Superiority of the sonication method against conventional periprosthetic tissue cultures for diagnosis of prosthetic joint infections.

INTRODUCTION: Diagnosis of periprosthetic infections is challenging. The aim of this study was to compare the diagnostic accuracy of conventional periprosthetic tissue culture and culture of sonication fluid of the explanted prostheses.

METHODS: We prospectively enrolled 114 patients undergoing revision hip or knee arthroplasty because of loosening of the prostheses, at our institution, between July 2012 and July 2016. Patients' medical history and demographic characteristics were recorded. The explanted hardware was separated in sterile containers and sonicated under sterile conditions. At least five samples of periprosthetic tissue were sent for culture and histological examination. We compared the culture of samples obtained by sonication of explanted hip and knee prostheses with conventional culture of periprosthetic tissue for the microbiological diagnosis of prosthetic joint infection.

RESULTS: Infectious Diseases Society of America guidelines were used for the definition of prosthetic joint infection. Sixty-one patients had periprosthetic infection and 53 aseptic loosening (73 hip prostheses and 41 knee prostheses). The sensitivity of sonication fluid culture was 77.04%, and the sensitivity of conventional tissue cultures was 55.73% (p value = 0.012). The specificities of the two methods were 98.11 and 94.34%, respectively. The sensitivity of the histopathological examination of the periprosthetic tissue was 72.10%. There were 17 patients with PJI where the isolated pathogen was detected in SFC but not in PTC, while in five cases the pathogen was detected only in PTC. There were nine patients where no bacteria were detected by any microbiological method and the diagnosis was based on clinical and histological findings, according to the guidelines.

CONCLUSIONS: The sonication method represents a reliable test for the diagnosis of prosthetic joint infections with a greater sensitivity and specificity than the conventional periprosthetic tissue cultures.