8

Compression of the spinal cord from cervical spondylosis was first described in 1911 by Bailey and Casamajor1 and in 1928 by Stookey,² who described a patient made quadriplegic from cervical spinal stenosis compressing the spinal cord. It was 1952, however, when Brain and colleagues⁵ described the role of vascular supply to the spinal cord and the manifestation of myelopathic symptoms, that cervical stenosis causing myelopathy was identified as a distinct entity. Lees and Turner⁴ further noted the lengthy clinical course of the disease accompanied with a long duration of nonprogressive disability.

Cervical spondylosis is an insidious, progressive disease process that presents with several symptoms frequently refractory to conservative nonoperative treatment (Fig. 8–1). Nevertheless, controversy exists over the optimal choice of surgical treatment for this disorder. Despite nonoperative therapy, posterior decompression is an appropriate treatment option for patients with progressive symptoms; however, traditional methods of cervical decompressive laminectomy require stripping of the posterior cervical muscular, as well as ligamentous attachments to the spine. In so doing, patients experience considerable postoperative pain from muscle spasms and muscle injury. Some patients will go on to develop iatrogenic swan neck deformity, which is particularly prevalent in younger individuals undergoing multilevel posterior cervical decompression. Relatively recent improvements in posterior spinal instrumentation (i.e., lateral mass plates and screw-rod constructs) have made fusion more attractive (Fig. 8–2); however, this method adds considerable cost to the procedure, does nothing to reduce iatrogenic muscle and ligamentous injury, and can result in considerable complications from poor screw placement.

The laminoplasty technique attempts to widen the spinal canal diameter by preserving the posterior spinal elements (i.e., the spinous processes and laminae), while maintaining the dynamic motion of the cervical spine (Fig. 8–3). Open-door expansile laminoplasty was developed by Hirabayashi⁵ in 1977 to treat compression of the cervical spinal cord; since then, it has become a treatment of choice for ossification of the posterior longitudinal ligament. Various modifications of this procedure were subsequently developed, all with the aim of increasing the cross-sectional area of the cervical spinal canal.^6,7 Laminoplasty is now most commonly used to address myelopathy due to multilevel degenerative cervical spondylosis. When compared with multilevel laminectomy without fusion, several human and animal studies have found laminoplasty to be superior.^8–10

When comparing laminoplasty with anterior decompressive procedures, neurologic improvement rates from myelopathy are similar.^11–15 Anterior approaches are advantageous because extrinsic compression is more predominantly ventral and sagittal deformities can be corrected more effectively; however, laminoplasty also offers distinct advantages over anterior surgery when treating multilevel disease. Since there is no formal intersegmental fusion, the incidence of adjacent segment disk degeneration is reduced and there is no risk of a failed arthrodesis. Laminoplasty is also typically performed over four to six spinal segments, so even moderately stenosed segments of the cervical spine are treated without incurring additional morbidity. In addition, complications associated with extensive anterior neck exposures (e.g., laryngeal palsy and dysphagia) are avoided.

Despite the advantages of laminoplasty, postoperative axial neck pain and loss of lordosis remain significant drawbacks of this procedure.16 These complications may be related to the detachment of muscular and ligamentous insertions of the spine when using a posterior approach, and attempts have been made to minimize the soft tissue dissection for surgical exposure. Shiraishi and Yato¹⁷ described a modification of French door laminoplasty that preserves the muscular attachments to the laminae and spinous processes in an attempt to surmount these problems. Tani et al¹⁰ modified the open-door technique so that the midline ligaments remain attached to the spinous processes, which are osteotomized from the laminae in an osteoplastic fashion. Although these techniques preserve the ligamentous anatomy, they still require extensive muscular stripping off the periosteum.

FIGURE 8–2 Intraoperative view showing decompressed spinal cord via laminectomy and lateral mass rod-screw construct overlying fusion bed.

A minimally invasive microendoscopic cervical laminectomy and laminoplasty techniques were developed to address many of the issues encountered with more traditional posterior cervical decompressive approaches (i.e., significant muscle, ligamentous, and bone removal; postoperative pain; and iatrogenic instability). The effectiveness of these techniques was first tested in cadaveric specimens before being applied in the clinical setting. This chapter will review both the cadaveric study and initial clinical experience with these techniques.

