Effect of aspirin on heterotopic ossification after total hip arthroplasty in men who have osteoarthrosis.

The severity of heterotopic ossification was determined from the radiographs of eighty-three men in whom osteoarthrosis had been treated with a primary total hip arthroplasty with cement. The medical records of these patients were then reviewed, with the reviewer having no knowledge of the radiographic findings. A similar operative approach and technique had been used in all patients. There was no association between the amount of intraoperative loss of blood or the duration of the operation and the severity of formation of heterotopic bone. The over-all rate of occurrence of heterotopic ossification was 72 per cent. Of the fifty-eight patients who had received aspirin throughout their course in the hospital, two (3 per cent) had severe ectopic ossification (grade III or IV8). In contrast, twelve (48 per cent) of the twenty-five patients who had received no aspirin or in whom aspirin had been discontinued so that anticoagulation could be begun had severe heterotopic ossification. The difference in the severity of the ossification between the two groups is significant (p less than 0.0001).