Friday, September 28, 2018 3:00 PM–4:00 PM abstracts: the gravity of obesity: 229. Risk factors for readmission and complications in obese and severely obese patients undergoing elective posterior lumbar spine fusion

BACKGROUND CONTEXT Obesity is an important risk factor for complications after lumbar spine fusion, and poses unique challenges regarding safety and quality of care. Nonetheless, this patient population is not well studied. PURPOSE To determine risk factors for readmission in obese and morbidly obese patients. STUDY DESIGN/SETTING Retrospective aase control study. PATIENT SAMPLE Adult patients age >18 undergoing primary posterior lumbar fusion in the State Inpatient Databases of New York, Florida, North Carolina, Utah, and California. OUTCOME MEASURES Odds ratios of demographics, comorbidities, and surgery characteristics in multivariate analysis of 90-day readmission. METHODS Data were queried using ICD-9 codes. Patients who underwent surgery in the last quarter of the data set, revision surgery, or surgery for cancer, infection, or trauma were excluded. Independent analyses were performed for three separate groups of patients: patients were identified as obese using codes for obesity or BMI >30, but not morbid obesity or BMI > 40, severely obese using codes for morbid obesity or BMI > 40, and normal if they had none of the above codes nor codes for overweight or underweight. Data were queried for demographics, comorbidities, surgery characteristics, and 90-day hospital readmission. Logistic multivariate regressions were performed to determine risk factors for readmission. RESULTS We analyzed 24,349 obese, 9,835 severely obese patients and 257,986 normal patients. The 90-day hospital readmission rate was 14.5%, 17.5%, and 12.1% in the obese, severely obese, and normal groups, respectively. In the obese group, risk factors for readmission included female gender, Black or Hispanic race, Medicare or Medicaid insurance, the addition of anterior or lateral interbody fusion, >3 levels treated, cerebrovascular disease, chronic pulmonary disease, congestive heart failure (CHF), diabetes without and with chronic complication, myocardial infarction, peptic ulcer disease, peripheral vascular disease, renal disease, and mental health disease, In the severely obese group, risk factors for readmission included female gender, Medicare or Medicaid insurance, >3 levels, CHF, diabetes without and with chronic complication, hemi or paraplegia, mild liver disease, and renal disease. In the normal group, all studied variables were risk factors for readmission. CONCLUSIONS Ninety-day hospital readmission rates in obese and severely obese patients undergoing elective posterior lumbar fusion are high. Risk factors include demographic variables such as race and insurance status, as well as various comorbid conditions, but not age. Similar risk factors were seen in normal weight patients, however with less risk, suggesting a synergistic effect of obesity with other risk factors. This study provides valuable insight into modifiable risk factors that may be potential targets for preoperative optimization and guidance on risk adjustment in this unique patient population.