Dynamic spine models designed by chiropractors. Our spine models are scientifically accurate, showing details in the discs, lumbar, pelvis and cervical spine. They can be used to demonstrate a range of clinical conditions which contribute to back pain or discomfort. Our models use an elastomeric two-part intervertebral disc design to show important anatomical features so are perfect for chiropractors, osteopaths, spine surgeons, physiotherapists and medicine students. See the back under compression and conditions such as disc herniation, epidural punctures and more.

simulation model

Goal of the Study?

In this disc simulation model article from the BMC Musculoskeletal Disorders open access journal 1 the authors created detailed nonlinear 3D finite element models of the C2-C3 Functional Spine Unit.  The simulation models were tested, verified and then used to predict various biomechanical injuries such as tissue swelling and degeneration.


Why are they doing this study?

Spine simulation models, if constructed accurately, can be a very efficient tool to predict the impact of various biomechanical spine loading strains and stresses.  They must mimic as closely as possible real-world conditions.  Also, the range that the models are effective must be established.  Building an accurate simulation model that operates over a wide range of variables is the ultimate goal but it takes many incremental improvements to reach this stage.  This study represents one of these attempts at improving current spine simulation models.


What was done?

Three  3D Finite Element (FE) fibre-reinforced C2-C3 functional spinal disc models were developed with Linear Elastic (LE), Hyperelastic (HE) and biphasic Intervertebral Disc (IVD) behaviours. These three models were tested through two different loading modes; cyclic compression and sagittal bending, both flexion and extension.  Measurements included deformed disc height, disc fluid pressure, range of motion and stresses.  The three models were first validated with previous experimental models for compression, flexion and extension loading conditions and then compared to each other with the goal of finding the most robust model.

What did they find?

The two single-phase models; LE and HE failed to accurately describe the long-term intervertebral disc height decrease under cyclic compression loading when compared to other experimental data.  They were both a little closer under extension loads. All three models were accurate in predicting stresses during the flexion loading trials.  Overall the biphasic IVD model was the most robust.  It gave the best results in flexion and compression but was limited in extension loading.  Since this was only a partition spine model, C2-C3 there were issues with the inability to predict load sharing.  Given the inability to accurately predict load sharing the authors believe that a full spine model must be developed.


Why do these findings matter?

Cervical injuries and fractures are common in many contact-oriented activities and can be life-altering, as they can cause a permanent loss of neural functions.  Since it is impossible to test these conditions on people, simulation models must be developed.  These mechanical models must be robust and mimic as closely as possible real-world conditions.  The better these models are, the better we are able to test and understand various treatment alternatives.

Goal of the Study?

Lumbar spinal stenosis affects approximately 11% of the population, primarily in the adult population.1 In this article, the authors worked to provide a clinical update giving practitioners a “what you need to know” perspective on the ins and outs of clinical practice.


Why are they doing this study?

Because of its prevalence and challenge to accurately diagnose, it is important to understand the clinical presentation of lumbar spinal stenosis from a symptomatology standpoint. This careful attention to a patient’s symptoms can help guide an appropriate care plan. The clinical challenge can be cloudy as other conditions like vascular claudication can lead even the best clinicians down the wrong diagnostic path.


What was done?

A review of the anatomy is important when understanding the clinical symptoms of lumbar spinal stenosis. In this clinical update, the authors revisit the degenerative changes of the spinal canal and the intervertebral foramen related to spacing and the nerves that travel through these spaces.

Spinal Canal Spacing, Lumbar Spinal Stenosis Education Model

Lumbar spinal stenosis model


What did they find?

As the discs lose height, the associated anatomical changes can lead to narrowing. Degenerative discs lose height over time, and in doing so, the facets approximate, leading to hypertrophy of the bony architecture. Facet arthropathy (as seen in the Lumbar Spinal Stenosis Dynamic Disc Model) can take up valuable spinal real estate for lateral recess and intervertebral foramen; furthermore, discs lose height, discs bulge. And with this bulging, just as a tire bulges when it loses air pressure, it can often take up spinal canal spacing. This can also lead to the ligamentum flavum bulging itself (also thought of as buckling or thickening), encroaching on the valuable room the vasculature around the cauda equina must have to function.

