C1 (Atlas) Fractures Treatment & Management

Updated: Apr 07, 2022
  • Author: J Allan Goodrich, MD; Chief Editor: Jeffrey A Goldstein, MD  more...
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Approach Considerations

Recognition and identification of a Jefferson fracture is the indication for treatment. Treatment consists of spinal stabilization to protect the patient from nervous system damage. Children may represent less unstable cases, presumably because of periosteal stability, and they are often treated with a collar. The body of C1 (the atlas) is not visible radiographically until age 1 year.

Even in the absence of a C1 fracture, assessment of stability must include the associated structures. An atlanto-occipital dislocation or disruption and C1-C2 instability, particularly when the transverse ligament may be disrupted, poses severe risk to the brainstem 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 brainstem and upper spinal cord.  

The images below illustrate a type II odontoid symptomatic nonunion in a patient with continued neck pain followed by another fall, resulting in bilateral fractures of the posterior arch of C1.

Sagittal reformat of CT cervical spine showing pos Sagittal reformat of CT cervical spine showing posterior displacement and chronic nonunion of the dens.
Bilateral posterior arch fractures in the axial pl Bilateral posterior arch fractures in the axial plane of the CT cervical spine in the same patient after a second fall.
Lateral radiograph after C1-2 posterior fusion. Lateral radiograph after C1-2 posterior fusion.
AP radiograph showing hybrid C1-2 posterior fixati AP radiograph showing hybrid C1-2 posterior fixation with bilateral C1 screws and right sided C2 pedicle screw with a left to right intralaminar or translaminar C2 screw.

Specific treatment should be based on analysis of the mechanism and extent of the injury. 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 otherwise cannot easily be addressed directly, because both the anterior and posterior components of the ring are disconnected by the fracture and are not amenable to instrumentation or direct repair.

No significant contraindications for treatment exist, because the lack of stabilization, which commonly is initially provided either with traction or with a halo brace, can have fatal consequences. Any contraindications are mitigated by the potential for serious and even fatal neurologic consequences without treatment, as well as by the observation that halo with vest or traction can be relatively effective in immobilizing the upper cervical spine, with low associated morbidity.

Primary internal fixation of C1 fractures with lateral mass screws and transverse connector has been reported without the need for C1-C2 arthrodesis, resulting in preservation of cervical motion. [17]  Anterior transoral, isolated posterior, and combined posterior–anterior transoral approaches have been reported. For each approach, only small case series are available. [18]

Guidelines for the management of spine injuries have been published by the American College of Surgeons (ACS) [19] (see Guidelines).


Medical Therapy

Patients with C1 fractures typically have sustained some form of trauma. Prehospital care recommended by Emergency Medical Services (EMS) and the ACS dictates immediate stabilization of the cervical spine at the scene with the use of a hard backboard, a rigid cervical collar, lateral support and a mechanism to stap all the above to the backboard. Of course, the customary attention to the ABCs (airway, breathing, and circulation) is expected. If the airway is compromised or air exchange is inadequate, intubation without moving the head is crucial (C-spine protection).

Careful evaluation and frequent reassessment are essential because the patient may have sustained a concussion with the impact to the head (the common injury that produces the C1 fracture) and, because of a clouded sensorium, may not be able to be fully evaluated or to report neck pain. Patients with a diminished alertness and orientation should carefully undergo imaging studies to exclude underlying pathology.

Vertebral artery dissection and neurologic decline may occur with cervical trauma, emphasizing the above recommendation for arteriography. Basilar artery occlusion has been reported with chemical and mechanical thrombolysis, resulting in basilar artery patency and clinical improvement, [20] whereas prior cases of basilar artery occlusion reported death and locked-in syndrome.


Surgical Therapy

Choice of approach

Treatment of a C1 fracture consists of stabilization or immobilization in a satisfactorily reduced position to allow reliable healing. This illustrates the necessity of identifying associated injuries; for example, if a Jefferson fracture is identified but an associated odontoid fracture, transverse ligament rupture, or other problem is present, halo treatment may be modified or less successful. The transverse ligament is not necessarily expected to heal tightly or reliably, though a fractured bone may have its mechanical integrity restored if the fracture fragments are well opposed when healed.

With a C1 fracture, the posterior aspect of the ring becomes disconnected from the anterior aspect, which is stabilized around the odontoid; thus, a posterior fusion of the occiput to C1 would be inadequate to stabilize the spine and consequently would extend at a minimum to C2. Customarily, instrumentation attaches a type of contoured rod or plate from the occiput down to C2 to stabilize the area and facilitate healing.

