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1

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

PubMed Central

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 (?=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

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

2014-01-01

2

Stability of the noncircular screw pinch  

NASA Astrophysics Data System (ADS)

The magnetohydrodynamic stability of a slightly noncircular screw pinch with arbitrary cross-sectional shape is investigated analytically and numerically using two models: the surface-current model and the force-free model. For the surface-current model the noncircular correction to the instability growth rate is given in analytical form: (1) for the case nq is about or equal to m, where q is the safety factor and m and n are the azimuthal and longitudinal mode numbers of the instability, and (2) for the special case of purely transverse perturbations (n = 0). For the force-free model, the noncircular correction to the marginal stability condition is obtained. This is done analytically for nq is about or equal to m, and for fixed boundary internal modes.

Miller, G.

1980-11-01

3

Biomechanical stability of bioabsorbable screws for fixation of acetabular osteotomies.  

PubMed

The purpose of this study was to compare the biomechanical stability of triple innominate osteotomies fixed with either bioabsorbable or stainless steel screws. Triple innominate osteotomies were performed on composite hemipelves and fixed with either three 4.5-mm bioabsorbable screws or three stainless steel 4.5-mm screws. Two screws were placed from the iliac wing into the acetabular fragment, and 1 screw was placed from below the acetabular fragment into the iliac wing. Eight specimens for each screw type were biomechanically tested in an anatomical position (replicating weight bearing) and in a flexed and abducted position (replicating spica cast positioning). Specimens were cyclically loaded between 10 and 450 N to simulate the hip contact force in this population. Lower screws were then removed, and specimens were tested under identical conditions. Fragment displacement (mm) and construct stiffness (N/mm) were compared with a 2-way analysis of variance (P < 0.05). There were no significant differences between materials for fragment displacement or construct stiffness. Anatomical position showed significantly less displacement than spica position for both materials. Initial displacement in the spica position was significantly less during lower loads for stainless steel fixation. Bioabsorbable screws demonstrate comparable biomechanical stability to stainless steel screws in anatomical and spica positions at physiological loads. Flexion and abduction of the femur adversely affect the stability of the construct for both materials. Bioabsorbable screws behave similarly to steel screws when stabilizing triple innominate osteotomies and would have the advantage of not requiring a second surgery for screw removal. Confirmation of biocompatibility should be completed before widespread clinical application. PMID:17414017

Adamczyk, Mark J; Odell, Tim; Oka, Richard; Mahar, Andrew T; Pring, Maya E; Lalonde, François D; Wenger, Dennis R

2007-01-01

4

Biomimetic design of musculoskeletal humanoid knee joint with patella and screw-home mechanism  

Microsoft Academic Search

We are trying to create a novel musculoskeletal humanoid robot which has a humanlike structure. In this paper, we present a new knee joint which is usually simplified in robotics for high controllability. The knee joint has three human mimetic points, patella, screw-home mechanism and four-linked linkage. Patella is for a longer moment arm. Screw-home mechanism is for locking knee

Yuki Asano; Hironori Mizoguchi; Masahiko Osada; Toyotaka Kozuki; Junichi Urata; Tamon Izawa; Yuto Nakanishi; Kei Okada; Masayuki Inaba

2011-01-01

5

Pedicle Screw-Based Posterior Dynamic Stabilization: Literature Review  

PubMed Central

Posterior dynamic stabilization (PDS) indicates motion preservation devices that are aimed for surgical treatment of activity related mechanical low back pain. A large number of such devices have been introduced during the last 2 decades, without biomechanical design rationale, or clinical evidence of efficacy to address back pain. Implant failure is the commonest complication, which has resulted in withdrawal of some of the PDS devices from the market. In this paper the authors presented the current understanding of clinical instability of lumbar motions segment, proposed a classification, and described the clinical experience of the pedicle screw-based posterior dynamic stabilization devices. PMID:23227349

Sengupta, Dilip K.; Herkowitz, Harry N.

2012-01-01

6

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

SciTech Connect

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.

Trumm, Christoph Gregor, E-mail: christoph.trumm@med.lmu.de [University of Munich, Department of Clinical Radiology (Germany); Rubenbauer, Bianca; Piltz, Stefan [University of Munich, Department of Surgery (Germany); Reiser, Maximilian F.; Hoffmann, Ralf-Thorsten [University of Munich, Department of Clinical Radiology (Germany)

2011-02-15

7

Proprioception and joint stability  

Microsoft Academic Search

In the present paper the current clinical knowledge about proprioception is given for the shoulder, knee, ankle, elbow and the radiocarpal joint. Proprioceptive capabilities are decreased after joint injuries such as ACL or meniscus tears, shoulder dislocation, ankle sprain and in joints with degenerative joint disease. Some surgical procedures seem to restore the proprioceptive abilities; others do not. Elastic knee

J. Jerosch; M. Prymka

1996-01-01

8

Interferometric measurement of dimensional and thermal stability of joints  

NASA Astrophysics Data System (ADS)

In this work we demonstrate how absolute length measurements by interferometry, as used for regular gauge block calibration, can be applied to measure the dimensional drift behavior of connections joined by gluing or screwing and how these joining techniques are influenced by thermal treatment. While it is common to investigate the intrinsic stability of material samples by repeated length measurements, there exist growing demands in precision engineering to characterize the stability of assemblies, i.e. of joined material pieces. In order to enable investigation of joining techniques representative joints were fabricated by a number of methods as wringing, screwing and gluing. By using gauge block shaped samples as joining parts parallelism and flatness could be achieved which is needed for interferometric length measurements. The stability of the joints has been investigated longitudinally and laterally to the connection interface, and also mutual tilting of the parts was detected by analysis of the phase topographies. With the use of sample joints, the behavior of connection elements used in ultrahigh-precision instruments can now be examined on an accuracy level of about one nanometer. Results of approximately one year of observation show that screwed joints do not exhibit a significant change of length or orientation. They also did not show response to temperature variations of +/-10°C, which is different for adhesive joints where dimensional changes of up to 100 nm were observed.

Lorenz, Hagen; Schödel, René

2014-08-01

9

Factors associated with the stability of titanium screws placed in the posterior region for orthodontic anchorage  

Microsoft Academic Search

Recently, implant anchors such as titanium screws have been used for absolute anchorage during edgewise treatment. However, there have been few human studies reporting on the stability of implant anchors placed in the posterior region. The purpose of this study was to examine the success rates and to find the factors associated with the stability of titanium screws placed into

Shouichi Miyawaki; Isao Koyama; Masahide Inoue; Katsuaki Mishima; Toshio Sugahara; Teruko Takano-Yamamoto

2003-01-01

10

Comparison of Superior Level Facet Joint Violations During Open and Percutaneous Pedicle Screw Placement  

PubMed Central

Background Superior-level facet joint violation by pedicle screws may result in increased stress to the level above the instrumentation and may contribute to adjacent segment disease (ASD). Previous studies have evaluated facet joint violations in open or percutaneous screw cases, but there are no reports describing a direct institutional comparison. Objective To compare the incidence of superior-level facet violation for open versus percutaneous pedicle screws, and evaluate patient and surgical factors that impact this outcome. Methods We reviewed 279 consecutive patients who underwent an index instrumented lumbar fusion from 2007 to 2011 for degenerative spine disease with stenosis with or without spondylolisthesis. We used a CT grading system which represents progressively increasing grades of facet joint violation. Patient and surgical factors were evaluated to determine their impact on facet violation. Results Our cohort consisted of 126 open and 153 percutaneous cases. Percutaneous procedures had a higher overall violation grade (p=0.018) and greater incidence of high-grade violations (p=0.0059) compared to open procedures. Bivariate analysis showed significantly greater violations in percutaneous cases for age<65, obesity, pedicle screws at L4, and 1- and 2-level surgeries. Multivariate analysis showed the percutaneous approach and depth of the spine to be independent risk factors for high-grade violations. Conclusion This study demonstrates greater facet violations for percutaneously placed pedicle screws compared to open. PMID:22843132

Babu, Ranjith; Park, Jong G.; Mehta, Ankit I.; Shan, Tony; Grossi, Peter M.; Brown, Christopher R.; Richardson, William J.; Isaacs, Robert E.; Bagley, Carlos A.; Kuchibhatla, Maragatha; Gottfried, Oren N.

2012-01-01

11

[The effect of an angle-stable plate-screw connection and various screw diameters on the stability of plate osteosynthesis. An FE model study].  

PubMed

In a finite element model of a human femur with an attached stainless steel six-hole plate exposed to a load equivalent to that set up by standing on one leg, pressures on the face of the screw holes, bending stresses in the screws, and axial bone stresses in the mid-plate transverse section were determined. The calculations were performed for minor thread diameters of 3 mm, 5 mm and 8 mm. Further calculations were done assuming a fixator-like rigid screw-plate connection. As a model of a fracture a medial bone defect was chosen. The results show a definitive influence of the screw diameter and the screw-plate connection on the load distribution in the system. Increasing screw diameter makes for lower bone stresses combined with increased bending stability, a larger part of the load being carried by the plate. The rigid screw-plate connection (plate fixator) causes less bone stresses, but high bending stresses are set up the points of screw-plate fixation. Maximal stresses for screw and bone are found at the end of the plate, caused by the large difference in the E-module between the steel plate and the bone. End-plate bone and screws are loaded in excess of their material limits when 3 mm core diameters are used, and sometimes when 5 mm core diameters are used, under the assumed conditions. When a medial bone defect reducing the bone cross-sectional area by 44% is present, the loads on the inner screws increase by a factor of 3 and the loads of the distant screws, by a factor of only 1.3. The maximal pressure in the bone cross section increases 4-fold. PMID:2281325

Seide, K; Zierold, W; Wolter, D; Kortmann, H R

1990-12-01

12

Joint stabilizing projects in defense  

SciTech Connect

Joint defensive projects could increase stability and decrease the alert rates of strategic forces. Areas include the defense of the US, Commonwealth of Independent States (CIS), and their allies against third world threats; protection against each other`s accidental or unauthorized launches; and defense against intentional attacks. The most promising area appears to be defining interfaces for the handover of satellite warning and trajectory information, which applies to most phases of theater defense and mutual protection. 19 refs.

Canavan, G.H.; Browne, J.C.; Joseph, R.J.

1992-06-01

13

Joint stabilizing projects in defense  

SciTech Connect

Joint defensive projects could increase stability and decrease the alert rates of strategic forces. Areas include the defense of the US, Commonwealth of Independent States (CIS), and their allies against third world threats; protection against each other's accidental or unauthorized launches; and defense against intentional attacks. The most promising area appears to be defining interfaces for the handover of satellite warning and trajectory information, which applies to most phases of theater defense and mutual protection. 19 refs.

Canavan, G.H.; Browne, J.C.; Joseph, R.J.

1992-06-01

14

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

PubMed

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

Manfré, Luigi

2014-10-31

15

Comparison of in-vitro motion and stability between techniques for index metacarpophalangeal joint radial collateral ligament reconstruction  

PubMed Central

Purpose To evaluate a technique using interference screws to reconstruct the radial collateral ligament (RCL) of the index finger metacarpophalangeal (MP) joint. We hypothesized that this technique would provide equivalent stability and flexion as a 4-tunnel reconstruction. Methods The RCL was isolated in 17 cadaveric index fingers. A cyclic load was applied to the intact RCL across the MP joint to assess flexion, ulnar deviation at neutral (UD@0), and ulnar deviation at 90° of MP joint flexion (UD@90). The RCL was excised from its bony origin and insertion. Each reconstruction (4-tunnel and interference screw) was performed sequentially on each specimen in randomized order. Testing was repeated after each reconstruction. Differences from the intact state were compared between the techniques using paired t-tests for all joint positions (flexion/UD@0/UD@90). Results There was no statistically significant difference in UD@0 or UD@90 between the intact state and after interference screw reconstruction. Compared to the intact state, there was significantly less UD@0 and significantly more UD@90 after 4-tunnel reconstruction. There was no statistically significant difference between techniques when comparing change in -UD@0 or change in UD@90. Change in flexion was statistically significantly different, indicating that the interference screw technique better replicated intact MP joint flexion compared to the 4-tunnel technique. Discussion Interference screw reconstruction of the index RCL provided stability comparable to 4-tunnel reconstruction but is less technically challenging. These results substantiate our clinical experience that interference screw technique provides an optimal combination of stability and flexion at the index MP joint. Clinical Relevance Using an interference screw to reconstruct the index RCL is less challenging and provides stability and range of motion that closely resembles the native MP joint. PMID:23747165

Dy, Christopher J.; Tucker, Scott M.; Carlson, Michelle Gerwin

2013-01-01

16

Stabilization of the sacroiliac joint.  

PubMed

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

Shaffrey, Christopher I; Smith, Justin S

2013-07-01

17

Biomechanical study of the influence of stability for the pedicle screws fixation by injured vertebral screw when the pedicle cortex perforation.  

PubMed

Objective To explore the impact of pedicle cortex perforation on the stability of internal fixation of the vertebral body fracture,and to compare the stability of the vertebrae with pedicle cortex perforation after the injured vertebra transpedicular screw fixation by different ways. Methods A total of 36 fresh thoracic and lumbarvertebrae samples of adult sheep (T13-L1) were equally divided into four groups (A,B,C and D) by using the random number table method. The vertebral compression fracture was performed in the L1 vertebral body of the four groups using the Chiba's method. Four pedicle screws were fixed on the upper and lower injured vertebrae of four groups. In addition,the group C was fixed into a pedicle screw through the injured vertebrae;D group was set two pedicle screws through the injured vertebrae. Then the samples of group B,C,and D were removed a quarter of either side of lateral T14 thoracic pedicle,which was considered as the pedicle cortex perforation model. Four groups were performed fatigue test of 10 000 times by(300±105)N load. The drawing force of the screw and the stability of injured thoracolumbar vertebrae were measured and the differences in every group were compared. Results The axial compressive stiffness and maximum drawing force of screws in the other three groups were significantly higher than those in group B (all P=0.000). The maximum range of motion in four directions of group B were significantly larger than those of the other three groups (all P=0.000). The stiffness and the drawing force in groups C and D were significantly larger than those in the group A (all P=0.000),and the maximum range of motion in four directions of the two groups were lower than that of group A (P=0.002,P=0.005). Every testing indicator in group C had no significant difference when compared with group D (P>0.05). Conclusions The pedicle cortex perforation seriously affects the stability of the fractured vertebral body. The injured vertebra transpedicular screw can increase the stability of internal fixation. PMID:25176211

Shi, Yan; Feng, Su; Zhi-Min, Zhang

2014-08-31

18

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

Code of Federal Regulations, 2011 CFR

...welded joint with complete penetration at the weld root except that for design temperatures colder than ?10 °C (14 °F) the butt weld must be double welded or must be welded...gauge (142 psig) must be removed after the weld is completed; (2) A consumable...

2011-10-01

19

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

Code of Federal Regulations, 2012 CFR

...welded joint with complete penetration at the weld root except that for design temperatures colder than ?10 °C (14 °F) the butt weld must be double welded or must be welded...gauge (142 psig) must be removed after the weld is completed; (2) A consumable...

2012-10-01

20

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

Code of Federal Regulations, 2010 CFR

...welded joint with complete penetration at the weld root except that for design temperatures colder than ?10 °C (14 °F) the butt weld must be double welded or must be welded...gauge (142 psig) must be removed after the weld is completed; (2) A consumable...

2010-10-01

21

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

Code of Federal Regulations, 2013 CFR

...welded joint with complete penetration at the weld root except that for design temperatures colder than ?10 °C (14 °F) the butt weld must be double welded or must be welded...gauge (142 psig) must be removed after the weld is completed; (2) A consumable...

2013-10-01

22

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

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

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

2012-01-01

23

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

PubMed Central

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

2014-01-01

24

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

PubMed Central

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

2011-01-01

25

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

PubMed Central

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

2012-01-01

26

Thermal stability of glued wood joints measured by shear tests  

Microsoft Academic Search

The thermal stability of glued wood joints is an important criterion to determine the suitability of adhesives in the field\\u000a of engineered wood. During their product life, glued wood joints can be exposed to high temperatures in various ways (direct\\u000a exposure to the sun, fire, etc.). Thereby the cohesiveness of the adhesive must not degrade. This raises the question of

Sebastian Clauß; Matus Joscak; Peter Niemz

2011-01-01

27

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

PubMed Central

Purpose Volar plating for distal radius fractures has caused extensor tendon ruptures secondary to dorsal screw prominence. This study was designed to determine the biomechanical impact of placing unicortical distal locking screws and pegs in an extra-articular fracture model. Methods Volar-locking distal radius plates were applied to 30 osteoporotic distal radius models. Radii were divided into 5 groups based on distal locking fixation: bicortical locked screws, 3 lengths of unicortical locked screws (abutting the dorsal cortex [full length], 75% length, and 50% length to dorsal cortex), and unicortical locked pegs. Distal radius osteotomy simulated a dorsally comminuted, extra-articular, fracture. Each constructs stiffness was determined under physiologic loads (axial compression, dorsal bending volar bending) before and after 1000 cycles of axial conditioning and prior to axial loading to failure (2mm of displacement) and subsequent catastrophic failure. Results Cyclic conditioning did not alter constructs stiffness. Stiffness to volar bending and dorsal bending forces were similar between groups. Final stiffness(N/mm) under axial load was statistically equivalent for all groups: bicortical screws(230), full-length unicortical screws(227), 75% length unicortical screws(226), 50% length unicortical screws(187), unicortical pegs(226). Force(N) at 2 mm displacement was significantly less for 50% length unicortical screws(311) compared to bicortical screws(460), full-length unicortical screws(464), 75% length unicortical screws(400), and unicortical pegs(356). Force(N) to catastrophic fracture was statistically equivalent between groups but mean values for pegs(749) and 50% length unicortical(702) screws were 16-21% less than means for bicortical(892), full-length unicortical(860), and 75% length(894) unicortical constructs. Discussion Locked unicortical distal screws of at least 75% length produce construct stiffness similar to bicortical fixation. Unicortical distal fixation for extra-articular distal radius fractures should be entertained to avoid extensor tendon injury since it does not appear to compromise initial fixation. Clinical Relevance Biomechanical comparison of distal fixation techniques during volar locked plating for distal radius fracture. PMID:22305729

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

2013-01-01

28

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

Microsoft Academic Search

Internal fixation is the established dorsal standard procedure for the treatment of thoracolumbar fractures. The main problem\\u000a of the procedure is the false positioning of the pedicle screws. The exact determination of pedicle screws has up to now only\\u000a been possible through postoperative computed tomography. This study was intended to clarify the diagnostic value of intraoperative\\u000a 3D scans after pedicle

Markus Beck; Thomas Mittlmeier; Philip Gierer; Christoph Harms; Georg Gradl

2009-01-01

29

Dynamic Lumbar Pedicle Screw-Rod Stabilization: Two-Year Follow-Up and Comparison with Fusion  

PubMed Central

Background: A lumbar pedicular dynamic stabilization system (LPDSS) is an alternative to fusion for treatment of degenerative disc disease (DDD). In this study, clinical and radiological results of one LPDSS (Saphinaz, Medikon AS, Turkey) were compared with results of rigid fixation after two-year follow-up. Methods: All patients had anteroposterior and lateral standing x-rays of the lumbar spine preoperatively and at 3 months, 12 months and 24 months after surgery. Lordosis of the lumbar spine, segmental lordosis and ratio of the height of the intervertebral disc spaces (IVS) measured preoperatively and at 3 months, 12 months and 24 months after surgery. All patients underwent MRI and/or CT preoperatively, 3months, 12 months and 24 months postoperatively. The ratio of intervertebral disc space to vertebral body height (IVS) and segmental and lumbar lordosis were evaluated preoperatively and postoperatively. Pain scores were evaluated via Visual Analog Scale (VAS) and Oswestry Disability Index (ODI) preoperatively and postoperatively. Results: In both groups, the VAS and ODI scores decreased significantly from preoperatively to postoperatively. There was no difference in the scores between groups except that a lower VAS and ODI scores were observed after 3 months in the LPDSS group. In both groups, the IVS ratio remained unchanged between preoperative and postoperative conditions. The lumbar and segmental lordotic angles decreased insignificantly to preoperative levels in the months following surgery. Conclusions: Patients with LPDSS had equivalent relief of pain and maintenance of sagittal balance to patients with standard rigid screw-rod fixation. LPDSS appears to be a good alternative to rigid fixation. PMID:20448815

Ozer, Ali Fahir; Crawford, Neil R; Sasani, Mehdi; Oktenoglu, Tunc; Bozkus, Hakan; Kaner, Tuncay; Aydin, Sabri

2010-01-01

30

Instrumented hip joint replacements, femoral replacements and femoral fracture stabilizers.  

PubMed

This paper reviews instrumented hip joint replacements, instrumented femoral replacements and instrumented femoral fracture stabilizers. Examination of the evolution of such implants was carried out, including the detailed analysis of 16 architectures, designed by 8 research teams and implanted in 32 patients. Their power supply, measurement, communication, processing and actuation systems were reviewed, as were the tests carried out to evaluate their performance and safety. These instrumented implants were only designed to measure biomechanical and thermodynamic quantities in vivo, in order to use such data to conduct research projects and optimize rehabilitation processes. The most promising trend is to minimize aseptic loosening and/or infection following hip or femoral replacements or femoral stabilization procedures by using therapeutic actuators inside instrumented implants to apply controlled stimuli in the bone-implant interface. PMID:25234709

Soares Dos Santos, Marco P; Ferreira, Jorge Af; Ramos, António; Simões, José Ao; Morais, Raul; Silva, Nuno M; Santos, Paulo M; Reis, Manuel C; Oliveira, Tatiana

2014-11-01

31

Human-Humanoid Joint Haptic Table Carrying Task with Height Stabilization using Vision  

E-print Network

Human-Humanoid Joint Haptic Table Carrying Task with Height Stabilization using Vision Don Joven, a first step is taken towards using vision in human-humanoid haptic joint actions. Haptic joint actions robot. We then demonstrate all this by an experiment where a human and the HRP-2 humanoid jointly

Paris-Sud XI, Université de

32

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

SciTech Connect

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.

Bernardin, John D [Los Alamos National Laboratory; Flores, Eugene M [Los Alamos National Laboratory

2009-01-01

33

Modified C1 lateral mass screw insertion using a high entry point to avoid postoperative occipital neuralgia.  

PubMed

For the past decade, a screw-rod construct has been used commonly to stabilize the atlantoaxial joint, but the insertion of the screw through the C1 lateral mass (LM) can cause several complications. We evaluated whether using a higher screw entry point for C1 lateral mass (LM) fixation than in the standard procedure could prevent screw-induced occipital neuralgia. We enrolled 12 consecutive patients who underwent bilateral C1 LM fixation, with the modified screw insertion point at the junction of the C1 posterior arch and the midpoint of the posterior inferior portion of the C1 LM. We measured postoperative clinical and radiological parameters and recorded intraoperative complications, postoperative neurological deficits and the occurrence of occipital neuralgia. Postoperative plain radiographs were used to check for malpositioning of the screw or failure of the construct. Four patients underwent atlantoaxial stabilization for a transverse ligament injury or a C1 or C2 fracture, six patients for os odontoideum, and two patients for C2 metastasis. No patient experienced vertebral artery injury or cerebrospinal fluid leak, and all had minimal blood loss. No patient suffered significant occipital neuralgia, although one patient developed mild, transient unilateral neuralgia. There was also no radiographic evidence of construct failure. Twenty screws were positioned correctly through the intended entry points, but three screws were placed inferiorly (that is, below the arch), and one screw was inserted too medially. When performing C1-C2 fixation using the standard (Harms) construct, surgeons should be aware of the possible development of occipital neuralgia. A higher entry point may prevent this complication; therefore, we recommend that the screw should be inserted into the arch of C1 if it can be accommodated. PMID:23117140

Lee, Sun-Ho; Kim, Eun-Sang; Eoh, Whan

2013-01-01

34

A Novel Pedicle Screw with Mobile Connection: A Pilot Study  

PubMed Central

To prevent adjacent disc problems after spinal fusion, a pedicle screw with a mobile junction between the head and threaded shaft was newly developed. The threaded shaft of the screw has 10 degrees mobility in all directions, but its structure is to prevent abnormal translation and tilting. This screw was evaluated as follows: (1) endurance test: 106 times rotational stress was applied; (2) biological reactions: novel screws with a mobile head and conventional screws with a fixed head were inserted into the bilateral pedicles of the L3, L4, and L5 in two mini pigs with combination. Eight months after surgery, vertebral units with the screw rod constructs were collected. After CT scan, the soft and bony tissues around the screws were examined grossly and histologically. As a result, none of the screws broke during the endurance test stressing. The mean amount of abrasion wear was 0.0338?g. In the resected mini pig section, though zygapophyseal joints between fixed-head screws showed bony union, the amount of callus in the zygapophyseal joints connected with mobile-head screws was small, and joint space was confirmed by CT. No metalloses were noted around any of the screws. Novel screws were suggested to be highly durable and histologically safe. PMID:24724103

Oshima, Masashi; Ajiro, Yasumitsu; Uei, Hiroshi

2014-01-01

35

Biomechanical Analysis of Differing Pedicle Screw Insertion Angles  

PubMed Central

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 0.398±0.38 mm, and 0.689±0.96 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

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

2007-01-01

36

Experimental study of walking motion stabilization for biped robot with flexible ankle joints  

Microsoft Academic Search

This paper describes an approach of motion stabilization for biped robots with flexible ankle joints. The flexible joints cause the resonant oscillation under conventional control. In our approach, the deviated center of gravity (COG) due to the ankle's deflections is measured in real-time by laser distance sensor mounted on the hip. Assuming the two mass model at COG, the equivalent

Naoki Oda; Masanori Ito

2009-01-01

37

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

PubMed

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

Hagert, Elisabet; Hagert, Carl-Göran

2010-11-01

38

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

Microsoft Academic Search

We currently know little about how animals achieve dynamic stability when running over uneven and unpredictable terrain, often characteristic of their natural environment. Here we investigate how limb and joint mechanics of an avian biped, the helmeted guinea fowl Numida meleagris, respond to an unexpected drop in terrain during running. In particular, we address how joint mechanics are coordinated to

A. Biewener; M. Daley

2007-01-01

39

The effects of joint and link flexibilities on the dynamic stability of force-controlled manipulators  

Microsoft Academic Search

The effects of joint and link flexibilities on the dynamic stability of two-link force-controlled manipulators are investigated. The complaint equations of motion involving joint and link flexibilities are presented. Three force control methods, which include the stiffness method, the damping method, and the hybrid method, are considered for the analysis. The linearized equations of motion about the equilibrium positions are

Bing C. Chiou; MO Shahinpoor

1989-01-01

40

Comparison of Cotrel-Dubousset pedicle screws and hooks in the treatment of idiopathic scoliosis  

Microsoft Academic Search

Eighty-two patients with idiopathic scoliosis were treated by Cotrel-Dubousset instrumentation between 1987 and 1991. Twenty were treated with hooks only, 47 with screws and hooks, and 15 with screws only. The methods were compared and the findings showed that screw fixation can be used in the thoracic spine without neurological complications. The screws provided immediate stability with rigid fixation, together

S. I. Suk; C. K. Lee; H. J. Min; K. H. Cho; J. H. Oh

1994-01-01

41

Internal Reduction Established by Occiput-C2 Pedicle Polyaxial Screw Stabilization in Pediatric Atlantoaxial Rotatory Fixation  

Microsoft Academic Search

Atlantoaxial rotatory fixation is an uncommon disorder of childhood, which can be treated conservatively whendiagnosed early. Although spontaneous correction occasionally occurs, most of the patients usually benefit from collar or traction therapies. If there is no intervention or if all external therapeutic modalities fail, the deformity may become chronic and irreducible. In such rare cases, surgical correction and stabilization are

Deniz Belen; Serkan Simsek; Kazim Yigitkanli; Murad Bavbek

2006-01-01

42

Theories of Cartel Stability and the Joint Executive Committee  

Microsoft Academic Search

This article reexamines the experience of the Joint Executive Committee, an 1880s railroad cartel, to assess the applicability of the Green and Porter (1984) and Rotemberg and Saloner (1986) theories of price wars. After discussing necessary modifications to the theories, I estimate a number of dynamic models to explore the causes of price wars, the cyclical nature of pricing, and

Glenn Ellison

1994-01-01

43

Simultaneous anterior and posterior screw fixations confined to the axis for stabilization of a 3-part fracture of the axis (odontoid, dens, and hangman fractures): report of 2 cases.  

PubMed

Fractures of the axis are considered to be one of the most common injuries to the cervical spine, accounting for more than 20% of all cervical spine fractures. Multiple fractures of the axis are much rarer, accounting for 1% of all cervical fractures. Management of such complex fractures is still challenging, and there is no strong consensus for the treatment. The authors describe the cases of 2 patients who presented with 3-part fractures of the axis consisting of an odontoid Type II fracture and a Levine-Edwards Type IA fracture, which were treated with concurrent insertion of an anterior odontoid screw and bilateral posterior pedicle screws. The cases presented were characterized by 1) a Type II odontoid fracture; 2) a Type IA traumatic spondylolisthesis with no or a little translation and angulation of C-2 on C-3 in a ring fracture of the axis; and 3) no disorders at the C2-3 disc on MR images. Therefore, the authors performed surgery confined to the axis by concurrently inserting an anterior odontoid screw and posterior bilateral pedicle screws without arthrodesis of C2-3. This was followed with cervical soft collar fixation for only 1-2 weeks. The outcomes were favorable, including good osteosynthesis, high primary stability, early patient mobilization, and preserved range of motion of the cervical spine at C2-3 as well as at C1-2. PMID:24409982

Shinbo, Jun; Sameda, Hiroaki; Ikenoue, Sumio; Takase, Kan; Yamaguchi, Takeshi; Hashimoto, Eiko; Enomoto, Takahiro; Kanazuka, Aya; Mimura, Masaya

2014-03-01

44

Surgical screw segmentation for mobile C-arm CT devices  

NASA Astrophysics Data System (ADS)

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.

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

2014-03-01

45

Fatigue Effects on Knee Joint Stability During Two Jump Tasks in Women  

PubMed Central

Dynamic knee joint stability may be affected by the onset of metabolic fatigue during sports participation that could increase the risk for knee injury. The purpose of this investigation was to determine the effects of metabolic fatigue on knee muscle activation, peak knee joint angles, and peak knee internal moments in young women during 2 jumping tasks. Fifteen women (mean age: 24.6 ± 2.6 years) participated in one nonfatigued session and one fatigued session. During both sessions, peak knee landing flexion and valgus joint angles, peak knee extension and varus/valgus internal moments, electromyographic (EMG) muscle activity of the quadriceps and hamstrings, and quadriceps/hamstring EMG cocontraction ratio were measured. The tasks consisted of a single-legged drop jump from a 40-cm box and a 20-cm, up-down, repeated hop task. The fatigued session included a Wingate anaerobic protocol followed by performance of the 2 tasks. Although participants exhibited greater knee injury–predisposing factors during the fatigued session, such as lesser knee flexion joint angles, greater knee valgus joint angles, and greater varus/valgus internal joint moments for both tasks, only knee flexion during the up-down task was statistically significant (p = 0.028). Metabolic fatigue may perhaps predispose young women to knee injuries by impairing dynamic knee joint stability. Training strength-endurance components and the ability to maintain control of body movements in either rested or fatigued situations might help reduce injuries in young women athletes. PMID:20300024

Ortiz, Alexis; Olson, Sharon L.; Etnyre, Bruce; Trudelle-Jackson, Elaine E.; Bartlett, William; Venegas-Rios, Heidi L.

2010-01-01

46

Determinants of Stability in International Joint Ventures: Evidence from a Developing Country Context  

Microsoft Academic Search

Though the number of international joint ventures (IJVs) from developing countries has grown considerably, little has been reported on their operations and performance. The extant literature is based largely on IJVs from developed countries. To help fill this knowledge gap, this paper examines the determinants of stability from a study of 59 IJVs from developing and developed countries operating in

A. B. Sim; M. Yunus Ali

2000-01-01

47

Stability and oscillations in a slow-fast flexible joint system with transformation delay  

NASA Astrophysics Data System (ADS)

Flexible joints are usually used to transfer velocities in robot systems and may lead to delays in motion transformation due to joint flexibility. In this paper, a link-rotor structure connected by a flexible joint or shaft is firstly modeled to be a slow-fast delayed system when moment of inertia of the lightweight link is far less than that of the heavy rotor. To analyze the stability and oscillations of the slow-fast system, the geometric singular perturbation method is extended, with both slow and fast manifolds expressed analytically. The stability of the slow manifold is investigated and critical boundaries are obtained to divide the stable and the unstable regions. To study effects of the transformation delay on the stability and oscillations of the link, two quantitatively different driving forces derived from the negative feedback of the link are considered. The results show that one of these two typical driving forces may drive the link to exhibit a stable state and the other kind of driving force may induce a relaxation oscillation for a very small delay. However, the link loses stability and undergoes regular periodic and bursting oscillation when the transformation delay is large. Basically, a very small delay does not affect the stability of the slow manifold but a large delay affects substantially.

Jiang, Shan-Ying; Xu, Jian; Yan, Yao

2014-08-01

48

Stability and oscillations in a slow-fast flexible joint system with transformation delay  

NASA Astrophysics Data System (ADS)

Flexible joints are usually used to transfer velocities in robot systems and may lead to delays in motion transformation due to joint flexibility. In this paper, a link-rotor structure connected by a flexible joint or shaft is firstly modeled to be a slow-fast delayed system when moment of inertia of the lightweight link is far less than that of the heavy rotor. To analyze the stability and oscillations of the slow-fast system, the geometric singular perturbation method is extended, with both slow and fast manifolds expressed analytically. The stability of the slow manifold is investigated and critical boundaries are obtained to divide the stable and the unstable regions. To study effects of the transformation delay on the stability and oscillations of the link, two quantitatively different driving forces derived from the negative feedback of the link are considered. The results show that one of these two typical driving forces may drive the link to exhibit a stable state and the other kind of driving force may induce a relaxation oscillation for a very small delay. However, the link loses stability and undergoes regular periodic and bursting oscillation when the transformation delay is large. Basically, a very small delay does not affect the stability of the slow manifold but a large delay affects substantially.

Jiang, Shan-Ying; Xu, Jian; Yan, Yao

2014-10-01

49

Multistrand titanium cable for the coracoclavicular stabilization of acute acromioclavicular joint dislocation.  

PubMed

The aim of this retrospective study was to evaluate the outcome of the surgical treatment of acute complete acromioclavicular (AC) joint dislocation with multistrand titanium cable for coracoclavicular (CC) stabilization. Forty-two patients with acute complete AC joint dislocation, Rockwood III, IV, V, were treated with CC stabilization using multistrand titanium cable. Thirty-nine patients could be evaluated after a mean follow-up period of 42 months (range, 34-60). The mean VAS score improved from 5.6 +/- 1.5 to 0.4 +/- 1.2 (p < 0.05). The mean Constant score from 64.8 +/- 8.9 preoperatively to 95.3 +/- 9.3 (p < 0.05). Radiographs showed anatomical reduction in 32 out of 39 patients. Cable breakage occurred in 2 patients. CC stabilization with multistrand titanium cables is an effective and safe alternative to other procedures. This procedure provides immediate joint stabilization and allows early mobilization with satisfying functional recovery. PMID:25090789

Ye, Tianwen; Ouyang, Yueping; Chen, Aimin

2014-06-01

50

Hamstring tendon fixation using interference screws: a biomechanical study in calf tibial bone  

Microsoft Academic Search

It has recently been shown that graft fixation close to the ACL insertion site is optimal in order to increase anterior knee stability. Hamstring tendon fixation using interference screws offers this possibility and a round threaded titanium interference screw has been previously developed. The use of a round threaded biodegradable interference screw may be equivalent. In addition, to increase initial

A Weiler; RF Hoffmann; AC Stähelin; HJ Bail; CJ Siepe; NP Südkamp

1998-01-01

51

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

PubMed Central

Summary We currently know little about how animals achieve dynamic stability when running over uneven and unpredictable terrain, often characteristic of their natural environment. Here we investigate how limb and joint mechanics of an avian biped, the helmeted guinea fowl Numida meleagris, respond to an unexpected drop in terrain during running. In particular, we address how joint mechanics are coordinated to achieve whole limb dynamics. Based on muscle–tendon architecture and previous studies of steady and incline locomotion, we hypothesize a proximo-distal gradient in joint neuromechanical control. In this motor control strategy, (1) proximal muscles at the hip and knee joints are controlled primarily in a feedforward manner and exhibit load-insensitive mechanical performance, and (2) distal muscles at the ankle and tarsometatarso-phalangeal (TMP) joints are highly load-sensitive, due to intrinsic mechanical effects and rapid, higher gain proprioceptive feedback. Limb kinematics and kinetics during the unexpected perturbation reveal that limb retraction, controlled largely by the hip, remains similar to level running throughout the perturbed step, despite altered limb loading. Individual joints produce or absorb energy during both level and perturbed running steps, such that the net limb work depends on the balance of energy among the joints. The hip maintains the same mechanical role regardless of limb loading, whereas the ankle and TMP switch between spring-like or damping function depending on limb posture at ground contact. Initial knee angle sets limb posture and alters the balance of work among the joints, although the knee contributes little work itself. This distribution of joint function results in posture-dependent changes in work performance of the limb, which allow guinea fowl to rapidly produce or absorb energy in response to the perturbation. The results support the hypothesis that a proximo-distal gradient exists in limb neuromuscular performance and motor control. This control strategy allows limb cycling to remain constant, whereas limb posture, loading and energy performance are interdependent. We propose that this control strategy provides simple, rapid mechanisms for managing energy and controlling velocity when running over rough terrain. PMID:17234607

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

2008-01-01

52

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

SciTech Connect

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.

L. KWEI; B. SMITH; ET AL

2001-02-01

53

Cannulated screw with solid core insert: stronger than cannulated screws.  

PubMed

We conducted a study to determine if there is a significant difference in ultimate load, yield strength, and fatigue strength between solid core screws and cannulated screws and if a solid core insert placed inside a cannulated screw would have biomechanical effects similar to those of a solid core screw. Five screw designs were tested: Synthes 4.5-mm solid core and 4.5-mm cannulated and our prototype 4.0-mm solid core, 4.0-mm cannulated, and 4.0-mm cannulated with solid core insert. Biomechanical testing with 3-point bending was used to determine ultimate load, yield strength, and cycles to failure for 6 screws of each design. Ultimate load, yield strength, and cycles to failure were significantly (P < .05) lower in the Synthes 4.5-mm cannulated screws than in the Synthes solid core screws and significantly lower in the prototype cannulated screws than in the prototype solid core screws (P < .05) and prototype cannulated screws with solid core inserts (P < .05). There was no significant difference (P > .05) in ultimate load, yield strength, or cycles to failure between the prototype cannulated screws with solid core inserts and the prototype solid core screws. PMID:25251531

Dundon, John M; Gould, Gregory C; Herbenick, Michael A; Hamilton, J Adam

2014-09-01

54

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

PubMed Central

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

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

2014-01-01

55

Helical screw viscometer  

DOEpatents

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.

