Heterotopic Ossification

1. What are the risk factors for heterotopic ossification (HO)? How long after injury is HO most likely to develop?
2. What are the symptoms of HO? What are the most common joints to be involved?
3. What are complications of HO?
4. What are tests used to diagnose HO?
5. What are methods and medications used to prevent HO?
6. How is HO treated?

Answers:
1. The risks are prolonged coma (>2 wks), immobility, limb spasticity, increased tone, long-bone fractures, pressure ulcers, edema. Most common 3-4 months post-injury.
2. Pain, decreased ROM, local swelling, erythema, warmth, muscle guarding, low-grade fever. The joints usually involved are hips (most common, elbows/shoulders, knees.
3. Decreased ROM, pain, bony ankylosis, peripheral nerve compression, vascular compression, lymphedema.
4. Serum alk phos, bone scan (very sensivitive, 2-4wks post-injury), plain films (used to confirm maturity of HO).
5. ROM, control of tone, NSAIDs, radiation (used in THA patients).
6. Diphosphonates, NSAIDs, ROM, surgery (after HO mature, at 12-18 months).