Frequency and risk factors for symptomatic pulmonary embolism following spinal fusion surgery exceeding 6 hours:...

Major spinal fusion involving extensive surgery time carries substantial thromboembolic risk, yet the incidence and determinants of pulmonary embolism (PE) in complex procedures remain insufficiently defined.

To estimate the frequency of symptomatic PE after instrumented spinal fusion lasting ≥6 hours and to develop, as a hypothesis-generating model derivation study, a 2-stage clinical prediction score integrating pre- and intraoperative risk factors.

Retrospective single-center cohort study.

A total of 351 adults underwent instrumented fusion ≥6 hours for degenerative disease, deformity or trauma (2016-2023).

Primary outcome: PE within 90 days confirmed by CT-angiography.

PE severity according to American Heart Association (AHA) and European Society of Cardiology (ESC), perioperative risk factors, functional outcome (modified MacNab criteria), complications (Therapy-Disability-Neurology, TDN classification), and mortality at discharge, 90 days, and 12 months.

Risk factors were evaluated through multivariable logistic regression with multiple imputation. A hierarchical prediction model was constructed (Stage 1: preoperative variables; Stage 2: intraoperative modifiers). Model performance was assessed using area under the receiver operating characteristic curve (AUC), calibration metrics, and bootstrap validation.

Symptomatic PE occurred in 10.8% (n=38), diagnosed at median postoperative day 2. Independent preoperative predictors were fusion ≥8 segments (odds ratio [OR] 3.81, 95% confidence interval [CI] 1.91-7.61) and a lumbar lordosis-thoracic kyphosis inflection at L2-L5 (OR: 2.87, 95% CI: 1.21-6.77). Intraoperative risk modifiers included osseous bone-anchoring complications (OR: 5.07, 95% CI: 1.59-16.20) and fibrinogen administration per gram (OR: 1.55, 95% CI: 1.09-2.21). Apparent discrimination in the derivation cohort was good (AUC 0.818; optimism-corrected 0.787 after bootstrap internal validation); external validation is lacking. PE patients had higher intensive care unit (ICU) admission (84.2% vs 56.2%, p=.001) and markedly increased mortality at discharge (OR: 13.3, p=.005), at 90 days (OR: 5.7, p=.029), and at 12 months (OR: 4.52, p=.039).

In adults undergoing extensive instrumented spinal fusion exceeding 6 hours, symptomatic PE was observed in 10.8% of cases, occurred early, and was associated with substantial morbidity and mortality despite institutional prophylaxis. Findings should be interpreted in the context of symptom-triggered imaging without routine postoperative VTE screening, likely underestimating the total PE burden. This hypothesis-generating, internally validated 2-stage model illustrates the feasibility of dynamic perioperative risk stratification in this specific subgroup but cannot be recommended for clinical implementation before prospective multicenter external validation.