P144. The effect of operative duration on postoperative VTE rates in spinal surgery

Abstract

<h3>BACKGROUND CONTEXT</h3> The relationship between operative duration and its effect on postoperative venous thromboembolism (VTE) remains unclear in spine surgery. Previous studies have been limited in cohort size or have lacked adequate variability of surgical duration to determine the extent of effect surgery length has on VTE rates. Information regarding patient demographics and the effect of surgical durations on VTE are critical to establish appropriate guidelines for determining which patients could benefit from postoperative chemoprophylaxis. <h3>PURPOSE</h3> To determine the effect of operative duration on postoperative VTE rates in patients undergoing elective thoracolumbar spinal procedures. <h3>STUDY DESIGN/SETTING</h3> Retrospective cohort study. <h3>PATIENT SAMPLE</h3> Patients >18 years of age who underwent thoracolumbar spinal fusion between 2007-2021 were retrospectively identified. A 10:1 propensity match incorporating patient demographics and surgical characteristics was conducted to match and compare patients for postoperative VTE events. <h3>OUTCOME MEASURES</h3> Postoperative VTE events, cut-to-close duration, prior history of clots, Oswestry Disability Index (ODI), Mental (MCS-12) and Physical (PCS-12) Component Summary of the Short-Form 12, visual analog scale (VAS) Back, VAS Leg. <h3>METHODS</h3> A structured query language (SQL) search was used to identify patients who underwent a thoracolumbar surgery and had a postoperative VTE. Only patients with deep VTEs were included. Demographics, surgical characteristics and patient reported outcome measures (PROMs) were collected from the electronic medical record. Patients were categorized into a VTE and non-VTE group. Categorical comparisons were analyzed using Pearson chi-square analysis or Fisher's Exact test. Continuous variables were analyzed using independent samples t-test or Mann-Whitney U test. A binary logistic regression was then performed to determine if cut-to-close duration was a predictor of increased postoperative VTE events—controlling for demographics and a history of clots. A receiver operating characteristic (ROC) curve using Youden's index was created to determine a "cutoff" time for predicting increased likelihood of a VTE based on surgical duration. <h3>RESULTS</h3> A total of 1,456 patients (122 VTE, 1,334 non-VTE) were included. The VTE group was younger (61.5 vs 65.5, p<0.001), predominantly male (60.8% vs 44.5%, p=0.001), experienced a previous VTE (15.6% vs 2.92%, p<0.001) and had higher cut-to-close time (304 mins vs 209 mins, p<0.001). However, there was no difference in CCI between groups (1.08 vs 0.66, p=0.119). When evaluating PROMs, the VTE group had worse 1-year postoperative minus preoperative (∆) ODI (-11.79 vs -21.99, p=0.039), ∆PCS-12 (4.30 vs 8.52, p=0.045), and ∆VAS Leg (-1.41 vs -4.08, p=0.001). Operative duration was an independent predictor of increased postoperative VTE rates on bivariate regression analysis (β=0.01, p<0.001). When evaluating the ROC, a cutoff time of 245 mins was identified (AUC [95% CI] = 0.672 [0.615 – 0.728]) as an optimal predictor of increased risk for a VTE. <h3>CONCLUSIONS</h3> A history of a prior VTE was associated with greater VTE rates during elective thoracolumbar surgery. Patients with a VTE had worse 1-year ∆ODI, ∆PCS-12, and ∆VAS Leg indicating that patients have worse overall improvement after VTE development, even after the VTE has been treated. Additionally, a higher operative duration is an independent risk factor for postoperative VTE. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.