Disodium etidronate in the prevention of heterotopic ossification following spinal cord injury (preliminary report).

Heterotopic ossification is a frequent complication following spinal cord injury with 16 per cent to 53 per cent of patients developing varying degrees of pathologic ossification. The diphosphonates are known to block the transformation of amorphous calcium phosphate into crystalline hydroxyapatite. Therefore, one of the diphosphonates, disodium etidronate (generic name of disodium ethane-1-hydroxy-1, 1-diphosphonate (EHDP) was selected fro clinical trials to study the effectiveness of EHDP in preventing heterotopic ossification following spinal cord injury. In a double-blind, clinical study of 149 spinal cord injury patients, disodium etidronate has proven its effectiveness in the prevention of heterotopic ossification. The extent of heterotopic ossification development as measured by the total heterotopic ossification X-ray grade was significantly less in EHDP-treated patients compared to placebo-treated patients (P less than 0-05). For maximal effectiveness, EHDP treatment must be started before the onset of the pathological process initiating the development of heterotopicossification. Further studies are necessary to determine the optimal time to institute EHDP treatment, length of treatment, and minimal effective dose. EHDP is the first hterapeutic agent known to alter the formation of heterotopic ossification after spinal injury and may prove useful in other conditions where heterotopic ossification prevention is clinically indicated.