The purpose of the study is to determine whether Arcoxia is effective in preventing heterotopic ossification after total hip arthroplasty.

Rationale: Heterotopic ossification is a frequent complication after total hip replacement. Nonsteroidal anti-inflammatory drugs (NSAIDs) are known to effectively prevent heterotopic ossification, but gastrointestinal complaints are reported frequently. Selective cyclooxygenase-2 (COX-2) inhibiting NSAID produce less gastrointestinal side effects.

Objective: Preventing heterotopic ossification. Study design: A prospective two-stage study design for phase-2 clinical trials with 42 patients to determine if Arcoxia (a COX-2 inhibitor) 90-mg oral prevents heterotopic ossification. In the first stage, 19-patients are included. Another 23-patients are included when at least 90-percent of patients in first stage have Brooker classification 0, 1 or 2 at 6-months follow-up.

Study population: 42-patients with cemented total hip arthroplasty age 18 - 75 yr old.

Intervention: All subjects receive 90-mg Arcoxia oral for 7-days. Main study parameters/endpoints: The main study parameter is the degree of heterotopic ossification assessed on AP radiographs using the Brooker classification.

Nature and extent of the burden and risks associated with participation, benefit and group relatedness: No risks are associated with participating into the research. Besides the oral intake of Arcoxia, no extra burden is associated with participating in the study. The postoperative care does not change. Radiographic examinations will be routinely performed the day before surgery, immediately after operation, at 6-weeks and 6-months after surgery. The degree of heterotopic ossification will be determined by x-ray assessment.

Inclusion Criteria:

• Patients with primary or secondary hip osteoarthritis who are scheduled for cemented total hip replacement at the Radboud University Nijmegen Medical Centre, Nijmegen, the Netherlands.
• Written informed consent is obtained from the patient or the legally accepted representative.

Exclusion Criteria:

• Patients with rheumatoid arthritis, ankylosing spondylitis, or femoral neck fractures
• Patients with previous allergic reaction on non-steroidal anti-inflammatory drugs
• Patients with gastrointestinal complaints at admission, a history of gastrointestinal ulcers or perforations, inflammatory bowel-disease, hepatic dysfunction, renal dysfunction with a clearance below 30 ml/min and cardiac insufficiency.
• Patients with blood pressure consistently > 140/90 mmHg and who have not been adequately controlled.

Small sample size. However, due to ethical considerations, a two phase model is necessary to indicate effectivity of Etoricoxib in prevention HO in this phase.