary immobilization using ring-screws in adults].

    PubMed

    Dunet, E; Nallet, E; Badjina, F; Marx, O

    1997-11-01

    We have been unsatisfied with the mandibular ligatures (binding) using Ivy type steel dental wire alone or with arch bars. The principal risks are: instability of ligature in patients with missing teeth AIDS, Hepatitis B and Hepatitis C infections periodental lesions We propose the use of anterior titanium implant screws or the monocortical "piton" which have been used up till now in maxillofacial bone reconstruction. Eight patients in one year have benefited from this procedure. This involved the implant of 32 "pitons" in fractured jaws and, for this study, in parasymphyseal areas PMID:9471681

  2. Contribution to the ideal efficiency of screw propellers

    NASA Technical Reports Server (NTRS)

    Hoff, Wilhelm

    1942-01-01

    The stipulation of best thrust distribution is applied to the annular elements of the screw propeller with infinitely many blades in frictionless, incompressible flow and an ideal jet propulsion system derived possessing hyperbolic angular velocity distribution along the blade radius and combining the advantage of uniform thrust distribution over the section with minimum slipstream and rotation losses. This system is then compared with a propeller possessing the same angular velocity at all blade elements and the best possible thrust distribution secured by means of an induced efficiency varying uniformly over the radius. Lastly, the case of the lightly loaded propeller also is discussed.

  3. 2DEG on a cylindrical shell with a screw dislocation

    NASA Astrophysics Data System (ADS)

    Filgueiras, Cleverson; Silva, Edilberto O.

    2015-09-01

    A two dimensional electron gas on a cylindrical surface with a screw dislocation is considered. More precisely, we investigate how both the geometry and the deformed potential due to a lattice distortion affect the Landau levels of such system. The case showing the deformed potential can be thought in the context of 3D common semiconductors where the electrons are confined on a cylindrical shell. We will show that important quantitative differences exist due to this lattice distortion. For instance, the effective cyclotron frequency is diminished by the deformed potential, which in turn enhances the Hall conductivity.

  4. Role of screw axes in dissolution of willemite

    NASA Astrophysics Data System (ADS)

    Lin, Chung-Cherng; Pouyan, Shen

    1993-04-01

    Static dissolution on the basal plane {0001} of willemite in extremely acid aqueous solutions has produced the curved etch hillocks, indicating anisotropic <101¯0> dissolution. This abnormal dissolution behavior cannot be attributed to defects or active lattice site density, which are equal for all {101¯0} planes, but can be reasonably explained if the detachment of the active lattice sites (namely, ZnO 4) proceeds along the alternate screw axes via a closest neighbor path. The effects of alloyed impurities, etchant variety, and pH value on the formation of etch hillocks are discussed.

  5. Electromyogram synergy control of a dexterous artificial hand to unscrew and screw objects

    PubMed Central

    2014-01-01

    Background Due to their limited dexterity, it is currently not possible to use a commercially available prosthetic hand to unscrew or screw objects without using elbow and shoulder movements. For these tasks, prosthetic hands function like a wrench, which is unnatural and limits their use in tight working environments. Results from timed rotational tasks with human subjects demonstrate the clinical need for increased dexterity of prosthetic hands, and a clinically viable solution to this problem is presented for an anthropomorphic artificial hand. Methods Initially, a human hand motion analysis was performed during a rotational task. From these data, human hand synergies were derived and mapped to an anthropomorphic artificial hand. The synergy for the artificial hand is controlled using conventional dual site electromyogram (EMG) signals. These EMG signals were mapped to the developed synergy to control four joints of the dexterous artificial hand simultaneously. Five limb absent and ten able-bodied test subjects participated in a comparison study to complete a timed rotational task as quickly as possible with their natural hands (except for one subject with a bilateral hand absence), eight commercially available prosthetic hands, and the proposed synergy controller. Each test subject used two to four different artificial hands. Results With the able-bodied subjects, the developed synergy controller reduced task completion time by 177% on average. The limb absent subjects completed the task faster on average than with their own prostheses by 46%. There was a statistically significant improvement in task completion time with the synergy controller for three of the four limb absent participants with integrated prostheses, and was not statistically different for the fourth. Conclusions The proposed synergy controller reduced average task completion time compared to commercially available prostheses. Additionally, the synergy controller is able to function in a small workspace and requires less physical effort since arm movements are not required. The synergy controller is driven by conventional dual site EMG signals that are commonly used for prosthetic hand control, offering a viable solution for people with an upper limb absence to use a more dexterous artificial hand to screw or unscrew objects. PMID:24655413

  6. Determining the residence time distribution of various screw elements in a co-rotating twin-screw extruder by means of fluorescence spectroscopy

    NASA Astrophysics Data System (ADS)

    Lepschi, Alexander; Gerstorfer, Gregor; Miethlinger, Jürgen

    2015-05-01

    The Residence Time Distribution (RTD) is key to optimizing the mixing ability of an extruder. For both sensitive and reactive materials, it is important to know how long particles remain in the barrel and how long the polymer remains, for instance, in a kneading element. To assess the influence of different screw configurations on the RTD, a low-concentration tracer particle was injected into the feeding section and measured inline by fluorescence spectroscopy1 both inside the barrel and at the extruder exit. The measurements were conducted using polypropylene with different amounts of organic peroxide. Measuring the residence time at various positions along the screw allows the RTD to be determined for just one screw element. Furthermore, we show the influence of different screw configurations on the polydispersity of polypropylene.

  7. Joint fluid Gram stain

    MedlinePlus

    Gram stain of joint fluid ... A sample of joint fluid is needed. The fluid sample is sent to a lab where a small drop is placed in a ... on how to prepare for the removal of joint fluid, see joint fluid aspiration .

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

    PubMed

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

    2016-01-01

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

  9. 29 CFR 1926.305 - Jacks-lever and ratchet, screw, and hydraulic.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 29 Labor 8 2011-07-01 2011-07-01 false Jacks-lever and ratchet, screw, and hydraulic. 1926.305 Section 1926.305 Labor Regulations Relating to Labor (Continued) OCCUPATIONAL SAFETY AND HEALTH... Power § 1926.305 Jacks—lever and ratchet, screw, and hydraulic. (a) General requirements. (1)...

  10. 29 CFR 1926.305 - Jacks-lever and ratchet, screw, and hydraulic.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 29 Labor 8 2013-07-01 2013-07-01 false Jacks-lever and ratchet, screw, and hydraulic. 1926.305 Section 1926.305 Labor Regulations Relating to Labor (Continued) OCCUPATIONAL SAFETY AND HEALTH... Power § 1926.305 Jacks—lever and ratchet, screw, and hydraulic. (a) General requirements. (1)...

  11. 29 CFR 1926.305 - Jacks-lever and ratchet, screw, and hydraulic.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 29 Labor 8 2012-07-01 2012-07-01 false Jacks-lever and ratchet, screw, and hydraulic. 1926.305 Section 1926.305 Labor Regulations Relating to Labor (Continued) OCCUPATIONAL SAFETY AND HEALTH... Power § 1926.305 Jacks—lever and ratchet, screw, and hydraulic. (a) General requirements. (1)...

