Does body mass index influence intraoperative costs and operative times for open transforaminal lumbar interbody fusion? A time-driven activity-based costing analysis.

BACKGROUND

The increasing prevalence of obesity has raised concerns about its impact on surgical outcomes and healthcare costs. This study evaluates the influence of Body Mass Index (BMI) on intraoperative costs and operative times during open Transforaminal Lumbar Interbody Fusion (TLIF) procedures using a Time-Driven Activity-Based Costing (TDABC) approach.

METHODS

A retrospective analysis was conducted on 279 patients who underwent TLIF between 2019 and 2022. Patients were categorized into 5 BMI cohorts: healthy weight (BMI 18.5-24.99), overweight (BMI 25.0-29.99), Class I obese (BMI 30.0-34.99), Class II obese (BMI 35.0-39.99), and Class III obese (BMI >40). Intraoperative costs were calculated using TDABC methodology, with costs segmented into supply and personnel expenses. Operative times were measured in 3 phases: surgery time (incision to closure), OR time (patient entering to leaving), and turnover time. Multivariable regression models assessed the relationship between BMI and various intraoperative time and cost metrics, adjusting for potential confounders.

RESULTS

BMI was significantly associated with increased operative times and personnel costs. Each unit increase in BMI corresponded to an additional 1.90 minutes in the operating room (p = .01) and a $25.72 increase in personnel costs (p = .008). However, no significant association was found between BMI and total or supply costs. Regression analyses indicated that obese patients did not significantly differ from healthy weight patients in terms of total intraoperative costs.

CONCLUSIONS

Higher BMI is associated with increased operative times and personnel costs in TLIF procedures, though it does not significantly impact total intraoperative costs when controlling for confounders. These findings suggest that BMI may not need to be a significant deterrent in patient selection for TLIF under bundled payment models.