A true flexion teardrop fracture appears as a small fractured bony fragment at the anteroinferior border of the vertebral body. Generally, these occur at mid-cervical levels, and are three-column injuries with anterior column fractures, disruption of the posterior longitudinal ligament, and facet disruption. On plain radiographs, this injury is best seen on lateral view, with kyphosis and anterolisthesis at the affected level. The most common radiographic features also include prevertebral soft tissue swelling, a triangular anterior vertebral body avulsion fracture (teardrop fragment), posterior vertebral body subluxation, possible vertebral body displacement into the spinal canal, and spinous process fracture.
Flexion teardrop fractures are the most severe injuries to the cervical spine. They are caused by hyperflexion of the neck with additional compressive forces that result in disruption of the posterior ligaments. Flexion teardrop fractures are highly unstable fractures and may be associated with spinal cord injury in up to 50% of cases. Treatment may include rigid c-collar in certain patient populations that have minimal fracture displacement, minimal kyphosis, no neurologic symptoms, and no posterior longitudinal ligament injury. Otherwise, treatments include a halo or operative intervention.
Figure 11.1 Flexion Teardrop Fracture.
Cross-table lateral radiograph of the cervical spine shows a flexion teardrop injury at the C5 level. In addition to the fracture of the anterior, inferior aspect of the C5 vertebral body, there is disruption of the facet joints, with widening and malalignment of the posterior elements between C4 and C5.
Extension corner avulsion fractures result from avulsion of the anterior longitudinal ligament from the inferior margin of C2, and are a result of extreme hyperextension. These fractures are sometimes referred to as “extension teardrop” injuries, due to the triangular fracture fragment produced, but should be distinguished from the flexion teardrop fracture pattern. In extension corner avulsion fractures, the alignment of the posterior aspect of the vertebral bodies and the posterior elements remain normal, and thus it is a single-column fracture. On plain radiographs, this fracture is best seen on lateral views and is frequently associated with prevertebral soft tissue swelling.
Extension corner avulsion fractures are the result of severe hyperextension of the neck. This injury most commonly occurs during MVCs or diving accidents. Extension corner avulsion fractures may be unstable in extension. Treatment is usually conservative with a rigid cervical collar. Surgical treatment is rarely needed, but may be necessary if there are more complex injury patterns involving the posterior longitudinal ligament.
Extension corner avulsion or “extension teardrop” fractures are most common at C2.
Distinguish extension corner avulsion fractures from the more ominous flexion teardrop fractures by the lack of posterior element involvement in extension corner injuries.
Figure 11.4 Extension Corner Avulsion Fractures.
A: Lateral cervical spine radiograph demonstrates a triangular fracture fragment arising from the anterior inferior endplate of C2 (arrow) and prevertebral soft tissue swelling. Notice that the alignment of the posterior vertebral body cortex remains normal in this single-column injury. B: The reformatted sagittal CT images in the same patient redemonstrate the extension injury fracture and normal middle and posterior column alignment.
Anterior subluxation injuries occur when the posterior ligaments are torn and disrupted as a result of hyperflexion. This injury is most common at lower cervical levels and can result in kyphosis at the level of injury, anterior displacement of the involved vertebra (<25% the diameter of the vertebral body), displacement of the articulating facets, anterior narrowing and posterior widening of the disk space, and increased interlaminar/interspinous distances. As the injury progresses from less to more severe, ligamentous disruption can be accompanied by unilateral or bilateral perched and then jumped facets. Anterior subluxation is best appreciated radiographically on lateral radiographs, however, MRI is a far more sensitive modality for detecting ligamentous injury not accompanied by significant bony displacement. Some anterior subluxation injuries are radiographically occult.
Figure 11.5 Anterior Subluxation Injury.
A: Lateral radiograph of the cervical spine demonstrates subtle interlaminar widening at the C5–6 interspace (arrow) in this patient with a hyperflexion strain injury. B: Sagittal T2-weighted MR image in the same patient demonstrates disruption of the ligamentum flavum at the C5–6 level (arrow), with a small post-traumatic disk bulge.
Anterior subluxation injury occurs after forceful hyperflexion of the spine. It is rarely associated with neurologic injury. This injury is generally regarded as stable since the anterior column ligaments remain intact. However, there is a risk of delayed instability with significant displacement when the neck is flexed and therefore, these injuries should be regarded as potentially unstable. Surgical intervention may be required to prevent delayed neck instability.
Nontraumatic anterior subluxation can occur in rheumatoid arthritis and is most common at C5/6.