Anatomy and Pathophysiology

The cervical spine consists of seven vertebrae. The first two vertebrae (i.e., the atlas and axis) compose the high cervical region and are considered integral components of the craniovertebral junction. These vertebrae are unique in structure and are rarely involved in the degenerative process of cervical spondylosis. Cervical vertebrae C3 through C7, which are otherwise known as the subaxial spine, are distinct from the high cervical vertebrae by the presence of uncovertebral joints and the morphology of the vertebral bodies. The lateral masses of the cervical spine are composed of superior and inferior articular processes, which are thinnest at the C6 and C7 level and have dimensions that increase from depth to height to width.¹⁹ The spinal canal has a triangular configuration with a varied sagittal diameter of ~17 to 18 mm from C3 to C6 to 15 mm at C7.^20–23 In vitro biomechanical testing has determined that the anterior column of the cervical spine transmits 36% of the applied load, whereas each pair of facets transmits 32% of the total load, stressing the importance of the posterior structures in cervical stability.²⁴

The diameter of the spinal cord is not uniform in the cervical spine region. The spinal cord occupies one half of the spinal canal at the level of C1. At the C5 to C7 level, the cord expands and occupies three fourths of the canal diameter, which increases the incidence of cord compression at the lower cervical spine. Cailliet25 determined that cervical spinal canal stenosis is more uniform and restrictive in the diagonal anteroposterior diameter than the transverse. Spinal canal size is a predisposing factor to symptomatic cervical stenosis. Those patients with congenitally smaller canals are potentially at increased risk. A canal AP diameter less than 13 mm has been established as a diagnostic standard of medullary symptoms from spondylotic encroachment.^25,26

The anterior spinal artery (ASA) provides 60 to 70% of the cervical spinal cord’s vascular supply.²⁷ Although the ASA’s midsagittal position is at risk from direct compression from disk protrusion or degenerative hypertrophies, its segmental medullary feeders provide collateral blood flow to enhance cord perfusion. Mannen²⁸ and Jellinger²⁹ reported that the lower cervical arteries are more predisposed to artherosclerotic changes.

The normal cervical spine has a sagittal lordotic curvature mainly attributed to the intervertebral disk height, which accounts for 22% of the overall length of the cervical spine. The disk space height is greatest at the anterior aspect of the interspace and accounts for the natural lordotic curvature of the cervical spine. Motion is greatest at the intervertebral disks, and compressive and tensile forces are distributed throughout the cervical spine. Loss of cervical lordosis is often attributed to dehydration of the intervertebral disks and may contribute to altered biomechanical forces throughout the cervical spine, resulting in reactive hyperostosis changes of the adjacent vertebral end plates and development of a spondylotic bar resulting from posterior disk protrusion. Posterior disk herniation may contribute to impingement of the exiting nerve root and produce radiculopathic symptoms. In combination, these physiologic alterations may contribute to overriding of the uncinate processes, leading to destruction of the uncovertebral joint space. Further progression of this degenerative process may lead to subsequent hypertrophy of the facet joints and ligamentum flavum and ossification of the posterior longitudinal ligament. Moreover, manifestation of pain is attributed to compression or stretching of the sinuvertebral nerve and altered integrity or distortion of the apophyseal facet joints, ligamentous elements, and cervical musculature. Further-more, hypermobility at the adjacent levels may further induce hypertrophy at the respective motion segment and threaten encroachment on the spinal cord and nerve roots.

In addition, the pincher phenomenon entails dynamic contributions that are additive to cord encroachment. In flexion, the AP diameter decreases 2 to 3 mm, and the superior rim of the posterior vertebral body produces tension on the spinal cord. Although tension of the spinal cord is minimized in extension, the cord is susceptible to compression by buckling of the ligamentum flavum. Lateral motion of the neck on the side of compression may further reduce foraminal diameter and produce or exacerbate symptoms. In addition, compensatory subluxation may develop above the level of the rigid spondylotic segment.

