Abstract
Introduction
In the era of alternative payment models, providers and healthcare systems must understand the implications of potentially-modifiable risk factors on outcomes that affect overall cost. High BMI is associated with increased rates of complications (infection, loosening) in primary total hip arthroplasty (THA), but less is known about its impact on cost. In addition, the effects of low BMI on outcomes and cost are less-understood. This study sought to evaluate the relationship between BMI and length of stay (LOS), complications, thirty-day readmissions, inpatient cost, and need for post-acute services.
Methods
A retrospective database analysis was conducted of 34,679 primary THAs performed between 2013–2017 in 29 hospitals in an integrated health system. Patient BMI was compared with operative time, LOS, complication rate, thirty-day readmission rate, inpatient cost, and post discharge disposition. Logistic regression was performed treating complications and readmission as outcomes and controlling for age.
Results
Operative time increased linearly with BMI and cut-to close time for the highest BMI cohort was approximately twice that of the lowest. Average inpatient cost did not vary significantly with BMI. Length of stay was greatest at the extremes of BMI (4.0 days for BMI 10–15; 3.75 days for BMI >50) and approximately twice that of normal BMI patients. Risk of complications and thirty-day readmissions were greatest in the highest BMI cohort compared to normal BMI (OR 3.7 and 4.9 respectively) and significantly increased in the lowest BMI cohort (OR 2.2 and 3.0 respectively). Post discharge utilization of home health care and skilled nursing increased at the extremes of BMI. The rate of discharge to skilled nursing in the lowest BMI cohort was 50%, approximately five times that of normal BMI.
Conclusions
LOS, complications, thirty-day readmissions, and need for post-acute home health or skilled nursing services all increased geometrically at the extremes of BMI and were significantly greater than those of patients with normal BMI. In a bundled payment model, there are significant cost pressures at both ends of the BMI spectrum given the added risk of complications, readmissions, and post-acute costs. In addition, increased complications and readmissions could result in a failure to meet quality measures in CMS bundle programs and thereby jeopardize payment of gainshares.
Patients with extreme BMI should be counseled about the increased risk of complications after THA, and nutritional status/ obesity optimized pre-operatively if possible. Payors must recognize the increased risks and costs associated with THA in these patients and adjust payments accordingly to maintain access for those unable to achieve a normal BMI.
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