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Sample records for screw joint stability

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

    PubMed Central

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

    2009-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2011-08-01

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

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

    PubMed Central

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

    2015-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Rudawska, Anna; Cisz, Sławomir; Warda, Tomasz

    2014-12-01

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

  5. Pedicle Screw-Based Posterior Dynamic Stabilization: Literature Review

    PubMed Central

    Sengupta, Dilip K.; Herkowitz, Harry N.

    2012-01-01

    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

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

    SciTech Connect

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

    2011-02-15

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

  7. Metacarpophalangeal and interphalangeal joint arthrodesis: a comparative study between tension band and compression screw fixation.

    PubMed

    Breyer, J M; Vergara, P; Parra, L; Sotelo, P; Bifani, A; Andrade, F

    2015-05-01

    A retrospective, comparative cohort study was performed of metacarpophalangeal or proximal interphalangeal joint arthrodesis with either tension band (n = 28) or compression (Acutrak Mini) screw (n = 29) methods. We compared rate of union, healing time, complications, and re-operation rate. Union was achieved in 26/28 (92.8%) of the tension band group (9.4 weeks) and 24/28 (85.7%) of the compression screw group (9.8 weeks). Only 28 patients in the screw group were assessed for union as one patient in the screw group sustained a fracture at the time of insertion and was converted to tension band fixation. The complication rate was 8/28 (28.6%) in the tension band group and 8/29 (27.6%) in the compression screw group. Re-operation rate was 9/28 (32.1%) in the tension band group and 1/29 (3.6%) in the compression screw group. Our findings indicate that bone healing, healing time, and complications are similar in both groups. The tension band technique had a significantly higher re-operation rate (hardware removal), but was the technique for salvage following failure of the screw technique.

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

    PubMed Central

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

    2016-01-01

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

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

    PubMed

    Tarukado, Kiyoshi; Tono, Osamu; Doi, Toshio

    2015-10-01

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

  10. The effect of polyethylene creep on tibial insert locking screw loosening and back-out in prosthetic knee joints.

    PubMed

    Sanders, Anthony P; Raeymaekers, Bart

    2014-10-01

    A prosthetic knee joint typically comprises a cobalt-chromium femoral component that articulates with a polyethylene tibial insert. A locking screw may be used to prevent micromotion and dislodgement of the tibial insert from the tibial tray. Screw loosening and back-out have been reported, but the mechanism that causes screw loosening is currently not well understood. In this paper, we experimentally evaluate the effect of polyethylene creep on the preload of the locking screw. We find that the preload decreases significantly as a result of polyethylene creep, which reduces the torque required to loosen the locking screw. The torque applied to the tibial insert due to internal/external rotation within the knee joint during gait could thus drive locking screw loosening and back-out. The results are very similar for different types of polyethylene.

  11. Joint stabilizing projects in defense

    SciTech Connect

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

    1992-06-01

    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.

  12. Joint stabilizing projects in defense

    SciTech Connect

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

    1992-06-01

    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.

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

    NASA Astrophysics Data System (ADS)

    Pan, Chengyi; Zhang, Jianyi

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

  14. Transgluteal posterior column screw stabilization for fractures of the acetabulum: a technical trick.

    PubMed

    Connelly, Camille L; Archdeacon, Michael T

    2012-10-01

    The traditional exposure of high posterior column or transverse acetabular fractures can pose a challenge for lag screw stabilization. The authors describe an adjunctive percutaneous transgluteal lag screw technique for the internal fixation of the high posterior column. In the senior author's experience, this technique has been helpful to achieve the optimal trajectory for a stable perpendicular lag screw to maintain an anatomical reduction. In our experience, this technique has been used in conjunction with the standard Kocher-Langenbeck exposure and posterior column plating techniques.

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

    PubMed

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

    2016-01-01

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

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

    PubMed

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

    2002-01-01

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

  17. Cruciate coupling and screw-home mechanism in passive knee joint during extension--flexion.

    PubMed

    Moglo, K E; Shirazi-Adl, A

    2005-05-01

    The screw-home mechanism and coupling between forces in cruciate ligaments during passive knee joint flexion were investigated for various boundary conditions, flexion axis alignments and posterior cruciate ligaments (PCL)/anterior cruciate ligament (ACL) conditions. A developed non-linear 3D finite element model was used to perform detailed elasto-static response analyses of the human tibiofemoral joint as a function of flexion angle varying from 10 degrees hyper-extension to 90 degrees flexion. The tibia rotated internally as the femur flexed and externally as the femur extended. The re-alignment of the flexion axis by +/-5 degrees rotation about the axial (distal-proximal) axis, transection of the ACL and changes in cruciate ligament initial strains substantially influenced the 'screw-home' motion. On the other hand, restraint on this coupled rotation diminished ACL forces in flexion. A remarkable coupling was predicted between ACL and PCL forces in flexion; forces in both cruciate ligaments increased as the initial strain or pretension in one of them increased whereas they both diminished as one of them was cut or became slack. This has important consequences in joint functional biomechanics following a ligament injury or replacement surgery and, hence, in the proper management of joint disorders. PMID:15797589

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

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

    PubMed

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

    2003-01-01

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

  20. Stability of anterior vertebral body screws after kyphoplasty augmentation. An experimental study to compare anterior vertebral body screw fixation in soft and cured kyphoplasty cement.

    PubMed

    Linhardt, O; Lüring, C; Matussek, J; Hamberger, C; Herold, T; Plitz, W; Grifka, J

    2006-10-01

    The goal of this cadaver study was to compare the stability of anterior vertebral body screws after implantation in soft or cured kyphoplasty cement. Anterior vertebral body screws were inserted in a total of 30 thoracolumbar vertebrae of ten different human specimens: ten screws were implanted in non-augmented vertebrae (group 1), ten screws were placed in soft cement (group 2), and ten screws were placed in cured cement (group 3). The screws were then tested for biomechanical axial pullout resistance. Mean axial pullout strength was 192 N (range: 10-430 N) in group 1, 364 N (range: 65-875 N) in group 2, and 271 N (range: 35-625 N) in group 3. The paired Student's t-test demonstrated a significant difference between pullout strength of groups 1 and 2 (p= 0.0475). No significant difference was seen between pullout strength of groups 1 and 3 (p= 0.2646) and between groups 2 and 3 (p= 0.3863). We achieved a 1.9 times higher pullout strength with kyphoplasty augmentation of osteoporotic vertebrae compared with the pullout strength of non-augmented vertebrae. Implantation of anterior vertebral body screws in cured cement is a satisfactory method. With this method we found a 1.4 times higher pullout strength than non-augmented vertebrae.

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

    PubMed

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

    2016-01-01

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

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

    PubMed Central

    İnceoğlu, Serkan

    2015-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

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

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

    NASA Astrophysics Data System (ADS)

    Sherman, William

    2005-03-01

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

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

    PubMed

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

    2016-04-01

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

  6. Pedicle screw-based posterior dynamic stabilizers for degenerative spine: in vitro biomechanical testing and clinical outcomes.

    PubMed

    Chamoli, Uphar; Diwan, Ashish D; Tsafnat, Naomi

    2014-09-01

    Dynamic stabilization in a degenerate symptomatic spine may be advantageous compared with conventional fusion procedures, as it helps preserve motion and minimizes redistribution of loads at instrumented and adjacent segments. This article presents a systematic review of biomechanical and clinical evidence available on some of the pedicle screw based posterior dynamic stabilization (PDS) devices. Using Medline, Embase, and Scopus online databases, we identified four pedicle-screw-PDS devices for which both, biomechanical testing and clinical follow-up data are available: Graf artificial ligaments, Isobar TTL, Polyetheretherketone rods, and Dynesys. The current state-of-the-art of pedicle-screw-PDS devices is far from achieving its desired biomechanical efficacy, which has resulted in a weak support for the posited clinical benefits. Although pedicle-screw-PDS devices are useful in salvaging a moderately degenerate functionally suboptimal disc, for severe disc degeneration cases fusion is still the preferred choice. We conclude that a pedicle-screw-PDS device should aim at restoring load sharing amongst spinal elements while preserving the qualitative and quantitative nature of spinal motion, especially minimize posterior shift of the helical axis of motion. More precise and objective assessment techniques need to be standardized for in vivo evaluation of intervertebral motion and load sharing amongst spinal elements across different pedicle-screw-PDS devices.

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

    PubMed

    Kaiser, A D; Whiteside, L A

    1990-10-01

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

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

    PubMed Central

    Isman, Eren; Taner, Lale; Kurkcu, Mehmet

    2015-01-01

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

  9. Simulation-based particle swarm optimization and mechanical validation of screw position and number for the fixation stability of a femoral locking compression plate.

    PubMed

    Lee, Chian-Her; Shih, Kao-Shang; Hsu, Ching-Chi; Cho, Tomas

    2014-01-01

    Locking compression plates (LCPs) have been used to fix femoral shaft fractures. Previous studies have attempted to identify the best LCP screw positions and numbers to achieve the fixation stability. However, the determined screw positions and numbers were mainly based on the surgeons' experiences. The aim of this study was to discover the best number and positions of LCP screws to achieve acceptable fixation stability. Three-dimensional numerical models of a fractured femur with the LCP were first developed. Then, the best screw position and number of LCPs were determined by using a simulation-based particle swarm optimization algorithm. Finally, the results of the numerical study were validated by conducting biomechanical tests. The results showed that the LCP with six locking screws resulted in the necessary fixation stability, and the best combination of positions of locking screws inserted into the LCP was 1-5-6-7-8-12 (three locking screws on either side of the bone fragment with two locking screws as close as practicable to the fracture site). In addition, the numerical models and algorithms developed in this study were validated by the biomechanical tests. Both the numerical and experimental results can provide clinical suggestions to surgeons and help them to understand the biomechanics of LCP systems.

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

    PubMed

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

    2013-11-01

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

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

    PubMed Central

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

    2008-01-01

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

  12. 46 CFR 154.524 - Piping joints: Welded and screwed couplings.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... lengths without flanges must be joined by one of the following: (a) A butt welded joint with complete penetration at the weld root except that for design temperatures colder than −10 °C (14 °F) the butt weld...

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

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... lengths without flanges must be joined by one of the following: (a) A butt welded joint with complete penetration at the weld root except that for design temperatures colder than −10 °C (14 °F) the butt weld...

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

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... lengths without flanges must be joined by one of the following: (a) A butt welded joint with complete penetration at the weld root except that for design temperatures colder than −10 °C (14 °F) the butt weld...

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

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... lengths without flanges must be joined by one of the following: (a) A butt welded joint with complete penetration at the weld root except that for design temperatures colder than −10 °C (14 °F) the butt weld...

  16. 46 CFR 154.524 - Piping joints: Welded and screwed couplings.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... lengths without flanges must be joined by one of the following: (a) A butt welded joint with complete penetration at the weld root except that for design temperatures colder than −10 °C (14 °F) the butt weld...

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

    PubMed

    Kimura, Tetsuya; Kouzaki, Motoki

    2013-04-01

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

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

    PubMed

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

    2016-02-01

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

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

    PubMed Central

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

    2015-01-01

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

  20. The dimensional stability of lightly-loaded epoxy joints

    SciTech Connect

    Badami, V G; Lawton, K M; Patterson, S R; Tajbakhsh, H

    1998-08-27

    The use of adhesives to bond metal mounting structures to optical components can significantly simplify the design of an optical system. In precision applications, dimensional instability of the adhesive must be included as a component of the overall error budget. This paper describes the qualification testing of a balanced heterodyne interferometer system in a carefully controlled environment for the purpose of measuring joint stability. Results of this qualification test are reported.

  1. Intrapelvic reduction and buttress screw stabilization of dome impaction of the acetabulum: a technical trick.

    PubMed

    Casstevens, Christopher; Archdeacon, Michael T; dʼHeurle, Albert; Finnan, Ryan

    2014-06-01

    Superomedial impaction of the anterior dome of the acetabulum is a known risk factor for poor outcomes after open reduction and internal fixation of acetabular fractures. The authors, using the anterior intrapelvic (modified Stoppa) approach to the acetabulum, describe a novel technique to help reduce and stabilize marginal impaction of the acetabular dome. In the senior author's experience, this technique has been helpful to achieve adequate reduction and stabilization.

  2. Biomechanical evaluation of an interfacet joint decompression and stabilization system.

    PubMed

    Leasure, Jeremi M; Buckley, Jenni

    2014-07-01

    A majority of the middle-aged population exhibit cervical spondylosis that may require decompression and fusion of the affected level. Minimally invasive cervical fusion is an attractive option for decreasing operative time, morbidity, and mortality rates. A novel interfacet joint spacer (DTRAX facet screw system, Providence Medical) promises minimally invasive deployment resulting in decompression of the neuroforamen and interfacet fusion. The present study investigates the effectiveness of the device in minimizing intervertebral motion to promote fusion, decompression of the nerve root during bending activity, and performance of the implant to adhere to anatomy during repeated bending loads. We observed flexion, extension, lateral bending, and axial rotation resonant overshoot mode (ROM) in cadaver models of c-spine treated with the interfacet joint spacer (FJ spacer) as stand-alone and supplementing anterior plating. The FJ spacer was deployed bilaterally at single levels. Specimens were placed at the limit of ROM in flexion, extension, axial bending, and lateral bending. 3D images of the foramen were taken and postprocessed to quantify changes in foraminal area. Stand-alone spacer specimens were subjected to 30,000 cycles at 2 Hz of nonsimultaneous flexion-extension and lateral bending under compressive load and X-ray imaged at regular cycle intervals for quantitative measurements of device loosening. The stand-alone FJ spacer increased specimen stiffness in all directions except extension. 86% of all deployments resulted in some level of foraminal distraction. The rate of effective distraction was maintained in flexed, extended, and axially rotated postures. Two specimens demonstrated no detectable implant loosening (<0.25 mm). Three showed unilateral subclinical loosening (0.4 mm maximum), and one had subclinical loosening bilaterally (0.5 mm maximum). Results of our study are comparable to previous investigations into the stiffness of other stand

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

    PubMed

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

    2016-10-01

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

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

    PubMed

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

    2016-10-01

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

  5. [Surgical management of complete Tossy III acromioclavicular joint dislocation with the Bosworth screw or the Wolter plate. A critical evaluation].

    PubMed

    Broos, P; Stoffelen, D; Van de Sijpe, K; Fourneau, I

    1997-08-01

    The long-term results with an average of 4.3 years of 87 patients with an AC-dislocation grade III according to Tossy, treated operatively with a Bosworth screw or a Wolter plate are described and submitted to critical evaluation. Of the patients 16% had implant failures. Redislocation was seen in 25% of the patients, calcifications in 39% and arthritis in 41%. The end-result was good or excellent in 60% of the patients and fair or bad in 40%. The only factor, influencing the end result was the redislocation rate (p < 0.05). These moderate results surprised and disappointed us. They made us conclude that the grade III acromioclavicular dislocation is no absolute indication for surgical treatment, as is often suggested in literature. No significant differences could be revealed between both surgical techniques.

  6. Pull-out strength of cemented solid versus fenestrated pedicle screws in osteoporotic vertebrae

    PubMed Central

    Leichtle, C. I.; Rothstock, S.; Happel, J.; Walter, F.; Shiozawa, T.; Leichtle, U. G.

    2016-01-01

    Objectives Cement augmentation of pedicle screws could be used to improve screw stability, especially in osteoporotic vertebrae. However, little is known concerning the influence of different screw types and amount of cement applied. Therefore, the aim of this biomechanical in vitro study was to evaluate the effect of cement augmentation on the screw pull-out force in osteoporotic vertebrae, comparing different pedicle screws (solid and fenestrated) and cement volumes (0 mL, 1 mL or 3 mL). Materials and Methods A total of 54 osteoporotic human cadaver thoracic and lumbar vertebrae were instrumented with pedicle screws (uncemented, solid cemented or fenestrated cemented) and augmented with high-viscosity PMMA cement (0 mL, 1 mL or 3 mL). The insertion torque and bone mineral density were determined. Radiographs and CT scans were undertaken to evaluate cement distribution and cement leakage. Pull-out testing was performed with a material testing machine to measure failure load and stiffness. The paired t-test was used to compare the two screws within each vertebra. Results Mean failure load was significantly greater for fenestrated cemented screws (+622 N; p ⩽ 0.001) and solid cemented screws (+460 N; p ⩽ 0.001) than for uncemented screws. There was no significant difference between the solid and fenestrated cemented screws (p = 0.5). In the lower thoracic vertebrae, 1 mL cement was enough to significantly increase failure load, while 3 mL led to further significant improvement in the upper thoracic, lower thoracic and lumbar regions. Conclusion Conventional, solid pedicle screws augmented with high-viscosity cement provided comparable screw stability in pull-out testing to that of sophisticated and more expensive fenestrated screws. In terms of cement volume, we recommend the use of at least 1 mL in the thoracic and 3 mL in the lumbar spine. Cite this article: C. I. Leichtle, A. Lorenz, S. Rothstock, J. Happel, F. Walter, T. Shiozawa, U. G. Leichtle. Pull

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

    PubMed

    Mullon, Charles; Keller, Laurent; Lehmann, Laurent

    2016-08-01

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

  8. Biomechanical stability of a volar locking-screw plate versus fragment-specific fixation in a distal radius fracture model.

    PubMed

    Cooper, Ellis O; Segalman, Keith A; Parks, Brent G; Sharma, Krishna M; Nguyen, Augustine

    2007-04-01

    Eight matched pairs of cadaveric radii were osteotomized by removing a 4-mm dorsal wedge of bone at the level of the sigmoid notch designed to simulate dorsal comminution. They were then fixed with either a volar locking-screw plate or fragment-specific fixation. All constructs underwent biomechanical testing in a custom-designed, custom-fabricated 4-point bending device. No statistically significant difference in stiffness was noted between the groups. Linear displacement and angulation at the osteotomy site were significantly less in the group with fragment-specific fixation at loads expected to be encountered during postoperative rehabilitation. Angulation at the osteotomy site was significantly less in the locking-screw plate group at higher loads.

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

    NASA Astrophysics Data System (ADS)

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

    2014-04-01

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

  10. An injectable cementing screw for fixation in osteoporotic bone.

    PubMed

    McKoy, B E; An, Y H

    2000-01-01

    With the aging population, osteoporosis and osteoporotic fractures are becoming more prevalent. Adequate screw fixation in this type of bone is difficult. Screws are often cemented in bone to help obtain purchase. However, current cementing techniques do not ensure implant stability. Here we present a new cannulated screw with side ports that can be injected with polymethylmethacylate (PMMA) for fixation in osteoporotic bone. We compared the ultimate holding power of this cannulated screw injected with PMMA to a solid screw with the same dimensions secured with PMMA by the standard technique. Both screws were placed into embalmed and fresh frozen lumbar vertebral bodies and pulled out using a mechanical testing system. The cannulated screw had a 278% greater holding power compared to the standard screw (p < 0.006). The cannulated screw provided a significant increase in holding power in osteoporotic bone. This novel screw is promising for fixation in osteoporotic bone and warrants clinical evaluation.

  11. Biomechanical comparison of locking plate and crossing metallic and absorbable screws fixations for intra-articular calcaneal fractures.

    PubMed

    Ni, Ming; Wong, Duo Wai-Chi; Mei, Jiong; Niu, Wenxin; Zhang, Ming

    2016-09-01

    The locking plate and percutaneous crossing metallic screws and crossing absorbable screws have been used clinically to treat intra-articular calcaneal fractures, but little is known about the biomechanical differences between them. This study compared the biomechanical stability of calcaneal fractures fixed using a locking plate and crossing screws. Three-dimensional finite-element models of intact and fractured calcanei were developed based on the CT images of a cadaveric sample. Surgeries were simulated on models of Sanders type III calcaneal fractures to produce accurate postoperative models fixed by the three implants. A vertical force was applied to the superior surface of the subtalar joint to simulate the stance phase of a walking gait. This model was validated by an in vitro experiment using the same calcaneal sample. The intact calcaneus showed greater stiffness than the fixation models. Of the three fixations, the locking plate produced the greatest stiffness and the highest von Mises stress peak. The micromotion of the fracture fixated with the locking plate was similar to that of the fracture fixated with the metallic screws but smaller than that fixated with the absorbable screws. Fixation with both plate and crossing screws can be used to treat intra-articular calcaneal fractures. In general, fixation with crossing metallic screws is preferable because it provides sufficient stability with less stress shielding.

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

    SciTech Connect

    Bernardin, John D; Flores, Eugene M

    2009-01-01

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

  13. Translational and rotational knee joint stability in anterior and posterior cruciate-retaining knee arthroplasty.

    PubMed

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

    2011-12-01

    This study investigated passive translational and rotational stability properties of the intact knee joint, after bicruciate-retaining bi-compartmental knee arthroplasty (BKA) and after posterior cruciate retaining total knee arthroplasty (TKA). Fourteen human cadaveric knee specimens were used in this study, and a robotic manipulator with six-axis force/torque sensor was used to test the joint laxity in anterior-posterior translation, valgus-varus, and internal-external rotation. The results show the knee joint stability after bicruciate-retaining BKA is similar to that of the native knee. On the other hand, the PCL-retaining TKA results in inferior joint stability in valgus, varus, external rotation, anterior and, surprisingly, posterior directions. Our findings suggest that, provided functional ligamentous structures, bicruciate-retaining BKA is a biomechanically attractive treatment for joint degenerative disease.

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

    PubMed

    Hagert, Elisabet; Hagert, Carl-Göran

    2010-11-01

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

  15. A larger critical shoulder angle requires more rotator cuff activity to preserve joint stability.

    PubMed

    Viehöfer, Arnd F; Gerber, Christian; Favre, Philippe; Bachmann, Elias; Snedeker, Jess G

    2016-06-01

    Shoulders with rotator cuff tears (RCT) tears are associated with significantly larger critical shoulder angles (CSA) (RCT CSA = 38.2°) than shoulders without RCT (CSA = 32.9°). We hypothesized that larger CSAs increase the ratio of glenohumeral joint shear to joint compression forces, requiring substantially increased compensatory supraspinatus loads to stabilize the arm in abduction. A previously established three dimensional (3D) finite element (FE) model was used. Two acromion shapes mimicked the mean CSA of 38.2° found in patients with RCT and that of a normal CSA (32.9°). In a first step, the moment arms for each muscle segment were obtained for 21 different thoracohumeral abduction angles to simulate a quasi-static abduction in the scapular plane. In a second step, the muscle forces were calculated by minimizing the range of muscle stresses able to compensate an external joint moment caused by the arm weight. If the joint became unstable, additional force was applied by the rotator cuff muscles to restore joint stability. The model showed a higher joint shear to joint compressive force for the RCT CSA (38.2°) for thoracohumeral abduction angles between 40° and 90° with a peak difference of 23% at 50° of abduction. To achieve stability in this case additional rotator cuff forces exceeding physiological values were required. Our results document that a higher CSA tends to destabilize the glenohumeral joint such that higher than normal supraspinatus forces are required to maintain modeled stability during active abduction. This lends strong support to the concept that a high CSA can induce supraspinatus (SSP) overload. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:961-968, 2016. PMID:26572231

  16. The Sensorimotor System, Part I: The Physiologic Basis of Functional Joint Stability

    PubMed Central

    Riemann, Bryan L.; Lephart, Scott M.

    2002-01-01

    Objective: To define the nomenclature and physiologic mechanisms responsible for functional joint stability. Data Sources: Information was drawn from an extensive MEDLINE search of the scientific literature conducted in the areas of proprioception, neuromuscular control, and mechanisms of functional joint stability for the years 1970 through 1999. An emphasis was placed on defining pertinent nomenclature based on the original references. Data Synthesis: Afferent proprioceptive input is conveyed to all levels of the central nervous system. They serve fundamental roles in optimal motor control and sensorimotor control over functional joint stability. Conclusions/Applications: Sensorimotor control over the dynamic restraints is a complex process that involves components traditionally associated with motor control. Recognizing and understanding the complexities involved will facilitate the continued development and institution of management strategies based on scientific rationales. PMID:16558670

  17. Effects of individual strengthening exercises for the stabilization muscles on the nutation torque of the sacroiliac joint in a sedentary worker with nonspecific sacroiliac joint pain

    PubMed Central

    Yoo, Won-gyu

    2015-01-01

    [Purpose] We investigated the effects of individual strengthening exercises for the stabilization muscles on the nutation torque of the sacroiliac joint in a sedentary worker with nonspecific sacroiliac joint pain. [Subject] A 36-year-old female complained of pain in the sacroiliac joints. [Methods] The subject performed individual strengthening exercises for the stabilization muscles for nutation torque of the sacroiliac joint for 3 weeks. Pain-provocation tests and visual analog scale (VAS) scores were evaluated before and after the exercises. [Results] After performing the individual strengthening exercises for the erector spinae, rectus abdominis, and biceps femoris muscles for 3 weeks, the subject displayed no pain in the pain provocation tests, and the VAS score was 2/10. [Conclusion] The individual strengthening exercises for the stabilization muscles of the sacroiliac joint performed in the present study appear to be effective for sedentary workers with sacroiliac joint pain. PMID:25642098

  18. Fatigue effects on knee joint stability during two jump tasks in women.

    PubMed

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

    2010-04-01

    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

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

    PubMed

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

    2012-05-11

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

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

    PubMed

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

    2012-05-11

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

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

    PubMed Central

    Kim, Eun-Kyung; Kim, Seong-Gil

    2016-01-01

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

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

    PubMed

    Kim, Eun-Kyung; Kim, Seong-Gil

    2016-03-01

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

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

    PubMed

    Martin, J W; Whiteside, L A

    1990-10-01

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

  4. The effect of resistance exercise direction for hip joint stabilization on lateral abdominal muscle thickness

    PubMed Central

    Jung, Ju-Hyeon; Lee, Sang-Yeol

    2016-01-01

    The aim of this study was to determine the effects of resistance direction in hip joint stabilization exercise on change in lateral abdominal muscle thickness in healthy adults. Twenty-six healthy adults were randomly allocated to either a hip stabilization exercise by hip straight resistance group (n=12) or a hip diagonal resistance group (n=14). The outcome measures included contraction thickness ratio in transversus abdominis (TrA), internal oblique (IO) and external oblique, and TrA lateral slide were assessed during the abdominal drawing-in maneuver by b-mode ultrasound. The researcher measured the abdominal muscle thickness of each participant before the therapist began the intervention and at the moment intervention was applied. There was a significant difference in lateral abdominal muscle thickness between the straight resistance exercise of hip joint group and the diagonal resistance exercise of hip joint group. Significant differences were found between the two groups in the percentage of change of muscle thickness of the TrA (P=0.018) and in the thickness ratio of the TrA (P=0.018). Stability exercise accompanied by diagonal resistance on the hip joint that was applied in this study can induce automatic contraction of the IO and TrA, which provides stability to the lumbar spine. PMID:27807520

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

    PubMed

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

    2015-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

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

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

    PubMed Central

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

    2015-01-01

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

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

    PubMed Central

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

    2015-01-01

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

  9. Dynamic Postural-Stability Deficits After Cryotherapy to the Ankle Joint

    PubMed Central

    Fullam, Karl; Caulfield, Brian; Coughlan, Garrett F.; McGroarty, Mark; Delahunt, Eamonn

    2015-01-01

    Context  Decreased postural stability is a primary risk factor for lower limb musculoskeletal injuries. During athletic competitions, cryotherapy may be applied during short breaks in play or during half-time; however, its effects on postural stability remain unclear. Objective  To investigate the acute effects of a 15-minute ankle-joint cryotherapy application on dynamic postural stability. Design  Controlled laboratory study. Setting  University biomechanics laboratory. Patients or Other Participants  A total of 29 elite-level collegiate male field-sport athletes (age = 20.8 ± 1.12 years, height = 1.80 ± 0.06 m, mass = 81.89 ± 8.59 kg) participated. Intervention(s)  Participants were tested on the anterior (ANT), posterolateral (PL), and posteromedial (PM) reach directions of the Star Excursion Balance Test before and after a 15-minute ankle-joint cryotherapy application. Main Outcome Measure(s)  Normalized reach distances; sagittal-plane kinematics of the hip, knee, and ankle joints; and associated mean velocity of the center-of-pressure path during performance of the ANT, PL, and PM reach directions of the Star Excursion Balance Test. Results  We observed a decrease in reach-distance scores for the ANT, PL, and PM reach directions from precryotherapy to postcryotherapy (P < .05). No differences were observed in hip-, knee-, or ankle-joint sagittal-plane kinematics (P > .05). We noted a decrease in mean velocity of the center-of-pressure path from precryotherapy to postcryotherapy (P < .05) in all reach directions. Conclusions  Dynamic postural stability was adversely affected immediately after cryotherapy to the ankle joint. PMID:26285088

  10. Comparison of Biomechanical Characteristics and Pelvic Ring Stability Using Different Fixation Methods to Treat Pubic Symphysis Diastasis

    PubMed Central

    Yao, Feng; He, Yu; Qian, Hebu; Zhou, Dongsheng; Li, Qinghu

    2015-01-01

    Abstract The intention of this study was to compare the biomechanical characteristics using 5 internal fixation methods used clinically to stabilize a pubic symphysis diastasis (PSD, Tile type B1). A 3-dimensional finite element model of PSD was simulated using 5 implants, including single superior plate (Single-Plate), superior and anterior plate (Dual-Plate), single cannulated screw (Single-Screw), crossed dual cannulated screws (Cross-Screw), and parallel dual cannulated screws (Para-Screw). Three loads were distributed in all models, including dual-leg standing, single-leg stance, and rotation. To evaluate the biomechanical properties, the construct stiffness, the stress distribution, and the von Misses stress were recorded and analyzed. To evaluate pelvic ring stability, the micromotion of the pubic symphysis and iliosacral joint was analyzed. Disruption of pubic symphysis dramatically decreased the pelvic ring stability. Cross-screw and Para-Screw showed higher stiffness than other methods. All implants endured the maximum von Misses stress under single-leg stance. For Plate-Screw system, the maximum stress occurred at a place where it strides over pubic symphysis and adjacent Plate-Screw interface. The single implant and Para-Screw had a tendency to fail. Para-Screw showed the best fixation effect under dual-leg conditions. Cross-screw showed superior antishearing force capacity under single-leg stance. Dual-Plate provided maximum antihorizontal rotation. Para-Screw provided the maximum stabilization for the posterior pelvic ring. This study showed the biomechanical advantages of dual-implant for PSD only from the finite element view. The Para-Screw provided high construct stiffness under 3 load conditions. The single implant and Para-Screw had a tendency to fail. The better anterior and posterior pelvic stabilization were obtained by the dual-implant fixation than other methods. Therefore, the Cross-Screw and Dual-Plate fixation methods should be preferred

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

    PubMed Central

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

    2015-01-01

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

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

    PubMed

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

    2015-12-01

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

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

    PubMed

    Dumas, R; Cheze, L

    2008-08-01

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

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

    PubMed

    Heitmann, Stewart; Ferns, Norm; Breakspear, Michael

    2011-01-01

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

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

    PubMed

    Yang, Feng; Pai, Yi-Chung

    2010-02-10

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

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

    SciTech Connect

    L. KWEI; B. SMITH; ET AL

    2001-02-01

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

  17. Comparison of Biomechanical Characteristics and Pelvic Ring Stability Using Different Fixation Methods to Treat Pubic Symphysis Diastasis: A Finite Element Study.

    PubMed

    Yao, Feng; He, Yu; Qian, Hebu; Zhou, Dongsheng; Li, Qinghu

    2015-12-01

    The intention of this study was to compare the biomechanical characteristics using 5 internal fixation methods used clinically to stabilize a pubic symphysis diastasis (PSD, Tile type B1).A 3-dimensional finite element model of PSD was simulated using 5 implants, including single superior plate (Single-Plate), superior and anterior plate (Dual-Plate), single cannulated screw (Single-Screw), crossed dual cannulated screws (Cross-Screw), and parallel dual cannulated screws (Para-Screw). Three loads were distributed in all models, including dual-leg standing, single-leg stance, and rotation. To evaluate the biomechanical properties, the construct stiffness, the stress distribution, and the von Misses stress were recorded and analyzed. To evaluate pelvic ring stability, the micromotion of the pubic symphysis and iliosacral joint was analyzed.Disruption of pubic symphysis dramatically decreased the pelvic ring stability. Cross-screw and Para-Screw showed higher stiffness than other methods. All implants endured the maximum von Misses stress under single-leg stance. For Plate-Screw system, the maximum stress occurred at a place where it strides over pubic symphysis and adjacent Plate-Screw interface. The single implant and Para-Screw had a tendency to fail. Para-Screw showed the best fixation effect under dual-leg conditions. Cross-screw showed superior antishearing force capacity under single-leg stance. Dual-Plate provided maximum antihorizontal rotation. Para-Screw provided the maximum stabilization for the posterior pelvic ring.This study showed the biomechanical advantages of dual-implant for PSD only from the finite element view. The Para-Screw provided high construct stiffness under 3 load conditions. The single implant and Para-Screw had a tendency to fail. The better anterior and posterior pelvic stabilization were obtained by the dual-implant fixation than other methods. Therefore, the Cross-Screw and Dual-Plate fixation methods should be preferred in the

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

    PubMed

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

    2009-02-01

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

  19. Simple Coating with Fibronectin Fragment Enhances Stainless Steel Screw Osseointegration in Healthy and Osteoporotic Rats

    PubMed Central

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

    2015-01-01

    Metal implants are widely used to provide structural support and stability in current surgical treatments for bone fractures, spinal fusions, and joint arthroplasties as well as craniofacial and dental applications. Early implant-bone mechanical fixation is an important requirement for the successful performance of such implants. However, adequate osseointegration has been difficult to achieve especially in challenging disease states like osteoporosis due to reduced bone mass and strength. Here, we present a simple coating strategy based on passive adsorption of FN7-10, a recombinant fragment of human fibronectin encompassing the major cell adhesive, integrin-binding site, onto 316-grade stainless steel (SS). FN7-10 coating on SS surfaces promoted α5β1 integrin-dependent adhesion and osteogenic differentiation of human mesenchymal stem cells. FN7-10-coated SS screws increased bone-implant mechanical fixation compared to uncoated screws by 30% and 45% at 1 and 3 months, respectively, in healthy rats. Importantly, FN7-10 coating significantly enhanced bone-screw fixation by 57% and 32% at 1 and 3 months, respectively, and bone-implant ingrowth by 30% at 3 months compared to uncoated screws in osteoporotic rats. These coatings are easy to apply intra-operatively, even to implants with complex geometries and structures, facilitating the potential for rapid translation to clinical settings. PMID:26100343

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

    PubMed

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

    2015-09-01

    Metal implants are widely used to provide structural support and stability in current surgical treatments for bone fractures, spinal fusions, and joint arthroplasties as well as craniofacial and dental applications. Early implant-bone mechanical fixation is an important requirement for the successful performance of such implants. However, adequate osseointegration has been difficult to achieve especially in challenging disease states like osteoporosis due to reduced bone mass and strength. Here, we present a simple coating strategy based on passive adsorption of FN7-10, a recombinant fragment of human fibronectin encompassing the major cell adhesive, integrin-binding site, onto 316-grade stainless steel (SS). FN7-10 coating on SS surfaces promoted α5β1 integrin-dependent adhesion and osteogenic differentiation of human mesenchymal stem cells. FN7-10-coated SS screws increased bone-implant mechanical fixation compared to uncoated screws by 30% and 45% at 1 and 3 months, respectively, in healthy rats. Importantly, FN7-10 coating significantly enhanced bone-screw fixation by 57% and 32% at 1 and 3 months, respectively, and bone-implant ingrowth by 30% at 3 months compared to uncoated screws in osteoporotic rats. These coatings are easy to apply intra-operatively, even to implants with complex geometries and structures, facilitating the potential for rapid translation to clinical settings. PMID:26100343

  1. Cortical bone screw fixation in ionically modified apatite cements.

    PubMed

    Barralet, J E; Duncan, C O; Dover, M S; Bassett, D C; Nishikawa, H; Monaghan, A; Gbureck, U

    2005-05-01

    Hydroxyapatite cements are used in reconstruction of the face; usually in well-defined cavities where the cement can be stabilized without the need for internal fixation. A hydroxyapatite cement that could enable screw fixation and some loading therefore has considerable potential in maxillofacial reconstruction. It has been demonstrated recently that water demand of calcium phosphate cements can be reduced by ionically modifying the liquid component. This study investigated the capacity of an ionically modified precompacted apatite cement to retain self-tapping cortical bone screws. Screw pullout forces were determined in the direction of the screw long axis and perpendicular to it, using cortical bone and polymethylmethacrylate cement as a control. In bending pullout tests, measured forces to remove screws from ionically modified precompacted cement were insignificantly different from cortical bone. However, pullout forces of bone screws from hydroxyapatite cement decreased with aging time in vitro.