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

1983-06-30

56

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

PubMed Central

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

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

2013-01-01

57

Blocks and Screws  

NSDL National Science Digital Library

In this lesson, each student is given a block of wood and a screw (or nail), and is asked to put the screw into the block, without any tool (like a screwdriver or hammer). Their efforts, with varying success, lead to a discussion of contrivances, using various items and strategies as make-do (contrived) tools for which they were not intended, and an exploration of many examples of contrivances or adaptive compromises and other imperfections in the living world, especially in humans. This situation may be better explained by evolution rather than the result of intelligent design.

Patterson, Tim

58

Effects of muscular activation patterns on the ankle joint stabilization: An investigation under different Degrees of Freedom  

Microsoft Academic Search

Altered biomechanical demands of a stabilization task lead to specific changes in coordination patterns among the involved muscles. The objective of this work was to investigate the effects of increased Degrees of Freedom (DoF) of an external object on the stabilization process of the ankle joint in a voluntary force production task. Four muscles (vastus medialis, VM; tibialis anterior, TA;

Kati Wuebbenhorst; Volker Zschorlich

2011-01-01

59

Stochastic stability analysis for joint process driven and networked hybrid systems  

NASA Astrophysics Data System (ADS)

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.

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

2014-05-01

60

Fixation of mandibular fractures with biodegradable plates and screws  

Microsoft Academic Search

Objective. Little data exist regarding the use of biodegradable plates and screws for the internal fixation of human mandibular fractures. The purpose of this study was to evaluate the stability of biodegradable, self-reinforced poly-L-lactide plates and screws for the internal fixation of fractures of the human mandible. Study Design. Twenty-two individuals (14 male, 8 female; average age, 26.3 years) with

Kaan C. Yerit; Georg Enislidis; Christian Schopper; Dritan Turhani; Felix Wanschitz; Arne Wagner; Franz Watzinger; Rolf Ewers

2002-01-01

61

Effects of muscular activation patterns on the ankle joint stabilization: An investigation under different Degrees of Freedom.  

PubMed

Altered biomechanical demands of a stabilization task lead to specific changes in coordination patterns among the involved muscles. The objective of this work was to investigate the effects of increased Degrees of Freedom (DoF) of an external object on the stabilization process of the ankle joint in a voluntary force production task. Four muscles (vastus medialis, VM; tibialis anterior, TA; peroneus longus, PL; gastrocnemius medialis, GM) were recorded using surface electromyography and synchronized to dynamometric data. The subject's task was to exert force against the external object by performing a knee extension under 0, 1 or 3 DoF. Forces were measured using three dimensional force transducers and temporal coordination was assessed using the cross-correlation function (CCF). While the force decreased with increasing DoF the muscles showed a selective gain scaling in order to stabilize the ankle joint. Muscles fulfilling mainly stabilizing functions (TA and PL) tended to increase their activities, while the muscles with motor functions either decreased (GM) or increased (VM). The CCF revealed different intermuscular coordination strategies depending on the environmental condition, showing an advanced phasing in the ankle stabilizing PL in unstable environmental conditions (3 DoF). Nevertheless, the overall sequence of muscle activation was preserved. It is concluded that the process of joint stabilization is controlled in dependency of the status of the external system. The associated neuromuscular system adjustments underline the role of movement coordination in the stabilization process. PMID:21050773

Wuebbenhorst, Kati; Zschorlich, Volker

2011-04-01

62

Stability of the metatarsophalangeal joint of the lesser toes: a cadaveric study.  

PubMed

Dorsal instability of the metatarsophalangeal joint (MTPJ) of the lesser toes is an important cause of forefoot pain. Both conservative and surgical treatment options have been proposed. However, the role of each static stabilizing structure has not been elucidated. We hypothesized that isolated sectioning of the plantar plate (PP) would result in greater dorsal translation compared to isolated sectioning of the medial collateral ligaments (MCL) or lateral (LCL) collateral ligaments, or the extensor hood (EH), and that combined injury to two or more structures would result in greater dorsal translation compared to isolated PP injury. Fifty-four cadaveric lesser toe specimens were randomized into groups for individual and combined sectioning of the PP, EH, and LCL and MCL. A 30 N axial load was applied to each specimen in the plantar-dorsal direction and dorsal translation of the phalanx was measured for each condition. ANOVA was used to compare groups. A 19% change in MTP translation was found from intact after sectioning the PP. No significant difference in translation was seen after individual sectioning of the EH, MCL, or LCL. A significant increase in translation occurred from intact with the following sectioning combinations: MCL + LCL, 37%; EH +?MCL + LCL, 45%; and PP +?MCL + LCL, 63%. Thus, the PP is the main restraint for dorsal MTPJ translation. MCL and LCL have important partial contribution to MTPJ stability. Injury to the PP, individually, or combined injuries to the PP, EH, MCL, or LCL, appear to cause significant instability that may warrant more aggressive treatment. PMID:22696467

Suero, Eduardo M; Meyers, Kathleen N; Bohne, Walter H O

2012-12-01

63

Low noise lead screw positioner  

NASA Technical Reports Server (NTRS)

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.

Perkins, Gerald S. (inventor)

1986-01-01

64

Reconstruction of lateral knee joint stability following resection of proximal fibula tumors  

PubMed Central

Managing tumors of the proximal fibula may require en bloc resection of the fibular head with the attachment site of the lateral collateral ligament (LCL) and biceps femoris tendon. The aim of the present study was to evaluate knee stability and the Musculoskeletal Tumor Society (MSTS) functional score of patients with proximal fibula tumors. Twenty-nine patients with proximal fibula tumors were retrospectively reviewed (18 patients in the reconstruction group and 11 patients in the non-reconstruction group). A comparative analysis was conducted of knee stability (measuring the degree of lateral joint space opening using varus stress radiographs with a 30º knee flexion) and MSTS functional score between the two groups. The mean follow-up period was 42.8±20.9 months (range 24–117) and 40.8±26.0 months (range 24–117) for the reconstruction and the non-reconstruction groups, respectively. Fifteen patients (83.3%) in the reconstruction group had a stable knee, one (5.6%) had grade 1 instability and two (11.1%) had grade 2 instability. Four patients (36.4%) in the non-reconstruction group had a stable knee, three (27.3%) had grade 1 instability, one (9.1%) had grade 2 instability and three (27.3%) had grade 3 instability. Patients who underwent reconstructive surgery exhibited a higher rate of knee stability compared with those in the non-reconstruction group (P<0.05). The MSTS function scores were 93% (range, 93–100%) for the reconstruction group and 87% (range, 60–100%) for the non-reconstruction group (P<0.05). Reconstruction of the LCL and biceps femoris tendon to the lateral tibial metaphysis with a suture anchor was a safe, reliable and simple technique following resection of proximal fibula tumors. PMID:24396415

ZHAO, SHI-CHANG; ZHANG, CHANG-QING; ZHANG, CHUN-LIN

2014-01-01

65

Effects of EMG processing on biomechanical models of muscle joint systems: Sensitivity of trunk muscle moments, spinal forces, and stability  

Microsoft Academic Search

Biomechanical models are in use to estimate parameters such as contact forces and stability at various joints. In one class of these models, surface electromyography (EMG) is used to address the problem of mechanical indeterminacy such that individual muscle activation patterns are accounted for. Unfortunately, because of the stochastical properties of EMG signals, EMG based estimates of muscle force suffer

Didier Staudenmann; Jim R. Potvin; Idsart Kingma; Dick F. Stegeman; Jaap H. van Dieën

2007-01-01

66

A description of the dynamics of manipulators using screw theory  

NASA Astrophysics Data System (ADS)

The paper is concerned with the derivation of Lagrange equations of the second kind for a manipulator consisting of N links each of which is coupled with the preceding link (except for the first link, which is coupled with a fixed base) through a single-degree-of-freedom joint. The joints can be translational or rotational; each joint is treated as a rigid body, and the possibility of allowing for elasticity in the hinges and joints is demonstrated. The kinetic energy is determined using the theory of kinematic screws.

Akselrod, B. V.

1985-04-01

67

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

NASA Astrophysics Data System (ADS)

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

Bulut, Gökhan

2014-08-01

68

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

PubMed Central

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

Dazard, Jean-Eudes; Rao, J. Sunil

2012-01-01

69

Helical screw expander evaluation project  

Microsoft Academic Search

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

R. McKay

1982-01-01

70

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

SciTech Connect

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.

Christianson, M.

1989-04-01

71

Split spline screw  

NASA Technical Reports Server (NTRS)

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.

Vranish, John M. (inventor)

1993-01-01

72

Carbon nanotube Archimedes screws.  

PubMed

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

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

2010-12-28

73

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

PubMed Central

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

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

2014-01-01

74

Evaluation of contributions of orthodontic mini-screw design factors based on FE analysis and the Taguchi method.  

PubMed

This study determines the relative effects of changes in bone/mini-screw osseointegration and mini-screw design factors (length, diameter, thread shape, thread depth, material, head diameter and head exposure length) on the biomechanical response of a single mini-screw insertion. Eighteen CAD and finite element (FE) models corresponding to a Taguchi L(18) array were constructed to perform numerical simulations to simulate mechanical responses of a mini-screw placed in a cylindrical bone. The Taguchi method was employed to determine the significance of each design factor in controlling strain. Simulation results indicated that mini-screw material, screw exposure length and screw diameter were the major factors affecting bone strain, with percentage contributions of 63%, 24% and 7%, respectively. Bone strain decreased obviously when screw material had the high elastic modulus of stainless/titanium alloys, a small exposure length and a large diameter. Other factors had no significant on bone strain. The FE analysis combined with the Taguchi method efficiently identified the relative contributions of several mini-screw design factors, indicating that using a strong stainless/titanium alloys as screw material is advantageous, and increase in mechanical stability can be achieved by reducing the screw exposure length. Simulation results also revealed that mini-screw and bone surface contact can provide sufficient mechanical retention to perform immediately load in clinical treatment. PMID:20466376

Lin, Chun-Li; Yu, Jian-Hong; Liu, Heng-Liang; Lin, Chih-Hao; Lin, Yang-Sung

2010-08-10

75

Sacroiliac screw fixation: A mini review of surgical technique  

PubMed Central

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

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

2014-01-01

76

[The biomechanics of screws, cerclage wire and cerclage cable].  

PubMed

In contrast to fracture fixation, when performing an osteotomy the surgeon is able to plan preoperatively. The resulting fixation and compression of the bone fragments are the most important points. A stable osteosynthesis should prevent dislocation of bone fragments and improve bone healing. Beside plates, cerclages can be used for tension band or diaphysis bone fixation. Moreover, cortical or cancellous screws can be used for osteotomy fixation. This work describes biomechanical principles for fixation after an osteotomy with cerclages and cortical or cancellous screws. It also summarizes the materials and geometries used, as well as their influence on the stability of the osteosynthesis. PMID:23615626

Schröder, C; Woiczinski, M; Utzschneider, S; Kraxenberger, M; Weber, P; Jansson, V

2013-05-01

77

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

PubMed

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

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

2013-07-01

78

The dynamic condylar screw in the management of subtrochanteric fractures: does judicious use of biological fixation enhance overall results?  

Microsoft Academic Search

Subtrochanteric fractures are fraught with certain anatomic, biologic and biomechanical challenges. Evolution of implants\\u000a like the Gamma nail, fixed-angle nail plates, compression hip screws and dynamic hip screws with trochanteric stabilization\\u000a plates underlines a persistent quest for a better implant. We studied the dynamic condylar screw DCS as an implant on a series\\u000a of 30 consecutive patients with subtrochanteric fractures.

Manzoor Ahmed Halwai; Shabir Ahmed Dhar; Mohammed Iqbal Wani; Mohammed Farooq Butt; Bashir Ahmed Mir; Murtaza Fazal Ali; Imtiyaz Hussain Dar

2007-01-01

79

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

PubMed Central

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

2012-01-01

80

An Articulating Tool for Endoscopic Screw Delivery  

E-print Network

This paper describes the development of an articulating endoscopic screw driver that can be used to place screws in osteosynthetic plates during thoracoscopic surgery. The device is small enough to be used with a 12 mm ...

Petrzelka, Joseph Edward

81

The stabilization of a north-seeking platform using a dynamically tuned Hooke's joint gyroscope  

Microsoft Academic Search

The paper shows that the ideally tuned Hooke's joint gyroscope is capable of operating as a gyrocompass. The dynamic response of the compass is examined in detail and its accuracy as a north-seeking device is assessed. It is shown that small amounts of mistuning will result in gross errors. The need for precision tuning is eliminated by supporting the gyroscope

J. S. Burdess; C. H. J. Fox

1980-01-01

82

A Study of Cartel Stability: The Joint Executive Committee, 1880-1886  

Microsoft Academic Search

This article employs weekly time series data on the Joint Executive Committee railroad cartel from 1880 to 1886 to test empirically the proposition that observed prices reflected switches from collusive to noncooperative behavior. An equilibrium model of dynamic oligopoly with asymmetric firms, together with explicit functional form assumptions about costs and demand, determines the estimating equations and stochastic structure of

Robert H. Porter

1983-01-01

83

Bimanual coordination involving homologous and heterologous joint combinations: when lower stability is associated with higher flexibility  

Microsoft Academic Search

Variability in behavior is often put in an unfavorable light as a marker of lack of skill. Here, we provide evidence that increased variability during preferred patterns of coordination is associated with higher flexibility in adopting new patterns. Twelve right-handed subjects performed cyclical bimanual flexion and extension patterns with four homologous and six heterologous joint combinations involving shoulder, elbow, wrist,

Oron Levin; Ellen Suy; Jurgen Huybrechts; Sophie Vangheluwe; Stephan P Swinnen

2004-01-01

84

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

PubMed Central

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

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

2014-01-01

85

[An original technique for stabilizing the metacarpopharyngeal joints of the ulnar hand: "The transosseous capsuloplasty with anterior-posterior drilling"].  

PubMed

In reconstructive surgery of the ulnar clawhand deformity, the metacarpophalangeal joints of the digits and the thumb must be stabilised. The "capsuloplasty with anteroposterior drilling", which is described in this paper is an original technique whose first goal is to make this stabilisation easier and with an effectiveness at least equal to the classic and difficult Zancolli techniques. It consists, after a longitudinal opening of the volar plate, of drilling an anteroposterior hole at the level of the metacarpal neck using a square point awl, a small dorsal incision allowing protection of the extensor tendons. A needle with a non absorbable thread takes the first half of the palmar plate, goes through the hole and is brought out on the dorsal aspect of the hand, then a Halsted forceps is passed keeping close to the metacarpal neck to bring the needle to the palmar side and finally take the second half of the palmar plate. The knots are tied with the metacarpophalangeal joints in 25 degrees flexion. From June 1997 to April 2001, 25 patients suffering from ulnar nerve palsy and ten patients suffering from combined ulnar and median nerve palsy have benefited from this technique to correct the clawhand deformity and Froment's sign. No pre or postoperative complications were reported. With a mean follow-up of 24 months all the metacarpophalangeal joints operated have very good stability and improved strength. PMID:11723778

Belmahi, A M; Gharib, N; Abbassi, A

2001-10-01

86

Biomechanical and histomorphometric analyses of monocortical screws at placement and 6 weeks postinsertion.  

PubMed

Maxillofacial screws are increasingly being used in orthodontics to provide anchorage for tooth movement. The objective of this study was to determine the biomechanical stability as well as the bone tissue response of screws at 6 weeks postinsertion in a canine model. Seven skeletally mature male dogs received 102 screws (2 x 6 mm or 2 x 8 mm) at predetermined sites. Twenty screws became loose or were lost during the 6-week undisturbed healing period. Forty-eight screws were randomized for mechanical testing and 34 for histology. Peak pullout strength was recorded and approximately 80-microm sections were examined for histomorphometric parameters. Statistical analyses were conducted by analysis of variance and Tukey-Kramer method. Mean +/- SE peak pullout strengths for the various sites ranged from 153.5 +/- 37.6 N to 389.3 +/- 32.5 N with no significant (P < .05) differences at immediate placement and 6 weeks postinsertion. Bone contact ranged from 79% to 95%. Histomorphometric analyses indicated higher bone formation rate in the mandible than in the maxilla and a gradient of decreasing turnover with increasing distance from the screw interface. These results provide the clinical orthodontist with an estimate of the holding power of these screws and an understanding of early biological healing response associated with self-drilling screws. PMID:16836174

Huja, S S; Rao, J; Struckhoff, J A; Beck, F M; Litsky, A S

2006-01-01

87

Biomechanical comparison of inside–outside screws, cables, and regular screws, using a sawbone model  

Microsoft Academic Search

Our aim was to conduct a biomechanical comparison of the pull-out strengths of inside–outside (I\\/O) screws, cables, and bone screws to determine whether I\\/O screws provide greater pull-out resistance than cables or bone screws, and their effectiveness with the screw diameter. There is no remarkable biomechanical experimental study comparing the I\\/O technique with conventional spinal techniques. The diameter of the

Yusuf Sukru Caglar; Fuat Torun; Thomas Glenn Pait; William Hogue; Melih Bozkurt; Serdar Özgen

2005-01-01

88

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

Microsoft Academic Search

Chronic ankle instability (CAI) is a frequent sport orthopaedic entity. Although many risk factors have been studied extensively,\\u000a little is known how it is influenced by the osseous joint configuration. Based on lateral X-rays, the radius of the talar\\u000a surface and the tibial coverage of the talus (sector ?) were measured on a DICOM\\/PACS system in 52 patients with CAI

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

2007-01-01

89

Stability of Boolean networks: The joint effects of topology and update rules  

NASA Astrophysics Data System (ADS)

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.

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

2014-08-01

90

Biomechanical evaluation of bending strength of spinal pedicle screws, including cylindrical, conical, dual core and double dual core designs using numerical simulations and mechanical tests.  

PubMed

Pedicle screws are used for treating several types of spinal injuries. Although several commercial versions are presently available, they are mostly either fully cylindrical or fully conical. In this study, the bending strengths of seven types of commercial pedicle screws and a newly designed double dual core screw were evaluated by finite element analyses and biomechanical tests. All the screws had an outer diameter of 7 mm, and the biomechanical test consisted of a cantilever bending test in which a vertical point load was applied using a level arm of 45 mm. The boundary and loading conditions of the biomechanical tests were applied to the model used for the finite element analyses. The results showed that only the conical screws with fixed outer diameter and the new double dual core screw could withstand 1,000,000 cycles of a 50-500 N cyclic load. The new screw, however, exhibited lower stiffness than the conical screw, indicating that it could afford patients more flexible movements. Moreover, the new screw produced a level of stability comparable to that of the conical screw, and it was also significantly stronger than the other screws. The finite element analysis further revealed that the point of maximum tensile stress in the screw model was comparable to the point at which fracture occurred during the fatigue test. PMID:25060212

Amaritsakul, Yongyut; Chao, Ching-Kong; Lin, Jinn

2014-09-01

91

Biomechanical evaluation of the impact of various facet joint lesions on the primary stability of anterior plate fixation in cervical dislocation injuries: a cadaver study.  

PubMed

Object Injuries of the subaxial cervical spine including facet joints and posterior ligaments are common. Potential surgical treatments consist of anterior, posterior, or anterior-posterior fixation. Because each approach has its advantages and disadvantages, the best treatment is debated. This biomechanical cadaver study compared the effect of different facet joint injuries on primary stability following anterior plate fixation. Methods Fractures and plate fixation were performed on 15 fresh-frozen intact cervical spines (C3-T1). To simulate a translation-rotation injury in all groups, complete ligament rupture and facet dislocation were simulated by dissecting the entire posterior and anterior ligament complex between C-4 and C-5. In the first group, the facet joints were left intact. In the second group, one facet joint between C-4 and C-5 was removed and the other side was left intact. In the third group, both facet joints between C-4 and C-5 were removed. The authors next performed single-level anterior discectomy and interbody grafting using bone material from the respective thoracic vertebral bodies. An anterior cervical locking plate was used for fixation. Continuous loading was performed using a servohydraulic test bench at 2 N/sec. The mean load failure was measured when the implant failed. Results In the group in which both facet joints were intact, the mean load failure was 174.6 ± 46.93 N. The mean load failure in the second group where only one facet joint was removed was 127.8 ± 22.83 N. In the group in which both facet joints were removed, the mean load failure was 73.42 ± 32.51 N. There was a significant difference between the first group (both facet joints intact) and the third group (both facet joints removed) (p < 0.05, Kruskal-Wallis test). Conclusions In this cadaver study, primary stability of anterior plate fixation for dislocation injuries of the subaxial cervical spine was dependent on the presence of the facet joints. If the bone in one or both facet joints is damaged in the clinical setting, anterior plate fixation in combination with bone grafting might not provide sufficient stabilization; additional posterior stabilization may be needed. PMID:25014498

Oberkircher, Ludwig; Born, Sebastian; Struewer, Johannes; Bliemel, Christopher; Buecking, Benjamin; Wack, Christina; Bergmann, Martin; Ruchholtz, Steffen; Krüger, Antonio

2014-10-01

92

Arthroscopic Treatment of Slipped Capital Femoral Epiphysis Screw Impingement and Concomitant Hip Pathology  

PubMed Central

Impingement caused by screws used for stabilization of slipped capital femoral epiphysis can be treated arthroscopically. Although troublesome screws have traditionally been removed by open techniques, arthroscopic removal can successfully be achieved. In addition to affording the patient the benefits of minimally invasive surgery, surgeons also have the ability to arthroscopically address any concomitant hip pathology responsible for pain, including femoroacetabular impingement and labral tears. PMID:25264513

Howse, Elizabeth A.; Wooster, Benjamin M.; Mannava, Sandeep; Perry, Brad; Stubbs, Allston J.

2014-01-01

93

Helical screw expander evaluation project  

NASA Technical Reports Server (NTRS)

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.

Mckay, R.

1982-01-01

94

Helical screw expander evaluation project  

NASA Astrophysics Data System (ADS)

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.

McKay, R.

1982-03-01

95

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

PubMed

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

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

2014-10-01

96

The stabilization of a north-seeking platform using a dynamically tuned Hooke's joint gyroscope  

NASA Astrophysics Data System (ADS)

The paper shows that the ideally tuned Hooke's joint gyroscope is capable of operating as a gyrocompass. The dynamic response of the compass is examined in detail and its accuracy as a north-seeking device is assessed. It is shown that small amounts of mistuning will result in gross errors. The need for precision tuning is eliminated by supporting the gyroscope on a single-degree-of-freedom platform. It is shown that if the platform is driven via feedback of the gyrorotor displacement in azimuth then the response of the combined system is essentially that of the ideal gyroscope. The overall system is insensitive to mistuning errors and will automatically align the gyrospin axis with true north irrespective of any initial offset. The effects of damping, mass unbalance, and platform misalignment are assessed.

Burdess, J. S.; Fox, C. H. J.

1980-03-01

97

Surgical treatment of Rockwood grade-V acromioclavicular joint dislocations  

PubMed Central

Background and purpose Long-term outcome after surgery for grade-V acromioclavicular joint dislocation has not been reported. We performed a retrospective analysis of functional and radiographic outcome 15–22 years after surgery. Patients and methods We examined 50 patients who were treated at our hospital between April 1985 and December 1993. Various methods of stabilization were used: K-wires (n = 36), 4.5-mm screw (n = 12), or biodegradable screw (n = 2). Osteosynthesis material was removed after 6–8 weeks. Mean follow-up time was 18 (15–22) years. Outcomes were assessed with the Constant shoulder (CS) score, Disabilities of the Arm, Shoulder, and Hand (DASH) score, the simple shoulder test (SST), the Copeland shoulder impingement test, the cross-arm test, pain, stability of the AC joint, and complications. From radiographs, we evaluated AC and glenohumeral (GH) arthrosis, osteolysis of the lateral clavicle, and alignment of the clavicle with the acromion. Results Mean values were 90 (75–100) in CS score, 5.1 (0–41) in DASH score, and 11 (2–12) in SST. There was no statistically significant difference in CS score between the injured shoulder and the uninjured shoulder. The AC joint was clinically stable in 42 patients. In 38 patients, the clavicle alignment with the acromion was normal in radiographs. Lateral clavicle osteolysis (10 patients) appeared to be associated with permanent AC joint dislocation. Interpretation Surgery with a temporary fixation for acute grade-V AC joint dislocation leads to successful long-term functional results. Only minor disability occurred in some patients. PMID:23409813

2013-01-01

98

Wet Granulation in a Twin-Screw Extruder: Implications of Screw Design  

E-print Network

as an efficient and flexible technique for continuous high-shear wet granulation. Extruders can readily processWet Granulation in a Twin-Screw Extruder: Implications of Screw Design M.R. THOMPSON, J. SUN MMRI granulation in twin-screw extrusion machinery is an attractive tech- nology for the continuous processing

Thompson, Michael

99

Biomechanical comparison of pedicle screws versus spinous process screws in C2 vertebra  

PubMed Central

Background: Biomechanical studies have shown C2 pedicle screw to be the most robust in insertional torque and pullout strength. However, C2 pedicle screw placement is still technically challenging. Smaller C2 pedicles or medial localization of the vertebral artery may preclude safe C2 pedicle screw placement in some patients. The purpose of this study was to compare the pullout strength of spinous process screws with pedicle screws in the C2. Materials and Methods: Eight fresh human cadaveric cervical spine specimens (C2) were harvested and subsequently frozen to ?20°C. After being thawed to room temperature, each specimen was debrided of remaining soft tissue and labeled. A customs jig as used to clamp each specimen for screw insertion firmly. Screws were inserted into the vertebral body pairs on each side using one of two methods. The pedicle screws were inserted in usual manner as in previous biomechanical studies. The starting point for spinous process screw insertion was located at the junction of the lamina and the spinous process and the direction of the screw was about 0° caudally in the sagittal plane and about 0° medially in the axial plane. Each vertebrae was held in a customs jig, which was attached to material testing machine (Material Testing System Inc., Changchun, China). A coupling device that fit around the head of the screw was used to pull out each screw at a loading rate of 2 mm/min. The uniaxial load to failure was recorded in Newton'st dependent test (for paired samples) was used to test for significance. Results: The mean load to failure was 387 N for the special protection scheme and 465 N for the protection scheme without significant difference (t = ?0.862, P = 0.403). In all but three instances (38%), the spinous process pullout values exceeded the values for the pedicle screws. The working distances for the spinous process screws was little shorter than pedicle screws in each C2 specimen. Conclusion: Spinous process screws provide comparable pullout strength to pedicle screws of the C2. Spinous process screws may provide an alternative to pedicle screws fixation, especially with unusual anatomy or stripped screws.

Liu, Guan-yi; Mao, Lu; Xu, Rong-ming; Ma, Wei-hu

2014-01-01

100

Helical rotary screw expander power system  

Microsoft Academic Search

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

R. A. McKay; R. S. Sprankle

1974-01-01

101

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

PubMed Central

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

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

2014-01-01

102

The biomechanics of guided growth: does screw size, plate size, or screw configuration matter?  

PubMed

Guided growth with the eight-plate is a commonly used technique to correct angular limb deformities in children. However, the optimal combination of plate size, screw size, and screw configuration has not been determined. Using osteotomized femoral sawbones and a rail frame, we developed a growth model to examine the effect of these variables at 6-month, 12-month, and 18-month growth increments. The mean annual coronal plane change was 11.3°. Screw size and plate size were not associated with the rate of angular correction. Screw configuration was important, with parallel screws resulting in optimal correction at all time points compared with divergent screws (P<0.05). PMID:24322536

Schoenleber, Scott J; Iobst, Christopher A; Baitner, Avi; Standard, Shawn C

2014-03-01

103

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

PubMed Central

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

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

2008-01-01

104

Semi-Empirical Screw Compressor Chiller Model  

E-print Network

A screw chiller model which is based on a first principles, semi-empirical analysis that describes the system performance based on observations of the thermodynamic processes is developed. This model is a modified method to empirically derive...

Nelson, I. C.; Culp, C.; Graves, R. D.

105

Additional Drive Circuitry for Piezoelectric Screw Motors  

NASA Technical Reports Server (NTRS)

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.

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

2004-01-01

106

Intramedullary screw fixation of lateral malleolus fractures.  

PubMed

A biomechanical evaluation of intramedullary versus buttress plate and lag screw fixation of lateral malleolus fractures is combined with a clinical evaluation of 44 patients with lateral malleolus fractures who underwent intramedullary screw fixation. The biomechanical study was performed in experimentally produced, Weber B, supination-eversion ankle fractures. The fractures were fixed with one of the two above fixation methods and then placed under a torsional load to failure. Sixteen cadaver ankles were tested as compared with native bone. The intramedullary screw provided 66.5% the resistance of torsion, and the buttress plate and lag screw provided 61.5% the resistance to torsion. There was no statistical difference between these two groups. The 44 fractures treated with an intramedullary screw were reviewed retrospectively. There was one failure of fixation, and one prominent hardware problem. Time to full weightbearing averaged 7.2 weeks. These results suggest that intramedullary screw fixation of noncomminuted lateral malleolus fractures provides stable fixation with good clinical results. This technique has the advantages of providing dynamic intramedullary fixation with limited surgical dissection and no subcutaneous hardware. PMID:7849975

Bankston, A B; Anderson, L D; Nimityongskul, P

1994-11-01

107

The effect on neuromuscular stability, performance, multi-joint coordination and proprioception of barefoot, taping or preventative bracing  

Microsoft Academic Search

ObjectiveThe objective of this study was to assess the effects of taping and preventive bracing on functional balance, jumping performance, multi-joint coordination and proprioception on comparison to barefoot and each other.

Derya Ozer; Gamze Senbursa; Gul Baltaci; Mutlu Hayran

2009-01-01

108

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

PubMed Central

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

Cornelius, Carl-Peter; Ehrenfeld, Michael

2010-01-01

109

Comparison of Pullout Strength between 3.5-mm Fully Threaded, Bicortical Screws and 4.0-mm Partially Threaded, Cancellous Screws in the Fixation of Medial Malleolar Fractures  

Microsoft Academic Search

Displaced medial malleolus fractures are considered unstable and typically require open reduction and internal fixation for anatomic reduction and early joint range of motion. These fractures are usually fixated with either compression lag screws or tension band wiring depending on the fracture pattern, size of the distal fragment, and bone quality. When fracture fixation fails, it is typically in pullout

Jason D. Pollard; Ali Deyhim; Ryan B. Rigby; Nathan Dau; Christy King; Lawrence M. Fallat; Cynthia Bir

2010-01-01

110

Mechanical Stability of the Subtalar Joint After Lateral Ligament Sectioning and Ankle Brace ApplicationA Biomechanical Experimental Study  

Microsoft Academic Search

Background: The roles of each ligament supporting the subtalar joint have not been clarified despite several biomechanical studies. The effects of ankle braces on subtalar instability have not been shown.Hypothesis: The ankle brace has a partial effect on restricting excessive motion of the subtalar joint.Study Design: Controlled laboratory study.Methods: Ten normal fresh-frozen cadaveric specimens were used. The angular motions of

Tomoaki Kamiya; Hideji Kura; Daisuke Suzuki; Eiichi Uchiyama; Mineko Fujimiya; Toshihiko Yamashita

2009-01-01

111

Effect of Screw Length on Bioabsorbable Interference Screw Fixation in a Tibial Bone Tunnel  

Microsoft Academic Search

Initial tibial fixation strength is the weak link after anterior cruciate ligament reconstruction with a quadrupled hamstring tendon graft fixed with bioabsorbable interference screws. The purpose of this study was to determine the biomechanical differences between 28-mm and tapered 35-mm interference screws for tibial fixation of a soft tissue graft in 16 young cadaveric tibias. Failure mode, displacement before failure,

Jeffrey B. Selby; Darren L. Johnson; Peter Hester; David N. M. Caborn

2001-01-01

112

The Turn of the Screw: Optimal Design of an Archimedes Screw  

Microsoft Academic Search

The geometry of an Archimedes screw is governed by certain external parameters (its outer radius, length, and slope) and certain internal parameters (its inner radius, number of blades, and the pitch of the blades). The external parameters are usually determined by the location of the screw and how much water is to be lifted. The internal parameters, however, are free

Chris Rorres

2000-01-01

113

Resorbable screws versus pins for optimal transplant fixation (SPOT) in anterior cruciate ligament replacement with autologous hamstring grafts: rationale and design of a randomized, controlled, patient and investigator blinded trial [ISRCTN17384369  

PubMed Central

Background Ruptures of the anterior cruciate ligament (ACL) are common injuries to the knee joint. Arthroscopic ACL replacement by autologous tendon grafts has established itself as a standard of care. Data from both experimental and observational studies suggest that surgical reconstruction does not fully restore knee stability. Persisting anterior laxity may lead to recurrent episodes of giving-way and cartilage damage. This might at least in part depend on the method of graft fixation in the bony tunnels. Whereas resorbable screws are easy to handle, pins may better preserve graft tension. The objective of this study is to determine whether pinning of ACL grafts reduces residual anterior laxity six months after surgery as compared to screw fixation. Design/ Methods SPOT is a randomised, controlled, patient and investigator blinded trial conducted at a single academic institution. Eligible patients are scheduled to arthroscopic ACL repair with triple-stranded hamstring grafts, conducted by a single, experienced surgeon. Intraoperatively, subjects willing to engage in this study will be randomised to transplant tethering with either resorbable screws or resorbable pins. No other changes apply to locally established treatment protocols. Patients and clinical investigators will remain blinded to the assigned fixation method until the six-month follow-up examination. The primary outcome is the side-to-side (repaired to healthy knee) difference in anterior translation as measured by the KT-1000 arthrometer at a defined load (89 N) six months after surgery. A sample size of 54 patients will yield a power of 80% to detect a difference of 1.0 mm ± standard deviation 1.2 mm at a two-sided alpha of 5% with a t-test for independent samples. Secondary outcomes (generic and disease-specific measures of quality of life, magnetic resonance imaging morphology of transplants and devices) will be handled in an exploratory fashion. Conclusion SPOT aims at showing a reduction in anterior knee laxity after fixing ACL grafts by pins compared to screws. PMID:15723704

Stengel, Dirk; Matthes, Gerrit; Seifert, Julia; Tober, Volker; Mutze, Sven; Rademacher, Grit; Ekkernkamp, Axel; Bauwens, Kai; Wich, Michael; Casper, Dirk

2005-01-01

114

Management of fracture-dislocation of the lower cervical spine with the cervical pedicle screw system  

PubMed Central

INTRODUCTION Usually, cervical pedicle screw fixation has been considered too risky for neurovascular structures. The purpose of this study was to investigate the method and efficacy of the cervical pedicle screw system for fracture-dislocation of the cervical spine because of its rigid fixation. PATIENTS AND METHODS A prospective study was conducted involving 48 patients with cervical spine fracture-dislocation who underwent cervical pedicle screw fixation surgery between January 2003 and January 2007. All patients had various degrees of cord injury, and they were classified according to the American Spinal Cord Injury Association (ASIA) Impairment Scale: 18 cases were grade A, 15 grade B, 10 grade C, and 5 grade D. RESULTS Six months after the operation, all patients had achieved solid bony fusion and stable fixation of the related segments. Thirty patients with incomplete spinal cord injury improved their ASIA Impairment Scale classification by 1 to 2 grades after the operation. Eighteen patients with complete spinal cord injury had no improvement in neural function. However, nerve root symptoms such as pain and numbness were alleviated to some extent. CONCLUSIONS The cervical pedicle screw system is an effective and reliable method for the restoration of cervical stability. Sufficient pre-operative imaging studies of the pedicles and strict screw insertion technique should be emphasised. PMID:20487593

Zhou, Feng; Zou, Jun; Gan, Minfeng; Zhu, Ruofu; Yang, Huilin

2010-01-01

115

Efficacy analysis of pedicle screw internal fixation of fractured vertebrae in the treatment of thoracolumbar fractures  

PubMed Central

The present study aimed to discuss the method and effect of posterior internal fixation of thoracolumbar fractures strengthened by the vertical stress pedicle screw fixation of fractured vertebrae. Patients with single thoracolumbar fractures were examined retrospectively. Fourteen patients (group A) had been treated with vertical stress pedicle screw fixation of a fractured vertebra and sixteen patients (group B) received traditional double-plate fixation, as a control. All patients were diagnosed with fresh fractures with a complete unilateral or bilateral pedicle and no explosion of the inferior half of the vertebral body or inferior endplate. In group A, patients received conventional posterior distraction and lumbar lordosis restoration, as well as pedicle screws in the fractured vertebra in a vertical direction to relieve stress to achieve a local stress balance. All patients were followed up postoperatively for 4–18 months (average, 12.6 months). The vertical stress pedicle screw fixation assisted in the reduction of vertebrae fracture, which reduced the postoperative Cobb’s angle loss. There was a significant difference in the change of Cobb’s angle between the two groups one year after surgery (P<0.01). Conditional application of pedicle screws in a single thoracolumbar fracture enhances the stability of the internal fixation system and is conducive to the correction of kyphosis and maintenance of the corrective effects. PMID:23407593

HUANG, WEIJIE; LUO, TAO

2013-01-01

116

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

NASA Astrophysics Data System (ADS)

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.

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

117

Temperature calculation for extruder screws with internal heat pipes  

NASA Astrophysics Data System (ADS)

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.

Lakemeyer, C.; Schöppner, V.

2014-05-01

118

Effect of bone material properties on effective region in screw-bone model: an experimental and finite element study  

PubMed Central

Background There have been numerous studies conducted to investigate the pullout force of pedicle screws in bone with different material properties. However, fewer studies have investigated the region of effect (RoE), stress distribution and contour pattern of the cancellous bone surrounding the pedicle screw. Methods Screw pullout experiments were performed from two different foams and the corresponding reaction force was documented for the validation of a computational pedicle screw-foam model based on finite element (FE) methods. After validation, pullout simulations were performed on screw-bone models, with different bone material properties to model three different age groups (<50, 50–75 and >75 years old). At maximum pullout force, the stress distribution and average magnitude of Von Mises stress were documented in the cancellous bone along the distance beyond the outer perimeter pedicle screw. The radius and volume of the RoE were predicted based on the stress distribution. Results The screw pullout strengths and the load–displacement curves were comparable between the numerical simulation and experimental tests. The stress distribution of the simulated screw-bone vertebral unit showed that the radius and volume of the RoE varied with the bone material properties. The radii were 4.73 mm, 5.06 mm and 5.4 mm for bone properties of ages >75, 75?>?ages >50 and ages <50 years old, respectively, and the corresponding volumes of the RoE were 6.67 mm3, 7.35 mm3 and 8.07 mm3, respectively. Conclusions This study demonstrated that there existed a circular effective region surrounding the pedicle screw for stabilization and that this region was sensitive to the bone material characteristics of cancellous bone. The proper amount of injection cement for augmentation could be estimated based on the RoE in the treatment of osteoporosis patients to avoid leakage in spine surgery. PMID:24952724

2014-01-01

119

Screw expander for light duty diesel engines  

NASA Technical Reports Server (NTRS)

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.

1983-01-01

120

Apparatus to test insertion and removal torque of bone screws.  

PubMed

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

Koistinen, A; Santavirta, S; Lappalainen, R

2003-01-01

121

Affect Attunement during Early Mother-Infant Interactions: How Specific Intensities Predict the Stability of Infants' Coordinated Joint Attention Skills  

E-print Network

. (1998). Social cognition, joint attention, and communicative competence from 9 to 15 months of age Positive Affect Multi-media coding scale calibrated across all infants Phase 3: Maternal Affect during ME-time; K = .77 Codes: Neutral; & Low, Moderate, & High Positive Affect Multi-media coding scale calibrated

O'Toole, Alice J.

