Heterotopic ossification is bone forming in the wrong place, usually between muscle fibers. It's also called myositis ossificans. Indomethacin is an anti-inflammatory drug. It's been used the longest to prevent HO.

Newer studies show that another anti-inflammatory (naproxen) may work better with fewer problems. Treatment is usually started the day after surgery. It's often used for about six weeks. A study in 1998 showed that one week is all that's really needed to prevent HO.

Check with your father's doctor about his need for an anti-inflammatory. If it's been long enough since the operation with no sign of HO, he may be able to stop taking the drug. Don't stop this medication without his doctor's approval first.