  2. Bilateral Pedicle and Crossed Translaminar Screws in C2.

    PubMed

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

    2015-10-01

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

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

    PubMed

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

    2013-10-01

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

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

    SciTech Connect

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

    2007-01-30

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

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

    NASA Astrophysics Data System (ADS)

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

    2007-01-01

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

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

    PubMed Central

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

    2015-01-01

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

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

    PubMed Central

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

    2016-01-01

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

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

    PubMed

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

    2016-01-01

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

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

    PubMed Central

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

    2016-01-01

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

  10. Surgical treatment of a concurrent type 5 acromioclavicular joint dislocation and a failed anterior glenohumeral joint stabilization.

    PubMed

    Rashid, Abbas; Lawrence, Christopher; Tytherleigh-Strong, Graham

    2016-10-01

    Traumatic glenohumeral joint dislocation and acromioclavicular joint subluxations tend to occur in young active males. Use of the coracoid process either as a transfer in recurrent instability or in suspensory reconstructions of the coracoclavicular ligaments have gained popularity. However this requires careful consideration in the event of concomitant injuries if they both require surgery. PMID:27660658

  11. Surgical treatment of a concurrent type 5 acromioclavicular joint dislocation and a failed anterior glenohumeral joint stabilization.

    PubMed

    Rashid, Abbas; Lawrence, Christopher; Tytherleigh-Strong, Graham

    2016-10-01

    Traumatic glenohumeral joint dislocation and acromioclavicular joint subluxations tend to occur in young active males. Use of the coracoid process either as a transfer in recurrent instability or in suspensory reconstructions of the coracoclavicular ligaments have gained popularity. However this requires careful consideration in the event of concomitant injuries if they both require surgery.

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

    PubMed Central

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

    2014-01-01

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

  13. Analysis of Modeling Parameters on Threaded Screws.

    SciTech Connect

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

    2015-06-01

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

  14. Ball Screw Actuator Including a Compliant Ball Screw Stop

    NASA Technical Reports Server (NTRS)

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

    2015-01-01

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

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

    PubMed

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

    2012-01-01

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

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

    PubMed Central

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

    2012-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2007-01-01

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

  18. Comparison of Expansive Pedicle Screw and Polymethylmethacrylate-Augmented Pedicle Screw in Osteoporotic Sheep Lumbar Vertebrae: Biomechanical and Interfacial Evaluations

    PubMed Central

    Zhang, Bo; Xie, Qing-yun; Wang, Cai-ru; Liu, Jin-biao; Liao, Dong-fa; Jiang, Kai; Lei, Wei; Pan, Xian-ming

    2013-01-01

    Background It was reported that expansive pedicle screw (EPS) and polymethylmethacrylate-augmented pedicle screw (PMMA-PS) could be used to increase screw stability in osteoporosis. However, there are no studies comparing the two kinds of screws in vivo. Thus, we aimed to compare biomechanical and interfacial performances of EPS and PMMA-PS in osteoporotic sheep spine. Methodology/Principal Findings After successful induction of osteoporotic sheep, lumbar vertebrae in each sheep were randomly divided into three groups. The conventional pedicle screw (CPS) was inserted directly into vertebrae in CPS group; PMMA was injected prior to insertion of CPS in PMMA-PS group; and the EPS was inserted in EPS group. Sheep were killed and biomechanical tests, micro-CT analysis and histological observation were performed at both 6 and 12 weeks post-operation. At 6-week and 12-week, screw stabilities in EPS and PMMA-PS groups were significantly higher than that in CPS group, but there were no significant differences between EPS and PMMA-PS groups at two study periods. The screw stability in EPS group at 12-week was significantly higher than that at 6-week. The bone trabeculae around the expanding anterior part of EPS were more and denser than that in CPS group at 6-week and 12-week. PMMA was found without any degradation and absorption forming non-biological “screw-PMMA-bone” interface in PMMA-PS group, however, more and more bone trabeculae surrounded anterior part of EPS improving local bone quality and formed biological “screw-bone” interface. Conclusions/Significance EPS can markedly enhance screw stability with a similar effect to the traditional method of screw augmentation with PMMA in initial surgery in osteoporosis. EPS can form better biological interface between screw and bone than PMMA-PS. In addition, EPS have no risk of thermal injury, leakage and compression caused by PMMA. We propose EPS has a great application potential in augmentation of screw stability

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

    PubMed Central

    Kim, Seok-Gyu; Son, Mee-Kyoung

    2015-01-01

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

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

    PubMed

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

    2014-09-01

    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.

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

    PubMed

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

    2013-10-01

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

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

    PubMed

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

    2007-01-01

    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 from substantial estimation errors. Recent studies have shown that improvements in muscle force estimation can be achieved through adequate EMG processing, specifically whitening and high-pass (HP) filtering of the signals. The aim of this paper is to determine the effect of such processing on outcomes of a biomechanical model of the lumbosacral joint and surrounding musculature. Goodness of fit of estimated muscle moments to net moments and also estimated joint stability significantly increased with increasing cut-off frequencies in HP filtering, whereas no effect on joint contact forces was found. Whitening resulted in moment estimations comparable to those obtained from optimal HP filtering with cut-off frequencies over 250 Hz. Moreover, compared to HP filtering, whitening led to a further increase in estimated joint-stability. Based on theoretical models and on our experimental results, we hypothesize that the processing leads to an increase in pick-up area. This then would explain the improvements from a better balance between deep and superficial motor unit contributions to the signal. PMID:16765965

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

    SciTech Connect

    Darsell, Jens T.; Weil, K. Scott

    2008-09-08

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

  4. Helical screw viscometer

    DOEpatents

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

    1983-06-30

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

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

    PubMed

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

    2003-01-01

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

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

    PubMed

    Cashaback, Joshua G A; Cluff, Tyler

    2015-02-26

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

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

    PubMed

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

    2015-01-01

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

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

    SciTech Connect

    Christianson, M.

    1989-04-01

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

  9. Intertrochanteric fractures in elderly high risk patients treated with Ender nails and compression screw

    PubMed Central

    Gangadharan, Sidhartha; Nambiar, MR

    2010-01-01

    Background: Ender and Simon Weidner popularized the concept of closed condylocephlic nailing for intertrochanteric fractures in 1970. The clinical experience of authors revealed that Ender nailing alone cannot provide secure fixation in elderly patients with osteoporosis. Hence we conducted a study to evaluate the efficacy of a combined fixation procedure using Ender nails and a cannulated compression screw for intertrochanteric fractures. Materials and Methods: 76 patients with intertrochanteric fractures were treated using intramedullary Ender nails and cannulated compression screw from January 2004 to December 2007. The mean age of the patients was 80 years (range 70-105 years).Using the Evan’s system of classification 49 were stable and 27 unstable fractures. Inclusion criteria was high risk elderly patients (age > 70 years) with intertrochanteric fracture. The exclusion criteria included patients with pressure sores over the trochanteric region. Many patients had pre-existing co-morbidities like diabetes mellitus, hypertension, COPD, ischemic heart disease, CVA and coronary artery bypass surgery. The two Ender nails of 4.5mm each were passed across the fracture site into the proximal neck. This was reinforced with a 6.5 mm cannulated compression screw passed from the sub trochanteric region, across the fracture into the head. Results: The mean follow-up was 14 months (range 9-19 months) Average time to fracture union was 10 weeks (range 6-16 weeks). The mean knee ROM was 130° (± 5°). There was no case of nail penetration into hip joint. In five cases with advanced osteoporosis there was minimal migration of Ender nails distally. Conclusions: The Ender nailing combined with compression screw fixation in cases of intertrochanteric fractures in high risk elderly patients could achieve reliable fracture stability with minimal complications. PMID:20697482

  10. Calcaneocuboid joint and stability of the longitudinal arch of the foot at high and low gear push off.

    PubMed Central

    Bojsen-Møller, F

    1979-01-01

    The calcaneocuboid joint was studied in ligamentous specimens of ten human feet, and in skeletons of two gorillas (Gorilla gorilla beringei), six chimpanzees (Pan troglodytes), three orangutans (Pongo pygmaeus) and 25 human feet. The movement of the transverse tarsal joint was further studied in a living foot on a walk-way with a glass plate inserted, and with an underlying mirror. In man the joint is shaped as an asymmetrical sector of one end of an hour-glass shaped surface of revolution with its main axis oriented longitudinally in the foot. The calcaneocuboid joint becomes close packed by a pronation of the forefoot in relation to the hind foot because of a congruency between the joint surfaces obtained in this position and because the calcaneus overhangs the cuboid dorsally and stops the movement. At low gear push off the foot is inverted and the calcaneocuboid joint loose packed. The stresses are absorbed across the fibular, postaxial border of the foot. At high high gear push off there is a functional pronation of the forefoot with a stabilization of the transverse tarsal joint and a more effective tightening of the plantar aponeurosis. The foot becomes a rigid lever for propulsion. In contrast to the human condition, the anthropoid calcaneus has an anteromedial extension associated with symmetry of the calcaneocuboid joint. The calcaneus does not overhang the cuboid and there appears to be no close packed position. Correspondingly, the anthropoid foot has a mid-tarsal break at each push off in addition to the metatarsophalangeal break. Images Fig. 4 Fig. 5 Fig. 6 Fig. 7 PMID:511760

  11. 21 CFR 888.3070 - Pedicle screw spinal system.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... immobilization and stabilization of spinal segments in skeletally mature patients as an adjunct to fusion in the...; spinal tumor; and failed previous fusion (pseudarthrosis). These pedicle screw spinal systems must comply... stabilization of spinal segments in the thoracic, lumbar, and sacral spine as an adjunct to fusion in...

  12. 21 CFR 888.3070 - Pedicle screw spinal system.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... immobilization and stabilization of spinal segments in skeletally mature patients as an adjunct to fusion in the...; spinal tumor; and failed previous fusion (pseudarthrosis). These pedicle screw spinal systems must comply... stabilization of spinal segments in the thoracic, lumbar, and sacral spine as an adjunct to fusion in...

  13. 21 CFR 888.3070 - Pedicle screw spinal system.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... immobilization and stabilization of spinal segments in skeletally mature patients as an adjunct to fusion in the...; spinal tumor; and failed previous fusion (pseudarthrosis). These pedicle screw spinal systems must comply... stabilization of spinal segments in the thoracic, lumbar, and sacral spine as an adjunct to fusion in...

  14. 21 CFR 888.3070 - Pedicle screw spinal system.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... immobilization and stabilization of spinal segments in skeletally mature patients as an adjunct to fusion in the...; spinal tumor; and failed previous fusion (pseudarthrosis). These pedicle screw spinal systems must comply... stabilization of spinal segments in the thoracic, lumbar, and sacral spine as an adjunct to fusion in...

  15. 21 CFR 888.3070 - Pedicle screw spinal system.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... immobilization and stabilization of spinal segments in skeletally mature patients as an adjunct to fusion in the...; spinal tumor; and failed previous fusion (pseudarthrosis). These pedicle screw spinal systems must comply... stabilization of spinal segments in the thoracic, lumbar, and sacral spine as an adjunct to fusion in...

  16. NUT SCREW MECHANISMS

    DOEpatents

    Glass, J.A.F.

    1958-07-01

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

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

    PubMed Central

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

    2015-01-01

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

  18. Stereotactic atlantoaxial transarticular screw fixation.

    PubMed

    Laherty, R W; Kahler, R J; Walker, D G; Tomlinson, F H

    2005-01-01

    Atlantoaxial stabilisation can be performed using a variety of surgical techniques. Developments in spinal instrumentation and stereotactic technology have been incorporated into these procedures. We have recently adopted frameless stereotaxy to assist in such operations. A retrospective study of patients treated by the authors and using frameless stereotaxy from 2001 to 2002 was performed. Each patient underwent pre-operative fine-cut CT in the position of fixation. Using these images, screw trajectory was planned. Stereotaxis and fluoroscopy was utilised during fixation. A post-operative CT was performed. There were nine patients. Bilateral screw placement was achieved in eight. In the remaining case stereotactic planning predicted the single screw fixation. There were no post-operative complications. Post-operative CT showed screw placement corresponding to the planned trajectory in all 17 screws. Stabilisation was achieved in all. Stereotactic atlantoaxial screw fixation is an accessible, safe and accurate method for the management of C1-2 instability. PMID:15639416

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

    PubMed

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

    2014-09-01

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

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

    PubMed

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

    2015-01-01

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

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

    PubMed

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

    2015-01-01

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

  2. Low noise lead screw positioner

    NASA Technical Reports Server (NTRS)

    Perkins, Gerald S. (Inventor)

    1986-01-01

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

  3. Engineering design and construction of a spinning conducting shell to stabilize the RWM in a cylindrical, line-tied screw pinch

    NASA Astrophysics Data System (ADS)

    Kendrick, Roch; Forest, Cary

    2007-11-01

    The primary goal of the rotating wall machine is to demonstrate the stabilization of the resistive wall mode using rotating metal walls. This poster describes the design and construction of a spinning shell for the rotating wall machine. The plasma is a 1 meter long, 10 cm radius cylindrical plasma column that has recently shown the existence of a resistive wall mode for sufficiently large currents. The plasma is surrounded by two shells: one is a 0.5 mm thick, stationary shell at the plasma boundary (with a shell time of 7 ms); and the second is a 0.5 mm thick shell at 12 cm radius, mounted inside a carbon fiber spinning tube. The carbon fiber tube is in turn supported by foil bearings and driven by an air turbine, technologies which should easily allow the shell to spin at rotation frequencies up to 100 Hz. These frequencies should be adequate for demonstrating the stabilization of the MHD.

  4. A new material (single crystal sapphire screw) for internal fixation of the mandibular ramus.

    PubMed

    Iizuka, T; Fujimoto, H; Ono, T

    1987-02-01

    A new single crystal sapphire bone screw which has favourable properties such as chemical stability, mechanical strength and biocompatibility, was applied for rigid internal fixation of the sagittal split osteotomies in 86 cases since 1982. Radiographic findings supported the excellent biocompatibility of the material; there was no noticeable bone loss around the screw and the excellent bone adaptation to the threaded portion was observed. The screws can mechanically support the split mandibular rami until bone union occurs. Complications due to the screw were not encountered in follow-up periods of 0.5-3.5 years.

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

    PubMed

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

    2015-01-01

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

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

    PubMed

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

    2011-03-01

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

  7. Screw/stud removal tool

    NASA Technical Reports Server (NTRS)

    Daniels, K.; Herrick, D. E.; Rothermel, L.

    1980-01-01

    Tool removes stubborn panheaded screws or studs where conventional tools would be either too weak or inconvenient to use. Screws with damaged heads or slots can also be removed this way. Tool can be worked with one hand and easily fits limited-access and blind areas. It can be made in various sizes to fit different screwheads.

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

    PubMed Central

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

    2012-01-01

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

  9. Acromioclavicular joint injuries: diagnosis and management.

    PubMed

    Simovitch, Ryan; Sanders, Brett; Ozbaydar, Mehmet; Lavery, Kyle; Warner, Jon J P

    2009-04-01

    Acromioclavicular joint injuries represent nearly half of all athletic shoulder injuries, often resulting from a fall onto the tip of the shoulder with the arm in adduction. Stability of this joint depends on the integrity of the acromioclavicular ligaments and capsule as well as the coracoclavicular ligaments and the trapezius and deltoid muscles. Along with clinical examination for tenderness and instability, radiographic examination is critical in the evaluation of acromioclavicular joint injuries. Nonsurgical treatment is indicated for type I and II injuries; surgery is almost always recommended for type IV, V, and VI injuries. Management of type III injuries remains controversial, with nonsurgical treatment favored in most instances and reconstruction of the acromioclavicular joint reserved for symptomatic instability. Recommended techniques for stabilization in cases of acute and late symptomatic instability include screw fixation of the coracoid process to the clavicle, coracoacromial ligament transfer, and coracoclavicular ligament reconstruction. Biomechanical studies have demonstrated that anatomic acromioclavicular joint reconstruction is the most effective treatment for persistent instability.

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

    PubMed

    Breahna, Anca Nicoleta; Meads, Bryce Maurice

    2015-10-01

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

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

    PubMed Central

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

    2016-01-01

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

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

    SciTech Connect

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

    1996-12-31

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

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

    PubMed

    Breahna, Anca Nicoleta; Meads, Bryce Maurice

    2015-10-01

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

  14. Examining executive function in the second year of life: coherence, stability, and relations to joint attention and language.

    PubMed

    Miller, Stephanie E; Marcovitch, Stuart

    2015-01-01

    Several theories of executive function (EF) propose that EF development corresponds to children's ability to form representations and reflect on represented stimuli in the environment. However, research on early EF is primarily conducted with preschoolers, despite the fact that important developments in representation (e.g., language, gesture, shared joint attention) occur within the 1st years of life. In the present study, EF performance and the relationship between EF and early representation (i.e., joint attention, language) were longitudinally examined in 47 children at 14 and 18 months of age. Results suggest that the 2nd year of life is a distinct period of EF development in which children exhibit very little coherence or stability across a battery of EF tasks. However, by 18 months, a subset of child participants consistently passed the majority of EF tasks, and superior EF performance was predicted by 14-month representational abilities (i.e., language comprehension and some episodes of initiating joint attention). This research suggests that the transition from foundational behavioral control in infancy to the more complex EF observed in preschool is supported by representational abilities in the 2nd year of life.

  15. The screw propeller

    NASA Astrophysics Data System (ADS)

    Larrabee, E. E.

    1980-07-01

    Marine and air screw propellers are considered in terms of theoretical hydrodynamics as developed by Joukowsky, Prandtl, and Betz. Attention is given to the flow around wings of finite span where spanwise flow exists and where lift and the bound vorticity must all go smoothly to zero at the wing tips. The concept of a trailing vortex sheet made up of infinitesimal line vortexes roughly aligned with the direction of flight is discussed in this regard. Also considered is induced velocity, which tends to convect the sheet downward at every stage in the roll-up process, the vortex theory of propellers and the Betz-Prandtl circulation distribution. The performance of the Gossamer Albatross and of a pedal-driven biplane called the Chrysalis are also discussed.

  16. Carbon nanotube Archimedes screws.

    PubMed

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

    2010-12-28

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

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

    PubMed

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

    2012-09-01

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

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

    PubMed Central

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

    2014-01-01

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

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

    PubMed Central

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

    2015-01-01

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

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

    PubMed

    Denard, Patrick J

    2016-08-01

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

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

    PubMed

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

    2013-07-01

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

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

    PubMed

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

    2013-07-01

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

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

    NASA Astrophysics Data System (ADS)

    Akin, Mutluhan

    2013-03-01

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

  4. CMM probe compensation methods for measuring complex screw surface

    NASA Astrophysics Data System (ADS)

    Zhao, Qiancheng; Yang, Tianlong; Yin, Xiyun

    2013-01-01

    At present, probe compensation is the key problem in measuring geometric parameters of complex screw surface with CMM due to its complicated 3D shape, aiming at this problem, some new measurement methods are proposed based on geometric feature models, expressing the screw surface and its offset surface separately. Supposing the parameter lead of a screw surface is known, it's realized by scanning one single profile to complete probe compensation and calculate out all parameters, and the probe compensation is done by two improved methods, named as modified cross product and offset surface virtual measurement respectively, the theory and detailed process of which are discussed in this paper. After performing systematic experiments of profile scan, probe compensation and error evaluation, results show that the new measurement methods provide higher precision, stability and realizability.

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

    PubMed Central

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

    2016-01-01

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

  6. Does Repair of a Hill-Sachs Defect Increase Stability at the Glenohumeral Joint?

    PubMed Central

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

    2016-01-01

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

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

    PubMed

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

    2016-01-01

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

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

    PubMed

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

    2014-10-01

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

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

    PubMed Central

    2012-01-01

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

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

    PubMed Central

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

    2016-01-01

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

  11. Lumbosacral fixation using the diagonal S2 screw for long fusion in degenerative lumbar deformity: technical note involving 13 cases.

    PubMed

    Park, Ye-Soo; Kim, Hong-Sik; Baek, Seung-Wook; Lee, Sang-Hyun

    2013-09-01

    Placing instrumentation into the ilium has been shown to increase the biomechanical stability and the fusion rates, but it has some disadvantages. The diagonal S2 screw technique is an attractive surgical procedure for degenerative lumbar deformity. Between 2008 and 2010, we carried out long fusion across the lumbosacral junction in 13 patients with a degenerative lumbar deformity using the diagonal S2 screws. In 12 of these 13 patients, the lumbosacral fusion was graded as solid fusion with obvious bridging bone (92%). One patient had a rod dislodge at one S2 screw and breakage of one S1 screw and underwent revision nine months postoperatively. So, we present alternative method of lumbopelvic fixation for long fusion in degenerative lumbar deformity using diagonal S2 screw instead of iliac screw.

  12. Chronic pelvic pain arising from dysfunctional stabilizing muscles of the hip joint and pelvis

    PubMed Central

    Lee, Dae Wook; Lim, Chang Hun; Han, Jae Young

    2016-01-01

    Chronic pelvic pain in women is a very annoying condition that is responsible for substantial suffering and medical expense. But dealing with this pain can be tough, because there are numerous possible causes for the pelvic pain such as urologic, gynecologic, gastrointestinal, neurologic, or musculoskeletal problems. Of these, musculoskeletal problem may be a primary cause of chronic pelvic pain in patients with a preceding trauma to the low back, pelvis, or lower extremities. Here, we report the case of a 54-year-old female patient with severe chronic pelvic pain after a transcutaneous electrical nerve stimulation (TENS) accident that was successfully managed with image-guided trigger point injections on several pelvic stabilizing muscles. PMID:27738508

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

    PubMed Central

    Ueno, Fabrício Hidetoshi; Pisani, Marina Justi; Machado, André Nunes; Rodrigues, Fábio Lucas; Fujiki, Edison Noburo; Rodrigues, Luciano Miller Reis

    2015-01-01

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

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

    PubMed

    Śliwczyński, Ł; Krehlik, P

    2015-03-01

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

  15. Joint Instability and Osteoarthritis

    PubMed Central

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

    2015-01-01

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

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

    PubMed Central

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

    2016-01-01

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

  17. Early clinical results with cortically based pedicle screw trajectory for fusion of the degenerative lumbar spine.

    PubMed

    Glennie, R Andrew; Dea, Nicolas; Kwon, Brian K; Street, John T

    2015-06-01

    This study reviews the outcomes and revision rates of degenerative lumbar fusion surgery using cortical trajectory pedicle screws in lieu of traditional pedicle screw instrumentation. Pedicle screw fixation can be a challenge in patients with low bone mineral density. Wide posterior approaches to the lumbar spine exposing lateral to the facet joints and onto transverse processes causes an additional degree of muscular damage and blood loss not present with a simple laminectomy. A cortical bone trajectory pedicle screw has been proposed as an alternative to prevent screw pullout and decrease the morbidity associated with the wide posterior approach to the spine. We present a series of eight consecutive patients using a cortical bone trajectory instead of traditional pedicle screw fixation for degenerative conditions of the lumbar spine. A retrospective review of our institutional registry data identified eight patients who had cortical screws placed with the assistance of O-arm Stealth navigation (Medtronic Sofamor Danek, Memphis, TN, USA) from 2010-2013. We analyzed the need for revision, the maintenance of reduction and the incidence of screw pullout or breakage. Our review demonstrated that two of eight patients were revised at an average of 12months. The reasons for these revisions were pseudarthrosis and caudal adjacent segment failure. All patients who were revised had frank screw loosening. We present early clinical results of a new technique that has been shown to have a better fixation profile in laboratory testing. Our less than favorable early clinical results should be interpreted with caution and highlight important technical issues which should be considered.

  18. Pure Varus Injury to the Knee Joint.

    PubMed

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

    2015-06-01

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

  19. Cancellous Screws Are Biomechanically Superior to Cortical Screws in Metaphyseal Bone.

    PubMed

    Wang, Tim; Boone, Christopher; Behn, Anthony W; Ledesma, Justin B; Bishop, Julius A

    2016-09-01

    Cancellous screws are designed to optimize fixation in metaphyseal bone environments; however, certain clinical situations may require the substitution of cortical screws for use in cancellous bone, such as anatomic constraints, fragment size, or available instrumentation. This study compares the biomechanical properties of commercially available cortical and cancellous screw designs in a synthetic model representing various bone densities. Commercially available, fully threaded, 4.0-mm outer-diameter cortical and cancellous screws were tested in terms of pullout strength and maximum insertion torque in standard-density and osteoporotic cancellous bone models. Pullout strength and maximum insertion torque were both found to be greater for cancellous screws than cortical screws in all synthetic densities tested. The magnitude of difference in pullout strength between cortical and cancellous screws increased with decreasing synthetic bone density. Screw displacement prior to failure and total energy absorbed during pullout strength testing were also significantly greater for cancellous screws in osteoporotic models. Stiffness was greater for cancellous screws in standard and osteoporotic models. Cancellous screws have biomechanical advantages over cortical screws when used in metaphyseal bone, implying the ability to both achieve greater compression and resist displacement at the screw-plate interface. Surgeons should preferentially use cancellous over cortical screws in metaphyseal environments where cortical bone is insufficient for fixation. [Orthopedics.2016; 39(5):e828-e832.].

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

    PubMed Central

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

    2015-01-01

    Problems that screw cannot be inserted may occur in screw-rod fixation techniques such as Harms technique. We compared the biomechanical stability imparted to the C-2 vertebrae by four designed posterior screw and rod fixation techniques for the management of odontoid fractures. A three-dimensional finite element model of the odontoid fracture was established by subtracting several unit structures from the normal model from a healthy male volunteer. 4 different fixation techniques, shown as follows: ① C-1 lateral mass and C-2 pedicle screw fixation (Harms technique); ② C-1 lateral mass and unilateral C-2 pedicle screw fixation combined with ipsilateral laminar screw fixation; ③ Unilateral C-1lateral mass combined with ipsilateral C-1 posterior arch, and C-2 pedicle screw fixation; and ④ Unilateral C1 lateral mass screw connected with bilateral C2 pedicle screw fixation was performed on the odontoid fracture model. The model was validated for axial rotation, flexion, extension, lateral bending, and tension for 1.5 Nm. Changes in motion in flexion-extension, lateral bending, and axial rotation were calculated. The finite element model of the odontoid fracture was established in this paper. All of the four screw-rod techniques significantly decreased motion in flexion-extension, lateral bending, and axial rotation, as compared with the destabilized odontoid fracture complex (P<0.05). There was no statistically significant difference in stability among the four screw techniques. We concluded that the first three fixation techniques are recommended to be used as surgical intervention for odontoid fracture, while the last can be used as supplementary for the former three methods. PMID:26309508

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

    PubMed Central

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

    2015-01-01

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

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

    PubMed

    Oda, Jon E; Thacker, Mihir M

    2013-05-01

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

  3. Biomechanical competence of six different bone screws for reconstructive surgery in three different transplants: Fibular, iliac crest, scapular and artificial bone.

    PubMed

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

    2016-06-01

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

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

    PubMed

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

    2016-06-01

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

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

    PubMed Central

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

    2016-01-01

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

  6. Anticipatory control of center of mass and joint stability during voluntary arm movement from a standing posture: interplay between active and passive control.

    PubMed

    Patla, Aftab E; Ishac, Milad G; Winter, David A

    2002-04-01

    Anticipatory control of upright posture is the focus of this study that combines experimental and modeling work. Individuals were asked to raise or lower their arms from two initial postures such that the final posture of the arm was at 90 degrees with respect to the body. Holding different weights in the hand varied the magnitude of perturbation to postural stability generated by the arm movement. Whole body kinematics and ground reaction forces were measured. Inverse dynamic analysis was used to determine the internal joint moments at the shoulder, hip, knee and ankle, and reaction forces at the shoulder. Center of mass (COM) of the arm, posture (rest of the body without the arms) and whole body (net COM) were also determined. Changes in joint moment at the hip, knee and ankle revealed a significant effect of the direction of movement. The polarities of the joint moment response were appropriate for joint stabilization. Net COM change showed a systematic effect of the direction of movement even though the arm COM was displaced by the same amount and in the same direction for both arm raising and lowering conditions. In order to determine the effects of the passive forces and moments on the posture COM, the body was modeled as an inverted pendulum. The model was customized for each participant; the relevant model parameters were estimated from data obtained from each trial. The ankle joint stiffness and viscosity were adjusted to ensure postural equilibrium prior to arm movement. Joint reactive forces and moments generated by the arm movements were applied at the shoulder level of this inverted pendulum; these were the only inputs and no active control was included. The posture COM profile from the model simulation was calculated. Results show that simulated posture COM profile and measured posture COM profile are identical for about 200 ms following the onset of arm movement and then they deviate. Therefore, the initial control of COM is passive in nature and the

  7. Rad52 promotes second-end DNA capture in double-stranded break repair to form complement-stabilized joint molecules.

    PubMed

    Nimonkar, Amitabh V; Sica, R Alejandro; Kowalczykowski, Stephen C

    2009-03-01

    Saccharomyces cerevisiae Rad52 performs multiple functions during the recombinational repair of double-stranded DNA (dsDNA) breaks (DSBs). It mediates assembly of Rad51 onto single-stranded DNA (ssDNA) that is complexed with replication protein A (RPA); the resulting nucleoprotein filament pairs with homologous dsDNA to form joint molecules. Rad52 also catalyzes the annealing of complementary strands of ssDNA, even when they are complexed with RPA. Both Rad51 and Rad52 can be envisioned to promote "second-end capture," a step that pairs the ssDNA generated by processing of the second end of a DSB to the joint molecule formed by invasion of the target dsDNA by the first processed end. Here, we show that Rad52 promotes annealing of complementary ssDNA that is complexed with RPA to the displaced strand of a joint molecule, to form a complement-stabilized joint molecule. RecO, a prokaryotic homolog of Rad52, cannot form complement-stabilized joint molecules with RPA-ssDNA complexes, nor can Rad52 promote second-end capture when the ssDNA is bound with either human RPA or the prokaryotic ssDNA-binding protein, SSB, indicating a species-specific process. We conclude that Rad52 participates in second-end capture by annealing a resected DNA break, complexed with RPA, to the joint molecule product of single-end invasion event. These studies support a role for Rad52-promoted annealing in the formation of Holliday junctions in DSB repair. PMID:19204284

  8. Screw-fed pump system

    SciTech Connect

    Sprouse, Kenneth M

    2014-11-25

    A pump system includes a pump that includes a first belt and a second belt that are spaced apart from each other to provide generally straight sides of a passage there between. There is an inlet at one end of the passage and an outlet at an opposite end of the passage, with a passage length that extends between the inlet and the outlet. The passage defines a gap distance in a width direction between the straight sides at the passage inlet. A hopper includes an interior space that terminates at a mouth at the passage inlet. At least one screw is located within the interior space of the hopper and includes a screw diameter in the width direction that is less than or equal to the gap distance.

  9. Helical screw expander evaluation project

    NASA Technical Reports Server (NTRS)

    Mckay, R.

    1982-01-01

    A one MW helical rotary screw expander power system for electric power generation from geothermal brine was evaluated. The technology explored in the testing is simple, potentially very efficient, and ideally suited to wellhead installations in moderate to high enthalpy, liquid dominated field. A functional one MW geothermal electric power plant that featured a helical screw expander was produced and then tested with a demonstrated average performance of approximately 45% machine efficiency over a wide range of test conditions in noncondensing, operation on two-phase geothermal fluids. The Project also produced a computer equipped data system, an instrumentation and control van, and a 1000 kW variable load bank, all integrated into a test array designed for operation at a variety of remote test sites. Data are presented for the Utah testing and for the noncondensing phases of the testing in Mexico. Test time logged was 437 hours during the Utah tests and 1101 hours during the Mexico tests.

  10. Stress concentrations in screw threads

    NASA Technical Reports Server (NTRS)

    Ohara, G. P.

    1980-01-01

    The concept of stress concentration in screw threads was defined using the sheer transfer rate as the fundamental quantity. The stress concentration is plotted for a fixed geometry. The Heywood equation was used to generate the basic plots and NASTRAN was used to extend the analysis to the case both where flanks of an individual thread tooth are in contact. The case where a finite axial stress is superimposed is discussed.

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

    PubMed

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

    1990-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-01-01

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

  13. Assessment of different screw augmentation techniques and screw designs in osteoporotic spines

    PubMed Central

    Chavanne, A.; Spitaler, R.; Kropik, K.; Aigner, N.; Ogon, M.; Redl, H.

    2008-01-01

    This is an experimental study on human cadaver spines. The objective of this study is to compare the pullout forces between three screw augmentation methods and two different screw designs. Surgical interventions of patients with osteoporosis increase following the epidemiological development. Biomechanically the pedicle provides the strongest screw fixation in healthy bone, whereas in osteoporosis all areas of the vertebra are affected by the disease. This explains the high screw failure rates in those patients. Therefore PMMA augmentation of screws is often mandatory. This study involved investigation of the pullout forces of augmented transpedicular screws in five human lumbar spines (L1–L4). Each spine was treated with four different methods: non-augmented unperforated (solid) screw, perforated screw with vertebroplasty augmentation, solid screw with vertebroplasty augmentation and solid screw with balloon kyphoplasty augmentation. Screws were augmented with Polymethylmethacrylate (PMMA). The pullout forces were measured for each treatment with an Instron testing device. The bone mineral density was measured for each vertebra with Micro-CT. The statistical analysis was performed with a two-sided independent student t test. Forty screws (10 per group and level) were inserted. The vertebroplasty-augmented screws showed a significant higher pullout force (mean 918.5 N, P = 0.001) than control (mean 51 N), the balloon kyphoplasty group did not improve the pullout force significantly (mean 781 N, P > 0.05). However, leakage occurred in some cases treated with perforated screws. All spines showed osteoporosis on Micro-CT. Vertebroplasty-augmented screws, augmentation of perforated screws and balloon kyphoplasty augmented screws show higher pullout resistance than non-augmented screws. Significant higher pullout forces were only reached in the vertebroplasty augmented vertebra. The perforated screw design led to epidural leakage due to the position of the

  14. [The temporomandibular joint of the domestic cat (Felis silvestris catus)].