Direct lateral mass screws have been reported, allowing reduction and compression across the fracture but also, more significantly, preserving upper cervical motion segments. [21]  This technique has been reported to be associated with occipital neuralgia [22] ; it will find its place in the author’s armamentarium as further experience is amassed. A computer-aided analysis by Krassnig et al suggested that such screws should be positioned with a slightly converging 16° angle and a slightly ascending 10° angle and that intraoperative multiplanar imaging should be employed to minimize the risk of harm to the vertebral artery or the spinal canal. [23]

A fractured odontoid fragment cannot be removed via the posterior approach; if a neurologic deficit or threat to the brainstem is present (the alar ligament may have an attached portion of the odontoid migrate superiorly into the foramen magnum to compress the brainstem at the pontomedullary junction), neurosurgical posterior decompression of the foramen magnum could be performed in a halo.

Alternative consideration may be given to a transoral approach or an anterior retropharyngeal approach for the combination of a Jefferson fracture and a fracture of the odontoid. The traditional treatment is a halo vest or cast until the Jefferson fracture is healed. Then, additionally, if the odontoid fracture healing has become delayed or a nonunion is present, this can be treated by a C1-C2 arthrodesis, but the procedure must be delayed for the ring of C1 to heal.

For this combined fracture, anterior open reduction and internal fixation (ORIF) of the odontoid may be performed, with two screws placed in an oblique fashion, starting at the inferior anterior edge of C2 and directed cephalad to engage the odontoid. With a C1 fracture, this is done in conjunction with a halo vest.

An alternative would be a Magerl approach of a posterior open reduction, accompanied by internal fixation of C1-C2. For this procedure, two screws are placed in an oblique fashion starting at the inferior edge of the C2 lamina, and then they cross the C1-C2 facet joint between the vertebral artery, which is lateral, and the spinal cord and brainstem, which are medial.

The use of intraoperative navigation has been reported to be useful in helping guide the placement of screws during surgical treatment of C1 and C2 fractures. In one study involving 17 patients (median age, 47.6 years), a total of 67 screws were placed. [24] Intraoperative computed tomography (CT) revealed that 62 screws (92.6%) were placed correctly, four (5.9%) with minor cortical violation, and one (1.5%) incorrectly (immediately corrected). The findings suggested that intraoperative CT reduces the risk of screw misplacement and consequent complications.

In a study of 10 patients with unstable hangman fracture (age range, 17-81 years), 52 screws were placed under O-arm guidance (20 in C2 pedicle, 20 in C3 lateral mass, and 12 in C4 lateral mass). [25] One C2 pedicle screw (5%) was misplaced. At follow-up (range, 3-21 months), no new-onset neurologic deficits had developed. Bony fusion was achieved in all patients, and full rotation at C1-C2 was preserved. The findings suggested that C2 pedicle screws can be precisely placed with O-arm guidance and that intraoperative CT can confirm screw position.

Alternative approaches

Disruption of the ring of C1 makes stabilization by a C1-C2 fusion in the customary posterior fashion impossible; however, a C1-C2 direct fixation with Magerl screws may stabilize the anterior ring to the body of C2. The role of this C1-C2 fusion is not yet universally accepted, but with experience, the indications and role will be more clearly defined.

A transoral resection of C1 may be preferred to an alternative technique, decompression posteriorly to the foramen magnum, particularly for a migrating odontoid fragment from an associated type 2 Anderson-D'Alonzo odontoid fracture with a Jefferson fracture. A significant amount of rotation of the atlas on the axis would be lost with this fusion, but the fusion would preserve the flexion and extension of the occipital condyle and head on the lateral masses, which would also be lost in an occipital C2 fusion (the traditional approach).

With regard to C1-C2 fixation, wires have been used for a significant time with excellent results. Gallie described fusion where wires are passed onto the arch of C1 and into the spinous process of C2. [26]

In 1978, Brooks and Jenkins then presented a more stable construct. [27]  Rather than placing the bone graft over the posterior elements, grafts are wedged between the posterior arch of C1 and C2, and the wires are passed under both C1 and C2, so that they can more effectively stabilize the bone grafts in their respective positions and increase the area for fusion. However, this procedure requires passing the wires more laterally, with careful attention to the vascular structures.

In 2002, Richter et al presented six different techniques for biomechanical comparison, preferring transarticular screws but considering isthmic screws with a claw or lateral mass screws and isthmic screws as an alternative with somewhat less immediate stability. [28]

In 2003, Cornefjord et al reported on a series of patients treated with Olerud cervical fixation. [29]  In this report, odontoid fracture occurred in 18 patients, rheumatoid instability in six, and odontoid nonunion and os odontoideum in one patient each, with clinical follow-up (20 patients followed for 6-27 months) suggesting no serious complications and a high frequency of fusion healing.

