Saline Solution Lavage and Reaspiration for Culture with a Blood Culture System Is a Feasible Method for Diagnosing Periprosthetic Joint Infection in Patients with Insufficient Synovial Fluid

Background: Culture is a key step for detecting periprosthetic joint infection (PJI) before surgery. However, using saline solution lavage and reaspiration in patients with insufficient synovial fluid remains controversial. The objective of this study was to evaluate this technique. Methods: This study included 286 aspirations performed by 1 surgeon in patients after total joint arthroplasty during the period of April 2015 to August 2018. If >1.0 mL of synovial fluid was obtained, then we directly used the fluid for culture. For cases in which <= 1.0 mL of synovial fluid was aspirated, 10 mL of saline solution was injected and the joint was reaspirated for culture. The samples were injected into 2 blood culture bottles for anaerobic bacterial culture and aerobic bacterial and fungal culture, and were inoculated for 14 days in a BACT/ALERT 3D blood culture system unless microorganisms were detected. A PJI diagnosis was determined on the basis of the modified Musculoskeletal Infection Society criteria. Results: Saline solution lavage and reaspiration were used in 82 cases (47 PJI cases and 35 non-PJI cases), while direct aspiration was used in 204 cases (99 PJI cases and 105 non-PJI cases). The overall rate for the use of saline solution lavage was 28.7% (82 of 286). Among knee cases, the saline solution lavage rate was 15.0% (21 of 140), and among hip cases, the rate was 41.8% (61 of 146). The overall sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of culture were 0.795 (95% confidence interval [CI], 0.720 to 0.857), 0.957 (95% CI, 0.909 to 0.984), 0.951(95% CI, 0.896 to 0.982), and 0.817 (95% CI, 0.749 to 0.873); and for "dry tap" cases, they were 0.851(95% CI, 0.717 to 0.938), 0.857 (95% CI, 0.697 to 0.952), 0.889 (95% CI, 0.760 to 0.963), and 0.811 (95% CI, 0.648 to 0.920), respectively. Conclusions: Saline solution lavage and reaspiration for culture in patients with insufficient synovial fluid before surgery may be a sound practice.