Upper cervical spine trauma

1

What are the major types of injuries involving the upper cervical (occiput–C2) region?

The major types of injuries can be classified based on anatomic location as:

• 1.

  Occipitocervical articulation

  • Occipital condyle fractures

  • Craniocervical dissociation

• 2.

  Atlas (C1) and atlantoaxial joints

  • Atlas fractures

  • Transverse atlantal ligament (TAL) injuries

  • Atlantoaxial instabilities

• 3.

  Axis (C2) and C2–C3 joints

  • Odontoid fractures

  • Traumatic spondylolisthesis of the axis

  • Axis body fractures

  • C2 body fractures and C2–C3 dislocations

2

How common are upper cervical spine injuries and who is most affected?

It is estimated that one-third of cervical spine trauma involves the upper cervical region (occiput-C2) and two-thirds involves the subaxial cervical region (C3–T1). There is a clear bimodal distribution of upper cervical injuries in adults with younger, mainly male, patients aged 25–40 years affected by road traffic accidents and falls from a height, while the second spike affects patients 65 years and older and mainly results from ground-level falls. In patients over 65 years of age, odontoid fractures are the most common isolated spine fracture and have the highest morbidity and mortality of any spine fracture—up to 50% depending upon age and comorbidities. In the pediatric population, upper cervical injuries are more common in patients less than 8 years of age due to their high head-to-body ratio while subaxial injuries are more common in older patients. Of special importance is the association between head injuries and upper cervical spine injuries. Approximately 5% of patients with moderate or severe head injuries can be expected to have an upper cervical spine injury, while 20% of patients with an established cervical spine fracture-dislocation may also have a concomitant head injury. Up to one-third of upper cervical spine injuries are associated with spinal cord, cranial nerve or cervical nerve root injuries.

3

How are upper cervical spine injuries diagnosed?

It can be relatively easy to miss upper cervical spine injuries due to initial clinical focus on head injury or other trauma, as well as the relative subtlety of these injuries. Frequently, no specific symptoms or findings on physical examination strongly point to the presence of a significant osseous or ligamentous injury involving the upper cervical region. Symptoms are notoriously vague and may include headaches, suboccipital pain, greater occipital neuralgia, neck pain, local tenderness and swelling, or neurologic deficits, including cranial nerve deficits, myelopathy or spinal cord injury. Not infrequently, the patient may be unconscious or intubated following trauma. A neurologic evaluation following the American Spinal Injury Association (ASIA) guidelines is recommended, and should include assessment and documentation of bilateral lower cranial nerve function. Use of clinical risk profiling based on injury mechanism (i.e., fall from 10 feet or higher, motor vehicle crash at 35 mph or higher, presence of head injury, facial trauma, pelvis fracture, multiple rib fractures, or focal neurologic deficits) can increase injury awareness and highlight the necessity for obtaining neuroimaging studies. Pediatric patients less than 8 years of age present as a particularly concerning subgroup due to their relatively large head size relative to their torso, relatively lax ligaments, and poorly matured cervical joint contours. Victims of child abuse and pediatric patients who were struck by a vehicle or were involved in car crashes while being restrained in a modern car seat with a four-point torso restraint system should raise high suspicions for such possible injuries.

Computed tomography (CT) with sagittal and coronal plane reformatted views is required to assess the full magnitude of injury, and is the imaging modality of choice for initial evaluation of cervical trauma in severely injured patients. Plain radiographs remain important as they can show over 90% of upper cervical spine injuries and can assess craniocervical alignment and instability. Magnetic resonance imaging (MRI) is indicated for patients with cervical spinal cord injury, suspected ligament injuries that are not evident with other imaging modalities, and to assess related pathologies such as vertebral artery injuries. T2 fat-suppressed images are especially useful to assess ligamentous injuries, hemorrhage, as well as cord signal changes. If CT documents a cervical spine fracture with displacement of transverse foramina, an additional study to confirm vertebral artery integrity is indicated, such as a CT-angiogram or MR angiography. During the acute injury evaluation phase, the patient should remain immobilized with a rigid cervical collar.

4

What are some special considerations related to injuries involving the upper cervical (occiput–C2) region that are a consequence of the unique anatomic features of this spinal region?

