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Herniated Lumbar Disk – Review and Modeling

Published May 5th, 2o16 in the New England Journal of Medicine 1 is a review paper on herniated lumbar disk. Dr. Deyo opens the manuscript with a case presentation of  41-yr-old man. He develops progressive increasing lower back and leg pain from doing yard work. This involved pulling out large bushes. With a positive straight leg raise at 40 degrees, the most probable diagnosis is herniated lumbar disk.

About two-thirds of adults experience back pain some time in their life. Sciatica is often used to describe the result of a disk herniation as the sciatic nerve is the downstream nerve effected. A more appropriate term is lumbar radiculopathy. This is due to the proximal origin of the issue and the sensory and motor findings that presents along the sciatic nerve distribution.

Herniated Lumbar Disk

To help with patient education of a herniated lumbar disk, accurate modeling of the nucleus pulposus and annulus fibrosus is developed by Dynamic Disc Designs Corp. Now, a patient can understand the geometry and forces involved to create a disk herniation and may think twice about repeating the activity that causes the problem initially. Accurate patient education of herniated lumbar disk to reveal the mechanism of the injury is very helpful in the management of the condition. This is both in onset and rehabilitation as load with flexion causes the nucleus to push posteriorly.

herniated lumbar disk. lumbar, disk

Herniated lumbar intervertebral disk – important for patients to see how this happened

It is important for patients to understand what caused their symptoms as to change future behaviours. It is known that a herniated lumbar disk is caused by hydraulic compression of overloading the spine into a flexion moment as the posterior annulus is compromised causing radial fissures 2. And now, this never before seen event can be shown with a knowledge transfer to the patient in an easily understandable dynamic model to help improve outcomes.


  1. Richard A. Deyo, M.D., M.P.H., and Sohail K. Mirza, M.D., M.P.H. Herniated Lumbar Intervertebral Disk. The New England Journal of Medicine. May 5, 2016 1763-72
  2.  Samuel P. Veres, BEng, Peter A. Robertson, MD, Neil D. Broom, PhD The Morphology of Acute Disc Herniation. A Clinically Relevant Model Defining the Role of Flexion. SPINE 2009 Volume 34, Number 21, pp 2288–2296
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Intervertebral Disc – Stress Shielded by Facets – Dynamic Education

intervertebral disc, model, facets, stress shielded, dynamic, spine, patient education

The intervertebral disc annulus can be shielded by the facets. This is important for the patient to understand to help motivate exercise strategies to relieve their back pain.

Researchers have seen in studies that bending the spine backwards (extension) helps resist compression of the spine discs 1 especially when the disc has already lost some height. 2 3 When crafting exercises, and if the facets are not considered a pain generator, bending backwards, especially in the unloaded position, can be an effective strategy to help heal discogenic pain.

Several mechanisms have been proposed on why extension-based exercises aid in the reduction of back pain. One likely path is the direction the nucleus moves as the spine is bent backwards. It has been shown in several studies that the nucleus moves away from the posterior annulus in spinal extension 4 5 6 7 8 9

Dynamic Disc Designs Corp. is the only spine modeling company that demonstrates these findings in a dynamic spine education platform. The Professional and Academic LxH models allows clear visualization of the nucleus as the model moves through 6 degrees of freedom. Patient education that motivates and drives compliance through knowledge to improve clinic outcomes for spine.

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Osteoarthritis model – subchondral bone

osteoarthritis model, spine, facet, disc height loss

Osteoarthritis is a burden on the people of this world and a major cause of disability. It is considered a degenerative disorder, affecting the aging population as it erodes cartilage, disrupting subchondral bone, leading to osteophytosis, muscle weakening and inflammation to the structures within the joint. 1 An accurate osteoarthritis model would be very helpful for spine.

