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Academy of Chiropractic’s

MD Relationship Program

Spinal Biomechanics 

Does Spinal Degeneration CAUSE Hypermobility and Ligament Laxity

From:  William J Owens Jr DC DAAMLP

 

 

Dr. Duane Paterson asked the following question.  It is an important one so I thought as I wrote this up to answer his question I would share it with the group.

"Is there research to indicate that osteoarthritis can cause instability, and if so how do you defend a trauma patient who demonstrates ligament laxity and moderate to severe OA?"

Let’s talk first about how the body responds to traumatic injury.  The first step is understand Wolff’s Law, which governs the response of osseous structures to mechanical stress.

 

Wolff's law, developed by the German anatomist and surgeon Julius Wolff (1836–1902) in the 19th century, states that bone in a healthy person or animal will adapt to the loads under which it is placed.  If loading on a particular bone increases, the bone will remodel itself over time to become stronger to resist that sort of loading. The internal architecture of the trabeculae undergoes adaptive changes, followed by secondary changes to the external cortical portion of the bone, perhaps becoming thicker as a result. The inverse is true as well: if the loading on a bone decreases, the bone will become less dense and weaker due to the lack of the stimulus required for continued remodeling.  This reduction in bone density (osteopenia) is known as stress shielding and can occur as a result of a hip replacement (or other prosthesis). The normal stress on a bone is shielded from that bone by being placed on a prosthetic implant.

 

The remodeling of bone in response to loading is achieved via mechanotransduction, a process through which forces or other mechanical signals are converted to biochemical signals in cellular signaling. Mechanotransduction leading to bone remodeling involve the steps of mechanocoupling, biochemical coupling, signal transmission, and cell response.

 

The specific effects on bone structure depends on the duration, magnitude and rate of loading, and it has been found that only cyclic loading can induce bone formation.  When loaded, fluid flows away from areas of high compressive loading in the bone matrix. Osteocytes are the most abundant cells in bone and are also the most sensitive to such fluid flow caused by mechanical loading.  Upon sensing a load, osteocytes regulate bone remodeling by signaling to other cells with signaling molecules or direct contact. Additionally, osteoprogenitor cells, which may differentiate into osteoblasts or osteoclasts, are also mechanosensors and may differentiate one way or another depending on the loading condition. 

Computational models suggest that mechanical feedback loops can stably regulate bone remodeling by reorienting trabeculae in the direction of the mechanical loads.

 

https://en.wikipedia.org/wiki/Wolff%27s_law

 

Next, we have to consider how connective tissue responds to mechanical stress.  Connective tissue included, ligaments, tendons and muscle.  We use the term CONNECTIVE instead of SOFT…It gives a better description of the action of this type of tissue as opposite to just simply comparing it to bone.  Davis’ Law is defined as follows.

 

The term Davis's law is named after Henry Gassett Davis, an American orthopedic surgeon known for his work in developing traction methods. Its earliest known appearance is in John Joseph Nutt's 1913 book Diseases and Deformities of the Foot, where Nutt outlines the law by quoting a passage from Davis's 1867 book, Conservative Surgery:

 

"Ligaments, or any soft tissue, when put under even a moderate degree of tension, if that tension is unremitting, will elongate by the addition of new material; on the contrary, when ligaments, or rather soft tissues, remain uninterruptedly in a loose or lax state, they will gradually shorten, as the effete material is removed, until they come to maintain the same relation to the bony structures with which they are united that they did before their shortening. Nature never wastes her time and material in maintaining a muscle or ligament at its original length when the distance between their points of origin and insertion is for any considerable time, without interruption, shortened."

 

Davis's writing on the subject exposes a long chain of competing theories on the subject of soft tissue contracture and the causes of scoliosis. Davis's comments in Conservative Surgery were in the form of a sharp rebuke of lectures published by Louis Bauer of the Brooklyn Medical and Surgical Institute in 1862.  In his writing, Bauer averred that "a contraction of ligaments is a physiological impossibility". Bauer sided with work published in 1851 by Julius Konrad Werner, director of the Orthopedic Institute of Konigsberg, Prussia; Bauer and Werner, in turn, were contradicting research published by Jacques Mathieu Delpech in 1823.

