Date Published: March 6, 2012
Publisher: Hindawi Publishing Corporation
Author(s): Lance K. Mitsunaga, Eric O. Klineberg, Munish C. Gupta.
Laminoplasty is one surgical option for cervical spondylotic myelopathy. It was developed to avoid the significant risk of complications associated with alternative surgical options such as anterior decompression and fusion and laminectomy with or without posterior fusion. Various laminoplasty techniques have been described. All of these variations are designed to reposition the laminae and expand the spinal canal while retaining the dorsal elements to protect the dura from scar formation and to preserve postoperative cervical stability and alignment. With the right surgical indications, reliable results can be expected with laminoplasty in treating patients with multilevel cervical myelopathy.
While multilevel cervical stenosis may occur for a variety of reasons, it is usually due to cervical spondylosis or ossification of the posterior longitudinal ligament (OPLL). Options for decompression of the canal include either anterior or posterior approaches. For multilevel disease, most surgeons prefer posterior decompression. Posterior decompression has the advantage of addressing multiple levels with one incision. However, this approach is hindered by the late complication of kyphosis with decompression alone or the loss of motion and adjacent segment degeneration if posterior decompression is performed in conjunction with fusion [1, 2]. Laminoplasty is a technique that indirectly decompresses the spinal cord and preserves neck motion by avoiding fusion. This is accomplished by hinging the laminae open on one or both sides to allow the spinal cord to migrate posteriorly away from anterior compressive structures. Laminoplasty was initially described by the Japanese in the early 1970s to treat ossification of posterior longitudinal ligament . By leaving the dorsal structures in situ, laminoplasty was developed to avoid the problems associated with laminectomy, such as kyphosis, instability, and delayed neurologic problems due to scar invasion. Laminoplasty has become increasingly popular in North America as experience with laminoplasty techniques has grown and its application has expanded to treat other causes of multilevel cervical stenosis besides OPLL, such as cervical spondylotic myelopathy (CSM). The goals of this chapter are to discuss the advantages and disadvantages of laminoplasty, key technical points regarding different laminoplasty techniques, along with the complications and outcomes of laminoplasty.
Laminoplasty allows the spinal cord and the neuroforamen to be decompressed without directly removing anterior pathology. By preserving the dorsal elements of the spine, laminoplasty preserves spine stability and alignment and decreases the risk of postlaminectomy kyphosis and instability [1, 4–23]. Additionally, since fusion is not required, complications such as fixation failure, pseudarthrosis, loss of motion, and adjacent segment degeneration do not occur. This may allow earlier mobilization and rehabilitation compared to other surgical options. In addition, laminoplasty can avoid graft-related complications such as graft extrusion, settling, collapse, dislodgement, and fracture. The financial costs associated with laminoplasty are potentially minimized, as well, without the need for lateral mass screws and rods used during fusion. With laminectomy, epidural scar formation can form between the dura and muscle leading to postoperative pain and neurologic compression [24–26]. However, with laminoplasty, the lamina is preserved and it protects the dura from this “postlaminectomy membrane.” Preserving the lamina also makes revision procedures requiring posterior approaches safer. Finally, laminoplasty has the advantage of avoiding the potential morbidity that can accompany anterior approaches, such as dysphagia, recurrent laryngeal nerve injury, dysphonia, and injury to the esophagus or carotid sheath contents.
Laminoplasty does not address neck pain, if that is a component of a patient’s symptomatology. Laminoplasty may even cause worse neck pain than anterior procedures, especially in the early postoperative period, due to the extensive muscle stripping that accompanies this procedure. This has been shown to be especially true if the dissection and laminoplasty is carried down to C7 [27, 28]. Although laminoplasty does not require fusion, range of motion is still reduced following laminoplasty [4, 8, 18, 20, 29–37]. Once the laminoplasty hinge has been opened, it requires some stabilization to maintain the expanded position during healing. This fixation is associated with some cost, bone graft may be required, and there is the potential for nonunion or failure. In addition, the longitudinal incision associated with laminoplasty may be less cosmetic than anterior incisions.
Cervical laminoplasty is indicated for cases of cervical myelopathy or myeloradiculopathy due to central stenosis extending more than three intervertebral disc spaces. This can be due to multilevel degenerative cervical spondylosis, OPLL, multilevel disc herniations, certain spinal cord tumors, neuromuscular disorders, acute traumatic central cord syndrome, or developmental cervical stenosis.
