Infections Associated with Prosthetic Knee and Prosthetic Hip.

Arthroplasty of the knee and hip is a common procedure. There is a risk of infection with primary arthroplasty, with an incidence of 1% to 2%. Significant cost and morbidity are associated with infection of the prosthetic joint. Most infections (60% to 70%) are caused by staphylococci, but approximately 10% are caused by streptococci and/or enterococci, whereas the remainder are caused by gram-negative enteric aerobes or anaerobic flora. Surgical revision is often required for cure because the biofilm that adheres to the infected prosthesis precludes antibiotic therapy from being effective. Biofilm formation occurs consistently as a consequence of host protein deposition on the prostheses, which serve as ligands for bacterial receptors. Once established, biofilm infections require removal of the prosthesis in order to effect a cure. Clinical and radiologic features are not specific for the diagnosis. Culture is specific but not sensitive enough to establish a pathogen in all cases. Surgical approaches are varied and range from debridement with retention of the prostheses to amputation of the limb. The most favored approach is the two-stage delayed reimplantation, in which patients receive specific antibiotic therapy for 6 weeks or more. Several additional antibiotics other than vancomycin are available for methicillin-resistant staphylococcal infection, but these are still unproven in the treatment of osteomyelitis or prosthetic joint infection.