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1

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

Microsoft Academic Search

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 =

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

2010-01-01

2

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

Microsoft Academic Search

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

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

2011-01-01

3

The path of screw insertion for stabilization of the scapholunate joint: a cadaveric study.  

PubMed

The aim of this study was to determine the path of screw placement to avoid breaching the articular surface of both lunate and scaphoid bones at the radiocarpal and midcarpal joints. An Acutrak screw was inserted into the right scapholunate joint of ten cadavers starting immediately distal to the tip of the radial styloid and aiming for the tip of the ulnar styloid. The articular surfaces of the scaphoid and lunate bones in all ten cadavers were exposed and examined. A computed tomography (CT) scan of four wrists was performed. Eight of the ten cadavers had no perforation or destruction of the articular surfaces. Screw stabilization of the scapholunate joint can be performed without perforation or destruction of the lunate or scaphoid surfaces. We recommend that if this form of fixation is being used then the screw should be inserted commencing at the radial styloid tip and aiming for ulnar styloid tip, under radiological guidance. PMID:24641760

Flannery, O M; Murphy, L C; Dockery, P; O'Sullivan, M E

2014-01-01

4

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

PubMed Central

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

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

2014-01-01

5

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

PubMed

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

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

2014-04-01

6

The effect of transpedicular screw misplacement on late spinal stability  

Microsoft Academic Search

Summary ¶ Background. In this article the authors investigated the consequences of misplaced thoracolumbar pedicle screws on late spinal stability. Method. This study consisted of 16 patients with screws in the proper position (Group A) and a further 16 patients with screw misplacement (Group B) who had previously undergone transpedicular screw fixation following thoracolumbar injury. The authors retrospectively evaluated the

S. C. Aç?kba?; F. Y. Arslan; M. R. Tuncer

2003-01-01

7

Technique for utilization of an interference screw for split peroneus brevis tendon transfer in lateral ankle stabilization.  

PubMed

We present a technique for split peroneous brevis lateral ankle stabilization using an interference screw as the fixation device. The interference screw provided stable fixation by way of physiologic tension and restored lateral ankle instability while preserving the range of motion in the surrounding joints. PMID:24239429

Didomenico, Lawrence A; Cross, Davina J; Giagnacova, Albert

2014-01-01

8

Overview of Pedicle Screw-Based Posterior Dynamic Stabilization Systems  

Microsoft Academic Search

\\u000a Using pedicle screws and rods in the lumbar spine has been familiar to spine surgeons since the 1980s. Originally, these constructs\\u000a were used to stabilize the spine while bony incorporation of the fusion bone graft occurred. Now, there are many options for\\u000a devices that are all built upon this early pedicle screw concept. While the placement of the screws has

Richard D. Guyer; Donna D. Ohnmeiss; Kevin R. Strauss

9

Does ischial screw fixation improve mechanical stability in revision total hip arthroplasty?  

PubMed

Ischial screw fixation, albeit technically challenging, is postulated to provide additional mechanical stability in revision total hip arthroplasty (THA). Hemipelvis specimens were prepared to simulate revision THA, and an acetabular component with supplemental screw fixation was implanted. Three configurations were tested: 2 dome screws alone, 2 dome screws plus an additional screw within the dome, and 2 dome screws plus an ischial screw. Force displacement data were acquired during mechanical testing. An increase in mechanical stability was observed in acetabular components with supplemental screw fixation into either the posterior column or ischium (P?.031) compared to isolated dome fixation. In addition, supplemental ischial screw fixation may provide a modest advantage over a screw placed posteroinferiorly within the acetabular dome during revision THA. PMID:19679432

Meneghini, R Michael; Stultz, Allison D; Watson, Jill S; Ziemba-Davis, Mary; Buckley, Christine A

2010-10-01

10

Proprioception and joint stability  

Microsoft Academic Search

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

J. Jerosch; M. Prymka

1996-01-01

11

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

NASA Astrophysics Data System (ADS)

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

Cao, Lei; Song, Yuntao

2012-09-01

12

Acromioclavicular Joint Fixation Using an Acroplate Combined With a Coracoclavicular Screw  

PubMed Central

Background Appropriate treatment of acromioclavicular joint dislocation is controversial. Acroplate fixation is one of the most common treatment methods of acromioclavicular joint (ACJ) dislocation. Based on the risk of re-dislocation after Acroplate fixation, we assumed that combined fixation with an Acroplate and a coracoclavicular screw helps improve the outcome. Objectives The main purpose of the current study was to compare the outcome of ACJ dislocation treated with an Acroplate alone and in combination with coracoclavicular screw. Patients and Methods This study was carried out on 40 patients with ACJ dislocation types III to VI who were divided randomly into two equal groups: Acroplate group (P) and Acroplate in combination with coracoclavicular screw group (P + S). The screws were extracted 3-6 months postoperatively. The patients were followed for 1 year and Imatani’s score was calculated. Finally, the data were compared between the groups. Results The mean Imatani’s score was significantly higher in P + S group (83.4 ± 14.1) than P group (81.2 ± 10.3) (P < 0.001). The mean duration of surgery was the same in the two groups (59.8 ± 9.4 minutes in group P V.s 64.3 ± 10.9 minutes in group P + S; P = 0.169). There were no cases of re-dislocation, degenerative changes and ossification and all patients returned to their previous jobs or sporting activities. Conclusions Using a coracoclavicular screw combined with an Acroplate can improve the patients’ function after ACJ disruption without any significant increase in surgical duration. Authors recommend this technique in the fixation of ACJ dislocation.

Tavakoli Darestani, Reza; Ghaffari, Arash; Hosseinpour, Mehrdad

2013-01-01

13

Registration of localization, occlusion and occluding materials for failing screw joints in the Brånemark implant system.  

PubMed

This study is based on data from routine follow-up registration following functional loading of a consecutive number of osseointegrated prostheses at the Dental School, University of Oslo. Fifty-six patients with 240 Brånemark implants were examined 2-4 months after the implants were loaded, and a protocol form for collecting information about the status of the treatment was completed. The examinations included registration of oral hygiene, pathological alterations in soft and hard tissues, type of material used in contacting occlusal surfaces, occlusal design and technical and mechanical failures. All superstructures, except CeraOne single-tooth prostheses, were unscrewed for inspection of implant and screw joint mobility. Eighty-three per cent of the implants were found in the upper and lower frontal segments of the jaws. The survival rate for individual implants in this study was 94%, which is well within the generally accepted level for osseointegrated implant systems. Plaque and soft tissue complications were low and could not be associated with the early losses of implants. Group function was the preferred design of the occlusal contact pattern (53.4%), followed by 37% for canine guidance and about 9% for balanced articulation. Fourteen abutment screws and 7 gold screws loosened during the period between permanent loading and the first follow-up registration. A majority of the failures occurred in osseointegrated bridges occluding with complete dentures in the opposite jaw. The failing screw joints were found in 25% of the patients, which means that one fourth of the patients needed extra mending appointments. The failures are assumed to be iatrogenic, and measures to avoid them are discussed. PMID:7669867

Wie, H

1995-03-01

14

Triple arthrodesis stabilization: a quantitative analysis of screw versus staple fixation in fresh cadaveric matched-pair specimens.  

PubMed

Qualitative analyses of midfoot stabilization in triple arthrodeses utilizing bone staple versus 4.5-mm cannulated cancellous screw fixation, with and without washers, were performed in fresh cadaveric specimens. Twenty-two trials (11 matched-pair feet) were used for direct comparison. Stiffness, defined as force/displacement, was determined at each talonavicular and calcaneocuboid joint. Ultimate load failure points of each specimen were also calculated. Trial results showed no statistically significant difference in stiffness or ultimate failure between these two forms of midfoot fixation for triple arthrodeses. PMID:9879042

Payette, C R; Sage, R A; Gonzalez, J V; Sartori, M; Patwardhan, A; Vrbos, L

1998-01-01

15

Joint stabilizing projects in defense  

SciTech Connect

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

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

1992-06-01

16

The study of lifetime of polymer and composite bone joint screws under cyclical loads and in vitro conditions  

Microsoft Academic Search

The “strain-life time” method has been adapted for life-time prediction of polymer and composite bone joint screws. Mechanical\\u000a and fatigue properties of screws made of biostable (polysulfone), biosorbable (poly(lactide-co-glycolide) and short carbon\\u000a fibre reinforced polymer composite materials have been examined in this study. The lifetime predictions under in vitro conditions were calculated for polymer and composite implants. The forecasting of

Ch?opek Jan; Kmita Grzegorz

2005-01-01

17

Effects of screw eccentricity on the initial stability of the acetabular cup in artificial foam bone of different qualities.  

PubMed

Acetabular cup loosening is one of the major failure models of total hip replacement (THR), which is mostly due to insufficient initial stability of the cup. Previous studies have demonstrated that cup stability is affected by the quality of the host bone and the surgical skill when inserting screws. The purpose of this study was to determine the effects on the initial stability of the acetabular cup of eccentric screws in bone of different qualities. In this study, hemispherical cups were fixed into bone specimens constructed from artificial foam with three elastic moduli using one to three screws. The effects of two types of screw eccentricity (offset and angular) on the stability of the acetabular cup were also evaluated. The experimental results indicate that in the presence of ideal screwing, the cup was stable in bone specimens constructed from foam with the highest elastic modulus. In addition, increasing the number of ideal screws enhanced the cup stability, especially in bone specimens constructed from soft foam. Moreover, the cup stability was most affected by offset eccentric screw(s) in the hard-foam bone specimens and by angular eccentric screw(s) in the soft-foam bone specimens. The reported results indicate that the presence of screw eccentricity affects the initial stability of the acetabular cup. Surgeons should keep this in mind when performing screw insertions in THR. However, care is necessary when translating these results to the intraoperative situation due to the experiments being conducted under laboratory conditions, and hence, future studies should attempt to replicate the results reported here in vivo. PMID:19995362

Hsu, Jui-Ting; Lin, Dan-Jae

2010-01-01

18

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

PubMed Central

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

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

2013-01-01

19

A Rare Case of Hypopharyngeal Screw Migration after Spine Stabilization with Plating  

PubMed Central

Anterior cervical spine fusion and stabilization with plating are well-established surgical procedures for the treatment of myelopathy, cervical spine traumas, and spinal infectious diseases. Various complications have been described in the literature, more frequently, intraoperative bleeding, peri- or postoperative hypopharyngeal, and/or esophageal ruptures with mediastinal deep infection and loosening and extrusion of the screws from the plating. Screw migration has also been observed as a complication of the procedure, either early in the postoperative period or delayed, even after many years. In some instances, the esophageal perforation can recover spontaneously with absence of complications, even if a case of plate failure and graft migration with lethal sudden airways obstruction has been reported. We describe a case of hypopharyngeal screw migration after cervical spine stabilization with plating never described before in the literature.

Salis, G.; Pittore, B.; Balata, G.; Bozzo, C.

2013-01-01

20

Anatomic considerations of costotransverse screw placement in the thoracic spine  

Microsoft Academic Search

BACKGROUNDNumerous techniques have been reported to restore spinal stability and to correct spinal deformities, including rods with wires\\/hooks, and rods or plates with pedicular screws. It was thought that posterior fixation of the thoracic spine through the costotransverse joint may be another alternative.METHODSNine cadavers were obtained for study of screw fixation of the costotransverse joint for posterior thoracic instrumentation. The

Rongming Xu; Nabil A Ebraheim; Yiangjia Ou; Martin Skie; Richard A Yeasting

2000-01-01

21

A comparison of stress distributions for different surgical procedures, screw dimensions and orientations for a Temporomandibular joint implant.  

PubMed

Finite element analysis is a useful analytical tool for the design of biomedical implants. The aim of this study was to investigate the behavior of temporomandibular joint implants with multiple design variables of the screws used for fixation of the implant. A commercially available implant with full mandible was analyzed using a finite element software package. The effects of different design variables such as orientation, diameter and stem length of the screws on the stress distribution in bone for two different surgical procedures were investigated. Considering the microstrain in bone as a principal factor, the acceptable ranges for screw diameter and length were determined. Parallel orientation of the screws performed better from a stress point of view when compared to the zig-zag orientation. Sufficient contact between the implant collar and mandibular condyle was shown to reduce the peak stresses which may lead to long term success. The distance between screw holes in the parallel orientation was much closer when compared to the zig-zag orientation. However, the stresses in bone near the screw hole area for the parallel orientation were within acceptable limits. PMID:21816398

Chowdhury, Amit Roy; Kashi, Ajay; Saha, Subrata

2011-09-23

22

The importance of lag screw position for the stabilization of trochanteric fractures with a sliding hip screw: a subject-specific finite element study.  

PubMed

Using finite element analysis, we compared the biomechanical performance of a CT scan-based three-part trochanteric fracture model (31-A2 in the AO classification) stabilized with a sliding hip screw for nine different positions of the lag screw (3 × 3 arrangement, from anterior to posterior and from inferior to superior). Our results showed that the volume of bone susceptible to yielding in the head and neck region is the lowest for inferior positions and increases as the lag screw is moved superiorly. Overall, for this specific subject, the models less likely to lead to cut-out are the ones corresponding to inferior middle and inferior posterior positions of the lag screw. In our study, the tip-apex distance (TAD) was anti-correlated with the risk of cut-out, as quantified by the volume of bone susceptible to yielding, which suggests that a TAD >25 mm cannot be considered to be an accurate predictor of lag screw cut-out. Further clinical studies investigating lag screw cut-out should attempt to find more reliable predictors of cut-out that should better reflect the biomechanics and subject-specificity of the femoral head. PMID:23138576

Goffin, Jérôme M; Pankaj, Pankaj; Simpson, A Hamish

2013-04-01

23

[Combination of intramedullary nail and covered screw osteosynthesis for managing distal tibial fracture with ankle joint involvement].  

PubMed

Fractures of the distal metaphysis of the tibia often include an extension into the ankle. Intramedullary nailing combined with covered screw osteosynthesis should reduce the high incidence of soft tissue and ankle problems and should be an alternative to open plate fixation, with good ultimate functional outcome. Between January 1993 and December 1995, a prospective study on 49 patients with distal metaphyseal tibia fracture and involvement of the ankle was performed. All the fractures were treated with intramedullary nailing combined with covered screw osteosynthesis, and plate fixation in cases of fibula fractures. There were 27 men and 22 women with an average age of 46.4 +/- 12.7 years (range 21-90). In most studies of the use of intramedullary nailing in distal tibial fractures the classification has been inadequate. Therefore a new classification according to Robinson et al. (1995) was used: 10 fractures were type II B (20.4%), 13 were type II C (26.5%), and 26 patients suffered a combination of type II B and type II C (53.1%). This fracture type was defined as type II D for use in this study. The severity of soft tissue injury was recorded using the Gustilo system in case of open (n = 19) and the Tscheme system in case of closed fractures (n = 30). In 31 patients distal tibia fracture was accompanied by a fracture of the fibula, which was first stabilized using a plate. For reconstruction of the distal articular surface, covered screw osteosynthesis was done. At the next step intramedullary nails were inserted and were statically locked proximally and distally. From January 1993 to February 1994, the reamed AO standard nail was used. After introduction of the unreamed tibial nail (UTN) all fractures were treated by this implant. Full load on the operated leg was allowed after 8 weeks. Union of the fracture was assessed by standard radiological and clinical criteria. Misalignment was defined as more than 5 degrees of angular rotation. Further surgery due to a valgus deformity in the ankle joint had to be done in three cases. There were no deep infections. Three patients had a superficial infection in the ankle area, but surgical debridement was not necessary. A leg shortening was found in 4 cases, but it was less than 1 cm in every case. Therefore, surgical correction was not done. Patients were reviewed at intervals of 2, 6, and 12 weeks, and after 6, and at least 12 months. All 49 patients were finally reviewed after an average time of 15.7 months (range 12-38). Bone fusion was reached 12.8 weeks (range 9-21) after the operative treatment. A specific assessment of the ankle symptoms was made using the score of Olerud and Molander (1984). In 29 patients excellent results were recorded. A satisfactory result was attained with 17 patients and just 3 patients were found to be unsatisfactory. Although proximity of distal tibia fracture to the ankle makes the treatment more complicated than for fractures of the tibial diaphysis, closed intramedullary nailing combined with covered screw fixation is a good alternative to open reduction and plate fixation. The major advantages are closed procedure and simplified interlocking techniques. Therefore, closed intramedullary nailing combined with covered screw fixation is a safe and effective method of managing this type of fracture. PMID:10025240

Rzesacz, E H; Könneker, W; Reilmann, H; Culemann, U

1998-12-01

24

Stability of cervical spine after one-level corpectomy using different numbers of screws and plate systems.  

PubMed

Anterior corpectomy and reconstruction using a plate with locking screws are standard procedures for the treatment of cervical spondylotic myelopathy. Although adding more screws to the construct will normally result in improved fixation stability, several issues need to be considered. Past reports have suggested that increasing the number of screws can result in the increase in spinal rigidity, decreased spine mobility, loss of bone and, possibly, screw loosening. In order to overcome this, options to have constrained, semi-constrained or hybrid screw and plate systems were later introduced. The purpose of this study is to compare the stability achieved by four and two screws using different plate systems after one-level corpectomy with placement of cage. A three-dimensional finite-element model of an intact C1-C7 segment was developed from computer tomography data sets, including the cortical bone, soft tissue and simulated corpectomy fusion at C4-C5. A spinal cage and an anterior cervical plate with different numbers of screws and plate systems were constructed to a fit one-level corpectomy of C5. Moment load of 1.0 N m was applied to the superior surface of C1, with C7 was fixed in all degrees of freedom. The kinematic stability of a two-screw plate was found to be statistically equivalent to a four-screw plate for one-level corpectomy. Thus, it can be a better option of fusion and infers comparable stability after one-level anterior cervical corpectomy, instead of a four-screw plate. PMID:24622982

Rosli, Ruwaida; Abdul Kadir, Mohammed R; Kamarul, Tunku

2014-04-01

25

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

NASA Astrophysics Data System (ADS)

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).

Sherman, William

2005-03-01

26

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

PubMed

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. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 102A: 3324-3340, 2014. PMID:24382799

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

2014-09-01

27

Three column stabilization through posterior approach alone: transpedicular placement of distractable cage with transpedicular screw fixation.  

PubMed

The combination of anterior and posterior instrumentation provides the most stable repair for burst fractures of the thoracolumbar spine. However, the use of both approaches on a trauma patient may increase morbidity. Stabilization of three columns through only one approach can provide an effective outcome. We treated eight patients with burst fracture involving the thoracic or lumbar vertebrae by the application of anterior and posterior stabilization instruments through only the posterior approach. The desired stabilization was obtained in all patients. The advantages are the absence of the risks of the anterior approach, facilitation of the placement of anterior and posterior stabilization devices through only one approach, preserving the unity of the anterior longitudinal ligament, the effect of the anterior corpus in preventing displacement of the cage, application of compression on the pedicle screw system to both decrease the kyphosis angulation due to collapse of vertebra and to help the stabilization of the cage, repair of the dural tears at the posterior side, prevention of cage displacement by distraction and thus leaning on the endplates, and ease of performance by a neurosurgeon alone. PMID:18219186

Ayberk, Giyas; Ozveren, Mehmet Faik; Altundal, Naci; Tosun, Hakan; Seckin, Zekai; Kilicarslan, Kasim; Kaplan, Metin

2008-01-01

28

Relative stability of tension band versus two-cortex screw fixation for treating fifth metatarsal base avulsion fractures.  

PubMed

This study assesses the strength of fixating avulsion fractures of the fifth metatarsal base with a 4.0-mm partially threaded cancellous screw crossing two cortices as compared to tension banding. Our data showed statistically significant fixation strength improvement over tension banding for avulsion fractures (p < 0.02) in both polystyrene foam models and fresh, nonpreserved frozen cadaveric samples. In cadavers, the screw fixations were able to withstand more than three times the load sustained by the tension band fixations. The study utilized the Instron 8500 tensiometer to apply physiologic loads to test the constructs until failure. The displacement and load data at failure show the limitations of both fixations. By increasing the load resistance while maintaining compression, the bicortical cancellous screw fixation created greater stability at the avulsion fracture of the fifth metatarsal base as compared to tension band stabilization. PMID:10789099

Husain, Z S; DeFronzo, D J

2000-01-01

29

[Biomechanical study of the initial stability of various arthrodesis methods for the upper ankle joint].  

PubMed

Arthrodesis of the ankle joint is commonly, performed to treat severe arthritis. Three different techniques have been biomechanically evaluated for initial stability: fusion with three isolated tibio-talar lag screws (type I), which was inaugurated by Wagner; a second fusion technique with two isolated tibio-talar lag screws and an anterior tibio-talar three-hole 3.5 mm AO compression plate (type II); and type-II fusion with an additional lag screw through the center hole of the anterior plate (type III). Ten fresh cadaver ankles were used for biomechanical evaluation. Bone stock quality was compared before fusion by CT scan and osteodensitometry. Osteopenic ankle joints (bone density less than 80% of the median density) were excluded. Each ankle fusion was stressed with 15 Nm in a universal testing machine (UTS 10, Ulm, Germany) in antero-posterior and medio-lateral directions and in a rotational torque technique. The movements at the fusion gap were recorded by computer-assisted image analysis. A video camera recorded the displacement of four active markers on both sides of the fusion line during loading in real time. A computer-assisted calculation of the dislocation at the fusion gap was performed. This technique provides comparable results except for systemic failure induced by the fixation device of the testing machine. The results revealed comparable initial stability with types I (0.063 mm/Nm) and III (0.074 mm/Nm; P = 0.95) ankle fusion. Type-II fusion was significantly less favorable concerning initial stability (0.14 mm/Nm; P < 0.01, Duncan's test for multiple comparisons). Our biomechanical results advertise isolated lag screws for ankle fusion. PMID:7502090

Pommer, A; Dávid, A; Hahn, M P; Ostermann, P A; Muhr, G

1995-10-01

30

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

PubMed Central

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

2011-01-01

31

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

Microsoft Academic Search

Percutaneous insertion of cannulated pedicle screws has been recently developed as a minimally invasive alternative to the\\u000a open technique during instrumented fusion procedures. Given the reported rate of screw misplacement using open techniques\\u000a (up to 40%), we considered it important to analyze possible side effects of this new technique. Placement of 60 pedicle screws\\u000a in 15 consecutive patients undergoing lumbar

Constantin Schizas; Jacky Michel; Victor Kosmopoulos; Nicolas Theumann

2007-01-01

32

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

PubMed

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. PMID:24090880

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

2014-01-01

33

Contribution of the xenograft bone plate-screw system in lumbar transpedicular stabilization of dogs: an in-vitro study  

Microsoft Academic Search

We performed biomechanical comparison of a xenograft bone plate-screw (XBPS) system for achieving cadaveric lumbar transpedicular stabilization (TS) in dogs. Twenty dogs' cadaveric L2-4 lumbar specimens were harvested and their muscles were removed, but the discs and ligaments were left intact. These specimens were separated to four groups: the L2-4 intact group as control (group I, n = 5), the

Hakan Salci; Sani Sarigul; Seref Dogan; Huseyin Lekesiz; Resat Ozcan; O. Sacit Gorgul; Kaya Aksoy

2008-01-01

34

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

PubMed

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 ?m and 800 rpm), granules were in-line blended with magnesium stearate and directly compressed using a Modul™ P tablet press (tablet weight: 430 mg, main compression force: 12 kN). Granule (loss on drying, particle size distribution, friability, flow) and tablet (weight uniformity, hardness, thickness, friability, content uniformity, disintegration time, and dissolution) quality was evaluated in function of process time. For each of the logged process outcomes, a stabilization period was needed to reach steady-state conditions. Slightly deviating particle size distribution and friability results for milled granules were observed during start-up due to initial layering of the mill screen. However, no deviating tablet quality was detected in function of process time. For multiple hours, granule and tablet quality was constant in function of process time. Furthermore, process data trends were highly repeatable. Consequently, the ConsiGma™-25 system can be considered as a stable and repeatable system for the continuous production of tablets via wet granulation. PMID:23702273

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

2013-11-01

35

Failure of Small Joint Arthrodesis from Resorption Around a Compression Screw in a Patient with Lupus-Associated Arthritis Mutilans: Case Report  

PubMed Central

We report the unusual case of a patient with systemic lupus erythematosus (SLE)-associated arthritis mutilans. Arthritis mutilans is a variant of erosive arthritis that is more commonly reported with psoriatic and rheumatoid arthritis and not with SLE. Joint fusion has been shown to be the most effective measure to preserve bone length and prevent further erosive joint changes in arthritis mutilans. We attempted to enhance success of a thumb interphalangeal joint fusion in our patient by adding compression across the fusion with implant screws, given the difficulty of achieving solid bone fusion ordinarily. Osteolysis around the compression screw resulted in arthrodesis failure. We were finally able to achieve successful fusion with iliac crest corticocancellous bone grafts and Kirschner wire fixation. Implant athroplasty in patients with bone loss is risky as it often furthers joint instability because of bone resorption around the prosthesis. This is a point of caution regarding use of any implant (including large screws) in patients with arthritis mutilans, as osteolysis around the implant may occur.

Aliu, Oluseyi; Peltier, Marcia

2007-01-01

36

Abrasion of abutment screw coated with TiN  

PubMed Central

STATEMENT OF PROBLEM Screw loosening has been a common complication and still reported frequently. PURPOSE The purpose of this study was to evaluate abrasion of the implant fixture and TiN coated abutment screw after repeated delivery and removal with universal measuring microscope. MATERIAL AND METHODS Implant systems used for this study were Osstem and 3i. Seven pairs of implant fixtures, abutments and abutment screws for each system were selected and all the fixtures were perpendicularly mounted in liquid unsaturated polyesther with dental surveyor. After 20 times of repeated closing and opening test, the evaluation for the change of inner surface of implant and TiN-coated abutment screw, and weight loss were measured. Mann-Whitney test with SPSS statistical software for Window was applied to analyze the measurement of weight loss. RESULTS TiN-coated abutment screws of Osstem and 3i showed lesser loss of weight than non-coated those of Osstem and 3i (P < .05, Mann-Whitney test). CONCLUSION Conclusively, TiN coating of abutment screw showed better resistance to abrasion than titanium abutment screw. It was concluded that TiN coating of abutment screw would reduce the loss of preload with good abrasion resistance and low coefficient of friction, and help to maintain screw joint stability.

Jung, Seok-Won; Son, Mee-Kyoung; Chung, Chae-Heon

2009-01-01

37

Muscle contribution to elbow joint valgus stability.  

PubMed

Repetitive valgus stress of the elbow can result in excessive strain or rupture of the native medial ulnar collateral ligament (MUCL). The flexor-pronator mass (FPM) may be particularly important for elbow valgus stability in overhead-throwing athletes. The aim of this study was to identify the relative contribution of each muscle of the FPM--that is, the flexor carpi ulnaris (FCU), flexor digitorum superficialis (FDS), flexor carpi radialis (FCR), and pronator teres (PT)--and of the extensor-supinator mass, including the extensor carpi ulnaris (ECU), extensor digitorum communis (EDC), extensor carpi radialis longus and brevus, and brachioradialis, to elbow valgus stability at 45 degrees and 90 degrees of elbow flexion angles. Eight fresh-frozen elbow specimens (mean age at death, 73.75 +/- 14.07 years) were tested. With the skin and subcutaneous tissue removed but all muscles left intact, each individual muscle of the FPM and extensor-supinator mass was loaded at 3 levels of force. During loading, strain on the MUCL and the kinematics of the elbow were measured simultaneously. Kinematic measurements were later repeated when the MUCL was fully cut. At 45 degrees and 90 degrees of elbow flexion, individual loading of the FCU, FDS, and FCR caused significant relief to the MUCL whereas the PT produced no significant change. Furthermore, of these flexor muscles, the FCU provided the greatest MUCL relief at both 45 degrees and 90 degrees . In contrast, loading of the ECU at 45 degrees of elbow flexion produced a significant increase in MUCL strain. All FPM muscles caused significant elbow varus movement at both 45 degrees and 90 degrees when loaded individually. At 90 degrees , the FCU created more motion than both the FCR and PT but not the FDS, and the FDS created more motion than the PT. The EDC and ECU created significant valgus movement at 45 degrees and 90 degrees , which became insignificant when the MUCL was transected. Our study suggested that the FCU, FDS, and FCR may function as dynamic stabilizers, with the FCU being the primary stabilizer for elbow valgus stability, incorporating with the MUCL for all tested joint configurations. Our findings also suggest that the ECU and EDC increased MUCL strain and elbow valgus movement at both 45 degrees and 90 degrees . PMID:17936028

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

2007-01-01

38

The Stability of Joint Ventures: Reciprocity and Competitive Rivalry  

Microsoft Academic Search

The focus of the following empirical analysis is the influence of reciprocity and long-term relationships on the stability of joint ventures. These cooperative incentives are offset by industry structural conditions, which may promote competitive rivalry among the partners. To separate these effects on joint venture survival, the hypothesized relationships are proxied by variables drawn from industry and questionnaire data, and

Bruce Kogut

1989-01-01

39

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

PubMed

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

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

2012-03-01

40

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

PubMed Central

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

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

2012-01-01

41

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

PubMed Central

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

2014-01-01

42

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

PubMed Central

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

2012-01-01

43

Dual lag screw cephalomedullary nail versus the classic sliding hip screw for the stabilization of intertrochanteric fractures. A prospective randomized study.  

PubMed

This study is a randomized prospective study comparing two fracture fixation implants, the extramedullary sliding hip screw (SHS) and the dual lag screw cephalomedullary nail, in the treatment of intertrochanteric femoral fractures in the elderly. One hundred and sixty-five patients with low-energy intertrochanteric fractures, classified as AO/OTA 31A, were prospectively included during a 2-year period (2005-2006). Patients were randomized into two groups: group A included 79 hip fractures managed with sliding hip screws and group B included 86 fractures treated with cephalomedullary nails. Delay to surgery, duration of surgery, time of fluoroscopy, total hospital stay, implant-related complications, transfusion requirements, re-operation details, functional recovery, and mortality were recorded. The mean follow-up was 36 months (24-56 months). The mean surgical time was statistically significantly shorter and fluoroscopy time longer for the group B. No intraoperative femoral shaft fractures occurred. There was no statistically significant difference in the functional recovery score, reoperation, and mortality rates between the 2 groups. A new type of complication, the so-called Z-effect phenomenon, was noticed in the cephalomedullary nail group. There are no statistically significant differences between the two techniques in terms of type and rate of complications, functional outcome, reoperation and mortality rates when comparing the SHS and the cephalomedullary nail for low-energy AO/OTA 31A intertrochanteric fractures. Our data do not support recommendations for the use of one implant over the other. PMID:23086659

Kouvidis, G; Sakellariou, V I; Mavrogenis, A F; Stavrakakis, J; Kampas, D; Galanakis, J; Papagelopoulos, P J; Katonis, P

2012-11-01

44

[Screw fixation of craniocervical junction].  

PubMed

In recent years an increase has been observed of the use of screw techniques for the fixation of the craniocervical junction. For clinical use two techniques have been introduced: (1) transarticular screw fixation, and (2) transpedicular screw fixation. In the former the screw is inserted through the C2 lateral mass, the fissure of the C1-C2 joint, and the C1 lateral mass. (2) in the latter the screw is inserted into the C2 pedicle and anchored in C2 vertebral body. Transarticular or pedicle screws can be easily connected to longitudinal elements such as rods or plates, and combined with lateral mass screws of the remaining cervical vertebrae or occipital screws. In comparison to sublaminar wiring or interlaminar clamping the screw techniques: (a) strengthen the stiffness of the construct and speed up fusion, (b) allow fixation in the absence or deficiency of laminae as a result of trauma or laminectomy, and (c) can selectively include only the affected segments. Increased construct stiffness is due to deep anchorage of the screw in bone providing thus a solid grip on the vertebra. Both techniques require preoperative assessment of the course of the vertebral artery using imaging methods. In about 18% of cases abnormal course of the artery precludes screw use. Pedicle screw insertion requires direct control of the medial and superior walls of C2 pedicle with dissector introduced into the vertebral canal, which requires removal of the atlantoaxial ligament. Additional control can be achieved with lateral fluoroscopy. The entry point for transarticular screw is on the lateral mass of the odontoid 2-3 mm laterally to the medial margin of C2 facet and 2-3 mm above the C1/C2 articular fissure. The screw trajectory is 0-10 degrees in horizontal plane and towards the anterior C1 tuberculum in sagittal plane. PMID:10791042

Maciejczak, A; Radek, A

1999-01-01

45

Stability of inter-joint coordination during circle drawing: Effects of shoulder-joint articular properties  

Microsoft Academic Search

The present study addressed the effect of articular conformity of the shoulder joint on the stability of inter-joint coordination during circular drawing movements. Twelve right-handed participants performed clockwise and counter-clockwise circular drawing movements at nine locations in the mid-sagittal plane. The task was paced acoustically at 1.0, 1.5 and 2.0 Hz and performed without visual control. Displacements of seven infrared

Jurjen Bosga; Ruud G. J. Meulenbroek; Stephan P. Swinnen

2003-01-01

46

Intraoperative three-dimensional fluoroscopy assessment of iliosacral screws and lumbopelvic implants stabilizing fractures of the os sacrum  

Microsoft Academic Search

Introduction  Percutaneous iliosacral screw fixation of unstable sacrum fractures has gained popularity since its introduction in the 1990s.\\u000a The combination with lumbopelvic implants allows the application even in situations of higher instability. Both manual and\\u000a navigated screw insertion in the sacrum and vertebra bodies shows unchanged relevant malpositions. The current standard to\\u000a control the screw position is postoperative computed tomography. The

Markus Beck; Markus Kröber; Thomas Mittlmeier

2010-01-01

47

Cannulated screws for odontoid screw fixation and atlantoaxial transarticular screw fixation. Technical note.  

