ABSTRACT
Since osseous healing in the fracture of the femoral neck is carried out by endosteal bone formation, the size of contact area of the fracture fragments and impaction are of prime importance. It is not uncommon to be faced with the problem of back out of the internal fixation devices during healing period. It seems unnecessary to emphasize the benefit of sliding to close the gap between the fracture fragments. We report a retrospective study of 25 cases of the femoral neck fractures treated by closed reduction and fixation with multiple Knowles pins, paying particular attention to the amount and duration of sliding back out of the fixation devices and relating these to the final results of fracture union. Our clinical study led us to the following conclusions; 1. The shortoning of the femoral neck over 3mm occurred in 16 cases(64%) out of 25 cases. The average amount of back out of Knowles pin is 6mm. 2. Most of the shortening occurred during the first 8 weeks after surgery and extrusion of the nail is frequent findings in unstable fractures and osteoporoses. 3. Backing out over 12 weeks after surgery was associated frequently with delayed union and non-union. 4. Collapse or shortening is nceessary to promote a bone to bone contact and bone healing.