HETEROTOPIC OSSIFICATION AFTER PRIMARY CEMENTED AND NONCEMENTED TOTALHIP-ARTHROPLASTY IN PATIENTS WITH OSTEOARTHRITIS AND RHEUMATOID-ARTHRITIS

Objective: To compare the frequency and severity of heterotopic ossifi cation (HO) in patients with osteoarthritis or rheumatoid arthritis wh o undergo cemented or noncemented total hip arthroplasty. Design: A pr ospective case study. Setting: A university referral centre. Patients: One hundred and sixty one patients underwent 184 total hip arthroplas ties. The 184 hips were categorized as follows: cemented total hip art hroplasty - 60 osteoarthritic hips, 26 hips affected by rheumatoid art hritis; noncemented total hip arthroplasty - 67 osteoarthritic hips, 3 1 hips affected by rheumatoid arthritis. Interventions: Total hip arth roplasty. A standard approach was used to implant either a cemented or noncemented prosthesis. Radiographs were obtained of each hip preoper atively, immediately postoperatively and 6 weeks, 3 months, 6 months a nd 1 year postoperatively. Main Outcome Measures: Radiographs were gra ded in blind fashion for HO, according to the criteria of Brooker. Mod ified Harris hip scores were calculated at 1 and 2 years postoperative ly. Results: HO (incidence of Brooker grades 2, 3 and 4) was greater a fter cemented (22%) than noncemented (9%) total hip arthroplasty in os teoarthritic hips (p < 0.05), but there was no significant difference between the two types of prosthesis in hips affected by rheumatoid art hritis. When both types of prosthesis were considered together there w as no significant difference in the incidence of HO between osteoarthr itic hips (15%) and hips affected by rheumatoid arthritis (12%). With respect to Harris hip score, the presence of grade 4 HO was associated with a significantly (p < 0.05) lower score (50.6) than grade 3 (89.4 ) and grade 2 (91) HO. Conclusions: Cemented total hip arthroplasty in creases the frequency of HO only in osteoarthritic hips. Compared with Brooker's grades 2 and 3 HO, grade 4 HO significantly lowers the Harr is hip score after total hip arthroplasty.