Charles V. Toman, MD - 4/11/2009

Question
Dr. Toman,
 I have a question regarding heterotopic ossification? I had a hip revision done and I grew heterotopic ossification as a complication. It was quite severe, as I could not move the hip at all. We waited 10 months and it was mature so it was removed. I then had 1 round of radiation on the hip. My question is: In your opinion how often does the heterotopic bone come back and to what degree? It has been 3 months since my last surgery and I do believe it is coming back? Thank you so much for your answer.

Answer
Deb,

Heterotopic Ossification (HO) is unfortunately one of the more difficult and persistent complications encountered following hip replacement surgery.  Some experts believe that HO results from the proliferation and differentiation of stem cells to osteoblasts in the soft tissues. It is very commonly seen in patients who have had significant head injuries as well.  In these patients it is much more severe.  The best initial treatment for HO is prevention.  Careful technique, draining wounds, prevention of hematoma formation are the main ways to prevent the problem from occuring.  Despite attention to these details, HO still occurs in a small population of patients.  When treating HO that is already making itself known ie limited or painful ROM, presence on Xrays, we typically allow it to "mature"  which typically takes 9-12 months.  Attempting to remove it earlier would only further aggravate an annoying and disabling process. Surgeons have 2 options for prophylaxis following excision of HO, anti-inflammatory medications or radiation.  Usually the anti-inflammatory medication used is Indomethacin and it is prescribed for 6 weeks.  Radiation therapy is typically a single dose right around the time of the procedure.  Typically, one of these 2 methods is helpful in minimizing recurrent HO.  

Many patients, despite one of these treatments, still remain at least partially symptomatic.  In cases of HO around the hip, the calcification occurs in the critical abductor muscle.  Additionally the HO can encase the sciatic nerve and other critical structures, which may limit your surgeon's ability to completely remove the HO.

The bottom line is that you are likely to have a long recovery and you may not regain full function of your hip.

Discuss your concerns with your surgeon.  He or she may want to order an X-ray to evaluate if there is any evidence of recurrent HO.

I wish I could advise you of a medication or therapy that you as the patient could take or do to decrease the chances of a recurrence of your HO.

To specifically answer your question, HO is near impossible to completely eradicate and the degree of recurrence is most commonly proportional to your initial degree of HO.  If you have significant involvement initially you have a higher chance of it recurring if it is excised even with prophylaxis.

Hopefully this has been helpful.  I am sorry that you are having such a hard time with this hip revision.  Please let me know if there is anything else I can help you with or if there are any other specific points that you would like answered.