DEFINITION

Cervical laminoplasty is a surgical technique first described in 19833 that allows for decompression of the cervical cord from a posterior approach. The procedure is designed to open and reconstruct the cervical lamina, thus creating more available space for the spinal cord while at the same time preserving motion and normal alignment.

Cervical spondylosis is a degenerative condition which can lead to multilevel spinal cord compression resulting in myelopathy. Congenital stenosis superimposed on spondylosis may predispose patients to myelopathy. Other conditions such as ossification of the posterior longitudinal ligament (OPLL), trauma, infection, and neoplasm can also result in myelopathy.

The goal of laminoplasty is to alleviate circumferential compression of the spinal cord by decompressing the posterior aspect of the spinal canal and allowing the spinal cord to drift away from ventral compressive structures.

 

 

ANATOMY

 

The cervical spine is composed of seven vertebrae normally arranged in lordotic alignment. The occiput-C1 articulation is responsible for 50% of neck flexion and extension and the C1-C2 atlantoaxial articulation is responsible for 50% of total rotation. Lateral bending below the C2-C3 level is coupled with rotation due to the 45-degree inclination of the cervical facet joints.

 

The subaxial vertebral segments of C3-C7 are similar to each other and distinct from C1 (atlas) and C2 (axis). The subaxial vertebrae articulate via zygapophyseal (facet) joints posteriorly and uncovertebral joints of Luschka laterally.

 

Intervertebral discs are located between the vertebral bodies of C2-C7. The discs are composed of an inner nucleus pulposus and an outer annulus fibrosus.

 

Anteriorly, the spinal canal is bounded by the vertebral bodies, the intervertebral discs, and the posterior longitudinal ligament. The pedicles form the lateral boundary of the spinal canal. Posteriorly, the ligamentum flavum runs from the anterior surface of the superior lamina to the posterior surface of the inferior lamina (FIG 1).

 

PATHOGENESIS

 

Cervical spondylotic changes are the most common reason for cervical myelopathy.

 

Spondylosis is characterized by intervertebral disc desiccation and height loss, which leads to annular bulging and osteophyte formation around the uncovertebral and facet joints. In the dorsal spinal canal, thickening or buckling of the ligamentum flavum further decreases canal and foraminal cross-sectional area.

 

Circumferential spinal cord compression causes derangement at a cellular level, which leads to clinical deficits. In addition to static spinal cord compression, instability leads to motion that may aggravate myelopathy.

 

NATURAL HISTORY

 

There is a paucity of recent literature that documents the true natural history of cervical spondylotic myelopathy because modern practice is to perform a surgical decompression once significant myelopathy has been diagnosed. Early studies described a stepwise decline in neurologic function punctuated by stable periods, although some patients exhibited a continuous functional decline or no decline at all.

 

The clinical course may wax and wane over a period of years. Sensory symptoms may be transient, but motor symptoms tend to persist and progress. Although surgical intervention may relieve symptoms and halt progression, neurologic deficits may be permanent.

 

PATIENT HISTORY AND PHYSICAL FINDINGS

 

The diagnosis of cervical myelopathy may be difficult secondary to the variability in clinical findings. Pain is frequently not a significant complaint in myelopathic patients unless it is associated with root compression or facet arthrosis. Patients may present with subtle findings or profound neurologic deficits.

 

Patients commonly present with the insidious onset of gait disturbance, trouble with balance, and hand clumsiness. They may report burning pain in the upper extremities, difficulty with handwriting and fine motor control, diffuse

 

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numbness, or weakness of grasp. Advanced cases can present with flaccid weakness or bowel and bladder dysfunction.

 

 

 

 

FIG 1 • Anatomy of cervical vertebrae.

 

The physical examination should begin with an assessment of gait, which may be wide-based, hesitant, stiff, or spastic. Patients may be unable to walk heel-to-toe or may have poor balance during toe raise.

 

Sensory findings may be variable. Pain, temperature, vibratory, and light touch sensation may be decreased.

