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Study Finds Evidence Chronic WAD Sensory Hypersensitivity Linked to Cervical Zygapophyseal Joints

Zygapophyseal Joint Pain in Chronic Whiplash Patients

A study 1 of sensory hypersensitivity in patients suffering from chronic whiplash associated disorder 6 months or more after being involved in a motor vehicle collision (MVC) found that the hypersensitivity was reduced, and pain thresholds were increased after receiving a medial branch block (MBB) procedure of the cervical spine.  The results of the study indicate the cervical zygapophyseal joints most likely contribute to sensory hypersensitivity caused by peripheral and centrally mediated pain.

 

What’s at Stake?

A common problem of people who have been involved in MVC’s is chronic whiplash associated disorder (WAD). According to research, between 32-56 percent of those involved in MVC’s may continue to suffer from related disability or pain 6 months or longer after their accident. Research has implicated the cervical zygapophyseal joint as a possible source of chronic hypersensitivity in 54-60 percent of subjects with WAD—evidence that is supported across multiple biomechanical and neurophysiological studies. It is thought that tissues that had been seemingly unaffected by the MVC experience sensory hypersensitivity when the body’s pain processing mechanisms are altered in the spinal cord. This sensory hypersensitivity and central nervous system hyperexcitability decrease the pain thresholds in the body, creating an exaggerated response for thermal, electrical, or mechanical stimuli for WAD patients. The prognosis for WAD patients suffering from sensory hypersensitivity is poor, and better understanding of the phenomenon could improve long-term treatment outcomes.

The Study

 

The pretest-posttest exploratory study involved 18 volunteers (15 females, 3 males) with an average age of 45 years and who had experienced WAD for 6 months or longer, with numerous neck complaints, body tenderness, and decreased range of motion. A control group of 18 healthy patients (15 females, 3 males) with an average age of 45 years also participated in the study. A group of chronic WAD patients with pain reported for 6 months or longer and who had a minimum of 80 percent decrease in neck pain intensity following an intra-articular zygapophyseal joint block procedure also took part in this study. Exclusionary criteria included pregnancy, previous history of headaches or neck pain requiring treatment, central or peripheral neurological problems, coronary artery or peripheral vascular disease.

Researchers rated the subjects’ pain intensity levels on a scale of 1-10 before and after receiving MBB procedures. Quantitative sensory testing (QST) based upon pressure pain thresholds (PPT’s) and cold pain thresholds (CPT’s) were conducted on the control and WAD groups. All measures were recorded, including patient demographic variables and their current MVC litigation status.

Cold Pain Threshold Testing

A 30mm x 30mm thermode set to 32 degrees Celsius placed over the anaesthetized articular pillars of the cervical zygapophyseal joints measured cold pain thresholds in the test subjects as the temperature was decreased at the rate of 1 degree Celsius per second. Patients used a self-controlled switch to indicate when the sensation of cold turned to pain as each bilateral site was tested. (The minimum temperature was 1 degree Celsius.) The average values were gathered for analysis.

Pressure Pain Threshold Testing

The articular pillars of the cervical zygapophyseal joints, peripheral nerve trunk of the median nerve, and the tibialis anterior were measured in the PPT tests, with the subjects using a self-controlled switch to indicate when the sensation of pressure turned to one of pain. The tests were performed three times bilaterally on each site, with a pause of 10 seconds between each test. The average values were recorded and later statistically analyzed.

Cervical spine model to demonstrate zygapophyseal joints

Dynamic Cervical Model

Diagnostic Cervical Zygapophyseal Joint Blockade

The patient group with chronic WAD underwent two diagnostic zygapophyseal joint block procedures—one, prior to the study, where a spinal needle was inserted with fluoroscopic guidance into the joint while the patient was in the prone position. An injection containing a local anesthetic and a corticosteroid was made into the affected zygapophyseal joint. If these patients experienced a relief of pain intensity of at least 80 percent but their pain later returned, they received the second MBB injection. In this study, none of the patients were excluded from the second MBB, as each of them had experienced at least an 80 percent reduction of pain from the first procedure, with the return of pain post-procedure.

