Sonication cultures of removed orthopaedic implants to improve the microbiological diagnosis of prosthetic joint infection

INTRODUCTION The infection is a severe complication of total joint arthroplasty. Microbiological diagnosis is not very sensitive, because microorganisms are typically present in a biofilm on the surface of the prosthesis in which they are incorporated. Sonication of orthopaedic implants has been proposed to improve the microbiologic diagnosis of prosthetic-joint infection. In this study, we evaluated the correspondence between intra-operative cultures and cultures on sonication fluid of explanted prosthetic implants. OBJECTIVES To evaluate the feasibility and usefulness of sonication fluid cultures of explanted orthopaedic implants to improve the microbiological diagnosis of postoperative infection. METHODS From November 2010 to June 2011, we removed and sonicated 25 implants (12 total knee arthroplasties, 6 total hip arthroplasties, 2 intramidollary nails, and 5 antibiotic cement spacers). The sonication fluid was cultured and underwent multiplex PCR. We compared intra-operative conventional cultures with examinations carried out on the sonicated fluid, calculating sensitivity and specificity of both diagnostic methods. CONCLUSION In this preliminary study the culture of samples obtained from sonication of explanted orthopaedic implants was proven to be more sensitive than the conventional intraoperative culture. To the best of our knowledge, no previous studies demonstrated growth of bacteria on a cement joint spacer.