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One of the many complications of severe head trauma is heterotopic ossification (HO), the formation in various parts of the body of new bony masses in tissue (such as muscle) that usually does not calcify. Prophylactic treatments such as active and passive motion, splinting, anti-inflammatory drugs, diathermy, ultrasound, and low-dose radiation all have had limited success in preventing such ossification.
The results of two preliminary studies, however, indicate that etidronate disodium, an agent most commonly used to treat Paget's disease, has proved useful in preventing primary HO as well as its recurrence after surgical removal of aberrant bony masses.
Etidronate and other diphosphonates are analogues of pyrophosphate, which is involved with calcification in vivo. Diphosphonates apparently retard both the formation and dissolution of hydroxyapatite crystals, thereby preventing bone resorption (as occurs in Paget's disease) as well as ectopic soft tissue calcification.
Although diphosphonates have been used to prevent HO in
Macek C. Aberrant ossification halted after head trauma. JAMA. 1983;249(8):993. doi:10.1001/jama.1983.03330320007003