Frequently Asked Questions

I had a knee replacement five years ago that went fairly well until I developed a condition called heterotopic ossification. We finally got that mess straightened out and now I need an ankle replacement on the same side (same problem from a skiing injury years ago). What are the chances I'll develop this ossification problem in the ankle? Anything I can do to prevent it?

Problems that develop after surgery for joint replacement can include heterotopic ossification (bone forms in soft tissue where it doesn't belong). This complication is not uncommon after hip and knee replacements. And we know the same holds true for ankle joint replacement. Why does this problem develop, who is at risk, and what can be done to prevent it? These are three good questions with limited answers at this time. No one knows for sure why or how mature bone forms in the muscles and tendons around the joint. Some experts suggest both local and systemic factors. Why do some people end up with heterotopic ossification (HO) after surgery and others do not is also something of a mystery. There are known risk factors but not all patients with those risk factors develop HO. Some of the risk factors that have been identified so far include: male sex, older age, and infection. Bone trauma, extensive soft tissue dissection during surgery, and the formation of any hematomas (pocket of blood) during surgery are additional risk factors. The condition of the soft tissues before surgery may be another factor. Patients who have scar tissue around the ankle (from previous injuries or surgery) may be at increased risk for heterotopic ossification. More scar tissue means longer operative times. The more the soft tissues are disrupted and bleeding, the greater the risk of a healing, inflammatory response. And along with the movement of inflammatory cells to the area comes the migration of bone-marrow cells leading to the bone formation of HO. From a recent study in South Korea, it also looks like selecting the correct implant size is important. The patients in their study who developed heterotopic ossification group had some problems with bone response to an implant that was too small for them. Contact between one portion of the tibial component of the implant and the tibial bone may have contributed to bone stimulation leading to bone formation. Your concern is a valid one and should be discussed with your surgeon before the procedure. There are things the surgeon can do to prevent heterotopic ossification. Minimizing the operative time and amount of surgical dissection along with prescribing antiinflammatories for you top the list. Other aspects of surgical technique and preparation of the implant are within his or her control as well.

Keun-Bae Lee, MD, PhD, et al. Heterotopic Ossification After Primary Total Ankle Arthroplasty. In The Journal of Bone and Joint Surgery. April 2011. Vol. 93. No. 8. Pp. 751-758.

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