Background Heterotopic periarticular ossification (PAO) is very common (more than 60%) after total hip replacement (THR). Without any prevention severe grades of Brooker 3 and 4 occur in about 20%. Grade 3 and 4 means also loss of function and sometimes pain. Prevention of severe grades (Brooker 3–4) is indicated in all cases of THR and is possible by radiation therapy or oral administration of NSAIDs like indometacin or diclofenac.

Objectives Standard NSAIDs have the potential risk of severe gastrointestinal events (perforation, ulceration and bleeding, PUB). Especially patients with THR are usually old and suffering from many diseases. These patients have an increased risk of GI-complications. Rofecoxib is a selective inhibitor of COX-2 with reduced risk of PUBs. Although the cause and actions of PAO are not well understand it is generally accepted that COX-2 plays an important role.

Methods In a prospective study we compared the results of 25 mg rofecoxib once daily on preventing severe PAO after THR with results of diclofenac out of the literature. Our 137 patients take 25 mg rofecoxib once daily starting on the first or second day after THR. The mean duration of drug administration was 13.8 days. 72 hips could be evaluated after 3 months, further 65 hips after 6 months.

Results The ossification was evaluated on pre- and postoperative x-rays of the pelvis. There was no difference between the results after 3 and 6 months. 96 (70%) of the hips showed no signs of PAO, 40 (29%) hips had Brooker 1 (ossifications up to one cm), only one hip (1%) Brooker 2 and none of the hips had severe bone formation Brooker 3 or 4 (bridging ossification between femur and pelvis). Results of diclofenac or irradiation therapy in the literature show similar results: Brooker 1 and 2: 11–40% and no severe Brooker 3 and 4.

Conclusion 25 mg of the COX-2 inhibitor Rofecoxib administered once daily after THR starting one or two days after surgery for 2 weeks can securely prevent the formation of periarticular ossification (PAO) of severe grade (Brooker 3 and 4). Minor ossification without functional impairment (Brooker 1–2) were found in 30%. 70% of the hips showed no signs of postoperative ossification. These findings are comparable to the results of prevention with irradiation therapy or standard NSAIDs like diclofenac (100–150 mg).

References

1. Brooker AF, Bowermann JW, Robinson RA, Riley LH. Ectopic ossification following THR: incidence and a method of classification. J Bone Joint Surg Am. 1973;55:1629–32

2. Eulert J, Knelles D, Barthel T. Heterotope Ossifikationen. Orthopäde 1997;6:399–406

3. Sell S, Willms R, Jany R, et al. The suppression of heterotopic ossification: radiation versus NSAID therapy – a prospective study. J Arthroplasty 1998;13:854–9