A Novel Method for Stratification of Major Complication Risk using Body Mass Index Thresholds for Patients Undergoing Total Hip Arthroplasty: A National Cohort of 224,413 Patients

Document Type

Journal Article

Publication Date



The Journal of arthroplasty




INTRODUCTION: Elevated body mass index (BMI) is associated with complications following Total Hip Arthroplasty (THA). Since obese individuals are almost 10 times more likely to require THA compared to nonobese individuals, we need to understand the risk-benefit continuum when considering THA in obese patients. We aimed to determine data-driven thresholds for BMI at which the risk of major complications following THA significantly increases. METHODS: Patients were identified in a national database who underwent primary THA from 2010 to 2020. BMI thresholds were identified using the stratum-specific likelihood ratio (SSLR) methodology, which is an adaptive technique that allows for identification of BMI cutoffs at which the risk of major complications is significantly increased. BMI cutoffs identified using SSLR were used to create a logistic regression model. RESULTS: 224,413 patients were identified with a mean age of 66 ± 10, BMI 32 ± 6. 7, and 7,186 (3%) sustained a major complication. BMI thresholds were defined as 19-31, 32-37, 38-49 and 50+. Overall, the absolute risk of major complications increased from 2.9% in the lowest BMI strata to 7.5% in the highest BMI strata. Compared to patients with a BMI between 19-31, the odds of sustaining a major complication sequentially increased by 1.2, 1.6, and 2.5-times for patients in each higher BMI strata (all, p<0.05). CONCLUSIONS: We have identified BMI cutoffs using stratum-specific likelihood ratios that categorizes patients into 4 categories of risk for major complications in a nationally representative patient sample. These thresholds can be used in the surgical decision-making process between patients and surgeons.


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