Abstract
Introduction: Low-grade PJI remains a diagnostic dilemma in the medical community. It is mainly caused by low-virulent bacteria that cause chronic infection. This is mainly due to the formation of biofilms on the implant surface. This biofilm formation poses a diagnostic challenge that causes difficulties in the microbiological diagnosis of the infection by conventional culture methods. Sonication culture of implants has proven to be useful for biofilm forming bacteria. Therefore, we examined the evaluation of low-grade PJI using sonication culture methods and searched for influencing factors. The methods: Between October 2016 and November 2019 we retrospectively examined adult patients with suggestive clinical and laboratory findings of low-grade PJI. The patient's medical history, demographic information, prosthesis type, laboratory findings and length of hospital stay were collected. The results of the microbiological culture were divided into the results of the conventional preoperative and intraoperative culture method and the results of the sonication. In addition, laboratory chemical diagnostics of the joint punctures and CRP determination were performed. Additionally, the influence of prosthesis design and fixation technique, with and without cement, was investigated. The Results: Fifty-two patients with a mean age of 70.5 years were included in this study. The female population was more frequently affected. The most frequently affected joints were hip and knee. A higher percentage of pathogen detection was found at sonication with 60% of positive cultures, compared to 52% of intraoperative and 40% of preoperative conventional positive culture findings. The majority of patients were monomicrobial infections, with Staphylococcus epidermidis being the most frequently detected etiologic pathogen. The sonication culture was best able to detect a polymicrobial infection in 14% of cases compared to 6% of intraoperative and 4% of preoperative conventional cultures. Patients with a polymicrobial infection showed higher CRP values (P = 0.0172) and longer hospitalization (P = 0.0017) than monomicrobial infected patients. The results of the intraoperative conventional culture showed the highest congruence with the results of the sonication culture (concordance of 79%) compared to the preoperative culture. An infectious histopathological classification confirmed the microbiological ultrasound findings in 69% of cases with an infectious category. Cemented fixation showed a trend towards less positive microbiological findings, and total hip arthroplasty showed the highest detection of bacteria by sonication culture compared to bicondylar surface knee replacement (P = 0.0072). Conclusion: The sonication culture proved to be an important microbiological diagnostic tool, especially for the detection of polymicrobial infections in cases of low-grade PJI. This method has an established place in the diagnosis of low-grade PJI. The prosthesis design and the cemented fixation technique seem to have an influence on the detection of bacteria.
Highlights
Low-grade Periprosthetic joint infection (PJI) remains a diagnostic dilemma in the medical community
Low grade PJI is defined as the condition in which there is a lack of acute local inflammatory signs and it is commonly associated with an “unexplained” pain, swelling and reduced functional capacity of the joint which can show up even years after surgery [13]
Since our results showed that sonication culture was best able to detect polymicrobial PJI, we assessed to determine the existence of a clinical relevance of these findings
Summary
Low-grade PJI remains a diagnostic dilemma in the medical community. It is mainly caused by low-virulent bacteria that cause chronic infection. The absence of microorganisms identification might be attributable to biofilms, situation in which colonies are not produced from the samples taken and cultured into conventional growth methods [10] Due to this fact, relatively new culturing methods have been tried to be able to increase the diagnostic reliability of infections, among them, the sonication culture through sound waves in the ultrasound spectrum mechanically removes adhered bacteria in the biofilms, on the implanted prosthetics. Relatively new culturing methods have been tried to be able to increase the diagnostic reliability of infections, among them, the sonication culture through sound waves in the ultrasound spectrum mechanically removes adhered bacteria in the biofilms, on the implanted prosthetics This technique has been represented as a simple and sensible method to improve the microbiologic diagnosis of PJI [11] [12]. We retrospectively analyzed the benefits of sonication culture in low grade PJI patients
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