In children, there is a physiologic anterior subluxation of C2 on C3 due to ligamentous laxity (pseudosubluxation). Pseduosubluxation exists if the spinolaminar line drawn between C1 and C3 intersects or is within 2 mm anterior to the C2 spinolaminar line.
Figure 11.6 Anterior Subluxation Injury.
MRI of the cervical spine in a different patient shows marrow edema in the C6 spinous process, as well as increased T2 signal in multiple interspinous spaces. Ligamentum flavum disruption is visible at C6–7. The interspinous signal denotes a hyperflexion sprain injury (whiplash).
In a unilateral facet dislocation injury (unilateral “locked” or “jumped” facet), the posterior ligaments are disrupted due to flexion and rotation. One of the inferior articular facets of the upper vertebra moves superior and anterior to the superior articular facet of the lower vertebra, coming to rest in the intervertebral foramen. On lateral views, the involved vertebra will be displaced anteriorly 25-50% the diameter of the vertebral body, and rotational deformity may be visible. Oblique radiographs may help further assess facet malalignment. AP view will show offset of the line connecting the spinous processes. Look for a “naked” facet on axial CT imaging. Fractures of involved facet tips may occur in association with this injury.
Unilateral facet dislocation usually occurs following a rotational injury combined with forward or lateral flexion of the neck. This injury is also referred to as a unilateral “locked facet.” Neurologic impairment is uncommon. Unilateral facet dislocations are generally stable injuries since the vertebrae are “locked” into place, however, more complex facet fracture patterns may be present, increasing the potential for instability and delayed neurologic injury. These patients are usually treated with halo traction to reduce the facet dislocation and restore alignment.
If neurologic impairment is present, it is usually a peripheral nerve injury secondary to impingement at the intervertebral foramen.
Anterior subluxation injury, unilateral facet dislocation, and bilateral facet dislocation are on a spectrum from mild to more severe anterolisthesis on lateral radiographs.
Figure 11.7 Unilateral Facet Dislocation.
Lateral view of the cervical spine demonstrates a unilateral facet dislocation at the C4–5 level. Note the malalignment of the facet articulation (arrow), and 25% anterolisthesis at C4–5. A rotational deformity is present at the site of injury, typical of unilateral facet dislocations. Vertebrae above the level of injury appear in true lateral projection, while more inferior levels demonstrate rotation. (Image contributor: Jake Block, MD.)
Figure 11.8 Unilateral Facet Dislocation.
A-C: Sagittal reconstructed CT images from a trauma series show normally reduced facet articulations on one side (A). The midline CT image (B) demonstrates the involved C4 vertebral body displaced 25% with respect to C5 inferiorly, typical of unilateral facet dislocation. (C) CT reconstructed sagittal images through the contralateral facet joints show the inferior articular facet of C5 displaced anterior to the superior articular facet of C5, thus a unilateral jumped facet (given the reduced contralateral articulation).
In a bilateral facet dislocation (bilateral “locked” or “jumped” facets), the anterior longitudinal ligaments, annulus fibrosus, and posterior ligamentous complex are injured. This allows both of the inferior articular facets of the superior vertebra to move anterior to the superior articular facets of the inferior vertebra. On lateral view, there is a displacement of greater than 50% of the AP diameter of the vertebral body, and abrupt kyphosis at the affected level. On AP view, there is widening of the interspinous distance at the injury level. On CT scan, the “naked facet” sign shows the uncovered articulating processes.
Bilateral facet dislocations occur after extreme neck flexion and anterior subluxation. This is an unstable injury since the integrity of all the stabilizing ligaments and articular facet joints is lost. Disk herniation can occur and contribute to spinal-cord impingement. Careful neurologic exam is imperative as neurologic deficits occur in approximately 75% of patients. Initial management includes closed reduction followed by surgical stabilization.
Unlike unilateral facet dislocations, bilateral facet dislocation injuries are distinguished by anterolisthesis of 50% or greater, and lack of rotational deformity at the level of injury.
CT is important to evaluate for associated facet and posterior arch fractures.
Figure 11.9 Bilateral Facet Dislocation.
A: Lateral radiograph with displacement of both inferior articular facets of C4 anterior to the superior articular facets of C5. Note 50% anterior displacement of C4 on C5, and the lack of rotational deformity typical of bilateral facet dislocation injuries. B-D: Sagittal reconstructed CT images through the cervical spine redemonstrate the severe hyperflexion related bilateral facet dislocation. Notice greater than 50% anterolisthesis of C4 on C5. E: An axial CT image through the bilateral dislocation shows four discrete round structures, the articular facets of C4 and C5, without normally anticipated anatomic overlap (“naked facet” sign).
