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At least 73 records · Page 4Linked to original sources
PubMed1994

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

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.

Bone Nails↗
PubMed1990

Arthrodesis of the ankle with cancellous-bone screws and fibular strut graft. Biomechanical analysis.

The stability of an arthrodesis with two cancellous-bone screws across the ankle joint was evaluated in eighteen ankles from fresh-frozen cadavera. Tibiotalar motion was recorded in response to the following loading modes: medial-lateral moment, plantar flexion-dorsiflexion moment, and internal-external tibial torque. The series of loading tests was performed with two cancellous-bone screws through the tibia into the talus and a lateral fibular strut graft fixed with a proximal and a distal screw. The tests were repeated after the strut graft was removed, and again after it had been reapplied. The amount of motion at the site of the arthrodesis was greatest with tibial torque and was least with medial-lateral bending; this was true for specimens with or without a fibular strut graft. Removal of the strut graft allowed increased tibiotalar motion for all modes of loading; increases in motion were far greater for specimens of poor bone quality.

Aged↗
PubMed1983

Fatigue failure of cortical bone screws.

An experimental study of the fatigue life of cortical bone screws under conditions which stimulated in vivo usage was performed. The two most important factors influencing fatigue life were axial screw tension (the force normal of the plate to bone) and the cyclic shearing load. All screws failed at the root of the thread in the interface between the plate and the bone. A modified screw design effectively resisted fatigue under the described experimental conditions.

Biomechanical Phenomena↗
PubMedDate not supplied

Biomechanical comparison of orthofix pins and cortical bone screws in a canine humeral condylar fracture model.

OBJECTIVE: To compare shear stability of simulated humeral lateral condylar fractures reduced with either a self-compressing pin or cortical bone screw. STUDY DESIGN: In vitro biomechanical tests. SAMPLE POPULATION: Bilateral cadaveric canine humeri (n=18) without evidence of elbow disease. METHODS: Lateral condylar fracture was simulated by standardized osteotomy. Bone fragments were stabilized with a self-compressing pin or a cortical bone screw (2.7 or 3.5 mm) inserted in lag fashion. Specimens were mounted in a materials testing system and the condylar fragment displaced in a proximal direction until failure. Mechanical testing variables derived from load-deformation curves were compared between stabilization methods using a Student's paired t-test. RESULTS: There were no statistically significant differences for mechanical testing variables between pin and screw stabilized specimens at expected walk and trot loads. Three yield points subjectively coincided with yield of the interfragmentary interface (Y1), bone at the implant interface (Y2), and implant deformation (Y3). Displacements at Y1 were 48-156% greater for pin than screw stabilized specimens. Y2 and Y3 loads were higher for screw than pin stabilized specimens, but likely supraphysiologic for dogs convalescing after surgical repair. CONCLUSIONS: A self-compressing pin or a cortical bone screw inserted in lag fashion both provided adequate strength in applied shear to sustain expected physiologic loads through the repaired canine elbow during postoperative convalescence. CLINICAL RELEVANCE: Because self-compressing pins were easy to implant and mechanical properties were not significantly different than cortical screws at expected physiologic loads, pins should be considered for the repair of traumatic humeral condylar fractures.

Animals↗
PubMedDate not supplied

Herbert bone screw fixation of the Austin bunionectomy.

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.

Bone Screws↗
PubMed1993

Extraction strength of cannulated cancellous bone screws.

The purpose of this study was to determine whether the alterations in the relative dimensions of thread and core diameter that accompany cannulation of cancellous bone screws affect their holding strength. The screws were inserted in bovine femoral cancellous bone and mounted in the load train of a materials testing system. They were then extracted under servo-hydraulic displacement control. The tests were repeated in synthetic cancellous material. From the corresponding load-displacement histories, the maximum force values attained were determined as the screws' holding strengths. The results of tests from 17 matched pairs of bovine femora, and of 15 tests of each screw in synthetic material, were recorded. No significant differences in extraction strength between 7.0-mm cannulated and 6.5-mm standard cancellous bone screws were found. Based on tests in the bovine femur and synthetic cancellous material, this study showed that the extraction strength of cancellous bone screws is not altered by the changes in thread-to-core ratio accommodating cannulation.

Animals↗
PubMed1977

[Standardization of implants shown by "bone-screws" (author's transl)].

