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

 

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.

Dr. Jerome Fryer (CEO of Dynamic Disc Designs Corp):

“Hello everyone. Dr. Jerome Fryer here of Dynamic Disc Designs. I just want to reach out to those customers that have one of my models. There’s been a lot of talk lately on social media regarding how models can be scary. I don’t know how they’re scary. Models are not scary. It really depends on the user and these models are not intended to scare anybody. It’s to teach them their own anatomy, so they can improve their posture and biomechanics to relieve their symptoms. It’s a team player. It’s like a car. You can go out there ram into people or you can drive defensively and respectfully. Anyway, so one thing that’s important when you’re using the model is to relay realistic biomechanics  and use the model in a way that simulates real-time and load.

You want to use it in a way that actually represents the actual tissue. You can talk about all sorts of things, but you can talk about disc height changes as the disc over the course of the day loses a percentage of its height. You can talk about normal loading patterns of the disc as it relates the associated nerves. But, what I would encourage is just to use real-time forces. For example if someone goes to sit down, they change their lumbar angle and they compress their disc. When they sit for a period of time, the disc actually loses further height. You want to show the subtle endplate angle changes as it relates to the facet joint for example, or in the suspected case of disc herniation, you can actually create a disc herniation.

Single-Level Disc Herniation

Model of Single-Level Disc Herniation.

One example is the changing fluid expression over the course of the day. This is an important little graph to help patients understand how first thing in the morning you’ll actually lose their height very quickly in the disc height, so the facets will actually approximate with the changing intradiscal pressure, and then over the course of the day the disc height will slowly reduce. Some people talk about around 4:00 or 5:00 in the evening as the day progresses, my symptoms become pronounced. Then also with first lie down too. You can see there’s a quick change in disc height. Anyways, I just wanted to share with you that it’s how you use the model and you want to use it in ways that are realistic with regards to movement.”

 

 

 

A new study 1 sought to create an etiology-based system of classification by identifying and characterizing typical endplate irregularities and found that tidemark avulsions were a predominant pathology in the cadaveric spine sample images. This represents a previously unidentified observation and, along with the histologic classification system developed in the study, should assist practitioners in organizing their patients into categories that will help to diagnose, research, and treat their spine symptoms.

 

The Study

Researchers used magnetic resonance imaging (MRI) to analyze and categorize 15 donated human cadaveric spines from 11 males and four females between the ages of 49 to 67 years old. Each of the spine samples showed evidence of moderate to severe disc degeneration. Motion segments were excluded if they appeared with imaging to have experienced pre-mortem surgery, deformity, or fracture. No medical history about the donors was obtained.

Histological Observation

Spinal segments were extracted using a band saw, and their various features were stained with different colors for observation. Each of the sections were imaged with polarized lights under a microscope, and two raters developed a classification system to identify and record various focal tissue-scale endplate irregularities and their anatomical location.

Researchers noticed a novel histological phenomenon wherein there appeared to be a separation of the annulus from the vertebra at the tidemark (the insertion point of outer annular fibers into the calcified layer of cartilage). They immune-stained the “tidemark avulsions” to search for the 9.5 neuronal marker protein gene using a polymer detection system. Each of the slides was then analyzed to identify the presence or absence of nerves in the bone nearest the endplate irregularity.

endplate irregulariities, models

Models to help explain back pain as it relates to endplate irregularities.

MRI Analysis

Each spine was studied via MRI to identify the presence of absence of tidemark avulsions, and their location was noted. Two orthopedic specialist clinicians were used to assess the findings. These researchers—neither of whom was previously used as a rater— were blinded to the histologic findings.

Findings

The endplate irregularities were grouped into three categories based upon their features and location. They were then subcategorized to further classify their pathologies.

The categories and subcategories identified were:

  • Avulsions: There was a separation of the tissue at the place where the disc joined the vertebra. Two types of avulsions were observed—tidemark (separation occurring at the tidemark location, where outer annulus fibers join the layer of calcified cartilage, and CEP-bone avulsion—occurring where the bone meets the cartilage endplate (CEP).
  • Nodes: Traumatic nodes occurred when there was a herniation of the nuclear materials reaching through the endplate. When abnormal fibrocartilage ingrowth or bony erosions were found, the were classified as Erosive.
  • Rim degeneration: This classification was reserved for samples that showed loss of organization in the annular fiber, bone marrow alterations, or degradation of the bone-marrow interface.

Endplate Irregularity Observations

The most common irregularities noted were rim degeneration (50 %) and avulsions (35%). Nodes were less common (15%) and found mostly in the thoracic spine, where the avulsions and rim degenerations were found in the lumbar spine samples. Eighty-seven percent of the noted avulsions were found in the anterior discs.

Though linear regression showed little association between endplate irregularities and age, the largest number of tidemark avulsions (90%) were found in the oldest spine samples. Interestingly, the annular fibers in the tidemark avulsions appeared to change their direction after crossing the tidemark. Of the 35 discs that showed tidemark avulsions, 14 of them contained multiple avulsions. Marrow changes and increased innervation was noted along vertebral bones beside endplate irregularities. An increase of nerve density was observed even in bones adjacent to very small tidemark avulsions.

Conclusion

The ability to identify tidemark avulsions on MRI may help practitioners identify and treat disc-vertebra injuries in a targeted way. High density images in the study showed that fluid can collect around avulsion irregularities, potentially creating gas in the extra-cellular spaces surrounding thee separation. High-intensity regions in MRI may indicate disc delamination or potentially painful lesions.  It is possible that tidemark avulsions may create anterior widening and create a scenario wherein the disc may detach from the vertebra. Overall, the findings of this study should contribute to a beneficial system of classification, allowing clinicians to more effectively diagnose and treat their lower back pain patients.

