22 Aug 2011
anterior cervical discectomy and fusion
Anterior Cervical Discectomy and Fusion (abbreviated as ACDF) is a surgical procedure for alleviating the severe pain due to nerve root compression caused by a cervical disk herniations. ACDF surgery has been routinely performed since the 1950’s and it is a very reliable procedure. It works best in patients who have an identifiable cause of nerve root compression that has not responded to non-operative care consisting of physical therapy, medical management, and possibly a steroid injection.
First the anatomy. In this first set of watercolors we see a small segment of the cervical spine. The white strip in the middle is the spinal cord and the surrounding fluid called the CSF. The back of the intervertebral disk is flush with the bone above and below, and there is no pressure on the spinal cord. In the second axial image the spinal cord looks like a white kidney bean in the center of the spinal canal. The cord is symmetric and there is no pressure on any part of the cord. In the third image we see a disk herniation. Some of the shock-absorbing viscous protein in the center of the disk has been squeezed into the spinal canal and it is pressing on the spinal cord. The fourth axial image demonstrates how the cord is often deformed asymmetrically. In this case, the disk herniation is pushing on the left side of the spinal cord and the patient is likely to have left sided nerve root pain.
Now the MRI scan. This is a sequence of pictures of someone with a C6/7 disk herniation on the left side. The first image is mid-sagittal MRI scan. This image is a “slice” from the center of the neck and we can clearly see all of the relevant anatomic structures. If we move over to the left side by 5 mm, we can see the prominent disk herniation at C6/7. The third image is annotated so that the disk herniation and the cervical spinal cord are more visible. Please click on each image to enlarge the size of the picture.
Cross-sectional anatomy — the axial slice. The beauty of MRI scans is that we can use them to look at the human body in any plane. The three images above are called the sagittal slices, but often the axial images are the key to the diagnosis. The first image in this sequence is called the reference image. In this image there is a blue line parallel to the C6/7 disk space. This blue line is the reference plane for images #2 and #3. These two images are a “slice” through the center of the neck and they are oriented as if we were at the feet of the patient looking up towards the head. The anatomic structures on our right are on the patient’s left. In image #3 I have annotated the disk herniation in order to demonstrate where the nerve root compression is occurring. In the fourth image, I present an axial image from the same patient, just above the level of the herniation, so that you can see what the normal dimensions of the spinal canal look like.
Not all cervical disk herniations need to be treated surgically. Lots of research has shown that many people will improve over time and their symptoms will spontaneously resolve. Patient’s who are good candidates for an ACDF typically meet the following criteria:
- Their arm pain is worse than their neck pain
- Their pain has been present for at least 6 to 8 weeks without any trend towards gradual improvement
- The disk herniation is large, a free or extruded fragment, and appears to be causing significant nerve root compression
- They have tried a course of physical therapy, NSAIDs, and possibly a selective nerve root block and each time the pain has come back.
Anterior Cervical Disectomy and Fusion, for the most part, is now an outpatient operation. I perform this operation at Monterey Peninsula Surgery Center and the majority of patients go home the same day.
In my hands, my patients do very well with an anterior cervical discectomy and fusion with a allograft and a locking plate applied to the anterior aspect of the cervical spine. They tend to have immediate resolution of their neck and arm pain, their weakness resolves quickly, and they return to normal activities within 6 weeks. Using a microscopic surgical technique I am able to visualize and remove the herniated portion of the disk and with an allograft bone I am able to restore normal disk height without using bone from the hip or the pelvis. For example, here are 2 X-rays from a C5/6 ACDF performed as an outpatient for someone with severe arm pain and a large herniated disk
There are a few side effects after an ACDF…
Will I lose normal range of motion?
One of the most common questions that I get asked is whether the range of motion of the neck will be affected by the operation. Most patients are concerned about the loss of normal range of motion of the cervical spine if they have a fusion, but this rarely seems to be the case. In the first place, about 90% of lateral rotation — twisting the head from sided to side — occurs at the level of C1/C2, and this area is never included in a standard ACDF. Secondly, by the time someone needs an ACDF, usually their spine has developed some arthritis and the range of motion of the disks and spinal segments that need to be fused is already lost as part of the degenerative process. For example, here are a series of pictures from an active duty US serviceman who needed a multi-level cervical fusion for symptoms of cervical myelopathy associated with kyphosis. The pre-operative xrays and MRI scans are shown, and the post-operative xray shows excellent correction of his cervical kyphosis. Clinical pictures taken 3 years after the operation demonstrate that he has a nearly normal range of motion of the cervical spine.
The surgical incision — will it be noticeable?
The surgical incision for an anterior cervical discectomy and fusion runs parallel to the normal lines of the skin in the neck, which are called Langer’s Lines. The skin in this area is typically relatively moveable and it does not form significant scars. For example, here is the incision of a patient who has a 2 level anterior cervical discectomy and fusion about 2 or 3 months before this picture was taken. In this image, the scar is barely noticeable, and with time ti will continue to fade even further.
According to the literature, temporary or persistent dysphagia (the medical term for difficulty swallowing) can occur in up to 18% of post-operative ACDF patients, but this is much more common in multi-level operations. Typically, a patient will notice that it feels like something is stuck in their throat, or they can’t swallow pills or meat easily. If a patient develops difficulty swallowing, the symptoms will usually resolve over time, and while most people return to normal within a few days, complete improvement may take many months. Dyspagia appears to be secondary to local response to traction and manipulation of the soft tissues of the neck since this complication occurred just as commonly when the procedure was performed in the past without the use of a locking plate applied to the front of the cervical spine.