Elevated Serum Alkaline Phosphatase is an Independent Predictor of Complications after Lumbar Spinal Fusion

Background Alkaline phosphatase (ALP) is an enzyme which has been proven useful as a biomarker for bone turnover and inflammation. We hypothesized that high serum ALP levels are associated with increased complication rates following lumbar spinal fusion. Methods Lumbar spinal fusion procedures from 2005-2019 were queried from the national Surgical Quality Improvement Program (NSQIP) database. Serum alkaline phosphatase levels were stratified into low <44 IU/L, normal 44-147 IU/L, and high >147 IU/L. A risk-adjusted multivariate logistic regression was used to analyze ALP as an independent risk factor for complications. Results A total of 16,441 patients who underwent lumbar fusion procedures were included. Adjusted multivariate logistic regression analysis demonstrated that patients with a high serum ALP level had a significantly increased risk for developing septic shock (OR 4.68, 95% CI 1.83-11.97), pneumonia (OR 2.89, 95% CI 1.59-5.25), requiring a transfusion (OR 2.09, 95% CI 1.68-2.59), reoperation within 30 days (OR 1.68, 95% CI 1.12-2.52), readmission within 30 days (OR 1.60, 95% CI 1.16-2.21), increased length of stay (OR 1.87, 95% CI 1.49-2.36), and nonhome discharge (OR 2.18, 95% CI 1.80-2.66). Clinical Relevance Serum alkaline phosphatase is a valuable and readily available tool for preoperative risk stratification of patients undergoing lumbar spinal fusion. Conclusions Elevated serum ALP in patients undergoing lumbar fusion procedures is associated with increased risk for multiple in-hospital complications as well as higher rates of readmission and reoperation.