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Artificial disc replacement
While hip and knee joint replacement surgery or arthroplasty has grown increasingly common since its advent in the early 1960s with a high degree of patient satisfaction, spine arthroplasty (or artificial disc replacement) has not been a viable option in the United States until recently.
The challenge has been to develop a suitable replacement for the intervertebral discs. The replacement must not only be safe to implant, reliable and long lasting, it also must have the ability to mimic the complex range of movement required of a disc implant. Efforts to find a solution to these challenges have been ongoing for more than 40 years.
Several artificial disc replacements for both the neck (cervical) and back (lumbar) spine are currently being offered to appropriate candidates at select U.S. centers.
Cedars-Sinai was one of the first medical centers on the West Coast involved in the Food and Drug Administration-approved study to implant, evaluate and study two revolutionary artificial disc implants - the Bryan and the Charite® SB-III artificial discs for the neck and the back, respectively. Cedars-Sinai spine surgeons have successfully implanted hundreds of devices for the treatment of degenerative disc disease.
Left: Bryan Cervical Disc. Photo courtesy of Medtronic Sofamor Danek. Right: Charite Lumbar Artificial Disc. Photo courtesy of DePuy. Charite Lumbar Artificial Disc and Bryan Cervical Disc are approved for distribution in the United States by the FDA.
An Alternative to Traditional Spinal Fusion
Age, genetics and everyday wear-and-tear of routine activities eventually can contribute to damage and degeneration of the discs that cushion the bones of the spine (the vertebrae). To treat degenerative disc disease, doctors usually begin with conservative (nonsurgical) medical treatment. When conservative therapy fails, other approaches, possibly including surgery, may be recommended. Currently, the gold standard for surgical treatment of problematic degenerative disc disease is spinal fusion. This procedure attempts to permanently lock two or more spinal vertebrae together so they cannot move except as a single unit. This may alleviate pain in a motion segment.
Spinal fusion, however, has well known potential disadvantages, including:
- Loss of motion and flexibility
- Permanently altered motion characteristics and biomechanics
- Potential for accelerated degeneration of the discs above and below the fused level that can lead to more pain and the need for more surgery
Artificial disc replacement offers a reversible, viable alternative to fusion that possibly avoids the accepted shortcomings of fusion. By inserting an artificial disc instead of performing spinal fusion, there is the possibility of reducing damage to nearby discs and joints. This is because artificial disc replacement allows for motion preservation, near normal distribution of stress along the spine and restoration of pre-degenerative disc height.
How a Disc Is Replaced
Surgeons at Cedars-Sinai were at the forefront of using cervical and lumbar artificial discs. The evolution for hip and knee replacement has taken more than 40 years to reach its current stage of technology in materials, design and technique. Although the idea of an artificial disc is not new, artificial disc replacement technology is more common. The unique biomechanical challenges of artificial disc replacement had presented a challenge of both design and material.
Although revolutionary in material and design, the technique to install an artificial disc (whether in the neck or back) is now common and generally safe. In both traditional disc surgery and artificial disc replacement, the procedure begins by removing the gelatinous disc between the vertebrae.
Bryan® Cervical Artificial Disc
The surgical procedure to implant a Bryan® cervical artificial disc is similar in approach and technique to traditional cervical spine surgery that has been used for more than five decades. A small incision, usually less than an inch long, is made in the skin of the neck just off the midline of the spine. Vital structures like nerves, arteries and the esophagus (the tube that connects the mouth and the stomach) are gently pulled out of the way so the surgeon can have access to the spine.
The disc is removed using a microscope and surgical instruments made for this purpose. Once the disc has been safely removed in its entirety, the empty disc space is prepared by milling or shaping the endplates (bottom of each vertebrae) to incorporate the Bryan cervical artificial disc replacement. The artificial disc is placed while the disc space between the two vertebrae (the bones of the spine) is held open.
Once firmly in place, tension is taken off the vertebral bodies above and below compressing the artificial disc and holding it in place. Both surfaces of the Bryan cervical artificial disc are made of porous beaded titanium metal that helps to incorporate and encourage bony ingrowth for long-term stability. The metal endplates surround a polyurethane core and saline cushion. Care and restrictions following surgery, as well as potential complications, are similar to those that occur with spinal fusion.
Charite® Lumbar Artificial Disc
Charite® lumbar artificial disc replacement is performed by a team of fellowship-trained surgeons who have different areas of expertise. The first step of the surgery is to make a small incision low on the abdomen below the navel. This is done by a special surgeon and is designed to spare the muscles any unneeded damage and safely move away nearby blood vessels and organs. This makes it possible for the spine surgeon to safely work on the appropriate level in the spine. The spine surgeon cleans away and completely removes the damaged disc from the bones of the spine.
Two metal plates are pressed into the bony endplates above and below the space now vacated by the disc. Metal spikes hold these plates in place on the bone. Eventually bone will grow over and around the metal plates. A plastic spacer made of a polyethylene core is put between the plates. The patient's own body weight compresses the spacer after the surgery is complete. The device allows for six degrees of freedom.
Recovery from artificial disc replacement and care afterwards are much like that for other anterior approaches to lumbar spine surgery. In some cases, recovery is faster than for a traditional fusion surgery. There is generally less pain from the procedure and typically fewer complications. The materials used in both artificial disc replacements are similar the materials used in routine hip and knee replacement surgery. The materials are designed not to cause sensitivities once in the body.
As one of the leaders in motion preservation surgery and artificial disc replacement, Cedars-Sinai remains at the forefront in experience and expertise. Cedars-Sinai continually strives to provide safe and effective advances in spine surgery to give patients the greatest benefits and satisfaction possible.
Our exceptionally well trained staff of both orthopedic and neurosurgery fellowship-trained surgeons (as well as other nonsurgical specialists) provides a multidisciplinary approach to help give patients the best possible spine care and treatment.