['The pathogenesis of heterotopic ossification (HO) is still unclear and the preventive measures and therapies are usually insufficient. The authors compared free radical scavengers with placebo in order to assess the magnitude of their inhibitory effect on the development of HO.', 'A standard immobilization-manipulation model was used to induce HO in the hind legs of twenty female New Zealand albino rabbits. The animals were divided into two groups and received daily either placebo or a free radical scavenger (A/A) cocktail in a randomized double-blind fashion. Every four days an X-ray was taken and the thickness and length of new bone formation were measured at the thigh by two investigators independently.', "Fisher's exact test revealed a significant difference in the development of heterotopic ossification between the placebo group and the A/A group (70% versus none, respectively ; P=0.0031)."] Do free radical scavengers have a preventive effect on heterotopic bone formation following manipulation of immobilized rabbit legs?