Identification of an Operative Time Threshold for Substantially Increased Postoperative Complications Among Elderly Spine Surgery Patients

Study Design Retrospective cohort study. Objectives To identify whether thresholds exist beyond which operative duration or age increases risks for complications among patients ≥65 years undergoing elective spine surgery. Methods Elective inpatient spine procedures unrelated to infection/trauma/tumor diagnoses in patients <65 years recorded in the 2006-2019 American College of Surgeons National Surgical Quality Improvement database were identified. Univariate analyses was used to compare 30 day complication rates among 5 operative duration and age-stratified groups. To quantify the risk of prolonged operative duration on complications, multivariate analyses were performed controlling for confounders. A generalized linear model was used to assess the individual and combined effect strength of age and operative duration on complication rates. Results Among 87,705 patients stratified by operative duration, 30 day complication rates rose nonlinearly as operative duration increased, with a sharp rise after 4.0-4.9 hours (28.3% at 4.0-4.9 hours, 51.7% at ≥5 hours, P < .001). Multivariate analysis found operative duration was independently associated with increased risk of overall complications (odds ratio 1.10→1.69, P < .001) and medical complications (odds ratio 1.19→1.98, P < .001). Although complication rates rose by age (all P < .001), age was not independently predictive of overall complications within any operative duration group on multivariate analysis. Operative duration had a greater effect (η2 P = .067) than age (η2 P = .003) on overall complication rates. Conclusions Increased operative duration was strongly associated with 30 day complication rates, particularly beyond a threshold of 5 hours. Furthermore, operative duration had a notably larger effect on overall complication rates than age.