KEYWORDS: endplate irregularities, tidemark avulsions, endplate pathologies, histologic classification system, separation of the annulus from the vertebra at the tidemark, CEP-bone avulsion, traumatic nodes, rim degeneration

 

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. “

 

When it comes to managing chronic pain, including lower back pain (LBP), evidence suggests that patients who feel supported through caring, interested practitioners, self-help groups, and a steady stream of helpful information designed to assist them in understanding the source and treatment of their discomfort. These patients are more likely to experience a better treatment outcome and psychological well-being than patients without such systems in place. Educating patients about their condition using on-hand pamphlets, dynamic visual devices, and images can help them to feel empowered and better able to cope with their ailments. Care-givers who take the time to establish a human connection with their LBP patients create a more positive healthcare experience and inspire confidence and improved patient-physician relations. Patients who trust their practitioner report better long-term LBP treatment and maintenance outcomes than those who are unhappy with their care.

Because chronic pain patients face obstacles to efficient and reliable self-management of their conditions, practitioners should endeavor to create an environment conducive to patient empowerment by providing support, easy-to-understand information, and confidence-building support structures that encourage family members, friends, and co-workers to better understand chronic pain and its effect on a patient’s lifestyle and career. By utilizing a combination of educational, biomechanical, psychosocial, and physiological supports, care-givers can help to foster a less-limiting and more proactive approach to the self-management of LBP in their patients.

Barriers to Pain Self-Management

  • Managing chronic pain is time-consuming and requires sustained effort.
  • The discomfort associated with experiencing daily LBP can leave a patient feeling fatigued, discouraged, and unmotivated.
  • Unsupportive clinicians, family members, friends, bosses, and co-workers may leave patients feeling alone, misunderstood, and frustrated with their care.
  • Poor understanding of their condition can make patients fearful, uncertain, or anxious regarding their therapy. They may catastrophize their symptoms or avoid potentially therapeutic exercise because they fear to exacerbate their injury.

Solutions to Patient Self-Empowerment  

  • Educate patients about their condition by using visual aids, dynamic models, and clear language to assist them in differentiating the “self” from the pain.
  • Use cognitive techniques, empathy, active listening, positive motivation, and peer validation to help the patient accept the pain as merely one aspect of a greater self and recognize that the pain need not define or limit life’s potential.
  • Create a supportive, collaborative relationship between the patient, care-giver, family, friends, and co-workers by encouraging open communication and an empathetic response. Provide a safe, therapeutic environment in which healthy, supportive alliances can be formed.

A recent literature review 1 found the most effective chronic pain self-management supports involved effective communication, a clinician-patient relationship that fostered self-discovery, occasional “booster” sessions after an initial course of treatment, and involvement in peer support groups. By practicing person-centric care and taking the time to educate their patients about their condition, practitioners can inspire confidence and empower self-reliance that will assist in the long-term management of chronic pain.

KEYWORDS: self-management strategies for the treatment of chronic lower back pain, managing chronic pain, dynamic visual devices, patient empowerment, improved patient-physician relations

patient educational tools

Recent studies12 on the effects of patient education in reducing stress and promoting long-term positive patient outcomes indicate that providing literature and visual aids that clearly describe or demonstrate the patient’s condition can help relieve anxiety and encourage a positive psychological state that fosters better health outcomes. Examples of patient educational tools include illustrated pamphlets, photographs, radiograph images, charts, and finely detailed dynamic design models to provide an overall contextual effect in framing treatment and health expectations.

Reframe Treatment Expectations by Providing Context

Clinicians, chiropractors, and physical therapists who are prepared with effective aids to answer their patients’ questions about disc herniation, bulging discs, disc degeneration, annular fissure, osteoarthritis, stability, hypermobility, nerve pain, sheer instability, neutral loading, recumbency, facet or disc pain, disc height changes with static loads, diurnal changes, and other spinal conditions can look forward to a better patient-practitioner experience, more patient cooperation,  and a better long-term treatment outcome for their patients than those who rely on simple diagnosis and treatment procedures without effective patient education.

Empower Patients with Biopsychosocial Approach

By providing patients with a better understanding of their condition through the use of dynamic models or other visual devices, practitioners improve patient-clinician treatment collaboration and empower patients to take a more active role in their own healing agenda. This biopsychosocial approach to treatment has been shown in studies to generate more positive, long-lasting treatment outcomes and improve relationships between patients and practitioners, fostering trust, communication, and respect.

When practitioners take the time to help patients understand their condition, the patient feels more supported and engaged in the healing process and report being generally happier with their treatment plan. Using a person-centered approach to healing, the practitioner is concerned not only with a patient’s diagnosis and treatment, but is also concerned about the patient’s perception of his diagnosis and treatment experience. This perception, according to studies, is more positive and empowering when the practitioner takes the time to fully address the patient’s concerns and questions and uses visual aids, images, charts, literature, dynamic designs, and other tools to demonstrate what the patient is experiencing and how the treatment will work.

Keywords: dynamic models and other tools in patient education, use of dynamic models or other visual devices, finely detailed dynamic design models, patient educational tools, biopsychosocial approach to treatment, disc herniation, bulging discs, disc degeneration, annular fissure, osteoarthritis, stability, hypermobility, nerve pain, sheer instability, neutral loading, recumbency, facet or disc pain, disc height changes with static loads, diurnal changes