Historically, osteoarthritis has been looked at from the perspective of cartilage wear with newer insights and interest at the subchondral level. (sub = below + chondro = cartilage) In a paper published in Arthritis and Research Therapy, researchers gave special attention to the subchondral bone. 2

In the perspective of the spine, disc height loss has an influence on the facet joints which are synovial joints. 3 It is disc height loss (a measure of vertebra approximation or closeness) that has shown to have the greatest impact on the biomechanics of a spinal motion segment. In particular, it narrows the intervertebral foramen, causes disc bulging as well as annular stress, and the narrowing can have an effect on the vascular flow in and around the nerves that exit the spine directly influencing nerve roots. There are few other degenerative conditions that can have such a large impact effect on the musculoskeletal system. 4

In Figure 1. of Subchondral bone in osteoarthritis: insight into risk factors and microstructural changes 2 a beautiful histological image showcases the microanatomy of the: calcified cartilage, uncalcified cartialge, the subchondral bone along with the tide mark and cement line of a normal synovial joint. This is an important area of the facet joint.

osteoarthritis model

As mechanical stress is placed onto the uncalcified cartilage, stress will translate through this avascular structure and into the subchondral bone. Chondrocytes secrete glycosaminoglycans (GAGs) and collagen type II-rich extracellular matrix (ECM) that are essential for the maintenance and regeneration of the cartilage which acts to protect subchondral bone. 6 Articular cartilage is mainly water, contributing to 80% of its weight. 7 Interestingly, we have seen that there is a diurnal variation of the cartilage in cartilage 8 similar to what we see in the discs. 9

The bottom line is our tissues that marry our bones together are dynamic and are in constant change to mechanical forces. Disc height loss of the spine will cause the facet joints in the spine to compress and lead to arthritis if not carefully managed.

Dynamic Disc Designs develops models to help in the greater understanding of how a compressed disc can have a multitude of mechanical effects on a spinal motion segment. Understanding the load distribution as it occurs naturally with diurnal variation, lying down, or with injury lifting, or prolonged sitting can be of great assistance in managing the treatment of spinal osteoarthritis as a result of disc height loss and facet arthrosis. Patient education proves to improve outcomes of osteoarthritis when patients understand what not to do first and secondly, why it is important to continue to do safe exercise. 6

The Professional LxH Model demonstrates hyaline cartilage and perichondrial vascularization, while the Lumbar Spinal Stenosis Model demonstrates subchondral sclerosis helping in the education of facet osteoarthritis. A dynamic osteoarthritis model for spine is important to have if educating is a part of a physician’s clinical life.

“Helping doctors be better teachers”


  1. Grynpas MD, Alpert B, Katz I, Lieberman I, Pritzker KP: Subchondral bone in
    osteoarthritis. Calcif Tissue Int 1991, 49:20–26.
  2.  Li et al. Arthritis Research & Therapy 2013 2013, 15:223 http://arthritis-research.com/content/15/6/223
  3.  Arbit, E., Pannullo, S., 2001. Lumbar stenosis: a clinical review. Clin. Orthop. Relat. Res.(Mar), 137–143.
  4.  Disc height loss and restoration via injectable hydrogel influences
    adjacent segment mechanics in-vitro Christian Balkovec , Andrea J. Vernengo, Stuart M. McGill Clinical Biomechanics 36 (2016) 1–7
  5.  Li et al. Arthritis Research & Therapy 2013 2013, 15:223 http://arthritis-research.com/content/15/6/223
  6.  Blazek AD, Nam J, Gupta R, Pradhan M, Perera P, Weisleder NL, Hewett TE, Chaudhari AM, Lee BS, Leblebicioglu B1, Butterfield TA, Agarwal S. Exercise-driven metabolic pathways in healthy cartilage. Osteoarthritis Cartilage. 2016 Feb 27. pii: S1063-4584(16)01025-6. doi: 10.1016/j.joca.2016.02.004. [Epub ahead of print
  7.  The basic science of articular cartilage: structure, composition, and function. Sophia Fox AJ, Bedi A, Rodeo SA. Sports Health. 2009 Nov;1(6):461-8.
  8.  J Biomech. 2013 Feb 1;46(3):541-7. doi: 10.1016/j.jbiomech.2012.09.013. Epub 2012 Oct 24. Diurnal variations in articular cartilage thickness and strain in the human knee.Coleman JL, Widmyer MR, Leddy HA, Utturkar GM, Spritzer CE, Moorman CT 3rd, Guilak F, DeFrate LE.
  9.  Botsford, D. J. MD; Esses, S. I. MD, FRCS(C); Ogilvie-Harris, D. J. MB, FRCS(C)  In Vivo Diurnal Variation in Intervertebral Disc Volume and Morphology. Spine: April 15, 1994
  10.  Blazek AD, Nam J, Gupta R, Pradhan M, Perera P, Weisleder NL, Hewett TE, Chaudhari AM, Lee BS, Leblebicioglu B1, Butterfield TA, Agarwal S. Exercise-driven metabolic pathways in healthy cartilage. Osteoarthritis Cartilage. 2016 Feb 27. pii: S1063-4584(16)01025-6. doi: 10.1016/j.joca.2016.02.004. [Epub ahead of print
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sciatica – coughing, sneezing and straining

