Each year in the U.S., more than 200,000 spinal fusion surgeries are performed to relieve excruciating pain caused by damaged discs in the low back and neck areas. Patients researching regional centers that are qualified to implant artificial discs are learning that there is great variation among spine surgeons in the type of discs used, and IF the doctor recommends any artificial disc surgery for a particular diagnosis.
Perhaps the most anticipated advance in spine surgery over the past 20 years was the arrival of the artificial disc. The first artificial disc in the United States received formal approval by the Food and Drug Administration (FDA) for widespread use in the United States on October 26, 2004. While this technology is somewhat new to the U.S., artificial discs have been in use in Europe for more than 15 years.
It is important to remember that this technology is still evolving with new implants continually in development. Your spine surgeon is the best resource to discuss if it is appropriate for you, and what model of artificial disc is best suited for your case.
The number and type of artificial discs available in the United States is expected to grow as new models emerge on the scene and surgeons become trained in their use. Each disc is designed for use either in the low back (lumbar area) or neck (cervical area).
In addition, other artificial disc models are available on a limited basis through “clinical trials” where a patient agrees to be part of clinical study designed to measure the success of a new disc model, which will be part of an FDA study. Patients who participate in a clinical trial can gain access to the most current technology, even though it has yet to gain FDA approval for use in the U.S.
The artificial disc concept is intended to be an alternative for spinal fusion surgery. Each year in the U.S., more than 200,000 spinal fusion surgeries are performed to relieve excruciating pain caused by damaged discs in the low back and neck areas.
During a fusion procedure, the damaged disc is typically replaced with bone from a patient’s hip or from a bone bank. Fusion surgery causes two vertebrae to become locked in place, putting additional stress on discs above and below the fusion site, which restricts movement and can lead to further disc herniation with the discs above and below the degenerated disc. An artificial disc replacement is intended to duplicate the function level of a normal, healthy disc and retain motion in the spine.
When a natural disc herniates or becomes badly degenerated, it loses its shock-absorbing ability, which can narrow the space between vertebrae. In fusion surgery, the damaged disc isn’t repaired but rather is removed and replaced with bone that restores the space between the vertebrae. However, this bone locks the vertebrae into place, which can then damage other discs above and below.
A common aspect of all artificial discs is that they are designed to retain the natural movement in the spine by duplicating the rotational function of the discs Mother Nature gave us at birth. Most artificial disc designs have plates that attach to the vertebrae and a rotational component that fits between these fixation plates. These components are typically designed to withstand stress and rotational forces over long periods of time. Still, like any manmade material, they can be affected by wear and tear.
Some of the main benefits of the artificial disc parallel that of knee replacement and hip replacement. This can include the following benefits:
Because of the weight of the body and the rotational stress that the trunk places on discs in the low back (lumbar) area, more stress is placed on artificial discs in the lumbar area than in the neck (cervical) area, which only supports the weight of the head.
A second issue relates to the ease of the artificial disc surgery and any necessary revision surgery to replace a worn out artificial disc. Because the surgeon must access the front of the spine, an incision is made in the abdomen for lumbar discs and in the front of the neck for cervical discs. Generally speaking, many spine surgeons believe access to the cervical discs can be easier than the lumbar discs.
When treating knee and hip replacement patients, orthopedic surgeons try to postpone the implantation of an artificial joint until a patient is at least 50 years old so that they do not outlive their artificial joint, which typically lasts anywhere from 15 to 20 years. Revision surgery, which may be necessary to replace a worn-out artificial joint, can be complex.
This is also a concern with the artificial disc. Unlike knee and hip replacement patients who are typically in their 50s or 60s, many patients can benefit from artificial disc technology at a much younger age — in their 20s or 30s. Therefore, the implantation of an artificial disc in younger patients can raise a surgeon’s concern about the potential life span of the artificial disc in the spine and the need for revision surgery to replace a worn-out artificial disc, which can be complex.
The artificial disc is projected to have a dramatic impact on the field of spine, just as the introduction of the artificial joint had for those with damaged knee or hip joints. Before the introduction of the artificial knee or artificial hip, these joints were fused. Fusion of a knee or hip today would be unthinkable, thanks to artificial knees and hips. Finally, this new technology is being brought to the field of spine.
Synthes offers the Prodisc-L (lumbar) and Prodisc-C (cervical), both are FDA approved for use in the United States. The Prodisc-L design is based on a ball and socket principle and is composed of three implant components, two metal endplates and a plastic inlay. The Prodisc-L implant materials are typically used in total joint replacement and have been used for at least two decades in spinal arthroplasty procedures. Patients suffering from symptomatic cervical disc disease at one level from C3 to C7 may benefit from ProDisc-C total disc replacement. The purpose of ProDisc-C artificial disc surgery is to remove the diseased disc, restore normal disc height and provide potential for motion at the disturbed segment.
Choice of the disc involves the expertise of the experienced spine surgeon to match the best alternative to the patient. Dr. John Regan is a pioneer, developing a number of new approaches that reduce patient recovery time and improve outcomes, and offering the newest treatment in spine surgery.
FDA approval typically comes after extensive clinical studies that compare a group of patients who requested an artificial disc, with a control group of patients with similar problems who received traditional fusion surgery. Synthes' study, for example, included about 500 patients, of which about half received the new artificial disc and half had traditional fusion surgery.
