sitting and back pain

Many people experience back pain with sitting.

In a recent study published in the American Academy of Physical Medicine and Rehabilitation titled : Changes in Lumbar Disk Morphology Associated With Prolonged Sitting Assessed by MagneticResonance Imaging  these authors used mid sagittal lumbar magnetic resonance imaging to evaluate continuous sitting and sitting with positional changes every 15 minutes.

They asked subjects in one group to sit continuous for 4 hrs while comparing a group that would stand up every 15 minutes and perform 5 seconds of lumbar flexion, 5 seconds of lumbar extension, 5 seconds of lumbar bending to the right, and then 5 seconds of lumbar bending to the left before returning to a seated position.

They did not find any significant changes in the disc morphology except at L4-5 after day 1 but not day 2 and concluded that L4-5 height changes were not significant with brief positional changes every 15 minutes.

At Dynamic Disc Designs, Dr. Jerome Fryer reviews papers to continue to develop models for professionals. He applauds the authors of this paper and finds the results of the manuscript predictable.  He explains ” the discs respond to unloading forces. If one suspects the discs as the pain generator associated with sitting, then postural strategies to improve disc health should include unloading forces” like in his paper, Magnetic resonance imaging and stadiometric assessment of the lumbar discs after sitting and chair-care decompression exercise: a pilot study whereby changes to disc were seen using the upper extremities to unload during positional changes of 15 minutes of sitting

If the net forces with positional changes are in the constant direction of gravity, (I.E, – y ) then the discs do not get a significant break
-Dr. Jerome Fryer explains

He also understands that his research is limited by way of subjects, but continues to see outcomes in practice with this type of off loading strategy.

As we continue to move forward in a world of more sitting, strategies that include off loading of the spine will be of more interest.  The intervertebral discs are hydraulic structures that lose up to 25% of height over the course of the day while vertical. Recumbancy and sleep has already showed how these structures recover. Sivian et al. showed in Biorheology how the disc cells behave. If we do not off load the discs, they will not have a chance to recover.

Dynamic Disc Designs continues to develop lumbar models and cervical models to help explain research in hopes to develop better techniques to improve spine health with our ever increasing world of technology and back pain with sitting.

annulus angle and disc height loss

Disc height loss is the common theme in back pain.

And with early disc height loss, hypermobility is related. But how are they associated to one another? Barr in 1948 (1) was the first to describe instability. His description of low back pain related to disc height and the passive stabilizers. A nice review of lumbar instability as an evolving concept was written by Beazell et al. These authors discussed the evolution through Farfan and his model, to Kirkadly-Willis and the three phases of degeneration as well Panjabi’s added concepts of neurological control. To understand the relationship between disc height loss and the development of hypermobility, it may be helpful to highlight the anatomy. In Panjabi’s and Adams “Biomechanics of the Spine”, there is a description of the annulus angles in alternating lemellae at 35 degrees from the horizontal explaining the tensile resistance with movement. What appears to not be described is the relationship of the annulus fibres when a disc loses its height. Below are a series of images, developed by Dr. Jerome Fryer, to help explain the displacement factor.

Annulus Fibrosus

Annulus Orientation

Each disc consists of concentric, alternating in orientation, fibrous sheets that encompass a hydraulic centre core named the nucleus pulposus. Once the disc height is reduced, the annulus angles change. If the length of the annulus fibres do not change, a displacement factor of hypermobility can occur.

annulus angle

Annulus angle change with disc height loss

disc height loss

Disc height loss leads to displacement

As it is often a therapeutic goal to increase spinal stability, increasing disc heights should be at the forefront.

The common theme seen in back or neck pain is intervertebral disc height loss. It is the earliest radiological finding in the degenerative cascade. This height loss leads to many geometrical and morphological changes that results, initially, in hypermobility which often leads to pain. This has been discussed thoroughly in the literature.

The three important changes related to disc height loss include:

  1. increased annular and endplate stress
  2. development of hypermobility
  3. facet approximation with reduced joint space width

These anatomical areas are important because this is where the innervation exists that contributes to pain.

