Do you need spine surgery?

VBT and ASC Surgeries Compared

…and how is Anterior Scoliosis Correction is an improvement over VBT

A normal curvature of the spine includes two inward bends and an outward curve. The inward bends are called lordosis and occur at the neck and lower back, while the outward curve (kyphosis) occurs at the upper back. For some people, their spines do not form in a natural front-to-back S-shape. Instead, their spine curves may flow side-to-side. These abnormal curvatures of the spine form a condition called scoliosis. While surgery is not indicated for every case, a doctor may recommend surgery for severe cases.

In the past, spinal fusion was the gold standard for scoliosis treatment. However, this treatment dramatically decreased patients’ range of motion and flexibility. Fortunately, patients are no longer restricted to spinal fusion treatment. Today, there are two forms of non-fusion scoliosis surgery for children and adults — vertebral body tethering and anterior scoliosis correction. Before deciding on a specific treatment plan, take a look at our guide, “VBT and ASC Surgeries Compared.”

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Dr. A

M. Darryl Antonacci, MD, FACS
Spine Surgeon and Director

Dr. B

Randal R. Betz, MD
Spine Surgeon

Dr. C

Laury A. Cuddihy, M.D.
Spine Surgeon

Non-Fusion Scoliosis Surgery Options

Non-fusion scoliosis surgery is often praised for its shortened post-surgery recovery time, as patients were able to return to sports and physical activities quicker than they would have with spinal fusion. While this may be high on the list of positives for children and teenagers (especially young athletes), it is not the only benefit non-fusion surgical options provide scoliosis patients. These surgeries are minimally invasive and allow patients to maintain their spinal flexibility and mobility. Plus, patients experience less potential for neck and back pain and degenerative disc disease later in life with VBT and ASC surgeries compared to spinal fusion. With both VBT and ASC providing benefits, how do you know which is right for you or your child? We’ve compared VBT and ASC surgeries, so you can make an informed decision about which non-fusion surgery is the most ideal for your case of scoliosis.

Vertebral Body Tethering (VBT)

When VBT was first introduced as a treatment option for scoliosis, it was revolutionary. It moved away from spinal fusion, allowing patients to not only experience a normal curvature of the spine but also regain spinal mobility and flexibility. But unfortunately, only a few people were candidates for VBT procedures. A patient with a lateral curve greater than 60°, a stiff spine, or complete spinal growth would not be eligible for the surgery. Because the efficacy of the surgery depended on the patient’s natural spinal growth, only growing adolescents with idiopathic scoliosis could benefit from VBT. Fortunately, there was a more innovative approach to scoliosis treatment just around the corner. And with these advancements, the “VBT vs. ASC surgery” debate was born.

Anterior Scoliosis Correction (ASC)

While similar in benefits, there are key differences between VBT and ASC surgeries. Compared to vertebral body tethering, ASC is the more advanced technique for treating scoliosis. Through this treatment, surgeons are able to apply stronger corrective forces to the spine, release ligaments limiting the correction of the curve, and protect the muscles for a quicker recovery. During ASC surgery, small incisions are made anteriorly (through the side). Then, using a scope and a camera, the surgeon separates the muscles to reach the spine, where they will place screws in the spine bones and connect them with a cord. The tension in the cord will bring the spine into proper alignment. You can see how effective this treatment is by reviewing before and after-surgery photos of patients from the Institute of Spine & Scoliosis. When comparing VBT vs. ASC surgery, we must distinguish the differences between eligible candidates. While VBT is typically recommended for adolescent patients with idiopathic scoliosis, ASC can work well for adolescent and adult patients. In fact, ASC is often the ideal solution for patients with extreme scoliosis cases. In addition to patients with small, flexible curves and growing spines, ASC treats patients with curves greater than 65°, stiff spines, and complex curves. With this type of surgery, patients can see corrections similar to those achieved with rods but with greater spine flexibility and shorter recovery times.

Is ASC Surgery the Right Option for You?

Now that you know more about VBT and ASC surgeries, compared their eligibility requirements, and reviewed their benefits, you may be wondering which option is right for you. An experienced spinal surgeon can help you make the right choice based on the size of your curvature, your activity level, and your personal goals for treatment. The Institute for Spine & Scoliosis has paved the way for ASC treatment in adults and children in New Jersey, New York, Pennsylvania, and beyond. Get your case reviewed by the nationally-renowned spine and scoliosis surgeon, Dr. Antonacci, and experience a greater quality of life.

Anterior Scoliosis Correction (ASC) Versus
Vertebral Body Tethering (VBT):

What is the difference?

Anterior Scoliosis Correction ASC and VBT

The distinction between Anterior Scoliosis Correction (ASC) and Vertebral Body Tethering (VBT)  is an important one best represented by who can be treated. See: ASC Questions and Answers




Curve 40-65 degreesYesYes
Flexible CurvesYesYes
Growing SpineYesYes
Curves over 65 degreesYesNo
Stiff CurvesYesNo
Mature AdolescentsYesNo
Adult CurvesYesNo
Complex CurvesYesNo
*uniquely pioneered by Drs. ABC

Drs. ABC ASC Milestones “Firsts”

  • First Lumbar Scoliosis ASC (T11 to L3): May 2014
  • First Double curve, nonoverlapping screws (T5 to T11 and T12 to L2): May 2014
  • First Double curve, overlapping screws (T5 to T11 and T11to L2): May 2015
  • First VBS to ASC Revision (T11 to L3): Dec 2014
  • First Disc Release (T5 to L1, 3 level release T7/8, T8/9, T9/10): Jan 2015
  • First ASC above Spondylolisthesis T4 to 11 and T11 to L3, following L4-S1 fusion: Aug 2015
  • First ASC for Spinal cord Injury T11 to L5: July 2015
  • First Congenital ASC T7 to L1, with T10 hemi excision: Dec 2015
  • First Oldest ASC patient (51y/o): Aug 2015, and oldest case of 53y/o
  • First Early Onset ASC T7 to L3: Feb 2018 – 7y/o
  • Youngest EOS ASC T7 to L2: Sept 2018 – 5y/o
Recorded November 2020. This interview is for educational purposes and covers information provided by Dr. Darryl Antonacci regarding his opinions on ASC (Anterior Scoliosis Correction) Non-Fusion Scoliosis Surgery.
(link to YouTube Video for more info)
Play Video


Dr. Lee:

Hi, I’m Dr Derek Lee. It’s my pleasure to welcome Dr. Darrell Antonacci, who’s a spine surgeon at the Institute for Spinal Scoliosis. Welcome, Doctor.


