Heterotopic bone formation following resurfacing total hip arthroplasty.

Heterotopic bone (HO), a rare association with total hip arthroplasty (THA), has recently been shown to be more of a problem with resurfacing hip arthroplasty (RHA). It has been speculated to be the result of greater soft tissue dissection required for this procedure. HO most commonly develops in males and patients with bilateral disease. To better understand if this problem does occur in RHA, groups of patients with RHA on one side and conventional THA on the other were evaluated. We retrospectively identified 45 patients that had RHA on one side and conventional cemented THA on the other. Follow-up has been up to 25 years. HO was graded at every clinical visit using the Brooker Classification. In the RHA group, there were 32 hips without evidence of HO, ten with grade 1, and three with grades 2 or 3. In the THA group, there were 36 hips without any HO, eight with grade 1, and one with grade 2. There was no statistical difference between either types of hip arthroplasty in HO formation overall or in the development of more severe grades. Motion was not significantly affected with the more severe grades. Our data obtained from a bilateral patient model suggests that RHA does not predispose to a greater development of HO. In doing a RHA, one should be aware that there might be an increased likelihood of HO in males with bilateral disease.