 

Mixed upper and lower motor neuron findings may be present depending on the degree of cord compression, concomitant nerve root compression, or peripheral nerve dysfunction.

 

The Lhermitte sign is positive when extreme neck flexion or extension results in electrical sensation down the arms or body and is a sign of spinal cord compression. Pathologic reflexes include the scapulohumeral reflex (indicating compression above the C3 level) or inverted radial reflex (indicating compression at C5 or C6).

Other findings include the Hoffman sign, clonus (>3 beats), Babinski sign, slow grip and release, unsteady Romberg (posterior column), and abnormal finger escape (T1 level).

 

IMAGING AND OTHER DIAGNOSTIC STUDIES

 

Plain anteroposterior (AP) and lateral standing radiographs of the cervical spine are useful for initial evaluation of sagittal alignment and the extent of spondylotic changes (such as disc space narrowing, osteophytes, kyphosis, joint subluxation, and spinal canal stenosis; FIG 2A).

 

 

Flexion and extension views provide information about possible spinal instability.

 

 

 

 

FIG 2 • A. Preoperative lateral cervical spine radiograph demonstrating spondylotic changes: diffuse disc height loss and osteophyte formation. B. Sagittal T2-weighted MRI showing multilevel cervical disc protrusions and circumferential stenosis at C3-C4, C4-C5, and C5-C6, resulting in cord deformation. Cord signal changes can be seen at C3-C4 and C4-C5, indicative of cord damage. C. Sagittal CT reconstruction showing large ossified posterior longitudinal ligament extending from C2 to C6. There is evidence of failed anterior

decompression by an outside facility. D. Axial CT image demonstrating a large ossified posterior longitudinal ligament.

 

 

Typically, magnetic resonance imaging (MRI) is the imaging modality of choice for diagnosing spinal cord compression. It can visualize the spinal cord and canal dimensions without any ionizing radiation. The spinal cord parenchyma can be visualized to help evaluate the extent of spinal cord damage. MRI is also useful for visualization of compressive soft tissue such as ligamentum hypertrophy and disc herniation (FIG 2B).

Because it is usually obtained supine, MRI is less reliable than standing x-ray for evaluation of sagittal alignment.

 

Computed tomography (CT) is superior to MRI for defining bony anatomy and is useful for evaluating OPLL (FIG 2C,D). The addition of contrast dye myelogram combined with the CT (CT-myelogram) can improve the ability to assess spinal cord compression in the setting of previous hardware placement that would obscure an MRI with scatter artifact.

 

DIFFERENTIAL DIAGNOSIS

Stroke

Peripheral compression neuropathy (ie, carpal tunnel syndrome, cubital tunnel) Parkinson disease

Muscular dystrophy or dystonia Syringomyelia

Tumor

Vascular disease Autoimmune disorders Epidural abscess Nerve injury

Drug intoxication

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Multiple sclerosis Amyotrophic lateral sclerosis Cerebellar dysfunction Idiopathic movement disorder

Peripheral neuropathy (B12 deficiency)

 

 

SURGICAL MANAGEMENT

 

Laminoplasty was specifically designed to decompress the spinal cord while avoiding the kyphotic deformities that had previously complicated laminectomy alone. Laminoplasty may be associated with fewer complications than laminectomy and fusion2,8 and has lower implant costs. It may also have fewer complications than

multilevel anterior corpectomy.1

 

Laminoplasty creates effective posterior decompression of the subaxial cervical spine by allowing for dorsal cord expansion and drift while preserving motion.5 Dome laminectomy of C2 can be added if needed.

 

Theoretical advantages of laminoplasty over laminectomy and fusion include relative motion preservation, less soft tissue dissection, shorter operative time, diminished blood loss (in experienced hands), and less concern about smoking status and nonsteroidal anti-inflammatory drug (NSAID) use (which would increase the nonunion risk in fusion surgery).