The clay shoveler fracture is an avulsion fracture of the spinous process of any of the lower cervical or upper thoracic vertebra. The spinous process tip is displaced inferiorly. In a simple clay shoveler fracture, the vertebral bodies are normally aligned and the lamina is not affected. More extensive fracture patterns may extend to involve the lamina and spinal canal. This injury is best seen on lateral radiograph.
Patients with this type of fracture often present following a hyperflexion injury during contraction of the paraspinous muscles. This injury is classically seen after shoveling clay or snow, but may also occur during an MVC or forceful blow to the back. Pain is usually located between the shoulder blades. This is considered a stable fracture (unless the avulsion extends into the lamina) and the usual treatment is with a cervical collar.
Jefferson’s fracture is classically considered a four-part fracture of the C1 ring (atlas) with combined anterior and posterior arch fractures, although two and three-part fractures also occur. On plain radiographs, this fracture is best seen on an open-mouth odontoid view. On this view, the distance between the C1 ring lateral masses and odontoid process will be increased either unilaterally or bilaterally. In addition, there will be lateral displacement of the articular portion of the ring of C1 in relation to the lateral margin of C2. However, CT is still the most sensitive way to detect this fracture. Avulsion fractures of the transverse ligament from the inner ring of C1 indicates further instability.
Jefferson’s fracture occurs secondary to an axial load injury while the neck is in a neutral position. The most common mechanisms for this fracture are from a dive into shallow water, an impact against the roof of a vehicle in an MVC, or from a fall. These fractures are unstable. Treatment depends on the severity of fracture of the anterior arch and whether or not the transverse ligament is functionally intact. Treatment can include a rigid cervical collar, traction, a halo, or surgery.
A hangman’s fracture involves the fracture of both vertebral pedicles at C2 (axis) with or without translation of C2 on C3. It is also referred to as traumatic spondylolisthesis of the axis. This injury is classified into three types, which help stratify the degree of injury and guide treatment. The types are based on the degree of translation of C2 on C3 and associated amount of angulation with type 3 being the most severe. Any anterior translation of C2 on C3 seen on radiographs should prompt a CT even if no fracture is seen. Despite the appearance of anterior displacement and kyphosis at C2-3, these injuries are hyperextension injuries. This is often not an isolated fracture, with many patients having cervical spine injury at additional contiguous or noncontiguous levels.
This injury results from forceful hyperextension of the head with neck distraction. MVCs and falls are responsible for the majority of these injuries. Type 1 Hangman’s fractures are stable, types 2 and 3 are unstable. These fractures are unlikely to cause neurologic injury, except in type 3 fractures, where the likelihood of spinal cord injury is higher. Type 1 fractures are usually treated with a c-collar, type 2 fractures are usually treated with a halo vest, and type 3 fractures may require operative management.
Odontoid (axis) fractures occur at C2 and are classified into three types. Type 1 odontoid fractures occur at the tip of the odontoid process (dens) above the level of the alar ligaments (that connect the dens to the occiput). Type 2 odontoid fractures occur at the base of the odontoid process and type 3 odontoid fractures occur through the C2 vertebral body. These injuries may be evident on both the open-mouth odontoid radiograph, as well as the lateral projection of the cervical spine. Careful evaluation of the bone cortex of the anterior portion of the C2 vertebra on the lateral x-ray is critical for detecting subtle nondisplaced type 2 or type 3 fractures.
Flexion loading is the usual cause of injury; however, this injury can also occur from extension loading. These fractures usually occur following an MVC or fall. Type 1 odontoid fractures are stable and neurologic injury is uncommon since the alignment of C1 on C2 is maintained. Type 1 fractures are very rare, with many abnormalities occurring at the tip of the dens indicative of developmental variations (osodontoideum) rather than fractures. Type 2 odontoid fractures are unstable, prone to nonunion, and are more frequently associated with neurologic deficits. These are the most common type of odontoid fractures. Type 3 fractures may be comminuted and unstable and may be associated with neurologic injury if fragments are displaced. Management depends on the type of fracture and may include a c-collar, a halo vest, or operative intervention.
Figure 11.19 Type 2 Odontoid Fractures.
A, B: Lateral and open mouth odontoid views of the cervical spine show subtle disruption and step off at the base of the odontoid process (arrowheads) and a fracture plane through the base of the dens. C: Reformatted CT image in the coronal plane better illustrate the fracture line and show that the vertebral body is not involved.
Figure 11.20 Type 3 Odontoid Fractures.
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