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.

Results

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.

Discussion

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. “

 

Lumbar Foramen

 An in vivo study of cross-sectional lumbar foramen dimensions during a weight-lifting activity showed that all levels of the lumbar intervertebral foramen (LIVF) area decreased, except for the L5-S1 segment during lumbar extension, which had consistent measurements of the foramen, height, and width throughout the activity. The results of the study could provide insight into ways to improve the diagnosis or treatment of lumbar foramen stenosis.

Purpose of the Study

Radiculopathy caused by nerve root compression is a common symptom of LIVF stenosis and is often treated surgically, through the implantation of an interspinous device or decompression. Because the LIVF is surrounded by mobile facet joints, its shape undergoes changes during typical daily movement. As it changes shape, it may put pressure on nerve roots or other structures that may cause pain. Complications arising from the changing dynamic anatomy of the LIVF during activity can lead to failed back surgery syndrome, so understanding how movement and weight-bearing affects the LIVF is important to effective treatment and maintenance of back pain.

The Study

An MRI study of 10 healthy subjects (five male, five female) in supine, relaxed positions was conducted, and 3D spine models were constructed based upon the results of the scans. The lumbar spines of the subjects were then imaged during lumbar extension postures of 45 degrees to a maximally-extended position, while the subjects were holding an 8-pound dumbbell in both hands. These scans were also used to create 3D vertebral models of the in-vivo dimensions during activity, and a data analytic design was created to determine the area, height, and width of the L2-S1 vertebral levels during the activity for 45-degree flexion, upright position, and maximal extension.

Results

Researchers found that the LIVF area in L2-L3, L3-L4, and L4-L5 decreased during weight-lifting activity. The LIVF widths also showed a similar decrease, but the heights remained throughout the extension activity. However, the foramen area, height, and width at L5-S1 did not change during the weight-lifting. Overall, the data for all other areas demonstrated a change of approximately 10 percent from 45 degrees flexion to an upright standing posture, and again from upright standing to maximal extension. This information underscores how patients with LIVF stenosis may experience nerve root impingement pain during extension postures and feel relief from that pain during flexion. Understanding the in vivo dynamics of the functioning lumbar spine may help practitioners in the treatment and diagnosis of lumbar foramen stenosis.

 

lumbar spinal stenosis, spinal canal narrowing

A superior view of our Lumbar spinal stenosis model with a dynamic disc bulge and dynamic ligamentum flavum.

KEYWORDS: Lumbar Foramen Dimensions During Activity, in vivo study of cross-sectional lumbar foramen dimensions during a weight-lifting activity, insight into ways to improve the diagnosis or treatment of lumbar foramen stenosis, Radiculopathy caused by nerve root compression, Complications arising from the changing dynamic anatomy of the LIVF during activity, nerve root impingement pain during extension postures

Diurnal Disc Shape

The spine undergoes natural shape and fluid changes over the course of 24 hours. Often, back pain symptoms vary as well over the day and night cycle.  But the small changes and the links to pain have not been researched thoroughly. Here, a group of researchers from Duke University looked at the reliability of measuring intervertebral disc shape with recumbent MRI. This large avascular structure is linked to back pain and has significant diurnal variation in the human body. It would seem wise to further understand its diurnal disc shape changes.

Some people feel pain in the mornings and others feel things more so at the end of the day. Yet others feel pain more so when they lie down.

The intervertebral disc hydraulically keeps vertebrae separated. Water is squeezed out throughout the day as the human frame is vertical, and this water gets resorbed when an individual lays down. During the process, the disc changes shape and height. And when pain is involved, these shape and height changes can bear increased ( or decreased ) physical stress on structures that may be inflammatory. These can include annular fissures, disc bulges, disc herniations, disc protrusions, encroaching nerve or rootlets of nerves and the shingling of facet joints, just to name a few.

The purpose of this study was to determine intra and inter-rater reliability using MRI to measure diurnal changes of the intervertebral discs.

They did find excellent reliability, and interestingly they saw the most significant change in the posterior annulus region of L5-1. The diurnal variations were in line with what others had seen in previous work. Boos at al. in 1996 saw a 1-2mm change over the course of an 8h workday while Hutton et al. in 2003 saw a volume change of 1-2 cm3.

This research is essential if we are to fully understand back pain origins. Often pain syndromes related to the lower back present with symptoms that are diurnal. At Dynamic Disc Designs, we have models to help explain these subtle but significant changes to the discs, assisting patients to understand the onset of their pains and the diurnal disc shape and the natural variations.