122

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

NASA Astrophysics Data System (ADS)

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.

Darsell, Jens T.; Weil, K. Scott

2008-09-01

123

Transmission of a Screw Dislocation Across a Coherent, Nonslipping Interface  

E-print Network

1 Transmission of a Screw Dislocation Across a Coherent, Nonslipping Interface Yao Shen materials (B), Energy methods (B), Transmission across interfaces Abstract Current research of slip transmission of a screw dislocation across a coherent, non-slipping interface is presented

Anderson, Peter M.

124

A technique for retrieving fractured implant screws.  

PubMed

The use of dental implants as a source of support and retention for fixed restorations is common. This report describes the use of a fragment removal instrument together with the use of ultrasonic instrumentation to retrieve a screw fragment. PMID:24268685

Imam, Ahmad Y; Moshaverinia, Alireza; Chee, Winston W L; McGlumphy, Edwin A

2014-01-01

125

Visuality in The Turn of the Screw: \\  

Microsoft Academic Search

Scarry is referring to the half-formed, transitory, vanishing quality of ghosts—a quality shared, more or less, by any mental image we might choose to form in the mind's eye. In this sense The Turn of the Screw is a perfect ghost story. It is a story about seeing ghosts, about picturing them, and perhaps about imagining them altogether. In fact,

Josh Rothman

126

Radiographic study of iliac screw passages  

PubMed Central

Background The optimal iliac screw path was determined to provide references for lumbosacral-pelvic reconstruction. Methods Radiographic data of 100 patients with normal pelvis were selected for this study. Four paths were designed. Paths A, B, and C were from the starting point of the crossing point of the chiotic line and posterior iliac crest (CLIC, located at 24.0 mm above the posterior superior iliac spine) to the upper edge of the acetabulum, anterior inferior iliac spine, and acetabulum center, respectively. Path D was from the starting point of the posterior superior iliac spine to the anterior inferior iliac spine. The lengths of the different paths of screw passage and bone plate thicknesses of two narrow places were measured and analyzed. Results Paths A, B, and D were approximately equal in length, but the thickness of the iliac plate in path A was significantly thicker than those in paths B and D. No significant difference was found between the iliac thickness of paths A and C, but the passage length of path A was significantly longer than that of path C. Conclusion Path A had the longest passage length and thickest iliac plate and could accommodate the relatively longest and thickest iliac screw. Thus, path A was the optimal iliac screw passage. PMID:24885171

2014-01-01

127

Screw-Together George W. Hart  

E-print Network

Screw-Together Cube George W. Hart Dept. Computer Science Stony Brook University http related forms. Martin Gardner credits a related three-piece cube dissection to John E. Morse [1]. William and George Miller is commercially available at [3]. I came to appreciate the elegance of this family of forms

128

Fatigue strength of common tibial intramedullary nail distal locking screws  

PubMed Central

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

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

2009-01-01

129

Surgeon's view of pedicle screw implantation for the monitoring neurophysiologist.  

PubMed

Pedicle screws have become the gold standard of spinal instrumentation over the past decade owing to their biomechanical superiority. Despite their advantages, pedicle screw instrumentation is potentially dangerous, and surgeons wish to improve accuracy of screw placement to avoid complications associated with screw misplacement. The anatomy of the pedicles is variable throughout the spine, and several landmarks and trajectories have been suggested to aid safe placement of pedicle screws in the spine. Several techniques such as x-ray and computed tomography scan imaging coupled with computer-aided navigation are available to improve accuracy of screw insertion. Intraoperative neuromonitoring with the help of triggered electromyographic recordings has evolved as an objective evidence of assessing pedicle breach and proximity of the screw to neural structures. While all imaging and electrophysiological modalities should be applied on an individualized basis, finally no adjunctive technique can fully replace the need for surgical expertise and experience. PMID:23207586

Joglekar, Siddharth B; Mehbod, Amir A

2012-12-01

130

[Scaphoid percutaneous osteosynthesis by screw using computer assisted surgery: an experimental study].  

PubMed

Scaphoid fractures are sometimes difficult to diagnose and even more difficult to fix. Recent progress such as miniaturization of osteosynthesis material, adoption of the percutaneous route, and widening of the indications to include undisplaced fractures has still not abolished complications. In this context, computer assisted surgery (CAS) may be useful and deserves further study. To apply it to the scaphoid, it is initially necessary to immobilize the "wrist hand fingers" unit in a device adapted to make it a rigid unit. It is then necessary to choose the correct configuration of CAS system. The pedicular fluoroscopic navigation system, which is apparently similar to scaphoid screw insertion, was chosen for this study. The goal of this study is to define the osteosynthesis bases of the scaphoid with CAS. A fresh anatomical subject divided at the elbow joint was prepared at the DETERCA laboratory of the university Bordeaux 2. The solid "wrist hand fingers" unit was immobilized in extension and ulnar deviation of the wrist by a malleable, stable and radio transparent device. The first stage consisted of a calibration of the surgical instruments and the "wrist hand fingers" unit, with a three-dimensional optical localization system. The guide wire was simulated by a gauged stylet. When the axis and the length of the screw had been determined virtually, insertion of the guide wire was carried out under guidance of the virtual images of the computer's screen, without the assistance of the fluoroscopy. Finally the canulated screw was inserted over the guide wire. Insertion was stopped when the screw reached the intra osseous virtually predetermined length. A check using conventional fluoroscopy made it possible to ensure the correct positioning of the screw. Our results show that it is possible to insert a screw into a scaphoid without conventional fluoroscopy, by using the fluoroscopic navigation system. The procedure was performed without difficulty, apart from the need for calibration of the navigation tools one by one. The solid immobilization device, although having the potential for micromovement, did not lead to any misdirection of the guide wire or screw. Our technique cannot be employed at the moment in live human surgery. Its limits are of a geometrical nature "two images available in two planes", data processing "non-specific software dedicated", instrumental "instrument calibration, micromobility of the immobilisation device" and live surgery "no current validation on a fractured scaphoid". Meantime, the development of a percutaneous scaphoid osteosynthesis procedure by CAS can only bring advantages: reduction in the learning curve, widening of the indications, comfort in the technique, reduction in the errors of ostesynthesis and, reduction in the exposure to x-rays. In the current state of knowledge, the method would only be applicable to undisplaced fractures. PMID:16121623

Liverneaux, P

2005-01-01

131

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

PubMed

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

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

2013-09-01

132

Helical Screw Expander Evaluation Project. Final report  

Microsoft Academic Search

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

McKay

1982-01-01

133

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

PubMed Central

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

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

2014-01-01

134

Failure of cement-augmented pedicle screws in the osteoporotic spine: a case report.  

PubMed

The treatment of patients with osteoporosis and spinal abnormalities that require surgical intervention is difficult because of the challenge of achieving fixation in osteoporotic bone. As the population ages, this challenge is becoming a common problem in the field of spinal surgery. Although numerous publications exist about the biomechanical benefits of various fixation devices and techniques, no standard of care has emerged that offers a clear method for accomplishing spinal stabilization in such patients. This case presents the failure mode of cement-augmented pedicle screws in a patient with severe osteoporosis, a description of the methods used to attain fixation and spinal stability during the revision surgery, and the outcome achieved for the patient 1 year after surgery. An 82-year-old female with a T9 burst fracture and a history of osteoporosis underwent minimally invasive instrumentation from T5 to T12, fusion from T7 to T11, and decompression from T8 to T10. Four weeks after surgery, the patient returned to the hospital because of back pain. Imaging studies showed that the pedicle screws at T11 and T12, which were augmented with polymethylmethacrylate (PMMA), had pulled out of the vertebral bodies. The pedicle screws failed by disengaging from the PMMA and displacing posteriorly and inferiorly. The PMMA did not appear to move during this process. A revision surgery was performed, in which the posterior construct was extended caudally and cephalad, the pedicle screws were augmented with PMMA, and a titanium hook and woven polyester band were used to increase the points of fixation. At 1-year follow-up after revision, our patient showed radiographic evidence of fusion, and the construct continued to maintain stability in the osteoporotic spine. PMID:24319620

Mesfin, Addisu; Komanski, Christopher B; Khanna, A Jay

2013-09-01

135

Examination of the suitability of alpha-tocopherol as a stabilizer for ultra-high molecular weight polyethylene used for articulating surfaces in joint endoprostheses.  

PubMed

The lifetime of articulating surfaces in joint endoprostheses made of ultra-high molecular weight polyethylene (UHMW-PE), especially of UHMW-PE-cups of hip-endoprostheses, is usually limited to 10-15 years due to material failure as a result of oxidation of the UHMW-PE in vivo. In this study the suitability of the natural antioxidant alpha-tocopherol (vitamin E) as a stabilizer for UHMW-PE in these applications was investigated. Specimens with 0.1%, 0.2%, 0.4% and 0.8% w/w alpha-tocopherol as well as unstabilized samples were sintered and sterilized with gamma-rays at 25 kGy in accordance with standard processing methods of cups for total hip-endoprostheses. These specimens were aged in pure oxygen at 70 degrees C and 5 bar as well as in aqueous H2O2 at 50 degrees C. The degree of oxidation was observed by means of FTIR-spectroscopy, DSC analysis and mechanical testing. The FTIR-measurements showed that alpha-tocopherol can prolong the lifetime of UHMW-PE in an oxidative environment by a factor of more than 2.5. In the mechanical tests no embrittlement could be observed with the stabilized samples. A comparison with the standard antioxidant system Irganox 1010/Irgafos 168 (Ciba-Geigy, Switzerland) was carried out and revealed that alpha-tocopherol can even exceed the stabilization effect of this widely-used antioxidant system. PMID:15348641

Wolf, C; Krivec, T; Blassnig, J; Lederer, K; Schneider, W

2002-02-01

136

Experimental investigation of the use of drag reducing agents in conjunction with twin-screw multiphase pumps  

E-print Network

: 1) simple screw pump, 2) single screw pump, 3) twin-screw pump, and 4) three-screw pump. The simple screw pump is an extensive version of the axial-flow, or propeller, pump. It is based on the principle of Archimedes screw and has been developed...: 1) simple screw pump, 2) single screw pump, 3) twin-screw pump, and 4) three-screw pump. The simple screw pump is an extensive version of the axial-flow, or propeller, pump. It is based on the principle of Archimedes screw and has been developed...

Carrillo Plazas, Gabriel D

2012-06-07

137

Transforaminal lumbar interbody fusion using unilateral pedicle screws and a translaminar screw  

PubMed Central

Lumbar spinal fusion is advancing with minimally invasive techniques, bone graft alternatives, and new implants. This has resulted in significant reductions of operative time, duration of hospitalization, and higher success in fusion rates. However, costs have increased as many new technologies are expensive. This study was carried out to investigate the clinical outcomes and fusion rates of a low implant load construct of unilateral pedicle screws and a translaminar screw in transforaminal lumbar interbody fusion (TLIF) which reduced the cost of the posterior implants by almost 50%. Nineteen consecutive patients who underwent single level TLIF with this construct were included in the study. Sixteen patients had a TLIF allograft interbody spacer placed, while in three a polyetheretherketone (PEEK) cage was used. Follow-up ranged from 15 to 54 months with a mean of 32 months. A clinical and radiographic evaluation was carried out preoperatively and at multiple time points following surgery. An overall improvement in Oswestry scores and visual analogue scales for leg and back pain (VAS) was observed. Three patients underwent revision surgery due to recurrence of back pain. All patients showed radiographic evidence of fusion from 9 to 26 months (mean 19) following surgery. This study suggests that unilateral pedicle screws and a contralateral translaminar screw are a cheaper and viable option for single level lumbar fusion. PMID:19015896

Lee, Sandra; Vaidya, Rahul

2008-01-01

138

Screw dislocations in GaN  

SciTech Connect

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.

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

2002-02-15

139

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

Microsoft Academic Search

Segmental pedicle screw fixation is rapidly becoming a popular method of spinal instrumentation. Few studies have investigated\\u000a the rates of adjacent superior segment facet joint violation. The purpose of our study were to investigate the incidence of\\u000a superior segment facet joint violation after pedicle screw instrumentation in the lumbar spine and to evaluate technical factors\\u000a related to the incidence. A

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

2008-01-01

140

Optimized rotor pitch distributions for screw spindle vacuum pumps  

Microsoft Academic Search

Screw spindle vacuum pumps are characterised by a high suction performance and the ability to achieve high pressure ratios. Screw spindle vacuum pumps have varying progressions for the rotor pitch gradient, depending on the manufacturer. From a scientific point of view, the question arises which rotor gradient along the rotors has to be preferred for a particular set of operating

D. Pfaller; A. Brümmer; K. Kauder

2011-01-01

141

Transmission of a Screw Dislocation Across a Coherent, Slipping Interface  

E-print Network

1 Transmission of a Screw Dislocation Across a Coherent, Slipping Interface Yao Shen(a) and Peter M of interfacial sliding during dislocation transmission. A straight screw dislocation parallel to a bimaterial. Interfacial sliding is predicted to increase the critical applied shear crit of interfaces for transmission

Anderson, Peter M.

142

Fatigue strength of common tibial intramedullary nail distal locking screws  

Microsoft Academic Search

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

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

2009-01-01

143

FORMING PROCESS OF SCREW SPIKE IN DOUBLE CONFIGURATION  

Microsoft Academic Search

Summary. In this paper technology of screw spikes manufacturing, based on the flashless forging and hot rolling in double configuration, is presented. The forging takes place in closed dies and the obtained workpiece is rolled in its middle part on cross-wedge rolling mill in order to make screw thread. As the result of this process, it is possible to eliminate

COMPLAS VIII; S. Wero?ski; Andrzej Gontarz; Zbigniew Pater

144

Bicondylar Hoffa Fracture Successfully Treated with Headless Compression Screws  

PubMed Central

Bicondylar coronal plane fracture, eponymically named Hoffa fractures, is an extremely rare injury. We present a case of isolated unilateral bicondylar Hoffa fracture that was successfully treated with open reduction and internal fixation using headless compression screws with satisfactory results. We inserted posteroanteriorly oriented Acutrak screws perpendicular to the fracture plane via lateral parapatellar arthrotomy, which provided excellent compression across the fracture. PMID:25140263

Kuroda, Ryosuke; Kurosaka, Masahiro

2014-01-01

145

Application studies of CFRTP hexagon socket head cap screws  

NASA Astrophysics Data System (ADS)

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.

Sano, Akihiko; Matsumoto, Masaru

146

DESIGN OF OIL-LESS HELICAL TWIN SCREW MACHINES  

Microsoft Academic Search

A twin screw machine is described as oil-less when the working chamber between the contacting helical rotors and the casing, which is usually flooded by oil, operates with no oil or a very small quantity of oil injected in it. Such a mode of operation has been shown to be viable in two experimental projects in which three screw machine

Ian K Smith; Ahmed Kovaèeviæ

147

MATHEMATICAL ANALYSIS OF OIL INJECTED TWIN SCREW COMPRESSOR  

Microsoft Academic Search

Mathematical analysis of oil injected twin-screw compressor is carried out on the basis of the laws of perfect gas, and standard thermodynamic relations. Performance of an oil injected twin-screw compressor depends on a large number of design parameters. A computer model for calculating compressor performance and to validate the results with experimental data is developed. The flow coefficients required to

N. Seshaiah; R. K. Sahoo

148

Performance Analysis of Oil Injected Twin Screw Compressor  

Microsoft Academic Search

Oil injected twin-screw air compressors are widely used for medium pressure applications in cryogenic industries. Conversion of these compressors for helium applications is in great demand due to their inherent advantages. A mathematical model of an oil injected twin-screw compressor has been constructed basing on the laws of perfect gas and standard thermodynamic relations to evaluate compressor efficiencies. The complete

N. Seshaiah; Subrata Kr; Ranjit Kr; Sunil Kr

2006-01-01

149

Performance of Screw Compressor for Small-Capacity Helium Refrigerators  

NASA Astrophysics Data System (ADS)

A helium compressor is one of the important components comprising a cryogenic refrigerator. The purpous of this investigation is to develop a new small-capacity helium screw compressor. The performance of a single-stage compressor at high compression ratio and the cooling performance of the compressor are investigated. A semi-hermetic screw compressor with new profile screw rotors, with which high performance can be obtained, is utilized in this investigation. Lubricating oil is applied to cool the compressor motor and the compressed gas. As a result, an overall isentropic efficiency of 80% is obtained when helium is compressed to a compression ratio of 19.8 with a single-stage screw compressor. At the same time, the temperature of a compressor motor and discharge gas can be maintained at low levels. Therefore, it is found that a single-stage screw compressor can compress helium to high compression ratio.

Urashin, Masayuki; Matsubara, Katsumi; Izunaga, Yasushi

150

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

PubMed

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

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

2014-09-01

151

A Class of Kinematically Simple 7Revolute Jointed Serial Manipulators and their Velocity-Degenerate (Singular) Configurations  

Microsoft Academic Search

The velocity degeneracies (singularities) for a class of 7-revolute jointed manipulators are found. Within the class, unnecessary lengths and 4-jointed spherical groups of joints are avoided; successive joints are perpendicular or parallel. The concept of screw reciprocity is used to find the velocity-degenerate configurations. For manipulators based on a spherical-revolute-spherical (shoulder-elbow-wrist) joint arrangement, it is confirmed that four condition-sets lead

Ron P. PodhorodeskiT; Roger Boudreau

2007-01-01

152

A Surgical Method for Determining Proper Screw Length in ACDF  

PubMed Central

Objective We describe a surgical tool that uses the distractor pin as a reference for determining proper screw length in ACDF. It is critical that screw purchase depth be as deep as possible without violating or penetrating the posterior cortical wall, which ensures strong pull out strength. Methods We enrolled 81 adult patients who underwent ACDF using an anterior cervical plate from 2010 to 2012. Patients were categorized into Groups A (42 patients: retractor pin used as a reference for screw length) and B (39 patients: control group). Intraoperative lateral x-rays were taken after screwing the retractor pin to confirm the approaching vertebral level. The ratio of retractor pin length to body anteroposterior (A-P) diameter was measured as a reference. Proper screw length was determined by comparison to the reference. Results The average distance from screw tip to posterior wall was 3.0±1.4mm in Group A and 4.1±2.3mm in Group B. The ratio of screw length to body sagittal diameter was 86.2±5.7% in Group A and 80.8±9.0% in Group B. Screw length to body sagittal diameter ratios higher than 4/5 occurred in 33 patients (90%) in Group A and 23 patients (59%) in Group B. No cases violated the posterior cortical wall. Conclusion We introduce a useful surgical method for determining proper screw length in ACDF using the ratio of retractor pin length to body A-P diameter as a reference. This method allows for deeper screw purchase depth without violation of the posterior cortical wall.

Park, Hae-Gi; Kang, Moo-Sung; Kim, Kyung-Hyun; Park, Jeong-Yoon; Kim, Keun-Su

2014-01-01

153

Screw Compressor Characteristics for Helium Refrigeration Systems  

NASA Astrophysics Data System (ADS)

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 mechanisms, as well as to implement practical solutions.

Ganni, V.; Knudsen, P.; Creel, J.; Arenius, D.; Casagrande, F.; Howell, M.

2008-03-01

154

Spline-locking screw fastening strategy  

NASA Technical Reports Server (NTRS)

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.

Vranish, John M.

1992-01-01

155

Spline-Locking Screw Fastening Strategy (SLSFS)  

NASA Technical Reports Server (NTRS)

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.

Vranish, John M.

1991-01-01

156

Minimal invasive treatment for scaphoid fractures using the cannulated herbert screw system.  

PubMed

Internal fixation of scaphoid fractures avoids the problems associated with prolonged plaster immobilization and, at the same time, allows an early return to activity for these mostly young patients.Internal fixation of the scaphoid is greatly facilitated by the use of specially designed headless bone screws, such as the Herbert bone screw, originally developed specifically for internal fixation of the scaphoid; furthermore, the advent of cannulated scaphoid screws has made closed (percutaneous fixation) stabilization of the scaphoid a reality. Indeed, this method has now become the treatment of choice for the majority of acute scaphoid fracture, bringing with it all the advantages of internal fixation without the disadvantages of open surgery.However, the success of closed treatment is also dependent on an accurate assessment of the fracture, and for this reason, we now advocate the routine use of computed tomography preoperatively. Because of the complex, 3-dimensional shape of the scaphoid, simple x-rays alone are inadequate, whereas computed tomography, parallel to the long axis of the scaphoid, allows excellent visualization of the fracture and any associated deformity, which must be corrected at the time of surgery.We describe here our method of treating acute scaphoid fractures, and we report the outcome of minimally invasive fixation. PMID:16518213

Moser, Veith L; Krimmer, Hermann; Herbert, Timothy J

2003-12-01

157

Effect of occipitocervical fusion with screw-rod system for upper cervical spine tumor  

PubMed Central

Background Craniospinal junction tumors are rare but severe lesions. Surgical stabilization has been established to be an ideal treatment for upper cervical tumor pathology. The purpose of this study was to evaluate the effect of a screw-rod system for occipitocervical fusion. Methods A total of 24 cases with C1 and C2 cervical tumor underwent occipitocervical fusion with Vertex screw-rod internal fixation from January 2005 to December 2012. Preoperative X-ray and MRI examinations were performed on all patients before the operation, after the operation, and during last follow-up. The JOA score was used to assess neurological function pre and postoperatively. Results All the patients were followed up for 6 to 42 months with an average of 24 months. The result of X-ray showed that bony fusion was successful in 18 patients at 3 months and 6 patients at 6 months of follow-ups. There was no deterioration of spinal cord injury. The JOA Scores of neurological function increased significantly. Conclusion The screw-rod system offers strong fixation and good fusion for occipitocervical fusion. It is an effective and reliable method for reconstruction of upper cervical spine tumor. PMID:24884456

2014-01-01

158

C2 Pars/Pedicle Screws in Management of Craniocervical and Upper Cervical Instability  

PubMed Central

Study Design A retrospective study. Purpose To evaluate the efficacy and the safety of craniocervical and upper cervical stabilization by using C2 pars/pedicle screw fixations. Overview of Literature The management of craniocervical and upper cervical instability has progressed over the past two decades due to good achievements in the instrumentation and the increased awareness on spinal anatomy and biomechanics. However, there is insufficient studies or solid conclusions on this topic, thus, we tried to investigate and present our findings. Methods Twenty-two patients were operated upon and were followed up from March 2008 to October 2010. One patient had craniocervical instability (post-surgical), 15 patients had atlantoaxial instability of different etiologies (trauma, tumors, inflammatory and degenerative) and 6 patients had hangman fractures. Patients' ages ranged from 18 to 52 years old. with 5 female patients and 17 male patients. Results Radiological follow ups performed immediately post-operation showed good screw positioning and complete reductions in nearly all the cases. All patients were followed up for more than one year. Sound fusions were observed among all patients. Conclusions The use of pars/pedicle screws is a very effective, sound, safe and easy surgical modality for treating craniocervical, atlantoaxial and upper cervical instabilities. Increasing studies for the biomechanics of this important region and longer periods of follow-ups are necessary to document the usefulness of this modality when treating such patients. PMID:24761197

2014-01-01

159

A computational biomechanical investigation of posterior dynamic instrumentation: combination of dynamic rod and hinged (dynamic) screw.  

PubMed

Currently, rigid fixation systems are the gold standard for degenerative disk disease treatment. Dynamic fixation systems have been proposed as alternatives for the treatment of a variety of spinal disorders. These systems address the main drawbacks of traditional rigid fixation systems, such as adjacent segment degeneration and instrumentation failure. Pedicle-screw-based dynamic stabilization (PDS) is one type of these alternative systems. The aim of this study was to simulate the biomechanical effect of a novel posterior dynamic stabilization system, which is comprised of dynamic (hinged) screws interconnected with a coiled, spring-based dynamic rod (DSDR), and compare it to semirigid (DSRR and RSRR) and rigid stabilization (RSRR) systems. A validated finite element (FE) model of L1-S1 was used to quantify the biomechanical parameters of the spine, such as range of motion, intradiskal pressure, stresses and facet loads after single-level instrumentation with different posterior stabilization systems. The results obtained from in vitro experimental intact and instrumented spines were used to validate the FE model, and the validated model was then used to compare the biomechanical effects of different fixation and stabilization constructs with intact under a hybrid loading protocol. The segmental motion at L4-L5 increased by 9.5% and 16.3% in flexion and left rotation, respectively, in DSDR with respect to the intact spine, whereas it was reduced by 6.4% and 10.9% in extension and left-bending loads, respectively. After instrumentation-induced intradiskal pressure at adjacent segments, L3-L4 and L5-S1 became less than the intact in dynamic rod constructs (DSDR and RSDR) except in the RSDR model in extension where the motion was higher than intact by 9.7% at L3-L4 and 11.3% at L5-S1. The facet loads were insignificant, not exceeding 12N in any of the instrumented cases in flexion. In extension, the facet load in DSDR case was similar to that in intact spine. The dynamic rod constructions (DSDR and RSDR) led to a lesser peak stress at screws compared with rigid rod constructions (DSRR and RSRR) in all loading cases. A dynamic construct consisting of a dynamic rod and a dynamic screw did protect the adjacent level from excessive motion. PMID:24599026

Erbulut, Deniz U; Kiapour, Ali; Oktenoglu, Tunc; Ozer, Ali F; Goel, Vijay K

2014-05-01

160

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

PubMed Central

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

2014-01-01

161

Fracture mechanisms of retrieved titanium screw thread in dental implant.  

PubMed

Titanium and its alloy are increasingly attracting attention for use as biomaterials. However, delayed fracture of titanium dental implants has been reported, and factors affecting the acceleration of corrosion and fatigue have to be determined. The fractured surface of a retrieved titanium screw and metallurgical structures of a dental implant system were analyzed. The outer surface of the retrieved screw had a structure different from that of the as-received screw. It was confirmed that a shear crack initiated at the root of the thread and propagated into the inner section of the screw. Gas chromatography revealed that the retrieved screw had absorbed a higher amount of hydrogen than the as-received sample. The grain structure of a titanium screw, immersed in a solution known to induce hydrogen absorption, showed features similar to those of the retrieved screw. It was concluded that titanium in a biological environment absorbs hydrogen and this may be the reason for delayed fracture of a titanium implant. PMID:12033593

Yokoyama, Ken'ichi; Ichikawa, Tetsuo; Murakami, Hiroki; Miyamoto, Youji; Asaoka, Kenzo

2002-06-01

162

New device to treat chronic subdural hematoma--hollow screw.  

PubMed

Different surgical approaches exist for the treatment of chronic subdural hematoma. None of these approaches is superior to the other, so a minimal-invasive device (a hollow screw) was developed. The system consists of a stable hollow screw of surgical steel with a perforated tip, a hand-drill, screwdriver with guide, and collection bag. To place the screw in the skull local anesthesia is necessary followed by stab incision and percutaneous trephination. The screw is then placed in the bone and the guide removed. After spontaneous drainage and irrigation, a closed drainage system with a collection bag is connected with the screw. First results with the new technology are promising, with a high rate of completely treated patients and a low rate of complications. Two of 86 patients had a local skin infection after implantation of the screw, and in 22 patients the procedure was repeated due to one or more cases of recurrent or residual hematoma. No neurological deterioration was caused by the screw or the surgical approach. The advantages of this new system are: quick and simple procedure, minimal invasive, excellent function, inexpensive and reusable. PMID:10048060

Emonds, N; Hassler, W E

1999-01-01

163

Intersection of screw dislocations in fcc crystals during torsional deformation  

NASA Astrophysics Data System (ADS)

Dislocation reactions, including dislocation intersections during various processes in crystals, play an important and often crucial role. This is most pronounced during plastic deformation of crystalline solids, which attracts particular interest from researchers. Intersection of screw dislocations in fcc crystals during their deformation by uniaxial tension and compression was studied by A. Cottrell [1]. It was shown that the intersection of similar screw dislocations moving toward each other results in the formation of interstitial thresholds on them; in the case of intersection of opposite screw dislocations, vacancy thresholds are formed on them.

Myshlyaev, M. M.

2012-03-01

164

Noninvasive method for retrieval of broken dental implant abutment screw  

PubMed Central

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

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

2014-01-01

165

Dynamic Ball & Socket Joint Force Simulator  

E-print Network

The stability of an implant in the bone, one factor in joint replacement survival, is usually tested using biaxial fatigue loading. These loading protocols do not replicate physiological loading conditions. The Dynamic Ball and Socket Joint Force...

Farmer, Ryan Neal

2011-07-26

166

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

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

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

2014-01-01

167

Screw dislocation driven growth of nanomaterials.  

PubMed

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

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

2013-07-16

168

Use of anteroposterior view fluoroscopy for targeting percutaneous pedicle screws in cases of spinal deformity with axial rotation.  

PubMed

Object Over the past decade percutaneous pedicle screws have become popular for the minimally invasive treatment of spinal disorders. However, until the last 5 years the presence of a significant spinal deformity was regarded as a relative contraindication for percutaneous instrumentation. Recent advances in surgical technique and intraoperative technology have made percutaneous fixation in complex spinal pathologies more commonplace. The authors report their experience using a parsimonious method for uniplanar fluoroscopic targeting of pedicles in challenging cases. Methods The authors performed a retrospective analysis of patients with adult spinal deformity who underwent percutaneous pedicle screw instrumentation from 2008 to 2013. Cases were included if a spiral slice postoperative CT scan was obtained. All cases had a minimum of 10° of axial rotation and typically had additional accompanying anatomical abnormalities. Screws were assessed for any pedicle violations as well as any impingement of the surrounding facet joints. Results A total of 410 pedicle screws were placed in 36 patients with an average 6.4 levels of instrumentation per patient. The mean age was 67 years (range 44-86 years) and there were 25 females. Of the 410 screws, 29 (7.1%) had some medial or lateral pedicle violation. Of these, 15 (3.7%) were Grade 1, 6 (1.4%) were Grade 2, and 8 (2.0%) were Grade 3 violations. Of the Grade 3 violations, 2 each were at the L-4, L-5, and S-1 levels, and 1 each was at the T-10 and L-1 levels. Two of the patients had symptoms and both underwent screw repositioning, one during the same admission and the other in a delayed fashion. Both were at the L-5 and S-1 levels with anatomically highly medialized pedicles. There were no motor deficits, and both removals were for numbness. Of the 72 screws at the proximal end of the construct, there were 6 facet violations (8.3%). Four (5.6%) of these were Grade 1, 1 (1.4%) was Grade 2, and 1 (1.4%) was Grade 3. Conclusions The anteroposterior fluoroscopic technique can be effectively used by spinal surgeons to cannulate the pedicles in patients with rotational deformities. The complication rate in this challenging population is acceptable and is in accordance with the existing literature. However, caution should be used at L-5 and S-1 when the pedicle is narrow and highly medialized, rendering an indistinct medial wall on anteroposterior imaging. PMID:25170657

Ahmad, Faiz U; Wang, Michael Y

2014-11-01

169

In vitro study of accuracy of cervical pedicle screw insertion using an electronic conductivity device (ATPS part III)  

Microsoft Academic Search

Reconstruction of the highly unstable, anteriorly decompressed cervical spine poses biomechanical challenges to current stabilization\\u000a strategies, including circumferential instrumented fusion, to prevent failure. To avoid secondary posterior surgery, particularly\\u000a in the elderly population, while increasing primary construct rigidity of anterior-only reconstructions, the authors introduced\\u000a the concept of anterior transpedicular screw (ATPS) fixation and plating. We demonstrated its morphological feasibility, its

Heiko Koller; Wolfgang Hitzl; Frank Acosta; Mark Tauber; Juliane Zenner; Herbert Resch; Yasutsugu Yukawa; Oliver Meier; Rene Schmidt; Michael Mayer

2009-01-01

170

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

171

Screw Type Steam Compressors for Mechanical Vapor Recompression (MVR) Systems  

E-print Network

SCREW TYPE STEAM COMPRESSORS FOR MECHANICAL VAPOR RECOMPRESSION (MVR) SYSTEMS K. KAWAMURA AND THOMAS-L. APALOO MYCOM CORPORATION, LOS ANGELES, CALIFORNIA MATSUDA, MAYEKAWA MFG. CO., TOKYO, JAPAN ABSTRACT In processes of evaporation...SCREW TYPE STEAM COMPRESSORS FOR MECHANICAL VAPOR RECOMPRESSION (MVR) SYSTEMS K. KAWAMURA AND THOMAS-L. APALOO MYCOM CORPORATION, LOS ANGELES, CALIFORNIA MATSUDA, MAYEKAWA MFG. CO., TOKYO, JAPAN ABSTRACT In processes of evaporation...

Kawamura, K.; Apaloo, Thomas-L.

172

Distal tibial fracture post syndesmotic screw removal: an adverse complication  

Microsoft Academic Search

Fractures of the ankle are common injuries. Some ankle fractures have an associated injury to the syndesmosis, necessitating\\u000a fixation with one or more screws. Generally, the overall outcome post ankle fracture is good. However, several complications\\u000a have also been described. The current authors describe a distal tibial fracture following syndesmotic screw removal. A 77-year-old\\u000a woman was admitted with a bimaleollar

Mustafa Citak; Manuel Backhaus; Gert Muhr; Thomas Kälicke

173

Segmental pedicle screw instrumentation in idiopathic thoracolumbar and lumbar scoliosis  

Microsoft Academic Search

The role of posterior correction and fusion in thoracolumbar and lumbar scoliosis as well as pedicle screw instrumentation\\u000a in scoliosis surgery are matters of debate. Our hypothesis was that in lumbar and thoracolumbar scoliosis, segmental pedicle\\u000a screw instrumentation is safe and enables a good frontal and sagittal plane correction with a fusion length comparable to\\u000a anterior instrumentation. In a prospective

H. Halm; T. Niemeyer; T. Link; U. Liljenqvist

2000-01-01

174

Helical Screw Expander Evaluation Project. Final report  

SciTech Connect

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.

McKay, R.

1982-03-01

175

Joints in a Cornstarch Analog  

NSDL National Science Digital Library

Joints are very important to problems in applied geology (fluid flow, slope stability), but three-dimensional exposures of simple joint sets are not readily accessible from my campus. I developed this exercise based on the experiments of Miller (2001) to give students hands-on practice describing and interpreting joints. For the exercise, I prepare a cornstarch-water mixture a few days in advance and pour it into plastic petri dishes. I add a "flaw" to each dish (typically a small pebble). As the cornstarch dries, vertical joints develop. In class, each group of 3-4 students is provided a petri dish of desiccated cornstarch. Students are asked to draw a map of the joints, paying particular attention to intersection angles. (The joints curve to intersect at 90 degrees.) They determine relative ages of the joints using abutting relationships. (Typically 3-6 generations of joints.) Students next dissect the sample and describe the surface textures of the larger joints and the location of the flaw. The cornstarch produces beautiful plumose structure (hackles). Students then interpret the joint propagation direction from the surface textures, and note the origin of the joint. (Typically, a first- or second-generation joint initiates at the flaw.) Students discuss the role of flaws in the initiation of joints in their groups.

Crider, Juliet

176

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

Microsoft Academic Search

We assessed syndesmotic set screw strength and fixation capacity during cyclical testing in a cadaver model simulating protected weight bearing. Sixteen fresh frozen legs with artificial syndesmotic injuries and a syndesmotic set screw made of stainless steel or titanium, inserted through three or four cortices, were axially loaded with 800N for 225,000 cycles in a materials testing machine. The 225,000

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

2005-01-01

177

An analytical investigation of high-temperature heat pump system with screw compressor and screw expander for power recovery  

Microsoft Academic Search

An analytical investigation of a high-temperature heat pump system was developed to estimate the thermal cycle and to assess the thermal fluids for their high-temperature delivery (up to 180°C) capacities without decomposition or the use of lubricant mechanisms. Then, a screw-type compressor was applied in the above conditions. Furthermore, a screw expander was also used as a replacement for the

I. Tamura; H. Taniguchi; H. Sasaki; R. Yoshida; I. Sekiguchi; M. Yokogawa

1997-01-01

178

Exercise and the Knee Joint.  

ERIC Educational Resources Information Center

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,…

Clarke, H. Harrison, Ed.

1976-01-01

179

Ideal Kink Modes In a Line-Tied Screw Pinch With Finite Plasma Pressure*  

NASA Astrophysics Data System (ADS)

A new method for computing ideal magnetohydrodynamic linear eigenmodes in a cylindrical screw pinch with line-tying boundary conditions is presented. In this method, plasma volume is reflected over one of the end plates, and equations and field components are continued on the extended volume with the continuation rules prescribed by the line-tying boundary conditions. Field components in the combined volume are expanded in Fourier series in the axial coordinate. The resulting set of coupled differential equations is solved numerically in the radial coordinate yielding growth rates and eigenmodes for the system. Example of an m=1 (m is poloidal mode number) internal kink instability in force-free plasma equilibrium with uniform pressure is considered. In contrast to a periodic screw pinch, marginally stable perturbations are essentially compressible in line-tied geometry. Finite compressibility makes the mode more stable in addition to usual line-tying stabilization in zero pressure plasma. The critical length corresponding to marginal stability increases with the increase of plasma beta. A universal axial dependence for marginally stable density perturbations ?(r, z) = ?(r) exp(- i z / q(r)) is predicted analytically and confirmed numerically (q = r Bz/B? ). The work was supported by the U.S. D.O.E. and N.S.F.

Mirnov, V. V.; Svidzinski, V. A.; Li, H.

2008-11-01

180

m =1 ideal kink modes in a line-tied screw pinch with finite plasma pressure  

NASA Astrophysics Data System (ADS)

A new method for computing ideal magnetohydrodynamic linear eigenmodes in a cylindrical screw pinch with line-tying boundary conditions at the axial ends is presented. In this method, plasma volume is reflected over one of the end planes, and equations and field components are continued into the extended volume with the continuation rules prescribed by the line-tying boundary conditions. Field components in the combined volume are expanded in Fourier series in the axial coordinate. The resulting set of coupled differential equations is solved numerically in the radial coordinate by a finite difference method yielding growth rates and eigenmodes for the system. An example of an m =1 (m is the poloidal wave number) internal kink instability in a force-free plasma equilibrium with uniform pressure is considered. In contrast to a periodic screw pinch, marginally stable perturbations are essentially compressible in the line-tied geometry. Finite compressibility makes the mode more stable in addition to the usual line-tying stabilization in zero pressure plasma. The critical length corresponding to the marginal stability increases with the increase of plasma beta. A universal axial dependence for marginally stable density perturbations ?(r ,z)=?(r)exp[-iz?(r)] is predicted analytically and confirmed numerically, where ?(r ) depends on the equilibrium magnetic field components as ?(r )=B¯?/rB¯z.

Svidzinski, V. A.; Mirnov, V. V.; Li, H.

2008-09-01

181

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

NASA Astrophysics Data System (ADS)

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.