PubMed

Cannulated screw systems use thin Kirschner wires (K-wires) that have been drilled into the bone to direct screw trajectories accurately into small bone fragments. Use of the K-wires avoids overdrilling the pilot holes and allows fixation of adjacent bone fragments during screw insertion. Hollow tools and hollow screws are inserted into the bone over the K-wires. Cannulated screw fixation is useful in the cervical spine to stabilize odontoid fractures and to treat atlantoaxial instability. This report describes techniques for successful cannulated screw insertion and methods to minimize complications. Cannulated screws have several distinct advantages compared to noncannulated screws: 1) the K-wires guide the screw position into the bone; 2) the K-wire trajectory can be repositioned easily if the original trajectory was not ideal; 3) the K-wires allow continuous fixation of adjacent unstable bone fragments; and 4) the K-wires prevent migration of unstable bone fragments during screw insertion. Complications associated with the K-wire (breakage, repositioning, and advancement) can be minimized using precise operative techniques, a specialized tool system, and intraoperative fluoroscopic monitoring. A unique cannulated screw tool system was developed specifically for upper cervical fixation to allow percutaneous drilling using long tunneling devices, tissue sheaths, drill guides, and long K-wires. These tools allow delivery of cannulated fracture-fixation screws at a low angle to the spine through long soft-tissue trajectories. Cannulated screws have significant advantages compared to noncannulated screws for fixation of the unstable cervical spine. PMID:7490629

Dickman, C A; Foley, K T; Sonntag, V K; Smith, M M

1995-12-01

48

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

PubMed Central

Internal fixation is the established dorsal standard procedure for the treatment of thoracolumbar fractures. The main problem of the procedure is the false positioning of the pedicle screws. The exact determination of pedicle screws has up to now only been possible through postoperative computed tomography. This study was intended to clarify the diagnostic value of intraoperative 3D scans after pedicle screw implantation in thoracolumbar spine surgery. The direct intraoperative consequences of the 3D scans are reported and the results of the 3D scans are compared with the postoperative computed tomography images. Intraoperative 3D scans were prospectively carried out from June 2006 to October 2008 on 95 patients with fractures of the thoracolumbar spine that have been treated with internal fixation. Screws positions were categorised intraoperatively, screws in relevant malposition were repositioned immediately. A computed tomography of the involved spinal section was carried out postoperatively for all patients. The positions of the pedicle screws were determined and compared in the axial reconstructions of both procedures. Four hundred and fourteen pedicles with enclosed screws were evaluated by the 3D scans. The time needed for carrying out the 3D scan amounts to an average of 8.2 min. Eleven screws (2.7%) in ten patients were primarily intraoperatively repositioned on the basis of the 3D scan evaluation. Two of 95 patients had to have false positions of the screws revised secondarily following evaluation of the computed tomographies. The secondary postoperative revision rate of the patients amounts to 2.1%. In relation to the number of screws, this is a revision rate of 0.5%. The postoperative computed tomographies showed 323 pedicles without cortical penetration by the screws (78.0%). Ninety-one screws penetrated the pedicle wall (22%). It was possible to postoperatively compare the position classifications of 406 pedicle screws. The CT showed 378 correct screw positions, while 28 screws were positioned falsely. On the basis of the 3D scans, 376 of 378 correct positions were correctly assessed. Twenty-one of 28 false positions could be correctly classified. The sensitivity of all 3D scans reached 91.3% and the specificity 98.2%. The position of 97.8% of the pedicle screws was correctly recognised by the intraoperative 3D scan. Nine screws were classified falsely (2.2%). The comparison of the classification results showed significantly higher error findings by the 3D scan in the spinal section T1–10 (P = 0.014). The image quality of the 3D scan correlates significantly with the width of the scanned pedicle, with the body mass index, the scanned spinal section and the extent of the fixation assembly. 3D scans showed a high accuracy in predicting pedicle screw position. Primary false placement of screws and primary neurovascular damage cannot be avoided. But intraoperative evaluation of the 3D scans resulted in a primary revision rate of 2.7% of the pedicle screws and we could lower the secondary revision rate to 0.5%.

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

2009-01-01

49

The role of the dorsal vertebral cortex in the stability of transpedicular screws. A biomechanical study in human cadaveric vertebrae.  

PubMed

The aim of this biomechanical study was to investigate the role of the dorsal vertebral cortex in transpedicular screw fixation. Moss transpedicular screws were introduced into both pedicles of each vertebra in 25 human cadaver vertebrae. The dorsal vertebral cortex and subcortical bone corresponding to the entrance site of the screw were removed on one side and preserved on the other. Biomechanical testing showed that the mean peak pull-out strength for the inserted screws, following removal of the dorsal cortex, was 956.16 N. If the dorsal cortex was preserved, the mean peak pullout strength was 1295.64 N. The mean increase was 339.48 N (26.13%; p = 0.033). The bone mineral density correlated positively with peak pull-out strength. Preservation of the dorsal vertebral cortex at the site of insertion of the screw offers a significant increase in peak pull-out strength. This may result from engagement by the final screw threads in the denser bone of the dorsal cortex and the underlying subcortical area. Every effort should be made to preserve the dorsal vertebral cortex during insertion of transpedicular screws. PMID:16645123

Karataglis, D; Kapetanos, G; Lontos, A; Christodoulou, A; Christoforides, J; Pournaras, J

2006-05-01

50

Circumferential stabilization with ghost screwing after posterior resection of spinal metastases via transpedicular route  

Microsoft Academic Search

Various surgical methods have been described for treating spinal metastases, namely, en bloc spondylectomy, minimally invasive\\u000a techniques, and anterior and posterior approaches. The main goals in surgical intervention for these lesions are tumor removal\\u000a and establishment of strong, durable stabilization. The least invasive method is always preferred. Posterior transpedicular\\u000a spondylectomy meets all these needs, as this method achieves tumor excision

Alparslan Senel; Ahmet Hilmi Kaya; Enis Kuruoglu; Fahrettin Celik

2007-01-01

51

Atlantoaxial fixation using the polyaxial screw-rod system  

PubMed Central

The aim of this study is to evaluate the first results of the atlantoaxial fixation using polyaxial screw–rod system. Twenty-eight patients followed-up 12–29 months (average 17.1 months) were included in this study. The average age was 59.5 years (range 23–89 years). The atlantoaxial fusion was employed in 20 patients for an acute injury to the upper cervical spine, in 1 patient with rheumatoid arthritis for atlantoaxial vertical instability, in 1 patient for C1–C2 osteoarthritis, in 2 patients for malunion of the fractured dens. Temporary fixation was applied in two patients for type III displaced fractures of the dens and in two patients for the atlantoaxial rotatory dislocation. Retrospectively, we evaluated operative time, intraoperative bleeding and the interval of X-ray exposure. The resulting condition was subjectively evaluated by patients. We evaluated also the placement, direction and length of the screws. Fusion or stability in the temporary fixation was evaluated on radiographs taken at 3, 6, 12 weeks and 6 and 12 months after the surgery. As concerns complications, intraoperatively we monitored injury of the nerve structures and the vertebral artery. Monitoring of postoperative complications was focused on delayed healing of the wound, breaking or loosening of screws and development of malunion. Operative time ranged from 35 to 155 min, (average 83 min). Intraoperative blood loss ranged from 50 to 1,500 ml (average 540 ml). The image intensifier was used for a period of 24 s to 2 min 36 s (average 1 min 6 s). Within the postoperative evaluation, four patients complained of paresthesia in the region innervated by the greater occipital nerve. A total of 56 screws were inserted into C1, their length ranged from 26 to 34 mm (average, 30.8 mm). All screws were positioned correctly in the C1 lateral mass. Another 56 screws were inserted into C2. Their length ranged from 28 to 36 mm (average 31.4 mm). Three screws were malpositioned: one screw perforated the spinal canal and two screws protruded into the vertebral artery canal. C1–C2 stability was achieved in all patients 12 weeks after the surgery. No clinically manifested injury of the vertebral artery or nerve structures was observed in any of these cases. As for postoperative complications, we recorded wound dehiscence in one patient. The Harms C1–C2 fixation is a very effective method of stabilizing the atlantoaxial complex. The possibility of a temporary fixation without damage to the atlantoaxial joints and of reduction after the screws and rods had been inserted is quite unique.

Vyskocil, Tomas; Sebesta, Petr; Kryl, Jan

2006-01-01

52

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

PubMed Central

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

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

2011-01-01

53

Kinetic analysis of anterior cervical discectomy and fusion supplemented with transarticular facet screws.  

PubMed

OBJECT The clinical success rates of anterior cervical discectomy and fusion (ACDF) procedures are substantially reduced as more cervical levels are included in the fusion procedure. One method that has been proposed as an adjunctive technique for multilevel ACDF is the placement of screws across the facet joints ("transfacet screws"). However, the biomechanical stability imparted by transfacet screw placement (either unilaterally or bilaterally) has not been reported. Therefore, the purpose of this study was to determine the acute stability conferred by implementation of unilateral and bilateral transfacet screws to an ACDF construct. METHODS Eight C2-T1 fresh-frozen human cadaveric spines (3 female and 5 male; mean age 50 years) were tested. Three different instrumentation variants were performed on cadaveric cervical spines across C4-7: 1) ACDF with an intervertebral spacer and standard plate/screw instrumentation; 2) ACDF with an intervertebral spacer and standard plate/screw instrumentation with unilateral facet screw placement; and 3) ACDF with an intervertebral spacer and standard plate/screw instrumentation with bilateral facet screw placement. Kinetic ranges of motion in flexion-extension, lateral bending, and axial rotation at 1.5 Nm were captured after each of these procedures and were statistically analyzed for significance. RESULTS All 3 fixation scenarios produced statistically significant reductions (p < 0.05) in all 3 bending planes compared with the intact condition. The addition of a unilateral facet screw to the ACDF construct produced significant reductions at the C4-5 and C6-7 levels in lateral bending and axial rotation but not in flexion-extension motion. Bilateral facet screw fixation did not produce any statistically significant decreases in flexion-extension motion compared with unilateral facet screw fixation. However, in lateral bending, significant reductions at the C4-5 and C5-6 levels were observed with the addition of a second facet screw. The untreated, adjacent levels (C2-3, C3-4, and C7-1) did not demonstrate significant differences in range of motion. CONCLUSIONS The data demonstrated that adjunctive unilateral facet screw fixation to an ACDF construct provides significant gains in stability and should be considered a potential option for increasing the likelihood for obtaining a successful arthrodesis for multilevel ACDF procedures. PMID:24559463

Traynelis, Vincent C; Sherman, Jonathan; Nottmeier, Eric; Singh, Vaneet; McGilvray, Kirk; Puttlitz, Christian M; Leahy, Patrick Devin

2014-05-01

54

Biomechanical evaluation of an interfacet joint decompression and stabilization system.  

PubMed

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-alone minimally invasive technologies. The FJ spacer system effectively increased stiffness of the affected level comparable to predicate systems. Results of this study indicate the FJ spacer increases foraminal area in the cervical spine, and decompression is maintained during bending activities. Clinical studies will be necessary to determine whether the magnitude of decompression observed in this cadaveric study will effectively treat cervical radiculopathy; however, results of this study, taken in context of successful decompression treatments in the lumbar spine, are promising for the continued development of this product. Results of this biomechanical study are encouraging for the continued investigation of this device in animal and clinical trials, as they suggest the device is well fixated and mechanically competent. PMID:24389961

Leasure, Jeremi M; Buckley, Jenni

2014-07-01

55

Screw locking elements: a means to modify the flexibility of osteoporotic fracture fixation with DCPs without compromising system strength or stability.  

PubMed

This paper analyses whether it is possible to use dynamic compression plates (DCPs) and screw locking elements (SLEs) to vary the flexibility of osteoporotic fracture fixation without compromising the strength and stability of the construct. Compression, torsion and four-point bending static strength tests were conducted. Cyclic load tests of up to 10,000 load cycles were also carried out to determine stiffness performance. Four fixation systems were mounted onto polyurethane bone models. Group 1 consists of the DCP and six cortical screws. Group 2, idem, but with the addition of two SLEs. Group 3, idem, but with the addition of six SLEs. Group 4 used the locking compression plate (LCP) and locking screws. The results indicated no significant difference (p>0.05) in the strength of groups 2-4. It was also observed that the torsional stiffness of group 3 (0.30 Nm/°) was higher than that of group 2 (0.23 Nm/°) and similar to that of group 4 (0.28 Nm/°). Compression stiffness of group 4 (124 N/mm) was higher than that of group 2 (102 N/mm), but lower than that of group 3 (150 N/mm). No notable differences were observed for structural bending stiffness. It is concluded that by using the DCP with SLEs it is possible to modify the stiffness of the fixation construct for the repair of osteoporotic fractures and, in this way, facilitate the conditions suitable on secondary bone healing. PMID:21982962

Yánez, A; Cuadrado, A; Carta, J A; Garcés, G

2012-07-01

56

Treatment of upper cervical spine instability with posterior fusion plus atlantoaxial pedicle screw.  

PubMed

Clinical results of posterior fusion plus pedicle screw fixation in the treatment of upper cervical spine instability were taken under consideration. 24 patients with atlantoaxial instability were treated with C1-2 pedicle screws and rods fixation under general anesthesia. There were 18 males and 6 females with mean age of 49.8 years (age range 17-69 years). The postoperative radiographs verified good position of all screws, with satisfactory atlantoaxial reduction. Follow-up for 3-45 months (average 23 months) showed no spinal cord and vertebral artery injury or interfixation failure. Atlantoaxial alignment and stability were restored without complication due to instrumentation. In conclusion, posterior atlantoaxial pedicle screw and rod fixation provide immediate three-dimensional rigid fixation of atlantoaxial joint and are more effective techniques compared with previously reported techniques. PMID:24687596

Ma, Chao; Wu, Jibin; Zhao, Meng; Dai, Weixiang; Wu, Dehui; Wang, Zhaohong; Feng, Jie; Liu, Chao; Li, Yiming; Zhao, Qinghua; Tian, Jiwei

2014-07-01

57

Orientation of the "Lisfranc screw".  

PubMed

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

Panchbhavi, Vinod K

2012-11-01

58

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

NASA Astrophysics Data System (ADS)

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 density (SED) distribution after the anatomic single-bundleACL 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 9mm 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.

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

2014-03-01

59

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

NASA Astrophysics Data System (ADS)

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.

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

2014-04-01

60

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

PubMed

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

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

2013-01-01

61

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

SciTech Connect

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

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

2009-01-01

62

A Novel Pedicle Screw with Mobile Connection: A Pilot Study  

PubMed Central

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

Oshima, Masashi; Ajiro, Yasumitsu; Uei, Hiroshi

2014-01-01

63

Stability and instability of the glenohumeral joint: the role of shoulder muscles.  

PubMed

Shoulder muscles contribute to both mobility and stability of the glenohumeral joint. To improve treatments for shoulder instability, we focused on the contribution of the shoulder muscles to glenohumeral joint stability in clinically relevant positions. Both computational and experimental models were used. A computational model of the glenohumeral joint quantified stability provided by active muscle forces in both mid-range and end-range glenohumeral joint positions. Compared with mid-range positions, the resultant joint force at end-range positions was more anteriorly directed, indicating that its contribution to glenohumeral joint stability was diminished. In end-range positions, simulated increases in rotator cuff muscle forces tended to improve stability whereas increases in deltoid or pectoralis major muscle forces tended to further decrease stability. To validate these results, a cadaveric model, simulating relevant shoulder muscles, was used to quantify glenohumeral joint stability. When infraspinatus muscle activity was decreased, compressive forces decreased. When pectoralis major muscle activity was increased, anteriorly directed forces increased. If anteriorly directed forces increase or compressive forces decrease, stability of the glenohumeral joint decreases. This cadaveric model was then used to evaluate the effect of placing the joint in the apprehension position of abduction, external rotation, and horizontal abduction. Consistent with the results of our computational model, apprehension positioning increased anteriorly directed forces. Knowledge gained from these models was then used to develop a cadaveric model of glenohumeral joint dislocation. Dislocation resulted from the mechanism of forcible apprehension positioning when the appropriate shoulder muscles were simulated and a passive pectoralis major muscle was included. Capsulolabral lesions resulted that were similar to those observed in vivo. Shoulder muscle forces are usually powerful stabilizers of the glenohumeral joint, especially in mid-range positions when the passive stabilizers are lax. However, muscle forces can contribute to instability as well. Certain muscle forces decrease glenohumeral joint stability in end-range positions. We found this to be the case with both active and passive pectoralis major forces. Improved understanding of the contribution of muscle forces not only toward stability but also toward instability will improve rehabilitation protocols for the shoulder and prove useful in the treatment of joint instability throughout the body. PMID:15726085

Labriola, Joanne E; Lee, Thay Q; Debski, Richard E; McMahon, Patrick J

2005-01-01

64

Axial loading cross screw fixation for the Austin bunionectomy.  

PubMed

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

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

2011-01-01

65

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

Microsoft Academic Search

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

Naoki Oda; Masanori Ito

2009-01-01

66

Modified trajectory of c2 laminar screw - double bicortical purchase of the inferiorly crossing screw.  

PubMed

The crossing laminar screw fixation might be the most recently developed approach among various fixation techniques for C2. The new construct has stability comparable to transarticular or transpedicular screw fixation without risk of vertebral artery injury. Quantitative anatomical studies about C2 vertebra suggest significant variation in the thickness of C2 lamina as well as cross sectional area of junction of lamina and spinous process. We present an elderly patient who underwent an occipito-cervical stabilization incorporating crossed C2 laminar screw fixation. We preoperatively recognized that she had low profiles of C2 lamina, and thus made a modification of trajectory for the inferiorly crossing screw. We introduce a simple modification of crossing C2 laminar screw technique to improve stability in patients with low laminar profiles. PMID:19096618

Rhee, Woo-Tack; You, Seung-Hoon; Jang, Yeon-Gyu; Lee, Sang-Youl

2008-02-01

67

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

PubMed

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

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

2008-12-01

68

Minifragment Screw Fixation of Oblique Metacarpal Fractures: A Biomechanical Analysis of Screw Types and Techniques  

PubMed Central

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

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

2008-01-01

69

Surgical screw segmentation for mobile C-arm CT devices  

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

70

[Analysis of migration of screwed acetabular components following revision arthroplasty of the hip joint. Results of single-image roentgen analysis].  

PubMed

Out of 57 revised acetabular components, which were regularly checked, 47 had been replaced by a cemented Müller's acetabular reinforcement ring resp. a cementless Müller's Sl-shell with flange. Both types of cups are anchored in the acetabular roof with cancellous bone screws (tab. 1). 42 cases with radiograph series permitted a detailed analysis with the EBRA-method, a computer aided method for the evaluation of acetabular spatial migration based on standard radiographs of the pelvis. The clinical results were very satisfying (tab. 6). The screwed acetabular components migrated little, although, some essential displacements of the center of rotation (in relation to the anatomical position) had to be accepted. As was recognizable with today's inaccurate methods of measuring the center of the head, the displacement too far towards cranial influenced the migration tendency less than an excessive lateralisation. Especially satisfying is the fact, that no increased migration was observed after reconstruction bone grafting of severe acetabular defects, provided that at least a partly direct contact between the acetabular component and the original bone stock was obtained. For the first time EBRA shall be introduced here as a method which shows the migration and the spatial inclination of the acetabular cup in a vector chart. PMID:7941687

Dihlmann, S W; Ochsner, P E; Pfister, A; Mayrhofer, P

1994-01-01

71

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

PubMed Central

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.

Riemann, Bryan L.; Lephart, Scott M.

2002-01-01

72

Biodegradable magnesium-based screw clinically equivalent to titanium screw in hallux valgus surgery: short term results of the first prospective, randomized, controlled clinical pilot study  

PubMed Central

Purpose Nondegradable steel-and titanium-based implants are commonly used in orthopedic surgery. Although they provide maximal stability, they are also associated with interference on imaging modalities, may induce stress shielding, and additional explantation procedures may be necessary. Alternatively, degradable polymer implants are mechanically weaker and induce foreign body reactions. Degradable magnesium-based stents are currently being investigated in clinical trials for use in cardiovascular medicine. The magnesium alloy MgYREZr demonstrates good biocompatibility and osteoconductive properties. The aim of this prospective, randomized, clinical pilot trial was to determine if magnesium-based MgYREZr screws are equivalent to standard titanium screws for fixation during chevron osteotomy in patients with a mild hallux valgus. Methods Patients (n=26) were randomly assigned to undergo osteosynthesis using either titanium or degradable magnesium-based implants of the same design. The 6 month follow-up period included clinical, laboratory, and radiographic assessments. Results No significant differences were found in terms of the American Orthopaedic Foot and Ankle Society (AOFAS) score for hallux, visual analog scale for pain assessment, or range of motion (ROM) of the first metatarsophalangeal joint (MTPJ). No foreign body reactions, osteolysis, or systemic inflammatory reactions were detected. The groups were not significantly different in terms of radiographic or laboratory results. Conclusion The radiographic and clinical results of this prospective controlled study demonstrate that degradable magnesium-based screws are equivalent to titanium screws for the treatment of mild hallux valgus deformities.

2013-01-01

73

Screw-locking wrench  

NASA Technical Reports Server (NTRS)

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

Vranish, John M. (Inventor)

2007-01-01

74

Biomechanical and histological evaluation of an expandable pedicle screw in osteoporotic spine in sheep  

Microsoft Academic Search

Transpedicular fixation can be challenging in the osteoporotic spine as reduced bone mineral density compromises the mechanical\\u000a stability of the pedicle screw. Here, we sought to investigate the biomechanical and histological properties of stabilization\\u000a of expandable pedicle screw (EPS) in the osteoporotic spine in sheep. EPSs and standard pedicle screws, SINO screws, were\\u000a inserted on the vertebral bodies in four

Shiyong Wan; Wei Lei; Zixiang Wu; Da Liu; Mingxuan Gao; Suochao Fu

2010-01-01

75

An Anatomic Study of the Stabilizing Ligaments of the Trapezium and Trapeziometacarpal Joint  

Microsoft Academic Search

We provide a detailed and comprehensive anatomic description of the ligaments stabilizing the trapezium and trapeziometacarpal joint. Sixteen ligaments were identified. Fourteen ligaments inserted onto the trapezium and 2 others attached independently to the thumb metacarpal. The ligaments inserting onto the trapezium were the superficial anterior oblique, deep anterior oblique (beak ligament), dorsoradial, posterior oblique, ulnar collateral, dorsal trapezio-trapezoid, volar

Paul C. Bettinger; Ronald L. Linscheid; Richard A. Berger; William P. Cooney; Kai-Nan An

1999-01-01

76

The synergistic action of the anterior cruciate ligament and thigh muscles in maintaining joint stability  

Microsoft Academic Search

The synergistic action of the ACL and the thigh muscles in maintaining joint stability was studied experimentally. The EMG from the quadriceps and hamstring muscle groups was recorded and analyzed in three separate experimental procedures in which the knee was stressed. The test revealed that direct stress of the ACL has a moderate inhibitory effect on the quadriceps, but simultaneously

M. Solomonow; R. Baratta; B. H. Zhou; H. Shoji; W. Bose; C. Beck; R. DAmbrosia

1987-01-01

77

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

Microsoft Academic Search

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

A. B. Sim; M. Yunus Ali

2000-01-01

78

Transarticular screw fixation for atlantoaxial instability - modified Magerl's technique in 38 patients  

PubMed Central

Background Symptomatic atlantoaxial instability needs stabilization of the atlantoaxial joint. Among the various techniques described in literature for the fixation of atlantoaxial joint, Magerl's technique of transarticular screw fixation remains the gold standard. Traditionally this technique combines placement of transarticular screws and posterior wiring construct. The aim of this study is to evaluate clinical and radiological outcomes in subjects of atlantoaxial instability who were operated using transarticular screws and iliac crest bone graft, without the use of sublaminar wiring (a modification of Magerl's technique). Methods We evaluated retrospectively 38 subjects with atlantoaxial instability who were operated at our institute using transarticular screw fixation. The subjects were followed up for pain, fusion rates, neurological status and radiographic outcomes. Final outcome was graded both subjectively and objectively, using the scoring system given by Grob et al. Results Instability in 34 subjects was secondary to trauma, in 3 due to rheumatoid arthritis and 1 had tuberculosis. Neurological deficit was present in 17 subjects. Most common presenting symptom was neck pain, present in 35 of the 38 subjects. Postoperatively residual neck and occipital pain was present in 8 subjects. Neurological deficit persisted in only 7 subjects. Vertebral artery injury was seen in 3 subjects. None of these subjects had any sign of neurological deficit or vertebral insufficiency. Three cases had nonunion. At the latest follow up, subjectively, 24 subjects had good result, 6 had fair and 8 had bad result. On objective grading, 24 had good result, 11 had fair and 3 had bad result. The mean follow up duration was 41 months. Conclusions Transarticular screw fixation is an excellent technique for fusion of the atlantoaxial complex. It provides highest fusion rates, and is particularly important in subjects at risk for nonunion. Omitting the posterior wiring construct that has been used along with the bone graft in the traditional Magerl' s technique achieves equally good fusion rates and is an important modification, thereby avoiding the complications of sublaminar wire passage.

2010-01-01

79

Complications of transpedicular screw fixation in the cervical spine.  

PubMed

Today, posterior stabilization of the cervical spine is most frequently performed by lateral mass screws or spinous process wiring. These techniques do not always provide sufficient stability, and anterior fusion procedures are added secondarily. Recently, transpedicular screw fixation of the cervical spine has been introduced to provide a one-stage stable posterior fixation. The aim of the present prospective study is to examine if cervical pedicle screw fixation can be done by low risk and to identify potential risk factors associated with this technique. All patients stabilized by cervical transpedicular screw fixation between 1999 and 2002 were included. Cervical disorders included multisegmental degenerative instability with cervical myelopathy in 16 patients, segmental instability caused by rheumatoid arthritis in three, trauma in five and instability caused by infection in two patients. In most cases additional decompression of the spinal cord and bone graft placement were performed. Pre-operative and post-operative CT-scans (2-mm cuts) and plain X-rays served to determine changes in alignment and the position of the screws. Clinical outcome was assessed in all cases. Ninety-four cervical pedicle screws were implanted in 26 patients, most frequently at the C3 (26 screws) and C4 levels (19 screws). Radiologically 66 screws (70%) were placed correctly (maximal breach 1 mm) whereas 20 screws (21%) were misplaced with reduction of mechanical strength, slight narrowing of the vertebral artery canal (<25%) or the lateral recess without compression of neural structures. However, these misplacements were asymptomatic in all cases. Another eight screws (9%) had a critical breach. Four of them showed a narrowing of the vertebral artery canal of more then 25%, in all cases without vascular problems. Three screws passed through the intervertebral foramen, causing temporary paresis in one case and a new sensory loss in another. In the latter patient revision surgery was performed. The screw was loosened and had to be corrected. The only statistically significant risk factor was the level of surgery: all critical breaches were seen from C3 to C5. Percutaneous application of the screws reduced the risk for misplacement, although this finding was not statistically significant. There was also a remarkable learning curve. Instrumentation with cervical transpedicular screws results in very stable fixation. However, with the use of new techniques like percutaneous screw application or computerized image guidance there remains a risk for damaging nerve roots or the vertebral artery. This technique should be reserved for highly selected patients with clear indications and to highly experienced spine surgeons. PMID:15912352

Kast, E; Mohr, K; Richter, H-P; Börm, W

2006-03-01

80

Image-Guided Computer-Assisted Spine Surgery: A Pilot Study on Pedicle Screw Fixation  

Microsoft Academic Search

As the pedicle offers a strong point of attachment to the spine, several instrumentation systems using screws that go through the pedicle into the vertebral body have been developed to provide internal stability. All pedicle screw systems share the risk of damage to adjacent neural structures as a result of improper screw placement. A computer-assisted system allowing precise preoperative planning

Lutz Nolte; Lucia Zamorano; E. Arm; H. Visarius; Zaowei Jiang; U. Berlerman; O. Schwarzenbach

1996-01-01

81

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

Microsoft Academic Search

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

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

1998-01-01

82

Dynamic stability analysis of jointed rock slopes using the DDA method: King Herod's Palace, Masada, Israel  

Microsoft Academic Search

A dynamic, two-dimensional, stability analysis of a highly discontinuous rock slope is demonstrated in this paper. The studied rock slope is the upper terrace of King Herod's Palace in Masada, situated on the western margins of the seismically active Dead Sea Rift. The slope consists of sub-horizontally bedded and sub-vertically jointed, stiff, dolomite blocks. The dynamic deformation of the slope

Y. H. Hatzor; A. A. Arzi; Y. Zaslavsky; A. Shapira

2004-01-01

83

'Screw'--appendicitis.  

PubMed

We report a rare case of appendicitis due to screw in the appendix in a 4-year old boy. An appendicectomy was done. Foreign body appendicitis should be treated with early surgical intervention. PMID:17827638

Samujh, Ram; Mansoor, Khizer; Khan, Imran; Mannan, A

2007-08-01

84

Survey of Screw Feeders.  

National Technical Information Service (NTIS)

This report presents the results of a survey to determine the availability of screw feeders for use in areas related to coal feeding in the field of coal conversion. 15 references. (ERA citation 09:037045)

G. Sine

1983-01-01

85

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

PubMed Central

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.

Heitmann, Stewart; Ferns, Norm; Breakspear, Michael

2012-01-01

86

Axial and Angled Pullout Strength of Bone Screws in Normal and Osteoporotic Bone Material  

Microsoft Academic Search

Orthopedic surgery often involves the use of bone screws to stabilize fractures. Screw fixation can be extremely difficult\\u000a in osteoporotic (OP) bone because of its compromised strength. Pullout strength is commonly used to measure screw fixation\\u000a strength. In this study, axial and angled screw pullouts (ranging from 0° to 40°) were performed on 0.09 g.cm-3, 0.16 g.cm-3 and 0.32 g.cm-3

P. S. D. Patel; D. E. T. Shepherd; D. W. L. Hukins

87

U.S./U.S.S.R. Joint Studies on Plastic Films and Soil Stabilizers. Volume 2. Glossary: Plastic Films and Soil Stabilizers.  

National Technical Information Service (NTIS)

This report covers many joint studies carried out as part of a U.S./U.S.S.R. team for Joint Study in Plastic Films and Soil Stabilizers on the subject field of Plastics in Hydrotechnical Construction. Vol. II is the Russian/English, English/Russian Glossa...

L. O. Timblin F. V. Reckner

1982-01-01

88

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

SciTech Connect

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

L. KWEI; B. SMITH; ET AL

2001-02-01

89

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

PubMed Central

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

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

2014-01-01

90

Bone properties of the humeral head and resistance to screw cutout  

PubMed Central

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

Frich, Lars Henrik; Jensen, Niels Christian

2014-01-01

91

Fixation pull-out response measurement of bone screws and porous-surfaced posts.  

PubMed

Screws and posts are used in various implant designs to contribute to the short- and long-term fixation stability of artificial joints. This study was undertaken to measure the detailed pull-out load-displacement response of bone screws, beaded porous coated posts, and smooth-surfaced posts in both proximal tibial cancellous bone and polyurethane material under monotonic static and repetitive cyclic loadings. The effect of a number of parameters such as insertion site on the proximal tibia, rate of displacement, insertion depth, outside diameter, drill size, repetitive loading and boundary conditions were studied. Bone screws resisted significantly larger loads than posts of the same size. Smooth-surfaced posts demonstrated much larger (about twice) pull-out forces than beaded porous coated posts of the same size. The pull-out force in the proximal tibia was markedly larger at the medial region followed by the lateral region. The central region exhibited the least force. The resistance of screws and posts diminished with repetitive cyclic loads/displacements, especially when these were larger than 50% of their respective values at pull-out force evaluated under monotonic static loading conditions. The smooth-surfaced posts showed superior performance in maintaining their resistance in fatigue than did the porous coated posts and bone screws. The pull-out force was found to also depend on the pull-out material arrangement and boundary conditions. Pull-out results measured with a specific test design should not, therefore, be compared with those performed using different design configurations. PMID:7962012

Shirazi-Adl, A; Dammak, M; Zukor, D J

1994-10-01

92

Polymethylmethacrylate-Augmented Screw Fixation for Stabilization of the Osteoporotic Spine : A Three-Year Follow-Up of 37 Patients  

PubMed Central

Objective The purpose of this study was to determine the efficacy, radiological findings, clinical outcomes and complications in patients with lumbar stenosis and osteoporosis after the use of polymethylmethacrylate (PMMA) augmentation of a cannulated pedicle screw. Methods Thirty-seven patients with degenerative spinal stenosis and osteoporosis (T-score < -2.5) underwent lumbar fusion using the Dream Technology Pedicle Screw (DTPS™, Dream Spine Total Solutions, Dream STS, Seoul, Korea) between 2005 and 2007. The clinical outcomes were evaluated by using the visual analog scale (VAS) and the Prolo scale. Radiologic findings were documented through computed tomography (CT) and plain films. Results Thirty-seven patients were evaluated and included, 2 males and 35 females with an average bone mineral density (BMD) of 0.47g/cm2. The average age of the patients was 68.7 (range, 57-88). The preoperative VAS for low back and leg pain (7.87 ± 0.95 and 8.82 ± 0.83) were higher as compared with postoperative VAS (2.30 ± 1.61 and 1.42 ± 0.73) with statistical significance (p = 0.006, p = 0.003). According to the Prolo scale, 11, 22, one and three patients were in excellent, good, fair and poor conditions, respectively. The average amount of the injected cement per one cannulated screw was 1.83 ± 0.11 mL. Conclusion The results show favorable outcome both clinically and radiographically for 37 patients who underwent lumbar fusion using DTPS™ and PMMA. Based on the results, the use of this surgical method can be a safe and effective option for the operation on the osteoporotic spine.

Moon, Bong Ju; Choi, Eun Young; Zhang, Ho Yeol

2009-01-01

93

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

PubMed Central

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

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

2013-01-01

94

Helical screw viscometer  

DOEpatents

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

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

1983-06-30

95

Blocks and Screws  

NSDL National Science Digital Library

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

Patterson, Tim

96

Innovation: the induction heated screw.  