Dr. Antonacci:

Thank you for having me.

Career path to spine surgeon.


Dr. Lee:

I always like to ask surgeons from the start, what was your initial interest in medicine and how did you basically evolve in terms of becoming an orthopedic spine surgeon?


Dr. Antonacci:

I’m the youngest of six kids and five of us are in the medical field. And so I have this pathway ahead of me of following all my brothers and sisters as they went through medicine.

And then I always tell people also, once you get to medical school and slightly into that, there’s a field of medicine for every personality.

And I gravitated toward spine surgery and then I focused on many different areas. I’m in practice now for almost 20 years. I have spent several years and focusing on different aspects of spine surgery until about seven years ago, I started focusing very specifically on scoliosis with the technique that we’re talking about today.

Assembling the ABC team – Dr. Antonacci, Dr. Betz, Dr. Cuddihy.


Dr. Lee:

I know initially you were in private practice by yourself, but then you started to create the famous ABC team.

Can you talk about how that developed and how you brought everyone together.


Dr. Antonacci:

Correct. So as I was saying. About seven years ago is when I started to bring that team together and the way that work was, I’ve always been in this practice here in Princeton, New Jersey, which is about thirty to five forty minutes from Shriners Hospital in Philadelphia.

And I was always a consultant there for many years since I started. Dr. Betz used to be the head of Shriners Hospital, as you know. And so I’ve known him since the 90s. And I used to go once a week to Shriners Hospital, do volunteer surgery and work in a volunteer capacity.

And over the years, as we developed, as you know, the technique for VBT and things at Shriners, I kept saying to Dr. Betz, why don’t you leave Shriners, come join my practice so that I’ll focus just on VBT and I’ll give up all metal rod surgery and all that I was doing for the prior 15 years. We’ll focus just on VBT and as a think tank, we’ll focus on that.

And Dr. Cuddihy, who is the C doctor A is me, Dr. B, Betz, and Dr. C, Cuddihy. She was our fellow at Shriners 12 years ago. So 12 years ago, she left there, became a partner, and she’s been assisting me on every single surgery for the last 12 years.

And so that’s how we formed. And six, seven years ago, I said, Dr. Betz, we’re talking about it. And as I said, you know, he doesn’t really operate. I do all the surgery with Dr. Cuddihy.

But as a think tank, we were able to progress the field dramatically fast because it’s different than being in your own practice or being in your own university setting where you don’t necessarily have the feedback of someone. And with the think tank, the three of us, that’s how we’ve made so much progress.

Evolution of ASC (Anterior Scoliosis Correction)


Dr. Lee:

So initially with your exposure and Dr. Betz and Shriners and the development of Vertebral Body Stapling and then to VBT and then to ASC, what did you see early on in terms of the potential of VBT that made you want to focus almost solely on VBT.

Anterior fusion: 2007-2008


Dr. Antonacci:

It’s all about history and context, right? And how you evolve. And it’s very interesting. If you go back to about 2007 or 2008, there was about a group of 30 of us in the country, in the US, that we were trying to do metal rods more from the front than the back. And we were just trying to do that. And it was me and Dr. Lonner in New York.

We used to work together and we were the group in New York that was doing the metal rods from the front. Shriner’s was doing some metal rods and then a group in California also.

Out of those 30 people, about five of us at Shriner’s and Peter Newton in California started to do VBT about seven, eight years ago. Why we chose metal rods from the front was simply about invasiveness of surgery.  If you know metal rods from the back, that’s a very large surgery. As you know, it takes just about a year to recover from a metal rod fusion whether you go from the front or back.

But if you go from the front, you can get back to school faster. It’s not as invasive, a surgery. There is a natural plane when you’re working inside the chest and the back is a man-made plane, you have to strip a lot of muscle. So even if you’re doing metal rod fusion surgery, it’s still a faster recovery from the front.

And so those 30 people at that time, 2007, 2008, 2009, we were focusing on doing metal rods from the front.

Development of VBT: 2012-2013

Then around 2012, 2013, the idea started evolving between Shriner’s and the group in California about placing a flexible cord instead of the metal rod. And that came about because the cord has been around since 1999. It was developed for low back surgery and that original instrumentation set was for low back surgery.

We were not thinking of it in terms of scoliosis until about 2011, 2012. And that evolved, like I said, out of the group of Shriners, us and out of California.

And by the time we were talking about the cord, or thinking about it, we had gotten really slick with anterior metal rod surgery, to a point where we were doing the metal rod surgery through a scope, through a telescope.

And so it didn’t apply to every surgery because obviously, if you’re working through a scope, you can only handle certain types of curves.

But when we started to think about using a flexible cord instead of a metal rod, it was a natural extension for us to say, OK, instead of sticking the metal rod in, we’ll skip the metal rod, and put in the cord through the same technique. That initial technique became VBT.

Thoracoscopic approach for VBT is limited to 60 degree curves and 30 degree correction

And very specific reason for that and very specific reasons for the word tether. If you have a curve that is bigger than 60 degrees, well, with the scope and the cameras, you can’t get to it.

So we knew that we couldn’t do any curves above 60. If you are trying to correct a curve with the scope, well, we knew we could only get (the curve) down to about 30 (degrees) with metal rods, you could get a little bit better because the rod is stiff and it would push down the curve. With a cord, you can’t get the correction below 30 (degrees).

VBT parameters were initially defined by thoracoscopic access.

So instead of saying, well, let’s change the technique, we basically said, well, that means we can’t do curves that are over 60 (degrees) in the chest. We have to have curves that are flexible, 30 (degrees) on their own. We’re going to hold them at 30.

We’re going to tether it and let it grow itself out. That’s where the word “tethering” came from, because we knew that it was a passive surgery. We weren’t actively correcting.

So we defined the candidates for the technique. And that was about nine years ago. So if the curve is over 60 degrees, you can’t do it, it has to be flexible to 30 on its own. and you have to have a growing kid.

