Fig. 2

A 32-year-old man with osteonecrosis of the femoral head was treated with our modified trapdoor procedure. Anterior–posterior X-ray (a) and frog-position X-ray (b) show femoral head necrosis with segmental collapse. Coronal CT confirmed ONFH with collapse (c). Coronal T1 (d) and STIR (e) showed ONFH with edema. Postoperative radiography (f) showed necrotic bone that had been curetted and replaced with tricortical iliac block graft. Coronal CT (g) showed that necrotic bone had been curetted and replaced with a tricortical iliac block graft. The graft was in accordance with the contour of the femoral head. Anterior–posterior X-ray (h) and frog-position X-ray (i) obtained 1 year postoperatively show that the graft had healed to the host bone without collapse. Anterior–posterior X-ray (j) and frog-position X-ray (k) obtained 4 years postoperatively show that the graft had healed to the host bone, without collapse. Anterior–posterior X-ray (l) and frog-position X-ray (m) obtained 8 years postoperatively show that the contour of the femoral head was intact without collapse. Coronal T1 MR images (n) obtained 4 years postoperatively showed that the contour of the femoral head was intact, with the replacement of the necrotic bone by a viable bone, and normal cartilage at the femoral head. Axial STIR MR images (o) obtained 4 years postoperatively show that the contour of the femoral head remained intact; a portion of the necrotic bone has been replaced with a viable bone