Cervical Subaxial Laminectomy, Instrumentation, and Fusion (C3 to Upper Thoracic)

Mathew Cyriac

John M. Rhee

Illustrative Case

A 54-year-old man with multilevel cervical spondylotic myeloradiculopathy (Figures 5-1 and 5-2).

Figure 5-1 ▪ A-C, Radiographs demonstrate slight C2-7 kyphosis on the neutral lateral x-ray that corrects to straight alignment on extension. Anteroposterior x-ray shows neutral coronal alignment and readily visible C7 pedicles for instrumentation.

Figure 5-2 ▪ A, Corresponding magnetic resonance imaging demonstrates multilevel cord compression from C3-6 in a congenitally narrow canal, with the worst levels being C3-4 (B) and C4-5 (C) (axial cuts shown). Retrovertebral cord compression is also present behind the bodies of C4 and C5. One can imagine by evaluating the sagittal cut that the canal would most likely be adequately decompressed after a multilevel laminectomy from C3-6, especially because the alignment on the extension x-ray predicts the possibility of greater lordosis in the final surgical construct than is seen on this supine MRI.

General Indications

Multilevel (≥3 motion segment) myelopathy, particularly in the presence of multilevel retrovertebral cord compression that would otherwise require multilevel corpectomy instead.
Neutral or kyphotic alignment that is flexible enough to be correctable to an acceptable alignment with positioning.
- If the patient is lordotic and has minimal to no axial neck pain, laminoplasty is generally preferred instead.
Preoperative imaging studies suggesting that both the anterior and the posterior aspects of the cord will be adequately decompressed by performing a laminectomy.

Radiologic Assessment

Evaluate the preoperative cervical sagittal alignment on the lateral and extension x-ray, as well as supine sagittal computed tomography (CT) or magnetic resonance imaging (MRI). This will estimate the amount of lordosis that can be passively achieved with positioning.
- If, based on review of imaging, an acceptable sagittal alignment cannot be achieved with positioning, anterior or combined anterior-posterior surgery may be needed.
Estimate on the sagittal MRI the likely path that the cord will take after laminectomy given the anticipated postoperative sagittal alignment. If imaging suggests that a posterior decompression will not allow for adequate decompression of the anterior aspect of the cord, then an anterior or combined anterior-posterior approach may be needed. Sometimes, a staged anterior operation can be done later, after an initial posterior laminectomy and fusion, with subsequent focal anterior decompression if needed.
Judgment is needed when determining the approach. Although preferable, not every patient necessarily needs to have a lordotic cervical spine. Some degree of kyphosis may be acceptable as long as the cord is properly decompressed with reasonable overall cervical sagittal balance.
We routinely obtain CT scans when performing laminectomy with fusion in order to evaluate the bony surgical morphology, including the size and angulation of the lateral masses and pedicles, and to evaluate to neuroforamina (Figure 5-3).
In patients with significant kyphosis, or poor bone quality, we generally recommend proximal fixation up to C2, which provides a more stable proximal anchor point. In the present case, C3 was chosen because the alignment is only mildly kyphotic and anticipated bone quality was good. Refer to Chapter 7 (C1-2 instrumentation and fusion) for details regarding C2 instrumentation.

Figure 5-3 ▪ A, B, Left parasagittal and axial computed tomography used to estimate the lateral mass lengths and cephalad angulation. Note the lines (labeled 1 and 2) on the parasagittal CT demonstrating the approximate paths of lateral mass screws.

Positioning

See Chapter 4 (Laminoplasty) for basic elements of positioning prone for posterior cervical surgery. Although similar, the laminectomy and fusion patient will be positioned with greater focus on sagittal alignment, because the fusion will lock the patient into that position.
Avoid excessive extension in severely myelopathic patients prior to decompression as it can cause neurologic injury.
In general, we attempt to mimic the patient’s neutral lateral or extension x-ray with positioning.
- A C-arm is used to verify position prior to prepping and draping (Figure 5-4).
- Beware that with extension, asymptomatic foraminal stenosis may actually become symptomatic as the foramen narrows further with extension and is locked into place with the instrumentation. Careful scrutiny of parasagittal CT scans through the foramina can assist in identifying such areas. If significant foraminal narrowing is present and is likely to further worsen after positioning in the final desired alignment, consideration should be given to foraminotomy, even if that foramen is asymptomatic preoperatively (Figure 5-5).
In select cases, further extension can be added by repositioning the Mayfield after thorough decompression (of not only the cord but also the roots) and before locking down the instrumentation in order to maximize lordosis.

Figure 5-4 ▪ A, B, Lateral fluoroscopy view prior to incision shows that overall sagittal alignment is similar to, but slightly more lordotic than, the preop neutral lateral x-ray.

Figure 5-5 ▪ Parasagittal computed tomography shows significant left-sided C4-5 and C5-6 foraminal stenosis (arrows). Even though this patient had only right-sided symptoms, we performed foraminotomy prophylactically on the left side in this case for the reasons mentioned in the text.

Anesthesia/Neuromonitoring Concerns

In myelopathic patients, we ask anesthesia to maintain mean arterial pressures above 80 to 85 mm Hg.
We generally use neuromonitoring for myelopathy cases. If a deformity is corrected, we employ MEP. If not, then SSEP is our preferred method of neuromonitoring in these cases.

Localization of Incision

The incision is localized by using palpable surface landmarks (eg, the spinous processes). Because a supplemental fusion is added, it is not as critical to avoid detaching the C2 muscle insertions as it is when performing laminoplasty, but we still attempt to maintain extensor muscle integrity as much as possible.

Approach