Goal of the Study?

In this preliminary study, 1 the authors compared the effects of loading compression and traction on lumbar disc measurements, particularly the magnitude and distribution pattern of fluid within lumbar discs, in relation to intervertebral disc degeneration.


Why are they doing this study?

Intervertebral disc degeneration (IVDD) is associated with many biochemical and morphological changes in the disc that contribute to degeneration and negatively impact normal function. With degeneration, there are changes to the amount of fluid and the distribution pattern of this fluid within the disc. The authors argue that this may provide unique biomarkers that can help with diagnosing and classifying degeneration. The authors hypothesize that using T2- weighted MR images will enable better insight into disc degeneration. It only changes in response to variations in fluid distribution and these potential degeneration biomarkers. 


What was done?

A total of 35 volunteers between the ages of 18-65 were recruited: 20 with and 15 without low back pain (LBP). Using a custom MRI compatible loading table, the participants spent 20 minutes in the supine, unloaded position; then they spent 20 minutes loaded in axial compression and then 20 minutes with axial traction. A compressive load equal to 50% of each subjects’ body weight was applied to simulate loading and traction. For lumbar discs, the height, angle, width, mean-T2 and T2 weighted centroid (T2WC) locations were calculated. Disc degeneration was measured using the 5-point scale by Pfirrmann et al.


What did they find?

Most of the effect size (ES) differences the authors found in response to loading were seen from compression to traction. They observed small but statistically significant changes with an inferior and posterior shift in L4-5 (ES: 0.4, 0.14) and L5-S1 (ES: 0.25, 0.33) T2 weighted centroid. More degeneration was associated with larger anterior displacement and more superior displacement of the disc T2WC. Moreover, degeneration was not associated with changes in disc width, but with greater degeneration, there were larger decreases in an extension of segmental angles.

From unloaded to compression, they found statistically significant small posterior shifts for the disc T2WC at the L1-2 level (ES: 0.39). They also saw an increase in L5-S1 width (ES: 0.22), an anterior shift in L1-2 T2WC (ES: 0.39), and L3-4 (mean 2.1˚) and L4-5 (1.8˚) extension angle. Additionally, with more degeneration, there were larger inferior movements of the disc T2WC, but not changes in disc width. 

Overall, their findings on compression to traction demonstrated the most significant findings in the lower lumbar levels. They also found a magnitude difference associated with the severity of disc degeneration. This supported their hypothesis that fluid distribution-related measurements illustrating the effects of degeneration and lumbar disc loading.


Why do these findings matter?

Biomarkers can help to illustrate how the lumbar spine responds to different loading conditions and can be used to monitor degenerative changes in the lumbar spine.


At Dynamic Disc Designs, we appreciate the dynamics of the discs and how professionals can communicate these small changes to patients as it relates to their dynamic symptoms and the solutions of back pain.

Lumbar Disc Model

Goal of the Study?

In this review 1 the authors evaluated the efficacy of physical therapy interventions such as electrotherapy, exercise therapy, lumbar traction and manual therapy in the management of lumbar prolapsed intervertebral disc (PIVD).

Why are they doing this study?

Lumbar PIVD (or herniation) is one of the most common musculoskeletal disorders affecting approximately 10% of the population. It has a significant impact both individually and societally as it is associated with disability, pain and a loss of productivity. Currently, both surgical and non-surgical approaches are used for treatment. However, recently there has been a push to reduce the need for spinal surgery as this approach has several complications, including pain, infection and, in some cases, post-operative paralysis. Unlike surgical interventions, conservative approaches such as physical therapy do not have such complications and are cost-effective. However, there is a need to understand the efficacy of physical therapy for lumbar PIVD.


What was done?

The authors did a systematic review and meta-analysis using randomized controlled trials (RCTs) focused on the efficacy of physical therapy management in lumbar PIVD. They included all trials published in English from the beginning to January 2019. They then used specific software to review the included studies. In total, 2594 studies were collected from the database queries, with 11 fitting the selection criteria; however, six were excluded as they did not contain sufficient data.


What did they find?

This meta-analysis showed statistically significant improvement in pain and disability after physiotherapy treatment in patients with lumbar PIVD, compared to control. While physiotherapy interventions did increase single leg raise (SLR) range, the finding was not statistically significant compared to the control group. 

Overall, the researchers found that physiological and biomechanical interventions such as correction of the displaced disc, decompression, opening of the foramina and increase in intervertebral space may lead to improved spinal mobility, contributing to a reduction in pain and disability.


Why do these findings matter?

Providing evidence-based care for LBP is important for patient quality of life and reducing the economic and societal burden of illness. 


Lumbar intervertebral disc herniation

A controlled radiologic follow-up study 1 in the journal “Spine” decided to observe whether or not clinical symptoms changed due to changes in cord excursion with the SLR test.

What Was the Context?

Sciatica is known to have an economical, physical, and psychological impact on numerous people around the globe. It has been described as the type of pain that originates from the buttock distally in the lower limb in the sciatic nerve’s distribution.