Kyphotic deformity is a contraindication for laminoplasty. In the kyphotic spine, laminoplasty does not address the cord compression anteriorly and leads to decreased canal expansion and dorsal migration of the cord . In addition, laminoplasty can contribute to spine instability and worsen the kyphosis in these cases. Ideal laminoplasty patients have lordotic cervical spine alignment and no instability on dynamic radiographs. Laminoplasty can be done in neutral spines (generally defined as less than 4 degrees of either kyphotic or lordotic angulation) but lordotic alignment is preferable since multiple studies have documented loss of lordosis after laminoplasty [12, 20, 29, 30, 39–51]. In patients with radiographic evidence of instability, laminoplasty alone may worsen the instability and should be accompanied by fusion. The ideal laminoplasty patient also has minimal complaints of neck pain. Laminoplasty may not address neck pain and, in fact, may even worsen neck pain. However, the presence of mild neck pain is not a contraindication to laminoplasty, provided the patient accepts the risk of postoperative neck pain. Stenosis at one or two levels is not an indication for laminoplasty since the short length of decompression achieved in these cases does not yield the same amount of spinal cord migration away from anterior structures. Post-laminoplasty instability may also be an issue in patients with rheumatoid arthritis, which is a relative contraindication for laminoplasty .
As always, a thorough history and physical exam, especially a thorough neurologic exam, are imperative prior to performing a laminoplasty. Radicular symptoms may suggest the need for a foraminotomy, while significant neck pain may indicate the patient for posterior fusion in combination with laminoplasty. AP/lateral views of the cervical spine and CT myelogram or MRI of the cervical spine is also critical. These imaging modalities can be used to correlate with clinical findings and to assist with surgical planning. They are also important if cervical foraminotomy is needed as they can be used to help assess the level(s) and location of nerve root compression. Upright plain films are used to determine preoperative kyphosis and one’s ability to perform posterior surgery. Flexion-extension films should be evaluated for any evidence of instability that may need to be addressed with a posterior fusion.
We prefer to use the 180-degree operating room setup and a Mayfield tong attachment with gelfoam bolster pads on a standard table. The Mayfield tongs allow control and stability of the cervical spine during positioning. Other alternative operating room table and positioning options include a Jackson frame with a Mayfield tong attachment or a Stryker or Jackson frame with Gardner tong traction.
Oyama et al. first described cervical laminoplasty in Japanese in 1973 as a treatment for OPLL . In this initial expansive laminoplasty procedure, the “Z-plasty” of the cervical spine, the spinous processes are removed, the lamina is thinned to the lamina-facet junction, and a Z-shaped cut is made between the laminae which are opened and fixed with suture or wire (Figure 2). Since its initial description by Oyama, laminoplasty techniques have been constantly refined. Most of these changes relate to how the cuts in the lamina or spinous process are made and how the laminae are secured in an open position—with wires or heavy sutures, bone anchors or bone blocks, hydroxyapatite blocks, miniplates, local spinous process autograft, and combinations thereof. All variations in laminoplasty techniques maintain the common theme, however, of repositioning the laminae, expanding the canal, and preserving the dorsal elements to maintain stability. In general, none of these technical variations have proven to be any safer or efficacious than the other. There are generally three categories of laminoplasty techniques: the “open door” laminoplasty, the “double door” laminoplasty, and the various muscle-sparing laminoplasty techniques. We will describe these techniques in detail in the following sections.
Hirabayashi et al. simplified the Z-plasty described by Oyama in the early 1980s with his unilateral expansive open-door laminoplasty [4, 34]. In this technique, a hinge is created on one side of the lamina-spinous process-ligamentum flavum complex. This allows the roof of the canal to be opened on the contralateral side leading to an expansion of the spinal canal.
In Hirabayashi’s expansive open-door laminoplasty, the spinal cord is decompressed asymmetrically since the door opens on one side and hinges on the other. In contrast, the double-door laminoplasty, described by Kurokawa in 1982, expands the canal symmetrically as the opening is created in the midline . This is accomplished by splitting the spinous processes in the midline with the left and right hemilaminae hinging on the lamina-spinous process-ligamentum flavum complex bilaterally (Figure 10(a)). In the double-door technique, the same positioning, draping, and midline posterior exposure as the open-door technique is performed. This exposure is carried out laterally to the middle of the lateral masses. Preserve the semispinalis muscle attachments to the C2 spinous process as much as possible. Troughs are drilled bilaterally with a high-speed drill or burr at the lamina-lateral mass junction from C3 to C7, just medial to the pedicle (Figures 10(b) and 10(c)). The inner cortex, as with the open-door technique, is only thinned. The spinous processes are then split down the middle. A drill or burr is used to thin the lamina and a Kerrison punch is used to open the lamina in the midline. The midline laminar splits can be opened with laminar spreaders (Figure 10(d)). The laminae are lifted off the spinal cord in the midline and held open like a French door. This allows the spinal cord to drift posteriorly in the enlarged canal.