The classic presentation is the patient reporting of not being able to distance walk as they have previously. They also report that standing often generates lower leg symptoms or buttock/leg weakness and relief of these symptoms by sitting and/or using the upper extremities to offload and flex the spine, like that seen with the shopping cart posture.

The authors point out that lateral recess stenosis and foraminal stenosis can mimic radiculopathy as seen in sciatica related to a disc herniation and report that a combination of these symptoms and subtypes is common.


How is Lumbar Spinal Stenosis Diagnosed?

A careful history and examination are at the roots of a proper diagnosis. Imaging has been relatively unreliable and likely due to the static nature of MRI and CT. It is suggested that clinicians can ask suspected patients to walk or to have patients extend the lumbar spine for thirty seconds to recreate the symptoms.

The authors have created these points and to be mindful of patients over 50 present with these symptoms:

  • pain in lower extremities/buttocks while walking
  • flexion to relieve
  • relief if using the upper extremities to push down and generate lumbar flexion like that seen using a shopping cart or riding a bicycle
  • unsteady motor disturbance while walking
  • tingling or numbness in the legs while walking
  • pulses equal and bilateral in lower extremities
  • low back pain


How do Clinicians Talk about Lumbar Spinal Stenosis with their patients?

Lumbar Spinal Stenosis Model

What tools do you use to educate your patients?




cervical degenerated herniated spine model

Goal of the Study?

The objective of this study 1 was to establish a three-dimensional finite element (3D-FE) model of the cervical disc and spinal cord to simulate an intervertebral disc compression injury of the spinal cord by controlling the expansion of specific parts of the disc model

herniated disc model

Why are they doing this study?

Cervical spondylotic myelopathy (CSM) is one of the most common spinal cord disorders in people older than 55. It is a degenerative disease that impairs the function of the spinal cord due to progressive and chronic compression. In advanced stages it can cause neurological issues ranging from neck stiffness, arm pain, numbness in the hands to more severe symptoms such as quadriplegia (tetraplegia).

To date, many of the in vivo and in vitro experimental studies focusing on impingement or compression are unable to simulate the sophisticated nature of spinal cord injuries. The authors speculate that computational models are better able to evaluate mechanical forces and spinal cord deformations. In particular, they argue that FE models may provide a way to more accurately simulate disc compression and therefore predict future deterioration and onset of CSM.

What was done?

The researchers developed a 3D FE (finite element) model of the cervical disc and spinal cord. This model was comprised of four distinct materials to represent the white matter, gray matter, pia matter and annulus ground. Cervical disc protrusions were simulated by applying thermal expansion to multiple FE unites to trigger bulging of the cervical disc either directly or indirectly.  

Three models of symmetric cervical disc herniation (median, paramedian and lateral) were created by evenly raising the temperature of corresponding FE units to 30 °C. The asymmetric hernia model was developed by rising the temperature of the paramedian type model gradually from 22 to 30 °C. They then used a linear regression analysis to determine the relationship between the various models and temperature changes.

What did they find?

Overall, the researchers found a correlation between rising temperatures and the gradual increase of severity of disc herniation. In all four models, herniated masses were observed at the region where thermal expansion occurred. In the asymmetric hernia model, the protrusion was more severe on the side with a high temperature increase than on the side with a lower temperature.  

They found that spinal cord compressions resulting from intervertebral disc protrusion were observed in all models, except the lateral type. The greater the cervical cord was compressed by the protruding disc, the larger the area with higher stress. Moreover, as the level of compression increased, the deformation of the spinal cord intensified and the stress was dispersed to the anterior horn and intermediate gray of the grey matter, which could explain the progression of neurological symptoms.  

Why do these findings matter?

A better understanding of the biologic mechanisms of spinal cord damage caused by chronic mechanical stress is required to improve diagnosis, treatment and clinical outcomes. In particular, FE models may provide a way to more accurately simulate disc compression  and herniated discs and therefore predict future deterioration and onset of CSM.


