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.


Low rate loading of intervertebral disc disease

low rate loading of intervertebral disc

Low rate loading of intervertebral disc disease (IVD) demonstrated enhanced net transport into the intervertebral disc In Vivo in a recent study published in The Spine Journal.

These authors looked low rate loading (0.5hz )  of rabbit subjects and measured the uptake of gadodiamide. What they found was low rate loading improved lumbar disc clearance from the nucleus when compared to the unloaded subjects’ discs.

Dynamic Disc Designs Corp. applauds the authors on this publication. Mechano factors in understanding the regenerative potential of degenerated discs is an important field to continue to research. Understanding the basic anatomical science of biorheology in and around the intervertebral discs will lead to better manual treatment strategies in the future.

These authors provided an important puzzle piece in revealing the frequencies discs best respond to. Mimicking the natural biomechanical forces that discs experience in the human body like blood pressure (which is 1.33Hz at 80 beats per minute) and breathing (which is 0.25Hz at 18 breaths per minute) should provide ongoing clues as to the optimal bio-frequencies that will provide the most promise in regeneration.

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Back Pain with Sitting

sitting and back pain

Many people experience back pain with sitting.

In a recent study published in the American Academy of Physical Medicine and Rehabilitation titled : Changes in Lumbar Disk Morphology Associated With Prolonged Sitting Assessed by MagneticResonance Imaging  these authors used mid sagittal lumbar magnetic resonance imaging to evaluate continuous sitting and sitting with positional changes every 15 minutes.

They asked subjects in one group to sit continuous for 4 hrs while comparing a group that would stand up every 15 minutes and perform 5 seconds of lumbar flexion, 5 seconds of lumbar extension, 5 seconds of lumbar bending to the right, and then 5 seconds of lumbar bending to the left before returning to a seated position.

They did not find any significant changes in the disc morphology except at L4-5 after day 1 but not day 2 and concluded that L4-5 height changes were not significant with brief positional changes every 15 minutes.

At Dynamic Disc Designs, Dr. Jerome Fryer reviews papers to continue to develop models for professionals. He applauds the authors of this paper and finds the results of the manuscript predictable.  He explains ” the discs respond to unloading forces. If one suspects the discs as the pain generator associated with sitting, then postural strategies to improve disc health should include unloading forces” like in his paper, Magnetic resonance imaging and stadiometric assessment of the lumbar discs after sitting and chair-care decompression exercise: a pilot study whereby changes to disc were seen using the upper extremities to unload during positional changes of 15 minutes of sitting

If the net forces with positional changes are in the constant direction of gravity, (I.E, – y ) then the discs do not get a significant break
-Dr. Jerome Fryer explains

He also understands that his research is limited by way of subjects, but continues to see outcomes in practice with this type of off loading strategy.

As we continue to move forward in a world of more sitting, strategies that include off loading of the spine will be of more interest.  The intervertebral discs are hydraulic structures that lose up to 25% of height over the course of the day while vertical. Recumbancy and sleep has already showed how these structures recover. Sivian et al. showed in Biorheology how the disc cells behave. If we do not off load the discs, they will not have a chance to recover.

Dynamic Disc Designs continues to develop lumbar models and cervical models to help explain research in hopes to develop better techniques to improve spine health with our ever increasing world of technology and back pain with sitting.

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Intradiscal pressure and height

Disc Height Model

Intradiscal pressure depends on the understanding disc height loss and its relationship to load.

In a recent publication titled: Intradiscal pressure depends on recent loading and correlates with disc height and compressive stiffness, these authors tackled an important topic to help reveal the deformation an intervertebral disc will experience when subjected to prolonged and oscillatory loads. Often in clinical settings patients will experience low back pain as a result of cumulative and repetitive loads on the spine. It is therefore important to educate the patient on the reasons why pain may generate as the vertebrae begin to approximate. In their methods they tested 15 lumbar goat discs and found that as the pressures decreased over time, the heights of the discs were reduced significantly.  Past ideas around intradiscal pressure and height loss did not think that recent loading events played as much of a role as seen in this publication. Over the course of 4.5 hours of varying high and low dynamic loading, the disc heights reduced significantly. In human discs it is well known that spine pain is more likely to generate from a disc that is compressed vs. one that has normal height. Dynamic Disc Designs construct dynamic disc models to help the educator explain the pain sites in an interactive and research supported way. Explore.


Facet joint innervation

Synovial Joint - Synovial Fold

Facet joint innervation is much more than just the medial branches.

In a manuscript by Mapp and Walsh titled : Mechanisms and targets of angiogenesis and nerve growth in osteoarthritis , they reviewed articles that addressed angiogenesis and nerve ingrowth of the synovial joint including the osteochondral environment in the paradigm of osteoarthritis.

These researchers looked at the anatomical environment of the osteochondral junction as well as the meniscal tissue. They suggested it was a difficult task to determine what ‘normal’ is when factoring in the age-related factors. Angiogenesis is a normal part of development but it is also pathological when looking at cancer and osteoarthritis mechanisms. Angiogenesis cultivates nerve ingrowth as neurovascular bundles travel together. Most pain from the facet is thought to come from the medial branches but there are also nerves from the subchondral area that are similar to the basivertebral nerve innervating the endplate. As cartilage is damaged, underlying subchondral bone can be exposed where the tide mark exists and it is thought to drive this angiogenesis and nerve ingrowth.

