Summary Cervical lateral mass fracture separations of the lateral mass-facet are uncommon cervical spine injuries characterized by a high degree of instability and neurologic deficits Diagnosis is made using a CT scan of the cervical spine Treatment usually involves posterior decompression and two-level instrumented fusion Epidemiology Demographics male:female ratio 2:1 mean age 35 y/o (20-70 y/o) Anatomic location C6 > C5 > C7 > C4 > C3 Etiology Pathophysiology mechanism of injury traffic accident, fall, or heavy object landing on the head hyperextension, lateral compression, and rotation of the cervical spine Associated conditions instability affects 2 levels due to involvement of the superior and inferior facets on either side of the fractured articular mass anterior translation (listhesis) fractured vertebrae (77%) superior adjacent vertebrae (24%) inferior adjacent vertebrae (10%) coronal translation (33%) vertebral body collapse (33%) less common in type A separation fracture subtypes Classification Kotani classification Kotani Classification Fracture Type Fracture Description Rates of Anterior Translation (Same Level) Rates of Anterior Translation (Adjacent Level) Type A: Separation fracture Two fracture lines in unilateral lamina and pedicle 91% 20% Type B: Comminution type Multiple fracture lines with lateral wedging in the coronal plane 50% Type C: Split type Vertical fracture line in the coronal plane with invagination of the superior articular process of the caudal vertebra 80% 0% Type D: Traumatic spondylolysis Bilateral horizontal fracture lines of the pars interarticularis, leading to separation of the anterior-posterior spinal elements 100% 50% Presentation History common mechanisms (Allen and Ferguson classification) extension-compression lateral flexion results in type B comminuted subtype flexion-distraction Symptoms neurologic symptoms common (up to 66%) radicular pain, radiculopathy, or spinal cord injury/myelopathy can be classified by Frankel grade or ASIA impairment scale Physical exam inspection torticollis and/or paravertebral muscle spasm neurovascular radicular pain and numbness myelopathy Imaging Radiographs recommended views AP, lateral, and oblique findings disc space narrowing often difficult to detect on plain radiographs instability >3.5 mm displacement >10° kyphosis >10° rotation difference compared with adjacent vertebra sensitivity and specificity low sensitivity 38% identified on plain radiographs CT indications further evaluation of fracture morphology fracture line can extend: rostrally/caudally into adjacent superior/inferior facets ventrally into foramen transversarium, transverse process, and pedicle dorsally into lamina findings translation of fractured/adjacent vertebrae in sagittal and coronal planes uncovertebral joint subluxation degree of vertebral body destruction MRI findings disruption of ligaments 50-75% rupture of anterior longitudinal ligament (ALL) 30-35% disruption of posterior longitudinal ligament (PLL) 10-75% disruption of interspinous and supraspinous ligaments (ISL and SSL) disruption of intervertebral disc bone bruising Treatment Nonoperative NSAIDs, rest, and immobilization indications stable injuries without neurologic deficit hyperextension/rotation deformities are poorly immobilized in a halo techniques Miami J collar halo vest outcomes long-term results of nonoperative treatment are less favorable may be successful in the absence of instability surveillance is necessary to detect late instability and persistent pain spontaneous fusion rate is only 20% Operative posterior decompression and two-level instrumented fusion indications most cases preferred approach, as main injured structures are posterior nonoperatively managed cases with late instability and persistent pain techniques two-level lateral mass or pedicle screw and rod fixation lateral mass plating outcomes risk of anterior disc space collapse and late kyphotic deformity midline fusion does not control rotation two-level ACDF indications minimally displaced injuries where posterior approach is unnecessary to obtain direct reduction techniques controls anterior collapse and rotation iliac crest bone graft single posterior pedicle screw indications type A separation fracture without instability anterior and posterior decompression and fusion indications if additional anterior column support is needed if anterior approach is initially attempted with unsuccessful reduction (due to complicated fracture morphology or late presentation) Complications Vertebral artery injury from pedicle screw placement Late kyphotic deformity Late instability (anterior translation) Chronic neck pain Radiculopathy