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Many techniques have been developed for the surgical management of compressive cervical myelopathy. They can be divided into anterior, posterior, and circumferential procedures. In the patient with neutral to lordotic cervical sagittal alignment, posterior decompressive procedures remain a good surgical option. Available posterior cervical procedures include laminoforaminotomy, laminectomy, laminectomy and fusion, and laminoplasty.
Although laminoforaminotomy procedures are a viable surgical option for the management of cervical radiculopathy, they are not adequate for the management of myelopathy and symptomatic spinal cord compression. Laminectomy alone, without stabilization, has fallen out of favor because of the risk of postlaminectomy kyphosis and associated neural compression. As a result, laminectomy and fusion and laminoplasty remain the primary posterior surgical options for the management of cervical myelopathy.
Although laminectomy and fusion remain excellent techniques for management of cervical myelopathy, by definition the inclusion of spinal fusion along with instrumentation results in the loss of cervical motion. Furthermore, although controversial, the development of postlaminectomy membrane has been identified as a potential source of late neurologic regression. As a result, laminoplasty has evolved in an attempt to address these concerns.
In selected patients, laminoplasty allows for spinal cord decompression, avoids the loss of cervical range of motion (ROM), maintains spinal stability without the need for spinal fusion, and potentially avoids the complications associated with scar membrane formation. Various techniques have been developed; however, the two most commonly described and investigated are the open-door and French-door techniques ( Figs. 35-1 and 35-2 ). The purpose of this chapter is to review the indications for surgery, surgical techniques, and complications and outcomes of cervical laminoplasty.
History and Examination Findings
The history and examination of the patient for a cervical laminoplasty are analogous to those in any other patient with cervical myelopathy or myeloradiculopathy and are covered more fully in Chapter 13 , Chapter 14 , respectively. In the history, patients classically report gradually progressive changes in gait and upper extremity clumsiness. Patients may describe weakness or stiffness in the lower extremities or difficulty with fine motor skills manifested by changes in handwriting or difficulty with buttons or zippers. Bowel dysfunction and bladder dysfunction are late findings and are rarely presenting symptoms. Neck stiffness and axial neck pain are commonly associated nonspecific findings, but it is important to address the proportion of pain resulting from facet arthrosis or disk degeneration because this will not be improved by surgical treatment.
The physical examination is directed at determining the pattern of deficits, namely upper motor neuron dysfunction, manifested by weakness and incoordination in the upper and lower extremities. Gait examination is critical and classically demonstrates stiffness or spasticity. Hyperreflexia and pathologic reflexes such as the Babinski sign and patellar clonus are supportive findings. Examination maneuvers such as heel-toe walking, repetitively making a fist, or holding finger adduction and extension can elicit myelopathic signs. Particular attention should be paid to deltoid function preoperatively because postoperative C5 root palsy is a known complication of all cervical spine procedures, and in particular with posterior canal expanding procedures such as laminoplasty and laminectomy and fusion.
Several scoring methods have been developed to standardize the assessment of cervical spondylotic myelopathy. The Japanese Orthopedic Association’s (JOA) scoring system is the most frequently used, with higher scores relating to greater disability. The modified JOA score was developed and is frequently used in Western societies because the original JOA system includes considerations such as the ability to use chopsticks.
Imaging Studies
Initial imaging should begin with anteroposterior and lateral plain upright cervical radiographs. Coronal and sagittal alignment should be noted. Because posterior cervical canal expanding procedures rely on posterior spinal cord drift to achieve decompression, lordotic sagittal alignment is required. Patients with kyphotic alignment will not achieve sufficient decompression because of continued anterior compression even after laminoplasty. Neutral sagittal alignment remains a relative contraindication and should be considered on an individualized basis. Lateral upright flexion and extension cervical radiographs are also valuable and may identify the presence of hypermobility, cervical spondylolisthesis, or other evidence of cervical instability that may preclude proceeding with primary cervical laminoplasty ( Figs. 35-3 and 35-4 ).