  12. Breakage of a Lag Screw of Cephalomedullary Nail: A Technique of Removal

    PubMed Central

    Tantigate, Direk; Mahaisavariya, Banchong; Sukjaitham, Kitichai

    2015-01-01

    A broken lag screw of the cephalomedullary nail is a rare condition. Removal of the retained lag screw from the femoral head is also very challenging. This article describes a surgical technique and the modified instrument that was available in the operating room for removing the broken implant by closed technique. PMID:26217475

  13. Non-invasive ultrasound based temperature measurements at reciprocating screw plastication units: Methodology and applications

    NASA Astrophysics Data System (ADS)

    Straka, Klaus; Praher, Bernhard; Steinbichler, Georg

    2015-05-01

    Previous attempts to accurately measure the real polymer melt temperature in the screw chamber as well as in the screw channels have failed on account of the challenging metrological boundary conditions (high pressure, high temperature, rotational and axial screw movement). We developed a novel ultrasound system - based on reflection measurements - for the online determination of these important process parameters. Using available pressure-volume-temperature (pvT) data from a polymer it is possible to estimate the density and adiabatic compressibility of the material and therefore the pressure and temperature depending longitudinal ultrasound velocity. From the measured ultrasonic reflection time from the screw root and barrel wall and the pressure it is possible to calculate the mean temperature in the screw channel or in the chamber in front of the screw (in opposition to flush mounted infrared or thermocouple probes). By means of the above described system we are able to measure axial profiles of the mean temperature in the screw chamber. The data gathered by the measurement system can be used to develop control strategies for the plastication process to reduce temperature gradients within the screw chamber or as input data for injection moulding simulation.

  14. Thoracic Pedicle Screw Placement Guide Plate Produced by Three-Dimensional (3-D) Laser Printing.

    PubMed

    Chen, Hongliang; Guo, Kaijing; Yang, Huilin; Wu, Dongying; Yuan, Feng

    2016-01-01

    BACKGROUND The aim of this study was to evaluate the accuracy and feasibility of an individualized thoracic pedicle screw placement guide plate produced by 3-D laser printing. MATERIAL AND METHODS Thoracic pedicle samples of 3 adult cadavers were randomly assigned for 3-D CT scans. The 3-D thoracic models were established by using medical Mimics software, and a screw path was designed with scanned data. Then the individualized thoracic pedicle screw placement guide plate models, matched to the backside of thoracic vertebral plates, were produced with a 3-D laser printer. Screws were placed with assistance of a guide plate. Then, the placement was assessed. RESULTS With the data provided by CT scans, 27 individualized guide plates were produced by 3-D printing. There was no significant difference in sex and relevant parameters of left and right sides among individuals (P>0.05). Screws were placed with assistance of guide plates, and all screws were in the correct positions without penetration of pedicles, under direct observation and anatomic evaluation post-operatively. CONCLUSIONS A thoracic pedicle screw placement guide plate can be produced by 3-D printing. With a high accuracy in placement and convenient operation, it provides a new method for accurate placement of thoracic pedicle screws. PMID:27194139

  15. Foreign body reaction after PLC reconstruction caused by a broken PLLA screw.

    PubMed

    Kim, Tae-Kwon; Jeong, Tae-Wan; Lee, Dae-Hee

    2014-12-01

    Foreign body reactions may occur in patients who receive bioabsorbable implants during orthopedic surgery for fractures and ligament repair. The authors describe a 34-year-old man who presented with a palpable tender mass on the lateral aspect of the left knee of 1 month's duration. He underwent posterior cruciate ligament and posterolateral corner reconstruction 3 years earlier. Physical examination showed a 1×1-cm soft, nontender mass without localized warmth on the lateral epicondyle of the distal femur. Magnetic resonance imaging showed a broken screw fragment surrounded by a cyst-like mass. Under general anesthesia, the surgeon excised the screw fragment and the fibrotic mass, enclosing it in the subcutaneous tissue at the lateral epicondyle, the site at which a poly-L-lactic acid bioabsorbable screw had been inserted to fix the graft for posterolateral corner reconstruction. Histologic evaluation showed a foreign body reaction to the degraded screw particles. To the authors' knowledge, this report is the first description of a patient presenting with a delayed foreign body reaction to a broken poly-L-lactic acid bioabsorbable screw at the lateral femoral epicondyle after posterolateral corner reconstruction. Because delayed foreign body reactions can occur at any site of poly-L-lactic acid bioabsorbable screw insertion, care should be taken to avoid screw protrusion during ligament reconstruction because it can lead to screw breakage and delayed foreign body reaction. PMID:25437089

  16. 29 CFR 1926.305 - Jacks-lever and ratchet, screw, and hydraulic.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 29 Labor 8 2014-07-01 2014-07-01 false Jacks-lever and ratchet, screw, and hydraulic. 1926.305 Section 1926.305 Labor Regulations Relating to Labor (Continued) OCCUPATIONAL SAFETY AND HEALTH... Power § 1926.305 Jacks—lever and ratchet, screw, and hydraulic. (a) General requirements. (1)...

  17. 29 CFR 1926.305 - Jacks-lever and ratchet, screw, and hydraulic.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 29 Labor 8 2010-07-01 2010-07-01 false Jacks-lever and ratchet, screw, and hydraulic. 1926.305... Power § 1926.305 Jacks—lever and ratchet, screw, and hydraulic. (a) General requirements. (1) The... secured at once. (ii) Hydraulic jacks exposed to freezing temperatures shall be supplied with an...

  18. MODELING UNDERGROUND STRUCTURE VULNERABILITY IN JOINTED ROCK

    SciTech Connect

    R. SWIFT; D. STEEDMAN

    2001-02-01

    The vulnerability of underground structures and openings in deep jointed rock to ground shock attack is of chief concern to military planning and security. Damage and/or loss of stability to a structure in jointed rock, often manifested as brittle failure and accompanied with block movement, can depend significantly on jointed properties, such as spacing, orientation, strength, and block character. We apply a hybrid Discrete Element Method combined with the Smooth Particle Hydrodynamics approach to simulate the MIGHTY NORTH event, a definitive high-explosive test performed on an aluminum lined cylindrical opening in jointed Salem limestone. Representing limestone with discrete elements having elastic-equivalence and explicit brittle tensile behavior and the liner as an elastic-plastic continuum provides good agreement with the experiment and damage obtained with finite-element simulations. Extending the approach to parameter variations shows damage is substantially altered by differences in joint geometry and liner properties.

  19. Enhancement of biodegradation and osseointegration of poly(ε-caprolactone)/calcium phosphate ceramic composite screws for osteofixation using calcium sulfate.

