The most common of all spine procedures is decompression. It is usually done to decompress the spinal cord within the central canal and its root through its foraminal exit. The lamina or the roof of the spinal canal is the most accessible route through the canal. Different laminectomy procedures can be done to decompress the cord through this procedure.
Depending on the extent of canal compression brought about by trauma, congenital defects, infection, tumor or ageing, only half or whole of the lamina can be removed in order to achieve the goal of decompression. Removing the whole lamina however creates iatrogenic instability because it involves the destruction of the facet joints.
Laminectomy procedures involve retracting the muscles of the back in order to gain access to the lamina. It should be noted that the lamina serves as important structures for the attachment of the back muscles. In order to preserve the integrity of the lamina, surgeons would usually employ just creating small windows in the lamina called laminotomy. Laminotomy preserves the lamina and prevents the usual post-operative instability brought about by laminectomy.
When the pathology of compression comes from the damage to the vertebral body due to damage brought about by trauma, infection or tumor, laminectomy procedures cannot provide the necessary decompression. An anterior approach to the spine is usually needed to enable vertebrectomy procedures. Vertebrectomy involves removing the vertebral body partially or as a whole in order to decompress the canal and clean it. This however leaves a large defect that will need reconstruction.
Depending on the region of the spine that is affected, vertebrectomy procedures entail entering the chest cavity or the abdominal cavity. Vertebrectomy is technically more demanding and less straightforward than laminectomy procedures. It will also always involve a stabilization procedure to reconstruct the big defect left by removing the vertebra. The defect is much larger considering that the discs above and below has to be removed as well to provide a solid platform for the reconstruction procedure.
Unlike laminectomy procedures, the stability of the spinal column is seldom compromised. Vertebrectomy though it produces the desired decompression will always leave the spine very unstable. Thus stabilization techniques are carried out to reconstruct the anterior column of the spine. Sometimes anterior reconstruction has to be augmented with posterior stabilization. As shown below a truamatic vertebral compression-burst fracture will necessitate vertebrectomy to remove retropulsed bone fragments in the canal. After vertebrectomy and removal of discs above and below the injured vertebra, bone grafts were applied to stabilize the instablity of the spine.
After a vertbrectomy an anterior reconstruction can be done by inserting a bone graft into the defect. This is aimed to provide stability to the segment by way of fusing the vertebrae above and below the defect. Stand alone grafts can be used but in instances that all columns of the spine are unstable posterior instrumentation is also applied to augment the anterior reconstruction.
In most instances, a well planned laminectomy or laminotomy decompress the central canal adequately. It is important to note however that the foraminae on both sides can be the site of stenosis for the nerve roots. One can adequately perform a "foraminotomy" through the opening we have already created thru the lamina. By using special bone punch instruments we can enlarge the foraminal openings that have been constricted by osteophytes and encroaching ligamentum flavum. In instances where we need to perform a "foraminectomy" all we need to do is to do a wide laminectomy and remove the facet joints. Once the facet joints have been removed we have essentially performed a foraminectomy. Latter however induces iatrogenic instability and thus will necessitate stabilization procedures as well.
Laminectomy and laminotomy are usual access corridors for "discectomy" procedures. In cases where the disc herniates and causes severe symptoms because of compression to the nerve roots it has to be removed already. Discectomy entails removing the disc irritating the nerve root. Partial discectomy often solves the problem. Total discectomy is hard to perform owing to the intricate construct and anatomy of the disc.
In the cervical spine, laminectomy procedures significantly weakens the architecture and integrity of the spine and leads to instability and late onset deformity after a period of time. The lamina is usually preserved to prevent this late onset instability and deformity. "Laminoplasty" is a decompressive procedure where the lamina is not totally removed but simply flipped open to one side with a thinned out bone hinge on the other side. Though laminectomy provides a wider and bigger decompression, laminoplasty provides an acceptable degree of decompression without creating instability.