Multiple studies of unilateral lumbar laminotomy have demonstrated successful bilateral decompression for spinal stenosis. These investigations involved extensions of the open surgical procedure, which uses a laterally placed incision to access a contralaterally directed trajectory.30 In this manner, a high-speed drill, Kerrison rongeurs, and curettes can be used to undercut the inner surface of the laminae, affecting a central decompression while preserving all of the midline musculoligamentous structures. In initial clinical studies, effective spinal canal enlargement with concomitant symptom alleviation approximated the results with open surgery. Cadaveric studies using a similar approach have demonstrated that this technique is also feasible in the cervical spine and can result in canal expansion averaging 43%.³¹

Five cadaveric specimens were imaged pre- and postoperatively with CT/myelogram. Approximately 50 cc of Omnipaque contrast agent was injected into the subdural space of the cervical spine, followed by CT imaging. In the cadaver laboratory, the cadaver specimen was placed on a radiolucent table in the prone position with the lateral fluoroscopic C-arm in place. The C4–C5 level was first identified with a spinal needle and lateral fluoroscopic imaging, and a small incision was made ~2 cm lateral to the midline. A K-wire was then passed under fluoroscopic visualization and docked on the C4–C5 lamina-facet junction. The initial muscle dilator was passed over the K-wire and docked securely on bone, and the K-wire was removed. Subsequent dilators were then passed, and an 18 mm diameter tubular retractor was passed over the final dilator and locked in place. The muscle dilators were removed, and the endoscopic assembly white balanced, focused, and passed down the tube for visualization during the case (Fig. 8–4, Medtronic Sofamor Danek, Memphis, TN). The soft tissue overlying the lamina and medial facet was removed using a Bovie cautery. Fluoroscopic imaging in both the AP and lateral projections was used to aid in proper surgical orientation and location. With the endoscopic assembly facing away from the surgeon, the ipsilateral lamina was removed using a high-speed drill and Kerrison punch. This allowed for good visualization using the 30-degree angulation of the endoscope, as well as for ipsilateral cervical foraminotomy. Wanding the tubular retractor-endoscopic assembly rostral and caudal, a multilevel (up to four levels) unilateral laminectomy was performed (Fig. 8–5) Once the ipsilateral laminectomy was performed, the endoscope was repositioned, facing the surgeon on the tubular retractor. This allowed for contralateral cervical decompression. The spinous process was identified, and drilling of the underside of the spinous process and contralateral lamina was performed. This maintained the bony integrity of the spinous process and contralateral lamina without any muscular or ligamentous removal; therefore, much of the bone, muscular, and ligamentous integrity was presented. This may reduce the incidence of postoperative muscle pain, spasms, and iatrogenic instability seen in more traditional approaches. Postoperative CT-myelogram confirmed adequate cervical-decompression (Fig. 8–6). Open cadaveric dissection revealed adequate spinal cord decompression, while preserving much of the posterior bony and muscular attachments of the cervical spine (Fig. 8–7).

FIGURE 8–4 Endoscopic assembly in place with tubular re-tractor (Medtronic Sofamor Danek, Memphis, TN) in a cadaveric specimen.

Initial Clinical Experience

The initial clinical experience has been performed on patients with one- and two-level cervical stenosis.

Our initial studies of minimal access surgery necessarily began in the cadaver laboratory. To investigate minimally invasive laminoplasty, six formalinized human cadavers underwent preoperative spiral axial CT scans from C3 to C7 with 3 mm cuts. None of the cadavers showed evidence of ossification of the posterior longitudinal ligament or spinal stenosis. Stab incisions 2 cm long were made bilaterally at C4–C5 and C5–C6, 2 cm lateral to the midline. A Steinmann pin was then placed into each of these incisions to obtain a medially directed trajectory to the lamina-facet junction. The METRx MD-tubular dilator retractor (Medtronic Sofamor Danek, Memphis, TN) system was then inserted and dilated up to the 22 mm diameter port. The laminae and facets were then visualized, and any intervening soft tissue was removed with pituitary rongeurs. By manipulating the tubular retractor to favor either a rostral or a caudal trajectory in the sagittal plane, exposure of one or two segments above and below the level of the incision was possible. Visualization was aided by the use of an operating microscope. A 3 mm longitudinal trough at the laminafacet junction was drilled with a G8–130 bit (Medtronic Midas Rex, Fort Worth, TX) through both the inner and outer cortices. This process was repeated through each of the four incisions to prepare for dorsal elevation of the five laminae from C3 to C7. On the open-door side of the laminoplasty, the ligamentum flavum was removed at the lamina-facet junction with a 1 mm Kerrison rongeur. The ligamentum flavum was left undisturbed on the hinge side to prevent collapse of the dorsal construct into the spinal canal. The laminae were then lifted en bloc from this side with a curved curette, and a 10 mm length spacer was fashioned at C4 and C6 from rib allograft inserted to maintain the dorsal elevation of the laminae (Fig. 8–8).