Results

The WAD patients demonstrated clinically significant changes in their sensory hyperactivity measurements after the blockade of the cervical zygapophyseal joint. These changes included a decrease in CPT’s and increase of PPT’s in the cervical spine and distal sites. This finding is unique in the study of chronic WAD patients and suggests that minimizing the source of pain—in this case, the zygapophyseal joint—may help modulate sensory hypersensitivity in chronic WAD patients, at least in the short-term. The study authors urge larger trials with long-term follow-ups of patients to gather more information and improve the treatment outcomes of patients with WAD.

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Arthritic Changes Related to Age and Sex – Histology and Modeling

arthritic changes, lumbar models, cervical models

Arthritic changes are very common. They are often related to a person’s pain with neck pain as one of the highest ranked common causes of disability. In this specific research article 1, the authors looked at the micro-details of neck synovial joints. With osteoarthritis known to be related to neck pain, they were looking to reveal higher anatomical detail and they were also curious about whether men or women have more of these problems.

With both neck and back pain being multifactorial (which may include both psychological and social aspects) degenerative changes within the synovial joints play a significant structural role with the development of spondylosis. This is a general term to describe a disorder of the musculoskeletal system with an emphasis on joint space narrowing, intervertebral disc height loss and frequent formation of bony spurs.

The architecture of the cervical facet joints is quite well known with most of the current knowledge around the smooth (or lack of smoothness) hyaline cartilage to allow the joint to receive and distribute loads in an efficient manner. However, there has not been much quantitative data revealing the anatomy under the hyaline cartilage designated as the subchondral bone. This bone under the cartilage (sub, meaning below and chondral, meaning cartilage) has been of recent interest as there exist nerves in this area that can cause pain. This is thought to be similar to the basivertebral nerve of the vertebral body. The innervation of the facet, however, has ascending fibres travelling through the posterior primary division which can be seen in this Medial Branch Dynamic Disc Model.

 

modeling hyaline cartilage, models

Hyaline Cartilage Modeling in our Professional and Academic LxH Dynamic Disc Models

basivertebral nerve lumbar model

Basivertebral nerve of a lumbar vertebra.

Previous research has shown that the thickness of the hyaline cartilage is .4mm in women and .5mm in men with the subchondral bone making up approximately 5% of the total cartilage thickness. It is also known that with increasing age the cartilage starts to flake off (called fibrillation) and researchers also coin the stripping of cartilage from the bone, denudation. This means being nude. A joint surface within a covering. Other terms used to describe the break down of the hyaline cartilage is erosion, fissuring and deformation. All in all, the terminology all mean that the hyaline is thinning.

arthritic changes, subchondral, joint, model

Subchondral thickening – arthritic changes

How did they do it?

These researchers looked at 72 recently deceased people and examined their joints. They used microscopes to look closely at the facet joints to help understand the pathogenesis of the arthritic changes.

When they observed the osteocartilaginous junction, the morphological changes included: flaking, splitting, eburnation, fissuring, blood vessel invasion and osteophytes. They looked at the length of the cartilage, the hyaline cartilage thickness, the calcified cartilage thickness and the subchondral bone thickness.

They found that males tended to have more severe degenerative changes described by flaking and severe fissures in the facet cartilage. Click To Tweet

Points of Key Interest

  • this was a study that looked at 1132 unique cervical spine facets from 72 humans
  • males were found to have more degenerative changes of the osteocartilaginous junction
  • the thickness of the calcified cartilage and subchondral bone increased with age whereas the hyaline cartilage decreased
  • the osteocartilaginous junction is particularly important in the pathogenesis of osteoarthritis in the cervical spine facet joints

 

At Dynamic Disc Designs, we work to bring research to the practitioner so when there is a teaching moment, Professionals are ready to explain pain triggers as they relate to a patients symptoms and movements. Empowering people about their own anatomy helps in the crafting of customized treatment plans for each unique pain patient. Explore our dynamic models and help a patient understand their arthritic changes and what that means to them.