    PubMed

    Wu, Chang-Chin; Hsu, Li-Ho; Tsai, Yuh-Feng; Sumi, Shoichiro; Yang, Kai-Chiang

    2016-01-01

    Internal fixation devices, which can stabilize and realign fractured bone, are widely used in fracture management. In this paper, a biodegradable composite fixator, composed of poly(ε-caprolactone), calcium phosphate ceramic and calcium sulfate (PCL/CPC/CS), is developed. The composition of CS, which has a high dissolution rate, was expected to create a porous structure to improve osteofixation to the composite fixator. PCL, PCL/CPC, and PCL/CPC/CS samples were prepared and their physical properties were characterized in vitro. In vivo performance of the composite screws was verified in the distal femurs of rabbits. Results showed that the PCL/CPC/CS composite had a higher compressive strength (28.55  ±  3.32 MPa) in comparison with that of PCL (20.64  ±  1.81 MPa) (p  < 0.05). A larger amount of apatite was formed on PCL/CPC/CS than on PCL/CPC, while no apatite was found on PCL after simulated body fluid immersion. In addition, PCL/CPC/CS composites also had a faster in vitro degradation rate (13.05  ±  3.42% in weight loss) relative to PCL (1.79  ±  0.23%) and PCL/CPC (4.32  ±  2.18%) (p  < 0.001). In animal studies, PCL/CPC/CS screws showed a greater volume loss than that of PCL or PCL/CPC at 24 weeks post-implantation. Under micro-computerized tomography observation, animals with PCL/CPC/CS implants had better osseointegration in terms of the structural parameters of the distal metaphysis, including trabecular number, trabecular spacing, and connectivity density, than the PCL screw. This study reveals that the addition of CS accelerates the biodegradation and enhanced apatite formation of the PCL/CPC composite screw. This osteoconductive PCL/CPC/CS is a good candidate material for internal fixation devices. PMID:27041468

  20. Trabecular bone strength is not an independent predictive factor for dynamic hip screw migration--A prospective multicenter cohort study.

    PubMed

    Müller, Marc A; Hengg, Clemens; Krettek, Christian; van der Velde, Detlef; Eberdorfer, Siegfried; Stange, Richard; Hofmann, Gunther O; Platz, Andreas; Suhm, Norbert

    2015-11-01

    This study assessed whether mechanically measured trabecular bone strength is an independent predictor of dynamic hip screw (DHS) stability, i.e., DHS migration (DHSM) after the fixation of proximal femoral fractures. One-hundred and seven patients older than 50 years with proximal femoral fractures were included. During fracture fixation, a mechanical probe (DensiProbe™ Hip) was inserted at the site where the DHS tip would ultimately be positioned. Peak torque to breakaway the trabecular bone was measured. Fracture reduction, primary implant position and postoperative DHSM were assessed by radiographs taken postoperatively, at 6 and 12 weeks after surgery. Univariate regression analysis revealed no association between peak torque and DHSM (R(2) = 0.025, p = 0.135). DHSM correlated with the primary DHS position, i.e., the distance between the DHS and (i) the central femoral neck axis (CNFAD, R(2) = 0.230; p < 0.0001) and (ii) the apex of the femoral head (R(2) = 0.110; p = 0.001). DHSM did not correlate with areal BMD of the contralateral proximal femur. Multivariable regression modeling revealed the CFNAD as predictive factor for screw migration. The primary implant position measured by the CFNAD, rather than DensiProbe™ Hip measured bone strength, is an independent predictor of DHSM. PMID:25929756

  1. Neurovascular risks of sacral screws with bicortical purchase: an anatomical study.

    PubMed

    Ergur, Ipek; Akcali, Omer; Kiray, Amac; Kosay, Can; Tayefi, Hamid

    2007-09-01

    The aim of this cadaver study is to define the anatomic structures on anterior sacrum, which are under the risk of injury during bicortical screw application to the S1 and S2 pedicles. Thirty formaldehyde-preserved human male cadavers were studied. Posterior midline incision was performed, and soft tissues and muscles were dissected from the posterior part of the lumbosacral region. A 6 mm pedicle screw was inserted between the superior facet of S1 and the S1 foramen. The entry point of the S2 pedicle screw was located between S1 and S2 foramina. S1 and S2 screws were placed on both right and the left sides of all cadavers. Then, all cadavers were turned into supine position. All abdominal and pelvic organs were moved away and carefully observed for any injury. The tips of the sacral screws were marked and the relations with the anatomic structures were defined. The position of the sacral screws relative to the middle and lateral sacral arteries and veins, and the sacral sympathetic trunk were measured. There was no injury to the visceral organs. In four cases, S1 screw tip was in direct contact with middle sacral artery. In two cases, S1 screw tip was in direct contact with middle sacral vein. It was observed that the S1 screw tips were in close proximity to sacral sympathetic trunk on both right and the left sides. The tip of the S2 screw was in contact with middle sacral artery on the left side only in one case. It is found that the tip of the S2 screw was closely located with the middle sacral vein in two cases. The tip of the S2 pedicle screw was in contact with the sacral sympathetic trunk in eight cases on the right side and seven cases on the left side. Lateral sacral vein was also observed to be disturbed by the S1 and S2 screws. As a conclusion, anterior cortical penetration during sacral screw insertion carries a risk of neurovascular injury. The risk of sacral sympathetic trunk and minor vascular structures together with the major neurovascular structures and viscera should be kept in mind. PMID:17846804

  2. Neurovascular risks of sacral screws with bicortical purchase: an anatomical study

    PubMed Central

    Ergur, Ipek; Kiray, Amac; Kosay, Can; Tayefi, Hamid

    2007-01-01

    The aim of this cadaver study is to define the anatomic structures on anterior sacrum, which are under the risk of injury during bicortical screw application to the S1 and S2 pedicles. Thirty formaldehyde-preserved human male cadavers were studied. Posterior midline incision was performed, and soft tissues and muscles were dissected from the posterior part of the lumbosacral region. A 6 mm pedicle screw was inserted between the superior facet of S1 and the S1 foramen. The entry point of the S2 pedicle screw was located between S1 and S2 foramina. S1 and S2 screws were placed on both right and the left sides of all cadavers. Then, all cadavers were turned into supine position. All abdominal and pelvic organs were moved away and carefully observed for any injury. The tips of the sacral screws were marked and the relations with the anatomic structures were defined. The position of the sacral screws relative to the middle and lateral sacral arteries and veins, and the sacral sympathetic trunk were measured. There was no injury to the visceral organs. In four cases, S1 screw tip was in direct contact with middle sacral artery. In two cases, S1 screw tip was in direct contact with middle sacral vein. It was observed that the S1 screw tips were in close proximity to sacral sympathetic trunk on both right and the left sides. The tip of the S2 screw was in contact with middle sacral artery on the left side only in one case. It is found that the tip of the S2 screw was closely located with the middle sacral vein in two cases. The tip of the S2 pedicle screw was in contact with the sacral sympathetic trunk in eight cases on the right side and seven cases on the left side. Lateral sacral vein was also observed to be disturbed by the S1 and S2 screws. As a conclusion, anterior cortical penetration during sacral screw insertion carries a risk of neurovascular injury. The risk of sacral sympathetic trunk and minor vascular structures together with the major neurovascular structures and viscera should be kept in mind. PMID:17846804