Although scoliotic deformity in the coronal plane is not an absolute contraindication to laminoplasty, it should be considered a relative contraindication. Limited information is available to determine whether appropriate posterior spinal cord drift can occur in a patient with substantial cervical scoliosis but with maintained lordosis. These cases should be considered on an individual basis as well.
Magnetic resonance imaging remains the advanced imaging study of choice. In patients with cervical myelopathy, magnetic resonance imaging may reveal evidence of myelomalacia ( Fig. 35-5 ). In addition, careful attention should be paid to sagittal alignment and the location and level of compression. As discussed earlier, kyphotic sagittal alignment is a contraindication to proceeding with cervical laminoplasty. In addition, the number of levels of compression is important to assess. Patients with three levels or more of compression may benefit from a posteriorly based decompressive procedure. The surgeon should also carefully determine whether the compression is anterior, posterior, or circumferential.
In general, the surgical approach should address the site of the compressive disorder. For example, a large one- or two-level anterior cervical disk herniation may be best addressed with an anterior spine surgical procedure, rather than posterior laminoplasty. One exception may be if the anterior compression is secondary to ossification of the posterior longitudinal ligament (OPLL). In these cases, provided the sagittal alignment is lordotic, the preference of some surgeons may still be to perform a posteriorly based canal expanding procedure. The pathophysiology, challenges, and concerns of managing OPLL are covered more completely in Chapter 16 .
A computed tomography scan, with or without myelography, may have benefit in selected cases. It can help determine whether the compression is bony or ligamentous. In patients who have undergone previous surgical procedures, or when a question of congenital bony malformations arises, computed tomography scans can better define the bony anatomy and identify conditions that may preclude laminoplasty as a surgical option. However, the use of this imaging modality in routine laminoplasty is not necessary.
Indications and Contraindications
Indications
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Cervical myelopathy or myeloradiculopathy
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Multilevel cervical spondylosis with resultant spinal cord compression
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Symptomatic OPLL
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Cervical canal stenosis narrower than 12 mm in anteroposterior diameter
Contraindications
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Kyphotic deformity
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Predominant neck pain symptoms
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One- or two-level disease
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OPLL with established kyphosis, hypermobility, evidence of cervical spondylolisthesis, or other evidence of cervical instability
Relative Contraindications
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Neutral sagittal spinal alignment
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Coronal plane scoliotic deformity
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Rheumatoid arthritis
Overview of Current Types of Laminoplasty
Although several types of laminoplasty have been described, they can be broadly divided into the two categories of open-door and French-door techniques. In both techniques, hinges are formed at the junction of the lateral mass and the lamina. The lamina is expanded laterally or in the midline in the open-door and French-door techniques, respectively. Regardless of the surgical technique described, the goal of cervical laminoplasty is to perform decompression of the spinal cord by repositioning the lamina while maintaining structural stability and alignment of at the spine.
By preserving the posterior elements and muscular attachments, the risk of postlaminectomy kyphosis, loss of motion, and adjacent segment degeneration is decreased. In addition, this technique may allow for earlier mobilization and rehabilitation compared with other surgical options while avoiding graft-related complications such as graft fracture, extrusion, dislodgment, and settling. By preserving the lamina, the risk of postoperative scar that is frequently seen after laminectomy is avoided, as is the potential development of postlaminectomy membrane. As discussed earlier, laminoplasty does not address neck pain, and in fact it may even aggravate those symptoms, particularly in the immediate postoperative period as a result of extensive muscle dissection.
In open-door laminoplasty, the spinal canal is expanded by placing a complete (opening) trough on one side and a partial greenstick trough on the contralateral (hinge) side. In general, the opening side of the lamina is usually placed on the more symptomatic (stenotic) side, or the side with the worse radicular symptoms. The trough is made at the junction of the lamina and lateral mass junction. Care should be taken not to violate the facet joint capsule. Once the troughs have been made, the lamina is gently opened to the desired degree.
