Title: Development of a reference chart to monitor postoperative swelling following total knee arthroplasty.Purpose: Lower extremity swelling is a feature of total knee arthroplasty. Until recently, clinicians lacked tools to accurately measure swelling in clinical settings, but bioelectrical impedance assessment has shown promise in this regard. The purpose of this study was to develop a reference chart of lower extremity swelling following total knee arthroplasty.Method: Fifty-six participants (54% male, mean age = 64 years) were followed for the first 7 weeks following total knee arthroplasty, during which frequent lower extremity bioelectrical impedance assessments were performed. Using Generalized Additive Models for Location Scale and Shape, a reference chart for swelling was developed with bioelectrical impedance assessment data from the first 40 patients enrolled in the study (223 observations) and preliminarily tested for performance in the remaining 16 patients' data (96 observations).Results: The reference chart illustrates approximately 10% per day increase for the first 3 days following surgery. Peak swelling occurs 6-8 days following surgery; the 10th percentile demonstrates a peak of 25%, whereas the 90th percentile peaks at 47%. In the test data, this reference chart demonstrated accurate coverage at each estimated centile.Conclusion: The reference chart provides a novel framework for monitoring swelling following total knee arthroplasty and may augment clinical decisions to improve postoperative swelling management.Implications for rehabilitationThe use of bioelectrical impedance assessment provides an accurate and easily implemented approach for rehabilitation professionals to measure swelling.The reference chart provided allows for monitoring of patient recovery of swelling following total knee arthroplasty.Precise depictions of where a patient's swelling is in reference to others will improve clinical decision making at the individual level.
Keywords: Total knee arthroplasty; bioelectrical impedance assessment; generalized additive models for location scale and shape; monitoring; reference chart; swelling.