The leading case of sciatica has been observed to be the LIDH or lumbar intervertebral disc herniation. The SLR or the straight leg raise test is a standard used around the world for diagnosing LIDH-led sciatica. However, the test is deemed insufficient in isolation.

That is why better knowledge regarding the neural biomechanics associated with SLR needs to be provided to improve test interpretation.

What Was the Objective?

Due to the nerve root excursion being impaired in people with lumbar intervertebral disc herniation during intraoperative investigations and because of this reduction being expressed in the conus medullaris (in LIDH having patients), the current research team followed up with the same patients over 1.5 years.

The objective was to investigate if there existed a relationship between the reduction of neural movement and symptomatology in patients having symptomatic radiculopathy. The study also investigated if such a relationship remained in people who have recovered.

What Methods Were Used?

In the 1.5 years follow-up, a total of 14 patients were reassessed clinically as well as radiologically using a 1.5T MRI scanner. All of the patients had significant sciatic symptoms because of a subacute single-level posterolateral LIDH.

The team quantified the conus medullaris’ displacement during SLR (bilateral and unilateral). The quantified collected data was compared to the data from the baseline.

Variables that were strongly associated with a decrease in LBP (Low Back Pain) and radicular symptoms were identified using the backward variable selection method and the multivariate regression models.

What Did the Results Show?

According to the results, the current data showed a significant increase in neural sliding (with respect to quantified maneuvers) when compared to the baseline values. Take note; the increase in neural sliding was observed to correlate significantly with a reduction in LBP and radicular symptoms.

The improvement of neural sliding was confirmed to be the primary variable associated with the improvement in a patient’s self-reported symptoms.

In conclusion, the shared data was deemed as the first noninvasive type of data that showed support regarding the relationship between the increase of neural adaptive movement and the resolution of LBP as well as radicular symptoms in in vivo and a human subject (who is structurally intact).

Does Biomechanics Research Hold the Answer to Effective Low Back Pain Treatment

Studies have shown biomechanics playing a role in LBP or Low Back Pain development. It’s even considered to have links to the persistent and (or) recurrent nature of LBP. However, there’s still debate related to whether biomechanics (on its own) can offer the basis of intervention. A viewpoint-counterpoint debate 1 in the Journal of Orthopedic & Sports Physical Therapy set out to answer some questions.

Why Focus on Biomechanics?

Biomechanics is a term that relates to the mechanics of the human body. This includes the body’s neuromuscular control. Numerous studies about LBP have focused on such an area. With the issue of LBP being bio-psycho-social in nature, some believe that LBP research particularly focusing on Biomechanics may have the answers to effective LBP treatments.

The current commentary has considered whether there’s any potential in the field of biomechanics research for advancements in LBP treatment strategies. With LBP being experienced by millions of people around the globe, finding effective treatments should be a priority.

Addressing Both Sides

The current commentary has used a viewpoint-counter viewpoint format to look at both sides of the biomechanics and LBP related argument. Such a format has allowed it to be different than perspectives that only approach biomechanics.

Delaminated Circumferential

What more did it do?

Along with the viewpoint-counter viewpoint format, this commentary also described models that place a lot of emphasis on biomechanical factors. Furthermore, the reactions to specific viewpoints have been displayed as foundations for future clinical practice and research to better understand the potential of biomechanics in mapping LBP treatment.

What Was Concluded?

The commentary concluded that authors of the ‘counterpoint’ as well as ‘viewpoint positions’ agree about chronic non-specific LBP having bio-psycho-socio components that vary depending on individual experiences. They also agreed that biomechanics plays a role in such development. However, none of the biomechanical models could present a valid argument that it alone should be the focus of Low Back Pain Treatment. There’s a lot of potential in a bio-psycho-socio approach that includes biomechanics.

disc height

In this Spine Education video, Dynamic Disc Designs’ Dr. Jerome Fryer demonstrates the benefits of helping lower back pain patients better understand their condition by using dynamic models and visual aids.

“How often do you encounter a patient that explains that their symptoms are worse as the day progresses?” he asks.

Though clinicians understand the key to a graduating pain syndrome involves a complex biomechanical and biochemical matrix in the spine, back pain patients don’t need extensive medical knowledge to appreciate the dynamics of what is happening in their bodies. A simple visual aid can help clarify and simplify their predicament and potential solutions.


Hands-On Demo of Diurnal Expression of Fluid from the Disc

Using a dynamic disc model, Fryer demonstrates the diurnal expression of fluid from the disc as the disc height changes over the course of the day.

“We know that the disc height is tallest in the morning,” he says, holding a fully expanded disc model to the camera and then slowly squeezing the dynamic model to demonstrate the loss of height that occurs throughout the day.

“As the day progresses, the disc height will slowly lose its height [causing the facets] to imbricate or shingle. If a patient [complains] their symptoms are more present as the day progresses, you [use] this graph 1 to demonstrate what’s happening in their spine.

“As the person gets up in the morning, there is a quick change in the disc height in the first 10 minutes,” he says, pointing out a steep curve on the graph.