National Technical Information Service (NTIS)

The Research and Development Division at EDF has developed an original technique for heating, drying or baking powder products: the induction heated Archimedes screw. Its main characteristic is simultaneous heating of the screw and the sleeve. (author). 4...

B. Paya

1993-01-01

97

Stochastic stability analysis for joint process driven and networked hybrid systems  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

98

[The value of miniature compression screws in maxillofacial surgery].  

PubMed

According to the well-known principle of compression, a new kind of screw has been developed. It is a development of the miniaturized Michelet-Champy osteosynthesis device which we have used for the last 10 years in maxillofacial surgery. These traction-screws were initially elaborated for rigid stabilization after sagittal ramus osteotomies such as Obwegeser-Dal Pont. Usually, three screws are inserted at each side, via a transjugal approach. It is then possible to remove the intermaxillary fixation device at the end of the surgical procedure. However, these screws are also useful in other cases: for other kinds of mandibular osteotomies (visor osteotomy for instance), in traumatology (oblique mandibular or condylar fractures) or for fixation of onlay bone grafts on the facial structures. When iliac bone grafts, which are essentially cancellous bone are used, it is possible to use a small metallic ring to avoid penetration of the head of the screw into the graft. The screws can be inserted by a cutaneous punctiform incision when it is impossible to pass the screwdriver through the buccal incision. In all cases, this material is particularly easy to insert, allows good fixation, permits a solid interosseous compression, and is particularly well tolerated. The main drawback is the difficulty of choosing the right length of the screws because only two lengths are available at the present time. Despite this problem, these mini traction-screws seem to be useful for maxillofacial surgeons. PMID:2470321

Boutault, F; Cadenat, H; Poirot, A; Bodin, H

1989-01-01

99

Antibiotic cement screw for postoperative infection after gamma nailing.  

PubMed

Few articles describe the management of postoperative infection occurring after the use of an intramedullary nail in the treatment of femoral intertrochanteric fractures. Implant removal is frequently selected for postoperative infection control, especially in chronic cases. However, removal of the intramedullary nail causes a high rate of femoral neck fractures, challenging surgeons to prevent such fractures with few guidelines for how this can be done. This article presents 2 cases of postoperative infection following intramedullary nail implant in elderly women. After removal of the infected implant and meticulous debridement, an antibiotic cement screw (a cannulated screw enveloped with antibiotic-impregnated bone cement) was inserted from the lag screw hole into the femoral head. At the latest follow-up (mean, 18 months postoperatively), neither femoral neck fracture nor infection had occurred in either patient. The antibiotic cement screw is expected to provide stability and prevent fracture at the femoral neck region, and its more intimate contact with the medullary canal allows a higher concentration of local antibiotics than intravenous application. The antibiotic cement screw is recommended especially for infection after gamma nailing. We also introduce a simple, reproducible method for constructing an antibiotic cement screw large enough to fit the lag screw hole using bone cement, cannulated screw, antibiotics, and a chest tube. PMID:19708621

Noda, Mitsuaki; Saegusa, Yasuhiro; Takakura, Yoshiyuki; Kuroda, Ryosuke; Doita, Minoru

2009-08-01

100

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

SciTech Connect

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.

Locci, Ivan E. [University of Toledo at NASA Glenn Research Center at Lewis Field, Cleveland, OH 44135 (United States); Nesbitt, James A.; Ritzert, Frank J.; Bowman, Cheryl L. [NASA Glenn Research Center at Lewis Field, Cleveland, OH 44135 (United States)

2007-01-30

101

Treatment of Symptomatic Distal Interphalangeal Joint Arthritis with Percutaneous Arthrodesis: a Novel Technique in Select Patients  

PubMed Central

Arthrodesis of the distal interphalangeal (DIP) joint is a reliable means of achieving pain relief in a symptomatic DIP joint afflicted by a variety of degenerative, inflammatory, or posttraumatic conditions. Successful arthrodesis is more reproducible when rigid compression of the joint is achieved. The emergence of an increasing number of commercially available headless or variable pitch compression screws reflects the growing trend among hand surgeons to utilize rigid stabilization of the DIP joint so that motion at more proximal levels can be initiated immediately without affecting arthrodesis rates. Successful closed percutaneous DIP arthrodesis can be achieved in a patient with hypertrophic osteoarthropathy, passively correctable deformity, and patients at increased risk for perioperative soft tissue complications associated with open arthrodesis. We present a novel percutaneous DIP fusion technique utilizing a cannulated headless compression screw in a select group of patients. The sagittal plane diameters of the distal and middle phalanges are templated. Cannulated headless compression screws, 2.4 and 3.0 mm, with short or long terminal threads at the leading end of the screw are selected based upon patient-specific anatomic considerations. Pain-free status and radiographic fusion were achieved in both patients (gout arthropathy, n?=?1; posttraumatic arthritis, n?=?1) at an average of 6 weeks postoperatively. Our current indications, along with pearls and pitfalls with this technique, are reviewed. In select patients, this percutaneous DIP joint arthrodesis is advantageous in comparison with open fusion techniques.

Ruchelsman, David E.; Hazel, Antony

2010-01-01

102

Treatment of symptomatic distal interphalangeal joint arthritis with percutaneous arthrodesis: a novel technique in select patients.  

PubMed

Arthrodesis of the distal interphalangeal (DIP) joint is a reliable means of achieving pain relief in a symptomatic DIP joint afflicted by a variety of degenerative, inflammatory, or posttraumatic conditions. Successful arthrodesis is more reproducible when rigid compression of the joint is achieved. The emergence of an increasing number of commercially available headless or variable pitch compression screws reflects the growing trend among hand surgeons to utilize rigid stabilization of the DIP joint so that motion at more proximal levels can be initiated immediately without affecting arthrodesis rates. Successful closed percutaneous DIP arthrodesis can be achieved in a patient with hypertrophic osteoarthropathy, passively correctable deformity, and patients at increased risk for perioperative soft tissue complications associated with open arthrodesis. We present a novel percutaneous DIP fusion technique utilizing a cannulated headless compression screw in a select group of patients. The sagittal plane diameters of the distal and middle phalanges are templated. Cannulated headless compression screws, 2.4 and 3.0 mm, with short or long terminal threads at the leading end of the screw are selected based upon patient-specific anatomic considerations. Pain-free status and radiographic fusion were achieved in both patients (gout arthropathy, n?=?1; posttraumatic arthritis, n?=?1) at an average of 6 weeks postoperatively. Our current indications, along with pearls and pitfalls with this technique, are reviewed. In select patients, this percutaneous DIP joint arthrodesis is advantageous in comparison with open fusion techniques. PMID:22131929

Ruchelsman, David E; Hazel, Antony; Mudgal, Chaitanya S

2010-12-01

103

Biomechanical Behaviour of Double Threaded Screw in Tibia Fixation  

Microsoft Academic Search

The aim of the work was assessment of stability of tibia fixation realized with the use of double threaded screw. Biomechanical\\u000a analysis of the tibia – double threaded screw system was carried our for the implant made of two biomaterials used in bone\\u000a surgery – Cr-Ni-Mo stainless steel and Ti-6Al-4V alloy. Finite element method was applied to calculate displacements, strains

Witold Walke; Jan Marciniak; Zbigniew Paszenda; Marcin Kaczmarek; Jerzy Cieplak

2008-01-01

104

Hydromechanical stability of slip-fit joints in the light-water-breeder-reactor vessel (LWBR Development Program)  

Microsoft Academic Search

An experimental program was conducted to determine the hydro-mechanical stability of slip-fit joints with water flowing through an annular gap. Tests were performed while varying the radial gap width, insertion length, pipe stiffness, eccentricity and exit flow geometry. The results provide an experimental basis from which stable slip-fit joints can be designed over a range of variables related to the

S. G. Beus; R. E. Schwirian

1982-01-01

105

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

PubMed

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

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

2002-01-01

106

Low noise lead screw positioner  

NASA Technical Reports Server (NTRS)

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

Perkins, Gerald S. (inventor)

1986-01-01

107

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

SciTech Connect

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.

Darsell, Jens T.; Weil, K. Scott

2008-09-08

108

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

PubMed Central

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

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

2014-01-01

109

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

PubMed Central

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

Dazard, Jean-Eudes; Rao, J. Sunil

2012-01-01

110

Biomechanical analysis of anterior cervical spine plate fixation systems with unicortical and bicortical screw purchase  

Microsoft Academic Search

Anterior plate fixation with unicortical screw purchase does not involve the risk of posterior cortex penetration and possible injuries of the spinal cord. However, there are very few biomechanical data about the immediate stability of non-locking plate fixation with unicortical or bicortical screw placement. The aim of the present study was to evaluate the immediate biomechanical properties in terms of

Wolfgang Lehmann; Michael Blauth; Daniel Briem; Ulf Schmidt

2004-01-01

111

Surface polishing positively influences ease of plate and screw removal.  

PubMed

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

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

2010-01-01

112

Split spline screw  

NASA Technical Reports Server (NTRS)

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

Vranish, John M. (inventor)

1993-01-01

113

Design optimization of the hip nail-plate-screws implant.  

PubMed

This paper is aimed at determining the number of screws and the dimensions of the appliance components of a hip nail-plate screw implant such that their sizes are a minimum (i.e. the implant weight is minimum), without the stresses in the appliance components as well as in the bone shaft exceeding the allowable limits. The implant-bone structure is idealized as a hybrid frame, composed of appliance components and the supporting femur bone elements, which act integrally to support the maximal load (during the gait cycle) at the hip joint. For various configurations of the implant, entailing different numbers of screws, the optimization technique is employed to determine the size of the members (nail, plate and screws) for a lightweight design. Implant configurations are analyzed for two, three, four and five nail configurations. The analysis of the hybrid (implant femur) frame, during each integrative object function and design parameter evaluation, is done by the Finite Element Method. The optimization problem is solved by the sequential unconstrained minimization technique (with the introduction of interior penalty function terms). It is found, from the results of analyses of the four hybrid frames, that the appliance frame, with two screws, yields the minimum-weight structurally safe design. PMID:8925648

Elkholy, A H

1995-12-01

114

Multidisciplinary design optimization of lumbar transpedicular screws  

Microsoft Academic Search

Some of the complications associated with the use of transpedicular screws for spinal fusions include the large diameters of the screws and screw breakagein vivo. Recent advances in multidisciplinary design optimization techniques have provided a unique approach to incorporate the structural, biological, and manufacturing disciplines involved in the design process of spinal screws, allowing the development of smaller and safer

H. A. Serhan; C. L. Bloebaum; G. J. Bennett

1995-01-01

115

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

PubMed Central

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

2010-01-01

116

Clinical Outcome of Modified Cervical Lateral Mass Screw Fixation Technique  

PubMed Central

Objective The purpose of this study was 1) to analyze clinically-executed cervical lateral mass screw fixation by the Kim's technique as suggested in the previous morphometric and cadaveric study and 2) to examine various complications and bicortical purchase that are important for b-one fusion. Methods A retrospective study was done on the charts, operative records, radiographs, and clinical follow up of thirty-nine patients. One hundred and seventy-eight lateral mass screws were analyzed. The spinal nerve injury, violation of the facet joint, vertebral artery injury, and the bicortical purchases were examined at each lateral mass. Results All thirty-nine patients received instrumentations with poly axial screws and rod systems, in which one hundred and seventy-eight screws in total. No vertebral artery injury or nerve root injury were observed. Sixteen facet joint violations were observed (9.0%). Bicortical purchases were achieved on one hundred and fifty-six (87.6%). Bone fusion was achieved in all patients. Conclusion The advantages of the Kim's technique are that it is performed by using given anatomical structures and that the complication rate is as low as those of other known techniques. The Kim's technique can be performed easily and safely without fluoroscopic assistance for the treatment of many cervical diseases.

Kim, Seong-Hwan; Seo, Won-Deog; Kim, Ki-Hong; Yeo, Hyung-Tae; Choi, Gi-Hwan

2012-01-01

117

U.S./U.S.S.R. Joint Studies on Plastic Films and Soil Stabilizers. Volume 3. Laboratory and Field Studies in Plastic Films.  

National Technical Information Service (NTIS)

This report covers many joint studies carried out as part of a U.S./U.S.S.R. team for Joint Study in Plastic Films and Soil Stabilizers on the subject field of Plastics in Hydrotechnical Construction. Vol. III reports on the major Laboratory and Field Stu...

V. A. Krupin P. A. Suhorukov W. R. Morrison J. G. Starbuck

1982-01-01

118

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

PubMed Central

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

2012-01-01

119

Polyaxial locking and compression screws improve construct stiffness of acetabular cup fixation: a biomechanical study.  

PubMed

Bone ingrowth into uncemented acetabular components requires intimate cup-bone contact and rigid fixation, which can be difficult to achieve in revision hip arthroplasty. This study compares polyaxial compression locking screws with non-locked and cancellous screw constructs for acetabular cup fixation. An acetabular cup modified with screw holes to provide both compression and angular stability was implanted into a bone substitute. Coronal lever out, axial torsion and push-out tests were performed with an Instron testing machine, measuring load versus displacement. Polyaxial locking compression screws significantly improved construct stiffness compared with non-locked or cancellous screws. This increased construct stiffness will likely reduce interfacial micromotion. Further research is required to determine whether this will improve bone ingrowth in vivo and reduce cup failure. PMID:24360790

Milne, Lachlan P; Kop, Alan M; Kuster, Markus S

2014-05-01

120

Comparison study of the pullout strength of conventional spinal pedicle screws and a novel design in full and backed-out insertions using mechanical tests.  

PubMed

Recently, new pedicle screw designs have been developed. However, these designs' performances are still unclear, especially when backed out after insertion. The objective of this study was to investigate the performances of different screw designs when backed out from full insertion. Seven conventional designs of the pedicle screw and one novel design were inserted into polyurethane foam (0.32 g/cm(3)). All screws were first fully inserted (43 mm) and were backed out 360°. Axial pullout tests were performed and the reaction force was measured. The results showed that the conical screw of type 1 with a small inner diameter provided the highest pullout strength in both full insertion and backed-out insertion (2401.85 and 2169.82 N, respectively). However, this screw's pullout strength significantly decreased (9.7%) when backed out from full insertion. There was no significant difference between the conical screw of type 1 with a small inner diameter and double duo core screw (p > 0.01) in backed-out insertion. The cylindrical screw with a small diameter, dual inner core screw and double dual core screw also provided good results in both full insertion (2115.44, 2182.99 and 2226.93 N, respectively) and backed-out conditions (2065.80, 2014.28 and 1941.29 N, respectively). The increased pullout strength of the conical design could be due to the effect of bone compaction. However, the screw exhibited less consistent pullout strength when backed out when compared with the other designs. The conical screw should be inserted to the precise position without turning back, especially in osteoporosis patients. The dual inner core screw and double dual core screw could provide greater stability in both conditions. Care should be taken when using both the cylindrical screw with a small thread depth and the dual outer core screw. PMID:24496916

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

2014-03-01

121

Biomechanical and histological evaluation of an expandable pedicle screw in osteoporotic spine in sheep  

PubMed Central

Transpedicular fixation can be challenging in the osteoporotic spine as reduced bone mineral density compromises the mechanical stability of the pedicle screw. Here, we sought to investigate the biomechanical and histological properties of stabilization of expandable pedicle screw (EPS) in the osteoporotic spine in sheep. EPSs and standard pedicle screws, SINO screws, were inserted on the vertebral bodies in four female ovariectomized sheep. Pull-out and cyclic bending resistance test were performed to compare the holding strength of these pedicle screws. High-resolution micro-computed tomography (CT) was performed for three-dimensional image reconstruction. We found that the EPSs provided a 59.6% increase in the pull-out strength over the SINO screws. Moreover, the EPSs withstood a greater number of cycles or load with less displacement before loosening. Micro-CT image reconstruction showed that the tissue mineral density, bone volume fraction, bone surface/bone volume ratio, trabecular thickness, and trabecular separation were significantly better in the expandable portion of the EPSs than those in the anterior portion of the SINO screws (P < 0.05). Furthermore, the trabecular architecture in the screw–bone interface was denser in the expandable portion of the EPS than that in the anterior portion of the SINO screw. Histologically, newly formed bone tissues grew into the center of EPS and were in close contact with the EPS. Our results show that the EPS demonstrates improved biomechanical and histological properties over the standard screw in the osteoporotic spine. The EPS may be of value in treating patients with osteoporosis and warrants further clinical studies.

Wan, Shiyong; Wu, Zixiang; Liu, Da; Gao, Mingxuan; Fu, Suochao

2010-01-01

122

Thoracic pedicle screw fixation for spinal deformity.  

PubMed

Techniques to improve segmental fixation have advanced the ability to correct complex spinal deformity. The purpose of instrumentation is to correct spinal deformity or to stabilize the spine to enhance the long-term biological fusion. The ultimate goal of spinal deformity surgery is the creation of a stable, balanced, pain-free spine centered over the pelvis in the coronal and sagittal planes. The minimum number of segments should be fused. These concepts remain challenging in the setting of deformity and instability. Successful results can be obtained if the surgeon understands the technology available, its capabilities, biological limitations, and the desired solution. The authors prefer to use thoracic pedicle screws when treating patients with spinal deformity because they provide greater corrective forces for realignment. This allows shorter-segment constructs and the possibility of true derotation in correction. In this article the authors focus on the use of thoracic transpedicular screw fixation in the management of complex spinal disorders and deformity. PMID:15766224

Rosner, Michael K; Polly, David W; Kuklo, Timothy R; Ondra, Stephen L

2003-01-15

123

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

PubMed

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

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

2006-10-01

124

Lumbosacral Fixation Using the Diagonal S2 Screw for Long Fusion in Degenerative Lumbar Deformity: Technical Note Involving 13 Cases  

PubMed Central

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.

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

2013-01-01

125

Restoration of horizontal stability in complete acromioclavicular joint separations: surgical technique and preliminary results  

PubMed Central

Background Our purpose was to investigate the clinical efficacy of arthroscope-assisted acromioclavicular ligament reconstruction in combination with double endobutton coracoclavicular ligament reconstruction for the treatment of complete acromioclavicular joint dislocation. Methods During the period from February 2010 to October 2012, ten patients with Rockwood types IV and V acromioclavicular joint dislocation were hospitalized and nine were treated with acromioclavicular ligament reconstruction combined with double endobutton of coracoclavicular ligament reconstruction. The improvement in shoulder functions was assessed using a Constant score and visual analog scale (VAS) system. Results The mean follow-up period was 33.6?±?5.4 months. The mean Constant scores improved from 25.2?±?6.6 preoperatively to 92.4?±?6.5 postoperatively, while the mean VAS score decreased from 5.9?±?1.4 to 1.2?±?0.9; significant differences were observed. The final follow-up revealed that excellent outcomes were achieved in eight patients and good outcome in two patients. Conclusion Arthroscope-assisted acromioclavicular ligament reconstruction in combination with double endobutton of coracoclavicular ligament reconstruction is an effective approach for treatment of acute complete acromioclavicular joint dislocation.

2013-01-01

126

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

PubMed

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

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

2014-04-01

127

Metallurgical examination of gun barrel screws  

SciTech Connect

The examination was conducted to determine the extent of degradation that had occurred after a series of firings; these screws prevent live rounds of ammunition from being loaded into the firing chamber. One concern is that if the screw tip fails and a live round is accidentally loaded into the chamber, a live round could be fired. Another concern is that if the blunt end of the screw begins to degrade by cracking, pieces could become small projectiles during firing. All screws used in firing 100 rounds or more exhibited some degree degradation, which progressively worsened as the number of rounds fired increased. (SEM, metallography, x-ray analysis, and microhardness were used.) Presence of cracks in these screws after 100 fired rounds is a serious concern that warrants the discontinued use of these screws. The screw could be improved by selecting an alloy more resistant to thermal and chemical degradation.

Bird, E.L.; Clift, T.L.

1996-06-01

128

The Pull-Out Strength of Transpedicular Screws in Posterior Spinal Fusion  

Microsoft Academic Search

Finite element methods are widely used for the analysis of the failure mechanisms of spinal fixation systems and the stress\\u000a distribution patterns within vertebral bodies as an important part in clinical evaluation of spinal injuries. For the purpose\\u000a of fixation and stabilization of the spine using pedicle screws the pull-out strength of the screw is one of the most important

P. Chazistergos; G. Ferentinos; E. A. Magnissalis; S. K. Kourkoulis

129

Cervical anterior transpedicular screw fixation. Part I: Study on morphological feasibility, indications, and technical prerequisites  

Microsoft Academic Search

Multilevel cervical spine procedures can challenge the stability of current anterior cervical screw-and-plate systems, particularly\\u000a in cases of severe three-column subaxial cervical spine injuries and multilevel plated reconstructions in osteoporotic bone.\\u000a Supplemental posterior instrumentation is therefore recommended to increase primary construct rigidity and diminish early\\u000a failure rates. The increasing number of successfully performed posterior cervical pedicle screw fixations have enabled

Heiko Koller; Axel Hempfing; Frank Acosta; Michael Fox; Armin Scheiter; Mark Tauber; Ulrich Holz; Herbert Resch; Wolfgang Hitzl

2008-01-01

130

A Case of Pedicle Screw Loosening Treated by Modified Transpedicular Screw Augmentation with Polymethylmethacrylate  

PubMed Central

We report a case of pedicle screw loosening treated by modified transpedicular screw augmentation technique using polymethylmethacrylate (PMMA), which used the anchoring effect of hardened PMMA. A 56-year-old man who had an L3/4/5 fusion operation 3 years ago complained of continuous low back pain after this operation. The computerized tomography showed a radiolucent halo around the pedicle screw at L5. We augmented the L5 pedicle screw with modified pedicle screw augmentation technique using PMMA and performed an L3/4/5 pedicle screw fixation without hook or operation field extension. This modified technique is a kind of transpedicular stiffness augmentation using PMMA for the dead space around the loosed screw. After filling the dead space with 1-2 cc of PMMA, we inserted a small screw. Once the PMMA hardened, we removed the small screw and inserted a thicker screw along the existing screw threading to improve the pedicle screws' pullout strength. At 10 months' follow-up, x-ray showed strong fusion of L3/4/5. The visual analogue scale (VAS) of his back pain was improved from 9 to 5. This modified transpedicular screw augmentation with PMMA using anchoring effect is a simple and effective surgical technique for pedicle screw loosening. However, clinical analyses of long-term follow-up and biomechanical studies are needed.

Kang, Suk-Hyung; Kim, Kyoung-Tae; Park, Seung Won

2011-01-01

131

Recent results of the toroidal screw pinch SPICA 2  

NASA Astrophysics Data System (ADS)

With discharges in the slow screw pinch mode (without shock wave heating), high beta plasmas were studied. In this mode the power crowbar banks are switched on when the predischarge current and the bias field reach their maximum value. At these low plasma currents (less than 70 kA) the stabilization by the conducting wall could not prevent disastrous plasma-wall contact. It is concluded that for this mode of operation a pulsed vertical field is essential.

Lassing, H. S.; Lok, J.; Vandermeer, A. F. G.; Navratil, G. A.; Oepts, D.; Oomens, A. A. M.; Verreck, M.

1988-06-01

132

Algorithms for Joint Optimization of Stability and Diversity in Planning Combinatorial Libraries of Chimeric Proteins  

Microsoft Academic Search

In engineering protein variants by constructing and screen- ing combinatorial libraries of chimeric proteins, two complementary and competing goals are desired: the new proteins must be similar enough to the evolutionarily-selected wild-type proteins to be stably folded, and they must be dierent enough to display functional variation. We present here the first method, Staversity, to simultaneously optimize stability and diversity

Wei Zheng; Alan M. Friedman; Chris Bailey-kellogg

2008-01-01

133

Anterior transarticular screw fixation for atlantoaxial arthrodesis: A report of two cases.  

PubMed

The sequelae of atlantoaxial instability (AAI) range from axial neck pain to life-threatening neurologic injury. Instrumentation and fusion of the C1-2 joint is often indicated in the setting of clinical or biomechanical instability. This is the first clinical report of anterior Smith-Robinson C1-2 transarticular screw (TAS) fixation for AAI. The first patient presented with ischemic brain tissue secondary to post-traumatic C1-2 segment instability from a MVC 7 years prior to presentation. The second patient presented with a 3 year history of persistent right-sided neck and upper scalp pain. Both were treated with transarticular C1-2 fusion through decortication of the atlantoaxial facet joints and TAS fixation via the anterior Smith-Robinson approach. At 16 months follow-up, the first patient maintained painless range of motion of the cervical spine and denied sensorimotor deficits. The second patient reported 90% improvement in her pre-operative symptoms of neck pain and paresthesia. Anterior Smith-Robinson C1-2 TAS fixation provides a useful alternative to the posterior Goel and Magerl techniques for C1-2 stabilization and fusion. PMID:24737928

Carrier, C S; Sama, A A; Girardi, F P; Lebl, D R

2013-07-01

134

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

PubMed

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

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

2014-07-01

135

Surgical treatment of Rockwood grade-V acromioclavicular joint dislocations  

PubMed Central

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

2013-01-01

136

Stabilization of acute, complete acromioclavicular joint dislocations with a new C hook implant.  

PubMed

Although coracoclavicular fixation is currently popular for type III acromioclavicular (AC) dislocations, a surgical gold standard is lacking. The purpose of this study was to evaluate the preliminary outcome of surgical treatment of complete AC dislocations with a new nitinol C hook implant. When the implant is cooled (<5 degrees C), it softens enough to be easily inserted under the coracoid process with a hole drilled in the clavicle. Cooling is induced with ice water. When the implant reaches body temperature, it hardens and anatomic reduction is achieved. Patients with acute type III AC dislocations were prospectively evaluated. The AC ligament was reinserted with the use of a bone anchor, and the position of the joint was restored by fixing it with a new C hook. Clinical and radiographic control checkups were carried out at 3, 8, and 12 weeks and 2 years postoperatively. Certain patient-related variables, functional status, symptom severity, and patient satisfaction were assessed. By 12 weeks, all patients had achieved full functional status. Radiographs showed accurate anatomic reduction. Overall subjective satisfaction was very good in all cases. No complications or implant failures occurred. On the basis of this pilot study, the new C hook implant provides secure anatomic reduction with very good functional recovery and patient satisfaction. The main benefit of the implant is the ease of insertion. It preserves the articular surfaces and allows slight movement of the AC joint during abduction of the arm. The C hook implant is a new surgical concept with potentially better patient recovery. PMID:14564264

Ryhänen, Jorma; Niemelä, Erkki; Kaarela, Outi; Raatikainen, Timo

2003-01-01

137

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

PubMed Central

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

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

2008-01-01

138

Intra-operative computer navigation guided cervical pedicle screw insertion in thirty-three complex cervical spine deformities  

PubMed Central

Background: Cervical pedicle screw fixation is challenging due to the small osseous morphometrics and the close proximity of neurovascular elements. Computer navigation has been reported to improve the accuracy of pedicle screw placement. There are very few studies assessing its efficacy in the presence of deformity. Also cervical pedicle screw insertion in children has not been described before. We evaluated the safety and accuracy of Iso-C 3D-navigated pedicle screws in the deformed cervical spine. Materials and Methods: Thirty-three patients including 15 children formed the study group. One hundred and forty-five cervical pedicle screws were inserted using Iso-C 3D-based computer navigation in patients undergoing cervical spine stabilization for craniovertebral junction anomalies, cervico-thoracic deformities and cervical instabilities due to trauma, post-surgery and degenerative disorders. The accuracy and containment of screw placement was assessed from postoperative computerized tomography scans. Results: One hundred and thirty (89.7%) screws were well contained inside the pedicles. Nine (6.1%) Type A and six (4.2%) Type B pedicle breaches were observed. In 136 levels, the screws were inserted in the classical description of pedicle screw application and in nine deformed vertebra, the screws were inserted in a non-classical fashion, taking purchase of the best bone stock. None of them had a critical breach. No patient had any neurovascular complications. Conclusion: Iso-C navigation improves the safety and accuracy of pedicle screw insertion and is not only successful in achieving secure pedicle fixation but also in identifying the best available bone stock for three-column bone fixation in altered anatomy. The advantages conferred by cervical pedicle screws can be extended to the pediatric population also.

Rajasekaran, S.; Kanna, P. Rishi Mugesh; Shetty, T. Ajoy Prasad

2010-01-01

139

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

PubMed

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

Oda, Jon E; Thacker, Mihir M

2013-05-01

140

Slippage between screwdriver and bone screw.  

PubMed

Cortical 3.5-mm stainless steel screws with hexagonal heads and corresponding screwdrivers from two manufacturers were investigated. Measurement of dimensions and torsional testing were done to study slippage between the screw and the driver bit. There were only small differences in dimensions between the manufacturers. Ultimate torque values obtained were at the level of 2.7 N-m where reaming of the screw socket took place. Additional rotation resulted in approximately (1/2) of the maximum torque. Subsequent torque testing in the opposite direction, corresponding to removal of the screw, revealed that the torque values were equally low in that direction. Additional insertion and removal of bone screws with hexagonal sockets are hampered after only one episode of slippage. It is justified to consider new shapes of drive bits and corresponding screw head sockets, such as a fluted multiedge configuration. PMID:12439282

Behring, Jon K; Gjerdet, Nils R; Mølster, Anders

2002-11-01

141

New phenomena concerning a screw dislocation interacting with two imperfect interfaces  

Microsoft Academic Search

Dislocation mobility and stability in nanocrystals and electronic materials are influenced by the material composition and interface conditions. Its mobility and stability then affect the mechanical behaviors of the composites. In this paper, we first address, in detail, the problem of a screw dislocation located in an annular coating layer which is imperfectly bonded to the inner circular inhomogeneity and

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

2007-01-01

142

[Torque measurement of self-threading bone screws. Test procedure for new surgical screws].  

PubMed

Different systems of self-cutting screws are tested by a measuring instrument to test the torsional strain. Modern methods of measuring techniques are applied to get results of the torsional force and the torque by screwing into the bones. To get a self-cutting screw system several methods of biomechanical properties must be applied. A variety of quality tests, of biomechanical screws, are used, before performing the operations, that flaws may be detected. PMID:2639546

Heinl, T; Neumayer, B

1989-12-01

143

Intra-operative screw trimming in direct screw fixation of the odontoid process fracture — Technical note  

Microsoft Academic Search

Summary For a satisfactory direct screw fixation of fractures of the odontoid process it is necessary to use a screw of the proper total length and thread length, but such an optimal ready-made screw is not always available. The authors describe a technique of intra-operative screw trimming using a high-speed diamond drill. This adjustment is easily and quickly performed. It

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

1992-01-01

144

Biodegradable Interference Screw Fixation Exhibits Pull-Out Force and Stiffness Similar to Titanium Screws  

Microsoft Academic Search

Recently, increased interest in biodegradable interference screws for bone-tendon-bone graft fixation has led to numerous screws becoming available. The implants are made from different polymers and have different designs, which might influence their mechanical properties. Several studies have reported a wide range of mechanical results for these screws using different biomechanical models. The aim of the present study is to

Andreas Weiler; Henning J. Windhagen; Michael J. Raschke; Andrea Laumeyer; Reinhard F. G. Hoffmann

1998-01-01

145

A novel screw guiding method with a screw guide template system for posterior C-2 fixation.  

PubMed

Object Accurate insertion of C-2 cervical screws is imperative; however, the procedures for C-2 screw insertion are technically demanding and challenging, especially in cases of C-2 vertebral abnormality. The purpose of this study is to report the effectiveness of the tailor-made screw guide template (SGT) system for placement of C-2 screws, including in cases with abnormalities. Methods Twenty-three patients who underwent posterior spinal fusion surgery with C-2 cervical screw insertion using the SGT system were included. The preoperative bone image on CT was analyzed using multiplanar imaging software. The trajectory and depth of the screws were designed based on these images, and transparent templates with screw guiding cylinders were created for each lamina. During the operation, after templates were engaged directly to the laminae, drilling, tapping, and screwing were performed through the templates. The authors placed 26 pedicle screws, 12 pars screws, 6 laminar screws, and 4 C1-2 transarticular screws using the SGT system. To assess the accuracy of the screw track under this system, the deviation of the screw axis from the preplanned trajectory was evaluated on postoperative CT and was classified as follows: Class 1 (accurate), a screw axis deviation less than 2 mm from the planned trajectory; Class 2 (inaccurate), 2 mm or more but less than 4 mm; and Class 3 (deviated), 4 mm or more. In addition, to assess the safety of the screw insertion, malpositioning of the screws was also evaluated using the following grading system: Grade 0 (containing), a screw is completely within the wall of the bone structure; Grade 1 (exposure), a screw perforates the wall of the bone structure but more than 50% of the screw diameter remains within the bone; Grade 2 (perforation), a screw perforates the bone structures and more than 50% of the screw diameter is outside the pedicle; and Grade 3 (penetration), a screw perforates completely outside the bone structure. Results In total, 47 (97.9%) of 48 screws were classified into Class 1 and Grade 0, whereas 1 laminar screw was classified as Class 3 and Grade 2. Mean screw deviations were 0.36 mm in the axial plane (range 0.0-3.8 mm) and 0.30 mm in the sagittal plane (range 0.0-0.8 mm). Conclusions This study demonstrates that the SGT system provided extremely accurate C-2 cervical screw insertion without configuration of reference points, high-dose radiation from intraoperative 3D navigation, or any registration or probing error evoked by changes in spinal alignment during surgery. A multistep screw placement technique and reliable screw guide cylinders were the key to accurate screw placement using the SGT system. PMID:24785974

Kaneyama, Shuichi; Sugawara, Taku; Sumi, Masatoshi; Higashiyama, Naoki; Takabatake, Masato; Mizoi, Kazuo

2014-08-01

146

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

Microsoft Academic Search

BACKGROUND: Pedicle screws with PMMA cement augmentation have been shown to significantly improve the fixation strength in a severely osteoporotic spine. However, the efficacy of screw fixation for different cement augmentation techniques, namely solid screws with retrograde cement pre-filling versus cannulated screws with cement injection through perforation, remains unknown. This study aimed to determine the difference in pullout strength between

Lih-Huei Chen; Ching-Lung Tai; De-Mei Lee; Po-Liang Lai; Yen-Chen Lee; Chi-Chien Niu; Wen-Jer Chen

2011-01-01

147

Tricorrectional bunionectomy with AO screw fixation.  