 

The Law continues to state…

 

Tendons are soft tissue structures that respond to changes in mechanical loading. Bulk mechanical properties, such as modulus, failure strain, and ultimate tensile strength, decrease over long periods simulations, human test subjects can experience gastrocnemius tendon strength loss of up to 58% over a 90-day period. Test subjects who were allowed to engage in resistance training displayed a smaller magnitude of tendon strength loss in the same micro-gravity environment, but modulus strength decrease was still significant.

 

Conversely, tendons that have lost their original strength due to extended periods of inactivity can regain most of their mechanical properties through gradual re-loading of the tendon, due to the tendon's response to mechanical loading. Biological signaling events initiate re-growth at the site, while mechanical stimuli further promote rebuilding. This 6-8 week process results in an increase of the tendon's mechanical properties until it recovers its original strength. However, excessive loading during the recovery process may lead to material failure, i.e. partial tears or complete rupture. Additionally, studies show that tendons have a maximum modulus of approximately 800 MPa [Megapascal Pressure Unit]; thus, any additional loading will not result in a significant increase in modulus strength. These results may change current physical therapy practices, since aggressive training of the tendon does not strengthen the structure beyond its baseline mechanical properties; therefore, patients are still as susceptible to tendon overuse and injuries.

 

https://en.wikipedia.org/wiki/Davis%27s_law

 

What this tells us is the body will work to stabilize injured bone or connective tissue based on what happened to it.  Bone will remodel along stress lines and ligaments, tendons and muscle, trying to return the relationship to surrounding structures back to what it was BEFORE the injury.  Wolff’s Law will cause calcium to be laid down and bone to thicken, this is what causes osteophyte formation to occur.  That is designed to STABILIZE the bones relationship to abnormal biomechanical pressure and movement.  To us as Chiropractors, this is a direct explanation of the phases of Subluxation Degeneration.  Which is visualized in the following picture.

 

Screen Shot 2018 11 10 at 9.52.33 AM

 

We can also visualize this process in anatomic models as well.   

 

Screen Shot 2018 11 10 at 9.53.50 AM

 

As this ossesus process is taking place, the body is, in relation to Davis’ Law, tightening ligaments and the ossification bridge from bone to ligament starts to occur.  As the ligaments shorten to help stabilize the joint, their stiffness increases due to the integration of calcium into the cellular matrix.  This adds stability and STIFFNESS to the joint.  Over time, if left unchecked the ossification bridge will completely fill and stabilize the joint space and create a FUSED segment.  That will eliminate most or all motion in that motor unit.

So, when the body is injured we see that the integrity of the connective tissue is altered through tearing of the cellular matrix which creates HYPERMOBILITY and Ligament Laxity.  The body’s natural reaction is to stabilize this joint complex in line with Wolff’s and Davis’ Law. As that process continues the joint moves from HYPERMOBILE to HYPOMOBILE to FUSED.  Now we can see and understand that joint degeneration does NOT result in HYPERMOBILITY, it results in HYPOMOBILITY.  Therefore in the medical legal world, ligament hypermobility cannot be pre-existing for all the above reasons.  That is why it is critical to perform a proper evaluation on your patients IMMEDIATELY following the trauma and identifying the ABSENCE of degenerative changes on radiograph.  There is a 4-6 month window before they would start.

Lastly, we can say without any scientific doubt that once the connective tissue is injured, the cascade of degenerative and stabilizing events will start to occur.  That is why future care plans and long term monitoring of spinal injury are a critical part of our documentation.  It is not a question of IF osteoarthritis will occur, but WHEN…

 

 

 

 

 

PLEASE TAKE NOTICE: © Copyright CMCS Management, Inc - Dr. Mark Studin 2015 - This information is intended for educational purposes only. Any review, retransmission, dissemination or other use of, or taking of any action in reliance upon is prohibited.