“As the day progresses, the disc height is lost.”

Annular Disruption in Degenerated Discs Reduce Capacity to Maintain Height

Fryer says the situation can be even more extreme when a patient is suffering from degeneration in the disc because the disc can no longer hold its full height, due to disruption in the annulus.

“Helping patients understand symptoms as the day progresses will help them understand why it hurts,” he says. “That gives you more empowered strategies to help patients get motivated, if its posture, or even recumbency, or exercise, or getting out of a chair to help with the disc height changes. These dynamic disc models are very powerful in helping patients with self-awareness.”

For more information on dynamic disc models and patient teaching aids, visit Dynamic Disc Designs.

properties of the annulus, disc model

Researchers examined the effects of endplate fractures  1 on the mechanical properties of the annulus fibrosis (AF) in porcine spinal segments and found that laminate adhesion strength was significantly compromised in the fractured spines. The findings suggest that microdamage may occur beyond the vertebra, into the interlamellar matrix of the AF—information that could be helpful in the diagnosis and treatment of adolescent spinal growth-plate fractures.

The Study

The authors of this study wished to examine the effects of high-intensity pressurization on the intervertebral discs (IVD) to see how it effected the mechanical and physiological properties of the posterior AF. They used 28 fresh, recently-thawed functional porcine spinal units from 14 porcine specimens that were approximately six months old.  Control units were also used as a comparative measure against the units subjected to pressure.

A hydraulic pump and high-pressure inflation needle were used to pump hydraulic fluid into the IVD of specimens. The researchers were careful not to pierce the AF in the samples. Pressure in the needle was measured by a pressure transducer and converted from analogue to digital at 2048 Hz. The needle was subsequently removed, and the vertebral bodies were assessed for damage. Although fractured endplates created an audible ‘pop,’ the condition was only confirmed after dissection of the IVD. The control-group segments were not tested for fractures. Measurements were taken following the dissection, and the end-plate area was quantified. Bilayer AF samples were then dissected and tested for tensile endurance in the circumferential direction. A second multi-layered sample was then dissected and subjected to delamination and a peel test. Mathematical ratios were then plotted to mark the variable results for each sample.


End-plate size measurements remained consistent across the control and fracture group samples. Bilayer stiffness, toe-region stretch ratio and stress, and stress at 30% stretch were consistent in the control and fracture group samples. However, there was a clinically-significant variance in peel strength—but not peel strength variability— between the two groups. In the fracture group, the peel strength was 31 percent lower than in the control group. Dissection and manual delamination were significantly easier in the fracture group of samples, as well.


The results of this study indicate that growth-plate fracture damage may not be limited to the vertebra and may cause microdamage in the nearby AF. This was indicated by the reduction of laminate adhesion strength in the posterior AF of the fracture IVD samples subjected to pressure in the tests. This information should be taken into account when practitioners are examining and treating adolescent or childhood vertebral fractures involving the endplates.


KEYWORDS: damage during spinal growth-plate fractures, effects of endplate fractures on the mechanical properties of the annulus fibrosis, effects of high-intensity pressurization on the intervertebral discs, mechanical and physiological properties of the posterior AF, delamination and a peel test, Bilayer stiffness, toe-region stretch ratio and stress


spine pain, models

Ed Cambridge: “Our colleague Jerome Fryer created some models for us, and this is some of the work that has come out of our lab with you and Christian Balkovec about the dynamic changes we see after herniation. Where we have disc height loss at one level, creating hypermobility at the adjacent level. So here you can see, when you move the spine around there is a stiffening effect down in the lower joint and in the upper joint hypermobility. That’s what we see when an injury propagates from one joint to the next. The patient says, “Well, the pain used to be lower but now its starting to creep up my back a little bit.” “

Stuart McGill: “Fabulous. Another little take on that … By the way, these are all cast from real human specimens. So this is the real deal. Once again, Dynamic Disc Designs has been so clever in representing the biofidelity. We start to see how this disc has been damaged, and it’s quite lax as we move it around. So those micro-movements now are triggering pain just at that level. And this joint has normal stiffness, but then look what happens. Over time, the join changes because of the change in mechanics. The lax disc now cases a bit more arthritis in those facet joints, because they are now responsible for much more motion. So then, look what happens to the cascade. As the person now extends, look what happens. The joint that was hypermobile has now bound up, has no mobility because the facets have bound up and all the motion is now left at the previously stiffened joint. The polar opposite. And then you need some kind of mobility to pop those facet joints open again after they’ve been jammed.”

inflammatory mediators

The changing spine and the anatomy. Professional LxH Dynamic Disc Model

Stuart McGill:  “So, when you understand the cascade of change that happens at a joint, it might be kicked off with a little bit of a flattened disc, which puts more load in the facet joints, which causes a little bit of arthritic growth. In two years, the joint has changed and so have the pain patterns and the mechanics. So, it really does lend insight to allow us to understand the cascade of how the patient reports those changes and their pain changes over the years. And it better allows us to show them what to do to wind down the pain sensitivity. “