Eye-Opening...

[Justin]

I read as many fulltext articles about ADR that my brain can fit. This publication really "stuck" with me after reading it. This article focuses on patients with scoliotic tendencies and the appropriateness of ADR in such situations. As I was reading the discussion, I noticed the discussion turned to normal patients (those that presented as a "normal" ADR case with no scoliosis pre-ADR) experiencing surgically induced scoliosis after ADR:

At tertiary referral centers for motion preservation, there are already alarming numbers of iatrogenic scoliosis deformities (Figure 2) either caused or exacerbated by lumbar disc replacement, particularly with unconstrained devices.

This abstract doesn't do the fulltext justice, but I wanted to pass this interesting read along:


Biomechanical Analysis of Rotational Motions After Disc Arthroplasty: Implications for Patients With Adult Deformities
[Surgical Decision-Making]
McAfee, Paul C. MD; Cunningham, Bryan W. MMech, Eng; Hayes, Victor MD; Sidiqi, Farhan MD; Dabbah, Michael MD; Sefter, John C. DO; Hu, Nianbin MD; Beatson, Helen BS

From the Spine and Scoliosis Center, St. Joseph’s Hospital, Baltimore, MD.
The device(s)/drug(s) that is/are the subject of this manuscript is/are being evaluated as part of an ongoing FDA-approved investigational protocol (IDE) or corresponding national protocol for cervical disc replacement and lumbar disc replacement intended for degenerative disc disease.
Corporate/Industry funds were received in support of this work. Although one or more of the author(s) has/have received or will receive benefits for personal or professional use from a commercial party related directly or indirectly to the subject of this manuscript, benefits will be directed solely to a research fund, foundation, educational institution, or other nonprofit organization which the author(s) has/have been associated.
Address correspondence and reprint reprints to Paul C. McAfee, MD, Scoliosis and Spine Center, O’Dea Medical Building #104, 7505 Osler Drive, Towson, MD 21204; E-mail: mack8132@aol.com


Abstract
Study Design. An anatomic and biomechanical bench-top basic scientific comparative analysis to determine the appropriateness of total disc replacement (TDR) in a lumbar spine with scoliotic tendencies.

Objectives. Only limited data are currently available studying the application of disc replacement adjacent to scoliosis fusions. Theoretically, motion preservation should help delay the continuum of lumbar degeneration adjacent to scoliosis fusions and rotationally unstable lumbar segments.

Summary of Background Data. As a tertiary referral center for failed TDR, we noticed an alarming number of lumbar spinal rotational iatrogenic instability patterns but none occurring in the cervical spine. It is appropriate to analyze the bench-top rotational stability of disc replacement to predict whether this new technology is feasible for a larger prospective clinical study in the treatment of degenerative scoliosis.

Methods. Measurements were taken from 60 human specimens from the Hamann-Todd Osteological Collection: 1) to determine the rotational arc of influence (AOI) = the angle formed from the center of axial rotation to the outermost extent of the facet joints; and 2) to determine the relative anatomic size discrepancy between the left and right facets proportionately with the cross-sectional area of the intervertebral disc = facet/endplate ratio (FER). Biomechanical testing was performed using fresh frozen human cadaveric spines with the following conditions to determine the rotational stability: 1) intact; 2) resection of ALL, anulus, disc, and PLL simulating the preparation for a TDR; 3) a more radical anular resection; 4) entire 360° anular resection; and 4) insertion of the respective unconstrained-type disc replacement. Using a 6 degrees of freedom spine simulator, unconstrained pure moments of ±8.0 Nm (lumbar) and ±3.0 Nm (cervical) were used for axial rotation with quantification of the operative level range of motion and neutral zone, with data normalized to the intact spine condition.

Results. There were anatomic limitations in the lumbar spine that make it less desirable to apply uncon-strained disc replacements; indeed, the spine was at risk for iatrogenic lumbar scoliosis. The anulus fibrosis, anterior longitudinal ligament, and the posterior longitudinal ligament are critical structures in preventing iatrogenic scoliosis. The lumbar facet joints are more posteriorly located and are smaller relative to the intervertebral disc, compared with this association in the cervical spine. Because the facet capsular ligaments are mechanically less effective with lower tensile strength in the lumbar spine, multiple-level arthroplasty tends to accentuate scoliotic tendencies; this is independent of prosthetic design and surgical technique.