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

182

A Biomechanical Comparison of Intralaminar C7 Screw Constructs with and without Offset Connector Used for C6-7 Cervical Spine Immobilization : A Finite Element Study  

PubMed Central

Objective The offset connector can allow medial and lateral variability and facilitate intralaminar screw incorporation into the construct. The aim of this study was to compare the biomechanical characteristics of C7 intralaminar screw constructs with and without offset connector using a three dimensional finite element model of a C6-7 cervical spine segment. Methods Finite element models representing C7 intralaminar screw constructs with and without the offset connector were developed. Range of motion (ROM) and maximum von Mises stresses in the vertebra for the two techniques were compared under pure moments in flexion, extension, lateral bending and axial rotation. Results ROM for intralaminar screw construct with offset connector was less than the construct without the offset connector in the three principal directions. The maximum von Misses stress was observed in the C7 vertebra around the pedicle in both constructs. Maximum von Mises stress in the construct without offset connector was found to be 12-30% higher than the corresponding stresses in the construct with offset connector in the three principal directions. Conclusion This study demonstrated that the intralaminar screw fixation with offset connector is better than the construct without offset connector in terms of biomechanical stability. Construct with the offset connector reduces the ROM of C6-7 segment more significantly compared to the construct without the offset connector and causes lower stresses around the C7 pedicle-vertebral body complex. PMID:24003366

Qasim, Muhammad; Natarajan, Raghu N.; An, Howard S.

2013-01-01

183

Pedicle screw piercer with warning device - A technique to increase accuracy of pedicle screw placement  

PubMed Central

Background: Pedicle screw fixation has achieved significant popularity amongst spinal surgeons for both single and multilevel spinal fusion. Suboptimal placements of pedicle screws may lead to neurological and vascular complications. There have been many advances in techniques available for navigating through the pedicle; however, these techniques are not without drawbacks. The purpose of this study was to investigate the efficacy and feasibility of the pedicle piercer with warning device. Materials and Methods: Eight normal adult thoracolumbar specimens from cadavers consisting of 80 vertebras (T8–L5) were selected and randomly allocated into four groups. Each group contained 20 vertebra. Group 1 was tested for maximum pressure of the piercer within the vertebrae (F1). Group 2 was tested for maximum pressure of the warning piercer penetrating front cortex of the vertebral body (F2). Group 3 was tested for the maximum pressure of piercer penetrating vertebral body endplate (F3) and pedicle notch (F41, F42). Group 4 was tested for maximum pressure of the piercer penetrating the vertebral lateral cortex (F6), the medial and lateral cortex of pedicle (F51, F52). In the second experiment of this study, 4 normal adult specimens consisting of 40 vertebra and 80 pedicles were used for testing the alarm effects of pedicle piercer. The following indicators were adopted for the tests including true positive/negative, false positive/negative, sensitivity, specificity, availability, Youden index, and diagnostic efficiency. SPSS 16.0 was used for statistical analysis. Results: There were statistically significant differences between F1, and F2, F3, F41, F42, F51, F52 respectively (P < 0.05). F1 = 8.970 ± 0.2698, F3 = 13.055 ± 0.6718. We found that the threshold value of piercer warning was from 9.6 to 12.3 Kgf. Sensitivity was 92.31%, specificity was 95.12%, usability was 87.45%, Youden index was 87.43% and diagnostic efficiency was 92.5% respectively. Conclusion: Warning piercer is a safe, simple, sensitive device for detecting pedicle breach during regular pedicle screw placement surgery.

Bin, Lin; Yong, He; Yang, Xu; Bi, Zhang; Mo, Sha; Zhi-Min, Guo

2014-01-01

184

Endovascular aortic injury repair after thoracic pedicle screw placement.  

PubMed

Our objective was to describe the management and prevention of thoracic aortic injuries caused by a malposition of pedicle screws in corrective surgery of major spine deformities. Positioning pedicle screws in thoracic vertebras by posterior approach exposes to the risk of injury of the elements placed ahead of the thoracic spine, as the descending thoracic aorta. This complication can result in a cataclysmic bleeding, needing urgent vascular care, but it can also be totally asymptomatic, resulting in the long run in a pseudoaneurysm, justifying the systematic removal of the hardware. We report the case of a 76-year-old woman who underwent spinal correction surgery for thoraco-lumbar degenerative kypho-scoliosis. Immediately after the surgery, a thoracic aortic injury caused by the left T7 pedicle screw was diagnosed. The patient underwent a two-step surgery. The first step was realized by vascular surgeons and aimed to secure the aortic wall by short endovascular aortic grafting. During the second step, spine surgeons removed the responsible screw by posterior approach. The patient was discharged in a rehabilitation center 7 days after the second surgery. When such a complication occurs, a co-management by vascular and spine surgeons is necessary to avoid major complications. Endovascular management of this kind of vascular injuries permits to avoid an open surgery that have a great rate of morbi-mortality in frail patients. Nowadays, technologies exist to prevent this kind of event and may improve the security when positioning pedicle screws. PMID:25023930

Pesenti, S; Bartoli, M A; Blondel, B; Peltier, E; Adetchessi, T; Fuentes, S

2014-09-01

185

Screw dislocations in GaN grown by different methods  

SciTech Connect

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.

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

2003-05-27

186

Ball screw preload loss detection using ball pass frequency  

NASA Astrophysics Data System (ADS)

A technique of determining the onset of preload loss in a ball screw feed drive system via monitoring the change of ball pass frequency is proposed. The ball pass frequency of a ball screw with preload is smaller than that of ball screw without preload due to friction caused by the preload. Results from both simulations and experiments show that the ball pass frequency can be detected using the method of Angular Velocity Vold-Kalman Filtering Order Tracking (AV VKF-OT). And AV VKF-OT provides a much better performance as compared to the traditional order tracking in terms of resolution and accuracy. Tests were conducted on ball screw feed drive systems with different preloads for the performance assessment of the ball pass frequency detection. Results show that the preload loss increases the ball pass frequency and also induces the side band around the ball pass frequency, which provides promising criteria in detecting the onset of preload loss of ball screws.

Tsai, P. C.; Cheng, C. C.; Hwang, Y. C.

2014-10-01

187

Role of Dynesys as Pedicle-Based Nonfusion Stabilization for Degenerative Disc Disorders  

PubMed Central

Posterior nonfusion pedicle-screw-based stabilization remains a controversial area of spine surgery. To date, the Dynesys system remains the most widely implanted posterior nonfusion pedicle screw system. We review the history of Dynesys and discuss clinical outcome studies and biomechanical evaluations regarding the Dynesys system. Indications for surgery and controversies are discussed. Recommendations are made regarding technical implantation. PMID:23326673

Anand, Neel; Baron, Eli M.

2012-01-01

188

Role of dynesys as pedicle-based nonfusion stabilization for degenerative disc disorders.  

PubMed

Posterior nonfusion pedicle-screw-based stabilization remains a controversial area of spine surgery. To date, the Dynesys system remains the most widely implanted posterior nonfusion pedicle screw system. We review the history of Dynesys and discuss clinical outcome studies and biomechanical evaluations regarding the Dynesys system. Indications for surgery and controversies are discussed. Recommendations are made regarding technical implantation. PMID:23326673

Anand, Neel; Baron, Eli M

2012-01-01

189

[Observations on before and after employ of screw of implant denture with SEM].  

PubMed

The loss of screw is one of the clinic complication in MDIC implant denture cases. The purpose of this study is to find the cause of loss of screw. The authors has studied MDIC implant denture with SEM before and after employ of the screw and found that the causes of screw loss were crevice corrosion and friction pressure. Crevice corrosion may promote the loss of screw. Base the above condition, it is necessary to select Ti-alloy screw and associat with anticorrosive measure in MDIC implant denture construction. PMID:10677963

Song, Y; Xu, J; Ma, X

1997-03-01

190

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

PubMed

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

Dong, Liang; Tang, Wen Cheng

2014-01-01

191

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

PubMed Central

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

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

2014-01-01

192

Mild coal gasification screw pyrolyzer development and design  

SciTech Connect

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.

Camp, D.W.

1990-08-01

193

[Dental reconstruction with non-precious metal screws and posts].  

PubMed

A short review of the current methods for restoring destroyed dental crowns by mechanical retentive elements. The causes leading to failure in such restorations are mentioned in a short review of literature. Main causes are corrosive changes in posts and screws anchored in root canals. This is why a special chapter deals with the problem of corrosion. A systematic enumeration of various corrosions in posts and screws is illustrated by a choice of clinical and radiological illustrations. The author's own metallurgical analytic investigations of the posts and screws available commercially allow to divide them into 4 typical nonprecious metal groups: Inox steel, cromium nickel steel, cromium nickel molybdene steel and brass alloys. The reasons for resistance to corrosion lie in the different metallographic structures and processing methods. Further investigations are finished and will be published later in this journal. PMID:392757

Wirz, J; Johner, M; Pohler, O

1979-11-01

194

SEM and fractography analysis of screw thread loosening in dental implants.  

PubMed

Biological and technical failures of implants have already been reported. Mechanical factors are certainly of importance in implant failures, even if their exact nature has not yet been established. The abutment screw fracture or loosening represents a rare, but quite unpleasant failure. The aim of the present research is an analysis and structural examination of screw thread or abutment loosening compared with screw threads or abutment without loosening. The loosening of screw threads was compared to screw thread without loosening of three different implant systems; Branemark (Nobel Biocare, Gothenburg, Sweden), T.B.R. implant systems (Benax, Ancona, Italy) and Restore (Lifecore Biomedical, Chaska, Minnesota, USA). In this study broken screws were excluded. A total of 16 screw thread loosenings were observed (Group I) (4 Branemark, 4 T.B.R and 5 Restore), 10 screw threads without loosening were removed (Group II), and 6 screw threads as received by the manufacturer (unused) (Group III) were used as control (2 Branemark, 2 T.B.R and 2 Restore). The loosened abutment screws were retrieved and analyzed under SEM. Many alterations and deformations were present in concavities and convexities of screw threads in group I. No macroscopic alterations or deformations were observed in groups II and III. A statistical difference of the presence of microcracks were observed between screw threads with an abutment loosening and screw threads without an abutment loosening. PMID:17897496

Scarano, A; Quaranta, M; Traini, T; Piattelli, M; Piattelli, A

2007-01-01

195

Failure of synthes anterior cervical fixation device by fracture of Morscher screws: a biomechanical study.  

PubMed

Anterior cervical fixation using the Synthes system has become increasingly popular. Two screw types for anchoring the plates include a "solid" titanium expansion screw and a plasma-sprayed fenestrated expansion screw that permits bony ingrowth. These screws were compared clinically and in the laboratory. In our first 20 cases using Synthes plates secured by Morscher fenestrated screws, 3 failures were observed, unilaterally in 1 patient and bilaterally in 2 others. In the unilateral screw failure, the contralateral screw was "solid" and did not fail. In the mechanical studies, screws were secured in the Synthes plate and embedded into methylmethacrylate and subjected to a sinusoidal bending moment to the mid-shaft of the screw. Load deflection data and cycles to failure were recorded. Fenestrated screws were found to demonstrate nearly twice as much deformation at failure and tolerated significantly fewer cycles to failure than did "solid" screws (p < 0.05). Because benefits of bony ingrowth into the screw are not well identified, the risks of fenestrated screw failure should preclude their routine use. PMID:8003828

Hollowell, J P; Reinartz, J; Pintar, F A; Morgese, V; Maiman, D J

1994-04-01

196

Long-term results of cemented and screwed acetabular components.  

PubMed

The authors report their experience in the use of various types of acetabular components (cemented and screwed) in 253 hip prostheses with "Biodirect" femoral component and ceramic femoral head. A long-term follow-up of 148 hip prostheses (58.5% of the total) was carried out, 36 Müller type polyethylene and 61 Biolox ceramic acetabular components, and 51 screwed sockets of various models were used. From a clinical and radiographical standpoint, the ceramic acetabular component proved the most valid in the short and medium term, confirming the favourable biomechanical conditions which derive from ceramic/ceramic coupling. PMID:8567260

Agrifoglio, E; Federici, A; Sanguineti, F; Maxena, S; Giacchè, P

1993-01-01

197

Virtual estimates of fastening strength for pedicle screw implantation procedures  

NASA Astrophysics Data System (ADS)

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.

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

2014-03-01

198

Knee joint stabilization therapy in patients with osteoarthritis of the knee and knee instability: Subgroup analyses in a randomized, controlled trial.  

PubMed

Objective: To test whether knee stabilization therapy, prior to strength/functional training, may have added value in reducing activity limitations only in patients with knee osteoarthritis who have knee instability and (i) low upper leg muscle strength, (ii) impaired knee proprioception, (iii) high knee laxity, or (iv) frequent episodes of knee instability. Design: Subgroup analyses in a randomized controlled trial comparing 2 exercise programmes (with/without knee stabilization therapy) (STABILITY; NTR1475). Patients: Participants from the STABILITY-trial with clinical knee osteoarthritis and knee instability (n?=?159). Methods: Effect modification by upper leg muscle strength, knee proprioception, knee laxity, and patient-reported knee instability were determined using the interaction terms "treatment group*subgroup factor", with the outcome measures WOMAC physical function (primary), numeric rating scale pain and the Get up and Go test (secondary). Results: Effect modification by muscle strength was found for the primary outcome (p?=?0.01), indicating that patients with greater muscle strength tend to benefit more from the experimental programme with additional knee stabilization training, while patients with lower muscle strength benefit more from the control programme. Conclusion: Knee stabilization therapy may have added value in patients with instability and strong muscles. Thus it may be beneficial if exercises target muscle strength prior to knee stabilization. PMID:24910399

Knoop, Jesper; van der Leeden, Marike; Roorda, Leo D; Thorstensson, Carina A; van der Esch, Martin; Peter, Wilfred F; de Rooij, Mariëtte; Lems, Willem F; Dekker, Joost; Steultjens, Martijn P M

2014-06-25

199

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

Code of Federal Regulations, 2010 CFR

...Jacks-lever and ratchet, screw, and hydraulic. 1926.305 Section 1926.305...Jacks—lever and ratchet, screw, and hydraulic. (a) General requirements. ...otherwise secured at once. (ii) Hydraulic jacks exposed to freezing...

2010-07-01

200

Biomechanical comparison of unilateral and bilateral pedicle screws fixation for transforaminal lumbar interbody fusion after decompressive surgery -- a finite element analysis  

PubMed Central

Background Little is known about the biomechanical effectiveness of transforaminal lumbar interbody fusion (TLIF) cages in different positioning and various posterior implants used after decompressive surgery. The use of the various implants will induce the kinematic and mechanical changes in range of motion (ROM) and stresses at the surgical and adjacent segments. Unilateral pedicle screw with or without supplementary facet screw fixation in the minimally invasive TLIF procedure has not been ascertained to provide adequate stability without the need to expose on the contralateral side. This study used finite element (FE) models to investigate biomechanical differences in ROM and stress on the neighboring structures after TLIF cages insertion in conjunction with posterior fixation. Methods A validated finite-element (FE) model of L1-S1 was established to implant three types of cages (TLIF with a single moon-shaped cage in the anterior or middle portion of vertebral bodies, and TLIF with a left diagonally placed ogival-shaped cage) from the left L4-5 level after unilateral decompressive surgery. Further, the effects of unilateral versus bilateral pedicle screw fixation (UPSF vs. BPSF) in each TLIF cage model was compared to analyze parameters, including stresses and ROM on the neighboring annulus, cage-vertebral interface and pedicle screws. Results All the TLIF cages positioned with BPSF showed similar ROM (<5%) at surgical and adjacent levels, except TLIF with an anterior cage in flexion (61% lower) and TLIF with a left diagonal cage in left lateral bending (33% lower) at surgical level. On the other hand, the TLIF cage models with left UPSF showed varying changes of ROM and annulus stress in extension, right lateral bending and right axial rotation at surgical level. In particular, the TLIF model with a diagonal cage, UPSF, and contralateral facet screw fixation stabilize segmental motion of the surgical level mostly in extension and contralaterally axial rotation. Prominent stress shielded to the contralateral annulus, cage-vertebral interface, and pedicle screw at surgical level. A supplementary facet screw fixation shared stresses around the neighboring tissues and revealed similar ROM and stress patterns to those models with BPSF. Conclusions TLIF surgery is not favored for asymmetrical positioning of a diagonal cage and UPSF used in contralateral axial rotation or lateral bending. Supplementation of a contralateral facet screw is recommended for the TLIF construct. PMID:22591664

2012-01-01

201

Interface effects on elastic behavior of a screw dislocation around double nanowires  

NASA Astrophysics Data System (ADS)

The elastic behavior of a screw dislocation around double nanowires (NWs) is addressed with taking into account the interface stress effect in controlling mechanical response of nanoscale structures. The stress boundary conditions at the interface of the NWs are modified by incorporating surface/interface stress. The analytic solution of complex functions of the right NW, the infinite matrix and the left NW are obtained by applying the complex variable method. The equilibrium positions and the image force acting on the dislocation of a screw dislocation near one of the NWs are discussed in detail and compared with those obtained within the classical theory of elasticity. It is shown that the NWs possess a significant local softening or hardening at the interface, which can change the nature of the equilibrium positions for the dislocation. The radius ratio between NWs has profound effects on the equilibrium position. Additionally, the soft NW with the positive interface stress inhibits the dislocation motion to enhance its own structural stability.

Li, Jia; Fang, Qihong; Liu, Youwen

2014-06-01

202

Hybrid dynamic modeling of a high-speed ball-screw drive system  

Microsoft Academic Search

The longitudinal and torsional vibration of a lead-screw usually limits the closed-loop performance of a high-speed ball-screw drive system. It is difficult to accurately characterize the high frequency dynamics of the ball-screw drive system via a traditional lumped modeling method. This paper proposes a hybrid parameter modeling method. The model contains a distributed parameter model of the lead-screw with the

Yan Liu; Tong Zhao; Hui Zhang

2010-01-01

203

New phenomena concerning a screw dislocation interacting with two imperfect interfaces  

NASA Astrophysics Data System (ADS)

Dislocation mobility and stability in nanocrystals and electronic materials are influenced by the material composition and interface conditions. Its mobility and stability then affect the mechanical behaviors of the composites. In this paper, we first address, in detail, the problem of a screw dislocation located in an annular coating layer which is imperfectly bonded to the inner circular inhomogeneity and to the outer unbounded matrix. Both the inhomogeneity-coating interface and coating-matrix interface are modeled by a linear spring with vanishing thickness to account for the possible damage occurring on the interface. An analytic solution in series form is derived by means of complex variable method, with all the unknown constants being determined explicitly. The solution is then applied to the study of the dislocation mobility and stability due to its interaction with the two imperfect interfaces. The most interesting finding is that when the middle coating layer is more compliant than both the inner inhomogeneity and the outer unbounded matrix and when the interface rigidity parameters for the two imperfect interfaces are greater than certain values, one stable and two unstable equilibrium positions can exist for the dislocation. Furthermore, under certain conditions an equilibrium position, which can be either stable or unstable (i.e., a saddle point), can exist, which has never been observed in previous studies. Results for a screw dislocation interacting with two parallel straight imperfect interfaces are also presented as the limiting case where the radius of the inner inhomogeneity approaches infinity while the thickness of the coating layer is fixed.

Wang, X.; Pan, E.; Roy, A. K.

2007-12-01

204

Joint Occupancy.  

ERIC Educational Resources Information Center

This annotated bibliography includes summaries of 15 articles and reports dealing with the joint use of buildings and facilities by schools and other public or private organizations. An introductory section describes the historical origins and development of the joint occupancy concept and examines the various economic and philosophical arguments…

Higham, Charlene Ellison

205

Ceramic joints  

DOEpatents

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.

Miller, Bradley J. (Worcester, MA); Patten, Jr., Donald O. (Sterling, MA)

1991-01-01

206

Incorporation of prefabricated screw, pneumatic, and solenoid valves into microfluidic devices  

E-print Network

Incorporation of prefabricated screw, pneumatic, and solenoid valves into microfluidic devices S This paper describes a method for prefabricating screw, pneumatic, and solenoid valves and embedding them a technique for creating standardized, prefabricated valves of three types--screw valves, pneumatic valves

Prentiss, Mara

207

Outcome Assessment after Aptis Distal Radioulnar Joint (DRUJ) Implant Arthroplasty  

PubMed Central

Background: Conventional treatments after complicated injuries of the distal radioulnar joint (DRUJ) such as Darrach and Kapandji-Sauvé procedures have many drawbacks, which may eventually lead to a painful unstable distal ulna. The development of DRUJ prosthesis has significantly evolved over the past years. In this study, we assessed the outcome results of patients after DRUJ implant arthroplasty using the Aptis (Scheker) prosthesis. Methods: We identified 13 patients with 14 prosthesis during the past 10 years. Patients underwent DRUJ arthroplasty due to persistent symptoms of instability, chronic pain, and stiffness. Records and follow-up visits were reviewed to find the final post-operative symptoms, pain, range of motion, and grip strength with a mean follow-up of 12 months (range: 2-25 months). Also, patients were contacted prospectively by phone in order to administer the disabilities of the arm shoulder and hand (DASH), patient rated wrist evaluation (PRWE), and visual analogue scale (VAS), and to interview regarding satisfaction and progress in daily activities. Eleven patients out of 13 could be reached with a median follow-up time of 60 months (range: 2 to 102 months). Results: No patient required removal of the prosthesis. Only two patients underwent secondary surgeries in which both required debridement of the screw tip over the radius. The median DASH score, PRWE score, VAS, and satisfaction were 1.3, 2.5, 0, and 10, respectively. The mean range of flexion, extension, supination, and pronation was 62, 54, 51, and 64, respectively. Conclusions: Distal radioulnar joint injuries are disabling and patients usually undergo one or more salvage surgeries prior to receiving an arthroplasty. The Scheker prosthesis has shown satisfactory results with 100% survival rate in all reports. The constrained design of this prosthesis gives enough stability to prevent painful subluxation. PMID:25386579

Kachooei, Amir Reza; Chase, Samantha M; Jupiter, Jesse B

2014-01-01

208

Piezoelectric actuators for screw-in cartridge valves  

Microsoft Academic Search

Research has been undertaken to explore the possibility of using smart materials for the actuation of screw-in cartridge valves. Four types were considered and a piezoelectric (PZT) stack was selected as the most appropriate actuator. The concept of a spool valve piloted by a PZT valve was chosen for investigation. A mathematical model of a hydraulic system with a spool

Xiaoping Ouyang; Derek Tilley; Patrick Keogh; Huayong Yang; Nigel Johnson; Chris Bowen; Peter Hopkins

2008-01-01

209

Probabilistic model and experimental identification of screw-attachment in  

E-print Network

for the screw-attachment of large light partition wall between plasterboard (CPC) plate and metallic frame in Materials Characterisation Location: New Forest, ENGLAND Date: JUN 17-19, 2009, New Forest : United Kingdom element is a large light partition wall with plasterboard using metallic frame. The plasterboard

Paris-Sud XI, Université de

210

The Use of Small Titanium Screws for Orthodontic Anchorage  

Microsoft Academic Search

The use of conventional dental implants for orthodontic anchorage is limited by their large size. The purpose of this study was to quantify the histomorphometric properties of the bone-implant interface to analyze the use of small titanium screws as an orthodontic anchorage and to establish an adequate healing period. Overall, successful rigid osseous fixation was achieved by 97% of the

T. Deguchi; T. Takano-Yamamoto; R. Kanomi; J. K. Hartsfield; W. E. Roberts; L. P. Garetto

2003-01-01

211

Intelligent Operation Parameters Optimization for Screw Conveyor Based on PSO  

Microsoft Academic Search

Particle swarm optimization (PSO) is a population based stochastic optimization technique. As a result, PSO algorithm is widely used in mechanical engineering design field. Screw conveyors are used extensively in agriculture and processing industries for elevating and\\/or transporting bulk materials over short to medium distances. They are very effective for conveying dry particulate solids, giving good control over the throughput.

Jianghui Cai; Wenjun Meng

2010-01-01

212

Screw dislocation in a two-phase isotropic thin film  

NASA Astrophysics Data System (ADS)

By using the complex potential and conformal mapping techniques, the stress field of a straight screw dislocation lying parallel to the surface of a two-phase isotropic thin film of equal thickness in each phase and a welded interface is analyzed. The solution, when reduced to a single-phase thin film, is in agreement with that derived by Liebfried and Dietze using an infinite array of image dislocations. The presence of a second phase is found to increase the magnitude of the stress components for the screw dislocation except for ?xz near the interface where the effect is the reverse. The image force on the dislocation near the interface can be attractive or repulsive depending upon whether the dislocation is situated in the hard or soft phase. In the case where the dislocation is situated in the soft phase, the total image force tends to drive the screw dislocation to the surface. Furthermore, the screw dislocation is found to be unstable at the interface. The elastic solution for an interfacial dislocation becomes a special case.

Chu, S. N. G.

1982-04-01

213

A molecular "screw-clamp": accelerating click reactions in miniemulsions.  

PubMed

The interface as a "screw clamp": the copper-free 1,3-dipolar azide-alkyne cycloaddition at the interface of nanodroplets in miniemulsions was studied in detail by NMR spectroscopic methods. The reaction at the oil-water interface proved to exhibit higher rate constants, increased molecular weights and high regioregularity compared to the reaction in solution. PMID:25068922

Alexandrino, Evandro M; Buchold, Philipp; Wagner, Manfred; Fuchs, Adrian; Kreyes, Andreas; Weiss, Clemens K; Landfester, Katharina; Wurm, Frederik R

2014-09-18

214

Throttling means for geothermal streams. [helical screw expander  

Microsoft Academic Search

A helical screw expander for deriving energy from geothermally heated water is described. The expander includes a pair of helical rotors with helical structures fitted in an expansion chamber. The geothermally heated water is introduced into said chamber through a throttle port located at an end face of the expansion chamber, whereby precipitation which occurs as a consequence of reduction

Sprankle

1976-01-01

215

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

216

Positive identification facilitated by implanted metallic plate and screws.  

PubMed

Personal identification is an essential subject in forensic practice. With skeletonized remains, an anthropological examination is performed for personal identification. Here we describe the positive identification of skeletonized human remains from the serial numbers of implanted metallic plate and screws. PMID:19534396

Kinoshita, Hiroshi; Motomura, Hiroyuki; Kasuda, Shogo; Nishiguchi, Minori; Matsui, Kiyoshi; Takahashi, Motonori; Ouchi, Harumi; Minami, Takako; Yamamura, Takehiko; Otsu, Nao; Yoshida, Shie; Adachi, Nobuyuki; Ohta, Takehiko; Hishida, Shigeru

2009-04-01

217

Screw fixation of medial malleolar fractures: a cadaveric biomechanical study challenging the current AO philosophy.  

PubMed

The AO Foundation advocates the use of partially threaded lag screws in the fixation of fractures of the medial malleolus. However, their threads often bypass the radiodense physeal scar of the distal tibia, possibly failing to obtain more secure purchase and better compression of the fracture. We therefore hypothesised that the partially threaded screws commonly used to fix a medial malleolar fracture often provide suboptimal compression as a result of bypassing the physeal scar, and proposed that better compression of the fracture may be achieved with shorter partially threaded screws or fully threaded screws whose threads engage the physeal scar. We analysed compression at the fracture site in human cadaver medial malleoli treated with either 30 mm or 45 mm long partially threaded screws or 45 mm fully threaded screws. The median compression at the fracture site achieved with 30 mm partially threaded screws (0.95 kg/cm(2) (interquartile range (IQR) 0.8 to 1.2) and 45 mm fully threaded screws (1.0 kg/cm(2) (IQR 0.7 to 2.8)) was significantly higher than that achieved with 45 mm partially threaded screws (0.6 kg/cm(2) (IQR 0.2 to 0.9)) (p = 0.04 and p < 0.001, respectively). The fully threaded screws and the 30mm partially threaded screws were seen to engage the physeal scar under an image intensifier in each case. The results support the use of 30 mm partially threaded or 45 mm fully threaded screws that engage the physeal scar rather than longer partially threaded screws that do not. A 45 mm fully threaded screw may in practice offer additional benefit over 30 mm partially threaded screws in increasing the thread count in the denser paraphyseal region. PMID:24293597

Parker, L; Garlick, N; McCarthy, I; Grechenig, S; Grechenig, W; Smitham, P

2013-12-01

218

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

NASA Astrophysics Data System (ADS)

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.

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

2011-04-01

219

Distal radioulnar joint injuries  

PubMed Central

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

Thomas, Binu P; Sreekanth, Raveendran

2012-01-01

220

Imaging of the patellofemoral joint.  

PubMed

The patellofemoral (PF) joint is a complex articulation, with interplay between the osseous and soft tissue structures to maintain the balance between knee mobility and stability. Disorders of the PF joint can be a source of anterior knee pain (AKP). In this article, radiographic and magnetic resonance imaging of the PF joint are reviewed, including normal anatomy, imaging techniques, and imaging-based measurements. Common imaging findings associated with AKP are reviewed, including symptomatic normal variants, tendinopathy, apophysitis, osteoarthritis, chondromalacia patella, trochlear dysplasia, excessive lateralization of tibial tuberosity, patellar maltracking, patellar dislocation and fractures, anterior bursitis, Morel-Lavallée effusions, and fat pad edema. PMID:24993408

Thomas, Stephen; Rupiper, David; Stacy, G Scott

2014-07-01

221

Comparison between the rigidity of bicortical screws and a miniplate for fixation of a mandibular setback after a simulated bilateral sagittal split osteotomy  

Microsoft Academic Search

Purpose: This investigation compared the biomechanical stability of three bicortical screws with that of a single four-hole miniplate after 5-mm mandibular setback after a bilateral sagittal split osteotomy (BSSO) in cadaver mandibles.Materials and Methods: Thirty human cadaver hemimandibles underwent BSSO followed by two different rigid fixation techniques. All specimens had no third molar, bony pathology, or evidence of mandibular fracture,

Wichit Tharanon

1998-01-01

222

Nonisothermal model of single screw extrusion of generalized Newtonian fluids  

SciTech Connect

A nonisothermal model of the single screw extrusion processing of generalized Newtonian fluids is presented. Various temperature dependent forms of a generalized Newtonian fluid constitutive equation representing the Herschel-Bulkley fluid and its simplifications, including Bingham plastic, power law of Ostwald-de Waele, and Newtonian fluids, are applicable. The model includes the generally ignored transverse convection terms of the equation of energy. The importance of keeping the transverse convection terms in the analysis is demonstrated by applying the model and comparing findings to experimental results involving the transverse flow temperature distributions in single screw extruders, available in the literature. The numerical instabilities, arising principally from the convection terms, generally encountered in high-Peclet-number extrusion flows, could be eliminated by the use of the streamline upwind/Petrov-Galerkin formulation. The model is sufficiently general to accommodate Navier's wall slip at the wall boundary condition commonly encountered during the processing of gels and concentrated suspensions.

Lawal, A.; Kalyon, D.M. (Stevens Inst. of Technology, Hoboken, NJ (United States). Highly Filled Materials Inst.)

1994-07-01

223

Analysis of Eyring-Powell fluid in helical screw rheometer.  

PubMed

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

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

2014-01-01

224

Wet-gas compression in twin-screw multiphase pumps  

E-print Network

)?????????????????? 9 2.3 Martin and Scott (2003)????????????????? 10 2.4 Cooper & Prang (2004)?????????????????. 12 2.5 University of Hannover (2004)??????????????. 13 2.6 Model Comparisons and Thermal Issues??????????.. 14 III METHODS... screws, a GVF of 95% is recommended to ensure that there is sufficient liquid in the pump. 3.4 High Viscosity Fluid Circulation Singh 6,7 , Martin 8,9 , and Cooper & Prang 13 have all presented evidence that shows that increasing the viscosity...

Chan, Evan

2009-05-15

225

Empirical modeling of a Lysholm helical screw expander  

Microsoft Academic Search

Testing of a Lysholm helical screw expander having a rotor diameter of 5.12 inches and an expansion ratio of 5.3 was performed with simulated geothermal fluid at an inlet pressure of 120 psia. The inlet quality, engine speed and pressure ratio were independently varied to produce a three-dimensional data matrix of 104 data points. Statistical curve fitting methods were adapted

K. A. Brown

1984-01-01

226

Cellulose and the twofold screw axis: modeling and experimental arguments  

Microsoft Academic Search

Crystallography indicates that molecules in crystalline cellulose either have twofold screw-axis (21) symmetry or closely approximate it, leading to short distances between H4 and H1? across the glycosidic linkage. Therefore,\\u000a modeling studies of cellobiose often show elevated energies for 21 structures, and experimental observations are often interpreted in terms of intramolecular strain. Also, some computer models\\u000a of cellulose crystallites have

Alfred D. French; Glenn P. Johnson

2009-01-01

227

The effect of stem material and surface treatment on the torsional stability at the metal-cement interface of upper limb joint replacement systems.  

PubMed

Stem surface treatment and material are two design factors that may affect the onset of implant loosening. For upper limb applications, no known in vitro studies have addressed the role of these two factors on cemented implant stability. Therefore, the purpose of this study was to compare the torsional stability of cemented titanium and cobalt chrome stems with varying surface treatments in vitro. Thirty implant stems of circular cross-section (Ø = 8mm) were machined from cobalt chrome (n = 15) and titanium (n = 15). For each type, stems were subdivided into three groups for application of clinically relevant surface treatments: smooth, sintered beads, or plasma spray. Stems were potted in bone cement, allowed 24 h to cure, and placed in a materials testing machine. Stems were tested under cyclic torsion (1-30 Nm), using a staircase loading protocol. Failure was defined as either the first rapid increase in stem rotation without resistance, or attaining a maximum torque of 30 Nm. Implant stems with non-smooth surfaces offered greater resistance to torsion (p < 0.05), with the plasma spray treatment outlasting the beaded and smooth stems (p < 0.05). Titanium offered superior interface strength (p < 0.05) but reduced resistance to motion (p < 0.05) when compared to cobalt chrome. Therefore, these design features should be considered during upper limb implant design. PMID:24644238

Hosein, Yara K; King, Graham J W; Dunning, Cynthia E

2014-08-01

228

Twin screw wet granulation: the study of a continuous twin screw granulator using Positron Emission Particle Tracking (PEPT) technique.  

PubMed

In this paper, Positron Emission Particle Tracking (PEPT) techniques are utilised to track the trajectory of single particles through the mixing and conveying zones of a Twin Screw Granulator (TSG). A TSG consisting of conveying zones and mixing zones is used in this study. The mixing zones are arranged with kneading discs at an angle of 30°, 60° or 90°. Experiments were carried out using different mixing configurations with various screw speed and total mass flow rate. The PEPT data obtained were then utilised to obtain the residence time distribution (RTD) and the Peclet number in an attempt to gain some insight into the mixing of the process. The fill level of the granulator was also estimated to study the mechanism of granulation. As might be expected, it was shown that the residence time of the granulation process increases with decreasing screw speed. It also increases with increasing angle of the arrangement of kneading blocks in the mixing zones, but will decreases when powder feed rate is increased. The fill level of the mixing zone in particular increases when the screw speed decreases or when powder feed rate increases. Furthermore, the fill level of the granulator will increase when the mixing zone configuration changes from 30° to 90°. It is shown that the granulator is never fully filled, even using 90° mixer elements implying limited compaction which may explain why the granules produced are porous compared with those from a high shear mixer. Interestingly, the RTD analysis reveals that the extent of axial mixing in the mixing zone of the granulator does not change significantly for different configurations and process conditions. There is evidence of a tail in the RTD which implies some material hold up and channelling. PMID:22561951

Lee, Kai T; Ingram, Andy; Rowson, Neil A

2012-08-01

229

Handbook on dynamics of jointed structures.  

SciTech Connect

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.

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

2009-07-01

230

Feasibility of Bilateral Crossing C7 Intralaminar Screws: A Cadaveric Study  

PubMed Central

Objective When the pedicle screw insertion technique is failed or not applicable, C7 intralaminar screw insertion method has been used as an alternative or salvage fixation method recently. However, profound understanding of anatomy is required for safe application of the bilaterally crossing laminar screw at C7 in clinic. In this cadaveric study, we evaluated the anatomic feasibility of the bilateral crossing intralaminar screw insertion and especially focused on determination of proper screw entry point. Methods The C7 vertebrae from 18 adult specimens were studied. Morphometric measurements of the mid-laminar height, the minimum laminar thickness, the maximal screw length, and spino-laminar angle were performed and cross-sectioned vertically at the screw entry point (spino-laminar junction). The sectioned surface was equally divided into 3 parts and maximal thickness and surface area of the parts were measured. All measurements were obtained bilaterally. Results The mean mid-laminar height was 13.7 mm, mean minimal laminar thickness was 6.6 mm, mean maximal screw length was 24.6 mm, and mean spinolaminar angle was 50.8±4.7°. Based on the measured laminar thickness, the feasibility of 3.5 mm diameter intralaminar screw application was 83.3% (30 sides laminae out of total 36) when assuming a tolerance of 1 mm on each side. Cross-sectional measurement results showed that the mean maximal thickness of upper, middle, and lower thirds was 5.0 mm, 7.5 mm, and 7.3 mm, respectively, and mean surface area for each part was 21.2 mm2, 46.8 mm2, and 34.7 mm2, respectively. Fourteen (38.9%) sides of laminae would be feasible for 3.5 mm intralaminar screw insertion when upper thirds of C7 spino-laminar junction is the screw entry point. In case of middle and lower thirds of C7 spino-laminar junction, 32 (88.9%) and 28 (77.8%) sides of laminae were feasible for 3.5 mm screw insertion, respectively. Conclusion The vertical cross-sectioned area of middle thirds at C7 spinolaminar junction was the largest area and 3.5 mm screw can be accommodated with 77.8% of feasibility when lower thirds were the screw entry point. Thus, selection of middle and lower thirds for each side of screw entry point in spino-laminar junction would be the safest way to place bilateral crossing laminar screw within the entire lamina. This anatomic study result will help surgeons to place the screw safely and accurately.

Baek, Tae-Hyun; Hong, Jae-Taek; Kim, Daniel H.; Shin, Dongsuk; Lee, Sang-Won

2014-01-01

231

Joint hypermobility  

Microsoft Academic Search

Joint hypermobility is an area of neglect in rheumatology. That is not to say it is overlooked by rheumatologists. It is spotted when sought, but for many unfortunate patients, here the story ends. The act of recognition becomes the goal in itself rather than the medium through which effective therapy can be provided. This chapter serves to reinforce the clinical

Rodney Grahame

2003-01-01

232

Research on energy conversion mechanism of a screw centrifugal pump under the water  

NASA Astrophysics Data System (ADS)

In order to research screw centrifugal pump impeller power capability and energy conversion mechanism, we used Navier-Stokes equation and standard k-? equation turbulence model on the basis of the Euler equations to carry out screw centrifugal pump internal flow numerical simulation. This was explored by simulating specific design conditions; the medium is water, variation of speed and pressure of flow filed under the action of the impeller, and the screw centrifugal impeller shroud line and wheel line segment take monitoring sites. The monitoring points are between dynamic head and static head change to analyze the energy conversion capability along the impeller corners of screw centrifugal pump. The results show that the energy of fluid of the screw centrifugal pump is provided by spiral segment, the spiral segment in front of the impeller has played a multi-level role, it has significant reference value to research the energy conversion mechanism of screw centrifugal pump under solid-liquid two phase.

Quan, H.; Li, R. N.; Su, Q. M.; Han, W.; Cheng, X. R.; Shen, Z. J.