The original expansive open-door laminoplasty technique used sutures to hold the hinge open and maintain the decompression ( Fig. 35-6 ). This technique remains in use, but it can be complicated by a “spring back” phenomenon and subsequent neurologic deterioration. In an attempt to address this complication, bone grafts, hydroxyapatite, and other spacers have been developed to maintain patency of the open door. Hydroxyapatite spacers have been shown to have equal bone bonding and fusion rates as autograft, and neurologic recovery rates are similar to those in other reports using traditional laminoplasty. Finally, titanium miniplates have been used either alone or in conjunction with the various spacers; however, they can be associated with increased operative time, blood loss, and other potential complications.
Conversely, the French-door technique uses a midline sagittal split of the spinous processes to decompress the spinal cord and an incomplete hinge trough on both sides ( Fig. 35-7 ). The technique was introduced by Kurokawa and uses bone blocks between the halves of the spinous process to maintain decompression. Hydroxyapatite spacers and anchor sutures have also been used as alternatives to autograft.
Surgical Technique
Patient Positioning
The setup for cervical laminoplasty is similar to that for other posterior cervical procedures and should be based on the surgeon’s preference and individualized to the patient. At the authors’ institution, the radiolucent table with a Mayfield attachment is used. Consideration for fiberoptic intubation and neurophysiologic monitoring should be performed according to the protocol of the institution and the surgeon. The operating table should be placed in the reverse Trendelenburg position. This allows for improved visualization and decreases bleeding. The patient’s shoulders are taped, and imaging is obtained as needed to confirm visualization.
Head positioning varies. However, neutral positioning during the surgical procedure prevents excessive spinal cord compression while allowing for increased space between the lamina and improving the ability to complete the troughs and perform any necessary foraminotomies.
Exposure
A longitudinal midline incision is made from the C2 to C7 spinous processes.
The subcutaneous fat and deep cervical fascia are dissected, exposing the nuchal ligament, which is then divided in the midline, with care taken to protect the supraspinous and interspinous ligaments. Staying within the midline in the nuchal ligament helps to decrease bleeding.
The lamina is exposed by dissecting subperiosteally from the spinous process to the lateral mass. Care is taken to protect the facet capsule, the soft tissue attachments to the facet joints, and the extensor muscle attachments of the C2 spinous process. This aspect is important to help reduce the risk of junctional kyphosis and segmental instability. The senior author prefers to preserve the spinous processes whenever possible.
Laminoplasty
Depending on the laminoplasty technique described, either an open (complete) trough or hinge (incomplete) trough is made on each side. This is performed at the lamina-facet junction ( Fig. 35-8 ). The complete trough is typically made with a combination of a burr and a Kerrison rongeur. The lamina is thinned until a 1- or 2-mm Kerrison rongeur can be safely passed. The ligamentum is gently divided at each level.
In the case of the hinge trough, the outer cortex is sequentially thinned with a burr. Once troughs are completed on both sides, the ligamentum flavum is divided at the superior and inferior aspect of the laminoplasty, and the lamina is carefully hinged open. This can be performed using a combination of an angled curet under the lamina on the open side, or on the spinous process in the French-door technique. The multiple fine attachments commonly found from the dura to the undersurface of the lamina are carefully dissected free as necessary.
The hinge side trough can be deepened as necessary to help open up the laminoplasty; however, care should be taken to do this sequentially, to avoid inadvertent fracture of the lamina on the hinge side. If this occurs, plating systems exist to achieve fixation of the hinge side back to the lamina-facet junction. If the French-door technique is being used, the base of the spinous processes is split sagittally down to the inner cortex. In this case, bilateral hinge troughs are created to allow for opening of the lamina from the midline.
Foraminotomy
Occasionally, foraminotomy may be required in addition to laminoplasty. This may be indicated for patients with myeloradiculopathy with significant neuroforaminal stenosis. Because of the association of C5 root palsy with posterior canal expanding procedures, some surgeons have advocated performing bilateral C4-C5 foraminotomies. The argument for routine prophylactic decompression, however, remains controversial.
If a foraminotomy is being considered, typically performing it on the open trough side of the laminoplasty is easiest. This procedure is usually performed after the lamina is elevated and the laminoplasty is complete. If the foraminotomy must be performed on the hinge side, then consideration should be given to performing it before the laminoplasty. Performing the foraminotomy after the laminoplasty on the hinge side places the lamina at risk of fracturing. Care should be taken to preserve at least 50% of the facet joint to reduce the risk of instability. A more complete description of posterior cervical keyhole laminoforaminotomy is given in Chapter 36 .
