Von Bahr Screws Research Articles

Treatment of the displaced femoral neck fracture, as reflected in Acta Orthopaedica Scandinavica

Treatment of the displaced femoral neck fracture, as reflected in Acta Orthopaedica Scandinavica

Internal fixation versus primary prosthetic replacement in acute femoral neck fractures: A prospective, randomized clinical study

A prospective, randomized clinical study has been performed on 104 patients with an acute femoral neck fracture, comparing internal fixation (von Bahr screws) with primary prosthetic replacement (Christiansen endoprosthesis). Immediate weight bearing was allowed in both groups. The postoperative mortality rate was similar in the two groups. Internal fixation proved to be a less time-consuming operation, gave a shorter hospitalization time and was associated with a significantly reduced morbidity rate compared with prosthetic replacement. No blood transfusion was needed in the internal fixation group. Primary prosthetic replacement was associated with earlier postoperative mobilization, probably gave a more definitive treatment with fewer reoperations, and showed better results at 1-year follow-up.

In vitro femoral stiffness after femoral neck osteotomy and osteosynthesis with defined surgical errors.

In our search for an osteosynthesis device that would tolerate the surgical errors of the inexperienced surgeon, we tested in vitro femoral stiffness in 75 human osteoporotic femora after internal fixation of a cervical neck osteotomy using three commonly used devices: two von Bahr screws (A. Ericsson AB, Sweden), two cannulated screws (Uppsala type, Olmed AB, Sweden), and two hookpins (LiH, PSAB, Sweden). The first device has its main grip in the cancellous bone by threads; the second has grip in cancellous and subchondral bone by threads; and the third, which has no threads, has its grip in cancellous bone by a hook pin. The intact specimen was in all instances stiffer (22-63%) than the osteosynthesized specimen (p < 0.001). An osteosynthesized femur with perfectly reduced bone ends was 14-23% stiffer than when reduction of the bone ends was insufficient, irrespective of device malposition (p < 0.001). Insufficient reduction of the osteotomy leaving a 20 degrees dorsal angulation of the femoral head combined with too far ventrally placed screws resulted in the lowest femoral stiffness. If reduction of osteotomy was sufficient, screws placed too far ventrally or converging screws did not result in decreased stiffness compared with optimal screw placement. Irrespective of the quality of reduction, osteosynthesis with the Uppsala screw resulted in all instances in a higher stiffness than using the other devices (p < 0.01). With the Uppsala screw design, femoral stiffness after optimal osteosynthesis was reduced by 22% compared with the intact femur, and in the most unfavorable position with combined malreduction and malpositioning it was reduced by 42%. Corresponding values for the von Bahr screws were 29% and 46%, respectively, and for the LiH screws 47% and 63%, respectively. Use of a device with threads and grip in the subchondral bone is recommended for fixation of femoral neck fractures in osteoporotic bone. Furthermore, the importance of anatomical reduction for fracture fixation is emphasized.

Femoral Stiffness After Osteosynthesis of a Subcapital Osteotomy in Osteoporotic Bone: An In-Vitro Comparison of Nine Fixation Methods

Restitution of normal bone mechanics after osteosynthesis of a proximal femoral fracture in the elderly is assumed to be a prerequisite for optimal healing. To find the most appropriate fixation device for this purpose, the stiffness of 79 cadaver femora from donors with a history of osteoporosis was measured during axial loading before and after a subcapital osteotomy stabilized with one of nine different osteosynthesis devices. Only an osteotomy stabilized with an experimental device consisting of 2 von Bahr screws (Ericsson AB, Göteborg, Sweden) supported by acrylic cement gave similar mean values as the intact femur. A femur stabilized with the Deyerle device (Biomet, Bridge End, Wales, U.K.), with cannulated screws type Uppsala (Olmed AB, Uppsala, Sweden), or with von Bahr screws had an approximately 20-30% lower stiffness than tested intact. However, these devices provided a higher femoral stiffness than the hook-pin technique type LiH (Söderström AB, Gothenburg, Sweden), cannulated screws (Smith & Nephew, Memphis, TN, U.S.A.), a sliding screw plate (Smith & Nephew), a compression screw with variable length (Biomet), or an experimental screw providing expansion and compression. Despite attempted compression of the osteotomy by some of the devices, all of the commercially available devices resulted in a decrease of femoral stiffness after fixation, which may adversely influence the healing of femoral neck fractures in the elderly. Only a combination of screws and bone cement resulted in normal femoral stiffness, probably because of better device anchorage in the osteoporotic cancellous bone. However, this combination might have the potential risk of vascular damage.

Cortical screw support in femoral neck fractures. A radiographic analysis of 87 fractures with a new mensuration technique.

In 87 femoral neck fractures, operated on with 2 von Bahr screws and followed for up to 2 years, the positions of the fixating screws were determined with a new mensuration technique which compensates for the variations in hip rotation in routine radiographs. The union rate of the fractures was related to the position of the screws. A posterior placement of the proximal screw and an inferior placement of the distal screw in both the femoral head and neck improved the outcome substantially.