Generally, spinal pain generators can be categorized into three distinct areas…all affected by disc height loss:

  1. discogenic and associated sinuvertebral nerve
  2. vertebral endplate disruption and associated basivertebral nerve
  3. facetogenic with medial branch and subchondrial innervation

A better understanding of the relationship between disc height loss and hypermobility will help us move toward developing models–as this relationship is thought to be the beginning stage of degeneration. A focus on the related biorheology to maintain disc height will be of paramount importance in the decades to come in the prevention of reduced joint space width of the opposing endplates and facet hyaline cartilaginous surfaces.

  1. Barr JS. Low-back and sciatic pain: results of treatment. J Bone Joint Surg Am 1951;33-A: 633–49.
Spine Models - Dynamic Disc Designs Corp.

Spine models have been used for decades, if not centuries, to convey spinal problems.

Models on the market have been static and not dynamic. Simply, pain is most often dynamic in nature so it is hard to understand why some professionals still use models that do not move to educate their patients. The spine is a dynamic structure with the intervertebral disc at the core, working as a hydraulic resistor against excess movement in the prevention of approximating structures. Dynamic Disc Designs understands that the true core of the spine is in the intervertebral disc, and more specifically, the nucleus pulposus.  It is in the greater understanding of this tissue where the answers most lie regarding treatment and prevention.

Dynamic models are new and have been pioneered by Dynamic Disc Designs. Starting with real human specimens, Dr. Jerome Fryer works backwards, sculpting the soft tissues to give a real representation of the cartilagenous tissues. Specimens are chosen carefully to show facet arthropathy in the narrowing of the lateral recess, for example, in the development of spinal stenosis. Other models have been crafted to show a younger disc with normal disc height but often seen in the case of disc herniation. Discogenic pain is also a common source of pain so therefore, innervation of the outer annulus is included with the Professional LxH Model.

One of the main pride pieces to Dynamic Disc Designs is the feedback and interaction Dr. Jerome Fryer receives from his customers. For example, do you know what innervates the endplate? Have you heard of Becker’s triangle? All these details have come from our years of attending spinal conferences like NASS and The Congress of Neurological Surgeons. Many professionals provide personal feedback and offer inspiration to new product development. Dr. Jerome Fryer (President and Chief Innovations Officer) finds these conferences an important part of staying current and imperative in receiving feedback on what doctors are looking for and require in the fast paced clinical world to educate their patients in an effective way.

Join us in San Francisco at booth # 810 for the North American Spine Society Convention.

Disc Height Model

Intradiscal pressure depends on the understanding disc height loss and its relationship to load.

In a recent publication titled: Intradiscal pressure depends on recent loading and correlates with disc height and compressive stiffness, these authors tackled an important topic to help reveal the deformation an intervertebral disc will experience when subjected to prolonged and oscillatory loads. Often in clinical settings patients will experience low back pain as a result of cumulative and repetitive loads on the spine. It is therefore important to educate the patient on the reasons why pain may generate as the vertebrae begin to approximate. In their methods they tested 15 lumbar goat discs and found that as the pressures decreased over time, the heights of the discs were reduced significantly.  Past ideas around intradiscal pressure and height loss did not think that recent loading events played as much of a role as seen in this publication. Over the course of 4.5 hours of varying high and low dynamic loading, the disc heights reduced significantly. In human discs it is well known that spine pain is more likely to generate from a disc that is compressed vs. one that has normal height. Dynamic Disc Designs construct dynamic disc models to help the educator explain the pain sites in an interactive and research supported way. Explore.

Synovial Joint - Synovial Fold

Facet joint innervation is much more than just the medial branches.

In a manuscript by Mapp and Walsh titled : Mechanisms and targets of angiogenesis and nerve growth in osteoarthritis , they reviewed articles that addressed angiogenesis and nerve ingrowth of the synovial joint including the osteochondral environment in the paradigm of osteoarthritis.

These researchers looked at the anatomical environment of the osteochondral junction as well as the meniscal tissue. They suggested it was a difficult task to determine what ‘normal’ is when factoring in the age-related factors. Angiogenesis is a normal part of development but it is also pathological when looking at cancer and osteoarthritis mechanisms. Angiogenesis cultivates nerve ingrowth as neurovascular bundles travel together. Most pain from the facet is thought to come from the medial branches but there are also nerves from the subchondral area that are similar to the basivertebral nerve innervating the endplate. As cartilage is damaged, underlying subchondral bone can be exposed where the tide mark exists and it is thought to drive this angiogenesis and nerve ingrowth.