The increasing use of orthopaedic implants makes international efforts of standardization with their objectives unification and benefit of the patient necessary and sufficient. In 1975 an ISO-Draft for "bone-screws" has been finished. To get experimental data there was a test series of breaking bone-screws of five producers by torsional stress. Comparable screws showed considerable differences. The control of conformity to standards gave partially distinct differences to the standard profile and different hardness values, what affects to the screws' security of twisting off.

Bone Screws↗
PubMedDate not supplied

Rigid internal fixation of the Mitchell-Hawkins osteotomy/bunionectomy with the Herbert Bone Screw.

The author reports on his use of the Herbert Bone Screw to obtain rigid internal fixation of the Mitchell-Hawkins osteotomy-bunionectomy procedure (distal metatarsal osteotomy). A pilot drill with a built-in stop to prevent overpenetration is used first and then the screw can be inserted with jig, or it may be inserted manually if the osteotomy is stablized temporarily with a Kirschner wire. The screw is an excellent fixation device and does not have to be removed because it is made of inert materials and has no protrusive head.

Adult↗
PubMed2003

A drill-free bone screw for intermaxillary fixation in military casualties.

Drill-free bone screws are a simple and quick method of establishing intermaxillary fixation requiring a minimum amount of specialist training or equipment. These screws offer significant advantages over other methods of intermaxillary fixation and are well suited for use in military casualties.

Bone Screws↗
PubMed1989

Intra-articular talar fractures: repair using the Herbert bone screw.

Intra-articular fractures of the talus remain a problem because of the difficulty in achieving and maintaining anatomic reduction, and because of the risk of degenerative arthritis of the hindfoot if such reduction is not achieved. We report our experience with three cases in which intra-articular talar fractures were repaired by use of the Herbert bone screw. In addition, we discuss the biomechanical features of the Herbert bone screw which make it particularly well suited for intra-articular fractures of the talus.

Adult↗
PubMedDate not supplied

Comparison of tension band wire and cancellous bone screw fixation for medial malleolar fractures.

A comparison study of the relative strength of tension-band fixation versus cancellous bone screw fixation of medial malleolar ankle fractures was performed on ten fresh-frozen lower limbs from five cadavers. The mean force recorded at clinical failure using cancellous screws was 60.98 N (range 33.49 to 117.86 N) compared with 129.30 N using tension-band fixation (range 85.20 to 194.64 N). Therefore, cancellous screws exhibited only 47.16% the strength of tension-band wiring at clinical failure.

Aged↗
PubMedDate not supplied

A biomechanical comparison of headless tapered variable pitch and AO cortical bone screws for fixation of a simulated lateral condylar fracture in equine third metacarpal bones.

OBJECTIVE: To compare drilling, tapping, and screw-insertion torque, force, and time for the 4.5-mm AO and 6.5-mm Acutrak Plus (AP) bone screws, and to compare the mechanical shear strength and stiffness of a simulated complete lateral condylar fracture of the equine third metacarpal bone (MC3) stabilized with either an AO or AP screw. STUDY DESIGN: In vitro biomechanical assessment of screw-insertion variables, and shear failure tests of a bone-screw-stabilized simulated lateral condylar fracture. SAMPLE POPULATION: Eight pairs of cadaveric equine MC3s METHODS: Metacarpi were placed in a fixture and centered on a biaxial load cell in a materials-testing system to measure torque, compressive force, and time for drilling, tapping, and screw insertion. Standardized simulated lateral condylar fractures were stabilized by either an AO or AP screw and tested in shear until failure. A paired t test was used to assess differences between screws, with significance set at P < .05. RESULTS: Insertion and mechanical shear testing variables were comparable for AO and AP insertion equipment and screws. CONCLUSION: The 6.5-mm tapered AP screw can be inserted in equine third metacarpal condyles and is mechanically comparable with the 4.5-mm AO screw for fixation of a simulated lateral condylar fracture. CLINICAL RELEVANCE: Considering the comparable mechanical behavior, the potential for less-persistent soft-tissue irritation with the headless design, and the ability to achieve interfragmentary compression by inserting the screw in one hole drilled perpendicular to the fracture plane, the 6.5-mm tapered AP screw may be an attractive alternative for repair of incomplete lateral condylar fractures in horses.

Animals↗
PubMed1989

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

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.

Bone Screws↗