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At least 109 records · Page 6Linked to original sources
PubMed1986

Subcapital fractures of the femur. Treatment by reduction and fixation and 3 spongy bone screws.

The authors reviewed 21 cases of subcapital fracture of the femur treated by reduction and fixation with 3 spongy bone screws (AO type) between 1980 and 1983. There were 4 failures (2 non-union and 2 ischaemic necrosis, one definite and one suspected). In all patients with a reasonable life expectancy the treatment should be reduction and fixation, but the technique must be extremely accurate. If open reduction is necessary to ensure perfect reduction, it must be by the anterior route so as not to inflict further damage on the blood supply. Fixation must be rigid and sustained. This can be best achieved by using 3 screws of the AO spongy type which also ensures a degree of compression which enhances consolidation.

Adolescent↗
PubMed2005

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

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

Adult↗
PubMed2006

The number of screws, bone quality, and friction coefficient affect acetabular cup stability.

One of the major causes of loosening of cementless acetabular cup implants is insufficient initial stability. This study used three-dimensional finite element models of the pelvis and acetabular components to investigate the effects of the number of screws, bone quality, and friction coefficient of the acetabular cup on the initial stability under normal walking. A commercially available hemispherical acetabular cup with five screw holes was used as the default model. The stiffness of the pelvis and the friction coefficient of the cup were systematically varied, within a realistic range, to assess the initial stability of the acetabular cup. The simulations showed that the inserted screws provide only a localized reduction in the relative micromotion between the cup and pelvis therefore inserting several screw closed together might not be useful. Changes in the pelvic stiffness have a non-linear effect on the initial stability of acetabular cup and the subchondral bone provides good support for fixation of the cementless cup. The friction coefficient of the acetabular cup plays a limited role, comparing with the factor of bone quality, in resisting relative micromotion in the cup-pelvis interface.

Alloys↗
PubMed2004

Ankle arthrodesis using dowel bone graft and cancellous-bone screws: a mechanical study in cadavers.

BACKGROUND: There are numerous techniques for ankle arthrodesis. MATERIAL AND METHODS: We studied the stability of an ankle arthrodesis with the use of two cross-screws combined with dowel graft technique in 14 fresh-frozen ankles from amputees. The arthrodesis was performed by a dowel graft technique, in the coronal plane in 7 specimens (group 1) and in the diagonal plane in the remaining 7 (group 2). Allocation into the two groups took place after normalization according to the bone mineral content of the specimens. All ankles were fixed with two 6.5-mm diameter cancellous-bone screws, with the ankle in neutral position. Tibiotalar motion was measured during 5 Nm torque loading in plantar flexion-dorsiflexion, abduction-adduction and eversion-inversion planes of the ankle joint. Two testing sequences were performed and the mean value of both tests in each direction was used for the analysis. RESULTS: In all 3 planes, the torque applied caused more motion with the dowel graft in the coronal plane (group 1) than with the graft in the diagonal plane (group 2). The differences between the two groups were significant for abduction-adduction and eversion-inversion planes. Statistical analysis of differences between the first and second test showed significantly greater stiffness in group 2 than in group 1 in plantar flexion-dorsiflexion torque. INTERPRETATION: The placement of a dowel graft in the diagonal plane in comparison to the coronal plane significantly increased the initial stability of an ankle arthrodesis.

Ankle Joint↗
PubMed2000

Comparison of two systems for rigidly connecting 2.0-mm bone screws to an implantable device: in vitro stability testing.

The stability of a screw-fixed implantable device can be improved by eliminating the freedom of movement between the screws and the device. Two systems have been developed for rigidly connecting 2. 0-mm bone screws to an implantable device, and the aim of this study was to test and compare the stability of the two systems. In system A, a fixing disc locked the screw-head. In system B, the thread of the screw locked directly into the device. The stability of the connection was tested by measuring the resistance against a torque on the screw, against shear loading, against push-out loading, and against dynamic shear loading (70 N) for 5 million cycles. Both systems met the required minimum values for the resistance against a torque, shear loading and push-out loading, and dynamic shear loading did not cause movements between the screw and the device. We conclude that both systems are stable, but prefer system B because it is easier to make and implant than system A.

Bone Plates↗
PubMed1996

Cancellous bone screw thread design and holding power.

This study was designed to isolate and evaluate the parameters of host density, outer diameter (OD), root diameter (RD), and pitch in cancellous bone screw design and their effect on holding power. Special emphasis was placed on screw pitch, which has been evaluated infrequently in the literature. Three groups of stainless steel V thread screws (group I, OD 4.5 mm, RD 3.0 mm; group II, OD 6.4 mm, RD 3.5 mm; group III, OD 6.4 mm, RD 4.2 mm) were machined with progressive increases in pitch from 12 to 32 threads per inch (TPI). Two densities of synthetic cancellous bone material (Pedilen, Ottobock, Minneapolis, MN, U.S.A.), 0.15 g/ml and 0.22 g/ml, were then prepared and molded into sheets 1.9 cm thick and the screw threads completely engaged. Push-out tests were performed using a servohydraulic testing machine (MTS, Minneapolis, MN, U.S.A.). Fifteen trials of each screw were tested in each material. The effect on holding power of the different parameters of the custom screws in order of importance was (a) host material density, (b) OD (c) pitch, and (d) RD. The groups with a 6.4-mm OD had a much greater holding power than did the group with a 4.5-mm OD (p < 0.001). A decrease in screw pitch (increased threads per inch) did itself have a significant improved effect on fixation for all groups in both pedilen densities (p < 0.001). In the two 6.4-mm screw groups studied, the difference in the two root diameters (4.2 mm vs. 3.5 mm) showed the smaller root diameter to give a greater holding power in the less dense 0.15 g/ml pedilen (p < 0.001). In the more dense 0.22 g/ml pedilen there was no difference (p = 0.26) between the root diameters. To optimize holding power, cancellous screws may be designed with a decreased pitch (increased TPI) over those commercially available today. Cannulated screws must have a larger cancellous thread root diameter to leave room for the central cannulation; this may decrease their holding power in less dense cancellous bone but not in denser bone.

