Subaxial Cervical Spine Fractures: Historical Systems and Advancements With the AO Spine Classification

Study DesignSystematic Review.ObjectivesA vast array of historical subaxial cervical spine fracture classifications. This initially comprised crude non-hierarchial schemes based upon mechanism on injury alone including compression, flexion, extension or lateral flexion. Allen and Ferguson advanced this by offering 6 categories of subaxial cervical spine injuries. Beyond this, Aebi and Nazarian appreciated the nuances of whether was was ligamentous injury in addition to pure bony involvement. These existing simplistic classifications failed to guide clinicians as to whether operative or non-operative management is appropriate. We describe the evolution of existing subaxial cervical spine classification systems and the development of the AO Cervical Spine Injury Classification System.MethodsA systematic review of MEDLINE, EMBASE and Cochrane Databases was performed in keeping with the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines to identify all existing subaxial cervical spine classification systems.Results483 articles were initially retrieved which were distilled to 11 articles which pioneered individual classification systems. The AO Cervical Spine Injury Classification System resolves this with its hallmark 3 categories of escalating injury types from the type A compression injuries, to type B tension band injuries and finally the grossly unstable type C translation/displacement injuries. The addition of modifiers such as critical disc herniation or stiffening bony disease further strengthens the encompassing nature of this classification.ConclusionsThe AO Spine Cervical Spine Injury Classification System is a testament of the historical classification grading schemes but provides a structured means of evaluating injuries. This progressive system provides a foundation upon which objective scoring management methods can be developed to guide operative or non-operative management.