BACKGROUNDMany kinds of approaches have been used for minimally invasive surgery of total hip arthroplasty (MIS-THA). However, until now when considering the balance of efficacy and associated surgical injury there is no approach widely accepted for MIS-THA. In this study, a modified anterolateral muscle sparing approach was developed to optimize MIS-THA.

METHODSTwenty adult cadaver specimens (40 hips) were used for anatomic research. The distance from anterior origin of the gluteus medius on the iliac crest to the anterior superior iliac spine was measured; the course of the superior gluteal nerve and the distances from the nerve to the regional anatomic landmarks were recorded. Simulated surgeries were performed in three fresh cadaver specimens to evaluate the soft tissues injury around incisions. From October 2004 to June 2006, 57 patients (57 hips) were treated with anterolateral muscle sparing minimally invasive total hip arthroplasty, of which 17 were femoral neck fractures, 9 osteoarthritis, 16 developmental dysplasia of hip (DDH) and 15 avascular necrosis (AVN). All the operations were performed by the same senior surgeon. Operation time, blood loss and drainage volume were recorded and the correlation between the local complications and the native anatomical characteristics was especially noted. All cases were followed for at least 12 months.

RESULTSThe distance from the anterior origin of the gluteus medius to anterior superior iliac spine along the iliac crest was (61+/-4) mm (range, 55-68 mm), and the distance from inferior branch of the superior gluteal nerve to the anterior tubercle of the greater trochanter was (74+/-6) mm (range, 60-88 mm). In simulated surgeries, excessive distraction of tissue was found to be the main cause of the anterior border injury of the gluteus medius muscle. Of the 57 patients treated with anterolateral muscle sparing MIS-THA, the average incision length was 9 cm (range 7.5-13 cm). Blood transfusions were performed in 11 patients. During the operations, anterior border injury in deep layers of the gluteus medius was found in 9 patients. Posteromedial perforation of the prosthesis stem on the femoral side was found in 2 patients, which were revised immediately. No positive Trenderlenburg sign was found during the 12 months of follow-up.

CONCLUSIONSThe incision of the anterolateral muscle sparing approach should be directed from the anterior tubercle of the greater trochanter toward 6 cm posterior to the anterior superior iliac spine. The proximal part of the incision should be within 6 cm from the anterior tubercle of the greater trochanter, and it is safe to be extended distally. The anterolateral muscle sparing approach is a minimally invasive approach for total hip arthroplasty, through which the surgeon can operate on the acetabulum and femoral sides in a single incision without muscle detachment, and fluoroscopy assistance is not needed. The surgeon should pay more attention to protecting the gluteus medius from injury by distraction before femoral neck cutting and during the preparation of the femoral side.