Fig. 1

Surgical steps. a A 12 cm incision was made along the line between iliac and patella at the starting point of 4 cm below the anterior superior iliac spine of the affected side. b The ascending and transverse branches of the lateral circumflex femoral artery emerge were exposed through the intermuscular spaces space between tensor fasciae latae muscle and sartorius muscle and between the vastus lateralis muscle and rectus femoris muscle. c The bone window was designed on the femoral neck (about 3 cm × 1.2 cm). d Under direct vision, the necrotic lesions were removed with an osteotome and a grinding drill. The articular cartilage surface and the thin layer of subchondral bone were preserved. The femoral neck of the bone window was debrided and the partial capsule was removed. e The required length, width, and thickness of the iliac bone flap were measured (typically 4 cm × 2 cm × 1.2 cm). f An iliac bone flap of 4 cm × 2 cm × 1.2 cm was harvested, the ramus communicans of the deep circumflex iliac vessels and the iliac crest vessels were cut and ligated. Retrograde dissection was performed until the starting point of the deep circumflex vessel, and the deep circumflex iliac vessels were cut off after confirming that the blood supply of iliac bone was reliable. g The iliac bone flap was properly trimmed. After successful trial, the cancellous bone was implanted into the femoral head, and the iliac bone flap was inserted into the bone groove. h Under the microscope, the deep circumflex iliac vessels were anastomosed with the transverse branch (or ascending branch) of the lateral circumflex femoral artery and their accompanying veins