|The Artificial Disc Is Not A "New" Disc But A Metal Replacement|
The "Artificial Disc"
What is the artificial disc? How does it work? Many people have heard wondrous stories of this new device and many have fantastic visions of what it looks like or how it works.
The artificial disc was developed in Germany in the 1960's and has been used in Europe for around 15 years. It is not a artificial disc at all but is a stainless steel mobile "fusion". The device is inserted through the abdomen into the disc space once the disc is removed. The operation involves a large (approximately 4 to 5 inch) abdominal incision, moving the abdominal contents and the major blood vessels to gain access to the anterior spine. This is not a minor operation and it usually involves two surgeons. Nonetheless, no spine operation is minor, and recovery appears to be similar to most abdominal or spinal surgeries.
The concept of the artificial disc is simple. One, remove the real disc since it is causing pain, and two, allow mobility so that the remaining discs do not eventually fail as they do with most fusions. The artificial disc does allow this mobility but only has success rates similar to conventional fusions. No good studies have been done on whether the long term disc herniation rates are lower for fusions or artificial discs. Nonetheless, success rates are similar for fusions versus artificial discs in that success rates for U.S. studies reveal around 68% good to excellent1. European studies reveal higher success rates at 79%2. The higher success rates associated with European studies are not unusual but consider the American studies to be more accurate.
Contraindications for the procedure include: infection, spinal stenosis, spondylolisthesis, posterior facet joint disease, significant radiculopathy, osteoporosis and any prior spinal fusion. Thus, artificial discs are probably not amenable to most patients over the age of 50 due to some degree of spinal stenosis.
In this day and age, people want "replacement" parts that will make them "like new". Does the artificial disc give long term success?
That is the big unknown. Artificial joints have been around for years and as time progressed it was found that they were only temporary replacements. They were temporary because they eventually loosened and the artificial joints had to be replaced with new artificial joints due to pain and dysfunction. This might sound easy, but in reality it is not. To replace an artificial joint is very difficult and mortality and morbidity are high. The surgery is twice as long and involves much greater blood loss and complications. The question is whether this will happen with the artificial disc. That is unknown, but given that it happens with every other replacement "joint" product, one can only imagine that it will occur with the artificial disc. This concerns us because it may be 10 years after these steel devices are inserted that they loosen up and thus it hasn't been discovered yet. This could lead to a large group of people with back instability and pain due to bad artificial discs which cannot be easily replaced. Thus, probably the best solution is to resolve back problems without any artificial material being utilized.
Another option is a gel-filled sack by Raymedica that fits within the disc itself and thus only the inside of the disc is removed. This gel filled prosthesis can be inserted through a conventional discectomy or even possibly endoscopically. This offers a soft spacer that retains disc height without a major surgery involving an artificial disc. It appears promising but there are several questions about this device. What prevents the device from moving or even herniating? How long does this gel product or sack actually last before the extreme forces of the spine destroy the device? With this device there are no good studies to date an it is not yet FDA approved in the United States. Movement of the device is a major concern since any movement may compress the spinal cord and cause paralysis or nerve injury.
What are our alternatives to these therapies? There are several options available. For disc related pain, we still believe the best starting treatment for degenerative disc disease is to perform an endoscopic discectomy since this is relatively benign and offers a 60 to 70% success rate without the insertion of any foreign material. Percutaneous discectomies can also be utilized in some cases. For some cases, we offer intradiscal injections of various substances that can help heal the disc. Thus, there are several non-hardware treatments for back pain such as bio-absorbable fusions which temporarily fuse the spine.
Nonetheless, all spinal surgery has similar results. Success rates of around 70% are considered the norm for most spine related surgery. Keep this in mind when deciding what type of surgery to utilize. That is why we recommend the least invasive approach for any spine related problem.
1. A 1997 independent study, conducted by the Texas Back Institute and the Institutes for Spine and Biomedical Research, followed 67 patients who underwent intervertebral disc replacement with the SB Charité III device
2. A 1997 study conducted in France by Lemaire et al reviewed 105 cases undergoing SB Charité III prosthetic disc replacement.
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