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At least 127 records · Page 7Linked to original sources
PubMed1987

Apparent absence of local response to bone screws in guinea pigs with contact sensitivity.

Guinea pigs sensitized to nickel, cobalt, or chromium were used to study if impaired fixation occurred as a result of allergy against metal implants in bone. Screws made from stainless-steel (ASTM F55, F138-139) or cobalt chromium (ASTM F75-76) were inserted in the right and left proximal tibiae, and the mechanical strength of the fixation to the bone was evaluated after 4 months. In addition, we studied the histology on decalcified sections of the implant bone interface from the distal femur where the same type of screws had been inserted. To see if changes in bone density occurred in the proximal tibia as a result of allergy, the amount of ash was determined. Although the animals maintained their contact sensitivity throughout the experimental period, there were no differences between allergic and control animals for any of the parameters studied. All screws were well fixed in the tibia at the end of the experiment, and histologically we did not find any significant differences between allergic and control animals by qualitative examination. The experiment supports our earlier results from a 6-week experiment and indicates that contact allergy may be unimportant for the fate of orthopedic implants.

Animals↗
PubMed2006

Clinical study of horizontal alveolar distraction with modified micro bone screws and subsequent implant placement.

The aim of this study was to evaluate the clinical relevance of horizontal distraction osteogenesis (DO) with bone micro screws for reconstructing knife-edge alveolar crests before implant placement. Horizontal DO was performed in upper and lower alveolar crests of seven patients with resorption class IV according to Cawood and Howell. After osteotomy and a 1-week latency period, micro bone screws were reset daily for horizontal expansions by 0.5 mm. Dental implants were placed in the distracted area following a consolidation period of 12 weeks. Computer tomography was performed before DO and implant placement. Morphometric analysis showed a mean gain of 34.01 mm(2) (95% confidence interval [CI]: 10.55-57.48) in bone area and of 3.06 mm (95% CI: 1.81-4.31) in horizontal width, i.e. the horizontal dimension of the alveolus was approximately doubled within the first 5 mm of height. All 12 implants placed into the distracted area fulfilled the success criteria of stable osseointegration after 1 year of functional loading according to Albrektsson and colleagues. Despite the limited number of patients treated, data from the clinical study of horizontal DO with bone micro screws suggest that the generation of sufficient hard tissue in previously knife-edge alveolar crests for subsequent implant placement was possible.

Adult↗
PubMed1994

Biomechanical properties of small bone screws.

PURPOSE: To evaluate systematically the biomechanical properties of 13 popular screw designs, ranging from 0.8 to 2.0 mm in diameter. METHODS: Screws were characterized in terms of external, core, and drill diameter; cutting flute and head design; material; pitch, thread depth; and height of shank (unthreaded portion) and shank with plate. They were tested in standardized bone specimens (2 x 2.5cm slabs of fresh bovine femur) 1, 2, 3, and 4-mm thick. For each screw-bone thickness combination, 10 trials were conducted to determine push-out force (POF) and another 10 trials to determine insertion (IT) and maximum torque (MT) yielding a total of 1,040 tests. RESULTS: Among the 13 different screws, in 1-mm thick bone, both the lowest (108.5 N) and highest (294.9 N) POF were created by 2-mm screws (P < .001); that with the lowest POF had a long unthreaded shank and pitch, that with highest POF had a short unthreaded shank and pitch. Screws with 0.8- to 1.5-mm diameters showed no differences in POF. The 2-mm screw with the lowest POF also had the lowest MT in 1-mm thick bone compared with the other 2-mm screws (P < .001). In thicker bones (> 2 mm), two 2-mm screws showed 30% to 50% lower MT than the other same size screws (P < .001) because their head slots stripped easily. When all screws were considered together for a particular bone thickness, torque was strongly predicted by screw diameter (MT: r = .94, P < .001; IT: r = 0.92, P < .001). Screws with the same diameters varied significantly in IT because of differences in self-tapping cutting flute design. CONCLUSION: External diameter, unthreaded shank height, head slot, and self-tapping cutting flute design had the greatest impact on screw strength and efficiency in thin cortical bone. Thread depth, core diameter, and metal type did not affect performance significantly. Under these highly standardized in vitro conditions, the ideal 2-mm screw has an unthreaded shank that is as short as possible, and the pitch is about 0.8 mm. Additional aspects of a clinical situation beside holding strength must, however, be considered when choosing a screw.

Analysis of Variance↗
PubMed1977

[Compression osteosynthesis with percutaneous bone screws--clinical aspects and radiographic findings].

In a previous paper (Jacobs 1976) the development of an apparatus was described which achieved a compression osteosynthesis through the use of percutaneous bone screws without encroaching on the area of the fracture. As indication for this procedure we consider the condition which is described under the synonyms "post-traumatic osteomyelitis", "osteitis" and "fracture infection". Clinical experience is described with consideration of technical measurements - for the first time in vivo measurements of interfragmental compression in the patient and X-ray findings.

Animals↗
PubMed2000

Use of specialized bone screws for intermaxillary fixation.

