Date of Award

January 2014

Document Type

Open Access Thesis

Degree Name

Medical Doctor (MD)



First Advisor

Jonathan N. Grauer

Subject Area(s)

Surgery, Medicine


Prior studies on the impact of obesity on spine surgery outcomes have focused mostly on lumbar fusions, do not examine lumbar discectomies or decompressions, and have shown mixed results regarding complications. There is also a paucity of literature regarding the effect of obesity on cervical spinal fusion outcomes. The purpose of this thesis was therefore to analyze whether obesity as measured by BMI influences the complication rates, operation times, and lengths of stay in patients undergoing lumbar or cervical spine surgery.

To this end, we conducted a retrospective cohort analysis of prospectively collected data on lumbar and cervical surgeries using the American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP) database from 2005-2010. Patients undergoing lumbar surgery (anterior fusion, posterior fusion, TLIF/PLIF, discectomy, or decompression) and anterior cervical fusion were categorized into 4 BMI groups: non-obese (18.5-29.9 kg/m2), obese I (30-34.9 kg/m2), obese II (35-39.9 kg/m2), obese III (> 40 kg/m2). Posterior cervical patients were categorized into 2 groups based on BMI: non-obese (18.5-29.9 kg/m2) and obese (> 30 kg/m2) due to the smaller sample size. Patients in the obese categories were compared to patients in the non-obese categories using χ2, Fisher's exact test, student's t-test, and/or ANOVA. Multivariate linear/logistic regression models were used to adjust for preoperative comorbidities.

Data were available for 10,387 patients undergoing lumbar surgery. Among all lumbar surgery patients, 25.6% were obese I, 11.5% obese II, and 6.9% obese III. On multivariate analysis, obese I and III had a significantly increased risk of urinary complications and obese II and III patients had a significantly increased risk of wound complications. Only obese III patients, however, had a statistically increased risk of having increased time spent in the operating room, an extended length of stay, pulmonary complications and of having > 1 complication (all P < 0.05). Regarding cervical fusions, data were available for 3,671 and 400 patients who underwent anterior or posterior cervical fusion, respectively. On multivariate analyses for both anterior and posterior cervical fusions, there were no differences for overall and system-specific complication rates, lengths of hospital stay, re-operation rates, and mortality among the obesity groups when compared to the non-obese groups.

In conclusion, obese patients appear to have higher complication rates than patients who are non-obese after lumbar surgery but not after cervical surgery. After lumbar surgery, the complication rates seem to increase substantially for obese III patients. These patients have longer times spent in the operating room, extended hospitals stays and an increased risk for wound, urinary, pulmonary complications and for having at least one or more complication overall. Surgeons should be aware of the increased risk of multiple complications, longer lengths of stay, and longer surgeries for patients with BMI > 40 kg/m2 after lumbar surgery.