The Forgotten Role of Clinical Findings in Detecting Periprosthetic Joint Infection: Back to Basics

Background: Periprosthetic joint infection (PJI) continues to be a diagnostic puzzle. Current diagnostic modalities are based almost exclusively on laboratory findings and the role of clinical findings remains largely unknown.

Methods and Materials: This was a single institution study evaluating 279 patients undergoing revision surgery for failed total knee arthroplasty (TKA) between 2001 and 2016. Acute revisions (< 3 month) were excluded. Patients were classified as undergoing septic revisions based on major MSIS criteria. Aseptic revisions were defined as cases of single stage revision that did not have suspected PJI, fulfill MSIS criteria, or subsequently fail within one year of follow-up. Clinical findings were assessed including pain, fever, presence of joint effusion or erythema, and reduced range of motion. Serum and synovial laboratory markers were also evaluated. The diagnostic value of each diagnostic test was assessed and a Fagan’s nomogram was constructed. A subset of MSIS-negative patients operated on for infection were used to demonstrate the added value of various clinical findings.

Results: Overall 279 patients (147 septic and 132 aseptic) with a full clinical evaluation documented were included in the final analysis. Fever and erythema were the most important clinical findings for diagnosing PJI with a positive likelihood ratio (LR) of 10.78 (range 4.46-26.02) and 8.08 (range 3.84-17.02), respectively. Effusion had a LR of 2.42 (range 1.87-3.14). Pain and reduced ROM were not as strongly correlated with diagnosis of PJI; LR was 1.02 (range 0.97-1.07) and 1.51 (1.24-1.84), respectively. Of the 46 patients treated for PJI but who were MSIS-negative, 33 patients (94.3%) had a post-test probability of infection greater than 90% when taking into account their clinical findings.

Discussion: Clinical findings are elementary variables in the diagnostic algorithm for PJI. They should be used to guide which future diagnostic tests should be ordered and influence the interpretation of their results. Fever and erythema are highly specific findings in patients with PJI and should perhaps be added to any future diagnostic criteria.