2013-12-01

233

Thoracic Aortic Stent-Graft Placement for Safe Removal of a Malpositioned Pedicle Screw  

SciTech Connect

We describe a case of percutaneous placement of a thoracic aortic stent-graft for safe removal of a malpositioned pedicle screw in a 52-year-old man. The patient had undergone posterior thoracic spinal instrumentation for pyogenic spondylitis and spinal deformity 8 months previously. Follow-up CT images showed a malpositioned pedicle screw which was abutting the thoracic aorta at the T5 level. After percutaneous stent-graft placement, the malpositioned pedicle screw was safely and successfully removed.

Hu Hongtao [Henan Tumor Hospital, Department of Radiology (China); Shin, Ji Hoon, E-mail: jhshin@amc.seoul.kr; Hwang, Jae-Yeon; Cho, Young Jun; Ko, Gi-Young; Yoon, Hyun-Ki [University of Ulsan College of Medicine, Asan Medical Center, Department of Radiology and Research Institute of Radiology (Korea, Republic of)

2010-10-15

234

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

PubMed

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?screw orientation, the screws oriented at 23 degrees cephalad had a significantly higher failure force than their respective counterparts at 0 degrees (p?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

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

2014-02-01

235

Joint Replacement (Finger and Wrist Joints)  

MedlinePLUS

... A-Z Hand Anatomy Find a Hand Surgeon Joint Replacement Email to a friend * required fields From * To * ... be possible to treat arthritic joints surgically, including “joint replacement” procedures. What does it mean to have a “ ...

236

Accuracy of Free Hand Pedicle Screw Installation in the Thoracic and Lumbar Spine by a Young Surgeon: An Analysis of the First Consecutive 306 Screws Using Computed Tomography  

PubMed Central

Study Design A retrospective cross-sectional study. Purpose The purpose of this study is to evaluate the accuracy and safety of free-hand pedicle screw insertion performed by a young surgeon. Overview of Literature Few articles exist regarding the safety of the free-hand technique without inspection by an experienced spine surgeon. Methods The index surgeon has performed spinal surgery for 2 years by himself. He performed fluoroscopy-assisted pedicle screw installation for his first year. Since then, he has used the free-hand technique. We retrospectively reviewed the records of all consecutive patients undergoing pedicle screw installation using the free-hand technique without fluoroscopy in the thoracic or lumbar spine by the index surgeon. Incidence and extent of cortical breach by misplaced pedicle screw was determined by a review of postoperative computed tomography (CT) images. Results A total of 36 patients received 306 free-hand placed pedicle screws in the thoracic or lumbar spine. A total of 12 screws (3.9%) were identified as breaching the pedicle in 9 patients. Upper thoracic spine was the most frequent location of screw breach (10.8%). Lateral breach (2.3%) was more frequent than any other direction. Screw breach on the right side (9 patients) was more common than that on the left side (3 patients) (p<0.01). Conclusions An analysis by CT scan shows that young spine surgeons who have trained under the supervision of an experienced surgeon can safely place free-hand pedicle screws with an acceptable breach rate through repetitive confirmatory steps. PMID:24967036

Lee, Chang-Hyun; Kim, Yongjung J; Kim, Ki-Jeong; Jahng, Tae-Ahn; Kim, Hyun-Jib

2014-01-01

237

All-Arthroscopic Suprapectoral Long Head of Biceps Tendon Tenodesis With Interference Screw-Like Tendon Fixation After Modified Lasso-Loop Stitch Tendon Securing  

PubMed Central

Arthroscopic suprapectoral techniques for tenodesis of the long head of the biceps tendon (LHB) are appropriate for the treatment of proximal biceps lesions. Several types of techniques and fixation devices have been described and evaluated in biomechanical studies regarding primary stability. In this technical note, we describe an all-arthroscopic suprapectoral technique using the 6.25-mm Bio-SwiveLock device (Arthrex, Naples, FL) for an interference screw–like bony fixation after having armed the tendon with a lasso-loop stitch. Both the interference screw fixation and securing of the lasso-loop tendon have been well described and approved in biomechanical tests concerning the primary stability. One advantage of this technique performed from the glenohumeral space, in addition to the strong and secure fixation with ingrowth of the tendon in a bony canal, is the avoidance of touching the soft tissue above the bicipital groove, which results in a smooth fitting of the tendon into its natural canal and therefore avoids mechanical irritation of the stump at the rotator interval. In conclusion, the all-arthroscopic suprapectoral LHB tenodesis performed from the glenohumeral space with the modified lasso-loop stitch for securing of the tendon and the 6.25-mm Bio-SwiveLock suture anchor for interference screw–like bony tendon fixation is an appropriate technique for the treatment of LHB-associated lesions. PMID:23766976

Patzer, Thilo; Kircher, Jorn; Krauspe, Ruediger

2012-01-01

238

Joint hypermobility.  

PubMed

Joint hypermobility is an area of neglect in rheumatology. That is not to say it is overlooked by rheumatologists. It is spotted when sought, but for many unfortunate patients, here the story ends. The act of recognition becomes the goal in itself rather than the medium through which effective therapy can be provided. This chapter serves to reinforce the clinical and epidemiological importance of a common disorder whose significance is under-appreciated and impact largely ignored. In contradistinction to our earlier chapter, published in 2000, which took for its remit the heritable disorders of connective tissue in general, the current one focuses on the commonly encountered (so-called benign) joint hypermobility syndrome, its recognition, epidemiology, clinical features and management according to the most recent literature. PMID:15123047

Hakim, Alan; Grahame, Rodney

2003-12-01

239

Analysis of failure following anterior screw fixation of Type II odontoid fractures in geriatric patients.  

PubMed

Anterior screw fixation of Type II odontoid fractures has been recommended. Only few publications analyse the mechanism of failure in geriatric patients. We reviewed 18 male and 15 female patients aged 65 and above for parameters that influence the development of postoperative loss of correction, delayed union or non-union. Patients were stratified in two groups: 21 cases in Group A (union) and 12 patients in Group B (loss of correction, delayed union, non-union, revision surgery). Statistically significant correlation (p < 0.05) could be detected between failure to heal and: (1) degenerative changes in the atlanto-odontoid joint, (2) severity of osteoporosis in the odontoid process, (3) posterior oblique fracture type, (4) suboptimal fracture reduction, (5) suboptimal position of implant following demanding intraoperative conditions, (6) quality of fracture compression and (7) severity of fracture comminution. The overall morbidity and mortality rates were 29.0 and 8.6%, respectively. Our results indicate that these factors should be addressed regarding the selection of the operative treatment method in the geriatric patient. PMID:21728075

Osti, Michael; Philipp, Helmut; Meusburger, Berthold; Benedetto, Karl Peter

2011-11-01

240

Helical rotary screw expanders to generate electricity from geothermal brines  

SciTech Connect

A 1-megawatt, self-contained, helical rotary screw expander power plant to generate electricity of a geothermal brine wellhead was evaluated. The test support equipment, including a computer-controlled data system, an instrumentation and control van, and a 1000-kilowatt, variable bank were investigated. It was stated that the power was technically feasible although it operated at only about 45% average efficiency. Its technology transfer testing program involved Mexico, Italy, and New Zealand. The mineral laden geothermal brines of Mexico are more prone to scale formation than the Utah brine, and the power plant showed an increase in efficiency to a maximum of 62%.

Not Available

1983-09-01

241

Biocompatibility of ultra-high molecular weight polyethylene (UHMW-PE) stabilized with alpha-tocopherol used for joint endoprostheses assessed in vitro.  

PubMed

Adding the natural antioxidant alpha-tocopherol to ultra-high molecular weight polyethylene (UHMW-PE) can remarkably delay the oxidation of hip cups made thereof. However, alpha-tocopherol is likely to undergo different chemical transformations during manufacturing and sterilization of hip cups than in human metabolism. Therefore, the biocompatibility of the putative transformation products has to be investigated. In-vitro tests with L929 mice fibroblast-cells gave no evidence for cytotoxicity. To further ensure the biocompatibility, in-vitro tests with human cells were carried out in this study. Two different human cell lines, one adherent cell line, HF-SAR, and one suspension culture, GSJO, were tested on UHMW-PE-tablets (diameter: 15 mm; thickness: 2 mm; processed according to standard procedures for artificial hip-cups) with and without alpha-tocopherol with respect to cell viability, proliferation and morphology by means of cell counting, WSt-1 proliferation assay and scanning electron microscopy. Similar proliferation rates were found with both polyethylene samples. Further, we found intact morphology in light and electron microscopy on each substrate. The morphologic characteristics of skin fibroblasts were not changed by any material. Normal adherence and spreading of the fibroblasts was found on controls of glass, as well as on polystyrene and on stabilized and unstabilized polyethylene. The characteristic behaviour as suspension of the GSJO cells remained unchanged. The mitochondrial activity, as studied by WST-1 cell proliferation reagent, was identical on each substrate during the whole observation period of 7 days. PMID:17277986

Wolf, Christian; Lederer, Klaus; Pfragner, Roswitha; Schauenstein, Konrad; Ingolic, Elisabeth; Siegl, Veronika

2007-06-01

242

Prosopis pubescens (screw bean mesquite) seedlings are hyperaccumulators of copper.  

PubMed

Due to health reasons, toxic metals must be removed from soils contaminated by mine tailings and smelter activities. The phytoremediation potential of Prosopis pubescens (screw bean mesquite) was examined by use of inductively-coupled plasma optical emission spectroscopy. Transmission electron microscopy was used to observe ultrastructural changes of parenchymal cells of leaves in the presence of copper. Elemental analysis was used to localize copper within leaves. A 600-ppm copper sulfate exposure to seedlings for 24 days resulted in 31,000 ppm copper in roots, 17,000 ppm in stems, 11,000 in cotyledons and 20 ppm in the true leaves. For a plant to be considered a hyperaccumulator, the plant must accumulate a leaf-to-root ratio <1. Screw bean mesquite exposed to copper had a leaf-to-root ratio of 0.355 when cotyledons were included. We showed that P. pubescens grown in soil is a hyperaccumulator of copper. We recommend that this plant should be field tested. PMID:23612918

Zappala, Marian N; Ellzey, Joanne T; Bader, Julia; Peralta-Videa, Jose R; Gardea-Torresdey, Jorge

2013-08-01

243

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

PubMed Central

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

2014-01-01

244

PROPRIOCEPTION OF ANKLE JOINT IN YOUNG HOCKEY PLAYERS  

Microsoft Academic Search

factors that leads to progressive degeneration of the joint and continued deficits in joint dynamics, balance, and coordination. Much clinical research has demonstrated that individuals with proprioception and neuromuscular response deficits as a result of injury, lesions, and joint degeneration are less capable of maintaining postural stability and equilibrium. However, no normal reference data on ankle proprioception represented by kinesthesia

Jing Xian Li; Blaine Hoshizaki

245

Use of the intraosseous screw for unilateral upper molar distalization and found well balanced occlusion  

Microsoft Academic Search

BACKGROUND: The aim of this study was to present a temporary anchorage device with intraosseous screw for unilateral molar distalization to make a space for the impacted premolar and to found well balanced occlusion in a case. CASE PRESENTATION: A 13-year-old male who have an impacted premolar is presented with skeletal Class I and dental Class 2 relationship. The screw

Ibrahim Erhan Gelgor; Ali Ihya Karaman; Tamer Buyukyilmaz

2006-01-01

246

Chemical Engineering Science 54 (1999) 999--1013 Analysis of nonisothermal screw extrusion processing of  

E-print Network

Abstract Analytical solutions are developed for the flow and heat transfer in nonisothermal screw extrusionChemical Engineering Science 54 (1999) 999--1013 Analysis of nonisothermal screw extrusion processing of viscoplastic fluids with significant back flow Adeniyi Lawal *, Dilhan M. Kalyon Department

247

Analysis of nonisothermal screw extrusion processing of viscoplastic fluids with significant back flow  

Microsoft Academic Search

Analytical solutions are developed for the flow and heat transfer in nonisothermal screw extrusion processing of viscoplastic fluids with pressure back flow. The screw geometry is assumed to be shallow and the flight width small, thus enabling the flow to be modeled as that occurring between two infinitely long parallel plates, i.e., the generalized Couette flow. The constitutive equation is

Adeniyi Lawal; Dilhan M. Kalyon

1999-01-01

248

Retrieval of a fractured abutment screw thread from an implant: a case report  

Microsoft Academic Search

This report describes the management of a loose cement-retained implant supported crown where the thread of the abutment screw had fractured away from the body of the screw and was retained within the implant. The importance of multi-disciplinary skills in the treatment of patients with implants is discussed.

L. Rickman; J. Satterthwaite

2008-01-01

249

Terramechanics-based propulsive characteristics of mobile robot driven by Archimedean screw mechanism on soft soil  

Microsoft Academic Search

This paper describes the mathematical modeling and the propulsive characteristics of a novel robot driven by Archimedean screw mechanisms, named Screw Drive Rover. For secure locomotion on soft soil, the proposed rover would become one of the good solutions because of its robustness to slipping and getting stuck in the soil. Furthermore, the rover is expected to move in various

Kenji Nagaoka; Masatsugu Otsuki; Takashi Kubota; Satoshi Tanaka

2010-01-01

250

Tracking Control of Flexible Ball Screw Drives With Runout Effect and Mass Variation  

Microsoft Academic Search

Most machine tools rely on precision ball screw drives to accurately position the workpiece relative to the tool. The quality of the machining outcome depends significantly on the tracking performance of the workpiece position over a desired trajectory. This paper addresses the minimization of the tracking error in a ball screw drive system in the presence of dynamic variations. Three

Daniel Sepasi; Ryozo Nagamune; Farrokh Sassani

2012-01-01

251

Initial fixation strength of polylactic acid interference screws in anterior cruciate ligament reconstruction  

Microsoft Academic Search

The initial fixation properties of bioresorbable polylactic acid (PLA) interference screws designed for anterior cruciate ligament reconstruction were evaluated using an in vitro bovine model. The surgical technique of interference screw fixation of the bone-patellar tendon-bone autograft complex performed clinically was reproduced in an adult bovine model. The reconstructed knee was tested oriented in 30 degrees of flexion to allow

JA Abate; PD Fadale; MJ Hulstyn; WR Walsh

1998-01-01

252

Development of Solid-Lubricated Ball-Screws for Use in Space.  

National Technical Information Service (NTIS)

Ball-screws lubricated by solid lubricant films containing molybdenum disulphide are developed. The ball-screws (shaft diameter: phi 25 mm, length: 667 mm) were operated under a load of 40 to 120 N at a speed of 1.5 to 200 rpm at 10(exp -5) Pa. First, bal...

M. Chiba, T. Gyougi, M. Nishimura, K. Seki

1991-01-01

253

Electrical characterization of 4H-SiC avalanche photodiodes containing threading edge and screw dislocations  

Microsoft Academic Search

The reverse voltage current characteristics and electroluminescence of small area 4H-SiC avalanche photodiodes were investigated and correlated with the presence of threading screw and edge dislocations. Localized electroluminescence was observed at threading dislocations at voltages close to breakdown whereas diodes without any extended defects exhibited uniform light emission in the active area. Diodes containing either edge or screw dislocations were

R. A. Berechman; M. Skowronski; S. Soloviev; P. Sandvik

2010-01-01

254

Investigation of a Multiphase Twin-screw Pump Operating at High Gas Volume Fractions  

E-print Network

The use of twin-screw pumps for moving fluids is not new technology but its application to wet gas compression (high gas volume fraction [GVF]) is still considered relatively new. There are many advantages for using twin-screw pumps for oil field...

Kroupa, Ryan Daniel

2012-07-16

255

Mathematical modeling of the working cycle of oil injected rotary twin screw compressor  

Microsoft Academic Search

Oil injected twin-screw air and gas compressors are widely used for medium pressure applications in many industries. Low cost air compressors can be adopted for compression of helium and special gases, leading to significant cost saving. Mathematical analysis of oil injected twin-screw compressor is carried out on the basis of the laws of perfect gas and standard thermodynamic relations. Heat

N. Seshaiah; Subrata Kr. Ghosh; R. K. Sahoo; Sunil Kr. Sarangi

2007-01-01

256

16 CFR Figure 6 to Part 1633 - Burner Assembly Showing Arms and Pivots (Shoulder Screws), in Relation to, Portable Frame...  

Code of Federal Regulations, 2010 CFR

...Screws), in Relation to, Portable Frame Allowing Burner Height Adjustment 6 Figure 6 to Part 1633 Commercial Practices...Screws), in Relation to, Portable Frame Allowing Burner Height Adjustment...

2010-01-01

257

16 CFR Figure 6 to Part 1633 - Burner Assembly Showing Arms and Pivots (Shoulder Screws), in Relation to, Portable Frame...  

Code of Federal Regulations, 2013 CFR

...Screws), in Relation to, Portable Frame Allowing Burner Height Adjustment 6 Figure 6 to Part 1633 Commercial Practices...Screws), in Relation to, Portable Frame Allowing Burner Height Adjustment...

2013-01-01

258

16 CFR Figure 6 to Part 1633 - Burner Assembly Showing Arms and Pivots (Shoulder Screws), in Relation to, Portable Frame...  

...Screws), in Relation to, Portable Frame Allowing Burner Height Adjustment 6 Figure 6 to Part 1633 Commercial Practices...Screws), in Relation to, Portable Frame Allowing Burner Height Adjustment...

2014-01-01

259

Management of acromioclavicular joint injuries.  

PubMed

Acromioclavicular joint injuries are among the most common shoulder girdle injuries in athletes and most commonly result from a direct force to the acromion with the arm in an adducted position. Acromioclavicular joint injuries often present with associated injuries to the glenohumeral joint, including an increased incidence of superior labrum anterior posterior (SLAP) tears that may warrant further evaluation and treatment. Anteroposterior stability of the acromioclavicular joint is conferred by the capsule and acromioclavicular ligaments, of which the posterior and superior ligaments are the strongest. Superior-inferior stability is maintained by the coracoclavicular (conoid and trapezoid) ligaments. Type-I or type-II acromioclavicular joint injuries have been treated with sling immobilization, early shoulder motion, and physical therapy, with favorable outcomes. Return to activity can occur when normal shoulder motion and strength are obtained and the shoulder is asymptomatic as compared with the contralateral normal extremity. The management of type-III injuries remains controversial and is individualized. While a return to the previous level of functional activity with nonsurgical treatment has been documented in a number of case series, surgical reduction and coracoclavicular ligament reconstruction has been associated with a favorable outcome and can be considered in patients who place high functional demands on their shoulders or in athletes who participate in overhead sports. Surgical management is indicated for high-grade (?type IV) acromioclavicular joint injuries to achieve anatomic reduction of the acromioclavicular joint, reconstruction of the coracoclavicular ligaments, and repair of the deltotrapezial fascia. Outcomes after surgical reconstruction of the coracoclavicular ligaments have been satisfactory with regard to achieving pain relief and return to functional activities, but further improvements in the biomechanical strength of these constructs are necessary to avoid loss of reduction and creep with cyclic loading. PMID:24382728

Li, Xinning; Ma, Richard; Bedi, Asheesh; Dines, David M; Altchek, David W; Dines, Joshua S

2014-01-01

260

Atlantoaxial transarticular screw fixation and posterior fusion using ultra-high-molecular-weight polyethylene cable.  

PubMed

This article attempts to evaluate the effectiveness of the ultra-high-molecular-weight polyethylene (UHMW-PE) cable system in atlantoaxial transarticular screw fixation and posterior fusion through the clinical results of 10 postoperative patients with atlantoaxial subluxation secondary to rheumatoid arthritis. Among them, one patient with only one screw placed owing to an anomalous vertebral artery had the correction loss of the 3-mm atlas-dens interval after surgery. Another patient had a second operation to remove the screw and cable after 2 years 11 months because a unilateral transarticular screw had come to protrude through the lateral mass of the atlas ventrally. All patients had achieved C1-C2 osseous fusion without any complications associated with this cable system. The UHMW-PE cable is a very useful material as sublaminar wiring in atlantoaxial transarticular screw fixation and posterior fusion. PMID:16189448

Yonezawa, Ikuho; Arai, Yasuhisa; Tsuji, Takaaki; Takahashi, Masaki; Kurosawa, Hisashi

2005-10-01

261

Use of a quantitative pedicle screw accuracy system to assess new technology: Initial studies on O-arm navigation and its effect on the learning curve of percutaneous pedicle screw insertion  

Microsoft Academic Search

BackgroundA quantitative screw accuracy system is proposed that allows for high-fidelity discrimination between various methods of pedicle screw insertion. Our purpose was to study the utility of a quantitative screw accuracy scoring system to assess new imaging technologies and their effects on the minimally invasive spine learning curve.

Joseph A. Sclafani; Gilad J. Regev; Jonathan Webb; Steven R. Garfin; Choll W. Kim

2011-01-01

262

Magnetic resonance imaging analysis of the bioabsorbable Milagro™ interference screw for graft fixation in anterior cruciate ligament reconstruction  

Microsoft Academic Search

Ligament graft fixation with bioabsorbable interference screws is a standard procedure in cruciate ligament replacement. Previous\\u000a screw designs may resorb incompletely, and can cause osteolysis and sterile cysts despite being implanted for several years.\\u000a The aim of this study was to examine the in vivo degradation and biocompatibility of the new Milagro™ interference screw (Mitek,\\u000a Norderstedt, Germany). The Milagro™ interference screw

K.-H. Frosch; T. Sawallich; G. Schütze; A. Losch; T. Walde; P. Balcarek; F. Konietschke; K. M. Stürmer

2009-01-01

263

Novel free-hand T1 pedicle screw method: Review of 44 consecutive cases  

PubMed Central

Summary of Background Data: Multilevel posterior cervical instrumented fusions are becoming more prevalent in current practice. Biomechanical characteristics of the cervicothoracic junction may necessitate extending the construct to upper thoracic segments. However, fixation in upper thoracic spine can be technically demanding owing to transitional anatomy while suboptimal placement facilitates vascular and neurologic complications. Thoracic instrumentation methods include free-hand, fluoroscopic guidance, and CT-based image guidance. However, fluoroscopy of upper thoracic spine is challenging secondary to vertebral geometry and patient positioning, while image-guided systems present substantial financial commitment and are not readily available at most centers. Additionally, imaging modalities increase radiation exposure to the patient and surgeon while potentially lengthening surgical time. Materials and Methods: Retrospective review of 44 consecutive patients undergoing a cervicothoracic fusion by a single surgeon using the novel free-hand T1 pedicle screw technique between June 2009 and November 2012. A starting point medial and cephalad to classic entry as well as new trajectory were utilized. No imaging modalities were employed during screw insertion. Postoperative CT scans were obtained on day 1. Screw accuracy was independently evaluated according to the Heary classification. Results: In total, 87 pedicle screws placed were at T1. Grade 1 placement occurred in 72 (82.8%) screws, Grade 2 in 4 (4.6%) screws and Grade 3 in 9 (10.3%) screws. All Grade 2 and 3 breaches were <2 mm except one Grade 3 screw breaching 2-4 mm laterally. Only two screws (2.3%) were noted to be Grade 4, both breaching medially by less than 2 mm. No new neurological deficits or returns to operating room took place postoperatively. Conclusions: This modification of the traditional starting point and trajectory at T1 is safe and effective. It attenuates additional bone removal or imaging modalities while maintaining a high rate of successful screw placement compared to historical controls.

Rivkin, Mark A.; Okun, Jessica F.; Yocom, Steven S.

2014-01-01

264

Joint Sealants for Horizontal Pavement Joints—Specifically Bridge Joints  

Microsoft Academic Search

The various types of materials that have been used to seal bridge joints have been reviewed. Some of the bridge engineers joint material requirements have been listed together with the advantages and disadvantages of the three most widely used bridge joint sealants being specified and used today. It is felt that the cold applied two component asphalt-modified polyurethane sealants come

Thomas J. Green

1969-01-01

265

Gear-Cutting Tool for Screw-Compressor Rotors  

NASA Astrophysics Data System (ADS)

A built-up hob for a screw-compressor rotor is proposed. The hob is composed of cutter blades and a hob head. The blade is cut out from a tempered planar plate of high speed tool steel by wire-cut electrodischarge machining (EDM). During the wire cutting process, the wire electrode has a fixed angle to ensure both the side and the end relief angle of the cutting edge, so that the rake face regrinding sharpens the cutting edge without changing the profile of the rake face. In other words, theoretically, the hob has no accuracy deterioration due to rake face regrinding. The formulae of rack tooth profile are derived from the female rotor tooth profile experssed by numerical formulae. Next, the fundamental helicoid of the hob the profile of the cutting edge of the blade are calculated. The hob was fabricated and the rotor hobbing was carried out.

Kaneko, Katsumi; Kawasaki, Kazumasa; Tamura, Hisashi

266

Repair of spondylolytic defect with a cable screw reconstruction.  

PubMed

We present the clinical and radiological results of surgical repair for refractory spondylolysis in 20 patients at a minimum follow-up of 2 years. Seventeen of them were reassessed after 5 years. The Oswestry scores revealed good to excellent results in 90% (18/20 patients), indicating a good outcome with surgical repair using two techniques: the Scott procedure or pedicle screw and wire technique. Radiological pseudarthosis was 10%, which was quite consistent with reported series. CT scanning of the 14 patients after a mean of 13 months revealed complete healing of the fracture in 7 patients, partial in 2 and frank non-union in 5. Overall, CT examination with reversed gantry showed only 7/14 (50%) healing, indicating that radiological healing on plain X-ray is not always suggestive of complete bony healing. However, CT healing is not a sine qua non of good to excellent clinical outcome. PMID:17431623

Pai, Vasudeva S; Hodgson, Bruce; Pai, Vishal

2008-02-01

267

Role of the O-arm and Computer-assisted Navigation of Safe Screw Fixation in Children with Traumatic Rotatory Atlantoaxial Subluxation  

PubMed Central

Study Design A retrospective analysis of 7 patients with traumatic rotatory atlanto-axial subluxation. Overview of Literature Cases of traumatic rotatory atlantoaxial subluxation in children are difficult to be stabilized. Surgical challenges include: narrow pedicles, medial vertebral arteries, vertebral artery anomalies, fractured pedicles or lateral masses, and fixed subluxation. The use of O-arm and computer-assisted navigation are still tested as aiding tools in such operative modalities. Purpose Report of clinical series for evaluation of the safety of use of the O-arm and computed assisted-navigation in screw fixation in children with traumatic rotatory atlantoaxial subluxation. Methods In the present study, 7 cases of rotatory atlantoaxial traumatic subluxation were operated between December 2009 and March 2011. All patient-cases had undergone open reduction and instrumentation using atlas lateral mass and axis pedicle screws with intraoperative O-arm with computer-assisted navigation. Results All hardware was safely placed in the planned trajectories in all the 7 cases. Intraoperative O-arm and computer assisted-navigation were useful in securing neural and vascular tissues safety with tough-bony purchases of the hardware from the first and only trial of application with sufficient reduction of the subluxation. Conclusions Successful surgery is possible with using the intraoperative O-arm and computer-assisted navigation in safe and proper placement of difficult atlas lateral mass and axis pedicle screws for rotatory atlantoaxial subluxation in children. PMID:23275810

Orief, Tamer; Almusrea, Khaled; Alfawareh, Mohamed; Soualmi, Lahbib; Orz, Yasser

2012-01-01

268

Synthesis and Helical Structures of Poly(?-alkynamide)s Having Chiral Side Chains: Effect of Solvent on Their Screw-Sense Inversion.  

PubMed

New ?-alkynamides, (S)-HC?CCH2 CONHCH2 CH(CH3 )CH2 CH3 (1) and (S)-HC?CCH2 CH2 CONHCH(CH3 )CH2 CH2 CH2 CH2 CH3 (2) were synthesized and polymerized with a rhodium catalyst in CHCl3 to obtain cis-stereoregular poly(?-alkynamide)s (poly(1) and poly(2)). Polarimetric, CD, and IR spectroscopic studies revealed that in solution the polymers adopted predominantly one-handed helical structures stabilized by intramolecular hydrogen bonds between the pendent amide groups. This behavior was similar to that of the corresponding poly(N-alkynylamide) counterparts (poly(3) and poly(4)) reported previously, whereas the helical senses were opposite to each other. The helical structures of the poly(?-alkynamide)s were stable upon heating similar to those of the poly(N-alkynylamide)s, but the solvent response was completely different. An increase in MeOH content in CHCl3 /MeOH resulted in inversion of the predominant screw-sense for poly(1) and poly(2). Conversely, poly(3) was transformed into a random coil, and poly(4) maintained the predominant screw-sense irrespective of MeOH content. The solvent dependence of predominant screw-sense for poly(1) and poly(2) was reasonably explained by molecular orbital studies using the conductor-like screening model (COSMO). PMID:25264082

Suzuki, Yuji; Miyagi, Yu; Shiotsuki, Masashi; Inai, Yoshihito; Masuda, Toshio; Sanda, Fumio

2014-11-10

269

Flow and pressure characteristics within a screw compressor  

NASA Astrophysics Data System (ADS)

The angle-resolved mean and turbulence characteristics of the axial air flow inside a screw compressor with both male and female rotors have been measured, using a laser Doppler velocimeter (LDV) with high spatial and temporal resolution at different radial and axial locations for speeds of 800-1600 rpm, discharge pressures of 1-1.6 bar and discharge temperatures of 33-90°C. The velocity measurements were performed through a special transparent window fixed near the discharge port. The results confirmed the ability of the LDV technique to characterise the flow inside the compressor working chamber; an angular resolution of 1.5° was able to fully describe the velocity field within the machine. The flow variation between the different working chambers was established as well as the spatial variation of the axial mean velocity and turbulence velocity fluctuation within the working chamber. The effect of discharge port opening on the axial mean and RMS velocities was found to be significant near the leading edge of the rotors causing an increase in the mean and RMS velocities of the order of 4.2Vp in mean (where Vp is the axial pitched velocity) for male rotor and 5.4Vp for, female rotor and this effect is less pronounced on the flow near the root of the rotor. Moreover, to obtain a better understanding of the flow motion, a high sampling rate pressure transducer was used to provide the internal angular static pressure variation. These measurements are used to validate the in-house CFD model of the fluid flow within twin screw compressors which, in turn, allows reliable optimisation of various compressor designs.

Guerrato, D.; Nouri, J. M.; Stosic, N.; Arcoumanis, C.

2007-10-01

270

Alkaline twin-screw extrusion pretreatment for fermentable sugar production  

PubMed Central

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

2013-01-01

271

An investigation of the effects of hydroxyapatite coatings on the fixation strength of cortical screws.  

PubMed

Hydroxyapatite (HA) are commonly applied to orthopaedic implants for acceleration of osteointegration and so overcoming the loosening problems such as in cortical screws. Electrophoretic deposition (EPD) of hydroxyapatite was applied for coating of cortical screws in this work. The effects of hydroxyapatite-coated and uncoated cortical screws on insertion and extraction torque were investigated through in vivo experiments. Three groups of screws were undertaken: first group with no coating, second group coated with HA and the third group coated with HA+interlayer, a synthetic calcium silicate compound. Five sheep were operated, and 60 cortical (20 x 3) screws from those of groups were implanted in cortical femurs to observe the effect of HA and interlayer on screws. Results show that as an alternative to plasma spray coating method, the EPD process enables to produce a quick, easy, cheap and uniform adjustable coating layer. Also from biomechanical and SEM examinations, HA coating by EPD method of cortical screws resulted in extremely improved fixation with reduced risk of loosening problem. PMID:15694605

Yildirim, O S; Aksakal, B; Celik, H; Vangolu, Y; Okur, A

2005-04-01

272

Effect of bone mineral density and amorphous diamond coatings on insertion torque of bone screws.  

PubMed

In this study, the potential of high-quality amorphous diamond (AD) coatings in reducing the torque and failures of bone screws was studied. Torque values were recorded for 32 stainless steel screws, 2.7 or 3.5 mm in diameter and 60 mm in length. Half of the screw sets were coated with the AD coating before installing in predrilled holes of human cadaveric femoral bone samples. The bone samples were selected from two groups of four persons with mean ages of 34 years (range 25-41 years) and 75 years (range 73-77 years), respectively. The bone mineral density (BMD) values of the samples were determined exactly at the screw insertion site by peripheral quantitative computed tomography (pQCT). In the mechanical tests, insertion and removal torques were measured. BMD had a significant effect on insertion torque; the maximum torque (adjusted with respect to the screw diameter) was significantly higher for the young bone than for the old bone (p < 0.05). By using a polished AD coating, insertion torque was decreased even up to 50% in comparison with the screws without coating. The results suggest that AD coating provides a stable, smooth surface and reduces the risk of screw failures. PMID:15878374

Koistinen, Arto; Santavirta, Seppo S; Kröger, Heikki; Lappalainen, Reijo

2005-10-01

273

Radiation-free Insertion of Distal Interlocking Screw in Tibial and Femur Nailing: A Simple Technique  

PubMed Central

Background: Distal interlocking screw insertion in intramedullary nailing of long-bone fracture is a challenging task for orthopedic surgeons. It is difficult particularly when the surgeon is in his learning stage or when image intensifier is not available. We describe a radiation-free technique of distal interlocking screw insertion which is easy and practicable. Materials and Methods: In this technique, a same length nail is placed over the skin (outer nail) and through its distal-most screw hole, a 3.2 mm drill bit is inserted to drill the distal locking screw hole of the intramedullary nail (inner nail). With a small skin incision over the distal screw holes, the distal-most screw hole is identified; the bone window overlying the screw hole is widened with an awl and a locking bolt is inserted with a washer under direct visualization. The other distal interlocking screw is simply drilled by matching the other three holes of the outer and inner nails. We have operated 86 patients (39 femoral shaft fracture and 47 tibial shaft fracture) in 1 year where this technique was used. There were 41 open fracture and 45 closed fracture. Results: Within 6 months of follow-up, bony union was achieved in 36 of 39 femur fractures and 45 of 47 tibial fractures. No unwanted complications were observed during the postoperative period and in follow-up. Conclusion: This method of radiation-free distal interlocking screw insertion is simple and can be used in third world country where image intensifier facility is not available. However, surgeons are encouraged to use image intensifier facility where the facility is available. PMID:23066456

Soni, Ritesh Kumar; Mehta, Surender Mohan; Awasthi, Bhanu; Singh, Janith Lal; Kumar, Amit; Thakur, Lokesh; Tripathy, Sujit Kumar

2012-01-01

274

Navigated pedicle screw placement using computed tomographic data in dorsolumbar fractures  

PubMed Central

Background: Computed tomographic (CT) based navigation is a technique to improve the accuracy of pedicle screw placement. It is believed to enhance accuracy of pedicle screw placement, potentially avoiding complications arising due to pedicle wall breach. This study aims to assess the results of dorsolumbar fractures operated by this technique. Materials and Methods: Thirty consecutive skeletally mature patients of fractures of dorsolumbar spine (T9–L5) were subjected to an optoelectronic navigation system. All patients were thoroughly examined for neurological deficit. The criterion for instability were either a tricolumnar injury or presence of neurological deficit or both. Patients with multilevel fractures and distorted spine were excluded from study. Time taken for insertion of each pedicle screw was recorded and placement assessed with a postoperative CT scan using Laine's grading system. Results: Only one screw out of a total of 118 screws was misplaced with a Laine's Grade 5 placement, showing a misplacement rate of 0.847%. Average time for matching was 7.8 min (range 5-12 min). Average time taken for insertion of a single screw was 4.19 min (range 2-8 min) and total time for all screws after exposure was 34.23 min (range 24-45 min) for a four screw construct. No neurovascular complications were seen in any of the patients postoperatively and in subsequent followup of 1-year duration. Conclusion: CT-based navigation is effective in improving accuracy of pedicle screw placement in traumatic injuries of dorsolumbar spine (T9-L5), however additional cost of procuring CT scan to the patient and cost of equipment is of significant concern in developing countries. Reduced radiation exposure and lowered ergonomic constraints around the operation table are its additional benefits.

Kapoor, Saurabh; Sharma, Rajbahadur; Garg, Sudhir; Jindal, Rohit; Gupta, Ravi; Goe, Anshul

2014-01-01

275

Wall-locking of kink modes in a line-tied screw pinch with a rotating wall  

SciTech Connect

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.

Paz-Soldan, C.; Brookhart, M. I.; Hegna, C. C.; Forest, C. B. [Physics Department, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States)

2012-05-15

276

Screw-rotation twinning through helical movement of triple-partials  

NASA Astrophysics Data System (ADS)

By in situ uniaxial-tensile tests with dynamic and atomic scale observation, we report the quantitative investigation of strain-induced deformation-twinning process through incoherent twin boundary propagation in nanocrystalline Au. The consecutive and quantitative strain maps revealed that a strong compressive strain, up to 5.8%, was formed. A screw-rotation twinning mechanism by consecutive and collective screw-rotations of triple-partials along a [111] screw-axis is proposed. This twin generates a macro-strain of 0.707, same as the conventional shear twins, but in a helical manner.

Liu, Pan; Du, Kui; Zhang, Jianxin; Wang, Lihua; Yue, Yonghai; Ma, Evan; Zhang, Yuefei; Zhang, Ze; Chen, Mingwei; Han, Xiaodong

2012-09-01

277

Sapphire screws and strength test on them at liquid nitrogen temperature  

NASA Astrophysics Data System (ADS)

We fabricated several sapphire screw threads and performed a strength test on them at the liquid nitrogen temperature of 77 K. The screw threads were subjected to and withstood a 3000 N load. To the best of our knowledge, this is the first strength test of sapphire screw threads at a cryogenic temperature. The result suggests a new way of connecting sapphire components. Although sapphire is already used in many applications, the result may provide a new way to use the material as a structural element in even more applications.

Hirose, Eiichi; Sakakibara, Yusuke; Igarashi, Yukihiko; Ishii, Takashi

2014-10-01

278

Four-Screw Plate Fixation vs Conventional Fixation for Diaphyseal Fractures of the Forearm  

PubMed Central

Background: Standard treatment of diaphyseal fractures of the forearm is open reduction and fixation using dynamic compression plates (DCP) and screws. This technique uses screw placement in all 6 or more of the plate holes except the hole over the fracture line. We hypothesized that DCP with selective 4-screw bicortical placement can provide adequate fixation for these fractures. Objectives: The aim of this study was to evaluate the results of conventional 6 or more screw fixation versus 4 screw fixation for adults with diaphyseal fractures of the forearm. Patients and Methods: In this prospective study, 128 fractures of the ulna, radius or both bones of the forearm in 87 patients were treated in either one of these two groups: Open reduction and internal fixation (ORIF) with conventional DCP and screws or ORIF using DCP and selective 4- screw placement. Fractures were transverse or oblique in pattern without gross comminution. In a total of 41 patients with fractures, 28 single ulnar and 18 single radius fractures were included. Follow-up visits were done at 3-6 and 12-16 weeks and at 6 months. Outcome with respect to union an nonunion rates, union time, infection, and device failure was noted. Results: No change in alignment was noted in any patient. Union time in conventional and selective bicortical 4-screw fixation was 74.8 days and 73.6 days respectively which showed no significant difference (P = 0.064). Union rate and infection was 92.1% and 3.2% in conventional and 95.3% and 0% in the selective group respectively. Non-union was observed in 5 and 3 cases of fractures in conventional and the selective group respectively. Conclusions: For treatment of the transverse or oblique diaphyseal fractures of the forearm, fixation by a same length 3.5 mm DCP with selective 4-screw cortical fixation (2 screws on each side of the fracture site) had similar results in comparison with conventional 6 or more DCP screws. Because of lesser impact on host bone and smaller incision, the selective 4-screw insertion can be an alternative technique for treatment of these fractures. PMID:24829892

Mehdi Nasab, Seyed Abdolhossein; Sarrafan, Nasser; Sabahi, Saeed

2012-01-01

279

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

PubMed Central

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

O'Shea, Kieran; Burke, Tom

2006-01-01

280

Posterior pelvic ring fractures: Closed reduction and percutaneous CT-guided sacroiliac screw fixation  

Microsoft Academic Search

Purpose  To assess the midterm results of closed reduction and percutaneous fixation (CRPF) with computed tomography (CT)-guided sacroiliac\\u000a screw fixation in longitudinal posterior pelvic ring fractures.\\u000a \\u000a \\u000a \\u000a Methods  Thirteen patients with 15 fractures were treated. Eleven patients received a unilateral, two a bilateral, screw fixation.\\u000a Twenty-seven screws were implanted. Continuous on-table traction was used in six cases. Mean radiological follow-up was 13\\u000a months.

