35 Cervical Laminoplasty

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tom of unilateral radiculopathy, the opening of the ipsilateral to the symptomatic .... Hilibrand AS, Carlson GD, Palumbo MA, Jones PK, Bohlman HH. Radiculop-.
35  Cervical Laminoplasty Takashi Kaito and Kazuo Yonenobu

Until the 1970s, laminectomy was the only posterior decompression procedure for the cervical spine. However, postoperative neurologic deterioration supposedly due to the operative procedure (e.g., insertion of a rongeur or curette into the spinal canal) was not uncommon. The introduction of high-speed drills enabled delicate and safe decompression of the nerve tissue. Regardless, some cases exhibited postoperative neurologic deterioration believed to be due to the loss of mechanical stability, especially kyphotic deformity, caused by the excision of the posterior elements or scar tissue (i.e., laminectomy membrane) forming and occupying the void after the laminectomy. Accordingly, in 1973, Oyama and Hattori1 invented the Z-plasty, which both secures the decompression of the spinal canal and preserves the posterior bony elements. After the first description of enlargement of the spinal canal without resecting the laminae, Hirabayashi et al2,3 reported open-door laminoplasty and Kurokawa et al4 reported double-door laminoplasty (i.e., spinous process-­ splitting laminoplasty, also called French door laminoplasty). Since then, many modified techniques based on these two laminoplasty techniques have been described,5–10 aiming to secure the stability of enlarged spinal canal and minimizing invasiveness to the muscle and ligamentous structures. Although the preservation of posterior elements afforded by laminoplasty is thought to help reduce the incidence of postlaminectomy kyphosis and provide rigidity for the reconstructed spine, there is no con­ clusive evidence supporting this hypothesis.11 This chapter describes the concept of cervical laminoplasty and the detailed techniques.

Patient Selection: Indications and Contraindications AU1

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Despite the lack of conclusive evidence regarding the superiority of laminoplasty, laminectomy, or multilevel anterior cervical decompression and fusion (ACDF), setting the major indication of laminoplasty to be compressive cervical myelopathy due to developmental canal stenosis, multilevel spondylosis, and continuous or mixed-type ossification of the posterior longitudinal ligament (OPLL) requiring multilevel decompression is a reasonable treatment strategy. A retrospective comparative study between laminoplasty and multilevel ACDF demonstrates that the incidence of complications is higher in ACDF than laminoplasty even though both procedures have similar clinical results.12 ACDF is a standard procedure for one- or two-level cervical disk herniation.13 Laminoplasty can also be performed in cases in which spontaneous involution is expected.14 Laminoplasty is an alternative to ACDF, especially in young patients with concomitant developmental canal stenosis, and can help avoid adjacent segment disease.15 In cases presenting with concomitant radiculopathy, foraminotomy can be easily combined. Neutral to lordotic alignment is advantageous for laminoplasty to allow indirect

decompression of anterior factors by shifting the spinal cord posteriorly. In cases presenting with kyphotic alignment, neurologic recovery after laminoplasty is inferior to that in cases with neutral to lordotic alignment.16 In addition, local severe spinal cord compression from the anterior (i.e., local OPLL) is a negative prognostic factor for neurologic recovery after laminoplasty.17–19 Moreover, the addition of posterior fusion is recommended if local instability exists.

Advantages • Enables simultaneous decompression for multilevel spinal cord compression • Low incidence of serious complications as compared with ACDF • Low incidence of adjacent segment disease as compared with ACDF • Foraminotomy for radiculopathy can be performed if necessary. • Reduced incidence of postlaminectomy kyphosis • External fixation (i.e., collar use) can be omitted. • Theoretically, cervical range of motion can be preserved as compared with multilevel ACDF.20

Disadvantages • High incidence of axial pain (i.e., in the neck and shoulders) • In cases with severe anterior compression or severe cervical kyphosis, laminoplasty may not provide sufficient indirect decompression. • Segmental motor palsy (commonly C5 and rarely C6 and C7) occurs in ~ 5% of laminoplasties,21,22 though the incidence is similar with multilevel ACDF.23 • Cervical alignment cannot be changed.