Discussion. Implantation of the lumbar TDR never restored the motion segment back to the rotational stability of the intact segment achieving a range of 120% to 140% rotational range of motion compared with the intact condition. This rotational instability proved to be additive as a two-level lumbar TDR resulted in between 240% and 260% increase in rotational instability compared with the intact condition.

Conclusion. The neutral zone of the intact cervical spine was restored even using an unconstrained cervical TDR. The greater inherent rotational constraints of the cervical spine make it more amenable to stable multilevel arthroplasty compared with the lumbar spine.

From the fulltext....


Conclusion
1. There are four main rotational stabilizing considerations in the functional spinal unit, and all four favor cervical versus lumbar rotational integrity.
2. Compared with the intact nonoperated motion segment, the preparation for both cervical and lumbar disc replacements compromises the axial rotational stability of both the cervical and lumbar spine: resection of the ALL, stretching or “release” of the PLL, increasing the disc space height which “unlocks” the posterior facet joints, and removal of portions of the uncovertebral joints in the cervical spine.
3. With an unconstrained prosthesis, the uncovertebral joint can be resected and the rotational stability of the intact cervical segment can be restored, but not with bilateral uncovertebral joint resection.
4. Implantation of an unconstrained lumbar disc replacement fails to restore the acute rotational stability of the lumbar spine. However, with an unconstrained prosthesis in the cervical spine, the rotational stability is restored within the NZ of the intact condition. With multilevel or successive lumbar artificial disc replacement, the instability is additive: what is lost in resecting the anulus, ALL, and PLL is not compensated for totally in the acute postoperative condition.
Key Points
* Total disc replacement accentuates scoliotic tendencies in the lumbar spine.
* There are four main rotational stabilizing considerations in the functional spinal unit, and all four favor cervical versus the lumbar rotational integrity.
* There is a larger arc of influence for the cervical facets (153.6°) compared with the lumbar facet joints (98.0°).
* The combined joint surface area of the cervical facets relative to the cervical disc cross-sectional area (0.519) is almost twice the magnitude of the same association in the lumbar spine (0.293).

[cathydownunder]

I read this article with interest, as you can see from my profile I have scoliosis(idiopathic). I also have/had flatback syndrome which is referred to here (iatrogenic scoliosis).From what I've read it usually occurs after long lumbar fusions, I've never seen a correlation between it and TDR? It's the long instrumentation that stops the natural lordosis so I don't understand how a 1 level TDR could have so much impact?
My scoliosis is 35* so is considered moderate. One of the things my surgery was hoping to address was to give me back some of the lordosis I'd lost, and according to hubby it appears to have worked. Because my scoliosis is thoracolumbar I had the fusion above the TDR as that's where the main curve is and where the most instability and rotation occurs. Of course a lumbar curve has to compensate in the thoracic region to balance itself out leading to other pain and degenerative issues there so it's a no-win situation.
I'd be interested to hear anyone else's point of view on this topic and if they've had the problems indicated. I don't recall seeing anybody on the board with scoliosis besides me.
Cathy

[Justin]

Bumping this up, as I got an email today from a patient that has ADR-induced scoliosis.

[Liz]

thanks justin.

this is an article that highly disturbed me when i saw it for the first time post-op (unfortunately).

out of curiosity can you disclose if this patient had multi-level lumbar ADR w/an unconstrained device (like Charite or Kineflex)?
if i can help at all feel free to pass along my info to this patient.

Cathy and i have corresponded about our struggles w/ADR and idiopathic scoliosis.

i have seen one of the authors of this article... he thinks my lumbar curve (which is my compensatory curve) has increased by 5 degrees post-op but this is up for debate. he thought i'd be much worse off if i had Charite or even Kineflex.

it's interesting that the stability of the cervical spine does not seem to be affected by multi-level ADR.

some people's degenerative scoliosis has supposedly been helped by ADR, but you just don't know where you'll end up and it's a mess to fix it. patients also need to ask about whether the entire annulus will be removed for ADR as the authors indicate 360 re-section can lead to more instability. just the front of mine were removed.

