What is the goal of the Study?
This Study aims to learn more about in-vitro models of disc degeneration. In this review paper, the authors sought a clinical perspective on the current state of in-vitro modelling related to the disruption, overloading and biochemical changes within the intervertebral disc.1
Why are they doing this Study?
Learning what causes disc degeneration is important as it leads to much disability. We have learned the spine’s primary function is to support and transmit loads while protecting the neural structures. However, understanding real human disc tissue can be challenging to study because of several factors, including one of the biggest obstacles to obtaining approval from review boards for the ethical use of humans. Because of challenges like this, spine researchers use in vitro-models. These models, for the most part, include at least one fundamental aspect of the actual disc in a human. In this review paper, the researchers looked at all the in-vitro models of disc herniation to provide an overview of the best modelling strategies to investigate advancing disc degeneration.
Interestingly, this is why Dynamic Disc Designs (ddd) models named their company this way, in the spirit of offering hope of regenerative potential to degenerated discs.
Degenerative disc disease (DDD) is the leading cause of lower back pain.2 Disc degeneration is a multifactorial condition that precedes DDD. Intervertebral disc disease involves a disruption of the biomechanics and is identified by its change in the hydration of the extracellular matrix (the stuff in between disc cells).
Interestingly, intervertebral degeneration is often asymptomatic and not painful. However, degenerative disc disease (DDD) is painful and can be defined as intervertebral degeneration progress from an asymptomatic to a symptomatic state. Even though intervertebral disc degeneration is widespread, the etiology of DDD remains unclear. What moves an ageing disc state (disc degeneration) to a disease state remains to be answered. If this could be more clearly revealed, then appropriate mitigation strategies could be implemented for millions of low back pain sufferers.
A hallmark characteristic of a degenerated disc is the loss of water-binding proteins (proteoglycans) in the nucleus pulposus. This can reduce the pressure of the disc, causing disc height loss—some reporting a 3% loss per year.3 This reduces the disc’s load-carrying capacity of a vertebra and can cause more compressive load to the facet joints and induce arthritis over time.
The primary purpose of this study is to evaluate the current state of replicating disc degeneration in-vitro. It looks into the degeneration models and descriptors used in identifying disc degeneration. This is also a look into the tests used in models of disc degeneration with the clinical advantages and disadvantages of these models. Finally, there is a recommendation of the most suitable models and encourage potential areas of future pursuit.
Reviewed papers were searched for in PubMed and Google Scholar between March 2020 and Sept 2021. The keywords they searched for included: disc degeneration, in-vitro, intervertebral disc and lumbar spine.
What did they find?
Disc degeneration was found to be a complex entity, which is nothing new for researchers. They highlighted that a popular degeneration strategy of needle puncture of a disc was not a great representation of what occurs naturally with real human disc degeneration. They suggested that this type of in-vitro model strategy should be considered more an injury model than a degeneration model. And overall, after considering all the differing types of in-vitro modelling of the disc, they found no one model can replicate all the features of human intervertebral disc degeneration. Suggestions include looking at cyclic compression loading models with differing postures.
Why do these findings matter?
Learning what causes micro failures and the leap from normal ageing to a disease state of the discs is important because efforts to mitigate advanced degeneration and disability could be averted if targeted treatments were applied. These findings matter because it helps direct future researchers to learn more about degenerated disc disease.
At Dynamic Disc Designs, we have worked to craft the best modelling to help spine professionals discuss degenerative disc disease and the strategies to mitigate disability outcomes. Our 3d models include a dynamic disc with an annulus and a nucleus to show the dynamics of disc bulging, disc herniation and dynamic disc height loss.
- In-vitro models of disc degeneration – A review of methods and clinical relevance ↩
- Role of biomechanics in intervertebral disc degeneration and regenerative therapies: what needs repairing in the disc and what are promising biomaterials for its repair? ↩
- Spine biomechanics J. Biomech. 38 (10), 1972–1983 ↩