• A wide range of injury mechanisms exist: Because of the fragile nature of the bony and ligamentous components of the upper cervical spine, injuries are relatively common, especially in the setting of closed head trauma. Typical injury mechanisms include flexion, extension, or compressive forces applied to the head during motor vehicle accidents, falls from a height, or sporting injuries, but also include injuries due to low-energy injury mechanisms in the aging population.

• Upper cervical spine stability and mobility are dependent upon the integrity of both osseous and ligamentous structures: Suspicion regarding the presence of occult upper cervical ligament injuries is vital as missed injuries may lead to serious complications, including secondary dislocations. As in other regions of the spine, capsuloligamentous injuries have a much poorer chance for stable healing with nonsurgical means compared with osseous fractures. Small bone fragments at joint edges provide an important tip-off regarding the presence of an underlying more profound ligamentous disruption (“tip of the iceberg fragment”). It is important to recognize that certain injuries such as craniocervical dislocations may spontaneously reduce, leaving deficient structural stability, which is not apparent on imaging.

• Concomitant and noncontiguous spinal injuries often occur: The upper cervical spine is unique in that it functions as an “integrated motion unit” and an injury in one area may adversely affect another spinal segment or region. Combination injuries involving the upper cervical spine are common. For instance, more than 50% of C1 posterior arch fractures are associated with a second injury in the cervical region (“indicator fracture”), which may include odontoid fractures, traumatic spondylolisthesis of the axis, occipital condyle fractures, C2 teardrop fractures, cervical burst fractures, and lateral mass fractures. Close scrutiny for noncontiguous injuries or related pathology is therefore important in patients with upper cervical spine injuries.

• Atypical neurologic injury patterns may be encountered: From a neurologic injury perspective, the relatively large size of the spinal canal provides some protection from spinal cord injury as the majority of upper cervical injuries are not associated with neurologic deficit. However, major dislocations of the upper cervical spine are usually not survivable injuries due to compromise of the respiratory and cardiac centers in the medulla and upper cervical cord. Disruption of the craniocervical ligaments is reported as the leading cause of fatal motor vehicle occupant trauma. In survivors, high-energy incomplete upper cervical spinal cord injuries may present as cervicomedullary syndromes or cranial nerve injuries. Part of routine neurologic assessment for patients with upper cervical spine injuries includes cranial nerve evaluation with documentation of any abnormal findings. In addition, traumatic brain injury is noted more commonly following upper cervical spine injuries compared with injuries in other spinal regions.

• Upper cervical spine injuries may be associated with vascular injuries: Vertebral artery injuries, as well as carotid injuries, are increasingly diagnosed through use of imaging protocols that are routinely activated in the presence of fractures involving the transverse processes or distractive spine injuries. The vertebral artery regions that are susceptible to injury include the V3 and V4 sections of the artery where it is positioned laterally in relation to the atlantoaxial joints (V3) and on the superior aspect of the atlas arch (V4). Vertebral artery injuries in these regions can be diagnosed with CT-angiography or MRI.

5

How is upper cervical spine stability determined in an acute injury setting?

Certain injuries are clearly recognized by their appearance as “unstable” based on clinical and/or imaging criteria. For instance, any patient with a neurologic and/or vascular injury in combination with an upper cervical spine fracture-dislocation has an unstable injury. Most craniocervical ligamentous disruptions are unstable. Upper cervical spine fractures with more than 3 mm displacement or 5° of angulation are likely unstable. Note that a determination of instability does not necessarily equate to a need for surgical intervention, but recognition of instability does necessitate that extra precautions are taken when choosing potential nonsurgical treatment options. In some patients it may be challenging to determine whether the spine is stabile even after conclusion of comprehensive neuroimaging studies. For patients who remain neurologically intact and show minimal or no upper cervical bony displacement but are considered at risk of harm due to potential osteoligamentous instability, some additional studies that may potentially inform treatment decision making include:

Two-step lateral radiographs: For a patient who is a reasonable candidate for potential treatment with a rigid collar, the first step is to obtain a lateral radiograph centered on the upper cervical spine with the patient in the recumbent lateral position. If there is no concerning displacement noted, the patient is assisted to the upright position and clinically reassessed. If the patient’s clinical status is unchanged, the second step is to repeat the lateral radiograph with the patient upright in the collar and compare this radiograph to the supine imaging study. If the patient remains comfortable and reports no new neurologic symptoms, and radiographic alignment and injury displacement are unchanged, it is reasonable to conclude that the injury is relatively stable and can undergo a trial of physician-supervised brace treatment.

