Heterotopic bone formation after total hip arthroplasty.

Formation of heterotopic bone can cause pain and limit motion, thus ruin what would otherwise have been an excellent result after total hip arthroplasty. The cause of bone formation remains controversial, and diphosphonates have been ineffective in its prevention. Radiotherapy and nonsteroidal anti-inflammatory drugs, however, are effective preventative agents. Once the bone is formed, however, surgical excision is the only effective treatment.