Trauma

10.1055/b-0034-102686

Trauma

In regard to the mechanisms of spine injury, and in particular referencing the cervical spine, flexion injuries lead to anteriorly wedged vertebral body fractures ( Fig. 3.39 ). In a severe flexion injury there can be disruption of the posterior longitudinal ligament and the interspinous ligaments ( Fig. 3.40 ), facet distraction, and anteroposterior subluxation (posterior ligament complex disruption). In the most severe cases, bilateral facet dislocation can occur. Extension injuries lead to posterior element fractures, and in a severe extension injury there can be disruption of the anterior longitudinal ligament and subluxation. In axial load injuries (e.g., from diving into shallow water), vertebral body compression (burst) fractures and lateral element fractures occur ( Fig. 3.41 ).

**Fig. 3.39** Hyperflexion injury with vertebral body fractures and posterior soft tissue injury. There is extensive abnormal high signal intensity in the posterior paraspinous musculature/ligamentous complex (*), consistent with a more severe flexion injury. There is minimal loss of height (and anterior wedging) of the C7 vertebral body with abnormal high signal intensity in the superior portion, consistent with an acute compression deformity. A similar injury involves the superior portion of T3 (*arrow*). Beginning at the C6–C7 level and extending caudally, there is a large posterior extradural fluid collection. This had the signal intensity characteristics of CSF on all pulse sequences, and was felt to represent an extradural CSF collection due to a dural tear.

**Fig. 3.40** Interspinous ligament injury. On CT, this injury is visualized only indirectly by widening of the interspinous distance (*). On MR, edema within the ligament can be directly visualized (*arrow*), with the extensive posterior paraspinous edema/hemorrhage an additional indication of the severity of the injury in this patient.

**Fig. 3.41** Traumatic C3 burst fracture. An axial load injury has resulted in a burst fracture of C3, with mild loss of height and edema seen throughout the vertebral body. A vertically oriented, fracture plane is seen on the sagittal T2-weighted image extending through the C3 vertebral body. Retropulsion of the posterior portion of the C3 vertebral body into the spinal canal results in mild spinal canal compromise with mild cord flattening. There is no evidence of cord edema in this region. Edema in the posterosuperior portion of the C4 vertebral body is consistent with an additional acute fracture. Prevertebral soft tissue edema (only partially depicted) extended from the skull base to the C4 level.

In high velocity auto accident injuries, axial load injury may result in compression of multiple contiguous vertebral bodies, in particular involving the thoracic spine ( Fig. 3.42 ). Rotational injuries rarely occur in isolation, rather typically with flexion, and result in lateral mass fractures and unilateral facet subluxations or dislocations.

**Fig. 3.42** Compression fractures, acute (traumatic), thoracic spine (MR). Edema within the superior half of every visualized thoracic vertebral body is consistent with microfractures, with the clinical history being that of a motor vehicle accident with an axial load injury. Note that the edema is better demonstrated on the T2-weighted image with fat saturation (as abnormal high signal intensity), for example within T12 (*white arrow*) than on the T1-weighted spin echo scan (with low signal intensity). This difference is accentuated due to the age of the patient, 17 years old, with a predominance of hematopoietic marrow. There is mild loss of vertebral body height at T11 with a suggestion of a discrete fracture line (*black arrow*) and minimal retropulsion. There is no significant spinal canal compromise at any level. There is minimal loss of vertebral body height involving the superior portion of the T8 and T10 vertebral bodies.

Fractures can be classified as stable or unstable on the basis of the three-column concept. The anterior column is defined as the anterior two-thirds of the vertebral body, the middle column the posterior one-third, and the posterior column extending from the posterior vertebral body margin to the tip of the spinous process. Injury of two of the three columns, or the middle column, is considered an unstable fracture. CT with multiplanar reformatted images is critical for the evaluation of osseous injury (including the assessment of bony canal compromise and the presence of bone fragments therein), with MR extremely valuable for evaluation of the spinal cord and injuries involving, or in which the important element is, soft tissue (e.g., an epidural hematoma, or acute disk herniation). Acquisition of T2-weighted scans with fat suppression (or alternatively the use of STIR) is important for the demonstration of marrow edema (and improved detection, as compared to CT, of vertebral body microfractures) and soft tissue injury (e.g., involving the paraspinal musculature). Although marrow edema is commonly seen on MR in acute fractures, it is not always present. In the cervical spine on CT, review of high-resolution reformatted sagittal and coronal images is mandatory, in addition to thin section (source) axial images.

