Anterior Cervical Diskectomy and Fusion

Howard S. An, MD

Thomas D. Cha, MD, MBA

Dr. An or an immediate family member has received royalties from U & I; serves as a paid consultant to or is an employee of Smith & Nephew, Life Spine, Zimmer, Pioneer, Advanced Biologics, and Halozyme; has stock or stock options held in Pioneer, Spinal Kinetics, U & I, Anulex, and Articular Engineering; has received research or institutional support from Synthes, Baxter, Spinalcyte, Globus Medical, and the National Institutes of Health; has received nonincome support (such as equipment or services), commercially derived honoraria, or other non-research-related funding (such as paid travel) from Synthes and Rush University Medical Center; and serves as a board member, owner, officer, or committee member of the International Society for the Study of the Lumbar Spine, Spinal Kinetics, Pioneer, Medyssey, Advanced Biologics, and Articular Engineering. Neither Dr. Cha nor any immediate family member has received anything of value from or has stock or stock options held in a commercial company or institution related directly or indirectly to the subject of this chapter.

PATIENT SELECTION

Anterior cervical diskectomy and fusion, first described by Robinson and Smith¹ in the 1950s to treat radicular symptoms, has been a very successful procedure as evidenced by the frequency of its use. The clinical evaluation of patients with cervical degenerative disorders requires interpretation of patient symptoms, meticulous physical examination, and appropriate selection of diagnostic tests. A useful approach for the clinician is to categorize the symptoms and findings as axial neck pain, radiculopathy, myelopathy, or some combination of the three.

Indications

The indications for surgical intervention in cervical radiculopathy include failure of a 3-month trial of nonsurgical treatment to relieve persistent or recurrent radicular arm pain with or without neurologic deficit and the presence of a progressive neurologic deficit. Neuroradiographic findings must be consistent with the clinical signs and symptoms, and the duration and magnitude of symptoms must be sufficient to justify surgery.²

The surgical indications for the treatment of cervical myelopathy are not as well defined as they are for the treatment of radiculopathy. A patient with a mild, long-standing, and nonprogressive myelopathy without significant disability can be observed closely. Surgical intervention is recommended in the following situations: (1) progressive myelopathy, (2) moderate or severe myelopathy that is stable and of short duration (<1 year), and (3) mild myelopathy that affects routine activities of daily living. The age of the patient or severity of the disease is not a contraindication for surgery. It is imperative, however, that the patient understand that the goal of surgery is to prevent neurologic worsening, although most of the patient’s neurologic function improves following surgical decompression.

PREOPERATIVE IMAGING

Several neuroradiologic imaging techniques are available to closely evaluate patients with cervical radiculopathy and myelopathy. Because each modality has its own inherent strengths and weaknesses, a combination of examinations is often required. Initial assessment begins with plain radiographic AP and lateral views. Oblique views are useful to evaluate bony narrowing of the foramina. Flexion-extension views are useful when instability is suspected or when evaluating the rigidity of sagittal plane deformity. Findings such as disk space narrowing, developmental canal stenosis, subluxations and malalignments, and vertebral osteophyte formation must be evaluated in the context of the patient’s symptoms. Abnormal findings on plain radiographs may not identify the cause of the clinical picture; therefore, further correlative studies may be necessary before recommending specific treatment. Changes on plain radiographs may also confirm the clinical suspicion of typical degenerative disease and reassure the clinician and the patient that appropriate therapy is being followed.

MRI is the most sensitive modality for assessing the morphology of the spinal cord and its relation to the spinal canal as well as for providing direct information about nerve root or cord compression. MRI also shows intramedullary cord changes that may relate to disease prognosis. MRI is less sensitive in detecting foraminal stenosis, however, and does not demonstrate cortical
margins as well as CT. CT scans with 45° oblique reconstruction views allow enhanced assessment of the neural foramina (Figure 1).

Myelography is occasionally used in the setting of unclear pathology and in patients with preexisting metal implants that would produce artifact in other modalities. A plain AP radiograph with water-soluble myelography can demonstrate exiting nerve roots at the level of the pedicle or the typical filling defect seen with nerve root compression. The lateral view may show spinal cord compression by the disk or posterior vertebral osteophytes and/or hypertrophied ligamentum flavum. Afterward, CT can be done for three-dimensional depictions; however, as with myelography, neural compression by deformity of the dural sac or nerve roots can only be inferred, and the etiology of contrast blockade cannot be determined.

Rarely, electromyography/nerve conduction velocity studies may be used to confirm suspected radiculopathy or to further evaluate symptoms with atypical findings. These tests may be most useful when attempting to differentiate root compression and a peripheral neuropathy. Nuclear medicine bone scanning, local diagnostic injections, diskography, and cerebrospinal fluid analysis have a limited role in the diagnostic process.