LAUSR

INTRODUCTION Accurate and prompt microbiological diagnosis of prosthetic joint infection (PJI) is crucial for successful antimicrobial treatment. Studies have shown the diagnostic utility of sonication of explanted implants in total joint arthroplasty but all did not use consensus statements for defining PJI. We evaluated the diagnostic utility of culture of samples obtained by sonication of explanted implants compared with periprosthetic tissue cultures (PTC) for the diagnosis of PJI using Musculoskeletal Infection Society (MSIS) consensus criteria. We also assessed the utility of culture of sonicate fluid for determining the microbial profile of PJI compared with standard culture methods. MATERIALS AND METHODS Forty consecutive revision arthroplasty cases were enrolled. Three to five periprosthetic tissue samples were obtained during each explant procedure. The 40 explanted implants were collected in sterile containers and sonicated under sterile conditions. MSIS criteria were used for the definition of PJI. RESULTS Twenty - seven patients had PJI and thirteen were aseptic failures. Of the PJI cases, there were nine cases of early PJI's, 10 of delayed PJI's and eight of late PJI's. Twenty-five (92.5%) of the twenty-seven patients with PJI, had positive cultures in the sonicate fluid of implants and in 18 (66.7%) of them cultures of the periprosthetic tissues were also positive. Both PTC and SFC cultures of implants were negative in all the 13 cases of aseptic failure. Sensitivity of sonicate fluid culture (SFC) of implants was greater than PTC (92.5% vs. 66.7%), P = .02. The specificity of both was 100%. The incidence of gram-positive and gram-negative bacteria was nearly equal by both methods. However, SFC showed an increased ability to detect Gram-positive pathogens which was evidenced by better recovery of coagulase-negative staphylococci. CONCLUSIONS Sonication of explanted implants is a simple and valuable microbiological technique and its routine use improves the diagnostic sensitivity of PJI.