Multilevel Cervical Corpectomy: Anterior-Only Versus Circumferential Instrumentation

Anterior cervical corpectomy is a well-established procedure that has been used successfully in the treatment of numerous conditions, including infection, deformity, trauma, and cervical spondylotic myelopathy. Although posteriorly based procedures were the treatment of choice at the time cervical myelopathy was initially described, over the course of time anterior corpectomy has gained much popularity. Although some meta-analyses have reported equivocal results in comparisons between anterior and posterior decompression for the treatment of myelopathy, several series from single centers demonstrate satisfactory outcomes over long periods of follow-up for anterior cervical corpectomy. Anterior cervical corpectomy allows a more direct decompression and reduces the number of host-graft interfaces necessary for successful fusion. Hilibrand and colleagues demonstrated improved clinical outcomes for anterior cervical corpectomy compared with multilevel diskectomy and fusion, and other studies have documented better neurologic outcomes and less axial neck pain with corpectomy than with posterior procedures.

Potential complications after anterior cervical corpectomy include graft- and hardware-related problems. Hardware failure, graft pistoning, graft dislodgment, and pseudarthrosis have all been documented following corpectomy, with the risk of failure increasing with the number of cervical levels involved. Vaccaro and colleagues documented a 50% failure rate for corpectomy procedures involving more than two levels.

At present, the question remains regarding the optimal mode of fixation following cervical corpectomy at more than one level. Although anterior-posterior instrumentation is known to enhance stability relative to standalone anterior plate fixation, the added cost, increased operative time, greater blood loss, and less favorable complication profile of posterior instrumentation are not necessarily justified for every multilevel corpectomy. This chapter reviews the existing literature regarding circumferential instrumentation versus standalone anterior fixation after multilevel corpectomy and provides an algorithm based on best available evidence to inform decision making in regard to this issue.

Case Presentation

A 54-year-old man had a long history of progressive gait instability and upper extremity paresthesias. He had minimal issues with neck pain and had been previously treated with mild conservative measures.

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PMH: Unremarkable
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PSH: Unremarkable
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Exam: The patient had subjectively decreased sensation in the arms and hands bilaterally, and a positive Lhermitte sign. The patient also exhibited the Hoffman sign bilaterally and inverted brachioradialis reflexes. Ambulatory evaluation revealed a frankly ataxic gait.
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Imaging: Plain radiographs showed diffuse spondylosis throughout the subaxial cervical spine ( Figure 13-1 ). T2-weighted magnetic resonance imaging (MRI) studies are shown in Figures 13-2 through 13-4 . MRI revealed significant cervical stenosis in the setting of degenerative disk disease and broad-based disk bulges from C3 to C7. Cord signal changes were also evident at C3-4 (see Figure 13-3 ) and C5-6 (see Figure 13-4 ).

FIGURE 13-1

Lateral radiograph revealing diffuse spondylosis in the subaxial cervical spine.

FIGURE 13-2

Sagittal T2-weighted MRI scan showing significant cervical degenerative disk disease with broad-based disk bulging at C3-4, C5-6, and C6-7. Cord signal changes are evident at C3-4 and C5-6 ( arrows ).

FIGURE 13-3

Axial T2-weighted MRI scan showing significant stenosis at C3-4 with cord signal changes ( arrow ).

FIGURE 13-4

Axial T2-weighted MRI scan demonstrating significant stenosis at C5-6.

Based on the patient’s history, physical examination findings, and radiographic imaging studies the decision was made to proceed with a three-level anterior cervical corpectomy and instrumented fusion.

Surgical Options

For any case in which a multilevel corpectomy is indicated, the operative surgeon can choose to rely on anterior plate fixation alone or apply circumferential instrumentation with an anterior plate and a posterior fixation construct. The use of anterior plate fixation increases stiffness and reduces cervical motion following corpectomy. Such devices have been shown to improve fusion rates and reduce the incidence of strut graft subsidence. The addition of posterior spinal instrumentation further enhances construct stability through a tension-band effect. Posterior lateral mass fixation also improves stability due to the fact that it involves multiple points of segmental fixation, lies further from the axis of motion in the cervical spine, and achieves better fixation in the lateral masses than screws placed within the vertebral bodies. In addition, the presence of multiple points of fixation allows forces to be dissipated across several segments rather than concentrated at the ends of a construct.