Choice of Operative Approach Since the original report of laminoplasty, numerous modified procedures aiming to secure the enlarged spinal canal and minimize muscle detachment have been developed.5–10 However, laminoplasty aims to preserve posterior bony elements while expanding the spinal canal. There are two main laminoplasty techniques: open-door and double open-door laminoplasty. Although two randomized controlled studies and three retrospective comparative studies report that these techniques are not significantly different with respect to neurologic recovery,24–28 there is a lack of definitive evidence to conclude the superiority of either technique. This is partly because these techniques have been taught and developed in mentor–mentee relation-

35  Cervical Laminoplasty ships, meaning many surgeons are performing only one of these techniques.

Preoperative Tests Physical Examination The level diagnosis of myelopathy should be based on meticulous evaluation of deep tendon reflexes, including the presence of pathological reflexes, motor and sensory loss, and bowel and bladder dysfunction.

Imaging Evaluation Cervical alignment, canal diameter, and instability should be evaluated on plain radiographs. Computed tomography (CT) scan can help determine if spinal cord compression is due to ossified/calcified tissue or soft tissue. Knowing the precise dimensions and configuration of bone tissue is useful for selecting the location and depths of the troughs. Magnetic resonance imaging (MRI) can depict not only extrinsic compression of the spinal cord, especially soft tissue factors, but also the intrinsic changes of the spinal cord itself. Therefore, MRI is the most valuable tool for the diagnosis of cervical spondylotic myelopathy and exclusive diagnoses of tumors, infections, syrinx, and myelitis.

Surgical Procedure Operative Position AU2

The surgeon must avoid excessive cervical spine extension during the intubation process. In cases of severe myelopathy, fiberscopic intubation is recommended. We routinely use the Mayfield head holder, which offers rigid immobilization of the cervical spine and places the patient on a Hall frame to decrease abdominal pressure. The shoulders are taped down on both sides to provide traction, enabling better intraoperative radiographic visualization of the lower cervical spine. A slight flexed position of the neck makes the laminoplasty easier by diminishing the overlap of the laminae and facet joints; meanwhile, too much flex makes the exposure process difficult by increasing the tension of the paraspinal muscles. If spinal fusion techniques are to be applied, the position of the neck should be changed to a neutral position beforehand. The table is tilted into the reverse Trendelenburg position to make the incision site flat and avoid blood congestion in the operative field.

Incision and Exposure The C2 and C7 spinous processes are usually easily palpable from the skin. After the dorsal midline skin incision from C2 to C7, the nuchal ligament between the right and left paraspinal muscles and is in an avascular plane and is divided at the midline. After the division of the nuchal ligament, all of the spinous processes are easily palpable. Laminoplasty originally involved exposure from C3 to C7. Laterally, the exposure of the inner half of the lateral mass is sufficient for the subsequent procedure. The semi­ spinalis muscle attached to C2 should be maximally preserved to prevent the postoperative development and progression of kyphosis as well as mitigate postoperative axial pain. In cases in which there is overlap of the C2 and C3 laminae or compression of the cord at C2-C3, partial resection of the ventral portion of the semispinalis muscle enables dome-shaped laminoplasty of C2 and elevation of C3 lamina. The resection of muscles attached to the C7 spinous process (i.e., trapezium and rhomboideus minor muscles) is also reported to be associated with postoperative axial

Fig. 35.1  Optimal exposure for laminoplasty from C3 to C6. Muscles attaching to C2 and C7 are completely preserved.

pain. Therefore, we usually implement laminoplasty from C3 to C629 (Fig. 35.1). In cases requiring decompression at the C6-C7 level, partial laminectomy of C7 (i.e., the cranial third) is added while keeping the muscles attached to C7 intact.

Open-Door Laminoplasty Following the exposure of the dorsal aspect of the cervical spine, the spinous processes of C3 through C7 (C6) are cut at the base with a Liston bone-cutting forceps and kept for use as bone grafts (Fig. 35.2a). Bone wax is used to stop bleeding from the cut surface of the bone. Bilateral troughs are made at the junction of lateral mass and lamina. To control the springiness of the elevated lamina, the open side of the “open door” is drilled first. A trough is made across each lamina using a high-speed drill with a 4-mm steel bur. Continuous irrigation is used to prevent thermal damage to the surrounding tissue and aid visualization of the bottom of the trough. After the inner cortex is exposed, the bur is replaced with a diamond bur. The drilling continues until the epidural venous plexus at the cranial half of the lamina and the yellow ligament at the caudal half of the lamina can be visualized through the thinned inner cortex. Because of the inclination of the lamina and overlap of cranial lamina, the cranial portion of the lamina tends to be insufficiently thinned; surgeons must keep this in mind during the drilling process. After sufficiently thinning the inner cortex, an 8- to 10-mm raspatory is inserted into the trough and twisted. If the inner cortex is sufficiently thinned, the lamina makes a snapping sound when moved (Fig. 35.2b). Meanwhile, if there is a concomitant symptom of unilateral radiculopathy, the opening of the ipsilateral to the symptomatic side facilitates the concurrent foraminotomy. If the surgeon is right handed, the left side is chosen to be the open side. In cases of OPLL with severe laterality of the compressive factor, the compressive side is chosen as the open side. The trough