And if you go look up the qualifications for VBT, even today, those are the qualifications. Yes. And it’s also only in the chest.

ASC mini-open approach gave access to bigger curves and greater correction past 30 degrees (2003-2004)

So when seven years ago, six years ago, when I got Randy to leave Shriners and join the practice, that light bulb went off within about two months of us being together.

And that light bulb was, well, the only reason I’m not doing a bigger curve, the only reason I’m not doing a stiffer curve, the only reason I’m not doing a more mature curve with someone that doesn’t have growth is because I’m limited by the camera and the scope system.


Dr. Antonacci:

I converted the surgery to a mini open procedure. That mini open procedure is not any more invasive because you’re still working within the chest. It’s still, you know, at this point, still four weeks back to school, six weeks back to sports, even with the mini open incision as opposed to a camera about the same… but it opened up the whirlwind bag of who we can treat.

530+ cases of ASC to date. 45% percent of cases are over 60 degrees. (Nov 2020)


Dr. Antonacci:

And so now we were looking at our data, we’ve done 530 or so cases of ASC (as of the date of this recording), which is the evolution of VBT, and I’ll get to that. But if we look at that bag of five hundred and thirty cases, about 45%, almost half the practice, are curves that are well over 60 degrees. We’re talking 70, 80, 90 degrees. And I’ll show you this.

Importance of de-rotation of the curve to produce greater corrections


Dr. Antonacci:

So it really transformed what we could treat just by modifying the procedure. Once I made a mini open incision, I got the ribs out of the way. The ribs were no longer in my way. And one of the biggest initial impacts that I had was in the type of correction we could do.

And if you want to look back and we can at the limitations of what VBT is, the primary curves, they all go in and they rotate. That’s what they look like, a C or an S on an X-ray. But they’ve gone in and they’ve rotated. So the correction should be one that de-rotates.

Curve de-rotation with VBT is difficult because ribs are in the way. ASC allows for de-rotation because the ribs are out of the way. Therefore greater corrections are possible.

With VBT and tethering. You can only get it to correct down to 30. But you can’t derotate at all because the ribs are in the way. And if you can’t derotate, even if it grows, it grows flat. So it doesn’t de-rotate.


Dr. Antonacci:

VBT, I try to make the analogy of, like, if you… to patients… if you talk about metal rods, metal rods is like the rotary phone. VBT was like the first flip phone. When we made the extension from VBT to ASC, it’s not a different technique in terms of different screws, different cords.

Same cord screws concept, but the way you get there and what you can do converted VBT from a flip phone to the first iPhone and now five, six years later, five hundred thirty cases later, we’re at iPhone six and seven. But if you’re doing VBT, you’re still on a flip phone. And in that, the key distinction is the rotation.

VBT limited to 30 degree correction


Dr. Lee:

Can I ask you a couple of follow up questions about that… Now when you were mentioning that with the thorascopic, minimally invasive approach, limited by a 60 degree curve, but only getting down to 30, is that why surgeons who are doing VBT are correcting, you know, in that range, twenty five, thirty degrees because they can’t get any tighter>


Dr. Antonacci:

They can get it any lower down. You can’t get it below 30(degrees). So if you go to some of those first cases… why did that light bulb go off? Well, one of the first cases was a teenager that came in with a 50 degree curve, which is within VBT (criteria), but they were mature. They were 16, they weren’t 12 (years old). So they had no growth. So I can’t leave it with 30 degrees.

I have to make it straighter than that. But I can’t get it straighter than that unless I’m doing a mini open procedure, and some of the techniques that we evolved for ASC.

ASC quickly became a corrective procedure.


Dr. Antonacci:

So ASC very quickly became a corrective procedure, not a passive tether procedure. And so I refuse in my practice to even call what we do tethering. I don’t use a tether. I use a cord. It’s that much of a pet peeve for me because it’s that big a difference.


Dr. Lee:

I understand, because I was under the impression that curves were corrected to, you know, 50 percent from 50 to twenty five to 30 because of the fear of overcorrection?

Importance of anterior longitudinal ligament release in ASC.


Dr. Antonacci:

That’s for the growing child and even with ASC principles applied to the growing child, the principle of the ASC, it’s like that toy snake in the store. You can curve it and it locks and then you can’t unlock it unless you release it. And then it goes to where you want. That’s like these curves.

The curves go in and they rotate. So even if you have a 50 or 60 degree curve, it only goes to a certain point in its correction. And the reason for that is there’s a tight ligament on the inside of the curve, the anterior longitudinal ligament, which is meshed very tightly with these abnormal disk spaces because they’re tight on one side, they’re a little fibrotic.

And so if you try to de spin and correct this curve, you can’t do it unless you release it like a cut in a pie. Once you release the ligament, that’s like releasing that snake toy, all of a sudden you can de-spin it. You can take the torque out of it, you can de-torque it.

ASC allows for reduction of hypokyphosis when ALL is released.

And so that’s the difference between VBT and ASC. VBT doesn’t do that at all. So when it grows in a growing kid, it grows flat. But with ASC, if you release it and even though you don’t want to go below 20 or so degrees correction with a growing child, when they grow, they start to grow with the roundness.

That’s why you see the clinical picture where before surgery, they have really shallowness between the scapula. But with VBT, if you look afterwards, they still have that shallowness. But if you look at ASC, they start to round out.


Dr. Lee:

All right.


Dr. Antonacci:

And even in the growing child, you just don’t correct as far with ASC, but you still need to release and you still need to do that. So as they grow, they de-torque themselves.


Dr. Lee:

And of course, you’re referring to, you know, the primary drive, one of the primary drivers for scoliosis, which is the loss of the kyphosis of the thoracic spine leading to flatback hypokyphosis.


Dr. Antonacci:

And almost every curve, like I said, they go in and they rotate. And when you look from the side or from the back, that’s a flat shallowness between the scapula.

ASC innovation was driven by the expansion of parameters to help more mature curves.


Dr. Lee:

Did you conceive of doing the anterior release of the A.L.L. (anterior longitudinal ligament) in terms of trying to address the sagittal curve or the lack of…


Dr. Antonacci:

It started in terms of the patients that started to come in. So that slightly older patient where I knew if I couldn’t… So that was one of the first step was going from the camera to the mini open and then from the mini open to the one or two releases because I needed to get it below 20 degrees.

