What is Heterotopic Ossification?

The term “heterotopic ossification” refers to the growth of bone material in the soft tissues of the body, including muscles, tendons and fascia. The severity of the condition varies; some patients have only small nodules of excess bone that can be noted on X-rays, but others suffer severe and debilitating pain. The cause of this condition is not fully understood, and the most effective treatment for the condition is aggressive surgery, although some doctors have had success with radiation.
The word “heterotopic” essentially means “wrong place,” and “ossification” refers to the formation of bone. Originally, heterotopic ossification was grouped under the heading “myositis ossificans,” along with an assortment of similar conditions. This term is no longer widely used in reference to heterotopic ossification, because the problem is not confined to the muscles. A related condition, ossifying fibromyopathy, usually confines itself to the fibrous tissue of the body, and periarticular ossification can be found in the region around the joints.
Research has suggested that heterotopic ossification might be linked to injuries to the spinal cord, along with neurological conditions. It appears that mixed signals in the body stimulate normally dormant osteoprogenitor cells, causing them to start growing bone. When these cells are in the soft tissues of the body, it results in heterotopic ossification. The condition often appears in the form of periarticular ossification, especially around the site of hip injuries.
When heterotopic ossification is caused by trauma or an injury, it is known as heterotopic ossification traumatica, and a case with no known cause is called atraumatica. Heterotopic bone formation also has been known to strike amputees, especially those who have experienced violent or traumatic amputations. In amputees, the condition can cause serious problems, because surgeons might have to amputate part of the residual limb to treat the condition, thus making the amputation even more severe.
Although it is not inherently painful, heterotopic ossification can become painful. Severe cases might restrict the patient’s movement or cause internal bruising and injury. Typically, anti-inflammatories and pain medication will be prescribed to bring the rate of soft tissue swelling down and ease the pain that is associated with the condition. If it becomes clear that the condition is spreading, the patient might have to have surgery to remove the offending bone material, in the hopes of removing the rogue osteoprogenitor cells. In some cases, a surgeon might have to replace an entire joint, if the new bone formation has surrounded or damaged the joint too extensively.