Augustinus Ludwig Jacob; Peter Messmer; Klaus-Wilhelm Stock; Norbert Suhm; Bernard Baumann; Pietro Regazzoni; Wolfgang Steinbrich

1997-01-01

281

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

PubMed Central

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

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

2013-01-01

282

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

PubMed Central

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

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

2013-01-01

283

Spacesuit mobility joints  

NASA Technical Reports Server (NTRS)

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.

Vykukal, H. C. (inventor)

1978-01-01

284

Spacesuit mobility knee joints  

NASA Technical Reports Server (NTRS)

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.

Vykukal, H. C. (inventor)

1979-01-01

285

Medial column stabilization.  

PubMed

This article presented a brief review of medial column stabilizing procedures. The various types of procedures that have been advocated for different deformities have been discussed. It is important to keep in mind that fusion of any of the medial column joints should not be performed as an isolated procedure in flexible flatfoot deformity. Medial column stabilization is only a component procedure when surgically managing a flexible flatfoot. When choosing procedures to correct a flexible flatfoot, thorough preoperative evaluation is important. It is also important to realize that conservative measures should be exhausted before attempting any type of stabilization of the medial column for flexible flatfoot deformity. Specific criteria for flexible flatfoot surgery should include severe uncontrollable deformity, an inability to wear standard foot gear, and persistent pain and disability despite exhaustive conservative therapy. A medial column stabilization is also an excellent procedure for those patients who have end-stage degenerative joint disease of the medial longitudinal arch. PMID:1893342

Catanzariti, A R

1991-07-01

286

[Prosthetics of metacarpophalangeal joints].  

PubMed

Only a few of the large number of implants developed during the last decades for replacement of the metacarpophalangeal (MCP) joint have proven to be reliable. The rates of loosening and mechanical failure of almost all types of constrained prostheses are so high that their use cannot be recommended at present. For more than 40 years silicone arthroplasty according to Swanson has been regarded as the gold standard in the prosthetic replacement of the MCP joint. In long-term studies this device provided good pain relief and a lasting correction of preoperative ulnar deviation. The degree of patient satisfaction continues to be high after more than 10 years. With the NeuFlex spacer, a modification of the original Swanson implant, a better range of motion and a reduction of wear-related problems is expected. In this study the results of 130 NeuFlex spacers after a mean time of 3.6 years were examined and 82% of the patients were completely pain free. The mobility of the joints improved from 40 degrees preoperatively to 54 degrees after 3.6 years. Radiologically periprosthetic erosions or osteolyses were seen in approximately 15% of implants. A minimal sinking of the stems developed in 24%, a massive one in 6% and 13% of the spacers were broken. Thus the use of the NeuFlex implant resulted in a better range of motion compared to the Swanson spacer, but the problem of radiological appearance remained unchanged. For unlinked prostheses sufficient soft tissue stability is mandatory as well as wear-resistant surface materials. The pyrocarbon prosthesis according to Beckenbaugh is the only implant for which long-term results are available. In a prospective study we evaluated 28 Ascension pyrocarbon prostheses with a mean follow-up of 4 years. Stability was not found to be a problem. Subjective results were satisfactory, the range of motion remained unchanged, however 46% of prosthesis stems exhibited radiolucent seams, 7 prostheses (25%) were rated as loose and 5 of those had to be replaced by a silicone implant. Use of the implant was abandoned, as it was unreliable regarding bony fixation. There are promising concepts in some new prostheses but independent data are still lacking. PMID:17717677

Hilker, A; Miehlke, R-K; Schmidt, K

2007-09-01

287

Analysis of stress induced by screws in the vertebral fixation system  

PubMed Central

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

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

2014-01-01

288

Three point lead screw positioning apparatus for a cavity tuning plate  

NASA Technical Reports Server (NTRS)

Three lead screws are provided for adjusting the position of a traversing plate. Each of the three lead screws is threaded through a collar that is press fitted through the center of one of three pinion gears. A sun gear meshes with all three pinion gears and transversely moves the three lead screws upon actuation of a drive gear. The drive gear meshes with the sun gear and is driven by a handle or servomotor. When the handle or servomotor rotates the drive gear, the sun gear rotates causing the three pinion gears to rotate, thus, causing transverse movement of the three lead screws and, accordingly, transverse movement of the transversing plate. When the drive gear rotates, the traversing plate is driven in and out of a microwave cavity. Thus, the length or size of the cavity can be tuned while maintaining the traversing plate in an exact parallel relationship with an opposing plate on another end of the cavity.

Calco, Frank S. (inventor)

1993-01-01

289

Mechanically Working Fully-Automatic Plant for the Regeneration of Used Aluminum Cap Screws for Bottles.  

National Technical Information Service (NTIS)

A mechanical separation process for used aluminum cap screws for bottles is described. A prototype separation plant was developed and constructed. Test results indicate low energy consumption, no water pollution, and no emission of noxious vapors.

V. Schach, H. Schach

1983-01-01

290

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

...SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR (CONTINUED) SAFETY AND HEALTH REGULATIONS FOR CONSTRUCTION Tools-Hand and Power § 1926.305 Jacks—lever and ratchet, screw, and hydraulic. (a) General requirements. (1)...

2014-07-01

291

Modeling of wet gas compression in twin-screw multiphase pump  

E-print Network

Twin-screw multiphase pumps experience a severe decrease in efficiency, even the breakdown of pumping function, when operating under wet gas conditions. Additionally, field operations have revealed significant vibration and thermal issues which can...

Xu, Jian

2009-05-15

292

Intermaxillary fixation screw for endotracheal tube fixation in the edentulous patient with facial burns.  

PubMed

Endotracheal tube fixation in patients with severe facial burns and edentulism is a challenge. We describe a simple and elegant method to secure the endotracheal tube in such patients by means of an intermaxillary fixation screw. PMID:24948409

Fleissig, Y; Rushinek, H; Regev, E

2014-10-01

293

Screw implantation in the globe: the risk of delayed hardware migration from craniofacial repair.  

PubMed

Plating system modification has enabled the use of rigid fixation in younger patients having maxillofacial surgery. One of the common reported complications of the use of plates and screws in children is screw migration due to skeletal maturation. Ophthalmic complications due to maxillofacial surgery reported to date include oculomotor and abducens palsies, lacrimal damage and vision loss due to infection, retrobulbar hemorrhage, and compartment syndrome. We describe a complication unique to screw migration resulting in orbital fixation and near-globe rupture in a patient with Treacher Collins syndrome. We hope to alert our colleagues to the potential risk of screw and hardware migration and breakage, particularly in the setting of craniofacial surgery performed on a child before maturation of craniofacial osseous structures. PMID:24036744

Sadiq, Mohammad Ali A; Prabhu, Sanjay P; Fearon, Jeffrey A; Taghinia, Amir H; Dagi, Linda R

2013-09-01

294

Biomechanical measurements of cortical screw purchase in five types of human and artificial humeri.  

PubMed

Humerus shaft fracture fixation is largely dependent on cortical screw purchase in host bone. Only 2 prior studies assessed cortical screw purchase in human humeral shafts, but were of very limited scope and did not fully assess humerus material properties. Also, no studies evaluated the human dried or artificial humeri both commercially available from Sawbones. Vashon, WA, USA. Therefore, present authors measured cortical screw purchase in human fresh-frozen (FF) (n=19), human embalmed (EM) (n=18), human dried (DR) (n=14), artificial "normal" (AN) (n=13), and artificial "osteoporotic" (AO) (n=13) humeri. Each humerus had 2 bicortical screws of 3.5-mm diameter inserted 20mm apart through the shaft's anterior and posterior cortices. Absolute force, displacement, and energy for screw-bone interface failure were measured by screw pullout tests, afterwhich data were normalized by total surface area engaged at the screw-bone interface. For absolute force, AN humeri reached a higher load than EM (p=0.001) and AO (p<0.001) humeri, whilst AN humeri achieved lower normalized force than DR humeri (p=0.018). For absolute displacement, AO humeri achieved a lower level than FF humeri (p=0.013), whilst for normalized displacement AN humeri had lower levels than all other groups (p?0.005) and AO humeri had lower values than EM humeri (p=0.029). For absolute and normalized energy, there were no statistical differences (p?0.066). Human bone mineral density (BMD) ranged from 0.7 to 1.8g/cm(2) and was linearly correlated to screw pullout parameters in 14 of 18 cases (R=0.61 to 0.96), whilst humerus age was not. Consequently, it is recommended that human fresh-frozen, human embalmed, and human dried humeri can be used interchangeably for cortical screw purchase, since they were statistically equivalent for all comparisons. However, artificial humeri were involved in all statistical differences observed and, thus, may not replicate cortical screw purchase in human humeri. To date, this is the most comprehensive study on cortical screw purchase in human and artificial humeral shafts. PMID:24295967

Aziz, Mina S R; Nicayenzi, Bruce; Crookshank, Meghan C; Bougherara, Habiba; Schemitsch, Emil H; Zdero, Radovan

2014-02-01

295

Design and Construction of a High Pressure System for Evaluating Multiphase Twin-Screw Pumps  

E-print Network

DESIGN AND CONSTRUCTION OF A HIGH PRESSURE SYSTEM FOR EVALUATING MULTIPHASE TWIN-SCREW PUMPS A Thesis by THEODORE ISAAC HATCH Submitted to the Office of Graduate and Professional Studies of Texas A&M University in partial fulfillment... 2013 Theodore Isaac Hatch ABSTRACT Twin-screw pumps are currently sold by manufacturers without adequate data predicting the pump behavior when pumping multiphase mixtures. In light of the fact that pump behavior is known to change...

Hatch, Theodore Isaac

2013-08-26

296

High viscous liquids as a source in micro-screw heat exchanger: fabrication, simulation and experiments  

Microsoft Academic Search

Viscous liquids can be encountered in many applications of micro devices. In this paper, an experimental and numerical simulation\\u000a of a micro screw concentric tube heat exchanger is presented to determine the overall heat transfer coefficient and the amount\\u000a of heat created by friction. The screw surface area and the increase in the viscosity of the liquid can raise the

Haifa El-Sadi; Nabil Esmail; Andreas K. Athienitis

2007-01-01

297

Enzymatic hydrolysis of sago starch in a twin-screw extruder  

Microsoft Academic Search

Simultaneous gelatinisation and liquefaction of sago starch with a thermostable ?-amylase in a co-rotating twin-screw extruder was investigated. Maltodextrins with dextrose equivalent (DE) ranging from 0 to 10 were produced. Response surface methodology was used to study the influence of barrel temperature (70–130 °C), screw speed (70–160 rpm), enzyme concentration (0–1.0%) and feed moisture content (28.5–50.5%) on the extrudate properties.

S. Govindasamy; O. H. Campanella; C. G. Oates

1997-01-01

298

Horizontal ridge expansion and implant placement using screws: a report of two cases  

PubMed Central

Implants are typically placed after performing ridge expansion by inserting screws of gradually increasing thickness and good clinical outcomes are often obtained. We placed 11 implants in 6 patients, and one implant failed during osseointegration but it was replaced immediately after removal and successful prosthetic treatments were completed. During these surgeries, buccal cortical plate complete fractures do not occur. Inserting screws for ridge expansion is a successful and predictable technique for implant placement in narrow alveolar bone. PMID:25368836

Kim, Young-Kyun

2014-01-01

299

Electrical characterization of 4H-SiC avalanche photodiodes containing threading edge and screw dislocations  

NASA Astrophysics Data System (ADS)

The reverse voltage current characteristics and electroluminescence of small area 4H-SiC avalanche photodiodes were investigated and correlated with the presence of threading screw and edge dislocations. Localized electroluminescence was observed at threading dislocations at voltages close to breakdown whereas diodes without any extended defects exhibited uniform light emission in the active area. Diodes containing either edge or screw dislocations were found to have excess leakage currents and breakdown prematurely compared to diodes without dislocations.

Berechman, R. A.; Skowronski, M.; Soloviev, S.; Sandvik, P.

2010-06-01

300

Positioning of screw holes group based on digital camera and digital control drilling  

Microsoft Academic Search

Positioning of screw holes is an important production procedure for steel construction connecting with bolts. In this paper,\\u000a a new production method is presented, in which the digital camera is used for taking pictures of screw holes and other techniques\\u000a are advanced. This paper also indicates that the pixels of CCD chip in photogrammetry should be chosen as all geometric

Feng Wenhao; Li Jiansong; Yan Li; Su Guozhong; Yuan Xiuxiao; Zhong Shengzhang; Ji Huiming

2004-01-01

301

Morphology Evolution in PC\\/PE Blends with and without Compatibilization During Twin-Screw Extrusion  

Microsoft Academic Search

The morphology evolution in polycarbonate\\/polyethylene (PC\\/PE) blends with and without compatibilization in a twin-screw extruder was studied using a scanning electron microscope (SEM). The effects of screw speed and compatibilizer on the morphology of PC\\/PE blend during the extrusion were discussed in detail. It was found that the shape and size of the dispersed phase in the uncompatibilized PC\\/PE blend

Bo Yin; Jie Lan; Lan-Peng Li; Ming-Bo Yang

2010-01-01

302

Late-Onset Screw Migration into Iliac Vessels 21 years after Hip Arthrodesis  

PubMed Central

Iatrogenic injuries to the vascular system are a rare but serious complication of hip surgery. We report a case of an 83-year-old man who presented with intrapelvic migration of a screw into the space between the external iliac artery and vein 21 years after hip arthrodesis. The patient was treated with laparotomy, and the damaged artery was excised and sutured. This is the first case of a late vascular complication secondary to screw migration after hip arthrodesis. PMID:25336996

Hirai, Taishi; Inaba, Yutaka; Kobayashi, Naomi; Takakagawa, Shu; Yukizawa, Yohei; Ike, Hiroyuki; Saito, Tomoyuki

2014-01-01

303

Chondrocyte response to in vitro mechanical injury and co-culture with joint capsule tissue  

E-print Network

Acute traumatic joint injury in young adults leads to an increased risk for the development of osteoarthritis (OA) later in life irrespective of surgical intervention to stabilize the injured joint. Although the mechanism ...

Lee, Jennifer H. (Jennifer Henrica)

2005-01-01

304

Development of solid-lubricated ball-screws for use in space  

NASA Technical Reports Server (NTRS)

Ball-screws lubricated by solid lubricant films containing molybdenum disulphide are developed. The ball-screws (shaft diameter: phi 25 mm, length: 667 mm) were operated under a load of 40 to 120 N at a speed of 1.5 to 200 rpm at 10(exp -5) Pa. First, ball-screws made of stainless steel SUS 440C were studied using test equipment originally designed for this study. To reduce weight, the next step taken was to develop a ball-screw made of 6Al-4V-titanium. Long wear-life of more than 1 x 10(exp 7) revolutions was achieved with solid lubricated ball-screws made of SUS 440C and 6Al-4V-titanium in a hard vacuum. According to the surface profile of the shaft measured after 1 x 10(exp 7) revolutions, more solid lubricant remained on the surface of 6Al-4V-titanium than that of stainless steel. Auger and EPMA analysis confirmed lubrication was maintained by solid lubricant on nuts and screws after the lubricant films on the balls were worn off.

Chiba, Masatoshi; Gyougi, Toru; Nishimura, Makoto; Seki, Katsumi

1991-01-01

305

Prevention of unrecognized joint penetration during internal fixation of hip fractures: a geometric model based on Steinmetz Solid.  

PubMed

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: ?. The theoretical risk of UJP for any screw therefore can be as high as 21.5% ((4-?)/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

Mao, Yujiang; Song, Jie; Wei, Jie; Wang, Manyi

2010-01-01

306

The empirical modeling of a Lysholm screw expander  

SciTech Connect

This is a description of the development of an engine model for the prediction of mass flow rate, power, efficiency and exhaust quality for a Lysholm Screw Expander at a given set of operating conditions. The testing of an expander having a rotor diameter of 130 mm (5.12 inches) and an expansion ratio of 5.3 was performed with simulated geothermal fluid at an inlet pressure of 0.827 MPa (120 psia). The inlet quality, engine speed and pressure ratio were independently varied to produce a three-dimensional data matrix of 104 data points. Statistical curve fitting methods were adapted to produce equations for mass flow rate and power output in terms of the three variables associated with the data matrix. These explicit equations were combined with a numerical steam table subroutine to produce an engine model. The predictive ability observed during the validation of the model is adequate for use in system modeling, such as a hybrid geothermal energy conversion system. Mass flow rates were predicted to within 3% of the measured values. For most conditions, predictions of power were within 3% of the measured values. The predictions for exhaust quality were within 1/2% of the measured values. Predictions of engine efficiency reflected the combined errors in prediction of power and mass flow rate. The maximum error in efficiency predictions was 1 part in 20.

Stiedel, R.F.; Brown, K.A.; Pankow, D.H.

1983-08-01

307

Empirical modeling of a Lysholm helical screw expander  

NASA Astrophysics Data System (ADS)

Testing of a Lysholm helical screw expander having a rotor diameter of 5.12 inches and an expansion ratio of 5.3 was performed with simulated geothermal fluid at an inlet pressure of 120 psia. The inlet quality, engine speed and pressure ratio were independently varied to produce a three-dimensional data matrix of 104 data points. Statistical curve fitting methods were adapted to produce equations for mass flow rate and power output in terms of the three variables associated with the data matrix. These explicit equations were combined with a steam table subroutine to produce a computer model for prediction of mass flow rate, power, efficiency and exhaust quality at a given set of operating conditions. The predictive ability observed during validation of the model is adequate for use in modeling of hybrid geothermal energy conversion systems. Mass flow rates were predicted to within 2.7% of the measured values. For most conditions, predictions of power were within 3.3% of the measured values. Predictions of efficiency reflected the combined errors in prediction of power and mass flow rate.

Brown, K. A.

1984-06-01

308

Transforaminal lumbar interbody fusion using unilateral pedicle screw fixation plus contralateral translaminar facet screw fixation in lumbar degenerative diseases  

PubMed Central

Background: Transforaminal lumbar interbody fusion (TLIF) has been used in lumbar degenerative diseases. Some researchers have applied unilateral fixation in TLIF to reduce operational trauma without compromising the clinical outcome, but it is always suspected biomechanically unstable. The supplementary contralateral translaminar facet screw (cTLFS) seemed to be able to overcome the inherent drawbacks of unilateral pedicle screw (uPS) fixation theoretically. This study evaluates the safety, feasibility and efficacy of TLIF using uPS with cTLFS fixation in the treatment of lumbar degenerative diseases (LDD). Materials and Methods: 50 patients (29 male) underwent the aforementioned surgical technique for their LDD between December 2009 and April 2012. The results were evaluated based on visual analogue scale (VAS) of the leg and back, Japanese Orthopedic Association (JOA) score and Oswestry Disability Index (ODI) were recorded. The radiographic examinations in form of X-ray, computed tomography (CT) or magnetic resonance imaging was done preoperatively and 1 week, 3 months, 6 months, 12 months and 24 months postoperatively. The student t-test was used for comparison between the preoperative values and postoperative counterparts. P < 0.05 was considered to be statistically significant. Results: Among 50 patients, 22 received one level fusion and 28 two level's, with corresponding operation time and estimated blood loss being approximately 90 min, 150 ml and 120 min, 200 ml, respectively. No severe complications happened perioperatively. The mean VAS (back, leg) scores dropped from (7.6, 7.5) preoperatively to (2.1, 0.6) at 12 months’ followup, ODI from 49.1 preoperatively to 5.6 and JOA score raised from 10.6 preoperatively to 28.5, all P < 0.001, suggesting of good clinical outcome. From the three-dimensional reconstructed CT, 62 out of 70 segments displayed solid fusion with fusion rate of 88.6% at 12 months postoperatively. Conclusions: TLIF using uPS fixation plus cTLFS fixation is a safe, feasible and effective technique in the treatment of one or two level lumbar degenerative diseases short termly. PMID:25143640

Liu, Fubing; Jiang, Chun; Cao, Yuanwu; Jiang, Xiaoxing; Feng, Zhenzhou

2014-01-01

309

Seismic response of rock joints and jointed rock mass  

SciTech Connect

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.

Ghosh, A.; Hsiung, S.M.; Chowdhury, A.H. [Southwest Research Inst., San Antonio, TX (United States). Center for Nuclear Waste Regulatory Analyses

1996-06-01

310

Electro-Thermal Simulation Studies of SiC Junction Diodes Containing Screw Dislocations Under High Reverse-Bias Operation  

NASA Technical Reports Server (NTRS)

The objective of this work was to conduct a modeling study of SiC P-N junction diodes operating under high reverse biased conditions. Analytical models and numerical simulation capabilities were to be developed for self-consistent electro-thermal analysis of the diode current-voltage (I-V) characteristics. Data from GRC indicate that screw dislocations are unavoidable in large area SiC devices, and lead to changes in the SiC diode electrical response characteristics under high field conditions. For example, device instability and failures linked to internal current filamentation have been observed. The physical origin of these processes is not well understood, and quantitative projections of the electrical behavior under high field and temperature conditions are lacking. Thermal calculations for SiC devices have not been reported in the literature either. So estimates or projections of peak device temperatures and power limitations do not exist. This numerical study and simulation analysis was aimed at resolving some of the above issues. The following tasks were successfully accomplished: (1) Development of physically based models using one- and two-dimensional drift-diffusion theory for the transport behavior and I-V characteristics; (2) One- and two-dimensional heat flow to account for internal device heating. This led to calculations of the internal temperature profiles, which in turn, were used to update the electrical transport parameters for a self-consistent analysis. The temperature profiles and the peak values were thus obtainable for a given device operating condition; (3) Inclusion of traps assumed to model the presence of internal screw dislocations running along the longitudinal direction; (4) Predictions of the operating characteristics with and without heating as a function of applied bias with and without traps. Both one and two-dimensional cases were implemented; (5) Assessment of device stability based on the operating characteristics. The presence of internal non-uniformities, particularly filamentary structures, was probed and demonstrated; (6) Cause and physical origins of filamentary behavior and unstable I-V characteristics were made transparent; (7) It was demonstrated that diodes containing defects would be more prone to thermal breakdown associated with the temperature dependent decrease in the thermal conductivity; and (8) Finally, negative differential resistance (S-shaped NDR) which can potential lead to device instability and filamentary behavior was shown to occur for diodes containing a line of defects such as could be associated with a screw dislocation line.

Joshi, R. P.

2001-01-01

311

Reusable Solid Rocket Motor Nozzle Joint 5 Redesign  

NASA Technical Reports Server (NTRS)

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.

Lui, R. C.; Stratton, T. C.; LaMont, D. T.

2003-01-01

312

Biplane double-supported screw fixation (F-technique): a method of screw fixation at osteoporotic fractures of the femoral neck.  

PubMed

The present work introduces a method of screw fixation of femoral neck fractures in the presence of osteoporosis, according to an original concept of the establishment of two supporting points for the implants and their biplane positioning in the femoral neck and head. The provision of two steady supporting points for the implants and the highly increased (obtuse) angle at which they are positioned allow the body weight to be transferred successfully from the head fragment onto the diaphysis, thanks to the strength of the screws, with the patient's bone quality being of least importance. The position of the screws allows them to slide under stress with a minimal risk of displacement. The method was developed in search of a solution for those patients for whom primary arthroplasty is contraindicated. The method has been analysed in relation to biomechanics and statics. For the first time, a new function is applied to a screw fixation-the implant is presented as a simple beam with an overhanging end. PMID:21966288

Filipov, Orlin

2011-10-01

313

Butt Joint Tool Commissioning  

SciTech Connect

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.

Martovetsky, N N

2007-12-06

314

Deviation analysis of atlantoaxial pedicle screws assisted by a drill template.  

PubMed

Although C1-C2 pedicle screw fixation provides an excellent fusion rate and rigid fixation, this technique has a potential risk. It is essential to develop an accurate screwing method to avoid this neurovascular injury. To develop and validate the accuracy of a novel navigational template for C1-C2 pedicle screw placement in cadaveric specimens, computed tomography scans with 1-mm-wide cuts were obtained of 32 cadaveric cervical specimens. The authors developed 64 three-dimensional full-scale templates that were created by computer modeling with a rapid prototyping technique from the computed tomography data. Drill templates were constructed with a custom trajectory for each level and side. The drill templates were used to guide the establishment of a pilot hole for screw placement. The average distances between ideal and actual entry points of the C1 pedicle screws in the x, y, and z axes were 0.16±0.46 mm, 0.11±0.52 mm, and -0.01±0.54 mm, respectively, on the left side and 0.11±0.49 mm, 0.01±0.56 mm, and -0.09±0.59 mm, respectively, on the right side. The average distances between ideal and actual entry points of the C2 pedicle screws in the x, y, and z axes were 0.05±0.54 mm, 0.20±0.59 mm, and -0.06±0.58 mm, respectively, on the left side and 0.17±0.55 mm, 0.1±0.58 mm, and -0.01±0.49 mm, respectively, on the right side. Factors related to human error and imprecision are responsible for most malpositioning of instrumentation. The rapid prototyping drill template for C1-C2 screw placement is described to minimize human error, although it introduces error related to computer software and variation in manufacturing. PMID:24810817

Hu, Yong; Yuan, Zhen-Shan; Kepler, Christopher K; Albert, Todd J; Xie, Hui; Yuan, Jian-Bing; Dong, Wei-Xin; Wang, Cheng-Tao

2014-05-01

315

A new free-hand pedicle screw placement technique with reference to the supraspinal ligament  

PubMed Central

We sought to compare the safety and accuracy of a new free-hand pedicle screw placement technique to that of the conventional technique. One hundred fifty-three consecutive adult patients with simple fracture in the thoracic or/and lumbar spine were alternately assigned to either the new free-hand or the conventional group. In the new free-hand technique group, preoperative computerized tomography (CT) images were used to calculate the targeted medial-lateral angle of each pedicle trajectory and the pedicle screw was inserted perpendicular to the correspond-ing supraspinal ligament. In the conventional technique group, the medial-lateral and cranial-caudal angle of each pedicle trajectory was determined by intraoperatively under fluoroscopic guidance. The accuracy rate of pedicle screw placement, the time of intraoperative fluoroscopy, the operating time and the amount of blood loss during operation were respectively compared. All screws were analyzed by using intraoperative radiographs, intraoperative triggered electromyography (EMG) monitoring data, postoperative CT data and clinical outcomes. The accuracy rate of pedicle screw placement in the new free-hand technique group and the conventional technique group was 96.3% and 94.2% (P < 0.05), respectively. The intraoperative fluoroscopy time of the new technique group was less than that of the conventional technique group (5.37 seconds vs. 8.79 seconds, P < 0.05). However, there was no statistical difference in the operating time and the amount of blood loss during operation (P > 0.05). Pedicle screw placement with the free-hand technique which keeps the screw perpendicular to the supraspinal ligament is an accurate, reliable and safe technique to treat simple fracture in the thoracic or lumbar spine. PMID:24474966

Li, Juming; Zhao, Hong; Xie, Hao; Yu, Lipeng; Wei, Jifu; Zong, Min; Chen, Feng; Zhu, Ziqiang; Zhang, Ning; Cao, Xiaojian

2014-01-01

316

Repair of Microdamage in Osteonal Cortical Bone Adjacent to Bone Screw  

PubMed Central

Up to date, little is known about the repair mode of microdamage in osteonal cortical bone resulting from bone screw implantation. In this study, self-tapping titanium cortical bone screws were inserted into the tibial diaphyses of 24 adult male rabbits. The animals were sacrificed at 1 day, 2 weeks, 1 month and 2 months after surgery. Histomorphometric measurement and confocal microscopy were performed on basic fuchsin stained bone sections to examine the morphological characteristics of microdamage, bone resorption activity and spatial relationship between microdamage and bone resorption. Diffuse and linear cracks were coexisted in peri-screw bone. Intracortical bone resorption was significantly increased 2 weeks after screw installation and reach to the maximum at 1 month. There was no significant difference in bone resorption between 1-month and 2-months groups. Microdamage was significantly decreased within 1 month after surgery. Bone resorption was predisposed to occur in the region of <100 µm from the bone-screw interface, where had extensive diffuse damage mixed with linear cracks. Different patterns of resorption cavities appeared in peri-screw bone. These data suggest that 1) the complex microdamage composed of diffuse damage and linear cracks is a strong stimulator for initiating targeted bone remodeling; 2) bone resorption activities taking place on the surfaces of differently oriented Haversian and Volkmann canals work in a team for the repair of extensive microdamage; 3) targeted bone remodeling is a short-term reaction to microdamage and thereby it may not be able to remove all microdamage resulting from bone screw insertion. PMID:24586702

Wang, Lei; Ye, Tingjun; Deng, Lianfu; Shao, Jin; Qi, Jin; Zhou, Qi; Wei, Li; Qiu, Shijing

2014-01-01

317

Mechanical model and contouring analysis of high-speed ball-screw drive systems with compliance effect  

Microsoft Academic Search

The compliance effect of a high-speed ball-screw feed-drive system is modelled in this work. A mechanical model of a ball-screw feed drive system including the motor, ball-screw, coupling, supporting bearing, linear guide and machine structure was developed. It was found that at high acceleration, the mechanical compliance caused a significant contouring error. Smoothing the acceleration and deceleration control input command

J.-S. Chen; Y.-K. Huang; C.-C. Cheng

2004-01-01

318

Biomechanical comparison of different combinations of hook and screw in one spine motion unit - an experiment in porcine model  

PubMed Central

Background The biomechanical performance of the hooks and screws in spinal posterior instrumentation is not well-characterized. Screw-bone interface failure at the uppermost and lowermost vertebrae is not uncommon. Some have advocated for the use of supplement hooks to prevent screw loosening. However, studies describing methods for combined hook and screw systems that fully address the benefits of these systems are lacking. Thus, the choice of which implant to use in a given case is often based solely on a surgeon’s experience instead of on the biomechanical features and advantages of each device. Methods We conducted a biomechanical comparison of devices instrumented with different combinations of hooks and screws. Thirty-six fresh low thoracic porcine spines were assigned to three groups (12 per group) according to the configuration used for of fixation: (1) pedicle screw; (2) lamina hook and (3) combination of pedicle screw and lamina hook. Axial pullout tests backward on transverse plane in the direction normal to the rods were performed using a material testing machine and a specially designed grip with self-aligned function. Results The pullout force for the pedicle screws group was significantly greater than for the hooks and the combination (p??0.05). Conclusions Pedicle screws achieve the maximal pullout strength for spinal posterior instrumentation. PMID:24913189

2014-01-01

319

Biocompatibility testing of NiTi screws using immunohistochemistry on sections containing metallic implants.  

PubMed

NiTi is one of the most innovative concepts to have appeared in the field of metallic biomaterials in recent years but its biocompatibility remains controversial. We evaluated the biocompatibility of Nitinol screws using immunohistochemistry to observe the distribution of bone proteins during bone remodeling process around NiTi implant. Results were compared with screws made of Vitallium, c.p. titanium, Duplex austenitic-ferritic stainless steel (SAF), and Stainless Steel 316L. Screws were implanted in rabbit tibia for 3, 6, and 12 weeks. Embedding was performed in the hard resin Technovit, and for the immunohistochemical procedure undecalcified sections with bone-anchored implants could thus be used. The immunostaining method developed seemed to be a reliable technique to stain proteins in undecalcified sections. Biocompatibility results of the NiTi screws compared with the other screws showed a slower osteogenesis process characterized by no close contact between implant and bone, disorganized migration of osteoblasts around the implant, and a lower activity of osteonectin synthesis. PMID:8884502

Berger-Gorbet, M; Broxup, B; Rivard, C; Yahia, L H

1996-10-01

320

A video guided solution for screw insertion in orthopedic plate fixation  

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

321

Continuous twin screw granulation: influence of process variables on granule and tablet quality.  

PubMed

The aim of the current study was to screen theophylline (125 mg) tablets manufactured via twin screw granulation in order to improve process understanding and knowledge of process variables that determine granule and tablet quality. A premix of theophylline anhydrate, ?-lactose monohydrate and PVP (ratio: 30/67.5/2.5,w/w) was granulated with demineralized water. Experiments were done using the high-shear wet granulation module (based on twin screw granulation) of the ConsiGma™-25 unit (a continuous tablet manufacturing system) for particle size enlargement. After drying, granules were compressed using a MODUL™ P tablet press (compression force: 10 kN, tablet diameter: 12 mm). Using a D-optimal experimental design, the effect of several process variables (throughput (10-25 kg/h), screw speed (600-950 rpm), screw configuration (number (2, 4, 6 and 12) and angle (30°, 60° and 90°) of kneading elements), barrel temperature (25-40°C) and method of binder addition (dry versus wet)) on the granulation process (torque and temperature increase in barrel wall), granule (particle size distribution, friability and flowability) and tablet (tensile strength, porosity, friability, disintegration time and dissolution) quality was evaluated. The results showed that the quality of granules and tablets can be optimized by adjusting specific process variables (number of kneading elements, barrel temperature and binder addition method) during a granulation process using a continuous twin screw granulator. PMID:22687571

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

2012-09-01

322

The Retroacetabular Angle Determines the Safe Angle for Screw Placement in Posterior Acetabular Fracture Fixation  

PubMed Central

Introduction. A method for the determination of safe angles for screws placed in the posterior acetabular wall based on preoperative computed tomography (CT) is described. It defines a retroacetabular angle and determines its variation in the population. Methods. The retroacetabular angle is the angle between the retroacetabular surface and the tangent to the posterior acetabular articular surface. Screws placed through the marginal posterior wall at an angle equal to the retroacetabular angle are extraarticular. Medial screws can be placed at larger angles whose difference from the retroacetabular angle is defined as the allowance angles. CT scans of all patients with acetabular fractures treated in our institute between September 2002 to July 2007 were used to measure the retroacetabular angle and tangent. Results. Two hundred thirty one patients were included. The average (range) age was 42 (15–74) years. The average (range) retroacetabular angle was 39 (30–47) degrees. The average (range) retroacetabular tangent was 36 (30–45)?mm. Conclusions. Placing the screws at an average (range) angle of 39 (33–47) degrees of anterior inclination with the retroacetabular surface makes them extraarticular. Angles for medial screws are larger. Safe angles can be calculated preoperatively with a computer program. PMID:24959359

Tadros, Ayman M. A.; Oxland, Thomas R.; O'Brien, Peter

2013-01-01

323

Designs and Techniques That Improve the Pullout Strength of Pedicle Screws in Osteoporotic Vertebrae: Current Status  

PubMed Central

Osteoporosis is a medical condition affecting men and women of different age groups and populations. The compromised bone quality caused by this disease represents an important challenge when a surgical procedure (e.g., spinal fusion) is needed after failure of conservative treatments. Different pedicle screw designs and instrumentation techniques have been explored to enhance spinal device fixation in bone of compromised quality. These include alterations of screw thread design, optimization of pilot hole size for non-self-tapping screws, modification of the implant's trajectory, and bone cement augmentation. While the true benefits and limitations of any procedure may not be realized until they are observed in a clinical setting, axial pullout tests, due in large part to their reproducibility and ease of execution, are commonly used to estimate the device's effectiveness by quantifying the change in force required to remove the screw from the body. The objective of this investigation is to provide an overview of the different pedicle screw designs and the associated surgical techniques either currently utilized or proposed to improve pullout strength in osteoporotic patients. Mechanical comparisons as well as potential advantages and disadvantages of each consideration are provided herein. PMID:24724097

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

2014-01-01

324

Designs and techniques that improve the pullout strength of pedicle screws in osteoporotic vertebrae: current status.  

PubMed

Osteoporosis is a medical condition affecting men and women of different age groups and populations. The compromised bone quality caused by this disease represents an important challenge when a surgical procedure (e.g., spinal fusion) is needed after failure of conservative treatments. Different pedicle screw designs and instrumentation techniques have been explored to enhance spinal device fixation in bone of compromised quality. These include alterations of screw thread design, optimization of pilot hole size for non-self-tapping screws, modification of the implant's trajectory, and bone cement augmentation. While the true benefits and limitations of any procedure may not be realized until they are observed in a clinical setting, axial pullout tests, due in large part to their reproducibility and ease of execution, are commonly used to estimate the device's effectiveness by quantifying the change in force required to remove the screw from the body. The objective of this investigation is to provide an overview of the different pedicle screw designs and the associated surgical techniques either currently utilized or proposed to improve pullout strength in osteoporotic patients. Mechanical comparisons as well as potential advantages and disadvantages of each consideration are provided herein. PMID:24724097

Shea, Thomas M; Laun, Jake; Gonzalez-Blohm, Sabrina A; Doulgeris, James J; Lee, William E; Aghayev, Kamran; Vrionis, Frank D

2014-01-01

325

Optimal technique of screw placement in the ischial tuberosity for posterior acetabular fractures.  

PubMed

Thirty dry adult bony specimens and eight embalmed cadavers were used to report on the morphological data of the ischial tuberosity and to determine the most optimal technique for ischial tuberosity screw placement for open reduction and internal fixation of posterior acetabular fractures. The average width, height, and depth of the ischial tuberosity were 27.0 mm, 32.2 mm, and 32.4 mm, respectively. The average angles between the posterior and medial aspects and between the posterior and lateral aspects of the ischial tuberosities were 79.5 degrees, and 111.5 degrees, respectively. The risk to the internal pudendal neurovascular bundle increases with either a more medially placed screw or a laterally placed screw that is angled medially. The tendinous origin of the hamstrings becomes quite substantial (7-10 mm thick) at a point 2 cm distal to the inferior acetabular margin. The exposure of the ischial tuberosity should therefore be restricted to this level. The entry point of the screws should be 5 mm or 10 mm medial to the lateral margin of the ischial tuberosity, and the screws should be directed 35-40 degrees, 45-50 degrees, and 50-55 degrees caudally at the level of the inferior acetabular margin and 1 cm and 2 cm below it, respectively, to obtain the most favorable bony purchase. PMID:8667107

Xu, R; Ebraheim, N A; Biyani, A; Yeasting, R A

1996-01-01

326

Large displacement spherical joint  

DOEpatents

A new class of spherical joints has a very large accessible full cone angle, a property which is beneficial for a wide range of applications. Despite the large cone angles, these joints move freely without singularities.

