Purpose The purpose of this study is to describe the location of positive cultures in infected total hip arthroplasty, the infecting organisms, and their relation, if any, to systemic and local host factors using the USC staging system for prosthetic joint infection.
Materials and Methods A retrospective analysis of 50 consecutive cases of periprosthetic total hip infections between 1993 and 2003 was performed. All patients were staged using the USC staging system for prosthetic joint infection. A specific protocol was implemented in the process of operating on each patient. A single surgeon performed all operations and obtained all cultures. At prosthesis resection, intraoperative cultures were obtained from the following locations: acetabular bone, femoral metaphysis, femoral proximal diaphysis, femoral distal diaphysis, joint fluid, hip capsule, synovium, and sinus tract if present. All specimens were sent for aerobic, anaerobic, AFB, and fungal cultures. The patients then underwent reimplantation, amputation, or permanent resection depending upon each individual clinical scenario.
Results Intraoperative cultures were taken in all patients with an overall positive culture rate of 42%. Monomicrobial infections were prevalent in 50% of cases, polymicrobial infection were found in 43% of cases, and there was no culture growth in 7% of cases. Aspiration alone was 56% sensitive in detecting infection. The individual sensitivies of the bone cultures were acetabular bone at 62%, distal diaphyseal femur at 46%, proximal diaphyseal femur at 42%, and metaphyseal femur at 30%. The individual sensitivies of the soft tissue cultures showed the sinus tract at 50%, joint fluid at 36%, synovium at 29%, and joint capsule at 27%. The combination of cultures of acetabular bone, metaphyseal femur, and proximal and distal diaphyseal femur the sensitivity increased to 83%. Aspiration with bone cultures showed a sensitivity of 93%.
Conclusions Alone, preoperative hip aspiration is not highly sensitive. Bone cultures increase the sensitivity in diagnosing total hip arthroplasty infection. We could not establish a relationship between culture results or polymicrobiality and systemic or local host factors.
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