ACDF is a procedure often performed to remove a herniated or degenerative disc. Narrowing of the vertebral canal, a condition called spinal stenosis, can cause chronic pain, numbness, and muscle weakness in both upper and lower extremities. Bone spurs can also develop resulting in foraminal stenosis thus compressing the exiting spinal nerves.

The surgical approach during an ACDF is from the anterior, or front, of the neck. An anterior approach allows the surgeon access to the disc space without disturbing the spinal cord, spinal nerves, and posterior neck musculature. An incision is made and midline structures and musculature are retracted to expose the vertebral bodies and disc space. Bone and disc fragments are removed in order to decompress the spinal cord and nerve roots. After the disc space is cleaned out, a bone graft is placed in a metal cage and fit between the vertebral bodies. The adjacent vertebrae are held in place with a metal plate and screws. The ultimate goal of the surgery is to create a bony fusion between the adjacent vertebrae, which occurs as a result of the bone graft placement. The metal hardware simply acts as a cast, stabilizing the spine until fusion occurs (Fig. 12.4).

A common complication in anterior cervical surgery is vocal cord paralysis resulting from an injury to the recurrent laryngeal nerve (RLN). Patients with RLN palsy may experience hoarseness, develop a cough, or lose their voice completely and it may take several months for the nerve to recover [4, 5]. EMG monitoring using a special endotracheal tube has been shown to be useful in detecting injury to the RLN. Monitoring the RLN is discussed in detail in another chapter of this book.

Multimodality monitoring for anterior cervical fusions should include upper and lower SSEPs and Tc-MEPs to monitor spinal cord function, as well as EMG from the myotomes at risk to provide protection for the nerve roots. Positional injury may also be detected with upper extremity SSEP monitoring.

If spinal stenosis cannot be relieved by an anterior approach, or if the patient’s spine is not stable enough for this approach, the surgeon may opt for a posterior cervical laminectomy and fusion (PCF). The object of this procedure is decompression of the neural elements and stabilization of the cervical spine. Posterior fusions are also performed for instability of the cervical spine resulting from trauma or a degenerative pathology.

For PCF surgery, the patient is placed in a prone position (on their abdomen) with the head made immobile by placing in a special frame called a Mayfield (Fig. 12.5). The head is held in the Mayfield with pins. After the incision is made in the back of the neck, the surgeon will then dissect down through the subcutaneous tissues to the fascia overlying the spinous processes. Retractors are inserted to hold the muscle away from the spine, and the surgeon will begin to remove the lamina and other bony elements in order to decompress the spinal cord and nerve roots.

Various types of instrumentation are used to posteriorly fuse the cervical spine. Wiring can be used to stabilize the upper cervical vertebral segments (C1 and C2). Cervical vertebrae have anatomical structures not found elsewhere in the spine called the lateral masses, which are larger than the pedicles and are satisfactory targets for screw insertion. Placement of lateral mass screws and rods provides equal or greater biomechanical stability when compared to anterior plating or interspinous wiring techniques [6] (Fig. 12.6). Placement of lateral mass screws does not depend on the integrity of the laminae, pedicle, or spinous processes to achieve fixation as in case of cervical wiring and pedicle screws. The limitations of lateral mass fixation include risk of injury to the adjacent nerve roots, vertebral arteries, or facet joint [6, 7].

Similar to ACDFs, multimodality monitoring using SSEPs and Tc-MEPs to monitor the spinal cord and EMGs to monitor the nerve roots is the preferred monitoring plan for PCF.

When the cervical disease involves more than just the disc space or a single level, it may be necessary to remove the vertebral body and adjacent discs in a procedure called a corpectomy. This can be necessary for multilevel stenosis, tumor removal, or vertebral infection. The approach is similar to that of an ACDF. Once a majority of the affected vertebral bodies and disc material have been removed, a graft—typically shaped bone or a titanium cage—is fitted to support the anterior vertebral column (Fig. 12.7). The cervical spine is further stabilized with a metal plate and screws similar to that used in an ACDF. If the spine appears unstable after the anterior corpectomy, a PCF may be necessary to provide long-term stability. Recommended IOM is similar to that of an ACDF [8].

Scoliosis describes an abnormal, side to side, curvature of the spine. The two most common forms of scoliosis are degenerative and idiopathic (adolescent). Degenerative scoliosis is caused by a deterioration of the facet joints and occurs most commonly in people over 65. Surgery is often performed to reduce pain. Older patients may have osteoporosis and may require many levels of instrumentation to achieve a complete fusion. Idiopathic or adolescent scoliosis is seen in children and teenagers and usually is discovered during routine doctor’s exams. It is necessary to prevent the curvature from progressing as the child ages. If the curve measures <20°, surgeons often choose to brace the spine or continue to observe the progression of the curvature. Surgery for adolescents with scoliosis is only recommended when the curvature is >45° and continuing to progress [9]. A high degree of curvature may put the patient at risk for cardiopulmonary compromise as the curve of the spine rotates the chest and decreases the vital capacity (ability to breathe).