PubMed

A 16-month preliminary study was performed on 58 patients for corrective surgery of hallux abducto valgus, with AO4 screw fixation. The procedure is a modification of the bi-plane Austin procedure, called a tricorrectional bunionectomy. The authors present the procedure with objective and subjective findings. The principles of bone healing and internal fixation using AO screw fixation are discussed. PMID:2625507

Boggs, S I; Selner, A J; Roth, I E; Bernstein, A L

1989-01-01

148

Solar power units with screw expanders  

Microsoft Academic Search

A low-power solar electric generator based on a screw expander which drives an ac motor is presented. The choices of flat plate or concentrating Rankine or Brayton cycle, and an oil-injected screw expander motor in the development of the unit are examined, and the effects of Mediterranean and subtropical locations on plant performance are discussed. Results of solar engine performance

J. M. Merigoux; P. Pocard

1980-01-01

149

Mechanics of the taper integrated screwed-in (TIS) abutments used in dental implants.  

PubMed

The tapered implant-abutment interface is becoming more popular due to the mechanical reliability of retention it provides. Consequently, understanding the mechanical properties of the tapered interface with or without a screw at the bottom has been the subject of a considerable amount of studies involving experiments and finite element (FE) analysis. This paper focuses on the tapered implant-abutment interface with a screw integrated at the bottom of the abutment. The tightening and loosening torques are the main factors in determining the reliability and the stability of the attachment. Analytical formulas are developed to predict tightening and loosening torque values by combining the equations related to the tapered interface with screw mechanics equations. This enables the identification of the effects of the parameters such as friction, geometric properties of the screw, the taper angle, and the elastic properties of the materials on the mechanics of the system. In particular, a relation between the tightening torque and the screw pretension is identified. It was shown that the loosening torque is smaller than the tightening torque for typical values of the parameters. Most of the tightening load is carried by the tapered section of the abutment, and in certain combinations of the parameters the pretension in the screw may become zero. The calculations performed to determine the loosening torque as a percentage of tightening torque resulted in the range 85-137%, depending on the values of taper angle and the friction coefficient. PMID:15519343

Bozkaya, Dinçer; Müftü, Sinan

2005-01-01

150

Techniques and accuracy of thoracolumbar pedicle screw placement  

PubMed Central

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

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

2014-01-01

151

Improved extraction torque of hydroxyapatite-coated pedicle screws.  

PubMed

Loosening of the screws is a problem in instrumentation with pedicle screws. Coating with hydroxyapatite improves the holding characteristics for metal implants, but the possible effects on the anchorage of pedicle screws have not been described. In this study, seven patients were operated on with spinal instrumentation using four stainless steel pedicle screws. Hydroxyapatite-coated screws were used in either the upper or the lower of the instrumented levels. The insertion torque was measured. In four cases the screws were removed after 10-22 months and the extraction torque was measured. The mean insertion torque was found to be significantly greater in the hydroxyapatite-coated screws (107 Ncm) than in the standard screws (76 Ncm). In three cases, the extraction torque for the hydroxyapatite-coated screws exceeded the range for the torque wrench (600 Ncm), while the conventional screws were loose (< 5 Ncm). In one case, the extraction torque was 475 and 550 Ncm for the coated screws, and 5 and 25 Ncm for the conventional screws. The difference in extraction torque was significant. Hydroxyapatite coating was shown to have improved the purchase of pedicle screws very effectively. By using fully coated screws, as in the present study, extraction was extremely difficult compared to extraction of conventional stainless steel screws, which were regularly loose. By reducing the area of the screws that is coated, it may be possible to achieve an enhanced purchase while extraction will be easier when compared to fully coated screws. PMID:11189923

Sandén, B; Olerud, C; Johansson, C; Larsson, S

2000-12-01

152

Evidence-based support for S1 transpedicular screw entry point modification  

PubMed Central

Background In the literature, ‘below and lateral to the superior S1 facet’ is defined as the basic technique for screw introduction. Until a recently published modification, no analysis for alternative starting point has been proposed nor evaluated, although some surgeons claim to use some modifications. In this study, we analyse the data from anatomical and radiological studies for optimal starting point in transpedicular S1 screw placement. Methods A Medline search for key word combination: sacrum, anatomy, pedicle, screws and bone density resulted in 26 publications relevant to the topic. After a review of literature, two articles were chosen, as those including the appropriate set of data. The data retrieved from the articles is used for the analysis. The spatial relation of S1 facet, pedicles and vertebral body with cortical thickness and bone density in normal, osteopenic and osteoporotic sacrum is analysed. Results Presented data advocates for more medial placement of the screws due to higher bone density and lower bone loss in osteoporosis. Medial shift of the starting point does not increase the risk of spinal canal perforation. Osteoarthritic changes within the facet can augment the posterior supporting point for screw. The facet angular orientation is similar to convergent screw trajectory. Conclusions Modified technique for S1 screw placement takes advantage of latest anatomical and clinical data. In our opinion, technique modification improves the reproducibility and may increase stability and the screws within the posterior cortex of the S1 vertebra. Further biomechanical and clinical study should be performed to prove its superiority to classical technique.

2014-01-01

153

Screw-released roller brake  

NASA Technical Reports Server (NTRS)

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.

Vranish, John M. (Inventor)

1999-01-01

154

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

PubMed

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

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

2014-03-01

155

Dislocation of the proximal tibiofibular joint in association with a tibial shaft fracture: two case reports and a literature review.  

PubMed

Dislocation of the proximal tibiofibular joint (PTFJ) in association with a displaced tibial shaft fracture and an intact fibula is an exceedingly rare injury. We present 2 cases of tibia fractures associated with an intact fibula and a PTFJ dislocation. The first case involves a man who sustained a closed spiral fracture of the distal tibial shaft, with an intact fibula, an anterolaterally dislocated PTFJ, and a partial tear of the lateral collateral ligament. The tibia was percutaneously plated, and the PTFJ was reduced and then stabilized with temporary screw fixation. The second case involves a woman who sustained a closed fracture of the tibia in association with a PTFJ dislocation. The tibia was fixed with an intramedullary nail, and the PTFJ was similarly reduced and fixed with a temporary screw. We also provide a brief literature review focusing on classification of PTFJ dislocations, mechanism of injury, associated injuries, and treatment options. PMID:17849030

Johnson, Bryce A; Amancharla, Maneesh R; Merk, Bradley R

2007-08-01

156

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

Microsoft Academic Search

Reconstruction after multilevel decompression of the cervical spine, especially in the weakened osteoporotic, neoplastic or\\u000a infectious spine often requires circumferential stabilization and fusion. To avoid the additional posterior surgery in these\\u000a cases while increasing rigidity of anterior-only screw-plate constructs, the authors introduce the concept of anterior transpedicular\\u000a screw (ATPS) fixation. We demonstrated its morphological feasibility as well as its indications

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

2008-01-01

157

The anatomic variability of human cervical pedicles: considerations for transpedicular screw fixation in the middle and lower cervical spine  

Microsoft Academic Search

Transpedicular screw fixation has recently been shown to be successful in stabilizing the middle and lower cervical spine.\\u000a Controversy exists, however, over its efficacy, due to the smaller size of cervical pedicles and the proximity of significant\\u000a neurovascular structures to both lateral and medial cortical walls. To aid the spinal surgeon in the insertion of pedicle\\u000a screws, a number of

Eon K. Shin; Manohar M. Panjabi; Neal C. Chen; Jaw-Lin Wang

2000-01-01

158

Screw pull-out force is dependent on screw orientation in an anterior cervical plate construct.  

PubMed

Two common justifications for orienting cervical screws in an angled direction is to increase pull-out strength and to allow use of longer screws. This concept is widely taught and has guided implant design. Fixed versus variable angle systems may offer strength advantages. The purpose of our study is to test the influence of screw orientation and plate design on the maximum screw pull-out load. Variable and fixed angle 4.0 x 15 mm and 4.0 x 13 mm self-tapping screws were used to affix a Medtronic Atlantis cervical plate to polyurethane foam bone samples (density 0.160/cm). This synthetic product is a model of osteoporotic cancellous bone. The fixed angle screws can only be placed at 12 degrees convergent to the midline and 12 degrees in the cephalad/caudal ("12 degrees up and in") direction. Three groups were tested: (1) all fixed angle screws, (2) variable angle, all screws 12 degrees up and in, (3) variable angle, all screws 90 degrees to the plate. Plate constructs were pulled off with an Instron DynaMight 8841 servohydrolic machine measuring for maximum screw pull-out force. There was no difference between group 1, fixed angle (288.4 +/- 37.7 N) (mean +/- SD) and 2, variable angle group (297.7 +/- 41.31 N P< or =0.73). There was a significant increase in maximum pull-out force to failure for the construct with all screws at 90 degrees (415.2+/-17.4 N) compared with all screws 12 degrees "up and in" (297.4 +/- 41.3 N, P< or =0.0016). Group 3 done with 13 mm screws, showed a trend toward better pull-out strength, compared to group 2 w/15 mm screws (345.2 +/- 20.5 vs. 297.4 +/- 41.3, P< or =0.06). In this plate pull-out model, screw orientation influences maximum force to failure. When all 4 screws are 90 degrees to the plate the construct has the greatest ability to resist pullout. Fixed angle designs show no advantage over variable angle. These findings are contrary to current teaching. PMID:17607102

DiPaola, Christian P; Jacobson, Justin A; Awad, Hani; Conrad, Bryan P; Rechtine, Glenn R

2007-07-01

159

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

PubMed Central

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

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

2005-01-01

160

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

PubMed Central

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

Cornelius, Carl-Peter; Ehrenfeld, Michael

2010-01-01

161

[Total joint arthroplasty].  

PubMed

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

Mibe, Junya; Yamamoto, Kengo

2013-07-01

162

Cervical anterior transpedicular screw fixation. Part I: Study on morphological feasibility, indications, and technical prerequisites.  

PubMed

Multilevel cervical spine procedures can challenge the stability of current anterior cervical screw-and-plate systems, particularly in cases of severe three-column subaxial cervical spine injuries and multilevel plated reconstructions in osteoporotic bone. Supplemental posterior instrumentation is therefore recommended to increase primary construct rigidity and diminish early failure rates. The increasing number of successfully performed posterior cervical pedicle screw fixations have enabled more stable fixations, however most cervical pathologies are located anteriorly and preferably addressed by an anterior approach. To combine the advantages of the anterior approach with the superior biomechanical characteristics of cervical pedicle screw fixation, the authors developed a new concept of a cervical anterior transpedicular screw-and-plate system. An in vivo anatomical study was performed to explore the feasibility of anterior transpedicular screw fixation (ATPS) in the cervical spine. The morphological study was conducted based on 29 cervical spine CT scans from healthy patients and measurements were performed on the pedicle sizes, angulations, vertebral body depth, height and width at C2 to T1. Significant morphologic parameters for the new technique are discussed. These parameters include the sagittal and transverse intersection points of the pedicle axis with the anterior vertebral body wall, as well as the distances between sagittal intersection points from C2 to T1. On the basis of these results, standard spine models were reconstructed and used for the conceptual development of a preclinical release prototype of an anterior transpedicular screw-and-plate system. The morphological feasibility of the new technique is demonstrated, and its indications, biomechanical considerations, as well as surgical prerequisites are thoroughly discussed. In the future, the technique of cervical anterior transpedicular screw fixation might diminish the number of failures in the reconstruction of multilevel and three-column cervical spine instabilities, and avoid the need for supplemental posterior instrumentation. PMID:18224358

Koller, Heiko; Hempfing, Axel; Acosta, Frank; Fox, Michael; Scheiter, Armin; Tauber, Mark; Holz, Ulrich; Resch, Herbert; Hitzl, Wolfgang

2008-04-01

163

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

Microsoft Academic Search

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

Chris Rorres

2000-01-01

164

Repair of meniscal tears with the absorbable Clearfix screw: results after 1–3 years  

Microsoft Academic Search

Introduction  Total meniscus resection usually leads to osteoarthritis of the knee joint. Preservation and refixation of the injured menisci are therefore of great clinical importance.Materials and methods  The present study examines 40 meniscal injuries in 37 patients that were arthroscopically treated with Clearfix meniscal screws (Mitek, Norderstedt, Germany) in the period from August 1999 to December 2002. The mean patient age was

K.-H. Frosch; M. Fuchs; A. Losch; K. M. Stürmer

2005-01-01

165

[Endoprosthesis of the shoulder joint designed by the authors - surgical technique.].  

PubMed

Endoprostheses of the shoulder joint are nowadays already standard procedures in the surgical repertoir of orthopaedic and traumatological departments. Indication for the operation are degenerative diseases with destruction of the articular surface, non-reconstructible fractures of the upper end of the humerus, in particular in elderly patients and tumours in the area of the proximal portion of the humerus. The main cause of inadequate function of endoprostheses of the shoulder joint is insufficiency of the rotator cuff. This may be due either to its primary destruction by the basic disease (e. g. rheumatoid arthritis) or imperfect reconstruction during surgery. The majority of authors use during reconstruction of the rotator cuff a simple procedure, i. e. suture to the proximal portion of the endoprosthesis. In some instances the implementation of the suture is difficult or there is the risk the stiches will cut through during rehabilitation. Favourable experience with reconstruction of the rotator cuff during non-anatomical reconstruction of fractures of the proximal humerus by screwing of the insertion lamellae of the greater and lesser tubercle made the authors try to use this principle in the construction of a new type of endoprosthesis, which is described in detail in the submitted paper. Subsequently the authors describe also differences in the surgical technique during implantation of the endoprosthesis in patients with degenerative diseases and in traumatological indications. In their opinion the advantage is that in traumatic indications of replacement of the shoulder joint the suggested implant makes reliable and relatively easy fixation of both tubercles with insertions of the rotator cuff to the endoprosthesis possible and simultaneously also attachment to the fragment of the diaphysis. In fragments of the greater tubercle this can be achieved by the use of a clawed splint which is fixed by one screw inserted via the corticalis of the diaphysis into the stem of the endoprosthesis. This ensures the stability of the endoprosthesis in the proximo-distal direction as well as against rotation. The fragment of the lesser tubercle is fixed by one screw to the body of the endoprosthesis. The authors assume that reconstruction of the rotator cuff and at the same time stabilization of the shank of the endoprosthesis by one screw and a clawed splint differs fundamentally and is a new approach to the solution of this very complicated problem. Despite the initial clinical experience the authors are aware of certain technical shortcomings of the implant and instrumentarium and continue to work on their elimination. Key words: endoprosthesis of the shoulder joint, reconstruction of the rotator cuff. PMID:20470573

Sosna, A; Fric, V

1996-01-01

166

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

PubMed Central

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

HUANG, WEIJIE; LUO, TAO

2013-01-01

167

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

NASA Astrophysics Data System (ADS)

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

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

2010-03-01

168

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

PubMed Central

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

2014-01-01

169

Temperature calculation for extruder screws with internal heat pipes  

NASA Astrophysics Data System (ADS)

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

Lakemeyer, C.; Schöppner, V.

2014-05-01

170

Evaluation of long-term antinociceptive properties of stabilized hyaluronic acid preparation (NASHA) in an animal model of repetitive joint pain  

PubMed Central

Introduction Clinical trials provided controversial results on whether the injection of hyaluronan preparations into osteoarthritic joints reduces pain. Problems of clinical studies may be the substantial placebo effects of intra-articular injections, different severity and rate of progression of the disease and others. We hypothesize that the use of preclinical pain models may help to clarify whether a certain hyaluronan exerts antinociceptive effects upon intra-articular injection. In the present study we tested in the bradykinin/prostaglandin E2 (PGE2) model primarily the putative antinociceptive effect of stabilized hyaluronic acid from a non animal source (NASHA), a stabilized hyaluronic acid based gel for intra-articular treatment of OA. We established a dose-response relationship for NASHA and we compared NASHA to other hyaluronans with different formulations that are in clinical use. Methods To induce transient joint pain episodes bradykinin and PGE2 were repetitively administered intra-articularly and unilaterally into rat knee joints during short anaesthesia. After establishment of the predrug nociceptive responses, a single intra-articular injection of saline or NASHA at different concentrations was administered and pain responses to further bradykinin/PGE2 injections were monitored up to 56 days after NASHA. Furthermore, the obtained effective dose was compared to clinically defined concentrations of Hylan GF20 and sodium hyaluronate. The primary outcome measures were primary mechanical hyperalgesia at the knee joint and pain-induced weight bearing. Results On day 1 after injection, all tested hyaluronan preparations showed an antinociceptive effect >50% compared to saline. Single injections of higher doses of NASHA (50, 75 and 100 ?l) were antinociceptive up to 56 days. When injection volumes in rat knee joints were adapted to clinical injection volumes in humans, the antinociceptive effects of the cross-linked NASHA and Hylan GF20 had a longer duration than that of the non cross-linked sodium hyaluronate (with a slightly better effect of NASHA than Hylan GF20). Conclusions In the bradykinin/PGE2 model of joint pain a single injection of all hyaluronan preparations provided significant antinociceptive effects compared to saline. It appeared that the duration of the antinociceptive effect of the cross-linked hyaluronan preparations NASHA and Hylan GF20 was more prolonged. In addition, the gel beads structure allowing only a slow release of hyaluronic acid (NASHA) may even enhance this prolonged antinociceptive effect.

2011-01-01

171

Apparatus to test insertion and removal torque of bone screws.  

PubMed

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

Koistinen, A; Santavirta, S; Lappalainen, R

2003-01-01

172

Screw expander for light duty diesel engines  

NASA Technical Reports Server (NTRS)

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

1983-01-01

173

Low energy high pressure miniature screw valve  

DOEpatents

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.

Fischer, Gary J. (Sandia Park, NM); Spletzer, Barry L. (Albuquerque, NM)

2006-12-12

174

Effect of screw diameter, insertion technique, and bone cement augmentation of pedicular screw fixation strength.  

PubMed

This study investigated (1) the effect of screw diameter and insertion technique in lumbar vertebrae, and insertion site in the sacrum, on the axial pullout force and transverse bending stiffness of pedicle screws, and (2) the effect of bone cement augmentation using polymethylmethacrylate (PMMA) and the biodegradable composite, poly(propylene glycol-fumarate) on axial pullout force and transverse bending stiffness of pedicle screws inserted into lumbar vertebrae. The axial pullout force and transverse bending stiffness of a 6.25-mm Steffee screw and a 6-mm Kluger screw did not differ significantly in vertebral bodies of similar equivalent bone mineral density. The axial pullout force of Schanz screws was significantly increased with a 1-mm increase in screw diameter. However, there was no significant increase in transverse bending stiffness. In the sacrum, an approach through the S1 facet produced significantly higher axial pullout forces and transverse bending stiffness than the approach described by Harrington and Dickson. PMMA and a biodegradable composite bone cement poly(propylene glycol-fumarate) both increased the axial pullout force. PMMA also increased the transverse bending stiffness. PMID:8222439

Wittenberg, R H; Lee, K S; Shea, M; White, A A; Hayes, W C

1993-11-01

175

[Luxation-fractures of the radiocarpal joint. Clinical study of 6 cases and general review].  

PubMed

The authors present a series of six cases of radio-carpal fracture-dislocation, which occurred between 1978 and 1989. The results were analysed with a follow-up of between 3 months and 11 years. This rare lesion (0.2% of all joint dislocations) is often caused by a severe injury, although the mechanism remains obscure. Radiological lesions consist of a combination of anterior or posterior carpal dislocation, fractures of the radial styloid and ulnar styloid processes, fracture of the anterior or posterior lip of the radius. This association of radiological lesion was also found in review of literature so that radio-carpal fracture-dislocation can be considered to be a real and a distinct entity. The authors recommend a surgical treatment, after immediate joint reduction, including stabilization with cancellous screw, sometimes Kirschner wires. However, anatomic reduction must be obtained, to ensure a good functional result. PMID:1712614

Le Nen, D; Riot, O; Caro, P; Le Fevre, C; Courtois, B

1991-01-01

176

Transarticular screw fixation of C1-2 for the treatment of arthropathy-associated occipital neuralgia.  

PubMed

Two patients with occipital neuralgia due to severe arthropathy of the C1-2 facet joint were treated using atlantoaxial fusion with transarticular screws without decompression of the C-2 nerve root. Both patients experienced immediate postoperative relief of occipital neuralgia. The resultant motion elimination at C1-2 eradicated not only the movement-evoked pain, but also the paroxysms of true occipital neuralgia occurring at rest. A possible pathophysiological explanation for this improvement is presented in the context of the ignition theory of neuralgic pain. This represents the first report of C1-2 transarticular screw fixation for the treatment of arthropathy-associated occipital neuralgia. PMID:21214317

Pakzaban, Peyman

2011-02-01

177

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

PubMed Central

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

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

2007-01-01

178

Critical-heat-flux experiment on the screw tube under one-sided-heating conditions  

SciTech Connect

Development of high-heat-flux components such as the divertor plate of fusion experimental machines is essential for removal of high heat loads with heating on one side. For this purpose, the authors machined a tube with an inside wall like a nut, namely, a screw tube, to enhance heat transfer efficiency and simplify the machining process. The screw tube is compared with a swirl tube, originally developed by Oak Ridge National Laboratory, and the Hypervapotron, developed by Joint European Torus (JET). The spirally machined inside wall can enlarge the heat transfer area and make a little vortex flow only close to the wall. The performance of the screw tube is characterized by a critical-heat-flux experiment that uses water flow velocities ranging from 4 to 20 m/s with a water inlet pressure of 1.0 MPa. As a result, the screw tube has a higher incidence of CHFs compared with the smooth tube and the Hypervapotron and performs similarly to the swirl tube at identical flow velocities. 15 refs., 10 figs., 2 tabs.

Araki, Masanori; Sato, Kazuyoshi; Suzuki, Satoshi; Akiba, Masato [Japan Atomic Energy Research Inst., Ibaraki (Japan)

1996-07-01

179

Improving Interagency Planning and Execution at the Operational Level: Creating a Stability and Reconstruction Component Within a Joint Task Force.  

National Technical Information Service (NTIS)

Over the past fifteen years, many have argued that the military's overwhelming battlefield successes stem from the Goldwater-Nichols Defense Reformation Act of 1986. While few can debate the efficacy of joint US military operations in a high-intensity con...

M. P. Dombrowski

2006-01-01

180

Stiffness between different directions of transpedicular screws and vertebra  

Microsoft Academic Search

Objective. This study was undertaken to evaluate the variation in bone density within the vertebral body and to determine the biomechanical stiffness of the screw-bone interface for different superior-inferior transpedicular screw orientations in the vertebral body.Design. The stiffness of three directions of screw placement (upper, middle, and lower) were measured in two modes of loading (flexion and torsion). All screws

Shing-Sheng Wu; W. Thomas Edwards; Hansen A. Yuan

1998-01-01

181

Plasma processing for inducing bioactivity in stainless steel orthopaedic screws  

Microsoft Academic Search

The work presented in this paper is centred on applying plasma processing for inducing bioactivity (ability of a material to bond with bone) in otherwise bioinert stainless steel screws commonly used in orthopaedic surgery. As-received cortical stainless steel screws were hydroxylated using a patented two-step plasma process developed by the authors. The bioactivity of the screws thus processed was investigated

Sunil Kumar; Darren Simpson; Roger St. C. Smart

2007-01-01

182

Self-tapping screw fixation of the Austin osteotomy.  

PubMed

The authors present an alternative method of fixation for the Austin bunionectomy using the Richards self-tapping screw. A description of the screw and method of application is included. In more than 250 osteotomies fixated by this technique, no complications inherent to the self-tapping screw have been encountered. PMID:2319102

Klein, M S; Ognibene, F A; Erali, R P; Hendrix, C L

1990-01-01

183

Biomechanical evaluation of a new composite bioresorbable screw.  

PubMed

A new bioresorbable composite cannulated screw has been developed for small bone fracture fixation. The LG ("Little Grafter") screw is manufactured from Biosteon, which is a composite of poly L-lactic acid and hydroxyapatite. This study aimed to compare interfragmentary compression generated by this new screw with conventional metal screws commonly used in scaphoid fracture fixation. Four small metallic screws were compared with the LG screw, using a bone model produced from rigid polyurethane foam. The screws included the Acutrak, Asnis III, Herbert and Herbert-Whipple screws. The mean maximum compression forces for the LG screw, the Asnis and the Acutrak were comparable (LG 32.3 N, Asnis 32.8 N, Acutrak 38.3 N), whereas those using the Herbert and the Herbert-Whipple screw were significantly lower (Herbert 21.8 N, Herbert-Whipple 19.9 N). The bioresorbable LG screw has been shown to have good compressive properties compared to commonly used small bone fragment compression screws. PMID:16361004

Bailey, C A; Kuiper, J H; Kelly, C P

2006-04-01

184

Nylon screws make inexpensive coil forms  

NASA Technical Reports Server (NTRS)

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.

Aucoin, G.; Rosenthal, C.

1978-01-01

185

Computer simulation of screw dislocation in aluminum  

NASA Technical Reports Server (NTRS)

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

Esterling, D. M.

1976-01-01

186

Improvements to the single screw extruder  

NASA Technical Reports Server (NTRS)

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.

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

1977-01-01

187

Improvements In Ball-Screw Linear Actuators  

NASA Technical Reports Server (NTRS)

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

Iskenderian, Theodore; Joffe, Benjamin; Summers, Robert

1996-01-01

188

Radiographic study of iliac screw passages  

PubMed Central

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

2014-01-01

189

Lapidus bunionectomy: Early evaluation of crossed lag screws versus locking plate with plantar lag screw.  

PubMed

We compared outcomes of the Lapidus bunionectomy fixated with crossed lag screws versus a locking plate with a plantar lag screw. Forty patients who underwent Lapidus bunionectomy between August 2001 and May 2006 were evaluated in a combined retrospective and prospective fashion. Crossed lag screws were used in 19 of the patients, and a locking plate with a plantar lag screw was used in 21 of the patients. Other than fixation, the only interventional difference pertained to postoperative weight bearing, where those receiving the plate initiated full weight bearing on the operated foot at 4 weeks postoperative, as compared to 6 weeks for those receiving crossed screws. Overall, the mean preoperative AOFAS hallux score was 41.75 +/- 2.52, and the postoperative score was 90.48 +/- 8.41 (P < .0001). The overall mean preoperative first intermetatarsal angle was 15.3 degrees +/- 2.32 degrees , and long term the angle was 5.03 degrees +/- 2.86 degrees (P < .0001). When comparisons were made based on the method of fixation, use of an adjunct Akin osteotomy and surgery performed before 2003 were statistically significantly associated with crossed screw fixation, and the preoperative AOFAS score was statistically significantly higher in the locking plate fixation group. There were no statistically significant differences related to postoperative complications between the 2 fixation groups. In conclusion, the Lapidus bunionectomy fixated with a locking plate and a plantar lag screw allows earlier weight bearing in comparison with crossed lag screws, without a difference in complications. Level of Clinical Evidence: 2. PMID:19232969

Saxena, Amol; Nguyen, Aidan; Nelsen, Elise

2009-01-01

190

Multifragmentary Tibial Pilon Fractures: Midterm Results After Osteosynthesis with External Fixation and Multiple Lag Screws  

PubMed Central

Osteosynthesis of intraarticular tibial pilon fractures is preferably achieved using locking plates via a minimally invasive technique. If combined with severe soft tissue damage there is a high risk of wound-healing deficits after plate osteosynthesis. Thus our aim was to find an alternative method of treatment for those cases with combined soft tissue injuries. We report on five cases with comminuted fractures of the joint surface combined with critical soft tissue condition that were treated with lag screws and external fixation (AO) applied across the ankle joint. All five patients were followed up, undergoing clinical and radiological examination. Using this approach we achieved fracture healing of comminuted fractures without further complications. Clinical follow-up after an average of 55.6 (36–75) months revealed a mean AOFAS score of 81 (62–100). We therefore propose combined treatment using lag screws with external fixation as a practical treatment option for those fractures for which lag screws combined with a locking plate are not feasible or when there is a high risk of wound-healing deficits due to severe soft tissue damage.

Kiene, Johannes; Herzog, Jan; Jurgens, Christian; Paech, Andreas

2012-01-01

191

Failure of femoral head fixation: a cadaveric analysis of lag screw cut-out with the gamma locking nail and AO dynamic hip screw  

Microsoft Academic Search

The most commonly reported failure mode of sliding hip screws in published literature is cut-out of the lag screw. This study investigates the resistance to failure of the femoral head, with lag screws used in two types of sliding hip screws, the gamma locking nail (Howmedica) and the dynamic hip screw (DHS) (Synthes). The investigation consisted of biomechanical tests under

R. C. Haynes; R. G. Pöll; A. W. Miles; R. B. Weston

1997-01-01

192

Joint effects of pleiotropic selection and stabilizing selection on the maintenance of quantitative genetic variation at mutation-selection balance.  

PubMed

In quantitative genetics, there are two basic "conflicting" observations: abundant polygenic variation and strong stabilizing selection that should rapidly deplete that variation. This conflict, although having attracted much theoretical attention, still stands open. Two classes of model have been proposed: real stabilizing selection directly on the metric trait under study and apparent stabilizing selection caused solely by the deleterious pleiotropic side effects of mutations on fitness. Here these models are combined and the total stabilizing selection observed is assumed to derive simultaneously through these two different mechanisms. Mutations have effects on a metric trait and on fitness, and both effects vary continuously. The genetic variance (V(G)) and the observed strength of total stabilizing selection (V(s,t)) are analyzed with a rare-alleles model. Both kinds of selection reduce V(G) but their roles in depleting it are not independent: The magnitude of pleiotropic selection depends on real stabilizing selection and such dependence is subject to the shape of the distributions of mutational effects. The genetic variation maintained thus depends on the kurtosis as well as the variance of mutational effects: All else being equal, V(G) increases with increasing leptokurtosis of mutational effects on fitness, while for a given distribution of mutational effects on fitness, V(G) decreases with increasing leptokurtosis of mutational effects on the trait. The V(G) and V(s,t) are determined primarily by real stabilizing selection while pleiotropic effects, which can be large, have only a limited impact. This finding provides some promise that a high heritability can be explained under strong total stabilizing selection for what are regarded as typical values of mutation and selection parameters. PMID:12242254

Zhang, Xu-Sheng; Hill, William G

2002-09-01

193

MR imaging for early complications of transpedicular screw fixation.  

PubMed

This series comprises ten patients treated with transpedicular screw fixation, who suffered early postoperative problems such as radicular pain or motor weakness. Besides plain radiographs, all patients were also evaluated with MR imaging. Three patients were reoperated for either repositioning or removal of the screws. MR images, especially T1-weighted ones, were very helpful for visualizing the problem and verifying the positions of the screws. In cases of wide areas of signal void around the screws, the neighboring axial MR images at either side, which have fewer artifacts, gave more information about the screws and the vertebrae. PMID:10333155

Colak, A; Kutlay, M; Demircan, N; Seçer, H I; Kibici, K; Ba?ekim, C

1999-01-01

194

Addition of an anti-rotation screw to the dynamic hip screw for femoral neck fractures.  

PubMed

The authors investigated the use of an anti-rotation screw with the dynamic hip screw (DHS) during internal fixation of Garden I and II femoral neck fractures. Sixty-five patients with Garden I and II femoral neck fractures (mean age, 70 years) were treated with internal fixation at the authors' institution. In 31 patients, a 2-hole DHS was used alone (group 1), and in 34 patients, the DHS was combined with an anti-rotation screw placed in the cranial part of femoral head and neck (group 2). Patients' preinjury function and mental level were assessed using the Barthel index and the Abbreviated Mental test, respectively. The outcome measures included cost implications, operative time, and intraoperative radiation dose. The modified Harris Hip Score and a radiological assessment were performed at a mean of 11 months (range, 8-24 months) postoperatively. The use of the anti-rotation screw was associated with a longer operative time (mean, 44.54 minutes in group 1 vs 51.52 minutes in group 2; P<.0001) and more fluoroscopy screening (mean dose area product, 28.39 cGy/cm(2) in group 1 vs 44.33 cGy/cm(2) in group 2; P=.03). The additional cost of using an anti-rotation screw was £106 ($170) per case. No difference existed between the 2 groups with regard to radiological union, onset of avascular necrosis, and rate of revision surgeries. An anti-rotation screw, used with the dynamic hip screw, involves extra costs, prolongs operative time, and requires more intraoperative fluoroscopy screening but offers no advantages with regard to fracture union. PMID:23823042

Makki, Daoud; Mohamed, Ahmed M; Gadiyar, Rajeev; Patterson, Marc

2013-07-01

195

In vivo surface analysis of titanium and stainless steel miniplates and screws.  

PubMed

This study was undertaken to characterize the surfaces of Champy titanium and stainless steel miniplates and screws that had been used to stabilize fractures of the mandible in an animal model. Miniplates and screws were retrieved at 4, 12, and 24 weeks after surgery. Low-vacuum scanning electron microscopy (SEM) of autoclaved unused (control) and test miniplates from the same production batches was undertaken. Energy-dispersive X-ray (EDX) analysis was used to identify compositional variations of the miniplate surface, and Vickers hardness testing was performed. At autopsy, clinical healing of all fractures was noted. SEM analysis indicated no perceptible difference in the surface characteristics of the miniplates at all time intervals. Aluminium and silicon deposits were identified by EDX analysis over the flat surfaces. There was extensive damage to some screw heads. It is concluded that there were no significant changes in the surface characteristics of miniplates retrieved up to 24 weeks after implantation in comparison with controls. Damage to the screws during insertion due to softness of the materials may render their removal difficult. There was no evidence to support the routine removal of titanium or stainless steel miniplates because of surface corrosion up to 6 months after implantation. PMID:8986551

Matthew, I R; Frame, J W; Browne, R M; Millar, B G

1996-12-01

196

Outcome of the Dynamic Helical Hip Screw System for Intertrochanteric Hip Fractures in the Elderly Patients  

PubMed Central

Introduction: The dynamic helical hip system (DHHS; Synthes, Paoli, Pennsylvania) differs from the standard dynamic sliding hip screw (SHS) in that in preparing for its insertion, reaming of the femoral head is not performed, thereby preserving bone stock. It also requires less torque for insertion of the helical screw. The associated plate has locking options to allow locking screw fixation in the femoral shaft, thereby decreasing the chance of the plate pulling off. While biomechanical studies have shown improved resistance to cutout and increased rotational stability of the femoral head fragment when compared with traditional hip lag screws, there is limited information on clinical outcome of the implant available in the literature. Methods: We report a single surgeon series of 87 patients who were treated for their per-trochanteric hip fractures with this implant to evaluate their clinical outcome and compare it with a cohort of 344 patients who were treated with the standard SHS. All data were prospectively collected, most as part of a structured Geriatric Fracture Care Program. Results: The 2 groups were similar demographically, and medically, with similar rates of in-hospital complications and implant failure. Failure in the DHHS group was attributable to use of the implant outside its indications and repeated fall of the patient. Conclusion: This limited case series showed that the DHHS outcomes are comparable with that of the SHS. Whether there is any benefit to its use will require larger, prospective randomized controlled trials.

