SURGICAL CONSIDERATIONS
Description: Posterior cervical laminectomy (removal of lamina), foraminotomy (opening of the neural foramina), and laminotomy (removal of a portion of the lamina) are posterior procedures for decompression of the neural elements in the C-spine. These procedures are used to treat cervical radiculopathy 2° degenerative disc disease (e.g., herniated discs, osteophytes). The major advantage of foraminotomy over an anterior approach is that it does not require fusion and, thus, preserves the motion of the involved vertebral segments and obviates the need for immobilization for fusion. It also permits decompression of multiple levels, if required. Disadvantages of foraminotomy include an increased incidence of neck pain and the fact that it is not an effective approach to midline disc herniation. Decompressive laminectomy can be used to treat cervical canal stenosis (congenital or degenerative) and for removal of intraspinal masses (tumors, AVMs, infective granulomas), which may be extradural, intradural, extramedullary, or intramedullary. Depending on the location of the tumor, the surgeon may need to open the dura and/or spinal cord. Obviously, the intradural intramedullary tumors involve more risk and are more delicate to remove. Many laminae may be removed to expose and excise the tumor. Surgical adjunctive tools (e.g., CUSA, laser, surgical microscope.) may be used to aid in removal of the tumor. Intraop evoked potential monitoring may be used during these procedures to test the integrity of the dorsal columns. After the tumor has been removed, the wound is closed in layers, as in a simple laminectomy.
Surgery is performed in the prone or sitting position through a posterior midline incision over the involved vertebrae. The paraspinal muscles are dissected off the spinous processes, and lamina and bone are removed piecemeal. The extent of the procedure depends on the indications for treatment. Hemostasis is achieved with bipolar cautery, and raw bone surfaces are sealed with bone wax. Topical hemostatic agents are used to aid in hemostasis in the epidural gutters. If the patient has an intradural tumor or process, such as syringomyelia, the dura is opened, and the operating microscope is used for this portion of the procedure. After the intradural procedure is complete, the dura is closed, and the surgeon may wish to test the integrity of the closure with a Valsalva-like maneuver (sustained inspiration to 30-40 cm H2O). The wound is closed in layers, and a drain may be left in the epidural space. Multilevel laminectomies with foraminotomies (involving partial removal of cervical facet joints) can result in late-onset cervical kyphosis, an extremely difficult condition to treat. These patients are usually considered for concomitant posterior fusion and instrumentation, especially in the presence of cervical segmental instability.
Newer less-traumatic techniques can be used to perform foraminotomies and discectomies in the cervical spine in a minimally invasive (MIS) fashion. These use one of many tubular retractor systems (e.g., METRx [Medtronic, Memphis, TN, USA]). These afford similar exposure but minimize blood loss, scar, and pain by spreading the muscles. The disadvantage is unfamiliar exposure, difficulty with retractor placement, and potential of neurological injury by inadvertent penetration of the interlaminar space.
Posterior cervical wiring techniques include (a)
interspinous wiring (
Fig. 1.3-8) (wires are passed through drilled holes in the base of adjacent spinous processes and then tightened); (b)
sublaminar wiring with Luque rods or rectangles (sublaminar wires are passed at each level on both sides and are tightened over the rods or rectangles); and (c)
a triple-wire technique with the first wire being passed through drill holes at the base of each spinous process, and the second and third wires passed through the same holes and then through drill holes in the previously placed bone
grafts. This latter technique is biomechanically sound because it places the bone grafts in compression. Wiring techniques, although stable in flexion, however, are less stable in extension and rotation, and they cannot be performed in patients with prior laminectomy or requiring laminectomy.
In the
posterior cervical lateral mass screw fixation technique, the C-spine is exposed through a midline incision over the involved vertebral segments. The lateral mass (bony column between facet joints) is identified, drilled, and tapped. Cortical screws are passed into the lateral mass and fixed with plates or rods. The trajectory of the screws in the lateral mass is to the upper outer corner in the classic Magerl technique. The entry point should be approximately 1 mm medial to the midpoint of the lateral mass (
Fig. 1.3-9). The axial trajectory angulation should be 25°, and the
sagittal angulation should be 45°, which is inline with the facet joints (
Figs 1.3-10 and
1.3-11). Adjacent facet joints are decorticated, and bone grafts are placed. Lateral mass plating provides a rigid multisegmental fixation and can be performed in patients with prior laminectomy. The major risks involved with this procedure are nerve-root and vertebral artery injuries.
Cervical pedicle screw plate fixation is an effective alternative to lateral mass fixation. In this technique, screws are passed under fluoroscopic guidance into the cervical pedicles and secured to plates or rods. This procedure is technically demanding, as the cervical pedicles are narrow and in close proximity to nerve roots, vertebral artery, and spinal cord, and their trajectories are typically unfamiliar. This technique is biomechanically stable and permits the
correction of deformity by application of compression or distraction forces. It is most commonly performed at C2 where the pedicles are relatively larger.
Usual preop diagnosis: Cervical radiculopathy (nerve-root compression); cervical myelopathy (spinal-cord compression); cervical disc disease (herniation or degeneration of one or more cervical discs); C-spine injury
Variant procedures: Patients with panvertebral disease (involving anterior and posterior elements of the spine) and three-column spinal instability often require combined anterior and posterior decompression, reconstruction, and instrumentation. Anterior screw plates provide a strong tension band to resist vertical/horizontal translation and neck extension; however, they are less able to resist flexion or rotation. By contrast, posterior cervical plates strongly resist flexion or rotation, but are less able to resist extension. Thus, in the presence of three-column spinal instability, combined anterior and posterior instrumentation often is required. This technique provides rigid fixation of spinal segments and avoids the need for rigid external orthotic devices.
Combined instrumentation techniques are challenging and require several special considerations. Patients with any unstable C-spine may require fiberoptic intubation, intraop cervical traction, and electrophysiological monitoring. Anterior and posterior cervical instrumentation is usually carried out in a single surgical session although may be staged. The transition between the anterior and posterior approaches requires a specialized operating table (e.g., Jackson spinal table or Stryker frame) and careful coordination among the entire OR team. The long duration of surgery may be associated with increased incidence of respiratory complications, blood loss, and prolonged ICU stays. In rare instances, an additional anterior or posterior approach may be performed (“540-degree procedure”).
Usual preop diagnosis: C-spine injury causing three-column (severe, unstable) injuries; cervicothoracic junctional pathologies; correction of kyphotic deformities; panvertebral disorders involving C-spine (neoplasms, infection, spondylitic myelopathy); failed symptomatic anterior cervical fusions