Anterior Cervical Discectomy and Fusion
A cervical discectomy may be performed when a herniated disc pinches a nerve in the neck and non-surgical treatment has not resulted in sufficient relief. The primary symptoms of a cervical disc herniation are usually numbness, weakness and/or pain in the arm, and/or neck pain. The goal of the cervical discectomy is to remove the disc that is pinching the nerve, eliminating the cause of the pain and numbness.
The surgical approach is through the front of the neck which provides exposure from the second cervical vertebrae to where the cervical spine meets the thoracic spine.
The discectomy is commonly done in conjunction with an anterior cervical fusion, which involves placing bone graft/intervertebral spacer into the disc space between the vertebrae. The bone graft helps the vertebrae above and below it grow into a single unit. This ‘fusion’ prevents local deformity (kyphosis), and helps prevent collapse of the disc space, thereby providing adequate room for the nerve roots and spinal cord.
Most cervical fusions are performed between the C5-C6 levels or C6-C7 levels. Fusion surgeries are most effective when they involve only one vertebral segment. Since two vertebral segments need to be fused to stop the motion, a C5-C6 fusion would be a one level fusion. Multilevel fusion may be necessary in cases of severe instability/or multilevel spinal stenosis but most cases require only a one or two level fusion.
Indications for anterior cervical discectomy
Surgery is generally considered for patients who have not responded to six to twelve weeks of non-surgical treatment (such as medications, physical therapy), or acutely in those patients with severe arm pain. Generally, if the pain starts to subside during this period of time, continued non-surgical treatment is advisable. Surgery is more for the arm pain than for the numbness/weakness. Pain is a result of pinching or the nerve, and if the pain resolves, one can assume that the nerve is in a good healing position and will heal with time, leading to partial or complete resolution of the numbness/weakness.
Overall, reports reveal a significant improvement of symptoms for most patients who undergo an anterior cervical decompression and fusion. For example, 95-98% of patients will experience significant relief of their arm pain. Relief of neck pain is not quite as reliable. The limited amount of muscle dissection helps limit postoperative pain. There is little chance of the disc herniation recurring following this surgery because most of the disc is removed during the operation.
The surgery is much more reliable for alleviating arm pain, or arm pain combined with other symptoms, than for neck pain alone (such as neck pain from degenerative disc disease).
An anterior cervical discectomy is a relatively common surgery that follows an established process to remove the affected disc.
- The skin incision is about one inch, horizontal and can be made on the left or right hand side of the front of the neck to establish a path to the disc.
- The disc causing the pain is then identified by inserting a needle into the disc space and doing an x-ray to confirm that the surgeon is at the correct level of the spine.
- The disc is removed by first cutting the outer annulus fibrosis (fibrous ring around the disc) then removing the nucleus pulposus (soft inner core of the disc).
- The nerve root is then decompressed directly by removing any disc material or bone spurs.
- Using the same incision, bone graft or an intervertebral spacer is then inserted into the space between the vertebral bodies where the disc used to be. Over the course of several months (3 to 18 months), the patient’s own bone will grow into and around the bone graft/intervertebral body spacer and incorporate the graft as its own. This process creates one continuous bone surface between the two vertebrae.
- An anterior cervical plate is used in many cases for further stabilization. It is a small, thin plate that is applied to the front of the vertebral bodies above and below the graft. Two screws hold the plate onto each of the vertebral bodies.
There are several bone graft options for the fusion:
- Autograft bone. The bone is taken from the patient’s hip, but the extra incision required can cause postoperative pain and increase surgical complications.
- Allograft bone. No additional incision is required, but fusions are generally slower to set-up than with autograft bone. They eventually yield success rates equivalent to autograft bone in one level fusions. To enhance the healing rate – especially if more than one level is fused – allograft may be combined with anterior plating of the spine, which yields a fusion rate equivalent to autograft bone.
- Bone graft substitutes and support instrumentation. Although synthetic bone products are not FDA-approved specifically for an anterior cervical interbody fusion, there are products that mimic the structure of bone and are especially effective when combined with bone marrow aspirate taken through a needle from the iliac crest.
Potential risks and complications
Anterior cervical discectomies can result in the following potential complications:
- Temporary difficulty in swallowing (common but usually not severe)
- Temporary hoarseness (1%)
- Bleeding or infection (very rare)
- Damage to the trachea/esophagus (extremely rare)
- Continued pain
- Nerve root damage (about 1 in 10,000 chance)
- Damage to the spinal cord (about 1 in 10,000 chance)
Anterior cervical fusions can result in continued pain if the fusion does not fuse completely, requiring surgery to re-fuse the segment. Other complications include:
- Bone graft dislodgment or extrusion if instrumentation is not used (1 – 2%)
- A slight risk or infection if allograft (cadaver) bone is used for the fusion
After fusion surgery, it can take three to six months (and sometimes up to 18 months) for the fusion to successfully set up. During the first weeks to months, patients’ activities may be restricted so that the bone graft will not be put at risk. After initial maturity of the fusion is clear, restrictions will be relaxed and permanent restrictions are generally not needed or advisable, since the bone graft will get stronger with some level of stress. The use of cervical braces after surgery is variable and is dependent mostly on the recommendations of the particular surgeon. After initial maturity of the fusion is clear, restrictions will be relaxed and permanent restrictions are generally not needed or advisable, since the bone graft will get stronger with some level of stress. The use of cervical braces after surgery is variable and is dependent mostly on the recommendations of the particular surgeon.
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