Sonication in the diagnosis of fracture-related infections (FRI)—a retrospective study on 230 retrieved implants

Abstract

Background In fracture-related infections (FRI), both the diagnosis of the infection and the identification of the causative pathogen are crucial to optimize treatment outcomes. Sonication has been successfully used for periprosthetic joint infections (PJI); however, its role in FRI remains unknown. Our aim was to determine the diagnostic accuracy (sensitivity, specificity) of sonicate fluid culture (SFC). The primary objective was to compare SFC with peri-implant tissue culture (PTC) overall and among subgroups using the consensus definition by Metsemakers et al. The secondary objective was to determine the yield of SFC in possible fracture-related infections (PFRI). Methods From March 2017 to May 2019, 230 cases of retrieved implants were retrospectively reviewed. To perform sonication, explants were placed in sterile polypropylene jars intraoperatively. After treatment in an ultrasonic bath (Bandelin, Berlin, Germany), sonicate fluid was incubated into blood culture bottles, and conventional culturing was eventually performed. Sensitivity and specificity were determined using two-by-two contingency tables. McNemar’s test was used to compare proportions among paired samples while Fisher’s exact test was used for comparison between categorical variables. Results Of the 230 cases, 107 were identified as FRI, whereas 123 were aseptic revision cases (ARC). Of the latter, 105 were labeled as PFRI. Sensitivity of SFC was higher in comparison with PTC, although this did not reach statistical significance (90.7% vs. 84.1%; p = .065). The specificity of SFC was significantly lower than that of PTC (73.2% vs. 88.6%; p = .003). In PFRI, SFC yielded significantly more positive results than PTC (33/105 vs. 14/105; p = .003). Overall, 142 pathogens were identified by SFC, whereas 131 pathogens were found by PTC. Conclusions We found that sonication of fracture fixation devices may be a useful adjunct in FRI, especially in “low-grade” infections lacking confirmatory clinical criteria. Standardized diagnostic protocols are warranted in order to further optimize the diagnostic accuracy.

Implant surface culture may be a useful adjunct to standard tissue sampling culture for identification of pathogens accounting for fracture-device-related infection: a within-person randomized agreement study of 42 patients

“…Aside from TSC, new emerging techniques have recently been developed, also aimed at increasing the detection rate of FDRI-associated microorganisms. Based on a retrospective analysis of 230 cases, Bellova et al ( 7 ) found that sonicate fluid culture might be a useful adjunct in diagnosis of FDRI, especially for low-grade infections. Outcomes of an updated meta-analysis revealed that traditional tissue sampling was more sensitive while sonication fluid sampling was more specific, and, thus, the authors suggested the integration of both methods to obtain optimal results ( 23 ).…”

“…However, the positive rate of culture is not high ( 6 ). In order to increase the positive rate, different adjunctive strategies had been introduced, such as sonicate fluid culture ( 7 ) and intramedullary tissue culture ( 8 ).…”

Current Concepts of Fracture-Related Infection

“…Recently, different adjunctive strategies for pathogen identification were reported, aiming at increasing the detection rate. Bellova et al [ 55 ] reported the efficiency of sonication in the diagnosis of FRI, and outcomes of 230 retrieved implants revealed that sonication of fracture devices may be a useful adjunct for FRI. In a meta-analysis focusing on the diagnostic accuracy of sonication fluid aspiration for FRI, Ahmed et al [ 56 ] reported that the sensitivity and specificity of the sonication method were 86% and 98%, with the tissue sample culture as 98% and 38%, respectively.…”