I couldn’t leave it at 20. And then a teenager came in with a lumbar curve. That’s not VBT, VBT is defined as a chest curve with scope and lumbar curve is obviously a mini open procedure. And so it evolved in that way.

And it all involved in this practice, all the milestone for developing the advances of most VBT to ASC and then for ASC occurred in this practice. And that’s how it evolved. It evolved by answering the issues that were coming up. So if you’re 17 and you have no growth and you have a 60 degree flexible curve, I can’t leave you with 30 degrees. I have to make you straight.


Dr. Lee:

Absolutely, and with VBT being born out of the concept of bone growth modulation and one, two, or three years of growth left…a lot of surgeons, it becomes a bit of a controversial topic because, you know, with VBT, there has to be growth. But with you, you’re going towards, you know, late Sanders, late Risser.

Oldest ASC patient is 53 years old.


Dr. Antonacci:

The oldest patient I’ve operated on is 53 years old. And we’ve done many in their 40s and 20s and 30s.

We’re not restricted. The ASC opened up, like I said, like the bag. It’s almost like you can treat almost every type of scoliosis with ASC.

ASC combines principles of bone remodeling and tissue laxity.

It combines both remodeling and the other principal, which is tissue laxity. So if you put braces on your teeth, dentists will migrate your teeth over.

There’s remodeling occurring, but there’s also a loosening and restoring occuring. And so if you pull on your skin for a day, it bounces back.

If you pull on your skin for three days, not quite as tight. So if you release the spine and you bring it over and you hold it there for a few weeks, when it re-heals, it’s re healing with a new torque system.

That torque is not driving it back the way it is in VBT. VBT there’s actually a fairly high failure in VBT, the reason for the failure is because you don’t get it below 30 and then you’re keeping that internal torque there and that internal torque (so) when if that cord breaks wants it to go way back because you never got rid of the internal torque.

Target curve correction for both growing and mature teenagers


Dr. Lee:

So are you saying that you have to get below 30 degrees correction and as close to zero as possible in order to reduce the amount of torque and the soft tissues from pulling it back?


Dr. Antonacci:

In a growing and a non growing teenager, you have to get them almost as straight as possible. In a growing teenager, you’re still going to have a target sweet spot of that 20 degrees to allow for the growth by releasing this spine and then letting it re-heal it gets a new set point. That set point is 25 degrees and then it will grow from there.

If you in VBT, if you’re just pulling it down and holding in at 25 or 30, there’s no set point, it always wants to go back and so if it doesn’t grow quite far enough it will rebound back.


Dr. Lee:

So are you saying that for VBT with a growing child to 20 degrees, it has to be at least 20 degrees or less?


Dr. Antonacci:

It depends on their phase, where they are. You’re dialing in a certain remaining amount, depending on where they are in their growth phase. But the principle difference being that you’re releasing and starting from that new set point.

Staged surgeries for 90+ degree curves.

And we know that from our in this practice, we know that from our huge curves where I’ve done 90, 100 degree curves. And what happens, I can get them from like braces, I can’t get them from over here to here in one shot. If it’s a 90-100 degree curve, I need to correct them down to about 50 the first time.

Then I let them wait for five, six, nine months. They’re getting flexible at 50 and 60. Then I go back and I revise that and bring it down to where we need to go.

VBT vs ASC revisions

That’s the difference also between ASC and VBT. VBT you can’t do that because you can’t do revisions with scopes and it’s almost impossible. And that’s again, the further step that a lot of VBT surgeons, if you ask them, well, we can’t do revisions and we’re going to modify to a fusion if something goes wrong. It’s not the case with ASC because with ASC we do a mini open, you actually can do the revisions.


Dr. Lee:

You have to you also, well I assume, you deflate the lung when you do a mini open, right?


Dr. Antonacci:

So that is the same with VBT


Dr. Lee:

Yes. So what’s the difference in terms of the VBT surgeons not being able to do a number of revisions?


Dr. Antonacci:

Because when you deflate the lung, first of all, a good understanding for families is you don’t damage the lung by doing this. Every time you take a breath, you inflate the lung.

Every time you exhale, it deflates. And so this is like the inner tube of a tire. We let the air out of the tire. We do our work, and then we blow the tire back up, whether it’s VBT or ASC, same thing.

But with VBT, when you’re working through a scope, that scar tissue plane that heals between the lung and the chest wall, which is part of the normal healing process, when you go back in with the scope, you can’t see.

There’s no plane for the camera to get into because it’s all scarred down. And so it’s virtually impossible to do a revision. Almost every revision that you’re going to do is going to end up being a mini open type revision.


Dr. Lee:

Right, OK. And with the mini open, you can do it multiple times.


Dr. Antonacci:

It’s actually not very hard at all. So what’s interesting about that, going back to revisions or even staged surgeries where we do these big curves, the second surgery is usually easier than the first.

So teenager goes back to school around four weeks after ASC and six weeks to sports.  After a revision or staged surgery, they’re going back to sports around four weeks.

It’s actually easier to get over. That’s a huge difference between that and metal rod. If you have a revision with a metal rod, it took you three or four months to go back to school with a metal rod and took you about a year to be allowed to go do any sport.

And you can’t do what you used to do. And then if you have a revision or a staged(surgery), that’s another year recovery and that surgery is bigger than the first surgery, more blood loss, more infection. With ASC it’s the opposite.

That’s a… I just want to mention that one other point about metal rods. If you did one hundred metal rod surgeries for a moderate sized curve, there is a certain percentage that are going to need blood transfusions. You know, it could be 30 percent, 50 percent. Depends on how big the curve is. You could do almost any curve with ASC or VBT and you’re not going to need a blood transfusion. It’s a huge difference in size.

Location of thoracic and lumbar mini-open access points.


Dr. Lee:

This just a technical question, but with the mini open approach, with the ASC, do you use the same incision for lumbar curves as well as you would for thoracic curves in terms of its approach.


Dr. Antonacci:

So my incisions are under the arm and so they stay tucked under the arm. Whether you have to do a thoracic curve higher, if it’s a lumbar curve it’s lower down, and depending on the side, all my incisions are tucked under the arm. So you can’t really see them from the front. You can’t really see from the back.


