Our lumbar models are identical in size and geometry to a real cadaveric specimen. With careful construction of the soft tissues including a flexible intervertebral disc including an annulus fibrosus and a nucleus puplosus,  each model is meticulously hand-crafted to provide the most accurate modeling to help the musculoskeletal practitioner to engage with patients in a convincing way.

Lumbar models have historically been static and immobile, but at Dynamic Disc Designs, we have developed flexible lumbar models to help relay essential movements to the patient related to their pain triggers. Having a patient genuinely understand their body mechanics empowers the patient and improves outcomes.

Patient-centered care must include translational strategies to help a pain sufferer understand their origins. A dynamic lumbar model helps execute efficient and accurate patient education.

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Study Finds Annulus Fibrosus GAG Content Alters the Mechanics of Disc Torsion

Facet Joints, GAG, Annulus Fibrosus, Torsion

A recent study evaluated the role of facet joints in torsion using four different compressive preload conditions in healthy and degenerated lumbar discs—with, and without facet joints. The study also sought to develop a quantitative relationship between structure and function in tissue and torsion mechanics. The study found that annulus fibrosis GAG content substantially affects the mechanics of disc torsion.

Purpose of the Study

Because there is a large population of lower back pain (LBP) sufferers whose jobs involve excessive loading and rotating the lumbar spine, the authors of this study sought to quantify and understand how the facet joints in healthy and degenerated discs would behave under axial rotation scenarios. They did this by observing in vivo changes in spinal segments during torsional behavior. The intervertebral disc (IVD) is capable of stability and flexibility during most movement, receiving stresses and sharing them with the nearby facet joints and other surrounding structures. The facet joints should protect the disc from overload and degeneration by restricting motions that would cause damage to the spine, but some complex motions that involve axial rotation and bending during heavy loading can increase the chance of micro-damage and disc failure. How well the IVD and facet joints share loads is determined by the mode of loading and posture. Previous studies have demonstrated that up to 25 percent of axial compressive forces may be supported by the facet joints. Between 40 to 65 percent of healthy disc joint rotational and shear forces are also supported by the facet joints. Therefore, it is important to understand how the facet joints in healthy and degenerated discs react during torsion.

Study Design

Researchers obtained and imaged seven human cadaveric lumbar spine segments aged 43 to 80 years-old. The musculature and ligaments were then removed, and the intact facet joints near the discs were subdivided mid-vertebrae prior to the samples being potted in bone cement. The segments were then wrapped in gauze and stored in a phosphate solution until brought to room temperature just before testing. They were then mounted onto a testing machine and secured with screws.

The segments underwent a moderate-to-low preloaded axial compression, followed by axial rotation through the center of the disc. The cycles of compression and rotation were performed for two hours to allow the formation of creep. Ten cycles of cyclic rotation, and the samples were tested under four axial compressive preloads and allowed to recover between each test. The facet joints were then removed, and the samples were tested again, using the same loading configuration. For each round of testing, the researchers recorded the levels of force, rotation angle, displacement, and torque.

Isolating and Imaging Each Disc

Each disc was isolated and imaged after mechanical testing. Researchers measured the disc area, anterior-posterior and lateral width using a custom algorithm. Disc height was measured from the posterior, anterior, left, and right lateral sides, as well as the center. A mathematic formula determined the applied axial stress, and the images were graded and compared with radiographic-based grades.


The results of the tests indicated a strong correlation between creep and axial compressive preload and the loss of disc height. Removing the facet joint had no effect on this phenomenon. The presence of facet joints and an axial compressive preload did have a strong effect on torsional mechanical properties, with torsional stiffness and range decreased 50 to 60 percent for compressive loads after removing the facet joints. Energy absorption decreased about 70 percent during rotation after facetectomy, and disc-joint strain increased 74 percent, compared to only 62 percent in disc strain energy using the same axial compression.

Annulus Fibrosis GAG content in degenerated discs greatly reduced torsion mechanics, while the facet joints are integral in keeping the spine from rotating too far and helping to reduce shear stress and damage to the disc. The relationship between the biochemical-mechanical and compression-torsion levels noted in this study may help to provide for more effective and targeted biological repair methods for degenerating discs of various levels.


