Substantial Clinical Benefit After Total Knee Arthroplasty Has Been Set Too High: An Analysis of the American Joint...

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.

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.

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).

The CMS relatively arbitrarily defined the SCB at a value that is too high for an operation that routinely yields >80% patient satisfaction.

Prognostic Level II . See Instructions for Authors for a complete description of levels of evidence.