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Animal Disc Models

Lumbar disc model

Animal disc models are a challenge. Understanding how we, humans, compare to our animalistic counterparts is a touchy subject. This month, some researchers looked at animal discs and compared them to human tissue.

Zhang et al. titled a manuscript : Histological Features of Endplates of the Mammalian Spine : From Mice to Men, and looked carefully at the micro-architecture of the disc endplate. They found significant differences between the species they compared. Of the animals they compared ( mouse, rat, rabbit, and goat) they found the mouse and rat had very little bony components to the endplate while the rabbit and goat had growth plates adjacent to the bony endplates. When compared to human, the human endplate had much thicker cartilage and  the growth plate exchanged for trabecular bone.

Animal disc models are a challenge to use in research. They are useful because they are easier to access, simpler to obtain review board of ethics approval and often cost effective. But reseachers must understand that extrapolating their findings to the human should be cautionary. Zhang et al. showed in this research that although animal discs are similar to humans in many ways, significant differences exist. In general, animal endplates have more hyaline cartilage while humans have more calcified cartilage.

Dynamic Disc Designs is a spine modeling company that highlights important research. We are constantly on the lookout. Endplate modeling is available.

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Creep and Disc Bulging

Patient education models

Discs are often at the core of spinal problems. Halloween is approaching and there isn’t a better time to highlight the importance of creep and disc bulging.

Many clinical symptoms related to spine present themselves in a time dependent fashion with patients often complaining of pain after a period of time standing or sitting. And very often when asked, they can tell physicians how much time needs to elapse before the symptoms of pain present. In a recent article by Pei et al, they defined bulging to occur at a maximum radial rate of 2.78%±1.09. They concluded that disc creep is a very important biomechanical repsonse and can effect spinal function.

Dynamic Disc Designs continues to provide spine professionals with dynamic models to help explain and understand pain generators. Perhaps “where” it hurts, may not be that complicated.

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Intradiscal Pressures in Sheep

Intradiscal Pressures

Animal models to understand the human lumbar intervertebral disc is an important topic. Recently, Wilke et al. looked at intradiscal pressures during daily activities in sheep-one of the most comparable animal models to humans.

Back pain is most linked to intervertebral disc degeneration which includes proteoglycan loss with accompanying water loss as well as disc height loss. But to understand the complexities of this, ethical approval to use humans in an in-vivo setting is challenging. Therefore, animal models have been and will continue to be a useful way to understand the internal aspect of the disc.

These researchers embedded a pressure transducer within the nucleus at the L2-3 and L4-5 levels of this animal. They then divided the measures into two main categories: active phase and rest phase. This was an arbitrary division because sheep do not have the same rest schedules as humans do. Interestingly, they found that intradiscal pressures were on average two to four times higher compared to humans. One would think because of their quadruped orientation and horizontal nature of the spine, the pressures would have thought to be less. This was not the case. Some of the ideas around why this was the case included the active muscular contraction of the longitudinal muscles to keep the forelimbs and hind-limbs in approximation with one another. In other words, if the distance between forelimbs and hind-limbs increased, the spine would sag.

Another interesting finding was they found intradiscal pressures lowest during the surgical procedure. They hypothesized that it was the medication that may have caused the muscles to relax and thus reduce the intradiscal pressures. Conversely and  postoperatively, the pressures were highest. Clinically, could the effect of muscle relaxants help reduce intradiscal pressures in humans? This could likely be the pharmaco-mechanical mechanism in prescribing muscle relaxants in humans but still requires supporting research.

Degenerated-Disc-Model

Overall, research like this is fundamental if we are to use animal models to study human intervertebal disc. Dynamic Disc Designs is committed to highlight fundamental research in the spirit of fostering research ideas to improve outcomes. Our spine education models help facilitate discussion.

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Clinical Spinal Complaints are often Diurnal

Disc Bulge Model

Many clinical spinal complaints are correlated to diurnal (which means the day-night cycle) influences.

It is well known that the intervertebral discs lose and regain hydraulic fluid over the course of this cycle. Specifically, we know water compresses out of the discs and lying down will re-imbibe the loss. Research has shown approximately 16% of change to the lower lumbar discs. Often, patients will have symptoms related to this as some complain of pain in the mornings when the discs are full of fluid and stretch open the annular tears in the discs.  This especially occurs under first get-up and when trying to put socks on. A dynamic intervertebral disc model can help the practitioner in the discussion of these pain generators with a dynamic disc to show height loss.

In the Journal of Biomechanics, other research is now looking at other cartilage in the body and specifically, the knee, to see if there are changes from loading and unloading environments.  The intervertebral discs in the spine carry the same cartilage as the knee (hyaline cartilage) and therefore this knee research relates to the spine.

Dynamic Disc Designs models are helpful is education of diurnal influences from a clinical level.  For example, when the disc squishes down the hyaline cartilage of the facets at the same spinal level can rub and irritate subchondral nerves. This is a common complaint of the spine and our models help the practitioner bridge the research knowledge to the patient in a platform to motivate changes that will improve outcomes.  Explore our roster and take control of your spinal education in a dynamic platform–just like the research shows.

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Spinal Manipulation Superior

Facet gapping Model

Spinal Manipulation found Superior to NSAIDS and Placebo In Spine, Apr 1, 2013 a group of researchers looked at spinal manipulation in a subgroup of admitted patients with excluding certain criteria outside of the nonspecific LBP group.

Many of the subjects did not sign the consent forms and therefore were excluded as well.  When high velocity low amplitude forces, as described as a diversified treatment performed by chiropractors, were compared to diclofenac and placebo HVLA treatment out performed the others significantly.   Visit http://www.ncbi.nlm.nih.gov/pubmed/23026869 for a read of the abstract.

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