KEYWORDS: AF GAG Content Alters the Mechanics of Disc Torsion, role of facet joints in torsion, axial rotation scenarios, correlation between creep and axial compressive preload and the loss of disc height, targeted biological repair methods for degenerating discs

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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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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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Disc Protrusion Seen Sitting – Upright MRI Reveals

Disc Protrusion, Pain, sitting, back pain, upright MRI

Disc protrusion is defined by an extension of nuclear material extending beyond the confines of the annulus (if the base of the material is larger than the material protruding). In the flexed position, the nucleus pulposus is driven backwards (posteriorly) into the spinal canal. If there are nerves in the area, related pains can extend down into the leg (or legs) causing sciatica.

MRI is our powertool for looking at disc injuries. It was developed in the early 1980s and primarily used to look for pathological conditions like cancer. And because it was and still is important to keep the patient still, lying down (recumbent) MRI was the standard.

However, when looking for load related pain, lying a patient down is not always the best strategy as often a patient’s symptoms disappear when they are on their backs. So it would seem reasonable to image patients in a vertical or upright position to look closely at the tissues as they are loaded….this only makes sense.

Here is an example of how the diagnosis was seen when the spine was placed in the seated position. This patient only had symptoms while sitting. And you can see why below.

Disc Protrusion with Upright MRI

Standing, Case, Modeling, MRI, Upright

Pain, sitting, back pain, upright MRI

In this case, the patient demonstrates further protrusion with sitting…and the upright MRI clearly shows this difference from standing to sitting. This is why it is important to consider upright MRI when the patient presents with a load dependent complaint. Upright MRI can help with the diagnosis.

All MRI images on this page are property of Medserena Upright MRI Centre.

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Vertebrae Model Helps in Back Pain Education

herniated disc model

No one can truly estimate how many patients walk into chiropractic offices each year complaining of back pain. Chances are that that number soars into the millions…maybe even more.

Although chiropractors certainly treat more than just back problems, surveys show that it is the most common reason for visits, with about 80 percent of all people reporting some back pain during their lifetime, according to the American Chiropractic Association. Furthermore, low back pain can be very costly, accounting for lots of missed work and excessive amounts of money allotted for disability payments.

Vertebrae Model Aids showing nerveYet, if people understood why this back pain is present, chances are they would be likely to change the habits that are the cause. In Canada, the Canadian Chiropractic Association has taken a crack at educating the public about back issues, offering a phone app called Straighten Up Canada, designed to offer tips to improve posture and spinal health. It’s a good start, but can a phone app provide patients (or potential patients) with the info they need to make the right choices when it comes to their musculoskeletal health? Or do they need something more?

Vertebrae Model Aids Visual Learners

Many of us are “visual” learners. While hearing information indeed allows us to absorb facts, actually seeing a visual demonstration often prompts us to gather more complete information and process it in our brains. Visual learners, for example, will retain more if they read a story rather than listen to one.

In learning about chiropractic and its advantages, visual learners are usually offered posters and other drawings in hopes that they’ll understand why they are suffering with back pain. But let’s go one step further. A 3-dimensional, hands-on visual, in most cases, allows for even more retention of information, so offering the patient a vertebrae model rather than just an artist’s rendering of the spine can better help these individuals understand their musculoskeletal problems.

Vertebrae Model AidsThat’s where the Dynamic Disc Designs products enter the picture. 3-D spine models like these, which can be held in one’s hand and manipulated as needed, will provide a clearer picture of the inner workings of the body, even for those who have little or no knowledge of anatomy. A vertebrae model such as the Professional LxH is sophisticated enough to be a teaching tool yet it provides chiropractors with the opportunity to clearly and simply demonstrate to patients a variety of issues involving the spine and back and how to fix them.

A well-made vertebrae model can assist chiropractors in demonstrating the specifics of issues such as dynamic disc bulge, disc herniation, facet inflammation, disc height loss, degenerative disc disease, nerve pinching, stenosis, medial branch innervation, discogenic problems, annular fissures, and more.

A visual demonstration takes less time than a lengthy question-and-answer session, allowing both the doctor and patient an opportunity to save time and stay on schedule. Furthermore, when you’re making a visual demonstration that’s easy to grasp, patients won’t feel as if you’re talking “over their head”, spouting medical jargon that might be hard for the average person to understand.

Doctors who’ve already used DDD spine models note that patients respond positively to them, many having “light bulb” moments when they finally understand why they are experiencing a certain type of pain. And, of course, a good chiropractor knows that patient education is just as important a part of the visit as the adjustment, and a well-educated patient is more apt to follow your suggestions, prompting referrals from satisfied patients and, therefore, helping your practice to grow.