Traction test: In the uncommon clinical scenario where CT and MRI are nondiagnostic and there is ongoing concern regarding the presence of a possible craniocervical dislocation that has spontaneously reduced, a traction test can be performed. This test is only indicated if all conventional imaging studies do not allow for a conclusive determination of stability. With the patient in the supine position, an image intensifier is used to obtain a baseline lateral radiographic image of the cervical spine. Traction weights are added in 5-lb increments (20-lb limit) using a head halter or Gardner-Wells tongs as the cervical region is monitored radiographically. If distraction of more than 2 mm between the occipital condyles and atlas or between the atlas and axis occurs, the test is considered positive for a spontaneously reduced craniocervical dislocation.

Flexion–extension radiographs: Although flexion–extension radiographs can effectively document cervical instability, these studies are of limited value and even potentially dangerous in the acute trauma setting. It is usually unadvisable to perform flexion–extension radiographs in the presence of known fractures and/or ligament injuries. Pain and muscle spasms may limit the actual motion excursion and convey a false sense of reassurance. In a subacute setting however, roughly definable as 2–3 weeks after an injury, or for the assessment of final healing of an injury 2–3 months following initiation of nonoperative treatment or following surgical reconstruction, flexion–extension radiographs remain a mainstay for determination of cervical spine stability. As in any diagnostic spine study, the patient should be instructed to stop any movement if they notice the onset of neurologic symptoms or undue pain.

6

What systems exist for classification of upper cervical spine injuries?

Historically there have been a large number of empirically based and eponymous classifications and subclassifications for injuries involving each segment of the upper cervical spine. These classifications are notoriously difficult to remember and some are of dubious clinical merit. However, as related terminology persists in current literature, familiarity with these classifications is needed until a comprehensive spine injury classification is widely adopted. Based on a series of international studies, AOSpine proposed a validated classification ( Fig. 56.1 ) that provides a more systematic description and stability assessment for all spine injuries, including the upper cervical spine using an A, B, C system. The AOSpine classification subdivides the upper cervical spine into three general regions. Each region is defined by an osseous element and the articulation below:

• Upper cervical spine regions

  • Region 1: Occipital condyle and craniocervical junction (Occ, O–C1)

  • Region 2: Atlas and atlantoaxial joints (C1, C1–C2)

  • Region 3: Axis and C2–C3 joints (C2 and C2–C3)

The AOSpine classification applies the A, B, C system to injuries in each region. This classification is hierarchical, progressing from least to most unstable, and is based on injury morphology. Two sets of modifiers are applied to each injury. One modifier classifies neurologic injury and the other identifies specific factors that may affect treatment, prognosis or adversely affect healing.

• A.

  Injury types

  • Type A injuries: Bone injuries without significant ligamentous, tension band, or discal injuries. These are stable injuries.

  • Type B injuries: Tension band/ligamentous injuries without complete separation of anatomic integrity. These may be either stable or unstable injuries.

  • Type C injuries: These are injuries with significant translation in any directional plane and separation of anatomic integrity. These are unstable injuries.

• 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

  • N5: Unexaminable patient

  • N+: Ongoing spinal cord compression

• C.

  Case-specific modifiers

  • M1: Injuries at high risk of nonunion with nonoperative treatment

  • M2: Injury with significant potential for instability

  • M3: Patient-specific factors adversely affecting healing potential

  • M4: Vascular injury or abnormality affecting treatment

7

What is the mechanism for occipital condyle fractures and how are these injuries classified?

Occipital condyle fractures typically result from a direct blow to the head or from a rapid deceleration injury. These injuries are frequently associated with C1 fractures and cranial nerve injuries. CT is used to classify these injuries according to the AOSpine classification or the Anderson and Montesano classification (below):

• Type 1: A stable comminuted fracture resulting from an axial loading injury.

• Type 2: A stable skull base fracture that extends into the occipital condyle.

• Type 3: An avulsion fracture of the condyle at the attachment of the alar ligament, either unilateral or bilateral.

This fracture type may be stable or unstable and may be associated with craniocervical dissociation.

8

How are occipital condyle fractures treated?

Stable injuries are treated with a rigid cervical orthosis, or less commonly with a halo orthosis. Unstableinjuries include those associated with displacement or craniocervical dissociation and require treatmentwith posterior occipitocervical fusion.