Clinical significance of heterotopic ossification after metal-on-metal total hip resurfacing

Few studies about how heterotopic ossification (HO) affects functional outcome after metal-on-metal total hip resurfacing (MOMHR) have been reported. The purpose of this study was to evaluate the incidence and clinical significance of HO after MOMHR. We retrospectively reviewed 122 consecutive patients, who underwent MOMHR from June 2006 to October 2008, with adequate follow-up information. All patients had four weeks of aspirin (325 mg twice a day) for DVT prophylaxis and two weeks of celecoxib (400 mg once a day) for pain control. All data were collected prospectively including radiographs and functional scores preoperatively, at three months and at one year postoperatively. An independent musculoskeletal radiologist, using the Brooker classification, reviewed radiographs. Unbalanced ANOVA analyses were performed to evaluate the effect of HO on outcome. The overall incidence of HO at three months was 62.1% (grade 1: 39.8%, grade 2: 20.4%, grade 3: 1.9%) and 75% at one year (grade 1: 41.7%, grade 2: 27.8%, grade 3: 5.5%). There were no significant differences in the functional status scores among Brooker grade 0 to 3 groups at three months and one year follow-up. The incidence of HO after MOMHR was 62.1% at three months and 75% at one year despite a post-operative regimen of aspirin and celecoxib. We found no evidence that predominantly Brooker grade 1 or 2 HO affected the clinical outcome at three months or one year when compared across all Brooker classes of patients.