Prognostication of Nontraumatic Avascular Necrosis of the Femoral Head

Abstract

After reviewing the radiographs of 149 hips with nontraumatic avascular necrosis of the femoral head (ANFH), a method for evaluating the prognosis in patients with ANFH in its early stages was devised. The evaluation was made primarily by classifying the radio-graphic features of each involved femoral head according to the location and size of its necrotic lesion. In a group of 120 hips, massive collapse occurred without exception in cases where both of the following criteria were true. First, in a standing position, the necrotic lesion involved more than the medial one third of the weight-bearing surface from the anteroposterior view. Second, from the lateral view, the lesion occupied more than 43% of the total area of the femoral head. However, in 29 hips, the extent and size of necrosis was less than the above, and no massive collapse occurred during the follow-up period of three to 15 years (average, 5.2 years). In these 29 hips, function was preserved. These data suggest that hips with a high risk for collapse can be reliably selected during the early stages of ANFH.