The stability of femoral neck fractures and its influence on healing.

We measured the stability of fixation in femoral neck fractures treated with von Bahr screws, investigated the influence of impaction and correlated peroperative stability with the clinical results. Stability was measured at operation using a metal probe fitted with strain gauges. Its tip was anchored in the subchondral bone of the femoral head and its lateral end was fixed in the lateral femoral cortex. The shearing force produced by longitudinal compression applied to the foot of the operated leg was recorded. The results in 41 consecutive patients all followed for 30 months, showed that fractures with early loosening or nonunion had all had significantly poorer stability than the fractures that had healed. Impaction improved stability in only 23 out of the 41 fractures; in the others stability had deteriorated or was unchanged.

Stability of femoral neck osteosynthesis: Comparison of fixation methods in cadavers

Fixation of vertical femoral neck osteotomies in 50 cadavers was performed with either von Bahr screws or a sliding hip compression screw. One specimen from each pair of femora was used for the osteotomy, the other serving as an intact control. At 0.05 r of torsion the load-deformation test showed that three von Bahr screws provided the strongest fixation, and this was confirmed by the the ultimate torsional moment test. Regardless of positioning, even two von Bahr screws were stronger than the sliding compression screw with or without an additional lag screw. The results indicate that the best torsional stability in femoral neck fractures can be obtained with three 5.5-mm screws.

Fixation of femoral neck fracture: Prospective comparison of von Bahr screws, Gouffon screws, and Hessel pins

We report a prospective study of 214 patients with femoral neck fractures operated on with multiple pinning. The fractures were randomly allocated to fixation with either von Bahr screws or Hessel pins in 1983 and 1984 or von Bahr or Gouffon screws in 1984 and 1985. After 2 years, the failure rate was one third in the von Bahr and the Gouffon screw groups and one half in the Hessel pin group. We conclude that the nonthreaded Hessel pin is inferior to the von Bahr and Gouffon screws for fixation of femoral neck fractures.

Statistical Analysis of Femoral Neck Fractures Based on 3053 Cases

Femoral neck fractures in 2289 women and 764 men (total 3053) from the years 1975-1977 in Stockholm County Council were retrospectively analyzed regarding social and demographic classification. Seventy-nine percent of the patients (2418 of 3053) were admitted directly from their homes, more commonly in central city areas (82%) than in rural areas (74%). Direct return home was possible in 36%, and 47% could return home after some weeks of institutionalized rehabilitation. There was no increase in fracture incidence found during the three-year period. More fractures occurred on Mondays and less on Sundays than during the rest of the week. The period of December through March showed the highest fracture rate. Diseases other than hip fractures were seen in approximately one-half (1492) of the patients. Internal fixation was performed in 2937 fractures, mainly with the von Bahr screws (1465 cases), Hessel/Nyström multiple pins (674 cases), Thornton nails (380 cases), or Rydell nails (224 cases). Primary hemiarthroplasties were performed in only 102 cases. The detailed analysis of this consecutive population-based femoral neck fracture material is intended as a base for more uniform treatment and rehabilitation of this group of resource-consuming patients.

Internal fixation versus endoprosthesis in the treatment of femoral neck fractures in the elderly. A prospective analysis of the comparative costs and the consumption of hospital resources.

The consumption of hospital resources and the costs involved in treating femoral neck fractures in the elderly were studied and a comparison was made between internal fixation (von Bahr screws) and primary prosthetic replacement (Christiansen's endoprosthesis). The 1-year results of screw fixation were excellent or good in 55% of the patients, fair in 17% and poor in 28%, compared with 79% excellent or good results, 13% fair and 8% poor results in the prosthetic group. As regards the initial stay in hospital, prosthetic replacement was found to be associated with 2.4 times higher costs. This difference was reduced, however, by a more expensive follow-up and more frequent readmissions and reoperations in the internal fixation group. Considering the total costs, prosthetic replacement was found to be 1.6 times more expensive than internal fixation.

Internal fixation of fractures of the neck of the femur using von Bahr screws and allowing immediate weight bearing: a prospective clinical study

This article presents the results of von Bahr screw fixation in 103 patients, allowing immediate weight bearing. After a follow-up period of 1 year, a failure rate of 18 per cent was recorded. Analysis of the series shows that the failures are due to inadequate reduction of the displacement during operation, especially when the head is in varus, and to bad positions of the screw. The high failure rate was not related to the initial displacement of the fracture.

Immediate weight-bearing after internal fixation of the femoral neck fractures using von Bahr screws. Preliminary report of a prospective clinical trial.

Osteosynthesis of displaced femoral neck fractures using von Bahr screws was performed in 50 patients. Immediate postoperative weight-bearing was allowed. After a follow-up period of 1 year a high incidence (20 per cent) of early failure (dislocation of the fractures with or withour screw movement) was found. Analysis of the material showed that the failure rate was influenced by the peroperative reposition of the fracture, especially the valgus/varus position of the caput fragment, and the position of the screws.