Does Body Mass Index Influence Intraoperative Costs and Operative Times for Anterior Cervical Discectomy and Fusion? A Time-Driven Activity-Based Costing Analysis.

OBJECTIVE:Spine surgeons are often unaware of drivers of cost variation for anterior cervical discectomy and fusion (ACDF). We used time-driven activity-based costing to assess the relationship between body mass index (BMI), total cost, and operating room (OR) times for ACDFs. METHODS:Total cost was divided into direct and indirect costs. Individual costs were obtained by direct observation, electronic medical records, and through querying multiple departments. Timestamps for all involved personnel and material resources were documented. Total intraoperative costs were estimated for all ACDFs from 2017 to 2022. All patients were categorized into distinct BMI-based cohorts. Linear regression models were performed to assess the relationship between BMI, total cost, and OR times. RESULTS:A total of 959 patients underwent ACDFs between 2017 and 2022. The average age and BMI were 58.1 ± 11.2 years and 30.2 ± 6.4 kg/m2, respectively. The average total intraoperative cost per case was $7120 ± $2963. Multivariable regression analysis revealed that BMI was not significantly associated with total cost (P = 0.36), supply cost (P = 0.39), or personnel cost (P = 0.20). Higher BMI was significantly associated with increased time spent in the OR (P = 0.018); however, it was not a significant factor for the duration of surgery itself (P = 0.755). Rather, higher BMI was significantly associated with nonoperative OR time (P < 0.001). CONCLUSIONS:Time-driven activity-based costing is a feasible and scalable methodology for understanding the true intraoperative costs of ACDF. Although higher BMI was not associated with increased total cost, it was associated with increased preparatory time in the OR.