At Dynamic Disc Designs, we create models to help convey important teaching and educational instructions for students and patients. Explore our range of modeling.

vacuum sign

Vacuum sign is a common radiological finding. It is also referred to as a vacuum phenomenon and often associated with degenerative spinal discs, knee joints, hip joints, and shoulder joints.  Degenerative spondylolisthesis is a spinal condition whereby one vertebra slips on another. However, it is sometimes difficult to ascertain whether this slippage is stable or not. A more than 4mm movement defines instability, but some have indicated only 2mm as clinically significant.

degenerative spondylolisthesis model

Degenerative Spondylolisthesis Dynamic Disc Model

In a research paper published in World Surgery, 1 a group of authors looked at the vacuum sign in the facet joint as an indication of degenerative instability of the spine. They wanted to investigate the relationship between the vacuum facet phenomenon and lumbar instability. Why, you may ask? More and more research is directing spine researchers to the cause of pain and disability to the imbalance of motion of the individual vertebral segments of the spine. Some have coined this motion sharing.

Each vertebral motion segment consists of two vertebrae, and a disc should have a certain stiffness level. That is, it should move similar to its adjacent segment above and below in the spinal column. For this study, they looked at L4 on L5 (which is a prevalent spinal level to degenerate with age) and used flexion/ extension X-rays in both the fully bent forward (flexion) and the fully bending backwards (extension) with degenerative spondylolisthesis. Additionally, when available, they also looked at CAT scans of these same patients. To determine the slippage degree, they used a dynamic motion index to measure the degree of slippage.

In a total of 67 patients examined, 35 patients had vacuum signs on their CAT scan, and 32 patients did not. The degree of slippage appeared to correlate with the vacuum sign as well. That is, the more the vertebrae had slipped forward, the more likelihood of the presence of the vacuum sign. With this, the authors concluded a linear correlation between the degree of slippage and the presence of vacuum sign.

Vacuum sign

Vacuum phenomenon or vacuum sign and mobility

Commentary by Jerome Fryer

Vacuum sign or vacuum phenomenon is often considered an incidental finding. However, based on the modelling research I’ve done, I believe that the vacuum sign can be a clue into joint mechanics’ stiffness. In 2017 I published an article related to the cracking event we are familiar with, and in there, I believe in having revealed the vacuum phenomenon. In the presence of cavitation, a joint will have less stiffness, and in time I hope we can collectively use these radiographic findings to help us determine which joint requires more stability in the treatment of them. JF

lordosis. degenrative joint disease

Flat Back (Lack of Lumbar Lordosis) and Disc Herniation

Lordosis, or the lack of it, has been thought to be a biomechanical precursor to disc herniation in the lumbar spine. To investigate this possible correlation, a group of researchers from Gothenburg University looked at sixteen young active young patients with a median age of 18yrs old who experienced a disc herniation and underwent discectomy surgery. 1

Lordosis is the curve in the lower back—which they measured before and after the surgery.


Researchers used the Roussouly 4-type classification system to measure the degree of lordosis in the lumbar spine.

The researchers found less lordosis in the subjects that had surgery for their disc herniation. In other words, disc herniation was twice as likely to be present in the group with a flatter back. All the disc herniations were found to be in the lowest two levels of the lumbar spine (L4-5 and L5-S1), consistent with other epidemiological studies. 2

Dynamic Disc Designs Models

At Dynamic Disc Designs Corp. we have worked to represent the anatomy accurately. Our Professional LxH  Dynamic Disc Model is created with 12mm of disc height anteriorly and 10mm posteriorly providing a slight lordotic curve. Further, the model has been created with a higher percentage of nucleus pulposus which is often found in younger lumbar spines. To demonstrate that disc herniation occurs more likely with less lordosis all one has to do is dynamically move the single-level model into a less lordosis position and manually create compression. With more lordosis, the nucleus has a more difficult time penetrating through the outer annulus fissure. This can be an important posture teaching point in the prevention of disc herniation.

If you want to take your patient education to a dynamic level, explore what Dynamic Disc Designs models can do for you, your practice and ultimately, your patients.

