DEAR DR. ROACH: On Nov. 2, 2020, I had a total right hip replacement. The surgery was successful, and the incision has healed completely. X-rays on the day of the surgery are clear. However, X-rays in April this year show something the surgeon called heterotopic ossification. It feels as if there is something large growing inside my hip. How often does this type of thing occur, and is surgery necessary for treatment?
A: "Heterotopic" is from the Greek roots meaning "another place," while ossification refers to making bone. So, heterotopic ossification is a bone in a place it doesn't belong.
Way back in my first year as a medical student, a professor paraphrased an Arabic saying: "An unlucky man finds bones in his tripe dinner." Even the ancients recognized that bones can sometimes show up in places they have no place being. I should note that ossification is different from calcification, which is just calcium deposits, often in soft tissues. Ossification means actual bone fragments.
The major cause of heterotopic ossification is trauma, and a hip replacement surgery is quite traumatic. The pieces of bone form in the soft tissues around the hip. Men are more likely to develop this than women, and different studies report from 53% up to 100% of people will develop some bone fragments, but only about 10% of people will develop large enough fragments to cause symptoms. If the symptoms (usually pain and stiffness) become advanced, then, yes, surgery is usually required to remove the fragments.
Some surgeons use a medication such as indomethacin or celecoxib (Celebrex), or even radiation therapy, to prevent HO in high-risk individuals. This group would include those who have had symptomatic HO previously.