Fig. 2From: Correlation between the efficacy of stem cell therapy for osteonecrosis of the femoral head and cell viabilitya The angle α was defined as the angle corresponding to the necrotic site on an MRI image. b The angle β was defined as the central angle corresponding to the femoral head in the same image (the angle between the connecting lines from the center of the femoral head to the femoral head-neck junction)Back to article page