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Browse our vertebrae model store.


Degenerated Spondylolisthesis Model

A spine model with grade 1 anterior spondylolisthesis - useful for explaining spinal stenosis symptoms

Degenerated spondylolisthesis is the most common form of spondylolisthesis.

This condition is known to lead to spinal stenosis and found quite commonly in the elderly. When revealed by imaging, doctors often have to explain what this means to a patient without an accurate spinal model. An example of some research published on Degenerated Spondylolisthesis, a systematic review in the Journal of Neurosurgical Spine evaluated the degree and relative importance of stability in Degenerated Spondylolisthesis. In their manuscript titled: Defining the inherent stability of degenerative spondylolisthesis -a systematic review they revealed that degenerative spondylolisthesis can slip even further and can cause further symptoms which can be an important finding in the consideration of surgery or not.

The value in having a dynamic spine model, like Dynamic Disc Design’s Degenerative Spondylolisthesis ModelDegenerated Spondylolisthesis

is to educate patients on specific movements related to degenerative spondylolisthesis. Designed with accurate anatomical features ensures the doctor can feel confident using a model that patients quickly understand like :

  • Vertebra listhesis
  • Narrowed spinal canal
  • Arthritic facets
  • Subchondral sclerosis, osteophytes
  • Reduced disc height
  • Thickened ligamentum flavum
  • Disc bulge

More so, a dynamic disc can demonstrate advancing listhesis with manual compression–furthering the slippage of one vertebra on another to enlighten the patient on the movement process.

A wonderful model companion to our Degenerative Spondylolisthesis Model is our LxD Lumbar Spinal Stenosis Model which also shows identical anatomical details but without a grade one anterior listhesis. It features realistic bone quality and built to last.

Dynamic Disc Design’s focus is to streamline the doctor’s patient education–often in time-restricted clinical settings. Models in the past have been often inaccurate, nonexistent for many different pathological states, and static. Our goals are to be scientifically trustworthy, anatomically accurate, dynamic and durable. Explore our models to be sure you have the right one for the right teaching moment. Effective patient education of spine starts with having the right models for the right moment. Make it count.

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Spondylolisthesis Models

Spondylolysis Spondylolisthesis - Dynamic Disc Designs

Spondylolisthesis is simply the slippage of one vertebra on another.

The medical Latin root comes from the Greek root spondylos” and “listhesis” which means vertebra slippage. They are defined by either a slippage forward, backward or sideways. These are labeled as an anterior, posterior or lateral listhesis, respectively. There are several degrees of slippage defined by grades (1-5).

There are several reasons as to why vertebrae slip out of alignment with the leading reason being arthritis and disc height loss in adults. Recently, in the Journal Medicine, researchers looked at the importance of dynamic loading in detecting degenerative spondylolisthesis. In children, it is the lowest of the lumbar vertebrae most commonly affected. Sudden bending backward activities can cause significant stress on the spinal structures related to spondylolisthesis.

To read more about spondylolisthesis, you can click here.

Products and Patient Education

Spondylolysis Spondylolisthesis

Below is a video to show the second most common spondylolisthesis, called a lytic listhesis. Lytic comes from the word, loosening. You can see the bone has actually fractured. This is sometimes found in active children.

Degenerative Spondylolisthesis

In order to see the most common spondylolisthesis models, you can see the video below of a degenerative spondylolisthesis model.

Multilevel L5 Spondylolysis Spondylolisthesis

In order to see a spondylolytic multilevel spondylolisthesis model you can watch the video below

Double Spondy Model

Our most recent and multilevel spondylolisthesis is shows both a lytic and non-lytic pars in the Double Spondy Model.

Professional LxH Disc Model

Another popular model is The Professional LxH  Model with the optional feature of a spondylolisthesis.

Spondy Option

Interestingly, spondylolisthesis sometimes doesn’t show up with regular recumbent x-ray, CT or MRI. There is growing knowledge that some spines are required to be loaded in order to see the slippage effectively. Often symptoms come with load. Dynamic Disc Models can help relay that message to patients. If a spondylolisthesis option is ordered with the Professional LxH Lumbar Model, ‘unroofing‘ will be able to be demonstrated.

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