Heterotopic bone formation after noncemented total hip arthroplasty. Location of ectopic bone and the influence of postoperative antiinflammatory treatment.

The regional-development of heterotopic bone around the hip and the influence of postoperative prophylaxis with antiinflammatory drugs were studied in 66 patients treated with 74 noncemented, porous-coated total hip arthroplasties (THA) using the McFarland approach. Thirty patients (34 hips) were treated with antiinflammatory drugs during the early postoperative period. Heterotopic bone developed in two different regions: central, around the neck of the femoral component, and lateral to the greater trochanter of the femur. Central ossifications were recorded in 53% of the hips and appeared significantly less frequently in patients postoperatively treated with antiinflammatory drugs. Lateral ossifications were recorded in 71% of the hips, and no significant prophylactic effect was found for postoperative antiinflammatory treatment. In response to the McFarland approach in THA, heterotopic ossifications may appear both centrally around the neck of the femoral component and lateral to the trochanter in the substance of the medial gluteal muscle. The latter may be comparable to post-traumatic myositis ossificans.