Bieg, Lothar F. (Albuquerque, NM); Benavides, Gilbert L. (Albuquerque, NM)

2002-01-01

327

Joint Injection/Aspiration  

MedlinePLUS

... osteoarthritis. What usually is injected into the joint space? Corticosteroids (such as methylprednisolone and triamcinolone formulated to ... for producing inflammation and pain within the joint space. Although corticosteroids may also be successfully used in ...

328

Minimally invasive arthrodesis for chronic sacroiliac joint dysfunction using the SImmetry SI Joint Fusion system  

PubMed Central

Chronic sacroiliac (SI) joint-related low back pain (LBP) is a common, yet under-diagnosed and undertreated condition due to difficulties in accurate diagnosis and highly variable treatment practices. In patients with debilitating SI-related LBP for at least 6 months duration who have failed conservative management, arthrodesis is a viable option. The SImmetry® SI Joint Fusion System is a novel therapy for SI joint fusion, not just fixation, which utilizes a minimally invasive surgical approach, instrumented fixation for immediate stability, and joint preparation with bone grafting for a secure construct in the long term. The purpose of this report is to describe the minimally invasive SI Joint Fusion System, including patient selection criteria, implant characteristics, surgical technique, postoperative recovery, and biomechanical testing results. Advantages and limitations of this system will be discussed. PMID:24851059

Miller, Larry E; Block, Jon E

2014-01-01

329

Arch & Chord Joint Detail; Crossbracing Center Joint Detail; Chord, ...  

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

Arch & Chord Joint Detail; Crossbracing Center Joint Detail; Chord, Panel Post, Tie & Diagonal Brace Joint Detail; Chord, Panel Post, Tie & Crossbracing Joint Detail - Dunlapsville Covered Bridge, Spanning East Fork Whitewater River, Dunlapsville, Union County, IN

330

Jointly Poisson processes  

Microsoft Academic Search

What constitutes jointly Poisson processes remains an unresolved issue. This report reviews the current state of the theory and indicates how the accepted but unproven model equals that resulting from the small time-interval limit of jointly Bernoulli processes. One intriguing consequence of these models is that jointly Poisson processes can only be positively correlated as measured by the correlation coefficient

D. H. Johnson; I. N. Goodman

2009-01-01

331

Instability of the distal radioulnar joint.  

PubMed

The distal radioulnar joint is a complex structure necessary for forearm motion and force transmission across the wrist. Anatomic and biomechanical advances have revealed broad contributions to distal radioulnar joint stability and refined our understanding of the forces acting across it. Instability often co-occurs with other modes of pathology, such as arthrosis or malunion; and appropriate diagnosis and treatment require a comprehensive understanding of all contributing factors. Distal radioulnar joint instability can be broadly categorized as primary, post-traumatic or post-surgical. Treatment strategies include percutaneous, arthroscopic, soft-tissue, osteotomy and arthroplasty techniques. The purpose of this article is to review distal radioulnar joint instability and its management. PMID:24619248

Zimmerman, R M; Jupiter, J B

2014-09-01

332

Visualization and understanding of the granulation liquid mixing and distribution during continuous twin screw granulation using NIR chemical imaging.  

PubMed

Over the last decade, there has been increased interest in the application of twin screw granulation as a continuous wet granulation technique for pharmaceutical drug formulations. However, the mixing of granulation liquid and powder material during the short residence time inside the screw chamber and the atypical particle size distribution (PSD) of granules produced by twin screw granulation is not yet fully understood. Therefore, this study aims at visualizing the granulation liquid mixing and distribution during continuous twin screw granulation using NIR chemical imaging. In first instance, the residence time of material inside the barrel was investigated as function of screw speed and moisture content followed by the visualization of the granulation liquid distribution as function of different formulation and process parameters (liquid feed rate, liquid addition method, screw configuration, moisture content and barrel filling degree). The link between moisture uniformity and granule size distributions was also studied. For residence time analysis, increased screw speed and lower moisture content resulted to a shorter mean residence time and narrower residence time distribution. Besides, the distribution of granulation liquid was more homogenous at higher moisture content and with more kneading zones on the granulator screws. After optimization of the screw configuration, a two-level full factorial experimental design was performed to evaluate the influence of moisture content, screw speed and powder feed rate on the mixing efficiency of the powder and liquid phase. From these results, it was concluded that only increasing the moisture content significantly improved the granulation liquid distribution. This study demonstrates that NIR chemical imaging is a fast and adequate measurement tool for allowing process visualization and hence for providing better process understanding of a continuous twin screw granulation system. PMID:24211658

Vercruysse, Jurgen; Toiviainen, Maunu; Fonteyne, Margot; Helkimo, Niko; Ketolainen, Jarkko; Juuti, Mikko; Delaet, Urbain; Van Assche, Ivo; Remon, Jean Paul; Vervaet, Chris; De Beer, Thomas

2014-04-01

333

An Alternative Explanation for a Screw-like Meteoric Train Photographed by Double-Station Observations  

NASA Astrophysics Data System (ADS)

Two-station observation of meteors, especially a meteor trains, provides an effective approach to the measurement of the physical parameters. We have collected four special groups of photographs of meteoric trains taken at two stations during Leonids 2001. One representative group has been measured and analyzed in detail. An analysis has been reported in our first paper. In this paper, an alternative explanation for the screw-like meteoric train is suggested based on some physical calculations. The results reveal that this train has a screw-like structure and, apparently, spoke beams. The mother meteor of this train may be negatively charged and moves forward along a left-hand screw trajectory under the effect of the geomagnetic field. The spoke beams might be the visual effect of the long time exposure of many particles released from the disintegrated meteoroid.

Wu, Guang-Jie

2007-12-01

334

Improved Screw Placement for Slipped Capital Femoral Epiphysis (SCFE) using Robotically-Assisted Drill Guidance  

PubMed Central

Slipped Capital Femoral Epiphysis (SCFE) is a common hip displacement condition in adolescents. In the standard treatment, the surgeon uses intra-operative fluoroscopic imaging to plan the screw placement and the drill trajectory. The accuracy, duration, and efficacy of this procedure are highly dependent on surgeon skill. Longer procedure times result in higher radiation dose, to both patient and surgeon. A robotic system to guide the drill trajectory might help to reduce screw placement errors and procedure time by reducing the number of passes and confirmatory fluoroscopic images needed to verify accurate positioning of the drill guide along a planned trajectory. Therefore, with the long-term goals of improving screw placement accuracy, reducing procedure time and intra-operative radiation dose, our group is developing an image-guided robotic surgical system to assist a surgeon with pre-operative path planning and intra-operative drill guide placement. PMID:25333154

Koutenaei, Bamshad Azizi; Guler, Ozgur; Wilson, Emmanuel; Thoranaghatte, Ramesh U.; Oetgen, Matthew; Navab, Nassir; Cleary, Kevin

2014-01-01

335

Bilateral Three-Level Lumbar Spondylolysis Repaired by Hook-Screw Technique  

PubMed Central

We report a case of bilateral three-level lumbar spondylolysis that was directly repaired by use of hook-screw technique. The patient complained of low back pain for 2 years that progressively worsened and was exacerbated with standing and walking. He also mentioned bilateral sciatalgia. The neurological examination was normal. Interestingly, we found bilateral lumbar spondylolysis in L3, L4, and L5 levels in imaging studies. After proving that spondylolysis was the source of the low back pain by local anesthetic agent injection, we used a direct technique for correction of spondylolysis by use of a hook-screw device plus decortications of lysis area and iliac crest autograft. We assessed the patient after surgery to evaluate pain recovery and fusion rate. The results were favorable and proved the efficacy of the hook-screw technique for treatment of symptomatic multilevel lumbar spondylolysis. PMID:24353947

Sharifi, Guive; Jahanbakhshi, Amin; Daneshpajouh, Behnam; Rahimizadeh, Abolfazl

2012-01-01

336

Stability: from biomechanical concept to chiropractic practice  

PubMed Central

This paper formalizes stability in a clinician-friendly way and then discusses ways for chiropractors to ensure stability of spinal joints that may have their stability compromized from manipulation. ImagesFigure 1Figure 4Figure 5Figure 6Figure 7

McGill, Stuart M

1999-01-01

337

A complete absorption mechanism of stacking fault tetrahedron by screw dislocation in copper  

NASA Astrophysics Data System (ADS)

It was frequently observed in experiments that stacking fault tetrahedron (SFT) can be completely absorbed by dislocation and generate defect-free channels in irradiated materials, but the mechanism is still open. In this paper, molecular dynamics (MD) was used to explore the dislocation mechanism of reaction between SFT and screw dislocation in copper. Our computational results reveal that, at high temperature, the SFT is completely absorbed by screw dislocation with the help of Lomer-Cottrell (LC) lock transforming into Lomer dislocation. This complete absorption mechanism is very helpful to understand the defect-free channels in irradiated materials.

Fan, Haidong; Wang, Qingyuan

2013-10-01

338

Vortex conception of rotor and mutual effect of screw/propellers  

NASA Technical Reports Server (NTRS)

A vortex theory of screw/propellers with variable circulation according to the blade and its azimuth is proposed, the problem is formulated and circulation is expanded in a Fourier series. Equations are given for inductive velocities in space for crews, including those with an infinitely large number of blades and expansion of the inductive velocity by blade azimuth of a second screw. Multiparameter improper integrals are given as a combination of elliptical integrals and elementary functions, and it is shown how to reduce elliptical integrals of the third kind with a complex parameter to integrals with a real parameter.

Lepilkin, A. M.

1986-01-01

339

Non-fusion instrumentation of the lumbar spine with a hinged pedicle screw rod system: an in vitro experiment  

PubMed Central

In advanced stages of degenerative disease of the lumbar spine instrumented spondylodesis is still the golden standard treatment. However, in recent years dynamic stabilisation devices are being implanted to treat the segmental instability due to iatrogenic decompression or segmental degeneration. The purpose of the present study was to investigate the stabilising effect of a classical pedicle screw/rod combination, with a moveable hinge joint connection between the screw and rod allowing one degree of freedom (cosmicMIA). Six human lumbar spines (L2–5) were loaded in a spine tester with pure moments of ±7.5 Nm in lateral bending, flexion/extension and axial rotation. The range of motion (ROM) and the neutral zone were determined for the following states: (1) intact, (2) monosegmental dynamic instrumentation (L4-5), (3) bisegmental dynamic instrumentation (L3–5), (4) bisegmental decompression (L3–5), (5) bisegmental dynamic instrumentation (L3–5) and (6) bisegmental rigid instrumentation (L3–5). Compared to the intact, with monosegmental instrumentation (2) the ROM of the treated segment was reduced to 47, 40 and 77% in lateral bending, flexion/extension and axial rotation, respectively. Bisegmental dynamic instrumentation (3) further reduced the ROM in L4-5 compared to monosegmental instrumentation to 25% (lateral bending), 28% (flexion/extension) and 57% (axial rotation). Bisegmental surgical decompression (4) caused an increase in ROM in both segments (L3–4 and L4–5) to approximately 125% and approximately 135% and 187–234% in lateral bending, flexion/extension and axial rotation, respectively. Compared to the intact state, bisegmental dynamic instrumentation after surgical decompression reduced the ROM of the two-bridged segments to 29–35% in lateral bending and 33–38% in flexion/extension. In axial rotation, the ROM was in the range of the intact specimen (87–117%). A rigid instrumentation (6) further reduced the ROM of the two-bridged segments to 20–30, 23–27 and 50–68% in lateral bending, flexion/extension and axial rotation, respectively. The results of the present study showed that compared to the intact specimen the investigated hinged dynamic stabilisation device reduced the ROM after bisegmental decompression in lateral bending and flexion/extension. Following bisegmental decompression and the thereby caused large rotational instability the device is capable of restoring the motion in axial rotation back to values in the range of the intact motion segments. PMID:19504129

Onder, U.; Martin, A.; von Strempel, A.

2009-01-01

340

To Determine the Percentage of Copper in a Brass Screw Using a Computer Interface with a Colorimeter.  

ERIC Educational Resources Information Center

Year 11 students investigated the real-world problem of whether screws are really brass. It allowed them to use the colorimeter and computer interface in a way that was easily understood and models normal practice in testing laboratories. Screws were dissolved in nitric acid and their absorbance of red light was compared with a standard curve.…

Horgan, Joan; Hedge, Robyn

1997-01-01

341

Direct extraction of oil from sunflower seeds by twin-screw extruder according to an aqueous extraction process: Feasibility  

E-print Network

Direct extraction of oil from sunflower seeds by twin-screw extruder according to an aqueous the feasibility of an aqueous process to extract sunflower seed oil using a co-rotating twin-screw extruder. Aqueous extraction was carried out using whole seeds and the influence of the operating conditions on oil

Paris-Sud XI, Université de

342

A Lyapunov based Adaptive Control of Nonlinear Microdynamics of a Ball Screw Driven Slide for Nanometer Positioning  

Microsoft Academic Search

A desire to improve the positioning accuracy of ball screws prompted an investigation into the dynamics of nanometer motion. Characterization of the ball screw indicated that nanometer motion is possible prior to friction breakaway via elastic deformation of the frictional contacts. The observed dynamics are nonlinear, and consequently result in inconsistent and unpredictable closed-loop response while under PI position control.

Peter I. Hubbel; Paul I. Ro

1992-01-01

343

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

PubMed Central

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

Pesenti, Sebastien; Peltier, Emilie; Adetchessi, Tarek; Dufour, Henry; Fuentes, Stephane

2014-01-01

344

Performance optimization of a counter rotating twin screw extruder for recycling natural rubber vulcanizates using response surface methodology  

Microsoft Academic Search

Response surface methodology has been used to predict the optimal processing parameters, viz. barrel temperature and screw speed, for devulcanization of natural rubber based waste rubber powder in a counter rotating twin screw extruder. Central composite rotatable design for two variables at five levels was chosen as the experimental design. The results obtained after measuring the responses were fitted as

B. Maridass; B. R. Gupta

2004-01-01

345

Greenâs Functions for a Bimaterial Consisting of Two Orthotropic Quarter Planes Subjected to an Antiplane Force and a Screw Dislocation  

NSDL National Science Digital Library

The image singularity approach is employed to construct the Greenâs function for a quarter plane and a bimaterial that consists of two quarter planes bonded together. The material is orthotropic, and is subjected to an antiplane force f and a screw dislocation with magnitude b. Explicit expressions are obtained for the antiplane forces and screw dislocations that are applied at the image singularities.

Ting, T. C.

2006-11-14

346

Core energy and Peierls stress of a screw dislocation in bcc molybdenum: A periodic-cell tight-binding study  

E-print Network

Core energy and Peierls stress of a screw dislocation in bcc molybdenum: A periodic-cell tight determine the core energy and Peierls stress of the a0/2 111 screw dislocation in bcc molybdenum at T=0. We show that a proper definition of the core energy necessarily involves choosing a reference direction a

Cai, Wei

347

Ex VivoExperiment on Radiofrequency Liver Ablation with Saline Infusion through a Screw-Tip Cannulated Electrode  

Microsoft Academic Search

Purpose: To investigate whether radiofrequency (RF) therapy with hypertonic saline infusion through a hollow screw-tip electrode can cause a lesion size suitable for liver tumor ablation. Materials and methods: RF tissue ablation of 180 sites was performed by using a hollow screw-tip electrode in 40 freshly excised swine livers. Under both power and temperature control modes, the ablation effects with

Yi Miao; Yicheng Ni; Stefaan Mulier; Kai Wang; Michael F. Hoey; Peter Mulier; Freddy Penninckx; Jie Yu; Ivan De Scheerder; Alber L. Baert; Guy Marchal

1997-01-01

348

Adaptive Postural Control for Joint Immobilization during Multitask Performance  

PubMed Central

Motor abundance is an essential feature of adaptive control. The range of joint combinations enabled by motor abundance provides the body with the necessary freedom to adopt different positions, configurations, and movements that allow for exploratory postural behavior. This study investigated the adaptation of postural control to joint immobilization during multi-task performance. Twelve healthy volunteers (6 males and 6 females; 21–29 yr) without any known neurological deficits, musculoskeletal conditions, or balance disorders participated in this study. The participants executed a targeting task, alone or combined with a ball-balancing task, while standing with free or restricted joint motions. The effects of joint configuration variability on center of mass (COM) stability were examined using uncontrolled manifold (UCM) analysis. The UCM method separates joint variability into two components: the first is consistent with the use of motor abundance, which does not affect COM position (VUCM); the second leads to COM position variability (VORT). The analysis showed that joints were coordinated such that their variability had a minimal effect on COM position. However, the component of joint variability that reflects the use of motor abundance to stabilize COM (VUCM) was significant decreased when the participants performed the combined task with immobilized joints. The component of joint variability that leads to COM variability (VORT) tended to increase with a reduction in joint degrees of freedom. The results suggested that joint immobilization increases the difficulty of stabilizing COM when multiple tasks are performed simultaneously. These findings are important for developing rehabilitation approaches for patients with limited joint movements. PMID:25329477

Hsu, Wei-Li

2014-01-01

349

16 CFR Figure 6 to Part 1633 - Burner Assembly Showing Arms and Pivots (Shoulder Screws) in Relation to, Portable Frame Allowing...  

Code of Federal Regulations, 2012 CFR

...Shoulder Screws) in Relation to, Portable Frame Allowing Burner Height Adjustment 6 Figure 6 to Part 1633 Commercial Practices...Shoulder Screws) in Relation to, Portable Frame Allowing Burner Height Adjustment...

2012-01-01

350

16 CFR Figure 6 to Part 1633 - Burner Assembly Showing Arms and Pivots (Shoulder Screws) in Relation to Portable Frame Allowing...  

Code of Federal Regulations, 2011 CFR

...Shoulder Screws) in Relation to Portable Frame Allowing Burner Height Adjustment 6 Figure 6 to Part 1633 Commercial Practices...Shoulder Screws) in Relation to Portable Frame Allowing Burner Height Adjustment...

2011-01-01

351

Atomic-scale Modeling of Interactions of Helium, Vacancies and Helium-vacancy Clusters with Screw Dislocations in Alpha-Iron  

SciTech Connect

The interactions of He and vacancy defects with <111> screw dislocations in alpha-Fe are modeled using molecular statics, molecular dynamics and transition state energy determinations. The formation energies and binding energies of interstitial He atoms, vacancies and He-vacancy clusters near and within dislocations in alpha-Fe are determined at various locations relative to the dislocation core. Using the dimer transition state method the migration energies and trajectories of the He and vacancy defects near and within the screw dislocation are also determined. Both interstitial He atoms and single vacancies are attracted to and trapped in the dislocation core region, and they both migrate along the dislocation line with a migration energy of about 0.4 eV, which is about half the migration energy of vacancies in the perfect crystal and about five times the migration energy for interstitial He in the perfect crystal. Divacancies and He-divacancy complexes have migration properties within the dislocation core that are similar to those in the perfect crystal, although the stability of these defects within the dislocation may be somewhat less than in the perfect crystal.

Heinisch, Howard L.; Gao, Fei; Kurtz, Richard J.

2010-05-01

352

Evaluation of tantalum 316 stainless steel transition joints  

NASA Technical Reports Server (NTRS)

Tubular transition joints providing a metallurgically bonded connection between tantalum and 316 stainless steel pipe sections were comparatively evaluated for durability under thermal cycling conditions approximating the operation of a SNAP-8 mercury boiler. Both coextruded and vacuum brazed transition joints of 50mm (2 inch) diameter were tested by thermal cycling 100 times between 730 C and 120 C(1350 F and 250 F) in a high vacuum environment. The twelve evaluated transition joints survived the full test sequence without developing leaks, although liquid penetrant bond line indications eventually developed in all specimens. The brazed transition joints exhibited the best dimensional stability and bond line durability.

Stoner, D. R.

1972-01-01

353

Gait pattern generation with knee stretch motion for biped robot using toe and heel joints  

Microsoft Academic Search

This paper presents a new alternative methodology to generate gait pattern with a knee stretched motion for biped robot utilizing toe and heel joints. During walking sequence, human heels act as passive joints that create some support area which enhances the stability of human walking. This research tries to replace human-heel like mechanism with a heel joint in the biped

Nandha Handharu; Jungwon Yoon; Gabsoon Kim

2008-01-01

354

Influence of bi- and tri-compartmental knee arthroplasty on the kinematics of the knee joint  

Microsoft Academic Search

BACKGROUND: The cruciate ligaments are important stabilizers of the knee joint and determine joint kinematics in the natural knee and after cruciate retaining arthroplasty. No in vitro data is available to biomechanically evaluate the ability of the anterior cruciate ligament (ACL) to maintain knee joint kinematics after bicruciate-retaining bi-compartmental knee arthroplasty (BKA). Therefore, the objective of the current study was

Markus Wünschel; JiaHsuan Lo; Torsten Dilger; Nikolaus Wülker; Otto Müller

2011-01-01

355

Apparatus and methods for cooling and sealing rotary helical screw compressors  

Microsoft Academic Search

In a compression system which incorporates a rotary helical screw compressor, and for any type of gas or refrigerant, the working liquid oil is atomized through nozzles suspended in, and parallel to, the suction gas flow, or alternatively the nozzles are mounted on the suction piping. In either case, the aim is to create positively a homogeneous mixture of oil

Fresco

1997-01-01

356

Transpedicular screwing of the seventh cervical vertebra: anatomical considerations and surgical technique  

Microsoft Academic Search

The purpose of this study was first to assess the feasibility of C7 transpedicular screwing with a morphological study and secondly to evaluate the safety of such a surgical technique when guided only by posterior landmarks. Eighteen C7 vertebrae, harvested from fresh human cadavers, were included in this study. First the morphometry of C7 pedicle was performed on computed tomography

C. Barrey; F. Cotton; J. Jund; P. Mertens; G. Perrin

2003-01-01

357

Hybrid computer-guided and minimally open surgery: anterior lumbar interbody fusion and translaminar screw fixation  

Microsoft Academic Search

Less invasiveness is the way forward for spinal surgery. Minimal disruption of tissue, preservation of muscle function, and restoration of normal spinal alignment are still the goals of most surgical procedures. An anterior lumbar fusion technique using a less invasive procedure with the addition of translaminar screws is described. The autograft is harvested from the vertebral body, thus avoiding the

N. Kumar; A. Wild; J. K. Webb; M. Aebi

2000-01-01

358

Twin screw oil-free wet compressor for compression–absorption cycle  

Microsoft Academic Search

The performance of a twin screw compressor operating under wet (two-phase) compression conditions in an ammonia–water compression absorption heat pump cycle is investigated both theoretically and experimentally. The paper reports on the influence of the location of liquid intake or, depending what applies, injection angle and mass flow rate of the injected liquid on compressor performance. Labyrinth seals separate the

C. A. Infante Ferreira; C. Zamfirescu; D. Zaytsev

2006-01-01

359

Molecular dynamics simulations of motion of edge and screw dislocations in a metal  

E-print Network

Molecular dynamics simulations of motion of edge and screw dislocations in a metal Jinpeng Chang a of California, Livermore, CA 94550, USA Accepted 1 June 2001 Abstract Motions of a straight edge dislocation configurations in each case are described, and estimate is made of the local driving force due to the image

Cai, Wei

360

Radical Polymerization of Styrene and Styrene–Butylmethacrylate in a Counterrotating Twin Screw Extruder  

Microsoft Academic Search

This article describes the copolymerization of styrene-butylmethacrylate (St-BMA) and the homopolymerization of styrene (St) in a counterrotating twin screw extruder. The effect of prepolymerization on both the product properties and process was studied. It turned out that the process of reactive extrusion was strongly influenced by prepolymerization. Also, the product properties were altered by prepolymerization. When the polymerization of St

A. J. van der Goot; L. P. B. M. Janssen

1997-01-01

361

Use of a laser guide to reduce screening time for the dynamic hip screw  

Microsoft Academic Search

A prospective, randomized study was used to evaluate a laser guide to aim the image intensifier during the treatment of 52 patients with intertrochanteric fractures of the proximal femur using a dynamic hip screw. The laser guide reduces the fluoroscopic screening time by 40 per cent (P < 0.05). We conclude that laser aiming of the image intensifier has a

A. H. N. Robinson; M. Moiz; J. P. Hallett

1996-01-01

362

A simple laser guide to reduce the screening time during the insertion of dynamic hip screws  

Microsoft Academic Search

A simple laser pointer can be used to guide the radiographer to position the image intensifier during the insertion of a dynamic hip screw in the treatment of fractures of the trochanteric area of the proximal femur. This significantly reduces the screening time and, by implication, the amount of radiation for the theatre staff and patient.

K. S. Conn; J. P. Hallett

1998-01-01

363

Late degradation tissue response to poly( l-lactide) bone plates and screws  

Microsoft Academic Search

Patients with fractures of the zygomatic bone were treated with high molecular weight poly(l-lactic) acid (PLLA) bone plates and screws. Three years after implantation four patients returned to our department with a swelling at the site of implantation. At the recall of the remaining patients we found an identical type of swelling after the same implantation period. To investigate the

J. E. Bergsma; W. C. de Bruijn; F. R. Rozema; R. R. M. Bos; G. Boering

1995-01-01

364

Value Proposition: Previous physical limitations of use of the screw pump  

E-print Network

invention is a screw pump with oil pockets inside the pump casing. Slots are connected to the suction and commercialization of the invention.. Intellectual property: Die intelligente Schraubenpumpe und das Verfahren zur Darmstadt Website: http://www.tu-darmstadt.de Professor Dr.-Ing. Peter Pelz Director of the Fluid Systems

Haller-Dintelmann, Robert

365

New Design and Rotor Retrofit to Improve Capacity and Performance of Refrigeration Screw Compressors  

Microsoft Academic Search

As manufacturing meth ods improve ,screw compressor components can be mademore accurately and hence with smaller operating clearances. This gives the opportunity both toimprove their efficiency and reduce manufacturing costs. However, toobtain the full benefit of these devel opments, improve ddesign procedures are need edto model the processes within these machines more precisely , than those based on the simplified

Zhiqiang Wang; Weimin Zhang; Nikola Stosic; Ahmed Kovacevic; Ian K. Smith; Elvedin Mujic

2006-01-01

366

Performance analysis of an oil-injected screw compressor and its application  

Microsoft Academic Search

Flow and heat transfer characteristics required for computer simulation of screw compressors are experimentally obtained and used in performance prediction, where the working medium is air. The heat transfer coefficient is determined from the experimental relation between the volumetric efficiency and the inlet temperature. Flow coefficients are obtained from the efficiency-clearance curves. Applying those coefficients to the performance simulation, good

Y Osada

1995-01-01

367

Improved rotor profiling based on the arbitrary sealing line for twin screw compressors  

Microsoft Academic Search

A major factor affecting the performance of twin screw compressors is clearance along the instant contact line as leakage passes through the blowhole. Thus, the projected sealing line in the transverse plane of mating rotors is an important basis for direct observation of the leakage. The conventional design process for the rotor tooth profile is to first generate the rotor

Yu-Ren Wu; Zhang-Hua Fong

368

Mixing and transport during pharmaceutical twin-screw wet granulation: experimental analysis via chemical imaging.  

PubMed

Twin-screw granulation is a promising continuous alternative for traditional batch high shear wet granulation (HSWG). The extent of HSWG in a twin screw granulator (TSG) is greatly governed by the residence time of the granulation materials in the TSG and degree of mixing. In order to determine the residence time distribution (RTD) and mixing in TSG, mostly visual observation and particle tracking methods are used, which are either inaccurate and difficult for short RTD, or provide an RTD only for a finite number of preferential tracer paths. In this study, near infrared chemical imaging, which is more accurate and provides a complete RTD, was used. The impact of changes in material throughput (10-17 kg/h), screw speed (500-900 rpm), number of kneading discs (2-12) and stagger angle (30-90°) on the RTD and axial mixing of the material was characterised. The experimental RTD curves were used to calculate the mean residence time, mean centred variance and the Péclet number to determine the axial mixing and predominance of convective over dispersive transport. The results showed that screw speed is the most influential parameter in terms of RTD and axial mixing in the TSG and established a significant interaction between screw design parameters (number and stagger angle of kneading discs) and the process parameters (material throughput and number of kneading discs). The results of the study will allow the development and validation of a transport model capable of predicting the RTD and macro-mixing in the TSG. These can later be coupled with a population balance model in order to predict granulation yields in a TSG more accurately. PMID:24768925

Kumar, Ashish; Vercruysse, Jurgen; Toiviainen, Maunu; Panouillot, Pierre-Emmanuel; Juuti, Mikko; Vanhoorne, Valérie; Vervaet, Chris; Remon, Jean Paul; Gernaey, Krist V; De Beer, Thomas; Nopens, Ingmar

2014-07-01

369

Determining the Best Treatment for Coronal Angular Deformity of the Knee Joint in Growing Children: A Decision Analysis  

PubMed Central

This study aimed to determine the best treatment modality for coronal angular deformity of the knee joint in growing children using decision analysis. A decision tree was created to evaluate 3 treatment modalities for coronal angular deformity in growing children: temporary hemiepiphysiodesis using staples, percutaneous screws, or a tension band plate. A decision analysis model was constructed containing the final outcome score, probability of metal failure, and incomplete correction of deformity. The final outcome was defined as health-related quality of life and was used as a utility in the decision tree. The probabilities associated with each case were obtained by literature review, and health-related quality of life was evaluated by a questionnaire completed by 25 pediatric orthopedic experts. Our decision analysis model favored temporary hemiepiphysiodesis using a tension band plate over temporary hemiepiphysiodesis using percutaneous screws or stapling, with utilities of 0.969, 0.957, and 0.962, respectively. One-way sensitivity analysis showed that hemiepiphysiodesis using a tension band plate was better than temporary hemiepiphysiodesis using percutaneous screws, when the overall complication rate of hemiepiphysiodesis using a tension band plate was lower than 15.7%. Two-way sensitivity analysis showed that hemiepiphysiodesis using a tension band plate was more beneficial than temporary hemiepiphysiodesis using percutaneous screws.

Sung, Ki Hyuk; Chung, Chin Youb; Lee, Kyoung Min; Lee, Seung Yeol; Choi, In Ho; Cho, Tae-Joon; Yoo, Won Joon; Park, Moon Seok

2014-01-01

370

In vivo preclinical evaluation of the influence of osteoporosis on the anchorage of different pedicle screw designs.  

PubMed

We investigate the anchorage of pedicle screws with different surface treatments in osteoporotic bone. Eight ewes were divided into two groups of four animals each: four sheep underwent bilateral ovariectomy (OVX Group), whereas the operation was simulated in the remaining group (SHAM Group). Eighteen months after the first operation, the Dynesys(®) System was fitted to the sheep using pedicle screws with three different surface treatments: untreated, rough blasted (uncoated) and bioactive coated (bioactive). Uncoated screws showed a significantly higher bone ingrowth value compared with the untreated screws in the OVX group (9.3%, p < 0.005) and a significantly lower bone ingrowth value in the SHAM group (-11.0%, p < 0.05). Furthermore, the bioactive pedicle screws had a significant lower bone ingrowth value than the untreated screws in the SHAM group (-12.1%, p < 0.05). These results suggest that both tested surface treatments of pedicular screws may provide an advantage in terms of bone quality and osseointegration, when implanted in osteoporotic vertebrae. PMID:21544593

Giavaresi, Gianluca; Fini, Milena; Giardino, Roberto; Salamanna, Francesca; Sartori, Maria; Borsari, Veronica; Spriano, Silvia; Bellini, Chiara M; Brayda-Bruno, Marco

2011-08-01

371

Coronal Plane Stability Before and After Total Knee Arthroplasty  

E-print Network

Coronal Plane Stability Before and After Total Knee Arthroplasty Robert A. Siston, PhD*,, ; Stuart of total knee arthroplasty depends in part on proper soft tissue management to achieve a stable joint. It is unknown to what degree total knee arthroplasty changes joint stability. We used a surgical navigation

Delp, Scott

372

Biomechanical analysis of different types of pedicle screw augmentation: a cadaveric and synthetic bone sample study of instrumented vertebral specimens.  

PubMed

This study aims to determine the pull-out strength, stiffness and failure pull-out energy of cement-augmented, cannulated-fenestrated pedicle screws in an osteoporotic cadaveric thoracolumbar model, and to determine, using synthetic bone samples, the extraction torques of screws pre-filled with cement and those with cement injected through perforations. Radiographs and bone mineral density measurements from 32 fresh thoracolumbar vertebrae were used to define specimen quality. Axial pull-out strength of screws was determined through mechanical testing. Mechanical pull-out strength, stiffness and energy-to-failure ratio were recorded for cement-augmented and non-cement-augmented screws. Synthetic bone simulating a human spinal bone with severe osteoporosis was used to measure the maximum extraction torque. The pull-out strength and stiffness-to-failure ratio of cement pre-filled and cement-injected screws were significantly higher than the non-cement-augmented control group. However, the cement pre-filled and cement-injected groups did not differ significantly across these values (p=0.07). The cement pre-filled group had the highest failure pull-out energy, approximately 2.8 times greater than that of the cement-injected (p<0.001), and approximately 11.5 times greater than that of the control groups (p<0.001). In the axial pull-out test, the cement-injected group had a greater maximum extraction torque than the cement pre-filled group, but was statistically insignificant (p=0.17). The initial fixation strength of cannulated screws pre-filled with cement is similar to that of cannulated screws injected with cement through perforations. This comparable strength, along with the heightened pull-out energy and reduced extraction torque, indicates that pedicle screws pre-filled with cement are superior for bone fixation over pedicle screws injected with cement. PMID:23669371

Chao, Kuo-Hua; Lai, Yu-Shu; Chen, Wen-Chuan; Chang, Chia-Ming; McClean, Colin J; Fan, Chang-Yuan; Chang, Chia-Hao; Lin, Leou-Chyr; Cheng, Cheng-Kung

2013-10-01

373

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

PubMed

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

Chi, Y L

1991-08-01

374

Joint warfare system (JWARS)  

Microsoft Academic Search

The Joint Warfare System (JWARS) is a campaign-level model of military operations that is currently being developed under contract by the Office of the Secretary of Defense (OSD) for use by OSD, the Joint Staff, the Services, and the War fighting Commands. The behavior of military forces can be simulated from ports of embarkation through to their activities in combat.

A. Simlote

2003-01-01

375

Campylobacter Prosthetic Joint Infection  

PubMed Central

A 75-year-old man was diagnosed with probable Campylobacter jejuni prosthetic knee infection after a diarrheal illness. Joint aspirate and operative cultures were negative, but PCR of prosthesis sonicate fluid was positive, as was stool culture. Nineteen additional cases of Campylobacter prosthetic joint infection reported in the literature are reviewed. PMID:24523462

Vasoo, Shawn; Schwab, Jeramy J.; Cunningham, Scott A.; Robinson, Trisha J.; Cass, Joseph R.; Berbari, Elie F.; Walker, Randall C.; Osmon, Douglas R.

2014-01-01

376

Hydrogen-induced change in core structures of {110}[111] edge and {110}[111] screw dislocations in iron  

PubMed Central

Employing the empirical embedded-atom method potentials, the evolution of edge and screw dislocation core structure is calculated at different hydrogen concentrations. With hydrogen, the core energy and Peierls potential are reduced for all dislocations. A broaden-core and a quasi-split core structure are observed for edge and screw dislocation respectively. The screw dislocation and hydrogen interaction in body-centred cubic iron is found to be not mainly due to the change of elastic modulus, but the variation of dislocation core structure. PMID:24067268

Wang, Shuai; Hashimoto, Naoyuki; Ohnuki, Somei

2013-01-01

377

Effect of threading screw and edge dislocations on transport properties of 4H-SiC homoepitaxial layers  

NASA Astrophysics Data System (ADS)

Local recombination properties of threading screw and edge dislocations in 4H-SiC epitaxial layers have been studied using electron beam induced current (EBIC). The minority carrier diffusion length in the vicinity of dislocations was found to vary with dislocation type. Screw dislocations had a more pronounced impact on diffusion length than the edge dislocations, evidencing stronger recombination activity. Temperature dependence of EBIC contrast of dislocations suggests that their recombination activity is controlled by deep energy levels in the vicinity of dislocation cores. This paper shows that the type of dislocation (screw or edge) can be identified from analysis of EBIC contrast.

Maximenko, S. I.; Freitas, J. A.; Myers-Ward, R. L.; Lew, K.-K.; VanMil, B. L.; Eddy, C. R.; Gaskill, D. K.; Muzykov, P. G.; Sudarshan, T. S.

2010-07-01

378

Posterior dynamic stabilization systems: DYNESYS.  

PubMed

Posterior dynamic stabilization systems have to neutralize injurious forces and restore painless function of the spine segments and protect the adjacent segments. Because degenerative disc disease has many clinical manifestations, pedicular screw systems and interspinous implants have their indications. A dynamic stabilization device has to provide stability throughout its lifetime, unless it activates or allows reparative processes with a reversal of the degenerative changes. Anchorage to the bone is crucial, at least for pedicular systems. This is a great demand on spinal implants and assumes rest and motion going together. Our experience with DYNESYS has shown that this method has limitations in elderly patients with osteoporotic bone or in patients with a severe segmental macro-instability combined with degenerative olisthesis and advanced disc degeneration. Such cases have an increased risk of failure. Only future randomized evaluations will be able to address the potential reduction of accelerated adjacent segment degeneration. The few posterior dynamic stabilization systems that have had clinical applications so far have produced clinical outcomes comparable with fusion. No severe adverse events caused by these implants have been reported. Long-term follow-up data and controlled prospective randomized studies are not available for most of the cited implants but are essential to prove the safety, efficacy, appropriateness, and economic viability of these methods. PMID:15950696

Schwarzenbach, Othmar; Berlemann, Ulrich; Stoll, Thomas M; Dubois, Gilles

2005-07-01

379

Low-profile titanium plate construct for early weightbearing with first metatarsophalangeal joint arthrodesis.  

PubMed

First metatarsophalangeal joint arthrodesis is a useful procedure for various first ray pathologic entities. Multiple constructs for fixation have provided successful fusion. A retrospective study of 21 feet (18 patients) was performed after first metatarsophalangeal joint fusion using crossed Kirschner wires or compression fixation with cannulated screws followed by the application of a 2-hole low-profile partially locking titanium plate. The median age was 59 (range 41 to 76) years, and we had 4 smokers and 3 patients with diabetes in our series. Postoperatively, a compression dressing with a posterior splint was applied. The patients then transitioned to a controlled ankle motion walker, and all patients reported full weightbearing by 2 weeks postoperatively. The mean follow-up duration was 11.43 (range 6 to 27) months. The overall primary fusion rate was 95.24% (20 of 21). Two nonunions occurred; one was asymptomatic and successfully consolidated at 12 months. The second nonunion required revisional surgery with an autogenous bone graft to heal successfully. This patient was noncompliant with the postoperative regimen and had a 48-pack year history of tobacco usage. Our results have shown early weightbearing after first metatarsophalangeal joint arthrodesis can be successfully initiated with splintage or lag screw fixation and a 2-hole, low-profile, partially locking titanium plate. PMID:23632068

Mann, Joshua J; Moon, Jared L; Brosky, Thomas A

2013-01-01

380

Deployable robotic woven wire structures and joints for space applications  

NASA Technical Reports Server (NTRS)

Deployable robotic structures are basically expandable and contractable structures that may be transported or launched to space in a compact form. These structures may then be intelligently deployed by suitable actuators. The deployment may also be done by means of either airbag or spring-loaded typed mechanisms. The actuators may be pneumatic, hydraulic, ball-screw type, or electromagnetic. The means to trigger actuation may be on-board EPROMS, programmable logic controllers (PLCs) that trigger actuation based on some input caused by the placement of the structure in the space environment. The actuation may also be performed remotely by suitable remote triggering devices. Several deployable woven wire structures are examined. These woven wire structures possess a unique form of joint, the woven wire joint, which is capable of moving and changing its position and orientation with respect to the structure itself. Due to the highly dynamic and articulate nature of these joints the 3-D structures built using them are uniquely and highly expandable, deployable, and dynamic. The 3-D structure naturally gives rise to a new generation of deployable three-dimensional spatial structures.

