Systematic investigation and comparison of diagnostic methods in implant-related infections and infectious non-unions in trauma surgery– results of a prospective study

Alongside surgical therapy, the successful treatment of infection-related nonunion depends on the accurate identification of pathogens so as to ensure targeted anti-infective treatment. The available diagnostic methods continue to exhibit low sensitivity. The aim of the study was to determine the most sensitive method for the accurate diagnosis of infection-related nonunion by comparing sonication with other diagnostic procedures. In a prospective comparative study, 100 patients with nonunions (study group, SG) and 100 patients with planned metal removal (control group, CG) were compared. The diagnostic methods employed included standard culture, enrichment in blood culture bottles after tissue homogenization, sonication with and without membrane filtration, and histopathology. Sensitivity, specificity, and predictive values were calculated. In 133 patients (SG n = 73; CG n = 60), at least one sample was tested positive for a bacterium. Infection was diagnosed in 72 patients (SG n = 45; CG n = 27). Coagulase-negative staphylococci and Cutibacterium acnes were the most frequently detected pathogens. Sonication achieved the highest sensitivity (80.6%) for detecting an infection but there was no significant difference as compared to the other methods. The combination of standard culture and sonication yielded the greatest overall sensitivity (97.2%), whereas the combination of tissue homogenization and histology achieved the best results for specificity (89.1%) and predictive values (82.3%). A high rate of pathogen detection was observed in clinically inapparent nonunions. Sonication was not clearly superior in our setting. In general, the combination of several diagnostic methods provided the most informative results. Therefore, sonication and tissue homogenization can both be considered useful additions to standard cultures.