CHAPTER SYNOPSIS:

Spinal deformity resulting from spinal trauma may be acute or chronic. In cases resulting in acute spinal cord injury, surgical correction of the deformity may be one component of the overall treatment plan. In the neurologically intact patient, decisions regarding correction can be more complicated. In cases of minor deformity, long-term sequelae of resulting kyphosis must be considered. In more significant late deformities, the risk for the often extensive soft tissue and bony releases necessary factor into the decision. This chapter illustrates these factors and the management of such cervical spine deformities.

IMPORTANT POINTS:

Most Common Injury Types Resulting in Cervical Spine Deformity

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  Compression fractures

  
  
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  Flexion-compression injuries (teardrop fractures)

  
  
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  Cervical burst fractures

  
  
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  Facet dislocations

Surgical Goals

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  Decompress the neural elements

  
  
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  Realign the spine

  
  
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  Restore stability

Surgical Approaches

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  Anterior or posterior depending on the primary goal, as well as the anatomy involved

  
  
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  The more chronic the deformity, the more likely a combined anterior and posterior approach will be necessary

SURGICAL PEARLS:

Anterior Approach

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  This approach is best for posttraumatic kyphosis correction.

  
  
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  Multilevel discectomy is useful for postlaminectomy kyphosis.

  
  
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  If the deformity is secondary to a vertebral body fracture, corpectomy is useful.

  
  
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  If greater than 20 degrees of correction is made, we prefer to add posterior stabilization and fusion.

Posterior Approach

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  A posterior approach is highly effective for treating chronically dislocated facet joints.

  
  
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  If alignment can be achieved but not maintained, lateral mass screw fixation is helpful.

SURGICAL PITFALLS:

Anterior Approach

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  Caution should be used not to fracture the end plates during the distraction process.

  
  
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  Spinal cord signals should be assessed before and after distraction maneuvers.

  
  
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  The surgeon should be prepared to perform posterior surgery if the reduction cannot be achieved or maintained.

Posterior Approach

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  Posterior surgery alone is not ideal for correction of cervical kyphosis.

  
  
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  Anterior discectomy and grafting is necessary if the reduction is not acceptable or a large disc herniation is noted on preoperative magnetic resonance imaging.

VIDEO AVAILABLE:

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INJURY TYPES

A number of injury types have a propensity to lead to posttraumatic kyphosis, particularly after nonoperative treatment. Compression fractures can be defined as fractures that lead to vertebral body height loss predominantly within its anterior portion. As the posterior vertebral body is largely intact, this can lead to acute angulation at the fracture site. If the posterior ligamentous complex (PLC), composed of the ligamentum nuchae, interspinous ligaments, and facet capsules, is intact, the chance for substantial amounts of kyphosis (more than 11 degrees) is low. If a patient has a benign-appearing compression fracture and a greater degree of kyphosis, the surgeon should strongly suspect a PLC injury. With PLC disruption, the injury would more accurately be described as a stage 3 flexion-compression injury as denoted by Allen et al.

High-energy (stage 4 and 5) flexion-compression injuries (also known as teardrop fractures ) almost invariably present with large degrees of kyphosis. This is usually accompanied by some degree of posterior translation (i.e., retrolisthesis) of the fractured vertebra on the subjacent vertebra. This plane of deformity does not necessarily affect overall spinal balance. More importantly, it is a sign that circumferential ligamentous disruption has occurred, and that the injury is mechanically unstable. Furthermore, retrolisthesis of bone can lead to canal compromise that may cause spinal cord compression.

Cervical burst fractures can also be associated with kyphosis. Though some confusion exists about the precise definition, for the purposes of this chapter, a burst fracture is defined as a comminuted vertebral body fracture with retropulsion of an independent fragment of bone from the posterior vertebral body wall. This should be distinguished from retrolisthesis. Burst fractures may or may not be associated with PLC disruption. As with most injuries, if the PLC is incompetent, then kyphosis can result.

Facet dislocations cause an immediate radiographic spinal deformity. They are thought to be caused by a flexion-distraction mechanism. Bilateral facet dislocations can have some kyphosis, but more predominantly, large translational deformities. Typically, more than 50% anterior translation of the dislocated vertebra on the subjacent one occurs. This injury can occur only if the PLC, facet capsule, posterior longitudinal ligament (PLL), and intervertebral disc have been disrupted. The only structure that could remain intact is the anterior longitudinal ligament (ALL). Bilateral facet dislocations are grossly unstable; as such, they are usually readily reducible with traction or intraoperative maneuvers. Unilateral facet dislocations are associated with more subtle deformity and are frequently missed. They usually exhibit less than 20% of vertebral body translation. Because it is a unilateral injury, the apparent translational deformity is actually a rotational malalignment. Unilateral facet dislocation can occur without substantial injury to the PLC, and thus are more difficult to reduce by either closed or open means.

Importantly, flexion-distraction can lead to PLC and facet capsule injury without facet dislocation. Subluxations often present with more kyphosis than frank dislocations. These injuries can also “self-reduce” before presentation in which initial radiographs and computerized tomograms (CT) may reveal little or no fracture or deformity. When suspected, a magnetic resonance image (MRI) is the modality of choice to detect soft-tissue or disc disruption. Scrutiny of these images to detect PLC disruption may be indication to acutely stabilize to avoid late-onset kyphosis, dislocation, and/or neurologic decline.

Other injuries are less likely to result in substantial deformities. Extension-type injuries, though often associated with spinal cord injury from spondylotic stenosis, infrequently result in a deformity that is not well tolerated. Upper cervical injuries, such as C1 burst (Jefferson) fractures and odontoid fractures, can be associated with obvious radiographic malalignment; however, these infrequently result in symptomatic cervical kyphosis because of compensation of the uninjured segments below.

PERTINENT ANATOMY

A number of structures should be well understood for optimal treatment decision making for posttraumatic cervical deformities. Paradoxically, it is disruption of one or more these structures that leads to the acute deformity, whereas contraction of another apposing structure that makes them fixed deformities over time.

The ALL spans the anterior disc spaces and vertebral bodies. It is a checkrein to cervical extension. The PLL spans the posterior vertebral body and disc spaces. As it is located closer to the axis of rotation, it is acts more as a checkrein to distraction. The PLC is a complex of structures, as described earlier, that acts as a checkrein to flexion. Disruption of one or more of these important ligamentous structures can affect their delicate balance and lead to instability.

In addition to supplying anchoring points for the spinal musculature and ligaments, the cervical vertebrae serve as the weight-bearing columns that support the head and neck. These structures can be thought of as so-called columns. The vertebral can be considered the anterior column, the two facet joints a right and left column, and the laminae and spinous process the posterior column. The vertebral body sustains primarily compressive loads. The facet joints can sustain some axial loads but primarily resist anterior translation. The posterior column sustains no axial or translation loads.

With an acute trauma, kyphosis can result from a variety of sources. With incompetence from a fracture, the vertebral body loses its ability to resist anterior compression, which can lead to kyphosis. PLC disruption can also lead to kyphosis from loss of the posterior tension band effect of the ligaments. If a kyphotic deformity has been present for a long period, the ALL can contract. Although this so-called healing may provide some stability, it also leads to a fixed misalignment of the spine. Similarly, chronically dislocated facet joints can be “fixed” in this position by contraction and fibrous scarring of the associated periarticular ligaments. Understanding of the contribution of these different structures to the deformity can direct the surgical approach for correction.