Shahinpoor, MO; Smith, Bradford

1991-01-01

381

Hip joint replacement - series (image)  

MedlinePLUS

... pain that limits what you can do. Hip joint replacement is usually done in people age 60 and ... Hip joint replacement is surgery to replace all or part of the hip joint with a man-made or artificial ...

382

Numerical and Experimental Evaluation on the Residual Stresses of Welded Joints  

NASA Astrophysics Data System (ADS)

Wings for the defense industry such as fighters, missiles, and rockets should show no deformation or damage on the structure. The structures of existing wings had holes for weight reduction. The plates and frames were fixed with rivets or screws, which limited the weight reduction possible. In this study, an improvement was made in jointing methods through EB welding and laser welding. Welding strength was measured through tension testing. In addition, finite element analysis was performed for the welding process so as to deduce the optimum welding condition.

Huh, Sun Chul; Park, Wonjo; Yang, Haesug; Jung, Haeyoung; Kim, Chuyoung

383

Pressure vessel flex joint  

NASA Technical Reports Server (NTRS)

An airtight, flexible joint is disclosed for the interfacing of two pressure vessels such as between the Space Station docking tunnel and the Space Shuttle Orbiter bulkhead adapter. The joint provides for flexibility while still retaining a structural link between the two vessels required due to the loading created by the internal/external pressure differential. The joint design provides for limiting the axial load carried across the joint to a specific value, a function returned in the Orbiter/Station tunnel interface. The flex joint comprises a floating structural segment which is permanently attached to one of the pressure vessels through the use of an inflatable seal. The geometric configuration of the joint causes the tension between the vessels created by the internal gas pressure to compress the inflatable seal. The inflation pressure of the seal is kept at a value above the internal/external pressure differential of the vessels in order to maintain a controlled distance between the floating segment and pressure vessel. The inflatable seal consists of either a hollow torus-shaped flexible bladder or two rolling convoluted diaphragm seals which may be reinforced by a system of straps or fabric anchored to the hard structures. The joint acts as a flexible link to allow both angular motion and lateral displacement while it still contains the internal pressure and holds the axial tension between the vessels.

Kahn, Jon B. (inventor)

1992-01-01

384

Acromioclavicular joint dislocations.  

PubMed

Acromioclavicular (AC) dislocation is a common injury especially among sportsmen. There is still a lack of consensus on whether to conserve or operate type III AC joint dislocations. Even among surgeons inclined to operate AC joint dislocations there is no unanimity on which surgical technique. There are a plethora of choices between mechanical fixation or synthetic materials or biologic anatomic reconstructions. Even among surgeons, there is a choice between open repairs and the latest-arthroscopic reconstructions. This review of AC joint dislocations intends to analyze the available surgical options, a critical analysis of existing literature, actual technique of anatomic repair, and also accompanying complications. PMID:24431027

Babhulkar, Ashish; Pawaskar, Aditya

2014-03-01

385

Anterior glenohumeral joint dislocations.  

PubMed

The glenohumeral joint is the most mobile articulation in the body and the most commonly dislocated diarthroidal joint. Anterior dislocation is by far the most common direction and can lead to instability of the glenohumeral joint, which ranges from subtle increased laxity to recurrent dislocation. Overtime, understanding of anterior shoulder dislocations and the resulting instability has improved. Likewise, significant advances in arthroscopic equipment have allowed use of the arthroscope to address anatomically the various lesions that cause instability. This article reviews the anatomy, pathophysiology, clinical evaluation, and treatment of anterior shoulder instability. PMID:18803980

Dodson, Christopher C; Cordasco, Frank A

2008-10-01

386

Three-dimensional finite element analysis of stress distribution in retention screws of different crown-implant ratios.  

PubMed

The retaining screw of the implant-supported dental prosthesis is the weakest point of the crown/implant system. Furthermore, crown height is another important factor that may increase the lever arm. Therefore, the aim of this study was to assess the stress distribution in implant prosthetic screws with different heights of the clinical crown of the prosthesis using the method of three-dimensional finite element analysis. Three models were created with implants (3.75 mm × 10 mm) and crowns (heights of 10, 12.5 and 15 mm). The results were visualised by means of von Mises stress maps that increased the crown heights. The screw structure exhibited higher levels of stresses in the oblique load. The oblique loading resulted in higher stress concentration when compared with the axial loading. It is concluded that the increase of the crown was damaging to the stress distribution on the screw, mainly in oblique loading. PMID:23947571

Moraes, S L D; Pellizzer, E P; Verri, F R; Santiago, J F; Silva, J V L

2015-05-01

387

A screw-like meteoric train photographed by double-station observations  

NASA Astrophysics Data System (ADS)

The double-station observation of a meteor is a kind of method for measuring the physical parameters of the meteor effectively. Four special groups of photographs about meteoric trains taken at two stations during Leonids 2001 have been collected. One representative group of them has been measured and analyzed in detail. The results reveal that this train has a screw-like structure and looks to have many spoke beams. The train moves forward in the form of left-hand screw. The horizontal drift velocity northward is 29.6 m s -1 and the vertical drift velocity upward is 12.3 m s -1. In addition, the material of the meteoric train has an outward expanding velocity up to about 79 m s -1. The possible explanation is that the persistent meteoric train is disturbed by the high altitude wind.

Wu, Guang-jie; Zhang, Zhou-sheng

2006-11-01

388

Cannulated screw and hexapodal fixator reconstruction for compound upper tibial fractures  

PubMed Central

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

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

2014-01-01

389

Characterization of the glide planes of the [001] screw dislocations in olivine using electron tomography  

NASA Astrophysics Data System (ADS)

A San Carlos olivine polycrystal has been deformed under uppermost mantle conditions, by compression at 900 °C, at a strain rate of 1.1 × 10-5 s-1, under a confining pressure of 300 MPa, using the Paterson press. Transmission electron tomography of dislocations has been performed by scanning transmission electron microscopy, by conventional transmission electron microscopy using the weak-beam dark-field technique, associated with precession or not, in order to determine the glide planes of [001] screw dislocations. This recent technique is the most suitable one since most [001] dislocations exhibit straight screw segments due to the high lattice friction on this character at low temperature. We find that [001] dislocations glide in (100), (010) and {110} as already reported, but also more unexpectedly in {120} and {130}. We show that at 900 °C, [001] {110} glide is dominant in polycrystals. We have, however, noted and characterized numerous cross-slip events in the specimen.

Mussi, Alexandre; Cordier, Patrick; Demouchy, Sylvie; Vanmansart, Claude

2014-07-01

390

Design of Flexure-based Precision Transmission Mechanisms using Screw Theory  

SciTech Connect

This paper enables the synthesis of flexure-based transmission mechanisms that possess multiple decoupled inputs and outputs of any type (e.g. rotations, translations, and/or screw motions), which are linked by designer-specified transmission ratios. A comprehensive library of geometric shapes is utilized from which every feasible concept that possesses the desired transmission characteristics may be rapidly conceptualized and compared before an optimal concept is selected. These geometric shapes represent the rigorous mathematics of screw theory and uniquely link a body's desired motions to the flexible constraints that enable those motions. This paper's impact is most significant to the design of nano-positioners, microscopy stages, optical mounts, and sensors. A flexure-based microscopy stage was designed, fabricated, and tested to demonstrate the utility of the theory.

Hopkins, J B; Panas, R M

2011-02-07

391

Development of a test rig for a helium twin-screw compressor  

NASA Astrophysics Data System (ADS)

A large helium cryogenic system is being developed for use in great science projects, such as the International Thermonuclear Experimental Reactor (ITER), Large Helical Device (LHD), and the Experimental Advanced Superconducting Tokamak (EAST). In this cryogenic system, a twin-screw compressor is a key component. Therefore, it is necessary to obtain the compressor performance. To obtain the performance characteristics, a test rig for the compressor has been built. All the important performance parameters, including adiabatic efficiency, volumetric efficiency, oil injection characteristic, and noise characteristic can be acquired with the rig when sensors are installed in the test system. With the test performance, the helium twin-screw compressor can be evaluated. Using these results, the design of the compressor can be improved.

Wang, B. M.; Hu, Z. J.; Zhang, P.; Li, Q.

2014-01-01

392

Joint spacing criterion for equivalent continuum model  

SciTech Connect

Currently, the Yucca Mountain Site Characterization Project is investigating the feasibility of the disposal of high-level radioactive waste in the unsaturated Topopah Spring formation. The Topopah Spring formation is a heavily fractured, predominantly vertically jointed, welded tuff, and the potential disposal area is cut by the Ghost Dance fault and bounded by several other faults structures. The joints in the tuff and the faults may have an impact on the emplacement drift or borehole stability, as well as on the movement of fluids through the rock mass. The design of the repository drifts and layout, the waste emplacement scheme, and the thermomechanical performance of the rock mass will be analyzed using various numerical models. These models may be based on different assumptions regarding the representation of the fracture behavior under given applied stresses, and will range from discrete models where individual mechanically active fractures are treated distinctly, to continuum models where the joint behavior is smeared over a representative volume. There is always the question of applicability of a model with respect to a given material domain to be analyzed. For the mechanical analysis of the rock mass response around a repository drift, the applicability of an equivalent continuum model is dependent on the joint spacing in the rock mass. Considering the joint spacings that may be encountered at the potential repository site, a ratio of joint spacing to the planned drift diameter may be adopted as a criterion for evaluating the applicability of the Compliant Joint Model (CJM) in the Yucca Mountain Site Characterization Project. In this paper, this criterion is established by reviewing basic continuum concepts and numerical approximation implications used to build the CJM and by examining rock mass conditions that may be encountered at the potential Yucca Mountain repository site.

Tsai, F.C.

1995-12-31

393

Atlantoaxial joint of atlanto-axial subluxation patients due to rheumatoid arthritis before and after surgery, morphological evaluation using CT reconstruction  

Microsoft Academic Search

This study investigated the preoperative morphology and postoperative fusion of the atlanto-axial joint (AAJ) in patients\\u000a with atlanto-axial subluxation (AAS) due to rheumatoid arthritis (RA) using computed tomography (CT). Furthermore, we examined\\u000a the relationship between the preoperative morphology of AAJ and other radiographic results. Thirty patients with AAS due to\\u000a RA treated by C1–2 transarticular screw fixation (TSF) were reviewed.

Yasunori Sorimachi; Haku Iizuka; Tsuyoshi Ara; Masahiro Nishinome; Yoichi Iizuka; Takashi Nakajima; Kenji Takagishi

2011-01-01

394

Internal friction study on the mobility of screw dislocations in undoped D. Qulard, P. Asti and J. L. Gauffier  

E-print Network

1291 Internal friction study on the mobility of screw dislocations in undoped InSb D. Quélard, P 1988) Résumé. 2014 La mobilité des dislocations a été étudiée dans InSb non dopé par frottement frequency internal friction in undoped InSb between 0.1 and 0.98 Tm. Samples characterized by a mainly screw

Paris-Sud XI, Université de

395

Breakdown degradation associated with elementary screw dislocations in 4H-SiC p +n junction rectifiers  

Microsoft Academic Search

It is well-known that SiC wafer quality deficiencies are delaying the realization of outstandingly superior 4H-SiC power electronics. While efforts to date have centered on eradicating micropipes (i.e., hollow core super-screw dislocations with Burgers vector>2c), 4H-SiC wafers and epilayers also contain elementary screw dislocations (i.e., Burgers vector=1c with no hollow core) in densities on the order of thousands per cm2,

P. G. NEUDECK; W. HUANG; M. DUDLEY

1998-01-01

396

Breakdown Degradation Associated with Elementary Screw Dislocations in 4H-SiC P(+)N Junction Rectifiers  

NASA Technical Reports Server (NTRS)

It is well-known that SiC wafer quality deficiencies are delaying the realization of outstandingly superior 4H-SiC power electronics. While efforts to date have centered on eradicating micropipes (i.e., hollow core super-screw dislocations with Burgers vector greater than 2c), 4H-SiC wafers and epilayers also contain elementary screw dislocations (i.e., Burgers vector = lc with no hollow core) in densities on the order of thousands per sq cm, nearly 100-fold micropipe densities. This paper describes an initial study into the impact of elementary screw dislocations on the reverse-bias current-voltage (I-V) characteristics of 4H-SiC p(+)n diodes. First, Synchrotron White Beam X-ray Topography (SWBXT) was employed to map the exact locations of elementary screw dislocations within small-area 4H-SiC p(+)n mesa diodes. Then the high-field reverse leakage and breakdown properties of these diodes were subsequently characterized on a probing station outfitted with a dark box and video camera. Most devices without screw dislocations exhibited excellent characteristics, with no detectable leakage current prior to breakdown, a sharp breakdown I-V knee, and no visible concentration of breakdown current. In contrast devices that contained at least one elementary screw dislocation exhibited a 5% to 35% reduction in breakdown voltage, a softer breakdown I-V knee, and visible microplasmas in which highly localized breakdown current was concentrated. The locations of observed breakdown microplasmas corresponded exactly to the locations of elementary screw dislocations identified by SWBXT mapping. While not as detrimental to SiC device performance as micropipes, the undesirable breakdown characteristics of elementary screw dislocations could nevertheless adversely affect the performance and reliability of 4H-SiC power devices.

Neudeck, P. G.; Huang, W.; Dudley, M.

1998-01-01

397

Twin-Screw Extrusion of Nano-Alumina–Based Simulants of Energetic Formulations Involving Gel-Based Binders  

Microsoft Academic Search

A 7.5-mm twin-screw extruder was developed specifically for the processing of energetic formulations involving nanoparticles. Prior to extrusion of energetic formulations, simulants of CMC, water, and alumina nanoparticle gels were extruded. Quantitative measures of degree of mixedness (statistics of concentration distributions) were obtained on samples processed with the twin-screw extruder and with conventional processing methods using wide-angle X-ray diffraction (WAXD)

S. Ozkan; H. Gevgilili; D. M. Kalyon; J. Kowalczyk; M. Mezger

2007-01-01

398

Hybrid computer-guided and minimally open surgery: anterior lumbar interbody fusion and translaminar screw fixation.  

PubMed

Less invasiveness is the way forward for spinal surgery. Minimal disruption of tissue, preservation of muscle function, and restoration of normal spinal alignment are still the goals of most surgical procedures. An anterior lumbar fusion technique using a less invasive procedure with the addition of translaminar screws is described. The autograft is harvested from the vertebral body, thus avoiding the morbidity associated with an iliac crest bone graft. The operative steps for the procedure are described. PMID:10766061

Kumar, N; Wild, A; Webb, J K; Aebi, M

2000-02-01

399

International test and demonstration of a 1MW wellhead generator: Helical screw expander power plant  

Microsoft Academic Search

A 1-MW wellhead generator was tested in 1980, 1981, and 1982 by Mexico, Italy, and New Zealand at Cerro Prieto, Cesano, and Broadlands, respectively. The total flow helical screw expander portable power plant, Model 76-1, had been built for the U.S. Government and field-tested in Utah, USA, in 1978 and 1979. The expander had oversized internal clearances designed for self-cleaning

R. A. McKay

1984-01-01

400

Altering the volumetric expansion ratio of a Lysholm helical screw expander  

Microsoft Academic Search

This is an analysis of the effects of the volumetric expansion ratio on the operating of a Lysholm helical screw expander. Extensive testing of the University of California Lysholm engine with a 5.3 volumetric expansion ratio was performed. The expansion ratio was reduced from 5.3 to 4.0. Tests were performed at a variety of speeds and qualities for a 5.0

M. K. Dunbar

1984-01-01

401

Analysis of a screw dislocation inside a circular inclusion with interfacial cracks in piezoelectric composites  

Microsoft Academic Search

The electroelastic interaction of a screw dislocation inside a circular inclusion with interfacial cracks in piezoelectric\\u000a composite materials under anti-plane shear and in-plane electric loads at infinity is investigated. The general solution to\\u000a this problem was obtained by means of Riemann-Schwarz's symmetry principle integrated with analysis of singularities of corresponding\\u000a complex potentials. As a typical example, closed form expressions of

Zheng Jian-long; Fang Qi-hong; Liu You-wen

2005-01-01

402

Unusual presentation of spinal cord compression related to misplaced pedicle screws in thoracic scoliosis  

Microsoft Academic Search

Utilization of thoracic pedicle screws is controversial, especially in the treatment of scoliosis. We present a case of a\\u000a 15-year-old girl seen 6 months after her initial surgery for scoliosis done elsewhere. She complained of persistent epigastric\\u000a pain, tremor of the right foot at rest, and abnormal feelings in her legs. Clinical examination revealed mild weakness in\\u000a the right lower

P. Papin; V. Arlet; D. Marchesi; B. Rosenblatt; M. Aebi

1999-01-01

403

Screw dislocation in hcp Ti?:?DFT dislocation excess energies and metastable core structures  

NASA Astrophysics Data System (ADS)

An extensive DFT search of (meta)stable structures of the \\frac{a}{3}\\langle1\\,1\\,\\bar{2}\\,0\\rangle screw dislocation in hcp-Ti is presented. It reveals that the stable core structures are never basal but always prismatic. This prismatic core dissociates into two partial dislocations in the same or neighboring prismatic planes depending on the initial position of the dislocation line, leading to either a symmetric or an asymmetric core. An alternative way of defining the core region from an electronic structure point of view is also proposed. It evidences clearly the symmetric or asymmetric character of the cores. We then introduce an ansatz for a straightforward and fast calculation of the excess energy, per unit length of dislocation, of a screw dislocation applicable to DFT calculations, in the cluster approach. The method is first validated on calculations of a \\frac{a}{3}\\langle1\\,1\\,\\bar{2}\\,0\\rangle screw dislocation in hcp-Ti, performed with an EAM potential from which exact excess energies can be extracted. Then, it is shown that it does work in a DFT calculation, through its application to the same screw dislocation in hcp-Ti with an accuracy of 8.4 meV/Å (1.8% of the excess energy for a cluster of 126 atoms per plane normal to the dislocation line). The comparison of the excess energies of the symmetric and assymmetric cores, calculated with the proposed ansatz, reveals that their energy difference is within the uncertainty of the method, which implies that the potential energy surface is very flat and that there could be many metastable core structures in hcp-Ti.

Tarrat, Nathalie; Benoit, Magali; Caillard, Daniel; Ventelon, Lisa; Combe, Nicolas; Morillo, Joseph

2014-07-01

404

Improved orthopedic arm joint  

NASA Technical Reports Server (NTRS)

Joint permits smooth and easy movement of disabled arm and is smaller, lighter and less expensive than previous models. Device is interchangeable and may be used on either arm at the shoulder or at the elbow.

Dane, D. H.

1971-01-01

405

Joint Services Electronics Program.  

National Technical Information Service (NTIS)

An annual report of the JSEP (Joint Services Electronics Program) in solid state electronics, quantum electronics, information electronics, control and optimization, and electromagnetic phenomena is presented. Results of the research to date are summarize...

M. Tinkham

1991-01-01

406

Joint Services Electronics Program.  

National Technical Information Service (NTIS)

An annual report of the JSEP (Joint Services Electronics Program) in solid state electronics, quantum electronics, information electronics, control and optimization, and electromagnetic phenomena is presented. Results of the research to date are summarize...

M. Tinkham

1987-01-01

407

Joint Services Electronics Program.  

National Technical Information Service (NTIS)

An annual report of the JSEP (Joint Services Electronic Program) in solid state electronics, quantum electronics, information electronics control and optimization and electromagnetic phenomenon is presented. Results of the research to date are summarized ...

M. Tinkham

1985-01-01

408

JOINT SEMINAR FINAL REPORT  

E-print Network

evolving from the Joint Seminar. - Peer-reviewed publications (journals, contribution to anthologies, working papers, proceedings, etc.) - Non peer-reviewed publications (journals, contribution to anthologies Application guidelines Length Clarity Intelligibility Procedures (submission, review, decision) Advising

Fuchs, Clemens

409

Culture - joint fluid  

MedlinePLUS

Joint fluid culture ... fungi, or viruses grow. This is called a culture. If such microorganisms are detected, other tests may ... is no special preparation needed for the lab culture. For information on preparing for the removal of ...

410

Correlation between microleakage and screw loosening at implant-abutment connection  

PubMed Central

PURPOSE This study aimed to evaluate the correlation between microleakage and screw loosening at different types of implant-abutment connections and/or geometries measuring the torque values before and after the leakage tests. MATERIALS AND METHODS Three different abutment types (Intenal hex titanium, internal hex zirconium, morse tapered titaniu?m) with different geometries were connected to its own implant fixture. All the abutments were tightened with a standard torque value then the composition was connected to the modified fluid filtration system. After the measurements of leakage removal torque values were re-measured. Kruskal-wallis test was performed for non-parametric and one-way ANOVA was performed for parametric data. The correlation was evaluated using Spearman Correlation Test (?=0.05). RESULTS Significantly higher microleakage was found at the connection of implant-internal hex zirconium abutment. Observed mean torque value loss was also significantly higher than other connection geometries. Spearman tests revealed a significant correlation between microleakage and screw loosening. CONCLUSION Microleakage may provoke screw loosening. Removing torque values rationally decrease with the increase of microleakage. PMID:24605204

Ayyildiz, Simel

2014-01-01

411

Tissue reaction to implants of different metals: a study using guide wires in cannulated screws.  

PubMed

Cannulated screws, along with guide wires, are typically used for surgical fracture treatment in cancellous bone. Breakage or bending deformation of the guide wire is a clinical concern. Mechanically superior guide wires made of Co-Cr alloys such as MP35N and L605 may reduce the occurrence of mechanical failures when used in combination with conventional (316L stainless steel) cannulated screws. However the possibility of galvanic or crevice corrosion and adverse tissue reaction, exists when using dissimilar materials, particularly in the event that a guide wire breaks, and remains in situ. Therefore, we designed an experiment to determine the tissue reaction to such an in vivo environment. Implant devices were designed to replicate a clinical situation where dissimilar metals can form a galvanic couple. Histological and SEM analyses were used to evaluate tissue response and corrosion of the implants. In this experiment, no adverse in vivo effects were detected from the use of dissimilar materials in a model of a broken guide wire in a cannulated screw. PMID:19844874

Devine, D M; Leitner, M; Perren, S M; Boure, L P; Pearce, S G

2009-01-01

412

Effects of screw speed on the properties of plasticized PLA/POSS composites  

NASA Astrophysics Data System (ADS)

The effect of screw speed on the flow behavior, mechanical, thermal and morphological properties of the melt compounded plasticized poly(lactic acid) (PLA)/polyhedral oligomeric silsesquioxanes (POSS) composites were investigated. Two types of POSS-aminopropylisobutyl-POSS (A-POSS) as the reactive one and the octaisobutyl-POSS (O-POSS) as the non-reactive one, were used at 1-10 wt% filler loadings. Poly(ethylene glycol) (PEG-8000 g/moles) was utilized as a plasticizer. PEG amount was kept constant at 10 wt% with respect to PLA. To investigate the compounding conditions on the properties of the composites, two different screw speeds (100 and 200 rpm) were used. It was found that incorporation of POSS particles to the PLA decreased the melt viscosity of the composites due to the slip-agent behavior of POSS molecules. The mechanical test results showed that composites compounded at 100 rpm have higher yield strength and modulus values. Moreover, a significant improvement in Izod impact strength of plasticized PLA composites compounded at 100 rpm was obtained (regardless of POSS type). SEM analysis showed that POSS particles dispersed homogeneously in polymer matrix at all loadings regardless of screw speed. It was revealed from DSC that POSS particles acted as a nucleating agent for PLA/PEG independently from mixing conditions. Moreover, the percent crystallinity was found to be higher in the presence of POSS.

Kodal, M.; Sirin, H.; Ozkoc, G.

2014-05-01

413

Numerical analysis of the internal flow field in screw centrifugal blood pump based on CFD  

NASA Astrophysics Data System (ADS)

As to the impeller blood pump, the high speed of the impeller, the local high shear force of the flow field and the flow dead region are the main reasons for blood damage. The screw centrifugal pump can effectively alleviate the problems of the high speed and the high shear stress for the impeller. The softness and non-destructiveness during the transfer process can effectively reduce the extent of the damage. By using CFD software, the characteristics of internal flow are analyzed in the screw centrifugal pump by exploring the distribution rules of the velocity, pressure and shear deformation rate of the blood when it flows through the impeller and the destructive effects of spiral blades on blood. The results show that: the design of magnetic levitation solves the sealing problems; the design of regurgitation holes solves the problem of the flow dead zone; the magnetic levitated microcirculation screw centrifugal pump can effectively avoid the vortex, turbulence and high shear forces generated while the blood is flowing through the pump. Since the distribution rules in the velocity field, pressure field and shear deformation rate of the blood in the blood pump are comparatively uniform and the gradient change is comparatively small, the blood damage is effectively reduced.

Han, W.; Han, B. X.; Y Wang, H.; Shen, Z. J.

2013-12-01

414

Computer-assisted virtual technology in intracapsular condylar fracture with two resorbable long-screws.  

PubMed

Our aim was to fix intracapsular condylar fractures (ICF) with two resorbable long screws using preoperative computer-assisted virtual technology. From February 2008 to July 2011, 19 patients with ICF were treated with two resorbable long screws. Preoperatively we took panoramic radiographs and spiral computed tomography (CT). Depending on their digital imaging and communications in medicine (DICOM) data, the dislocated condylar segments were restored using the SimPlant Pro™ software, version 11.04. The mean (SD) widths of the condylar head and neck from lateral to medial were 19.01 (1.28)mm and 13.84 (1.13)mm, respectively. In all patients, the mandibles and the ICF seen intraoperatively corresponded with the preoperative three-dimensional and virtual reposition. All patients were followed up for 6-46 months (mean 21). Occlusion and mouth opening had been restored completely in all but one patient, and absolute anatomical reduction was also achieved in most cases. Computer-assisted virtual technology plays an important part in the diagnosis of ICF, as well as in its preoperative design. Fixation with only two resorbable long screws is an effective and reliable method for fixing ICF. PMID:22546281

Wang, W H; Deng, J Y; Zhu, J; Li, M; Xia, B; Xu, B

2013-03-01

415

Mechanistic modeling of modular co-rotating twin-screw extruders.  

PubMed

In this study, we present a one-dimensional (1D) model of the metering zone of a modular, co-rotating twin-screw extruder for pharmaceutical hot melt extrusion (HME). The model accounts for filling ratio, pressure, melt temperature in screw channels and gaps, driving power, torque and the residence time distribution (RTD). It requires two empirical parameters for each screw element to be determined experimentally or numerically using computational fluid dynamics (CFD). The required Nusselt correlation for the heat transfer to the barrel was determined from experimental data. We present results for a fluid with a constant viscosity in comparison to literature data obtained from CFD simulations. Moreover, we show how to incorporate the rheology of a typical, non-Newtonian polymer melt, and present results in comparison to measurements. For both cases, we achieved excellent agreement. Furthermore, we present results for the RTD, based on experimental data from the literature, and found good agreement with simulations, in which the entire HME process was approximated with the metering model, assuming a constant viscosity for the polymer melt. PMID:25102114

Eitzlmayr, Andreas; Koscher, Gerold; Reynolds, Gavin; Huang, Zhenyu; Booth, Jonathan; Shering, Philip; Khinast, Johannes

2014-10-20

416

Joint hypermobility syndrome pain  

Microsoft Academic Search

Joint hypermobility syndrome (JHS) was initially defined as the occurrence of musculoskeletal symptoms in the presence of\\u000a joint laxity and hypermobility in otherwise healthy individuals. It is now perceived as a commonly overlooked, underdiagnosed,\\u000a multifaceted, and multisystemic heritable disorder of connective tissue (HDCT), which shares many of the phenotypic features\\u000a of other HDCTs such as Marfan syndrome and Ehlers-Danlos syndrome.

Rodney Grahame

2009-01-01

417

Panel Post & Diagonal Brace Joint Detail; Crossbracing Center Joint ...  

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

Panel Post & Diagonal Brace Joint Detail; Crossbracing Center Joint Detail; Chord, Panel Post, Tie Bar, & Diagonal Brace Joint Detail; Chord, Tie Bar, & Crossbracing Joint Detail - Medora Bridge, Spanning East Fork of White River at State Route 235, Medora, Jackson County, IN

418

High pressure ceramic joint  

DOEpatents

Many recuperators have components which react to corrosive gases and are used in applications where the donor fluid includes highly corrosive gases. These recuperators have suffered reduced life, increased service or maintenance, and resulted in increased cost. The present joint when used with recuperators increases the use of ceramic components which do not react to highly corrosive gases. Thus, the present joint used with the present recuperator increases the life, reduces the service and maintenance, and reduces the increased cost associated with corrosive action of components used to manufacture recuperators. The present joint is comprised of a first ceramic member, a second ceramic member, a mechanical locking device having a groove defined in one of the first ceramic member and the second ceramic member. The joint and the mechanical locking device is further comprised of a refractory material disposed in the groove and contacting the first ceramic member and the second ceramic member. The present joint mechanically provides a high strength load bearing joint having good thermal cycling characteristics, good resistance to a corrosive environment and good steady state strength at elevated temperatures.

Ward, Michael E. (Poway, CA); Harkins, Bruce D. (San Diego, CA)

1993-01-01

419

Biomechanics of the natural, arthritic, and replaced human ankle joint  

PubMed Central

The human ankle joint complex plays a fundamental role in gait and other activities of daily living. At the same time, it is a very complicated anatomical system but the large literature of experimental and modelling studies has not fully described the coupled joint motion, position and orientation of the joint axis of rotation, stress and strain in the ligaments and their role in guiding and stabilizing joint motion, conformity and congruence of the articular surfaces, patterns of contact at the articular surfaces, patterns of rolling and sliding at the joint surfaces, and muscle lever arm lengths. The present review article addresses these issues as described in the literature, reporting the most recent relevant findings. PMID:24499639

2014-01-01

420

Bilateral C1-C2 Transarticular Screw and C1 Laminar Hook Fixation and Bone Graft Fusion for Reducible Atlantoaxial Dislocation: A Seven-Year Analysis of Outcome  

PubMed Central

Background Bilateral C1-2 transarticular screw and C1 laminar hook fixation was developed on the basis of transarticular screws fixation. The modified technique has showed a better biomechanical stability than established techniques in previous study. However, long-term (minimum follow-up 7 years) outcomes of patients with reducible atlantoaxial dislocation who underwent this modified fixation technique have not still been reported. Methods A retrospective study was conducted to evaluate the outcome of 36 patients who underwent this modified technique. Myelopathy was assessed using the Ranawat myelopathy score and Myelopathy Disability Index. Pain scores were assessed using Visual Analogue Scale. Radiological imaging was assessed and the following data were extracted: the atlantodental intervals, the space available for cord, presence of spinal cord signal change on T2 weighted image, C1–C2 angle, C2–C7 angle and fusion rates. Findings All patients achieved a minimum seven-year follow up. 95% patients with neck and suboccipital pain improved after surgery; in their Visual Analogue pain scores, there was a greater than 50% improvement in their VAS scores with a drop of 5 points on the VAS (P<0.05). 92% of patients improved in the Ranawat myelopathy grade; the Myelopathy Disability Index assessment showed a preoperative mean score of 35.62 with postoperative mean 12.75(P<0.05). There was not any significant atlantoaxial instability at each follow-up time. The space available for cord increased in all patients. Postoperative sagittal kyphosis of the subaxial spine was not observed. After six months after surgery, bone grafts of all patients were fused. No complications related to surgery were found in the period of follow-up. Conclusions The long-term outcomes of this case series demonstrate that under the condition of thorough preoperative preparations, bilateral C1–C2 transarticular screw and C1 laminar hook fixation and bone graft fusion is a reliable posterior atlantoaxial fusion technique for reducible atlantoaxial dislocation. PMID:24498163

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

2014-01-01

421

Dissimilar metals joint evaluation  

NASA Technical Reports Server (NTRS)

Dissimilar metals tubular joints between 2219-T851 aluminum alloy and 304L stainless steel were fabricated and tested to evaluate bonding processes. Joints were fabricated by four processes: (1) inertia (friction) weldings, where the metals are spun and forced together to create the weld; (2) explosive welding, where the metals are impacted together at high velocity; (3) co-extrusion, where the metals are extruded in contact at high temperature to promote diffusion; and (4) swaging, where residual stresses in the metals after a stretching operation maintain forced contact in mutual shear areas. Fifteen joints of each type were prepared and evaluated in a 6.35 cm (2.50 in.) O.D. size, with 0.32 cm (0.13 in.) wall thickness, and 7.6 cm (3.0 in) total length. The joints were tested to evaluate their ability to withstand pressure cycle, thermal cycle, galvanic corrosion and burst tests. Leakage tests and other non-destructive test techniques were used to evaluate the behavior of the joints, and the microstructure of the bond areas was analyzed.

Wakefield, M. E.; Apodaca, L. E.

1974-01-01

422

Periprosthetic Joint Infections  

PubMed Central

Implantation of joint prostheses is becoming increasingly common, especially for the hip and knee. Infection is considered to be the most devastating of prosthesis-related complications, leading to prolonged hospitalization, repeated surgical intervention, and even definitive loss of the implant. The main risk factors to periprosthetic joint infections (PJIs) are advanced age, malnutrition, obesity, diabetes mellitus, HIV infection at an advanced stage, presence of distant infectious foci, and antecedents of arthroscopy or infection in previous arthroplasty. Joint prostheses can become infected through three different routes: direct implantation, hematogenic infection, and reactivation of latent infection. Gram-positive bacteria predominate in cases of PJI, mainly Staphylococcus aureus and Staphylococcus epidermidis. PJIs present characteristic signs that can be divided into acute and chronic manifestations. The main imaging method used in diagnosing joint prosthesis infections is X-ray. Computed tomography (CT) scan may assist in distinguishing between septic and aseptic loosening. Three-phase bone scintigraphy using technetium has high sensitivity, but low specificity. Positron emission tomography using fluorodeoxyglucose (FDG-PET) presents very divergent results in the literature. Definitive diagnosis of infection should be made by isolating the microorganism through cultures on material obtained from joint fluid puncturing, surgical wound secretions, surgical debridement procedures, or sonication fluid. Success in treating PJI depends on extensive surgical debridement and adequate and effective antibiotic therapy. Treatment in two stages using a spacer is recommended for most chronic infections in arthroplasty cases. Treatment in a single procedure is appropriate in carefully selected cases. PMID:24023542

Lima, Ana Lucia L.; Oliveira, Priscila R.; Carvalho, Vladimir C.; Saconi, Eduardo S.; Cabrita, Henrique B.; Rodrigues, Marcelo B.

2013-01-01

423

Improving stability of locking compression plates through a design modification: a computational investigation.  

PubMed

Femoral shaft fractures are common in both the young and elderly due to high-impact trauma and low-impact trauma, respectively. Its treatment by indirect reduction through use of locking compression plates (LCPs) has been on the rise. The LCP possess several advantages in fracture fixation, combining angular stability through use of locking screws with misalignment correction and fracture reduction onto the plate through use of conventional screws. However, there have been cases of plate breakage and fracture non-unions to warrant a study to improve its stability. A design modification is suggested for mid-diaphyseal fractures, whereby unused screw holes are removed. The structural stability of the modified and commercially available LCP is computationally analyzed using finite element modelling and a comparison made in terms of mechanical performance across different fracture lengths. A critical fracture length for which the commercially available LCP is functional as a fixator for mid-diaphyseal fractures was established. The maximum von Mises' stress attained by the commercially available LCP rose to as high as 105 MPa, whereas for the modified LCP, it did not exceed 25 MPa. As expected, these stresses were also found at screw holes, nearest to the fracture site. Critical fracture length allows clinicians to quantitatively distinguish between mid-diaphyseal fractures that can or cannot be treated by the use of LCP fixation. It is also believed that the proposed design modification will substantially increase the fatigue life of the fixator, especially at screw holes nearest to the fracture region, where most fatigue fractures are known to occur and will consequently be functional for greater fracture lengths. PMID:23582021

Anitha, D; Das De, Shamal; Sun, Khong Kok; Doshi, Hitendra K; Lee, Taeyong

2015-02-01

424

Joint awareness in different types of knee arthroplasty evaluated with the Forgotten Joint score.  

PubMed

The purpose of this study was to validate the 'Forgotten Joint' score (FJS-12), a 12-item questionnaire designed to analyze the patient's ability to forget the joint in everyday life, in French and to compare the results of this Patient Reported Outcome (PRO) score in patients who had other than total joint arthroplasties. The score was compared in 122 patients that had either medial unicompartmental (N=51), patellofemoral (N=21) or total knee arthroplasty (N=50). After having validated the FJS-12 in French, a similar PRO was observed in unicompartmental and postero-stabilized total knee arthroplasty. Patellofemoral resurfacing had a significantly lower score than the two other types of arthroplasty, which can be explained by a significantly younger and smaller patient group. PMID:23688851

Thienpont, Emmanuel; Opsomer, Gaetan; Koninckx, Angelique; Houssiau, Frederic

2014-01-01

425

Freehand thoracic pedicle screw technique using a uniform entry point and sagittal trajectory for all levels: preliminary clinical experience.  

PubMed

Object Experience with freehand thoracic pedicle screw placement is well described in the literature. Published techniques rely on various starting points and trajectories for each level or segment of the thoracic spine. Furthermore, few studies provide specific guidance on sagittal and axial trajectories. The goal of this study was to propose a uniform entry point and sagittal trajectory for all thoracic levels during freehand pedicle screw placement and determine the accuracy of this technique. Methods The authors retrospectively reviewed postoperative CT scans of 33 consecutive patients who underwent open, freehand thoracic pedicle-screw fixation using a uniform entry point and sagittal trajectory for all levels. The same entry point for each level was defined as a point 3 mm caudal to the junction of the transverse process and the lateral margin of the superior articulating process, and the sagittal trajectory was always orthogonal to the dorsal curvature of the spine at that level. The medial angulation (axial trajectory) was approximately 30° at T-1 and T-2, and 20° from T-3 to T-12. Breach was defined as greater than 25% of the screw diameter residing outside of the pedicle or vertebral body. Results A total of 219 thoracic pedicle screws were placed with a 96% accuracy rate. There were no medial breaches and 9 minor lateral breaches (4.1%). None of the screws had to be repositioned postoperatively, and there were no neurovascular complications associated with the breaches. Conclusions It is feasible to place freehand thoracic pedicle screws using a uniform entry point and sagittal trajectory for all lev