A hangman’s fracture is better described as bilateral fracture traversing the pars interarticularis of C2 with an associated traumatic subluxation of C2 on C3. It is the second most common fracture of the C2 vertebrae following a fracture of the odontoid process and is almost always stable without the need for surgical intervention. Steele’s rule of thirds states that the cross-sectional area at the level of the atlas may be divided into three equally represented parts: the dens, space, and the spinal cord. This increased area for the spinal cord at this level is what allows for the relative lack of neurologic injury associated with a hangman’s fracture. 
Schneider et al. coined the term hangman’s fracture in 1965. Despite the term implying a hyperextension and distraction injury; such as in the case of a judicial hanging, the more common mechanism of action is hyperextension and axial loading. These injuries are most commonly seen in motor-vehicle accidents, diving injuries, or contact sports.
Fractures of the cervical spine are present in 1% to 3% of all trauma cases, of which 9% to 18% are of the C2 vertebrae. The incidence of C2 fractures has doubled from 3 per 100,000 to 6 per 100,000 from 1997 to 2014 in data reported from the Swedish National Patient Registry. Fractures of the odontoid process are much more common, representing 35% to 78% of all C2 fractures in the general population and as much as 89% of patient’s older than 70 years old. Meanwhile, hangman’s fractures represent 11% to 25% of all C2 vertebrae fractures. 
It is vitally important to keep in mind the unique anatomy of the atlas-axis complex when treating their associated injuries. Unlike the subaxial cervical spine, the C1 to C2 complex does not contain an intervertebral disc; there are unique ligaments allowing for support of the cranium as well as providing the majority of cervical rotation. There is also a close relationship of the transverse foramen, which carries the vertebral artery through the cervical spine, with the C2 pedicle/pars interarticularis, which may slightly weaken this area allowing for a fracture to occur.
Multiple grading systems for hangman’s fractures exist; however, the Levine and Edwards classifications are the most widely used.
Levine and Edwards Classification
Angulation in this system is measured as the angle between the inferior endplate of C2 and C3. Anterior subluxation of C2 on C3 greater than 3 mm serves as a marker for C2 to C3 intervertebral disc disruption. It is important to recognize that this grading system is not applicaple in the pediatric population.
Francis Grading System
Two factors are taken into consideration for the Francis Grading system: angulation and displacement. Angulation is measured by the degree of anterior angulation off of the posterior vertebral line drawn straight up from the C3 vertebral body. Displacement is measured by the amount of anterolisthesis, either greater than or less than 3.5 mm.
Typical versus Atypical Fractures
It is important to recognize that not all C2, hangman’s type fractures can be described using these classification systems. A typical hangman’s fracture allows for separation of the anterior elements from the posterior elements of the C2 vertebrae, therefore increase the available space for the spinal cord. However, in the case of an atypical hangman’s fracture the posterior aspect of the C2 vertebral body, not the bilateral pars, is involved. This leads to a higher risk of neurologic injury as the space remaining for the spinal cord does not increase secondary to the fracture.
It is important to recognize that outside of the obvious motor vehicle collisions, and high-impact falls, low-energy and 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, anteroposterior (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. While nonunion may occur as frequently as 50% in odontoid fractures, nonunion is rare in hangman’s fractures with approximately 90% healing with immobilization alone. There is level III evidence that a hangman’s fracture may be initially managed with immobilization with a halo-vest or collar alone. This produces a reduction rate of 97% to 100% and the fusion rate of 93% to 100%. External orthosis should be maintained for 8 to 14 weeks. It is important to remember that halo-vest orthosis but is not very well tolerated in the elderly population, and therefore collar is recommended as first-line management.,,
Surgical fixation may be considered in the following scenarios:
Internal fixation can be achieved via anterior fixation or by a variety of posterior constructs.
C2 to C3 anterior cervical discectomy and fusion may be used with anterior plating to stabilize the C2 to C3 vertebral bodies. The main benefit of the anterior approach is the preservation of the C1 motion which drastically decreases the morbidity when compared to posterior fixation.
Posterior fixation technique selection requires significant review by a 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.
Differential diagnoses include pseudosubluxation (generaly C2 on C3) and Mach effect.
A rigid cervical collar should be immediately placed in the emergency room setting.
The majority of Hangman’s fractures may be successfully treated with external orthosis alone.
Vascular imaging should be performed in all C1 to C3 fractures.