The impact of body mass index on rehabilitation outcomes after lower limb amputation.

Purpose: To determine the effect of obesity on physical function and clinical outcome measures in patients who received inpatient rehabilitation services for lower extremity amputation.

Methods: A retrospective review was performed on patients with lower extremity amputation (n = 951). Patients were stratified into five categories adjusted for limb loss mass across different levels of healthy body mass index (BMI), overweight, and obesity. Outcomes included the Inpatient Rehabilitation Facility Patient Assessment Instrument functional scores (GG section), discharge home, length of stay (LOS), therapy time, discharge location, medical complications and acute care readmissions. Deep learning neural networks (DLNNs) were developed to learn the relationships between adjusted BMI and discharge home.

Results: The severely obese group (BMI > 40 kg/m²) demonstrated 7%-13% lower toileting hygiene functional scores at discharge compared to the remaining groups (p < .001). The severely obese group also demonstrated 8%-9% lower sit-to-lying and lying-to-sitting bed mobility scores than the other groups (both p < .001). Sit-to-stand scores were 16%-21% worse and toilet transfer scores were 12%-20% worse in the BMI > 40 kg/m² group than the other groups (all p < .001). Walking 50 ft with two turns was most difficult for the BMI > 40 kg/m² group, with mean scores 7%-27% lower than the other BMI groups (p = .011). Wheelchair mobility scores for propelling 150 ft were worst for the severely obese group (4.9 points vs. 5.1-5.5 points for all other groups; p = .021). The LOS was longest in the BMI > 40 group and shortest in the BMI < 25 group (15.0 days vs. 13.3 days; p = .032). Logistic regression analysis indicated that BMI > 40 kg/m² was associated with lower odds risk (OR) of discharge-to-home (OR = 0.504 [0.281-0.904]; p < .022). DLNNs found that adjusted BMI and BMI category were ranked 11th and 12th out of 90 model variables in predicting discharge home.

Conclusion: Patients with severe obesity (>40 kg/m²) achieved lower functional independence for several tasks and are less likely to be discharged home despite higher therapy volume than other groups. If a patient is going home, obesity will pose unique demands on the caregivers and resources can be put in place to help reintegrate the patient into life.