Cervical Laminectomy and Laminoforaminotomy

Summary of Key Points

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Cervical spondylosis with resultant compression of nerve root (radiculopathy) or spinal cord (myelopathy) is a common problem, with the latter being the most common cause of spinal cord dysfunction in adults.
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In cervical spondylytic myelopathy, spinal cord dysfunction is caused by both compressive and dynamic (motion/stretch) forces on the spine.
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Dorsal approaches to the cervical spine afford an effective means of addressing the compressive forces, particularly in multilevel cases, without a mandate for simultaneous fusion. Fusion can be added to the basic decompression to reduce dynamic forces in select myelopathy cases.
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Key to the dorsal cervical approaches is command of the anatomy and careful bony removal without violation of the pathologically narrowed spinal canal or neural foramen.
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The procedure can be accomplished in elderly patients and others with subsystem diseases that are associated with poor bone quality, as no hardware is required.
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The procedures are highly competitive on a cost basis, as no fusion is mandated (unless pathologic dynamic forces need to be addressed).

General Principles

Cervical degeneration in the form of disc herniation with subsequent spondylosis, facet arthropathy with ligamental hypertrophy, and allied pathologies is a common cause of neurologic compression. Cervical spondylotic myelopathy (CSM) is the most common cause of spinal cord dysfunction in adults. Cervical radiculopathy caused by disc herniation and spondylosis is also a common cause of pain and disability. Both of these pathologies may be effectively treated with surgical decompression.

Historically, surgical decompression of the cervical spine was accomplished by posterior approaches. However, beginning with Cloward in 1958, anterior approaches for disc removal gained increasing and significant popularity. In spite of decades of evaluation of both approaches, there is no class I or class II evidence to strongly support one approach over another in patients afflicted with this condition ; however, one current prospective randomized trial is aiming to answer this question.

Although the natural history of cervical radiculopathy is more benign and in many cases does resolve with conservative management, the trend toward earlier recovery and return to work favors surgical decompression. The natural history of the compressive myelopathy can have much more grave consequences. However, patient response to surgical decompression varies, eroding the efficacy of procedural long-term outcomes. The protean nature of myelopathy in the setting of spondylosis appears to originate from two principle forces on the spinal cord and associated structures: (1) reduction in the ventral/dorsal cervical canal volume leading to direct neurologic compression and (2) the dynamic forces (i.e., “stretch”) on the spinal cord during head motion in the presence of such compressive forces.

In essence, the spinal cord is stretched, or distracted, through a canal of diminished caliber, leading to spinal cord damage. Interestingly, the damage seen early in the disease process is often in the lateral region of the spinal cord. It has long been felt that, given the frequent ventral location of a compressive spur or similar pathology, an operative procedure must be directed to that location (i.e., anterior cervical discectomy). However, it has become apparent that it is the combination of both compressive and dynamic forces on the spinal cord that leads to dysfunction. This explains why a dorsal decompression may be equally effective with regard to neurologic outcome even in the face of significant ventral pathology.

In light of the static and dynamic forces involved in the genesis of myelopathy, all the ventral and dorsal surgical options that address either one, or both, of the involved factors have a role. A wide variety of procedures are available to address the clinical problem, with decompression as the primary goal. These surgical strategies include anterior discectomy (or corpectomy where indicated) and fusion, cervical laminectomy, cervical laminoplasty, and cervical laminectomy and fusion. Reviews have confirmed the clinical equipoise present in choosing a technique. Each procedure has its attendant downside in the form of complications. All have been shown to be effective in the overall population of CSM patients, but no single procedure has clearly outclassed the other options. The durability of cervical laminectomy may be less than other options, but this has not been fully validated.

Cervical laminectomy for decompression of the spinal cord or nerve roots has been demonstrated to be effective in the treatment of CSM. Although it addresses the compressive forces in CSM, it does not reduce the dynamic forces. Many patients do well with this strategy, and in appropriately selected patients, the procedure is safe and effective. In the authors’ experience, elderly patients who frequently have less spinal range of motion secondary to advanced spinal arthritic changes and younger patients with congenitally “shallow” but relatively “clean” central canals are favorable candidates. Posterolateral foraminotomy, as an adjunct to cervical laminectomy or as a stand-alone technique effectively addresses compressive pathologies specific to cervical nerve roots at the exit zone. A number of advantages can be ascribed to cervical laminectomy/laminoforaminotomy:

