ARE ARTIFICIAL DISCS AS GOOD AS MY NATIVE DISCS?
When we’re younger we tend to shrug off the occasional ache or pain. But when it comes to spinal pain, putting off doctor visits can mean a life spent dealing with chronic pain, which could lead to extended periods of medical treatment, and potentially multiple surgeries. To deal with spinal pain, one should consult with doctors early. Whether you’re a professional athlete or a work-from-home professional, the stresses you put on your spine can add up over time.
Fortunately, new scientific advancements made in spinal surgeries, particularly those involving artificial discs that can replace weakened spinal discs, offer patients new and more long-lasting ways to address spinal pain. Thanks to the tireless research and experimentation performed by spinal specialists across the world, we should feel more confident than ever before about our surgical options. Patient testimonies from successful procedures speak for themselves.
If you find yourself in the position of needing spinal work, particularly related to a bad disc in your spine, there are two main procedures that spine specialists routinely use. This article will explain each procedure, and detail why the progress made in total disc replacement surgeries point to even brighter futures for those afflicted with spinal pain. Artificial discs may be artificial, but they can offer chronic spine pain a close replica of a native disc that can enable normal movement and pain-free days.
THE ROLE OF NATIVE DISCS IN THE HUMAN SPINE
Before we get to the specifics of artificial disc surgery, we should first remember the purpose of one’s native (natural) spinal discs, as well as their biological composition. Many if not most of the core reasons patients inquire about spine surgery originate from disc-related concerns, including herniated discs or degenerative disc disease. The latter of those two maladies becomes increasingly common as we age, with 40 percent of adults over 40 suffering some version of degenerative disc disease, along with 80 percent of adults over 80.
No matter the root cause of patient pain, a common denominator for why patients suffer pain stems from the role discs play in the biology of the human spine.
A flashback to high school anatomy class: the spine consists of 33 bones, called vertebrae, that house the spinal cord, the informational delivery pathway of the central nervous system. One reason why spinal injuries and diseases can be so devastating, apart from their well-known pain levels, is that so much of what our bodies do rests on the information being communicated from the brain, to the spinal cord, and then to the rest of our bodies. Being such a crucial part of human anatomy, the spinal cord needs a strong defense system, and the vertebrae do just that.
But the vertebrae themselves need some help as well. This is where spinal discs come into play.
Spinal discs rest between the vertebrae of the spine, acting as cushions so that the bones don’t chafe against each other. From the side, a disc resembles a small tire laid flat. Given how numerous the vertebrae are, the plasticity of the discs serves a major role in making humans mobile. If human spines were arranged as a single piece of bone rather than an intricate sequence of bones, we would be much less flexible creatures. Backs couldn’t arch, and necks would be stiff to turn.
In contrast to the bones they help secure, spinal discs are made up of cartilage on their outer rings, with squishy, more gelatinous interior rings that consist of substances including collagen. The flexibility of the discs enables all sorts of movements and allows the vertebrae to prop up the head and brain stem while protecting the spinal cord.
But because these discs are less solid than the vertebrae they protect, they are particularly liable to weaken due to strain, injury, or age. The prevalence of degenerative disc disease among elderly patients stems from the fact that, like so many parts of our body, the spinal discs serve such a vital role in keeping our spines limber that they wear over time. As they corrode, the once-insulated vertebrae come into closer contact, resulting in patient discomfort or pain.
The erosion of spinal discs, therefore, presents a question to a spinal surgeon: should the disc be replaced somehow, or can the surgeon maintain the integrity of the spine in a different way?
SURGICAL ROUTE #1: TOTAL DISC REPLACEMENT (TDR)
Doctors perform two primary surgical interventions to address long-term back pain. Each one operates on a distinct approach for remedying injured spinal discs. Total disc replacement (TDR), as its name implies, involves replacing a patient’s problematic disc and substituting it for an artificially made disc that approximates the one being extracted. By contrast, anterior cervical discectomy and fusion (ACDF) does not aim to replicate the removed disc. In this operation, the surgeon removes a disc and fuses the spine together where the disc once sat. You could describe that process as transforming one bone segment into a new, larger one.
First, let’s look at what goes into TDR and artificial discs.
These artificial discs employed in TDR are often made from materials such as ultra-high molecular weight polyethylene (UHMWPE) or polycarbonate urethane (PCU). Versions also exist made from chrome and titanium alloys, stainless steel, and ceramics. These materials do their best to mimic the flexibility and shock absorption of the native discs. The development of new disc types that come closer to matching native discs remains an exciting forefront in spinal science.
Once a surgeon has judged that a patient is a good candidate for TDR, the doctor then schedules the patient for the procedure. Though back surgery sounds daunting, surgeons routinely perform TDR as an outpatient procedure, with the patient being able to go home the same day. TDR, like many developments in spinal surgery, counts itself as one of the many minimally invasive spinal procedures (like the rise in virtual reality-aided surgeries), which aim to extract diseased parts of the spine in the least intrusive fashion possible.
