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Published on: September 7, 2022
Baseline Characteristics Explain Sex Differences in Primary Total Knee Arthroplasty Outcomes: A Prospective
John M Bayram1, Swati Chopra2, Nicholas D Clement3
1School of Medicine, University of St Andrews, St Andrews, UK; Department of Orthopaedics, Golden Jubilee University National Hospital, Glasgow, UK; Edinburgh Orthopaedics, Royal Infirmary of Edinburgh, Edinburgh, UK.
Background:
Women report worse outcomes following total knee arthroplasty (TKA), but it remains unclear whether sex independently predicts outcomes or whether observed differences reflect baseline characteristics. This study aimed to characterize sex differences across a 4-year recovery period and determine whether they persist after adjusting for confounding factors.
Methods:
This prospective multicenter cohort study included 229 patients (114 women, 115 men; mean age 64 years) who underwent primary TKA. Patient-reported outcome measures (PROMs), including the Oxford Knee Score (OKS), Knee Injury and Osteoarthritis Outcome Score (KOOS) subscales, Forgotten Joint Score, and the EuroQol 5-Dimension, along with physical measures (Objective Knee Society Score and range of motion), were collected preoperatively, at six weeks, six months, and annually up to four years postoperatively. Linear mixed-effects models assessed sex differences in postoperative trajectories with three levels of adjustment: unadjusted; demographic-adjusted; and baseline-adjusted (including preoperative scores).
Results:
Women demonstrated lower-scoring postoperative trajectories than men across nearly all PROMs in unadjusted models, with the largest differences in functional outcomes (OKS: β = -2.7, P < 0.001; KOOS Activities of Daily Living: β = -5.7, P < 0.001). Women also had significantly worse preoperative scores across all knee-specific PROMs (P < 0.05). Demographic adjustment attenuated sex effects, leaving only OKS (P = 0.009) and KOOS Activities of Daily Living (P = 0.012) significant. After additional adjustment for preoperative scores, sex differences in all PROMs were eliminated (P > 0.05).
Conclusions:
Sex was not an independent predictor of TKA outcomes once baseline characteristics and preoperative scores were accounted for. Women present with less favorable preoperative profiles, including worse pain and function, higher body mass index, and greater prevalence of anxiety and depression. Improving preoperative status in women through earlier referral, optimized management of affective disorders, and targeted interventions may help narrow disparities in TKA outcomes.