 

Laminoplasty can be performed via open door (lateral opening trough with a single hinge) or French door (midline opening trough with bilateral hinges) techniques. Although the French door technique requires an additional hinge, it results in less epidural bleeding than the open door technique because the veins tend to be

 

lateral. Both techniques are effective in treating myelopathy.7 Indications

 

Spinal stenosis due to either cervical spondylosis, congenital stenosis, or OPLL that results in multilevel cord compression and cervical myelopathy6

 

Contraindications

 

 

Kyphotic sagittal alignment of more than 10 to 14 degrees can lead to worsening of kyphosis and poor neurologic outcomes because the spinal cord is unable to drift back.

 

 

Significant segmental instability Relative contraindications

 

Ossification of the ligamentum flavum: This condition is associated with dural adhesions, which can make opening the posterior arch difficult.

 

Previous posterior cervical surgery such as foraminotomies: Scar formation can produce adhesions that impede safe opening of the laminar arch.

 

Primary axial neck pain in the setting of myelopathy: Laminoplasty preserves motion, and hence the procedure is not designed to address pain generation from facet arthrosis and disc degeneration. Fusion procedures may provide greater benefit to patients with significant complaints of axial neck pain.

 

Preoperative Planning

 

Evaluation of the patient's active range of motion in flexion and extension assists with head positioning. Passive flexion and extension beyond the patient's natural range during positioning can lead to dangerous impingement or stretching of the tenuous cord and subsequent neurologic dysfunction.

 

Careful examination of CT scans to determine the bony anatomy of the dorsal cortices is helpful, with special attention given to the lamina-to-lateral mass junction.

 

French door laminoplasty may also be used in conjunction with fusion (in lieu of laminectomy) to increase the size of the fusion bed, although this makes instrumentation more challenging. A unilateral open door technique can also be used with fusion and lateral mass instrumentation if needed.

 

Positioning

 

Intubation is performed with caution in the myelopathic patient, starting with advanced notification to anesthesia personnel. Care should be taken not to extend the neck more than the patient's comfortable range of motion before sedation. The use of fiberoptic assistance should be considered in high-risk cases.

 

Application of a Mayfield head holder provides a stable platform during the procedure (FIG 3A).

 

The patient is placed prone onto chest bolsters. The abdomen should be as free as possible to reduce venous

bleeding and prevent ventilatory difficulty. Arms are padded and tucked at the patient's side (FIG 3B). Shoulders can be taped in gentle traction, although care must be taken to avoid stretching the brachial plexus.

 

The head is positioned in slight cervical flexion, which tensions the skin on the posterior neck folds and decreases shingling of lamina.

 

Intraoperative modification of neck flexion-extension is possible if needed by adjustment of the Mayfield tongs.

 

The bed is placed in reverse Trendelenburg to decrease venous bleeding and allow for a horizontal surgical field.

 

Spinal cord monitoring is routinely performed in myelopathic patients. This helps to monitor neurologic problems related to positioning as well as with the laminoplasty procedure itself.

 

Hair should be shaved to above the base of the occiput. The surgical field should be prepared from the nuchal line to roughly T4 to allow for possible wound extension.

 

 

 

 

FIG 3 • A. The patient's head is placed in a Mayfield head holder. B. The patient is placed prone onto chest bolsters with arms tucked at the sides. The head is placed in slight flexion. Spinal cord monitoring equipment is also seen.

 

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TECHNIQUES

• Incision and Dissection

  In the typical situation where C3-C7 lamina need to be decompressed, a posterior midline approach to the spinous processes is made using a longitudinal incision extending from C2 to T1. In situations where fewer levels need decompression, avoiding exposure of C2 or C7 can reduce postoperative pain and instability.

  Electrocautery is used to divide the subcutaneous fat in the midline to reach the tips of the spinous processes.

  Once the tips of the spinous processes have been found, a meticulous subperiosteal dissection is performed to expose the lamina. Careful attention should be paid to stay in the midline avascular plane to reduce bleeding.

  The dissection should extend laterally to fully expose the junction of the lateral mass and the lamina.

