ULTRASOUND-GUIDED SYNOVIAL BIOPSY FOR THE PREOPERATIVE DIAGNOSIS OF PERIPROSTHETIC JOINT INFECTION

Aim Prosthetic joint infection (PJI) is assessed using clinical history and examination, imaging studies and laboratory investigations which inform diagnostic tools such as that proposed by the European Bone and Joint Infection Society to determine the probability of infection. Infection is often confirmed by microbiology culture and histology from intraoperative samples, but ideally a diagnosis of infection is made preoperatively to guide management decisions. At our institution, a tertiary referral centre for PJI, ultrasound (US)-guided synovial biopsy is routinely used as an adjunct to preoperative joint aspiration. Our aim was to evaluate the sensitivity and specificity of microbiology and histology results from US-guided synovial biopsy samples when compared to intraoperative samples. Method In this retrospective study we analysed all prosthetic hip and knee US-guided biopsies performed at our institution over a 5 year period between 2018 and 2022. Microbiology and histology results from preoperative biopsy samples were individually compared to microbiology and histology findings from intraoperative samples. Results 381 biopsies were performed; 281 knee, 100 hip. US-guided biopsy results showed strong positive predictive values (PPVs) in hip biopsies (microbiology PPV (79.3%), histology PPV (85.7%)) and knee biopsies (microbiology PPV (77%), histology PPV (85%)). Biopsies showed low sensitivity in predicting intraoperative findings (hip microbiology sensitivity (62%), hip histology sensitivity (31%), knee microbiology sensitivity (70%), knee histology sensitivity (21%). Biopsies showed high specificity for knee (microbiology specificity (89%), histology specificity (97%)) and hip (microbiology specificity (73%), histology specificity (91%)). Conclusions This study demonstrates that US-guided biopsy is a valuable diagnostic aid for PJI with high specificities and PPVs. Furthermore US-biopsy is valuable when there is limited fluid for aspiration.