Anatomical study to avoid femoral nerve palsy in total hip arthroplasty

Abstract

Improper placement of the anterior retractor in total hip arthroplasty (THA) can cause femoral nerve palsy. We aimed to determine whether the femoral nerve distance on computed tomography can be predicted from radiographs. This study included 145 patients with hip dysplasia who underwent THA for hip osteoarthritis in one institution. The distance between the femoral nerve and anterior margin of the acetabulum (dFN) was measured in the horizontal section. Patients were divided into the short- and long-dFN groups. Age, sex, body height, body weight, and Crowe classification were compared between both groups using univariate analyses. Multivariate analysis was performed to identify predictors of dFN. Significance was set at p < 0.05. The mean dFN at each site of the femoral head was shorter proximally. The differences in body height and Crowe classification between both groups were significant. dFN (y) was positively correlated with body height (x1), Crowe classification (x2), and body weight (x3). The derived predictive formula was y = 9.24 + 9.74x1–3.55x2 + 0.065x3, with an adjusted coefficient of determination of 0.658 and p < 0.05 for all measurements. Patients with smaller body height, lower body weight, and severe hip deformity have a shorter dFN and a risk for femoral nerve palsy after THA; these require special attention.