Increased Body Mass Index is Associated with Increased Cost for Primary Total Hip Arthroplasty Irrespective of Complications or Readmissions.

Introduction: Surgeons participating in alternative payment models may encounter financial disincentives in caring for patients whose care requires higher costs for the treatment facility. While smaller studies have shown a positive relationship between body mass index (BMI) and cost in total hip arthroplasty (THA), this question has yet to be examined using data in a nationally representative dataset. We sought to leverage a national dataset to assess the relationship between BMI and cost in THA.

Methods: We queried the healthcare dataset from 2016 to 2022 to identify primary THAs using Current Procedural Terminology (CPT) and International Classification of Disease-Procedure Coding System (ICD-PCS) codes (27130, 0SR90xx, 0SRB0xx) with a corresponding osteoarthritis diagnosis (ICD-10-CM: M16). Patient demographics, characteristics, and cost variables were extracted directly from the dataset. Cost was defined by supplies, labor, and equipment and assessed over a 90-day period starting with the index surgical encounter. A multivariate generalized linear model estimated costs across eight BMI categories (World Health Organization (WHO) BMI categories, with BMI > 40 patients grouped into BMI 40 to 45, BMI 45 to 50, and BMI > 50). A linear regression model assessed the effect of BMI on costs. Both models controlled for age, sex, payer, race, the Elixhauser comorbidity index (ECI), and ethnicity.

Results: This study examined 10,366 primary THAs completed from 2016 to 2022. The mean BMI was 30.0 (SE ±0.1), the mean index cost was $14,632 (SE 52.9), and the mean 90-day cost was $16,527 (SE 145.4). Index and 90-day costs were lowest in the BMI 25 to 30 cohort ($14,344 and $15,865) and highest for the BMI > 50 cohort ($17,503 and $28,281), respectively. On multivariate analyses, index and 90-day cost increased by $23 and $69, respectively, for every one-point increase in BMI (P < 0.001).

Conclusions: Results from this nationally representative dataset demonstrate that increasing BMI is associated with increased index and 90-day costs for total hip arthroplasty. This information may be useful to stakeholders in the development of alternative payment models.