Malnutrition, Body Mass Index, and Associated Risk of Complications After Posterior Lumbar Spine Fusion: A 3:1 Matched Cohort Analysis

Abstract

The effect of malnutrition on outcomes after posterior lumbar fusion (PLF) remains understudied. This study analyzes the effect of malnutrition across a comprehensive range of body mass index (BMI) on complications after PLF. The Pearldiver Mariner database was queried between 2010 and 2020 using International Classification of Diseases (Ninth and Tenth Revisions) codes for malnutrition and Current Procedural Terminology codes for PLF. Patients were identified with preoperative BMI diagnosis codes and partitioned into one of the following BMI cohorts: underweight (BMI <20), normal (BMI 19-30), obese (BMI 30-40), and morbidly obese (BMI >40). An additional all-BMI cohort was created using patients with any BMI code. All cohorts were matched 1:3 to control patients within the same BMI group without malnutrition based on age, gender, and Charlson comorbidity index. Complication rates were calculated using the Pearson χ2 method with statistical significance set to P < 0.05. The number of patients in each cohort were 1106 (all-BMI), 227 (underweight), 808 (normal), 667 (obese), and 449 (morbidly obese). Statistical analysis showed that the all-BMI cohort had greater odds of complications related to instrumentation (odds ratio [OR]: 2.28; P < 0.001), need for revision fusion (OR: 2.04; P < 0.001), pulmonarycomplications (OR: 1.45; P < 0.001), sepsis (OR:2.89; P < 0.001), surgical site complications (OR: 1.87; P< 0.001), and urinary complications (OR: 1.41; P < 0.001). No difference was noted between the BMI-specific cohorts for complication risk. Our analysis indicates that malnutrition may independently increase PLF complication risk. Surgeons may consider preoperative optimization for malnutrition patients to reduce complication risk.