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Surgical intervention is indicated in patients with symptomatic cervical myelopathy resulting from spinal cord compression. Direct anterior multilevel cervical decompression and spinal fusion with instrumentation carry significant surgical morbidity. To avoid these anterior surgical complications, indirect multilevel posterior surgical decompression techniques were developed. Posterior decompression allows the spinal cord to migrate posteriorly away from the offending anterior spinal cord lesions.
Multilevel laminectomies without spinal fusion and instrumentation should be avoided because they may result in postoperative kyphotic spinal deformity. Motion-preserving laminoplasty is often the technique of choice in the posterior cervical surgical approach; however, it is contraindicated in patients with a painful kyphotic spine or K-line–negative spinal alignment. Multilevel laminectomies and spinal fusion with instrumentation eliminate the micromotion of the kyphotic spine and have better postoperative clinical outcomes than does laminoplasty in patients with K-line–negative alignment. This chapter describes the surgical indications for, contraindications to, pitfalls in, and tips for the successful execution of laminectomy and spinal fusion with instrumentation. All laminectomy and spinal fusion techniques described in this chapter refer to laminectomy and spinal fusion with instrumentation.
Preoperative Considerations
Cervical laminectomy with fusion is a surgical technique designed for patients presenting with three or more levels of spinal cord compression associated with spinal instability resulting from various clinical conditions ranging from cervical spondylotic myelopathy (CSM), to cervical trauma to spinal metastasis. In general, these patients present with cervical canal stenosis with spinal cord compression, resulting in a clinical diagnosis of cervical myelopathy. The patient typically reports “clumsy hands” symptoms that cause difficulties in writing or performing fine motor skill activities. The patient also reports an unsteady gait or even frequent falls. Clinical examinations often reveal findings of upper motor neuron lesions and long tract signs. Of these myelopathic signs, Lhermitte sign, bilateral Hoffmann sign, inverted radial reflex, inability to complete a finger grip-and-release test (20 times in 10 seconds), positive Romberg test result, and failure to perform tandem gait are the most representative of cervical myelopathy.
Radiologic imaging to confirm the diagnosis of cervical myelopathy and for surgical planning includes radiographs, magnetic resonance imaging (MRI), and computed tomography scans. Anteroposterior and lateral upright radiographs assess cervical spinal alignment, which is essential for surgical approach planning. Flexion and extension lateral cervical spine radiographs exclude segmental spinal instability and confirm cervical lordosis in the extension film. MRI is the gold standard for the diagnosis of cervical canal stenosis and its pathologic features. Computed tomography is indicated to confirm the diagnosis of ossification posterior longitudinal ligament (OPLL) and ossification of the yellow ligament.
Controversies exist between the anterior cervical approach and the posterior cervical approach in the surgical treatment of cervical myelopathy. The principle of the posterior cervical approach is based on the indirect spinal cord decompression method. Posterior decompression and expansion of the spinal canal diameter allow the spinal cord to migrate posteriorly away from the offending anterior spinal cord lesion and result in indirect spinal cord decompression without direct removal of the anterior spinal cord lesion.
The success of the posterior cervical approach depends on the sagittal alignment of the cervical spine, and this approach is contraindicated in patients with a grossly kyphotic cervical spine. Various investigators have reported that the appropriate cervical sagittal alignment for the posterior surgical cervical approach ranges from less than 10 degrees of kyphosis to neutral sagittal alignment. Rao and colleagues suggested that the posterior approach is indicated if cervical lordosis is present in the lateral extension cervical radiograph.
Fujiyoshi and associates used a novel K-line concept, in which the K-line was defined as a line that connects the midpoints of the spinal canal at C2 and C7 in the sagittal view. OPLL that did not extend posterior to the K-line was described as K-line positive, and OPLL that extended past the K-line was termed K-line negative. The observed outcome of laminoplasty was better in K-line–positive patients. In a follow-up study, Fujiyoshi and co-workers further reported that laminectomy and fusion resulted in a better outcome than did laminoplasty in patients with K-line–negative OPLL. Taniyama and colleagues validated the K-line concept in patients with CSM.
In general, the authors prefer the laminoplasty technique for the posterior cervical surgical approach. However, laminoplasty is not without limitations. Liu and colleagues described the following reasons for the revision of laminoplasty procedures: significant axial neck pain, segmental kyphosis, and anterior spinal cord compression of more than 50% of the spinal canal. The authors’ current indications for laminectomy and fusion with instrumentation are in older patients, with three of more levels of spinal cord compression from conditions such as OPLL or ossification of the yellow ligament, who have K-line–negative sagittal alignment and significant axial neck pain.
Surgical Technique
Anesthesia and Positioning
The patient, who is under general anesthesia, is positioned for a standard posterior cervical approach with the use of a radiolucent Mayfield clamp. Spinal cord monitoring using somatosensory-evoked potentials (SSEPs) and transcranial motor-evoked potentials (MEPs), with attention to placement of the deltoid electrode to detect C5 palsy, should be considered.
