Disc Replacement Surgery: An Overview

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Disc Replacement Surgery: An Overview




Guest:  Dr. John Glaser – Orthopedic Surgery

Host:  Dr. Linda Austin – Psychiatry


Dr. Linda Austin:  I’m Dr. Linda Austin.  I’m interviewing Dr. John Glaser who is Professor of Orthopedic Surgery here at the Medical University of South Carolina.  Dr. Glaser, let’s talk, today, about something that a lot of people are very interested in these days, the so-called motion-sparing technology for spine problems, back and neck.  Just what does that technology consist of?


Dr. John Glaser:  Well, there are a number of different forms of motion-sparing technology.  It is one of the newer and more exciting things in the spinal surgery field these days.  It has been around for a number of years but has, in the last 10 years or so, become much more popular and the technology has advanced significantly.  The one that we have gotten excited about and is now available in the United States is disc replacement surgery. 


In the past, if we were going to be doing structural surgery on the spine, meaning, addressing the motion segment, not just the disc, but the bones that are adjacent to it, we would end up doing a spine fusion, which, if properly selected, is a very good operation.  It’s still the most common one we do.  But there are some people that have a problem, such as a very painful disc degeneration, that really doesn’t need the entire fusion.  If we could replace the disc with something that allows some motion, we feel that, in the long run, this is going to be beneficial.  I have to add that it hasn’t been proven, in the long run, to be beneficial, but we believe that as time goes on and we follow people for many years, this will really be something that’s quite good.


We’ve had replacements of the low back, the lumbar discs, now, approved by the Food and Drug Administration for about three years.  And just recently, we had the first cervical spine disc replacement approved by the Food and Drug Administration.  So, we now have the capability, with the properly selected patient, to do this in the neck as well as the low back.


Dr. Linda Austin:  You mentioned properly selected patient.  Who is a good candidate for this surgery?


Dr. John Glaser:  In the low back, it’s generally a relatively young person who has one segment or one disc that is quite painful.  They’ve failed treatment with non-operative measures, and of course they need to be in enough pain to be willing to undergo a relatively large operation and who’s otherwise relatively healthy.  The percentage of people, for low back, who are good candidates for this is going to be lower than for the neck, primarily because the joints in the posterior, in the back part of the back, degenerate earlier in the low back than they do in the neck.  And if your joints are degenerated, it’s probably not worth doing a disc replacement.  But if you do not have degenerated joints and you have a severely painful disc, this can often be a good alternative.


Dr. Linda Austin:  Can you walk us through that surgery?  Just what is it that you, as a surgeon, are doing in this procedure?

Dr. John Glaser:  Well, we have to do this from the front of the spine.  There are some newer models that may go in from the back, but for right now, they go in from the front.  We, therefore, have to get exposure to the front of the spine.  In the lumbar spine, the low back, I often ask our vascular surgery colleagues to get me there because there are some major blood vessels in the way.  But once they have us to the area we want to work in, we basically take out the entire disc and we will remove any small spurs or anything that might be there.  Then we size the area to make sure that we have the proper implant and we place metal plates up against the bone of the vertebral bodies.  They’re held in place in different ways, but they’re basically held into the bone. In between, there’s a very high-density plastic, called high-molecular weight polyethylene, that’s placed in between the metal plates, that allows for the motion, trying to make this as close to normal as possible.


Dr. Linda Austin:  So then, does that plastic have a little bit of give and flexibility to it?  Is that what allows motion to occur?


Dr. John Glaser:  It has a very small amount of flexibility.  It’s shaped so that one side is concave and one side is convex.  One is curving in and the other is curving out.  It’s sort of a ball-and-socket type joint that allows for the motion between those pieces, and it’s very low friction.


Dr. Linda Austin:  How long does it take to perform that surgery?  In an uncomplicated case, it goes pretty much the way you think it’s going to go?


Dr. John Glaser:  The average is about two or three hours.  And much of that actually depends on how easy it is to get there. 


Dr. Linda Austin:  And then, how long is the recovery afterwards?


Dr. John Glaser:  The hospital stay is a few days.  People have a very sore belly for a few weeks.  After that, it varies, but many people, within four to six weeks, are feeling more functional and they can get up and around and do more.  And one of the nice things about this, as compared to a fusion, is that we don’t have to wait for the bone to heal.  Often times, once people feel good enough to get going, we let them get moving.  The full recuperation is still about six months or so, but a large majority of the gains are made in the first few months.


Dr. Linda Austin:  You mentioned that you use a frontal approach.  You go in through the belly, is that right?


Dr. John Glaser:  Yes.


Dr. Linda Austin:  Where is that scar, and how large is the scar?


Dr. John Glaser:  We generally go in a little bit to the left of the bellybutton.  Where it is depends on which level of the spine, but it’s usually somewhere between the bellybutton and the pubic bone.  The average size is three to four inches.  In some people, we do extend it up to five or six.  Occasionally, it can be less than that.  We need enough room to be able to have our instruments in and see things, so we do need a few inches of incision.