Cervical Spine Trauma

Specific osseous injuries in the cervical spine are subsequently discussed. Atlantooccipital dislocation (dissociation) occurs due to disruption of the ligaments between the occiput and C1. Increased distance is seen on coronal and sagittal reformatted CT images between the occipital condyles and the lateral masses of C1. MR visualizes both this finding and edema in the region of the disrupted stabilizing ligaments, reflecting the ligamentous injury itself. Atlantooccipital dislocation is often fatal. A Jefferson fracture is a burst fracture involving both the anterior and posterior arches of C1 (the atlas) ( Fig. 3.43 ). Unless the transverse atlantal ligament is disrupted, the patient is usually neurologically intact. Odontoid fractures occur with both flexion and extension injuries, and are primarily transverse in orientation (and thus can be difficult to detect on axial images). They are classified according to the location of the fracture line. Type I involve the upper portion of the odontoid ( Fig. 3.44 ), type II involve the junction of the odontoid and the body of C2 (these are the most common, and have the highest rate of nonunion), and type III extend into the body of C2 ( Fig. 3.45 ).

**Fig. 3.43** C1 fracture. Because C1 is a ring, when fractured there will typically be at least two fracture lines (as in this instance, with fractures of both the anterior [*black arrow*] and posterior [*white arrow*] arches). The Jefferson fracture, of which this is an example, is a burst fracture due to axial loading.

**Fig. 3.44** Type I odontoid fracture. There is a mildly distracted fracture involving the tip of the odontoid, seen on sagittal and coronal reformatted images. A type I fracture involves only the superior portion of the dens, as distinguished from a type II fracture that involves the base of the dens (not illustrated). In this patient, there is likely an additional atlantoaxial dissociation injury, with increased distance between the articular facets of C1 and C2 on the right.

**Fig. 3.45** Type III odontoid fracture. In type III, the fracture extends into the body of C2 (*black arrow*), as illustrated on a coronal reformatted image.

A Hangman fracture is a bilateral fracture of the C2 ring, which has many variants ( Fig. 3.46 ). The pedicles and even the vertebral body may be involved. Extension of the fracture into the transverse foramen, as with all such fractures, raises the question of damage to the vertebral artery. The C2 vertebral body will be displaced anteriorly relative to C3—sometimes this is minimal—(but with the laminae still aligned) on the lateral plain film, and on sagittal CT or MR. As opposed to other fractures of the cervical spine that often compromise the spinal canal, these fractures often widen the canal and neurologic symptoms may be absent or minimal (autodecompression). A Clay-shoveler fracture is an avulsion fracture of a spinous process, involving a lower cervical or upper thoracic vertebra, classically C6 or C7 ( Fig. 3.47 ).

**Fig. 3.46** Traumatic spondylolisthesis of C2 (hangman fracture). Sagittal images reveal coronally oriented fractures (*arrows*) bilaterally of the pars interarticularis of the axis (C2). In this instance there is little displacement or angulation.

**Fig. 3.47** Clay-shoveler fracture. Sagittal and axial CT images (**part 1**) depict a slightly displaced acute fracture of the C7 spinous process. Note the very sharp discontinuity of cortical bone, best seen on the axial section, defining this fracture as acute. On sagittal MR (**part 2**), the fracture of the spinous process can be identified (*white arrow*), but is more difficult to detect than on CT. Note the relative absence of edema within the bone adjacent to the fracture line, a common but nonintuitive finding in acute trauma. What CT does not depict however is the extensive nature and severity of the injury, reflected by the diffuse edema in the posterior paraspinal tissues (*) and the prevertebral edema/fluid (*black arrow*).

A teardrop fracture occurs due to flexion in combination with axial compression, resulting in a fracture involving the anteroinferior aspect of a cervical vertebral body ( Fig. 3.48 ). Bilateral facet fractures or dislocation occur due to flexion. A unilateral facet fracture involves both flexion and rotation. Vertebral body compression fractures can occur due to flexion ( Fig. 3.49 ). Hyperflexion typically involves injury to the posterior musculature and posterior ligamentous complex (detected in part on MR due to the accompanying edema), together with facet fracture/subluxation/dislocation ( Figs. 3.50 and 3.51). If the injury to the posterior paraspinal musculature is unilateral, the injury involved flexion with rotation.