Abstract
The Centers for Medicare and Medicaid Services (CMS) recently mandated the collection
of Patient-Reported Outcome-Based Performance Measures (PRO-PMs) for Medicare patients
undergoing inpatient total knee arthroplasty (TKA). The policy's generalizability
remains a concern. Therefore, we aimed to compare PROMs capture rates, patients' characteristics,
and achieving the substantial clinical benefit (SCB) threshold between inpatient and
outpatient Medicare TKA. A prospective cohort of Medicare patients aged ≥ 65 who underwent
primary TKA between 2016 and 2022 at a single health system was analyzed (n = 7,926). Patients were categorized as inpatient (length of stay [LOS] > 24 hours,
n = 2,812) or outpatient (LOS ≤ 24 hours, n = 5,114). Capture rates of CMS-mandated variables, baseline characteristics, and
1-year outcomes were compared. SCB was defined as a 20-point improvement in the Knee
Injury and Osteoarthritis Outcome Score for Joint Replacement (KOOS-JR) per CMS criteria.
Baseline capture rates were similar between groups (approximately 82.8%), but 1-year
KOOS-JR completion was lower for inpatients (53.3% vs. 62.4%). Inpatients had higher
comorbidity burden (CCI ≥ 2: 40% vs. 33%, p < 0.001), worse KOOS-JR (median 44.9 vs. 47.5, p < 0.001), lower VR-12 MCS scores (50.2 vs. 54.1, p < 0.001), and more frequent nonoperative joint pain (75.1% vs. 68.6%, p < 0.001) and back pain (67.4% vs. 63.8%, p < 0.001). Outpatients trended toward better SCB achievement (OR: 0.89, 95% CI: 0.78–1.00,
p = 0.054). Compared to outpatients, inpatient Medicare TKA patients had lower 1-year
PROM capture rates, more comorbidities, and worse baseline PROMs, with a trend toward
not meeting CMS SCB thresholds. These differences highlight limitations in using inpatient-only
data to assess national TKA outcomes, especially as outpatient procedures grow. Nonetheless,
future studies with higher power should validate these findings. The level of evidence
is III (retrospective).
Keywords
Medicare - total knee replacement - PROM
