Posterior Surgery for Cervical Trauma

Summary of Key Points

Cervical spine trauma is common and often amenable to a posterior approach for surgical fixation.
The role of surgical decompression and stabilization of the spine is determined by neural compression and stability of the spine.
When determining need for surgical fixation versus nonoperative management of cervical spine injuries, it is important to consider if there is bony involvement, as a fractured bone with maintained alignment offers surface area for bony fusion with external immobilization.
Injuries to the atlantooccipital junction are incredibly unstable and require prompt stabilization with an occipitocervical fusion.
A fracture of the atlas can often be managed nonoperatively; however, posterior surgical fixation is indicated when there is evidence of atlantoaxial instability, often associated with transverse atlantal ligament avulsion.
The majority of C2 fractures can be managed nonoperatively, including odontoid fractures and traumatic spondylolisthesis of the axis, unless there is significant displacement decreasing the ability for normal healing and/or resulting in neural compression.
Subaxial spine injures can often be managed nonoperatively as well; however, instability (defined as bilateral facet involvement) and/or severe ligamentous disruption or neural compression typically require surgical fixation.

Cervical spine trauma is common, and may present with a spectrum of neural injuries and destabilization of the spinal column. The optimal management of cervical spine trauma involves appropriate decompression of neural compression, as well as stabilization of the spine through nonoperative care or operative stabilization. The posterior approach to the cervical spine is versatile, and can address pathology from the occipitoatlantal joint to the cervicothoracic junction. Fracture patterns and patterns of instability are characteristic to different regions of the cervical spine. The purposes of this chapter are to review patterns of injury to the cervical spine and to discuss the role of nonoperative care and operative care, with an emphasis on the posterior approach to operative management.

Upper Cervical Spine Injuries

Occipitocervical Injury

Injuries to the occipitocervical junction include both occipital condyle fractures and atlantooccipital dislocation. Occipital condyle fractures are typically managed conservatively, whereas atlantooccipital dislocation requires surgical stabilization with an occipitocervical fusion.

Occipitocervical Fusion

Occipitocervical fusion is intended to treat any injury that results in craniocervical instability. The technique has evolved throughout the years, but recently it has involved placement of an occipital keel plate connected to cervical screws with a rod. Prior constructs involved wiring/cabling; however, this method has fallen out of favor because of decreased ability to withstand rotational stress, inability to decompress the cervical spine in areas where the laminar wires/cables traverse, erosion of wire through bone, and potential of leakage of cerebrospinal fluid (CSF) from suboccipital burr holes required for wiring to occiput.

Preparation/Positioning

Instability of the craniocervical junction leaves the patient vulnerable to excessive movements and subsequent neurological deterioration during surgery preparation and positioning. Because of this, intraoperative neuromonitoring is often used to monitor the integrity of the spinal cord during patient positioning. When positioning the patient, it is important to maintain both sagittal and coronal balance to ensure normal horizontal gaze and the ability to maintain normal swallowing function. The patient is placed in the prone position on a frame, typically with the head pinned into a Mayfield head clamp. Appropriate positioning before fusion can be confirmed with either intraoperative fluoroscopy or intraoperative computed tomography (CT). Of note, it is important to check neuromonitoring after positioning is finalized and before surgical start to ensure no changes occurred during positioning.

Occipital Instrumentation

The occipital plate must avoid important anatomic structures, while also having strong cortical purchase. Plate placement is guided by the location of the transverse sinus, which can be approximated to be just above the level of the superior nuchal line. It has been demonstrated that placement of the plate 2 cm caudal to the superior nuchal line is safe to avoid transverse sinus injury. Consideration should also be taken to position the plate below the inion to avoid hardware erosion and overlying skin breakdown, as this is the most prominent portion of the occiput. Furthermore, care should be taken to place the plate midline along the keel for normal alignment as well as fusion, as the suboccipital bone is thickest in the midline, allowing stronger screw purchase. For appropriate stability of the construct, we believe it is important to achieve bicortical screw purchase of the keel; however, in a cadaveric study it has been shown that the occipital bone is thick enough to allow either unicortical or bicortical purchase for a strong occipitocervical construct. In a series reported by Nockels et al., either unicortical or bicortical purchase was achieved without impact on outcomes. If the dura is compromised and a CSF leak is seen at time of screw placement, placement of the screw will prevent any further leakage. The thickness of the suboccipital bone increases from the foramen magnum to the level of the inion, from approximately 8.3 mm at the level of the nuchal line to 13.8 mm at the inion. This can help guide screw length choice when beginning pilot holes and tapping screws. It is important to ensure tapping along the entire screw length to prevent screw fracture during placement.

Cervical Spine Instrumentation

Instrumentation of the cervical spine is typically performed with a pars screw at C2 and lateral mass screws in the subaxial spine. The type of rod that we prefer to use is a hinged rod, which creates the occipitocervical angle without the need for manual rod contouring. The hinge, however, is typically in line with where the C1 lateral mass screw would be, resulting in the inability to instrument that vertebra. In one study comparing the two rod types, it was noted that use of a hinged rod was as effective as use of manually contoured rods because both had similar outcomes. No studies have yet demonstrated superiority of the hinged rod to the contoured rod, so the benefit of less rod fatigue remains theoretical.

Atlas/C1 Injury

Atlas Fracture

Atlas fractures require surgical fixation via a C1‒C2 fusion when there is an atlas burst fracture associated with transverse atlantal ligament (TAL) injury, suggesting atlantoaxial instability. If the lateral masses of C1 are involved and unable to be instrumented, the construct can be extended to the occiput. In isolated and unstable C1 burst fractures with an intact lateral mass, the C1 ring can be recreated by placing bilateral lateral mass screws at C1 with a rod perpendicular to the axis of the spine.

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