Cervical Laminectomy and Fusion

Cervical laminectomy and fusion constitute a procedure used in patients with clinical symptoms and radiographic evidence of cervical spondylotic myelopathy (CSM), which is a condition caused by repetitive dynamic injury to the spinal cord that leads to progressive neurologic decline. Once neurologic injury has occurred, it is commonly irreversible and the role of surgery is in preventing further decline rather than reversing damage that has already occurred. The first goal of this procedure is decompression of the spinal cord by means of a laminectomy and removal of the posterior elements causing stenosis of the spinal canal and thus cord compression. The second goal of this procedure is stabilization of the subaxial cervical spine, which can be achieved with lateral mass or pedicle instrumentation. Various techniques are employed to do this safely while avoiding neurovascular structures.

14.2 Indications

Cervical spondylotic myelopathy (CSM) is the leading cause of spinal cord dysfunction in the world. ¹^, ² The pathophysiology of this condition involves both biomechanical stress as well as ischemic damage which can cause significant neurologic decline over time. ¹^, ³^, ⁴ While the natural history of CSM is difficult to predict for a given patient, once neurologic damage has occurred, it tends to be a progressive and irreversible process without surgical intervention. The goal of surgery is to prevent progressive neurologic decline from repetitive dynamic injury secondary to spinal cord compression.

14.3 Patient Selection

The decision regarding which surgical approach to use should be made based on the patient’s anatomy and the characteristics of the pathology on imaging studies. Appropriate candidates for cervical laminectomy and fusion are those with signs and symptoms of cervical myelopathy who have evidence on magnetic resonance imaging and computed tomography (CT) of multilevel spinal cord compression caused by ventral osteophytes, ossification of the posterior longitudinal ligament, or buckling of the hypertrophied ligamentum flavum ( ▶ Fig. 14.1 a, b, ▶ Fig. 14.2 a, b). CT or X-ray myelography may also be used to make this diagnosis.

Fig. 14.1 (a) T2 sagittal magnetic resonance imaging of the cervical spine with evidence of mild C4–5 posterior compression and severe C5–6 and C6–7 anterior spondylotic compression. (b) Axial T2 MRI image of the C6–7 level showing severe spinal cord compression with T2 signal change in the spinal cord. (c) T2 sagittal MRI postoperative image of the cervical spine of the same patient after C4–7 laminectomy showing appropriate decompression of the spinal cord with dorsal movement of the spinal cord away from the anterior compressive pathology. Note that the T2 signal abnormality in the spinal cord is unchanged.

Fig. 14.2 (a) T2 sagittal magnetic resonance imaging (MRI) of the cervical spine depicting ossification of the posterior longitudinal ligament from C3–6 compressing the spinal cord anteriorly with T2 signal change in the spinal cord. Note strengthening of the cervical curvature. (b) Axial T2 MRI of the C5–6 level of the same patient depicting severe spinal cord compression. (c) T2 sagittal postoperative MRI of the same patient showing C3–7 laminectomy and decompression of the spinal cord, again showing the dorsal retraction of the spinal cord away from the anterior compressive spinal pathology.

Normal lordotic cervical spine curvature (approximately 40 degrees) in these patients is also a necessary criterion for cervical laminectomy and fusion surgery. ⁵^, ⁶ Adequate posterior decompression of the cervical spinal cord and the patient’s symptomatic improvement postoperatively depend on the ability of the spinal cord to fall away from the ventrally located compressive pathology once the dorsal bony and ligamentous elements of the cervical spine are removed ( ▶ Fig. 14.1 c, ▶ Fig. 14.2 c). Therefore, if either or both lateral cervical X-rays and reformatted sagittal CT scans show straightening of the normal cervical spine curvature or kyphotic deformity, posterior cervical decompressive surgery is contraindicated unless lordosis can be restored through intraoperative realignment or through the use of supplemental anterior cervical reconstruction ( ▶ Fig. 14.3 a–c). ⁷

Fig. 14.3 (a) T2 sagittal magnetic resonance imaging of a patient with severe spondylotic kyphotic deformity centered at C4–6 with both anterior and posterior compression of the cervical spinal cord from C3 to T1. (b) Sagittal reconstructed computed tomographic (CT) view of the same patient depicting the bony kyphotic deformity. (c) Postoperative sagittal reconstructed CT of the same patient after C4–5 vertebrectomy and posterior C3–7 laminectomy and fusion from C3 to T1.

