Radiologic utility of the Gehweiler and AO spine classification systems for C1 Trauma: A retrospective review from a Level I trauma center.

Objective: The purpose of our study was to identify adult trauma patients with an acute C1 burst fracture, evaluate for concomitant transverse atlantal ligament (TAL) injury, and apply the modified Gehweiler and AO spine classification systems to determine the utility of these classification systems in accurately defining C1 trauma. Materials and Methods: Adult trauma patients with an acute C1 fracture were identified retrospectively using Nuance mPower software. The C1 fracture was described based on whether the fracture involved the anterior arch, posterior arch, lateral mass, medial tubercle, and/or transverse process. If follow-up cervical magnetic resonance imaging (MRI) was performed, the presence and location of an associated TAL injury was recorded. The anatomic location of the C1 burst fracture and TAL injury, if present, were compared with the descriptive classification systems outlined by Gehweiler/Dickman (modified) and the AO Spine society. Any additional osseous trauma of the skull base and C1-C2 was also recorded along with relevant clinical history and management. Results: Thirty-nine patients were identified with an acute C1 burst fracture on cervical computed tomography (CT) with seventy-seven percent of patients undergoing follow-up cervical MRI. Observed fracture patterns were divided into five distinct types based on CT findings and further subdivided based on the integrity of the transverse altantal ligament on MRI. TAL tears were observed exclusively in type 3 fractures (anterior and posterior arch fractures) and type 4 fractures (anterior arch, posterior arch, and lateral mass fractures). The modified Gehweiler classification system failed to accurately describe the anatomic location of the C1 fracture in forty-four percent of patients, whereas the AO spine was too broad and failed to accurately describe fracture location in our cohort. Conclusions: The Gehweiler and AO spine classifications demonstrated significant shortcomings in the accurate description of patients with C1 trauma. Whereas the Gehweiler system did not accurately describe the anatomic location of the various C1 fractures, the AO spine system was too broad and failed to radiologically classify fracture location. Moreover, there was a high number of patients with AO spine type B injuries without atlantoaxial translation that nevertheless required C1-C2 fusion for atlantoaxial instability. We suggest the need for an updated classification system that takes into account both the CT (fracture location) and MRI (TAL integrity) appearance of C1 trauma. An updated classification strategy will offer a radiologic standardization of C1 trauma that will aid in future research studies and help optimize patient management.