    PubMed

    Knospe, C; Roos, H

    1994-06-01

    The mandibular joint of the cat is an incongruent cylindrical joint, which works as a hinge or screw joint. The course of motion is unilateral in the plane of the cutting edge of the molar/premolar border [symbol: see text]. The articular disc is a connective tissue membrane; its new function is decreasing the friction. PMID:7978349

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

    PubMed Central

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

    2015-01-01

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

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

    PubMed

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

    2015-01-01

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

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

    PubMed Central

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

    2015-01-01

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

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

    PubMed Central

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

    2016-01-01

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

  19. True anteroposterior view pedicle screw insertion technique

    PubMed Central

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

    2016-01-01

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

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

    PubMed

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

    2015-05-01

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

  1. Twin-Screw Extruders in Ceramic Extrusion

    NASA Astrophysics Data System (ADS)

    Wiedmann, Werner; Hölzel, Maria

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

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

    PubMed

    Jacobsen, C; Obwegeser, J A

    2010-12-01

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

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

    PubMed

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

    2013-02-01

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

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

    PubMed Central

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

    2016-01-01

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

  5. Proximal migration of hardware in patients undergoing midcarpal fusion with headless compression screws.

    PubMed

    Shifflett, Grant D; Athanasian, Edward A; Lee, Steve K; Weiland, Andrew J; Wolfe, Scott W

    2014-11-01

    Background Scaphoid excision and limited intercarpal fusion is a common surgical procedure performed for degenerative disorders of the wrist including scapholunate advanced collapse (SLAC) and scaphoid nonunion advanced collapse (SNAC) wrist deformities. Postoperative screw migration is a rare but devastating complication that can result in severe degenerative changes in the radiocarpal joint. Questions/Purposes The purpose of this study is to report on a series of patients who developed proximal migration of their hardware following limited intercarpal fusions with headless compression screws. Patients and Methods Four patients were identified between 2001 and 2012 who were indicated for and underwent scaphoid excision and midcarpal fusions with headless compression screw fixation and subsequently developed hardware migration with screw protrusion into the radiocarpal joint. Detailed chart review was performed. Results Mean age at surgery was 64 years (57-69 years). All patients had the diagnosis of SLAC wrist. Mean time to detection of failure was 6 months (4-8 months). All patients demonstrated radiographic union prior to failure based on plain films. Radiographs revealed screw backout with erosion of the radial lunate facet in all patients. Calculated carpal height ratios demonstrated a drop from an average 44.2% to 39.5% at the time of hardware migration. All four patients underwent hardware removal. One patient was not indicated for any further surgery, and two patients underwent further revision surgery. All three patients reported complete pain relief. One patient refused a salvage procedure and had subsequent persistent pain. Conclusions This study reports a serious complication of scaphoid excision and midcarpal fusion performed with headless compression screws. We advise surgeons to be aware of this potential complication and consider employing methods to reduce the risk of hardware migration. Additionally, we recommend at least 8 months of

  6. Proximal Migration of Hardware in Patients Undergoing Midcarpal Fusion with Headless Compression Screws

    PubMed Central

    Shifflett, Grant D.; Athanasian, Edward A.; Lee, Steve K.; Weiland, Andrew J.; Wolfe, Scott W.

    2014-01-01

    Background Scaphoid excision and limited intercarpal fusion is a common surgical procedure performed for degenerative disorders of the wrist including scapholunate advanced collapse (SLAC) and scaphoid nonunion advanced collapse (SNAC) wrist deformities. Postoperative screw migration is a rare but devastating complication that can result in severe degenerative changes in the radiocarpal joint. Questions/Purposes The purpose of this study is to report on a series of patients who developed proximal migration of their hardware following limited intercarpal fusions with headless compression screws. Patients and Methods Four patients were identified between 2001 and 2012 who were indicated for and underwent scaphoid excision and midcarpal fusions with headless compression screw fixation and subsequently developed hardware migration with screw protrusion into the radiocarpal joint. Detailed chart review was performed. Results Mean age at surgery was 64 years (57–69 years). All patients had the diagnosis of SLAC wrist. Mean time to detection of failure was 6 months (4–8 months). All patients demonstrated radiographic union prior to failure based on plain films. Radiographs revealed screw backout with erosion of the radial lunate facet in all patients. Calculated carpal height ratios demonstrated a drop from an average 44.2% to 39.5% at the time of hardware migration. All four patients underwent hardware removal. One patient was not indicated for any further surgery, and two patients underwent further revision surgery. All three patients reported complete pain relief. One patient refused a salvage procedure and had subsequent persistent pain. Conclusions This study reports a serious complication of scaphoid excision and midcarpal fusion performed with headless compression screws. We advise surgeons to be aware of this potential complication and consider employing methods to reduce the risk of hardware migration. Additionally, we recommend at least 8 months of

  7. Leg extensor muscle strength, postural stability, and fear of falling after a 2-month home exercise program in women with severe knee joint osteoarthritis.

    PubMed

    Rätsepsoo, Monika; Gapeyeva, Helena; Sokk, Jelena; Ereline, Jaan; Haviko, Tiit; Pääsuke, Mati

    2013-01-01

    BACKGROUND AND OBJECTIVE. The aim of this study was to compare the leg extensor muscle strength, the postural stability, and the fear of falling in the women with severe knee joint osteoarthritis (OA) before and after a 2-month home exercise program (HEP). MATERIAL AND METHODS. In total, 17 women aged 46-72 years with late-stage knee joint OA scheduled for total knee arthroplasty participated in this study before and after the 2-month HEP with strengthening, stretching, balance, and step exercises. The isometric peak torque (PT) of the leg extensors and postural stability characteristics when standing on a firm or a foam surface for 30 seconds were recorded. The fear of falling and the pain intensity (VAS) were estimated. RESULTS. A significant increase in the PT and the PT-to-body weight (PT-to-BW) ratio of the involved leg as well as the bilateral PT and the PT-to-BW ratio was found after the 2-month HEP compared with the data before the HEP (P<0.05). The PT and the PT-to-BW ratio of the involved leg were significantly lower compared with the uninvolved leg before the HEP (P<0.05). The center of the pressure sway length (foam surface) decreased significantly after the HEP (P<0.05). Significant correlations were found between the PT of the involved leg and the bilateral PT and the fear of falling and between the PT of the involved leg and the postural sway (foam surface) before the HEP. CONCLUSIONS. After the 2-month HEP, the leg extensor muscle strength increased and the postural sway length on a foam surface decreased. The results indicate that the increased leg extensor muscle strength improves postural stability and diminishes the fear of falling in women with late-stage knee joint OA.

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

    PubMed

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

    2014-11-01

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

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

    PubMed

    Wójtowicz, Piotr; Szafarowski, Tomasz; Migacz, Ewa; Krzeski, Antoni

    2015-01-01

    The anterior cervical spine surgery is a common procedure to stabilize vertebrae damaged by various diseases. The plates and screws are usually used in the spine fixation. This kind of instrumentation may detach from the bones which is a rare but well-known complication. A 77-year-old male presented to the otorhinolaryngology department with throat pain, choking, and dysphagia. At first the angioedema was diagnosed and he was treated conservatively. The endoscopy revealed laryngeal edema, being more defined on the right side with right vocal fold paresis. CT scans showed the stabilizing plate with two screws attached tightly and the back-out of the third screw toward soft tissue of the neck. In the meantime, his condition deteriorated and he needed tracheotomy. In few days the surgical removal of the dislocated screw was performed successfully. Although two-month follow-up reported no obstruction of the larynx, the vocal folds paresis with gradual functional improvement was observed. Long-term complication of anterior spine surgery sometimes may suggest laryngeal angioedema at first. If the conservative treatment is ineffective and there is a history of anterior spine surgery, the clinicians should consider the displacement of the plate or screws in differential diagnosis. PMID:25755901

  10. Screw-released roller brake

    NASA Technical Reports Server (NTRS)

    Vranish, John M. (Inventor)

    1999-01-01

    A screw-released roller brake including an input drive assembly, an output drive assembly, a plurality of locking sprags, a mechanical tripper nut for unlocking the sprags, and a casing therefor. The sprags consist of three dimensional (3-D) sprag members having pairs of contact surface regions which engage respective pairs of contact surface regions included in angular grooves or slots formed in the casing and the output drive assembly. The sprags operate to lock the output drive assembly to the casing to prevent rotation thereof in an idle mode of operation. In a drive mode of operation, the tripper is either self actuated or motor driven and is translated linearly up and down against a spline and at the limit of its travel rotates the sprags which unlock while coupling the input drive assembly to the output drive assembly so as to impart a turning motion thereto in either a clockwise or counterclockwise direction.

  11. Vertical-Screw-Auger Conveyer Feeder

    NASA Technical Reports Server (NTRS)

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

    2016-01-01

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

  12. Reinforcement of osteosynthesis screws with brushite cement.

    PubMed

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

    1999-08-01

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

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

    PubMed Central

    Cornelius, Carl-Peter; Ehrenfeld, Michael

    2010-01-01

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

  14. Acromioclavicular Joint Reconstruction.

    PubMed

    Scillia, Anthony J; Cain, E Lyle

    2015-12-01

    Our technique for acromioclavicular joint reconstruction provides a variation on coracoclavicular ligament reconstruction to also include acromioclavicular ligament reconstruction. An oblique acromial tunnel is drilled, and the medial limb of the gracilis graft, after being crossed and passed beneath the coracoid and through the clavicle, is passed through this acromial tunnel and sutured to the trapezoid graft limb after appropriate tensioning. Tenodesis screws are not placed in the bone tunnels to avoid graft fraying, and initial forces on the graft are offloaded with braided absorbable sutures passed around the clavicle. PMID:27284528

  15. Screw fixation diameter for fifth metatarsal jones fracture: a cadaveric study.

    PubMed

    Scott, Ryan T; Hyer, Christopher F; DeMill, Shyler L

    2015-01-01

    The fifth metatarsal Jones fracture is a well-documented injury occurring at the proximal diaphyseal-metaphyseal junction. Conservative versus surgical intervention has been discussed in published studies for the management of Jones fractures. Solid intramedullary fixation relies on accurate matching of the screw diameter to the intraosseous diameter. The purpose of the present cadaveric study was to determine the average intraosseous diameter of the proximal fifth metatarsal as it relates to screw size selection for Jones fracture stabilization. Twenty fresh-frozen cadaver legs were used for examination. The fifth metatarsal was completely dissected. A transverse osteotomy was performed from laterally to medially along the midline of the metatarsal. A digital caliper was used to measure the diameter of the medullary canal of the fifth metatarsal. The measurement was taken at the narrowest portion of the medullary canal just distal to the proximal metaphysis. The mean dorsal to plantar diameter of the fifth metatarsal was 6.475 ± 1.54 (range 4 to 12) mm and the mean medial to lateral diameter was 4.6 ± 0.85 (range 3 to 6) mm. Intramedullary screw fixation has shown beneficial results in the treatment protocol of fifth metatarsal Jones fractures. Our study has demonstrated that a 4.5-mm cannulated screw is the narrowest diameter screw that can be used in the average fifth metatarsal and still obtain adequate intraosseous purchase. When selecting the appropriate screw, the surgeon must be comfortable selecting the largest screw that will achieve the maximal interface with the dense cortical bone in both the medial to lateral and dorsal to plantar plane.

  16. Additional Drive Circuitry for Piezoelectric Screw Motors

    NASA Technical Reports Server (NTRS)

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

    2004-01-01

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

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

    PubMed

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

    2009-08-01

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

  18. A Simple and Reliable Method of Narrowing Genioplasty Using Biodegradable Screws.

    PubMed

    Lee, Tae Sung

    2016-01-01

    The T-osteotomy technique is widely performed to improve lower face aesthetics. During this narrowing genioplasty procedure, metal fixtures are required to rigidly fix the bone segments. Specifically, the use of biodegradable osteofixations has become a viable surgical option as more patients now have the desire to surreptitiously undergo aesthetic surgery. The present report describes a narrowing genioplasty procedure with the use of biodegradable screws only. When the T-osteotomy technique was performed to narrow the chin, the bone segments were first temporarily fixed with a 4-hole titanium plate and screws. Later during the operation, the plate and screws were replaced with 4 biodegradable screws with bicortical fixation. Completion of bone healing can be confirmed by follow-up radiographs taken 6 months after the surgery. Despite increasing demand for the use of absorbable materials in aesthetic surgeries, biodegradable fixation systems have not been widely used for aesthetic surgeries due to a perception of high cost, inconvenient manipulation, prolonged operative time, and suspicions on long-term stability. Our novel method of using only biodegradable screws allows such limitations to be easily overcome by surgeons.

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

    NASA Astrophysics Data System (ADS)

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

    2010-02-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2015-01-01

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

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

    PubMed

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

    2002-02-01

    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.

  2. Insertion Profiles of 4 Headless Compression Screws

    PubMed Central

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

    2013-01-01

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

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

    PubMed Central

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

    2015-01-01

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

  4. Joint swelling

    MedlinePlus

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

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

    NASA Astrophysics Data System (ADS)

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

    2012-03-01

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

  6. On the derivation of a tensor to calculate six degree-of-freedom, musculotendon joint stiffness: implications for stability and impedance analyses.

    PubMed

    Cashaback, Joshua G A; Potvin, Jim R; Pierrynowski, Michael R

    2013-10-18

    Major joints, such as the knee, shoulder, and spine, can buckle along the translational degrees-of-freedom (DoF), causing injury to ligaments and other passive tissues. Despite this, stability and impedance analyses have focused primarily on the rotational DoF. As such, mathematical models quantifying musculotendon translational stiffnesses remain limited and, to our knowledge, there are no published works that explicitly describes the interactions between DoF. Using an energy approach, we derived a six DoF stiffness tensor and provided the necessary equations needed to quantify the musculotendon stiffness of any joint. Using a knee model, we then compared the derived stiffness tensor against two commonly used measures: one that excludes translational DoF and another that excludes interactions between DoF. We found that both of these measures had large over-estimations of stiffness, particularly for the rotational DoF, compared to our derived tensor. These findings indicate that previous analyses may have found rotational DoF to be stable when they were unstable.

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

    PubMed

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

    2016-01-01

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

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

    PubMed

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

    2013-09-01

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

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

    PubMed

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

    2013-09-01

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

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

    PubMed Central

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

    2016-01-01

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

  11. Twin screw wet granulation: Binder delivery.

    PubMed

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

    2015-06-20

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

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

    PubMed

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

    2016-07-01

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

  13. The effect of insertion angle on orthodontic mini-screw torque

    PubMed Central

    Raji, Seyed Hamid; Noorollahian, Saeed; Niknam, Seyed Mohsen

    2014-01-01

    Background: Primary stability is an important factor for the clinical success of orthodontic mini-screws. The present study made an attempt to evaluate the effect of insertion angle changes on the maximum insertion and removal torque of orthodontic mini-screws. Materials and Methods: In this experimental study, 72 mini-screws (Dual Top Anchor System, Jeil, 1.6 mm diameter, 8 mm length) were used. They were randomly divided into four equal groups and inserted in poly-carbonate plates with 3 mm thickness. Then, their maximum insertion torque (MIT) and maximum removal torque (MRT) were recorded using a digital torque tester/screwdriver. Each group had a different insertion angle (90°, 75°, 60° and 45°). The data were analyzed by SPSS software (version 18) using one-way ANOVA and post-hoc Tukey's tests. The level of significance was set at 0.05. Results: The maximum MIT was observed in 45° insertion angle (14.84 Ncm) and the minimum MIT was reported in 75° insertion angle (12.66 Ncm). The maximum MRT was observed in 45° insertion angle (23.21 Ncm) and the minimum MRT was reported in the 90° insertion angle (17.43 Ncm). Conclusion: Oblique insertion of the mini-screws results in higher insertion and removal torques and probably more primary stability compared to the vertical insertion. PMID:25225557

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

    PubMed

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

    2015-02-01

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

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

    PubMed

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

    2015-02-01

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

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

    PubMed

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

    2016-09-01

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

  17. Screw expander for light duty diesel engines

    NASA Technical Reports Server (NTRS)

    1983-01-01

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

  18. Low energy high pressure miniature screw valve

    DOEpatents

    Fischer, Gary J.; Spletzer, Barry L.

    2006-12-12

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

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

    PubMed

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

    2016-06-01

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

  20. Screw dislocation in functionally graded magnetoelectroelastic solids

    NASA Astrophysics Data System (ADS)

    Wang, Yi-Ze; Kuna, Meinhard

    2014-02-01

    A screw dislocation in a functionally graded magnetoelectroelastic material is investigated. The material properties exponentially changing along both x and y directions are considered and the mechanical-electric-magnetic coupling is discussed. Closed-form expressions for the mechanical, electric and magnetic components are derived using the general stress function method. The solutions can be applied as a fundamental result and reduced into the classic and piezoelectric cases. The study puts forth a direct way for screw dislocation analysis in inhomogeneous structures with multifield coupling.

  1. Spline-Screw Multiple-Rotation Mechanism

    NASA Technical Reports Server (NTRS)

    Vranish, John M.

    1994-01-01

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

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

    PubMed

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

    2002-02-01

    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

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

    PubMed

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

    2014-06-11

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

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

    PubMed Central

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

    2014-01-01

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

  5. A Fluoroscopy-Free Technique for Percutaneous Screw Positioning During Arthroscopic Treatment of Depression Tibial Plateau Fractures.

    PubMed

    Thaunat, Mathieu; Camelo Barbosa, Nuno; Tuteja, Sanesh; Jan, Nicolas; Fayard, Jean Marie; Sonnery-Cottet, Bertrand

    2016-06-01

    This article aims to describe a simple and reliable technique that helps in positioning the cannulated percutaneous screws during fixation of depression-type tibial plateau fractures. After fracture reduction under arthroscopic control, an outside-in anterior cruciate ligament femoral guide is introduced through the tibial cortical metaphyseal window and positioned under endoscopic control just underneath the elevated fragment. When proper height is achieved, a guide pin is drilled from lateral to medial through the sleeve, 1 to 2 cm distal to the articular surface of the depressed fragment. The cannulated screw can then be introduced under endoscopic control, without fluoroscopic assistance, just under the previously elevated joint surface. This technique ensures optimal placement of the cannulated screw in the middle of the bony tunnel to obtain optimal subchondral bone support during fixation of the depressed tibial plateau fracture. PMID:27656370

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

    PubMed

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

    2015-05-01

    OBJECT Low bone mineral density in patients undergoing lumbar spinal surgery with screws is an especially difficult challenge because poor bone quality can severely compromise the maximum achievable purchase of the screws. A relatively new technique, the cortical bone screw trajectory, utilizes a medialized trajectory in the caudocephalad direction to engage a greater amount of cortical bone within the pars interarticularis and pedicle. The objectives of this cadaveric biomechanical study were to 1) evaluate a cortical screw system and compare its mechanical performance to the traditional pedicle screw system; 2) determine differences in bone quality associated with the cortical screw trajectory versus the normal pedicle screw insertion technique; 3) determine the cortical wall breach rate with both the cortical and traditional screw trajectories; and 4) determine the performance of the traditional screw in the cortical screw trajectory. METHODS Fourteen fresh frozen human lumbar spine sections (L1-5) were used in this study (mean age 57 ± 19 years). The experimental plan involved drilling and tapping screw holes for 2 trajectories under navigation (a traditional pedicle screw and a cortical screw) in both high-and low-quality vertebrae, measuring the bone quality associated with these trajectories, placing screws in the trajectories, and evaluating the competence of the screw purchase via 2 mechanical tests (pullout and toggle). The 3 experimental variants were 1) traditional pedicle screws placed in the traditional pedicle screw trajectory, 2) traditional pedicle screws placed in the cortical screw trajectory, and 3) cortical screws placed in the cortical screw trajectory. RESULTS A statistically significant increase in bone quality was observed for the cortical trajectories with a cortical screw (42%; p < 0.001) and traditional pedicle screw (48%; p < 0.001) when compared to the traditional trajectory with a traditional pedicle screw within the high

  7. Cyclic pull-out strength of hamstring tendon graft fixation with soft tissue interference screws. Influence of screw length.

    PubMed

    Stadelmaier, D M; Lowe, W R; Ilahi, O A; Noble, P C; Kohl, H W

    1999-01-01

    Blunt-threaded interference screws used for fixation of hamstring tendons in anterior cruciate ligament reconstructions provide aperture fixation and may provide a biomechanically more stable graft than a graft fixed further from the articular surface. It is unknown if soft tissue fixation strength using interference screws is affected by screw length. We compared the cyclic and time-zero pull-out forces of 7 x 25 mm and 7 x 40 mm blunt-threaded metal interference screws for hamstring graft tibial fixation in eight paired human cadaveric specimens. A four-stranded autologous hamstring tendon graft was secured by a blunt-threaded interference screw into a proximal tibial tunnel with a diameter corresponding to the graft width. Eight grafts were secured with a 25-mm length screw while the other eight paired grafts were secured with a 40-mm length screw. During cyclic testing, slippage of the graft occurred as the force of pull became greater with each cycle until the graft-screw complex ultimately failed. All grafts failed at the fixation site, with the tendon being pulled past the screw. There were no measurable differences in the mean cyclic failure strength, pull-out strength, or stiffness between the two sizes of screws. Although use of the longer screw would make removal technically easier should revision surgery be necessary, it did not provide stronger fixation strength than the shorter, standard screw as had been postulated. PMID:10569365

  8. Structural evolution and stabilities of neutral and anionic clusters of lead sulfide: joint anion photoelectron and computational studies.

    PubMed

    Koirala, Pratik; Kiran, Boggavarapu; Kandalam, Anil K; Fancher, Charles A; de Clercq, Helen L; Li, Xiang; Bowen, Kit H

    2011-10-01

    The geometric and electronic structures of both neutral and negatively charged lead sulfide clusters, (PbS)(n)/(PbS)(n)(-) (n = 2-10) were investigated in a combined anion photoelectron spectroscopy and computational study. Photoelectron spectra provided vertical detachment energies (VDEs) for the cluster anions and estimates of electron affinities (EA) for their neutral cluster counterparts, revealing a pattern of alternating EA and VDE values in which even n clusters exhibited lower EA and VDE values than odd n clusters up until n = 8. Computations found neutral lead sulfide clusters with even n to be thermodynamically more stable than their immediate (odd n) neighbors, with a consistent pattern also being found in their HOMO-LUMO gaps. Analysis of neutral cluster dissociation energies found the Pb(4)S(4) cube to be the preferred product of the queried fragmentation processes, consistent with our finding that the lead sulfide tetramer exhibits enhanced stability; it is a magic number species. Beyond n = 10, computational studies showed that neutral (PbS)(n) clusters in the size range, n = 11-15, prefer two-dimensional stacking of face-sharing lead sulfide cubical units, where lead and sulfur atoms possess a maximum of five-fold coordination. The preference for six-fold coordination, which is observed in the bulk, was not observed at these cluster sizes. Taken together, the results show a preference for the formation of slightly distorted, fused cuboids among small lead sulfide clusters.

  9. Pedicle screw placement with O-arm and stealth navigation.

    PubMed

    Patil, Suresh; Lindley, Emily M; Burger, Evalina L; Yoshihara, Hiroyuki; Patel, Vikas V

    2012-01-16

    Various navigation systems are available to aid pedicle screw placement. The O-arm replaces the need for fluoroscopy and generates a 3-dimensional volumetric dataset that can be viewed as transverse, coronal, and sagittal images of the spine, similar to computed tomography (CT) scanning. The dataset can be downloaded to the Stealth system (Medtronic Navigation, Louisville, Colorado) for real-time intraoperative navigation.The main objectives of the current study were to assess (1) accuracy of pedicle screw placement using the O-arm/Stealth system, and (2) time for draping, positioning of the O-arm, and screw placement. Of 188 screws (25 patients), 116 had adequate images for analysis. The average time for O-arm draping was 3.5 minutes. Initial O-arm positioning was 6.1 minutes, and final positioning was 4.9 minutes. Mean time for screw placement, including O-arm draping and positioning and array attachment, was 8.1 minutes per screw. Mean time for screw placement alone was 5.9 minutes per screw. Screw placements on final O-arm images were on average 3.14 mm deeper than on the snapshot navigation images. Three screws (2.6%) breached the medial cortex, and 3 screws (2.6%) were misaligned and did not follow the pilot hole trajectory.The use of the O-arm/Stealth system was associated with a low rate of pedicle screw misalignment. The time to place screws was less than previously reported with CT navigation, but longer than conventional techniques. It is important to be aware of the potential discrepancy between snapshot navigation images and actual screw placement on final O-arm images. Our findings suggest that final screw positions may be deeper than awl positions appear on navigation images.

  10. The effect of screw pullout rate on screw purchase in synthetic cancellous bone.

    PubMed

    Zdero, Rad; Schemitsch, Emil H

    2009-02-01

    Clinically, orthopaedic fracture fixation constructs are mounted using screws inserted into cancellous bone, while biomechanical studies are increasingly using commercially available synthetic bones. The goal of this study was to examine the effect of screw pullout rate on cancellous bone screw purchase strength in synthetic cancellous bone. Sixty synthetic cancellous bone cubes (40x40x40 mm(3)) each had one orthopaedic cancellous bone screw (major diameter=6.5 mm) inserted to a depth of 30 mm. Screws were extracted to obtain outcome measures of failure force, failure shear stress, failure energy, failure displacement, resistance force, and removal energy. The ten test groups (n=6 cubes per group) had screws extracted at pullout rates of 1 mmmin, 2.5 mmmin, 5 mmmin, 7.5 mmmin, 10 mmmin, 20 mmmin, 30 mmmin, 40 mmmin, 50 mmmin, and 60 mmmin. The aggregate average results for failure force, failure stress, failure energy, failure displacement, resistance force, and postfailure removal energy for combined pullout rates were, respectively, 984.8+/-63.9 N, 3.5+/-0.2 MPa, 298.3+/-41.7 J, 0.53+/-0.08 mm, 453.8+/-19.6 N, and 5420.1+/-489.7 J. Most statistical differences (40 of 47) involved either the 5 mmmin or the 60 mmmin rates being compared to other rates. Failure force, failure stress, and resistance force increased and were highly linearly correlated with pullout rate (R(2)=0.78, 0.76, and 0.74, respectively). Failure energy, failure displacement, and removal energy were relatively unchanged over the pullout range tested, yielding low correlation coefficients (R(2)<0.05). Failure force, failure stress, and resistance force were affected by bone screw pullout rate in synthetic cancellous bone, while failure energy, failure displacement, and removal energy remained unchanged. This is the first study to perform an extensive investigation of cancellous bone screw pullout rate in synthetic cancellous bone.

  11. Nylon screws make inexpensive coil forms

    NASA Technical Reports Server (NTRS)

    Aucoin, G.; Rosenthal, C.

    1978-01-01

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

  12. Improvements to the single screw extruder

    NASA Technical Reports Server (NTRS)

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

    1977-01-01

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

  13. The screw-helical voltage gating of ion channels.

    PubMed Central

    Keynes, R D; Elinder, F

    1999-01-01

    In the voltage-gated ion channels of every animal, whether they are selective for K+, Na+ or Ca2+, the voltage sensors are the S4 transmembrane segments carrying four to eight positive charges always separated by two uncharged residues. It is proposed that they move across the membrane in a screw-helical fashion in a series of three or more steps that each transfer a single electronic charge. The unit steps are stabilized by ion pairing between the mobile positive charges and fixed negative charges, of which there are invariably two located near the inner ends of segments S2 and S3 and a third near the outer end of either S2 or S3. Opening of the channel involves three such steps in each domain. PMID:10343407

  14. Pull-out strength of screws from polymethylmethacrylate cement.

    PubMed

    Motzkin, N E; Chao, E Y; An, K N; Wikenheiser, M A; Lewallen, D G

    1994-03-01

    We aimed to determine the optimal method of inserting a screw into polymethylmethacrylate (PMMA) cement to enhance fixation. We performed six groups of ten axial pull-out tests with two sizes of screw (3.5 and 4.5 mm AO cortical) and three methods of insertion. Screws were placed into 'fluid' PMMA, into 'solid' PMMA by drilling and tapping, or into 'curing' PMMA with quarter-revolution turns every 30 seconds until the PMMA had hardened. After full hardening, we measured the maximum load to failure for each screw-PMMA construct. We found no significant difference in the pull-out strengths between screw sizes or between screws placed in fluid or solid PMMA. Screws placed in curing PMMA were significantly weaker: the relative strengths of solid, fluid and curing groups were 100%, 97% and 71%, respectively. We recommend the use of either solid or fluid insertion according to the circumstances and the preference of the surgeon. PMID:8113302

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

    PubMed

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

    2012-07-01

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

  16. Cement leakage in pedicle screw augmentation: a prospective analysis of 98 patients and 474 augmented pedicle screws.

    PubMed

    Mueller, Jan U; Baldauf, Joerg; Marx, Sascha; Kirsch, Michael; Schroeder, Henry W S; Pillich, Dirk T

    2016-07-01

    OBJECTIVE Loosening and pullout of pedicle screws are well-known problems in pedicle screw fixation surgery. Augmentation of pedicle screws with bone cement, first described as early as 1975, increases the pedicle-screw interface and pullout force in osteoporotic vertebrae. The aim of the present study was to identify cement leakage and pulmonary embolism rates in a large prospective single-center series of pedicle screw augmentations. METHODS All patients who underwent cement-augmented pedicle screw placement between May 2006 and October 2010 at the authors' institution were included in this prospective cohort study. Perivertebral cement leakage and pulmonary cement embolism were evaluated with a CT scan of the area of operation and with a radiograph of the chest, respectively. RESULTS A total of 98 patients underwent placement of cement-augmented pedicle screws; 474 augmented screws were inserted in 237 vertebrae. No symptomatic perivertebral cement leakage or symptomatic pulmonary cement embolism was observed, but asymptomatic perivertebral cement leakage was seen in 88 patients (93.6%) and in 165 augmented vertebrae (73.3%). Cement leakage most often occurred in the perivertebral venous system. Clinically asymptomatic pulmonary cement embolism was found in 4 patients (4.1%). CONCLUSIONS Perivertebral cement leakage often occurs in pedicle screw augmentation, but in most cases, it is clinically asymptomatic. Cement augmentation should be performed under continuous fluoroscopy to avoid high-volume leakage. Alternative strategies, such as use of expandable screws, should be examined in more detail for patients at high risk of screw loosening.

  17. The effect of hydroxyapatite coated screw in the lateral fragility fractures of the femur. A prospective randomized clinical study.

    PubMed

    Pesce, V; Maccagnano, G; Vicenti, G; Notarnicola, A; Moretti, L; Tafuri, S; Vanni, D; Salini, V; Moretti, B

    2014-01-01

    Due to a growing numbers of lateral fragility fractures of the femur and their high social costs the need to work out an effective strategy in order to find a better solution for these patients is warranted. From January 2010 to July 2011, we carried out a prospective randomized clinical study comparing the results of patients with femoral lateral fractures treated by nail and cephalic hydroxyapatite coated screws (study group including 27 patients) compared to the patients with the same fractures treated with nail and head standard screws (control group including 27 patients). We defined the two parts of the femoral neck as ROI 1 (under the head screw) and ROI 2 (above the femoral screw) on the AP view. The bone density of the two areas was calculated using DEXA at T0 (1st day post-surgery), at T1 (40th day post-surgery), at T2 (3 months later), at T3 (1 year later). The clinical-radiography evaluations were based on the Harris Hip Score (HHS), ADL test and x-ray views of the hip. As far as the bone mineral density average of ROI 1 and ROI 2 is concerned, we found a significant statistical increase at T1 and T3 in the study group, while it was not significant in the control group. We could account for this data through the higher mechanical stability of hydroxyapatite coated screws than standard screws. In fact, this material was responsible for improved implant osteointegration. Thanks to a 1 year follow-up we were able to demonstrate the implant utility associated with augmentation and the importance of densitometry exams such as easily repeatable and low cost diagnostics to prevent the onset of complications linked to screw loosening.

  18. The applicability of PEEK-based abutment screws.

    PubMed

    Schwitalla, Andreas Dominik; Abou-Emara, Mohamed; Zimmermann, Tycho; Spintig, Tobias; Beuer, Florian; Lackmann, Justus; Müller, Wolf-Dieter

    2016-10-01

    The high-performance polymer PEEK (poly-ether-ether-ketone) is more and more being used in the field of dentistry, mainly for removable and fixed prostheses. In cases of screw-retained implant-supported reconstructions of PEEK, an abutment screw made of PEEK might be advantageous over a conventional metal screw due to its similar elasticity. Also in case of abutment screw fracture, a screw of PEEK could be removed more easily. M1.6-abutment screws of four different PEEK compounds were subjected to tensile tests to set their maximum tensile strengths in relation to an equivalent stress of 186MPa, which is aused by a tightening torque of 15Ncm. Two screw types were manufactured via injection molding and contained 15% short carbon fibers (sCF-15) and 40% (sCF-40), respectively. Two screw types were manufactured via milling and contained 20% TiO2 powder (TiO2-20) and >50% parallel orientated, continuous carbon fibers (cCF-50). A conventional abutments screw of Ti6Al4V (Ti; CAMLOG(®) abutment screw, CAMLOG, Wimsheim, Germany) served as control. The maximum tensile strength was 76.08±5.50MPa for TiO2-20, 152.67±15.83MPa for sCF-15, 157.29±20.11MPa for sCF-40 and 191.69±36.33MPa for cCF-50. The maximum tensile strength of the Ti-screws amounted 1196.29±21.4MPa. The results of the TiO2-20 and the Ti screws were significantly different from the results of the other samples, respectively. For the manufacturing of PEEK abutment screws, PEEK reinforced by >50% continuous carbon fibers would be the material of choice. PMID:27434650

  19. Twin screw granulation - review of current progress.

    PubMed

    Thompson, M R

    2015-01-01

    Twin screw granulation (TSG) is a new process of interest to the pharmaceutical community that can continuously wet granulate powders, doing so at lower liquid concentrations and with better product consistency than found by a high shear batch mixer. A considerable body of research has evolved over the short time since this process was introduced but generally with little comparison of results. A certain degree of confidence has been developed through these studies related to how process variables and many attributes of machinery configuration will affect granulation but some major challenges still lay ahead related to scalability, variations in the processing regimes related to degree of channel fill and the impact of wetting and granulation of complex powder formulations. This review examines the current literature for wet granulation processes studied in twin screw extrusion machinery, summarizing the influences of operational and system parameters affecting granule properties as well as strives to provide some practical observations to newly interested users of the technique.