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A relatively simple technique with a moderate number of technical steps
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An effective means of decompressing multilevel spinal cord compression (two to five levels) or of decompressing multiple nerve roots in the setting of multilevel radiculopathy
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The potential to address both myelopathic as well as radicular symptoms in settings of combined myeloradiculopathy
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No potential pseudarthrosis, as no fusion is included; similarly, no hardware-related failures or complications
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No hypermotility segmentation stress and delayed adjacent segment concerns because the motion of the spine is preserved (a motion-sparing procedure)
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A very low reoperation rate
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Usable in elderly patients in whom osteoporotic bone may not favor successful hardware implantation
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Fairly rapid multilevel procedures are possible, which may be advantageous in the patient with multiple subsystem issues (e.g., cardiac, renal) that increase perioperative risk

As with all surgical options in the treatment of CSM, there are a number of potential limitations. For one, there is a risk of delayed kyphosis over time. This is largely secondary to the loss of the posterior tension band (lamina and intraspinous ligaments). The exact incidence of postlaminectomy kyphosis is not well established, and the published reviews have generally been limited in patient numbers. Clinically relevant, as opposed to radiographically identified, incidental sagittal balance change is probably in the 5% to 10% range. This problem, to some degree, can be limited by proper technical performance (see the section on technique). In light of the preceding point, cervical laminectomy should be limited to patients with reasonable lordosis and not utilized in those with a frank kyphosis. Patients younger than age 20 are at greater risk for delayed cervical kyphosis after laminectomy. However, Lonser and colleagues described cervical laminectomy for tumor resection in a younger patient population with reasonable results and a low requirement for delayed stabilization.

Over the years, the senior author has used the following general guidelines for selecting patients as good candidates for cervical laminectomy:

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It can be used for patients with multilevel (more than two) canal size reduction and reasonable lordosis.
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In cases where decompressive laminectomy alone is used if an early to moderate myelopathy is present, but not dramatic signal change within the spinal cord on magnetic resonance imaging (MRI) (myelomalacia). In advanced cases of CSM, we generally favor simultaneous reduction of motion/dynamic forces by adding dorsal instrumentation (lateral mass screws) and fusion to the procedure. This preference is based on previous anecdotal experience, without strong scientific data to bolster the decision.
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Cervical laminectomy is a reasonable option in patients with a relatively “clean” canal (i.e., without dramatic ventral spurs, such as can be seen in congenital narrowing).
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It is a good option in elderly multilevel CSM patients with poor bone quality and severe subsystem diseases that would increase morbidity in more complex procedures.

Technique

Positioning

Two basic positions are available: prone or sitting. A less common approach is lateral decubitus.

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Prone . The patient is placed on appropriate padding material. The head is immobilized with three-point fixation in neutral position. Care must be taken to get a solid purchase in bone with the head holder because the weight of the head and neck in the prone position can lead to slippage with attendant lacerations and head shift. It is important to flex the knees to prevent migration of the patient on the table, which can lead to neck extension if the patient slides down the table during the procedure.
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Sitting . Over the years, the trend had been to avoid the sitting position as inherently hazardous due the risk of air embolization. A resurgence has been seen in this antiquated surgical position. Although air ingress can be seen in 5% to 8% of sitting cases, clinically significant air embolization is unusual. The risk of air embolization in cranial cases is higher because of the noncollapsible venous structures of the cranium. More than 1500 sitting cases accumulated in the literature attest to the safety, with proper technique. The sitting position provides a fairly bloodless field due to dependent flow of blood to the bottom of the field and reduced epidural venous tension. Nerve root decompression via dorsolateral foraminotomy can be facilitated for this reason.

Monitoring

A number of monitoring devices are available for use with posterior cervical decompression. However, the reported evidence does not support its routine use. There is extensive literature regarding the option of physiologic monitoring, but no clear scientific data or consensus exists. Central venous access and arterial line monitoring are not typically required unless indicated due to vascular access issues or other medical comorbidities. The literature supports the use of the sitting position without the use of a central line.

Incision and Dissection

A skin incision adequate for the proposed decompression is utilized. Excessive attempts to limit the incision may jeopardize the ease and safety of deep dissection. A standard subperiosteal dissection is employed just lateral to the laminar facet groove ( Fig. 65-1 ). There is no benefit to carrying the dissection more laterally into the facet/facet capsule because this only exacerbates the risk of delayed kyphosis. Remember that a small group of patients may have an occult spina bifida, so care must be taken to avoid dissection through such a midline breach.