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

    PubMed

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

    2016-03-01

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

  4. Standing placement of transphyseal screw in the distal radius in 8 Thoroughbred yearlings.

    PubMed

    Modesto, Rolf B; Rodgerson, Dwayne H; Masciarelli, Amanda E; Spirito, Michael

    2015-06-01

    This retrospective study describes placement of distal radial transphyseal screws in Thoroughbred yearlings with carpal varus deformities while standing, and identifes short- and long-term complications following the procedure. Data gathered from 2009 to 2013 identified 8 yearlings that met the inclusion criteria. Horses were sedated intravenously and a single 4.5-mm cortical screw was placed in the distal lateral radial physis following application of local anesthetic and surgical preparation of a pre-placed hole. All horses were evaluated weekly after surgery and screw removal was performed standing and under sedation when correction of the angular limb deformity was achieved. The mean time for screw removal was 46 days. No short- or long-term complications were identified. Findings indicate that placing a single transphyseal screw in the lateral aspect of the distal radial physis with the horse standing is a viable option to treat varus angular limb deformity of the carpus in horses. PMID:26028683

  5. A Newly Designed Screw- and Cement-Retained Prosthesis and Its Abutments.

    PubMed

    Heo, Young-Ku; Lim, Young-Jun

    2015-01-01

    The degree of misfit between a prosthesis and its supporting implants is a major concern in screw-retained prostheses because it can lead to screw loosening or mechanical failure of implant components. On the other hand, the difficulty of removing subgingival excess cement and the irretrievability of the superstructure are major drawbacks to cement-retained prostheses. A newly designed screw- and cement-retained prosthesis (SCRP) may solve these problems with its passivity, retrievability, and ease in the complete removal of excess cement, giving it the advantages of both screw-retained and cement-retained prostheses. This prosthetic system is mainly composed of a cement-retained framework with screw holes on the occlusal surface and specially designed cementable abutments for multiunit prostheses. The principle and structure of the SCRP system is described in this article. PMID:26523721

  6. Standing placement of transphyseal screw in the distal radius in 8 Thoroughbred yearlings

    PubMed Central

    Modesto, Rolf B.; Rodgerson, Dwayne H.; Masciarelli, Amanda E.; Spirito, Michael

    2015-01-01

    This retrospective study describes placement of distal radial transphyseal screws in Thoroughbred yearlings with carpal varus deformities while standing, and identifes short- and long-term complications following the procedure. Data gathered from 2009 to 2013 identified 8 yearlings that met the inclusion criteria. Horses were sedated intravenously and a single 4.5-mm cortical screw was placed in the distal lateral radial physis following application of local anesthetic and surgical preparation of a pre-placed hole. All horses were evaluated weekly after surgery and screw removal was performed standing and under sedation when correction of the angular limb deformity was achieved. The mean time for screw removal was 46 days. No short- or long-term complications were identified. Findings indicate that placing a single transphyseal screw in the lateral aspect of the distal radial physis with the horse standing is a viable option to treat varus angular limb deformity of the carpus in horses. PMID:26028683

  7. Molecular dynamics studies of the dissociated screw dislocation in silicon.

    PubMed

    Choudhury, R; Gattinoni, C; Makov, G; De Vita, A

    2010-02-24

    Characterizing the motion of dislocations through covalent, high Peierls barrier materials is a key problem in materials science, while despite the progress in experimental studies the actual observation of the atomistic behaviour involved in core migration remains limited. We have applied a hybrid embedding scheme to investigate the dissociated screw dislocation in silicon, consisting of two 30° partials separated by a stacking fault ribbon, under the influence of a constant external strain. Our 'learn on the fly' hybrid technique allows us to calculate the forces on atoms in the vicinity of the core region using the tight binding Kwon potential, whilst the remainder of the bulk matrix is treated within a classical approximation. Applying a 5% strain to the dissociated screw dislocation, for a simulation time of 100 ps at a temperature of 600 K, we observe movement of the partials through two different mechanisms: double kink formation and square ring diffusion at the core. Our results suggest that in these conditions, the role of solitons or anti-phase defects in seeding kink formation and subsequent migration is an important one, which should be taken into account in future studies. PMID:21386388

  8. Prevention of unrecognized joint penetration during internal fixation of hip fractures: a geometric model based on Steinmetz Solid.

    PubMed

    Mao, Yujiang; Song, Jie; Wei, Jie; Wang, Manyi

    2010-01-01

    Unrecognized joint penetration (UJP) by screw penetration through the articular surface undetectable on routine anteroposterior (AP) and lateral radiographs can cause serious complications. We have developed a geometric model to analyze UJP, and methods for the prevention of the problem. A Steinmetz Solid (SS) is the overlapping portion between two identical, vertically intersecting cylinders. The AP and lateral radiographs of a femoral head (simplified as a sphere) are projections of two cylinder-shaped images. A screw that appears to be within the femoral head in fact only lies within the cylinder. A screw apparently within the femoral head on both AP and lateral images is only confined to the SS generated by two cylinders, but not necessarily confined to the femoral head itself. We have therefore analyzed UJP using a geometric model based on SS. The geometric basis of UJP lies in the fact that the SS is larger than the sphere (femoral head) with a volume ratio of 4: π. The theoretical risk of UJP for any screw therefore can be as high as 21.5% ((4-π)/4). In reality, screws are always carefully placed to ensure a distance between the screw's tip and the edge of femoral head (tip-to-edge distance, or TED). This TED effectively lowers the risk of UJP by reducing the size of the screw-confining SS. When the SS entirely fits into (internally tangential to) the femoral head, the risk of UJP approaches zero. A TED fulfilling this requirement can be regarded as safe (approximately 0.29 x femoral head radius). With a femoral head diameter of 5 cm, the safe TED is approximately 7 mm. PMID:21157763

  9. Seismic response of rock joints and jointed rock mass

    SciTech Connect

    Ghosh, A.; Hsiung, S.M.; Chowdhury, A.H.

    1996-06-01

    Long-term stability of emplacement drifts and potential near-field fluid flow resulting from coupled effects are among the concerns for safe disposal of high-level nuclear waste (HLW). A number of factors can induce drift instability or change the near-field flow patterns. Repetitive seismic loads from earthquakes and thermal loads generated by the decay of emplaced waste are two significant factors. One of two key technical uncertainties (KTU) that can potentially pose a high risk of noncompliance with the performance objectives of 10 CFR Part 60 is the prediction of thermal-mechanical (including repetitive seismic load) effects on stability of emplacement drifts and the engineered barrier system. The second KTU of concern is the prediction of thermal-mechanical-hydrological (including repetitive seismic load) effects on the host rock surrounding the engineered barrier system. The Rock Mechanics research project being conducted at the Center for Nuclear Waste Regulatory Analyses (CNWRA) is intended to address certain specific technical issues associated with these two KTUs. This research project has two major components: (i) seismic response of rock joints and a jointed rock mass and (ii) coupled thermal-mechanical-hydrological (TMH) response of a jointed rock mass surrounding the engineered barrier system (EBS). This final report summarizes the research activities concerned with the repetitive seismic load aspect of both these KTUs.

