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Osteoarthritis model – subchondral bone

osteoarthritis model, spine, facet, disc height loss

Osteoarthritis is a burden on the people of this world and a major cause of disability. It is considered a degenerative disorder, affecting the aging population as it erodes cartilage, disrupting subchondral bone, leading to osteophytosis, muscle weakening and inflammation to the structures within the joint. 1 An accurate osteoarthritis model would be very helpful for spine.

Historically, osteoarthritis has been looked at from the perspective of cartilage wear with newer insights and interest at the subchondral level. (sub = below + chondro = cartilage) In a paper published in Arthritis and Research Therapy, researchers gave special attention to the subchondral bone. 2

In the perspective of the spine, disc height loss has an influence on the facet joints which are synovial joints. 3 It is disc height loss (a measure of vertebra approximation or closeness) that has shown to have the greatest impact on the biomechanics of a spinal motion segment. In particular, it narrows the intervertebral foramen, causes disc bulging as well as annular stress, and the narrowing can have an effect on the vascular flow in and around the nerves that exit the spine directly influencing nerve roots. There are few other degenerative conditions that can have such a large impact effect on the musculoskeletal system. 4

In Figure 1. of Subchondral bone in osteoarthritis: insight into risk factors and microstructural changes 2 a beautiful histological image showcases the microanatomy of the: calcified cartilage, uncalcified cartialge, the subchondral bone along with the tide mark and cement line of a normal synovial joint. This is an important area of the facet joint.

osteoarthritis model

As mechanical stress is placed onto the uncalcified cartilage, stress will translate through this avascular structure and into the subchondral bone. Chondrocytes secrete glycosaminoglycans (GAGs) and collagen type II-rich extracellular matrix (ECM) that are essential for the maintenance and regeneration of the cartilage which acts to protect subchondral bone. 6 Articular cartilage is mainly water, contributing to 80% of its weight. 7 Interestingly, we have seen that there is a diurnal variation of the cartilage in cartilage 8 similar to what we see in the discs. 9

The bottom line is our tissues that marry our bones together are dynamic and are in constant change to mechanical forces. Disc height loss of the spine will cause the facet joints in the spine to compress and lead to arthritis if not carefully managed.

Dynamic Disc Designs develops models to help in the greater understanding of how a compressed disc can have a multitude of mechanical effects on a spinal motion segment. Understanding the load distribution as it occurs naturally with diurnal variation, lying down, or with injury lifting, or prolonged sitting can be of great assistance in managing the treatment of spinal osteoarthritis as a result of disc height loss and facet arthrosis. Patient education proves to improve outcomes of osteoarthritis when patients understand what not to do first and secondly, why it is important to continue to do safe exercise. 6

The Professional LxH Model demonstrates hyaline cartilage and perichondrial vascularization, while the Lumbar Spinal Stenosis Model demonstrates subchondral sclerosis helping in the education of facet osteoarthritis. A dynamic osteoarthritis model for spine is important to have if educating is a part of a physician’s clinical life.

“Helping doctors be better teachers”

 

  1. Grynpas MD, Alpert B, Katz I, Lieberman I, Pritzker KP: Subchondral bone in
    osteoarthritis. Calcif Tissue Int 1991, 49:20–26.
  2.  Li et al. Arthritis Research & Therapy 2013 2013, 15:223 http://arthritis-research.com/content/15/6/223
  3.  Arbit, E., Pannullo, S., 2001. Lumbar stenosis: a clinical review. Clin. Orthop. Relat. Res.(Mar), 137–143.
  4.  Disc height loss and restoration via injectable hydrogel influences
    adjacent segment mechanics in-vitro Christian Balkovec , Andrea J. Vernengo, Stuart M. McGill Clinical Biomechanics 36 (2016) 1–7
  5.  Li et al. Arthritis Research & Therapy 2013 2013, 15:223 http://arthritis-research.com/content/15/6/223
  6.  Blazek AD, Nam J, Gupta R, Pradhan M, Perera P, Weisleder NL, Hewett TE, Chaudhari AM, Lee BS, Leblebicioglu B1, Butterfield TA, Agarwal S. Exercise-driven metabolic pathways in healthy cartilage. Osteoarthritis Cartilage. 2016 Feb 27. pii: S1063-4584(16)01025-6. doi: 10.1016/j.joca.2016.02.004. [Epub ahead of print
  7.  The basic science of articular cartilage: structure, composition, and function. Sophia Fox AJ, Bedi A, Rodeo SA. Sports Health. 2009 Nov;1(6):461-8.
  8.  J Biomech. 2013 Feb 1;46(3):541-7. doi: 10.1016/j.jbiomech.2012.09.013. Epub 2012 Oct 24. Diurnal variations in articular cartilage thickness and strain in the human knee.Coleman JL, Widmyer MR, Leddy HA, Utturkar GM, Spritzer CE, Moorman CT 3rd, Guilak F, DeFrate LE.
  9.  Botsford, D. J. MD; Esses, S. I. MD, FRCS(C); Ogilvie-Harris, D. J. MB, FRCS(C)  In Vivo Diurnal Variation in Intervertebral Disc Volume and Morphology. Spine: April 15, 1994
  10.  Blazek AD, Nam J, Gupta R, Pradhan M, Perera P, Weisleder NL, Hewett TE, Chaudhari AM, Lee BS, Leblebicioglu B1, Butterfield TA, Agarwal S. Exercise-driven metabolic pathways in healthy cartilage. Osteoarthritis Cartilage. 2016 Feb 27. pii: S1063-4584(16)01025-6. doi: 10.1016/j.joca.2016.02.004. [Epub ahead of print
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