Motor nerve palsy following primary total hip arthroplasty.

BACKGROUND Nerve palsy is a potentially devastating complication following total hip arthroplasty. The purpose of this study was to retrospectively identify risk factors for, and the prognosis associated with, a motor nerve palsy following primary total hip arthroplasty. METHODS Between 1970 and 2000, 27,004 primary total hip arthroplasties were performed at our institution. Forty-seven patients (0.17%) with postoperative motor nerve dysfunction were identified by a review of the complications log of a total joint database. The medical record of each patient provided the data for this study. The average age of the patients was fifty-seven years at the time of surgery. The patients had serial clinical examinations for a minimum of two years, or until neurologic recovery or death. The nerve palsies were classified as complete or incomplete, and only patients with objective motor weakness were included in the study. The limb lengths were measured on preoperative and postoperative radiographs, and those data were then compared with the limb lengths in a matched cohort of patients who had not sustained a nerve injury after a primary total hip arthroplasty. The extent of neurologic recovery, the need for braces or walking aids, and the use of medications for neurogenic pain were evaluated. RESULTS There were twenty-nine complete motor nerve palsies (sixteen peroneal, eleven sciatic, and two femoral) and eighteen incomplete motor nerve palsies (fourteen peroneal, three sciatic, and one femoral). A preoperative diagnosis of developmental dysplasia of the hip (p = 0.0004) or posttraumatic arthritis (p = 0.01), the use of a posterior approach (p = 0.032), lengthening of the extremity (p < 0.01), and cementless femoral fixation (p = 0.03) were associated with a significantly increased odds ratio for the development of a postoperative motor nerve palsy. Of the twenty-eight patients with a complete palsy who were available for follow-up, only ten (36%) had complete recovery of motor strength, which took an average of 21.1 months. Seven of the eighteen patients with an incomplete palsy fully recovered their preoperative strength. Twenty-one patients required walking aids, and fifteen required permanent use of an ankle-foot orthosis. Five patients required daily medication for chronic neurogenic pain. CONCLUSIONS Motor nerve palsy is uncommon following primary total hip arthroplasty. A preoperative diagnosis of developmental dysplasia of the hip or posttraumatic arthritis, the use of a posterior approach, lengthening of the extremity, and use of an uncemented femoral implant increased the odds ratio of sustaining a motor nerve palsy. The majority of the motor nerve deficits in our series, whether complete or incomplete, did not fully resolve.