Synovial biomarkers for differential diagnosis of painful arthroplasty

Background. The diagnosis and treatment of periprosthetic joint infection (PJI) remain true clinical challenges. PJI diminishes therapeutic success, causes dissatisfaction for the patient and medical staff, and often requires extensive surgical revision(s). At the present time, an extensive multimodal algorithmic approach is used to avoid time- and cost-consuming diagnostic aberrations. However, especially in the case of the frequent and clinically most relevant "low-grade" PJI, the current diagnostic "gold standard" has reached its limits. Evaluation. Synovial biomarkers are thought to close this diagnostic gap, hopefully enabling the safe differentiation among aseptic, (chronic) septic, implant allergy-related and the arthrofibrotic genesis of symptomatic arthroplasty. Therefore, joint aspiration for obtaining synovial fluid is preferred over surgical synovial tissue biopsy because of the faster results, greater practicability, greater patient safety, and lower costs. In addition to the parameters synovial IL-6, CRP, and leukocyte esterase, novel biomarkers such as antimicrobial peptides and other proinflammatory cytokines are currently highlighted because of their very high to excellent diagnostic accuracy. Conclusion. Independent multicenter validation studies are required to show whether a set of different innovative synovial fluid biomarkers rather than a few single parameters is favorable for a safe "one-stop shop" differential diagnosis of PJI.