Craniocervical Junction and Upper Cervical Spine Fractures: Historical Systems and Advancements with the AO Spine Classification.

Study DesignSystematic Review.ObjectivesTo describe existing craniocervical junction and upper cervical spine classification systems and their integration into a unified rational hierarchical system of the AO Spine Upper Cervical Injury Classification System (UCIC).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.Results859 articles were identified which yielded 10 established classification systems for injuries of the occipital condyles, craniocervical junction as well as atlas and axis. All systems were either non-hierarchical, conferred minimal clinical significance or failed to consider neurological status of patients. For example, the Traynelis classification simply relies upon describing the direction of displacement which has dubious clinical significance. Similarly, the Jefferson description of atlas fractures simply grades injuries by fracture line pattern. The AO Spine UCIC system synthesizes each published historical scheme into a rational graded method by which clinicians can assess the severity of injuries to this region. The three grades of injury range from type A being generally stable bony injuries, type B constituting potentially unstable (osseoligamentous) injuries and type C representing grossly unstable translational injuries.ConclusionThe AO Spine UCIC System is a validated methodoogy of integrating historical landmark grading systems and evolving this into a structured means of grading severity of injuries to guide timely clinical management. The implementation of this universal system will enable clinicians to consistently assess craniocervical junction injuries and implement appropriate managemen strategies. Future studies will examine outcomes after operative or non-operative management with progression to a standardized quantified algorithm.