We compared 90-day costs and outcomes for primary total knee arthroplasty patients among nonobese (body mass index [BMI] 18.5-24.9), overweight (25-29.9), obese (30-34.9), severely obese (35-39.9), morbidly obese (40-49.9), and super-obese (50+) cohorts.
We conducted a retrospective review of an institutional database of total knee arthroplasty patients from 2006 to 2013 with a minimum of 3-year follow-up. Sixty-five super-obese patients were identified, and five other cohorts were randomly selected in a 2:1 ratio (total, n = 715). Demographics, 90-day outcomes (costs, reoperations, and readmissions), and outcomes after 3 years (revisions and change scores for Short-Form Health Survey [SF-12], Knee Society Scores, and Western Ontario and McMaster Universities Arthritis Index) were aggregated.
The 90-day costs were significantly greater in the morbidly obese ($11,568 ± $1,960) and super-obese ($14,021 ± $7,903) cohorts relative to the smaller BMI cohorts ($9,938 – $10,352). The increased cost from readmissions was the main driver of costs. The outcome change scores were similar across all the BMI cohorts for Knee Society Scores, SF-12 Mental Health Composite Score, and Western Ontario and McMaster Universities Arthritis Index, but not for the SF-12 Physical Health Composite Score. At the midterm follow-up, there was no statistical difference in repeat surgery or aseptic revision rates. Septic revisions were significantly greater in the super-obese cohort relative to the other cohorts (6.2% vs 0.8-3.1%).
Health-care policy based purely on the economic costs may place morbidly obese and super-obese patients at risk of losing arthroplasty care, thereby denying them access to the comparable quality of life improvements.