Artificial Cervical Disc Replacement: ACDR
An artificial disc replacement in the neck replaces a diseased or damaged disc with a specialized implant that tries to preserve motion in the neck. This procedure is called an Artificial Cervical Disc Replacement, or ACDR. Discectomy refers to the fact that the diseased disc must be taken out first before it can be replaced. This procedure is also commonly referred to as a Cervical Arthroplasty procedure as it replaces a joint.
The spine is composed of individual bones called vertebrae. There are seven cervical vertebrae. They are stacked one on top of another and are separated by discs, which act as an elastic cushions or shock absorbers. The first two vertebrae are an exception and do not have discs. Discs have a soft center, the nucleus, surrounded by a tough outer ring, the annulus. Discs allow motion between the vertebrae. The interbody space is the disc space that is located between the vertebral body bones. Each vertebral segment creates a bony circle, called the spinal canal that protects the spinal cord and spinal nerves. The spinal cord, which is the nerve center of the body, connects the brain to the rest of the body. The spinal cord and nerves travel from the cervical spine down to the lowest point of your spine, the sacrum. Spinal nerves exit the spinal canal between the vertebrae at each level. Two nerves exit each level, one on the left and one on the right. These nerves exit through openings called foramen. The discs, bony structures, ligaments and strong muscles all work together to stabilize the spine.
Artificial Cervical Disc Replacement cannot treat spinal instability. It may be performed to treat the following conditions:
- Degenerative disc disease
- Spinal Stenosis
- Disc Herniation
This surgery is done under general anesthesia, meaning the patient goes to sleep. During the surgery the patient lies face up on a special surgical bed. The procedure is performed through a small incision on the front of the neck to gain access to the spine, usually in the neck’s natural crease. The trachea (windpipe), esophagus (stomach tube), and blood vessels lie in front of the spine and are carefully moved aside. This can cause some neck swelling after the surgery.
Once the surgeon safely creates a window to see the spine, the damaged disc is removed with surgical tools. This part of the surgery is called a discectomy. The surfaces of the vertebral bodies are prepared to accept the implant. The bones are slightly spread apart to make more room for the disc replacement. This realigns proper curvature and enlarges the openings to relieve pressure off any pinched nerves. The artificial disc is inserted into the space between the vertebrae and carefully secured into place.
Any spine surgery has surgical risks involved. You need to discuss these with your surgeon at your pre-operative appointment. Read about General Complications from Spine Surgery.
There are differences to a disc replacement compared to a fusion however both procedures are very effective and successful treatments. Both are long term and permanent solutions to treating disc levels. The determination for either surgery can be dependent on the patient’s disease pathology.
A disc replacement is designed to preserve spinal motion and keep the cervical spine properly aligned. A fusion surgery also keeps the cervical spine properly aligned, but any fusion decreases motion at that level. The first two vertebrae in the neck, C1-C2, contribute 60% of your head’s rotation. Approximately 50% of neck bending occurs between the occiput, or skull, and C1 vertebra. Each vertebra after that contributes approximately 7% of forward and backward bending and rotation. Many people with severe pain and spasms from neck problems have very limited motion. This motion will improve after surgery since most of the restriction is not structural, but muscular. Thus, even though a fusion may remove some mobility many people move more after surgery than before because they have less pain and spasms. Because a disc replacement retains motion, the replacement experience stresses. At this point, research does not show the lifespan of an implant; this may need to be replaced in the future by a fusion procedure.
A disc replacement is thought to reduce mechanical stress on levels of the spine above and below the replacement when compared to a fusion. Since degenerative disc disease stems mostly from genetic causes, people with spinal problems are generally more likely to develop more spinal problems in the future. There is debate as to whether a one level fusion surgery increases stress on the discs above and below causing accelerated degeneration. One argument is that fusion of one level is felt to create greater stress on the remaining “movable” joints leading to early failure. Another argument is that those discs are simply predisposed to degeneration. No study to date has proven that a fusion surgery accelerates this process. Regardless, preserving motion in the spine is an ideal outcome.