Biomechanical Phenomena↗
PubMed2005

Efficacy of bioabsorbable antibiotic containing bone screw in the prevention of biomaterial-related infection due to Staphylococcus aureus.

Impregnation of antimicrobial agents within biodegradable orthopedic implants provides a possibility for local antimicrobial prophylaxis of biomaterial-related infections. The objective of this study was to evaluate the efficacy of a bioabsorbable ciprofloxacin containing bone screw (Ab-PLGA) in the prevention of biomaterial-related infection due to Staphylococcus aureus in a rabbit model. Animals in Group I (n=8) received a Ab-PLGA screw contaminated with S. aureus, while animals in Group II (n=8) received a stainless steel (SS) screw contaminated with S. aureus. In two negative control groups, the animals received a Ab-PLGA screw (Group III, n=4) or a SS screw (Group IV, n=4) without bacterial contamination. 18F-FDG-PET imaging, performed at 6 weeks, was applied as a novel quantitative in vivo imaging modality of implant-related infection. Infection was verified by swab cultures, direct cultures of the retrieved implant, and quantitative cultures of pulverized bone. The concentrations of ciprofloxacin in serum and local bone tissue were determined by a high performance liquid chromatographic (HPLC) method with fluorescence (FLD) detection. In the group of contaminated Ab-PLGA screws, all cultures were negative. In the group of contaminated SS screws, all cultures of retrieved implants and six cultures out of eight of pulverized bone were positive for inoculated S. aureus. In negative control groups, all cultures were negative except one contaminant (S. cohnii) found in a SS screw culture. Verified infection of contaminated SS screws was collaborated by the increased 18F-FDG-PET uptake (P=0.004 compared with the group of contaminated Ab-PLGA screws). The mean bone tissue concentration of ciprofloxacin varied from 2.54 to 0.83 microg/g bone as a function of distance from the implantation site. The serum concentration of ciprofloxacin remained undetectable and below the resolution of the analytic method (<5.0 ng/ml). This study confirmed the in vivo efficacy of bioabsorbable antibiotic containing bone screw in the prevention of biomaterial-related infection due to S. aureus.

Absorbable Implants↗
PubMedDate not supplied

Displaced femoral neck fractures at the bone-screw interface after in situ fixation of slipped capital femoral epiphysis.

Two patients had displaced femoral neck fractures at the bone-screw interface after in situ fixation of slipped capital femoral epiphysis. Both fractures required closed reduction and internal fixation. Inadvertent derotation of the femur occurred in both patients and allowed fixation of the fracture through the intramedullary canal of the femoral neck without anterior penetration of the pins into the joint; a nonunion occurred in this patient. The other patient developed chondrolysis and avascular necrosis. Because the femoral neck is vulnerable to stress fractures in young adults, there is some question whether pins placed anteriorly through the femoral neck cortex should be removed.

Adolescent↗
PubMed1982

Dislocated femoral neck fractures. A follow-up study of 98 cases treated by multiple AO (ASIF) cancellous bone screws.

A series of 98 dislocated femoral neck fractures were treated by closed reduction and osteosynthesis with multiple AO (ASIF) cancellous bone screws. The patients were followed up for 2 years (or until death). The degree of dislocation did not have a statistically significant influence on the failure rate, which was, however, significantly correlated with poor reduction. Thirty-nine percent of the fractures were complicated by non-union or late segmental collapse. Forty-three of the patients participated in the 2 year follow-up examination. Of these patients, 38 had achieved excellent or good hip function. It was concluded that the reduction was the most important single factor in treatment of these factors.

Adult↗
PubMed2002

Slippage between screwdriver and bone screw.

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.

Bone Screws↗
PubMed1982

Bone screws and plates in orthognathic surgery.

The almost universal use of bone plates and screws in orthognathic surgical procedures is surveyed. Based upon considerable personal experience, it is advocated that this technique should be used for better stabilization of the fragments, leading to faster bone healing and therefore to less relapse. Other advantages such as shortening of the period of intermaxillary fixation and the possibility of immediate postoperative opening of the mouth are weighed against disadvantages, such as higher rate of nerve disturbance, and second intervention for removal of the osteosynthetic material. The conclusion is drawn that the application of bone screws and plates is a major improvement in the correction of deformities in the maxillo-facial region.

Bone Plates↗