At Dynamic Disc Designs, we believe research to be the foundation of our spine models so practitioners in musculoskeletal health feel confident in the use of an accurate model while they educate patients about their findings.  Historically, models have been inaccurate and most critically, static, making it very difficult for the doctor to be convincing to the patient in the accuracy of diagnosis.

Research is at the roots of any practice. It fuels practice guidelines and directs both the patient and practitioner down the best path of care. Our models help support that voyage. We have worked hard to bring the best to practitioners of musculoskeletal science by scouring databases of spine science, to arrive at the most accurate model for teaching possible.

With over 1000 papers read in full text, Dr. Jerome Fryer leads the way by making sure our models are keeping up to the standards of best evidence. Weekly literature searches on keywords that surround musculoskeletal health are at the core roots of Dynamic Disc Designs.

Dynamic Disc Model

This week, in Spine Journal, an ISSLS prize winning study was published on the dynamics of the disc.

What these researchers looked at was how nutrient uptake differed when the disc was exposed to:

  1. stationary position
  2. a high-rate, low frequency force and
  3. a low-rate, low frequency force

Their objective was to quantify the effects of mechanical loading rate on disc fluid movement into healthy and degenerative discs in vivo.

This research looked to measure what kind of forces could possibly draw more fluid into the discs. Conventional thought believed that ‘pumping’ of the disc did not have an influence on nutrient transport into discs as some previous work on diffusion rates into discs did not show that it mattered whether discs were moving or not. (Jill Urban) But now, new researchers showed that it is possible to influence nutrient flow into these avascular discs and best accomplished in a slow moving and constant way.

What they found was quite profound but makes some common sense. They observed that discs responded best to low-rate, low frequency forces. They used New Zealand white rabbits to test using an oscillative force equal to 0-200N (0-44lbs) over a 2 second period–similar to intermittent traction. Interestingly, they also found that the degenerated discs took up the fluid quicker than normal discs.

This research should have a significant influence on how we understand spine. It will influence exercise programs and also guide strategies in manual therapies like mobilization and decompression techniques.

Dynamic Disc Designs develops dynamic disc models to help with patient education and showcase the dynamics of the intervertebral discs in the management and treatment of spinal related disorders.


Disc Loading - Dynamic Disc Designs

The intervertebral disc is a unique structure and has a role in disc loading through its characteristics of poroelasticity.

It is the water-binding capacity of the nucleus pulposus that allows the disc to release and absorb water when disc loading and unloading occurs, respectively.

The intervertebral disc allows flexibility of the spinal column while having a fundamental role of vertebral spacing. The discs primarily resist axial loads during daily activities to be recovered in height during sleep and recumbency.

When discs degenerate, it is thought they lose their elasticity and the interstitial flow.

In a recent (Full Text) research article in Cells and Materials, Emanuel et al. looked to answer how a degenerated disc behaves differently in poroelasticity during disc loading.

These authors used 36 lumbar discs over ten days of disc loading. They categorized the discs into degeneration categories using Pfirrmann Score (PS) by way of MRI imaging.

What they found was degenerated disc have less binding capacity and respective poroelasticity when compared to normal discs. Degenerated discs lose more disc height when loaded and cause the vertebrae to approximate one another.


Dynamic Disc Designs highlights important research in the better understanding of dynamic disc concepts for effective patient education.

Facet Tropism - Disc Bulge

Facet Tropism is an asymmetry of the zygapophyseal joints and has been long thought to be related to intervertebral disc degeneration and back pain.

In a research article in The European Spine Journal, Wang et al. looked at how the degree of angle difference between the facets relates to disc bulge and back pain.

(Tropism comes from the Greek root (trope) which means to turn. In the embryological development of the vertebrae, some facets turn more than others and then in turn can have an affect on the overall biomechanics of the spine.)

In the research article (FULL TEXT) titled: “The relationship between degree of facet tropism and amount of dynamic disc bulge in lumbar spine of patients symptomatic for low back pain” , these researchers used Dynamic MRI to evaluate disc bulge and tropism by categorizing tropism into three distinct categories.

  1.  less than 6 degree difference = no tropism
  2.  6-11 degree difference = mild tropism
  3.  greater than 11 degree difference = severe tropism
What they found was that severe facet tropism was associated with disc bulge in only a subset of older patients.

Dynamic Disc Designs is a spine modeling company that highlights important research topics like facet tropism, and develops models that showcase natural anatomical details. Many of our models demonstrate facet tropism because they include real human variations.

Lumbar Model - Endplate Porosity

Porosity and thickness of the vertebral endplate depend on local mechanical loading.

In a recent publication in Spine, a group of researchers looked at the porosity and thickness of the vertebral endplate comparing mechanical stress from adjacent vertebrae to disc degeneration.

Much research has been uncovered regarding what contributes to back pain.  Some of the factors were reminded to us in the wonderful introduction to this research paper. Nutrient flow into the discs continue to be one of the hot topics in the cause and prevention of disc degeneration. Vertebral endplates are also important to understand in the realm of back pain because they are innervated by the basivertebral nerve. And modic changes are also known to cause back pain.

The endplate is a .8mm thick layer of hyaline cartilage backed by weakly bonded cortical bone which sandwiches the annulus and nucleus of the intervertebral disc. It is thinnest at the central region at the interface of the nucleus pulposus of the intervertebral disc and thickens to the periphery where the annulus resides. The perforations that contributes to the porosity are mainly at the interface where the nucleus exists. Regarding porosity, the hyaline cartilage is less permeable than cortical bone and therefore plays an important role in generating and maintaining intradiscal pressure to resist compression.  But at the same time, the permeability is important for nutrient supply to the disc.

