Extended Postoperative Risk of Venous Thromboembolism After Degenerative Spine Surgery: A Nationwide Cohort Study.

STUDY DESIGN: Retrospective population-based nationwide cohort study.

OBJECTIVE: To determine the incidence, risk factors, and optimal surveillance interval of postoperative VTE after degenerative spine surgery.

SUMMARY OF BACKGROUND DATA: VTE, including pulmonary embolism (PE), is a leading cause of postoperative morbidity and mortality after spine surgery. Recent evidence suggests that VTE risk may already be elevated before surgery, yet the temporal distribution of postoperative VTE risk and the appropriate duration of surveillance remain poorly defined.

METHODS: A total of 200,792 adults who underwent degenerative spine surgery in Korea between 2014 and 2018 were identified from the Korean Health Insurance Review and Assessment Service database. Overall VTE, PE, and VTE-related invasive procedures were estimated as incidence rates per 10,000 person-years over a mandatory one-year follow-up. Multivariable logistic regression with bootstrap validation was used to identify risk factors. Sequential trends were assessed across twelve 30-day intervals, with subgroup analyses stratified by age, spinal region, and comorbidities.

RESULTS: Postoperative VTE occurred in 1,282 patients (0.64%), PE in 321 (0.16%), and invasive procedures in 213 (0.11%), with annual incidence rates of 64, 16, and 11 per 10,000 person-years, respectively. Independent risk factors included older age, congestive heart failure, cerebrovascular and peripheral vascular disease, renal disease, end-stage renal disease, concurrent knee arthritis, and thoracic or lumbar surgery. Sequential analysis showed that 61% of all VTE events occurred within the first four postoperative months, peaking in month 2. Subgroup analyses demonstrated delayed return to baseline and additional late-phase peaks among older adults, patients with thoracic pathology, and those with renal comorbidities.

CONCLUSION: Postoperative VTE risk remains elevated for up to four months following degenerative spine surgery, with high-risk subgroups demonstrating additional late-onset events. These epidemiologic findings underscore the importance of maintaining thromboembolic vigilance beyond the conventional early perioperative window, though prospective studies will be necessary to translate these observations into actionable clinical guidelines.

LEVEL OF EVIDENCE: III.