O'Malley, Natasha T.; Deeb, Andrew-Paul; Bingham, Karilee W.; Kates, Stephen L.

2012-01-01

197

Cervical pedicle screw placement: feasibility and accuracy of two new insertion techniques based on morphometric data  

Microsoft Academic Search

This morphometric and experimental study was designed to assess the dimensions and axes of the subaxial cervical pedicles\\u000a and to compare the accuracy of two different techniques for subaxial cervical pedicle screw (CPS) placement using newly designed\\u000a aiming devices. Transpedicular fixation is increasingly used for stabilizing the subaxial cervical spine. Development of the\\u000a demanding technique is based on morphometric studies

M. Reinhold; F. Magerl; M. Rieger; M. Blauth

2007-01-01

198

Chitosan-coated Stainless Steel Screws for Fixation in Contaminated Fractures  

Microsoft Academic Search

Stainless steel screws and other internal fixation devices are used routinely to stabilize bacteria-contaminated bone fractures\\u000a from multiple injury mechanisms. In this preliminary study, we hypothesize that a chitosan coating either unloaded or loaded\\u000a with an antibiotic, gentamicin, could lessen or prevent these devices from becoming an initial nidus for infection. The questions\\u000a investigated for this hypothesis were: (1) how

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

2008-01-01

199

In vitro evaluation of conventional and locking miniplate\\/screw systems for the treatment of mandibular angle fractures  

Microsoft Academic Search

This in vitro study evaluated the influence of the type of miniplate and the number of screws installed in the proximal and distal segments on the stability and resistance of Champy's osteosynthesis in mandibular angle fractures. Sixty polyurethane hemimandibles with bone-like consistency were randomly assigned to four groups (n=15) and sectioned in the mandibular angle region to simulate fracture. The

P. D. Ribeiro-Junior; O. Magro-Filho; K. A. Shastri; M. B. Papageorge

2010-01-01

200

Orthogonal biplanar fluoroscopy-guided percutaneous fixation of a coracoid base fracture associated with acromioclavicular joint dislocation.  

PubMed

Coracoid process fractures that involve the coracoid base (inferior pillar) without a concomitant rupture of the coracoclavicular ligaments can destabilize the acromioclavicular joint with its subsequent dislocation; prophylactic or therapeutic operative treatment involving open reduction and internal fixation has been traditionally recommended. This report presents a new technique of percutaneous reduction and stabilization of the coracoid fracture with indirect acromioclavicular joint reduction under fluoroscopic guidance; biplanar visualization of coracoid process anatomy is obtained using 2 specific radiographic/fluoroscopic-beam angulations (Bhatia views), and this permits a guided placement of screws for controlled reduction of this dual injury. The technique is based on the author's original work on coracoid process anatomy and development of radiographic views for orthogonal visualization of coracoid pillars in their entirety. Technical tips to facilitate percutaneous fracture fixation and to avoid potential complications are discussed. PMID:22411122

Bhatia, Deepak N

2012-03-01

201

Sliding screw implants for extracapsular hip fractures.  

PubMed

Hip fractures are associated with significant mortality and morbidity for the patients, more dependent residual status, and increased socio-economic cost. Many hip-fracture patients experience severe functional impairment, and most never recover their pre-fracture level of function. Current research has sought to identify the most effective treatments to reduce the incidence of hip fractures, improve survival and quality of life, and minimize complications and disability. The treatment of these fractures in the elderly aims to return these people to their pre-fracture mobility and functional level. This article reviews the surgical treatment options for extracapsular hip fractures and discusses their associated advantages, disadvantages, and complications. Two types of implants are currently available: the dynamic hip screw (DHS), and the intramedullary hip nail with one or two sliding screws. In this review, no clear advantage of one implant over another for the treatment of extracapsular hip fractures was evident. Both the DHS and hip nails can be used successfully for the treatment of stable hip fractures; for unstable fractures and low subtrochanteric fractures, hip nails are preferred. Although hip nails are associated with limited exposure, lower blood loss and transfusion requirements, and shorter operative time, complications are more common with hip nails. Long-term survival and function are similar in the two approaches. Hip nails with two sliding screws do not seem to make the difference in clinical practice that is reported in biomechanical studies. PMID:23016784

Mavrogenis, Andreas F; Kouvidis, George; Stavropoulos, Nikolaos A; Stavrakakis, Loannis; Katonis, Pavlos; Papagelopoulos, Panayiotis J

2012-01-01

202

Factors affecting the pullout strength of cancellous bone screws.  

PubMed

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

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

1996-08-01

203

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

PubMed Central

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

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

2014-01-01

204

Dual load path ball screw with rod end swivel  

NASA Technical Reports Server (NTRS)

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

Wngett, Paul (Inventor)

2002-01-01

205

Modeling the Parker instability in a rotating plasma screw pinch  

NASA Astrophysics Data System (ADS)

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

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

2012-02-01

206

Screw-matrix method in dynamics of multibody systems  

Microsoft Academic Search

In the present paper the concept of screw in classical mechanics is expressed in matrix form, in order to formulate the dynamical\\u000a equations of the multibody systems. The mentioned method can retain the advantages of the screw theory and avoid the shortcomings\\u000a of the dual number notation. Combining the screw-matrix method with the tool of graph theory in Roberson\\/Wittenberg formalism.

Liu Yanzhu

1988-01-01

207

Clinical application of C2 laminar screw technique  

Microsoft Academic Search

C2 laminar screws have become an increasingly used alternative method to C2 pedicle screw fixation. However, the outcome of\\u000a this technique has not been thoroughly investigated. A total of 35 cases with upper cervical spinal instability undergoing\\u000a C2 laminar screw fixation were reviewed. All cases had symptoms of atlantoaxial instability, such as craniocervical junction\\u000a pain, and were fixed with the

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

2010-01-01

208

Simulation and analysis of resin flow in injection machine screw  

Microsoft Academic Search

A method with simulation and analysis of the resin flow in a screw is presented to ease the control of some problems that\\u000a may affect the efficiency and the quality of the product among existing screws in an injection machine. The physical model\\u000a of a screw is established to represent the stress, the strain, the relationship between velocity and stress,

Ling-feng Li; Samir Mekid

2008-01-01

209

Biomechanical comparison of screw-in suture anchor–suture combinations used for Bankart repair  

Microsoft Academic Search

Introduction  Bankart repair laxity may contribute to pathologic joint instability. This biomechanical study compared two screw-in suture\\u000a anchor–suture combinations under tensile loads.\\u000a \\u000a \\u000a \\u000a Methods  Twelve pairs of scapulae were implanted with either a 3 mm diameter, 14 mm long poly-l\\/d-lactide suture anchor with a suture eyelet (Group 1) or a 3.1 mm diameter, 11 mm long polylactide suture anchor with a molded\\u000a eyelet (Group 2). Constructs were

Brad S. Sparks; John Nyland; Akbar Nawab; Ethan Blackburn; Ryan Krupp; David N. M. Caborn

2010-01-01

210

Bilateral C1 laminar hooks combined with C2 pedicle screws fixation for treatment of C1-C2 instability not suitable for placement of transarticular screws.  

PubMed

The study design described here is a posterior C1-C2 fusion technique composed of bilateral C1 hooks and C2 pedicle screws. In addition, the clinical results of using this method on 13 patients with C1-C2 instability are reported. The objectives are to introduce a new technique for posterior C1-C2 fusion and to evaluate the clinical outcome of using it to treat C1-C2 instability. From October 2006 to August 2008, 13 patients (9 men and 4 women) with C1-C2 instability were included in this study: 3 had acute odontoid fractures, 4 had obsolete odontoid fractures, 4 had os odontoideum and 2 had traumatic rupture of the transverse ligament. All patients underwent posterior atlantoaxial fixation with bilateral C1 hooks and C2 pedicle screws. The mean follow-up duration was 25 months (range 13-30 months). Each patient underwent a complete cervical radiograph series, including anterior-posterior, lateral, and flexion-extension views, and a computed tomographic scan. The clinical course was evaluated according to the Frankel grading system. No clinically manifested injury of the nerve structures or the vertebral artery was observed in any of these cases. Five patients with neurological symptoms showed significant improvement in neurological function postoperatively. Bony fusion and construction stability were observed in all 13 patients (100%) on their follow-up radiographs, and no instrument failure was observed. Bilateral C1 hooks combined with C2 pedicle screws can be used as an alternative treatment method for C1-C2 dislocation, especially in cases not suitable for the use of transarticular screws. The clinical follow-up shows that this technique is a safe and effective method of treatment. PMID:20229279

Ni, Bin; Zhu, Zhuangchen; Zhou, Fengjin; Guo, Qunfeng; Yang, Jian; Liu, Jun; Wang, Fei

2010-08-01

211

Bilateral C1 laminar hooks combined with C2 pedicle screws fixation for treatment of C1-C2 instability not suitable for placement of transarticular screws  

PubMed Central

The study design described here is a posterior C1–C2 fusion technique composed of bilateral C1 hooks and C2 pedicle screws. In addition, the clinical results of using this method on 13 patients with C1–C2 instability are reported. The objectives are to introduce a new technique for posterior C1–C2 fusion and to evaluate the clinical outcome of using it to treat C1–C2 instability. From October 2006 to August 2008, 13 patients (9 men and 4 women) with C1–C2 instability were included in this study: 3 had acute odontoid fractures, 4 had obsolete odontoid fractures, 4 had os odontoideum and 2 had traumatic rupture of the transverse ligament. All patients underwent posterior atlantoaxial fixation with bilateral C1 hooks and C2 pedicle screws. The mean follow-up duration was 25 months (range 13–30 months). Each patient underwent a complete cervical radiograph series, including anterior–posterior, lateral, and flexion–extension views, and a computed tomographic scan. The clinical course was evaluated according to the Frankel grading system. No clinically manifested injury of the nerve structures or the vertebral artery was observed in any of these cases. Five patients with neurological symptoms showed significant improvement in neurological function postoperatively. Bony fusion and construction stability were observed in all 13 patients (100%) on their follow-up radiographs, and no instrument failure was observed. Bilateral C1 hooks combined with C2 pedicle screws can be used as an alternative treatment method for C1–C2 dislocation, especially in cases not suitable for the use of transarticular screws. The clinical follow-up shows that this technique is a safe and effective method of treatment.

Zhu, Zhuangchen; Zhou, Fengjin; Guo, Qunfeng; Yang, Jian; Liu, Jun; Wang, Fei

2010-01-01

212

Electro-magnetic archimedean screw motor-generator  

US Patent & Trademark Office Database

An Archimedes' screw serves as a rotor, inducer, impeller, and/or driver with motor and/or generator configurations that surround the screw by attaching to an outer cylinder of the screw. The screw acts as the motor's rotor axis with attached permanent magnets and or frame and the stator is built around the auxiliary circumference of this rotor. The rotor may also house half the bearings and can be used for the movement of fluids and/or solids, for cavitation-less drive of water vehicles, or for the generation of electrical power when the fluids become the motive force to drive the unit.

2004-05-25

213

Screws, Propellers and Fans Based on a Mobius Strip  

NASA Technical Reports Server (NTRS)

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.

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

1998-01-01

214

Devices and methods for interlocking surgical screws and nails  

US Patent & Trademark Office Database

The present invention demonstrates an improved interlocking nail and screw combination to repair fracture bones. The preferred combination uses an hourglass shaped intramedullary nail wherein the larger ends of the nail have holes capable of receiving screws. The holes may, or may not be conical. Further, the holes may or may not be threaded. The surgical screws have a variety of thread patterns, or lack threads. A non-threaded end is believed to improve healing because of a larger core diameter as compared to a comparably sized threaded screw end.

2013-05-07

215

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

PubMed Central

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 ?-? 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.

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

2014-01-01

216

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

PubMed

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 ?-? tantalum phase switch induced by increasing oxygen levels as observed by X-ray diffraction (XRD). It is concluded that DLC coatings are a feasible candidate for near zero wear articulations on implants, potentially even surpassing the performance of ceramic vs. ceramic. PMID:24921709

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

2014-01-01

217

Mixing effects of constituting elements of mixing screws in single and twin screw extruders  

Microsoft Academic Search

In extrusion, mixing of solids and melts has always been problematic, leading to diverse models describing the melting process. It is found that for foods based on cereals, only a few are valid, due to the simultaneous presence of water and high viscous non-Newtonian material. Mixing trials are summarised for single and twin screw extruders, with particulate solids of different

D. J. van Zuilichem; E. Kuiper; W. Stolp; T. Jager

1999-01-01

218

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

PubMed Central

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

Lee, Sandra; Vaidya, Rahul

2008-01-01

219

Postfusion pullout strength comparison of a novel pedicle screw with classical pedicle screws on synthetic foams.  

PubMed

Pullout is a very common failure mode on the use of pedicle screws. Numerous studies were completed to increase the pullout strength of pedicle screws especially for osteoporotic bones. In this study, a previously designed pedicle screw type was tested before and after fusion condition. Synthetic polyurethane foams were used in all tests. Three different grades of foams were used in tests to simulate severely osteoporotic, osteoporotic, and healthy bones. Test blocks were produced and characterized in our clinical biomechanics laboratory. Foaming of polyurethane was accepted as fusion process (bone in growth). Pedicle screw including radial holes (new design) was tested both before and after the fusion. It also exhibited remarkably higher pullout strength after fusion than before fusion and most of other alternatives stated in the literature. In total, 70% higher pullout strength was achieved with new design after fusion. On the other hand, new design did not dominate other alternatives when comparison was carried out on severely osteoporotic and healthy bones. To the knowledge of the authors, this is the first study investigating the postfusion properties on synthetic foams. PMID:23513982

Arslan, Arslan K; Demir, Teyfik; Ormeci, Mehmet F; Camu?cu, Necip; Türeyen, Kudret

2013-02-01

220

Additional Fixations for Sliding Hip Screws in Treating Unstable Pertrochanteric Femoral Fractures (AO Type 31-A2): Short-Term Clinical Results  

PubMed Central

Background To evaluate the utility of additional fixation methods and to suggest a method of reduction in the treatment of unstable pertrochanteric femur fractures with a sliding hip screw (SHS). Methods A retrospective study was performed on thirty patients with unstable pertrochanteric femur fractures, who were operated on with a SHS between September 2004 and September 2009 and were followed up for at least 6 months. The additional fixation devices were as follows; antirotation screw (21 cases), fixation of displaced fractures of the posteromedial bone fragment (cerclage wiring, 21 cases and screw, 2 cases) and trochanter stabilizing plate (27 cases). Clinically, the Palmer's mobility score and Jensen's social function group were used. Radiologically, alignment and displacement were observed. The tip-apex distance (TAD) and sliding of the lag screw were measured, and the position of the lag screw within the femoral head was also examined. Results The mean age at the time of surgery was 76 years (range, 56 to 89 years) and the average follow-up period was 25 months (range, 6 to 48 months). At the last follow-up, the average mobility and social function score was 6.2 (± 3.5) and 2.3 (± 1.5). Postoperatively, the alignment and displacement indices were adequate in almost all the cases. The mean amount of lag screw sliding and the mean TAD was 5.1 mm (range, 2 to 16 mm) and 6 mm (range, 3 to 11 mm) respectively. The lag screws were located in the center-center zone in 21 cases. The average period to union was 18.7 weeks without any cases of nonunion or malunion. Mechanical failure was noted in one case with breakage of the lag screw and clinical failure was noted in another case with persistent hip pain related to excessive sliding (16 mm). Conclusions With additional fixations, the unstable pertrochanteric femur fractures could be well stabilized by SHS until bone union.

Lee, Soo Ho; Cho, Hyung Lae; Ku, Jung Hoei; Choi, Jae Hyuk; Lee, Alex J

2011-01-01

221

Magnesium alloys as a biomaterial for degradable craniofacial screws.  

PubMed

Recently, magnesium (Mg) alloys have received significant attention as potential biomaterials 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 pure Mg and alloy AZ31 in vivo in a rabbit mandible. First, Mg and AZ31 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 this model can be used for future Mg alloy screw design. Then, Mg and AZ31 screws were implanted for 4, 8 and 12weeks, with two controls of an osteotomy site (hole) with no implant and a stainless steel screw implanted for 12weeks. Microcomputed tomography was used to assess bone remodeling and Mg/AZ31 degradation, both visually and qualitatively through volume fraction measurements for all time points. Histological analysis was also completed for the Mg and AZ31 at 12weeks. The results showed that craniofacial bone remodeling occurred around both Mg and AZ31 screws. Pure Mg had a different degradation profile than AZ31; however, bone growth occurred around both screw types. The degradation rate of both Mg and AZ31 screws in the bone marrow space and the muscle were faster than in the cortical bone space at 12weeks. 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

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

2014-05-01

222

USE OF RESORBABLE SCREWS FOR AUTOGENOUS ONLAY BLOCK GRAFT FIXATION: A HISTOLOGICAL ANALYSIS IN RABBITS.  

PubMed

Abstract Purpose:The aim of the present in vivo study is to histologically evaluate and compare the use of resorbable screws based on poli(L-co-D,L lactide) 70:30 for fixation of autogenous bone grafts in rabbit tibiae. Materials and Methods: as control group, titanium (Ti-6Al-4V Grade V) screws were used. For this purpose, fifteen white New Zeland male rabbits, with age of 6 months and weight between 3.8 - 4.5kg were used. From each animal, 2 total thickness bone grafts were removed from the cranial vault was stabilized with a resorbable screw while the other was stabilized with a metallic one. Animals were divided into 3 groups, according to the sacrifice period: 3, 8 and 16 weeks postoperatively. After histological processing, cuts were stained with hematoxilin and eosin and submitted for descriptive histological analysis under light microscopy. Results: it was found that the fixation system based on the polymer showed a histological behavior similar to metallic screws. For both groups the bone graft was incorporated, with the presence of bone formation between the graft and receptor site. In none of the groups were undesirable inflammatory responses or foreign body reactions observed. Conclusions: based on histological findings and on this experimental model it is possible to conclude that the internal fixation system based on the poli(L-co-D,L lactide) 70:30 polymer is effective for fixation of autogenous bone grafts, with results that are comparable to the titanium fixation system. PMID:23414521

Klüppel, Leandro E; Stabile, Glaykon Alex Vitti; Antonini, Fernando; Nascimento, Frederico Felipe; de Moraes, Márcio; Mazzonetto, Renato

2013-02-15

223

Influence of intra-operative joint gap on post-operative flexion angle in osteoarthritis patients undergoing posterior-stabilized total knee arthroplasty  

Microsoft Academic Search

Recently, we developed a new tensor for total knee arthroplasty (TKA) procedures enabling soft tissue balance assessment throughout\\u000a the range of motion while reproducing post-operative joint alignment with the patello-femoral (PF) joint reduced and the tibiofemoral\\u000a joint aligned. Using the tensor with a computer-assisted navigation system, we investigated the relationship between various\\u000a intra-operative joint gap values and their post-operative flexion

Tomoyuki Matsumoto; Kiyonori Mizuno; Hirotsugu Muratsu; Nobuhiro Tsumura; Naomasa Fukase; Seiji Kubo; Shinichi Yoshiya; Masahiro Kurosaka; Ryosuke Kuroda

2007-01-01

224

Arthroscopic meniscal repair with an absorbable screw: results and surgical technique  

Microsoft Academic Search

The results of a new method for arthroscopic all-inside meniscus repair using a biodegradable cannulated screw (Clearfix meniscal screw) were assessed in a medium-term follow-up prospective study. The Clearfix meniscal screw system consists of delivery cannulae, screw driver, and screw implants. After tear debridement, a screw is located on the driver and passed through the cannula to the insertion site,

Michael E. Hantes; Elias S. Kotsovolos; Dimitrios S. Mastrokalos; Joerg Ammenwerth; Hans H. Paessler

2005-01-01

225

Screw dislocations in GaN  

SciTech Connect

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

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

2002-02-15

226

Accuracy of Pedicle Screw Placement in Thoracic Spine Fractures  

Microsoft Academic Search

Background and Purpose: Transpedicular instrumentation in the thoracic spine is technically difficult because of small pedicle diameters. There are not many studies assessing in vivo accuracy, complications, and the revision rate of transpedicular screws in the thoracic spine. In this retrospective study 278 thoracic pedicle screws of 43 patients were assessed using a scoring system and postoperative computed tomography (CT)

Marty Zdichavsky; Michael Blauth; Christian Knop; Joachim Lotz; Christian Krettek; Leonard Bastian

2004-01-01

227

Axial Loading Cross Screw Fixation for the Austin Bunionectomy  

Microsoft Academic Search

The Austin procedure has become a common method of osteotomy for the correction of hallux abductovalgus when indicated. The V-type configuration is intrinsically stable but not without complications. One complication encountered is rotation and\\/or displacement of the capital fragment. We present the use of an axial loading screw in conjunction with a dorsally placed compression screw. The benefit to this

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

2011-01-01

228

Biceps tenodesis with interference screw: cyclic testing of different techniques.  

PubMed

Different surgical techniques exist for biceps tenodesis. The most secure fixation technique is with interference screws. The purpose of the study was to compare the biomechanical performance of three different interference screw biceps tenodesis fixation methods, which involve different tunnel preparation methods. Using a sheep shoulder model and metal interference screws, a bone wedge technique was compared to serial tunnel dilation and a control group. After a preload, all repairs were cyclically loaded (20-60 N) for 100 cycles followed by destructive testing. Biceps tenodesis using an interference screw--bone wedge technique showed statistically lower cyclic displacement (8.1 ± 6.4 mm) than serial dilatation with an interference screw (21.3 ± 8.4 mm) or interference screw fixation alone (18.3 ± 8.3 mm) (P = 0.02). There were no statistically significant differences in ultimate failure strength for any of the interference screw biceps tenodesis techniques tested. The tunnel preparation method chosen for interference screw fixed biceps tenodesis can have a positive effect on tenodesis performance. Using the bone wedge technique may allow a more rapid rehabilitation program applicable for the traumatic biceps tendon rupture seen in young, athletic patients with high demands. PMID:20549186

Hapa, Onur; Günay, Cüneyd; Kömürcü, Erkam; Cak?c?, Hüsamettin; Bozda?, Ergun

2010-12-01

229

Use of the cannulated bone screw in rearfoot surgery.  

PubMed

There are many types of rigid internal fixation devices available for podiatric surgery. The cannulated screw system is an easy and effective way to decrease surgical time. These screws are being used with great success for several rearfoot procedures, such as the triple arthrodesis, Dwyer calcaneal osteotomy, and posterior malleolar ankle fractures. PMID:2507621

Chieppa, W A; Sydnor, K H; Walter, J H

1989-01-01

230

Continuous expression of slurry in a screw press  

Microsoft Academic Search

An approximate method is described for predicting the steadystate performance of a screw press for the continuous expression of a slurry, with the worm channel being modified as the path between two flat plates. Screw expression of a slurry involves two mechanisms of dewatering which, for a batch operation, can be analyzed by the variable-pressure, variable-rate theory of filtration and

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

1985-01-01

231

Fatigue strength of common tibial intramedullary nail distal locking screws  

Microsoft Academic Search

BACKGROUND: Premature failure of either the nail and\\/or locking screws with unstable fracture patterns may lead to angulation, shortening, malunion, and IM nail migration. Up to thirty percent of all unreamed nail locking screws can break after initial weight bearing is allowed at 8–10 weeks if union has not occurred. The primary problem this presents is hardware removal during revision

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

2009-01-01

232

Screw Gluing Kerto-LVL Structures with Polyurethane.  

National Technical Information Service (NTIS)

The objective was to find out the applicability of screw-pressing technique and to determine factors affecting the strength and quality of glue line in screw-pressed Laminated Veneer Lumber (LVL) elements purposed to structural use. The production of thes...

M. Kairi E. Kaloinen S. Koponen T. Nokelainen M. Fonselius A. Kevarinmaeki

1999-01-01

233

A simple model of throughput calculation for single screw  

NASA Astrophysics Data System (ADS)

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.

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

2007-04-01

234

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

NASA Technical Reports Server (NTRS)

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

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

2004-01-01

235

Use of screws and cement in primary TKA with up to 20 years follow-up.  

PubMed

The purpose of this study was to investigate screws and cement for large tibial bone defects during primary TKA. Of 14,686 consecutive primary TKAs performed between December 1988 and February 2010, 256 received screws and cement for tibial defects. Cox regression was used for the analysis. 20-year survival probability was 0.9897 (screws) and 0.9339 (no screws) (P = .4225 log-rank). Tibial bone condition was significantly worse in knees receiving screws (P < .0001) with 73.0% having defects in the screws group and 3.4% (P < .0001) for non-screws. Radiolucency appeared in 13.7% (screws) and 6.4% (no screws) postoperatively. Screws were $137 each, wedges $910 to $2240. Knees with tibial defects and screws performed similarly if not better than knees without defects at substantially lower cost than alternatives. PMID:24456788

Berend, Michael E; Ritter, Merrill A; Keating, E Michael; Jackson, Michael D; Davis, Kenneth E

2014-06-01

236

Controlled retainer-screw access placement for screw-retained implant prosthesis.  

PubMed

An implant-supported prosthesis is often secured to the underlying gold cylinders by retaining screws. There must be access to these screws from the oral surface of the prosthesis. Conventional preparation of this access is from the oral surface. This approach is difficult because the underlying gold cylinder is obscured. It may be damaged by a rotary cutting instrument as the access is prepared above it, because the cylinder cannot be seen during the preparation. Alternatively, the access hole may be unnecessarily enlarged in an attempt to find the cylinder. This loss of structure may weaken the prosthesis. A new approach, using 18-gauge stainless steel wire as a rotary cutting instrument, permits preparation of the access chamber from the intaglio surface of the prosthesis. This reduces risk of damage to the gold cylinder and is less destructive to the overlying material. PMID:9028229

Cohen, S R; Lawrence, S; Orenstein, J H; Appleby, D C; Blitzer, R M

1996-09-01

237

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

PubMed Central

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

2014-01-01

238

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

PubMed Central

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

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

2014-01-01

239

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

PubMed Central

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

2014-01-01

240

[The minimally-invasive screw osteosynthesis of the medial femoral neck fracture in the very old. A prospective clinical study].  

PubMed

Increasing life expectancy has led to an increase of medial femoral neck fractures. Treatment by hip arthroplasty is a major surgical procedure for geriatric patients and imposes high healthcare costs. Manninger developed a cannulated screw system which allows a joint-sparing, less invasive, and stable internal fixation for the management of intracapsular femoral neck fractures. In a prospective study from January 1998 to August 2002, 63 patients older than 70 years with Garden type I to III fractures were treated by closed reduction and internal fixation with two Manninger screws on a traction table within the first 6 h after trauma. Mean time of follow-up was 21.5+/-16 months. Of the patients examined, 88.5% regained their preoperative stage of mobility. Two patients needed secondary hip arthroplasty. Due to low complication and failure rates and less medical expenses compared to treatment by hemiprosthesis the joint-sparing, less invasive internal fixation with two cannulated Manninger screws presents a safe and cost-efficient surgical technique for geriatric patients. PMID:15221073

Galla, M; Lobenhoffer, P

2004-05-01

241

SCREW COMPRESSOR CHARACTERISTICS FOR HELIUM REFRIGERATION SYSTEMS  

SciTech Connect

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

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

2008-03-01

242

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

PubMed Central

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

2014-01-01

243

Disorders of the sacroiliac joint.  

PubMed

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

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

2002-03-01

244

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

PubMed Central

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

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

2014-01-01

245

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

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

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

2014-06-01

246

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

PubMed Central

Reconstruction of the highly unstable, anteriorly decompressed cervical spine poses biomechanical challenges to current stabilization strategies, including circumferential instrumented fusion, to prevent failure. To avoid secondary posterior surgery, particularly in the elderly population, while increasing primary construct rigidity of anterior-only reconstructions, the authors introduced the concept of anterior transpedicular screw (ATPS) fixation and plating. We demonstrated its morphological feasibility, its superior biomechanical pull-out characteristics compared with vertebral body screws and the accuracy of inserting ATPS using a manual fluoroscopically assisted technique. Although accuracy was high, showing non-critical breaches in the axial and sagittal plane in 78 and 96%, further research was indicated refining technique and increasing accuracy. In light of first clinical case series, the authors analyzed the impact of using an electronic conductivity device (ECD, PediGuard) on the accuracy of ATPS insertion. As there exist only experiences in thoracolumbar surgery the versatility of the ECD was also assessed for posterior cervical pedicle screw fixation (pCPS). 30 ATPS and 30 pCPS were inserted alternately into the C3–T1 vertebra of five fresh-frozen specimen. Fluoroscopic assistance was only used for the entry point selection, pedicle tract preparation was done using the ECD. Preoperative CT scans were assessed for sclerosis at the pedicle entrance or core, and vertebrae with dense pedicles were excluded. Pre- and postoperative reconstructed CT scans were analyzed for pedicle screw positions according to a previously established grading system. Statistical analysis revealed an astonishingly high accuracy for the ATPS group with no critical screw position (0%) in axial or sagittal plane. In the pCPS group, 88.9% of screws inserted showed non-critical screw position, while 11.1% showed critical pedicle perforations. The usage of an ECD for posterior and anterior pedicle screw tract preparation with the exclusion of dense cortical pedicles was shown to be a successful and clinically sound concept with high-accuracy rates for ATPS and pCPS. In concert with fluoroscopic guidance and pedicle axis views, application of an ECD and exclusion of dense cortical pedicles might increase comfort and safety with the clinical use of pCPS. In addition, we presented a reasonable laboratory setting for the clinical introduction of an ATPS-plate system.

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

2009-01-01

247

Noninvasive method for retrieval of broken dental implant abutment screw.  

PubMed

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

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

2014-04-01

248

A novel technique for accurate Poller (blocking) screw placement.  

PubMed

Achieving good results with intramedullary nailing of oblique long bone fractures at the metaphyseal-diaphyseal junction can be difficult. There is a strong tendency for axial displacement and an association with characteristic malalignment of the short fragment. Poller or blocking screws have been shown to be effective in aiding fracture reduction. While several papers describe methods for screw placement, these are confusing to understand, difficult to follow in clinical practice and not always applicable. Here we describe a new, simple, reproducible and easy to use method for ensuring accurate Poller screw placement, in order to maximise the benefits of their use and achieve good overall results. PMID:24629702

Hannah, Andrew; Aboelmagd, Tariq; Yip, Grace; Hull, Peter

2014-06-01

249

Noninvasive method for retrieval of broken dental implant abutment screw  

PubMed Central

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

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

2014-01-01

250

Stress analysis of a centrally fractured rib fixated by an intramedullary screw.  

PubMed

The stress on an intramedullary screw rib fixation device holding together a centrally fractured human rib under in vivo force loadings was studied using finite element analysis (FEA). Validation of the FEA modelling using pullout from porcine ribs proved FEA to be suitable for assessing the structural integrity of screw/bone systems such as rib fixated by a screw. In the human rib fixation investigation, it was found that intramedullary bioresorbable Bioretec screws can fixate centrally fractured human ribs under normal breathing conditions. However, under coughing conditions, simulation showed Bioretec fixating screws to bend substantially. High stresses in the screw are mainly the result of flexion induced by the force loading, and are restricted to thin regions on the outside of the screw shaft. Stiffer screws result in less locally intense stress concentrations in bone, indicating that bone failure in the bone/screw contact regions can be averted with improvements in screw stiffness. PMID:23098197

Liovic, Petar; Sutalo, Ilija D; Marasco, Silvana F

2014-07-01

251

Joints in a Cornstarch Analog  

NSDL National Science Digital Library

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

Crider, Juliet

252

[Variations of transpedicular screw fixation and spinal dura opening].  

PubMed

The paper presents modified treatment protocols for spinal trauma and degenerative disease--transpedicular screw fixation based upon biomechanical adjustment and spinal dura opening. Both methods help to improve results of surgical treatment and decrease complication rate. PMID:23033595

Tumakaev, R F

2012-01-01

253

Screw-Type Compressors for Use in Heat Pump Systems.  

National Technical Information Service (NTIS)

Due to its particular advantages, i.e., small dimensions with relatively large volume flow velocity, high operational reliability and large control region, the screw-type compressor has gained wide acceptance in industrial refrigeration engineering. Air c...

R. Klein

1977-01-01

254

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

255

Biocompatibility studies of titanium-based alloy pedicle screw and rod system  

Microsoft Academic Search

Background context: Few histological studies of pedicle screw and rod systems have been done, and spinal surgery with pedicle screw and rod system is increasing.Purpose: To know the biocompatibility of pedicle screw and rod systems histologically. Study design\\/setting: Titanium-based alloy pedicle screws were removed from 20 patients. Histological studies of the tissue response to the screws were performed by light

Kazuhiro Yamaguchi; Hiroaki Konishi; Shinichiro Hara; Yoshinori Motomura

2001-01-01

256

Screw thread parameter measurement system based on image processing method  

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

257

Inertia Compensation While Scanning Screw Threads on Coordinate Measuring Machines  

NASA Astrophysics Data System (ADS)

Usage of scanning coordinate-measuring machines for inspection of screw threads has become a common practice nowadays. Compared to touch trigger probing, scanning capabilities allow to speed up the measuring process while still maintaining high accuracy. However, in some cases accuracy drastically depends on the scanning speed. In this paper a compensation method is proposed allowing to reduce the influence of inertia of the probing system while scanning screw threads on coordinate-measuring machines.

