Impact of insulin dependence on lumbar surgery outcomes

Study Design. Retrospective cohort study. Objective. The objective of our study was to evaluate the differential impact of insulin dependence on lumbar surgery outcomes, including surgical and medical complications, total length of hospital stay, nonhome bound discharge, and unplanned readmissions. Summary of Background Data. Although the negative effects of diabetes mellitus (DM) on joint arthroplasty outcomes are well documented, there is a paucity of studies evaluating those on spine surgery. Methods. Data files from 2005 to 2013 were reviewed and to collect data on patients undergoing lumbar spine surgery. χ 2 tests, for categorical variables, and one-way ANOVA, for continuous variables, were used to identify differences in perioperative variables among patients who do not have DM, who are insulin-independent (NIDDM), and who are insulin-dependent (IDDM). Binary logistic regression analysis assessed the effect of DM status on surgical outcomes. Significance was defined as P<0.05. Results. Significant differences were detected among the three groups in surgical and medical complication and unplanned readmission rates, as well as rates of nonhome-bound discharge. The NIDDM and IDDM groups experienced significantly longer mean total hospital length of stay at 3.2 and 3.9 days, respectively, compared with 2.6 days for nondiabetics (P<0.0001). Both NIDDM (OR, 1.226; P=0.017) and IDDM (OR, 1.499; P<0.0001) independently increased the risk for medical complications, whereas only IDDM (OR, 2.429; P<0.0001) was associated with surgical complications. IDDM was found to be associated with increased rate of 30-day unplanned readmission (OR, 1.353; P=0.005). Neither NIDDM nor IDDM had an effect on the likelihood of nonhome discharge. Conclusion. We hope our findings improve risk stratification efforts and informed consent for two DM patient populations. In addition, our findings advocate for appropriate risk stratification of a subgroup DM patients who are dependent on insulin and are at greater risk for surgical morbidity.