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An Independent Inter- and Intraobserver Agreement Evaluation of the AOSpine Subaxial Cervical Spine Injury Classification System

Urrutia, Julio MD; Zamora, Tomas MD; Yurac, Ratko MD; Campos, Mauricio MD; Palma, Joaquin MD; Mobarec, Sebastian MD; Prada, Carlos MD

doi: 10.1097/BRS.0000000000001302
Cervical Spine

Study Design. An agreement study.

Objective. The aim of this study was to perform an independent interobserver and intraobserver agreement assessment of the AOSpine subaxial cervical spine injury classification system.

Summary of Background Data. The AOSpine subaxial cervical spine injury classification system was recently described. It showed substantial inter- and intraobserver agreement in the study describing it; however, an independent evaluation has not been performed.

Methods. Anteroposterior and lateral radiographs, computed tomography scans, and magnetic resonance imaging of 65 patients with acute traumatic subaxial cervical spine injuries were selected and classified using the morphologic grading of the subaxial cervical spine injury classification system by 6 evaluators (3 spine surgeons and 3 orthopedic surgery residents). After a 6-week interval, the 65 cases were presented to the same evaluators in a random sequence for repeat evaluation. The kappa coefficient (κ) was used to determine the inter- and intraobserver agreement.

Results. The interobserver agreement was substantial when considering the fracture main types (A, B, C, or F), with κ = 0.61 (0.57–0.64), but moderate when considering the subtypes: κ = 0.57 (0.54–0.60). The intraobserver agreement was substantial considering the fracture types, with κ = 0.68 (0.62–0.74) and considering subtypes, κ = 0.62 (0.57–0.66). No significant differences were observed between spine surgeons and orthopedic residents in the overall inter- and intraobserver agreement, or in the inter- and intraobserver agreement of specific A, B, C, or F type of injuries.

Conclusion. This classification allows adequate agreement among different observers and by the same observer on separate occasions. Future prospective studies should determine whether this classification allows surgeons to decide the best treatment for patients with subaxial cervical spine injuries.

Level of Evidence: 3

*Department of Orthopaedic Surgery, School of Medicine, Pontificia Universidad Catolica de Chile, Santiago, Chile

Department of Orthopaedic Surgery, Clinica Alemana de Santiago, Santiago, Chile.

Address correspondence and reprint requests to Julio Urrutia, MD, Department of Orthopaedic Surgery, School of Medicine, Pontificia Universidad Catolica de Chile, Marcoleta 352, Santiago, Chile; E-mail:

Received 14 August, 2015

Revised 13 September, 2015

Accepted 6 October, 2015

The article submitted does not contain information about medical device(s)/drug(s).

No funds were received in support of this work.

No relevant financial activities outside the submitted work.

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