Intervertebral Disc Herniation

Fibrotic alterations in human annulus fibrosus correlate with progression of intervertebral disc herniation

Goal of the Study?

In this histological analysis article from the Arthritis Research and Therapy Journal 1 the authors’ goal was to better understand the mechanism behind annulus fibrosus failure and the progression of intervertebral disc herniation.


Why are they doing this study?

Intervertebral Disc Herniation (IVD herniation) disorders are a major cause of low back pain, often associated with aging and degeneration. During IVD degeneration, the Annulus Fibrosus (AF) integrity is compromised and its Extracellular Matrix (ECM) becomes disorganized which affects the integrity of the Nucleus Pulposus (NP).  Three types of disc herniation progression were identified:

  • Contained Disc Herniation –  IVD bulging occurs without the rupture of the AF.
  • Protrused Contained Disc Herniation – The Nucleus Pulposus extrusion is prevented by either the AF or the Posterior Longitudinal Ligament.
  • Uncontained Disc Herniation – both the AF and posterior longitudinal ligament rupture occurs and the Nucleus Pulposus extrudes into the epidural space.

The authors hypothesize that AF fibrosis is associated with hernia progression but to date, fibrotic alterations have not been systematically investigated in human IVD herniation.


What was done?

A total of 39 human herniated IVD samples were dissected to isolate the AF tissue.  Samples were categorized according to the above three types of disc herniation progression.  Six control sample discs without visible morphological alterations were obtained from younger adolescent idiopathic scoliosis patients undergoing surgery.  Both control and disc herniated samples were assessed using the five Pfirrmann grades followed by a complete histological analysis, first macroscopically separating out the NP and AF tissue and then processing them under Transmission Electron Therapy.


What did they find?

This systematic analysis suggests that important alterations in human Annulus Fibrosus (AF) tissue during herniation are associated with tissue fibrosis.  Structural changes in the distribution of the collagen fibres occur as the herniated AF progresses.  The collagen fibres tended to be thinner and less organized in uncontained herniation samples.  Cell-specific antibodies (𝛂-SMA) also tend to increase in the AF as disc herniation progresses.  These structural and biochemical fibrotic alterations appear to occur independently of age.  The study also suggested that the current Pfirrman classification tool does not appear to distinguish disc herniation progression. 



Why do these findings matter?

Tissue fibrosis in the Intervertebral Disc Herniation must be understood before new cellular and molecular treatments to stop disc herniation can be developed.  Currently, IVD herniation uses only the Pffirrman’s MRI-based classification system but this tool lacks suitability to assess herniation progression.  It is important to combine different classifications systems that embrace both image analysis and clinical evaluations to develop systematic markers that improve the diagnosis of the progression of  IVD disc herniation.


At Dynamic Disc Designs, our models, with a see-through clear lens to observe annulus fissuring, can help those that suffer from disc herniation problems see the nucleus dynamically make its way through the annular fibres. Understanding the flexion mechanics of a disc herniation can be helpful to prevent such an event. A dynamic disc model can deliver effective professional patient education to teach the loads that cause disc herniation.