Fixation of the injured mandible to the maxilla is a proven method of stabilizing mandibular fractures and ensuring proper occlusion. The authors report their results with new specialized intraoral bone screws (IMF Screw System; Howmedica Leibinger, Inc., Carrollton, TX) that are designed for the purpose of achieving intermaxillary fixation (IMF). Nineteen patients were placed into rigid IMF using IMF screws alone. Indications were nondisplaced mandibular fractures; symphyseal, body, and angle fractures; midfacial fractures requiring temporary IMF; and edentulous patients with any of these fracture types and an adequate prosthesis. All procedures were performed with the patient under general anesthesia. The authors found that the operative time was markedly shorter than with standard IMF techniques, patient satisfaction was high, and there were no infections related to the screws. All 19 patients remained in stable, accurate occlusion and had adequate healing. One patient continues to have paraesthesias in the mental nerve distribution after screw removal. Although there is the potential for tooth and nerve injury when screws are placed improperly, the IMF Screw System seems to be a safe and reliable method of achieving secure mandibular fixation.

Bone Screws↗
PubMedDate not supplied

Effect of cutting flute design on cortical bone screw insertion torque and pullout strength.

OBJECTIVE: To determine the effect of the number and length of cutting flutes on the insertion torque and pullout strength for self-tapping 4.5-millimeter cortical bone screws. DESIGN: Screws were self-tapped in the diaphysis of human cadaver femurs. Each of the six screw types studied had different designs with varying cutting flute lengths and numbers. Bone mineral density, insertion torque, and pullout strength were measured. SETTING: The study was conducted at an experimental biomechanics laboratory associated with a university medical center. OUTCOME MEASUREMENTS: Insertion torque and pullout strength were normalized by the local bone mineral density. RESULTS: The mean normalized insertion torque of the design with four full-length cutting flutes was less than the design with three full-length flutes and the two designs with one-third length flutes (p < 0.05). The mean normalized pullout strength of the screw with four full-length flutes was significantly greater than that of all screws with fewer than three flutes (p < 0.05). CONCLUSIONS: Priorities for a cutting flute design should ideally include ease of screw insertion, minimal soft tissue irritation, and maximal screw holding power. Screws with more than two flutes were easier to insert and did not cause cortical damage during insertion. The screw with four full-length flutes showed a trend toward being the easiest to insert and having the greatest holding strength.

Biomechanical Phenomena↗
PubMed1995

Mandibular osteosynthesis with intraoral miniplates and cortical bone screws.

Previously, this author and others described a technique of maxillomandibular fixation utilizing intraoral cortical bone screws and intermaxillary wires. This procedure has been very successful in achieving superior fixation of relatively undisplaced fractures in a fraction of the time previously required for arch bar application. A method was sought to extend the procedure to include displaced mandibular fractures as well. Miniplates have been utilized through the same intraoral approach to provide reduction of displaced fragments. Excellent fixation has been achieved with anatomical reduction while utilizing less than half the previous operating time. It appears that the majority of mandibular fractures can be treated with this combination of techniques.

Fracture Fixation, Internal↗
PubMed1992

Stabilization of a proximal femoral physeal fracture in a filly by use of cancellous bone screws.

A Salter-Harris type-II fracture of the proximal portion of the right femur in a 2-month-old filly was reduced and stabilized with three 6.5-mm-diameter, 100-mm-long cancellous bone screws through a dorsal approach to the right coxofemoral joint. The screws were removed after 11 months because the filly became lame in the affected limb. The surgical wounds dehisced despite preventive measures, most likely because of tightness of skin in the coxal region. Seven years after the original injury, the horse could perform vigorous paddock exercise without any disability. Early internal fixation of proximal femoral physeal fractures in foals can provide a good long-term prognosis.

Animals↗
PubMed1984

Cancellous bone screws for repair of proximal growth plate fractures of the tibia in foals.

Proximal growth plate fractures of the tibia in 4 foals were treated surgically. A medial approach was utilized in 3 cases and a lateral approach in the fourth. Bone screw fixation was achieved with cancellous screws and washers. In 3 cases, the screw shaft crossed the proximal tibial growth plate with no adverse effects. In all animals, there was rapid and cosmetic healing. At 8 to 18 months after surgery, all horses were sound at a walk, trot, and canter.

Animals↗
PubMed1992

Stability of an ankle arthrodesis fixed by cancellous-bone screws compared with that fixed by an external fixator. A biomechanical study.

Twenty-three fresh-frozen human specimens were subjected to ankle arthrodesis and fixation with two cancellous-bone screws. The specimens were then subjected to four newton-meters of manually applied tibial torque, plantar flexion-dorsiflexion moment, and medial-lateral bending moment; relative rotation between the tibia and the talus was recorded for each mode of testing. A Calandruccio triangular compression device was then applied to threaded pins penetrating the tibia and talus, the screws were removed, and the test sequence was repeated. Tibiotalar motions recorded with both systems of fixation were markedly affected by the quality of the bone. When less than 2 degrees of total tibiotalar rotation was recorded in response to four newton-meters of manually applied internal-external tibial torque, all specimens demonstrated less torsional rotation with the screw fixation than with the external fixator. The mean rotations produced by medial-lateral bending moment were equivalent for both systems of fixation. When torsional rotations with the use of screw fixation were greater than 2 degrees, all specimens demonstrated more torsional rotation with the screws than with the external fixator, and all but one specimen had more medial-lateral rotation with the screws than with the fixator. For applied plantar flexion-dorsiflexion moment, twenty-two of the twenty-three specimens demonstrated more rotation with the Calandruccio fixator than with the screws; this was due in part to motion permitted at the hinge points of the frame itself.

Aged↗