11.2.2\ Laminectomy

11.2.2.1\ Discussion

Hemilaminectomy or unilateral laminectomy consists of resecting the lamina via dissection on one side of the interspinous ligament. This procedure is mainly performed in order to gain access for foraminotomy or discectomy. The hemilaminectomy defect is readily apparent on CT and MRI, but can be of variable width (Fig. 11.3).

In some instances, when preservation of the interspinous ligament is necessary, after the unilateral hemilaminectomy is performed, the ligamentum flavum is removed bilaterally for bilateral decompression of the neural structures.

Bilateral laminectomy consists of removing the spinous process along with both laminae, thereby “unroofing” the posterior spinal canal. This procedure is commonly performed for spinal canal decompression, particularly related to degenerative disc disease, spinal stenosis, epidural infections, epidural or subdural hematomas, and tumor. Bilateral laminectomy can be performed in conjunction with other procedures such as discectomy, facetectomy, and/or fusion for restoring stability. Both CT and MRI can readily show changes related to laminectomy and are routinely used to assess patients after surgery, even in the presence of hardware (Fig. 11.4). If the dura is opened (durotomy) or resected during the procedure, duraplasty is often performed, in which artificial dural replacement materials are used (Fig. 11.5). Too tight closure of the dura or duraplasty material can lead to compression of the spinal canal contents. This can be evaluated via MRI, in which there is concavity of the dura or duraplasty material (Fig. 11.6). Spinal cord contusions can occur secondary to decompression of severe stenosis. Contusions lead to typically transient and rarely permanent neurological deficits, with severity depending on location, which can be delineated on MRI as T2 ­hyperintense lesions (Fig. 11.7). Spinal cord

infarct can result from disruption of the blood supply­ to the spinal cord and acutely appears as predominantly central high T2 signal with corresponding restricted diffusion on MRI (Fig. 11.8). This is due to hypoperfusion of the anterior spinal artery. Additional complications related to laminectomy are depicted in the “Failed Back Surgery” section.

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b

Fig. 11.3  Hemilaminectomy. Axial (a) and coronal (b) CT image demonstrates an opening in the left lamina (encircled)

Fig. 11.5  Laminectomy and duraplasty. Axial CT image (a) shows hyperattenuating Gore-Tex duraplasty material that lines the posterior spinal canal at laminectomy site

(arrow). The sagittal T2-weighted MRI (b) shows that the duraplasty material has low signal (arrow), similar to normal dura

Fig. 11.6  Tight durotomy closure. The patient experienced worsening radiculopathy after surgery. Sagittal T2-weighted MRI shows compression of the cauda equina nerve roots by the dura (arrow) after recent laminectomy. The patient returned to the operating room for release of the durotomy repair and duroplasty with immediate relief of symptoms

Fig. 11.7  Spinal cord contusion. The patient woke up with a right hemiparesis. Axial T2-weighted MRI shows edema in the right lateral cortical spinal tract after cervical laminectomy and fusion for cervical spine stenosis