Anatomy of the Sciatic Nerve in Relation to the Bernese Periacetabular Osteotomy: A Cadaveric Study

Prior studies have examined the role of hip and knee positioning, specifically hip extension and knee flexion, to reduce the risk of sciatic nerve palsy during the Bernese periacetabular osteotomy. They have qualitatively noted that the sciatic nerve moves farther from the connection between the ischial and posterior column osteotomies in hip extension than flexion but has not precisely measured this change in position. This cadaveric study aimed to quantitatively evaluate how hip positioning affects the location of the sciatic nerve relative to the connection between the ischial and posterior column osteotomies. We dissected four cadaveric specimens (three females and one male) with a mean age of 83.0 ± 7.8. An anterior Smith–Peterson approach was performed to allow the cuts for the periacetabular osteotomy (PAO). A posterolateral approach was taken to identify the sciatic nerve and its emergence from the pelvis. Measurements were performed on the width of the posterior column and, in both hip flexion and extension, the distance from the emergence of the sciatic nerve from the pelvis to the connection point between the ischial and posterior column osteotomies. Each measurement was performed independently by two observers. All data are reported as a mean ± standard deviation (range). The width of the posterior column was 4.84 ± 0.48 cm (range: 4.20–5.35 cm). The distances from the sciatic nerve's emergence to the osteotomy connection point in extension and flexion were 4.73 ± 0.79 and 2.93 ± 0.85 cm, respectively. The distance from the sciatic nerve's emergence to the osteotomy connection point was significantly greater in hip extension than hip flexion (p = 0.021). When the hip is flexed, the distance from the sciatic nerve to the posterior column osteotomy connection point is significantly less than when it is in extension. This anatomic finding is essential for surgical safety, as it provides further evidence on the importance of positioning for reducing the risk of sciatic nerve injury during a PAO.