Damage to the superior gluteal nerve after direct lateral approach to the hip

The superior gluteal nerve may be damaged during total hip arthroplasty. We prospectively studied 40 patients who had total hip arthroplasties using the Hardinge direct lateral approach to the hip to determine any correlation between superior gluteal nerve damage and abductor function. We used the Trendelenburg test to clinically evaluate abductor function preoperatively and I year postoperatively. We evaluated superior gluteal nerve function by electromyography preoperatively and at 4, 8, and 12 weeks until its normalization over a maximum of 24 weeks postoperatively. The Trendelenburg test was positive in 20 patients (50%) preoperatively and in 10 patients (25%) 1 year postoperatively. Seventeen patients (42.5%) had damage to the superior gluteal nerve visible on the first electromyographic evaluation performed 4 weeks postoperatively; three (7.5%) of these patients showed changes when reevaluated 6 months postoperatively; only one of the three patients had a positive Trendelenburg test I year postoperatively. Nine of the 37 patients with normal electromyography results had positive Trendelenburg tests. Our results suggest there are frequent electromyographic signs of damage to the superior gluteal nerve using the direct lateral approach to the hip. However, the damage tends to improve spontaneously and does not seem to cause clinically apparent abductor insufficiency.