Study design: International validation study.
Objective: To investigate the influence of the spine surgeons' level of experience on the intraobserver reliability of the novel AOSpine Thoracolumbar Spine Injury Classification system, and the appropriate classification according to this system.
Summary of background data: Wide variability has been demonstrated for intraobserver reliability of the AOSpine classification system. The spine surgeons' level of experience may play a crucial role in the appropriate classification of thoracolumbar fractures, and the degree of reproducibility of the same observer on separate occasions. However, this has not been previously investigated.
Methods: After a training on the classification system, high quality CT images together with clinical data from 25 patients with thoracolumbar fractures were independently assessed by 100 spine surgeons from across the world on 2 different occasions, 1 month apart from each other. The spine surgeons were allocated to a subgroup, according to their years of experience. Intraobserver reliability was calculated for each individual surgeon and for each subgroup, using the Kappa statistics (κ). Descriptive statistics was used to describe any differences between the subgroups. Analysis of any misclassifications was performed by calculating sensitivity and specificity estimates.
Results: Almost all surgeons demonstrated at least moderate intraobserver reliability. All surgeon subgroups demonstrated substantial reliability (κ = 0.67-0.69) for fracture subtype grading, and almost all subgroups demonstrated excellent reliability (κ = 0.79-0.83) for fracture morphology type regardless of subtype identified. In general, the fractures were most frequently misclassified by the most experienced surgeons. No major differences were observed among the subgroups when comparing the sensitivity and specificity rates.
Conclusion: This international study demonstrated that the spine surgeons' level of experience does not substantially influence the classification and intraobserver reliability of the recently described AOSpine Thoracolumbar Spine Injury Classification System.
Level of evidence: 4.