Cervical Laminoplasty: Indications and Techniques

Historical Background

Cervical spondylosis or ossification of the posterior longitudinal ligament (OPLL) causing cervical myelopathy have been traditionally managed with cervical laminectomy with or without concomitant arthrodesis. Cervical laminoplasty was introduced as a method to avoid postoperative complications associated with laminectomy, including kyphosis, spinal instability, perineural adhesions as well as delayed neurological deterioration. The concept of the procedure is based on allowing posterior shifting of the spinal cord into the augmented canal space following expansion of the lamina.

The first laminoplasty procedure was modified after Kirita’s technique for laminectomy, which involved thinning the lateral edges of the laminae proximal to the pedicles using an air drill followed by bending and lifting up. In 1973, Oyama and colleagues described the Z-plasty, a procedure that allowed for cervical spinal cord decompression, while preventing invasion of the postlaminectomy membrane by retaining the supportive laminae. ^, Later, Tsuji devised a variation of en bloc laminectomy during which laminae were left completely free from their bony attachments after cutting along an imaginary line separating laminar arches and articular processes. ^, The laminae were subsequently allowed to float on the cord without support from fixing sutures or bone grafts. Building on this technique, Hirabayashi published the open-door laminoplasty (unilateral hinge) and Kurokawa described the French-door laminoplasty (midline hinge). ^,

Indications and Contraindications

Cervical laminoplasty may be performed for the following conditions :

• 1.

  Multilevel cervical spondylotic stenosis with preserved lordotic curvature

• 2.

  Diffuse OPLL

• 3.

  Posterior spinal cord compression secondary to ligamentum flavum thickening

• 4.

  Intraspinal pathologies, such as tumor, infection, or hematoma, that require posterior access

On the contrary, laminoplasty should not be performed in the following cases:

• 1.

  Straightening of normal cervical lordosis or kyphotic alignment. More recently, surgeons have been performing laminoplasty with neutral alignment if K-line (a line connecting the midpoints of the spinal canal at C2 and C7) is negative and spine is stable or with kyphosis up to 10 degrees.

• 2.

  Cervical instability secondary to trauma, tumor invasion, degenerative disease or collagen disease, such as rheumatoid arthritis.

• 3.

  Massive pathology located ventrally that cannot be adequately decompressed from a posterior approach by posterior drift of the spinal cord.

Preoperative Planning and Patient Positioning

General endotracheal anesthesia is used and a preoperative dose of antibiotics (usually cefazolin 1 or 2 g) is given. Patient’s head is secured using a Mayfield clamp or through Gardner-Wells tongs and the patient is turned into a prone position on a Jackson table (OSI). Alternatively, chest rolls can be placed underneath the thoracic cage to decompress the abdomen, thus lowering intra-abdominal venous pressure and minimizing intraoperative blood loss. Afterward, the clamp is fixed to the table with the head and neck in a neutral or slightly flexed posture, or 15 lbs of traction is applied to the Gardner-Wells tongs. The shoulders are taped down to the table in order to allow for higher x-ray penetration and facilitate intraoperative imaging. Patient’s arms must be conscientiously cushioned at the axilla, elbow, and wrist. The spinous processes are palpated in order to mark the midline skin incision; the spinous processes of C2 and C7 tend to be the most easily identified. Finally, motor evoked potentials (MEPs) and somatosensory evoked potentials (SSEPs) are recorded both at baseline as well as during the procedure, and free-running electromyography (EMG) is used throughout the operation.

Dissection

A standard midline incision is made over the operative cervical levels, dissecting down to the fascia and the spinous processes, which is predominantly an avascular plane. Exposure is continued in a bilateral subperiosteal plane, dissecting the paraspinal muscles and retracting them laterally. During this step, care must also also taken to avoid exposure of the facet joint complex, as this is a motion-preserving procedure and arthrodesis is not performed. Following dissection, spinal levels are confirmed using fluoroscopy or X-ray localization. Cerebellar retractors may be used to maintain visualization after exposure is complete. It should be mentioned that C3–C7 levels are most commonly addressed; more recently, C2, T1 and even C1 can be decompressed using laminoplasty techniques.

Laminoplasty Techniques

Several variations of laminoplasty have been developed over the years. They all are based on the same concept: they widen the spinal canal while preserving the posterior elements to various degrees. The difference lies in where the cuts in the lamina or spinous processes are made and how the canal is kept open. More recent approaches utilize ceramic spacers, titanium miniplates or muscle-sparing techniques that aim to shorten operative time, improve procedure safety, and decrease postoperative muscle atrophy. Nevertheless, no procedure has been definitely shown to be more effective than others in terms of cervical sagittal balance, neurological recovery, or range of motion (ROM).

Creating the hinge is crucial to long-term success in any laminoplasty procedure. Troughs through the lamina are made using a high-speed air drill, typically around 3 mm in diameter. Caution should be taken to avoid excessive thinning of the lamina, or it may fracture or offer no springlike resistance to deformation. To find the proper resistance of the hinge, the complete (bicortical) laminar cut should be performed first. On the trough that will serve as the hinge, the lamina from the outer cortex is thinned through the cancellous bone until the inner cortex is identified. The inner laminar cortex on the hinge trough may be further thinned, as needed, until the laminoplasty segment can be opened with gentle finger pressure. Selective foraminotomies may be performed along with the laminoplasty procedure if there is evidence of radiculopathy on the EMG. ^,