Substantial Clinical Benefit After Total Knee Arthroplasty Has Been Set Too High

BACKGROUND: The U.S. Centers for Medicare & Medicaid Services (CMS) has set the substantial clinical benefit (SCB) for the Knee injury and Osteoarthritis Outcome Score for Joint Replacement (KOOS-JR) after primary total knee arthroplasty (TKA) at 20 points. We aimed to determine the percentages of patients who achieved the minimal clinically important difference (MCID) and the SCB for KOOS-JR at 1 year following TKA and to evaluate factors associated with benchmark achievement. METHODS: We queried the American Joint Replacement Registry (AJRR) and screened 1,284,404 primary TKA cases performed from 2018 to 2023. We determined attainment of the KOOS-JR distribution-based MCID (7.5), anchor-based MCID (14), and SCB (20) at 12 months by each patient. Associations of covariates with the achievement of the MCIDs and the SCB were evaluated using a generalized linear model for binary outcomes that accounted for clustering within institutions. Unadjusted and adjusted odds ratios (ORs) for the outcomes of interest with 95% confidence intervals (CIs) were reported. Covariates included the preoperative KOOS-JR, sex, race or ethnicity, body mass index (BMI), Charlson Comorbidity Index (CCI), fixation type, use of technology, year of the procedure, region, institution type, teaching status, and number of beds. RESULTS: Linked scores were recorded by 64,773 patients. The mean patient age was 68.35 ± 8.60 years, 61.29% of patients were female, and 83.52% of patients were non-Hispanic White. The KOOS-JR threshold achievement rate was 86.8% for the calculated distribution-based MCID, 76.5% for the anchor-based MCID, and 65.7% for the SCB. Patients with higher preoperative scores (adjusted OR, 0.93 [95% CI, 0.93 to 0.93]; p < 0.001), Asian patients (adjusted OR, 0.59 [95% CI, 0.46 to 0.74]; p < 0.001), Black patients (adjusted OR, 0.55 [95% CI, 0.49 to 0.62]; p < 0.001), Hispanic patients (adjusted OR, 0.71 [95% CI, 0.51 to 0.99]; p = 0.042), non-Hispanic patients of other races (adjusted OR, 0.84 [95% CI, 0.74 to 0.95]; p = 0.007), male patients (adjusted OR, 0.89 [95% CI, 0.85 to 0.94]; p < 0.001), and patients with higher BMI (adjusted OR, 0.93 [95% CI, 0.87 to 0.99]; p = 0.025) showed lower odds of achieving the SCB. A CCI of ≥5 was additionally found to be associated with lower odds of achieving the distribution-based MCID (adjusted OR, 0.89 [95% CI, 0.79 to 0.99]; p = 0.032) and anchor-based MCID (adjusted OR, 0.89 [95% CI, 0.81 to 0.97]; p = 0.012). CONCLUSIONS: The CMS relatively arbitrarily defined the SCB at a value that is too high for an operation that routinely yields >80% patient satisfaction. LEVEL OF EVIDENCE: Prognostic Level II . See Instructions for Authors for a complete description of levels of evidence.