  Exposure should not extend beyond the midportion of the lateral masses, unlike a traditional laminectomy and fusion exposure which requires wider access.

   

  TECH FIG 1 • A. Lamina exposure after subperiosteal dissection and spinous process removal. The dissection should extend laterally to expose the junction of the lateral mass and lamina. Attempts should be made to minimize disruption of the facet capsule. This will decrease longterm postoperative neck pain. Planned lines for opening and hinge trough creation have been marked using electrocautery and marking pen. B. A Kerrison rongeur is used to divide the interlaminar ligamentum flavum.

   

   

   

  The extensor muscle attachment to the C2 spinous process is carefully preserved to prevent iatrogenic focal kyphosis. The inferior C2 laminar margin is usually broad and should be exposed to aid in visualization of the C2-C3 junction.

   

  The spinous processes can be amputated at their base. Spinous processes are useful for bone graft (either for strutting open the lamina or for local morselized bone grafting of the hinge side). Avoid placing bone graft in the interlaminar spaces or across facet joints.

   

  Removing the spinous processes significantly improves exposure and reduces asymmetric posterior displacement of paraspinal musculature (TECH FIG 1A).

   

  The interlaminar ligamentum flavum between levels C2-C3 and C7-T1 (or the top and bottom interspaces) is removed. First, a rongeur is used to create a small opening in the interlaminar ligament flavum. Then a combination of curettes and Kerrison rongeurs is used to divide the remainder of the interlaminar ligamentum flavum (TECH FIG 1B).

• Trough Preparation

Open-Side Trough

 

The open side should be on the side with the more severe stenosis.

 

 

A 3.0- or 4.0-mm round or oval low-aggression high-speed burr is used to form the trough. The trough location is at the junction of the lamina and lateral mass.

 

For the opening side, bony layers should be removed in sequence: the outer cortex, then the cancellous middle layer, followed by most of the ventral cortex (TECH FIG 2A).

 

If the trough gets deeper than the diameter of the 4.0-mm burr without reaching the ventral cortex, the trough may be too lateral and heading toward the vertebral artery and should be redirected medially.

 

Once the ventral laminar bone is thinned sufficiently, complete the trough with a microcurette, a 1.0-mm Kerrison rongeur, or a diamond burr (TECH FIG 2B).

 

Care should be used at this time to avoid the epidural veins, which can create significant bleeding. Thrombin-soaked powdered Gelfoam and bipolar electrocautery can be used to control bleeding epidural veins.

French Door (Midline Splitting)

 

The French door technique involves creation of a midline opening trough and two lateral hinge troughs (TECH FIG 3A).

 

The midline of the posterior arch can be split by a variety of methods. One method is to remove the spinous process and use a 4.0-mm low-aggression burr to create a complete midline trough (TECH FIG 3B).

 

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TECH FIG 2 • A. Creation of the opening trough requires sequential removal of bony layers with a burr (open door technique depicted). B. After the initial burring, completion of the trough can be performed using a microcurette, a 1.0-mm Kerrison rongeur, or a diamond burr (French door technique depicted).

 

 

 

TECH FIG 3 • A. Axial CT of a French door laminoplasty showing a large bilateral surface area available for bone grafting. B. The French door technique uses a midline opening trough. In this image, the midline trough has been created. Planned lines for the hinge troughs are shown on either side.

 

 

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Hinge-Side Trough

 

The hinge side should be prepared after the opening trough has been created so that greenstick fracture of the hinge can be carefully assessed for pliability.

 

Preparing the hinge trough entails removal of only the dorsal cortex and cancellous layer (TECH FIG 4). Often, areas of thicker cortical bone preventing hinge closure are found at the most caudal and cephalad edges of each lamina.

 

Stiffness of the hinge should be tested periodically during preparation. The goal is to create a pliable yet firm hinge that yields to moderate opening force without breaking the inner cortex.

 

Hinge troughs used for the French door technique are prepared in the same anatomic location as troughs created for the open door technique. Similar to the open door technique, ventral laminar cortex should be preserved to create stable hinges.

