Osteoarthritis is common and causes much disability in the world to many. It is a joint condition that causes pain, which often leads people to seek therapy. Despite the efforts to learn the underlying causes, researchers have been confused as to the source and propagation of degenerative osteoarthritic changes. We know that surface injury to cartilage can occur from high-risk competitive sports and result in the development of osteoarthritis; the precise reasons as to this has eluded researchers in the field. Understanding the mechanobiology of the early stages of OA when micro-cracks start will be an important piece of the puzzle in the prevention of osteoarthritis.
Just this month, a group of researchers out of the University of Calgary, looked at the finer micro-structure of the cartilage. 1 They looked at crack propagation (micro-fracturing) of the cartilage to get a better understanding of the load and respective magnitude as it relates to the damage. Their objective included looking carefully at the local strain distribution of the cartilage nearby to the microcracks.
What did they do?
Cylindrical osteochondral punch plugs were harvested from pig knees and fixed to a custom design compression testing device. The cartilage thickness was measured at three different locations of the surface. To prevent dehydration, which can often occur in these testing environments and affect the results, they fully immersed the sample in a phosphate-buffered solution. The thickness of the cartilage was measured using light microscopy. Measures of strain were applied. To simulate the crack in the cartilage found in-vivo, vertical cuts were made in the cartilage at the most superficial part of the surface cartilage along with the middle zone.
What did they find out?
Axial strains were significantly more abundant at the damage zone compared to the non-damaged cartilage. This indicates that the ability of the cartilage to resist compression is less in the damaged or micro fractured cartilage, disrupting the biomechanics.
What can we take away from this study?
The drive to learn about osteoarthritis is essential. Billions of dollars are spent annually for a multitude of therapeutics, including joint replacement, injections, pharmaceuticals and manual therapy. By learning about how cracks propagate in the cartilage and, ultimately, how we prevent the development of osteoarthritis will be a great asset to the planet.
At Dynamic Disc Designs, we work to follow the research and work to bring that to the doctor-patient engagement process. Our latest modelling now includes a crack in the cartilage of the facet joint.