Dr. Linda Austin:  Now, when you do this operation in the cervical area, in the neck, you also use a frontal approach, I assume?


Dr. John Glaser:  Yes, that’s right.


Dr. Linda Austin:  I would think, anatomically, isn’t that kind of complicated?  You have the trachea or windpipe.  You have a lot of structures there to go through, don’t you, or go around?


Dr. John Glaser:  (laughter) We prefer to retract them than to go through them.  It’s actually easier to get to the front of the cervical spine than it is to get to get the front of the lumbar spine.  It’s a relatively common procedure.  We do most of our cervical surgery from the front.  That’s something that most of us, as orthopedic surgeons or neurosurgeons who do this, are very comfortable doing.  We do have to move the trachea and the esophagus one way and the carotid artery the other way.  And we do that, of course, carefully.  But once we do that, we’re right down on the front of the cervical spine.


Dr. Linda Austin:  And, when you replace the discs in the cervical area, is that also several days in the hospital, the same kind or recovery period you mentioned?


Dr. John Glaser:  It’s a little easier on people with the cervical disc replacement surgery, now, the surgical fusion surgery.  Many people are able to leave the hospital the next day.  There are some folks around the country who are doing them as outpatients.


Dr. Linda Austin:  What are the risks of these procedures?  What are the adverse consequences that, I’m sure, are rarely seen but nonetheless have to be thought about?


Dr. John Glaser:  Well, of course there are the same risks that are problems with all surgeries, such as infections and bleeding.  For the disc replacement, in particular, as compared to a fusion, some of the risks are that this is not bone and, therefore, it doesn’t actually ever heal into bone like bone does.  It can also, theoretically, wear out.  Our hip and knee replacement colleagues have been dealing with this problem for many years.  If you put these in younger active people, they’re going to be stressing them more and it may be that, down the road, this has to be revised or removed because things have worn out.  There have been a few reports of the disc replacements moving or slipping, which, of course, can be a problem, but, as you mentioned, that’s really pretty rare.


Dr. Linda Austin:  Are there ever, rarely, catastrophic events, other than, say, an anesthesia problem or something like that?


Dr. John Glaser:  Yes.  There have been, reported, some events with the disc slipping out in the low back.  And they slip out forward or anteriorly.  They don’t press against the nerves.  But the major vessels, the aorta and the inferior vena cava are there and they have been injured in very rare circumstances with this.


Dr. Linda Austin:  So, it’s a pretty safe operation but, of course, like all operations, you have to be aware that nothing is 100 percent guaranteed?


Dr. John Glaser:  That’s right. 


Dr. Linda Austin:  The point of the surgery, obviously, though, is to preserve motion and to relieve pain.  How successful are these procedures in doing that?


Dr. John Glaser:  If you were to poll people who have disc replacements, for up to two years now, they have a fairly high success rate.  About 60 to 70 percent of people would be classified a success.  And this was success was require before the Food and Drug Administration would allow it to be released.  By success, they have to have a decrease in their pain, an increase in their functional ability, and no deterioration of their neurologic status.  However, the implied part of that is that we don’t make people normal with this.  It is very rare for someone to be pain-free after any of these fine operations.  The goal is to cut the pain down so that it’s tolerable, and disc replacement, generally, does that quite well.  But we don’t make people teenagers again with it.


Dr. Linda Austin:  In your view, all things being equal, for, let’s say, a patient who is a good candidate for either surgery, which would you recommend to a family member, the spinal fusion or the disc replacement?  Or, is that not possible to answer in the way I asked?


Dr. John Glaser:  No.  That’s often times what I get asked.  I often will tell people, if they’re willing to face the uncertainty of something that we don’t know for sure what it will be like in 20 years, I think a disc replacement is a good idea.  But, the other side of that is that a fusion is still a good operation for the appropriate person.  We have a better understanding of the potential benefits and problems with that.  So, there’s really nothing wrong with going ahead with a fusion, if they choose to do that.  As an aside, I do have a family member with a disc replacement.  So, I guess that answers your question in that regard.


Dr. Linda Austin:  So, if you’re a person who is relatively young, lets’ say middle aged or younger, relatively healthy, preserving motion is really important, and you’re okay with a procedure that is not as proven over the long run, it might well make sense to get a disc replacement, as opposed to the stenosis where you can pretty much count on more restrictive range of motion for the rest of your life?  Am I thinking this through correctly?


Dr. John Glaser:  Yeah, I think so.  One thing I might say is, because we don’t know the long-term, we really don’t know how important motion preservation in disc replacement is.  My feeling is that it’s going to be beneficial in the long run, as compared to a fusion, but I haven’t seen that proven, so I can’t tell people that I have.


Dr. Linda Austin:  Dr. Glaser, thank you so much.


Dr. John Glaser:  Thank you.


If you have any questions about the services or programs offered at the Medical University of South Carolina or if you would like to schedule an appointment with one of our physicians, please call MUSC Health Connection:  (843) 792-1414.


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