The human spine is made up of 33 “motion segments”, divided into the cervical, thoracic, lumbar and sacral areas.
The cervical and lumbar regions of the spine are mobile, allowing for the flexibility of the neck and the lower back, and activities such as bending, turning, and twisting. Traditional surgical approaches to the cervical and lumbar spine often involve a fusion operation, where the motion of one or more of the motion segments is eliminated.
This, in turn, can render the spine stiff, and, in the long run, can result in degeneration of the adjacent discs, causing new compression on the spinal cord or the nerve roots. This process is referred to as “adjacent segment disease” and may require additional surgery.
Motion-preserving surgery refers generally to surgical options for the cervical and lumbar spine where a traditional fusion is avoided, and the natural motion of the spine is preserved.
In the cervical spine, motion-preserving approaches include cervical disc replacements and posterior cervical laminoplasty.
Cervical disc replacement
One of the traditional, and widely accepted, techniques in addressing cervical disc degeneration and stenosis is an anterior cervical discectomy and fusion (ACDF) operation. In this operation, the degenerative disc that is causing spinal cord or nerve root compression is removed, and a fusion is performed. A fusion involves placing bone graft and/or implants where the disc originally was in order to provide stability to the area. A fusion operation renders the segment stiff and reduces the spinal motion. One of the observed consequences of a cervical fusion operation is that, over time, the adjacent discs can break down, causing new compression on the spinal cord or the nerve roots. This process is referred to as “adjacent segment disease” and may require additional surgery.
A disc replacement operation, on the other hand, can effectively remove the degenerative disc that is causing spinal cord or nerve root compression, while preserving the motion of the spinal segment. This, in turn, eliminates additional demand from the other discs in the cervical spine, and is believed to reduce the risk of future disc breakdown at the other healthy discs. Also, a cervical disc replacement eliminates the potential issues associated with the need for a bone graft for spinal fusion, and allows for early postoperative neck motion.
It is important to remember that a disc replacement is a motion-preservation procedure and not a motion-creation procedure. This means that a severely arthritic segment that did not move before disc replacement is not likely to move after disc replacement. In fact, for patients with severe facet arthritis and neck pain in addition to arm pain, an anterior cervical discectomy and fusion might be a more suitable surgical option.
Most cervical disc replacements can be performed on an outpatient basis, with patients returning home the same day or after a one night stay in the hospital.
Posterior cervical laminoplasty
A laminoplasty is a surgical procedure that enlarges the spinal canal. For patients with severe spinal cord compression at multiple levels, who also have normal neck alignment and minimal neck pain, a laminoplasty offers a motion-sparing technique for spinal cord decompression. Similar to the lumbar spine, the “lamina” creates a rigid “roof” over the spinal canal.
During a laminoplasty, a hinge is created on one side of the lamina, and the other side is wedged open with the aid of a small metallic plate. This creates more room for the spinal cord without necessitating a fusion. Most patients will notice immediate relief of arm pain, and some improvement in hand numbness. A one or two night hospital stay is usually needed prior to going home.
It is important to work on strengthening of the muscles of the back of the neck after a laminoplasty, and isometric cervical extensor strengthening is begun as soon as tolerated.