Cervical Disk Herniation: Anterior Cervical Diskectomy and Fusion Versus Arthroplasty

Cervical disk herniation is a common problem affecting approximately 1 in 1000 adults in the United States. Although it typically causes radicular pain in a dermatomal distribution (radiculopathy), it can also cause motor weakness and myelopathic symptoms, such as gait difficulty, muscle spasticity, and bowel or bladder incontinence. In cases of isolated cervical radiculopathy without weakness, nonoperative treatment is usually recommended in the acute phase. Physical therapy and selective nerve root (or epidural) injections can alleviate symptoms and obviate the need for surgical intervention. If these treatments are not successful, surgical intervention may be considered. Surgical options include posterior laminoforaminotomy, anterior cervical diskectomy and fusion (ACDF), and cervical total disk replacement (TDR).

Case Presentation

A 42-year-old man had a 3-month history of left-sided arm pain that radiated from his neck to the level of his elbow. At presentation he described constant paresthesias and subjective weakness in his upper arm with overhead activities. He initially rated the pain at 8 out of 10 on a visual analog scale (VAS). When he first developed symptoms, he was prescribed nonsteroidal antiinflammatory medications and physical therapy, which minimally decreased his pain over the subsequent 2 weeks (pain rating of 6 out of 10). Two weeks after beginning physical therapy, the patient underwent a fluoroscopically guided C5-6 epidural steroid injection that provided some symptomatic relief, but with persistence of weakness.

•

PMH: Unremarkable
•

PSH: Unremarkable
•

Exam: The patient had normal spinal posture with 60 degrees of cervical flexion and 20 degrees of extension. Extension beyond 20 degrees produced pain in the left shoulder and the Spurling maneuver gave a positive result for both pain and numbness into the left arm. Motor examination revealed 4/5 strength in the patient’s left deltoid, external rotators, and biceps; he had normal 5/5 strength in all other muscle groups tested, including the right deltoid, external rotators, and biceps. Sensation to light touch was diminished over the lateral aspect of the shoulder on the left side, but preserved in all other dermatomal distributions in the left and right upper extremities. Reflexes were normal and symmetric in all extremities. No pathologic reflexes were present. His gait was normal with no evidence of cervical myelopathy.
•

Imaging: Plain radiographs demonstrated cervical spondylosis with anterior osteophytes at C4-5 and C5-6 ( Figure 1-1 , A and B ). There was no evidence of spondylolisthesis or instability with flexion extension ( Figure 1-1 , C and D ). Cervical magnetic resonance imaging (MRI) demonstrated central disk herniation at C4-5 and C5-6 with left greater than right foraminal stenosis ( Figure 1-2 ). A computed tomographic (CT) scan revealed little uncovertebral spurring and mild facet arthrosis at the lower cervical levels ( Figure 1-3 ).

FIGURE 1-1

Plain radiographs at presentation. A, AP view. B, Lateral view. C, Flexion. D, Extension.

FIGURE 1-2

MRI images at presentation. A, T2-weighted sagittal image. B, T2-weighted axial image at C4-5. C, T2-weighted axial image at C5-6.

FIGURE 1-3

CT scan before surgery. A, Left parasagittal view. B, Sagittal midline view. C, Right parasagittal view. No significant facet disease is demonstrated.

Surgical Options

Surgical indications for a herniated disk include disabling or progressive motor deficit or failure of radicular symptoms to respond to an appropriate nonoperative course of treatment. Surgical options for cervical disk herniation with indications for operative intervention include posterior laminoforaminotomy, anterior cervical diskectomy without fusion, ACDF, and cervical disk replacement. If the patient does not complain of neck pain and has only radicular symptoms, and imaging demonstrates a “soft” disk herniation, a posterior cervical laminoforaminotomy could adequately decompress the involved nerve root if the disk is lateral and not central. This procedure avoids the need for concomitant fusion. However, in patients with radiculopathy and persistent and severe neck pain, ACDF may be preferred. In addition, in the presence of anterior spinal cord compression or localized kyphosis, ACDF is preferred. Although ACDF has been successfully performed for decades, there are concerns that fusion alters spinal kinematics and leads to accelerated degeneration of adjacent segments. Cervical TDR has been suggested as an alternative to fusion with the advantage of preserving motion at the treated level and thereby theoretically reducing the risk of adjacent-level degeneration. The indications for cervical disk replacement include radiculopathy due to disk herniation with failure of nonoperative treatment or progressive or disabling motor loss. In addition, acute myelopathy secondary to a disk herniation may be amenable to treatment with decompression and TDR ( Table 1-1 ). In cases of advanced degenerative spondylosis, ACDF may be preferable to TDR. These would include cases showing severe loss of disk height, significant osteophyte formation, facet arthrosis, or ankylosis.