Adequate space between the patient’s face and the Mayfield clamp must be ensured to avoid facial compression by the clamp. The patient’s head, neck, and upper torso should be elevated above the level of the patient’s heart through reverse Trendelenburg positioning to reduce intraoperative spinal and epidural bleeding. Overzealous use of shoulder tapes to depress the patient’s shoulders to improve on the C6 to T1 fluoroscopic spinal image should be avoided because it may cause postoperative rotator cuff and brachial plexus injury (see Fig. 4-1 ).
Cervical lordosis is typically ensured preoperatively with the use of flexion and extension radiographs. Careful gentle manipulation of the Mayfield clamp under fluoroscopy guidance before laminectomy, instrumentation, and fusion may be considered. However, this can be a concern in patients with severe stenosis in whom extension before decompression can result in spinal cord compression. In general, because most cervical cord compression requiring surgical treatment occurs between C3 and C6 to C7, placement of the cervical spine in normal lordotic alignment is of no significant concern except when the planned spinal fusion will include the occipitocervical junction or the cervicothoracic junction.
A kyphotic or hyperlordotic occipitocervical junction may cause postoperative dysphagia and dysphonia. Care should be taken to match the preoperative erect sagittal occipito-C2 angle (an angle between the McGregor line and the line parallel to the base of the C2 body) with fluoroscopic images after occipitocervical fusion, to reduce postoperative complications. Avoiding cervicothoracic fusion in a patient with hyperlordotic or hyperextended alignment will reduce the patient’s postoperative distress resulting from an inability to see the feet during ambulation and when attending to genital hygiene.
Surgical Landmarks and Incisions
The surgical field is isolated using 3M Steri-Drape 1000 (3M, St. Paul, Minn.), from the external occipital protuberance to the spine of the scapula (see Fig. 4-1 ). Sterile scrub using povidone-iodine (Betadine) and removed with isopropyl alcohol is performed before definite surgical cleansing using povidone-iodine and surgical draping. This may reduce postoperative wound infection. The surgical incision is marked out by a straight line connecting the external occipital protuberance to the spinous process of C7 or T1. The extent of the surgical incision can be identified by fluoroscopy or by intraoperative palpation of C2 spinous process, which is the first palpable spinous process.
Meticulous midline dissection along the white median raphe minimizes bleeding and allows better preservation of surgical planes for wound closure. The median raphe can be identified and dissected effectively as follows. In one hand, the surgeon holds a self-retraining retractor to actively spread apart the paraspinal muscle. This places even tension on the muscles to help expose the midline raphe. In the other hand, the surgeon holds the diathermy device to dissect the raphe down to the spinous process.
Unnecessary muscle dissection beyond the intended spinal levels for decompression should be avoided, and when possible, the muscle insertions at C2 and C7 spinous processes should be preserved. Takeuchi and associates compared the axial neck pain after C4-C6 laminoplasty with C3 laminectomy and conventional C3-C7 laminoplasty. These investigators found that preserving the semispinalis cervicis muscle attachment to the C2 spinous process (which is more often damaged in C3 laminoplasty than in C3 laminectomy) reduces postoperative neck pain and stiffness. Similarly, Hosono and co-workers found that preserving the trapezius muscle insertion at the C7 spinous process reduces postoperative axial neck pain.
Because most cases of cervical canal stenosis with spinal cord compression arise from the C3 to the C6 to C7 spinal region, the authors prefer to perform laminectomies extending from lower C3 to upper C7. The C3 lamina is undercut, much like the C2 dome osteotomy, resulting in the preservation of the C2-C3 interspinous ligaments and the muscle attachments at the C2 spinous process. Upper C7 laminectomy is performed without disturbing the trapezius muscle insertion at the C7 spinous process. Spinal fusion and instrumentation are then performed from C3 to C7.
Spinal Instrumentation
Lateral Mass Screw Insertion
Spinal instrumentation is required for spinal stabilization to avoid postlaminectomy kyphosis, and it allows for spinal fusion. Screws holes are prepared before the laminectomy to avoid the loss of surgical anatomy required for screw insertion should laminectomy be performed first. Currently, two types of spinal instrumentation are available: lateral mass screw fixation and cervical pedicle screw fixation. In general, the authors prefer the use of lateral mass screws as the spinal fixation method of choice in most of degenerative cervical conditions including CSM and OPLL. Lateral mass screw insertion is quick, safe, and easily reproducible, and it provides adequate posterior spinal column stabilization in patients without anterior column disruption.
Various lateral mass screw insertion techniques have been described. The authors prefer the lateral mass screw entry point to be located just inferior and medial to the center of the lateral mass ( Fig. 34-1 ). This can be done first by visualizing an imaginary cross (“+”) placed at the center of the lateral mass. Next, the lateral mass screw entry point is located just medial and inferior to the center of this imaginary “+”. This places the starting point slightly within the inferomedial quadrant of the lateral mass. A burr is used to create a pilot hole at the lateral mass screw entry point for better anchorage of the screw drill bit. At the pilot hole, the screw trajectory is formed by aiming the tip of the screw drill bit toward the superior lateral corner of the index lateral mass while resting the shaft of the drill bit on top of the corresponding the spinous process of the vertebrae caudal to the index lateral mass screw hole.
