Etidronate disodium (Didronel^TM) is a synthetic diphosphonate analog of pyrophosphate, a naturally occuring inhibitor of bone metabolism Accepted indications for etidronate disodium therapy are symptomatic Paget's disease, heterotopic ossification and hypercalcemia of malignancy. Etidronate disodium has been extensively studied in heterotopic ossification The mechansim of action of eirdronate disodium in the prevention of heterotopic ossification is not known, Chemical and in vitro studies show that the drug adsorbs to hydroxyapatite crystals, thereby inhibiting their growth and dissolution. But clinical research has not irrefutably proved of disproved the effectiveness of etidronate disodium in prevention on clinical heterotopic ossification

The paper presents two cases of heterotopic bone formation following neurologic insult. A 36-years-old male sustained traumatic brain injury secondary to a traffic accident. Three months post injury, a physical examination revealed limitation of range of motion of Rt elbow joint. The serum alkaline phosphatase was 335 IU/L. Roentgenograms were unremarkable. A bone scan revealed increased uptakes in the region of the Rt elbow and shoulder. Another patient C8 quadriplegic developed limitation of range of motion of Lt hip joint. Etidronate disodium was used in a clinical trial to prevention of heterotopic ossification. Roentgenograms of the joins involved revealed formation of heterotopic bone after the drug was administered for 12 weeks. Further prospective studies will be planned

Keywords :Etidronate disodium, Heterotopic ossification