Degenerative Intervertebral Disc

Goal of the Study?

In this case-control study from the Journal of Investigative Surgery 1 the authors’ goal was to determine if a correlation exists between proteolytic enzymes and micro angiogenesis in degenerative intervertebral disc nucleus.  

 

Why are they doing this study?

Current pathological studies of intervertebral disc degeneration reveal apoptosis of nucleus pulposus cells in the intervertebral disc.  This leads to matrix reduction, conversion of type II collagen into type I and type III collagen, fibroblast proliferation, nerve fibre ingrowth and micro angiogenesis.  However, there is little information about pleiotropic enzymes associated with degenerative changes in vertebral disc herniation and angiogenesis.  This study was designed to assess how much the severity of the tissue generation was related to the level of pleiotropic enzymes in neovascularization and lumbar disc herniation.

 

 

What was done?

Forty patients with degenerative disc nucleus who had clear clinical symptoms of lumbar degenerative disease and cervical stenosis were selected as the case group.  Twenty patients that had cervical and lumbar vertebra injury caused by trauma and with matching demographics (age, gender, etc.) were selected as the control group. Three-milliliter venous blood was taken from the patients in each group and nucleus pulposus tissue was obtained. The embedded tissue wax block was dried, sliced and hematoxylin and eosin (H&E) dye used.  Various endothelial markers, proteolytic enzymes and content of type i/II/III collagen were measured and statistical correlations were calculated.

 

What did they find?

A statistically significant multiple linear relationships was found between the two independent endothelial markers; Alanine Aminopeptidase (APN) and Leucyl Aminopeptidase(LAP)  with the dependent variable Microvessel Density (MVD).  It was also determined that individually the effects of APN and LAP on MVD were statistically similar.

 

Why do these findings matter?

Protrusion of the disc to the epidural space appears to result in disintegration of inflammatory cells, granular tissue formation, neovascularization and activation of proteolytic enzymes. Correlation studies, such as this one attempt to find various relationships between independent and dependent variables.  This study examined the relationship between various endothelial markers to enhance our knowledge base and ultimately improve our clinical diagnosis ability.

 

At Dynamic Disc Designs, we create models with both an annulus and a nucleus so relevant research can be translated in educational and inter-professional circles. Patient education has been our priority but we are finding educational institutions are purchasing our models for the purpose of student learning.

disc herniations, sequestered lumbar disc herniation

Goal of the Study?

In this follow-up cohort study published in the Karger Open Access Journal 1 the authors assessed clinical and radiological follow-up results of surgical and non-surgical patients with a sequestered Lumbar Disc Herniation (LDH).  The goal was to determine if a difference existed between patients that had early surgery versus ones that had no surgical intervention.

 

Why are they doing this study?

The authors state that clinical and radiological follow-up studies on sequestered LDH patients who underwent surgery with those who had conservative treatment without surgery are very rare.  Some previous research has shown that early surgical intervention reduced pain faster in the short term, but both treatments had similar benefits in the medium and long term.  In this study, both pain and MRI images were used to analyze the difference between these two treatment modalities.

 

What was done?

LDH patients were identified by detecting a minimum of one plane herniated disc mass (fragmented) separated from the disc.  Of these 98 patients, 32 of them had had surgery within the first month of diagnosis.  These were designated the operated group. The other 66 patients in the non-operated group were treated conservatively with a variety of analgesic or myorelaxant drugs, physical therapy, exercises, lumbosacral orthosis rest, and epidural steroids.   Visual Analog Scale (VAS) and Oswestry Disability Index (ODI) scores were measured at the outset and at the first, third and six-month visits.  Radiological evaluation was performed by measuring the sequestered LDH level and herniation volume using MRI at the outset and at four and six months.  Based on the MRI images at the fourth month, the non-operated group was divided into 3 categories; non-regression (no change in disc volume), partial regression (> 25% herniation reduction) and complete resolution where herniated disc volume is absent.  Statistical techniques were used to compare the various groups.

 

 

What did they find?

In a comparing the group that had surgical intervention versus the group that did not have surgery, it was found that:

  • As a group, the 32 patients in the operated group had significantly lower ODI scores than the 66 patients in the non-operated group after the first and third months.  At the sixth month, both groups had similar clinical pain measurements.
  • Radiological improvements were observed in approximately 90% of non-operated patients who received conservative treatments.
  • At the outset there was no significant difference in the initial VAS and ODI pain measurement scores between the three non-operative subgroups; non-regression, partial regression and complete resolution, but at month one, three and six there were significantly higher pain scores for the non-regression group.

 

Why do these findings matter?

Based on this study, the authors recommend that patients with sequestered LDH receive conservative treatments and not surgical intervention at least for the first six months.  At the end of six months if spontaneous regression is not observed only then should surgery be considered.

 

At Dynamic Disc Designs we take our education seriously and craft models to help you deliver important clinically relavent, evidence-informed, patient education. In the case of a sequestered lumbar disc herniation, these authors suggest you give it six months of conservative care before considering surgery. Our Professional LxH Model can help show the patient the nucleus and its potential for resorption.

