Intervertebral Disk Degeneration – Fibrotic Remodelling, Time and Entropy
Lower back pain is an issue on this planet. It affects 632 million people worldwide and plagues 70-80% of US individuals at some point in their lives. The good news is that it is often self-resolving, but repeated bouts’ of recurrence are very frequent. The most popular low back pain diagnosis is intervertebral disk degeneration, with specific structural disruptions often contributing to pain. Therefore it is only logical for researchers to look at this structure to learn more about how the structure contributes to back pain.
We have known for years that the intervertebral disk is composed of two main structural components. The annulus fibrosus, which is the tough criss-cross oriented outer layer and the nucleus pulposus, which is an inner, softer gelatinous structure that holds water to help with the resistance against compression forces. To dive a little deeper, the annulus fibrosus consists of type 1 collagen, and the nucleus pulposus consists of type 2 collagen. If you want to explore the microstructure, you can visit Eyre et al.
The key structural element of the intervertebral disk looks to be the extra-cellular matrix. This is the ‘stuff’ between cells. The scaffolding, so to speak. The infrastructure within that holds things in place—or at least, is supposed to hold things in place.
In highlighting this research, James Iatradis, a well-known spine researcher, assembled a team to look at the intervertebral disk’s microstructure and look closely at what could be going on. In a Special Issue Article in the Journal Spine 1, his team used a special technique, named second harmonic generation imaging (SHG), to quantify the collagen content and structural make-up of intervertebral disk degeneration.
The concept of entropy, which is a physics term to describe order, or lack thereof, helped the researchers describe the disorganization of the degenerated tissue compared to the disk’s non-degenerated tissue. They found the tendency of the degenerated disk to be less organized with an increasing intensity seen with the imaging technique used. In other words, more chaos or entropy signalled disorder of the tissue. Collagen, in its healthy form, is organized. These researchers found the degenerated disks contained less microstructural organization and fibrotic remodelling.
This is an important paper. It demonstrates that tissues change over time. And with structural changes, there must be a biomechanical change. At Dynamic Disc Designs, we understand that the spine is in constant change and with that, we must learn and adapt as we age. Explore our wide-ranging dynamic models with varying properties to help with the education of the spine.