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 1 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 1 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.

Objective. The purpose of this series was to determine the frequency of abductor mechanism avulsion by sonography after total hip arthroplasty with the Hardinge approach (J Bone Joint Surg Br 1982; 64:17-19) and its relationship to the presence of insufficiency of this musculature in the postoperative period. Methods. Thirty-four consecutive patients were prospectively accessed in the postoperative period of hip arthroplasty by the Trendelenburg test, hip sonography, and abductor muscle electromyography. In patients who were found to have clinical insufficiency of the abductor musculature, we also measured the femoral offset in the preoperative and postoperative radiographs. Hip sonography was performed by an experienced musculoskeletal radiologist blinded to the other tests, and the tendons of the gluteus medius and gluteus minimus were visualized on longitudinal and transverse sections with a 7-to 10-MHz linear transducer. Results. Eight patients presented clinical insufficiency of the abductor musculature as detected by the Trendelenburg test. Four of these 8 patients with abductor insufficiency presented tendinous avulsion detected by sonography. One of the 4 patients with abductor insufficiency and normal sonographic findings had a decrease in the femoral offset caused by the arthroplasty itself. Two patients presented electromyographic changes of the abductor musculature, with no tendinous avulsion detected by sonography and no abductor insufficiency. Conclusions. We concluded that in patients undergoing total hip arthroplasty by the Hardinge approach in whom insufficiency of the abductor musculature develops, sonography is an interesting method of investigation because it identified the cause of this problem in most of our patients.

The experimental bone transport model proposed in the present study permits us to conclude that there is a clear difference between the ossification of the docking site and of the regenerate.

Level IV, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

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