Sciatica, disc, model

Sciatica is often worsened by coughing, sneezing and straining. It is a sign that patients complain about in the case of back pain. In some, the act of coughing or sneezing can actually cause a disc herniation.

In a recent study in The European Spine Journal, researchers wanted to find out if the act of coughing, sneezing or straining is important in the assessment of nerve root compression or disc herniation on MRI.

In “A diagnostic study in patients with sciatica establishing the importance of localization of worsening of pain during coughing, sneezing and straining to assess nerve root compression on MRI” 1 they found that the worsening of leg pain with these actions which includes increasing intradiscal pressure 2 has good diagnostic value for nerve root compression and disc herniation with MRI.

The research revealed the importance of asking whether the patient has these symptoms in the history taking.

At Dynamic Disc Designs, our models showcase how compression will extrude the nucleus….helping patient’s understand their pain.

Quote by the famous Karel Lewit:

“The first task for the physician is to show the patient the cause of their pain”.

  1.  Eur Spine J. 2016 May;25(5):1389-92. doi: 10.1007/s00586-016-4393-8. Epub 2016 Feb 2.
  2.  Spine (Phila Pa 1976). 1999 Apr 15;24(8):755-62. New in vivo measurements of pressures in the intervertebral disc in daily life. Wilke HJ1, Neef P, Caimi M, Hoogland T, Claes LE.
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Back pain and radiculopathy – upright mri research

Radiculopathy, upright mri

Back pain and radiculopathy is common….very common. Furthermore, it is very common for patients to explain that it ‘hurts’ more when they are vertical. Then why are we mainly looking at supine MRI for findings? Supine MRI is helpful in ruling out pathology and does offer higher resolution with the 1.5 and 3.0 Tesla…but this magnet power is not necessary to investigate biomechanical problems.

In a recent research paper published in The Journal of Craniovertebral Junction and Spine [full text], these group of researchers looked at seventeen adults (10 asymptomatic and 7 symptomatic) and used the .6 Tesla MRI to evaluate the lumbar spine and pelvis in the seated position.

They looked at the “foramen area, height, mid-disc width, width, thickness of ligamentum flavum, disc (bulge, height, width), vertebral body (height and width), and alignment (lordosis angle, wedge angle, lumbosacral angle).” 1

Some of the important results showed significant foramen narrowing and disc bulge was 48% greater in symptomatic volunteers compared to asymptomatic volunteers. Thickness of ligamentum flavum increased as well.

Overall, the researchers were cautious in their conclusive remarks…like all great researchers. But the bottom line is that we all know that symptoms related to spine are often worse being vertical. It is a bit of a no-brainer to continue to investigate the tissue in its load bearing state.

