dynamic disk

The dynamic disk plays a significant role in the resistance to compression. It is known to physically compress over the course of the day by as much as 20 percent with recovery achieved during sleep or recumbency. Its implications intertwined with back pain. 1 One of the focused investigations into its essential function has been its intrinsic ability to maintain and absorb water. Negatively charged proteoglycans contain properties that attract water, and it is this hydraulic characteristic believed to be at the core.

However much still is to be discovered; especially in the higher understanding how best to draw in fluid and recover the expulsion of this water under axial compression. In a manuscript published in the Journal of Biomechanics 2, researchers worked to answer the questions regarding loading and unloading of the dynamic disk.

The researchers revealed a new personality of the annulus fibrosis as playing a significant in the ability to absorb water. The annulus demonstrated both properties of viscoelasticity as well as the binding capacity to retain water. This information is new in the better understanding of how disks maintain vertebral spacing with regards to recovery. Load and unloading cycles are natural, but it is the intrinsic ability of the dynamic disk to maintain spacing over time that is important to continue to study. Congratulations to the authors for choosing a worthy investigation.

At Dynamic Disk Designs, we work to model the dynamic nature of the spinal structures to improve communication of spine science. Our work facilitates patient education and student teaching of spine. Having a model dynamic disk allows the better understanding of disk height loss over time to explain back pain mechanics and the respective hydraulic solutions.

posture, disc hydration

Disc hydration fluctuates naturally and diurnally. That is, over the course of the day/night cycle we (as humans) lose up to 20% of the water out of our spinal discs. 1 The intervertebral discs are sensitive to load and because of their visceo-elastic make-up they will deform under load. Most notable changes seem to occur under sustained or static loads. 2 3 4 5 6 Therefore, it is important to offload the spine, especially when one sits for an extended period of time.

Recently, a study published in the Lancet 7 looked at the 188 countries and followed them between 1990-2013 and revealed that the number one reason for disability was back pain. Yes, back pain! Not heart disease. Could we extract from this that it is perhaps the introduction of computers and more time sitting? There could be other factors but there little doubt that the human population is moving less and fixated in front of a computer….just like myself at the moment.

Lumbar Disc Changes Associated with Prolonged Sitting

Take a Break and Off-load

This 8 off-loading strategy is thought to relieve the compressive forces of the spine to allow it to refill slightly….interupting sustained compressive loads, which we know is harmful.

Interestingly, a paper published in the Journal of Human Evolution in 2000 9 looked at knuckle walkers and ‘compared to humans, all ape samples show dramatically less spinal disease, especially when considerng vertebral body involvement’ . The authors concluded that this significant difference was likely due to the gait mechanism. And obviously, they use their upper extremities to off-load their spines during the course of their gait cycle.

Therefore, it looks like if you behave more like an ape and use your upper extremities, your spine will benefit. Teach your patients to minimize compressive loads by integrating off-loading strategies in their day to decrease the creep and compressive responses in the spine…..keeping the discs hydrated to prevent disc height loss.


  1.  Urban,J.P., McMullin,J.F., 1988. Swelling pressure of the lumbar intervertebral discs: influence of age,spinal level, composition,and degeneration. Spine 13, 179–187.
  2.  Adams, M.A., Hutton,W.C., 1983. The effect of posture ont he fluid content of lumbar intervertebral discs. Spine (Philadelphia1976) 8, 665–671.
  3.  Kazarian, L.E., 1975. Creep characteristics of the human spinal column. Orthop. Clin. N. Am. 6, 3–18.
  4.  Keller,T.S., Spengler,D.M., Hansson,T.H. ,1987. Mechanical behavior of the human lumbar spine. Creep analysis during static compressive loading. J.Orthop.Res. 5, 467–478.
  5.  Koeller,W., Funke,F., Hartmann,F., 1984a. Biomechanical behavior of human intervertebral discs subjected to long lasting axial loading. Biorheology 21, 675–686.
  6.  Markolf, K.L.,1972. Deformation of the thoracolumbar intervertebral joints in response to external loads: a biomechanical study using autopsy material.J.Bone Jt. Surg.Am. 54,511–533.
  7. Lancet. 2015 Aug 22; 386(9995): 743–800. 
  8.  Fryer JC1, Quon JA, Smith FW. Magnetic resonance imaging and stadiometric assessment of the lumbar discs after sitting and chair-care decompression exercise: a pilot study. Spine J. 2010 Apr;10(4):297-305.
  9. Jurmain, R Degenerative joint disease in African great apes: an evolutionary perspective. Journal of Human Evolution (2000) 39, 185–203