  20. Translational mini-screw implant research.

    PubMed

    Rossouw, Emile

    2014-09-01

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

  1. Controversies relating to the management of acromioclavicular joint dislocations.

    PubMed

    Modi, C S; Beazley, J; Zywiel, M G; Lawrence, T M; Veillette, C J H

    2013-12-01

    The aim of this review is to address controversies in the management of dislocations of the acromioclavicular joint. Current evidence suggests that operative rather than non-operative treatment of Rockwood grade III dislocations results in better cosmetic and radiological results, similar functional outcomes and longer time off work. Early surgery results in better functional and radiological outcomes with a reduced risk of infection and loss of reduction compared with delayed surgery. Surgical options include acromioclavicular fixation, coracoclavicular fixation and coracoclavicular ligament reconstruction. Although non-controlled studies report promising results for arthroscopic coracoclavicular fixation, there are no comparative studies with open techniques to draw conclusions about the best surgical approach. Non-rigid coracoclavicular fixation with tendon graft or synthetic materials, or rigid acromioclavicular fixation with a hook plate, is preferable to fixation with coracoclavicular screws owing to significant risks of loosening and breakage. The evidence, although limited, also suggests that anatomical ligament reconstruction with autograft or certain synthetic grafts may have better outcomes than non-anatomical transfer of the coracoacromial ligament. It has been suggested that this is due to better restoration horizontal and vertical stability of the joint. Despite the large number of recently published studies, there remains a lack of high-quality evidence, making it difficult to draw firm conclusions regarding these controversial issues.

  2. [Anatomic features of the carpal joint of the cheetah (Acinonyx jubatuw), compared with the domestic cat (Felis catus)].

    PubMed

    Künzel, W; Probst, A

    1999-07-01

    The anatomy of the carpal joint of the cheetah (Acinonyx jubatus) was examined in seven specimens using dissection and corrosion casts as well as radiography, and compared to well-known data of the domestic cat (Felis catus). It was found that in the cheetah, as in the domestic cat, the intermedioradial, ulnar and accessory carpal bones, as well as the first, second, third and fourth carpal bones and the sesamoid bone of the abductor pollicis longus muscle, develop in a regular manner. The bones had a similar shape and the ligamentous apparatus was comparable, the most striking differences being the connection of all compartments of the joint cavity and the mediocarpal joint, working as a screw joint. The syndesmosis between the intermedioradial and ulnar carpal bones, instead of a synovial connection, is another adaptation for stabilization of the carpus of the cheetah during locomotion. The joint capsule is little spacious and in all three recesses can be differentiated. The first extends proximally palmar the ulnar carpal bone between the styloid process of the ulna and the accessory carpal bone, the second also extends proximally mediopalmar of the intermedioradial bone, and the largest third recess is located on the dorsal surface and extends proximally, laterally to the inserting tendon of the extensor carpi radialis muscle.

  3. Fracture fixation with two locking screws versus three non-locking screws

    PubMed Central

    Grawe, B.; Le, T.; Williamson, S.; Archdeacon, A.; Zardiackas, L.

    2012-01-01

    Objectives We aimed to further evaluate the biomechanical characteristics of two locking screws versus three standard bicortical screws in synthetic models of normal and osteoporotic bone. Methods Synthetic tubular bone models representing normal bone density and osteoporotic bone density were used. Artificial fracture gaps of 1 cm were created in each specimen before fixation with one of two constructs: 1) two locking screws using a five-hole locking compression plate (LCP) plate; or 2) three non-locking screws with a seven-hole LCP plate across each side of the fracture gap. The stiffness, maximum displacement, mode of failure and number of cycles to failure were recorded under progressive cyclic torsional and eccentric axial loading. Results Locking plates in normal bone survived 10% fewer cycles to failure during cyclic axial loading, but there was no significant difference in maximum displacement or failure load. Locking plates in osteoporotic bone showed less displacement (p = 0.02), but no significant difference in number of cycles to failure or failure load during cyclic axial loading (p = 0.46 and p = 0.25, respectively). Locking plates in normal bone had lower stiffness and torque during torsion testing (both p = 0.03), but there was no significant difference in rotation (angular displacement) (p = 0.84). Locking plates in osteoporotic bone showed lower torque and rotation (p = 0.008), but there was no significant difference in stiffness during torsion testing (p = 0.69). Conclusions The mechanical performance of locking plate constructs, using only two screws, is comparable to three non-locking screw constructs in osteoporotic bone. Normal bone loaded with either an axial or torsional moment showed slightly better performance with the non-locking construct. PMID:23610681

  4. Minimally Invasive Technique for PMMA Augmentation of Fenestrated Screws

    PubMed Central

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

    2015-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1998-01-01

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

  6. Use of polymethylmethacrylate to enhance screw fixation in bone.

    PubMed

    Cameron, H U; Jacob, R; Macnab, I; Pilliar, R M

    1975-07-01

    Pull-out testing of screws inserted into cement and bone under various conditions showed that the cement-screw complex was significantly stronger when the screw was placed in soft cement and the cement was allowed to polymerize without further manipulation. When screw fixation in osteoporotic bone was reinforced with cement, the bone was the weakest component in the system. Fixation under these conditions should be enhanced by increasing the area of contact between the cement and bone. By cooling the cement to prolong its working time, it could be injected with a syringe in such a way that maximum endosteal and periosteal contact was provided. PMID:1150708

  7. Magnesium Alloys as a Biomaterial for Degradable Craniofacial Screws

    PubMed Central

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

    2014-01-01

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

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

    PubMed Central

    Lee, Sandra; Vaidya, Rahul

    2008-01-01

    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

  9. Posterior spinal fusion using pedicle screws.

    PubMed

    Athanasakopoulos, Michael; Mavrogenis, Andreas F; Triantafyllopoulos, George; Koufos, Spiros; Pneumaticos, Spiros G

    2013-07-01

    Few clinical studies have reported polyetheretherketone (PEEK) rod pedicle screw spinal instrumentation systems (CD-Horizon Legacy PEEK rods; Medtronic, Minneapolis, Minnesota). This article describes a clinical series of 52 patients who underwent posterior spinal fusion using the PEEK Rod System between 2007 and 2010. Of the 52 patients, 25 had degenerative disk disease, 10 had lateral recess stenosis, 6 had degenerative spondylolisthesis, 6 had lumbar spine vertebral fracture, 4 had combined lateral recess stenosis and degenerative spondylolisthesis, and 1 had an L5 giant cell tumor. Ten patients had 1-segment fusion, 29 had 2-segment fusion, and 13 had 3-segment fusion. Mean follow-up was 3 years (range, 1.5-4 years); no patient was lost to follow-up. Clinical evaluation was performed using the Oswestry Disability Index and a low back and leg visual analog pain scale. Imaging evaluation of fusion was performed with standard and dynamic radiographs. Complications were recorded. Mean Oswestry Disability Index scores improved from 76% preoperatively (range, 52%-90%) to 48% at 6 weeks postoperatively, and to 34%, 28%, and 30% at 3, 6, and 12 months postoperatively, respectively. Mean low back and leg pain improved from 8 and 9 points preoperatively, respectively, to 6 and 5 points immediately postoperatively, respectively, and to 2 points each thereafter. Imaging union of the arthrodesis was observed in 50 (96%) patients by 1-year follow-up. Two patients sustained screw breakage: 1 had painful loss of sagittal alignment of the lumbar spine and underwent revision spinal surgery with pedicle screws and titanium rods and the other had superficial wound infection and was treated with wound dressing changes and antibiotics for 6 weeks. No adjacent segment degeneration was observed in any patient until the time of this writing. PMID:23823055

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

    PubMed Central

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

    2014-01-01

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

  11. Injection of coal by screw feed

    NASA Technical Reports Server (NTRS)

    Fisher, R.

    1977-01-01

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

  12. Quantitative Anatomy of C7 Vertebra in Southern Chinese for Insertion of Lateral Mass Screws and Pedicle Screws

    PubMed Central

    Chan, Chi Hin; Wong, Kam Kwong; Wong, Wing Cheung

    2016-01-01

    Study Design Retrospective study. Purpose To analyze the quantitative anatomy of C7 vertebra for insertion of lateral mass screws and pedicle screws in Southern Chinese patients. Overview of Literature C7 lateral mass is smaller when compared to other subaxial cervical levels, which limits the length of lateral mass screws that can be used. Some studies have suggested pedicle screws for better fixation. But, this option is limited by the narrow pedicle width. Methods We have obtained computed tomography (CT) cervical spine data in 0.625 mm slices from our radiology department. The patients were adults. CTs were from May to August, 2015. The lateral mass screw length was measured using Margerl's technique and pedicle width and pedicle screw trajectory were determined in three-dimensional reformated images. Results CT scans of cervical spines of 94 patients were obtained and 188 lateral masses and pedicles of C7 vertebrae were measured. The mean lateral mass screw length was 13.2 mm (standard deviation [SD] 1.6 mm), mean outer pedicle width was 5.9 mm (SD 1.0 mm) and mean pedicle screw trajectory was 29.4 degrees (SD 3.6 degrees). Most (91.0%) of the pedicles had an outer diameter ≥4.5 mm. Conclusions The mean lateral mass screw length was longer when compared with other similar studies, while the mean outer pedicle width was narrower. Nearly 10% of the pedicles were unable to accommodate 3.5 mm screws. These findings favor the use of lateral mass screws to provide a safe and stable fixation for C7 vertebrae in Southern Chinese patients, while the final choice of fixation method should only be confirmed after careful preoperative planning with CT scan. PMID:27559451

  13. Cement leakage in pedicle screw augmentation: a prospective analysis of 98 patients and 474 augmented pedicle screws.

    PubMed

    Mueller, Jan U; Baldauf, Joerg; Marx, Sascha; Kirsch, Michael; Schroeder, Henry W S; Pillich, Dirk T

    2016-07-01

    OBJECTIVE Loosening and pullout of pedicle screws are well-known problems in pedicle screw fixation surgery. Augmentation of pedicle screws with bone cement, first described as early as 1975, increases the pedicle-screw interface and pullout force in osteoporotic vertebrae. The aim of the present study was to identify cement leakage and pulmonary embolism rates in a large prospective single-center series of pedicle screw augmentations. METHODS All patients who underwent cement-augmented pedicle screw placement between May 2006 and October 2010 at the authors' institution were included in this prospective cohort study. Perivertebral cement leakage and pulmonary cement embolism were evaluated with a CT scan of the area of operation and with a radiograph of the chest, respectively. RESULTS A total of 98 patients underwent placement of cement-augmented pedicle screws; 474 augmented screws were inserted in 237 vertebrae. No symptomatic perivertebral cement leakage or symptomatic pulmonary cement embolism was observed, but asymptomatic perivertebral cement leakage was seen in 88 patients (93.6%) and in 165 augmented vertebrae (73.3%). Cement leakage most often occurred in the perivertebral venous system. Clinically asymptomatic pulmonary cement embolism was found in 4 patients (4.1%). CONCLUSIONS Perivertebral cement leakage often occurs in pedicle screw augmentation, but in most cases, it is clinically asymptomatic. Cement augmentation should be performed under continuous fluoroscopy to avoid high-volume leakage. Alternative strategies, such as use of expandable screws, should be examined in more detail for patients at high risk of screw loosening. PMID:26943258

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

    NASA Technical Reports Server (NTRS)

    Zahm, A F

    1918-01-01

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

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

    PubMed Central

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

    2015-01-01

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

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

    PubMed Central

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

    2015-01-01

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

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

    PubMed Central

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

    2015-01-01

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

  18. Ball Screw Actuator Including an Axial Soft Stop

    NASA Technical Reports Server (NTRS)

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

    2016-01-01

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

  19. A simple model of throughput calculation for single screw

    NASA Astrophysics Data System (ADS)

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

    2007-04-01

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

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

    PubMed Central

    Zhou, Yue; Li, Changqing; Liu, Huan

    2015-01-01

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

  1. Twin screw granulation - review of current progress.

    PubMed

    Thompson, M R

    2015-01-01

    Twin screw granulation (TSG) is a new process of interest to the pharmaceutical community that can continuously wet granulate powders, doing so at lower liquid concentrations and with better product consistency than found by a high shear batch mixer. A considerable body of research has evolved over the short time since this process was introduced but generally with little comparison of results. A certain degree of confidence has been developed through these studies related to how process variables and many attributes of machinery configuration will affect granulation but some major challenges still lay ahead related to scalability, variations in the processing regimes related to degree of channel fill and the impact of wetting and granulation of complex powder formulations. This review examines the current literature for wet granulation processes studied in twin screw extrusion machinery, summarizing the influences of operational and system parameters affecting granule properties as well as strives to provide some practical observations to newly interested users of the technique. PMID:25402966

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

    PubMed Central

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

    2015-01-01

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

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

    PubMed

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

    2014-05-01

    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

  4. Mechanics of Sheeting Joints

    NASA Astrophysics Data System (ADS)

    Martel, S. J.

    2015-12-01

    the joints can slide downslope; they can also buckle, resulting in a further breakdown of the rock. Understanding how sheeting joints evolve in three dimensions through time remains an outstanding challenge and would illuminate their affect on landscapes, slope stability, and fluid flow.

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

    PubMed Central

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

    2014-01-01

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

  6. 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

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

    2014-06-01

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

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

    PubMed Central

    Kim, Eun-Sook

    2013-01-01

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

  8. Exercise and the Knee Joint.

    ERIC Educational Resources Information Center

    Clarke, H. Harrison, Ed.

    1976-01-01

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

  9. Joint Disorders

    MedlinePlus

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

  10. Intermaxillary fixation screws versus Erich arch bars in mandibular fractures: A comparative study and review of literature

    PubMed Central

    Qureshi, Ahtesham Ahmad; Reddy, Umesh K.; Warad, N. M.; Badal, Sheeraz; Jamadar, Amjad Ali; Qurishi, Nilofar

    2016-01-01

    Objective: Various techniques have been employed from time to time to achieve maxillomamdibular fixation. Although arch bars provide an effective and versatile means of maxillomandibular fixation, their use is not without shortcomings. However the introduction of intermaxillary fixation screws (IMF) has eliminated many of these issues of arch bars. The aim of the present study was to compare the advantages and disadvantages of intermaxillary fixation screws over the Erich arch bars in mandibular fractures. Materials and Methods: Sixty dentulous patients who reported to Department of Oral and Maxillofacial Surgery, Al-Ameen Dental College and Hospital, Bijapur with mandibular fractures and required intermaxillary fixation as a part of treatment plan followd by open reduction and internal fixation under GA were selected and randomly divided into 2 groups of 30 patients each that is Group A and Group B. Group A included patients who received intermaxillary fixation with Erich arch bars. Group B includes patients who received intermaxillary fixation with IMF Screws. The parameters compared in both the groups included, surgical time taken, gloves perforation, post-operative occlusion, IMF stability, oral hygiene, patient acceptance and comfort and non-vitality characteristics. Results: The average surgical time taken and gloves perforations were more in Group A,the patient acceptance and oral hygiene was better in Group B, there was not much statistically significant difference in postoperative occlusion and IMF stability in both groups. Accidental root perforation was the only limitation of IMF screws. Conclusion: Intermaxillary fixation with IMF screws is more efficacious compared to Erich arch bars in the treatment of mandibular fractures. PMID:27563602

  11. Cortical screw trajectory for instrumentation and fusion in the setting of osteopathic compression fracture allows for percutaneous kyphoplasty for adjacent level compression fractures.

    PubMed

    Pacione, Donato; Kim, Irene; Wilson, Taylor A; Frempong-Boadu, Anthony

    2015-05-01

    Spinal fixation in the osteoporotic patient can be challenging due to the poor trabecular bone quality of the vertebral body. Patients with osteoporotic vertebral body compression fractures are at risk for future compression fractures at adjacent levels, especially after cement augmentation. The purpose of this technical report is to describe the utilization of a cortical screw trajectory along with kyphoplasty for a patient with an osteoporotic compression fracture as well as degenerative spinal disease. This trajectory allows for the possibility of percutaneous pedicle access in the event of future compression fractures. Our patient underwent a decompressive laminectomy and kyphoplasty at the level of an osteoporotic compression fracture. The fracture was stabilized with cortical screw instrumentation and fusion at a level above and a level below the fracture. Subsequently the patient developed an adjacent level fracture within the fusion construct. Due to the utilization of a cortical screw trajectory for the initial fusion, the traditional pedicle trajectory was still accessible. As a result, the new fracture was treated with a percutaneous kyphoplasty through a standard pedicle trajectory. In conclusion, the use of a cortical screw trajectory for stabilization of osteoporotic compression fractures provides for a stronger bone screw interface and avoids osteoporotic trabecular vertebral body bone. At the same time this trajectory allows for future percutaneous pedicular access in the event that the patient suffers future compression fractures.

  12. The effect of anterior cruciate ligament rupture on the timing and amplitude of gastrocnemius muscle activation: a study of alterations in EMG measures and their relationship to knee joint stability.

    PubMed

    Klyne, David M; Keays, Susan L; Bullock-Saxton, Joanne E; Newcombe, Peter A

    2012-06-01

    Changes in hamstring and quadriceps activity are well known in individuals with anterior cruciate ligament deficiency (ACLD) to potentially compensate for knee joint instability. However, few studies have explored gastrocnemius activity or its relationship to knee stability. The purpose of this study was therefore to examine the activation characteristics of medial gastrocnemius (MG) in ACLD subjects and relate any changes to knee joint laxity. Two subject cohorts were assessed: those with unilateral ACLD (n=15) and uninjured control subjects (n=11). Surface EMG of the left and right MG were recorded during a controlled single leg hop on each limb. Onset and offset of MG activation relative to take-off, during flight and landing were calculated as well as muscle activity (RMS). Passive antero-posterior knee laxity was measured with a KT1000 arthrometer during a maximal manual displacement test. Medial gastrocnemius activity on the injured side of ACLD participants demonstrated significantly prolonged activation in preparation to hop, minimal muscle inactivity prior to take-off, and increased duration of overall muscle activity when compared to the uninjured side and control subjects (p<0.05). Significant positive correlations were found between passive knee joint laxity and prolonged activation prior to knee bend. RMS of the muscle signal was not significantly different between limbs. Overall, MG on the ACLD side demonstrated longer activation, with minimal rest during the hop test, which may be an attempt to maintain knee stability. Furthermore, the strong relationship between knee laxity and prolonged muscle activation suggests that individuals with a loss of knee stability are more reliant on active control of the gastrocnemius muscle.

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

    PubMed

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

    2014-07-01

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

  14. Cortical bone trajectory screws for the middle-upper thorax

    PubMed Central

    Sheng, Sun-Ren; Chen, Jiao-Xiang; Chen, Wei; Xue, En-Xing; Wang, Xiang-Yang; Zhu, Qing-An

    2016-01-01

    Abstract To quantify the reference data concerning the morphometrics of the middle-upper thorax to guide the placement of cortical bone trajectory (CBT) screws. Eighty patients were studied on computed tomography (CT) scans. The reference anatomical parameters were measured. Next, 20 cadaveric specimens were implanted with CBT screws based on CT measurements. These specimens were then judged directly from the cadaveric vertebrae and X-ray. The maximum length of the trajectory, the maximum diameter, and the cephaled angle exhibited a slight increase trend while the transverse and sagittal angles of the pedicle tended to decrease from T3 to T8. We recommend that the width of CBT screw for middle-upper thoracic spine is 5.0 mm, the length is 25 to 35 mm. The cadaveric anatomical study revealed that 5/240 screws penetrated in the medial or lateral areas, 5/240 screws penetrated in the superior or inferior pedicle wall, and 2/240 screws did not fit into the superior endplate of the pedicle. The CBT screws are safe for the middle-upper thorax. This study provides a theoretical basis for clinical surgery. PMID:27583893

  15. Endovascular Treatment of a Vertebral Artery Pseudoaneurysm Following Posterior C1-C2 Transarticular Screw Fixation

    SciTech Connect

    Mendez, Jose C. Gonzalez-Llanos, Francisco

    2005-01-15

    We present a case of vertebral artery pseudoaneurysm after a posterior C1-C2 transarticular screw fixation procedure that was effectively treated with endovascular coil occlusion. Vertebral artery pseudoaneurysm complicating posterior C1-C2 transarticular fixation is extremely rare, with only one previous case having been reported previously. Endovascular occlusion is better achieved in the subacute phase of the pseudoaneurysm, when the wall of the pseudoaneurysm has matured and stabilized. Further follow-up angiographies are mandatory in order to confirm that there is no recurrence of the lesion.

  16. SCREW COMPRESSOR CHARACTERISTICS FOR HELIUM REFRIGERATION SYSTEMS

    SciTech Connect

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

    2008-03-01

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

  17. Spline-locking screw fastening strategy

    NASA Technical Reports Server (NTRS)

    Vranish, John M.

    1992-01-01

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

  18. Spline-Locking Screw Fastening Strategy (SLSFS)

    NASA Technical Reports Server (NTRS)

    Vranish, John M.

    1991-01-01

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

  19. Spline-Screw Payload-Fastening System

    NASA Technical Reports Server (NTRS)

    Vranish, John M.

    1994-01-01

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

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

    PubMed Central

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

    2014-01-01

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

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

    PubMed Central

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

    2016-01-01

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

  2. Biomechanical evaluation of lumbar pedicle screws in spondylolytic vertebrae: comparison of fixation strength between the traditional trajectory and a cortical bone trajectory.

    PubMed

    Matsukawa, Keitaro; Yato, Yoshiyuki; Imabayashi, Hideaki; Hosogane, Naobumi; Asazuma, Takashi; Chiba, Kazuhiro

    2016-06-01

    OBJECTIVE In the management of isthmic spondylolisthesis, the pedicle screw system is widely accepted surgical strategy; however, there are few reports on the biomechanical behavior of pedicle screws in spondylolytic vertebrae. The purpose of the present study was to compare fixation strength between pedicle screws inserted through the traditional trajectory (TT) and those inserted through a cortical bone trajectory (CBT) in spondylolytic vertebrae by computational simulation. METHODS Finite element models of spondylolytic and normal vertebrae were created from CT scans of 17 patients with adult isthmic spondylolisthesis (mean age 54.6 years, 10 men and 7 women). Each vertebral model was implanted with pedicle screws using TT and CBT techniques and compared between two groups. First, fixation strength of a single screw was evaluated by measuring axial pullout strength. Next, vertebral fixation strength of a paired-screw construct was examined by applying forces simulating flexion, extension, lateral bending, and axial rotation to vertebrae. RESULTS Fixation strengths of TT screws showed a nonsignificant difference between the spondylolytic and the normal vertebrae (p = 0.31-0.81). Fixation strength of CBT screws in the spondylolytic vertebrae demonstrated a statistically significant decrease in pullout strength (21.4%, p < 0.01), flexion (44.1%, p < 0.01), extension (40.9%, p < 0.01), lateral bending (38.3%, p < 0.01), and axial rotation (28.1%, p < 0.05) compared with those in the normal vertebrae. In the spondylolytic vertebrae, no statistically significant difference was observed for pullout strength between TT and CBT (p = 0.90); however, the CBT construct showed lower vertebral fixation strength in flexion (39.0%, p < 0.01), extension (35.6%, p < 0.01), lateral bending (50.7%, p < 0.01), and axial rotation (59.3%, p < 0.01) compared with the TT construct. CONCLUSIONS CBT screws are less optimal for stabilizing the spondylolytic vertebra due to their lower

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

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

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

  4. Adhesive-backed terminal board eliminates mounting screws

    NASA Technical Reports Server (NTRS)

    1965-01-01

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

  5. Bending strength and holding power of tibial locking screws.

    PubMed

    Lin, J; Lin, S J; Chiang, H; Hou, S M

    2001-04-01

    The bending strength and holding power of two types of specially designed tibial locking devices, a both-ends-threaded screw and an unthreaded bolt, were studied and compared with four types of commercially available tibial interlocking screws: Synthes, Howmedica, Richards, and Osteo AG. To test bending strength, the devices were inserted into a high molecular weight polyethylene tube and loaded at their midpoint by a materials testing machine to simulate a three point bending test. Single loading yielding strength and cyclic loading fatigue life were measured. To test holding power, the devices were inserted into tubes made of polyurethane foam, and their tips were loaded axially to measure pushout strength. The devices were tested with two different densities of foam materials and two different sizes of pilot holes. Insertion torque and stripping torque of the screws were measured first. Pushout tests were performed with each screw inserted with a tightness equal to 60% of its stripping torque. Test results showed that the yielding strength and the fatigue life were related closely to the inner diameter of the screws. The stripping torque predicted the pushout strength more reliably than did the insertion torque. All tested devices showed greater holding power in the foam with the higher density and with the smaller pilot holes. The both-ends-threaded screw had the highest pushout strength and a satisfactory fatigue strength. The unthreaded bolt had the highest fatigue strength but only fair holding power. Clinical studies of the use of these two types of locking devices are worthwhile.

  6. Percutaneous iliosacral screw placement using image guided techniques.

    PubMed

    Tonetti, J; Carrat, L; Lavalleé, S; Pittet, L; Merloz, P; Chirossel, J P

    1998-09-01

    A computer assisted technique of iliosacral screw placement that is applicable to unstable pelvic ring fractures is proposed. The goals are to operate noninvasively with a percutaneous procedure to decrease the complications of surgical exposure and to provide greater accuracy in locating the close neurovascular structures. Preoperative computed tomographic images of the pelvis are provided and a computed tomography three-dimensional model is built. In this model, the optimal trajectories for the drilling are planned. An ultrasound based registration is performed intraoperatively. This registration is the most original part of this work. After performing the passive drilling guidance step, the surgeon places the screws. The accuracy of the ultrasound based registration is checked by comparison with a standard surface based registration at the end of the test experiment. Each screw position is verified by a computed tomographic examination. Four human anatomic specimen pelves were tested with three screw insertions for each pelvis (12 screws). All of the screws were considered to be placed correctly. The method is safe and encourages the start of clinical application. PMID:9755769

  7. Robot-assisted Anterior Odontoid Screw Fixation: A Case Report.

    PubMed

    Tian, Wei; Wang, Han; Liu, Ya-Jun

    2016-08-01

    Anterior odontoid screw fixation has been proved to be effective but technically challenging because the difficult approach is associated with high risks of screw malposition and damage to surrounding vital structures. Navigation techniques are therefore increasingly being used to improve safety and accuracy. However, no robot-assisted odontoid screw fixation has yet been reported. We here report a 61-year-old woman with a type II dens fracture on whom anterior odontoid screw fixation was performed under the guidance of a newly developed robotic system (TiRobot, co-designed by Beijing Jishuitan Hospital and TINAVI Medical Technologies). One odontoid screw was safely and accurately placed, the calculated deviation between the planned and actual positions being 0.9 mm. No intraoperative complications were identified and the patient was discharged on Day 5. Follow-up studies after 2 weeks showed good clinical and radiological results. We believe this is the first reported case of robot-assisted anterior odontoid screw fixation. We consider that complicated procedures can become feasible, safe and accurate using TiRobot systems.

  8. Robot-assisted Anterior Odontoid Screw Fixation: A Case Report.

    PubMed

    Tian, Wei; Wang, Han; Liu, Ya-Jun

    2016-08-01

    Anterior odontoid screw fixation has been proved to be effective but technically challenging because the difficult approach is associated with high risks of screw malposition and damage to surrounding vital structures. Navigation techniques are therefore increasingly being used to improve safety and accuracy. However, no robot-assisted odontoid screw fixation has yet been reported. We here report a 61-year-old woman with a type II dens fracture on whom anterior odontoid screw fixation was performed under the guidance of a newly developed robotic system (TiRobot, co-designed by Beijing Jishuitan Hospital and TINAVI Medical Technologies). One odontoid screw was safely and accurately placed, the calculated deviation between the planned and actual positions being 0.9 mm. No intraoperative complications were identified and the patient was discharged on Day 5. Follow-up studies after 2 weeks showed good clinical and radiological results. We believe this is the first reported case of robot-assisted anterior odontoid screw fixation. We consider that complicated procedures can become feasible, safe and accurate using TiRobot systems. PMID:27627725

  9. Screw dislocation driven growth of nanomaterials.

    PubMed

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

    2013-07-16

    Nanoscience and nanotechnology impact our lives in many ways, from electronic and photonic devices to biosensors. They also hold the promise of tackling the renewable energy challenges facing us. However, one limiting scientific challenge is the effective and efficient bottom-up synthesis of nanomaterials. We can approach this core challenge in nanoscience and nanotechnology from two perspectives: (a) how to controllably grow high-quality nanomaterials with desired dimensions, morphologies, and material compositions and (b) how to produce them in a large quantity at reasonable cost. Because many chemical and physical properties of nanomaterials are size- and shape-dependent, rational syntheses of nanomaterials to achieve desirable dimensionalities and morphologies are essential to exploit their utilities. In this Account, we show that the dislocation-driven growth mechanism, where screw dislocation defects provide self-perpetuating growth steps to enable the anisotropic growth of various nanomaterials at low supersaturation, can be a powerful and versatile synthetic method for a wide variety of nanomaterials. Despite significant progress in the last two decades, nanomaterial synthesis has often remained an "art", and except for a few well-studied model systems, the growth mechanisms of many anisotropic nanostructures remain poorly understood. We strive to go beyond the empirical science ("cook-and-look") and adopt a fundamental and mechanistic perspective to the anisotropic growth of nanomaterials by first understanding the kinetics of the crystal growth process. Since most functional nanomaterials are in single-crystal form, insights from the classical crystal growth theories are crucial. We pay attention to how screw dislocations impact the growth kinetics along different crystallographic directions and how the strain energy of defected crystals influences their equilibrium shapes. Furthermore, such inquiries are supported by detailed structural investigation to

  10. Increasing pedicle screw anchoring in the osteoporotic spine by cement injection through the implant. Technical note and report of three cases.

    PubMed

    Fransen, Patrick

    2007-09-01

    Instrumented spinal fusion in patients with osteoporosis is challenging because of the poor bone quality and is complicated by an elevated risk of delayed hardware failure. The author treated two patients presenting with severe osteoporosis, spinal stenosis, and degenerative spondylolisthesis. He performed decompressive laminectomy, posterolateral fusion, and pedicle screw (PS) fixation involving screws with side openings that allow cement to be injected through the implant. The cement injection was conducted under fluoroscopic control without complications. Although this technique needs validation in a larger population of patients, the author believes that the injection of cement through these PSs can be performed safely in carefully selected patients. This technique creates not only a vertebroplasty-like effect that strengthens the vertebral body but also provides the additional stability afforded by the immediate anchoring of the screw, which may allow a shorter-length construct, save mobile segments, and finally reduce the risk of hardware failure. PMID:17877276

  11. Do abnormal hemipelvic bone stresses contribute to loosening and migration of screw-threaded cups?

    PubMed

    Learmonth, I D; Spirakis, A

    1994-03-01

    Excellent long-term results have been reported with the Charnley low-friction arthroplasty. Failure of the cemented acetabular component has been identified as a problem in the longer term, while cemented hip replacements in active young patients have exhibited a disconcerting incidence of early clinical or radiological failure. This resulted in the development of the cementless arthroplasty. Bone responds favourably to an optimal stress window and reacts dynamically to metal implants that have a greatly differing modulus of elasticity. This study represents a comparative qualitative analysis of the peri-acetabular hemipelvic stresses after loading two cementless (press-fit and screw-threaded) acetabular components inserted into identical bone models. A simplified model of the artificial hip joint was constructed and the very sensitive stress analysis technique of holographic interferometry was used for the investigation. Peri-acetabular stress concentrations were noted with the screw-threaded cup. This may predispose to bone resorption and it is suggested that these could be implicated in the migration of these cups described in published reports.

  12. 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

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

    2013-01-01

    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

  13. Changes in the radiological measurements of the tibiofibular syndesmal area in patients with Weber C ankle fractures who were treated with open reduction, internal fixation, and transyndesmal screw.

    PubMed

    Jasqui-Remba, S; Torres-Gómez, A; Salas-Morales, G A; Hernández-Martínez, A

    2015-01-01

    The tibiofibular syndesmosis provides stability to the ankle mortise. The ankle syndesmosis is compromised in all Weber C type injuries. The radiographic method described by Merle DAubigné considers the bony relationships as a measure of syndesmotic widening. We sought to investigate whether the patients with a C type ankle fracture treated with ORIF and placement of a transyndesmal screw have an increment of the tibiofibular space and decrease of the tibiofibular overlap after the transyndesmal screw is removed. Our sample included 52 patients with Weber C ankle fractures treated by ORIF and transyndesmal screw at a level II trauma center. We measured the tibiofibular clear space and tibiofibular overlap in each phase of the treatment. The transyndesmal screw was removed at day 55.56 (± 21.83). We found an increase of the tibiofibular overlap of 0.20 mm (± 2.29, p = 0.532); and 0.21 mm (± 0.97, p = 0.146) in the tibiofibular clear space. The changes of 2.38% in the tibiofibular overlap and 5.29% in the tibiofibular clear space between the postoperative and post-removal periods were not statistically significant. After removal of the syndesmal screw, there is a slight radiographic broadening of the syndesmosis; however, it is small and statistically not significant. PMID:27403518

  14. Changes in the radiological measurements of the tibiofibular syndesmal area in patients with Weber C ankle fractures who were treated with open reduction, internal fixation, and transyndesmal screw.

    PubMed

    Jasqui-Remba, S; Torres-Gómez, A; Salas-Morales, G A; Hernández-Martínez, A

    2015-01-01

    The tibiofibular syndesmosis provides stability to the ankle mortise. The ankle syndesmosis is compromised in all Weber C type injuries. The radiographic method described by Merle DAubigné considers the bony relationships as a measure of syndesmotic widening. We sought to investigate whether the patients with a C type ankle fracture treated with ORIF and placement of a transyndesmal screw have an increment of the tibiofibular space and decrease of the tibiofibular overlap after the transyndesmal screw is removed. Our sample included 52 patients with Weber C ankle fractures treated by ORIF and transyndesmal screw at a level II trauma center. We measured the tibiofibular clear space and tibiofibular overlap in each phase of the treatment. The transyndesmal screw was removed at day 55.56 (± 21.83). We found an increase of the tibiofibular overlap of 0.20 mm (± 2.29, p = 0.532); and 0.21 mm (± 0.97, p = 0.146) in the tibiofibular clear space. The changes of 2.38% in the tibiofibular overlap and 5.29% in the tibiofibular clear space between the postoperative and post-removal periods were not statistically significant. After removal of the syndesmal screw, there is a slight radiographic broadening of the syndesmosis; however, it is small and statistically not significant.

  15. Ceramic joints

    DOEpatents

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

    1991-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

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

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

    PubMed

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

    2015-12-30

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

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

    PubMed

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

    2015-12-30

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

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

    PubMed

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

    2015-01-01

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

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

    PubMed Central

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

    2015-01-01

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

  1. Helical Screw Expander Evaluation Project. Final report

    SciTech Connect

    McKay, R.

