Posterior Cervical Laminaplasty
Cervical stenosis can place pressure on the spinal cord in the neck region. The result of pinching of the spinal cord can be an insidious loss of coordination, loss of balance during walking, and even bowel and bladder incontinence.
If most of the compression is in the back, this condition can be treated with a posterior cervical laminectomy. The objective of this procedure is to remove the lamina (and spinous process) to give the spinal cord more room. The spinal cord is especially sensitive to injury, and once the progression of pinching leads to significant loss of function, this function may not be reversible even with removal of the offending agent(s).
If a posterior laminectomy alone is done, there is a post-operative risk of developing instability that may lead to pain and deformity.
In the image at left, note the resultant curve going the opposite way after the laminectomy, resulting in the spinal cord (blue) being draped over the bone and soft tissue.
To avoid the above problems that can result with lamina removal, instead the lamina can be reconstructed. This procedure is called the laminaplasty.
Laminaplasty - Step 1
The diagram at left shows one way to perform the laminaplasty. A cut is made of the lamina down the middle, then grooves are made at the edges of the lamina that allow the lamina to be hinged open. These cuts are shown in red in the diagram below. The compressed spinal cord is shown in blue. When the lamina is opened in such a manner, it can be held open by using a spacer of bone as shown below. Note the free and expanded spinal cord (in blue).
Laminaplasty - Step 2
The result is a conversion of the area for the spinal cord from a small triangular area to a large rectangular area. This elegant reconstruction allows for the muscles to attach to the new lamina and to provide protection from direct trauma to the spinal cord and protection from the spine falling forward.
In order to reduce the risk of post-operative instability and to avoid a fusion, some surgeons will recommend lifting the lamina on one side and leaving a hinge on the other side.
- The advantage of this technique is that it increases the size of the canal but leaves the posterior tether that helps keep the spine stable.
- The disadvantage is that it may not be as easy to decompress the nerves on both sides as they exit the foramen.
A laminectomy or laminaplasty may not be successful in releasing compression on the spinal cord if the spine is not in lordosis (normal swayback). In such a case, anterior cervical corpectomy may be necessary to treat the spinal cord compression.
As with cervical corpectomy (also done for cervical stenosis with myelopathy) the principal risk is deterioration in neurological functioning after the surgery.
To help manage this risk, the spinal cord function is often monitored during surgery by Somatosensory Evoked Potentials (SSEP’s). SSEP’s generate a small electrical impulse in the arms/legs, measure the corresponding response in the brain, and record the length of time it takes the signal to get to the brain. Any marked slowing in the length of time may indicate compromise to the spinal cord.
Other potential risks include:
- Dural tear (cerebrospinal fluid leak)
< 1% infection rate
- Increased pain
- “collapse” of the hinge
- Instability in the spinal column
- Progressive kyphosis
A dural tear, which occurs 1% - 2% of these surgeries, does not change the result of surgery, but post-operatively the patient may be asked to lay recumbent for one to two days to allow the leak to seal.