TABLE 1-1

Indications and Contraindications for Total Disk Replacement

Indications	Contraindications
Cervical radiculopathy refractory to nonoperative treatment and/or with objective motor weakness	Posterior column instability (e.g., iatrogenic or associated with trauma or rheumatoid arthritis)
Cervical myelopathy or myeloradiculopathy without retrovertebral stenosis	Retrovertebral stenosis (e.g., congenital cervical stenosis)
Isolated symptomatic cervical disk disease at one, two, or three levels	Chronic or active infectionAnkylosing spondylitis/diffuse idiopathic skeletal hyperostosis
	Ossification of the posterior longitudinal ligament
	Symptomatic facet arthrosis
	Osteoporosis
	Axial neck pain
	Obesity

For the patient described in the case study, he had his central disk herniations at both C4-5 and C5-6, so a posterior cervical laminoforaminotomy was not a good option. The risks, benefits, and alternatives to both ACDF and cervical disk replacement were discussed. At the time of the patient’s evaluation, a U.S. Food and Drug Administration (FDA) study of two-level cervical disk arthroplasties was in progress, and the patient was interested in participating in this study at the authors’ institution. All appropriate consents were obtained according to study protocols, and the patient was scheduled for two-level cervical disk replacement at C4-5 and C5-6.

Fundamental Technique

The surgical technique for cervical disk replacement is largely based on traditional ACDF techniques. The neck should be positioned in a neutral posture avoiding hyperextension. Anteroposterior and lateral fluoroscopic images should be checked after positioning to ensure adequate visualization of the treated level. The patient’s shoulders should be taped down if necessary to visualize the lower cervical levels (C6 and C7).

The surgical method utilizes the well-described Smith-Robinson exposure. After the skin is cut with a transverse incision based on anatomic landmarks and/or radiologic guidance, the platysma is exposed and incised. The deep cervical fascia is then exposed and incised anterior to the anterior border of the anterior belly of the sternocleidomastoid muscle. After palpating the carotid pulse and remaining medial to it, the surgeon uses blunt dissection to palpate the cervical spine. After the anterior cervical spine is adequately visualized, this structure is divided to expose the prevertebral fascia underneath. This is also divided vertically in the midline of the cervical spine. The midline is denoted by the gap seen by the medial borders of the longus colli.

Once the midline is adequately identified radiographically and marked, the longus colli muscles are elevated bilaterally ( Tips from the Masters 1-1 ). After the proper disk space is identified, the exposure of the disk space is completed laterally to the uncovertebral joints bilaterally.

Tips from the Masters 1-1

Identifying the midline is essential to appropriate implant placement.

After placement of craniocaudal distractors (Caspar-type pins in the vertebral body above and below the disk space) and self-retaining lateral retractors under the longus colli, diskectomy is performed ( Tips from the Masters 1-2 ).

Tips from the Masters 1-2

Careful attention must be paid to creating parallel end plates for implant insertion while minimizing weakening of the subchondral bone of the vertebral end plates.

In certain instances, contracture of the posterior longitudinal ligament (PLL) may limit parallel distraction of the vertebral end plates, which is typically required for appropriate prosthesis positioning, and thus division or removal of the PLL is necessary. If removal of the PLL or central osteophytes is required to effect neural decompression, this should be performed. When a TDR is carried out, the end plates should be preserved to avoid subsidence and heterotopic bone formation. A curette may be used to remove cartilaginous tissue to ensure parallel end plates. Use of a bur should be avoided to ensure minimal disruption of the end plates. Once the end plates are adequately prepared, careful attention is paid to the affected cervical foramina, and adequate foraminal decompression is ensured with curettes and/or Kerrison rongeurs to remove any residual posterior uncovertebral spurs ( Tips from the Masters 1-3 ). Adequate foraminal decompression is essential to relieving radiculopathy and minimizing recurrent symptoms in cervical disk replacement ( Tips from the Masters 1-4 ).

Tips from the Masters 1-3

Unlike after fusion, after total disk replacement motion will continue, so that symptoms will not be relieved unless complete direct foraminal decompression is achieved at surgery.

Tips from the Masters 1-4

In most instances, the prosthesis should be placed posteriorly in the disk space to allow for more normal kinematics.

Once the decompression is complete and the end plates prepared, attention is turned toward instrumentation. Using trial spacers, the implant of proper height and width is obtained. The widest implant able to be safely implanted should be selected to reduce the risks of subsidence. “Overstuffing” of the disk space will reduce implant motion, so the shortest implant (in a cranial-caudal direction) that is stable within the disk space should be used. Most trials have specific rotational specifications that require strict centering of the implant at the midline. After the properly fitted trial implant is placed, it is useful to obtain anteroposterior (AP) and lateral fluoroscopic images to confirm adequate positioning of the implant. After thorough irrigation and trialing, the TDR implant is placed, with careful attention to rotation, angulation, and depth. Whereas rotation is largely assessed with direct visualization and is based on identification of the midline at exposure, angulation and depth are best assessed with fluoroscopic guidance.

Postoperative course: The patient left the hospital on postoperative day 1, tolerating a soft diet. Upright cervical spine radiographs were obtained before discharge ( Figure 1-4 ). He wore his soft collar for 1 week and was seen for a clinical recheck at 2 weeks. His radiculopathy and neck pain resolved, and by 3 months after surgery he had resumed all usual activities. He required no pain medications. He was seen again at 3 months, 6 months, 12 months, 15 months, and 24 months. He was working in an unlimited capacity at 3 months; he was performing all of his recreational activities—including horseback riding and playing tennis—by 6 months. His motor strength and sensation returned to normal on the left side by his 6-month visit. Plain radiographs were taken at all visits and demonstrated a well-fixed prostheses with no evidence of lucency or migration ( Figure 1-5 ). As part of the FDA study, a CT scan was performed at 2 years ( Figure 1-6 ), which demonstrated osseous ingrowth and no evidence of lucency, migration, or osteolysis.