Kosarevsky, Sergey; Latypov, Viktor

2010-01-01

258

Intramedullary screw fixation for midshaft fractures of the clavicle  

Microsoft Academic Search

Open intramedullary fixation of 37 fresh midshaft clavicular fractures in 35 patients was performed using a 6.5 partially\\u000a threaded cancellous screw. Mean age was 38 years (range 18–65). The screw was inserted from the medial fragment after retrograde\\u000a drilling of that fragment. Average follow-up period was 21 months (range 9–36). Radiological evidence of union was apparent\\u000a in all cases within six to

Ayman Khalil

2009-01-01

259

Posterior Atalntoaxial Fusion with C1 Lateral Mass Screw and C2 Pedicle Screw Supplemented with Miniplate Fixation for Interlaminar Fusion : A Preliminary Report  

PubMed Central

Objective To investigate the feasibility of C1 lateral mass screw and C2 pedicle screw with polyaxial screw and rod system supplemented with miniplate for interlaminar fusion to treat various atlantoaxial instabilities. Methods After posterior atlantoaxial fixation with lateral mass screw in the atlas and pedicle screw in the axis, we used 2 miniplates to fixate interlaminar iliac bone graft instead of sublaminar wiring. We performed this procedure in thirteen patients who had atlantoaxial instabilities and retrospectively evaluated the bone fusion rate and complications. Results By using this method, we have achieved excellent bone fusion comparing with the result of other methods without any complications related to this procedure. Conclusion C1 lateral mass screw and C2 pedicle screw with polyaxial screw and rod system supplemented with miniplate for interlaminar fusion may be an efficient alternative method to treat various atlantoaxial instabilities.

Yoon, Sang-Mok; Baek, Jin-Wook

2012-01-01

260

Clinical applications of drill free screws in maxillofacial surgery.  

PubMed

Drill free screws are newly designed osteosynthesis screws with specially formed tips and cutting flutes, which act like a cork-screw and can be inserted into bone without predrilling. A prospective study on 82 patients was performed in order to investigate the efficiency of mini- and micro-drill free screws (DFS) in clinical use and to find out areas in maxillofacial traumatology and orthognathic surgery, where the application of this new type of screw may be recommended. Thirty-eight Le-Fort-osteotomies, 23 central and lateral midfacial fractures and 21 fractures of the mandible were fixed using the Champy titanium micro/miniplate system and in total 518 center-drive titanium micro-DFS (1.5 mm) and 392 center-drive titanium mini-DFS (2 mm) with lengths between 4 and 7 mm. The results showed that the grip of micro- and mini-DFS was sufficient for the fixation of bone fragments in the central and lateral midface and in the mandibular area. The insertion of DFS was simple and is recommended in the area of the central midface; the insertion of the screws was difficult, but possible in the anterior mandible and in the lateral midface. The application of DFS in the mandibular angle region is not recommended. PMID:10626259

Heidemann, W; Gerlach, K L

1999-08-01

261

Screw driver: an unusual cause of cervical spinal cord injury  

PubMed Central

Non-missile penetrating spinal injuries are rare. Screw driver injury, more especially to the cervical spine, represents an even rarer subset. To our knowledge, this is the first reported case from West Africa of cervical spinal cord injury from a screw driver. A middle-aged man was stabbed from the back with a screw driver. He presented with right-sided C4 Brown-Sequard syndrome with the impaling object in situ. Cervical spine x-rays showed the screw driver to have gone into the spine between the spinous processes of C4 and C5, traversing the spinal canal and lodged in the anterior part of the C4/5 intervertebral disc space. C4 and C5 laminectomies were performed and the screw driver removed under vision. The object was found to have traversed the right side of the cervical spinal cord. The dural tear was repaired. He had some neurologic improvement initially, but later declined. He died from severe pulmonary complications 2 weeks postinjury. Screw driver represents an unusual cause of non-missile penetrating cervical spinal injury. Its neurological effects and complications of the cord injury lead to significant morbidity and mortality.

Rabiu, Taopheeq Bamidele; Aremu, Abayomi Adeniran; Amao, Olusegun Adetunji; Awoleke, Jacob Olumuyiwa

2011-01-01

262

Lateral ankle fracture with missed proximal tibiofibular joint instability (Maisonneuve injury).  

PubMed

We present a case of a soccer player who sustained a lateral ankle fracture and the associated proximal anterolateral tibiofibular joint instability (Maisonneuve injury) was overlooked. After a non-contact injury the (incomplete) diagnosis of a lateral malleolar fracture (type Weber B, AO 44-B1) was made and the patient was surgically treated with open reduction and internal fixation including a distal syndesmosis screw. After removal of the syndesmosis screw (six weeks after surgery) the patient suffered from activity-related pain around the fibular head. After thorough clinical and radiologic examination, temporary screw transfixation of the fibular head and capsular repair under meticulous fluoroscopic control of fibular rotation helped to restore patient's sport activity level. This case report emphasizes the importance of precise clinical examination for detection of a proximal tibiofibular joint instability. Restoration of a well functioning and stable proximal tibiofibular joint may be difficult to achieve in previously operated and missed instabilities. PMID:18712356

Hirschmann, Michael T; Mauch, Christian; Mueller, Claude; Mueller, Werner; Friederich, Niklaus F

2008-10-01

263

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

PubMed Central

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

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

2014-01-01

264

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

PubMed

Reconstruction after multilevel decompression of the cervical spine, especially in the weakened osteoporotic, neoplastic or infectious spine often requires circumferential stabilization and fusion. To avoid the additional posterior surgery in these cases while increasing rigidity of anterior-only screw-plate constructs, the authors introduce the concept of anterior transpedicular screw (ATPS) fixation. We demonstrated its morphological feasibility as well as its indications in a previous study in Part I of our project. Consequently, the objectives of the current study were to assess the ex vivo accuracy of placing ATPS into the cervical vertebra as well as the biomechanical performance of ATPS in comparison to traditional vertebral body screws (VBS) in terms of pull-out strength (POS). Twenty-three ATPS were inserted alternately to two screws into the pedicles and vertebral bodies, respectively, of six cadaveric specimens from C3-T1. For insertion of ATPS, a manual fluoroscopically assisted technique was used. Pre- and post insertional CT-scans were used to assess accuracy of ATPS insertion in the axial and sagittal planes. A newly designed grading system and accuracy score were used to delineate accuracy of ATPS insertion. Following insertion of screws, 23 ATPS and 22 VBS were subjected to pull-out testing (POT). The bone mineral density (BMD) of each specimen was assessed prior to POT. Statistical analysis showed that the incidence of correctly placed screws and non-critical pedicles breaches in axial plane was 78.3%, and 95.7% in sagittal plane. Hence, according to our definition of "critical" pedicle breach that exposes neurovascular structures at risk, 21.7% (n = 5) of all ATPS inserted showed a critical pedicle breach in axial plane. Notably, no critical pedicle perforation occurred at the C6 to T1 levels. Pull-out testing of ATPS and VBS revealed that pull-out resistance of ATPS was 2.5-fold that of VBS. Mean POS of 23 ATPS with a mean BMD of 0.566 g/cm(2) and a mean osseus screw purchase of 27.2 mm was 467.8 N. In comparison, POS of 22 VBS screws with a mean BMD of 0.533 g/cm(2) and a mean osseus screw purchase of 16.0 mm was 181.6 N. The difference in ultimate pull-out strength between the ATPS and VBS group was significant (p < 0.000001). Also, accuracy of ATPS placement in axial plane was shown to be significantly correlated with POS. In contrast, there was no correlation between screw-length, BMD, or level of insertion and the POS of ATPS or VBS. The study demonstrated that the use of ATPS might be a new technique worthy of further investigation. The use of ATPS shows the potential to increase construct rigidity in terms of screw-plate pull-out resistance. It might diminish construct failures during anterior-only reconstructions of the highly unstable decompressed cervical spine. PMID:18224357

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

2008-04-01

265

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

PubMed Central

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

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

2008-01-01

266

Exercise and the Knee Joint.  

ERIC Educational Resources Information Center

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

Clarke, H. Harrison, Ed.

1976-01-01

267

?????????????????????????? ?????????????????????????????????????????????????? ??????????? ????????????????????? ??????????????????????????????? Effect of Screw Rotating Speed on the Properties of Poly lactic acid(PLA)\\/Organoclay Nanocomposites Prepared by a Twin Screw Extruder  

Microsoft Academic Search

This study analyzes the effect of different screw rotating speeds on the properties of nanocomposites prepared by melt compounding PLA with an organoclay in a co-rotating twin-screw extruder. Polyamide 12 was used as an additive. Two different screw rotating speeds, 65 rpm and 150 rpm, were used in this study. According to the tensile strength data, the Young's modulus and

Aniwat Hasook; Hiroki Muramatsu; Shuichi Tanoue; Yoshiyuki Iemoto; Tsunemune Unryu

268

Minimally Invasive Posterior Trans-muscular C1-C2 Screw Fixation Through an Anatomical Corridor to Preserve Occipitocervical Tension Band: Surgical Anatomy and Clinical Experience.  

PubMed

The C1-C2 joint is affected by multiple entities that may produce biomechanical instability. Optimal management for atlantoaxial instability has been searched by ways of different surgical techniques with different results, generating discussion between second effects of a particular treatment. Lateral dissections can place the axial neck musculature and ligaments at risk of neural denervations or vascular compromise. Either of these entities may result in significant postoperative atrophy, pain, and instability. Minimally invasive techniques for the treatment of spinal disorders allow to our patients less morbid procedures with equal or better results compared to conventional surgery. In the following paper, we review the anatomy of the atlantoaxial joint and propose a minimally invasive trans-muscular C1-C2 fusion technique using C1 lateral-mass screws and C2 pedicular screws. We describe cases with surgical, clinical, and radiographic follow-up. PMID:24265049

Díaz, Roberto; Berbeo, Miguel E; Villalobos, Luis M; Vergara, Manuel F; Osorio, Enrique

2014-01-01

269

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

PubMed

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. PMID:11218438

Learmonth, I D; Spirakis, A

1994-03-01

270

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

NASA Astrophysics Data System (ADS)

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

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

2008-11-01

271

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

PubMed Central

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

Lee, Jae Chul; Kim, Yon-Il

2008-01-01

272

Windshield-wiper loosening: a complication of in situ screw fixation of slipped capital femoral epiphysis.  

PubMed

A retrospective review of patients treated for slipped capital femoral epiphysis (SCFE) by in situ screw fixation with a cannulated titanium screw was performed. Of the 18 hips with at least 1-year follow-up, windshield-wiper loosening of the cannulated screw in the femoral head had occurred in three. In all three cases, the screw had been left protruding > 1.5 cm from the anterolateral cortex of the femur. We postulate that with hip motion the protruding screw is toggled by the anterolateral soft tissues, causing a windshield-wiper effect in the femoral head, leading to eventual screw loosening. We believe that leaving the screw protruding from the fascia lata is a potential source of screw loosening by the windshield-wiper mechanism and now routinely place the screw head within 1.5 cm of the anterolateral cortex of the femur. PMID:8376561

Maletis, G B; Bassett, G S

1993-01-01

273

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

NASA Astrophysics Data System (ADS)

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

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

274

Self-tapping versus standard tapped titanium screw fixation in the upper extremity.  

PubMed

Most screws used in fracture fixation necessitate a separate step for tapping of the screw hole. Titanium screw systems have been developed in which the screws can be inserted directly after a drill hole is made. These self-tapping screws thereby eliminate an operative step. A retrospective study was conducted that evaluated all wrist and hand procedures performed between January 1992 and December 1994 by 1 surgeon using screw fixation. The results of 39 cases treated with standard tapped titanium screws were compared with 28 cases treated with self-tapping titanium screws. Nearly identical union and complication rates were obtained in each group. Comparable results can be obtained with self-tapping screw fixation, which limits the number of instruments needed, eliminates an operative step, and thereby may diminish operative risk and shorten operative time. PMID:9556274

Bickley, M B; Hanel, D P

1998-03-01

275

[Arthrodesis of the talonavicular joint].  

PubMed

The talonavicular joint as part of the coxa pedis plays a pivotal role in the overall motion of the foot. The necessity for talonavicular fusion arises from isolated arthritis of posttraumatic, rheumatoid, degenerative, or idiopathic etiology. Posttraumatic arthritis is seen after malunited mid-tarsal (Chopart) fracture-dislocations and is frequently accompanied by malalignment due to an imbalance between the medial and lateral columns of the foot. In these cases a corrective arthrodesis becomes necessary. In cases of poor bone stock or arthritis of the calcaneocuboid joint, a double arthrodesis is preferred over isolated talonavicular fusion. Fusion with mini-plates is biomechanically superior to fusion with screws and especially staples, the latter being associated with non-union rates of up to 37%. Talonavicular fusion allows reproducible pain reduction in isolated arthritis with subjective patient satisfaction of between 86% and 100% in a literature review. The substantial reduction of movement in the triple joint complex leads to overload of the adjacent joints with development of arthritis in about 30% in the medium term. PMID:16193344

Rammelt, S; Marti, R K; Zwipp, H

2006-04-01

276

Austin bunionectomy using single screw fixation: five-year versus 18-month follow-up findings.  

PubMed

The authors present a follow-up of the Austin bunionectomy using a single 2.7-mm American Society of Internal Fixation (ASIF) screw. At a mean 5-year follow-up, 45 feet in 32 patients were evaluated with information from clinical examination, radiographic data, and responses to a patient questionnaire. When compared to the 18-month follow-up, good reduction of the intermetatarsal and the hallux abductus angle were maintained. Clinical findings, including the first metatarsophalangeal joint range of motion and hallux purchase power, remained acceptable, and a small number of new transfer lesions were noted. Patient satisfaction with appearance and overall satisfaction with the procedure remained excellent-to-good in 96% of the procedures. PMID:8807487

Goforth, W P; Martin, J E; Domrose, D S; Sligh, T S

1996-01-01

277

A processing method for orthodontic mini-screws reuse  

PubMed Central

Background: The possibility of mini-screws reuse would reduce treatment cost. The aim of this study is to introduce a new method (application of phosphoric acid 37% for 10 minutes followed by sodium hypochlorite 5.25% for 30 minutes) for cleansing of mini-screws and assessing the efficacy of this method. The effects of this processing on the insertion, removal, and fracture torques of mini-screws were evaluated. Materials and Methods: This experimental study was done in two parts. In part I the amount of calcium ion on mini-screws surfaces as an index of tissue remnants was assessed. In part II of this study, the effects of previous use, processing method, and resterilization on the insertion, removal, and fracture torques of mini-screws were assessed. Each part of this study had 3 groups; non-processed used (NP), processed used (P), and as-received (C). Each group had 16 samples in part I and 20 samples. Non parametric statistical tests were used in part I and one way ANOVA in part II. Results: The mean amount of calcium ion in groups non-processed (NP1), processed (P1), and control (C1) were 4.7, 0.43, and 0.02 ppm, respectively. The amount of calcium ion in group NP1 was significantly greater than in the other groups (P = 0.000), but the difference between groups P1 and C1 was not significant (P = 0.087). The mean insertion torque of group NP2 was lower than that of other groups (P < 0.05) but P2 and C2 did not have significant differences (P = 0.988). The mean of removal and fracture torque did not have significant differences among all groups. Conclusion: Cleaning of used mini-screws with phosphoric acid 37% (10 minutes) and sodium hypochlorite 5.25% (30 minutes) reduces tissue remnants to the level of as-received mini-screws. So it can be suggested as a processing method of used mini-screws. Previous insertion of mini-screws into the bone and above-mentioned processing method and resterilization with autoclave had no adverse effects on insertion, removal, and fracture torque values as mechanical properties indices.

Noorollahian, Saeed; Alavi, Shiva; Monirifard, Mohammad

2012-01-01

278

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

PubMed

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

Song, Y; Xu, J; Ma, X

1997-03-01

279

Planning and insertion of pedicle screws with computer assistance.  

PubMed

Transpedicular screw fixation relies on thorough knowledge of the pedicular anatomy and a reliable intraoperative technique. To enhance the safety and accuracy of screw insertion, computer-assisted systems have been introduced. Our in vitro study investigated the potential benefits of such a system for the preoperative planning and the intraoperative visualization. In part 1, the potentially possible range of screw paths (trajectories) through lumbar pedicles was analyzed. In part 2, the accuracy of actual pedicle-hole preparation with and without preoperative planning was assessed. It was shown that, especially in the lower lumbar regions, the possible range of trajectories is considerable, with inclinations of < or = 40 degrees in the transverse plane and a range of angulation in the sagittal plane of > 20 degrees. The computer assistance in preparation of 100 pedicle holes resulted in cortex perforation in only one case. Computer assistance therefore may be used as a valuable tool to minimize the risks of transpedicular screw insertion. It furthermore may assist in determining the desired screw orientation and length and transform this planning into the intraoperative pedicle-hole preparation. PMID:9113610

Berlemann, U; Monin, D; Arm, E; Nolte, L P; Ozdoba, C

1997-04-01

280

Modern posterior screw techniques in the pediatric cervical spine  

PubMed Central

Treatment of children with cervical spine disorders requiring fusion is a challenging endeavor for a variety of reasons. The size of the patients, the corresponding abnormal bony anatomy, the inherent ligamentous laxity of children, and the relative rarity of the disorders all play a part in difficulty of treatment. The benefits of modern posterior cervical instrumentation in children, defined as rigid screw-rod systems, have been shown to be many including: improved arthrodesis rates, diminished times in halo-vest immobilization, and improved reduction of deformities. The anatomy of children and the corresponding pathology seen frequently is at the upper cervical spine and craniocervical junction given the relatively large head size of children and the horizontal facets at these regions predisposing them to instability or deformity. Posterior screw fixation, while challenging, allows for a rigid base to allow for fusion in these upper cervical areas which are predisposed to pseudarthrosis with non-rigid fixation. A thorough understanding of the anatomy of the cervical spine, the morphology of the cervical spine, and the available screw options is paramount for placing posterior cervical screws in children. The purpose of this review is to discuss both the anatomical and clinical descriptions related to posterior screw placement in the cervical spine in children.

Hedequist, Daniel J

2014-01-01

281

Management of odontoid fractures with percutaneous anterior odontoid screw fixation  

PubMed Central

Minimally invasive techniques have revolutionized the management of a variety of spinal disorders. The authors of this study describe a new instrument and a percutaneous technique for anterior odontoid screw fixation, and evaluate its safety and efficacy in the treatment of patients with odontoid fractures. Ten patients (6 males and 4 females) with odontoid fractures were treated by percutaneous anterior odontoid screw fixation under fluoroscopic guidance from March 2000 to May 2002. Their mean age at presentation was 37.2 years (with a range from 21 to 55 years). Six cases were Type II and four were Type III classified by the Anderson and D’Alonzo system. The operation was successfully completed without technical difficulties, and without any soft tissue complications such as esophageal injury. No neurological deterioration occurred. Satisfactory results were achieved in all patients and all of the screws were in good placement. After a mean follow-up of 15.7 months (range 10–25 months), radiographic fusion was documented for 9 of 10 patients (90%). Neither clinical symptoms nor screw loosening or breakage occurred. Our preliminary clinical results suggest that the percutaneous anterior odontoid screw fixation procedure using a new instrument and fluoroscopy is technically feasible, safe, useful, and minimally invasive.

Wang, Xiang-Yang; Xu, Hua-Zi; Lin, Yan; Huang, Qi-Shan; Mao, Fang-Min; Ni, Wen-Fei; Wang, Sheng; Dai, Li-Yang

2007-01-01

282

Screw dislocations in GaN grown by different methods  

SciTech Connect

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

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

2003-05-27

283

Modern posterior screw techniques in the pediatric cervical spine.  

PubMed

Treatment of children with cervical spine disorders requiring fusion is a challenging endeavor for a variety of reasons. The size of the patients, the corresponding abnormal bony anatomy, the inherent ligamentous laxity of children, and the relative rarity of the disorders all play a part in difficulty of treatment. The benefits of modern posterior cervical instrumentation in children, defined as rigid screw-rod systems, have been shown to be many including: improved arthrodesis rates, diminished times in halo-vest immobilization, and improved reduction of deformities. The anatomy of children and the corresponding pathology seen frequently is at the upper cervical spine and craniocervical junction given the relatively large head size of children and the horizontal facets at these regions predisposing them to instability or deformity. Posterior screw fixation, while challenging, allows for a rigid base to allow for fusion in these upper cervical areas which are predisposed to pseudarthrosis with non-rigid fixation. A thorough understanding of the anatomy of the cervical spine, the morphology of the cervical spine, and the available screw options is paramount for placing posterior cervical screws in children. The purpose of this review is to discuss both the anatomical and clinical descriptions related to posterior screw placement in the cervical spine in children. PMID:24829871

Hedequist, Daniel J

2014-04-18

284

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

PubMed

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

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

1994-11-01

285

[Molar distalization by using vertically installed mini-screws].  

PubMed

Mini-screws can be used for orthodontic anchorage in distalizing maxillary and mandibular molars. With them, practitioners can avoid the undesirable reciprocal movement that so often occurs when teeth are used as anchorage units. In this article, we propose a method of vertical insertion of mini-screws that places them in positions that will not interfere with movement of tooth roots. This allows orthodontists to use mass movements of groups of teeth or even of entire arches, thus reducing the need for extractions, simplifying treatment procedures, and enlarging the range of therapeutic possibilities. We evaluate the indications for this vertical placement in different anatomic situations. We suggest different sites for mini-screw placement and illustrate them with many clinical cases. PMID:23206370

Lee, Ju-Young

2012-12-01

286

Optically driven Archimedes micro-screws for micropump application.  

PubMed

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. PMID:21643076

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

2011-04-25

287

Single crystal alumina for dental implants and bone screws.  

PubMed

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

Kawahara, H; Hirabayashi, M; Shikita, T

1980-09-01

288

Virtual estimates of fastening strength for pedicle screw implantation procedures  

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

289

Herbert bone screw fixation of the Austin bunionectomy.  

PubMed

This manuscript represents an alternative method of fixation for the Austin bunionectomy using the Herbert bone screw. A description of the modified Austin bunionectomy and fixation utilizing this system is presented. A discussion of potential and encountered complications is included. Two hundred and four osteotomies were fixated with the Herbert bone screw in 182 patients, with follow-up ranging from 6 months to 3 years. Early range of motion, rigid internal fixation with compression, and the elimination of pin tracks are the advantages of this method. PMID:3446706

Quinn, M R; DiStazio, J J; Kruljac, S J

1987-01-01

290

Optical conductivity of semiconductor crystals with a screw dislocation  

NASA Astrophysics Data System (ADS)

We study ac electronic transport in semiconductor crystals with a screw dislocation. The screw dislocation in the crystal results in an effective potential field that has a pronounced effect on the quantum mechanical electronic transport of the system. Alternating current conductivity at a frequency around 100 GHz has been calculated, showing upward shift in the peak position with increasing the Fermi energy. The result is in contrast to the persistency in the peak position observed in a dislocation-free crystal penetrated by magnetic flux, despite the apparent similarity between the two crystalline systems.

Taira, Hisao; Shima, Hiroyuki

2014-01-01

291

Interference screw failure in distal biceps endobutton repair: case report.  

PubMed

Endobutton (Arthrex, Naples, FL) fixation of distal biceps rupture with interference screw fixation provides for a secure repair, allowing for early motion. We present a case in which Endobutton fixation failed with a loose interference screw, rendering the distal biceps attachment incompetent. Revision surgery with an extensile approach, mobilization of the biceps, and repeat Endobutton fixation at a more distal site provided a secure fixation with an excellent clinical outcome. An understanding of the mechanism of failure might allow surgeons to perform this procedure with a lower incidence of complications. PMID:20807629

Naidu, Sanjiv H

2010-09-01

292

Experimental Results of Single Screw Mechanical Tests. A Follow-Up to SAND2005-6036.  

National Technical Information Service (NTIS)

The work reported here was conducted to address issues raised regarding mechanical testing of attachment screws described in SAND2005-6036, as well as to increase the understanding of screw behavior through additional testing. Efforts were made to evaluat...

J. S. Korellis K. L. Lee S. Lee X. McFadden

2006-01-01

293

Safety screw fixation technique in a case of coracoid base fracture with acromioclavicular dislocation and coracoid base cross-sectional size data from a computed axial tomography study.  

PubMed

Coracoid base fracture accompanied by acromioclavicular joint dislocation with intact coracoclavicular ligaments is a rare injury. Generally, an open reduction with screw fixation is the first treatment choice, as it protects the important structures around the coracoid process. This report presents a new technique of screw fixation for coracoid base fracture and provides anatomic information on cross-sectional size of the coracoid base obtained by computed tomography (CT). An axial image of the coracoid base was visualized over the neck of the scapula, and a guidewire was inserted into this circle under fluoroscopic guidance. The wire was inserted easily into the neck of scapula across the coracoid base fracture with imaging in only 1 plane. In addition, 25 measurements of the coracoid base were made in 25 subjects on axial CT images. Average length of the long and short axes at the thinnest part of the coracoid base was 13.9 ± 2.0 mm (range 10.6-17.0) and 10.5 ± 2.2 mm (6.6-15.1), respectively. This new screw fixation technique and measurement data on the coracoid base may be beneficial for safety screw fixation of coracoid base fracture. PMID:24770936

Kawasaki, Yoshiteru; Hirano, Tetsuya; Miyatake, Katsutoshi; Fujii, Koji; Takeda, Yoshitsugu

2014-07-01

294

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

PubMed Central

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

2012-01-01

295

[Management of proximal scaphoid bone pseudarthroses and fractures with the mini-Herbert screw via a dorsal approach].  

PubMed

32 patients, aged 16 to 49 years, were treated by osteosynthesis using the Herbert mini screw. The indications were five fractures (type B3, Herbert classification), two delayed unions (type C) and 25 nonunions (type D1 to D3, Filan and Herbert classification). Six patients received no bone grafts, 19 received cancellous bone graft from the radius. An interpositional iliac crest bone graft was used in four, and a vascularized bone graft from the distal radius in three cases respectively. The average postoperative immobilisation in a forearm splint was nine weeks. 26 patients could be recruited for clinical follow-up at an average of 14.5 months. The radiological results were assessed in 30 cases (94%). Bony consolidation was achieved in 26 cases (100% of the fractures, 84% of the nonunions). In three cases a loosening of the screw, and in three further cases a dislocation into the radiocarpal joint were observed. A humpback deformity was present in four cases. Three patients showed a persisting nonunion, one patient a fibrous union. Early degenerative changes of the radiocarpal joint were observed in six cases. The clinical follow up examination showed an average grip strength of 91% (JAMAR II), 94% for the three finger, and 95% for the pinch grip compared to the contralateral side. The mean postoperative pain score on the visual analog scale was one for resting conditions, eleven for motion and 33 under stress. The range of motion was 79% of the opposite side for extension/flexion and 83% for radial/ulnar deviation. The average DASH-score reached 15 points. The Herbert mini screw has proven to be a reliable implant for reconstruction of proximal pole fractures and nonunions of the scaphoid. PMID:11572122

Küntscher, M; Tränkle, M; Sauerbier, M; Germann, G; Bickert, B

2001-09-01

296

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

NASA Astrophysics Data System (ADS)

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

Li, Jia; Fang, Qihong; Liu, Youwen

2014-06-01

297

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

PubMed

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

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

2014-06-25

298

Virtual Passive Controller for Robot Systems Using Joint Torque Sensors  

NASA Technical Reports Server (NTRS)

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.

Aldridge, Hal A.; Juang, Jer-Nan

1997-01-01

299

Management of Unstable Thoraco-Lumbar Fractures with Pedicular Screw Instrumentation: A Series of 30 cases.  

PubMed

Introduction: Trauma to spine is one of the grave injuries. They cause infinite morbidity and disability to the patient. Lately consensus is evolving across the world for stabilization of unstable spines with fusion and instrumentation even though most authors agree that neurological recovery is independent of treatment modality. Objectives of this study are to evaluate effectiveness of spinal stabilization with pedicular instrumentation in the management of thoraco-lumbar fractures to restore structural stability, early ambulation and improving neurological status of the patient Material and Methods: During the period from October 2009 to September 2010, 33 cases of thoraco-lumbar spine fractures were treated operatively with posterior decompression and pedicular screw instrumentation. Of these, 3 cases were lost to follow up. Hence the results of 30 cases were evaluated. All patients were treated by posterior decompression and pedicular screw instrumentation. Neurological and radiological parameters were assessed during serial follow-ups. Observation and Results: The mean duration of follow-up was 11 months. Of the 30 patients 24 showed neurological improvement by at least 1 grade and average grade of improvement was 1.5 grades. Mean pre-operative sagittal angle (SA) was 19.9 degrees and sagittal index (SI) was 0.54. Mean post-operative SA was 9.3 degrees and SI was 0.72. Mean SA and SI during the final follow-up were 10.9 degrees and 0.69 respectively. Discussion and Conclusion: Neurological recovery and maintenance of radiological correction in our study were comparable to other studies. The results in our short series of 30 cases have been encouraging. But there is need for more cases and longer follow-ups to come to categorical conclusion. PMID:24392401

Hegde, Atmananda; Babu, Rajan; Shetty, Abhishek

2013-11-01

300

The effects of screw removal on bone strain in an idealized plated bone model.  

PubMed

An idealized plated bone model was used to test the hypothesis that selected screw removal could alter the bone strain field and be a viable treatment for stress protection osteoporosis. Eighteen bone screw modifications were evaluated for their effects on bone strain. The three variables studied were number, position, and length of screws. Removal of two or four bone screws from an eight hole plate significantly increased the strain per load on the bone model over the values with eight screws in the plate (p less than 0.05). The four screw configurations increased bone strain more than the six screw configurations. It also was shown that the position of screws in the plate could significantly alter the bone strain per load results. Removal of six bone screws from an eight hole plate also increased the bone strain per load, but to excess in some tests. In those configurations, the results were not statistically different from the unplated configuration. Replacement of the full length screws with eight half length screws that engaged only the near cortex significantly reduced bone strain per load as compared with eight bicortical bone screws. PMID:3238883

Korvick, D L; Monville, J D; Pijanowski, G J; Phillips, J W

1988-01-01

301

Evaluation of calcium sulfate paste for augmentation of lumbar pedicle screw pullout strength  

Microsoft Academic Search

Background context: Many authors have evaluated the components responsible for ultimate pullout strength of pedicle screws. In these studies, one important variable has been the screw fixation. Because pedicle screw fixation has increased in popularity over recent years, so has the need for augmentation in difficult situations. Polymethylmethacrylate (PMMA) has been established as the gold standard in terms of strength

Michael T Rohmiller; Dugan Schwalm; R. Chris Glattes; Tarek G Elalayli; Dan M Spengler

2002-01-01

302

Pushout strength of tibial locking screws: Development of finite element models  

Microsoft Academic Search

This study investigated the bone holding power of tibial locking screws by mechanical testing and finite element analysis. In mechanical tests, five types of commercially available tibial locking screws: Howmedica, Osteo AG, Richards type I, Richards type II, and Synthes were inserted in a cylinder of polyurethane foam bone. Axial load was applied to the screw tip to push the

Jinn Lin

2003-01-01

303

Development and Testing of a Screw Compressor Supermarket Refrigeration System: Phase II, Final Report  

Microsoft Academic Search

A laboratory prototype screw compressor refrigeration system was designed, fabricated and tested under various evaporator and ambient conditions. The design is based on a Dunham-Bush vertical hermetic screw compressor and other standard refrigeration components. Results indicate that a screw compressor rack with vapor injection can increase the thermodynamic efficiency of low temperature refrigeration in supermarkets by 20 to 28% compared

H. Hamed Borhanian; William M. Toscano; Kang P. Lee

1987-01-01

304

Design and construction of custom-made neoprene thumb carpo-metacarpal orthosis with thermoplastic stabilization for first carpo-metacarpal joint osteoarthritis.  

PubMed

Individuals with first carpo-metacarpal (CMC) osteoarthritis (OA) often experience pain and difficulty with functional activities. Thus, designing orthotics to improve function and decrease pain is common practice. These therapists designed an orthosis using a combination of neoprene and thermoplastic materials to create a soft orthosis that provides support to the first CMC joint - Victoria Priganc, PhD, OTR, CHT, CLT. PMID:23523512

Bani, Monireh Ahmadi; Arazpour, Mokhtar; Curran, Sarah

2013-01-01

305

Thermally-active screw dislocations in si nanowires and nanotubes.  

PubMed

Dislocations significantly influence the physical properties of nanomaterials. Nonequilibrium molecular dynamics simulations uncover significant reductions in thermal conductivity when <110> Si nanowires contain axial screw dislocations. The effect can act in combination with other known thermal conductivity limiting mechanisms, and thus can enable the further optimization of the figure of merit for a new family of complex thermoelectric nanomaterials. PMID:24574194

Xiong, Shiyun; Ma, Jihong; Volz, Sebastian; Dumitric, Traian

2014-05-01

306

Primary thoracoplasty and pedicle screw instrumentation in thoracic idiopathic scoliosis  

Microsoft Academic Search

Thoracoplasty in combination with spine fusion is an established method to address the rib cage deformity in idiopathic scoliosis. Most reports about thoracoplasty and scoliosis correction focused on Harrington or CD instrumentation. We report a retrospective analysis of 21 consecutive patients, who were treated with pedicle screw instrumentation for idiopathic thoracic scoliosis and concomitant thoracoplasty. Minimal follow up was 24

Kan Min; Beat Waelchli; Frederik Hahn

2005-01-01

307

Bone registration method for robot assisted surgery: pedicle screw insertion  

Microsoft Academic Search

SUMMARY A registration method that identifies bone geometry with respect to a robotic manipulator arm is presented. Although the method is generally applicable to many orthopaedic internal fixation, it was only demonstrated for the insertion of pedicle screws in vertebral bodies for spine fixation. The method relies upon obtaining an impression of the vertebral bodies. Computed Tomography scans of both

K Abdel-Malek; D P McGowan; V K Goel; D Kowalski; A Hager

1997-01-01

308

Theory of electrical resistance of multivalley semiconductors with screw dislocations  

Microsoft Academic Search

The diffusion theory of electrical resistance in multivalley semiconductors of Si-type with screw dislocations is developed. Intervalley electron transitions are taken into account. The effect of the inhomogeneous dislocation distribution on the electrical resistance of the crystal is considered.

