The term "heterotopic ossification" refers to the growth of bony material into 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 seen on x-rays, but others experience severe, 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 a variety of similar conditions. This term is no longer widely used in reference to heterotopic ossification, because the problem is not limited to the muscles. A related condition, fibromyopathy ossificans, is usually limited to the fibrous tissue of the body, and periarticular ossification can be found in the region around the joints.
Causes
Research has suggested that heterotopic ossification could be related to spinal cord injuries, 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 found in the soft tissues of the body, heterotopic ossification occurs. The condition often appears as periarticular ossification, especially around the site of hip injuries.
When heterotopic ossification is caused by trauma or injury, it is known as traumatic heterotopic ossification, and a case with no known cause is called atraumatic. Heterotopic bone formation is also known to strike amputees, especially those who have experienced violent or traumatic amputations. In amputees, the condition can cause serious problems, as surgeons may have to amputate part of the residual limb to treat the condition, making the amputation even more serious.
Treatment
Although not inherently painful, heterotopic ossification can become painful. Severe cases can restrict the patient's movement or cause bruising and internal injuries. Anti-inflammatory medications and pain relievers will usually be prescribed to reduce soft tissue swelling and relieve pain associated with the condition. If it becomes clear that the condition is spreading, the patient may have to undergo surgery to remove the offending bone material, in the hope of removing rogue osteoprogenitor cells. In some cases, a surgeon may have to replace an entire joint if new bone formation has surrounded or damaged the joint too much.