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.

Low back-related leg pain

Goal of the Study?

Low back-related leg pain is thought to be neuropathic in origin due to compromise of a nerve root(s) and is also commonly known as sciatica. In a study published in the Journal of Clinical Medicine 1 a group of authors looked to see if loading the spine during MRI imaging (axial loaded MRI) would help discern more specificity to the anatomical cause of the low back-related leg pain. These leg pain sufferers will often undergo recumbent MRI while their symptoms are in the vertical or axially loading posture. 

 

Why are they doing this study?

Many cases of sciatica can be challenging to diagnose because of the complexity of the disc mechanics and physiology. There are many nuances of sciatica, and each case can bring its own set of complexities. Learning to determine the source(s) of sciatica more accurately can be helpful in its therapeutic management.

 

What was done?

Ninety patients were recruited for this retrospective observational study. The participant’ ages ranged from 21-89 years and were screened by an orthopedic surgeon to exclude those with hip and knee problems from the study. Participants were asked to fill out a self-evaluation including the visual analog scale along with a pain drawing. Each participant was evaluated by an attending physician and underwent an axial-loaded 1.5T MRI with added weight. As a comparison, each participant.

The investigators looked for these variables:

 Cross-section of the dural sac
 Lumbar spinal stenosis grade with axial loading
 Disk herniation with axial loading
 Size of herniated disc with axial loading
 Size of hyperintensity zone with axial loading
 Ligamentum flavum ‘type’ with axial loading
 Intervertebral foraminal size with axial loading
 Foraminal stenosis
 Degenerative disc classification
 Degenerative facet arthropathy
 Edema of facet joint and effusion with axial loading
 Synovial cyst area with axial loading

 

What did they find?

The authors found that axial-loading subjects played a significant role in extracting findings that would otherwise not be seen with conventional recumbent MRI. Specifically, they found facet joint edema, atypical ligamentum flavum, was associated with low back-related leg pain.

 

Why do these findings matter?

Often, sciatica patients undergo MRI to identify a cause. However, recumbent MRI does not tell the whole picture as patients often report a worsening of symptoms when they are axially loaded. This study helped reveal the changes in the loaded state and can help clinicians make informed decisions about the symptoms patients express in a clinical setting. Understanding that the facets are under more load and the ligamentum flavum can buckle inwards towards the spinal canal can help the clinician understand the anatomy when assessing patients. Notably, the authors summarized that these axial-loaded findings could offer a dynamic picture of the instability contributing to sciatica.

 

At Dynamic Disc Designs we have developed models to help demonstrate load related changes to the spine. We believe that our models not only help the patients understand their symptoms better so they can make the appropriate adjustments to improve their sciatica, but they also help in the context of the education of spine pain in general.

Occupational low back pain

Goal of the Study?

In this Bibliometric Analysis [A bibliometric analysis of occupational low back pain studies from 2000 to 2020] the authors used two bibliometric tools; BibExcel and CiteSpace to examine 4,217 documents related to occupational low back pain (OLBP).  Bibliometric Analysis (BA) is the application of statistical methods and visualization tools to analyze books, articles and other publications.  BA attempts to put the articles into a series of clusters.  These clusters can be based on themes, country of origin, journal name, publication date, research institute, authors and something called co-citation.  Co-citation cluster analysis is the frequency of which two articles are cited together in the same document.  

 

Why are they doing this study?

Bibliometric Analysis of OLBP shows where the studies were done, who was doing the research, which industries dominated the high prevalence of OLBP and what was the research tendency over time.  Using bibliometric analysis can help researchers grasp the research structure and latest trends of OLBP.

 

What was done?

Over 4,000 articles from 2000 to 2020 were fed into the BibExcel and CiteSpace tools.  These articles were all from the subscription-based Web of Science academic database.  Terms related to OLBP were used to identify each article.  These articles were downloaded and fed through the two bibliometric tools identifying various clusters.

 

What did they find?

On a country basis, the BA analysis found that the USA, Canada and UK produced the highest number of contributions to OLBP research in the Web of Science databases.  Ontario’s Institute of Work & Heath was the most prolific institution producing over 70 articles on OLBP.  Other Canadian institutions making the top 10 were the University of Waterloo (#7), University of Toronto (#9) and University of Alberta (#10).  The top 2 contributing journals were the Journal of Occupational Rehabilitation (203 documents) and Spine (200 documents). 
Fifteen major OLBP research theme clusters were identified.  The two most popular ones were Musculoskeletal Disorder (227 documents) and Risk Factors (212 documents).  The two most recent themes were Biopsychosocial Approach and Core Outcome.

 

Why do these findings matter?

Occupational low back pain (OLBP) is regarded as one of the most common work-related musculoskeletal disorders.  OLBP not only has huge direct and indirect economic losses but is also responsible for the decline of quality of life.  Comprehensive bibliometric studies, such as this, provide general insight into aggregate performance in the OLBP field and can help identify further research directions.

lumbar stiffness

Goal of the Study?