In some studies, the percent of patients needing a second surgery was higher with traditional fusion than with artificial disc, implying that the new disc may have lower complications than fusion surgery.
The arrival of the artificial disc is tremendous news because of the widespread incidence of degenerative disc disease. A natural by-product of aging occurs through the loss of resiliency in spinal discs and a greater tendency to herniate, especially when placed under a heavy load, like when we lift objects.
In the U.S., recent studies report that 56% of Americans are overweight, and 25% are obese, which only puts more stress on aging discs. Also some unfortunate people have a family history of degenerative disc disease, which increases their risk of developing it.
In any event, expectations of aging baby boomers — those born between 1946 and 1964 now in their fifties and sixties — are for an active rather than sedentary retirement.
All of these trends are creating tremendous demand for a technological advance that promises to restore motion to damaged and aging backs and necks.
Prodisc-C © by Synthes, www.snythes.com
A common aspect of all artificial discs is that they are designed to retain the natural movement in the spine by duplicating the shock-absorbing and rotational function of the discs Mother Nature gave us at birth.
Most artificial disc designs have plates that attach to the vertebrae and a rotational component that fits between these fixation plates. These components are typically designed to withstand stress and rotational forces over long periods of time. Still, like any man made material, they can be affected by wear and tear.
Current considerations include tiny shavings that may be produced by the component pieces as they wear on each other after implantation. Other considerations relate to surgeons perception of how easy a particular disc is to implant in the spine — as well as how easy it is to REMOVE. Some discs, for example, have characteristics that enable them to be easily tapped into place which then lock them in place. The problem is if that disc needs to be taken out, it’s extremely difficult.
Prodisc-L © by Synthes, www.synthes.com
Consequently, manufacturers of artificial discs aim to design discs that are not only resistant to wearing out, but also easy to install and remove if revision surgery is needed. Doing all the above has proven to be a tall order.
Surgeons typically attend special courses conducted by the specific manufacturers of the various discs. The training is specific to the brand of artificial disc, because installation procedures and the instruments used vary slightly from disc to disc. Dr. Regan's private practice, for example, was one of the first centers trained and authorized by the manufacturer of its disc to perform implant surgery.
Not surprisingly, some health insurance companies are choosing to sit on the sidelines by refusing to pay for any artificial disc surgery, just like they refuse to pay for new drugs. Many health care providers see this only as just another tactic for certain insurance company to save expenses by restricting access to new advances for as long as they can argue the case.
Interestingly, however, some employers and workers compensation carriers in several states are endorsing artificial disc surgery and more than willing to pay for it. Why? Because historically fusion surgery has had such abysmal return to work rates among those who injure their backs on the job. From the employer’s perspective, those patients who have had fusion surgery are a lost cause. In their mind, artificial disc surgery is the best bet for getting the person back to the workplace.
During a fusion procedure, the damaged disc is typically replaced with bone from a patient’s hip or from a bone bank, and locked in place with metal plates and screws. Fusion surgery locks two vertebrae in place, putting additional stress on discs above and below the fusion site, which restricts movement and can cause other discs to herniate.
An artificial disc replacement, however, is designed to duplicate the function level of a normal, healthy disc and retain motion in the spine. Some experts estimate that over the next 10 years, more than half of patients who would otherwise receive a fusion will receive an artificial disc instead. Educated consumers nationwide are expected to migrate to regional spine centers for access to this latest technological advance in spine care.
Most artificial disc designs have plates that attach to the vertebrae and a rotational component that fits between these fixation plates. These components are typically designed to withstand stress and rotational forces over long periods of time. Still, like any man-made material, they can be affected by wear and tear, and damage from excessive loads.
Because of the weight of the body and the rotational stress that the trunk places on discs in the lumbar (low back) area, more stress is placed on artificial discs in the lumbar area vs. the cervical (neck) area, which only supports the weight of the head, explains Dr. John Regan, spine surgeon at Dr. Regan's private practice. “I favor artificial disc for cervical use currently, because wear and tear on an artificial disc in the neck area is much less than a lumbar artificial disc. Secondly, the neck area is more accessible in surgery than the front of the lumbar spine. So even if a revision surgery were required, it would be easier to do on the neck than lumbar area. All of this underscores how important it is for the patient to be well informed. You need to ask how proficient is the surgeon at artificial disc surgery. How many have they done? Are they fellowship-trained?”
When performing artificial disc replacement procedures for degenerative disc disease, Dr. Regan inserts a small prosthetic (artificial) disc comprising a polyethylene core that slides between two metal end plates. The end plates are attached to the vertebral body with anchoring teeth built along the rim of the end plates. The prosthetic discs replace the injured discs, helping to relieve chronic back pain. The polyethylene core allows movement of the spine, unlike fusions which prevent normal movement. The disc is made of the same material used in artificial hips and knees.
In summary, some spine surgeons may be cautious about the use of artificial discs for the following reasons:
Generally, the technology is very promising. Your spine surgeon can provide information if your problem can be addressed with this technology.
Due to the fact that the surgeon must access the front of the spine, an incision is made in the abdomen for lumbar discs and in the front of the neck for cervical discs. Typically, access to the cervical discs can be easier than the lumbar discs.
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