Spacers and Fixation Techniques
The use of bone graft or other mechanical spacers varies and has included autologous spinous process, allograft iliac crest bone graft, rib, and biologic spacers such as hydroxyapatite ( Fig. 35-9 ). The addition of fixation includes the use of wiring and plate and screw constructs ( Fig. 35-10 ). These techniques were developed to help address the concern for repeat closure of the laminoplasty site. The decision whether to include the use of a spacer and mechanical fixation varies from patient to patient and on the experience and preference of the surgeon. Newer descriptions use plate fixation without any bone on the opening trough side ( Fig. 35-11 ).
Closure
Deep drains are placed. The fascia and subcutaneous tissue are closed in layers, and the subcutaneous tissue and skin are closed in a routine manner.
Postoperative Care
Postoperative care has been debated in the literature, in particular with regard to the duration of immobilization following the surgical procedure. Some research has found a correlation with ROM loss and long-term axial pain symptoms. This finding has led some investigators to encourage early postoperative mobilization, which has been the authors’ preference as well ( Figs. 35-12 and 35-13 ). Advanced imaging is not routinely required; however, it can be obtained as needed to assess the decompression, the improvement or persistence of spinal cord signal change, bony osteotomies, and the location of the instrumentation ( Figs. 35-14 and 35-15 ).
Complications
Laminoplasty was developed to avoid the complications of laminectomy that result from loss of the posterior protective elements. However, axial pain, C5 palsy, spinal canal restenosis, and loss of cervical lordosis all complicate laminoplasty and have been the target of many technical improvements.
Axial pain is defined as pain from the nuchal to the periscapular or shoulder region, and its incidence varies widely in the literature from 5.2% to 61.5%. The origin of the increased pain does not appear to be clearly understood. However, early mobilization, reconstruction of the extensor musculature, anatomic reconstruction of semispinalis cervicis, and preservation of the C7 spinous process and its extensor musculature have all been associated with less axial pain, but more research is required to understand the etiology fully.
Postoperative C5 root palsies have been well described after both anterior and posterior spine surgical procedures. In particular, however, these palsies are associated with posterior canal expanding procedures such as laminectomy and fusion and laminoplasty. Clinically, these disorders are defined as loss of deltoid or biceps strength without other neurologic symptoms. The incidence of C5 palsy is also widely variable, with an average of 4.6%. Most patients develop symptoms within 2 weeks of the surgical procedure, but the duration also varies between 15 and 821 days or longer. Prophylactic foraminotomy has been described, but not all investigators agree about its effectiveness.
The incidence of spinal canal restenosis and recurrence of myelopathy has been reported to be as high as 40%, but data are lacking to determine the absolute rate because repeat neuroimaging is infrequently ordered without recurrent symptoms. Radiographic evidence of restenosis does not always correlate with clinical recurrence or progression of symptoms or necessitate additional surgical intervention.
Loss of cervical lordosis and of ROM is noted in virtually all studies of laminoplasty, with a mean decrease in ROM of 50%. Loss of cervical alignment, and in severe cases, more specifically postoperative kyphotic deformity can decrease neurologic recovery by preventing posterior migration of the spinal cord. Patients at high risk for postoperative kyphosis are those with myelopathy associated with cervical spondylosis, preoperative lordosis of less than degrees, and a kyphotic angle during flexion that exceeds the lordotic angle in extension. The combination of all three risk factors was associated with a 66.7% chance of developing postoperative kyphotic deformity.
Results
Laminoplasty is a well-established technique for posterior spinal cord decompression. A significant amount of evidence supports its use in the appropriate clinical situations. Most studies use preoperative and postoperative JOA scores to calculate neurologic recovery, which quantifies patients’ recovery compared with perfect recovery using the following formula:
Recovery rate ( % ) : ( Postoperative score − Preoperative score ) ( 17 − preoperative score ) × 100
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