Neurogenic Heterotopic Ossification

Abstract

Heterotopic ossification (HO) following neurological injury is defined as soft tissue bone formation which is most often seen after spinal cord or head injury and reported to occur after numerous other neurological insults. It can result in ankylosis of associated joints restricting patient mobility. Lesions present with signs of local inflammation. Evidence of ossification is noted on Technetium 99 bone scan and then on X-ray. Serum alkaline phosphatase may be elevated. Although it resembles the histopathology of myositis ossificans traumatica, its pathogenesis remains unclear. Current research favors exercise of joints to attenuate loss in range of motion. Ethane-1-hydroxy-1, 1-diphosphonic acid, a diphosphonate analogue of pyrophosphate, is the only medical treatment specifically indicated in heterotopic ossification. It has not been as effective as first hoped. Nonsteroidal anti-inflammatory drugs, warfarin, and X-radiation therapy hold promise as treatments. Surgical excision to remove ankylosing ectopic bone has been plagued by reoccurrence. Studies to better elucidate the etiology of HO, accelerate diagnosis of the condition, and accurately determine its risk of reoccurrence are needed. Further controlled studies of the various treatments are also warranted.