Anterior Cervical Corpectomy and Fusion and Hybrid Techniques

Preoperative Considerations

The classic signs and symptoms of cervical myelopathy should be elicited when obtaining a detailed patient history. Neck and arm pain may be present, but myelopathic patients with minimal to no pain may also be encountered. Typical symptoms include numbness and tingling in the hands or arms, decreased strength, diminished dexterity and coordination, and balance difficulty. Questions should center on tasks that require fine motor movements; patients will report difficulty buttoning buttons and picking up coins off the floor, and their handwriting may worsen.

Certain physical examination findings are indicative of cervical myelopathy and should be routinely evaluated. Flexion-extension radiographs of the neck may reproduce pain or electric shocks down the arms and back (Lhermitte sign). Strength and light touch in the upper extremities may or may not be normal. However, a careful monofilament examination of the palmar digits can reveal subtle impairment. Other physical examination findings suggestive of upper motor neuron disease include hyperreflexia, inverted radial reflex, Hoffmann sign, clonus, and Babinski sign. Tandem gait evaluation should be performed to assess coordination and balance.

Imaging studies should consist of anteroposterior, lateral, flexion, and extension views of the cervical spine ( Fig. 31-1 ). Sagittal and coronal alignment, as well as any dynamic instability, should be noted. MRI studies allow evaluation of the disks, spinal cord, nerve roots, and ligamentous structures. Compression of the spinal cord can lead to edema within the substance of the spinal cord itself that manifests as a hyperintense signal on T2-weighted images. In addition to the substance of the spinal cord, the vertebral arteries should be carefully evaluated on the MRI images. The vertebral artery most commonly enters the foramen transversarium at C6, but variability exists. Even when the vertebral artery resides within the foramen, it may take a medial course into the vertebral body; serious consequences can result if this is not identified preoperatively, and corpectomy is performed at that level.

MRI remains the imaging modality of choice; additional information can be gleaned from a CT scan with or without a myelogram. A more detailed depiction of the bony anatomy can be appreciated, and in revision procedures, previous fusions can be assessed. Regardless of the imaging modality selected, the surgeon must be able to extrapolate a three-dimensional understanding of the neural compression from two-dimensional images. This understanding allows the surgeon to determine whether diskectomy, corpectomy, or a hybrid approach is appropriate.

Surgical Considerations

Adequate decompression can be achieved from either an anterior or a posterior approach, depending on the patient’s alignment and direction of compression. Kyphosis that does not correct in extension typically requires an anterior approach. In the kyphotic spine, performing posterior decompression for anterior compressive disease does not allow posterior migration of the spinal cord. The patient will continue to be symptomatic from the neural compression postoperatively.

Neural compression that occurs posterior to the disk spaces can be easily addressed with ACDF. Compression that occurs posterior to the disk spaces may require corpectomy. Extruded disk fragments located posterior to the vertebral body, but near the disk space, can sometimes be removed with a ball-tipped micro-nerve hook. However, if the extruded fragment cannot be removed in this manner, corpectomy becomes necessary. In the setting of ossification of the posterior longitudinal ligament, less ambiguity exists. Compression posterior to the vertebral bodies requires corpectomy to be addressed anteriorly. For multilevel ACDF procedures, corpectomy can reduce the number of healing surfaces and can potentially improve fusion rates. Multiple corpectomies, however, can destabilize the spine because of the long lever arms involved. Patients in whom such constructs are contemplated should be considered for a hybrid construct. In this construct, segmental fixation is placed within the intervening retained vertebral bodies to increase construct stability and preclude the need for posterior fixation.

A previous anterior surgical procedure is a relative contraindication to a secondary anterior procedure. Performing the approach through the contralateral side allows the surgeon to avoid scar and work through native tissue planes. However, the competence of the recurrent laryngeal nerve and vocal cords must be assessed preoperatively by direct or indirect laryngoscopy. Injury to the recurrent laryngeal nerve on the previously operated side should dissuade one from approaching the cervical spine from the contralateral side because this may lead to bilateral vocal cord paralysis.

Surgical Technique