Patients generally present with a history of trauma and a symptom of pain in the neck. There is usually no cord compression and associated neurologic deficit, because the fracture widens the ring of C1, which at this level spinal canal is composed of one-third dens, cord, and space according to Steele’s rule.
If the patient has neurological deficit, it may be very severe. Those patients may present with a complete spinal cord injury and no neurologic function below the level of C1 and no voluntary breathing. In that case, endotracheal intubation, then a tracheostomy is essential because the patient requires respiratory assistance. If the C3-C5 area is intact, phrenic nerve stimulation may be effective.
In addition to anteroposterior and lateral views, radiographs of the upper cervical spine include the open mouth view. The open mouth view may identify a spreading or widening of the lateral masses or an asymmetry of the separation of the odontoid from the lateral masses, which, in an appropriately centered radiograph, may be consistent with spreading of the C1 ring or a C1 fracture (see the figure above). When examining AP or open mouth odontoid plain films, the rule of Spence can be applied: if the total overhang of C1 lateral masses on C2 facet is greater than 6.9 mm the transverse ligament is probably disrupted, requiring rigid immobilization (However, newer studies that consider radiographic magnification argue that a transverse ligament rupture should not be inferred unless the lateral mass displacement is >8.1 mm, rather than 6.9 mm).
Atlas fractures may be easily missed due to inadequate imaging of ocipitoatlantoaxial junction. Thus, in suspect cases, at thin CT cuts from C1 through C3 is indicated, because it is the best radiographic study to evaluate atlas fractures and rule out concomitant C2 injury.
imaging of an Atlas fracture consists of:
Although the patient neurologically intact, a Jefferson fracture may be unstable. Those patients are at grave risk for neurologic compromise if not promptly diagnosed and appropriately stabilized and treated. Treatment aims to achieve the spinal stabilization to protect the patient from further nerve damage, including that to the brain stem.
The specific treatment should be based on analysis of the mechanism and extent of the injury. Conservative or surgical treatments are available. The principal treatment is with a halo and vest or cast, which remains an effective current treatment for many of these fractures.
The treatment selection depends largely on the degree of offset of C1 on C2, whether there is damage to the transverse ligament, and associated cervical injuries. Fracture of the Atlas may occur in isolation or in combination with C2 (Axis) fracture. Nearly 1/3 of Atlas fractures are associated with a fracture of C2. Fractures of the ring of C1 may be associated with an odontoid fracture; thus, the combination of the two fractures should be considered. Furthermore, congenital anomalies of the arch (eg, agenesis of the posterior ring) may be present. Anterior subluxation of C1 on C2 may be present and, if so, often indicates a disruption of the transverse ligament. Even in the absence of a C1 fracture, assessment of stability must include the associated structures. An atlantooccipital dislocation or disruption and C1-2 instability, particularly that in which the transverse ligament may be disrupted, poses severe risk to the brain stem and upper spinal cord. Furthermore, with a C1 fracture, associations exist with unstable injuries such as odontoid fractures and other injuries to the upper cervical spine. In addition, the odontoid fragment may migrate into the foramen magnum, endangering the brain stem and upper spinal cord.Children may represent less unstable cases, presumably because of periosteal stability, and they are often treated with a collar. The body of C1 is not visible radiographically until age 1 year. In a younger patient with limited displacement of the C1, immobilization with a collar or halo and vest may be adequate. In more severe cases, particularly with associated injuries such as odontoid fracture, bypassing the C1 ring with an occipital-to-cervical fusion extending to C2 or lower may be necessary. Instrumentation spanning that area may stabilize the C1 ring, which cannot be otherwise easily addressed directly, because both the anterior and posterior components of the ring are disconnected by the fracture and not amenable to instrumentation or direct repair.
Jefferson G. Fracture of atlas vertebrae: report of four cases and a review of those previously recorded. Br J Surg 1920; 7:407–422.
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