Verified causes of failure in the treatment of femoral neck fractures with multiple Knowles pins.

The authors examine 152 cases of femoral neck fractures treated with Knowles pins in order to analyze the incidence and causes of nonunion and avascular necrosis. The displaced fractures were all treated with closed reduction, and weight-bearing was permitted after 30-45 days. Seventy fractures were followed up after an average of four years. Criteria are proposed for evaluating the quality of both the reduction and the internal fixation. Healing was achieved in all cases of Garden grade I and II fractures; the incidence of avascular necrosis was 4.1%. In the displaced fractures the incidence of nonunion was 15.2% and avascular necrosis 13%. Technical errors in either reduction or internal fixation were present in 50% of the necroses and in 100% of the nonunions. The quality of the reduction was the most important factor in fracture healing, yet an accurate reduction and a valid fixation could not completely overcome the risk of avascular necrosis in the femoral head.