The intervertebral disc is home to visceoelastic material than deforms under constant load. Its role is to keep vertebrae separated to avoid the bones to approximate one another. Many researchers have seen how the disc gets squashed more under a constant and sustained load. 1 2 3 4 5

compression of spine with prolonged sitting

disc height loss and sitting – spine education with dynamic model

Sustained load, as seen in sitting patients with low back pain, is a common clinical complaint that is difficult to describe for the attending doctor without an appropriate model. Why a patient experiences low back pain as a result of not doing anything can be difficult for the patient to understand but using a visceoelastic model that deforms under compression can be helpful in the compliance of improving posture strategies or in the simple drive to get up out of the chair.

Dynamic Disc Designs has just made life a lot easier for doctors to explain this compression phenomenon. Using only the finest materials, these patient education models for spine can be easily accessed to demonstrate how compression of sitting will reduce disc height loss–sending a clear message that the patient should do something to move and help recover the disc hydration.

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.

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.

Microgravity causes increased swelling to the intervertebral discs of astronauts yielding back pain.

In a study published in the European Spine Journal, researchers looked to understand more clearly the relationship of why disc herniation is multiplied by a factor of four after spaceflight. These researchers looked at the swelling disc height changes as it related to annular strain and how this impacted nuclear pressure while bending forward.

Herniation, protrusion, modelEight human lumbar functional segmental motion units were tested using a free-swelling technique to simulate the microgravity environment.

What they found was that by hyperinflating the discs with saline, so did the pressures within the intervertebral discs. There was also a connection seen with increased annular stress in flexion and compression.

Furthermore, Law’s et al. showed a decrease in flexibility when the discs where hyperhydrated–something that we are understanding more and more now, as Michael Adams published some time ago.

Dynamic Disc Design’s Fully Clear Lumbar Disc Model, for example, is ideal for demonstrating this exact mechanism to patients.

With this model, complicated research can be quickly explained to the patient in helping them understand why morning stiffness leads to decreased flexibility as the disc is hyperhydrated.

Use a flexion disc model to educate patients.

Research like this, which is so important to relay to patients as it helps explain their symptoms, is not always easy to communicate. Dynamic Disc Designs works to simplify the complex, making it easier for you, the professional, to convey important concepts that are easy to understand. Patients that understand are more compliant and this process will inevitably lead to better clinical outcomes. And in turn, it is the outcome that ultimately determines a doctor’s income.

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Disc Height - Patient Education

Disc degeneration is thought by many to be at the root of back and neck pain.

However, measuring degeneration has always been a challenge because of its elusive nature. One characteristic of degeneration that all agree on is disc height, or in other words, the spacing between vertebra. It is one of the most looked for finding on MRI, x-ray and CT when evaluating for a patient’s pain.

In a recent research paper by Andrew J. Teichtahl et al. in Arthritis Research & Therapy (2015) 17:297 DOI 10.1186/s13075-015-0820-1, these researchers found a dose-response relationship between the severity of disc degeneration and lumbar disc height.

The authors believe that their study provides the first evidence that lumbar disc height is a reliable and easily accessible measure in the determinant of lumbar disc degeneration.

Lumbosacral disc degeneration is very common with as many as one third of individuals showing disc degeneration in this region when investigated with MRI. Furthermore, with degeneration, it increases the risk by two-fold in the development of chronic low back pain. With these facts at hand, it is imperative to measure disc degeneration but this is not as easy as thought because of the varying definitions. Disc degeneration can be a complex condition with characteristics of cell proliferation, nucleus pulposus dehydration, annular fissures and clefts, endplate disruption and granulation changes.

Radiographic evidence of disc degeneration can also demonstrate endplate sclerosis, osteophytosis and joint space narrowing (aka, disc height). The most recognized technique to evaluate the degree of disc degeneration is the Pfirrmann’s method which is endorsed as a valid and reliable method of assessing intervertebral disc degeneration using MRI.

These researchers looked at MRIs from 72 community based individuals and found that disc height was the best quantitative measure as an outcome measure in epidemiological studies.

Dynamic Disc Models enables spine doctors to share important clinical findings ,like disc height, to patients in a dynamic and interactive way, demonstrating facet shingling, intradiscal findings and disc herniation on a dynamic platform to improve education of pain generators. An educated patient often is more compliant as they understand more clearly the movements and activities that can exacerbate their symptoms like excessive spinal flexion and incorrect lifting.