P55. Identifying the impact of body mass index on surgical and patient outcomes for cervical spine surgery

Abstract

<h3>BACKGROUND CONTEXT</h3> Body mass index (BMI) is a common factor known to contribute to spine pathologies such as low back pain, spinal deformities and disc degeneration. BMI, both above and below normal ranges, have been shown to relate to various outcomes after lumbar spine surgery. Effects of BMI specifically after cervical spine surgery is less commonly understood. <h3>PURPOSE</h3> The aim of this research review is to clarify the role of BMI in specific cervical spine surgery outcomes. We additionally seek to study whether obese patients can be classified homogeneously, or if there are substratifications in the outcomes of obese patients by BMI. <h3>STUDY DESIGN/SETTING</h3> Retrospective study. <h3>PATIENT SAMPLE</h3> For the current study, we queried the 2013-2019 Quality Outcomes Database (QOD) cervical module. The Quality Outcomes Database is a prospective, multicenter registry designed to evaluate demographic, clinical, and patient-reported outcomes (PROs) for spine surgery. <h3>OUTCOME MEASURES</h3> Various PRO metrics were identified for the cohort, including mJOA, NRS-AP, NRS-NP, NDI, and EQ-5D at 3- and 12-month follow-up after surgical intervention. <h3>METHODS</h3> Analysis of continuous outcomes was assessed using primarily multivariate linear regression. A quasipoisson regression was utilized for hospital length of stay to account for the overdispersion assessed in multiple outcomes. For PROs, improvement in outcomes were dichotomized to achieving the MCID or not at 12-months. <h3>RESULTS</h3> Class II and III obese patients have substantially greater risk factors and poor outcomes, whereas Class I and overweight patients are not substantially different than patients with normal BMI. Adjusted for different factors, patients with class II obesity had lower odds of reoperation at 30-days (OR = 0.44 (0.22 - 0.84), p = 0.02). Class III obese patients had higher odds of postoperative complications, such as cerebrospinal fluid (CSF) leak (OR = 3.70 (1.08 - 14.7), p = 0.044) and pulmonary embolism (OR = 4.69 (1.06 - 24.5), p = 0.045). Underweight patients had a higher rate of readmission at 3 months than other classes of BMI. Other important factors associated with 30-day postoperative complications, reoperation and 3-month readmission included race, approach, and baseline ASA class. Additionally, we also demonstrate how low BMI affects surgical outcomes and PROs, with higher rates of 3-month readmission and greater hospitalization lengths. Patients with class II and III obesity had lower odds at achieving optimal mJOA at 3 months (OR = 0.8 (0.67 - 0.94), p < 0.01, OR = 0.68 (0.56 - 0.82), p < 0.001, respectively) and 12 months (OR = 0.82 (0.68 - 0.98), p = 0.03, OR = 0.79 (0.64 - 0.98), respectively). There were no significant differences between achieving MCID for mJOA. <h3>CONCLUSIONS</h3> We demonstrate how low and high BMI have unique impacts on outcomes for cervical spine surgery. Future studies ought to examine how correcting high or low BMI impacts outcomes, and whether surgeons should more aggressively work to address BMI abnormalities preoperatively. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.