Effect of two nonsteroidal antiinflammatory drugs on heterotopic bone formation in a rabbit model.

Using the model described by Michelsson, 24 mature New Zealand white rabbits underwent mechanical induction of heterotopic ossification in the quadriceps of the right hind limb. The rabbits were equally divided into four groups: indomethacin-treated, piroxicam-treated, and their respective controls. The effect of drug therapy on the production of heterotopic bone was assessed by analyzing plain radiographs of the femur using the grading system described by Scott. The results demonstrated that, while indomethacin is effective in decreasing the formation of heterotopic bone, piroxicam--when used in the dosage previously demonstrated to have no deleterious effect on healing bone--is not. The analysis of piroxicam blood levels demonstrated that the experimental piroxicam dose is inadequate to produce effective plasma blood levels in the rabbit. Therefore, any potential benefit from using piroxicam, as opposed to other nonsteroidal antiinflammatory drugs regarding fracture healing and bone remodeling, cannot be applied for the prophylactic treatment of heterotopic bone formation.