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

    PubMed Central

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

    2015-01-01

    To evaluate the presence of pain at the site of the surgical incision and the need to remove the tibial fixation screw in anterior cruciate ligament (ACL) reconstruction, in relation to sex and body mass index (BMI). Methods: A group of 265 patients who underwent ACL reconstruction with ipsilateral flexor tendon grafts from the thigh in which the tibial fixation technique consisted of using a cortical screw and metal washer, between July 2000 and November 2007, were evaluated. Results: 176 patients were evaluated for an average of 33.3 ± 19.5 months; median of 29.5 months; IIQ: 17-45 months; minimum of 8 and maximum of 87 months. There was no statistical difference regarding complaints of pain at the site of the screw (p = 0.272) and the need to remove the tibial screw (p = 0.633) between sexes. There was no statistical difference regarding complaints of pain at the site of the screw (p = 0.08) and the need to remove the tibial screw (p = 0.379) according to BMI. Conclusion: The pain complaint rate at the screw site from the screw and metal washer method used for tibial fixation in ACL reconstruction was of the order of 25%, and the screw had to be removed in 10.8% of the cases. There was no predominance of pain complaints at the surgical wound between the sexes. There was a greater tendency to complain about pain among patients with BMI < 25. There was no predominance of screw and washer removal between the sexes or between individuals with different BMIs. PMID:27022587

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

    PubMed Central

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

    2015-01-01

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

  12. Accuracy and efficacy of thoracic pedicle screws in scoliosis with patient-specific drill template.

    PubMed

    Lu, Sheng; Zhang, Yuan Z; Wang, Zheng; Shi, Ji H; Chen, Yu B; Xu, Xing M; Xu, Yong Q

    2012-07-01

    With the rapid increase in the use of thoracic pedicle screws in scoliosis, accurate and safe placement of screw within the pedicle is a crucial step during the scoliosis surgery. To make thoracic pedicle screw placement safer various techniques are used, Patient-specific drill template with pre-planned trajectory has been thought as a promising solution, it is critical to assess the efficacy, safety profile with this technique. In this paper, we develop and validate the accuracy and safety of thoracic transpedicular screw placement with patient-specific drill template technique in scoliosis. Patients with scoliosis requiring instrumentation were recruited. Volumetric CT scan was performed on each desired thoracic vertebra and a 3-D reconstruction model was generated from the CT scan data. The optimal screw size and orientation were determined and a drill template was designed with a surface that is the inverse of the posterior vertebral surface. The drill template and its corresponding vertebra were manufactured using rapid prototyping technique and tested for violations. The navigational template was sterilized and used intraoperatively to assist with the placement of thoracic screws. After surgery, the positions of the pedicle screws were evaluated using CT scan and graded for validation. This method showed its ability to customize the placement and the size of each pedicle screw based on the unique morphology of the thoracic vertebra. In all the cases, it was relatively very easy to manually place the drill template on the lamina of the vertebral body during the surgery. This method significantly reduces the operation time and radiation exposure for the members of the surgical team, making it a practical, simple and safe method. The potential use of such a navigational template to insert thoracic pedicle screws in scoliosis is promising. The use of surgical navigation system successfully reduced the perforation rate and insertion angle errors, demonstrating the clear advantage in safe and accurate pedicle screw placement of scoliosis surgery. PMID:22467276

  13. The anatomy and biomechanics of the hip joint.

    PubMed

    Anderson, L C; Blake, D J

    1994-01-01

    The human hip is the largest ball and socket joint in the body. It differs in design from the more common hinge joint in order to meet the requirements of ambulation. The hip is an inherently stable joint because of its bony structure and its extensive ligamentous and muscular support. Regardless of this stability, the hip joint maintains a wide functional range of movement. This dichotomy of function has resulted in a complex organization of joint structure. A thorough understanding of the biomechanic forces exerted across the joint surfaces is essential to the understanding of both normal and pathologic function.The authors of this article will explore the complex structural anatomy of this joint system in light of the biomechanic principles that effect movement and weight bearing through the joint. PMID:24572054

  14. Unilateral Pedicle Screw Fixation with Bone Graft vs. Bilateral Pedicle Screw Fixation with Bone Graft or Cage: A Comparative Study

    PubMed Central

    Yang, Si-Dong; Chen, Qian; Ding, Wen-Yuan; Zhao, Jian-Qiang; Zhang, Ying-Ze; Shen, Yong; Yang, Da-Long

    2016-01-01

    Background The aim of this study was to explore the clinical efficacy of unilateral pedicle screw fixation with bone graft (UPSFB) in treating single-segment lumbar degenerative diseases (LDD), as compared to bilateral pedicle screw fixation with bone graft (BPSFB) or with cage (BPSFC). Material/Methods Medical records were retrospectively collected between 01/2010 and 02/2015 in Longyao County Hospital. According to surgical methods used, all patients were divided into 3 groups: UPSFB group, BPSFB group, and BPSFC group. Clinical outcomes were evaluated by blood loss, blood transfusion, duration of operation, hospital stay, postoperative complications, interbody fusion rate, reoperation rate, medical expenses, patient satisfaction survey, and JOA score. Results Ninety-five patients were included and underwent 2.5-year follow-up, with 7 patients lost to regular follow-up. As compared to the BPSFB group and BPSFC group, the UPSFB group had less blood loss and less blood transfusion, as well as shorter hospital stay (p<0.05). Medical expenses were far lower in the UPSFB group (p<0.001). There were no significant differences among the 3 groups in postoperative complications, interbody fusion rate, reoperation rate, JOA score, and patient satisfaction (all p>0.05). Conclusions As compared to BPSFB and BPSFC, UPSFB has the same reliability and effectiveness in treating single-segment LDD with unilateral radicular symptoms in a single lower extremity, with the additional advantage being less expensive. PMID:26988532

  15. Butt Joint Tool Commissioning

    SciTech Connect

    Martovetsky, N N

    2007-12-06

    ITER Central Solenoid uses butt joints for connecting the pancakes in the CS module. The principles of the butt joining of the CICC were developed by the JAPT during CSMC project. The difference between the CSMC butt joint and the CS butt joint is that the CS butt joint is an in-line joint, while the CSMC is a double joint through a hairpin jumper. The CS butt joint has to carry the hoop load. The straight length of the joint is only 320 mm, and the vacuum chamber around the joint has to have a split in the clamp shell. These requirements are challenging. Fig.1 presents a CSMC joint, and Fig.2 shows a CS butt joint. The butt joint procedure was verified and demonstrated. The tool is capable of achieving all specified parameters. The vacuum in the end was a little higher than the target, which is not critical and readily correctable. We consider, tentatively that the procedure is established. Unexpectedly, we discover significant temperature nonuniformity in the joint cross section, which is not formally a violation of the specs, but is a point of concern. All testing parameters are recorded for QA purposes. We plan to modify the butt joining tool to improve its convenience of operation and provide all features necessary for production of butt joints by qualified personnel.