 

 

 

TECH FIG 4 • Opening and hinge troughs for the open door technique. Preserved ventral cortex for the hinge trough is seen at the tip of the Penfield dissector.

• Opening the Laminoplasty

   

  Proceeding from caudal to cranial, a nerve hook or curved curette is used to elevate the lamina away from the spinal cord. A Kerrison rongeur can be used to divide ligamentous attachments, and bipolar forceps are used for cauterization of epidural veins.

   

  The laminae are then opened sequentially. This can be done with the assistance of a curved microcurette to raise the opening side and gently bend open each lamina hinge. Care should be taken to identify and lyse any epidural adhesions (TECH FIG 5A). Do not allow the newly opened door to fall violently back onto dorsal spinal cord.

   

   

   

  TECH FIG 5 • A. Completing the opening for the French door technique. With the assistance of a curved microcurette, the lamina is gently bent back on its hinge. Care should be taken to identify and lyse epidural adhesions. B. Completion of open door laminoplasty.

   

   

  Starting from C3 and proceeding to C7 allows for blood to flow away from the working area and reduces the overhang of the inferior edge of the superior lamina due to lamina shingling.

   

  Completion of opening lamina is carried out carefully with small curettes (TECH FIG 5B).

   

   

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• Posterior Arch Reconstruction

   

  The laminoplasty door is held open using a variety of techniques.

   

  Plate reconstruction has become popular because of the immediate mechanical security that plates provide (TECH FIG 6A,B). However, eventual mechanical stability relies on hinge-side bony healing to permanently hold the posterior arch open.

   

  Bone struts can also be used; this was the most frequently used method for many years. Autogenous grafts fashioned from the spinous processes of C6 and C7 can be used as well as rib allograft or machined cortical grafts (TECH FIG 6C).

   

  Reconstruction with bone has the advantage of allowing for full bony reconstruction of the lamina arch, as the bone struts usually fully incorporate. Furthermore, bone is easier and faster to place than plates

  and screws, but bone provides less initial mechanical stability to the arch and may (rarely) dislodge before healing of the hinge.

   

   

   

  TECH FIG 6 • A,B. Open door plates. A. First, a 6-mm lateral mass screw is placed. B. Then the lamina is opened and held in place with 4-mm screws. C. Machined cortical allograft. Grooves allow for better stability when interpositioned between lamina and lateral mass. D. Postoperative lateral radiograph after laminoplasty performed with alternating plate and graft technique. E. French door posterior arch reconstruction using midline plates. Adequate space must be maintained between the plate and cord to allow for expansion. F. A salvage plate can fix the lamina to the lateral mass in the event that the hinge is disrupted.

   

   

  Hybrid reconstruction with alternating plate and bone graft can also be used (TECH FIG 6D).

   

  With the French door technique, midline plates can be applied. Other materials have been used to keep the door open, including autograft, allograft, or hydroxyapatite (TECH FIG 6E, F).

   

  Alternatively, the door can be held open with sutures that go from the lamina to the lateral mass or facet capsules. Suture anchors have also been used.

• Wound Closure

 

 

A deep drain is placed, followed by a layered fascial and subcutaneous closure. Skin is closed using a subcuticular stitch.

 

 

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PEARLS AND PITFALLS

 

	Physical ▪ The Hoffman reflex can indicate spinal cord compression but can be positive in examination normal individuals.     Patient ▪ Slight cervical flexion facilitates exposure and closure by eliminating redundant position posterior skin folds and decreases overlap of lamina (laminar shingling) for improved identification of adjacent levels.     Opening ▪ If foraminotomies are planned, then the opening side should be made over the side ipsilateral side of nerve root compression. If asymmetric compression is present, it may be beneficial to open the more affected side. While creating the opening hinge, a color change in the cortex can be appreciated. As the deep (ventral) cortex is thinned, yellow areas (which correspond to ligamentum flavum) and blue areas (which correspond to veins or dura) can be seen through the bone. Care should be taken at this point as the ventral bone is now very thin.     Hinge-side ▪ The surgeon should avoid removing excessive bone on the hinge side, which trough would create a floppy hinge. The surgeon should always recheck that the opening side is complete if there is any difficulty elevating the lamina, instead of focusing solely on thinning the hinge side. If the hinge is completely incompetent, then it can be reconstructed with a salvage plate that fixates on the hinge side (see TECH FIG 6F).     Epidural ▪ The epidural veins should be ligated as far dorsal as possible. This decreases vein ligation bleeding by avoiding the ventral longitudinal veins.

