Heterotopic Ossification - Treatment

Treatment

The effect of Didronel, a bisphosphonate, ehtylhydroxydiphosphonets (EHDP), is to prevent calcium from being deposited in the bony matrix that has already been formed. EHDP (Didronel) does this by inhibiting the conversion of amorphous calcium phosphate to hydroxyapatite crystals which prevents mineralization of the bone matrix. Therefore, it is essential to make the diagnosis as soon as possible (preferably before any calcium shows up on x-ray) and start the Didronel immediately. Didronel will do nothing to remove calcium that has already been deposited. It is a preventative drug, and has no effect on existing ossification. It also has no effect on the underlying process which produces the bony matrix. There are no known side effects that would prohibit usage. Many physicians recommend prophylactic use of Didronel in all acute spinal cord injuries, but because of the cost this may not be practical. Some patients complain of nausea the first week, but this is rarely severe enough to stop treatment and usually subsides in a few days. There is no uniform agreement on how long Didronel should be continued. In most cases, there will be a brief flare-up of the heterotopic ossification following discontinuation of Didronel, and some cases an increase in the amount of calcium deposited. There are no completely reliable tests to indicate that the heterotopic ossification is inactive and treatment can be safely stopped. However, if the treatment is continued long enough this additional calcium deposition will be of minimal clinical significance. The patient needs to be observed closely for signs of recurrence whenever treatment is discontinued.

EHDP (Didronel) has been used for the prevention of postoperative heterotopic ossification, but the outcome has been contradictory. Indomethacin, a prostaglandin synthase inhibitor is an anti-inflammatory drug which also suppresses mesenchymal cells, and is effective in patients at high risk, when administered in different doses immediately after surgery for about 3 to 6 weeks, but non-steroidal anti-inflammatory drugs may trigger gastrointestinal or renal side effects, including bleeding. Recommended dosage for EHDP is 20 mg per kilogram per day for two weeks prior to surgery and 10 mg per kilogram per day postoperatively. However, some patients, particularly those with total hip replacement, must be maintained on 20 mg per kilogram per day postoperatively because the lower dosage will not be enough to prevent recurrence.

Radiation Therapy.

Prophylactic radiation therapy for the prevention of heterotopic ossification has been employed since the 1970s. A variety of doses and techniques have been used. Generally, radiation therapy should be delivered as close as practical to the time of surgery. A dose of 7-8 Gray in a single fraction within 24–48 hours of surgery has been used successfully. Treatment volumes include the peri-articular region, and can be used for hip, knee, elbow, shoulder, jaw or in patients after spinal cord trauma.

Single dose radiation therapy is well tolerated and is cost effective, without an increase in bleeding, infection or wound healing disturbances.

Other possible treatments.

Certain antiinflammatory agents, such as indomethacin, ibuprofen and aspirin, have shown some effect in preventing reoccurrence of heterotopic ossification after total hip replacement.

Conservative treatments such as passive range of motion exercises or other mobilization techniques provided by physiotherapists may also assist in preventing HO. A review article looked at 114 adult patients retrospectively and suggested that the lower incidence of HO in patients with a very severe TBI may have been due to early intensive physiotherapy in conjunction with pharmacological treatment. Another review article also recommended physiotherapy as an adjunct to pharmacological and medical treatments because passive range of motion exercises may maintain range at the joint and prevent secondary soft tissue contractures, which are often associated with joint immobility.