Dr. Lee:

In terms of your ASC, you also started to do, I guess, because of innovation that was necessary, and I assume you found that the health of the disc, especially with severe curves, mature curves, was problematic.

And you started to develop disc release techniques. Could you talk about that a little bit?

Disc release


Dr. Antonacci:

So. If you go back to the, you know, five hundred thirty cases, forty five percent are curves that are over 60 (degrees) outside the range of even VBT, you can’t treat those curves without releasing the spine. So it’s not even a question of should you do a release, you can’t do it unless you do a release …

So it’s almost a Catch 22.  It’s almost mandatory. As we started doing more and more releases in our bigger curves, it became very clear that they were as important to do in our smaller curves for that de-rotation component. And so if I started out six years ago and I was doing one or two releases per case, now I’m doing four or five, six, seven releases.

It depends. It’s even more involved with releases because that’s how you get your corrections. And that’s been a steady progress. That’s going from iPhone 2 to iPhone 4, basically. And it’s that process, the release involves, like I said, releasing the anterior longitudinal ligament. And again, people need to realize that these are not normal discs.

When they’re crunched over in their scoliosis curve, that portion in the corner is not normal. It’s fibrotic and tight. And so by releasing it, it re-heals.

Released discs re-heal

That’s another thing that’s not commonly understood out there. But you’ll see that if you go back on a staged surgery, that disc has actually reformed to some degree and is still mobile. And so we know that the disc does not mean it goes on to fusion by releasing it. In fact, what it does is it re-heals and there has even been some cases where we can see new nucleus pulposous.

Again, these are growing, a lot of times, these are teenagers that their whole body is blooming. So the disc reforms but it reforms, in a new position that’s been opened and spun back to a different position. It re-heals in that position. And then it’s mobile in that position. That’s what generally happens.


Dr. Lee:

So in a sense, you have the shape of the disc, especially at the apex, is going to be very much wedge shaped and when you release it and you reduce the tension and you de rotate it, it squares it off and it gives it an opportunity to heal…


Dr. Antonacci:

And it re-heals. But now it re-heals without that internal torque that wants it to go back.


Dr. Lee:

OK, because as you know, disc release tends to be a bit of a controversial topic.

Perspective on controversy surrounding disc release


Dr. Antonacci:

It’s a controversial topic for many. And it also, again, everything is context. So I spent half my life in adult surgery and so has Dr Betz and half in children’s surgery. Almost all the VBT surgeons out there are only pediatric surgeons. They haven’t had the exposure of adult lumbar spine surgery.

Like if you herniated a disc, or I herniated a disc today and it was one that required surgery, 99 percent of the time the surgery would be just pluck out the piece of disc that herniated and you would leave the disc alone and it would go on and heal. Right? So that’s where this information comes from, in part.

On top of that, a lot of the disc releases that we do are in the thoracic spine and thoracic discs are not as crucial as like L4 – 5 disc or L5 -S1 disc, which is low down and mechanical.


Dr. Lee:

OK, well, I was talking to another spinal surgeon recently, and he also does mature spine’s, immature spines, and he was very interested in the maturation of the disc in terms of as you exit adolescence, the shape and the biology of the disc changes becoming a little bit more rigid.

So he was… from his perspective, he was saying that. As you hold the tether going towards maturity, it’ll stabilize the spine somewhat. Have you noticed that as well in terms of, as part of your practice?


Dr. Antonacci:

What would stabilize the spine ..the cord?


Dr. Lee:

No, the disc kind of stiffens into its new shape as you hit maturity, then that would help to stabilize the spine.

Post ASC, curves stabilize within 1-2 months


Dr. Antonacci:

I think it stabilizes almost within a month or two. So, I mean, what we find in our situations is that it just re acclimates to the new position. Again, this is tissue remodeling, but it’s also tissue laxity. And so this is not against those principles.

It is using those principles. And those principles probably happen a lot faster than we think for the spine, it doesn’t happen more faster than we think for teeth. We migrate teeth right over and we pull on skin… that becomes saggy right away.

Mature spine ASC data


Dr. Lee:

I think the whole world is kind of waiting for you to release data on mature spine tethering in terms of…


Dr. Antonacci:

I don’t think the word tethering…


Dr. Lee:

Sorry… ASC


Dr. Antonacci: So I presented it last year in Finland on 440 cases. I presented the data at EuroSpine and that data was pretty clear. And now it’s about formalizing it into the papers and things like that. But the data has been presented internationally and that’s where I know.

Comparison of de-rotation with VBT, ASC and fusion

So I gave a talk right after Dr. Alanay who presented on VBT, and that’s how I know his de-rotation correction was two percent and our ASC correction was over 90 percent for de-rotation.

Comparison of curve correction with VBT, ASC and fusion

And in terms of the correction of the other plane, of your main plane, our average corrections are between 88 and 93 percent. The average correction of a metal rod is at most 75 percent and the average correction for VBT ( although that’s a growing child), so before the growth is about 56 percent, and with the growth up to 70 percent.

But these are mild curves, these are curves that are generally not bigger than 45 degrees.


Dr. Lee:

And you’re going quite a bit of the time with even more severe curves. Now in terms of because you mentioned that you do quite a few adult spines as well, do you find that it’s more difficult to stabilize those curves and especially with cords often rupturing over time? Because they’re an artificial material.  What’s your perspective on that?

Adult ASC curve stability and cord rupture


Dr. Antonacci:

So the only difference between the adult spine and the teenager spine is that it’s probably a little bit stiffer, probably requires more releasing, but you can end up with the same good result.  In terms of breakage, I explain it to patients this way. If you did one hundred metal rod surgeries for a double curve you’re going to break two out of 100.

Those metal rods are really strong. And so they’re going to last for three or four years and then they’re going to break. When they break those two patients that broke the rods have to have it revised, redone. And so that’s like 100 percent revision on their breakages. Not a high breakage rate, about two out of one hundred, but they do break.

And that surgery, if it took you a year to recover the first time, is going to take you a year to recover the second time. The blood loss is larger( and there’s a high rate of blood transfusion with the first surgery), the infection rate is higher. If you did 100 cord surgeries for the same type category curve, we wouldn’t transfuse any of the 100. We haven’t had an infection in 530 cases, we haven’t had a single infection. So that puts it way… And again, this is about natural plane versus a man-made plane.