These authors wanted to figure out the role of the porosity of the endplate and whether it is related to thickness or degeneration of the disc.

What the authors concluded was that porosity of the endplates were inversely proportional to the thickness being greatest in the central region. They also found that porosity increased with degeneration but not with age.

What they did interpret from the results was that certain areas of the endplate become thin because of reduced load and as well become more porous primarily because they become thin.

Clinically, this study is important because they showed that the nucleus pressure reduces as intervertebral disc degeneration progresses. This also has implications into vertebral fracture due to bone loss and increased porosity.

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low back pain - patient education

In a recent paper published in Patient Education and Counseling, these authors looked at how a doctor’s goal lined up with the patient’s goal in the management of low back pain.

Low back pain is the leading cause for disability worldwide, with a lifetime incidence of 80%.

What the authors of the research titled: “Patient led goal setting in chronic low back pain—What goals are important to the patient and are they aligned to what we measure? ” looked at was how the goals of a doctor was different to a patient’s goals.

The use of standardized outcomes for back pain often utilizes pain scales, range of motion, especially the act of bending forward without pain. Pain scales are perhaps important to the doctor but the goals of the patient includes a return to normal activity prior to injury.

Using bending forward as an outcome for function is well off the mark for outcomes as flexion stress in the disc often promotes inflammation and granulation tissue within the disc itself. Encouraging patients to ‘touch their toes’ as an outcome misinforms the discogenic pain patient (which is large percentage of back pain patients) of the movements that indicate outcomes.

Flexion stress on the spine compresses intervertebral discs that often leads to ongoing back pain in the long run. It may provide temporary relief from facet related pain, but disc height loss is inevitable if the spine is continuously flexed in this direction.

In Patient Education and Counseling, the authors looked at what was important to patients in goal setting of chronic low back pain. What they found was a patients’ goals were idiosyncratic and were not in line with therapists goals that usually include commonly used clinical measures.

Interpretation of the research:

The quirkiness of a patient’s goal often is governed by the education a patient receives about ‘why they hurt’. Chronic pain patients often struggle with understanding their own pain generators because of the plethora of mis-information about their diagnosis and solutions related to their problems. Giving a patient the understanding of their own dynamic spinal anatomy is one of the most powerful tools a therapist, doctor, spine surgeon, or chiropractor can do to help in the management of their symptoms. Teaching them something as simple as flexion and extension and how it relates to load is at the foundation of spine education.

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Discogenic pain is controversial–or is it?

Low back pain is common, really common, and responsible for the second most common reason why people visit their doctors. And yet, it still continues to elude scientists of its specific origin.

One convincing theme in low back pain are findings associated with the intervertebral discs. Often it is first recognized with reduced disc height on x-ray and then if persistent, followed up with MRI demonstrating the same but with evidence of hypointesity in a T2 weighted MRI. Most researchers agree that this finding indicates a reduction in water and proteoglycan content.

Discogenic Pain Model - Dynamic Disc Designs

Professional LxH Model demonstrating discogenic pain

Since the development of upright MRI, we are now able to see the spine under load and motion. This has provided us a window into the dynamic movement of the vertebrae and the discs in between them–showing spondylolisthesis in flexion and retrolisthesis in extension.

Some believe the only way to discern whether the disc itself is the painful anatomical structure, is to do a discogram. This is a procedure that punctures the disc with a needle and over pressurizes it to see if it is painful to the patient. This is kind of like over inflating a bicycle tire. The problem with this procedure is we know when a disc is punctured, it facilitates the degeneration process.

Discogenic pain is often a deep kind of pain because it is an anterior structure and heavily innervated. It is often relieved by lying down and worse with sitting.  It is also known to get sore after a long period of recumbency–like after a nights rest.

Engaging and educating patients about these symptoms can curtail their worries and helps when 3d models are used to explain the avoidance of activities that increase intradiscal pressures.

Dynamic Disc Designs enables the practiotioner to explain the inner workings of the disc. When patients understand flexion load stresses the posterior annulus, they quickly get motivated to maintain their lordosis with bending and lifting. This modification behaviour improves outcomes with spine.

Discogenic pain is for real. We are learning more and more about how the discs are at the core of low back pain.

Patient Education - Cervical Models

Dynamic cervical spine models have been static in the past.

Research demonstrates MRI can show problems like disc bulge and disc herniation even though patients do not have symptoms. Interestingly, there has been a shift in clinical thinking that many MRIs are ordered unnecessarily and can lead to unnecessary surgery.

What we are beginning to learn is that specific MRI imaging may be better at looking at pain generators in the cervical spine. In a recent publication in the Journal of Orthopedic Science, these researchers looked at T2 mapping as a way to indicate whether the discs are symptomatic or not.

This has always been the problem with MRI imaging. Most pain generators are dynamic in nature. That is, most of a patient’s pain comes with moving in certain direction or moving in a certain direction for an extended period of time. To date, the only way we were to determine whether the interevertebral disc is painful, is use of the gold standard discogram.

This is an invasive procedure that pokes the disc, with a needle, and over inflates it, like a tire, to see how much pain can be generated in the patient. The problem with this procedure is that if you poke a disc it begins to degenerate. Researchers use this model to study degeneration.

T2 mapping MRI is non-invasive–at least we have no evidence, yet, to suggest it is. And T2 mapping is also suggestive that it is looking at the water content of the intervertebral discs.

The future of understanding pain generators of the spine will be a the careful analysis of disc height loss, water content of the nucleus pulposus, and dynamic MRI imaging.

An accurate and dynamic cervical spine model can help explain load related pain generators like disc bulging and disc herniation. Treatments targeting the restoration of disc heights and the lordotic curve will lead the way in decades to come. Dynamic Disc Designs produces models to encourage research and education.