DOS 2018

192 · DOS Abstracts Moderate inter-rater and substantial intra-rater reproducibility of the Roussouly Classification System in patients with Adult Spinal Deformity Tanvir Johanning Bari, Dennis Winge Hallager, Niklas Tøndevold, Ture Karbo, Lars Valentin Hansen, Benny Dahl, Martin Gehrchen 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: The Roussouly Classification System was developed to describe the variation in sagittal spine shape in normal individuals. A recent study sug- gests that patients´ spine types could influence the outcome following spinal surgery. The utility of a classification system depends largely on its reproduc- ibility. Purpose / Aim of Study: To provide the inter- and intra-rater reproducibility of the Roussouly Classification System in a single- center prospective cohort of patients referred for Adult Spinal Deformity (ASD). Materials and Methods: Sixty-four consecutive patients were included in a blinded test-re-test setting using digital radiographs. All ratings were performed by 4 spine surgeons with different levels of experience. There was a 14-day in- terval between the two reading sessions. Inter- and intra-rater reproducibility was calculated using Fleiss’ Kappa and crude agreement percentages. Findings / Results: We found moderate inter-rater and substantial intra- rater reproducibility. The most experienced rater had significantly higher intra-rater reliability compared to the least experienced rater. The two most experienced raters also had the highest crude agreement percentage; however, also had a significant difference in distribution of spine types. Conclusions: The current study presents moderate inter-rater and substantial intra-rater reliability of the Roussouly Classification System. These findings are acceptable and comparable to previous results of reproducibility for a classifica- tion system in patients with ASD. Additional studies are requested to validate these findings as well as to further investigate the impact of the classification system on outcome following surgery. 133.