Yu. V. Kornyushin; P. Streda

1973-01-01

309

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

310

Twin-screw extrusion of ‘Pesta’-encapsulated biocontrol agents  

Microsoft Academic Search

‘Pesta’ granules in which fungal propagules are encapsulated in a wheat gluten matrix were prepared in multipound quantities by twin-screw extrusion and fluid bed drying. Dough formulations for extrusion contained wheat flour and kaolin, or wheat flour, kaolin and rice flour, plus water and fungal inoculum. Conidial inoculum of Colletotrichum truncatum, a pathogen of the weed hemp sesbania (Sesbania exaltata),

D. J. Daigle; W. J. Connick; C. D. Boyette; M. P. Lovisa; K. S. Williams; M. Watson

1997-01-01

311

An online measuring system for large screw threads  

NASA Astrophysics Data System (ADS)

An online measuring system can automatically detect large screw threads by using the neotype gauge head of threads, which includes a TESA inductance type transducer and a probe pin chosen according to the tooth-type of the screw thread. The contact measurement method was adopted on the basis of the synthetic measurement principle. The functional diameter of thread has experimentally been investigated and analyzed. The method of data processing is not only based on the principle of a precision measurement, but also on the principle of a dynamic test. The dynamic error is analyzed in this paper by spectrum analysis. The dynamic error is taken out and data of the functional diameter of the thread will be obtained. The analysis and the results of an actual measurement mentioned above show that the neotype gauge head of thread is capable to get the error and relative changes of the functional diameter of the screw thread. So the compatibility of saw-tooth thread can be evaluated. The system is not only suited for the test of saw-tooth thread, but also for that of other large threads with different tooth forms by using different types of probes. External threads as well as internal threads can be tested. Because the measurement strength of the neotype gauge head is much smaller than that of regular screw gauges, thus diminishing the measurement error resulting from the contact stress, the measurement precision of the gauging head can reach 1?m.

Zhang, Hongyan; Zhang, Guoxiong

2008-12-01

312

Conducting-polymer-driven actively shaped propellers and screws  

Microsoft Academic Search

Conducting polymer actuators are employed to create actively shaped hydrodynamic foils. The active foils are designed to allow control over camber, much like the ailerons of an airplane wing. Control of camber promises to enable variable thrust in propellers and screws, increased maneuverability, and improved stealth. The design and fabrication of the active foils are presented, the forces are measured

John D. Madden; Bryan Schmid; Serge R. Lafontaine; Peter G. A. Madden; Franz S. Hover; Karl McLetchie; Ian W. Hunter

2003-01-01

313

Maxillary expansion with the memory screw: a preliminary investigation  

PubMed Central

Objective The purpose of this study was to investigate the effects of a newly developed rapid maxillary expansion screw-the memory screw-over 6 months. Methods Five subjects, aged between 11.7 and 13.75 years, were enrolled in this study. All subjects underwent placement of a maxillary expansion appliance containing superelastic nickel-titanium open-coil springs in its screw bed. The parents of the patients and/or the patients themselves were instructed to activate the expansion screw by 2 quarter-turns 3 times a day (morning, midday, and evening; 6 quarter-turns a day). The mean expansion period was 7.52 ± 1.04 days. Dentoskeletal effects of the procedure, including dentoalveolar inclination, were evaluated. Measurements of all the parameters were repeated after 6 months of retention in order to check for relapse. Results Sella-Nasion-A point (SNA) and Sella-Nasion/Gonion-Menton angles increased, and Sella-Nasion-B point (SNB) angle decreased in all the subjects during the expansion phase. However, they approximated to the initial values at the end of 6 months. On the other hand, the increments in maxillary apical base (Mxr-Mxl) and intermolar widths was quite stable. As expected, some amount of dentoalveolar tipping was observed. Conclusions The newly developed memory expansion screw offers advantages of both rapid and slow expansion procedures. It widens the midpalatal suture and expands the maxilla with relatively lighter forces and within a short time. In addition, the resultant increments in the maxillary apical base and intermolar width remained quite stable even after 6 months of retention.

Halicioglu, Koray; Kiki, Ali

2012-01-01

314

Posterior lumbar interbody fusion using one diagonal fusion cage with transpedicular screw/rod fixation.  

PubMed

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 months postoperatively by the same assessor and put into four categories: excellent, good, fair, and poor. Operative time, blood loss, hospital expense, and complications were also recorded. All patients achieved successful radiographic fusion at 2 years, and this was achieved at 1 year in 25 out of 27 patients. At 2 years, clinical results were excellent in 15 patients, good in 10, fair in 1, and poor in 1. Regarding complications, one patient had a postoperative motor and sensory deficit of the nerve root. Reoperation was required in one patient due to migration of pedicle screws. No implant fractures or deformities occurred in any of the patients. PLIF using diagonal insertion of a single threaded cage with supplemental transpedicular screw/rod instrumentation enables sufficient decompression and solid interbody fusion to be achieved with minimal invasion of the posterior spinal elements. It is a clinically safer, easier, and more economical means of accomplishing PLIF. PMID:12709855

Zhao, Jie; Hou, Tiesheng; Wang, Xinwei; Ma, Shengzhong

2003-04-01

315

Distal interphalangeal joint arthrodesis using nitinol intramedullary fixation implants: X-fuse implants for DIP arthrodesis.  

PubMed

Arthrodesis has been shown to be a successful operative procedure for the treatment of intractable pain, instability, and deformity of the distal interphalangeal joint of the fingers, and interphalangeal joint of the thumb. Multiple fixation techniques have been used in the past including Kirschner wires, tension bands, headless screws, or lag screws. Clinical results are generally acceptable, but complication rates have been reported to vary between 10% and 20%. Complications include nonunion, pain, malunion, infection, nerve injury, and protruding hardware. The aim of this study is to describe an alternative technique for arthrodesis of the distal interphalangeal joint of the fingers or interphalangeal joint of the thumb using Nitinol implants for intramedullary fixation with a minimal complication rate. PMID:23970200

Seitz, William H; Marbella, Marko E

2013-09-01

316

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 ...

317

DIAPHRAGM ACTION OF SANDWICH PANELS IN PIN-JOINTED STEEL STRUCTURES: A SEISMIC STUDY  

Microsoft Academic Search

The paper focuses on the seismic response of steel pin-jointed frames braced by lightweight cladding panels. In particular, with the aim to investigate the performance of such a structural scheme when acting as a dissipative system, a wide numerical study has been developed. It is based upon available shear tests on screwed sandwich panels, whose experimental cyclic responses are properly

GIANFRANCO DE MATTEIS; RAFFAELE LANDOLFO

2000-01-01

318

An approach to the functional anatomy of the sacroiliac joints in vivo  

Microsoft Academic Search

Summary This first part of this paper is a review of the literature on the functional anatomy of the sacroiliac joint followed by a preliminary biomechanical study of the fresh post mortem pelvis. The latter was done in order to determine the coefficients of the screw matrix and the position of the instantaneous centers of rotation during the symmetrical movements

B. Lavignolle; J. M. Vital; J. Senegas; J. Destandau; B. Toson; P. Bouyx; P. Morlier; G. Delorme; A. Calabet

1983-01-01

319

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)

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)

De Bothezat, George

1920-01-01

320

Two-term approximation for growth rates of a guiding center screw pinch  

SciTech Connect

The guiding center plasma description of an isotropic, collisionless plasma is used to study the linear stability of the diffuse screw pinch in the special case when the poloidal magnetic field component is small compared with the axial magnetic field component. A two-term approximation for growth rates is derived from the linearized guiding center plasma equations by straightforward asymptotic expansion in terms of a small parameter that is proportional to (B/sub theta//rB/sub z/)such thatub r/=0. The two-term approximate solution is compared with exact solutions and the range of validity of the approximations is examined. The result obtained from the guiding center plasma model is compared and contrasted with that from ideal magnetohydrodynamics. It is shown that the isotropic guiding center plasma may be more unstable or less unstable than ideal magnetohydrodynamics for the same configuration, depending on the parameters.

Cayton, T.E.; Vahala, G.; Barnes, D.C.

1980-11-01

321

Maxillo Mandibular Fixation in Edentulous Scenarios: Combined MMF Screws and Gunning Splints.  

PubMed

A fracture of the maxillary or mandibular bone requires the afflicted to undergo a maxillo mandibular fixation for the establishment of pre traumatic occlusion. This process is quiet tedious and consumes a considerable period of time before any surgical procedure can commence. Such a situation can be complicated in case the individual with maxillomandibular fracture has sparse or absent dentition; for such cases a splint is fabricated or an erstwhile existing denture is used for maintaining a vertical jaw proportion. Stabilizing such splints to the jaw requires various invasive approaches that can bring into harm's way, adjacent soft tissue vital structures. We describe here an innovative technique combining the time tested method of the "gunning splint" and the advanced minimally invasive MMF screws for obtaining closed reduction in edentulous jaw fractures. PMID:24822016

Chaudhary, Zainab; Sharma, Rakesh; Krishnan, Sriram

2014-06-01

322

Fixation with C-2 laminar screws in occipitocervical or C1-2 constructs in children 5 years of age or younger: a series of 18 patients.  

PubMed

Object There are rare indications for upper cervical spine fusion in young children. Compared with nonrigid constructs, rigid instrumentation with screw fixation increases the fusion rate and reduces the need for halo fixation. Instrumentation may be technically challenging in younger children. A number of screw placement techniques have been described. Use of C-2 translaminar screws has been shown to be anatomically feasible, even in the youngest of children. However, there are few data detailing the clinical outcome. In this study, the authors describe the clinical and radiographic follow-up of 18 children 5 years of age or younger who had at least one C-2 translaminar screw as part of an occipitocervical or C1-2 fusion construct. Methods A retrospective review of all children treated with instrumented occipitocervical or C1-2 fusion between July 1, 2007, and June 30, 2013, at Riley Children's Hospital and Texas Children's Hospital was performed. All children 5 years of age or younger with incorporation of at least one C-2 translaminar screw were identified. Results Eighteen children were studied (7 boys and 11 girls). The mean age at surgery was 38.1 months (range 10-68 months). Indications for surgery included traumatic instability (6), os odontoideum (3), destructive processes (2), and congenital instability (7). A total of 24 C-2 translaminar screws were placed; 23 (95.8%) of 24 were satisfactorily placed (completely contained within the cortical walls). There was one medial cortex breach without neurological impingement. There were no complications with screw placement. Three patients required wound revisions. Two patients died as a result of their original condition (trauma, malignant tumor). The mean follow-up duration for the surviving patients was 17.5 months (range 3-60 months). Eleven (91.7%) of the 12 patients followed for 6 months or longer showed radiographic stability or completed fusion. Conclusions Use of C-2 translaminar screws provides an effective anchor for internal fixation of the upper cervical spine. In this study of children 5 years of age or younger, the authors found a high rate of radiographic fusion with a low rate of complications. PMID:24784980

Savage, Jennifer G; Fulkerson, Daniel H; Sen, Anish N; Thomas, Jonathan G; Jea, Andrew

2014-07-01

323

Nonunions around the knee joint  

PubMed Central

Nonunions of the distal femur are relatively rare but can occur with or without previous surgery. Many surgical methods have been described for the treatment of these nonunions including external fixation, intramedullary nailing, arthroplasty, and fixed angle plating. While arthroplasty may have a limited role in the elderly patient with osteoporosis and severe communiution, most nonunions can be reliably treated with revision fixation using a fixed angled device, lag screws, and bone grafting as needed. Fixed-angle plating also has the advantage of stabilising a small distal segment where intramedullary nailing has proven to be less effective. Any surgical intervention must include restoration of the normal mechanical axis of the distal femur for a satisfactory clinical outcome. Proximal tibia nonunions are a similarly rare clinical entity due to the excellent blood supply in the metaphysis. Extra-articular proximal tibial nonunions are often due to malreduction during the index surgery resulting in poor bone contact and biomechanical stability. Soft tissue forces and improper use of intramedullary implants often predispose these fractures to malalignment. Revision surgery consisting of deformity correction and at least a lateral tension band plate with lag screws has led to predictable union and good clinical results. Tibial plateau nonunions are exceedingly uncommon but are difficult to treat because of small, often devascularised fragments, post-surgical scarring, and osteopenia. Revision surgery with meticulous soft tissue handling to restore the articular surface and mechanical axis with repair of meniscal pathology gives the patient the best chance of recovering knee function.

Chan, Daniel B.; Jeffcoat, Devon M.; Lorich, Dean G.

2009-01-01

324

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

PubMed

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

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

1999-01-01

325

Percutaneous pedicle screw placement in the thoracic spine: A cadaveric study  

PubMed Central

Study Design: A cadaveric study to determine the accuracy of percutaneous screw placement in the thoracic spine using standard fluoroscopic guidance. Summary of Background Data: While use of percutaneous pedicle screws in the lumbar spine has increased rapidly, its acceptance in the thoracic spine has been slower. As indications for pedicle screw fixation increase in the thoracic spine so will the need to perform accurate and safe placement of percutaneous screws with or without image navigation. To date, no study has determined the accuracy of percutaneous thoracic pedicle screw placement without use of stereotactic imaging guidance. Materials and Methods: Eighty-six thoracic pedicle screw placements were performed in four cadaveric thoracic spines from T1 to T12. At each level, Ferguson anterior–posterior fluoroscopy was used to localize the pedicle and define the entry point. Screw placement was attempted unless the borders of the pedicle could not be delineated solely using intraoperative fluoroscopic guidance. The cadavers were assessed using pre- and postprocedural computed tomography (CT) scans as well as dissected and visually inspected in order to determine the medial breach rate. Results: Ninety pedicles were attempted and 86 screws were placed. CT analysis of screw placement accuracy revealed that only one screw (1.2%) breached the medial aspect of the pedicle by more than 2 mm. A total of four screws (4.7%) were found to have breached medially by visual inspection (three Grade 1 and one Grade 2). One (1.2%) lateral breach was greater than 2 mm and no screw violated the neural foramen. The correlation coefficient of pedicle screw violations and pedicle diameter was found to be 0.96. Conclusions: This cadaveric study shows that percutaneous pedicle screw placement can be performed in the thoracic spine without a significant increase in the pedicle breach rate as compared with standard open techniques. A small percentage (4.4%) of pedicles, especially high in the thoracic spine, may not be safely visualized.

Hardin, Carolyn A.; Nimjee, Shahid M.; Karikari, Isaac O.; Agrawal, Abhishek; Fessler, Richard G.; Isaacs, Robert E.

2013-01-01

326

Single allograft medial collateral ligament and posterior oblique ligament reconstruction: a technique to improve valgus and rotational stability.  

PubMed

We present a novel and simple method for single hamstring allograft MCL and PMC reconstruction, which can improve both joint valgus and external rotational stability and maximize utilization of allograft. All patients received arthroscopic evaluation through inferomedial and inferolateral knee incisions to ascertain whether there were intra-articular injuries. An 8-cm-length longitudinal incision was made from 1 cm above adductor tubercle to 5-cm proximal medial tibia joint line. The anterior tibia insertion was defined as 15 mm lateral from the medial tibia edge and 45 mm below the medial tibia joint line. The posterior tibia insertion was defined as 15 mm lateral from the medial tibia edge and 20 mm below the medial tibia joint line. A 5- or 6-mm reamer was used to drill the tibia tunnel along with guide pin, and a 6 or 7 mm drill was used to drill the femur tunnel to a depth of 25 or 30 mm until the proximal adductor tubercle. The allograft was harvested from tibia and placed into the tunnel and fixed with absorbable interference screw. All patients performed active rehabilitation exercises after the operation periodically. PMID:23807396

Dong, Jiangtao; Ji, Gang; Zhang, Yingze; Gao, Shijun; Wang, Fei; Chen, Baicheng

2014-08-01

327

Design and Characterization of an Improved Screw-Assisted Rotary Feeding System for Aerosolization of Ultra-Small Quantities of Particulate Solids  

Microsoft Academic Search

Many previous studies have examined solid-state particle discharge systems. However, several drawbacks have been encountered in terms of laboratory-scale particle feeding systems (e.g., high feeding rates, discontinuous feeding characteristics, the absence of long-term stability, and the use of high carrier gas volume rates). In this study, a state-of-the-art screw-assisted rotary feeding system was developed and evaluated in terms of aerosolization

Kang Soo Lee; Jae Hee Jung; Sang In Keel; Jin Han Yun; Yong Jin Kim; Hyung Keun Lee; Sang Soo Kim

2010-01-01

328

Stress fracture of the proximal femur after screw removal.  

PubMed

We describe a case of stress fracture of the proximal femur occurring in a patient after removal of an internal fixation device for a comminuted subtrochanteric fracture. The presenting clinical picture resembled a late postoperative infection with a positive technetium and gallium bone scan and normal radiological findings. The stress fracture occurred after removal of the fixation device when the patient started full weight-bearing. The patient was treated initially as having osteomyelitis until a second X-radiograph some weeks later demonstrated a stress fracture through one of the previous screw holes. This case illustrates well the possible complication of a insufficiency fracture subsequent to the occurrence of stress risers through screw holes in a weakened bone when submitted to normal load. The clinical presentation may sometimes resemble late postoperative infection. PMID:8775714

Velkes, S; Nerubay, J; Lokiec, F

1996-01-01

329

Medial migration of lag screw after gamma nailing.  

PubMed

Fractures of the proximal femur are common in the elderly population. Intramedullary nailing has become the standard treatment for intertrochanteric fractures although several extramedullary implants (e.g. dynamic hip screw (DHS), blade plate, locking compression plate (LCP), etc.) exist. However, despite this being a very common operation in traumatology, there are numerous associated complications. We report the rare complication of the migration of the medial lag screw into the pelvis at five and a half weeks postoperatively. The implant was removed and replaced by a total hip arthroplasty with simultaneous grafting of the acetabular defect and strapping of the greater trochanter. The evolution was favourable. We also present a review of the literature and analyze our case. PMID:24933440

Thein, Eric; De Cannière, Alexandre; Burn, Alexandre; Borens, Olivier

2014-08-01

330

Screw pumps provide high efficiency in transport of Orinoco bitumen  

SciTech Connect

One of the world`s largest known deposits of extra natural bitumen is located in the Orinoco River basin of eastern Venezuela. Production and transportation of an emulsion of bitumen and water is one of the major projects being directed by Petroleos de Venezuela S.A. This paper reviews the pump selection options considered in transporting this bitumen to a viable processing facility. The three pump types evaluated were centrifugal, reciprocating, or rotary screw. Performance and cost parameters are evaluated and the screw pump was determined to be the most economical, high performance choice. The paper goes on to describe the installation of the main transport lines and efficiency of these new pumps.

Brennan, J.R. [IMO Industries, Inc., Monroe, NC (United States)

1995-03-01

331

Analysis of Eyring-Powell fluid in helical screw rheometer.  

PubMed

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

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

2014-01-01

332

Delayed perforation of the aorta by a thoracic pedicle screw  

PubMed Central

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.

Birkenmaier, Christof; Fottner, Andreas; Jansson, Volkmar; Durr, Hans Roland

2008-01-01

333

[Metacarpophalangeal joint injuries and sequelae].  

PubMed

Injuries of the metacarpophalangeal joints of the thumb and fingers are of a bony or ligamentous nature. They can heal without subsequent problems if correctly diagnosed and treated but incorrect or absent diagnostics and therapy can result in chronic instability, dislocation, fusion as well as subsequent arthritis and functional limitations. They can lead to substantial impairment of the gripping function. Fractures with inclusion of joints and with fragments sufficiently large for refixation are as a rule treated operatively just as differences in torsion and instability. Persisting instabilities are secondarily stabilized by ligamentoplasty and arthritis of the metacarpophalangeal joint of the thumb is treated by fusion. For metacarpophalangeal joints of the fingers the main concern is preserving motion. Established salvage operations for arthritis include denervation, resection arthroplasty and systematic arthrolysis for impairment of the joint and contractures with intact joint surfaces. Even in chronic conditions, with appropriate treatment good functional results for metacarpophalangeal joints of the thumb and fingers can be achieved. This article presents the current pathophysiological principles and concepts for diagnostics and therapy of acute and chronic injuries of the metacarpophalangeal joints of fingers and thumbs. PMID:24700083

Meier, R

2014-04-01

334

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

PubMed Central

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

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

2009-01-01

335

Accuracy and safety of free-hand pedicle screw fixation in age less than 10 years  

PubMed Central

Background: Pedicle screws are being used commonly in the treatment of various spinal disorders. However, use of pedicle screws in the pediatric population is not routinely recommended because of the risk of complications. The present study was to evaluate the safety of pedicle screws placed in children aged less than 10 years with spinal deformities and to determine the accuracy and complication (early and late) of pedicle screw placement using the postoperative computed tomography (CT) scans. Materials and Methods: Thirty one patients (11 males and 20 females) who underwent 261 pedicle screw fixations (177 in thoracic vertebrae and 84 in lumbar vertebrae) for a variety of pediatric spinal deformities at a single institution were included in the study. The average age of patients was 7 years and 10 months. These patients underwent postoperative CT scan which was assessed by two independent observers (spine surgeons) not involved in the treatment. Results: Breach rate was 5.4% (14/261 screws) for all pedicles. Of the 177 screws placed in the thoracic spine, 13 (7.3%) had breached the pedicle, that is 92.7% of the screws were accurately placed within pedicles. Seven screws (4%) had breached the medial pedicle wall, 4 screws (2.3%) had breached the lateral pedicle wall and 2 screws (1.1%) had breached the superior or inferior pedicle wall respectively. Of the 84 screws placed in the lumbar spine, 83 (98.8%) screws were accurately placed within the pedicle. Only 1 screw (1.2%) was found to be laterally displaced. In addition, the breach rate was found to be 4.2% (11/261 screws) with respect to the vertebral bodies. No neurological, vascular or visceral complications were encountered. Conclusions: The accuracy of pedicle screw placement in pedicles and vertebral bodies were 94.6% and 95.8% respectively and there was no complication related to screw placement noted until the last followup. These results suggest that free-hand pedicle screw fixation can be safely used in patients younger than 10 years to treat a variety of spinal disorders.

Seo, Hyoung Yeon; Yim, Ji Hyeon; Heo, Jung Pil; Patil, Abhishek S; Na, Seung Min; Kim, Sung Kyu; Chung, Jae Yoon

2013-01-01

336

Subaxial subluxation after atlantoaxial transarticular screw fixation in rheumatoid patients  

PubMed Central

The most common cervical abnormality associated with rheumatoid arthritis (RA) is atlantoaxial subluxation, and atlantoaxial transarticular screw fixation has proved to be one of the most reliable, stable fixation techniques for treating atlantoaxial subluxation. Following C1–C2 fixation, however, subaxial subluxation reportedly can bring about neurological deterioration and require secondary operative interventions. Rheumatoid patients appear to have a higher risk, but there has been no systematic comparison between rheumatoid and non-rheumatoid patients. Contributing radiological factors to the subluxation have also not been evaluated. The objective of this study was to evaluate subaxial subluxation after atlantoaxial transarticular screw fixation in patients with and without RA and to find contributing factors. Forty-three patients who submitted to atlantoaxial transarticular screw fixation without any concomitant operation were followed up for more than 1 year. Subaxial subluxation and related radiological factors were evaluated by functional X-ray measurements. Statistical analyses showed that aggravations of subluxation of 2.5 mm or greater were more likely to occur in RA patients than in non-RA patients over an average of 4.2 years of follow-up, and postoperative subluxation occurred in the anterior direction in the upper cervical spine. X-ray evaluations revealed that such patients had a significantly smaller postoperative C2–C7 angle, and that the postoperative AA angle correlated negatively with this. Furthermore, anterior subluxation aggravation was significantly correlated with the perioperative atlantoaxial and C2–C7 angle changes, and these two changes were strongly correlated to each other. In conclusion, after atlantoaxial transarticular screw fixation, rheumatoid patients have a greater risk of developing subaxial subluxations. The increase of the atlantoaxial angel at the operation can lead to a decrease in the C2–C7 angle, followed by anterior subluxation of the upper cervical spine and possibly neurological deterioration.

Neo, Masashi; Sakamoto, Takeshi; Fujibayashi, Shunsuke; Yoshitomi, Hiroyuki; Nakamura, Takashi

2009-01-01

337

Coracoclavicular screw fixation for unstable distal clavicle fractures.  

PubMed

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

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

2005-07-01

338

Modified Austin bunionectomy with single screw fixation: a comparison study.  

PubMed

The authors present a new modification of the Austin bunionectomy with single 2.7-mm. cortical screw fixation, and a comparison study with the standard osteotomy fixation using a single Kirschner wire. The results include subjective postoperative evaluation as well as objective radiographic analysis. Suggestions are made that this type of procedure is indeed a viable alternative in a large patient population suffering from hallux abducto valgus deformities. PMID:2794359

Clancy, J T; Berlin, S J; Giordano, M L; Sherman, S A

1989-01-01

339

Management of odontoid fractures with percutaneous anterior odontoid screw fixation  

Microsoft Academic Search

Minimally invasive techniques have revolutionized the management of a variety of spinal disorders. The authors of this study\\u000a describe a new instrument and a percutaneous technique for anterior odontoid screw fixation, and evaluate its safety and efficacy\\u000a in the treatment of patients with odontoid fractures. Ten patients (6 males and 4 females) with odontoid fractures were treated\\u000a by percutaneous anterior

Yong-Long Chi; Xiang-Yang Wang; Hua-Zi Xu; Yan Lin; Qi-Shan Huang; Fang-Min Mao; Wen-Fei Ni; Sheng Wang; Li-Yang Dai

2007-01-01

340

Femoral nailing with transverse locking screws through the femoral neck  

Microsoft Academic Search

We treated 55 patients with subtrochanteric or comminuted femoral fractures with a transverse locking femoral nail (Alta, Howmedica). This nail was positioned more cephalad than usual so that at least one fixation screw was located in the femoral neck or head. Forty-seven fractures (20 subtrochanteric and 27 diaphyseal) were available for follow-up averaging 12 months (3-35). The time to radiographic

B. H. Ziran; A. D. Wasan; M. W. Chapman

2001-01-01

341

Metacarpophalangeal joint replacement with osseointegrated endoprostheses.  

PubMed

A new type of endoprosthesis for reconstruction of the metacarpophalangeal (MCP) joint has been tested. The novel arthroplasty consists of a joint mechanism with two screw-shaped fixtures for bone anchorage. These fixtures, of commercially pure titanium, are gently screwed into the anchoring bone on each side of the diseased joint, the aim being to achieve osseointegration, i.e. a direct contact between implant and bone without interposed soft tissue layers. The hand was immobilized in a dorsal splint for 8-10 days post-operatively after which a carefully controlled mobilization program was initiated. In principle, the titanium fixtures, the surgical technique and the primary immobilization represent an approach similar to that previously used in various reconstruction procedures of the jaw. This paper describes 5 case histories of reconstructions required because of osteoarthrosis in a single MCP joint. Prior to the operation, all patients suffered from severe problems resulting from their arthrotic joints and they had not been able to work for several months. After surgery they were evaluated by a clinical assessment program and X-rays were taken at various times of follow-up. As well as visual inspection all radiograms were subjected to densitometry by means of a computer-based image-analysis system in order to provide information on the development of bone density in the bone-to implant interface region. From a functional point of view the treatment with osseointegrated prostheses must be regarded as being successful. All patients were able to go back to their original work and their hands had a satisfactory range of movement and grip strength with no signs of impaired function on longer follow-up time. Clinical problems were one re-operation, one case of implant fracture and one case requiring exchange of the joint mechanism. The computer-assisted evaluation of the radiograms revealed the presence of calcified tissue in many sections where the naked eye was not capable of differentiating any bone. In conclusion, it seems possible to establish osseointegration of MCP-endoprostheses in the arthrotic human joint in complicated cases which were regarded as contraindicated for any other joint arthroplasty. PMID:3798034

Hagert, C G; Brånemark, P I; Albrektsson, T; Strid, K G; Irstam, L

1986-01-01

342

Handbook on dynamics of jointed structures.  

SciTech Connect

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

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

2009-07-01

343

Screwing/rolling head for pre-threaded caps  

US Patent & Trademark Office Database

The present invention relates to a screwing/rolling head 1 for screwing and sealing a pre-threaded cap 5 on to a threaded neck 6 of a container 7, the head 1 having a cap pressing member 4 capable of engaging the cap 5 and screwing it on to the container 7. The said cap pressing member 4 is associated for operation with a body 2 of the head 1 in such a way that it can be moved with respect to the body 2 between a first contracted configuration and a second extended configuration, in which the movement is rotary-translational with only one degree of freedom. The present invention also relates to a head 1 in which asymmetrical clutch means 18 are interposed between the cap pressing member 4 and the body 2, and a head 1 in which the body 2 comprises a first element 8 and a second element 9 connected to it with respect to rotation by means of a disengageable torque limiter 24.

2009-11-17

344

Modelling of the Heating Process in a Thermal Screw  

NASA Astrophysics Data System (ADS)

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.

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

2012-11-01

345

Determination of screw and nail withdrawal resistance of some important wood species.  

PubMed

In this study, screw and nail withdrawal resistance of fir (Abies nordmanniana), oak (Quercus robur L.) black pine (Pinus nigra Arnold) and Stone pine (Pinus pinea L.) wood were determined and compared. The data represent the testing of withdrawal resistance of three types of screws as smart, serrated and conventional and common nails. The specimens were prepared according to TS 6094 standards. The dimensions of the specimens were 5x5x15cm and for all of the directions. Moreover, the specimens were conditioned at ambient room temperature and 65+/-2% relative humidity. The screws and nails were installed according to ASTM-D 1761 standards. Nail dimensions were 2.5mm diameter and 50 mm length, conventional screws were 4x50mm, serrated screws were 4x45mm and smart screws were 4x50mm. Results show that the maximum screw withdrawal resistance value was found in Stone pine for the serrated screw. There were no significant differences between Stone pine and oak regarding screw withdrawal resistance values. Conventional screw yielded the maximum screw withdrawal resistance value in oak, followed by Stone pine, black pine and fir. Oak wood showed the maximum screw withdrawal resistance value for the smart screw, followed by Stone pine, black pine, and fir. Oak wood showed higher nail withdrawal resistances than softwood species. It was also determined that oak shows the maximum nail withdrawal resistance in all types. The nail withdrawal resistances at the longitudinal direction are lower with respect to radial and tangential directions. PMID:19325775

Aytekin, Alper

2008-04-01

346

Effect of abutment screw surface treatment on reliability of implant-supported crowns.  

PubMed

Purpose: To evaluate and compare the reliability of implant-supported single crowns cemented onto abutments retained with coated (C) or noncoated (NC) screws and onto platform-switched abutments with coated screws. Materials and Methods: Fifty-four implants (DT Implant 4-mm Standard Platform, Intra-Lock International) were divided into three groups (n = 18 each) as follows: matching-platform abutments secured with noncoated abutment screws (MNC); matching-platform abutments tightened with coated abutment screws (MC); and switched-platform abutments secured with coated abutment screws (SC). Screws were characterized by scanning electron microscopy and x-ray photoelectron spectroscopy (XPS). The specimens were subjected to step-stress accelerated life testing. Use-level probability Weibull curves and reliability for 100,000 cycles at 200 N and 300 N (90% two-sided confidence intervals) were calculated. Polarized light and scanning electron microscopes were used for fractographic analysis. Results: Scanning electron microscopy revealed differences in surface texture; noncoated screws presented the typical machining grooves texture, whereas coated screws presented a plastically deformed surface layer. XPS revealed the same base components for both screws, with the exception of higher degrees of silicon in the SiO2 form for the coated samples. For 100,000 cycles at 300 N, reliability values were 0.06 (0.01 to 0.16), 0.25 (0.09 to 0.45), and 0.25 (0.08 to 0.45), for MNC, MC, and SC, respectively. The most common failure mechanism for MNC was fracture of the abutment screw, followed by bending, or its fracture, along with fracture of the abutment or implant. Coated abutment screws most commonly fractured along with the abutment, irrespective of abutment type. Conclusion: Reliability was higher for both groups with the coated screw than with the uncoated screw. Failure modes differed between coated and uncoated groups. PMID:24818196

Anchieta, Rodolfo Bruniera; Machado, Lucas Silveira; Bonfante, Estevam Augusto; Hirata, Ronaldo; Freitas, Amilcar Chagas; Coelho, Paulo G

2014-01-01

347

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

NASA Astrophysics Data System (ADS)

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

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

2013-11-01

348

Comparison of the effects of rapid maxillary expansion caused by treatment with either a memory screw or a Hyrax screw on the dentofacial structures--transversal effects.  

