Ischemia of the lateral femoral cutaneous nerve during periacetabular osteotomy using Smith-Petersen approach

BACKGROUND: Lateral femoral cutaneous nerve (LFCN) injury is a common complication in the Smith-Petersen approach to the hip. This complication may be induced by neural ischemia or direct trauma during the procedure. The purpose of this study was to investigate the relationship between the neural ischemia of LFCN and postoperative sensory disturbance. MATERIALS AND METHODS: Nineteen patients who underwent periacetabular osteotomy through the Smith-Petersen approach were investigated. To evaluate neural ischemia, we measured the blood flow of LFCN using a laser Doppler flowmetry. The measurements were performed before and after osteotomy at the point 1 cm distal from the lower border of the inguinal ligament. LFCN was retracted to the medial side during the procedure. There was no direct trauma to LFCN in all cases. Postoperative sensory disturbance was evaluated at 2 weeks, 3 months, and 1 year follow-up after surgery. RESULTS: After osteotomy, the blood flow of LFCN was decreased to 2.4 from 3.3 ml min(−1) 100 g(−1) when compared with that before osteotomy (P < 0.01). Postoperatively, 14 of 19 patients had sensory disturbance at 2 weeks, 8 of 19 patients at 3 months, and 2 of 19 patients at 1 year follow-up. The blood flows of both patients who had persistent symptoms over 1 year after surgery had been decreased by more than 50% during operation. CONCLUSIONS: Decrease of blood flow of LFCN by more than 50% seems to cause persistent symptoms after surgery through the Smith-Petersen approach even if direct trauma to the nerve is avoided. Excessive traction by retractors is thought to be the main cause of blood flow reduction.