Asymmetry of the Cross-sectional Area of the Gluteus Medius Muscle Persists Eight Years after Total Hip Arthroplasty for Osteoarthritis of the Hip.

Abstract

ABSTRACTObjectives:The objective of the present study was to compare the cross-sectional areas (CSAs) of the gluteus medius on the affected and unaffected sides to assess long-term changes after total hip arthroplasty (THA).Methods: The data for 23 women who were diagnosed with unilateral hip osteoarthritis and who underwent primary THA via the posterolateral approach were retrospectively reviewed. The demographic data of the patients and the Japanese Orthopaedic Association hip scores were obtained from medical records. The CSA of the gluteus medius was measured on computed tomography images obtained at three different time points: preoperatively, 3 years postoperatively, and 8 years postoperatively.Results:The CSA of the gluteus medius on the affected side was significantly greater than the preoperative value at 3 (P<0.005) and 8 years postoperatively (P<0.001). The mean increase in the CSA relative to the preoperative value was 24.0% at 3 years and 37.5% at 8 years postoperatively. There was no significant change in the CSA of the unaffected side at any time point. The CSA of the gluteus medius was significantly smaller on the affected side than on the unaffected side preoperatively (P<0.001), 3 years postoperatively (P<0.001), and 8 years postoperatively (P<0.003).Conclusions:Because the gluteus medius is important for achieving stability when walking, it is important to maintain or increase the CSA of the gluteus medius by regular or long-term rehabilitation interventions (such as maintaining abductor muscle strength) from the early stages of osteoarthritis and to provide guidance on effective training both before and after THA.