Artificial Discs and Degenerative Disc Disease
An Interview with Kevin Foley, M.D.
SpineUniverse: Dr. Foley, there is currently much interest in artificial discs. Before we ask you about them, please give us some background. For example, for what condition might an artificial disc be used?
Dr. Foley: The condition for which artificial discs are currently being studied is Degenerative Disc Disease (DDD). This is very common affecting 40-50% of people over the age of 40 and becomes increasingly common as we age. It is a kind of wear and tear disease similar to osteoarthritis. Although it can occur at any spinal level, it is most common in the lumbar spine (low back). DDD can cause the discs to flatten losing their normal height. This height is important as it separates the disc above from the one below. When disc height is lost, the nerve pathways may become narrowed and cause nerve impingement, inflammation, and pain.
Patients have reported their symptoms as being as mild occasional backaches to chronic low back pain that is severe enough to limit their activities at work and play. The pain is typically mechanical in nature. This means the pain increases as more stress or load is placed on the low back. Bending, lifting, and twisting are the types of movement that may exacerbate DDD.
SpineUniverse: How do I know if I have DDD?
Dr. Foley: The physician makes the diagnosis based on the patient’s symptoms, a physical and neurological examination, and imaging studies. The imaging studies may include x-rays of the low back with the patient standing and bent forward and backward. The x-rays reveal the amount of disc space between each vertebra. Sometimes a test called a discography is performed to confirm the diagnosis. This test involves injecting contrast dye into a specific disc (or discs) to create a clearer image.
SpineUniverse: Will I need spine surgery?
Dr. Foley: Rarely does DDD require surgery. There are several non-surgical treatments including anti-inflammatory medication, physical therapy, epidural steroid injections, and exercise programs. Some patients have found chiropractic care to be beneficial. Surgery is only considered when the patient’s symptoms are debilitating; interfere with activities of daily living, and non-surgical treatment has failed after a reasonable period of time, usually at least six months.
SpineUniverse: What type of surgery is performed to treat DDD pain?
Dr. Foley: Fusion is the standard surgery for mechanical low back pain due to DDD.
SpineUniverse: Tell me about fusion. What does that mean?
Dr. Foley: Fusion permanently stops the motion of the spine at the level of the degenerated disc. This helps to relieve pain. Fusion for DDD is best when limited to one or two discs. Fortunately we have five discs in the lumbar spine. The un-fused discs take over to provide adequate function of the lower back.
Question: Is an artificial disc like a joint replacement?
Dr. Foley: The rationale is similar. An artificial disc is inserted into the degenerated disc space. This restores disc height, improves spine function, and helps to eliminate debilitating pain.
Question: Are artificial discs available in the United States?
Dr. Foley: There is an artificial disc clinical trial, which is being conducted under the oversight of the FDA (Food and Drug Administration). Technically, the study is an Investigational Device Exemption Trial (IDE). IDE trials are required by the FDA for new medical devices before approval for general use. The product under investigation is called PRODISC®. Dr. Thierry Marnay developed it in France in the early 1990’s. Although it was recently approved for use in Europe, it was only recently introduced in the United States. The PRODISC® is being studied at about 10 medical centers in the United States. There are also one or two other discs being studied in the United States.
Editor's Comment:The Food and Drug Administration (FDA) has approved the PRODISC®-L Total Disc Replacement (Synthes Spine, Inc. of West Chester, PA). This artificial disc is indicated for use in patients who are skeletally mature, have degenerative disc disease (DDD) at one level in the lumbar spine (from L3-S1), have no more than Grade 1 spondylolisthesis at the involved level, and have had no relief from pain after at least six months of nonsurgical treatment.
SpineUniverse: Is the surgery to insert an artificial disc complex?
Dr. Foley: The procedure is not that difficult for an experienced spine surgeon to master. A small incision is made in the abdomen and the degenerated disc is removed. The artificial disc is then inserted using specially designed tools. Although this procedure is not overly demanding for an experienced surgeon, it is still a major surgery, and carries with it all the risks of surgery.
SpineUniverse: Can suitable patients receive artificial discs in the United States?
Dr. Foley: My experience here is with PRODISC®, but my response applies to other studies too. PRODISC® is currently an unproven technology. Physicians and the FDA can’t be sure how effective PRODISC® is until it is compared to fusion, which is the surgical “gold standard”, over a long time period. The purpose of the clinical trial is to study this comparison. That means that every patient involved in the study cannot be guaranteed PRODISC®. Prospective patients are randomly chosen for the new implant. The trial has been set up so two patients receive the PRODISC® for every one patient who receives a fusion.
SpineUniverse: In summary, what is your current opinion of artificial discs Dr. Foley?
Dr. Foley: Again, my experience is only with PRODISC®. At this very early stage I view it as a very promising technology. As more patients enter the clinical trials, and we are able to following their results over a long period, we will better understand the true value of artificial discs.
SpineUniverse: Dr. Foley, thank you for your time and comments.
Dr. Foley: You’re welcome.
To learn about Dr. Foley’s practice, click here.