The number of patients requiring joint replacement is increasing due to its success in restoring function and pain relief, and the growing population of the elderly. One of the most serious complications of arthroplasty is joint prosthesis infection. Due to the absence of prospective, randomized, controlled studies, there is no consensus concerning diagnosis and treatment of prosthetic joint infections. The main objective of this trial is to evaluate the clinical efficacy of rifampin combination therapy versus monotherapy using cloxacillin or vancomycin in early staphylococcal infections after total hip and knee arthroplasty.

The study is a controlled randomized multicentre trial with 8 participating centres in Norway. We will include patients with the diagnosis of early infections (within 4 weeks post operatively)after hip or knee replacement. Patients with clinical signs of infection are scheduled for a standardized soft tissue revision. Diagnosis of staphylococci must be established by arthrocentesis or at surgical revision, and must grow in at least 2/8 cultures.The patients will randomly be assigned to antimicrobial therapy with or without rifampin by a randomization programme. Antibiotics will be given for 6 weeks. Two years follow-up. The study end points are final follow-up visit after two years or relapse of infection.

Inclusion Criteria:

• Prosthetic joint infections category 2 or 3 (early post.op infections within 4 weeks).
• Diagnosis of staphylococci.
• Clinically and radiographically stable implants kept in place after revision.

Exclusion Criteria:

• Infection with other microorganisms than staphylococci.
• Less than 2 years of expected survival.
• Predictable inability to comply with the treatment and/or follow-up visits.
• Contraindication to the use of study medication including acute or chronic liver disease.
• Lack of written consent.
• Fertile women.
• Patients taking less than 80% of the study medication.