Postprocedure spiral axial CT scans were obtained from C3 to C7 with 3 mm cuts (Fig. 8–9). CT images were then digitally analyzed using ImageJ software (National Institutes of Health, Bethesda, MD). Image measurements were obtained directly from the CT scans and were calibrated to the reference scale on the CT images by determining pixels per millimeter. Midsagittal dimensions were measured at the C5 level, and the canal area was estimated from a computer-drawn perimeter of the inner bony margins. Statistical analysis was performed with a paired t-test.

FIGURE 8–9 (A) Cadaveric preoperative axial CT scan at C5. (B) CT scan after placement of a 10 mm rib allograft to elevate the lamina.

The preoperative spinal canal area averaged 2.15 cm², and sagittal diameter averaged 1.24 cm at the C5 level. Postoperative spinal canal area averaged 3.09 cm² and sagittal diameter averaged 1.71 cm at the C5 level (Table 8–1). This reflected a 43% increase in spinal canal area and a 38% increase in sagittal diameter. These changes reflected a significant increase in canal diameter (p = .0001) and area (p = .0004).

Minimally Invasive Laminoplasty Clinical Experience

Our initial experience with minimally invasive laminoplasty is limited to four patients (Table 8–2). All procedures were performed to treat cervical spondylotic myelopathy with associated gait abnormalities. The surgical procedure was identical to the cadaveric study, with laminar osteotomies performed from C3 to C7 (Fig. 8–10). Spacers were placed at C4 and C6.

There was a mean improvement of 1.25 points on the Nurick score. Complications were limited to a single case with a dural laceration. This was treated without primary repair and did not result in transcutaneous CSF leakage. Technical challenges encountered included difficulty with lifting of the laminae, limiting the spacer height to less than 11 mm (Fig. 8–11).

Discussion

Cervical spondylosis may be the most common under-diagnosed spine disorder whose true incidence is unknown. The majority of patients present in the fifth decade of life, but the condition is not limited therein and is indiscriminant of age and degree of disease manifestation.^32,33 Levels below C3–C4 are primarily affected, with predominance at C5–C6, followed by C6–C7 and C4–C5.³⁴ Spondylotic manifestations are evident radiologically in 25 to 50% of the population by age 50, and they are seen in as many as 85% of individuals by their mid–60s.^35,36 Several disorders may mimic the symptoms of cervical spondylosis and need to be differentiated for proper diagnosis. Such disorders include torticollis, athetosis, chronic dystonia, cerebral palsy, syringomyelia, low-pressure hydrocephalus, cerebral hemisphere lesion, amyotrophic lateral sclerosis, Down syndrome, multiple sclerosis, and neoplastic lesions.

Several variables have been reported to affect surgical outcome, including patient age, duration of symptoms, levels of myelographic block, extent of cord signal change, severity of myelopathy, transverse area of the spinal cord, and canal diameter.^37–42 Compression of the spinal cord can be due in part to pathology located anterior, posterior, or lateral to dynamic factors.

Surgical treatment can be by either an anterior or a posterior approach. The anterior approach consists of decompression and interbody or strut grafting with or without instrumentation.43–46 The posterior approach consists of laminoplasty or laminectomy with fusion with or without internal fixation. The selection of the approach is often dependent upon surgeon preference, the source of cord compressing (i.e., either anterior or posterior), the age of the patient, the number of vertebral levels involved, and maintenance of lordotic alignment. The anterior approach is recommended in cases of kyphotic curvature. The posterior approach is preferred in cases with preserved lordosis and more than three levels of involvement. The principle advantage to the posterior approach is its relative ease and familiarity by most spinal surgeons. This approach has been clearly established as a safe and effective means of decompressing the cervical spinal cord and nerve roots.^47–49 Nonetheless, the efficacy of any surgical approach is to maintain spinal stability and provide sufficient decompression without compromise to sagittal balance.

FIGURE 8–11 (A) Preoperative and (B) postoperative CT scans in a patient with cervical spondylotic myelopathy who underwent minimally invasive cervical laminoplasty. (C) Four skin incisions used for access in the posterior neck.