[phylly]

Justin,
I have also been reading a great deal. I trusted my Dr. when he said that 2 levels were better than one level. Supposedly those patients also had healing of mild facet inflammation. Would the x-rays pots-op show the scoliosis?
Liz, I never asked about the annulus. Did you ask prior to surgery? I have trouble getting this type of info but I agree you can end up with a mess.
Phylly

[Justin]

Originally Posted by phylly

Justin,
I have also been reading a great deal. I trusted my Dr. when he said that 2 levels were better than one level. Supposedly those patients also had healing of mild facet inflammation. Would the x-rays pots-op show the scoliosis?
Liz, I never asked about the annulus. Did you ask prior to surgery? I have trouble getting this type of info but I agree you can end up with a mess.
Phylly

Hi Phylly,

X-rays would demonstrate scoliosis post-op. The surgeon will compare previous films to detect movement of the prothesis as well as any change in the curvature of your spine.

Liz... the patient was a multilevel Charite. She has a slight increase in her scoliotic curve that *was* present pre-op. She is doing well at the moment, but she is keeping a close eye on things.

I hope both of you are doing well.

[treefrog]

Justin, I'd like to read the full text of this article. Is the journal "Surgical Decision-Making", because I wasn't able to find it in my University's e-journal search.

Oh, never mind I was able to find it by doing a key word search. It is in Spine Volume: 31, Issue: 19 Suppl, Date: 2006 Sep 1, Pages: S152-60 (for anyone else interested).

Oh, and I'm glad to read that the ProDisc-L is semi-constrained, that's good news for me, as that is the one I am considering.

[phylly]

Justin,
I am interested to know how you are feeling? Did you ever hear from your Dr.? If you being worked up for other disc problems, what are they? Level 8 pain is terrible. That is where I am most evenings.

So far one Dr. feels I have mechanical pain that can only be fixed by a fusion to stop the movement. I am trying to reach Dr. D. who did my surgery but have only talked to his PA. Basically I am on schedule for a new CT myelogram to rule out any problems from the last decompression surgery and make sure that when they go in (IF I let them) they know exactly what is there. I have 3 more surgical consults in January and am getting a MRI neurogram If my ins approves it. i want to leave no stone unturned. I am even trying acupuncture but alas, nothing yet.

I envy those of you that have had relief for years. Sadly, my case is that small percentage of cases that fail. I keep wishing for something as small as a bone chip but no one thinks that could be it???

Please keep in touch with your progress. I know that I am very interested in what you find out and what you will do. I keep hoping that you feel better again soon.
Phylly

[KBear]

Originally Posted by phylly

Sadly, my case is that small percentage of cases that fail. Phylly

Phylly, I can not imagine having ADR fail. I feel so bad for all of you who have not had success. I'm sure it is a hard blow to take. It is good that you are continuing to search for answers and are being thorough.

Unfortunately, we all fit into the failure of conservative care. I was told that I was in the less than 10% group of people that do not heal on their own, or with conservative care. I know that was a hard realization to take, knowing that I had reached the end of that road. So, I cannot imagine being told that I was in the failure group for ADR too. Know, I pray for all of you to find the help you need and deserve. I pray that I am one of the ones that surgery does work for; but it is a chance we all take having ADR, or any other surgery for that matter.

Best Wishes,
Kathy

[cathydownunder]

I opened this post thinking it was a new one (didn't look at the date) and was surprised to see a reasonably sensible reply from myself. It's scary how since then my brain has pretty much turned to mush and I have difficulty with recall and articulation.
Im blaming my Lexapro and the Fibromyalgia fog or whatever else Ive got going on, but it sure isn't a pleasant feeling.
Back to the topic....Liz, I had little or no annulus to remove as I was pretty much bone on bone and I still had problems but it's certainly food for thought.
Also the Maverick disc is constrained so theoretically there should be little movement so I don't know why it didn't work on me.. hence the revision to Dynesys. So many questions....so few answers...
Justin as for the scoliosis......before first surgery was thoracolumbar 35*, xrays 2 years later show 45* (if accurate), with the progression only becoming evident post-op after being stable for 30 years. Hmmm.