The risk of stroke after spinal fusion surgery: A national cohort study

Background context: Postoperative stroke is a rare complication of spinal fusion surgery, but its relevant risk and incidence remain unclear. Purpose: To investigate the incidence and risk of stroke after spinal fusion surgery. Study design: Cohort study. Patient sample: All study subjects were extracted from a nationwide representative cohort of one million people from 2000 to 2005. Outcome measures: Stroke, including hemorrhagic and ischemic, during the study period. Methods: An exposure group of 2,249 subjects who received spinal fusion surgery during the study period was compared with 2,203 control subjects matched by age, sex, and propensity score. All were followed up for 3 years for all kinds of stroke. Demographics, comorbidities, and nonmeasurable covariates were matched between the two groups. Kaplan-Meier analyses were performed, with adjustments by Cox regression model. Results: There were 4,452 subjects, including 2,249 spinal fusion patients and 2,203 controls, who were followed up for 12,967 person-years. The incidence rates of any, hemorrhagic, and ischemic strokes were 9.95, 1.21, and 8.86, respectively, per 1,000 person-years in the spinal fusion group and 11.5, 1.69, and 9.93, respectively, in the comparison group. Patients who received spinal fusion surgery were less likely to have any stroke (crude hazard ratio [HR]=0.87, p=.393), hemorrhagic stroke (HR=0.72, p=.473), and ischemic stroke (HR=0.89, p=.582) than the comparison group but without statistical significance. After adjusting for demographics, comorbidities, and medications, there were still no significant differences for risks of any, hemorrhagic, and ischemic strokes (adjusted HR=0.89, 1.36, and 0.87; p=.522,.553, and.477, respectively) in the spinal fusion group. Conclusions: Patients receiving spinal fusion surgery have similar incidence rates of having a stroke within 3 years postoperation as those without surgery. Risks of any postoperative stroke are similar or insignificantly lower in the spinal fusion group.