    1982-03-01

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

  2. Understanding of edge and screw dislocations in nanostructures by modeling and simulations

    NASA Astrophysics Data System (ADS)

    Dontsova, Evgeniya

    The role of the extended dislocation defects in nanostructures only recently began to be explored. In bulk materials, dislocations are modeled only away from their cores within the framework of the continuum mechanics. It is known that applying continuum modeling in the core region leads to divergences. In nanostructures, the core region dominates and new investigation methods are needed. This work contributes to the fundamental understanding of the role of dislocations in important carbon and zinc oxide nanostructures, by using atomistic investigation methods. In quasi-zero-dimensional structures, thesis describes the first attempt to rationalize dislocation processes in carbon nano-onions. Experiments show that carbon nano-onions exhibit an unusual dislocation dynamics with unexpected attraction of outer edge dislocation towards the core. Atomistic calculations combined with rigorous energy analysis attribute this behavior to an unusual inward driving force on the outer edge dislocation associated with a reduction in the number of dangling bonds. Moving on to quasi-one-dimensional nanostructures, we study the stability of screw-dislocated zinc oxide structures in the wurtzite phase with a symmetry-adapted molecular dynamics methodology, which introduces a significant simplification in the simulation domain size by accounting for the helical symmetry explicitly. The goal is to provide the theoretical support for a universal screw-dislocation-driven growth mechanism suggested by recent experiments. Moreover, the effects of axial screw dislocations on the electronic properties in helical zinc oxide nanowires and nanotubes are explored. We demonstrate significant screw-dislocation-induced band gap modifications that originate in the highly distorted cores. Finally, using the same objective technique, we investigate the stability against torsional deformations of quasi-one-dimensional graphene nanoribbons with bare, F-, and OH-saturated armchair edges. The prevalence

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

    NASA Astrophysics Data System (ADS)

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

    2011-04-01

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

  4. Temporomandibular Joint, Closed

    MedlinePlus

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

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

    NASA Technical Reports Server (NTRS)

    Aldridge, Hal A.; Juang, Jer-Nan

    1997-01-01

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

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

    PubMed

    Dong, Liang; Tang, Wen Cheng

    2014-01-01

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

  7. In Vivo Kinematics of the Trapeziometacarpal Joint During Thumb Extension-flexion and Abduction-adduction

    PubMed Central

    Crisco, Joseph J.; Halilaj, Eni; Moore, Douglas C.; Patel, Tarpit; Weiss, Arnold-Peter C.; Ladd, Amy L.

    2014-01-01

    Purpose The primary aim of this study was to determine whether the in vivo kinematics of the trapeziometacarpal (TMC) joint differ as a function of age and sex during thumb extension-flexion and abduction-adduction motions. Methods The hands and wrists of 44 subjects (10 men and 11 women aged 18 to 35 years and 10 men and 13 women aged 40 to 75 years) with no symptoms or signs of TMC joint pathology were imaged with computed tomography (CT) during thumb extension, flexion, abduction, and adduction. The kinematics of the TMC joint were computed and compared across direction, age, and sex. Results We found no significant effects of age or sex, after normalizing for size, in any of the kinematic parameters. The extension-flexion and abduction-adduction rotation axes did not intersect, and both were oriented obliquely to the saddle-shaped anatomy of the TMC articulation. The extension-flexion axis was located in the trapezium and the abduction-adduction axis was located in the metacarpal. Metacarpal translation and internal rotation occurred primarily during extension-flexion. Discussion Our in vivo findings support previous cadaver and modeling studies that have concluded that the functional axes of the TMC joint are non-orthogonal and non-intersecting. However, in contrast to previous studies, we found extension-flexion and adduction-abduction to be coupled with internal-external rotation and translation. Specifically, internal rotation and ulnar translation were coupled with flexion, indicating a potential stabilizing screw-home mechanism. Clinical Relevance The treatment of TMC pathology and arthroplasty design require a detailed and accurate understanding of TMC function. This study confirms the complexity of TMC kinematics and describes metacarpal translation coupled with internal rotation during extension-flexion, which may explain some of the limitations of current treatment strategies and should help improve implant designs. PMID:25542440

  8. Posterior talar fracture with dislocation of both talo-navicular and subtalar joints: a variant type II of the Sneppens classification

    PubMed Central

    Galanopoulos, Ilias; Fogg, Quentin; Ashwood, Neil

    2012-01-01

    A 63-year-old man fell from a ladder, thus causing an axial compression injury to the right ankle. Severe deformity was evident and the ankle could not be reduced by simple manipulation. The skin was tented and appearing critically contused. Radiographs revealed an oblique fracture of the posterior aspect of the talar body with dislocation of both the talo-navicular and subtalar joints, an injury previously not described in the literature. The fracture–dislocation was anatomically reduced within 3 h of presentation and stability achieved with two headless buried compression screws. CT scan confirmed anatomical reduction and the patient remained non-weight bearing in a cast for 6 weeks. One year postoperatively, the patient remains pain-free with no radiological signs of avascular necrosis of the talus. This injury is unique and despite its severity and soft tissue compromise good quality reduction and internal fixation resulted in an excellent clinical outcome. PMID:22847568

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

    PubMed Central

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

    2015-01-01

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

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

    PubMed

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

    2015-01-01

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

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

    PubMed Central

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

    2015-01-01

    Introduction. Polyaxial screws had been only tested according to the ASTM standards (when they were perpendicularly positioned to the rod). In this study, effects of the pedicle screws angled fixation to the rod on the mechanical properties of fixation were investigated. Materials and Method. 30 vertically fixed screws and 30 screws fixed with angle were used in the study. Screws were used in three different diameters which were 6.5 mm, 7.0 mm, and 7.5 mm, in equal numbers. Axial pull-out and flexion moment tests were performed. Test results compared with each other using appropriate statistical methods. Results. In pull-out test, vertically fixed screws, in 6.5 mm and 7.0 mm diameter, had significantly higher maximum load values than angled fixed screws with the same diameters (P < 0.01). Additionally, vertically fixed screws, in all diameters, had significantly greater stiffness according to corresponding size fixed with angle (P < 0.005). Conclusion. Fixing the pedicle screw to the rod with angle significantly decreased the pull-out stiffness in all diameters. Similarly, pedicle screw instrumentation fixed with angle decreased the minimum sagittal angle between the rod and the screw in all diameters for flexion moment test but the differences were not significant. PMID:27019578

  12. Tips of the trade #38. The Herbert screw in closed reduction and internal fixation of the Jones fracture.

    PubMed

    Traina, S M; McElhinney, J P

    1991-08-01

    A technique of using a cannulated Herbert screw is presented for addressing the troublesome Jones fracture. This closed intramedullary fixation technique allows early healing without many of the screw head problems encountered in the more traditional AO screw techniques.

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

    PubMed

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

    2015-03-01

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

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

    PubMed Central

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

    2014-01-01

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

  15. Compliant joint

    NASA Technical Reports Server (NTRS)

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

    1990-01-01

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

  16. Joint Commission

    MedlinePlus

    ... Sunday 1:00 CST, November 6, 2016 Workplace Violence Prevention Resources The Joint Commission has launched “Workplace Violence Prevention Resources,” an online resource center dedicated to ...

  17. Joint Problems

    MedlinePlus

    ... ankles and toes. Other types of arthritis include gout or pseudogout. Sometimes, there is a mechanical problem ... for more information on osteoarthritis, rheumatoid arthritis and gout. How Common are Joint Problems? Osteoarthritis, which affects ...

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

    NASA Astrophysics Data System (ADS)

    Papes, Iva; Degroote, Joris; Vierendeels, Jan

    2015-08-01

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

  19. Endovascular aortic injury repair after thoracic pedicle screw placement.

    PubMed

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

    2014-09-01

    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

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

    PubMed

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

    2015-11-02

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

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

    PubMed

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

    2015-01-01

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

  2. [Chronic bony instability of the elbow joint].

    PubMed

    Geßmann, J; Königshausen, M; Schildhauer, T A; Seybold, D

    2016-10-01

    The high stability of the elbow joint is provided by the congruent articular surfaces in combination with soft tissue stabilizers. The main osseous contributor of elbow stability is the coronoid, which is therefore referred to as a primary stabilizer. The radial head as a secondary stabilizer together with the medial collateral ligament assures valgus stability and together with the coronoid it assures posterolateral stability. Insufficiency of the osseous stabilizers may lead to difficulties in the treatment of chronic dislocation and complex instability. Thereby reconstruction of the osseous constraints of the elbow joint is not performed in isolation from addressing insufficient soft-tissue stabilizers. Bony stabilizers and reconstructional procedures are discussed in this review.

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

    PubMed Central

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

    2014-01-01

    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

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

    PubMed Central

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

    2016-01-01

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

  5. Effects of lag screw design and lubrication on sliding in trochanteric nails.

    PubMed

    Kummer, Frederick J

    2010-01-01

    This study compared the sliding characteristics of three lag screw designs used with trochanteric nails and determined the effects of lubrication on sliding. They were tested by an established method to measure initiation and ease of lag screw sliding. These tests were then repeated with calf serum lubrication. There were significant differences (p < 0.05) between the loads required to initiate lag screw sliding that appeared to be related to design. Screw sliding was similar for all three designs; however, the presence of lag screw locking slots affected sliding in that region. Lubrication did not affect either parameter. Lag screw design aspects, such as diameter and, particularly, surface finish, affect sliding. Due to the small contact area between the lag screw and nail creating high interface stresses, lubrication had no effect on lag screw sliding.

  6. Extra-articular extraosseous migration of a bioabsorbable femoral interference screw after ACL reconstruction.

    PubMed

    Sharma, Vivek; Curtis, Christine; Micheli, Lyle

    2008-10-01

    Anterior cruciate ligament (ACL) reconstruction is quite commonly used to treat anterior knee instability. Surgeon preference and patient functional goals determine graft selection and graft fixation techniques. Interference screws are considered a safe and effective device for graft fixation in surgical ACL reconstruction. Poly-L-lactide acid (PLLA) bioabsorbable interference screws are becoming increasingly popular in ACL reconstruction surgery. There are several reasons why they may be more advantageous than metallic screws, including reduced graft laceration during insertion, ease of performance of revision procedures, avoidance of graft injury encountered with aperture fixation using metallic screws, and fewer artifacts on magnetic resonance images (MRI). Few studies describe complications associated with PLLA bioabsorbable screws, particularly extra-articular screw migration. This article presents a case of an extra-articular extraosseous migration of the femoral bioabsorbable interference screw. This case further demonstrates the problem of the femoral bioabsorbable interference screw.

  7. Efficiency study of oil cooling of a screw compressor

    SciTech Connect

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

    1989-04-01

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

  8. Optically driven Archimedes micro-screws for micropump application.

    PubMed

    Lin, Chih-Lang; Vitrant, Guy; Bouriau, Michel; Casalegno, Roger; Baldeck, Patrice L

    2011-04-25

    Archimedes micro-screws have been fabricated by three-dimensional two-photon polymerization using a Nd:YAG Q-switched microchip laser at 532nm. Due to their small sizes they can be easily manipulated, and made to rotate using low power optical tweezers. Rotation rates up to 40 Hz are obtained with a laser power of 200 mW, i.e. 0.2 Hz/mW. A photo-driven micropump action in a microfluidic channel is demonstrated with a non-optimized flow rate of 6 pL/min. The optofluidic properties of such type of Archimedes micro-screws are quantitatively described by the conservation of momentum that occurs when the laser photons are reflected on the helical micro-screw surface.

  9. C2 Pedicle Screw Placement: A Novel Teaching Aid

    PubMed Central

    Moisi, Marc; Chapman, Jens; Oskouian, Rod J; Tubbs, R. Shane

    2016-01-01

    The C2 pedicle screw is more biomechanically stable and provides patients with increased postoperative range of motion in comparison to other methods of C2 fixation. However, as a result of the proximity of the C2 pedicle to the transverse foramen, there is a considerable risk of intraoperative morbidity due to vertebral artery injury laterally or vertebral canal breach medially. Other than the use of cadavers for the demonstration and practice of C2 pedicle screw placement, there are currently few other readily available teaching aids for the training of residents and fellows. Herein, we describe a simple and cost effective modality for the demonstration, evaluation, and practice of C2 pedicle screw placement in a laboratory setting. PMID:27433409

  10. Which ankle fractures require syndesmotic stabilization?

    PubMed

    van den Bekerom, Michel P J; Lamme, Bas; Hogervorst, Mike; Bolhuis, Hugo W

    2007-01-01

    Syndesmotic ruptures associated with ankle fractures are most commonly caused by external rotation of the foot, eversion of the talus within the ankle mortise, and excessive dorsiflexion. The distal tibiofibular syndesmosis consists of the anterior inferior tibiofibular ligament, posterior inferior tibiofibular ligament, and interosseous ligament, and it is essential for stability of the ankle mortise. Despite the numerous biomechanical and clinical studies pertaining to ankle fractures, there are no uniform recommendations regarding the use of the syndesmotic screw for specific injury patterns and fracture types. The objective of this review was to formulate recommendations for clinical practice related to the use of syndesmotic screw placement. PMID:17980843

  11. Quantitative comparison between the straight-forward and anatomical insertion technique for pedicle screw placement

    NASA Astrophysics Data System (ADS)

    Knez, Dejan; Mohar, Janez; Likar, Boštjan; Pernuš, Franjo; Vrtovec, Tomaž

    2016-03-01

    Spinal deformity correction with vertebral fixation is nowadays the preferred surgical treatment, where pedicle screws are inserted through pedicles into corresponding vertebral bodies and afterwards connected with rods. In clinical practice, the straight-forward and anatomical insertion technique are currently being used for pedicle screw placement surgery. However, it is difficult to quantitatively compare both techniques and determine which technique is more adequate for each planned pedicle screw before surgery (i.e. preoperatively). In this paper, we therefore describe a framework for quantitative comparison between the straight-forward and anatomical insertion technique for pedicle screw placement surgery by evaluating the screw fastening strength. Quantitative comparisons were performed on computed tomography images of 11 patients with 74 manually planned pedicle screws, who underwent the vertebral fixation procedure. The first quantitative comparison was performed between the straight-forward and anatomical pedicle screw insertion technique, which resulted in a relatively high agreement with mean absolute difference of 0.0mm in screw diameter, 2.9mm in screw length, 1.2mm in pedicle crossing point and 6.5° in screw inclinations. The second quantitative comparison was performed between the best resulting pedicle screw insertion technique and manually obtained pedicle screw plans, which again resulted in a relatively high agreement with mean absolute difference of 0.5mm in screw diameter, 4.7mm in screw length, 2.4mm in pedicle crossing point and 6.0° in screw inclinations. Both the straight-forward and anatomical insertion technique proved approximately equal in terms of the screw fastening strength.

  12. A Case of Distal Femur Medial Condyle Hoffa Type II(C) Fracture Treated with Headless Screws

    PubMed Central

    Merh, Aditya; Shah, Malkesh; Golwala, Paresh

    2016-01-01

    Coronal plane fractures of the distal femur are less frequent compared to sagittal plane fractures. They were described by Hoffa in 1904 and are known as Hoffa fractures (AO type B3). They are isolated fractures of the femoral condyle and rare in occurrence. The objective in the treatment of these fractures is to achieve anatomical reduction of the articular surface and a stable fixation to prevent joint damage in future and prevent post-traumatic arthritis of the joint. We report the case of a young male patient who had a rare type of medial Hoffa fracture which was treated by open reduction and internal fixation using headless Herbert screws using a posterior approach. The fracture was united in eight weeks, and the patient had a full range of knee movement. We advocate this approach and modality of treatment for Hoffa type II(C) fractures.

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

    PubMed Central

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

    2016-01-01

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

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

    PubMed

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

    2016-01-01

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

  15. Role of oxygen at screw dislocations in GaN.

    PubMed

    Arslan, I; Browning, N D

    2003-10-17

    Here we report the first direct atomic scale experimental observations of oxygen segregation to screw dislocations in GaN using correlated techniques in the scanning transmission electron microscope. The amount of oxygen present in each of the three distinct types of screw dislocation core is found to depend on the evolution and structure of the core, and thus gives rise to a varying concentration of localized states in the band gap. Contrary to previous theoretical predictions, the substitution of oxygen for nitrogen is observed to extend over many monolayers for the open core dislocation. PMID:14611410

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

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

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

  17. Optimizing Stability in Femoral Neck Fracture Fixation.

    PubMed

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

    2015-10-01

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

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

    PubMed

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

    2016-01-01

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

  19. Fracture resistance of abutment screws made of titanium, polyetheretherketone, and carbon fiber-reinforced polyetheretherketone.

    PubMed

    Neumann, Eduardo Aloisio Fleck; Villar, Cristina Cunha; França, Fabiana Mantovani Gomes

    2014-01-01

    Fractured abutment screws may be replaced; however, sometimes, the screw cannot be removed and the entire implant must be surgically removed and replaced. The aim of this study was to compare the fracture resistance of abutment retention screws made of titanium, polyetheretherketone (PEEK) and 30% carbon fiber-reinforced PEEK, using an external hexagonal implant/UCLA-type abutment interface assembly. UCLA-type abutments were fixed to implants using titanium screws (Group 1), polyetheretherketone (PEEK) screws (Group 2), and 30% carbon fiber-reinforced PEEK screws (Group 3). The assemblies were placed on a stainless steel holding apparatus to allow for loading at 45o off-axis, in a universal testing machine. A 200 N load (static load) was applied at the central point of the abutment extremity, at a crosshead speed of 5 mm/minute, until failure. Data was analyzed by ANOVA and Tukey's range test. The titanium screws had higher fracture resistance, compared with PEEK and 30% carbon fiber-reinforced PEEK screws (p < 0.05). In contrast, no statistically significant difference was observed between the fracture resistance of the PEEK and the 30% carbon fiber-reinforced PEEK screws (p> 0.05). Finally, visual analysis of the fractions revealed that 100% of them occurred at the neck of the abutment screw, suggesting that this is the weakest point of this unit. PEEK abutment screws have lower fracture resistance, in comparison with titanium abutment screws. PMID:25098826

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

    PubMed

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

    2015-12-01

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

  1. Posterior cervical spine arthrodesis with laminar screws: a report of two cases.

    PubMed

    Nakanishi, Kazuo; Tanaka, Masato; Sugimoto, Yoshihisa; Ozaki, Toshifumi

    2007-04-01

    We performed fixation using laminar screws in 2 patients in whom lateral mass screws, pedicle screws or transarticular screws could not be inserted. One was a 56-year-old woman who had anterior atlantoaxial subluxation (AAS). When a guide wire was inserted using an imaging guide, the hole bled massively. We thought the re-insertion of a guide wire or screw would thus increase the risk of vascular injury, so we used laminar screws. The other case was an 18-year-old man who had a hangman fracture. Preoperative magnetic resonance angiography showed occlusion of the left vertebral artery. A laminar screw was inserted into the patent side (i.e., the right side of C2). Cervical pedicle screws are the most biomechanically stable screws. However, their use carries a high risk of neurovascular complications during screw insertion, because the cervical pedicle is small and is adjacent laterally to the vertebral artery, medially to the spinal cord, and vertically to the nerve roots. Lateral mass screws are also reported to involve a risk of neurovascular injuries. The laminar screw method was thus thought to be useful, since arterial injuries could thus be avoided and it could also be used as a salvage modality for the previous misinsertion. PMID:17471313

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

    NASA Astrophysics Data System (ADS)

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

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

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

    PubMed

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

    2015-12-01

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

  4. Significance of the Pars Interarticularis in the Cortical Bone Trajectory Screw Technique: An In Vivo Insertional Torque Study

    PubMed Central

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

    2016-01-01

    Study Design Retrospective study. Purpose Cortical bone trajectory (CBT), a more medial-to-lateral and shorter path than the traditional one for spinal fusion, is thought to be effective for severely degenerated vertebrae because screws are primarily stabilized at the posterior elements. We evaluated the efficacy of this approach through in vivo insertional torque measurement. Overview of Literature There has been only one prior in vivo study on CBT insertional torque. Methods Between January 2013 and April 2014, a total of 22 patients underwent posterior lumbar fusion using the CBT technique. The maximum insertional torque, which covers the radial strength needed for insertion, was measured for 113 screws, 8 of which were inserted for L5 spondylolysis. The insertional torque for cases with (n=8) and without (n=31) spondylolysis of L5 were compared using one-way analysis of variance (ANOVA). To evaluate vertebral degeneration, we classified 53 vertebrae without spondylolysis by lumbar radiography using semiquantitative methods; the insertional torque for the 105 screws used was compared on the basis of this classification. Additionally, differences in insertional torque among cases grouped by age, sex, and lumbar level were evaluated for these 105 screws using ANOVA and the Tukey test. Results The mean insertional torque was significantly lower for patients with spondylolysis than for those without spondylolysis (4.25 vs. 8.24 in-lb). There were no statistical differences in insertional torque according to vertebral grading or level. The only significant difference in insertional torque between age and sex groups was in men <75 years and women ≥75 years (10 vs. 5.5 in-lb). Conclusions Although CBT should be used with great caution in patient with lysis who are ≥75 years, it is well suited for dealing with severely degenerated vertebrae because the pars interarticularis plays a very important role in the implementation of this technique. PMID:27790318

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

    PubMed

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

    2016-04-01

    Internal fixation devices, which can stabilize and realign fractured bone, are widely used in fracture management. In this paper, a biodegradable composite fixator, composed of poly(ε-caprolactone), calcium phosphate ceramic and calcium sulfate (PCL/CPC/CS), is developed. The composition of CS, which has a high dissolution rate, was expected to create a porous structure to improve osteofixation to the composite fixator. PCL, PCL/CPC, and PCL/CPC/CS samples were prepared and their physical properties were characterized in vitro. In vivo performance of the composite screws was verified in the distal femurs of rabbits. Results showed that the PCL/CPC/CS composite had a higher compressive strength (28.55 ± 3.32 MPa) in comparison with that of PCL (20.64 ± 1.81 MPa) (p < 0.05). A larger amount of apatite was formed on PCL/CPC/CS than on PCL/CPC, while no apatite was found on PCL after simulated body fluid immersion. In addition, PCL/CPC/CS composites also had a faster in vitro degradation rate (13.05 ± 3.42% in weight loss) relative to PCL (1.79 ± 0.23%) and PCL/CPC (4.32 ± 2.18%) (p < 0.001). In animal studies, PCL/CPC/CS screws showed a greater volume loss than that of PCL or PCL/CPC at 24 weeks post-implantation. Under micro-computerized tomography observation, animals with PCL/CPC/CS implants had better osseointegration in terms of the structural parameters of the distal metaphysis, including trabecular number, trabecular spacing, and connectivity density, than the PCL screw. This study reveals that the addition of CS accelerates the biodegradation and enhanced apatite formation of the PCL/CPC composite screw. This osteoconductive PCL/CPC/CS is a good candidate material for internal fixation devices. PMID:27041468

  6. Biomechanical Evaluation of Supplemental Percutaneous Lumbo-Sacro-iliac Screws For Spino-pelvic Fixation Following Total Sacrectomy

    PubMed Central

    Le, Vu H.; Heckmann, Nathanael; Jain, Nickul; Wang, Lawrence; Turner, Alexander W. L.; Lee, Thay Q.; Bederman, S. Samuel

    2015-01-01

    Study Design This is a cadaveric biomechanical study evaluating the biomechanical properties of a novel spino-pelvic fixation technique with percutaneous lumbo-sacro-iliac (LSI) screws in an unstable total sacrectomy model. Objective To compare standard posterior dual rod spino-pelvic fixation alone with dual rod fixation supplemented with LSI screw fixation. Summary of Background Data Primary or metastatic tumors of the sacrum requiring a total sacrectomy can result in spino-pelvic instability if inadequate fixation is achieved. Many fixation techniques have been proposed to address this instability. However, to date, an optimal fixation technique has not been established. Methods Ten fresh-frozen cadaveric spino-pelvic specimens were randomized according to bone mineral density (BMD) to either posterior rod fixation (control group) or posterior rod fixation with supplemental LSI screws (LSI group). Following fixation, a total sacrectomy of each specimen was performed. Specimens where then potted and axially loaded in a caudal direction. Stiffness, yield load, energy absorbed at yield load, ultimate load, and energy absorbed at ultimate load were computed. A students t-test was used for statistical analysis with significance set at p<0.05. Results The average age and BMD were not significantly different between the control and LSI groups (age, p=0.255; BMD, p=0.810). After normalizing for BMD, there were no significant differences detected for any of the biomechanical parameters measured between the two fixation techniques: stiffness (p=0.857), yield load (p=0.219), energy at yield load (p=0.293), ultimate load (p=0.407), and energy at ultimate load (p=0.773). However, both fixation techniques were able to withstand physiological loads. Conclusions Our study did not demonstrate any biomechanical advantage for supplemental LSI screw fixation in our axial loading model. However, given the theoretical advantage of this percutaneous technique, further studies are

  7. Handbook on dynamics of jointed structures.

    SciTech Connect

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

    2009-07-01

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

  8. Global dynamic modeling of electro-hydraulic 3-UPS/S parallel stabilized platform by bond graph

    NASA Astrophysics Data System (ADS)

    Zhang, Lijie; Guo, Fei; Li, Yongquan; Lu, Wenjuan

    2016-08-01

    Dynamic modeling of a parallel manipulator(PM) is an important issue. A complete PM system is actually composed of multiple physical domains. As PMs are widely used in various fields, the importance of modeling the global dynamic model of the PM system becomes increasingly prominent. Currently there lacks further research in global dynamic modeling. A unified modeling approach for the multi-energy domains PM system is proposed based on bond graph and a global dynamic model of the 3-UPS/S parallel stabilized platform involving mechanical and electrical-hydraulic elements is built. Firstly, the screw bond graph theory is improved based on the screw theory, the modular joint model is modeled and the normalized dynamic model of the mechanism is established. Secondly, combined with the electro-hydraulic servo system model built by traditional bond graph, the global dynamic model of the system is obtained, and then the motion, force and power of any element can be obtained directly. Lastly, the experiments and simulations of the driving forces, pressure and flow are performed, and the results show that, the theoretical calculation results of the driving forces are in accord with the experimental ones, and the pressure and flow of the first limb and the third limb are symmetry with each other. The results are reasonable and verify the correctness and effectiveness of the model and the method. The proposed dynamic modeling method provides a reference for modeling of other multi-energy domains system which contains complex PM.

  9. Posterior lumbar interbody fusion using one diagonal fusion cage with transpedicular screw/rod fixation.

    PubMed

    Zhao, Jie; Hou, Tiesheng; Wang, Xinwei; Ma, Shengzhong

    2003-04-01

    Posterior lumbar interbody fusion (PLIF) using threaded cages has gained wide popularity for lumbosacral spinal disease. Our biomechanical tests showed that PLIF using a single diagonal cage with unilateral facetectomy does add a little to spinal stability and provides equal or even higher postoperative stability than PLIF using two posterior cages with bilateral facetectomy. Studies also demonstrated that cages placed using a posterior approach did not cause the same increase in spinal stiffness seen with pedicle screw instrumentation, and we concluded that cages should not be used posteriorly without other forms of fixation. On the other hand, placement of two cages using a posterior approach does have the disadvantage of risk to the bilateral nerve roots. We therefore performed a prospective study to determine whether PLIF can be accomplished by utilizing a single diagonal fusion cage with the application of supplemental transpedicular screw/rod instrumentation. Twenty-seven patients underwent a PLIF using one single fusion cage (BAK, Sulzer Spine-Tech, Minneapolis, MN, USA) inserted posterolaterally and oriented anteromedially on the symptomatic side with unilateral facetectomy and at the same level supplemental fixation with a transpedicular screw/rod system. The internal fixation systems included 12 SOCON spinal systems (Aesculap AG, Germany) and 15 TSRH spinal systems (Medtronic Sofamor Danek, USA). The inclusion criteria were grade 1 to 2 lumbar isthmic spondylolisthesis, lumbar degenerative spondylolisthesis, and recurrent lumbar disc herniations with instability. Patients had at least 1 year of low back pain and/or unilateral sciatica and a severely restricted functional ability in individuals aged 28-55 years. Patients with more than grade 2 spondylolisthesis or adjacent-level degeneration were excluded from the study. Patients were clinically assessed prior to surgery by an independent assessor; they were then reassessed at 1, 3, 6, 12, 18, and 24

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

    PubMed

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

    2014-11-20

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

  11. Ultraprecision Positioning by Preload Change of Lead Screws

    NASA Astrophysics Data System (ADS)

    Nakashima, Katuhiro; Tamaru, Yuuma; Takafuji, Kazuki

    Ultraprecision positioning is examined for a fine feed system utilizing the elastic deformation of lead screws accompanying the change in the preload in a double nut. The nonlinear deformation due to Hertzian contact of the ball screw can be ignored within a feed of 1μm under an dequate initial preload. No effect of table load on nanometer-order displacement is observed in the range from 10 to 50 kg. The table displacement obtained under an increase in the preload coincides well with the result under a decrease in the preload. Feed control with preload change based on a one-to-one correspondence of preload change and displacement is effective for avoiding the hysterisis phenomenon of the piezoelectric acturator adopted as a deformable spacing part in a double nut. In addition, the preload can be used as a measure to detect the table displacement in place of a position sensor which sometimes shows unreliability owing to unstable performance in the nanometer region. The minimum step feed deduced from preload change is 1nm for a sliding screw and 5nm for a ball screw.

  12. 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

  13. Dynamics of discrete screw dislocations on glide directions

    NASA Astrophysics Data System (ADS)

    Alicandro, R.; De Luca, L.; Garroni, A.; Ponsiglione, M.

    2016-07-01

    We consider a simple discrete model for screw dislocations in crystals. Using a variational discrete scheme we study the motion of a configuration of dislocations toward low energy configurations. We deduce an effective fully overdamped dynamics that follows the maximal dissipation criterion introduced in Cermelli and Gurtin (1999) and predicts motion along the glide directions of the crystal.

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

  15. 39. VIEW OF VESSEL STERNON IN DRYDOCK. NOTE TWIN SCREWS ...

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

    39. VIEW OF VESSEL STERN-ON IN DRYDOCK. NOTE TWIN SCREWS AND RUDDER. GENTLEMEN IN VIEW UNKNOWN Original 5'x5' photograph taken by Robert S. Douglas in 1966 - Pilot Schooner "Alabama", Moored in harbor at Vineyard Haven, Vineyard Haven, Dukes County, MA

  16. A Case of Implant Failure in Partial Wrist Fusion Applying Magnesium-Based Headless Bone Screws

    PubMed Central

    Emmerich, Judith

    2016-01-01

    This article presents a case of implant failure resulting in mechanical instability of a scaphotrapezotrapezoideal arthrodesis using magnesium-based headless bone screws. During revision surgery osteolysis surrounding the screws was observed as well as degraded screw threads already in existence at 6 weeks after implantation. The supposed osseous integration attributed to magnesium-based screws could not be reproduced in this particular case. Thus, it can be reasoned that the use of magnesium-based screws for partial wrist arthrodesis cannot be encouraged, at least not in dual use. PMID:27800201

  17. Use of computational fluid dynamics simulations for design of a pretreatment screw conveyor reactor.

    PubMed

    Berson, R Eric; Hanley, Thomas R

    2005-01-01

    Computational fluid dynamics simulations were employed to compare performance of various designs of a pretreatment screw conveyor reactor. The reactor consisted of a vertical screw used to create cross flow between the upward conveying solids and the downward flow of acid. Simulations were performed with the original screw design and a modified design in which the upper flights of the screw were removed. Results of the simulations show visually that the modified design provided favorable plug flow behavior within the reactor. Pressure drop across the length of the reactor without the upper screws in place was predicted by the simulations to be 5 vs 40 kPa for the original design.

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

    PubMed

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

    2016-01-01

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

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

    NASA Technical Reports Server (NTRS)

    De Bothezat, George

    1920-01-01

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

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

    PubMed Central

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

    2015-01-01

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

  1. Tomographic analysis for C2 screw placement in rheumatoid arthritis patients

    PubMed Central

    Astolfi, Rodrigo Schroll; Tachibana, Wilson Tadao; Letaif, Olavo Biraghi; Cristante, Alexandre Fogaça; Oliveira, Reginaldo Perilo; de Barros Filho, Tarcísio Eloy Pessoa

    2012-01-01

    Objective A morphological analysis of the bone structure of C2 in patients with rheumatoid arthritis in order to enhance the security of the stabilization procedures for this vertebra. Methods We retrospectively analyzed 20 CT scans of the cervical spine performed in patients with rheumatoid arthritis; the following parameters were measured: spinolaminar angle, thickness and length of C2 lamina. Results The mean values are: 5.92mm and 5.87mm for thickness of right and left laminae retrospectively, 27.75mm for right lamina length and 27.94mm for left lamina length, and 44.7º for spinolaminar angle. Conclusion The values obtained are consistent with studies in normal subjects published by other groups, with no apparent need for change in the screw placement technique. Level of Evidence IV, Case Series. PMID:24453603

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

    PubMed

    Dong, Liang; Tang, WenCheng; Bao, DaFei

    2015-03-01

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

  3. Bioresorbable screws reinforced with phosphate glass fibre: manufacturing and mechanical property characterisation.

    PubMed

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

    2013-01-01

    Use of bioresorbable screws could eliminate disadvantages associated with metals such as removal operations, corrosion, MRI interference and stress shielding. Mechanical properties of bioresorbable polymers alone are insufficient for load bearing applications application as screws. Thus, reinforcement is necessary to try and match or surpass the mechanical properties of cortical bone. Phosphate based glass fibres were used to reinforce polylactic acid (PLA) in order to produce unidirectionally aligned (UD) and unidirectionally plus randomly distributed (UD/RM) composite screws (P40 UD and P40 UD/RM). The maximum flexural and push-out properties for the composite screws (P40 UD and P40 UD/RM) increased by almost 100% in comparison with the PLA screws. While the pull-out strength and stiffness of the headless composite screws were ∼80% (strength) and ∼130% (stiffness) higher than for PLA, those with heads exhibited properties lower than those for PLA alone as a result of failure at the heads. An increase in the maximum shear load and stiffness for the composite screws (∼30% and ∼40%) in comparison to the PLA screws was also seen. Maximum torque for the PLA screws was ∼1000 mN m, while that for the composite screws were slightly lower. The SEM micrographs for P40 UD and P40 UD/RM screws revealed small gaps around the fibres, which were suggested to be due to buckling of the UD fibres during the manufacturing process.

  4. Bioresorbable screws reinforced with phosphate glass fibre: manufacturing and mechanical property characterisation.

    PubMed

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

    2013-01-01

    Use of bioresorbable screws could eliminate disadvantages associated with metals such as removal operations, corrosion, MRI interference and stress shielding. Mechanical properties of bioresorbable polymers alone are insufficient for load bearing applications application as screws. Thus, reinforcement is necessary to try and match or surpass the mechanical properties of cortical bone. Phosphate based glass fibres were used to reinforce polylactic acid (PLA) in order to produce unidirectionally aligned (UD) and unidirectionally plus randomly distributed (UD/RM) composite screws (P40 UD and P40 UD/RM). The maximum flexural and push-out properties for the composite screws (P40 UD and P40 UD/RM) increased by almost 100% in comparison with the PLA screws. While the pull-out strength and stiffness of the headless composite screws were ∼80% (strength) and ∼130% (stiffness) higher than for PLA, those with heads exhibited properties lower than those for PLA alone as a result of failure at the heads. An increase in the maximum shear load and stiffness for the composite screws (∼30% and ∼40%) in comparison to the PLA screws was also seen. Maximum torque for the PLA screws was ∼1000 mN m, while that for the composite screws were slightly lower. The SEM micrographs for P40 UD and P40 UD/RM screws revealed small gaps around the fibres, which were suggested to be due to buckling of the UD fibres during the manufacturing process. PMID:23122715

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

    PubMed

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

    2016-01-01

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

  6. A technique for indirect fabrication of an implant-supported, screw-retained, fixed provisional restoration in the esthetic zone.

