Registry study places the incidence of C2 fracture at 6 per 100,000 people. In Sweden, across 6370 patients with C2 fractures: 51% were male, and the average age was 72 years. Those who were younger, male, and presenting with spinal cord injury were more likely to undergo surgical intervention. In the pediatric cohort, C1 to C2 injuries represented 7.7% of spine fractures presenting through a multi-institutional series following after trauma from multiple blunt mechanisms.
Blunt trauma is the leading mechanism. Falls, motor vehicle accidents, assault, and other traumatic presentations usually cause the blunt trauma. It is important to recognize that in the elderly cohort low-energy cervical blunt trauma can create unstable high cervical spine fractures.
The incidence of C2 fractures increased 135% from 2000 to 2011 in the Medicare population. C2 fractures are associated with a 20% and 40% increased risk of mortality within 3 months and 2 years, respectively. The majority of C2 fracture types are type-II dens fractures. This is troublesome because these have a pseudoarthrosis (non-union) rate that exceeds 50%.
It is critical to appreciate the unique anatomy of the C2 vertebra. The dens extend superiorly to communicate with C1 via the ligamentous anatomy. Lack of intervertebral discs, unique ligamentous attachments, vertebra anatomy, and vertebral artery vasculature make this area biomechanically unique from the subaxial cervical spine. For example, C1-C2 is generally responsible for 50% of the rotation movement.
C2 fractures can be divided into 2 kinds: Odontoid and Hangman's.
Anderson and D’Alonzo classification is the most ubiquitous.
The Roy-Camille classification of odontoid fractures is another but less frequently used nomenclature format focusing on the direction of the fracture line.
Levine and Edwards Classification
It is important to recognize that low-energy, blunt trauma, especially in the elderly population, can induce significant unstable injury. History should also entertain risk factors for fracture such as osteoporosis, metastatic burden, or vitamin D deficiencies. Physical exam findings include pain with palpation in the posterior portion of the neck, radiculopathy, myelopathy, and possible posterior fossa findings secondary to vertebral artery injury. A strict neurologic exam including cranial nerves, sensory, motor, and rectal tone is mandatory.
Laboratory tests should be ordered as an adjunct in overall medical status. Normalized hemoglobin, hematocrit, PT/PTT, INR, and platelet counts will be needed for operative intervention.
Evaluation of with x-rays will provide limited but important information. Care must be taken to ensure proper radiographic imaging creates a picture from the occiput to the C7 through T1 disc space. This is essential in reviewing cervical spine trauma. Lateral, AP, and open mouth odontoid views are necessary. Approximately, 93% of cervical spine injuries are apparent with combined, lateral, AP, and odontoid view radiographs. X-rays are an excellent modality for determining alignment during the immediate injury, post-operative period, as well as long-term follow up.
CT scan is the most important modality for determining fracture etiology and ruling out injury with regards to a C2 fracture. Even if plain films are negative and clinical suspicion is high a CT scan is warranted. CT scan does not directly evaluate the spinal cord, soft tissue, or ligamentous construct. It is important to recognize the importance that complete imaging will require dedicated thin-cut CT reconstructions. Non-contrast CT scan is adequate for evaluation of the bony anatomy for fracture. This can be coupled with a CT angiogram (see below) for evaluation of the vascular anatomy.
Evaluation with MRI is important for the analysis of the ligamentous construct, disc space, spinal cord, nerve roots, and other soft tissue injuries. MRI is also useful for determining the acute nature of the fracture when this is otherwise unknown. This is done via non-contrasted imaging. T2 signal hyperintensities and STIR changes within the dens, ligaments, or soft tissue can illustrate an acute component. MRI is less dangerous than flexion-extension cervical injury. Furthermore, MRI evaluation is mandatory in the evaluation of the transverse ligament for the surgical decision matrix of non-displaced type II odontoid fractures. An intact transverse ligament is needed for the anterior placement of an odontoid screw.
Vascular imaging may be indicated. The vertebral artery’s second segment (V2) runs through the transverse foramen of C2 to C6 while V3 runs extradurally exiting the C2 foramen across the sulcus arteriosus. This can place it at risk for injury. Indeed, in one series 15% of patients with C1 to C2 fractures had a vertebral artery injury. Of which, type-III odontoid fractures posed the greatest risk. It is important to note that an untreated vertebral artery injury has a 24% stroke rate. CT angiography can be coupled to CT imaging upon fracture evaluation with consideration of kidney function. Level-III evidence suggests that patients with C1 to C3 fractures can be screened with multi-slice multi-detector CT angiography. At this time MR angiography cannot be listed as the sole imaging modality for the evaluation of vertebral artery injury. First-line investigation with percutaneous angiography is overly aggressive.
Treatment options include conservative management, cervical orthosis, halo-vest orthosis, and surgical procedures.
Rigid cervical collar represents the immediate first treatment. For type-I and type-III odontoid fractures this is generally adequate. This is also true for 90% of Hangman’s fractures. Halo-vest orthosis can be used as well for external fixation in certain cases of type-II odontoid fractures or angulated/displaced Hangman’s fractures but is not very well tolerated in the elderly population.
Internal fixation can be achieved via anterior fixation or by a variety of posterior constructs.
An odontoid screw can be placed for type-II odontoid fractures in good alignment with an intact transverse ligament in the acute setting. There is concern about the placement of the odontoid screw in the elderly population and instances of delayed non-union.
Posterior fixation technique selection requires significant review by neurosurgeon or orthopedic spine surgeon. It takes into consideration a variety of factors including surgeon experience, fracture location, vertebral artery location, biomechanical suitability, and anatomical variations. Vascular imaging is mandatory to illustrate the location of the vertebral artery in the V2 and V3 segments. Patient’s overall functional status, medical optimization, and bone health must be evaluated in the operative decision-making. This includes consideration for type-II odontoid fractures.