Body mass index and the risk of deep surgical site infection following posterior cervical instrumented fusion.

Abstract BACKGROUND Surgical site infection (SSI) following spine surgery is associated with increased morbidity, reoperation rates, hospital readmissions, and cost. The incidence of SSI following posterior cervical spine surgery is higher than anterior cervical spine surgery, with rates from 4.5% to 18%. It is well documented that higher body mass index (BMI) is associated with increased risk of SSI after spine surgery. There are only a few studies that examine the correlation of BMI and SSI after posterior cervical instrumented fusion (PCIF) using national databases, however, none that compare trauma and nontraumatic patients. PURPOSE The purpose of this study is to determine the odds of developing SSI with increasing BMI after PCIF, and to determine the risk of SSI in both trauma and nontraumatic adult patients. STUDY DESIGN This is a retrospective cohort study of a prospective surgical database collected at one academic institution. PATIENT SAMPLE The patient sample is from a prospectively collected surgical registry from one institution, which includes patients who underwent PCIF from April 2011 to October 2017. OUTCOME MEASURES A SSI that required return to the operating room for surgical debridement. METHODS This is a retrospective cohort study using a prospectively collected database of all spine surgeries performed at our institution from April 2011 to October 2017. We identified 1,406 patients, who underwent PCIF for both traumatic injuries and nontraumatic pathologies using International Classification of Diseases 9 and 10 procedural codes. Thirty-day readmission data were obtained. Patient's demographics, BMI, presence of diabetes, preoperative diagnosis, and surgical procedures performed were identified. Using logistic regression analysis, the risk of SSI associated with every one-unit increase in BMI was determined. This study received no funding. All the authors in this study report no conflict of interests relevant to this study. RESULTS Of the 1,406 patients identified, 1,143 met our inclusion criteria. Of those patients, 688 had PCIF for traumatic injuries and 454 for nontraumatic pathologies. The incidence of SSI for all patients, who underwent PCIF was 3.9%. There was no significant difference in the rate of SSI between our trauma group and nontraumatic group. There was a higher rate of infection in patients, who were diabetic and with BMI≥30 kg/m2. The presence of both diabetes and BMI≥30 kg/m2 had an added effect on the risk of developing SSI in all patients, who underwent PCIF. Additionally, logistic regression analysis showed that there was a positive difference measure between BMI and SSI. Our results demonstrate that for one-unit increase in BMI, the odds of having a SSI is 1.048 (95% CI: 1.007–1.092, p=.023). CONCLUSIONS Our study demonstrates that our rate of SSI after PCIF is within the range of what is cited in the literature. Interestingly, we did not see a statistically significant difference in the rate of infection between our trauma and nontrauma group. Overall, diabetes and elevated BMI are associated with increased risk of SSI in all patients, who underwent PCIF with even a higher risk in patient, who are both diabetic and obese. Obese patients should be counseled on elevated SSI risk after PCIF, and those with diabetes should be medically optimized before and after surgery when possible to minimize SSI.