    PubMed

    Lin, Wei-Shao; Ercoli, Carlo

    2009-12-01

    This article describes an alternative technique for the fabrication of an implant-supported, screw-retained, fixed provisional restoration in the esthetic zone. After an implant-level impression is made with a polyether impression material, the provisional restoration is fabricated indirectly. This technique is easy, saves time, and has economic advantages, while maintaining color stability and esthetic properties for the provisional restoration. It may be contraindicated for severely misaligned implants that require extensive reduction of the implant temporary abutments and denture teeth laminates.

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

    PubMed

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

    2007-06-01

    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

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

    PubMed

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

    1999-04-01

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

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

    NASA Astrophysics Data System (ADS)

    Tondu, Bertrand

    2003-05-01

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

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

    PubMed

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

    2016-06-01

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

  11. Joint assembly

    NASA Technical Reports Server (NTRS)

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

    2010-01-01

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

  12. Cortical screw support in femoral neck fractures. A radiographic analysis of 87 fractures with a new mensuration technique.

    PubMed

    Lindequist, S

    1993-06-01

    In 87 femoral neck fractures, operated on with 2 von Bahr screws and followed for up to 2 years, the positions of the fixating screws were determined with a new mensuration technique which compensates for the variations in hip rotation in routine radiographs. The union rate of the fractures was related to the position of the screws. A posterior placement of the proximal screw and an inferior placement of the distal screw in both the femoral head and neck improved the outcome substantially.

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

    PubMed Central

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

    2008-01-01

    Reconstruction after multilevel decompression of the cervical spine, especially in the weakened osteoporotic, neoplastic or infectious spine often requires circumferential stabilization and fusion. To avoid the additional posterior surgery in these cases while increasing rigidity of anterior-only screw-plate constructs, the authors introduce the concept of anterior transpedicular screw (ATPS) fixation. We demonstrated its morphological feasibility as well as its indications in a previous study in Part I of our project. Consequently, the objectives of the current study were to assess the ex vivo accuracy of placing ATPS into the cervical vertebra as well as the biomechanical performance of ATPS in comparison to traditional vertebral body screws (VBS) in terms of pull-out strength (POS). Twenty-three ATPS were inserted alternately to two screws into the pedicles and vertebral bodies, respectively, of six cadaveric specimens from C3–T1. For insertion of ATPS, a manual fluoroscopically assisted technique was used. Pre- and post insertional CT-scans were used to assess accuracy of ATPS insertion in the axial and sagittal planes. A newly designed grading system and accuracy score were used to delineate accuracy of ATPS insertion. Following insertion of screws, 23 ATPS and 22 VBS were subjected to pull-out testing (POT). The bone mineral density (BMD) of each specimen was assessed prior to POT. Statistical analysis showed that the incidence of correctly placed screws and non-critical pedicles breaches in axial plane was 78.3%, and 95.7% in sagittal plane. Hence, according to our definition of “critical” pedicle breach that exposes neurovascular structures at risk, 21.7% (n = 5) of all ATPS inserted showed a critical pedicle breach in axial plane. Notably, no critical pedicle perforation occurred at the C6 to T1 levels. Pull-out testing of ATPS and VBS revealed that pull-out resistance of ATPS was 2.5-fold that of VBS. Mean POS of 23 ATPS with a mean BMD of 0.566

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

    PubMed

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

    2015-08-01

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

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

    PubMed

    Walker, Logan; Willis, Nigel

    2015-01-01

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

  16. Acromioclavicular joint disorders.

    PubMed

    Turnbull, J R

    1998-04-01

    The acromioclavicular joint is commonly involved in athletic injuries. Most commonly, a sprain to the joint occurs with variability in the amount of ligamentous damage and displacement that occurs. In all but the most severe dislocations, treatment consists of initial sling immobilization and early functional rehabilitation. The outcome is usually excellent with full return of function following these injuries. The rarer types (IV, V, and VI) require operative reduction and fixation. Distal clavicle fractures are related injuries, which many times disrupt the stabilizing ligaments of the acromioclavicular joint. Many can be treated nonoperatively, but there are several subtypes that should be considered for early fixation to reduce complications of pain and shoulder dysfunction. An atraumatic, overuse condition, which is becoming more prevalent and seems related to weight training, is osteolysis of the distal clavicle. There is insidious onset of shoulder pain with symptoms and signs consistent with acromioclavicular pathology. Activity modification is the best method of controlling symptoms. Failure of the conservative approach necessitates operative excision of the distal clavicle.

  17. [Use of a periosteal flap in the surgical management of rupture of the acromioclavicular joint capsule and ligament. Preliminary report].

    PubMed

    Sánta, S; Varga, Z; Tasnády, Z

    1989-01-01

    Authors use in the treatment of acromioclavicular joint dislocations to increase the safety of the ligament sutures a periosteal flap, gained from the clavicle. The use of the periosteal flap to increase the strength of the acromioclavicular ligament sutures is described. In case of fixing the joint with a tension band the suspension of the cerclage on a screw for an easier removal is suggested.

  18. Efficiency study of oil cooling of a screw compressor

    SciTech Connect

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

    1990-01-01

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

  19. Release of elements from retrieved maxillofacial plates and screws.

    PubMed

    Bertoldi, C; Pradelli, J M; Consolo, U; Zaffe, D

    2005-09-01

    Vitallium appliances and surrounding tissues were investigated to evaluate the release and accumulation of elements. Four microplates, sixteen screws and surrounding tissues were removed from three patients presenting inflammation 4 to 6 years after surgery and were submitted to SEM and X-ray microprobe analysis. Histology was performed on paraffin or PMMA sections of tissues.A continuous release of elements from metallic appliances into soft tissues was observed. Cobalt, chromium, and nickel were detected in soft and boney tissues in close proximity to the appliance. Aluminium, as a component of screw coatings, accumulated in soft tissues, and a remarkable amount of aluminium was detected in the dense lamella of lamellar bone. The results suggest that coatings containing aluminium should be avoided and the time these appliances are allowed to remain in patients should be shortened. Further studies on element release and the fate of aluminium in bone are warranted.

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

    PubMed Central

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

    2014-01-01

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

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

    PubMed

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

    2008-09-01

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

  2. Effect of Micrometer-Scale Roughness of the Surface of Ti6Al4V Pedicle Screws in Vitro and in Vivo

    PubMed Central

    Schwartz, Zvi; Raz, Perry; Zhao, Ge; Barak, Yael; Tauber, Michael; Yao, Hai; Boyan, Barbara D.

    2008-01-01

    . There was a correlation between in vitro and in vivo observations, indicating that the use of screws with rough surfaces will result in better bone-implant contact and implant stability. Clinical Relevance: The osteointegration of screws with rough microtopographies is likely to be better than that of screws with smoother surfaces. PMID:18978418

  3. Intramedullary screw fixation of proximal fifth metatarsal fractures in athletes

    PubMed Central

    Massada, Marta Maria Teixeira de Oliveira; Pereira, Manuel Alexandre Negrais Pinho Gonçalves; de Sousa, Ricardo Jorge Gomes; Costa, Paulo Guimarães; Massada, José Leandro da Rocha

    2012-01-01

    Objective The purpose of this study was to review the short- and long-term clinical and radiological results of intramedullary compression screw fixation of proximal fifth metatarsal fractures in athletes. Methods Eleven male and six female active patients with fifth metatarsal zone II and zone III fractures fixed with a 4.5-mm cannulated compression screw were evaluated by chart review, review of radiographs, and clinical evaluation. Fifteen of the patients were high-level athletes (soccer: n=11; basketball: n=1; track and field: n=3) and two were recreational-level athletes. Mean follow-up from surgery to evaluation was 54 (38-70) months. Results Mean time to healing as shown on radiographs and mean time to return to full activity after surgery were 7.3 and 7.5 weeks, respectively. All patients were able to return to their previous levels of activity. There were no reports of union delay, nonunion or refracture to date. Conclusion In our patients, cannulated screw fixation of proximal fifth metatarsal fractures was a reliable procedure with low morbidity associated that provided athletes a quick return to activity. Level of Evidence I, Case Series. PMID:24453614

  4. Modelling of the Heating Process in a Thermal Screw

    NASA Astrophysics Data System (ADS)

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

    2012-11-01

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

  5. Optical screw-wrench for interlocking 2PP-microstructures

    NASA Astrophysics Data System (ADS)

    Köhler, J.; Zyla, G.; Ksouri, S. I.; Esen, C.; Ostendorf, A.

    2016-03-01

    Two-photon polymerization (2PP) has emerged as a powerful platform for processing three-dimensional microstructures with high resolution. Furthermore, by adding nanoparticles of different materials to the photopolymer the microstructures can be functionalized, e.g. magnetic or electric properties can be adjusted. However, to combine different functions within one microstructure or to manufacture complex microsystems, assembling techniques for multiple 2PP written building blocks are required. In this paper a qualitative approach for assembling microstructures utilizing optical forces is presented. Therefore, screw and nut shaped microstructures are produced by 2PP-technique and screwed together using a holographic optical tweezer (HOT). The interlocking structures are trapped and rotated into each other to cause connection. In this paper the used parameters and possible designs of the interlocking connection are discussed. These findings provide not only the assembling of building blocks to complex microstructures, rather different functionalized 2PP-microstructures can be combined by simply screwing them together with the use of optical forces.

  6. Outpatient percutaneous screw fixation of the acute Jones fracture.

    PubMed

    Mindrebo, N; Shelbourne, K D; Van Meter, C D; Rettig, A C

    1993-01-01

    Nine patients (8 men and 1 woman, ranging in age from 17 to 22 years) who sustained a Jones fracture were treated with percutaneous intramedullary screw fixation as outpatients. All of the patients were varsity athletes. Seven were Division I scholarship athletes. Beginning at 7 to 10 days after surgery, all patients were allowed weightbearing as tolerated with a CAM walker. Stationary bicycling, swimming, and Stairmaster were allowed at 2 to 3 weeks. The average return to running was 5.5 weeks (range, 3 to 10). The average return to full competition was 8.5 weeks (range, 7 to 12). No perioperative or postoperative complications occurred. Average followup was 2.5 years. All fractures attained clinical and radiographic union. We believe that outpatient percutaneous intramedullary screw fixation of the acute Jones fracture is a reasonable alternative for those active patients who would have difficulty with a non-weightbearing cast and crutches or who desire an expeditious return to activities. Time restraints are particularly critical for in-season or preseason athletes. With the outpatient screw fixation method, our patient population had predictable healing, and they returned to full sports participation within 12 weeks.

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

    PubMed

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

    2015-01-01

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

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

    PubMed

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

    2015-01-01

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

  9. Interference screw position and hamstring graft location for anterior cruciate ligament reconstruction.

    PubMed

    Simonian, P T; Sussmann, P S; Baldini, T H; Crockett, H C; Wickiewicz, T L

    1998-01-01

    Anterior cruciate ligament reconstruction with hamstring tendon graft and interference screw fixation has recently been considered. Concerns for the use of interference screws with soft tissue grafts include damage to the graft during screw insertion, decreased fixation strength, and a decrease in the bone-tendon contact area for healing within the tunnel when the screw is placed in an eccentric position. This last concern could be addressed by placing the interference screw centrally between the four limbs of the hamstring graft. The purpose of this study was to determine the mode of failure, the pullout force, and graft slippage before graft fixation failure of hamstring tendons fixed with an interference screw positioned eccentrically in relation to the hamstring tendons verses an interference screw positioned centrally between the four graft limbs. The semitendinosus and gracilis tendons were harvested from six, fresh cadaveric specimens. Each tendon was divided into two segments of equal length. Both the semitendinosus and gracilis tendon segments were looped to form four strands. The specimens were then fixed with a bioabsorbable interference screw in the two different positions and pulled from a standardized polyurethane foam. All tendons in both groups failed by pulling out from between the interference screw and tunnel, regardless of the screw position. No tendon was cut by the screw in either group. There was no significant difference between the forces required to produce specific amounts of graft slippage between the two fixation techniques tested. There was no significant difference between the average total slippage at maximum pullout, 11.8 mm for the screw placed in the eccentric position and 13.7 mm for the screw placed in the central position. The maximum pullout force averaged 265.3 N for the screw placed in the eccentric position, and 244.7 N for the screw placed in the central position; these values were not significantly different. Placement of

  10. Management of acromioclavicular joint injuries.

    PubMed

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

    2014-01-01

    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

  11. Laminar screw fixation in the subaxial cervical spine: A report on three cases

    PubMed Central

    Tanabe, Hironori; Aota, Yoichi; Saito, Tomoyuki

    2016-01-01

    Although laminar screw fixation is often used at the C2 and C7 levels, only few previous case reports have presented the use of laminar screws at the C3-C6 levels. Here, we report a novel fixation method involving the use of practical laminar screws in the subaxial spine. We used laminar screws in the subaxial cervical spine in two cases to prevent vertebral artery injury and in one case to minimize exposure of the lamina. This laminar screw technique was successful in all three cases with adequate spinal rigidity, which was achieved without complications. The use of laminar screws in the subaxial cervical spine is a useful option for posterior fusion of the cervical spine. PMID:27795952

  12. Fabrication of a screw-retained restoration avoiding the facial access hole: a clinical report.

    PubMed

    Garcia-Gazaui, Sabrina; Razzoog, Michael; Sierraalta, Marianella; Saglik, Berna

    2015-11-01

    Dental implant restorations may be either screw-retained or cemented onto an abutment. While each method has its advantages and disadvantages, cemented restorations are commonly used in the maxillary arch, usually because of esthetic concerns. Available bone in the anterior maxilla dictates the placement of the implant, which may result in a facially positioned screw-access opening. Still, a growing volume of literature states that periimplant soft tissues respond more favorably to screw-retained crowns than cement-retained crowns. This clinical report outlines a treatment with a new method of fabricating a custom abutment-crown combination for a screw-retained restoration. The technique allows the channel for the screw to be placed at an angle other than parallel to the implant body. In this case, the practitioner may choose either a screw-retained or cement-retained implant restoration, where previously only a cemented restoration was possible. PMID:26344192

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

    SciTech Connect

    Lambert, M.A.

    1996-06-01

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

  14. Short segment pedicle screw instrumentation and augmentation vertebroplasty in lumbar burst fractures: an experience

    PubMed Central

    Akbar, Saleem; Dhar, Shabir A.

    2008-01-01

    To assess the efficacy and feasibility of vertebroplasty and posterior short-segment pedicle screw fixation for the treatment of traumatic lumbar burst fractures. Short-segment pedicle screw instrumentation is a well described technique to reduce and stabilize thoracic and lumbar spine fractures. It is relatively a easy procedure but can only indirectly reduce a fractured vertebral body, and the means of augmenting the anterior column are limited. Hardware failure and a loss of reduction are recognized complications caused by insufficient anterior column support. Patients with traumatic lumbar burst fractures without neurologic deficits were included. After a short segment posterior reduction and fixation, bilateral transpedicular reduction of the endplate was performed using a balloon, and polymethyl methacrylate cement was injected. Pre-operative and post-operative central and anterior heights were assessed with radiographs and MRI. Sixteen patients underwent this procedure, and a substantial reduction of the endplates could be achieved with the technique. All patients recovered uneventfully, and the neurologic examination revealed no deficits. The post-operative radiographs and magnetic resonance images demonstrated a good fracture reduction and filling of the bone defect without unwarranted bone displacement. The central and anterior height of the vertebral body could be restored to 72 and 82% of the estimated intact height, respectively. Complications were cement leakage in three cases without clinical implications and one superficial wound infection. Posterior short-segment pedicle fixation in conjunction with balloon vertebroplasty seems to be a feasible option in the management of lumbar burst fractures, thereby addressing all the three columns through a single approach. Although cement leakage occurred but had no clinical consequences or neurological deficit. PMID:18193300

  15. Short segment pedicle screw instrumentation and augmentation vertebroplasty in lumbar burst fractures: an experience.

    PubMed

    Afzal, Suhail; Akbar, Saleem; Dhar, Shabir A

    2008-03-01

    To assess the efficacy and feasibility of vertebroplasty and posterior short-segment pedicle screw fixation for the treatment of traumatic lumbar burst fractures. Short-segment pedicle screw instrumentation is a well described technique to reduce and stabilize thoracic and lumbar spine fractures. It is relatively a easy procedure but can only indirectly reduce a fractured vertebral body, and the means of augmenting the anterior column are limited. Hardware failure and a loss of reduction are recognized complications caused by insufficient anterior column support. Patients with traumatic lumbar burst fractures without neurologic deficits were included. After a short segment posterior reduction and fixation, bilateral transpedicular reduction of the endplate was performed using a balloon, and polymethyl methacrylate cement was injected. Pre-operative and post-operative central and anterior heights were assessed with radiographs and MRI. Sixteen patients underwent this procedure, and a substantial reduction of the endplates could be achieved with the technique. All patients recovered uneventfully, and the neurologic examination revealed no deficits. The post-operative radiographs and magnetic resonance images demonstrated a good fracture reduction and filling of the bone defect without unwarranted bone displacement. The central and anterior height of the vertebral body could be restored to 72 and 82% of the estimated intact height, respectively. Complications were cement leakage in three cases without clinical implications and one superficial wound infection. Posterior short-segment pedicle fixation in conjunction with balloon vertebroplasty seems to be a feasible option in the management of lumbar burst fractures, thereby addressing all the three columns through a single approach. Although cement leakage occurred but had no clinical consequences or neurological deficit. PMID:18193300

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

    PubMed

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

    2012-08-01

    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

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

    SciTech Connect

    Hu Hongtao; Shin, Ji Hoon Hwang, Jae-Yeon; Cho, Young Jun; Ko, Gi-Young; Yoon, Hyun-Ki

    2010-10-15

    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.

  18. Anatomic Study of Anterior Transdiscal Axial Screw Fixation for Subaxial Cervical Spine Injuries

    PubMed Central

    Ji, Wei; Zheng, Minghui; Qu, Dongbin; Zou, Lin; Chen, Yongquan; Chen, Jianting; Zhu, Qingan

    2016-01-01

    Abstract Anterior transdiscal axial screw (ATAS) fixation is an alternative or supplement to the plate and screw constructs for the upper cervical spine injury. However, no existing literatures clarified the anatomic feasibility of this technique for subaxial cervical spine. Therefore, the objective of this study was to evaluate the anatomical feasibility and to establish guidelines for the use of the ATAS fixation for the subaxial cervical spine injury. Fifty normal cervical spines had radiographs to determine the proposed screw trajectory (the screw length and insertion angle) and the interbody graft-related parameters (the disc height and depth, and the distance between anterior vertebral margin and the screw) for all levels of the subaxial cervical spine. Following screw insertion in 8 preserved human cadaver specimens, surgical simulation and dissection verified the feasibility and safety of the ATAS fixation. Radiographic measurements showed the mean axial screw length and cephalic incline angle of all levels were 41.2 mm and 25.2°, respectively. The suitable depth of the interbody graft was >11.7 mm (the distance between anterior vertebral margin and the screw), but <17.1 mm (disc depth). Except the axial screw length, increase in all the measurements was seen with level up to C5–C6 segment. Simulated procedure in the preserved specimens demonstrated that ATAS fixation could be successfully performed at C2–C3, C3–C4, C4–C5, and C5–C6 levels, but impossible at C6–C7 due to the obstacle of the sternum. All screws were placed accurately. None of the screws penetrated into the spinal canal and caused fractures determined by dissecting the specimens. The anterior transdiscal axial screw fixation, as an alternative or supplementary instrumentation for subaxial cervical spine injuries, is feasible and safe with meticulous surgical planning. PMID:27495016

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

    PubMed

    Solitro, Giovanni F; Amirouche, Farid

    2016-04-01

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

  20. A reciprocal connection factor for assessing knee-joint function.

    PubMed

    Kim, Wangdo; Kohles, Sean S

    2012-01-01

    In the knee joint, interactions between instantaneous kinetics and kinematics associated with ligamentous and articular tissues are not fully understood. These structures may be represented by the instantaneous screw axis ($) (ISA) and static force vectors ($'). Geometric changes to the joint structure affecting motion have not been fully explained, especially after surgical reconstruction and replacement procedures. The ISA offers a joint-characterisation approach, which is dependent on the combined forces of ligaments, articular contacts and muscles. The standard four-bar linkage model in the sagittal plane demonstrates that the normal contact force and the lines of action of the cruciate ligaments always intersect at the centre of rotation of the joint. A kinematic knee model in which the articular surfaces in the lateral and medial compartments as well as the isometric fascicles in the engaged ligaments may be represented as five constraints in a one-degree-of-freedom parallel spatial mechanism. This study provides a theoretical foundation to elucidate the role of each of these elements in the control of the ISA. A recourse to the principle of virtual work explained through d'Alembert's principle for reducing a dynamics problem to an instantaneous static scenario allows screws to be applied to the biomechanics of human motion. The principle of reciprocity links these approaches together to explain the transmitting load between the tibia and the femur as well as the relative motion within the knee joint. A principal clinical implication of this study is the introduction of the reciprocal connection factor to evaluate knee kinematics and kinetics in one simple term, allowing the quantitative assessment of the outcome of knee-joint treatment and rehabilitation methods.

  1. Biomechanical evaluation of DTRAX® posterior cervical cage stabilization with and without lateral mass fixation

    PubMed Central

    Voronov, Leonard I; Siemionow, Krzysztof B; Havey, Robert M; Carandang, Gerard; Patwardhan, Avinash G

    2016-01-01

    Introduction Lateral mass screw (LMS) fixation with plates or rods is the current standard procedure for posterior cervical fusion. Recently, implants placed between the facet joints have become available as an alternative to LMS or transfacet screws for patients with cervical spondylotic radiculopathy. The purpose of this study was to evaluate the biomechanical stability of the DTRAX® cervical cage for single- and two-level fusion and compare this to the stability achieved with LMS fixation with rods in a two-level construct. Methods Six cadaveric cervical spine (C3–C7) specimens were tested in flexion–extension, lateral bending, and axial rotation to ±1.5 Nm moment without preload (0 N) in the following conditions: 1) intact (C3–C7), 2) LMS and rods at C4–C5 and C5–C6, 3) removal of all rods (LMS retained) and placement of bilateral posterior cages at C5–C6, 4) bilateral posterior cages at C4–C5 and C5–C6 (without LMS and rods), and 5) C4–C5 and C5–C6 bilateral posterior cages at C4–C5 and C5–C6 with rods reinserted. Results Bilateral posterior cervical cages significantly reduced range of motion in all tested directions in both single- and multilevel constructs (P<0.05). Similar stability was achieved with bilateral posterior cages and LMS in a two-level construct: 0.6°±0.3° vs 1.2°±0.4° in flexion–extension (P=0.001), (5.0°±2.6° vs 3.1°±1.3°) in lateral bending (P=0.053), (1.3°±1.0° vs 2.2°±0.9°) in axial rotation (P=0.091) for posterior cages and LMS, respectively. Posterior cages, when placed as an adjunct to LMS, further reduced range of motion in a multilevel construct (P<0.05). Conclusion Bilateral posterior cages provide similar cervical segmental stability compared with a LMS and rod construct and may be an alternative surgical option for select patients. Furthermore, supplementation of a lateral mass construct with posterior cages increases cervical spine stability in single- and multilevel conditions.

  2. Biomechanical evaluation of DTRAX® posterior cervical cage stabilization with and without lateral mass fixation

    PubMed Central

    Voronov, Leonard I; Siemionow, Krzysztof B; Havey, Robert M; Carandang, Gerard; Patwardhan, Avinash G

    2016-01-01

    Introduction Lateral mass screw (LMS) fixation with plates or rods is the current standard procedure for posterior cervical fusion. Recently, implants placed between the facet joints have become available as an alternative to LMS or transfacet screws for patients with cervical spondylotic radiculopathy. The purpose of this study was to evaluate the biomechanical stability of the DTRAX® cervical cage for single- and two-level fusion and compare this to the stability achieved with LMS fixation with rods in a two-level construct. Methods Six cadaveric cervical spine (C3–C7) specimens were tested in flexion–extension, lateral bending, and axial rotation to ±1.5 Nm moment without preload (0 N) in the following conditions: 1) intact (C3–C7), 2) LMS and rods at C4–C5 and C5–C6, 3) removal of all rods (LMS retained) and placement of bilateral posterior cages at C5–C6, 4) bilateral posterior cages at C4–C5 and C5–C6 (without LMS and rods), and 5) C4–C5 and C5–C6 bilateral posterior cages at C4–C5 and C5–C6 with rods reinserted. Results Bilateral posterior cervical cages significantly reduced range of motion in all tested directions in both single- and multilevel constructs (P<0.05). Similar stability was achieved with bilateral posterior cages and LMS in a two-level construct: 0.6°±0.3° vs 1.2°±0.4° in flexion–extension (P=0.001), (5.0°±2.6° vs 3.1°±1.3°) in lateral bending (P=0.053), (1.3°±1.0° vs 2.2°±0.9°) in axial rotation (P=0.091) for posterior cages and LMS, respectively. Posterior cages, when placed as an adjunct to LMS, further reduced range of motion in a multilevel construct (P<0.05). Conclusion Bilateral posterior cages provide similar cervical segmental stability compared with a LMS and rod construct and may be an alternative surgical option for select patients. Furthermore, supplementation of a lateral mass construct with posterior cages increases cervical spine stability in single- and multilevel conditions. PMID

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

    PubMed

    Demir, Teyfik

    2015-05-01

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

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

    PubMed

    Demir, Teyfik

    2015-05-01

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

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

    PubMed Central

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

    2012-01-01

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

  6. Joint x-ray

    MedlinePlus

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

  7. [Observations on optimizing the mechanical properties of osteosynthesis screws].

    PubMed

    Zitter, H

    1988-06-01

    According to two agreeing standards, the mechanical requirements for bone screws consist of a minimum breaking torque and of the minimum angle of rotation to failure of 180 degrees. Apparently it has been overlooked that these requirements admit austenitic steels with a very low yield strength, which reach the required torque at fracture only by the work-hardening brought about during the torsion test. As a high yield strength is a prerequisite of a stable fixation, a formulation is proposed which guarantees not only a high elastic torque but also an adequate work of deformation in the plastic state as an insurance against embrittlement. PMID:3407018

  8. Contribution to the ideal efficiency of screw propellers

    NASA Technical Reports Server (NTRS)

    Hoff, Wilhelm

    1942-01-01

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

  9. Minimally-invasive posterior lumbar stabilization for degenerative low back pain and sciatica. A review.

    PubMed

    Bonaldi, G; Brembilla, C; Cianfoni, A

    2015-05-01

    The most diffused surgical techniques for stabilization of the painful degenerated and instable lumbar spine, represented by transpedicular screws and rods instrumentation with or without interbody cages or disk replacements, require widely open and/or difficult and poorly anatomical accesses. However, such surgical techniques and approaches, although still considered "standard of care", are burdened by high costs, long recovery times and several potential complications. Hence the effort to open new minimally-invasive surgical approaches to eliminate painful abnormal motion. The surgical and radiological communities are exploring, since more than a decade, alternative, minimally-invasive or even percutaneous techniques to fuse and lock an instable lumbar segment. Another promising line of research is represented by the so-called dynamic stabilization (non-fusion or motion preservation back surgery), which aims to provide stabilization to the lumbar spinal units (SUs), while maintaining their mobility and function. Risk of potential complications of traditional fusion methods (infection, CSF leaks, harvest site pain, instrumentation failure) are reduced, particularly transitional disease (i.e., the biomechanical stresses imposed on the adjacent segments, resulting in delayed degenerative changes in adjacent facet joints and discs). Dynamic stabilization modifies the distribution of loads within the SU, moving them away from sensitive (painful) areas of the SU. Basic biomechanics of the SU will be discussed, to clarify the mode of action of the different posterior stabilization devices. Most devices are minimally invasive or percutaneous, thus accessible to radiologists' interventional practice. Devices will be described, together with indications for patient selection, surgical approaches and possible complications.

  10. Spacesuit mobility knee joints

    NASA Technical Reports Server (NTRS)

    Vykukal, H. C. (Inventor)

    1979-01-01

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

  11. Spacesuit mobility joints

    NASA Technical Reports Server (NTRS)

    Vykukal, H. C. (Inventor)

    1978-01-01

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

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

    PubMed Central

    2014-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Lepschi, Alexander; Gerstorfer, Gregor; Miethlinger, Jürgen

    2015-05-01

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

  14. 29 CFR 1926.305 - Jacks-lever and ratchet, screw, and hydraulic.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

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

  15. 29 CFR 1926.305 - Jacks-lever and ratchet, screw, and hydraulic.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

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

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

    Code of Federal Regulations, 2011 CFR

    2011-07-01

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

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

    Code of Federal Regulations, 2013 CFR

    2013-07-01

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

  18. Evaluation of torque maintenance of abutment and cylinder screws with Morse taper implants.

    PubMed

    Ferreira, Mayara Barbosa; Delben, Juliana Aparecida; Barão, Valentim Adelino Ricardo; Faverani, Leonardo Perez; Dos Santos, Paulo Henrique; Assunção, Wirley Gonçalves

    2012-11-01

    The screw loosening of implant-supported prostheses is a common mechanical failure and is related to several factors as insertion torque and preload. The aim of this study was to evaluate the torque maintenance of retention screws of tapered abutments and cylinders of Morse taper implants submitted to retightening and detorque measurements. Two groups were obtained (n = 12): group I-tapered abutment connected to the implant with titanium retention screw and group II-cylinder with metallic base connected to tapered abutment with titanium retention screw. The detorque values were measured by an analogic torque gauge after 3 minutes of torque insertion. The detorque was measured 10 times for each retention screw of groups I and II, totalizing 120 detorque measurements in each group. Data were submitted to ANOVA and Fisher exact test (P < 0.05). Both groups presented reduced detorque value (P < 0.05) in comparison to the insertion torque in all measurement periods. There was a statistically significant difference (P < 0.05) between the detorque values of the first measurement and the other measurement periods for the abutment screw. However, there was no statistically significant difference (P > 0.05) for the detorque values of all measurement periods for the cylinder screw. In conclusion, the abutment and cylinder screws exhibited torque loss after insertion, which indicates the need for retightening during function of the implant-supported prostheses.

  19. 29 CFR 1926.305 - Jacks-lever and ratchet, screw, and hydraulic.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

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

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

    PubMed Central

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

    2016-01-01

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

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

    PubMed

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

    2016-01-01

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

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

    PubMed

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

    2014-12-01

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

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

    NASA Astrophysics Data System (ADS)

    Straka, Klaus; Praher, Bernhard; Steinbichler, Georg

    2015-05-01

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

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

    PubMed

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

    2014-12-01

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

  5. The Efficacy of Lumbar Hybrid Stabilization Using the DIAM™ to Delay Adjacent Segment Degeneration: An Intervention Comparison Study With a Minimum Two-Year Follow-up.

    PubMed

    Lee, Chang-Hyun; Hyun, Seung-Jae; Kim, Ki-Jeong; Jahng, Tae-Ahn; Yoon, Sang Hoon; Kim, Hyun-Jib

    2013-04-29

    BACKGROUND:: Although posterior lumbar interbody fusion (PLIF) has a successful fusion rate, the long-term outcome of PLIF is occasionally below expectations because of adjacent segment degeneration (ASD). OBJECTIVE:: To evaluate the ability of hybrid stabilization using DIAM(Device for Interspinous Assisted Motion) to delay ASD. METHODS:: An intervention comparison study of 75 patients (hybrid, 25; PLIF, 50) was performed. The indications for hybrid stabilization were facet joint degeneration, Pfirrmann grade II-III, and stenosis at the rostral adjacent segment. The PLIF group consisted of patients matched for age, gender, and fusion. The hybrid stabilization procedure included traditional PLIF and DIAM installation at a superior adjacent segment. The outcomes were analyzed using linear mixed model analysis. Conditional logistic regression was performed to calculate the odds ratio for the association of surgical methods. RESULTS:: The hybrid group (24%) revealed fewer ASDs than the PLIF group (48%). Among ASDs, spondylolisthesis occurred more frequently in the PLIF group than the hybrid group. Hybrid surgery was significantly associated with ASD; the odds ratio for hybrid surgery was 0.28 when compared to PLIF. Foraminal height of the PLIF group decreased more than the hybrid group (P=.01). Segmental mobility showed a greater increase in the PLIF group than the hybrid group (P=.04). However, the clinical outcomes did not show significant differences between the groups. CONCLUSION:: Hybrid stabilization using DIAM and pedicle screws can be used for patients with facet degeneration at adjacent segments but should be further investigated.

  6. Using a porcelain furnace to debond cement-retained implant crown from the abutment after screw fracture: a clinical report.

    PubMed

    Saponaro, Paola C; Heshmati, Reza H; Lee, Damian J

    2015-04-01

    When a screw fracture occurs on a cement-retained, implant-supported restoration, the abutment and restoration are completely separated from the implant's internal connection. Traditionally, an access hole is drilled through the crown to retrieve the broken screw, and the restoration can be placed again as a screw-retained restoration. This clinical report documents a patient whose broken abutment screw was retrieved from the restoration by burning off the cement and separating from the abutment without drilling an access hole.

  7. A Newly Designed Screw- and Cement-Retained Prosthesis and Its Abutments.

    PubMed

    Heo, Young-Ku; Lim, Young-Jun

    2015-01-01

    The degree of misfit between a prosthesis and its supporting implants is a major concern in screw-retained prostheses because it can lead to screw loosening or mechanical failure of implant components. On the other hand, the difficulty of removing subgingival excess cement and the irretrievability of the superstructure are major drawbacks to cement-retained prostheses. A newly designed screw- and cement-retained prosthesis (SCRP) may solve these problems with its passivity, retrievability, and ease in the complete removal of excess cement, giving it the advantages of both screw-retained and cement-retained prostheses. This prosthetic system is mainly composed of a cement-retained framework with screw holes on the occlusal surface and specially designed cementable abutments for multiunit prostheses. The principle and structure of the SCRP system is described in this article.

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

    PubMed

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

    2005-10-01

    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

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

    PubMed

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

    2013-08-01

    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

  10. Theoretical study of kinks on screw dislocation in silicon

    NASA Astrophysics Data System (ADS)

    Pizzagalli, L.; Pedersen, A.; Arnaldsson, A.; Jónsson, H.; Beauchamp, P.

    2008-02-01

    Theoretical calculations of the structure, formation, and migration of kinks on a nondissociated screw dislocation in silicon have been carried out using density functional theory calculations as well as calculations based on interatomic potential functions. The results show that the structure of a single kink is characterized by a narrow core and highly stretched bonds between some of the atoms. The formation energy of a single kink ranges from 0.9to1.36eV , and is of the same order as that for kinks on partial dislocations. However, the kinks migrate almost freely along the line of an undissociated dislocation unlike what is found for partial dislocations. The effect of stress has also been investigated in order to compare with previous silicon deformation experiments which have been carried out at low temperature and high stress. The energy barrier associated with the formation of a stable kink pair becomes as low as 0.65eV for an applied stress on the order of 1GPa , indicating that displacements of screw dislocations likely occur via thermally activated formation of kink pairs at room temperature.

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

    PubMed

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

    2013-08-01

    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.

