Subaxial spine trauma: radiological approach and practical implications

The cervical spine is part of the axial skeleton and is responsible for protecting vital structures, such as the spinal cord and the vertebral arteries and veins. Traumatic injury to the cervical spine occurs in approximately 3% of blunt trauma injuries, and approximately 80% are below the level of C2. The AO Spine society divides the spine into four segments: the upper cervical spine (C0-C2), subaxial spine (C3-C7), thoracolumbar spine, and sacral spine. Various classifications have been proposed for the subaxial segment since that of Allen and Ferguson in 1982; however, none is universally accepted, and treatment remains controversial. The complex anatomy and biomechanics of the subaxial spine and the lack of a widely accepted classification system make these injuries difficult to evaluate on imaging. The Subaxial Injury Classification System (SLIC) uses fracture morphology, the integrity of discoligamentous complex, and neurological status to score the patient and determine between operative and non-operative management; however, other factors may influence management, such as time for immobilisation, osteoporosis, surgeon's experience, and hospital circumstances. SLIC classifies fracture morphology in a crescent order of severity based on Allen and Ferguson's classification. Compression fractures are the simpler ones, while both distraction injuries and translation/rotation are severe injuries, which are always associated with some degree of discoligamentous complex (DLC) injury. This article will review the indications for imaging, the basis of the SLIC classification, the different types of fracture morphology, evaluation of the DLC, and other features important in decision making in subaxial spine trauma.