Avascular necrosis of the femoral head after open reduction and internal fixation of femoral neck fractures: an inevitable complication?

Between 1980 and 1989 71 patients with a femoral neck fracture were treated at the University Hospital of Basel by a Dynamic Hip Screw (n = 54) or by three compression screws (n = 17). Fifty out of 71 patients (70%) were reviewed clinically and radiologically after an average of 116 months. 32/50 fractures (64%) had united. In 18/50 (36%) either avascular necrosis (12) or secondary fracture dislocation (6) had resulted in failure after an average of 29 months following injury. Despite these results, the patients assessment had been very good or good in 44 patients (88%) and fair only in six patients (12%). The cause of secondary dislocation proved to be mainly due to a technical failure at surgery. The incidence of avascular necrosis was significantly higher in displaced fractures compared to non-displaced fractures (p < 0.05), regardless of the quality of the reduction achieved (varus or valgus) or the time delay between accident and operation. However it was interesting to note, that more than one third of all avascular necrosis became apparent more than 3 years (4-10 years) after the accident.