ASC revision rate

But in terms of breakages, the cords are going to break more often than metal rods. But the revision rate is about the same with ASC. That’s not true for VBT. ASC, it’s true because when  the breakage occurs and you’ve taken out that torque, that desire to go back to the same spot is not there.

And so even if the cords break, they might settle a little bit, but not to the point where they require surgery. So when we analyze that was 440 cases and compared it, the revision rate is about the same as metal rods, but you’ll break more cords. But it doesn’t translate into the revisions because of the spine, if you released it well, and it re-heals to that new position that internal torque to go back to where it was is not there.


Dr. Lee:

OK, if I could just move back a little bit to the disc, and the disc health over time, was that part of your paper, your presentation in terms of disc health, or is that another paper?

Data on disc release and disc health long term


Dr. Antonacci:

That’s going to be something separate. What we can say at this point is that it does not lead to a discogenic back pain problem. I don’t see that. And what we notice on some of these staged surgeries or revisions is that there’s good new healing of the disc that occurs. So a lot of it is anecdotal.

A good study that we need to do is we’re going to go ahead and get MRIs on a certain group of people that had their surgery done, and a year later look at the disc. We’ve done that a few times. And the discs are OK, it’s not like they’re degenerating.

Why aren’t more surgeons performing ASC?


Dr. Lee:

Dr. Antonacci, what do you see in ASC that other surgeons aren’t? And why aren’t more surgeons basically following your lead. Are they just waiting for more data or what do you think it is?


Dr. Antonacci:

No, but it’s a big hurdle to start even VBT or for ASC. And so I’ve trained about nine surgeons throughout the world. I’ve done surgery in eight different countries, and about three of those eight have taken up ASC fairly well. The ones that have done that, do about 100 cases each. So right up until about a year ago, there was only about 15 people in the country doing VBT.

And so Dr Samdani at Shriner’s probably had the most, I don’t want to say most or not, (but he) has a lot of experience with VBT, but he was part of our Shriner’s group and then there were about eight to ten others doing VBT. If you want to start doing VBT or ASC, the first thing you have to do is align yourself with a thoracic surgeon because you’ve not typically worked a lot from the front.

You’ve done a lot of metal rods surgery from the back, and you really were never trained to work in the front. So I’ve done so many that I do my own approaches and we have a thoracic surgeon in the hospital, but they’re not there for me during surgery.

I don’t need them. But if you’re a new person starting out and all you’ve done is metal rod surgery for the last 15 years, you’re going to have to get a thoracic surgeon to help you start the case and do the case with (them). That’s a big stumbling block, a big hurdle. So even for VBT, that’s a hurdle.

What happened with VBT now, if you look at the VBT world right now, there’s probably 30 or 40 that are saying they do VBT, but there’s only 10 that really have experience with it. But there’s about 30 or 40 that say. And what happened about a year ago was the company, Zimmer, got their marketing approval for their instrumentation so that they could then say that they sell this for VBT.

They didn’t do it for ASC, they did it for VBT because that’s where the data was coming from…Shriner’s. And but once they got that marketing approval, they could then start putting on a weekend workshop here, weekend workshop there, to show surgeons what VBT is. And so VBT has gotten a little bit of a surge, a following in the last year, only in the last year because of that. Still a flip phone, not an iPhone.


Dr. Lee:

You can use both Zimmer and Globus with, but you tend to stick with Globus, I believe right?


Dr. Antonacci:

It’s irrelevant which one I use. It’s just a matter of sourcing and regularity and things like that.


Dr. Lee:

And I know Globus is… there’s competition, Zimmer, Globus, etc. in terms of instrumentation.


Dr. Antonacci:

And just for your viewers, I have no relationship with the company whatsoever.


Dr. Lee:

OK, fair enough. But are you aware of I believe Globus was supposed to release a bigger, thicker tether. Do you know any information about that?

Perspective on new cords


Dr. Antonacci:

It’s coming out at some point. I don’t think it’s going to be a major change that is required when we look at what issues there are. That’s not really the issues. I wouldn’t hesitate to have it with the cord that’s currently available versus that cord. So some of the iPhone7 or (iPhone)9 techniques that I do is I add more cords, like I’m not even doing just two cords.

Sometimes I’m adding supplement cords. And so that’s the new information with Globus. Yes, it will be a nice thing to have, but it’s not something that’s changing on the presence of my mind.


Dr. Lee:

Right. It’s not going to be necessarily revolutionary. Right. And since you brought it up, can you talk a little bit about your supplement cord?


Dr. Antonacci:

Yeah, it’s I’d rather not. It’s just belts and suspenders. It’s like where you might add a reinforcement cord here and there.

Perspective on use of double cords for de-rotation

I would tell you, I can tell you this…This is about my technique with the double cords and double screws. So VBT is clearly one screw per level because with the scope you can’t actually put two screws, you just physically can’t do it.

I migrated to the point where I do two lines of screws and two cords and the first cord and screw line helps de-rotate to here, the second cord screw line helps de rotate even further.

So it’s like tying a boat… you anchor the back end and then you swing the nose around. And that’s what some of the double cord double screw technique allows for. It also decreases breakages and things like that. But personally, I think the most important part of it is improving our de-rotations.


Dr. Lee:

Fascinating… And do you tend to limit that more to the lumbar spine in terms of…


Dr. Antonacci:

No it’s throughout. If you want to take some time, I can go through slides and things with you. But the technique that iPhone five, six, four, whatever it was, is almost double screws at every level. The only time you don’t is when the bone is so small you can’t really get in two screws.


Dr. Lee:

OK, why don’t we if you do have some slides, if we can go through. I was interested in your parameters for immature, maturing and adult spines. Would you be able to take us through that?


Dr. Antonacci:

Yeah. And just so you know, this is not prepared for you. This is the talk that I give to patients every time I talk to them with Zoom. It’s very nice to be able to do that. So here is I’m going to just share a screen. Good. You can see this now again.

OK, so I did get a little prepared by pulling up the right slides for you, but you know this over here, this might be a picture for you of like my ASC technique, which is like two cords, two screws, VBT technique, which is a single line.

