Diagnosis and isolation of a causative organism is imperative for successful treatment of periprosthetic joint infections (PJI). While there are several diagnostic algorithms using microbiology, serum and synovial markers, the preoperative diagnosis of a low-grade infection remains a challenge, particularly in patients with unsuccessful aspiration. An incisional biopsy may be used in these cases as additional diagnostic tool. In this retrospective study we evaluated microbiological findings, sensitivity, and specificity of open synovial biopsies in cases of inconclusive preoperative diagnostics. In a retrospective databank analysis (2010–2018), we identified 80 TKAs that underwent an open biopsy because of inconclusive results after applying the CDC Criteria (2010) or the MSIS (2011–2018) for PJI. Infection makers in the serum (C-reactive protein [CRP], leucocytes count and interleukin-6 [IL-6]) and in the synovial aspirate (leucocyte count, percentage of neutrophiles) prior to the biopsy were analyzed. All biopsies were performed by suprapatellar mini-arthrotomy. If a subsequent revision surgery was performed, the isolated organisms in the open biopsy were compared to the results in the revision surgery and sensitivity and specificity were calculated. Serum markers were checked for correlation with a positive result in the open biopsy using Cramer-V and Chi2-Test.Aim
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