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

    PubMed

    Nissen, Carl W

    2008-07-01

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

  13. Augmentation of screw fixation with injectable calcium sulfate bone cement in ovariectomized rats.

    PubMed

    Yu, Xiao-Wei; Xie, Xin-Hui; Yu, Zhi-Feng; Tang, Ting-Ting

    2009-04-01

    The objective of this study was to determine the effect of augmenting screw fixation with an injectable calcium sulfate cement (CSC) in the osteoporotic bone of ovariectomized rats. The influence of the calcium sulfate (CS) on bone remodeling and screw anchorage in osteoporotic cancellous bone was systematically investigated using histomorphometric and biomechanical analyses. The femoral condyles of 55 Sprague-Dawley ovariectomized rats were implanted with screw augmented with CS, while the contralateral limb received a nonaugmented screw. At time intervals of 2, 4, 8, 12, and 16 weeks, 11 rats were euthanized. Six pair-matched samples were used for histological analysis, while five pair-matched samples were preserved for biomechanical testing. Histomorphometric data showed that CS augmented screws activated cancellous bone formation, evidenced by a statistically higher (p < 0.05) percentage of osteoid surface at 2, 4, and 8 weeks and a higher rate of bone mineral apposition at 12 weeks compared with nonaugmented screws. The amount of the bone-screw contact at 2, 8, and 12 weeks and of bone ingrowth on the threads at 4 and 8 weeks was greater in the CS group than in the nonaugmented group (p < 0.05), although these parameters increased concomitantly with time for both groups. The CS was resorbed completely at 8 weeks without stimulating fibrous encapsulation on the screw surface. Also, the cement significantly increased the screw pull-out force and the energy to failure at 2, 4, 8, and 12 weeks after implantation, when compared with the control group (p < 0.05). These results imply that augmentation of screw fixation with CS may have the potential to decrease the risk of implant failure in osteoporotic bone.

  14. Hydroxyapatite and fluorapatite coatings on dental screws: effects of blast coating process and biological response.

    PubMed

    Dunne, Conor F; Twomey, Barry; Kelly, Ciara; Simpson, Jeremy C; Stanton, Kenneth T

    2015-01-01

    This paper describes the deposition of hydroxyapatite (HA) and fluorapatite (FA) onto titanium dental screws using a novel ambient temperature coating technique named CoBlast. The process utilises a coating medium and a blast medium sprayed simultaneously at the substrate surface. The blast medium was a sintered apatite (sHA) and two particles sizes (<106 and <180 µm) were used to assess their influence on the coating process. The influence of the coating process on the coating composition, coating adhesion, screw morphology and screw microstructure was examined. XRD analysis revealed the coating crystallinity was the same as the original HA and FA feedstock powders. Examining the screw's morphology, the threads of the CoBlasted screws exhibited rounding compared to the unmodified screw. This is due to the abrasive nature of the CoBlast process. The degree of rounding was more significant for the screws blasted with the 180 µm sHA than the 106 µm sHA. The blast media particle size significantly influences the surface roughness of both the substrate and coating and the microstructure of the substrate. The screws did not exhibit any loss of coating after insertion into a model bone material, indicating that the coating was strongly adhered to the substrate. There was no statistically significant difference in cell attachment and cell morphology on the unmodified substrates compared to the coated substrates. In conclusion, the CoBlast process can be used to deposit HA and FA onto complex geometries such as dental screws. The choice of blast medium particle size influences the screws morphology. The coating process does not negatively impact on the cell attachment and morphology in vitro.

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

    PubMed Central

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

    2015-01-01

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

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

    PubMed Central

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

    2015-01-01

    To evaluate the presence of pain at the site of the surgical incision and the need to remove the tibial fixation screw in anterior cruciate ligament (ACL) reconstruction, in relation to sex and body mass index (BMI). Methods: A group of 265 patients who underwent ACL reconstruction with ipsilateral flexor tendon grafts from the thigh in which the tibial fixation technique consisted of using a cortical screw and metal washer, between July 2000 and November 2007, were evaluated. Results: 176 patients were evaluated for an average of 33.3 ± 19.5 months; median of 29.5 months; IIQ: 17-45 months; minimum of 8 and maximum of 87 months. There was no statistical difference regarding complaints of pain at the site of the screw (p = 0.272) and the need to remove the tibial screw (p = 0.633) between sexes. There was no statistical difference regarding complaints of pain at the site of the screw (p = 0.08) and the need to remove the tibial screw (p = 0.379) according to BMI. Conclusion: The pain complaint rate at the screw site from the screw and metal washer method used for tibial fixation in ACL reconstruction was of the order of 25%, and the screw had to be removed in 10.8% of the cases. There was no predominance of pain complaints at the surgical wound between the sexes. There was a greater tendency to complain about pain among patients with BMI < 25. There was no predominance of screw and washer removal between the sexes or between individuals with different BMIs. PMID:27022587

  17. MODELING UNDERGROUND STRUCTURE VULNERABILITY IN JOINTED ROCK

    SciTech Connect

    R. SWIFT; D. STEEDMAN

    2001-02-01

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

  18. Biomechanical testing of the LCP--how can stability in locked internal fixators be controlled?

    PubMed

    Stoffel, Karl; Dieter, Ulrich; Stachowiak, Gwidon; Gächter, André; Kuster, Markus S

    2003-11-01

    New plating techniques, such as non-contact plates, have been introduced in acknowledgment of the importance of biological factors in internal fixation. Knowledge of the fixation stability provided by these new plates is very limited and clarification is still necessary to determine how the mechanical stability, e.g. fracture motion, and the risk of implant failure can best be controlled. The results of a study based on in vitro experiments with composite bone cylinders and finite element analysis using the Locking Compression Plate (LCP) for diaphyseal fractures are presented and recommendations for clinical practice are given. Several factors were shown to influence stability both in compression and torsion. Axial stiffness and torsional rigidity was mainly influenced by the working length, e.g. the distance of the first screw to the fracture site. By omitting one screw hole on either side of the fracture, the construct became almost twice as flexible in both compression and torsion. The number of screws also significantly affected the stability, however, more than three screws per fragment did little to increase axial stiffness; nor did four screws increase torsional rigidity. The position of the third screw in the fragment significantly affected axial stiffness, but not torsional rigidity. The closer an additional screw is positioned towards the fracture gap, the stiffer the construct becomes under compression. The rigidity under torsional load was determined by the number of screws only. Another factor affecting construct stability was the distance of the plate to the bone. Increasing this distance resulted in decreased construct stability. Finally, a shorter plate with an equal number of screws caused a reduction in axial stiffness but not in torsional rigidity. Static compression tests showed that increasing the working length, e.g. omitting the screws immediately adjacent to the fracture on both sides, significantly diminished the load causing plastic

  19. Efficacy of Osteoconductive Ceramics in Bioresorbable Screws for Anterior Cruciate Ligament Reconstruction

    PubMed Central

    Barth, Johannes; Akritopoulos, Panagiotis; Graveleau, Nicolas; Barthelemy, Renaud; Toanen, Cécile; Saffarini, Mo

    2016-01-01

    Background: Osteoconductive additives are used in resorbable interference screws for anterior cruciate ligament (ACL) reconstruction to improve graft incorporation and mitigate adverse effects. There are no published studies that compare biological performances of bioresorbable and biocomposite screws without artifacts due to different follow-up times and intrinsic patient characteristics. Purpose/Hypothesis: The purpose of this study was to evaluate the efficacy of osteoconductive agents in bioresorbable screws for ACL reconstruction at minimum follow-up of 2 years by intrapatient comparison. The hypothesis was that osteoconductive ceramics would result in slower resorption, improved ossification, and less tunnel widening. Study Design: Cohort study; Level of evidence, 2. Methods: A total of 28 ACL reconstructions at 2 centers were randomly assigned into 2 comparable groups: (1) the graft was fixed in the tibia using standard bioresorbable screws and in the femur using biocomposite screws with osteoconductive agents (biphasic calcium phosphate), and (2) the graft was fixed in the femur using a standard bioresorbable screw and in the tibia using a biocomposite screw with osteoconductive agents. Results: Twenty-seven patients completed evaluations at 29.9 ± 4.0 months. Resorption was complete for more bioresorbable (81%) than biocomposite (37%) screws (P = .0029), whereas satisfactory ossification was observed in more biocomposite (52%) than bioresorbable (15%) screws (P = .0216). The tunnel shape was normal in more biocomposite (81%) than bioresorbable (48%) screws (P = .0126), and marked cortical formation was twice more frequent for biocomposite (78%) than bioresorbable (37%) screws (P = .0012). Bioresorbable screws exhibited faster resorption in the femur (P = .0202) but not in the tibia (not significant). Conversely, biocomposite screws demonstrated better ossification, less tunnel widening, and more cortical formation in the tibia (P < .0001, P = .0227, and P

  20. Modeling flow, melting, solid conveying and global behavior in intermeshing counter-rotating twin screw extruders

    NASA Astrophysics Data System (ADS)

    Jiang, Qibo

    Intermeshing counter-rotating twin screw extruders are widely applied in polymer processing industry, especially in compounding and PVC profile processing. However, the design of this type of machines is generally based on experiences and error-and-try. In addition, most of the investigations on intermeshing counter-rotating twin screw extruders were made on the melt conveying region. There is a lack of adequate study on a complete extrusion process to this type of machines. In this study, models were developed to simulate the extrusion processes, including solid conveying, melting and metering, evaluate the performance of intermeshing counter-rotating twin screw extruders, and optimize the design of machines and operating conditions. Experiments were carried out on a laboratory modular intermeshing counter-rotating twin screw extruder to observe solid conveying, the melting process and the global behavior of this type of machine. The solid bed is formed in the solid conveying region. The inter-screw region plays a dominant role in the melting process. Based on our observations, models were developed to describe both the solid conveying and the melting process. Based on hydrodynamic lubrication theory, a melt conveying model was developed to characterize the pumping capacity of screw elements in intermeshing counter-rotating twin screw extruders. The effect of screw channel aspect ratio (screw channel depth/width) was incorporated into the melt conveying model to improve the prediction of screw pumping capacity. Calculations were made to investigate the effect of geometrical parameter on screw pumping capacity. Models of solid conveying, the melting process and melt conveying were integrated together and a global composite model was developed to characterize the whole intermeshing counter-rotating twin screw extrusion process. The global model is intended for both flood fed and metered starved fed conditions. This is the first composite model designed for this type

  1. Seismic response of rock joints and jointed rock mass

    SciTech Connect

    Ghosh, A.; Hsiung, S.M.; Chowdhury, A.H.

    1996-06-01

    Long-term stability of emplacement drifts and potential near-field fluid flow resulting from coupled effects are among the concerns for safe disposal of high-level nuclear waste (HLW). A number of factors can induce drift instability or change the near-field flow patterns. Repetitive seismic loads from earthquakes and thermal loads generated by the decay of emplaced waste are two significant factors. One of two key technical uncertainties (KTU) that can potentially pose a high risk of noncompliance with the performance objectives of 10 CFR Part 60 is the prediction of thermal-mechanical (including repetitive seismic load) effects on stability of emplacement drifts and the engineered barrier system. The second KTU of concern is the prediction of thermal-mechanical-hydrological (including repetitive seismic load) effects on the host rock surrounding the engineered barrier system. The Rock Mechanics research project being conducted at the Center for Nuclear Waste Regulatory Analyses (CNWRA) is intended to address certain specific technical issues associated with these two KTUs. This research project has two major components: (i) seismic response of rock joints and a jointed rock mass and (ii) coupled thermal-mechanical-hydrological (TMH) response of a jointed rock mass surrounding the engineered barrier system (EBS). This final report summarizes the research activities concerned with the repetitive seismic load aspect of both these KTUs.

  2. Self-assembly of left- and right-handed molecular screws.

    PubMed

    Xu, Fei; Khan, I John; McGuinness, Kenneth; Parmar, Avanish S; Silva, Teresita; Murthy, N Sanjeeva; Nanda, Vikas

    2013-12-18

    Stereoselectivity is a hallmark of biomolecular processes from catalysis to self-assembly, which predominantly occur between homochiral species. However, both homochiral and heterochiral complexes of synthetic polypeptides have been observed where stereoselectivity hinges on details of intermolecular interactions. This raises the question whether general rules governing stereoselectivity exist. A geometric ridges-in-grooves model of interacting helices indicates that heterochiral associations should generally be favored in this class of structures. We tested this principle using a simplified molecular screw, a collagen peptide triple-helix composed of either l- or d-proline with a cyclic aliphatic side chain. Calculated stabilities of like- and opposite-handed triple-helical pairings indicated a preference for heterospecific associations. Mixing left- and right-handed helices drastically lowered solubility, resulting in micrometer-scale sheet-like assemblies that were one peptide-length thick as characterized with atomic force microscopy. X-ray scattering measurements of interhelical spacing in these sheets support a tight ridges-in-grooves packing of left- and right-handed triple helices. PMID:24283407

  3. Self-assembly of left- and right-handed molecular screws.

    PubMed

    Xu, Fei; Khan, I John; McGuinness, Kenneth; Parmar, Avanish S; Silva, Teresita; Murthy, N Sanjeeva; Nanda, Vikas

    2013-12-18

    Stereoselectivity is a hallmark of biomolecular processes from catalysis to self-assembly, which predominantly occur between homochiral species. However, both homochiral and heterochiral complexes of synthetic polypeptides have been observed where stereoselectivity hinges on details of intermolecular interactions. This raises the question whether general rules governing stereoselectivity exist. A geometric ridges-in-grooves model of interacting helices indicates that heterochiral associations should generally be favored in this class of structures. We tested this principle using a simplified molecular screw, a collagen peptide triple-helix composed of either l- or d-proline with a cyclic aliphatic side chain. Calculated stabilities of like- and opposite-handed triple-helical pairings indicated a preference for heterospecific associations. Mixing left- and right-handed helices drastically lowered solubility, resulting in micrometer-scale sheet-like assemblies that were one peptide-length thick as characterized with atomic force microscopy. X-ray scattering measurements of interhelical spacing in these sheets support a tight ridges-in-grooves packing of left- and right-handed triple helices.

  4. Experimental study of friction in aluminium bolted joints

    NASA Astrophysics Data System (ADS)

    Croccolo, D.; de Agostinis, M.; Vincenzi, N.

    2010-06-01

    This study aims at developing an experimental tool useful to define accurately the friction coefficients in bolted joints and, therefore, at relating precisely the tightening torque to the bolt preloading force in some special components used in front motorbike suspensions. The components under investigation are some clamped joints made of aluminium alloy. The preloading force is achieved by applying a torque wrench to the bolt head. Some specific specimens have been appropriately designed and realized in order to study the tribological aspects of the tightening phase. Experimental tests have been performed by applying the Design of Experiment (DOE) method in order to obtain a mathematical model for the friction coefficients. Three replicas of a full factorial DOE at two levels for each variable have been carried out. The levels include cast versus forged aluminium alloy, anodized versus spray-painted surface, lubricated versus unlubricated screw, and first tightening (fresh unspoiled surfaces) versus sixth tightening (spoiled surfaces). The study considers M8x1.25 8.8 galvanized screws.

  5. Experimental investigation of granule size and shape dynamics in twin-screw granulation.

    PubMed

    Kumar, Ashish; Vercruysse, Jurgen; Bellandi, Giacomo; Gernaey, Krist V; Vervaet, Chris; Remon, Jean Paul; De Beer, Thomas; Nopens, Ingmar

    2014-11-20

    A twin-screw granulator (TSG), a promising equipment for continuous high shear wet granulation (HSWG), achieves the desired level of mixing by a combination of the appropriate screw configuration and a suitable set of process settings (e.g. feed rate, screw speed, etc.), thus producing a certain granule size and shape distribution (GSSD). However, the primary sizing and shaping mechanism behind the resulting distribution is not well understood due to the opacity of the multiphase system in the granulator. This study experimentally characterised the GSSD dynamics along the TSG barrel length in order to understand the function of individual screw modules and process settings, as well as their interaction. Particle size analysis of granules collected at the outlet of the TSG suggested significant interaction between the process and screw configuration parameters influencing the heterogeneity in the GSSD. By characterising the samples collected along the screw length, a variable influence of the screw modules at different process conditions was observed. At low liquid-to-solid ratio (L/S), the first kneading module seemed to play a significant role in mixing, whereas the second kneading module was found to be more involved in reshaping the granules. At high L/S and high throughput, aggregation mainly took place in the second kneading module changing the GSSD. The results obtained from this study will be further used for the calibration and validation of a mechanistic model and, hence, support future development of a more detailed understanding of the HSWG process in a TSG. PMID:25234863

  6. The use of bovine screws to promote bone formation using a tibia model in dogs

    PubMed Central

    Bianchini, Marco Aurélio; Pontual, Marco Antônio B; Bez, Leonardo; Benfatti, César Augusto M; Boabaid, Fernanda; Somerman, Martha J; Magini, Ricardo S

    2013-01-01

    The objective of this study was to evaluate the use of a unique resorbable bovine bone screw, to stimulate bone formation. Bovine bone screws were inserted in the tibia beagle dogs. Each animal received 8 screws, divided into Groups A (screws + no membranes), B (screws + titanium reinforced membranes) and C (bone defects treated with autogenous bone grafts). Animals were sacrificed at 2, 4 and 6 months. New bone was measured with a periodontal probe and reported an average of 7.4 mm in vertical bone gain for Group B, 3.6 mm for Group A and 1.7 mm for Group C. Submission to Kruskal-Wallis test showed statistical differences between groups (p<0,05). Histological examination revealed an intimate contact between the newly formed bone and the resorbing bone screws. Conclusion: Bovine bone screws provide environment for new bone formation and thus may provide an alternative therapy for enhancing bone formation vertically, including for regenerative procedures as well as prior to implant therapy. PMID:23058228

  7. FEM analysis of a new miniplate: stress distribution on the plate, screws and the bone

    PubMed Central

    Nalbantgil, Didem; Tozlu, Murat; Ozdemir, Fulya; Oztoprak, Mehmet Oguz; Arun, Tulin

    2012-01-01

    Objectives: Non-homogeneous force distribution along the miniplates and the screws is an unsolved question for skeletal anchorage in orthodontics. To overcome this issue, a miniplate structure was designed featuring spikes placed on the surface facing the cortical bone. The aim of this study was to examine and compare the force distribution of the newly designed plate-screw systems with the conventional one. Methods: A model of bone surface with 1.5 mm cortical thickness, along with the two newly designed miniplates and a standard miniplate-screw were simulated on the three-dimensional model. 200 g experimental force was applied to the tip of the miniplates and the consequential effects on the screws and cortical bone was evaluated using three-dimensional finite element method. Results: As a result of this finite element study, remarkably lower stresses were observed on the screws and the cortical bone around the screws with the newly designed miniplate when compared with the conventional one. Conclusion: The newly designed miniplate that has spikes was found effective in reducing the stress on and around the screws and the force was distributed more equivalently. PMID:22229002

  8. Biomechanical effects of plate area and locking screw on medial open tibial osteotomy.

    PubMed

    Luo, Chu-An; Lin, Shang-Chih; Hwa, Su-Yang; Chen, Chun-Ming; Tseng, Ching-Shiow

    2015-01-01

    Medial open high tibial osteotomy (HTO) has been used to treat osteoarthritis of the medial compartment of the knee. However, weaker plate strength, unstable plate/screw junction and improper surgery technique are highly related to the HTO outcomes. Two π-shape plates were designed and eight variations (two supporting area × four locking stiffness) were compared by finite-element method. The computed tomography-based tibia was reconstructed and both wedge micromotion and implant stresses were chosen as the comparison indices. The construct was subjected to surgical and physiological loads. The medial-posterior region is the most loaded region and the load through the posterior leg is about four times that through the anterior leg. This indicates that the two-leg design can form a force-couple mechanism to effectively reduce the implant stresses. The use of locking screws significantly decrease the screw and hole stresses. However, the extending plate reduces the stresses of screws and holes above the wedge but makes the distal screws and holes much stressed. Wedge micromotion is affected by extending plate rather than locking screw. Three factors contribute to effective stabilisation of unstable HTO wedge: (1) intimate tibia-plate contact at medial-posterior regions, (2) sufficient rigidity at plate-screw junctions and (3) effective moment-balancing design at distal tibia-plate interfaces.

  9. Mechanical Comparison of Headless Screw Fixation and Locking Plate Fixation for Talar Neck Fractures.

    PubMed

    Karakasli, Ahmet; Hapa, Onur; Erduran, Mehmet; Dincer, Cemal; Cecen, Berivan; Havitcioglu, Hasan

    2015-01-01

    For talar neck fractures, open reduction and internal fixation have been thought to facilitate revascularization and prevent osteonecrosis. Newer screw systems allow for placement of cannulated headless screws, which provide compression by virtue of a variable pitch thread. The present study compared the biomechanical fixation strength of cannulated headless variable-pitch screw fixation and locking plate fixation. A reproducible talar neck fracture was created in 14 fresh cadaver talar necks. Talar head fixation was then performed using 2 cannulated headless variable-pitch 4-mm/5-mm diameter (4/5) screws (Acutrak; Acumed, Hillsboro, OR) and locking plate fixation. Headless variable-pitch screw fixation had lower failure displacement than did locking plate fixation. No statistically significant differences were found in failure stiffness, yield stiffness (p = .655), yield load (p = .142), or ultimate load between the 2 fixation techniques. Cannulated headless variable-pitch screw fixation resulted in better failure displacement than locking plate fixation in a cadaveric talus model and could be considered a viable option for talus fracture fixation. Headless, fully threaded, variable-pitch screw fixation has inherent advantages compared with locking plate fixation, because it might cause less damage to the articular surface and can compress the fracture for improved reduction. Additionally, plate fixation can increase the risk of avascular necrosis owing to the wider incision and dissection of soft tissues.

  10. Cortical bone trajectory screws for the middle-upper thorax: An anatomico-radiological study.

    PubMed

    Sheng, Sun-Ren; Chen, Jiao-Xiang; Chen, Wei; Xue, En-Xing; Wang, Xiang-Yang; Zhu, Qing-An

    2016-08-01

    To quantify the reference data concerning the morphometrics of the middle-upper thorax to guide the placement of cortical bone trajectory (CBT) screws.Eighty patients were studied on computed tomography (CT) scans. The reference anatomical parameters were measured. Next, 20 cadaveric specimens were implanted with CBT screws based on CT measurements. These specimens were then judged directly from the cadaveric vertebrae and X-ray.The maximum length of the trajectory, the maximum diameter, and the cephaled angle exhibited a slight increase trend while the transverse and sagittal angles of the pedicle tended to decrease from T3 to T8. We recommend that the width of CBT screw for middle-upper thoracic spine is 5.0 mm, the length is 25 to 35 mm. The cadaveric anatomical study revealed that 5/240 screws penetrated in the medial or lateral areas, 5/240 screws penetrated in the superior or inferior pedicle wall, and 2/240 screws did not fit into the superior endplate of the pedicle.The CBT screws are safe for the middle-upper thorax. This study provides a theoretical basis for clinical surgery. PMID:27583893

  11. The effect of screw length and position on fixation of four-stranded hamstring grafts for anterior cruciate ligament reconstruction.

    PubMed

    Harvey, A R; Thomas, N P; Amis, A A

    2003-03-01

    The aim of this study was to examine interference screw fixation of four strand hamstring grafts for anterior cruciate ligament reconstruction in vitro. Bovine tibiae and cannon tendons were used. Screws were introduced from 'outside-in'. The tendons were loaded cyclically to 150 N to simulate walking and 450 N to simulate jogging. Slippage of the tendon from the anchorage was recorded after 100, 300 and 1000 cycles. Cortico-cancellous and cancellous only fixations were compared using a 7-mm screw in an 8-mm tunnel with a 7-mm graft. The effect of screw length was studied by comparing 8 x 25 and 8 x 45 mm screws. Graft slippage with cancellous only fixation was significantly greater than with cortico-cancellous screw fixation (Pscrew than with a 45-mm screw but, while this difference was not significant (P>0.105), the longer screws gave more consistent behaviour. We concluded that the screw should be placed so that its head engages the cortex, while increasing screw length within cancellous bone did not significantly improve graft fixation. Cyclical load testing reflects the repetitive forces imposed in the early post-operative period following hamstring anterior cruciate ligament reconstruction and is important for the evaluation of graft fixations. PMID:12649035

  12. Comparison of the bending performance of solid and cannulated spinal pedicle screws using finite element analyses and biomechanical tests.

    PubMed

    Shih, Kao-Shang; Hsu, Ching-Chi; Hou, Sheng-Mou; Yu, Shan-Chuen; Liaw, Chen-Kun

    2015-09-01

    Spinal pedicle screw fixations have been used extensively to treat fracture, tumor, infection, or degeneration of the spine. Cannulated spinal pedicle screws with bone cement augmentation might be a useful method to ameliorate screw loosening. However, cannulated spinal pedicle screws might also increase the risk of screw breakage. Thus, the purpose of this study was to investigate the bending performance of different spinal pedicle screws with either solid design or cannulated design. Three-dimensional finite element models, which consisted of the spinal pedicle screw and the screw's hosting material, were first constructed. Next, monotonic and cyclic cantilever bending tests were both applied to validate the results of the finite element analyses. Finally, both the numerical and experimental approaches were evaluated and compared. The results indicated that the cylindrical spinal pedicle screws with a cannulated design had significantly poorer bending performance. In addition, conical spinal pedicle screws maintained the original bending performance, whether they were solid or of cannulated design. This study may provide useful recommendations to orthopedic surgeons before surgery, and it may also provide design rationales to biomechanical engineers during the development of spinal pedicle screws. PMID:26208430

  13. Fully Threaded Versus Partially Threaded Screws: Determining Shear in Cancellous Bone Fixation.

    PubMed

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

    2015-01-01

    Many researchers have studied and compared various forms of intraosseous fixation. No studies have examined the effects of shear through stiffness and failure strength of a fully threaded versus a partially threaded screw. Our hypothesis was that the fully threaded lag screw technique would provide greater shear strength and resistance. Thirty-six synthetic sawbone blocks were used to test screw fixation. In group 1 (n = 9), 2 blocks were fixed together using a fully threaded 4.0-mm stainless steel cancellous bone screw and the lag technique. In group 2 (n = 8), 2 blocks were fixed together using the standard manufacturer-recommended method for inserting 4.0-mm partially threaded stainless steel cancellous bone screws. The constructs were then mechanically tested. Shear was applied by compressing each construct at an axial displacement rate of 0.5 mm/s until failure. The fully threaded screw had a significantly greater (p = .026) initial stiffness (106.4 ± 15.8 N/mm) than the partially threaded screw (80.1 ± 27.5 N/mm). The yield load and displacement for the fully threaded group (429.4 ± 11.7 N and 7.2 ± 0.35 mm) were 64% and 67% greater than those for the partially threaded screw group (261.4 ± 26.1 N and 4.3 ± 1.03 mm), respectively. The results of the present study have demonstrated the importance of a full-thread construct to prevent shear and to decrease strain at the fracture. The confirmation of our hypothesis questions the future need and use of partially threaded screws for cancellous bone fixation. PMID:26210079

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

    PubMed

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

    2015-01-01

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

  15. The Mechanical Effect of Rod Contouring on Rod-Screw System Strength in Spine Fixation

    PubMed Central

    Karakasli, Ahmet; Karaarslan, Ahmet A.; Ozcanhan, Mehmet Hilal; Ertem, Fatih; Erduran, Mehmet

    2016-01-01

    Objective Rod-screw fixation systems are widely used for spinal instrumentation. Although many biomechanical studies on rod-screw systems have been carried out, but the effects of rod contouring on the construct strength is still not very well defined in the literature. This work examines the mechanical impact of straight, 20° kyphotic, and 20° lordotic rod contouring on rod-screw fixation systems, by forming a corpectomy model. Methods The corpectomy groups were prepared using ultra-high molecular weight polyethylene samples. Non-destructive loads were applied during flexion/extension and torsion testing. Spine-loading conditions were simulated by load subjections of 100 N with a velocity of 5 mm min-1, to ensure 8.4-Nm moment. For torsional loading, the corpectomy models were subjected to rotational displacement of 0.5° s-1 to an end point of 5.0°, in a torsion testing machine. Results Under both flexion and extension loading conditions the stiffness values for the lordotic rod-screw system were the highest. Under torsional loading conditions, the lordotic rod-screw system exhibited the highest torsional rigidity. Conclusion We concluded that the lordotic rod-screw system was the most rigid among the systems tested and the risk of rod and screw failure is much higher in the kyphotic rod-screw systems. Further biomechanical studies should be attempted to compare between different rod kyphotic angles to minimize the kyphotic rod failure rate and to offer a more stable and rigid rod-screw construct models for surgical application in the kyphotic vertebrae. PMID:27651858

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

    PubMed Central

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

    2015-01-01

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

  17. The Mechanical Effect of Rod Contouring on Rod-Screw System Strength in Spine Fixation

    PubMed Central

    Karakasli, Ahmet; Karaarslan, Ahmet A.; Ozcanhan, Mehmet Hilal; Ertem, Fatih; Erduran, Mehmet

    2016-01-01

    Objective Rod-screw fixation systems are widely used for spinal instrumentation. Although many biomechanical studies on rod-screw systems have been carried out, but the effects of rod contouring on the construct strength is still not very well defined in the literature. This work examines the mechanical impact of straight, 20° kyphotic, and 20° lordotic rod contouring on rod-screw fixation systems, by forming a corpectomy model. Methods The corpectomy groups were prepared using ultra-high molecular weight polyethylene samples. Non-destructive loads were applied during flexion/extension and torsion testing. Spine-loading conditions were simulated by load subjections of 100 N with a velocity of 5 mm min-1, to ensure 8.4-Nm moment. For torsional loading, the corpectomy models were subjected to rotational displacement of 0.5° s-1 to an end point of 5.0°, in a torsion testing machine. Results Under both flexion and extension loading conditions the stiffness values for the lordotic rod-screw system were the highest. Under torsional loading conditions, the lordotic rod-screw system exhibited the highest torsional rigidity. Conclusion We concluded that the lordotic rod-screw system was the most rigid among the systems tested and the risk of rod and screw failure is much higher in the kyphotic rod-screw systems. Further biomechanical studies should be attempted to compare between different rod kyphotic angles to minimize the kyphotic rod failure rate and to offer a more stable and rigid rod-screw construct models for surgical application in the kyphotic vertebrae.

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

    PubMed

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

    2015-12-18

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

  19. The removal torque of titanium screw inserted in rabbit tibia treated by dual acid etching.

    PubMed

    Cho, Sung-Am; Park, Kyung-Tae

    2003-09-01

    Chemical acid etching alone of the titanium implant surface have the potential to greatly enhance osseointegration without adding particulate matter (e.g. TPS or hydroxyapatite) or embedding surface contaminants (e.g. grit particles). The aims of the present study were to evaluate any differences between the machined and dual acid etching implants with the removal torque as well as topographic analysis. A total of 40 custom-made, screw-shaped, commercially pure titanium implants with length of 5 mm and an outer diameter of 3.75 mm were divided into 4 groups, 10 screws in each, and chemical modification of the titanium implant surfaces were achieved using HF and HCl/H(2)SO(4) dual acid etching. The first exposure was to hydrofluoric acid and the second was to a combination of hydrochloric acid and sulfuric acid. The tibia metaphysics was exposed by incisions through the skin, fascia, and periosteum. One implant of each group was inserted in every rabbit, 2 in each proximal tibia metaphysics. Every rabbit received 3 implants with acid etched surfaces and 1 implant with a machined surface. Twelve weeks post-surgically, 7 rabbits were sacrificed, Subsequently, the leg was stabilized and the implant was removed under reverse torque rotation with a digital torque gauge (Mark-10 Corporation, USA) (Fig. 1). Twelve weeks after implant placement, the removal torque mean values were the dual acid etched implants (24%HF+HCl/H(2)SO(4), group C) required a higher average force (34.7 Ncm), than the machined surface implants (group A) (p=0.045) (Mann-Whiteney test). Scanning electron micrographs of acid etching of the titanium surface created an even distribution of very small (1-2 microm) peaks and valleys, while machining of the titanium surface created typical microscopically grooved surface characteristics. Nonetheless, there was no difference in surface topography between each acid etched implant groups. Therefore, chemically acid etching implant surfaces have higher

  20. Butt Joint Tool Commissioning

    SciTech Connect

    Martovetsky, N N

    2007-12-06

    ITER Central Solenoid uses butt joints for connecting the pancakes in the CS module. The principles of the butt joining of the CICC were developed by the JAPT during CSMC project. The difference between the CSMC butt joint and the CS butt joint is that the CS butt joint is an in-line joint, while the CSMC is a double joint through a hairpin jumper. The CS butt joint has to carry the hoop load. The straight length of the joint is only 320 mm, and the vacuum chamber around the joint has to have a split in the clamp shell. These requirements are challenging. Fig.1 presents a CSMC joint, and Fig.2 shows a CS butt joint. The butt joint procedure was verified and demonstrated. The tool is capable of achieving all specified parameters. The vacuum in the end was a little higher than the target, which is not critical and readily correctable. We consider, tentatively that the procedure is established. Unexpectedly, we discover significant temperature nonuniformity in the joint cross section, which is not formally a violation of the specs, but is a point of concern. All testing parameters are recorded for QA purposes. We plan to modify the butt joining tool to improve its convenience of operation and provide all features necessary for production of butt joints by qualified personnel.

  1. Gear-Cutting Tool for Screw-Compressor Rotors

    NASA Astrophysics Data System (ADS)

    Kaneko, Katsumi; Kawasaki, Kazumasa; Tamura, Hisashi

    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.

  2. Parallel operation of NH3 screw compressors - the optimum way

    NASA Astrophysics Data System (ADS)

    Pijnenburg, B.; Ritmann, J.

    2015-08-01

    The use of more smaller industrial NH3 screw compressors operating in parallel seems to offer the optimum way when it comes to fulfilling maximum part load efficiency, increased redundancy and other highly requested features in the industrial refrigeration industry today. Parallel operation in an optimum way can be selected to secure continuous operation and can in most applications be configured to ensure lower overall operating economy. New compressors are developed to meet requirements for flexibility in operation and are controlled in an intelligent way. The intelligent control system keeps focus on all external demands, but yet striving to offer always the lowest possible absorbed power, including in future scenarios with connection to smart grid.

  3. [Mechanical circulatory assist using a miniaturized Archimedes screw].

    PubMed

    von Segesser, L K; Bisang, B; Leskosek, B; Turina, M

    1991-01-01

    An axial flow blood pump (Archimedes screw) for intraarterial left ventricular assist was evaluated in comparison to standard roller pump left heart bypass (LHBP) in 13 bovine experiments (bodyweight 74 +/- 15 kg). Full systemic heparinization (ACT greater than 500 s) was used for LHBP in comparison to limited systemic heparinization (ACT greater than 180 s) for axial. A standard battery of blood samples was taken before and at regular intervals throughout perfusion: (table; see text) Transarterial access and relatively limited blood trauma appear to be the main advantages of the evaluated axial flow blood pump. However, the impossibility to assess the pump flow may be a major problem for the management of the failing left ventricle.

  4. Structural and torsional vibration analysis of a dry screw compressor

    NASA Astrophysics Data System (ADS)

    Willie, J.; Sachs, R.

