Evaluation and management of the infected total hip and knee.

Infection should be in the differentia for any painful total hip or knee. A thorough history and physical, complete set of radiographs and appropriate labs including C-reactive protein and erythrocyte sedimentation rate are essential in the initial evaluation. Ancillary tests such as aspiration and nuclear imaging may be helpful in unclear cases or when labs are concerning for infection. It is essential that all antibiotics are discontinued several weeks prior to gram stain and culture, if possible, to reduce the number of false negative test results. Classifying infection into acute versus late infection aids in the treatment plan. For acute infections presenting within 2 to 4 weeks of symptom onset, irrigation and debridement with polyethylene liner exchange and retention of components may be possible. When attempting component retention, thorough debridement and rapid treatment of the infection prior to the accumulation of any biofilm is paramount for a successful outcome. Other important prognostic factors to consider include the virulence of the microorganism as well as the immune status of the host. Despite expeditious management, irrigation and debridement of acute total hip and knee infections frequently leads to recurrent infection. Thus, patients should be counseled accordingly. Further management may be needed following an initial attempt at component retention. These options include resection arthroplasty with or without re-implantation, long term antibiotic suppressive therapy, arthrodesis and even above the knee amputation in rare circumstances. For chronic infections, a successful outcome depends on several factors including the baseline health status of the patient, implant removal with a thorough debridement followed by culture specific antibiotic treatment. Furthermore, methods of monitoring for persistent infection include following laboratory values such as the C-reactive protein, erythrocyte sedimentation rate, and cultures from joint aspirations. Whether to perform a direct exchange versus a delayed revision arthroplasty for chronic total hip and knee infections can be debated. Several published series have reported successful outcomes with single stage procedures when patients are carefully selected. However, the majority of chronic infections in the United States are treated with two stage resection, since this method has consistently provided the highest cure rates, with many current studies demonstrating >90% success.