In the operating room, the surgeon will make an incision either in the abdomen if the affected disc is in the lower (lumbar) part of the spine, or in the neck if part of the upper (cervical) part of the spine. After carefully working around surrounding structures, the surgeon will remove the problematic native disc, insert the artificial one, and then close up the opening incision. This description sounds simple enough, and to trained surgeons, it is straightforward, though great care has to be taken not to upset or disrupt the sensitive spinal cord.
SURGICAL ROUTE #2: ANTERIOR CERVICAL DISCECTOMY AND FUSION (ACDF)
With an ACDF procedure, the surgeon takes an alternative route to filling the void left by the removal of the native disc. This is known as a spinal fusion.
After performing a discectomy (removal of a disc), the surgeon will graft together the two vertebrae now missing cushion from the diseased native disc. Like artificial discs, these grafts come in several forms, including autografts (bone taken from the patient themselves), allografts (donor bone from another patient), or artificial grafts (made from many of the same substances used for artificial discs).
This may sound similar to TDR. After all, in each case, a disc is removed, and the surgeon then places the material in the space between the vertebrae that fulfills the job of a native disc. But a graft fuses the vertebrae together, making them function more like a single cohesive piece of bone, meaning the original structure of vertebra/disc/vertebra no longer exists.
The downside to this approach in comparison to TDR is obvious. By being grafted together, the vertebrae lose the flexibility enabled by the now-absent disc. Imagine for a moment that the bones of your finger didn’t have joints and that your finger bones were rigid, stick-like bones. Even if a patient only has one disc removed, the change in the spine’s constitution brought about by the graft necessarily reduces the movement capacity of the spine as a whole.
What’s more, many studies about using TDR instead of ACDF note that doctors have worried about degeneration in discs near to the extracted one after the vertebrae are fused together. With two vertebrae essentially acting as one post-fusion, the native discs immediately above and below the newly fused vertebrae find themselves buttressing a larger piece of bone than the ones they were used to before. This places additional stress on those discs, which in turn can lead to further degeneration, meaning the higher the likelihood the patient will need additional discectomies.
Spinal fusion rates are continuing to rise in the United States despite the fact that they have a reputation in the healthcare industry for being expensive and, in some cases, unnecessary. For this reason, many practiced neurosurgeons have moved away from recommending spinal fusions for more effective, less-invasive options.
WHAT ARE THE BENEFITS OF A TOTAL DISC REPLACEMENT OVER A SPINAL FUSION?
The growing body of medical literature on TDR shines with promise. A 2018 study in an orthopedic journal found TDR to be not only as effective as ACDF, but even better with respect to certain patient outcomes. The results of the study point to higher success rates for TDR patients at the two-year mark after the surgery, and between four and seven years after the surgery.
Another study comparing TDR to ACDF operations published in 2016 found another benefit in TDR’s favor. This study contrasted the experiences of two patient groups in a clinical trial. The first opted for a prosthetic disc called Mobi-C, an implant made up of two metal plates that sit on the interior of each exposed vertebrae following the removal of the native disc, and a plastic insert that rests between the two metal plates, simulating the native disc’s movement. The second group received a conventional ACDF treatment.
The result? Within five years post-operation, patients who underwent TDR had significantly lower rates of further spinal intervention after their initial procedure. There is good reason to believe, from this and other studies, that if you select TDR over ACDF, you will be less likely be on the operating table in the near future.
Because of the natural logic behind TDR – replacing a bad disc with a good one – and the inherent limitations of ACDF treatments, an obvious question emerges: why would anyone select to fuse their spine when they could simply replace their native disc with an artificial one?
Like any surgical situation in which there are multiple options, we can speak about the pros and cons of TDR and ACDF in the abstract, or at the broad level of a clinical trial. But to understand what is best for yourself, you should consult with your trusted spinal surgeon to get an assessment of your unique situation. While the research continues to mount more evidence for the benefits of TDR for pain relief and mobility improvement, there may be features about your spine that make alternative treatments preferable.
Moreover, there comes a point when TDR is no longer feasible for a patient. If one waits too long to deal with a degenerative disc, the native disc could lose enough height and durability to cause mobility issues with the affected area, making the insertion of an artificial disc untenable. Put simply: if you want to avoid a spinal fusion, make sure you catch issues with your native discs early enough to allow for an artificial disc to be swapped in. Prolonging any surgical recovery could result in a situation where, in a very painful way, your spine has already begun to fuse together.
WHEN SHOULD I ASK MY DOCTOR ABOUT ARTIFICIAL DISC SURGERY (TDR)?
If you start to feel recurring pains in your spine, it’s always good to consult with a doctor early on. Though the centrality of the spine for movement makes it a sensitive subject to broach for many, out of fear that something may be really wrong with them, there’s no reason to believe that surgery is necessarily the first option. Many over-the-counter and practical remedies for spinal pain exist, and over the course of several weeks or a couple of months, many patients recover through such conservative treatment options.
For those individuals who can’t subsist off non-surgical options, however, there is no better time than the present to consult with your spine specialist about the possibility of TDR. Not only can TDR remove lingering pain and bring life back to less mobile parts of injured spines, but it can also save you the grief of future medical interventions, whether surgical or otherwise.
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If you feel that you have detected the early stages of a disc-related spine issue, or are wondering if TDR may be right for you, contact us to schedule a consultation.