For interventions that may warrant corpectomy at three or more levels, the surgeon can also opt to perform a two-level corpectomy in the area of greatest pathologic change combined with an anterior cervical diskectomy and fusion at the remaining level or levels. This technique, termed hybrid decompression and fixation by some, offers the advantage of a single anterior surgery with a theoretically more biomechanically stable anterior construct than multilevel corpectomy with end fixation only.

Fundamental Technique

The initial portion of an anterior cervical corpectomy procedure, whether or not hybrid decompression-fixation or circumferential instrumentation will be used, is performed with the patient in a supine position on a radiolucent table. Careful thought should be given preoperatively to whether an awake, fiberoptic-assisted intubation is necessary. Spinal cord monitoring with measurement of somatosensory and motor evoked potentials and electromyography is also recommended during cervical corpectomy procedures.

Once the patient is intubated, an intravenous bag or towels are placed in the interscapular region to hyperextend the cervical spine. The patient’s head can be placed in a Mayfield headrest or cushioned head support based on surgeon preference. Importantly, the neck should be maintained in a neutral position within the patient’s functional range of motion as assessed before surgery. The arms are padded and secured close to the body by means of tucked sheets or arm sleds attached beneath the operating table. The shoulders may be secured to the end of the bed with tape to facilitate exposure ( Tips from the Masters 13-1 ).

Tips from the Masters 13-1

Shoulder traction should be performed with extreme caution, especially in cases of severe cervical spondylosis, to avoid neurapraxia of the cervical nerve roots.

The approach for a cervical corpectomy can be performed from the left or right side based on the surgeon’s preference. The incision should be plotted using standard anatomic landmarks in the cervical spine and centered over the operative levels. In certain circumstances a two-level corpectomy can be performed using a transverse incision similar to that utilized for an anterior cervical diskectomy. However, in most cases, a longitudinal incision along the anterior border of the sternocleidomastoid is recommended for multilevel corpectomies. The cervical levels to be included are exposed in a fashion identical to that used in the standard anterior exposure of the cervical spine. Exposure should extend to the middle of the vertebral body above and below the fullest extent of the corpectomy. Appropriate surgical levels should be confirmed with intraoperative fluoroscopy.

Once the appropriate surgical levels have been confirmed, Caspar pins can be placed in the middle of the vertebral bodies above and below the corpectomy levels. Pins should be carefully placed so as not to violate the end plates. A Caspar distraction device can then be used to perform gradual distraction across the operative levels, usually after the corpectomy has been completed, to facilitate cage or strut insertion. Care must be taken to avoid overdistraction, because this can lead to neurologic injury. A scalpel with a size 15 blade is then used to perform diskectomies at the disk spaces above, within, and below the corpectomy levels. Disk material is removed with a pituitary rongeur.

Once the diskectomies are complete, a rongeur is used to create an initial trough in the vertebral bodies to be included in the corpectomy. This bone material should be retained for grafting, especially if a titanium mesh or expandable cage is to be used for reconstruction. It is imperative to clearly establish the cervical midline before initiating the corpectomy to minimize the risk of iatrogenic vertebral artery injury during the procedure. Once an adequate trough has been fashioned in the vertebral bodies with the rongeur, a high-speed cutting bur can be used to complete most of the corpectomy, although it is recommended to switch to a diamond-tip bur once the surgeon visualizes posterior cortical bone or nears the posterior longitudinal ligament (PLL). Remaining cortical bone can be elevated from a nonossified PLL using curved curettes. The PLL may then be elevated from its cephalad insertion with a curved curette or nerve hook and removed in piecemeal fashion with Kerrison rongeurs. At this point the dura is exposed and the decompression is completed.

Vertebral end plates at the cephalad and caudal margins of the corpectomy site, and at the adjacent diskectomy site if a hybrid decompression-fixation is performed, should be prepared with curettes and/or a cutting bur. The surgeon’s graft of choice (autogenous or allogenic; fibula strut, iliac crest, titanium mesh cage, or expandable cage) is then tailored to span the defect made by the corpectomy ( Tips from the Masters 13-2 ). Unless an expandable cage is being used, the strut is inserted into the superior end plate first, followed by tamp impaction into the end plate at the caudal margin. When nonexpandable cages or struts are used, it is useful to slightly overdistract the corpectomy site before insertion. Once the cage is in an ideal position, the distraction can be relaxed, which will enhance the interference fit at the end plates.

Tips from the Masters 13-2

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