Many problems associated with laminoplasty such as axial neck pain, postoperative kyphosis, and segmental instability are thought to be related to neck muscle disruption [12, 33, 64–66]. Various techniques have been described to minimize disruption of muscular and ligamentous attachments to the lamina and spinous processes.
Performing a foraminotomy in association with laminoplasty is indicated in cases of significant radiculopathy or if there is radiographic evidence of neuroforaminal stenosis regardless of symptoms. This is done both to prevent the development of nerve root compression postoperatively and, possibly, to minimize postop neck pain due to nerve root stretch and compression. Some also recommend performing a foraminotomy based on abnormal neuromonitoring signals, especially those involving the C5 nerve root, which is particularly vulnerable to traction injury. Others, still, routinely perform bilateral C4-C5 foraminotomies to minimize the risk of a C5 root palsy.
Fusion is indicated with laminoplasty for patients with severe axial neck pain, evidence of instability, or bilateral radicular symptoms in addition to myelopathy. If fusion is planned, the exposure needs to be carried out laterally to the lateral aspect of the facet joints. Additionally, excision of facet capsules from C3 to C7 should be performed during the exposure. After the laminoplasty is complete, place lateral mass screws at C3 to C7. The start point is 1 mm medial to the center of the lateral mass with a 15-degree rostral and 30-degree lateral trajectory . Some prefer a pedicle screw at C7 for additional stability. After lateral mass decortication, allograft or cancellous iliac crest autograft is packed into the decorticated fusion bed.
After copious irrigation of the wound with normal saline, retractors are removed, hemostasis is achieved, and a deep drain is placed. A standard layered closure is then performed. We close the fascia covering the paravertebral musculature with a No. 0 vicryl suture in a Figure 8 fashion, followed by a No. 0 PDS running stitch. The subcutaneous layer is closed with No. 2-0 vicryl in an interrupted buried fashion. We close the skin with either a No. 3-0 monocryl suture using a running subcuticular technique or a No. 3-0 nylon baseball stitch.
The head of the bed should be kept at greater than 45 degrees for the first couple days after surgery to minimize venous bleeding. Patients are immobilized in a rigid cervical collar, such as an Aspen collar, for 3-4 weeks. Mobilization with physical therapy starts on postoperative day one, including bed transfers and ambulation. We obtain AP and lateral plain films of the cervical spine prior to patient discharge. Patients typically are discharged 24 to 48 hours after surgery and return for their first follow-up visit 3-4 weeks later, at which point we obtain repeat AP and lateral cervical spine films. We encourage patients to return to their day-to-day activities as soon as possible. At 3-4 weeks, patients can discontinue the use of their collar and initiate isometric neck exercises.
Multiple studies have shown that patients with cervical myelopathy due to cervical spondylosis or OPLL do reliably benefit from neurologic improvement following laminoplasty. Most studies report outcomes using the Japanese Orthopedic Association (JOA) scoring system, documenting mean preop and postop scores and rate of recovery. Recovery rates following laminoplasty of at least 50–70% are consistently reported in the literature, though recovery rates as high as 90% have been reported [8, 18, 20, 29, 36, 37, 44, 46, 47, 78, 86, 89–92].
Laminoplasty is becoming an increasingly popular treatment for multilevel cervical stenosis due to cervical spondylotic myelopathy, OPLL, and other causes. Laminoplasty minimizes the risk of certain complications associated with other surgical options, such as graft and fusion-related complications, postoperative kyphosis and instability, and the morbidity of an anterior approach. Laminoplasty does have its own set of potential complications, including laminar closure, axial neck pain, nerve root palsies, and loss of cervical motion and alignment. However, laminoplasty techniques are continuously being refined to address such potential shortcomings. Indeed, further prospective data with longer-term followup comparing laminoplasty techniques to other surgical options is necessary. Yet, outcomes in laminoplasty patients that are at least as good as anterior decompression and fusion and laminectomy can be expected. In the appropriate patient and with proper surgical technique, laminoplasty can be an excellent option for patients with multilevel cervical stenosis and myeloradiculopathy.