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230 II  Midcervical Spine

a

c

e

for the hinge side is subsequently made in the same manner (Fig. 35.2c). When drilling down to the surface of the inner cortex of the lamina at the hinge side (2-mm trough depth for C4 and C5 where no cancellous bone exists in many cases), the springiness of the laminae should be checked frequently to prevent laminar fracture of the hinge side. The laminae are elevated starting from the caudal lamina to the cranial lamina. The ligamentum flavum is cut under the trough and between the lamina at the cranial (C2-C3) and caudal (C6-C7 or C7-T1) ends, enabling the opening

b

d

Fig. 35.2  Open-door laminoplasty. (a) Removal of spinous process and trough for the open side. (b) Twist of raspatory in the trough at the open side. (c) Making the trough for the hinge side, ensuring the springiness of the lamina. (d) Drilling holes for the fixation of the autologous strut bone. (e) Opendoor laminoplasty using an autologous spinous process as a bone strut.

of the laminae over the extent of the laminoplasty. Hemostasis from the epidural venous plexus is achieved by bipolar cauterization. Collagen hemostatic agents may be used to gently tamponade bleeding sites. We use the autologous spinous processes from C6 and C7 (in case C7 spinous process is resected) as a supporting strut with a nonabsorbable 2-0 suture (Fig. 35.2d,e). In case the size and number of grafted materials are insufficient, hydroxyapatite spacers dedicated for open-door laminoplasty are placed instead. A bone autograft or hydroxyapatite spacers are placed at C4 and C6 for C3 to C6 or C3 to C7 laminoplasty. The

35  Cervical Laminoplasty placement of additional spacers can be considered if it is difficult to keep the nongrafted lamina elevated. The advantages of using autografts and hydroxyapatite spacers include low costs and the absence of radiographic artifacts.

Other Methods for Preventing Laminar Reclosure 1. From the hinge side: The original fixation method for laminae in open-door laminoplasty was suturing between the soft tissue at the hinge side and the spinous processes of the elevated laminae.2 Two sutures are placed through the articular capsules and surrounding soft tissues on the hinge side, and both ends of the suture placed through the capsules are pulled out through the cranial and caudal interspinous ligaments to the open side. Then the threads are ligated at the open side of the spinous process to prevent the lifted laminae from closing.30 The use of suture anchors was subsequently reported to ensure the elevation of the laminae. Nevertheless, the efficacy of suture anchors for preventing laminar reclosure remains controversial.6,31 2. From the open side: Titanium miniplates can be used to acquire further rigidity of the elevated laminae.32 The miniplates are attached to the laminae and ipsilateral lateral mass with screws. Although some reports indicate miniplate fixation is effective for reducing postoperative neck pain or preventing other complications, there is a lack of strong evidence indicating the comparative benefits of using miniplates.33

Other Modifications to Preserve the Muscles Attached to C2 and C7 The preservation of the muscles attached to C2 and C7 is reported to reduce postoperative axial pain and kyphotic deformity progression.34,35 Moreover, other modifications of laminoplasty procedures have been reported: 1. Laminectomy of C3 and laminoplasty from C4 to C7: In cases of degenerative cervical spine, the C2 and C3 laminae often overlap. In such cases, partial resection of the semispinalis muscle attached to C2 is required to elevate the C3 lamina. Laminectomy of C3 combined with laminoplasty at lower levels has been reported to minimize the resection of the semispinalis muscle.36

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2. Laminoplasty from C3 to C6: The C7 spinous process, which is the largest spinous process of the cervical spine, is also the origin of the trapezium and rhom­ boideus minor muscles. Preservation of the muscle attached to C7 by performing laminoplasty from C3 to C6 with or without partial laminectomy of the cranial third of C7 lamina has been reported to reduce post­ operative axial pain.29

Advantages • Two troughs for the elevation of the laminae can shorten the operative time. • In the original Hirabayashi procedure, no special implants are required to fix the elevated laminae. If the implants or autografts are placed as struts at the open side, the placement at every other lamina (i.e., skip placement) can provide satisfactory stability. • Can be easily combined with foraminotomy • The newly formed spinal canal is structurally stable compared with double open-door laminoplasty.37

Disadvantages • Exposure of the epidural venous plexus at the open side can increase the risk of bleeding. • Reclosure of the elevated laminae can occur if some kind of materials are not placed.

