SUMMARY Study of heterotopic ossification in the treatment of acetabular fractures The authors reviewed 252 patients with 256 acetabular fractures, with the goal of looking for predisposing factors to heterotopic ossification (HO). The type of fracture, the interval between the fracture and the operation, the approach, and the procedure were analyzed. Among the 80 hips conservatively treated, no HO was seen. Out of the 176 hips surgically treated, 29 (16.5%) showed HO. The type of fracture and the interval between lesion and surgical treatment had no influence on the incidence of HO. Kocher-Langenbeck’s approach showed the highest incidence of HO. No prophylactic treatment was used in pre and postoperative periods. The authors observed that careful surgical manipulation was the most important factor to prevent HO.