In this primary research article1, the authors had two goals: (a) Determine and quantify the relationship between biomechanical and neurophysiology measurements in lower back pain patients and (b) examine if the correlations differ when considered regionally (lumbar back) or segmentally.

 

Why are they doing this study?

To improve our understanding of Lower Back Pain etiology, better non-invasive measurement tools and techniques must be established and quantified. 

 

What was done?

A sample of 132 patients of the Spine Centre of Southern Denmark who had persistent non-specific Lower Back Pain was measured for three different sensitivities: (a) global spinal stiffness (GS) using a VerteTrack Device which applied a rolling weight across the S1 and T12 spine; (b) deep mechanical pressure pain sensitivity threshold (PPT) using pressure algometer which applied bilateral pressure at each lumbar segment and (c) superficial heat pain sensitivity threshold (HPT) using a handheld thermode at the midline of each lumbar segment. 

A series of statistical tests were performed to determine if there were any correlations between these three quantitative sensory metrics: Global Stiffness (GS), Pressure Pain Threshold (PPT) and Heat Pain Threshold (HPT).

 

What did they find?

The correlation coefficients (R) for each pair of these three quantitative sensory metrics; GS, PPT and HPT were calculated and tested for statistical significance. 

  • Correlation between GS and HPT were found to be poor and statistically insignificant (R = 0.23)
  • Correlation between GS and PPT were moderate (R = 0.38) and statistically significant
  • Correlation between HPT and PPT were good (R= 0.53) and statistically significant

Unexpectedly, the correlation between GS and PPT was positive, meaning participants with higher global stiffness had a higher pressure pain threshold. The authors expected the reverse. They based their explanation of this unexpected relationship on the body’s adaptive mechanical protection system. Pain is considered a protective response and a stiffer spine is more resilient to applied forces and therefore can tolerate a higher pain threshold.

The other’s unexpected anomaly was that for the three QST’s measured, no differences were found between the individual lumbar segments. This indicates that patients with persistent LBP are probably less able to perceive lumbar stiffness reliably, perhaps due to “Cortical Smudging”, an overlapping of the cortical homunculus. 

 

Why do these findings matter?

Around four out of five people have lower back pain at some point in their lives. It’s one of the most common reasons people visit healthcare providers. To successfully evaluate both the extent of LBP and the effectiveness of any treatment plan, a reliable metric must first be established. This study is an attempt to use stiffness (GS), heat (HPT) and pressure (PPT) as this critical metric.

 

At Dynamic Disc Designs, we have developed models with varying lumbar stiffness to help in the education of the possible sources of back pain. This new research is important in establishing greater understanding of the causes and solutions of low back pain.

 

 

Disc Degeneration Model

Goal of the Study?

In this primary research article 1, the authors aim to establish an animal model that can be extrapolated to the complex mechanical load of a human intervertebral disc during bending and compression loading.  They hypothesized that a disc herniation could be gradually induced by static complex loading.

 

Why are they doing this study?

Disc bulges or protrusions often pre-exist in patients with acute back pain, suggesting that repeated compressive loads may gradually result in a herniated intervertebral disc.  To the author’s knowledge, this assumption has never been verified using animal models.

 

What was done?

Twenty research rats were randomly divided into four equal groups.  Group #1 was the control; the other 15 rats had an external device implanted in the coccygeal 8-10 vertebrae to bend the spine at a fixed angle.  Group #2 had sham surgery but no compression load, Groups #3 and #4 were subject to a compression load of 1.8 N (0.184 kilogram force) and 4.5 N (0.459 kilogram force) respectively.  After 14 days, an MRI was performed on all 20 rats and a Pfirrmann classification system was used to classify the disc images into 5 categories.  The rats were then euthanized and the C8-10 vertebral body was removed and the Norcross calcification system was used to evaluate the degeneration on a scale of 10 for no degeneration and 2 for severe degeneration.  The dissections were also tested for Gene Expression and various statistical tests were performed.

 

What did they find?

No statistical difference was found between the control group and the sham surgery group, so bending alone seemed to have little or no effect on disc degeneration.  There was a slight difference but it was not significant.  The MRI and histological scores for the intervertebral disc degeneration were significantly higher in the two loaded groups than the sham or no load surgery group.  Group #4, heavily loaded had significantly more disc degeneration than the lightly loaded group.   Both loaded groups had significantly more disorganization in the nucleus pulposus and annulus fibrosus from a histological perspective than the sham surgery group.

 

Why do these findings matter?

Even though the disc structure of rodent tails are biomechanically and compositionally similar to human lumbar there are significant differences.  As such, it is difficult to extrapolate this research to humans in a disc degeneration model comparison.  But if it can be extrapolated, it indicates that a static complex loaded can induce posterior intervertebral disc protrusion when combining bending and compression but not during bending alone.

 

At Dynamic Disc Designs, we believe it can be very helpful to show patients the mechanism of a disc injury to help empower a patient about prevention and the solution strategies to their problems. Our dynamic disc models demonstrate that bending alone does not cause disc herniation but will herniate when compression is combined with flexion.