Wound drainage after arthroplasty and prediction of acute prosthetic joint infection: prospective data from a multicentre cohort study using a telemonitoring app.

Background: Differentiation between uncomplicated and complicated postoperative wound drainage after arthroplasty is crucial to prevent unnecessary reoperation. Prospective data about the duration and amount of postoperative wound drainage in patients with and without prosthetic joint infection (PJI) are currently absent. Methods: A multicentre cohort study was conducted to assess the duration and amount of wound drainage in patients after arthroplasty. During 30 postoperative days after arthroplasty, patients recorded their wound status in a previously developed wound care app and graded the amount of wound drainage on a 5-point scale. Data about PJI in the follow-up period were extracted from the patient files. Results: Of the 1019 included patients, 16 patients (1.6 %) developed a PJI. Minor wound drainage decreased from the first to the fourth postoperative week from 50 % to 3 %. Both moderate to severe wound drainage in the third week and newly developed wound drainage in the second week after a week without drainage were strongly associated with PJI (odds ratio (OR) 103.23, 95 % confidence interval (CI) 26.08 to 408.57, OR 80.71, 95 % CI 9.12 to 714.52, respectively). The positive predictive value (PPV) for PJI was 83 % for moderate to heavy wound drainage in the third week. Conclusion: Moderate to heavy wound drainage and persistent wound drainage were strongly associated with PJI. The PPV of wound drainage for PJI was high for moderate to heavy drainage in the third week but was low for drainage in the first week. Therefore, additional parameters are needed to guide the decision to reoperate on patients for suspected acute PJI.