A Preliminary Examination of the CMS Eligibility Criteria in Total-Joint Arthroplasty

Abstract

To analyze inpatient rehabilitation outcomes in total-knee arthroplasty (TKA) and total-hip arthroplasty (THA) patients using the 2004 Medicare 75% rule criteria. This retrospective study compared outcomes in unilateral TKA (UTKA), bilateral TKA (BTKA), and THA after interdisciplinary inpatient rehabilitation (n = 867). Patients were separated into three comparison pairs: 1) UTKA or BTKA, 2) age <85 yrs or > or =85 yrs, and 3) body mass index (BMI) <50 or > or =50 kg/m. Length of stay (LOS), functional independence measure (FIM) scores (total, motor, and cognitive), hospital charges, FIM efficiency, and discharge disposition were analyzed. BTKA improved total FIM score more than UTKA (43 vs. 38%; P = 0.039). TKA with BMI > or =50 kg/m had similar admission and discharge FIM motor scores compared with BMI <50 kg/m (P > 0.05). TKA patients > or =85 yrs had lower admission FIM scores, longer LOS (11.3 vs. 9.4 days), and 22% higher total charges than TKA patients younger than 85 yrs (P = 0.042). THA patients > or =85 yrs had 6-10% lower total FIM, FIM motor, and FIM cognition scores and were discharged to home less frequently than younger patients (P < 0.05). Total and daily charges were 21-162% higher in THA patients with BMIs > or =50 kg/m than in THA patients with BMIs <50 kg/m (P < 0.045). All patients made functional gains during rehabilitation. However, the most costly and lengthy rehabilitation occurred in TKA patients > or =85 yrs and THA patients with BMI > or =50 kg/m.