The posterior arch at C1 has minimal bone for the fusion to heal, and claw techniques to avoid passing sublaminar wires over the brainstem had some early discouraging results and were generally abandoned, leading to refinements and further investigation. Various techniques will continue to be compared and studied; this is clearly a challenging area.

Operative details

Patients must be maintained in protective immobilization, which, for adults, means more than just a soft collar. Ideally, they should be are in a halo from the point of initial treatment. Reduction of an atlas fracture may be achieved by means of ligamentotaxis with mild traction; however, traction is very risky, and such highly unstable injuries must be monitored extremely closely. Associated fractures must be promptly identified to direct subsequent treatment. Congenital abnormalities of the arch (eg, agenesis of the posterior ring) must be identified and taken into account in the treatment plan.

If the patient is awake and has a halo and vest applied, then the conversation and discussion with him or her during the procedure serves to demonstrate maintenance of safety and neurologic status. Patients who undergo surgical correction, particularly posterior arthrodesis, may be monitored with somatosensory evoked potentials.

After application of a halo, close radiographic follow-up is required to demonstrate that the fracture is maintained in a satisfactory position for healing. If surgical stabilization is appropriate, then monitoring the healing of the bone fusion with radiographs is also crucial postoperatively.

C1 lateral mass fixation [30]  involves a midline approach from the base of the skull to the subaxial spine, with the length of the incision depending on the number of levels to be incorporated. If occipitocervical fusion is planned, a longer incision will be necessary. C2 pedicle screw or pars fixation will require anatomic exposure of C2-C3; the procedure is fluoroscopically assisted, or O-arm navigation can be employed.

Careful exposure of the ring of C1 is carried out laterally, and the neurovascular bundle arising beneath the ring tracking laterally is exposed and dissected with a Penfield dissector so as to allow palpation of the lateral mass. Brisk venous bleeding is frequently encountered and can be controlled with a hemostatic agent (eg, Floseal; Baxter, Deerfield, IL) and a bipolar cautery. Packing with cottonoids and addressing the other side is an efficient way of achieving hemostasis.

A pilot hole with a 1- to 2-mm cylindrical burr followed by a 2.4-mm drill allows drilling of the lateral mass under fluroscopic control. Obtaining bicortical purchase improves biomechanical stability. The ideal starting point is the midpoint of the C1 lateral mass. The vertebral artery passes laterally and the spinal canal medially.

According to a study by Simsek et al, the ideal amount of medial angulation is 13.5º ± 1.9º, with a maximum medial angulation of 29.4º ± 3º; further medial angulation will result in penetration of the spinal canal. [31]  The ideal sagittal angle is 15.2º ± 2.6º, with a maximum cephalic angle of 29.6º ± 2.6º. Higher trajectories will result in screw penetration into the atlanto-occipital joint.

Neurovascular structures of concern include the vertebral artery laterally and superiorly and the internal carotid artery anteriorly. Careful analysis of preoperative imaging studies must be undertaken to recognize anomalous path of the vertebral artery


Postoperative Care

Mobilization after C1 fixation, C1-C2 fixation, or occipitocervical instrumentation and fusion is generally possible on the day of surgery or postoperative day 1. In the polytrauma patient, mobilization may depend on the coexisting injuries. A hard cervical collar is generally utilized for comfort and support.

Surgical drains are removed after output decreases a day or two after surgery. Incentive spirometry is encouraged on the day of surgery and as long as the patient remains hospitalized. Routine deep vein thrombosis (DVT) prophylaxis is performed by mechanical means. If there is a history of DVT or multiple risk factors for DVT, then anticoagulation can generally be started on postoperative day 1.



Patients with upper cervical instability are at risk for death; this risk is increased if the injury is not identified and recognized. Neurologic damage at this level could make the patient dependent on a ventilator; thus, extreme care is necessary in handling these patients during fracture healing.

Associated injuries to the occipitoatlantoaxial complex (C0-C2) must be considered and included in the treatment plan. Devastating neurologic injuries may develop as a consequence of vascular embarrassment resulting from the instability of these injuries.

C1 lateral mass fractures with displacement can result in settling of the occipital condyle and a cock-robin deformity of the head neck clinically. This usually necessitates complex reconstruction with occipital-to-subaxial fusion.


Long-Term Monitoring

Patients in the cervical collar or halo will require at least 8 weeks—most likely, 12 or more weeks—of immobilization until healing is documented on radiographs. This period is followed by one in which the patient is placed in a collar to protect the neck while he or she is being weaned from the halo and while the neck is gradually being rehabilitated in terms of intrinsic muscle stability and range of motion.