Limitations of VBT

But this is what I mean about the limitation of VBT. So these are not my cases. These are cases that are published by other surgeons. And first of all, you can notice that these are mild, moderate curves that they’re treating.

And this is what VBT would do in a growing child getting it to about 23(degrees) or so. This is obviously a more mature individual or later in their growth after it’s been corrected.

VBT doesn’t address thoracic hypokyphosis and resulting cervical kyphosis

But the main side view here is that it’s completely straight, right? It hasn’t de-rotated at all. If you compare this to an ASC, you can get that roundness back and what that does is improve your neck posture.

And we showed that I mean, me and some people at Shriners in 2011 published a whole study on the cervical neck issues with scoliosis, because (you can see my hands also on this), because that spine goes in and rotates, the neck will pitch forward. And so that’s what you see preoperatively.

You see this hypokyphosis and then the neck pitching forward. If you de-rotate and correct the roundness here, the neck will start to improve itself. But VBT does not do any of that. And that’s the limitation that we keep referring to.

Candidates for VBT vs ASC

Getting to your point about how you decide what and where. Well, this is (showing a comparison chart) what’s broken down in terms of what are candidates for VBT versus what are candidates for ASC.

And what you can say, see right away, is that the curve is generally, as we talked about, between 30 and 65 degrees. You can do VBT if it’s flexible or less than 30(degrees), you can do VBT.

If it’s a growing spine, you can do VBT. However, as I will /was trying to make the argument, no matter what, even in that category, you’re better off with ASC because it’s going to de-rotate your spine by greater than 90 percent. You’ll get improvement in your roundness of your back, whereas with VBT, it’s less than two percent.

This is the critical factor for you. And your average corrections are going to be much higher with the ASC. So then what does ASC do?

It does curves that are well over 65. It addresses the thoracic hypokyphosis… that’s that inwardness. You can do curves that are stiff or flexible. You can do curves that are old or young, adult curve and complex curves, and you can do staged surgery, none of which you can do with VBT..

Mechanism that frees up spine flexibility?


Dr. Lee:

So for improving the kyphosis, reducing the hypo kyphosis of the thoracic spine, is it what’s the mechanism of freeing up more flexibility? Is that due to the disc release?


Dr. Antonacci:

The anterior ligament is that tight band and that’s a big culprit in this with those corners of the discs where they’re degenerative and tight, and so releasing it allows the disc space to open and de stiffen.

And so in the surgery, when you’re on your side, that curve is in and up and maneuvers of the surgery are down and around, and that’s what brings it back down and that’s the technique.

You know, this is not new. Even with metal rod surgery, if you have a large 90 degree curve, 80 degree curve and you were going to do metal rods from the back and it was stiff, you would go to the front of the spine first, release the spine and then go to the back and do the metal rods. So none of these concepts are new. It’s just being applied in a very specific way.

ASC milestones

I just put this in here because, you know, just to emphasize that how we got here with the history of the process was… the first lumber case for ASC was in 2014.

That’s T11 to L3. Obviously not a VBT case, not a candidate for VBT, the lumber case. And then we went to the first double curves, the first with overlap, not overlapping screws or overlapping screws, converting the first Vertebral Body Stapling (VBS) to ASC.

Doing the first (disc) release was around January 2015 for this girl from the United Kingdom. Then combining scoliosis with correction of spondylolisthesis, the first ASC for spinal cord injury, first congenital ASC, the oldest ASC, the youngest ASC, etc. It all occurred in this practice because of this think tank.

Flexibility comparison between metal rod fusion vs ASC

I can show you some of the comparison between metal rod and even some video here. So obviously, this is someone I did with metal rods nine years ago and obviously a big incision, big surgery from the back, same type of curve.

This is one of the early ASCs, six years ago, similar corrections. But what you obviously… Can’t see the incisions very much, there’s no major muscle disruption at all. But when you look at the motion, this is where it becomes obvious.

If you look at the motion with the metal rod, you have to pivot below the metal rod. And if you are looking at the ASC, you can have normal rotation and curves and using the full aspect of your spine. Here he’s pivoting… she’s arching. Again on the extension… same thing… he has to pivot.

She can arch and use her whole spine. And if you do side to side, you see he pivots side to side, she arches side to side. And that’s the difference between cord and metal rod.

Cases: Thoracic ASC.

In terms of types of curves. Like obviously this is on the very high end of VBT, if you were to do it, but you wouldn’t release the spine and with VBT, you would never get it straight. And now this person obviously didn’t have a lot of growth left. And so I tried to make it as straight as possible.

This is what it looks like from the side, just like the model. This is the same girl, but this is nine days after surgery. So with ASC and even VBT, the recovery rates are quite quick because it’s less invasive surgery.

But where can you take ASC where you can’t take VBT? Well, as you can do 65 degree curves and get them like that, you can do 78 degree curves and get them like that. And this is clinically what it will look like.

And this is the difference also between VBT. Now you’ll see some roundness appearing. That’s the de-rotation effect I’ve pointed out and rotating and rounding out the back here. This was an 86 degree curve and this you can see how much roundness improvement of that thoracic kyphosis was achieved. And that was a multiple release type situation. Here’s a more mild curve 51 degrees. But even in this situation, you’ll see the roundness filling out much more appropriately.

Cases: ASC for extreme curves

Extreme cases, 90 degree curves with ASC, you can actually again, this was a staged surgery that was done in two parts, but going from 90 degrees to seven degrees and getting this kind of control. And here’s another, a different girl.

And the reason I brought this up is, again, this was a staged surgery, 90 degrees before about 13 or so degrees after. But you can see even in those severe cases and even with staged surgery, you can really get the motion with the cord.

Is there less cord breakage due to less tension with ASC?


Dr. Lee:

Quick question… with ASC, since you are releasing the, doing the anterior release A.L.L. and you’re doing multiple disc releases, you find that your tether breakage rates are less because there’s less torque trying to push it back to the original curve?


Dr. Antonacci:

My personal opinion on that is, yes, we have to go back now and analyze. So I have, you know, data for now, six years of single cord single screws… double cords, double screws… with releases, without releases. And so we’re going to have to get to and then mature and immature and the whole gamut.

ASC revision rate is about 3% for all cases.