    2015-08-01

    This paper investigates torsional vibration and pulsating noise in a dry screw compressor. The compressor is designed at Gardner Denver (GD) and is oil free and use for mounting on highway trucks. They are driven using a Power Take-Off (PTO) transmission and gear box on a truck. Torque peak fluctuation and noise measurements are done and their sources are investigated and reported in this work. To accurately predict the torsional response (frequency and relative angular deflection and torque amplitude), the Holzer method is used. It is shown that the first torsional frequency is manifested as sidebands in the gear train meshing frequencies and this can lead to noise that is the result of amplitude modulation. Sensitivity analysis of the drive train identifies the weakest link in the drive train that limits the first torsional frequency to a low value. Finally, the significance of higher mode shapes on inter-lobe clearance distribution of the rotors is investigated.

  5. Hoffa nonunion, two cases treated with headless compression screws.

    PubMed

    Somford, Matthijs Paul; van Ooij, Bas; Schafroth, Matthias U; Kloen, Peter

    2013-12-01

    A coronal fracture of the distal femoral condyle is a rare entity and a nonunion even more so. The coronal fractures, also known as Hoffa fracture, more often involve the lateral than the medial condyle. Open reduction and internal fixation are the primary treatment of choice. We describe two cases of nonunion of a Hoffa fracture (one medial and one lateral). Although the nonunion fragment was not attached to any soft tissues in both cases the fragment was noted to be vital both clinically and histologically. After operative treatment, consisting of debridement, compression with use of headless screws, and liberal use of bone graft both nonunions healed. At latest follow-up, both patients had excellent function and reported no or minimal pain.

  6. Anatomic Reconstruction of the Proximal Tibiofibular Joint.

    PubMed

    Warner, Brent T; Moulton, Samuel G; Cram, Tyler R; LaPrade, Robert F

    2016-02-01

    Proximal tibiofibular joint (PTFJ) instability can be easily missed or confused for other, more common lateral knee pathologies such as meniscal tears, fibular collateral ligament injury, biceps femoris pathology, or iliotibial band syndrome. Because of this confusion, some authors believe that PTFJ instability is more common than initially appreciated. Patients with PTFJ subluxation may have no history of inciting trauma or injury, and it is not uncommon for these patients to have bilateral symptoms and generalized ligamentous laxity. Currently, the optimal surgical treatment for patients with chronic PTFJ instability is unknown. Historically, a variety of surgical treatments have been reported. Initially, joint arthrodesis and fibular head resection were recommended. More recently, temporary screw fixation, nonanatomic reconstruction with strips of the biceps femoris tendon or iliotibial band, and reconstruction with free hamstring autograft have been described. The purpose of this report is to present our surgical technique for treatment of chronic PTFJ instability using an anatomic reconstruction of the posterior ligamentous structures of the PTFJ with a semitendinosus autograft. PMID:27274455

  7. Structural Health Monitoring of AN Aircraft Joint

    NASA Astrophysics Data System (ADS)

    Mickens, T.; Schulz, M.; Sundaresan, M.; Ghoshal, A.; Naser, A. S.; Reichmeider, R.

    2003-03-01

    A major concern with ageing aircraft is the deterioration of structural components in the form of fatigue cracks at fastener holes, loose rivets and debonding of joints. These faults in conjunction with corrosion can lead to multiple-site damage and pose a hazard to flight. Developing a simple vibration-based method of damage detection for monitoring ageing structures is considered in this paper. The method is intended to detect damage during operation of the vehicle before the damage can propagate and cause catastrophic failure of aircraft components. It is typical that only a limited number of sensors could be used on the structure and damage can occur anywhere on the surface or inside the structure. The research performed was to investigate use of the chirp vibration responses of an aircraft wing tip to detect, locate and approximately quantify damage. The technique uses four piezoelectric patches alternatively as actuators and sensors to send and receive vibration diagnostic signals.Loosening of selected screws simulated damage to the wing tip. The results obtained from the testing led to the concept of a sensor tape to detect damage at joints in an aircraft structure.

  8. Joint immobilization induced hypoxic and inflammatory conditions in rat knee joints.

    PubMed

    Yabe, Yutaka; Hagiwara, Yoshihiro; Suda, Hideaki; Ando, Akira; Onoda, Yoshito; Tsuchiya, Masahiro; Hatori, Kouki; Itoi, Eiji

    2013-01-01

    The purpose of this study was to examine the hypoxic and inflammatory conditions after immobilization in the joint capsule of rat knees. The unilateral knee joints of adult male rats were immobilized with an internal fixator (Im group) for 1 day, 3 days, and 1, 2, 4, 8, and 16 weeks. Sham-operated animals had holes drilled in the femur and tibia and screws inserted without a plate (control group). The number of cells and blood vessels in the capsule were histologically examined. The hypoxic condition in the capsule was histologically examined with a Hypoxyprobe™-1. The gene expressions related to the hypoxic (hypoxia inducible factor-1α, vascular endothelial growth factor, and fibroblast growth factor 2) and inflammatory conditions [interleukin-6 (IL-6), IL-1α, IL-1β, tumor necrosis factor-α, and tumor necrosis factor-β] were evaluated by quantitative reverse transcription polymerase chain reaction. The number of cells was unchanged at 1 day in the two groups; however, the number significantly increased at 3 days in the Im group. The number of blood vessels in the Im group gradually decreased. Strong immunostaining of Hypoxyprobe™-1 around the blood vessels was observed in the Im group. The gene expressions of hypoxia inducible factor-1α and fibroblast growth factor 2 were significantly higher in the Im group compared with those in the control group. The gene expressions of IL-6, IL-1α, IL-1β, and tumor necrosis factor-β were significantly higher in the Im group compared with those in the control group. These data indicated that joint immobilization induced hypoxic and inflammatory conditions in the joint capsule, which might be an initiating factor for joint contracture.

  9. Alkaline twin-screw extrusion pretreatment for fermentable sugar production

    PubMed Central

    2013-01-01

    Background The inevitable depletion of fossil fuels has resulted in an increasing worldwide interest in exploring alternative and sustainable energy sources. Lignocellulose, which is the most abundant biomass on earth, is widely regarded as a promising raw material to produce fuel ethanol. Pretreatment is an essential step to disrupt the recalcitrance of lignocellulosic matrix for enzymatic saccharification and bioethanol production. This paper established an ATSE (alkaline twin-screw extrusion pretreatment) process using a specially designed twin-screw extruder in the presence of alkaline solution to improve the enzymatic hydrolysis efficiency of corn stover for the production of fermentable sugars. Results The ATSE pretreatment was conducted with a biomass/liquid ratio of 1/2 (w/w) at a temperature of 99°C without heating equipment. The results indicated that ATSE pretreatment is effective in improving the enzymatic digestibility of corn stover. Sodium hydroxide loading is more influential factor affecting both sugar yield and lignin degradation than heat preservation time. After ATSE pretreatment under the proper conditions (NaOH loading of 0.06 g/g biomass during ATSE and 1 hour heat preservation after extrusion), 71% lignin removal was achieved and the conversions of glucan and xylan in the pretreated biomass can reach to 83% and 89% respectively via subsequent enzymatic hydrolysis (cellulase loading of 20 FPU/g-biomass and substrate consistency of 2%). About 78% of the original polysaccharides were converted into fermentable sugars. Conclusions With the physicochemical functions in extrusion, the ATSE method can effectively overcome the recalcitrance of lignocellulose for the production of fermentable sugars from corn stover. This process can be considered as a promising pretreatment method due to its relatively low temperature (99°C), high biomass/liquid ratio (1/2) and satisfied total sugar yield (78%), despite further study is needed for process

  10. Image-guided Spine Stabilization for Traumatic or Osteoporotic Spine Injury: Radiological Accuracy and Neurological Outcome

    PubMed Central

    SHIMOKAWA, Nobuyuki; ABE, Junya; SATOH, Hidetoshi; ARIMA, Hironori; TAKAMI, Toshihiro

    2016-01-01

    Significant progress has been made in image-guided surgery (IGS) over the last few decades. IGS can be effectively applied to spinal instrumentation surgery. In the present study, we focused our attention on the feasibility and safety of image-guided spine stabilization for traumatic or osteoporotic spine injury. The IGS spine fixation with or without minimally invasive surgery (MIS) techniques such as percutaneous screw placement, balloon kyphoplasty (BKP), or vertebroplasty (VP) were accomplished in 80 patients with traumatic or osteoprotic spine injury between 2007 and 2015. The injured vertebral levels included the following: cervical spine, 41; thoracic spine, 22; and lumbar spine, 17. Neurological condition before and after surgery was assessed using the American Spinal Injury Association Impairment Scale (AIS). A total of 419 pedicle, lateral mass, or laminar screws were placed, and 399 screws (95.2%) were found to be placed correctly based on postoperative computed tomography scan. Although 20 screws (4.8%) were found to be unexpectedly placed incorrectly, no neural or vascular complications closely associated with screw placement were encountered. Neurological outcomes appeared to be acceptable or successful based on AIS. The IGS is a promising technique that can improve the accuracy of screw placement and reduce potential injury to critical neurovascular structures. The integration of MIS and IGS has proved feasible and safe in the treatment of traumatic or osteoporotic spine injury, although a thorough knowledge of surgical anatomy, spine biomechanics, and basic technique remain the most essential aspects for a successful surgery. PMID:27063144

  11. Ankle fusion stability: a biomechanical comparison of external versus internal fixation.

    PubMed

    Hoover, Justin R; Santrock, Robert D; James, William C

    2011-04-11

    This biomechanical study compares bimalleolar external fixation to conventional crossed-screw construct in terms of stability and compression for ankle arthrodesis. The goals of the study were to determine which construct is more stable with bending and torsional forces, and to determine which construct achieves more compression.Fourth-generation bone composite tibia and talocalcaneal models were made to 50th percentile anatomic specifications. Fourteen ankle fusion constructs were created with bimalleolar external fixators and 14 with crossed-screw constructs. Ultimate bend, torque, and compression testing were completed on the external fixator and crossed-screw constructs using a multidirectional Materials Testing Machine (MTS Systems Corp, Eden Prairie, Minnesota). Ultimate bend testing revealed a statistically significant difference (P=.0022) with the mean peak load to failure for the external fixator constructs of 973.2 N compared to 612.5 N for the crossed-screw constructs. Ultimate torque testing revealed the mean peak torque to failure for the external fixator construct was 80.2 Nm and 28.1 Nm for the crossed-screw construct, also a statistically significant difference (P=.0001). The compression testing yielded no statistically significant difference (P=.9268) between the average failure force of the external fixator construct (81.6 kg) and the crossed-screw construct (81.2 kg).With increased stiffness in both bending and torsion and comparable compressive strengths, bimalleolar external fixation is an excellent option for tibiotalar ankle arthrodesis.

  12. Plastification of polymers in twin-screw-extruders: New visualization technic using high-speed imaging

    SciTech Connect

    Knieper, A. E-mail: Christian.Beinert@lbf.fraunhofer.de; Beinert, C. E-mail: Christian.Beinert@lbf.fraunhofer.de

    2014-05-15

    The initial melting of the first granules through plastic energy dissipation (PED) at the beginning of the melting zone, in the co-rotating twin-screw extruder is visualized in this work. The visualization was created through the use of a high speed camera in the cross section of the melting zone. The parameters screw speed, granule-temperature, temperature-profile, type of polymer and back pressure were examined. It was shown that the screw speed and the temperature-profile have significant influence on the rate of initial melting.

  13. Modelling Flow and Heat Transfer in Co-Rotating Twin-Screw Extruders

    NASA Astrophysics Data System (ADS)

    Teixeira, C.; Faria, R.; Covas, J. A.; Gaspar-Cunha, A.

    2007-04-01

    This work presents a modelling routine of co-rotating twin-screw extrusion, from hopper to die. The program accounts for a sequence of individual stages linked together by boundary conditions, namely starve-fed solids conveying, solids conveying under pressure, delay, melting, melt conveying without pressure and melt conveying under pressure. It predicts the evolution along the screw and die of temperature, shear rate, residence time, viscosity, mechanical power consumption, pressure and fill ratio. The results obtained showed adequate sensitivity to changes in operating conditions and screw geometry and are in agreement with current theoretical and experimental knowledge.

  14. Accuracy and safety of pedicle screw placement in neuromuscular scoliosis with free-hand technique

    PubMed Central

    Modi, Hitesh N.; Fernandez, Harry; Yang, Jae Hyuk; Song, Hae-Ryong

    2008-01-01

    It is a retrospective analytic study of 1,009 transpedicular screws (689 thoracic and 320 lumbosacral), inserted with free-hand technique in neuromuscular scoliosis using postoperative CT scan. The aim of paper was to determine the accuracy and safety of transpedicular screw placement with free-hand technique in neuromuscular scoliosis and to compare the accuracy at different levels in such population. All studies regarding accuracy and safety of pedicle screw in scoliosis represent idiopathic scoliosis using various techniques such as free-hand, navigation, image intensifier, etc., for screw insertion. Anatomies of vertebrae and pedicle are distorted in scoliosis, hence accurate and safe placement of pedicle screw is prerequisite for surgery. Between 2004 and 2006, 37 consecutive patients, average age 20 years (9–44 years), of neuromuscular scoliosis were operated with posterior pedicle screw fixation using free-hand technique. Accuracy of pedicle screws was studied on postoperative CT scan. Placement up to 2 mm medial side and 4 mm lateral side was considered within-safe zone. Of the 1,009 screws, 273 screws were displaced medially, laterally or on the anterior side showing that 73% screws (68% in thoracic and 82.5% in lumbar spine) were accurately placed within pedicle. Considering the safe zone, 93.3% (942/1009, 92.4% in thoracic and 95.3% in lumbar spine) of the screws were within the safe zone. Comparing accuracy according to severity of curve, accuracy was 75% in group 1 (curve <90°) and 69% in group 2 (curve >90°) with a safety of 94.8 and 91.2%, respectively (P = 0.35). Comparing the accuracy at different thoracic levels, it showed 67, 64 and 72% accuracy in upper, middle and lower thoracic levels with safety of 96.6, 89.2 and 93.1%, respectively, exhibiting no statistical significant difference (P = 0.17). Pedicle screw placement in neuromuscular scoliosis with free-hand technique is accurate and safe as other conditions. PMID:18830636

  15. The use of twin screw extruders for feeding coal against pressures of up to 1500 PSI

    NASA Technical Reports Server (NTRS)

    Wiedmann, W.; Mack, W. A.

    1977-01-01

    Recent tests with a twin-screw, co-rotating extruder which was successfully used to convey and feed coal against pressures of up to 1500 psi are described. Intermeshing and self-wiping, co-rotating twin-screws give greatly improved conveying and pressure built-up capabilities and avoid hangup and eventual decomposition of coal particles in the screw flights. The conveying action of intermeshing, self-wiping, co-rotating extruder systems approaches that of a positive displacement pump. With this feature, it is possible to maintain very accurate control over all aspects of product conveyance in the extruder, i.e., intake, conveyance and pressure buildup.

  16. Subtrochanteric femur fracture after removal of screws for femoral neck fracture in a child.

    PubMed

    Song, Kwang Soon; Lee, Si Wook

    2015-01-01

    Displaced femoral neck fractures are rare in children and are associated with a high rate of complications. Subtrochanteric fractures after cannulated screw fixation of femoral neck fractures in adults are well recognized, and there are several reports on the topic. However, there are no reports on complications related to hardware or subtrochanteric fractures after removal of the screws in the treatment of femoral neck fractures in children. Here we report the case of a 10-year-old boy who sustained a subtrochanteric fracture after the screw removal and healing that followed a femoral neck fracture. PMID:25566556

  17. Pressure suit joint analyzer

    NASA Technical Reports Server (NTRS)

    Vykukal, H. C.; Webbon, B. W. (Inventor)

    1982-01-01

    A measurement system for simultaneously measuring torque and angular flexure in a pressure suit joint is described. One end of a joint under test is held rigid. A torque transducer is pivotably supported on the other movable end of a joint. A potentiometer is attached to the transducer by an arm. The wiper shaft of the potentiometer is gripped by a reference arm that rotates the wiper shaft the same angle as the flexure of joint. A signal is generated by the potentiometer which is representative of the joint flexure. A compensation circuit converts the output of the transducer to a signal representative of joint torque.

  18. Fluoroscopy-guided pedicle screw accuracy with a mini-open approach: a tomographic evaluation of 470 screws in 125 patients

    PubMed Central

    Soriano-Sánchez, José Antonio; Gutiérrez-Partida, Carlos Francisco; Ramírez-Barrios, Luis Rodolfo; Ortíz-Leyva, Ramses Uriel; Rodríguez-García, Manuel; Sánchez-Escandón, Oscar

    2015-01-01

    Background Transpedicular screws are currently placed with open free hand and minimally invasive techniques assisted with either fluoroscopy or navigation. Screw placement accuracy had been investigated with several methods reaching accuracy rates from 71.9% to 98.8%. The objective of this study was to assess the accuracy and safety for 2-D fluoroscopy-guided screw placement assisted with electrophysiological monitoring and the inter-observer agreement for the breach classification. Methods A retrospective review was performed on 125 consecutive patients who underwent minimally invasive transforaminal lumbar interbody fusion and transpedicular screws placement between the levels of T-12 and S-1. Screw accuracy was evaluated using a postoperative computed tomography by three independent observers. Pedicle breach was documented when there was a violation in any direction of the pedicle. Inter-observer agreement was assessed with the Kappa coefficient. Results A total of 470 transpedicular screws were evaluated between the levels of T-12 and S-1. In 57 patients the instrumentation was bilateral and in 68 unilateral. A substantial degree of agreement was found between the observers AB (κ=0.769) and A-C (κ=0.784) and almost perfect agreement between observers B-C (κ=0.928). There were a total of 427.33 (90.92%) screws without breach, 39.33 (8.37%) minor breach pedicles and 3.33 (0.71%) major breach pedicles. The pedicle breach rate was 9.08% Trajectory pedicle breach percentages were as follows: minor medial pedicle breach 4.68%, minor lateral pedicle breach 3.47%, minor inferior pedicle breach 0.22%, and major medial breach 0.70%. No intraoperative instrumentation-related or postoperative clinical complications were encountered and no surgical revision was needed. Conclusions Our study demonstrated a high accuracy (90.2%) for 2-D fluoroscopy-guided pedicle screw using electromonitoring. Only 0.71% of the 470 screws had a major breach. Knowing the radiological spine

  19. A new shoulder model with a biologically inspired glenohumeral joint.

    PubMed

    Quental, C; Folgado, J; Ambrósio, J; Monteiro, J

    2016-09-01

    Kinematically unconstrained biomechanical models of the glenohumeral (GH) joint are needed to study the GH joint function, especially the mechanisms of joint stability. The purpose of this study is to develop a large-scale multibody model of the upper limb that simulates the 6 degrees of freedom (DOF) of the GH joint and to propose a novel inverse dynamics procedure that allows the evaluation of not only the muscle and joint reaction forces of the upper limb but also the GH joint translations. The biomechanical model developed is composed of 7 rigid bodies, constrained by 6 anatomical joints, and acted upon by 21 muscles. The GH joint is described as a spherical joint with clearance. Assuming that the GH joint translates according to the muscle load distribution, the redundant muscle load sharing problem is formulated considering as design variables the 3 translational coordinates associated with the GH joint translations, the joint reaction forces associated with the remaining kinematic constraints, and the muscle activations. For the abduction motion in the frontal plane analysed, the muscle and joint reaction forces estimated by the new biomechanical model proposed are similar to those estimated by a model in which the GH joint is modeled as an ideal spherical joint. Even though this result supports the assumption of an ideal GH joint to study the muscle load sharing problem, only a 6 DOF model of the GH joint, as the one proposed here, provides information regarding the joint translations. In this study, the biomechanical model developed predicts an initial upward and posterior migration of the humeral head, followed by an inferior and anterior movement, which is in good agreement with the literature. PMID:27381499

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

    PubMed

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

    2013-01-01

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

  1. The distal radioulnar joint. Anatomic and functional considerations.

    PubMed

    Kauer, J M

    1992-02-01

    The distal radioulnar joint is functionally coupled with the proximal radioulnar joint, thus forming a mechanism for the longitudinal rotation of the hand. Distal radioulnar mobility is derived from the geometry of the joint, joint surfaces, and radioulnar connections. There is a structural and functional separation between the distal radioulnar and carpal joints, giving the possibility of pronation and supination in every position of the hand to the forearm. As for the stability of the joints involved, the ulnar articular disk plays an essential role. Being part of both distal radioulnar and carpal joints, the disk has very specific morphologic features that not only are individualized to the function of both joints but also stabilize the joints in their independent movements. Developmental data give the strong impression of an architectural scheme, of which the distal radioulnar joint is only a part. Traumatic lesions at the distal radioulnar joint and disturbances in normal distal radioulnar alignment have to be viewed, therefore, in a wider context. PMID:1735231

  2. Comparative Analysis of Effect of Density, Insertion Angle and Reinsertion on Pull-Out Strength of Single and Two Pedicle Screw Constructs Using Synthetic Bone Model

    PubMed Central

    Varghese, Vicky; Kumar, Gurunathan Saravana

    2016-01-01

    Study Design Biomechanical study. Purpose To determine the effect of density, insertion angle and reinsertion on pull-out strength of pedicle screw in single and two screw-rod configurations. Overview of Literature Pedicle screw pull-out studies have involved single screw construct, whereas two screws and rod constructs are always used in spine fusions. Extrapolation of results using the single screw construct may lead to using expensive implants or increasing the fusion levels specifically in osteoporotic bones. Methods Single screw and two screw pull-out strength tests were carried out according to American Society for Testing and Materials F 543-07 on foam models to test the effect of density, insertion angle and reinsertion using poly axial pedicle screws. Results Bone density was the most significant factor deciding the pull-out strength in both single and two screw constructs. The difference in pull-out strength between single screw and two screw configurations in extremely osteoporotic bone model (80 kg/m3) was 78%, whereas in the normal bone model it was 48%. Axial pull-out value was highest for the single screw configuration; in the two screw configuration the highest pull-out strength was at 10°–15°. There was an 18% reduction in pull-out strength due to reinsertion in single screw configuration. The reinsertion effect was insignificant in the two screw configuration. Conclusions A significant difference in response of various factors on holding power of pedicle screw between single and two-screw configurations is evident. The percentage increase in pull-out strength between single and two screw constructs is higher for osteoporotic bone when compared to normal bone. Reinsertion has no significant effect on pull-out strength in the two screw rod configuration. PMID:27340518

  3. Acromioclavicular joint instability: anatomy, biomechanics and evaluation.

    PubMed

    Saccomanno, Maristella F; DE Ieso, Carmine; Milano, Giuseppe

    2014-01-01

    Acromioclavicular (AC) joint instability is a common source of pain and disability. The injury is most commonly a result of a direct impact to the AC joint. The AC joint is surrounded by a capsule and has an intra-articular synovium and an articular cartilage interface. An articular disc is usually present in the joint, but this varies in size and shape. The AC joint capsule is quite thin, but has considerable ligamentous support; there are four AC ligaments: superior, inferior, anterior and posterior. The coracoclavicular (CC) ligament complex consists of the conoid and trapezoid ligaments. They insert on the posteromedial and anterolateral region of the undersurface of the distal clavicle, respectively. The coracoid origin of the trapezoid covers the posterior half of the coracoid dorsum; the conoid origin is more posterior on the base of the coracoid. Several biomechanical studies showed that horizontal stability of the AC joint is mediated by the AC ligaments while vertical stability is mediated by the CC ligaments. The radiographic classification of AC joint injuries described by Rockwood includes six types: in type I injuries the AC ligaments are sprained, but the joint is intact; in type II injuries, the AC ligaments are torn, but the CC ligaments are intact; in type III injuries both the AC and the CC ligaments are torn; type IV injuries are characterized by complete dislocation with posterior displacement of the distal clavicle into or through the fascia of the trapezius; type V injuries are characterized by a greater degree of soft tissue damage; type VI injuries are inferior AC joint dislocations into a subacromial or subcoracoid position. The diagnosis of AC joint instability can be based on historical data, physical examination and imaging studies. The cross body adduction stress test has the greatest sensitivity, followed by the AC resisted extension test and the O'Brien test. Proper radiographic evaluation of the AC joint is necessary. The Zanca view

  4. Culture - joint fluid

    MedlinePlus

    Joint fluid culture ... fungi, or viruses grow. This is called a culture. If these germs are detected, other tests may ... is no special preparation needed for the lab culture. How to prepare for the removal of joint ...

  5. Temporomandibular Joint Dysfunction

    MedlinePlus

    The temporomandibular joint (TMJ) connects your jaw to the side of your head. When it works well, it enables you to ... For people with TMJ dysfunction, problems with the joint and muscles around it may cause Pain that ...

  6. Large displacement spherical joint

    DOEpatents

    Bieg, Lothar F.; Benavides, Gilbert L.

    2002-01-01

    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.

  7. Hip joint replacement

    MedlinePlus

    ... this page: //medlineplus.gov/ency/article/002975.htm Hip joint replacement To use the sharing features on this page, please enable JavaScript. Hip joint replacement is surgery to replace all or part ...

  8. [Total temporomandibular joint prostheses].

    PubMed

    Zwetyenga, N; Amroun, S; Wajszczak, B-L; Moris, V

    2016-09-01

    The temporomandibular joint (TMJ) is probably the most complex human joint. As in all joints, its prosthetic replacement may be indicated in selected cases. Significant advances have been made in the design of TMJ prostheses during the last three decades and the indications have been clarified. The aim of our work was to make an update on the current total TMJ total joint replacement. Indications, contraindications, prosthetic components, advantages, disadvantages, reasons for failure or reoperation, virtual planning and surgical protocol have been exposed.

  9. Three point lead screw positioning apparatus for a cavity tuning plate

    NASA Technical Reports Server (NTRS)

    Calco, Frank S. (Inventor)

    1993-01-01

    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.

  10. Magnesium-Based Compression Screws: A Novelty in the Clinical Use of Implants

    NASA Astrophysics Data System (ADS)

    Seitz, Jan-Marten; Lucas, Arne; Kirschner, Martin

    2016-04-01

    Magnesium alloys are currently subject to much research for use in biodegradable implant applications. The challenge in this field of material development comprises the design of an alloy that provides adequate mechanical and corrosion properties combined with an excellent biocompatibility. While there are many approaches in current literature only one Mg-based application shows the potential to hit the market. MAGNEZIX® Compression Screws are the world's first approved/CE-certified magnesium-based implants designed for use in biodegradable osteosyntheses applications in humans. Therefore, this paper focusses on challenges and current clinical results achieved by means of degradable compression screws. Insights into the screws' process chain and approval processes are given. As these innovative screws have already been on the market for 2 years long-term results based on their use in surgery are discussed.

  11. Hamate hook non-union treated with a break-away screw: a case report.

    PubMed

    Naito, Kiyohito; Yoshikawa, Kei; Kaneko, Kazuo; Obayashi, Osamu

    2013-01-01

    Hamate hook non-union is a relatively rare, but on the increase. We encountered a 25-year-old male baseball instructor with hamate hook non-union, and treated it with debridement of the fractured region and osteosynthesis using a break-away screw. Splint fixation was applied for three weeks after surgery, and active/passive range of motion exercises were actively performed thereafter. Bone union was noted three months after surgery. Transient ulnar paralysis resolved, and the patient could return to the same sports activity as that before injury six months after surgery. Since break-away screws are capable of loading a strong pressure on the fractured region and these screws can be inserted by preparing only a surgical field for guide wire insertion, requiring no soft tissue dissection to prepare a region for applying fixation materials, break-away screws are useful for the fixation of small bone fragments and osteosynthesis in a deep surgical field.

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

    PubMed

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

    2014-02-01

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

  13. CT-based 3-D visualisation of secure bone corridors and optimal trajectories for sacroiliac screws.

    PubMed

    Mendel, Thomas; Radetzki, Florian; Wohlrab, David; Stock, Karsten; Hofmann, Gunther Olaf; Noser, Hansrudi

    2013-07-01

    Sacroiliac screw (SI) fixation represents the only minimally invasive method to stabilise unstable injuries of the posterior pelvic ring. However, it is technically demanding. The narrow sacral proportions and a high inter-individual shape variability places adjacent neurovascular structures at potential risk. In this study a CT-based virtual analysis of the iliosacral anatomy in the human pelvis was performed to visualise and analyse 3-D bone corridors for the safe placement of SI-screws in the first sacral segment. Computer-aided calculation of 3-D transverse and general SI-corridors as a sum of all inner-bony 7.3-mm screw positions was done with custom-made software algorithms based on CT-scans of intact human pelvises. Radiomorphometric analysis of 11 CT-DICOM datasets using the software Amira 4.2. Optimal screw tracks allowing the greatest safety distance to the cortex were computed. Corridor geometry and optimal tracks were visualised; measurement data were calculated. A transverse corridor existed in 10 pelvises. In one dysmorphic pelvis, the pedicular height at the level of the 1st neural foramina came below the critical distance of 7.3mm defined by the outer screw diameter. The mean corridor volume was 45.2 cm3, with a length of 14.9cm. The oval cross-section measured 2.8 cm2. The diameter of the optimal screw pathway with the greatest safety distance was 14.2mm. A double cone-shaped general corridor for screw penetration up to the centre of the S1-body was calculated bilaterally for every pelvis. The mean volume was 120.6 cm3 for the left side and 115.8 cm3 for the right side. The iliac entry area measured 49.1 versus 46.0 cm2. Optimal screw tracks were calculated in terms of projected inlet and outlet angles. Multiple optimal screw positions existed for each pelvis. The described method allows an automated 3-D analysis with regard to secure SI-screw corridors even with a high number of CT-datasets. Corridor visualisation and calculation of optimal screw

  14. Joint Enrollment Report, 2014

    ERIC Educational Resources Information Center

    Iowa Department of Education, 2014

    2014-01-01

    The Iowa Department of Education collects information on joint enrollment in Iowa's 15 community colleges. Jointly enrolled students are high school students enrolled in community college credit coursework. Most jointly enrolled students enroll through Senior Year Plus (SYP) programs such as Postsecondary Enrollment Options (PSEO) and concurrent…

  15. Stability: from biomechanical concept to chiropractic practice

    PubMed Central

    McGill, Stuart M

    1999-01-01

    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

  16. 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

  17. Development of a high speed extrusion concept using a floating screw sleeve for solid-melt-separation

    NASA Astrophysics Data System (ADS)

    Karrenberg, Gregor; Wortberg, Johannes

    2015-05-01

    The High-Speed-S-Truder with floating screw sleeve is an alternative extrusion concept with solid-melt-separation. A fairly conventional 35 mm screw with a length of 21 D, which is accelerated by a 75 kW gearless, water cooled synchronous drive, conveys the resin into a 60 mm screw sleeve with a length of 10 D. Inside the sleeve the material is plasticizied and discharged into the outer screw channel of the sleeve through radial bores. Only the solid bed remains inside. The development of a melt pool - and thus a decrease of the plasticizing capacity - is avoided. The sleeve is rotated by drag forces only (approximately 10 - 15 % of the screw speed). Due to the low speed of the screw sleeve molten material is conveyed to a 4 D Dynamic Mixing Ring in a gentle manner. The DMRs floating ring and the screw sleeve are directly coupled. The granules in the screw channel are stopped by a barrier on the screw in front of the mixing device. So nearly no unmelted material can pass the system. For temperature management in the plastification and mixing zone a 3-zone heating/air-cooling system is used. Various kinds of experiments with the High-Speed S-Truder were conducted. Reachable throughputs with different types of material (LDPE, LLDPE, PP, PS) have been tested. Also three screw geometries, which are mainly varying in the channel depth, were compared. Experimental results and theoretical background will be described in this paper.

  18. Screw-retained crown restorations of single implants: A step-by-step clinical guide

    PubMed Central

    Assaf, Mohammad; Gharbyeh, Alaa’ Z. Abu

    2014-01-01

    This paper shows the clinical steps for preparing a screw-retained crown for the restoration of a single implant. Impression-taking using open-tray technique and delivery of the crown is presented in a step-by-step manner elucidated by detailed photographs. Furthermore, the advantages and disadvantages of screw-retained crowns are discussed in comparison with the cemented restorations. PMID:25512742

  19. Biomechanical Properties of a Novel Biodegradable Magnesium-Based Interference Screw.

    PubMed

    Ezechieli, Marco; Meyer, Hanna; Lucas, Arne; Helmecke, Patrick; Becher, Christoph; Calliess, Tilman; Windhagen, Henning; Ettinger, Max

    2016-06-27

    Magnesium-based interference screws may be an alternative in anterior/posterior cruciate ligament reconstruction. The well-known osteoconductive effects of biodegradable magnesium alloys may be useful. It was the purpose of this study to evaluate the biomechanical properties of a magnesium based interference screw and compare it to a standard implant. A MgYREZr-alloy interference screw and a standard implant (Milagro®; De Puy Mitek, Raynham, MA, USA) were used for graft fixation. Specimens were placed into a tensile loading fixation of a servohydraulic testing machine. Biomechanical analysis included pretensioning of the constructs at 20 N for 1 min following cyclic pretensioning of 20 cycles between 20 and 60 N. Biomechanical elongation was evaluated with cyclic loading of 1000 cycles between 50 and 200 N at 0.5 Hz. Maximum load to failure was 511.3±66.5 N for the Milagro® screw and 529.0±63.3 N for magnesium-based screw (ns, P=0.57). Elongations after preload, during cyclical loading and during failure load were not different between the groups (ns, P>0.05). Stiffness was 121.1±13.8 N/mm for the magnesium-based screw and 144.1±18.4 for the Milagro® screw (ns, P=0.32). MgYREZr alloy interference screws show comparable results in biomechanical testing to standard implants and may be an alternative for anterior cruciate reconstruction in the future. PMID:27433303

  20. Biomechanical Properties of a Novel Biodegradable Magnesium-Based Interference Screw

    PubMed Central

    Ezechieli, Marco; Meyer, Hanna; Lucas, Arne; Helmecke, Patrick; Becher, Christoph; Calliess, Tilman; Windhagen, Henning; Ettinger, Max

    2016-01-01

    Magnesium-based interference screws may be an alternative in anterior/posterior cruciate ligament reconstruction. The well-known osteoconductive effects of biodegradable magnesium alloys may be useful. It was the purpose of this study to evaluate the biomechanical properties of a magnesium based interference screw and compare it to a standard implant. A MgYREZr-alloy interference screw and a standard implant (Milagro®; De Puy Mitek, Raynham, MA, USA) were used for graft fixation. Specimens were placed into a tensile loading fixation of a servohydraulic testing machine. Biomechanical analysis included pretensioning of the constructs at 20 N for 1 min following cyclic pretensioning of 20 cycles between 20 and 60 N. Biomechanical elongation was evaluated with cyclic loading of 1000 cycles between 50 and 200 N at 0.5 Hz. Maximum load to failure was 511.3±66.5 N for the Milagro® screw and 529.0±63.3 N for magnesium-based screw (ns, P=0.57). Elongations after preload, during cyclical loading and during failure load were not different between the groups (ns, P>0.05). Stiffness was 121.1±13.8 N/mm for the magnesium-based screw and 144.1±18.4 for the Milagro® screw (ns, P=0.32). MgYREZr alloy interference screws show comparable results in biomechanical testing to standard implants and may be an alternative for anterior cruciate reconstruction in the future. PMID:27433303