Cervical laminectomy may result in instability and progressive kyphotic deformity in some adults, particularly when extensive resection of facets has been performed.^50,51 In particular, progressive kyphotic deformity and cervical instability are common in children following laminectomy.^50,52,53 Bone grafting and internal fixation using lateral mass plates have been reported to prevent the development of postlaminectomy instability and deformity.⁵⁴ Some authors believe development of a postlaminectomy membrane may yield late deterioration after laminectomy with or without fusion.⁵⁵

Postoperative Kyphosis

Although cases of symptomatic postlaminectomy kyphosis are well described, their incidence and relevance are unclear in the literature.56 The addition of fusion to the laminectomy procedure obviates these concerns.^54,57 Three groups of patients are at significant risk of developing postlaminectomy instability or spinal deformity: individuals under 25 years of age, trauma cases, and laminectomies combined with extensive facet dissection.⁵⁷

The development of postlaminectomy kyphosis is a significant risk in younger patients.^50,58,59 According to Cattell and Clark,⁵⁰ children are predisposed to instability due to skeletal and ligamentous laxity, neuromuscular imbalance, and the formation of bone deformities as a consequence of osseous development. Adults may not be susceptible to similar patterns of spinal degeneration because of ligamentous changes with aging. Yasuoka et al⁵³ report 90% of patients less than 15 years of age undergoing cervical or cervicothoracic laminectomy developed kyphotic spinal deformity. All patients less than 15 years of age with cervical laminectomy alone developed kyphosis. Significantly fewer patients older than 15 years of age developed spinal deformity after laminectomy. Excluding trauma cases and cases with facetectomy, no adult patient developed spinal deformity significant enough to require fusion.⁵²

In adult patients, development of postlaminectomy spinal deformity clearly correlates with facet disruption or resection. In cadaver studies, resection of greater than 50% of the facet joint and capsule is associated with acute instability.^60,61 Herkowitz⁶² reported a 25% incidence of kyphotic deformity within 2 years following cervical laminectomy and partial bilateral facetectomies. Capsule resection alone also results in increased cervical motion in cadaver studies.⁶³ Less severe destabilization of the cervical spine, perhaps yielding slowly progressive deformity in spinal alignment, may be expected with less severe facet joint and capsule injury.

Many cases have been reported of symptomatic postlaminectomy cervical kyphosis. Development of instability and spinal deformity may produce late deterioration in postlaminectomy patients.^63–65 Adams and Logue⁶⁶ correlated late deterioration in laminectomy patients with increased postoperative cervical spine motion. Numerous series attest to a late deterioration in postlaminectomy patients, with some series reporting up to 50% of patients affected;^66–68 however, kyphotic deformities may remain asymptomatic. Kaptain et al⁶⁹ reported a postlaminectomy kyphosis rate of 21% and noted no correlation between postoperative alignment and clinical outcome. In their report of long-term follow-up of cervical laminectomy patients, Crandall and Gregorius⁴⁹ found significant rates of early and late deterioration. They did not emphasize development of instability in their patient population; instead, they offered only limited radiographic follow-up.

Laminectomy with Fusion and Instrumentation

Due to concerns over postoperative worsening of spinal alignment following laminectomy alone, the addition of fusion to the procedure was added to prevent delayed malalignment and loss of sagittal balance. A variety of fusion techniques have been offered in the literature, including facet wiring, lateral mass plate fixation, and polyaxial screw and rod fixation. All share the goal of immediate cervical fixation to promote bone fusion.

Goel et al⁵¹ demonstrated in a cadaver model that posterior facet wiring limits the immediate instability generated by laminectomy. Kumar et al⁵⁴ found no instability, progression of spinal deformity, or late clinical deterioration after laminectomy with lateral mass plate fusion in a long-term follow-up of laminectomy with fusion patients.

Appropriate application of lateral mass plating screws has been scrutinized in an attempt to obtain proper placement, avoid neural and vascular injury, and ascertain optimal fixation. Two widely used techniques by Roy-Camille and Magerl have been established as relatively safe and effective;⁷⁰ however, in a comparison of these two techniques by Heller et al,⁷⁰ a 10.8 and 26.8% risk for nerve root injury was found to exist with the Roy-Camille and Magerl techniques, respectively. Moreover, the technique by Magerl was noted to have fewer facet joint violations, but proper screw trajectory was difficult to obtain at the cervicothoracic junction. To address such concerns, An et al¹⁹ proposed an alternative to these established screw placement techniques and noted that anatomical variations do exist, accounting for inconsistent interfacet distances commonly implemented as markers in screw trajectory methods. Nonetheless, instrumentation-related complications are always a concern, as well as the potential for loss of cervical alignment, nerve injury, facet penetration, pseudarthrosis, and iatrogenic foraminal stenois.^71–73 Lateral mass plating, however, has the capability for restoring lordosis.^74–76 Coupled with fusion, lateral mass plating further minimizes the risk of kyphotic deformity and instability. Kumar et al⁵⁴ presented 25 patients with lateral mass plate fusion, with follow-up on average at 47.5 months after laminectomy. Most patients presented with gait difficulty, upper extremity and hand weakness, and sensory disturbances. Eighty percent of patients had good outcomes, and 76% of patients had improved myelopathy scores. Moreover, no patient developed spinal deformity and patients with preoperative kyphosis or S-shaped deformities remained stable. There were no late deteriorations.

