Incidence of heterotopic ossification after hip resurfacing

Heterotopic ossification has been noted around total hip arthoplasty in numerous studies. With hip resurfacing growing in popularity, we have prospectively evaluated the incidence in a cohort undergoing hip resurfacing.

Two hundred and twenty consecutive hip-resurfacing procedures were prospectively reviewed at a minimum of 2 years follow up to assess the incidence of heterotopic ossification and its effect on function and clinical outcome. We also reviewed the preoperative diagnosis, age, sex and previous surgery.

The overall percentage of heterotopic ossification was 58.63%. The incidence of Brooker 1 was 37.27%, Brooker 2 was 13.18% and Brooker 3 was 8.18%. Male osteoarthritis had the highest incidence of heterotopic bone formation (HBF). Three men underwent excision of heterotopic bone, two for pain and stiffness and one for decreased range of movement. Both anteroposterior and lateral radiographs were reviewed for evidence of HBF. In all, 12.7% had no evidence of HBF in the first view but clearly had in the second view.

Overall, we found no evidence that HBF affected the clinical or functional outcome of the hip resurfacing at a mean of 3 years follow up. However, in light of the high incidence of HBF seen in a yet unproven long-term prosthesis, we conclude that the Cochrane database recommendations with regard to prophylaxis should be implemented.