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Chapter Summary
• Context: Traumatic injuries of the subaxial cervical spine (C3–C7) represent the majority of all cervical fractures and dislocations, accounting for substantial morbidity and traumatic quadriplegia in young active individuals (high-energy motor vehicle crashes, diving accidents) and elderly patients (low-energy ground-level falls on degenerative, stenotic spines). The subaxial spine combines wide range of motion with mechanical load bearing; acute traumatic failure involves complex combinations of axial compression, flexion, extension, rotation, and distraction. Injuries range from stable compression fractures to catastrophic distractive flexion injuries, unilateral or bilateral facet subluxation/dislocation ("locked facets"), and burst fractures with traumatic cord compression. Systematically evaluating mechanical stability relies on assessing the three columns and the integrity of the Posterior Ligamentous Complex (PLC: supraspinous and interspinous ligaments, ligamentum flavum, and facet capsules) and the anterior/posterior longitudinal ligaments. Modern classification systems—predominantly the AO Spine Subaxial Cervical Spine Injury Classification and the Subaxial Injury Classification (SLIC) score—integrate fracture morphology (Type A compression, Type B tension band/distraction, Type C translation/displacement, and Type F facet injuries), PLC status, neurological examination (N0–N4, Nx), and clinical modifiers (M1–M4). Multi-detector CT defines bony fracture morphology and facet apposition, while urgent MRI evaluates traumatic disc herniations, spinal cord edema/hemorrhage, and ligamentous disruption. Treatment strategy—closed traction reduction, anterior cervical discectomy and fusion (ACDF), posterior instrumented reduction and lateral mass/pedicle screw fusion, or combined circumferential stabilization—depends on cord compression, facet reduction, traumatic disc status, and construct biomechanics.
• Chapter Objective: To present the clinical evaluation, classification, biomechanical stability assessment, and surgical/non-operative management of subaxial cervical spine trauma (C3–C7). The reader should be able to apply the AO Spine and SLIC classification systems; recognize stable versus unstable injury patterns; assess facet joint subluxation and locked facet morphology; evaluate the role of urgent closed reduction vs. operative reduction in facet dislocations; recognize the danger of extruded traumatic disc herniations during reduction; and select anterior, posterior, or circumferential surgical approaches.
• Anatomy, Biomechanics, and Injury MechanismsThe subaxial cervical spine (C3–C7) features lordotic alignment, oblique facet joints (angled ~45° in the sagittal plane), uncovertebral joints of Luschka, and transverse foramina transmitting the vertebral arteries. The three-column concept and tension band integrity govern stability. Primary injury mechanisms include: 1) Compression/Axial loading (AO Type A): minor compression (A1/A2), burst fractures (A3 incomplete, A4 complete burst with retropulsion); 2) Distraction/Tension band failure (AO Type B): anterior tension band failure in hyperextension (B1/B3) or posterior tension band disruption in hyperflexion (B2); 3) Translation/Displacement (AO Type C): mechanical dislocation or subluxation in any plane; 4) Facet Injuries (AO Type F): F1 nondisplaced facet fracture, F2 displaced facet fracture, F3 floating lateral mass, F4 facet subluxation/dislocation (unilateral or bilateral locked facets).
• Classification Systems: AO Spine Subaxial and SLIC ScoreThe AO Spine Subaxial classification organizes injuries hierarchically by morphology (Types A, B, C, F), neurology (N0 intact, N1 transient, N2 radiculopathy, N3 incomplete cord, N4 complete cord, Nx unexaminable), and modifiers (M1 PLC indeterminate, M2 disc herniation, M3 metabolic/ankylosing disease, M4 vertebral artery injury). The Subaxial Injury Classification (SLIC) score grades three independent categories: 1) Fracture morphology (0–4 points: no abnormality = 0, compression = 1, burst = 2, distraction = 3, translation/rotation = 4); 2) Neurological status (0–4 points: intact = 0, root = 1, complete cord = 2, incomplete cord = 3, continuous cord compression +1); 3) PLC integrity (0–2 points: intact = 0, indeterminate = 1, disrupted = 2). A total SLIC score <=3 indicates non-operative management (rigid cervical collar); SLIC = 4 is equivocal; SLIC >=5 mandates surgical stabilization.
• Facet Dislocations and the Traumatic Disc DilemmaFacet subluxation and bilateral/unilateral locked facets (AO F4 / Type C) represent severe translation injuries with complete disruption of the posterior tension band and intervertebral disc. In awake, cooperative patients with bilateral locked facets and incomplete neurological deficits, immediate closed skeletal reduction with Gardner-Wells tongs (starting with 5 kg and adding 2–3 kg per level under continuous fluoroscopic and neurological monitoring) can rapidly decompress the spinal canal. However, pre-reduction MRI (or emergent intraoperative exploration) is vital because an extruded traumatic disc herniation retropulsed behind the displaced vertebral body can cause catastrophic spinal cord transection during closed or open posterior reduction maneuvers. If a massive extruded disc herniation is present on MRI, anterior cervical discectomy and decompression must precede facet reduction.
• Surgical Decision-Making and Operative ApproachesSurgical approach is tailored to pathology: 1) Anterior approach (ACDF or corpectomy with anterior plating): ideal for teardrop fractures, burst fractures (A3/A4) with anterior cord compression, and facet dislocations with herniated traumatic discs; 2) Posterior approach (lateral mass screw fixation C3–C6, pedicle screw fixation C7): preferred for highly unstable posterior tension band disruptions (B2), irreducible locked facets, floating lateral masses (F3), or ankylosing spondylitis fractures; 3) Combined 360° circumferential stabilization: required for severe multi-column comminution, severe osteopenia, or severe three-column dissociation.
• Clinical Application: In the emergency trauma center, managing subaxial cervical trauma requires immediate assessment of neurological status and facet alignment on CT. In an alert patient presenting with bilateral locked facets and acute quadriparesis, emergent closed reduction under conscious sedation or emergent operative reduction within 4 hours restores canal diameter and provides the highest chance of neurological recovery. If the patient is obtunded or if MRI shows an extruded herniated disc fragment lodged behind the dislocated vertebral body, perform an emergent anterior cervical discectomy first to remove the disc fragment, followed by anterior reduction and plating (or posterior instrumentation if anterior reduction fails). In geriatric patients presenting with central cord syndrome following minor hyperextension trauma without fracture (AO B3/M3), urgent MRI demonstrates cord edema and preexisting canal stenosis, guiding early decompressive surgery (<24 hours). In patients with facet fractures involving the transverse foramen (AO M4), obtain CT Angiography of the neck to evaluate vertebral artery occlusion or dissection.