Cervical laminectomy has been an established procedure providing sufficient decompression; however, extensive cervical laminectomy pitfalls entail sagittal curvature alterations that may contribute to progressive kyphotic deformity, instability resulting in compromise or destruction of bony or ligamentous structures, and scar tissue or perineural adhesions. Cervical laminoplasty has been developed in an attempt to diminish the complications and poor outcomes associated with laminectomies. Hattori77 first described laminoplasty in 1973 by his illustration of a Z-shaped method. The procedure generated interest in this technique and led to numerous laminoplasty variations, primarily from Japan, which are best classified as Z-shaped, midline or bilateral, and unilateral. The laminoplasty technique preserves posterior bony elements and spinoligamentous structures and minimizes muscle detachment, thus reducing the event of postoperative kyphotic deformity and instability often associated with laminectomy. Multilevel radiculopathy, myeloradiculopathy, and multilevel cerebrospinal meningitis (CSM) are indications for laminoplasty; however, an anterior approach is preferred for bilateral radiculopathy. Laminoplasty is thought to be a viable option if cervical lordosis is maintained with minimal to no preexisting neck pain. Additional indications for using the laminoplasty technique include involvement of more than three vertebral levels, CSM in younger patients, ossification of the posterior longitudinal ligament, and thickening of the ligamentum flavum.

Although various laminoplasty techniques have been developed and vary based on the location of the “hinge” to maintain the opening, an “open door” or unilateral laminoplasty is a common procedure whose initial exposure and intraoperative patient positioning are the same as the aforementioned laminectomy technique. The unilateral laminoplasty involves removal of the tips of the spinous processes of the involved levels and bilateral thinning at the lamina-facet junction to the inner cortex with a high-speed burr.⁷⁸ An opening is selected based on the patient’s dominant symptomatic side, and a hinge is maintained by preserving the inner cortical laminar layer. A vertebral spreader is then used to open the canal by reflecting the ipsilateral cut lamina, spinous process, and contralateral “green sticked” lamina to the contralateral side in an open-hinged fashion. As the canal is opened, the ligamentum flavum and soft tissue adhesions are carefully resected. It is often necessary to cut the most caudal and rostral ligamentous attachments to hinge the posterior spinous structures freely. Once opened, bone grafts, struts, sutures, plating, or a combination of such can be used to maintain the opening.

Although the risks of instability still remain, complications associated with laminectomy are reduced with laminoplasty. Matsunaga et al⁷⁹ noted that laminectomy had a 33% incidence of a buckling-type alignment, compared with 6% following laminoplasty. Unlike laminectomy following fusion and instrumentation, range of motion is preserved following laminoplasty.^10,80 This may be an advantage, particularly in younger patients with CSM. Nevertheless, complications may exist with laminoplasty and may arise in open-door settling, epidural hematoma formation, and nerve root injury.⁸¹

Several techniques exist for the treatment of cervical stenosis. Posterior approaches do afford the advantage of being familiar to spine surgeons. The techniques of laminectomy, laminectomy with fusion and instrumentation, and laminoplasty have advantages and disadvantages, as reviewed in this chapter; however, these traditional techniques require extensive muscle dissection, resulting in muscle denervation, atrophy, and postoperative pain. The microendoscopic cervical laminectomy and laminoplasty procedures described in this chapter are encouraging further development of less-invasive spinal techniques that result in less postoperative pain, quicker recoveries, maintainance of dynamic spinal motion, and reduced iatrogenic instability by maintaining the normal musculature, bone, and ligamentous anatomy of the cervical spine. Further clinical studies are required in accessing the clinical efficacy of these techniques for the treatment of cervical stenosis.

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