Yet another reason why Dynamic Disc Designs knew it was inevitable that a dynamic model would be to market. They were the first to pioneer this patient education movement. Be sure you are equipped.

flexible spine model nerves


  1.  Nguyen HS, Doan N, Shabani S, Baisden J, Wolfl a C, Paskoff G, et al. Upright magnetic resonance imaging of the lumbar spine: Back pain and radiculopathy. J Craniovert Jun Spine 2016;7:31-7.
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High Intensity Zone (HIZ) – Posterior Annulus

High Intensity Zone

A high intensity zone should not be overlooked-especially with a symptomatic patient. This is a bright white finding on MRI, most notable on the posterior annulus.

High Intensity Zone

In a recent study in The Journal of Medical Investigation, researchers looked at the pathogenesis of low back pain (with and without leg pain) and described it being caused by annular fissures and disc degeneration. 1 2.

Here are some key point of the research:

  1. They identified that more than two-thirds of the high intensity zones were found in the lower lumbar motion segments with the most at L4-5 followed by L5-1.
  2. They commented that they were unable to determine whether the intensity of the MRI magnet played a role in distinguishing HIZs.
  3. It is important to identify reliable measures to find HIZs.
  4. New treatment strategies are developing for the treatment of HIZ including laser.
  5. HIZs are not only a measure of degeneration but an active inflammatory tissue.

Dynamic Disc Designs develope models to help identify the movements that can stress the posterior annulus. Visit the Professional LxH Model to see an example of a high intensity zone.

High Intensity Zone, HIZ, Lumbar Disc


  1. Rozen D. Discogenic Low Back Pain. Pain Prac. 1: 278-86, 2007
  2. Peng B, Zhang Y, Hou S, Wu W, Fou X : Intradiscal Methylene blue injection for the treatment of chronic discogenic low back pain. Pain. 149 : 124-9 2010
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Dynamic Loading of Intervertebral Disc Maintains Cells

Dynamic, Disc , Modeling, Research

Dynamic Loading of the Intervertebral Disc – Ex vivo culturing and what can we learn?

For decades, the study of the intervertebral disc and the process that leads to degeneration has kept researchers very busy. This quest to fully understand the mechanisms that lead to water loss and proteoglycan content of the nucleus pulposus seems to be in the forebrain of spine investigators in hopes that it will provide clues on how to reverse the degenerative process…or at least prevent it.

Degenerative discs are arguably the most common cause of low back pain 1 with the cost affecting millions of people worldwide 2. The intervertebral disc plays a crucial role in the maintenence of bony vertebral spacing in the spine to allow movement. And when it starts to fail, it compromises the biomechanics. So, the search for regenerative strategies continues and hence the reason for this write-up.

One of the foregoing approaches to studying ways to rebuild human discs is to culture them outside of the body which is called ex vivo (outside life) research. In a recent publication in European Cells and Materials 3 these researchers were able to maintain cell life by loading the disc in a dynamic way. The branch of science that looks at how forces can influence real living tissues is called mechanobiology.

By stimulating the discs with motion, the cells remained alive for 14 days without any blood supply. Interestingly, the cells died when too much force was used whereas using medium cyclic forces maintained their viability. You can read the full text here.

This kind of research is VERY important in the greater understanding of how to keep the most important structure in the spine happy and viable. It also leads the way in revealing how much force is optimal (and the timing of it) for a healthy spine.


  1. Adams MA, Lama P, Zehra U, Dolan P (2015) Why do some intervertebral discs degenerate, when others (in the same spine) do not? Clin Anat 28: 195-204.
  2.  Katz JN (2006) Lumbar disc disorders and low-back pain: Socioeconomic factors and consequences. J Bone Joint Surg Am 88 Suppl 2: 21-24.
  3.  European Cells and Materials Vol. 31 2016 (pages 26-39).