Objectives: Microbial biofilms protect planctonic bacteria growing on the implants surfaces from detection and antibiotic treatment. To investigate the efficacy of sonication cultures in our patients with prosthetic joint infections we compared our findings with the results to those of periprosthetic tissue cultures and histology.

Methods: The sonication cultures of the explanted prosthesis were cultured according to the protocol by Trampuz et al. in the New England Journal of Medicin and using the routine method incubating the aspirated pus and periprosthetic material in brain-heart-infusion broth without sonication. To assess the most frequently affected component of the prosthesis all components were “sono-cultured” separately. The diagnosis of infection was based on the presence of bacteria or leucocytes in pus or tissue plus local signs and symptoms and/or systemic markers of inflammation (fever, leucocytosis, increased C-reactive protein)

Results: We investigated 60 patients with 40 septically and 20 aseptically explanted components of total knee (n=24), hip (n=21) tumor (n=6) and shoulder (n=2) endoprosthesis, as well as osteosynthetic material (n=6) and spinal instrumentation (n=1). The most frequently affected component of the hip prosthesis was the femoral head (100%) and the inlay (88%), of the knee prosthesis was the Patella (58%) and the tibia plateau (56%), of the tumor prosthesis were the polyethylene components (100%), of the shoulder prosthesis was the sphere and stem (each 100%), of the osteosynthesis material were the plate and screws (each 33%) and of the spine instrumentation were the rod and the screws (each 100%). From all detected pathogens in sonication cultures the most frequently were Staphylococcus aureus (25%), Staphylococcus epidermidis (22%) and Streptococci (13%). The sensitivity of sonication cultures and periprosthetic tissue cultures was 85% and 78% without preoperative antibiotic therapy compared with histological analysis of 100% sensitivity. The specificity was 89% for sonication cultures, 95% for periprosthetic tissue cultures and 100% for histological analysis.

Conclusion: Our results of separating the explanted components for sonication culture proved the detection of valid pathogens for every kind of endoprosthesis or implants and supplied further information for the focus of infection.