DOS 2018

240 · DOS Abstracts Ability of the Global Alignment and Proportion score to Predict Mechanical Failure following Adult Spinal Deformity surgery – Validation in 149 Patients with Two-year Follow-up. Tanvir Johanning Bari, Søren Ohrt-Nissen, Martin Gehrchen, Benny Dahl Spine Unit, Department of Orthopedic Surgery, Rigshospitalet, Copenhagen University Hospital; Department of Orthopedics and Scoliosis Surgery, Texas Children’s Hospital and Baylor College of Medicine, TX, USA Background: Surgical treatment for Adult Spinal Deformity (ASD) is associ- ated with a high risk of mechanical failure and consequent revision surgery. To improve prediction of mechanical complications, the Global Alignment and Proportion (GAP) score was developed with promising results. Development was based on the assumption that not all patients would benefit from the same fixed radiographic targets as pelvic incidence is an individual, morphological pa- rameter that greatly influences the sagittal curves of the spine. Purpose / Aim of Study: To validate the GAP score in a single-center cohort of ASD patients. Materials and Methods: All patients undergoing ASD surgery with ≥4 levels of instrumentation were consecutively included at a tertiary spine unit. Patients were followed for a minimum of two years. Pre- and postoperative GAP score and categories were calculated for all patients and the association with me- chanical failure and revision surgery was analyzed. Findings / Results: A total of 149 patients with a mean age of 57.4 years were included. Rates of mechanical failure and revision surgery were 51% and 35% respectively. The area under the curve (AUC) using receiver operating charac- teristic was classified as “no or low discriminatory power” for the GAP score in predicting either outcome (AUC=0.50 and 0.49 respectively). Similarly, there were no significant associations between GAP categories and mechanical failure or revision surgery when using Cochran-Armitage test of trend (p=0.28 and p=0.58 respectively). Conclusions: In a consecutive series of surgically treated ASD patients we found no significant association between postoperative GAP score and me- chanical failure or revision surgery. Despite minor limitations in similarities to the original study cohort, further validation studies or adjustments to the original scoring system are proposed. 181.