['Obesity has been associated with adverse surgical outcomes; however, limited information is available regarding the effect of obesity on cervical spinal fusion outcomes.', 'To determine the effect of obesity on complication rates after cervical fusions.', 'Retrospective cohort analysis of prospectively collected data on cervical fusion surgeries.', 'Patients in the ACS-NSQIP database from 2005 to 2010 undergoing cervical anterior or posterior fusion.', 'Primary outcome measures were 30-day postsurgical complications, including mortality, deep-vein thrombosis, pulmonary embolism, septic complications, system-specific complications, and having ≥1 complication overall. Secondary outcomes were time spent in the operating room, blood transfusions, length of stay, and reoperation within 30 days.', "Patients undergoing anterior or posterior cervical fusions in the 2005-2010 American College of Surgeons National Surgical Quality Improvement Program were selected using Current Procedural Terminology codes. Anterior cervical fusion patients were categorized into four groups on the basis of body mass index (BMI): nonobese (18.5-29.9 kg/m(2)), obese I (30-34.9 kg/m(2)), obese II (35-39.9 kg/m(2)), and obese III (≥40 kg/m(2)). Posterior cervical patients were categorized into two groups based on the basis of BMI: nonobese (18.5-29.9 kg/m(2)) and obese (≥30 kg/m(2)) due to the smaller sample size. Patients in the obese categories were compared with patients in the nonobese categories by the use of χ(2), Fisher's exact test, Student t test, and analysis of variance. Multivariate linear/logistic regression models were used to adjust for preoperative comorbidities. The authors report no sources of funding or conflicts of interest related to this study.", 'Data were available for 3,671 and 400 patients who underwent anterior or posterior cervical fusion, respectively. Obese class III patients only showed a greater incidence of deep-vein thrombosis after anterior fusions on univariate analysis. Obese patients only showed longer mean surgical times and total operating room times after posterior fusions on univariate analysis. On multivariate analyses, these differences did not remain significant. There were also no differences in multivariate analyses for overall and system-specific complication rates, lengths of hospital stay, reoperation rates, and mortality among the obesity groups when compared with the nonobese groups with anterior or posterior cervical fusions.'] Are anterior and posterior cervical fusion in patients with high body mass index associated with greater complications?