Effect of obesity on inpatient rehabilitation outcomes after total hip arthroplasty

Objective: This study examined whether obesity affected inpatient rehabilitation outcomes after total hip arthroplasty (THA). Research Methods and Procedures: This was a retrospective, comparative study conducted using a computerized medical database derived from THA patients at a university‐affiliated rehabilitation hospital (data from 2002 to 2005). Patients were divided into four brackets based on BMI: non‐obese (<25 kg/m²), overweight (25 to 29.9 kg/m²), moderate obesity (30 to 39.9 kg/m²), and severe obesity (≥40 kg/m²). All patients completed an interdisciplinary inpatient rehabilitation program after THA. Functional independence measure (FIM) scores, length of stay (LOS), FIM efficiency scores (FIM/LOS), hospital charges, and discharge disposition location were collected. Results: FIM scores improved from admission to discharge similarly in all groups (25 to 29.5 points). However, FIM efficiency, LOS, and total charges were curvilinearly related with BMI (all p < 0.05). Total hospital charges were highest in the severely obese group compared with the overweight group (p < 0.05). Non‐homebound discharge disposition rates were lower in non‐obese (13.1%) and severely obese groups (10.5%). Discussion: Elevated BMI does not prevent FIM gains in THA patients during inpatient rehabilitation. However, BMI is related with FIM efficiency, LOS, and hospital charges in a curvilinear fashion. Severely obese patients can achieve physical improvements but at a lower efficiency and greater cost.