  16. Screw Back-Out Following "Open-Door" Cervical Laminoplasty: A Review of 165 Plates

    PubMed Central

    Buchowski, Jacob M.; Riew, K. Daniel

    2015-01-01

    Study Design Retrospective study. Purpose To investigate safety profile of open door laminoplasty plates. Overview of Literature Few reports have documented potential complications related to the use of cervical laminoplasty plates. Methods Records and radiographs of consecutive plated laminoplasty patients of one academic surgeon were analyzed. Group 1 had screw back-out, defined as change in screw position, and group 2 did not. Results Forty-two patients (mean age, 56.9) underwent "open-door" cervical laminoplasty using 165 plates. Mean follow-up was 24 months (range, 12-49 months). Mean Nurick grade improved from 2.1 to 0.9 postoperatively. Cervical lordosis (C2-7) was 12.1° preoperatively and 10.0° postoperatively. Range-of-motion was 27.0° preoperatively and 23.4° postoperatively. Partial screw back-out was noted in 27 of 165 plates (16.4%) and in 34 of 660 screws (5.2%). Of the 34 screws, 27 (79.4%) were at either the most cranial (12/27, 44.4%) or the most caudal (15/27, 55.5%) level. Cranially, 11/12 screws (91.7%) had back-out. Caudally, 9/15 lateral mass screws (60.0%) backed-out versus 6 laminar screws (40.0%). Of the 22 patients with screw back-out, 15 (68.2%) occurred <3 months postoperative and 6 (27.3%) occurred 4-12 months postoperative. No statistical differences were found between group 1 and 2 for age, gender, preoperative and postoperative lordosis, focal sagittal alignment, range-of-motion, or Nurick grade. Despite screw backout in 22 patients, there were no plate dislodgements, laminoplasty closure, or neurological deterioration. Conclusions Although screw back-out may occur with the use of cervical laminoplasty plates, the use of these plates without a bone block appears to be safe and reliable. As screw back-out is most common at the cranial and caudal ends of the laminoplasty, we recommend using the maximum number of screws (typically 2 for the lateral mass and 2 for the spinous process) at these levels to secure the plate to the bone. PMID:26713115

  17. Modeling flow, melting, solid conveying and global behavior in intermeshing counter-rotating twin screw extruders

    NASA Astrophysics Data System (ADS)

    Jiang, Qibo

    Intermeshing counter-rotating twin screw extruders are widely applied in polymer processing industry, especially in compounding and PVC profile processing. However, the design of this type of machines is generally based on experiences and error-and-try. In addition, most of the investigations on intermeshing counter-rotating twin screw extruders were made on the melt conveying region. There is a lack of adequate study on a complete extrusion process to this type of machines. In this study, models were developed to simulate the extrusion processes, including solid conveying, melting and metering, evaluate the performance of intermeshing counter-rotating twin screw extruders, and optimize the design of machines and operating conditions. Experiments were carried out on a laboratory modular intermeshing counter-rotating twin screw extruder to observe solid conveying, the melting process and the global behavior of this type of machine. The solid bed is formed in the solid conveying region. The inter-screw region plays a dominant role in the melting process. Based on our observations, models were developed to describe both the solid conveying and the melting process. Based on hydrodynamic lubrication theory, a melt conveying model was developed to characterize the pumping capacity of screw elements in intermeshing counter-rotating twin screw extruders. The effect of screw channel aspect ratio (screw channel depth/width) was incorporated into the melt conveying model to improve the prediction of screw pumping capacity. Calculations were made to investigate the effect of geometrical parameter on screw pumping capacity. Models of solid conveying, the melting process and melt conveying were integrated together and a global composite model was developed to characterize the whole intermeshing counter-rotating twin screw extrusion process. The global model is intended for both flood fed and metered starved fed conditions. This is the first composite model designed for this type of machines. Simulations and experiment results were compared and it was found that they match very well. This global model was further successfully developed into user-friendly software, which is used to design, test and optimize intermeshing counter-rotating twin screw extruders.

  18. Trapeziometacarpal joint implants can be evaluated by roentgen stereophotogrammetric analysis.

    PubMed

    Hansen, T B; Larsen, K; Bjergelund, L; Stilling, M

    2010-07-01

    Both marker-based roentgen stereophotogrammetric analysis (RSA) and model-based RSA have been helpful evaluation tools in hip and knee arthroplasty. The purpose of this study was to test both model-based and marker-based RSA in the evaluation of total joint prostheses of the trapeziometacarpal joint. In a phantom study, the precision of marker-based RSA was tested with a cemented polyethylene cup and compared with the precision of model-based RSA in an uncemented Elektra screw cup. The precision of model-based RSA of the metacarpal stem was tested using an uncemented Elektra metacarpal stem. In a clinical study 11 patients had double stereo radiographs followed by RSA analysis. The precision of translation in both marker-based and model-based RSA was sufficient for clinical use, but rotation cannot be estimated with sufficient precision. PMID:20181771

  19. Reusable Solid Rocket Motor Nozzle Joint 5 Redesign

    NASA Technical Reports Server (NTRS)

    Lui, R. C.; Stratton, T. C.; LaMont, D. T.

    2003-01-01

    Torque tension testing of a newly designed Reusable Solid Rocket Motor nozzle bolted assembly was successfully completed. Test results showed that the 3-sigma preload variation was as expected at the required input torque level and the preload relaxation were within the engineering limits. A shim installation technique was demonstrated as a simple process to fill a shear lip gap between nozzle housings in the joint region. A new automated torque system was successfully demonstrated in this test. This torque control tool was found to be very precise and accurate. The bolted assembly performance was further evaluated using the Nozzle Structural Test Bed. Both current socket head cap screw and proposed multiphase alloy bolt configurations were tested. Results indicated that joint skip and bolt bending were significantly reduced with the new multiphase alloy bolt design. This paper summarizes all the test results completed to date.

  20. Experimental study of friction in aluminium bolted joints

    NASA Astrophysics Data System (ADS)

    Croccolo, D.; de Agostinis, M.; Vincenzi, N.

    2010-06-01

    This study aims at developing an experimental tool useful to define accurately the friction coefficients in bolted joints and, therefore, at relating precisely the tightening torque to the bolt preloading force in some special components used in front motorbike suspensions. The components under investigation are some clamped joints made of aluminium alloy. The preloading force is achieved by applying a torque wrench to the bolt head. Some specific specimens have been appropriately designed and realized in order to study the tribological aspects of the tightening phase. Experimental tests have been performed by applying the Design of Experiment (DOE) method in order to obtain a mathematical model for the friction coefficients. Three replicas of a full factorial DOE at two levels for each variable have been carried out. The levels include cast versus forged aluminium alloy, anodized versus spray-painted surface, lubricated versus unlubricated screw, and first tightening (fresh unspoiled surfaces) versus sixth tightening (spoiled surfaces). The study considers M8x1.25 8.8 galvanized screws.

  1. Pressure suit joint analyzer

    NASA Technical Reports Server (NTRS)

    Vykukal, H. C.; Webbon, B. W. (Inventor)

    1982-01-01

    A measurement system for simultaneously measuring torque and angular flexure in a pressure suit joint is described. One end of a joint under test is held rigid. A torque transducer is pivotably supported on the other movable end of a joint. A potentiometer is attached to the transducer by an arm. The wiper shaft of the potentiometer is gripped by a reference arm that rotates the wiper shaft the same angle as the flexure of joint. A signal is generated by the potentiometer which is representative of the joint flexure. A compensation circuit converts the output of the transducer to a signal representative of joint torque.