Large number of cord breaks do not require revision since spine rebalances and stabilizes

And so now those are great questions that need to be broken down and see. The overall revision rate for ASC is around three percent, and that’s all comers, even the 90 degree curve.

So that’s who needs a revision. So it’s a very low rate and that’s actually comparable to metal rods. But then within that group, you know, is there a slightly less breakage in one group versus another and with what techniques we’re doing at the time. I will tell you that the vast majority of breakages of cords are improvements in curve balance, not detriments.

And that sounds funny at the first level. And the answer to that is as you get into these older, more mature curves, I’m making them as straight as I think they need to be. But they always have others, they have a residual neck curve, they have a residual lumbar curve, but I made them as straight as possible.

That may not be where that brain and where that eye gaze wants to exactly be in space. And so what we may notice is that that cord may break at some point, but it improves their overall balance. We look at that x ray and then after that break, you know what? That actually looks a little bit better than when it wasn’t broken! That’s a good, good portion of the breaks.


Dr. Lee:

You have a hard number to the number of cord breaks you have witnessed over the years? Do you have an actual number to the cord breakage rates that you’ve seen?


Dr. Antonacci:

No, we haven’t looked at it that it’s not we look at it as a revision more than that. So if it breaks and it requires a revision, then that’s something that’s of an issue.

And that’s another teaching element that needs to get out there, is that, in my opinion, the vast majority of breaks are actually beneficial, not not-beneficial. That’s almost the opposite logic. You say, well, a break must be bad. No, actually, the truth is that most of the breaks are actually beneficial.

Not not benefitial. And so we try to get away from that by looking at, well, if it breaks, does it need a revision? And that revision rate is quite low.

Perspective on hybrid fusions and cords


Dr. Lee:

Now, some surgeons are kind of looking at hybrids in terms of selective fusion thoracic spine.


Dr. Antonacci:

So, again, the practice has gone through all this. And about five years ago, I did about nine, eight, seven, something like eight or nine hybrid situations where those were some of those initial cases. They had an 80, 90 degree thoracic curves and a flexible lumbar. So do we do a cord here, but we selectively fuse the upper portion.

And that does work to some degree, but there’s some residual imbalance because you have a rigid segment above and below a flexible cord. So I stopped doing those and that was after about eight or nine of those cases.

And then I started staging the surgeries. And now we’re getting results like this girl on your screen. So same thing here. You could say, well, let’s do a metal rod down to here and then flexible here. Why? When you can get this kind of result with the cord.


Dr. Lee:

So basically if you can , if you can get the results ASC wise and sometimes get a correction, then why go to fusion at all?


Dr. Antonacci:

Correct. I’m going to think about it in terms of even for the major 90 plus degree curves staging surgery like braces on your teeth, getting to where you want, as opposed to trying to replace your teeth in the portion and then move it.

Perspective on selective lumbar fusion with cord.


Dr. Lee:

And other surgical techniques included or that may be being investigated right now are selective fusion, maybe one or two levels for a lumbar spine and tethering those as well. But again, from your point of view, why when you can get the correction you get with ASC?


Dr. Antonacci:

Yeah, I think they’re just going through phases that we’ve been through. So let me just show you a couple more, because these are interesting other types of cases.

Case: Lumbar ASC.

So lumbar now, this is a teenager, this is a large and you can say, well, this can’t be VBT it doesn’t even qualify. So here’s a 70, almost 70 degree lumbar curve. This is what he looked like before the surgery.

And you can see the huge lumber rotation and very stiff. He only bends out to 40 degrees, and this is the day of surgery. Right, I can tell you that I probably did release up in this upper area, I probably stayed away from releasing down in this area, but I released up here and this is his correction. And if you look at his motion after the surgery, this is about two years after.


Dr. Lee:

You must enjoy your work.


Dr. Antonacci:

Very rewarding. It’s hard not to be rewarded.

Cases: Extreme curves, revision, over-correction.

And then, you know, how extreme can it get, this is a 90 degree same type of situation. And then I threw up some other curves for you to look at. But again, 85. This is 75 down in the waist. Another one. This is the VBT. This is not my case, but I did revise it.

This is a VBT that didn’t quite get the correction because you can only get it to 30, didn’t grow out. And so then I went back and I revised it with the ASC technique. And same with this one, too, this is an overcorrected VBT, again, it’s hard to say,  this is not VBT classically because they did do the lumbar portion as well.

But without the principles of ASC that you can and I’m not trying to say ASC is the perfect thing, but, you know, we’ve been through the process in this practice. And so this is the revision that I was able to achieve and can see the improvement with the double cords, double screws and how you can really get the proper contour. And here’s another. This was another revision that I had to do for somebody.

The Future of ASC


Dr. Lee:

When your practice is always evolving, where do you see it’s headed in terms of what’s the next version of ASC that you see coming down the pipeline?


Dr. Antonacci:

I think the principles need to be solidified in terms of, you know, you don’t need to reinvent the wheel, we’ve kind of invented it over the last five years in terms of where we’re at.

Don’t start doing this because we can tell you what that did. And a lot all this stuff is good. I don’t mean like.

You know, just because something didn’t pan out, it’s good relative to what it was before that at the time it was better. But you don’t need to five years later to select the metal rod fusion with the hybrid when we know you can do better, way better, with ASC itself, those kind of principles.

And where this might be going over time is just improvements in our implants but that will take probably a decade.

You know, it takes a long time to get through implant improvements that get processed properly. The cord that we use today, that original cord that came out from Zimmer, we started in 2011. That was approved in 1999 for low back surgery.

That’s where it came from. We used it from the low back system to here. And that means it had been studied for ten years prior to that all throughout the 90s. So it’s not a quick process. It’s about trying to maximize what you can do in the current field. And I think the improvements that will occur over the next several years is through teaching.

Like we’re going to have to expound this to others. VBT to me is not the answer. It was an answer at the time, but we’ve progressed so far past VBT and those principles need to get out there.


Dr. Lee:

Very good. Well, Dr. Antonacci, thanks very much for going over your information, your cases and your logic in terms of surgical decisions. Really appreciate it. I learned a lot. I think I have to review this about 10 times just to get a little bit more, have it sink into my brain a little more. Thank you very much and appreciate your time.


Dr. Antonacci:

Thanks, Derek. It was nice to talk to you.

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