Cervical instability secondary to trauma, neoplasm, or connective tissue disorders in conjunction with multilevel spinal cord compression is another indication for posterior cervical laminectomy and fusion as long as anterior column support is intact or has been surgically restored. The addition of posterior instrumentation, with or without laminectomy, has not been demonstrated to add a significant degree of morbidity to these cases, with similar complication profiles in anterior alone versus anterior-posterior fusions. ⁷

We recommend that cervical laminectomy and fusion be extended to at least one level above and below the areas affected by the cervical spine pathology. In general, we also recommend that any patient undergoing anterior cervical decompression and stabilization surgery at three or more levels should have supplemental posterior cervical fusion, with or without laminectomy, as indicated. This practice comes from evidence of a high incidence of anterior graft subsidence as bony fusion occurs weeks to months after the anterior procedure is performed. ⁷

14.3.1 Patient Counseling

It must be made clear to the patient that the purpose of surgery is not to reverse neurologic injury that has already taken place but rather to prevent further injury secondary to compression of the spinal cord. The risks and complications of cervical laminectomy and fusion with lateral mass screws are few and infrequent. ⁸ The immediate perioperative risks include the spinal cord (which includes quadriplegia with loss of bowel or bladder function); nerve root injury (including C5 palsy, which occurs in approximately 8% of posterior procedures ⁹); cerebrospinal fluid (CSF) fistula; vertebral artery perforation; and epidural hematoma. The long-term complications of the surgery are failure of instrumentation or fusion leading to kyphotic deformity, adjacent-segment disease, or wound dehiscence or infection.

14.4 Preoperative Preparation

14.4.1 Intubation and Patient Positioning

Patients with compression of the spinal cord are at increased risk of injury if the neck is manipulated rapidly or placed in excessive extension or flexion. For this reason, an awake fiberoptic nasal intubation is recommended as the gold standard in patients whose symptoms are reproducible by gentle extension of the neck while the patient is awake. It has been shown, however, that this proceure may not always be necessary. ¹⁰ The endotracheal tube must be secured to the patient tightly to prevent it from dislodging during final prone positioning. An arterial line is placed in patients to monitor blood pressures continuously throughout the procedure, and the blood pressure is maintained in a normotensive range, ideally keeping the mean arterial pressure at or greater than 85 mm Hg. ¹¹^, ¹² A single dose of prophylactic antibiotics is administered by the anesthesiologist within 1 hour before the incision is made.

The patient’s head is pinned into the three-point Mayfield head-holder (Integra LifeSciences Corporation, Cincinnati, Ohio) oriented in a coronal position while the patient is still in the supine position. The patient’s head and body are then turned slowly into the prone position onto a normal operating table with two large, parallel gel rolls. A Jackson spine cradle can also be used if necessary. A rigid cervical orthosis may be kept during positioning, depending on the stability of the spine and degree of vertebral canal stenosis. The Mayfield head-holder is attached to the bed, with the head and cervical spine in a neutral position. Slight military flexion (maintenance of extension of the subaxial cervical spine while providing flexion of the craniocervical and atlantoaxial joints) of the cervical spine may be useful to allow for better exposure of the posterior cervical spine anatomy ( ▶ Fig. 14.4).

Fig. 14.4 Intraoperative photo depicting the appropriate prone position of a patient in three-pin head-holder fixation, with the neck neutral or slightly flexed in preparation for cervical laminectomy and fusion.

