Heterotopic ossification

Heterotopic ossification (HO) is the abnormal process by which bone tissue forms outside of the skeleton in muscles and soft tissue. It forms following a traumatic injury, neurogenic injury, or genetic predisposition. The likelihood and severity of HO is linked to the severity of the injury. The most common sites of developing HO are the hip, knee, elbow and shoulder. While the exact mechanism of how HO develops is not known, it is believed to be a result of an abnormal muscle repair system, abnormal neurologic healing response below the level of injury, an abnormal inflammatory response, or a combination of them.

Heterotopic ossification presents differently in different stages. In the initial inflammatory stage, there is pain, redness, swelling, warmth, generalized tenderness; this can mimic other more serious medical conditions and should require urgent evaluation. In the late stage, there is more localized pain, decreased range of motion, and underlying tissue damage and complications. There are various blood or urine tests that can be useful in helping predict HO, but there is not one single gold standard lab. Triple bone scan, X-rays and CT scans are the most useful and reliable imaging studies to rule out other similar medical conditions and confirm the diagnosis of HO.

Heterotopic ossification does not have a single treatment to prevent its development or cure its progression. The goal of management should be to control pain, prevent long term complications, and allow the patient to continue to perform their own daily activities of living. This can be achieved through an array of options, ranging from physical therapy to prophylactic radiation and medications to surgical interventions. There are many emerging management styles of HO, but coordinating care between the patient, their support system, physicians, therapists, and other care takes should always remain the central focus.