Sunday, October 26, 2014

Can realignment of adolescent idiopathic scoliosis actually help prevent and/or reverse disc damage to lower lumbar discs?

For my last 19+ years of practice at both Duke Medical Center, and Hey Clinic, I have had a lot of experience caring caring for the full age spectrum of scoliosis, from 3yo congenital scoliosis, early onset scoliosis AIS, Scheuermann's kyphosis and adult deformity.   This "natural history" experience has given me long-range insight on how to counsel patients and families in the younger age groups, seeing well beyond what most pediatric orthopedic surgeon would see in their career caring for patients up through 18.

I am also always on the lookout for the latest research on the disc biology, biomechanics, and basic science as well as clinical studies that look at the issue of curve progression, disc degeneration as a function of spinal alignment, and facet arthritis causes for accelerated wear that we often see in scoliosis later in life.

Recently at our Scoliosis Research Society Meeting in Anchorage Alaska, Dr. LaFage gave a very nice podium presentation looking at 3D analysis of the lumbar disc MRI images before and after adolescent idiopathic scoliosis (AIS) surgery.  Doing special volumetric analysis, she was able to show that the lumbar discs below the main curve in adolescent idiopathic scoliosis showed some signs of dehydration prior to scoliosis surgery. This might suggest that there is some early damage being caused by the misalignment of the vertebral bodies above and below the disc, which can put excessive stress on the disc affecting the extracellular proteoglycan matrix, as well as the possible cartilage cells that maintain that matrix.  (My undergraduate thesis work at MIT in Bio-Electrical Engineering actually focused on cartilage biomechanics, and how to measure in the lab the affect of mechanical loading and natural electric fields on cartilage growth and regeneration... more on that another time)  What is really cool about Dr. Lafage's research is that she was able to show that over the 2 years after scoliosis surgery, the lumbar discs actually REHYDRATED after the surgical realignment of the spine above the discs.  This happened at ALL  lumbar levels when the pelvic incidence was low (most common in AIS), and in some levels with high pelvic incidence (PI).  This research suggests that the realignment was actually REVERSING the early damage to the lumbar discs, which would be our hope to allow those lower 2-4 lumbar discs to last the patient another 80+ years!  Dr. LaFage did show that the degree of the effect of the rehydration was affected by the underlying pelvic parameters, which have to do with how sloped the starting point of the lumbar spine is (Pelvic Incidence)  

This research is consistent with the natural history I've observed in many patients, who seem to do very well after AIS surgery with correction of not only their primary curve but the compensatory curves above and below which are not fused, but correct on their own in response to the correction of the primary curve(s).  These patients in most cases will maintain their lumbar disc height and have very little or any lumbar pain.  This is in contrast to the patients who never had their adolescent idiopathic curves fixed, who later in life can have not only progression of their primary curve, but also collapse of the lower lumbar discs, which were actually "normal" and outside of the scoliosis area to begin with.  These patients in some cases are in so much pain and/or have documented ongoing progressive deformity that surgery is needed to fix not only the primary curve, but now the worn out discs and facet joints in the lower lumbar area -- necessitating a larger surgery with fusion all the way down to the pelvis / iliac wings.  

While it is tough to considering having your child/adolescent have a major spine surgery as a healthy asymptomatic adult, it probably does make sense to seek out possible second opinions especially who can help you and your child, and spouse figure out what is best for the LONG run... the VERY LONG RUN -- the next 80+ years.  You only get one set of discs and facet joints, and decades of misalignment can definitely take a toll, just as a misaligned car can cause car tires to wear out well before the expected 80,000 miles.   

This issue of premature lumbar disc damage and destruction is especially and issue with the thoracolumbar curves, since they involve more misalignment of the lumbar discs.  The degree of trunk shift (asymmetric "hour glass") also has a major affect on the biomechanical loads on the lower lumbar discs, due to the increased "moment arm" of the axis of body weight which applies additional torque / stress on those lower lumbar discs.  So, it is good to take a wholistic view of the spinal alignment, not just looking at curve magnitudes but overall trunk balance, and as Dr. LaFage points out, other measurements like pelvic parameters which could affect stress on the lower discs and wear and tear.

Here is a video of Dr. LaFage's presentation with her wonderful French accent.  Enjoy!

Lloyd A. Hey, MD MS
Hey Clinic for Scoliosis and Spine Surgery

1 comment:

Martin Duchesne said...

This is excellent research representative of in vivo stresses of poor biomechanics on a fragile disc where scoliosis further predisposes to injury. I will send a direct email to you of my wife who has a lumbar 40 degree curve and resulting L5 / S1 annular tear. Obvious to my doctor of physical therapy trained eyes L facets are jammed together (rotation) and further insult from a tilted bicycle seat ridden for 56 miles (extreme lumbar flexion, ant tilted pelvis). All equals unbearable force on annulus fibrosis. We have been blessed to find your blog and learn from your knowledge on many fronts. Regards, Martin/Sara Duchesne PT, DPT