Originally Posted by mmglobal
Justin, thanks for the post... Great find!
This is a very interesting topic and one that we're all concerned with as we make our decisions about ADR. The perception of revisability of ADR has changed over the years. When I first started researching, we said, "No problem, try ADR and if it doesn't work, they can pop it out and fuse... no harm, no foul."
Later, ADR naysayers screamed gloom and doom, "NOT REVISABLE !" I can't tell you how many times I've read about doctors saying that there is a 25% chance of dying in a lumbar ADR revision surgery.
The truth lies somewhere in the middle.
If you need ADR surgery you are already in trouble. If you need revision surgery, you have even more trouble. Sadly, I know way too many people who have or will need revision surgery. I still believe in the technology and while I know many horror stories, I see the successes as well. For the most part the stories are good. However, I know people who are excellent candidates going to the top surgeons in the US and worldwide, who still have poor outcomes and have faced or will face revision surgery. About 1/3 of the people in the study Justin posted are people that I know very well. I can't describe how horrific the ordeal can be. Failed surgery... ongoing pain or serious complications... revision surgery and in some cases, multiple revision surgeries... and in some cases, complications from the revision. You'll note the reference to 'staged removal'. What this means is failed 2-level ADR followed by serious complications at one of the levels. All indications are that the remaining good level is OK and there is no reason to revise. Months later, the remaining ADR has a problem and there is third surgery. The patient has taken 18 months and 3 serious surgeries to arrive at the 2-level fusion she was trying to avoid in the first place.
The presentations I've seen and discussions I've participated in through the years have always revolved around the ability to mobilize the great vessels enough to have access to remove a prosthesis, and even more difficult to gain enough room to insert another prosthesis if that is the plan. Obviously, as we read in the article, there are other issues that are significant as well, but the big scare has to do with the great vessels. Keeled devices make the difficulties much, much worse. L5-S1 is easiest because it's almost always well below the bifurcation of the great vessels. L3-4 is next because it's usually well above the bifurcation. L4-5 is usually the most problematic because it's normally at (behind) the bifurcation. The great vessels come down from the heart and split into the branches that go down each leg. With the first surgery, they are easy to move. After the first surgery, they become 'scarred down' and are stuck to surrounding tissues by scar tissue that forms. Some ADR surgeons reduce the risk of future revision surgery by putting a barrier between the vessels and the tissue below. Since the incidence of revision surgery, especially with the surgeons that are that careful, is so low, that there is not much data on how effective the various barriers are.
Based on what I know from discussing this extensively over many years with some of the most experienced ADR surgeons in the US and overseas, I believe that the risks of revision surgery are nowhere as horrific as the gloom and doom folks would have us believe. It's also not nearly as good as they say. I know people with revisions by very experienced surgeons who still have serious complications.
A non-keeled device will be easier to remove than a keeled device because the surgeon can distract the disc space, break the plates loose from the vertebral bodies and take them out obliquely. They do not need to move the great vessels all the way out of the way if they can remove the prosthesis out the side... not straight out the front. Charite' will be easy because they can remove the core and deal with each plate individually. Flexicore will be difficult because of the height and it's all a unit...upper and lower elements (and the joint) must come out as one. However, since the Flexicore has no keel, I believe it can be removed from an oblique angle. ProDisc may also be removed obliquely even with a keel... after the core is removed and plate is broken loose, there should be enough distraction to allow enough clearance for the plate and the keel so it can be taken out from an angle instead of having to slide out straight out the front. However the Maverick with it's all metal design is problematic here. Because it's only a 2-piece device, there is no removing the core to have extra room to work with. Because the height of the keel, and the total height of the prosthesis, there is no reasonable way to provide enough distraction to allow the prosthesis to be taken out from an oblique angle. You cannot move the keel sideways through the vertebral body! The surgeon will need to either provide enough access to remove the prosthesis straight out the front, or she must seriously damage the vertebral body in an effort to remove it from an angle. IMHO, revisability issues are a showstopper when considering implanting a Maverick at L4-5. If there is a problem, taking it out will be much riskier than any of the other prostheses.
As with implantation, surgeon's experience and skill are paramount. Revision surgery is rare and complicated. Going to someone with great experience with revision may be even more important than with other surgeries... I believe that many patients revised in the US had surgical strategies that were dictated by clinical trial issues and the surgeons coming to grips with revisions issues without the benefit of ADR revision experience.
We all hope that we won't need revision surgery and I believe that the odds are in our favor. But, even if it's a 1% revision rate, that's still a lot of revision surgeries that will be needed, so these are important issues. I wish that I didn't know so many ADR revision patients, but I do. Each case is unique and the patients are presented with few options... all bad. If you are considering revision, please feel free to call me and I'll share what I know. I hope my phone never rings.
Mark
PS Remember... I'm not a doctor... Just sharing my perceptions of the things I've learned through the years... could be completely wrong...
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