Effect of obesity on inpatient rehabilitation outcomes following total knee arthroplasty

Objectives: To examine obesity effects on outcomes following inpatient rehabilitation in patients following primary total knee arthroplasty or revision total knee arthroplasty. Design: Retrospective, comparative study. Setting: Fifty-bed, university-affiliated rehabilitation hospital. Patients: Obese (N = 139; body mass index > 30 kg/m(2)) and non-obese (N = 146; body mass index < 30 kg/m(2)) total knee arthroplasty patients. Participants were further stratified based on total knee arthroplasty type, primary and revision for a total of four groups. Intervention: Interdisciplinary inpatient rehabilitation. Main measures: Range of motion, length of stay, Functional Independence Measure (FIM) scores, FIM efficiency scores, total and daily hospital charges, and discharge disposition location. Results: Range of motion and FIM scores improved from admission to discharge in both obese and non-obese patients regardless of total knee arthroplasty type. FIM efficiency was lower in revision than primary total knee arthroplasty (2.8 versus 3.6 patients/day-, P < 0.005) but not different between obese and non-obese groups. Total hospital charges were lower for the primary than for the revision patients (P<0.05), but were directly related with body mass index (r = 0.140, P < 0.05). Discharge disposition locations were not different among groups. Conclusion: Rehabilitation teams can expect comparable gains between obese and non-obese patients following total knee arthroplasty, but at a greater expense.