An Independent Inter- and Intraobserver Agreement Evaluation of the New AO Spine Thoracolumbar Spine Injury Classification System
Authors: Urrutia Julio , Zamora Tomas , Yurac Ratko , Campos Mauricio , Palma Joaquin , Mobarec Sebastian , Prada Carlos 
Published: May 2015

Introduction Thoracolumbar fracture classification systems have failed to demonstrate adequate comprehensiveness, or have demonstrated low reliability and reproducibility. The new AO Spine Thoracolumbar Spine Injury Classification System was recently published. It showed substantial reliability and reproducibility among the surgeons who developed it; however, an independent evaluation has not been performed. We performed an independent interobserver and intraobserver agreement evaluation of the new AO Spine Thoracolumbar Spine Injury Classification System. Patients and Methods Anteroposterior and lateral radiographs, and computed tomography scans of 70 patients with acute traumatic thoracolumbar injuries were selected and classified by six evaluators (three spine surgeons and three orthopedic surgery residents). The evaluators were unaware of the patients' identification, the original classification used in their clinical care, and the treatment they received. They classified the lesions according to the morphologic grading of the new AO Spine thoracolumbar spine injury classification system as an A, B, or C type injury; in cases with type A or type B injuries, an analysis for A or B subtypes lesions was also performed. After a 6-week interval, the 70 cases were presented in a random sequence to the same evaluators for repeat evaluation. The Kappa coefficient (κ) was used to determine the interobserver and intraobserver agreement. Results All the different fracture patterns as described by the new AO Spine thoracolumbar spine injury classification system were identified by at least one evaluator. The interobserver reliability was substantial when considering the fracture types (A, B, or C), with k = 0.62 (0.57–0.66). The interobserver agreement when considering the subtypes was moderate; k = 0.55 (0.52–0.57). The intraobserver reproducibility was also substantial, with 85.95% full intraobserver reproducibility considering the fracture type, with k = 0.77 (0.72–0.83), and it was also substantial when considering subtypes with 75.71% full agreement and k = 0.71 (0.67–0.76). No significant differences were observed between spine surgeons and orthopedic residents in the overall interobserver reliability and intraobserver reproducibility, or in the interobserver and intraobserver agreement of specific A, B, or C types of injuries. Conclusion Our study showed substantial agreement among different observers and by the same observer on separate occasions. Considering that this classification allows a better communication among physicians than previous schemes, it could be employed as a practical tool for everyday clinical use. Furthermore, clinical studies employing this classification should be considered more accurate, and their conclusions become more relevant to guide treatment decision making than studies using other classification schemes, especially in case of multicenter studies.