PubMed

The aim of the present study was to investigate and compare the effects of conventional Hyrax screw treatment and memory screw treatment on skeletal and dentoalveolar structures. Thirty-two patients with maxillary transversal deficiency were divided into two groups. The memory-screw group included 17 patients (nine females and eight males), while the Hyrax-screw group comprised 15 patients (eight females and seven males). Mean ages of the subjects in the memory-screw and Hyrax-screw groups were 13.00 ± 1.29 and 12.58 ± 1.50 years, respectively. Plaster models and postero-anterior cephalograms were taken from the patients at the beginning of the treatment (T1) and at the end of expansion (T2) and retention periods (T3). The mean expansion period was 7.76 ± 1.04 days in the memory-screw group and 35.46 ± 9.39 days in the Hyrax-screw group. 'Shapiro-Wilk Normality test' was used to determine whether the investigated parameters were homogeneous or not. To determine the treatment changes within the group, 'paired t-test' and 'Wilcoxon signed-ranks test' were applied to the homogeneous and non-homogeneous parameters, respectively. Comparison between the groups was carried out using 'Student's t-test' for homogeneous parameters and 'Mann-Whitney U-test' for the rest. Rapid maxillary expansion was carried out successfully in both the groups. However, the use of memory screw may be advantageous because it shortens the maxillary expansion period, provides additional expansion in the retention period, and generates light forces relative to the conventional Hyrax screw. PMID:21876219

Hal?c?o?lu, Koray; Yavuz, Ibrahim

2014-04-01

349

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

PubMed

Stem surface treatment and material are two design factors that may affect the onset of implant loosening. For upper limb applications, no known in vitro studies have addressed the role of these two factors on cemented implant stability. Therefore, the purpose of this study was to compare the torsional stability of cemented titanium and cobalt chrome stems with varying surface treatments in vitro. Thirty implant stems of circular cross-section (Ø = 8mm) were machined from cobalt chrome (n = 15) and titanium (n = 15). For each type, stems were subdivided into three groups for application of clinically relevant surface treatments: smooth, sintered beads, or plasma spray. Stems were potted in bone cement, allowed 24 h to cure, and placed in a materials testing machine. Stems were tested under cyclic torsion (1-30 Nm), using a staircase loading protocol. Failure was defined as either the first rapid increase in stem rotation without resistance, or attaining a maximum torque of 30 Nm. Implant stems with non-smooth surfaces offered greater resistance to torsion (p < 0.05), with the plasma spray treatment outlasting the beaded and smooth stems (p < 0.05). Titanium offered superior interface strength (p < 0.05) but reduced resistance to motion (p < 0.05) when compared to cobalt chrome. Therefore, these design features should be considered during upper limb implant design. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 102B: 1217-1222, 2014. PMID:24644238

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

2014-08-01

350

Method and apparatus for determining the preload for screws for dental implant systems  

US Patent & Trademark Office Database

A method and apparatus are provided for determining the preload in a dental implant system. The preload is determined by transmitting a sonic impulse, which is preferably an ultrasonic impulse, at a predetermined frequency to the head of the implant screw through a transducer, which may be incorporated into the head of the screw, the head of a wand which generates the sonic impulse, or the transducer and pulse-generating instrumentation may be incorporated into a torque generating instrument used to tighten the screw. The preload is determined by measuring the delay between the first and second reflections through the preloaded screw to determine a preload value and comparing that value with a pre-established baseline value for the screw, and comparing the difference with a predetermined table of values to determine the preload on the screw.

2002-03-19

351

Assembly means for standardized mechanical joint for pipeline appurtenances  

SciTech Connect

This patent describes an improvement in the standardized mechanical joint connection for use on waterworks or gas pipeline appurtenances wherein the shape or dimensions of the body of the appurtenances preclude the insertion and tightening of the standardized T-bolts. The improvement comprises: a. a screw having an externally threaded cylindrical portion, an hexagonally shaped head on one end of the externally threaded cylindrical portion. The hexagonally shaped head has the same dimensions across flats as the standardized nuts. The externally threaded cylindrical portion has length of such dimension that engagement of the externally threaded cylindrical portion with the internal threads of nut means is provided when a gland, gasket, socket, and spigot are contiguous prior to compression of the gasket, and interference with the externally threaded cylindrical portion is prevented when the screw is tightened and the gasket is compressed, and b. the nut means having an internally threaded elongated shape so as to prevent turning during tightening, means to provide linear contact with a standardized mechanical joint bell flange surface. The nut means has adjacent surfaces sloping away from the linear contact so as to provide for axial misalignment of the screw.

Kennedy, H. Jr.

1987-01-20

352

The mechanical role of laminar hook protection of pedicle screws at the caudal end vertebra  

Microsoft Academic Search

Biomechanical studies have shown hooks to be superior to pedicle screws in pull-out, especially in osteoporosis. This study evaluates the possible increase in stiffness of pedicle screws provided by laminar hooks while applying non-destructive forces to a vertebrectomy model assembled with Compact Cotrel Dubousset (CCD) instrumentation. Synthetic vertebrae were employed in a three-level vertebrectomy model. CCD screw-based three-level constructs with

J. Y. Margulies; R. S. Casar; S. A. Caruso; M. G. Neuwirth; T. R. Haher

1997-01-01

353

Investigation of melting in a modular intermeshing co-rotating twin screw extruder  

Microsoft Academic Search

Since the first patent regarding the co-rotating twin screw extruder was published in 1869, the co-rotating twin screw extruder has evolved into a high performance extruder, having self wiping capability, modular screw configuration, starved feed zone, kneading disc block elements, and special mixing devices. For this device, flow studies began in the mid 1960's but melting studies started in the

Ho-Chul Jung

2004-01-01

354

Accuracy and complications of transpedicular C2 screw placement without the use of spinal navigation  

Microsoft Academic Search

The objective of the study was to describe the technique, accuracy of placement and complications of transpedicular C2 screw\\u000a fixation without spinal navigation. Patients treated by C2 pedicle screw fixations were identified from the surgical log book\\u000a of the department. Clinical data were extracted retrospectively from the patients’ charts. Pedicle screw placement accuracy\\u000a was assessed on postoperative CT scans according

Christian-Andreas Mueller; Lukas Roesseler; Martin Podlogar; Attlila Kovacs; Rudolf Andreas Kristof

2010-01-01

355

Use of a 2.0-mm locking plate\\/screw system for mandibular fracture surgery  

Microsoft Academic Search

Purpose: In this study, we examined the use of a 2.0-mm locking bone plate\\/screw system in mandibular surgery. Patients and Methods: All patients who were treated with a 2.0-mm locking bone plate\\/screw system during an 8-month period for fractures of the mandible or other defects of the mandible were prospectively studied. Ease of use of locking plate\\/screw system, characteristics of

Edward Ellis; John Graham

2002-01-01

356

Use of a locking reconstruction bone plate\\/screw system for mandibular surgery  

Microsoft Academic Search

Purpose: This study examined the use of a locking reconstruction bone plate\\/screw system for use in mandibular surgery.Patients and Methods: All patients treated with a locking reconstruction bone plate\\/screw system for fractures of the mandible or continuity defects in an 18-month period were prospectively studied. Ease of use of the locking plate\\/screw system, characteristics of the fractures\\/defects, and complications were

Alan S Herford; Edward Ellis

1998-01-01

357

Joint pain  

Microsoft Academic Search

Joint pain may result from traumas or repeated microtraumas, as in sports injuries. Pain in osteoarthritis starts before any\\u000a objective finding. It has been demonstrated that in the first stages of this disease, pain is due to intraosseous venous engorgement\\u000a for the earlier thickening of the cortical bone under the articular cartilage. The mechanisms of inflammatory pain are more\\u000a complex

Massimo Zoppi; Elisabetta Beneforti

1999-01-01

358

Syndesmosis screws: How many, what diameter, where and should they be removed? A literature review.  

PubMed

Although screw fixation remains the most commonly used method of syndesmosis fixation, the ideal screw size, placement, and number remain controversial. In addition, there has been debate as to whether the screw should always be removed, and a number of studies have looked at radiological and functional outcomes. In addition a number of cadaveric models have been developed, but the correlation between cadaveric findings and functional outcomes remains unclear. This systematic review of the literature aims to summarise the available evidence on how many screws should be placed, of what diameter, through how many cortices, at what level, and whether they should be removed. PMID:24917210

Peek, A C; Fitzgerald, C E; Charalambides, C

2014-08-01

359

Development and Testing of a Screw Compressor Supermarket Refrigeration System: Phase II, Final Report.  

SciTech Connect

A laboratory prototype screw compressor refrigeration system was designed, fabricated and tested under various evaporator and ambient conditions. The design is based on a Dunham-Bush vertical hermetic screw compressor and other standard refrigeration components. Results indicate that a screw compressor rack with vapor injection can increase the thermodynamic efficiency of low temperature refrigeration in supermarkets by 20 to 28% compared to multiple reciprocating compressor racks. The payback period of the screw compressor refrigeration system relative to multiple reciprocating compressor systems is 1.1 to 1.5 years and the net present value savings range from 15 to 22 thousand dollars.

Borhanian, H. Hamed; Toscano, William M.; Lee, Kang P.

1987-02-01

360

CALAXO(R) Osteoconductive Interference Screw: The Value of Post-Market Surveillance  

PubMed Central

The CALAXO® osteoconductive interference screw was recalled in August 2007 due to reports of increased numbers of postoperative complications associated with screw swelling and prominence leading to the need for surgical debridement. This study reviews complications associated with CALAXO® screw use in a consecutive cohort of patients undergoing anterior cruciate ligament reconstruction surgery by the senior author at our institution. Over a 12 month period, 226 CALAXO® interference screws, either of 20mm length or 25mm length, were implanted in 112 patients, and postoperative complications were noted. The 25mm tibial screw was over 5 times (RR 5.2, 95% CI 1.8 to 15.3) more likely to be prominent than the 20mm screw (p-value = 0.002). Four surgical debridements were required in the 25mm tibial screw group; none were required in the 20mm group. We hypothesize that the inability to bury the longer screw length into the bone tunnel is associated with postoperative complications associated with the CALAXO® screw.

Cox, Charles L.; Homlar, Kelly C.; Carey, James L.; Spindler, Kurt P.

2013-01-01

361

C2 laminar screw and C1-2 transarticular screw combined with C1 laminar hooks for atlantoaxial instability with unilateral vertebral artery injury.  

PubMed

Transarticular screw fixation (TASF) is technically demanding, with high risk of vertebral artery (VA) injury. How to manage intraoperative VA injury and choose optimal alternative fixation becomes a concern of spinal surgeons. In this study, the management strategy for a patient with suspected intraoperative VA injury was analyzed. A 53-year-old woman developed type II odontoid fracture and brain stem injury due to a motor vehicle accident 3 months earlier. After conservative treatments, the brain stem injury improved, but with residual ocular motility defect in the right eye. The odontoid fracture did not achieve fusion with displacement and absorption of fracture fragments. After admission, atlantoaxial fixation using bilateral C1-2 transarticular screws (TASs) combined with C1 laminar hooks was planed. The first TAS was inserted successfully. Unfortunately, suspected VA injury developed during tapping the tract for the second TAS. Considering the previous brain stem injury and that directly inserting the screw to tamponade the hemorrhage might cause VA stenosis or occlusion, we blocked the screw trajectory with bone wax. C2 laminar screw was implanted instead of intended TAS on the injured side. The management strategy for suspected VA injury should depend on intraoperative circumstances and be tailored to patients. Blocking screw trajectory with bone wax is a useful method to stop bleeding. Atlantoaxial fixation using C2 laminar screw and C1-2 TAS combined with C1 laminar hooks is an ideal alternative procedure. PMID:21331546

Guo, Qunfeng; Liu, Jun; Ni, Bin; Lu, Xuhua; Zhou, Fengjin

2011-09-01

362

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

PubMed Central

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

Patzer, Thilo; Kircher, Jorn; Krauspe, Ruediger

2012-01-01

363

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

PubMed Central

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

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

2014-01-01

364

Tibial tubercle osteotomy with screw fixation for total knee arthroplasty.  

PubMed

This study investigated the efficacy of tibial tubercle osteotomy (TTO) with screw fixation as part of the surgical treatment of primary complicated total knee arthroplasty (TKA) and revision TKA. From January 2000 to April 2011, 15 patients (15 knees) underwent revision TKA and 20 patients (21 knees) underwent primary TKA. The average patient age was 68.7±8.7 years. Patients underwent follow-up at the authors' institution for an average of 60.6±32.9 months. Comparison of preoperative and postoperative Knee Society Scores and Knee Society Functional Scores showed significant postoperative improvement (P<.05). Moreover, postoperative range of motion of the knee improved from 88.5°±33.8° to 104.3°±18.2° (P<.05). Radiographic assessment showed that the average period to bone union was 10.8±5 weeks (range, 5-28 weeks), the average length of the bone fragment was 59.4±5.9 mm, the average width at the proximal end was 18.9±2.9 mm, and the average thickness at the proximal end of the osteotomy was 10.3±1.2 mm. Tibial tubercle osteotomy provided wide exposure for TKA while protecting the extensor mechanism. Solid bone-to-bone fixation was achieved using TTO with 2 screws, and although the overall complication rate was 8.3%, none of the complications were associated with TTO itself. It is recommended that the bone fragment be 60 mm long, 20 mm wide, and 10 mm thick at the proximal end. Appropriate size of the osteotomized bone and solid screw fixation are essential to prevent complications during this procedure. PMID:24762842

Chinzei, Nobuaki; Ishida, Kazunari; Kuroda, Ryosuke; Matsumoto, Tomoyuki; Kubo, Seiji; Iguchi, Tetsuhiro; Chin, Takaaki; Akisue, Toshihiro; Nishida, Kotaro; Kurosaka, Masahiro; Tsumura, Nobuhiro

2014-04-01

365

Atlantoaxial fixation using the polyaxial screw–rod system  

Microsoft Academic Search

The aim of this study is to evaluate the first results of the atlantoaxial fixation using polyaxial screw–rod system. Twenty-eight\\u000a patients followed-up 12–29 months (average 17.1 months) were included in this study. The average age was 59.5 years (range\\u000a 23–89 years). The atlantoaxial fusion was employed in 20 patients for an acute injury to the upper cervical spine, in 1 patient\\u000a with rheumatoid arthritis

Jan Stulik; Tomas Vyskocil; Petr Sebesta; Jan Kryl

2007-01-01

366

Biological and biomechanical evaluation of interface reaction at conical screw-type implants  

PubMed Central

Background Initial stability of the implant is, in effect, one of the fundamental criteria for obtaining long-term osseointegration. Achieving implant stability depends on the implant-bone relation, the surgical technique and on the microscopic and macroscopic morphology of the implant used. A newly designed parabolic screw-type dental implant system was tested in vivo for early stages of interface reaction at the implant surface. Methods A total of 40 implants were placed into the cranial and caudal part of the tibia in eight male Göttinger minipigs. Resonance frequency measurements (RFM) were made on each implant at the time of fixture placement, 7 days and 28 days thereafter in all animals. Block biopsies were harvested 7 and 28 days (four animals each) following surgery. Biomechanical testing, removable torque tests (RTV), resonance frequency analysis; histological and histomorphometric analysis as well as ultrastructural investigations (scanning electron microscopy (SEM)) were performed. Results Implant stability in respect to the measured RTV and RFM-levels were found to be high after 7 days of implants osseointegration and remained at this level during the experimented course. Additionally, RFM level demonstrated no alteration towards baseline levels during the osseointegration. No significant increase or decrease in the mean RFM (6029 Hz; 6256 Hz and 5885 Hz after 0-, 7- and 28 days) were observed. The removal torque values show after 7 and 28 days no significant difference. SEM analysis demonstrated a direct bone to implant contact over the whole implant surface. The bone-to-implant contact ratio increased from 35.8 ± 7.2% to 46.3 ± 17.7% over time (p = 0,146). Conclusion The results of this study indicate primary stability of implants which osseointegrated with an intimate bone contact over the whole length of the implant.

Buchter, Andre; Joos, Ulrich; Wiesmann, Hans-Peter; Seper, Laszlo; Meyer, Ulrich

2006-01-01

367

Investigation of melting in a modular intermeshing co-rotating twin screw extruder  

NASA Astrophysics Data System (ADS)

Since the first patent regarding the co-rotating twin screw extruder was published in 1869, the co-rotating twin screw extruder has evolved into a high performance extruder, having self wiping capability, modular screw configuration, starved feed zone, kneading disc block elements, and special mixing devices. For this device, flow studies began in the mid 1960's but melting studies started in the early 1990's. Former researchers have insisted on their own melting mechanisms because they found different melting mechanisms under their limited and unsystematic experimental conditions. In this dissertation, melting mechanisms were studied systemically to determine when they occur according to the various process operating conditions. This melting study was carried out using an amorphous polymer: polystyrene (PS), two semi-crystalline polymers: linear low density polyethylene (LLDPE) and polypropylene (PP), one powder type LLDPE, and four LLDPE compounds with aluminum flake or calcium carbonate, which were used to provide differences in filler size or content. We observed the screw melting initiation and melting propagation first and categorized melting regimes such as screw melting initiation (SM) internal melting initiation (IM) and barrel melting initiation (BM) as melting initiation mechanisms, and screw melting propagation internal melting propagation barrel melting propagation and bed instability (BI) as melting propagation mechanisms. We translated these melting initiation mechanisms and melting propagation mechanisms into mathematical models. Then we integrated these models into user friendly commercial software, Akro-Co-Twin ScrewR, developed previously at our laboratories. We simulated several homopolymers at various operating conditions using the Akro-Co-Twin ScrewR. The simulation results were compared with the experimental results and were found to be in good agreement within the range of simulation. Using this software, twin screw extruder process designers can design their own screw configurations by applying their own operating conditions and estimating the resulting performance of their co-rotating twin screw extruder.

Jung, Ho-Chul

368

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

PubMed Central

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.

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

2012-01-01

369

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

PubMed Central

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

2013-01-01

370

Use of an inverse dynamics method to compare the three-dimensional motion of the pelvic limb among clinically normal dogs and dogs with cranial cruciate ligament-deficient stifle joints following tibial plateau leveling osteotomy or lateral fabellar-tibial suture stabilization.  

PubMed

Objective-To compare the 3-D motion of the pelvic limb among clinically normal dogs and dogs with cranial cruciate ligament (CCL)-deficient stifle joints following tibial plateau leveling osteotomy (TPLO) or lateral fabellar-tibial suture (LFS) stabilization by use of an inverse dynamics method. Animals-6 clinically normal dogs and 19 dogs with CCL-deficient stifle joints that had undergone TPLO (n = 13) or LFS (6) stabilization at a mean of 4 and 8 years, respectively, prior to evaluation. Procedures-For all dogs, an inverse dynamics method was used to describe the motion of the pelvic limbs in the sagittal, frontal, and transverse planes. Motion and energy patterns for the hip, stifle, and tibiotarsal (hock) joints in all 3 planes were compared among the 3 groups. Results-Compared with corresponding variables for clinically normal dogs, the hip joint was more extended at the beginning of the stance phase in the sagittal plane for dogs that had a TPLO performed and the maximum power across the stifle joint in the frontal plane was greater for dogs that had an LFS procedure performed. Otherwise, variables in all planes were similar among the 3 groups. Conclusions and Clinical Relevance-Gait characteristics of the pelvic limb did not differ between dogs that underwent TPLO and dogs that underwent an LFS procedure for CCL repair and were similar to those of clinically normal dogs. Both TPLO and LFS successfully provided long-term stabilization of CCL-deficient stifle joints of dogs with minimal alterations in gait. PMID:24866511

Headrick, Jason F; Zhang, Songning; Millard, Ralph P; Rohrbach, Barton W; Weigel, Joseph P; Millis, Darryl L

2014-06-01

371

The anatomic variability of human cervical pedicles: considerations for transpedicular screw fixation in the middle and lower cervical spine.  

PubMed

Transpedicular screw fixation has recently been shown to be successful in stabilizing the middle and lower cervical spine. Controversy exists, however, over its efficacy, due to the smaller size of cervical pedicles and the proximity of significant neurovascular structures to both lateral and medial cortical walls. To aid the spinal surgeon in the insertion of pedicle screws, a number of studies have been performed to quantify the gross dimensions and angulations of the cervical pedicle. Notwithstanding these quantitative studies, there has been a conspicuous absence of research reporting the qualitative characteristics of the cervical pedicle. The purpose of our study was to provide comparative graphical data that would systematically document the anatomic variability in cervical pedicle morphology. Such information should better elucidate the complexity of the pedicle as a three-dimensional structure and provide the spinal surgeon with a more complete understanding of cervical pedicle architecture. Twenty-six human cervical vertebrae (C3-C7) from six fresh-frozen spines were secured to a thin sectioning apparatus to produce three 0.7-mm-thick pedicle slices along its axis. Radiographs taken of these pedicle slices were scanned, digitized, and traced to facilitate visual comparison. The pedicle slices were found to exhibit substantial variability in composition and shape, not only between individual spines and vertebral levels, but also within the pedicle axis. However, the lateral cortex was consistently found to be thinner than the medial cortex in all samples. These physical findings must be noted by surgeons attempting transpedicular screw fixation in the cervical spine. PMID:10766079

Shin, E K; Panjabi, M M; Chen, N C; Wang, J L

2000-02-01

372

Fixation of lapidus arthrodesis with a plantar interfragmentary screw and medial locking plate: a report of 88 cases.  

PubMed

Lapidus arthrodesis is a powerful procedure that can be used to correct pathologic features within the forefoot or midfoot. Many different methods of fixation for this procedure have been reported. The use of plating constructs has been shown to provide increased stability compared with screw-only constructs. The technique we have described consists of a plantar to dorsal retrograde lag screw across the arthrodesis site, coupled with a low-profile medial locking plate. A total of 88 consecutive patients were treated with this modification of the Lapidus procedure by 2 surgeons and were retrospectively evaluated. All patients followed an early postoperative weightbearing protocol. Patient age, gender, follow-up duration, interval to weightbearing and radiographic fusion, preoperative and postoperative intermetatarsal angle, hardware removal, preoperative and postoperative American Orthopaedic Foot and Ankle Society midfoot scores, and adjunct procedures were analyzed. The mean follow-up period was 16.76 ± 5.9 (range 12 to 36) months, and all healed fusions demonstrated radiographic union at a mean of 51 ± 19.1 (range 40 to 89) days. The patients were treated with weightbearing starting a mean of 10.90 ± 4.1 (range 5 to 28) days postoperatively. Complications included 15 patients (17%) requiring hardware removal, 2 cases (2%) of hallux varus, 6 cases (7%) of radiographic recurrent hallux valgus, and 2 patients (2%) with first metatarsocuneiform nonunion. The results of the present study have demonstrated that plantar lag screw fixation with medial locking plate augmentation for Lapidus arthrodesis allows for early weightbearing with satisfactory outcomes, improved clinical and radiographic alignment, and improved American Orthopaedic Foot and Ankle Society scores. PMID:23540755

Cottom, James M; Vora, Anand M

2013-01-01

373

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

PubMed

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

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

2007-06-01

374

Management of acromioclavicular joint injuries.  

PubMed

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

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

2014-01-01

375

Local and Spatial Joint Frequency Uncertainty and its Application to Rock Mass Characterisation  

Microsoft Academic Search

Stability is a key issue in any mining or tunnelling activity. Joint frequency constitutes an important input into stability\\u000a analyses. Three techniques are used herein to quantify the local and spatial joint frequency uncertainty, or possible joint\\u000a frequencies given joint frequency data, at unsampled locations. Rock quality designation is estimated from the predicted joint\\u000a frequencies. The first method is based

Steinar L. Ellefmo; Jo Eidsvik

2009-01-01

376

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

PubMed Central

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

2014-01-01

377

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

PubMed

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

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

2013-08-01

378

Finite element simulation of flow in twin screw extruder mixing elements  

Microsoft Academic Search

In the plastics industry, twin screw extruders are widely used for melting, dispersing and homogenizing polymers. There are a diversity of designs employed throughout the polymer industry, each one having different operating principles and applications. Among the different arrangements of twin screw systems, the intermeshing co- rotating configuration has been found to be one of the most efficient mixers and

Victor Sananes Bravo

1998-01-01

379

Graduated-Load Spring Washer System for Screws and Threaded Fasteners.  

National Technical Information Service (NTIS)

The present invention relates to spring washers and particularly to a graduated-load spring washer having a tailored configuration in screw or threaded fastener systems that will maintain large preloading and screw-locking force before, during and after j...

J. D. Rose

1988-01-01

380

Effect of bone quality on the forces generated by compression screws  

Microsoft Academic Search

Internal fixation of the fractured scaphoid bone is used to promote union between bone fragments and to decrease wrist immobilization. Headless screws are commonly used because they minimize interference with articular surfaces and reduce tissue irritation and immobilization. In the present experiment, compressive force was measured as a function of bone quality for two headless screw types, the Herbert and

K. J Faran; N Ichioka; M. A Trzeciak; S Han; J Medige; O. J Moy

1999-01-01

381

Numerical Simulation of Extrusion Characteristics for Co-rotating Tri-Screw Extruder  

Microsoft Academic Search

The flow of polyethylene melt in new tri-screw extruder was simulated using the finite element method (FEM). A special study of flow in central region was performed by analysis of the velocity, pressure, and resident time distribution (RTD). The extrusion characteristics of tri-screw extruder, namely the abilities of material conveying, mixing, and power consumption, were compared with those of twin

X. Z. Zhu; Y. J. Xie; H. Q. Yuan

2007-01-01

382

Numerical simulation of flow characteristics in new co-rotating triangle arrayed triple screw extruders  

Microsoft Academic Search

Triangle arrayed triple screw extruder (TATSE) is a new equipment of polymer processing, which is different from traditional single and twin-screw extruder in flow and mixing characteristics. The studies about TATSE are very limited and all have been in the conditions of qualitative analysis due to its complicated geometry. In order to understand the flow rule of polymer melt and

X. Z. Zhu; H. Q. Yuan; W. Q. Wang

2009-01-01

383

Late diagnosis of perforation of the aorta by a pedicle screw.  

PubMed

Although the clinical and biomechanical advantages of pedicle screws are well documented, the accuracy of their insertion is always a concern.Injury of neurovascular structures could be devastating. Perforation of the aorta from posteriorly placed screws is fortunately rare but could end up being lethal. We present a review of the current literature along with two illustrative cases with aorta perforation from posterior pedicle screws. An 82-year-old female with a history of thoracic kyphosis and a 26-year-old female with scoliotic deformity were referred to our institution owing to back pain. Both patients had undergone correction of their deformities and posterior fixation using posterior pedicle screws and rods 5 years previously. During the diagnostic work-up, which included CT scans, we incidentally found one pedicle screw to be malpositioned, exiting the vertebral body and perforating the aorta. The patients were offered a combined orthopaedic and vascular procedure, including screw removal and endovascular stenting of the aorta. Potential complications from the presence of a screw inside the pulsatile aorta, and the complexity of revision surgery should be well considered before proceeding to such a difficult surgical procedure. Systemic postoperative follow-up imaging and safer intraoperative practices during screw placement are important. PMID:24205763

Soultanis, Konstantinos Chr; Sakellariou, Vasileios I; Starantzis, Konstantinos A; Papagelopoulos, Panayiotis J

2013-08-01

384

Percutaneous screw fixation of a vertebral pedicle fracture under CT-guidance: A new technique  

Microsoft Academic Search

We report on a new minimally invasive technique for the vertebral pedicle fracture after placement of a prosthetic disc. This intervention is an adaptation of CT-guided sacroiliac and acetabular fracture screw fixation. This type of procedure enables the perfect placement and measurement of the screw, as well as an extremely small incision under local anesthesia. CT guided Transpedicular fixation could

Nicolas Amoretti; Pierre-Yves Marcy; Olivier Hauger; Patrick Browaeys; Marie-eve Amoretti; Istvan Hoxorka; Pascal Boileau

385

IN-LINE ULTRASONIC MONITORING OF POLYMER BLENDING IN A TWIN-SCREW EXTRUDER  

Microsoft Academic Search

Polymer blending using a twin-screw extruder is a widely used process in polymer processing industry by which more than one polymers are blended under molten state to achieve properties that are not available with each of the individual polymer. In the current work, high temperature ultrasonic sensors have been installed at several locations on a twin-screw extruder to monitor the

Z. Sun; J. Tatibouët; C.-K. Jen; H. L. Liang; C.-Y. Su

386

Stainless steel screws coated with bisphosphonates gave stronger fixation and more surrounding bone. Histomorphometry in rats  

Microsoft Academic Search

Coating of stainless steel screws with bisphosphonate in a fibrinogen matrix leads to an enhancement of the pullout strength 2 weeks after insertion in rat tibiae. This effect then increases over time until at least 8 weeks. The pullout force reflects the mechanical properties of the bone within the threads, which acts as a screw nut. The aim of the present study

K. Wermelin; F. Suska; P. Tengvall; P. Thomsen; P. Aspenberg

2008-01-01

387

Cervical Pedicle Screw Fixation: Anatomic Feasibility of Pedicle Morphology and Radiologic Evaluation of the Anatomical Measurements  

PubMed Central

Study Design All parameters were measured manually and with a computed tomography (CT) scanner. For the manual measurements, a Vernier scale instrument was used. Purpose This study evaluates quantitatively pedicles of middle and lower cervical spine (C3 to C7) and to evaluate the possibilities of using these structures as anchors in posterior cervical fusion. Overview of Literature Pedicle screws may be an alternative fixation technique for posterior cervical instrumentation. Methods Twenty-two bony sets of adult cervical spines were studied (110 vertebrae, 220 pedicles) from C3 down to C7. Results CT measurement of cervical pedicles appeared to be accurate and valuable for preoperative planning of cervical pedicle screw instrumentation. The study showed a high correlation between the values obtained by manual and CT measurements of pedicle dimensions. The technical challenge of insertion is the obvious theoretical drawback of the use of cervical pedicle screws. Many technical factors are important to consider, namely, the point of screw entry, the pedicle dimensions, the screw direction according to the pedicle angle and orientation, the screw diameter and length, and the method of screw introduction. Conclusions Transpedicular screw fixation of the cervical spine appears to be promising. Anatomic limitations should be clear to the surgeon. Further clinical and biomechanical studies are needed to settle this technique.

2014-01-01

388

Application of TRIZ to improve the layout for a screw packaging factory  

Microsoft Academic Search

Although the screw is a small peanut, it is really basic and necessary in our living. It is an integral part of almost all the industrial products. In this study, a systematic and innovative approach that use TRIZ (Teoriya Resheniya Izobreatatelskikh Zadatch) will be applied to solve the layout problems of an existing screw packaging factory. In this TRIZ approach,

Chia-Nan Wang; Wei-Ming Hsiung

2011-01-01

389

Use of computational fluid dynamics simulations for design of a pretreatment screw conveyor reactor.  

PubMed

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. PMID:15930572

Berson, R Eric; Hanley, Thomas R

2005-01-01

390

Guidewire Breakage: An Unusual Complication of Anterior Odontoid Cannulated Screw Fixation  

PubMed Central

The preferred treatment of a type II odontoid fracture is anterior odontoid screw fixation to preserve the cervical spine range of movement. This case report describes an unusual complication of guidewire breakage during anterior odontoid cannulated screw fixation for a 52-year-old patient who presented with a type II odontoid fracture after a motor vehicle accident. The distal segment of the guidewire was bent over the tip of the cannulated odontoid screw and broke off during guidewire withdrawal. The three months follow-up computed tomography examination of the cervical spine showed acceptable screw placement, good odontoid process alignment with incomplete fusion, and no migration of the fractured segment of the guidewire. It is recommended that the guidewire be withdrawn once the cannulated screw is passed through the fractured site into the odontoid process and a new guidewire be used in each surgical procedure instead of been reused to avoid metal stress fatigue that can result in easy breakage.

Bin-Nafisah, Sharaf; Almusrea, Khaled; Alfawareh, Mohamed

2011-01-01

391

Perceived exertion and discomfort associated with driving screws at various work locations and at different work frequencies  

Microsoft Academic Search

Eighteen subjects drove screws with air-powered tools into perforated sheet metal at three vertical and two horizontal work locations using three different work paces (8, 10, and 12 screws\\/min). Subjects drove screws with a pistol-shaped tool on the vertical orientation at knee, elbow, and shoulder height. They used an inline tool to drive screws on the horizontal surface. A horizontal

SHERYL S. ULIN; THOMAS J. ARMSTRONG; STOVER H. SNOOK; W. MONROE KEYSERLING

1993-01-01

392

Surgical Outcomes and Complications after Occipito-Cervical Fusion Using the Screw-Rod System in Craniocervical Instability  

PubMed Central

Objective Although there is no consensus on the ideal treatment of the craniocervical instability, biomechanical stabilization and bone fusion can be induced through occipito-cervical fusion (OCF). The authors conducted this study to evaluate efficacy of OCF, as well as to explore methods in reducing complications. Methods A total of 16 cases with craniocervical instability underwent OCF since the year 2002. The mean age of the patients was 51.5 years with a mean follow-up period of 34.9 months. The subjects were compared using lateral X-ray taken before the operation, after the operation, and during last follow-up. The Nurick score was used to assess neurological function pre and postoperatively. Results All patients showed improvements in myelopathic symptoms after the operation. The mean preoperative Nurick score was 3.1. At the end of follow-up after surgery, the mean Nurick score was 2.0. After surgery, most patients' posterior occipito-cervical angle entered the normal range as the pre operation angle decresed from 121 to 114 degree. There were three cases with complications, such as, vertebral artery injury, occipital screw failure and wound infection. In two cases with cerebral palsy, occipital screw failures occurred. But, reoperation was performed in one case. Conclusion OCF is an effective method in treating craniocervical instability. However, the complication rate can be quite high when performing OCF in patients with cerebral palsy, rheumatoid arthritis. Much precaution should be taken when performing this procedure on high risk patients.

Choi, Sung Ho; Park, Chan Woo; Kim, Woo Kyung; Yoo, Chan Jong; Son, Seong

2013-01-01

393

Accuracy of Intraoperative Computed Tomography-Based Navigation for Placement of Percutaneous Pedicle Screws  

PubMed Central

MISS techniques have gained recent popularity. The proposed benefits of these techniques include reduced tissue trauma, reduced blood loss, less perioperative pain, and a quicker recovery and return to normal activities. The purpose of this study was to evaluate the accuracy of intraoperative computed tomography (CT)-based navigation for placement of percutaneous pedicle screws in a cadaveric model. Outcome measures included accuracy of screw placement. Two cadaveric specimens were utilized. CT images were obtained using an O-Arm (Medtronic, Memphis, Tennessee, United States) and were coupled to the Stealth navigation system (Medtronic). Computer