Radiologic measurements associated with the prognosis and need for surgery in patients with subchondral insufficiency fractures of the femoral head

OBJECTIVE. The objective of this study was to identify the risk factors associated with the prognosis and need for surgery of patients with subchondral insufficiency fractures of the femoral head. MATERIALS AND METHODS. Twenty-nine consecutively registered patients with subchondral insufficiency fractures of the femoral head were divided into the two groups: a nonprogression of collapse group, which included patients who had no collapse or 2 mm or less of collapse of the femoral head and whose symptoms resolved (14 patients), and a progression of collapse group, which included patients who had more than 2 mm of collapse, for which surgery was indicated (15 patients). Both groups received the same conservative therapy. The following radiographic measurements were obtained: Sharp angle, center edge angle, acetabular roof angle, and acetabular head index. On MR images, band length, defined as the length of a lowsignal-intensity band in the coronal plane, and band length ratio, defined as the proportion of the band length relative to the weight bearing portion, were assessed for each patient. Bone mineral density measurements (T score) were available for 17 patients. RESULTS. In the univariate analyses, T score, Sharp angle, center edge angle, acetabular roof angle, acetabular head index, band length, and band length ratio were found to be significant prognostic factors. Multivariate analyses of T score, acetabular head index, and band length ratio showed that both acetabular head index and band length ratio were significant predictors. CONCLUSION. Both acetabular head index and band length ratio are important prognostic factors in the care of patients with subchondral insufficiency fractures of the femoral head.