A study 1 in the Frontiers in Bioengineering and Biotechnology investigated the in vitro glucose consumption as well as gene expression by NP cells (over time) while under varying oxygen tensions. The study’s objective was to gain data for understanding disc pathophysiology and to determine the therapeutic potential of notochordal NP cells.

Why such a Focus?

Low back pain or LBP is a common condition affecting millions of people around the globe. According to research, LBP has a relationship with the degeneration of the spine’s intervertebral discs. Furthermore, an imbalance in the catabolic and anabolic activity by disc cells is known to result in such degeneration. Due to intervertebral discs being avascular (in their nature), there may be an oxygen deficiency in the central NP or nucleus pulposus. While the mechanisms require further understanding, the matrix regulation and energy metabolism of the disc cells can be affected by the resulting hypoxia. Monitoring such affects might help with better LBP treatments down the line (including treatment and preventive strategies for degenerative intervertebral discs).

The Study

The current study cultured notochordal procine NP cells in agarose discs. The cultures were at 21, 5, or 1% oxygen tension for 1, 5, or 10 days. An RT-PCR was used to analyze the expression of 10 key matric genes, as well as Brachyury (T), by the said NP cells. A two-point method was used to measure the consumption of glucose.

Spinal bone

What were the significant Results?

The study’s results revealed that glucose consumption rates (by NP cells) were significantly affected by oxygen tension and culture time. Furthermore, significant changes were seen in T expression based on the culture time and oxygen level. Take note, better maintenance of the notochordal phenotype may be indicated due to how the T expression was significantly higher in the 1% oxygen tension on day 10 (compared to the other two groups).

What does it mean?

The study shared that (when it comes to agarose disc culture) a vital role is played by oxygen tensions level in maintaining the proper expression levels of matrix regulation genes of notochordal NP cells. The study offered data regarding the role of nutritional environment to support healthy NP cell expression. Better treatment strategies for disc regeneration might be helped by using the quantitative information gathered by this study. The data can also prove helpful to understand disc pathophysiology.

Does Spinal Posture Act as a Trigger for an Episodic Headache

A review 1, found in Current Pain and Headache Reports was conducted to see if there was indeed a valid link between spinal posture acting as a trigger for an episodic headache. While the review concluded more research is required, it did present some interesting results.

The Global Issue of Headaches

According to the WHO (World Health Organization), headaches are one of the ten most disabling conditions for human beings. Numerous factors have been studied to contribute to or give rise to the development of a headache. Secondary headaches have been observed to be due to an underlying etiology, for example, trauma, infections, and dysfunctional or abnormal cervical structures. Take note, primary as well as certain secondary headaches arise from complex multi-dimensional interactions between lifestyle, psychosocial, cognitive, biological, and environmental factors. Due to several triggers, identifying underlying mechanisms of headaches continues to be challenging.

Headaches and Spinal Positions

The current world encourages people to remain seated. According to studies, when daily computer use exceeds 3 hours, there’s a higher prevalence of musculoskeletal complaints. Such complaints include experiencing pain in the neck, head, or upper extremity. These complaints are suspected to be linked to slumped sitting postures.

A slumped sitting position involves an increased posterior pelvic rotation, forward head posture, and thoracic flexion. Such postures (if sustained) tend to increase the biomechanical momentum and torque, decrease proprioception, cause creep of spinal tissue, and limit postural variability.



Headaches and posture

Why do such a Review?

While an extensive framework for headache classification is provided by The International Classification of Headache Disorder, outcomes following physiotherapy do vary. Such variability might be explained due to the absence of protocol studies for identifying the role of spinal posture in headaches. That’s why conducting multi-dimensional profiling of patients (suffering from a headache) based on the interactions present between spinal posture, lifestyle, and psychosocial factors may be essential.

The current review had the objective to find support about whether spinal posture could trigger an episodic headache. The review considered a multi-dimensional view on tension-type and cervicogenic headache (this included modern pain neuroscience).

What Did It Find?

The current review described several pathways to support how spinal postures acted as a trigger for an episodic headache. Psychosocial factors could also act as a catalyst for the development of a headache through a maladaptive spinal posture.

However, further research is still required to determine the exact level of contribution of spinal postural dysfunctions and their ability to trigger a headache.