Impact of Iron Deficiency Anemia on Postoperative Outcomes of Thoracolumbar Spinal Fusion (2+ levels) on Patients with Adult Spinal Deformity with Minimum 2-Year Follow-Up.

Introduction: Iron deficiency anemia (IDA) is a common hematological disorder and cause of low hemoglobin. Preoperative anemia has been demonstrated to increase the risk of adverse outcomes after posterior cervical fusion and other spinal surgeries. The need for a transfusion during lumbar fusion has been shown to increase length of stay. This study aimed to assess the impact of IDA on outcomes after spinal fusion for adult spinal deformity (ASD). Methods: The New York Statewide Planning and Research Cooperative System (SPARCS) database was searched from 2009 to 2013 to identify all patients undergoing ≥2-level thoracolumbar spinal fusion (primary and revision) for ASD with a 2-year follow-up. The patients were then stratified by the presence or absence of IDA. Patients with IDA and patients without IDA were subjected to 1:1 propensity score matching based on age, sex, and obesity. Univariate analysis was employed to compare demographics, hospital parameters, and rates of adverse outcomes. Multivariate binary logistic regression with odds ratio (OR) was employed to identify independent risk factors for adverse postoperative outcomes. Results: A total of 524 patients (262 with IDA and 262 without IDA) were identified. Patients with IDA experienced higher rates of overall surgical complications (50.4% vs 23.7%, P<0.001), wound complications (3.4% vs 0.4%, P=0.011), and blood transfusion (10.3% vs 6.5%, P<0.001). No difference was observed in the rate of overall medical complications. Patients with and without IDA had comparable rates of readmission (8.0% vs 13.0%, P=0.064), although patients with IDA had lower rates of reoperation (7.6% vs 13.0%, P=0.044). There was no mortality in either cohort. IDA was independently associated with wound complications (OR=10.6, P=0.028), blood transfusion (OR=3.9, P<0.001), and surgical complications (OR=3.5, P<0.001). Conclusions: Baseline IDA was predictive of increased wound complications, postoperative blood transfusion, and overall surgical complications after thoracolumbar fusion surgery for ASD. Our findings could inform potential medical interventions to mitigate the risks of adverse outcomes in patients with IDA. Level of Evidence: III, retrospective cohort.