Lower cervical spine injuries

1

What are some criteria used to classify subaxial cervical spine injuries?

Many different classification systems have been proposed for subaxial cervical spine injuries based on a range of criteria, including radiographic instability, mechanism of injury, and injury morphology. While recognition of instability based on radiographic parameters such as relative sagittal plane translation >3.5 mm or relative sagittal plane angulation >11° is useful in clinical practice, classifications based on such criteria have not been widely accepted. Classifications based on mechanism of injury have been popularized but are limited by the challenges inherent in inferring injury type based on static imaging studies. Recent classification systems for subaxial cervical injuries assess injuries based on review of cervical computed tomography (CT), which may be supplemented by magnetic resonance imaging (MRI) and occasionally plain radiography, and consider a range of factors including injury morphology, disruption of the disco-ligamentous complex, neurologic status, and the status of the facet joints.

2

How are subaxial cervical spine injuries classified on the basis of injury morphology?

The injury location and morphology are important factors to assess when classifying a subaxial cervical spine injury. The cervical spine has been conceptualized in terms of four columns: anterior column (anterior and posterior longitudinal ligaments, vertebral body, disc, uncinate processes, and transverse processes), right and left lateral columns (pedicle, superior and inferior facet joints, facet joint capsules, and lateral mass), and posterior column (lamina, spinous processes, ligamentum flavum, and the posterior ligament complex). (1) Injuries may be isolated (bony or ligamentous involvement of a single column) or complex (both bony and ligamentous involvement of single column or involvement of multiple columns). The Cervical Spine Injury Severity Score was developed to quantify the mechanical instability of subaxial cervical injuries and guide treatment. The severity of the bony or ligamentous injury to each column is graded on a scale from 0 to 5, with 0 being uninjured and 5 being the most severely injured. The sum of the scores for each of the four columns represents the Cervical Spine Injury Severity Score and may range from 0 to 20. Surgical treatment is generally indicated for injuries with severity scores greater than 7 while injuries with severity scores less than 5 are generally treated nonoperatively ( Table 57.1 ).

3

What is the subaxial cervical injury classification scoring system?

The Subaxial Cervical Injury Classification (SLIC) scoring system ( Table 57.2 ) added neurologic status as a factor to consider in the classification of subaxial cervical spine injuries (10). The SLIC scoring system analyzes three injury characteristics to guide classification and treatment:

• Injury morphology: The injury pattern on imaging studies is classified as no injury, compression injury, burst injury, distraction injury, or rotational/translational injury.

• Disco-ligamentous complex integrity: The integrity of the spinal column soft tissue constraints, including the disc, annulus, anterior and posterior longitudinal ligaments, facet capsules, and posterior ligaments, is evaluated and described as none, indeterminate, or disrupted.

• Neurologic status: Neurologic status is assessed and described as no injury, root injury, complete cord injury, incomplete cord injury, or continuous cord compression. Incomplete neurologic injury in the setting of persistent neural compression is most likely to benefit from surgical intervention and is associated with the highest score.

Lack of consensus regarding nomenclature for injury morphology and identification of injury to the osteoligamentous complex led to additional classification efforts.

4

How are lower cervical spine injuries stratified according to the AOSpine subaxial cervical spine injury classification?

The AOSpine Subaxial Cervical Spine Fracture Classification (2) builds on the classic AO-Magerl spine classification to address limitations of previous injury classifications. Injuries are stratified based on fracture morphology, facet joint injury, neurologic status, and case-specific modifiers. Injuries are first identified by injury level and morphology. The three main injury morphologies are: type A, compression injuries with an intact tension band; type B, anterior or posterior tension band injuries that occur through distraction; type C, injuries with translation along any axis. Type F is applied when the dominant injury pattern involves the facets. The injury level and type are used to identify the injury. When multiple injury types occur in the same patient, the injury with the highest severity determines the grade. Any additional injuries and any modifiers that are present are identified in parentheses (i.e., facet injury, neurologic status modifier, case-specific modifier).

• A.