In most patients, the shoulders slump rostrally and should be pulled inferior and lateral with tape attached between the top of the shoulders and the foot of the operating table. One can place the patient in reverse Trendelenburg to further open up the posterior cervical area for adequate identification of the pertinent surgical landmarks. Avoidance of hypotension and the reverse Trendelenburg position may aid in the prevention of postoperative visual loss, which has a reported incidence of 0.002 to 0.2%. ¹³

14.4.2 Neurophysiologic Monitoring

Somatosensory evoked potentials (SSEPs) and motor evoked potentials (MEPs) may be monitored in patients with CSM undergoing posterior decompression and stabilization. To monitor SSEPs and MEPs throughout the procedure, total intravenous anesthesia must be used, and volatile inhaled anesthetics should be avoided. Electrodes are placed after the patient is asleep before final positioning. When feasible, it is recommended to establish baseline SSEPs after intubation before flipping to the prone position. It is often not possible to obtain MEPs owing to the residual effect of paralytics given for intubation. If SSEPs and MEPs are lost or decline along any step of the procedure, a stepwise approach should be taken to identify the possible cause. First, the surgeon should confer with the neurophysiologist to ensure the proper placement of electrodes and their connections. Second, the surgeon should confer with the anesthesiologist to ensure that no gas agents or paralytics were given. Once this is done, other measures that can be considered include increasing the blood pressure, inspecting the operative field for any signs of spinal cord compression, and ensuring that the patient’s alignment in the Mayfield did not change. If no easily correctable cause is identified, a wakeup test may be considered.

14.5 Operative Procedure

14.5.1 Incision and Soft Tissue Dissection

The midline is palpated, and the incision is marked using the spinous processes of the cervical vertebrae as a landmark. The spinous processes of C2, C6, and C7 are usually the most easily palpable. The C2 spinous process, which is typically bifid, is the first palpable spinous process. The vertebra prominens is typically C7, although C6 may occasionally be more prominent. The incision is made with a knife blade and carried down through the skin using a unipolar cautery. Great care should be taken to remain in the midline during the fascial dissection because it is a relatively avascular plane and provides a more expedient route to the muscular fascia and the cervical spinous processes.

Once the spinous processes are identified, the muscle is removed from them, medially to laterally, one side at a time, using the cautery and a periosteal retractor until the laminae are identified at each level. Muscle layers encountered from superficial to deep include the trapezius, splenius capitus and cervicis, semispinalis and spinalis cervicis, along with the interspinalis cervicis and rotatores cervicis. Using one hand to retract the muscle laterally and the other to continue releasing the tissue in a subperiosteal fashion has become the standard in this exposure. The muscle is then further dissected from the laminae to expose the lateral extent of the lateral masses and facet joints at each level. At the superior extent of the dissection, caution should be taken to avoid removal of the C2 soft tissue and muscular attachments, which confer stability to the spine at this level. At this point, lateral exposure can be maintained using self-retaining retractors ( ▶ Fig. 14.5 a). A curet is used to remove all additional soft tissue, specifically the synovium lining the interfacet spaces of interest to maximize bony fusion. A clamp is then placed on one of the exposed spinous processes, and an intraoperative X-ray is obtained to confirm the levels of the surgery.

Fig. 14.5 (a) Intraoperative photo of the cervical exposure required before performing a laminectomy and fusion after the subperiosteal dissection. (b) Intraoperative photo depicting the drilled bilateral troughs in the laminae of C3–7 for decompression of the spinal canal from posteriorly. Bilateral lateral mass pilot holes are also seen. T1 screws have already been placed in order to aid with the alignment of the lateral mass screws. (c) Intraoperative photo depicting the decompressed cervical thecal sac after completion of the laminectomy with bilateral lateral mass pilot holes and T1 pedicle screws in view. (d) Intraoperative photo showing the cervical lateral mass/pedicle screws without rods yet in place. Decortication can be done before or after this step. (e) Intraoperative photo showing the cervical lateral mass/pedicle screws with rods in place with the muscles retracted laterally by self-retaining retractors.

Only gold members can continue reading. Log In or Register to continue