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

    PubMed Central

    2011-01-01

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

  3. Load transfer in Christensen(®) TMJ in alloplastic total joint replacement for two different mouth apertures.

    PubMed

    Ramos, António; Mesnard, Michel

    2014-10-01

    This study analyses load transfer in the fossa component based on two numerical models of total temporomandibular joint (TMJ) implants for two mouth openings. The TMJ articulation is a very complex system with muscles, ligaments and cartilage. Until now, studies of TMJ implants have analysed only condylar behaviour. The finite element models were constructed based on CT scans of a cadaveric mandible and cranium, considering the bone geometry and position. The influence of five principal muscle actions was simulated for two mouth positions, 5 mm and 15 mm openings at the incisive tooth support. Strain distributions into the surrounding bone tissue were analysed in both models in the condyle and fossa components. The results demonstrate that in Christensen(®) TJR of the temporomandibular joint the fossa component is the more critical part, presenting more stress near the screw holes and contact regions with the cranium. The most critical region is around the first two screws and the least critical is in the condyle component. For the mandible condyle reconstructed with a Christensen(®) prosthesis, the 15 mm mouth opening was more critical, as compression was increased, but for the fossa component the most critical situation occurred with the 5 mm opening. The micromovements observed suggest that the number of screws could be reduced to increase osteointegration of screws in the mandible condyle. PMID:24954763

  4. Mechanical Comparison of Headless Screw Fixation and Locking Plate Fixation for Talar Neck Fractures.

    PubMed

    Karakasli, Ahmet; Hapa, Onur; Erduran, Mehmet; Dincer, Cemal; Cecen, Berivan; Havitcioglu, Hasan

    2015-01-01

    For talar neck fractures, open reduction and internal fixation have been thought to facilitate revascularization and prevent osteonecrosis. Newer screw systems allow for placement of cannulated headless screws, which provide compression by virtue of a variable pitch thread. The present study compared the biomechanical fixation strength of cannulated headless variable-pitch screw fixation and locking plate fixation. A reproducible talar neck fracture was created in 14 fresh cadaver talar necks. Talar head fixation was then performed using 2 cannulated headless variable-pitch 4-mm/5-mm diameter (4/5) screws (Acutrak; Acumed, Hillsboro, OR) and locking plate fixation. Headless variable-pitch screw fixation had lower failure displacement than did locking plate fixation. No statistically significant differences were found in failure stiffness, yield stiffness (p = .655), yield load (p = .142), or ultimate load between the 2 fixation techniques. Cannulated headless variable-pitch screw fixation resulted in better failure displacement than locking plate fixation in a cadaveric talus model and could be considered a viable option for talus fracture fixation. Headless, fully threaded, variable-pitch screw fixation has inherent advantages compared with locking plate fixation, because it might cause less damage to the articular surface and can compress the fracture for improved reduction. Additionally, plate fixation can increase the risk of avascular necrosis owing to the wider incision and dissection of soft tissues. PMID:25998471

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

    PubMed

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

    2006-02-01

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

  6. Screw versus suture fixation of Mitchell's osteotomy. A prospective, randomised study.

    PubMed

    Calder, J D; Hollingdale, J P; Pearse, M F

    1999-07-01

    We studied prospectively 30 patients who had a Mitchell's osteotomy secured by either a suture followed by immobilisation in a plaster boot for six weeks, or by a cortical screw with early mobilisation. The mean time for return to social activities after fixation by a screw was 2.9 weeks and to work 4.9 weeks, which was significantly earlier than those who had stabilisation by a suture (5.7 and 8.7 weeks, respectively; p < 0.001). Use of a screw also produced a higher degree of patient satisfaction at six weeks, and an earlier return to wearing normal footwear. The improvement in forefoot scores was significantly greater after fixation by a screw at six weeks (p = 0.036) and three months (p = 0.024). At one year, two screws had been removed because of pain at the site of the screw head. Internal fixation of Mitchell's osteotomy by a screw allows the safe early mobilisation of patients and reduces the time required for convalescence. PMID:10463733

  7. In-vitro development of a temporal abutment screw to protect osseointegration in immediate loaded implants

    PubMed Central

    2015-01-01

    PURPOSE In this study, a temporal abutment fixation screw, designed to fracture in a controlled way upon application of an occlusal force sufficient to produce critical micromotion was developed. The purpose of the screw was to protect the osseointegration of immediate loaded single implants. MATERIALS AND METHODS Seven different screw prototypes were examined by fixing titanium abutments to 112 Mozo-Grau external hexagon implants (MG Osseous®; Mozo-Grau, S.A., Valladolid, Spain). Fracture strength was tested at 30° in two subgroups per screw: one under dynamic loading and the other without prior dynamic loading. Dynamic loading was performed in a single-axis chewing simulator using 150,000 load cycles at 50 N. After normal distribution of obtained data was verified by Kolmogorov-Smirnov test, fracture resistance between samples submitted and not submitted to dynamic loading was compared by the use of Student's t-test. Comparison of fracture resistance among different screw designs was performed by the use of one-way analysis of variance. Confidence interval was set at 95%. RESULTS Fractures occurred in all screws, allowing easy retrieval. Screw Prototypes 2, 5 and 6 failed during dynamic loading and exhibited statistically significant differences from the other prototypes. CONCLUSION Prototypes 2, 5 and 6 may offer a useful protective mechanism during occlusal overload in immediate loaded implants. PMID:25932315

  8. Treatment of screw hole defects using bone graft materials: a histologic and biomechanic study.

    PubMed

    York, M J; Hutton, W C

    1996-01-01

    We surgically applied compression plates, secured with cortical screws, to the anterolateral surface of each radius in 20 dogs. Five weeks later, the plates and screws were removed. The dogs were then divided into four groups of 5, and each group had the screw holes in the left radii filled with a different form of bone graft material. The screw holes in the right radii received no graft material and served as controls. Five weeks later the dogs were euthanized, and the radii were removed and torqued to failure. All bones failed through a previous screw hole. An analysis of variance comparing all grafted radii to the ungrafted controls revealed no significant difference in torque to failure. This suggests that both grafted and ungrafted screw holes still increase stress at 5 weeks, and any period of protection after plate removal should be longer than 5 weeks. However, histology revealed that the holes filled with graft material had, in every case, more bone in the screw holes than did the holes in the ungrafted controls. PMID:8673590

  9. Wall-locking of kink modes in a line-tied screw pinch with a rotating walla)

    NASA Astrophysics Data System (ADS)

    Paz-Soldan, C.; Brookhart, M. I.; Hegna, C. C.; Forest, C. B.

    2012-05-01

    The effect of rotating conducting walls on mode-locking is studied in a line-tied, linear screw pinch experiment and then compared to a torque balance model which has been extended to include differential wall rotation. Wall rotation is predicted to asymmetrically affect the mode-unlocking threshold, with fast rotation eliminating the locking bifurcation. Static error fields are observed to lock the resistive wall mode (RWM) variant of the current driven kink instability by modifying the electromagnetic torque. Using locked modes, the stabilizing effect of wall rotation on the RWM is experimentally demonstrated by illustrating a reduction of the RWM growth rate and an extension of the RWM-stable operation window.