  Injury types

  • Type A injury: Compression injury with an intact tension band

    • A0: Soft tissue injury or minor fracture involving the lamina, transverse process, or spinal cord injury without bony injury as often seen in a central cord syndrome

    • A1: Compression fracture involving a single endplate without involvement of the posterior vertebral wall

    • A2: Coronal split or pincer-type fracture involving both endplates without any involvement of the posterior wall of the vertebral body

    • A3: Incomplete burst fracture involving a single endplate with involvement of the posterior vertebral body wall

    • A4: Complete burst fracture or sagittal split involving both endplates with involvement of the posterior vertebral wall, but without disruption of the posterior tension band

  • Type B injury: Anterior or posterior tension band injury

    • B1: Monosegmental osseous failure of the posterior tension band extending into the vertebral body

    • B2: Posterior tension band injury affecting capsule/ligamentous structures (may involve any combination of bony, capsuloligamentous, or ligamentous structures)

    • B3: Anterior tension band injury with disruption or separation of anterior structures (bone or disc) without translation, which is limited by intact posterior elements

  • Type C injury: Injury with translation in any axis

  • Type F injury: Dominant injury pattern involves the facet joints

    • F1: Nondisplaced facet fracture with a fragment size of <1 cm, involving <40% of the lateral mass

    • F2: Facet fracture with a fragment size of >1 cm in size, involving >40% of the lateral mass or any displaced fracture fragments

    • F3: Floating lateral mass due to ipsilateral disruption of the pedicle and lamina, which dissociates the superior and inferior articular processes from the vertebral body

    • F4: Facet subluxation or perched/dislocated facets

• B.

  Neurologic status modifiers

  • N0: Neurologically normal

  • N1: Transient neurologic deficit

  • N2: Radiculopathy or cranial nerve injury

  • N3: Incomplete spinal cord injury

  • N4: Complete spinal cord injury

  • NX: Unexaminable patient

  • N+: Ongoing spinal cord compression

• C.

  Case-specific modifiers

  • M1: Posterior capsuloligamentous complex injury without complete disruption

  • M2: Critical disc herniation

  • M3: Stiffening or metabolic bone diseases such as ankylosing spondylitis (AS), diffuse idiopathic skeletal hyperostosis (DISH), ossification of the posterior longitudinal ligament (OPLL) or ossification of the ligamentum flavum (OLF)

  • M4: Signs of vertebral artery injury

( Fig. 57.1 )

5

Describe the options for nonoperative care of subaxial cervical spine injuries.

Nonoperative care with an orthosis is appropriate for nondisplaced or minimally displaced subaxial cervical injuries that appear stable and are not associated with neurologic deficits, and for patients who are unable or unwilling to undergo surgery. The most common type of orthosis used for treatment of subaxial cervical injuries is a rigid cervical orthosis (CO). Rigid COs have a two-piece construction and current designs include apertures for ventilation, adjustable mandible and occipital components, and are ideally fitted by an orthotist. Trauma extrication collars or Philadelphia-type collars applied in emergency settings are not adequate for longer-term use postinjury. Soft cervical collars do not provide meaningful motion control and are not adequate for treatment of acute cervical injuries requiring motion restriction. Cervical thoracic orthoses (CTOs) are prescribed when greater motion restriction is desired in the lower cervical region and across the cervicothoracic junction. CTOs utilize chin and occipital supports attached to the trunk via straps or rigid circumferential supports. An alternative for providing increased stabilization of the lower cervical and upper thoracic regions is the attachment of a CO to a thoracic vest. CTOs are less well accepted by patients than COs due to lack of comfort and a high incidence of skin breakdown associated with their use. The most rigid orthosis available is a halo skeletal fixator, but it is poorly tolerated by patients and is infrequently used today. In patients in whom nonoperative treatment is initiated, it is important to obtain upright radiographs to assess spinal alignment after orthosis fitting. If spinal alignment is unchanged on upright radiographs, the patient remains comfortable, and no new neurologic symptoms are reported, a trial of physician-supervised orthotic treatment is initiated.