Small femoral offset is a risk factor for lateral femoral cutaneous nerve injury during total hip arthroplasty using a direct anterior approach

Introduction: Lateral femoral cutaneous nerve (LFCN) injury is a risk specific to the direct anterior approach (DAA) for total hip arthroplasty (THA). However, prevention strategies have not been established. This study aimed to identify the predisposing factors determining LFCN injury during THA via a DAA. Hypothesis: Patients with LFCN injury after THA via DAA would demonstrate predisposing factors. Material and methods: LFCN injury was identified using a patient questionnaire. Potential factors predisposing to LFCN injury were identified in four categories in patient records: patient factors (age, sex, BMI, diagnosis and range of hip motion), surgical factors (surgical time and surgeon's experience of the DAA), preoperative radiographic factors (neck-shaft angle, femoral offset, acetabular offset, total offset and length of muscle on computed tomography axial image) and radiographic changes (differences between each offset pre- and post-surgery). Multivariate analysis was performed to identify risk factors for LFCN injury during this surgery. Results: After application of inclusion and exclusion criteria, 102 hips (28 with LFCN injury; 74 without) in 102 patients (17 males, 85 females; mean age 66.0 years [range, 26-88 years]) were included. Univariate analysis of patients with and without LFCN injury revealed that small preoperative femoral offset and short preoperative long axis of the tensor fascia lata were statistically significant risk factors for LFCN injury (P=0.004, and P=0.01, respectively). Multivariate analysis showed that small preoperative femoral offset was the only independent risk factor for LFCN injury (odds ratio, 0.895; 95% Confidence Interval, 0.817-0.981; P=0.0018). Discussion: Smaller femoral offset was a significant risk factor for LFCN injury following THA via a DAA. Our recommendations are that careful attention should be paid to the skin-fascia incision and subcutaneous exposure, and that excessive retraction of the sartorius muscle and tensor fascia lata should be avoided, to reduce the risk of LFCN injury in patients with a small femoral offset. (C) 2016 Elsevier Masson SAS. All rights reserved.