TITLE:
Increased Detection of Polymicrobial Infections by Sonication and Significance of Prosthesis Design and Fixation Technique in Cases of Low-Grade PJI, a Retrospective Study
AUTHORS:
Nils Haustedt, Jorge Armando González Chapa, Moritz Hentschke, Adrian Geovanni Rosas Taraco
KEYWORDS:
PJI, Low Grade Infections, Biofilm, Sonication
JOURNAL NAME:
Open Journal of Orthopedics,
Vol.10 No.10,
October
22,
2020
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 preoperativeconventional 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.