Malreduction and avascular necrosis in subcapital fractures of the femur.

Five hundred subcapital fractures of the femur have been subjected to close analysis, and follow-up has been continued for as long as possible during the past fifteen years (Table I). In the course of this review, the quality of reduction has clearly emerged as the factor most commonly affecting both the early and late results of treatment. Accurate apposition of the fragments is already known to be conducive to union, but it also seems that the fate of the femoral head is determined by the degree of reduction. It has been found that subcapital fractures uniting in good position escape the radiological changes attributed to avascular necrosis, whereas these changes are regularly seen when union occurs after malreduction. These findings throw some doubt on the belief that ischaemia is the cause of breakdown in the capital fragment, and suggest that a biomechanical factor is involved.