  10. Comparison of the bending performance of solid and cannulated spinal pedicle screws using finite element analyses and biomechanical tests.

    PubMed

    Shih, Kao-Shang; Hsu, Ching-Chi; Hou, Sheng-Mou; Yu, Shan-Chuen; Liaw, Chen-Kun

    2015-09-01

    Spinal pedicle screw fixations have been used extensively to treat fracture, tumor, infection, or degeneration of the spine. Cannulated spinal pedicle screws with bone cement augmentation might be a useful method to ameliorate screw loosening. However, cannulated spinal pedicle screws might also increase the risk of screw breakage. Thus, the purpose of this study was to investigate the bending performance of different spinal pedicle screws with either solid design or cannulated design. Three-dimensional finite element models, which consisted of the spinal pedicle screw and the screw's hosting material, were first constructed. Next, monotonic and cyclic cantilever bending tests were both applied to validate the results of the finite element analyses. Finally, both the numerical and experimental approaches were evaluated and compared. The results indicated that the cylindrical spinal pedicle screws with a cannulated design had significantly poorer bending performance. In addition, conical spinal pedicle screws maintained the original bending performance, whether they were solid or of cannulated design. This study may provide useful recommendations to orthopedic surgeons before surgery, and it may also provide design rationales to biomechanical engineers during the development of spinal pedicle screws. PMID:26208430

  11. Rigid-drift magnetohydrodynamic equilibria for cylindrical screw pinches

    NASA Technical Reports Server (NTRS)

    Turner, L.

    1979-01-01

    The rigid-drift equations of MHD equilibria in cylindrical geometry are solved analytically in terms of an infinite series of hypergeometric functions for the case where the pressure is proportional to the square of number density and the current density is arbitrarily pitched. Solutions are obtained for a pure Z pinch, a pure theta pinch, and a general screw pinch. It is found that the shapes of the pressure and magnetic-field profiles are completely determined by the model once two parameters are specified: the local plasma beta on the axis and a quantity related to the pitch of the current density. A set of profiles that resemble those observed experimentally in reversed-field pinches is presented. The results also indicate that hollow pressure profiles and reversed Bz profiles can occur either simultaneously or independently and that the pressure always falls to zero at a finite value of the radius.

  12. Parallel operation of NH3 screw compressors - the optimum way

    NASA Astrophysics Data System (ADS)

    Pijnenburg, B.; Ritmann, J.

    2015-08-01

    The use of more smaller industrial NH3 screw compressors operating in parallel seems to offer the optimum way when it comes to fulfilling maximum part load efficiency, increased redundancy and other highly requested features in the industrial refrigeration industry today. Parallel operation in an optimum way can be selected to secure continuous operation and can in most applications be configured to ensure lower overall operating economy. New compressors are developed to meet requirements for flexibility in operation and are controlled in an intelligent way. The intelligent control system keeps focus on all external demands, but yet striving to offer always the lowest possible absorbed power, including in future scenarios with connection to smart grid.

  13. Structural and torsional vibration analysis of a dry screw compressor

    NASA Astrophysics Data System (ADS)

    Willie, J.; Sachs, R.

    2015-08-01

    This paper investigates torsional vibration and pulsating noise in a dry screw compressor. The compressor is designed at Gardner Denver (GD) and is oil free and use for mounting on highway trucks. They are driven using a Power Take-Off (PTO) transmission and gear box on a truck. Torque peak fluctuation and noise measurements are done and their sources are investigated and reported in this work. To accurately predict the torsional response (frequency and relative angular deflection and torque amplitude), the Holzer method is used. It is shown that the first torsional frequency is manifested as sidebands in the gear train meshing frequencies and this can lead to noise that is the result of amplitude modulation. Sensitivity analysis of the drive train identifies the weakest link in the drive train that limits the first torsional frequency to a low value. Finally, the significance of higher mode shapes on inter-lobe clearance distribution of the rotors is investigated.

  14. The helical screw expander evaluation project. [for geothermal wells

    NASA Technical Reports Server (NTRS)

    Mckay, R. A.

    1977-01-01

    A positive-displacement helical-screw expander of the Lysholm type has been adapted for geothermal service and successfully demonstrated in a 50 kW prototype power system. Evaluation of the expander by tests of a new model in a 1 MW power system under wellhead conditions in selected liquid-dominated geothermal fields is proposed. The objectives are to determine the performance characteristics of the expander and power system over a broad range of operating conditions and also to examine the concept of wellhead power plants. Throttling and fractionation of the fluids from the test wells is planned to simulate a wide range of wellhead pressures and steam fractions. Variation in the expander exhaust pressure is also planned. The investigation will include expander efficiency, corrosion, erosion, scale formation and control, and endurance testing. Interaction studies with the wells and an electric grid are also proposed.

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

    PubMed Central

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

    2015-01-01

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

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

    PubMed

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

    2015-01-01

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

  17. Alkaline twin-screw extrusion pretreatment for fermentable sugar production

    PubMed Central

    2013-01-01

    Background The inevitable depletion of fossil fuels has resulted in an increasing worldwide interest in exploring alternative and sustainable energy sources. Lignocellulose, which is the most abundant biomass on earth, is widely regarded as a promising raw material to produce fuel ethanol. Pretreatment is an essential step to disrupt the recalcitrance of lignocellulosic matrix for enzymatic saccharification and bioethanol production. This paper established an ATSE (alkaline twin-screw extrusion pretreatment) process using a specially designed twin-screw extruder in the presence of alkaline solution to improve the enzymatic hydrolysis efficiency of corn stover for the production of fermentable sugars. Results The ATSE pretreatment was conducted with a biomass/liquid ratio of 1/2 (w/w) at a temperature of 99°C without heating equipment. The results indicated that ATSE pretreatment is effective in improving the enzymatic digestibility of corn stover. Sodium hydroxide loading is more influential factor affecting both sugar yield and lignin degradation than heat preservation time. After ATSE pretreatment under the proper conditions (NaOH loading of 0.06 g/g biomass during ATSE and 1 hour heat preservation after extrusion), 71% lignin removal was achieved and the conversions of glucan and xylan in the pretreated biomass can reach to 83% and 89% respectively via subsequent enzymatic hydrolysis (cellulase loading of 20 FPU/g-biomass and substrate consistency of 2%). About 78% of the original polysaccharides were converted into fermentable sugars. Conclusions With the physicochemical functions in extrusion, the ATSE method can effectively overcome the recalcitrance of lignocellulose for the production of fermentable sugars from corn stover. This process can be considered as a promising pretreatment method due to its relatively low temperature (99°C), high biomass/liquid ratio (1/2) and satisfied total sugar yield (78%), despite further study is needed for process optimization and cost reduction. PMID:23834726

  18. Hip joint injection

    MedlinePlus

    ... injection is a shot of medicine into the hip joint. The medicine helps relieve pain and inflammation. It ... often caused by: Bursitis Arthritis Injury to the hip joint or surrounding area Overuse or strain from running ...