Double Open-Door Laminoplasty After standard exposure of the laminae and medial aspects of the facet joints, the spinous processes from C4 to C7 (C6) are cut at the height of the C3 spinous process. A trough is made with a 2-mm diamond bur at the center of the spinous process until the inner cortex of the lamina is sufficiently thin. A raspatory is then inserted into the trough and twisted. The division of the spinous processes at the midline is confirmed by the movement of the lamina given sufficient thinning. Bilateral troughs are subsequently made with a 3-mm diamond bur at the junction of the laminae and lateral mass. After the springiness of the halved lamina is confirmed to be equivalent between the right and left sides, the bisected lamia is opened bilaterally. Bone grafts made from resected spinous processes or ceramic spacers are inserted between the opened laminae and secured in place with non­ absorbable sutures (Fig. 35.3).

a

b Fig. 35.3  Double open-door laminoplasty. (a) Double open-door laminoplasty using an iliac crest bone graft. (b) Double open-door laminoplasty using a hydroxyapatite spacer.

232 II  Midcervical Spine Advantages • Bleeding from the epidural space is usually minimal because of the scarcity of venous plexus at the central portion. • Midline division of the laminae enables symmetrical expansion of the canal, though the clinical significance is unclear.

Disadvantages • Three troughs are required, which increases the time and complexity of the operation. • In cases in which the divided spinous processes are thin, the ceramic spacers can migrate with the resorption of the tip of the spinous process.37 • Some kind of spacer must be inserted into each opened lamina, which can increase operative time and costs.

Postoperative Care AU3

The drainage tube is removed 1 or 2 days after surgery. Sitting and walking are allowed from postoperative day 1. A neck collar is not used except for patients with severe neck pain. Cervical active range-of-motion exercises and isometric exercises are encouraged when pain is manageable.

Potential Complications and Precautions The overall incidence of surgical complications in laminoplasty is reported to be lower than that in multilevel ACDF.12 However, in addition to the common complications related to the cervical spine surgery (e.g., infection, hematoma, dural tear, nerve root injury, and spinal cord injury), there are several complications relatively characteristic of laminoplasty. Axial neck pain is not specific to laminoplasty but common in cervical posterior surgery. The preservation of muscles attached to C2 or C7 may reduce the incidence and severity of this complication.29,34,38 Furthermore, early mobilization of the neck may also mitigate symptoms. Segmental motor palsy (commonly C5 and rarely C6 and C7) occurs in ~ 5% of laminoplasties.21 Although segmental motor palsy usually shows favorable prognosis with full recovery within several months, some cases of severe palsy show incomplete recovery.21,22 Because the etiology (i.e., nerve root injury including tethering phenomenon and thermal damage39 or spinal cord disorder) has not been identified or may be multifactorial, several approaches have been attempted to decrease the incidence of this complication. The effect of prophylactic foraminotomy at bilateral C4-C5 for reducing the incidence of C5 palsy has been reported in a retrospective comparative study, but its effectiveness is inconclusive.40 Hinge-site fracture and subsequent laminar displacement can result in radiculopathy or myelopathy. The use of miniplate fixation when severe instability of the elevated laminae occurs secures the construct and may minimize the incidence of subsequent neurologic complications.

Conclusion Cervical laminoplasty is well indicated for multilevel spinal cord compression without kyphotic alignment and severe anterior compression of the cord. The major advantages of laminoplasty are that the procedure is not technically difficult, multiple seg-

ments can be decompressed simultaneously, and the incidence of serious complications is lower than with the anterior approach. Although the problems of axial neck pain and segmental motor palsy remain, several modified techniques are expected to reduce their incidences. Nevertheless, additional well-designed randomized controlled studies are required to confirm the superiority of laminoplasty over laminectomy, anterior cervical decompression and fusion, and laminectomy and fusion. Surgeons must choose the optimal procedure depending on the etiology of each case while keeping in mind the benefits and drawback of each.

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Author queries to Chapter 35: AU1: previous chapters have defined the D of ACDF as “diskectomy.” Can you align with them, for consistency? AU2: “Before positioning the patient” was deleted because it is an insufficient statement about patient positioning. Pls specify in what position the patient is placed, and include the statement at the point in this paragraph that positioning is performed. AU3: is “postoperative day 1” the day of surgery or the day after?

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