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Study Finds Annulus Fibrosus GAG Content Alters the Mechanics of Disc Torsion

Facet Joints, GAG, Annulus Fibrosus, Torsion

A recent study evaluated the role of facet joints in torsion using four different compressive preload conditions in healthy and degenerated lumbar discs—with, and without facet joints. The study also sought to develop a quantitative relationship between structure and function in tissue and torsion mechanics. The study found that annulus fibrosis GAG content substantially affects the mechanics of disc torsion.

Purpose of the Study

Because there is a large population of lower back pain (LBP) sufferers whose jobs involve excessive loading and rotating the lumbar spine, the authors of this study sought to quantify and understand how the facet joints in healthy and degenerated discs would behave under axial rotation scenarios. They did this by observing in vivo changes in spinal segments during torsional behavior. The intervertebral disc (IVD) is capable of stability and flexibility during most movement, receiving stresses and sharing them with the nearby facet joints and other surrounding structures. The facet joints should protect the disc from overload and degeneration by restricting motions that would cause damage to the spine, but some complex motions that involve axial rotation and bending during heavy loading can increase the chance of micro-damage and disc failure. How well the IVD and facet joints share loads is determined by the mode of loading and posture. Previous studies have demonstrated that up to 25 percent of axial compressive forces may be supported by the facet joints. Between 40 to 65 percent of healthy disc joint rotational and shear forces are also supported by the facet joints. Therefore, it is important to understand how the facet joints in healthy and degenerated discs react during torsion.

Study Design

Researchers obtained and imaged seven human cadaveric lumbar spine segments aged 43 to 80 years-old. The musculature and ligaments were then removed, and the intact facet joints near the discs were subdivided mid-vertebrae prior to the samples being potted in bone cement. The segments were then wrapped in gauze and stored in a phosphate solution until brought to room temperature just before testing. They were then mounted onto a testing machine and secured with screws.

The segments underwent a moderate-to-low preloaded axial compression, followed by axial rotation through the center of the disc. The cycles of compression and rotation were performed for two hours to allow the formation of creep. Ten cycles of cyclic rotation, and the samples were tested under four axial compressive preloads and allowed to recover between each test. The facet joints were then removed, and the samples were tested again, using the same loading configuration. For each round of testing, the researchers recorded the levels of force, rotation angle, displacement, and torque.

Isolating and Imaging Each Disc

Each disc was isolated and imaged after mechanical testing. Researchers measured the disc area, anterior-posterior and lateral width using a custom algorithm. Disc height was measured from the posterior, anterior, left, and right lateral sides, as well as the center. A mathematic formula determined the applied axial stress, and the images were graded and compared with radiographic-based grades.

Conclusion

The results of the tests indicated a strong correlation between creep and axial compressive preload and the loss of disc height. Removing the facet joint had no effect on this phenomenon. The presence of facet joints and an axial compressive preload did have a strong effect on torsional mechanical properties, with torsional stiffness and range decreased 50 to 60 percent for compressive loads after removing the facet joints. Energy absorption decreased about 70 percent during rotation after facetectomy, and disc-joint strain increased 74 percent, compared to only 62 percent in disc strain energy using the same axial compression.

Annulus Fibrosis GAG content in degenerated discs greatly reduced torsion mechanics, while the facet joints are integral in keeping the spine from rotating too far and helping to reduce shear stress and damage to the disc. The relationship between the biochemical-mechanical and compression-torsion levels noted in this study may help to provide for more effective and targeted biological repair methods for degenerating discs of various levels.

 

KEYWORDS: AF GAG Content Alters the Mechanics of Disc Torsion, role of facet joints in torsion, axial rotation scenarios, correlation between creep and axial compressive preload and the loss of disc height, targeted biological repair methods for degenerating discs

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Cervical Spine Anatomical Model

A cervical spine model with a herniated disc - for medical professionals

A Cervical Spine Anatomical Model Sheds Light on a Complex System

The cervical spine – more commonly known as the neck – is a complex configuration of the seven vertebral bodies that make up the upper part of the spine. But you already knew that, right?

If you are a doctor or other professional who works with issues of the cervical spine, chances are you’ve studied this part of the anatomy in depth and that you know all about the particulars of C1 through C7 and understand the importance of a healthy cervical spine. Good for you!

