Obesity and Inpatient Rehabilitation Outcomes Following Knee Arthroplasty: A Multicenter Study

OBJECTIVE: This multicenter study examined whether inpatient rehabilitation outcomes following total knee arthroplasty (TKA) were influenced by BMI. METHODS AND PROCEDURES: This was a retrospective, comparative study conducted using a computerized medical database and medical records derived from TKA patients, at 15 independent rehabilitation hospitals (N = 5,428). Patients were separated into four groups based on BMI: non-obese (BMI < 25 kg/m(2)), overweight (25-29.9 kg/m(2)), moderately obese (30-40 kg/m(2)), severely obese (BMI > or = 40 kg/m(2)). All patients completed an interdisciplinary inpatient rehabilitation program post-TKA. Total and individual functional independence measure (FIM) scores, length of stay (LOS), FIM efficiency scores, itemized hospital charges, and discharge disposition location, were collected. RESULTS: The percentage of total FIM change was 7.5% greater by the time of discharge in the non-obese than in the very severely obese (P < 0.05). FIM efficiency was lowest in the severely obese as compared to the remaining groups (3.7 points (pts)/day vs. 4.0-4.3 pts/day; P = 0.044). The change in the motor FIM score from admission to discharge was 6.7-15.6% greater in the non-obese than in the remaining groups (P < 0.05). The changes in cognition FIM, toilet transfer and walking without assistance scores were higher in the non-obese as compared to the severely obese group (P < 0.05). The severely obese group had higher total, physical and occupational therapy and pharmacy charges than the remaining groups (P < 0.05). DISCUSSION: An excessive BMI does not prevent gains during inpatient rehabilitation; however, these gains are made less efficiently and at a higher cost than those made when the BMI is low.