The craniocervical junction (CCJ) is a complex and unique osteoligamentous structure that balances maximum stability and protection of vital neurovascular anatomy with ample mobility and range of motion. With the increasing utilization and improved resolution of cervical magnetic resonance imaging, craniocervical injury is being more accurately defined as a spectrum of injury that ranges in severity from overt craniocervical disassociation to isolated injuries of one more of the craniocervical ligaments, which may also lead to craniocervical instability. Thus, it is vital for the radiologist and neurosurgeon to have a thorough understanding of the imaging anatomy and function of the CCJ.
Study Design Retrospective, cross-sectional Objectives To identify trauma patients with confirmed tears of the transverse atlantal ligament on cervical MRI and measure several parameters of atlanto-axial alignment on cervical CT, including the anterior atlantodens interval, to determine which method is most sensitive in predicting transverse atlantal ligament injury. Methods Adult trauma patients who suffered a transverse atlantal ligament tear on cervical MRI were identified retrospectively. The cervical CT and MRI exams for these patients were reviewed for the following: anterior and lateral atlantodens interval widening, lateral C1 mass offset, C1–C2 rotatory subluxation, and transverse atlantal ligament injuries on cervical MRI. Results Twenty-six patients were identified with a tear of the transverse atlantal ligament on cervical MRI. Twelve percent of these patients demonstrated an anterior dens interval measuring greater than 2 mm, 26% of patients demonstrated lateral mass offset of C1 on C2 (average offset of 2.4 mm), 18% of patients demonstrated an asymmetry greater than 1 mm between the left and right lateral atlantodens interval, and one patient demonstrated atlanto-axial rotation measuring greater than 20%. Ten patients had an accompanying C1 burst fracture and eight patients had a C2 fracture. One patient demonstrated widening of the atlanto-occipital joint space greater than 2 mm indicative of craniocervical dissociation injury. Conclusions An anterior atlantodens interval measuring greater than 2 mm is an unreliable methodology to screen trauma patients for transverse altantal ligament injuries and atlanto-axial instability. Moreover, C1 lateral mass offset, lateral atlantodens asymmetry, and atlanto-axial rotation were all poor predictors of transverse atlantal ligament tears.
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