Of course, if you’re a patient who’s having cervical spine problems, including severe neck pain, you’re probably not too adept at figuring out why it is that you’re hurting and what you can do to ease the pain. That’s why you’re going to a chiropractor, physiotherapy, massage therapist, or other professional. You hope that you’ll walk away with answers.

So, if you’re that medical professional to which people turn when they have cervical spine pain, what do YOU do to help them clearly understand what’s gone wrong inside their body? In many cases, we – as professionals – enjoy using our words to explain to our patients why they are in pain. We’ve all been there, most likely on both sides of the fence. You’ve no doubt done the explaining and have also been explained to…at least sometime during your life. But, being a medical professional, you’re at an advantage. You can largely understand what another doctor is explaining to you. Your patients may not fare as well.

zygapophyseal joints

But with visual aids, your verbal explanation can go a lot further. If cervical pain is your specialty, you should consider an investment in an education tool that tells the whole story through the sense of sight and touch, such as Dynamic Disc Design’s cervical spine anatomical models.

The company’s Professional CxH model, for example, provides patients (or students of cervical spine pathologies) a close look at the inner workings of this part of the body’s nervous system. It includes a two-part intervertebral disc with six degrees of natural motion with a red post-lateral nuclear migration upon manual compression, posterior longitudinal ligament (PLL), anterior longitudinal ligament (ALL) and periosteal fascia (POL) (adjacent to uncovertebral joint). Doctors find this model extremely helpful for discussions involving pain related to the uncovertebral joint, IVF narrowing, and dynamic disc changes related to the facets. A ligamentum flavum is available as an extra feature.

While the Professional CxH model is the most comprehensive 3D cervical spine anatomical model offered, Dynamic Disc Design’s also produces a cervical spinal stenosis model, an upper cervical model, a hypermobility cervical model, and a multi-level, multi-coloured cervical model. There’s also the one-of-a-kind Cervical Prox1.

Offering clients a look at a cervical spine anatomical model has a few distinct advantages. First of all, because many individuals learn best from visuals, they walk away with a clearer understanding of their problems. In addition, patients who truly believe they’ve “connected” with their doctor and believe that their doctor “understands them” are the ones that return. In short, you’ve helped them develop confidence in your knowledge and your abilities. That sort of connection makes for life-long patients.

Dynamic Disc Designs’ cervical spine anatomical models are affordable, even for those just starting their practice, and because they are well-made with careful attention to detail, they are not only super-accurate but also long-lasting, making them a sound investment for any doctor who treats the cervical spine. Check out the available selection and choose one or more that fit your needs.

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Diurnal Disc and Symptoms

Diurnal Disc - Dynamic Disc Designs

Back pain can be tricky to figure out but the diurnal disc can elude to the root of the issue if doctors are paying close attention to the history and associated relieving body position.

Spinal symptoms are often diurnal. In other words, patients can often explain the onset of their symptoms based on the time of day or night. A common complaint is stiffness in the morning or after a period of rest while lying down. Early morning stiffness has been thought to be a telltale sign of a degenerative disc. The behaviour of annular fissuring and wedging with the combination of early morning accelerated disc height loss, results in the symptoms of stiffness. To see this you can view the movement of the nucleus in any of our clear bones models.

Patients also complain that back and/or leg symptoms come on later on in the day and into the evening. The diurnal disc can lose up to 20% of its hydraulic height. We do know also, that with height loss, the facets slide and shingle into one another.

height loss, disc, core

Height changes of the intervertebral discs over 24 hrs

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You can see well within the contents of the video above, how the disc height can cause a shingling effect of the facets. Facets are pain generators, as can be seen in our medial branch model.

Generally, and I do mean generally, symptoms that come on later in the day are more likely to be from the facet joints. This can be further supported if the patient explains that sitting relieves their symptoms. A further possibility would be stenosis if the patient explains that sitting relieves leg symptoms. We know that sitting both opens the facet joints and the spinal canal of the lumbar spine.  This can be seen in many of of our spine models including our Stenosis Degenerated Model.

 

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