Fig. 1.

a, b Anteroposterior and frog lateral X-rays of bilateral hips showed that right hip was in ARCO stage II and JIC type C1. c, d, e preoperative MRI images showed right hip was involved serious ONFH but the lateral column was not involved. f, g the immediate radiographs followed by PTRS of right hip were shown. h, i even though mild subchondral bone collapse was observed, intact joint space was achieved with matched femoral head morphology at 9 years postoperatively, and the right hip was successfully preserved