The knee is the most commonly studied synovial joint. Interestingly, the meniscus (a fibrocartilage) is thought to be only innervated on the outer third. For those that have studied the intervertebral discs, this should sound familiar. We know in the spine, the outer third of the disc is innervated. It is also fibrocartilagenous with very little blood vessels. In this publication by Mapp and Walsh they talked about when the meniscus is damaged, nerve ingrowth into tissue that is normally not innervated, becomes innervated and sensitive.  We know this also occurs in the intervertebral discs and modeled in the Professional LxH Model.

Facet joint innervation is therefore found to exist not only with the capsular tissues that engulf the synovial joint but also deep within the joint itself. At the osteochondral junction nerves grow from the subchondral bone and into the underlying osteochondral areas. Furthermore, osteophytes (bone spurs) have been shown only to occur on the periphery of synovial joints. The exact mechanism of their development is not known. Some theorists believe they are a result of chondrocyte proliferation as they look like epiphyseal growth plates.

One common theme that resonates across all joint pathologies is the reduction of joint space width. Therapeutic strategies to increase joint space should always be explored when looking at ways to reduce pain.

Dynamic Disc Designs Corp. strives to provide a dynamic look at pain generators in a model platform that professionals can feel confident in using when explaining pain syndromes to their patients.


Progressive Disc Herniation – Dynamic Disc Designs

progressive disc herniation model

Progressive disc herniation often occurs to the annulus  over the course of many individual injuries.

Disc herniation is now classified into protrusion, extrusion, sequestered as well as contained or not contained. It is often progressive in nature. It all begins with radial tears to the inner most annulus when the lemellae delaminate as the hydraulic stresses out compete the tensile strength between the endplates.

As the outer annulus is innervated, continued stress and tearing to the fibres can begin to reach the innervation of the disc. Repetitive flexion pushes the nucleus pulposus posterior into the sensitive outer third of the anulus. When this fissure becomes chronically spread apart, often granulation tissue forms around the tear causing intradiscal inflammation. It is now believed that disc innervation is similarly innervated like an organ with sympathetic nerves which is why it may lead to chronic spinal pain syndromes. When these nerves (sinuvertebral nerves) embedded in the posterior annulus are irritated from the stresses of the nucleus–often done in lumbar and cervical flexion– people often complain of morning stiffness.  This is a cardinal sign of degenerative disc.

Dynamic Disc Designs manufactures models that provide the practitioner with models to describe a patient’s spinal symptoms. Whether the concept of nerve root entrapment due to extrusion requires surgery, or the patient is experiencing facetogenic pain due to disc height loss and would respond to manipulation, or the patient has a symptoms of stenosis due to a thickened ligamentum flavum and experiences bilateral leg symptoms after a period of walking, these new dynamic models are helpful in the connecting what doctors know and what patients are often confused about.  ddd hopes to build better doctor patient communication through more effective spine education for all spine professionals.

Dr. Jerome Fryer, the founder of ddd, has been lecturing on topics of education to professionals to help improve outcomes for spine.


Poromechanics of the Disc

Endplate, intervertebral disc

Poromechanics of the Disc is an important topic to understand regarding manual spinal treatment and prescribing exercise.

Manual treatments performed by chiropractors deliver forces that influence the disc. Even though spinal manipulation is thought to be a considered conservative method in the treatment of disc herniation, more recent investigation by way of pressure transducers with manipulation shows an alternative view.

There are many styles of manual treatment to the spine. Most classic is the side posture manipulation that renders a rotational force to the disc to gap the facet joint. The action of this can be seen in our spinal manipulation model. This has a primary effect on the facet but must also have an impact on the disc itself.

Other manual treatment strategies to the spine include flexion/distraction and decompression. These treatment strategies work on the poromechanics of the disc. This type of treatment looks to improve the hydraulics of the disc by creating low pressures within the disc to help improve disc height. In a recent publication in Arthritis and Cartilage, the authors looked at the poromechanics of the disc and graphically represented the flow through the endplate.

Dynamic Disc Designs strives to highlight research and represent this research through modeling to help improve clinical outcomes.

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Synovial Fold Release and Joint Cracking

Synovial fold, tag, meniscoid

Synovial Fold Release and Joint Cracking : a New Hypothesis for the Sound Generator has been created

In 2013, much work on simulating the synovial joint was conducted and led to in-vitro testing using ddd models to demonstrate the sound.
The mechanism of a cracking joint sound was produced with two factors in place.  The precursory details required to create the environment to produce the sound of an audible release were:

polished simulated cartilage surface and elastomeric simulated synovial fold. No fluid or gas was required.
  1. Negative pressure was required to induce the noise
  2. Negative pressure was required to re-produce the noise
  3. Different sound characteristics (differing tones) were observed when different material properties were used for the fold—both in size, shape and intrinsic qualities (ie., elongation, tensile strength and durometer).
Points to support this suction release phenomenon in a vitro testing environment.
  1. The noise generated from a suction cup release is not a gas rushing into the negative space but the elastic recoil of the cup material itself.
  2. This noise is generated both without fluid (in air) and in fluid (in water). This provides support that the sound is irrespective of the environment and more related to the elastic properties of the simulated fold.
Other points.
  1. Audible releases have different sound signatures. Not all events are identical.
  2. Audible releases of differing synovial joints make different sounds. For example, a 5th MCP joint makes a different sound when distracted when compared to the 1st MCP. This is believed to be due to the shape of the fold/hyaline interface.

Clinical translation? Once we begin to identify the process of the noise generator, this will help lead us to better understand the pressures in and around the cartilage to improve mechanobiological therapies.