Fig. 1From: The indications for core decompression surgery in patients with ARCO stage I-II osteonecrosis of the femoral head: a new, comprehensive prediction systemCalculation of the combined necrotic angle from magnetic resonance imaging scans. a: The angle of the necrotic area in the midcoronal image. b: The angle of the necrotic area in the midsagittal image. The combined necrotic angle = a + bBack to article page