 

 

POSTOPERATIVE CARE

 

A soft collar can be worn for comfort for 2 to 4 weeks after surgery.

 

When plate fixation has been used, immediate gentle active neck motion should be permitted to prevent stiffness.

 

Drain output is monitored and drains are typically removed 48 hours after surgery.

OUTCOMES

Cervical laminoplasty is a valuable treatment option for myelopathic patients with multilevel stenosis. It provides cord decompression while preserving some motion. With proper patient selection, this procedure provides excellent neurologic outcomes with few complications.

When compared to laminectomy with fusion, outcomes regarding neurologic improvement are similar. However, laminectomy with fusion has more frequent fusion-related complications such as nonunion, instrumentation failure, persistent pain from bone graft harvest site, subjacent degeneration requiring

reoperation, and a higher deep infection rate.2

When compared to corpectomy in patients without kyphotic alignment, outcomes regarding neurologic

 

improvement are similar. However, laminoplasty patients have fewer complications and require less pain

medication.8

 

 

 

COMPLICATIONS

Segmental nerve root palsy: This is most commonly a motor deficit affecting the C5 root that occurs a day or two after surgery and typically improves over the course of months.4

Axial neck pain has been reported at a high rate. However, the pain is typically mild and often described as stiffness.

Loss of cervical motion: Up to 50% loss of range of motion has been reported with some laminoplasty techniques.

Dural tears are infrequent but can be handled with either direct repair or glue with or without the addition of a lumbar diverting cerebrospinal fluid drain.

Hardware failure leading to laminar door closure has been reported. Infection and epidural hematoma can occur; however, the rates are very low.

 

 

REFERENCES

1. Edwards CC II, Heller JG, Murakami H. Corpectomy versus laminoplasty for multilevel cervical myelopathy: an independent matchedcohort analysis. Spine 2002;27(11):1168-1175.

    

    

2. Heller JG, Edwards CC II, Murakami H, et al. Laminoplasty versus laminectomy and fusion for multilevel cervical myelopathy: an independent matched cohort analysis. Spine 2001;26(12):1330-1336.

    

    

3. Hirabayashi K, Watanabe K, Wakano K, et al. Expansive opendoor laminoplasty for cervical spinal stenotic myelopathy. Spine 1983;8(7):693-699.

    

    

4. Imagama S, Matsuyama Y, Yukawa Y, et al. C5 palsy after cervical laminoplasty: a multicentre study. J Bone Joint Surg Br 2010;92(3):393-400.

    

    

5. Machino M, Yukawa Y, Hida T, et al. Cervical alignment and range of motion after laminoplasty: radiographical data from more than 500 cases with cervical spondylotic myelopathy and a review of the literature. Spine 2012;37(20):E1243-E1250.

    

    

6. Matsumoto M, Chiba K, Toyama Y. Surgical treatment of ossification of the posterior longitudinal ligament and its outcomes: posterior surgery by laminoplasty. Spine 2012;37(5):E303-E308.

    

    

7. Okada M, Minamide A, Endo T, et al. A prospective randomized study of clinical outcomes in patients with cervical compressive myelopathy treated with open-door or French-door laminoplasty. Spine 2009;34(11):1119-1126.

    

    

8. Yoon T, Hashimoto R, Raich A, et al. Outcomes following laminoplasty compared with laminectomy and fusion in patients with cervical myelopathy: a systematic review. Spine 2013;38(22 suppl 1): S183-S194.