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Artificial disc replacement

Remember that little concern about the next disc wearing out after fusion surgery? Even if only 1 in 6 is symptomatic, given the large number of fusion operations being done in the world it's a growing problem that we'd like to avoid in the future. We're trying to do that by rebuilding or replacing your discs rather than fusing them.

Replacing your discs, you ask? Yes. Total disc replacement (joint replacement is technically called "arthroplasty" - go to on the Web) is here. Disc replacements have been around and done regularly but in small numbers in Europe since the mid 1980's, but there is very little information available as to how well they work. They've been legal in Canada since 2002, but because of the cost our hospitals are not very enthusiastic about this surgery and very few have been done here. In the US the FDA has studied a group of 300 cases done with the oldest European-designed device (called the Charité III disc arthroplasty) by selected American surgeons and approved this first-into-market-device in late 2004; at least three others are close to approval in the US and there are many others in development.

Disc replacements have the potential to relieve the pain of a worn out disc without stiffening the spine, and we hope that the problem of the next disc "going out" some years later will be eliminated.

Artificial discs won't be for everybody, the best indication will probably be back-dominant pain in people with relatively early disc degeneration so in concept the rest of the spine remains in perfect health. One study suggested that only about 5% of spine surgery patients would qualify; most patients are simply too far gone by the time they get to us. If you've got spinal stenosis and need decompression a disc replacement wouldn't work, and if you've got a deformity like spondylolisthesis or scoliosis they won't do the job either, but they will be a big advance for many spine surgical patients.

Remember my concept of the "spinal degenerate balance"? In the early phases of disc degeneration the first thing to go is the central "nucleus" part of the disc, and only later does the tough outer rim or "annulus" break down. Later the disc collapses, alignment shifts and load moves backwards onto the facet joints which also become painful as they wear out and then swell with arthritis to often compress the adjacent nerve roots or even allow the spine to slip partially dislocate (remember we call that "spondylolisthesis").

For people whose discs are just starting to go there are even nucleus replacement devices, partial disc replacements, being developed. These are probably a few years down the line from becoming available, but the research to date is very promising.

It gets better than that. Say your disc is just starting to wear out and hurt a bit. In the animal lab, the gene therapy guys have been able to take out some disc cells with a needle, clone them, then re-inject the cloned cells to make the injured discs heal! Does this sound cool, or what? It's a long way from my being able to offer this to my patients in the office, but it will probably happen in the next decade or two. Short of that, we are starting to understand the biology of disc cell metabolism and it looks like there may be some simple drugs (pills or injections) that may be able to slow or stop disc degeneration; one of the bisphosphonate drugs prescribed for osteoporosis has shown some promise here, at least in mice.

Minimally Invasive Surgery (We call it MIS)

MIS is all the rage in health care right now but it's really nothing new, having started many decades ago when urologists first looked into a bladder through a surgical micro-telescope. Gynecologists do a lot of it, and it gained prominence when orthopedists began to "scope" knees in a big way in the 1970's.

It really went mainstream in the 1980's when General surgeons took what used to be a ten-days-in-hospital open gallbladder removal and made it a day surgery. Wow. The world thought, maybe the end of inpatient surgery is in sight?

That didn't happen, and it probably never will. Yes we're doing more and more MIS all the time, but yes we are still cutting.

In Spine MIS took off in the early 1990's with endoscopic fusion surgeries done through the abdomen, but the anatomy defeated technology there. We still really like it for some scoliosis work. It's popular in discectomy where we attempt to minimize the length of the skin incision by working through a small dilatable surgical "tube", but generally I'd say that MIS has been a disappointment. A critical look at the available research studies would support that. It's also quite costly.

We can do it for some procedures, in fact there are textbooks written about it, but to date some techniques have already been abandoned. We have yet to show any great benefit to the patient and outcomes are often somewhat inferior to open surgery. It sure sounds cool and what a way to get patients into the office and Docs to refer to you, but in my practice I'll go for "maximally effective" every time.

Writing these paragraphs takes me back to 1934 when the first disc surgery was done, these were huge operations involving multiple laminectomies with drainage of the spinal fluid and a major hospitalization with long recovery. For almost seventy-five years we've been improving technique and making these surgeries smaller without any change in outcome . Once we determine that your disc has to come out, it doesn't matter much how we do it. This has long been a concern and paradox to disc surgeons, but the lesson has not yet been extended to MIS as I think it will be in the future.

The most important determinants of outcome in spine surgery are the indications (what's wrong, and what can we do about it?) for the surgery as assessed and applied to your case by a well-trained surgeon, not the details of surgical technique. Your surgeon has to understand your problem before he or she can decide what might need to be done for you - and only then should we decide how to go about it. In the course of making that decision, your surgeon should not only understand but be able to communicate that understanding to you by explaining things clearly

That's why I wrote this in the first place. If you understand your spine problem, treatment options with or without surgery and how things will go after your operation, you will have a better operation!


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