39: Lumbar Internal Laminectomy

Published on 21/04/2015 by admin

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Last modified 21/04/2015

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Procedure 39 Lumbar Internal Laminectomy

Sunil Jeswani, Eli M. Baron, Neel Anand

Surgical Anatomy

The pars interarticularis should be identified, because violation of this structure may predispose to instability.

The location of the pedicle should be established early in the procedure. Localization is based on the pedicle of the inferior level being decompressed (e.g., the L5 pedicle in an L4-5 decompression.

Certain anatomic configurations of the lumbar spine facilitate easier decompression by this approach. If the transverse diameter of the lumbar spinal canal is congenitally narrowed, then the position of the posterior osseous roof of the spinal canal will be relatively vertical. This configuration will allow easy achievement of an optimal working angle of the microscope, which will facilitate contralateral decompression of bone and ligamentum flavum. Conversely, if the anteroposterior diameter of the spinal canal is congenitally narrowed, then the position of the osseous canal roof will be relatively horizontal. In this case, achieving an optimal working angle for the visualization of the contralateral structures will be more difficult.

Positioning

The patient is placed in the prone position, typically on a Wilson frame.

The lumbar spine is gently flexed to increase the width of the interlaminar space.

Positioning Pearls

• Alternatively the patient may be placed on a Jackson table. A decompression performed with the spine in extension may achieve a more thorough decompression as any compression is removed in a position more accurately simulating the neutral standing position.

Portals/Exposures

This technique is theoretically advantageous to bilateral microdecompression as well as standard laminectomy, because unilateral exposure may result in reduction of risk for disruption of spinal stability and less postoperative pain.

Because only the ipsilateral paraspinal musculature is dissected unilaterally, the contralateral paraspinal musculature remains intact, resulting in the preservation of the contralateral bone/muscle complex. This conceivably results in added postoperative stability compared with a bilateral approach.

A study by Adams and associates suggested that the muscular attachments to the posterior arch and the insertions of the muscular slips on the facet capsule serve to brace the facets, improving their ability to resist displacement.

Because dissection and retraction of the multifidus muscle is carried out unilaterally with this technique, less postoperative dead space results.

Postoperative dead space can have significant consequences. Increased volume of the dead space may result in increased blood loss. Moreover, increased dead space provides an ideal bacterial culture medium, with the potential for increasing the chance of a postoperative infection.

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