Motor Nerve Palsy After Primary Total Hip Arthroplasty: A Case-Control Analysis With Radiographic Review

Background Motor nerve palsy is a serious complication after primary total hip arthroplasty (THA). This study determined the incidence, risk factors, and prognosis of motor nerve palsies after primary THAs in a large series with radiographic review. Methods Among 10,604 primary THAs performed between 2001 and 2014, we identified 40 motor nerve palsies within 90 days of surgery. The mean patient age was 58 years (range, 17 to 88), 50% were women, and the mean body mass index was 31 (range, 18 to 50). Medical records were reviewed for confirmation of weakness, electromyography data, and surgical details. Logistic regressions and a 1:2 case-control analysis identified risk factors. Radiographic measurements were conducted for both groups. The mean follow-up was six years (range, 0.2 to 15). Results Given the cohort of 10,604 primary THAs and 40 motor nerve palsies, the incidence was 0.4%. The peroneal branch of the sciatic nerve was most affected (68%), followed by the entire sciatic nerve (18%). The operative extremity was lengthened in 39 of 40 cases, with a median overall lengthening of 10 mm compared to three mm in controls. Only 20% of patients who had a nerve palsy had complete motor recovery, which occurred over a mean of 28 weeks (range, seven to 57). Age, sex, body mass index, operative time, surgical approach, femoral offset, and inclination were not significant risk factors. Patients who had lumbar spine disease had a 21-fold increased odds of nerve palsy (odds ratio 21.3, 95% confidence interval 2.8 to 163.1). Conclusions Motor nerve palsies following THA are rare (0.4%) but serious, as only 20% had complete recovery. The peroneal branch of the sciatic nerve was most commonly affected. A very strong risk factor was lumbar spine disease. Although the absolute risk of a motor nerve palsy was low, surgeons should consider comorbid spine conditions when weighing the risks of THA.