Are Body Mass Index (BMI) Cutoffs Creating Racial, Ethnic, Gender, or Age Disparities in Patient Eligibility for Total Ankle Arthroplasty?

Abstract

Category: Ankle; Other Introduction/Purpose: The rising prevalence of obesity may drastically affect arthroplasty eligibility as Body Mass Index (BMI) remains a commonly used screening criterion. As obesity disproportionately affects Black adults and women, using such a criterion without scientific merit may lead to inequitable access to care. Particularly in total ankle arthroplasty – where weight has been previously attributed to aseptic implant failure – close examination of screening criteria is imperative. The purpose of this study was to evaluate for disparities in patient eligibility for total ankle arthroplasty (TAA) based on race, ethnicity, gender, and age by applying commonly used BMI cutoffs to the American College of Surgeons National Surgical Quality Improvement Program (ACS- NSQIP) database. Methods: Patients in the ACS-NSQIP database who underwent TAA from 2011- 2020 were retrospectively reviewed. BMI cutoffs of < 35, < 40, < 45, and < 50 were applied to the cohort to model the rate of surgical eligibility for TAA. Patients were deemed eligible for surgery if their BMI was less than each modeled BMI cutoff and ineligible if their BMI was equal to or greater than the cutoff. The relative eligibility rate, which was defined as the rate of eligibility minus the rate of ineligibility, was examined for each BMI cutoff. The cohorts were then stratified by race, ethnicity, gender, and age. Independent T-tests, Chi-squared tests, and Fisher’s exact tests were performed to compare differences at an α = 0.05. Results: 65.1% of all TAA patients were included after applying the exclusion criteria. Black patients had disproportionately lower rates of eligibility at the most stringent BMI cutoff of < 35kg/m² (p=0.004). Hispanic patients had generally lower rates of eligibility across all BMI cutoffs. In contrast, Asian American and Pacific Islander patients had higher rates of eligibility at the BMI cutoffs of < 35kg/m² (p=0.033) and < 40kg/m² (p=0.039), and White non-Hispanic patients had higher rates of eligibility across all BMI cutoffs. Females had lower eligibility rates across all BMI cutoffs. Ineligible patients were also younger compared to eligible patients across all BMI cutoffs. Conclusion: Stringent BMI cutoffs may disproportionately disqualify Black, female, and younger patients from receiving total ankle arthroplasty. The data suggests that current eligibility criteria may exacerbate disparity in access to TAA for historically vulnerable populations. While eligibility criteria exist to protect patients from interventions that put them at unacceptable risk, these criteria are not uniformly distributed across populations. Given these data and the rising obesity epidemic, additional highly powered studies are needed to determine the safety of TAA in patients with BMI 35-40 to ensure at-risk populations are not disproportionately excluded from mobility-improving surgery.