The knee is the most commonly studied synovial joint. Interestingly, the meniscus (a fibrocartilage) is thought to be only innervated on the outer third. For those that have studied the intervertebral discs, this should sound familiar. We know in the spine, the outer third of the disc is innervated. It is also fibrocartilagenous with very little blood vessels. In this publication by Mapp and Walsh they talked about when the meniscus is damaged, nerve ingrowth into tissue that is normally not innervated, becomes innervated and sensitive.  We know this also occurs in the intervertebral discs and modeled in the Professional LxH Model.

Facet joint innervation is therefore found to exist not only with the capsular tissues that engulf the synovial joint but also deep within the joint itself. At the osteochondral junction nerves grow from the subchondral bone and into the underlying osteochondral areas. Furthermore, osteophytes (bone spurs) have been shown only to occur on the periphery of synovial joints. The exact mechanism of their development is not known. Some theorists believe they are a result of chondrocyte proliferation as they look like epiphyseal growth plates.

One common theme that resonates across all joint pathologies is the reduction of joint space width. Therapeutic strategies to increase joint space should always be explored when looking at ways to reduce pain.

Dynamic Disc Designs Corp. strives to provide a dynamic look at pain generators in a model platform that professionals can feel confident in using when explaining pain syndromes to their patients.

progressive disc herniation model

Progressive disc herniation often occurs to the annulus  over the course of many individual injuries.

Disc herniation is now classified into protrusion, extrusion, sequestered as well as contained or not contained. It is often progressive in nature. It all begins with radial tears to the inner most annulus when the lemellae delaminate as the hydraulic stresses out compete the tensile strength between the endplates.

As the outer annulus is innervated, continued stress and tearing to the fibres can begin to reach the innervation of the disc. Repetitive flexion pushes the nucleus pulposus posterior into the sensitive outer third of the anulus. When this fissure becomes chronically spread apart, often granulation tissue forms around the tear causing intradiscal inflammation. It is now believed that disc innervation is similarly innervated like an organ with sympathetic nerves which is why it may lead to chronic spinal pain syndromes. When these nerves (sinuvertebral nerves) embedded in the posterior annulus are irritated from the stresses of the nucleus–often done in lumbar and cervical flexion– people often complain of morning stiffness.  This is a cardinal sign of degenerative disc.

Dynamic Disc Designs manufactures models that provide the practitioner with models to describe a patient’s spinal symptoms. Whether the concept of nerve root entrapment due to extrusion requires surgery, or the patient is experiencing facetogenic pain due to disc height loss and would respond to manipulation, or the patient has a symptoms of stenosis due to a thickened ligamentum flavum and experiences bilateral leg symptoms after a period of walking, these new dynamic models are helpful in the connecting what doctors know and what patients are often confused about.  ddd hopes to build better doctor patient communication through more effective spine education for all spine professionals.

Dr. Jerome Fryer, the founder of ddd, has been lecturing on topics of education to professionals to help improve outcomes for spine.

Endplate, intervertebral disc

Poromechanics of the Disc is an important topic to understand regarding manual spinal treatment and prescribing exercise.

Manual treatments performed by chiropractors deliver forces that influence the disc. Even though spinal manipulation is thought to be a considered conservative method in the treatment of disc herniation, more recent investigation by way of pressure transducers with manipulation shows an alternative view.

There are many styles of manual treatment to the spine. Most classic is the side posture manipulation that renders a rotational force to the disc to gap the facet joint. The action of this can be seen in our spinal manipulation model. This has a primary effect on the facet but must also have an impact on the disc itself.

Other manual treatment strategies to the spine include flexion/distraction and decompression. These treatment strategies work on the poromechanics of the disc. This type of treatment looks to improve the hydraulics of the disc by creating low pressures within the disc to help improve disc height. In a recent publication in Arthritis and Cartilage, the authors looked at the poromechanics of the disc and graphically represented the flow through the endplate.

Dynamic Disc Designs strives to highlight research and represent this research through modeling to help improve clinical outcomes.