Heterotopic ossification. Incidence in cemented versus cementless total hip arthroplasty

To resolve the debate whether cementless total hip arthroplasty (THA) carries an increased risk of heterotopic ossification (HO) as compared with cemented THA, 100 patients undergoing primary cemented THA (both acetabulum and femur) were individually matched to 100 patients undergoing primary cementless THA. Preoperative, 6-week postoperative, and 2-year postoperative radiographs were reviewed for the presence of HO using the Brooker classification. No subject in either group received any postoperative prophylaxis for HO. The matching parameters were age ( +/- 10 years), sex, weight ( +/- 10 lb.), diagnosis (all were osteoarthritis), Charnley class (A/B), and surgical approach (trochanteric osteotomy or modified Hardinge). The overall incidence of HO was 68% in the cemented group and 65% in the cementless group. The extent of HO (grade III) was significant in 9% of the cemented group and 5% of the cementless group. There was no grade IV HO (bone ankylosis) in either group. Neither the overall incidence nor the incidence of grade III HO was statistically different between the two groups. Patient sex and surgical approach had no interactive effect with type of component fixation on the incidence of HO. Fear of HO should not be a factor in the choice of fixation for THA.