Internal fixation of femoral neck fractures
Abstract: The incidence of femoral neck fractures in elderly people is rising requiring large health care resources. Internal fixation of the fracture is the treatment of choice in Scandinavia, but in 20-40% of the cases a late complication such as a segmental collapse of the femoral head after initial bone necrosis, or a non-union of the fracture because of non-healing, will occur. Because of the high disability associated with these local complications, revision surgery is needed, and in such a case the cost more than triples. Reduction of these local complications would avoid suffering and costs. The present study focuses on the analysis of technical principles for device design and internal fixation of femoral neck fractures, with the aim to reduce the number of local complications due to non-healing. The analysis is based on animal experiments, evaluation of patients who were treated with different internal fixation techniques, and finally biomechanical in-vitro tests of osteotomized femur specimens, which were stabilized wilh different internal fixation devices.The results indicate that late complications are associated with early pronounced femoral shortening; monitoring of femoral length had, therefore, a high accuracy (92%) in predicting the late outcome. A shortening of more than 5 mm at one month predicted a greater lhan 6-fold increase of the incidence oflate complications. Use of a device that enabled a rigid osteosynlhesis reduced the incidence of non-unions, thereby reducing the overall local complication rate by one-third, and the need for revision surgery was halved. The rate of late segmental collapse, which occurred in 14-19%, remained independent of choice of device.The healing of the fracture due to a stable fixation may accelerate the course to a segmental collapse in cases with initial osteonecrosis of lhe femoral head, due to vascular impairment at injury. Otherwise a stable fracture fixation, preventing a high postoperative deformation at the fracture site, was found to be a prerequisite for optimal fracture healing. Such a stable fixation can be optimally achieved with a device incorporating two or more threaded pins or screws, preferably cannulated, which are implanted With an a traumatic technique with high precision using guide systems to prevent unnecessary damage to bone. The optimal device for internal fixation of a femoral neck fracture should also have a good grip in osteoporotic cancellous ancl subchondral bone; the good grip of suitable threads may be enhanced by bone cement.
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