Spinal Mechanics

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Dr Harrison Fryette made a huge contribution to our understanding of how the spine works in the last century. However,  knowledge has moved on a long way since his theories. His theories were a valuable part of history, but history they are. For completeness, his articulation theories are stated because they represent a good way to describe joint lesions:



This law applied to the whole spine. Unfortunately, in practice his theories when applied to the whole spine would lock it substantially in an instant. This is the problem with focus theories when one area of articulation is looked without reference to its function or how its articulation integrates with the other spinal and sacroiliac joints during every day movements.


Fryette’s simple theories were loosely correct for the lumbar and cervical vertebral joints, though the actual mechanism of articulation is more complicated. However, his theories are completely inaccurate when describing how the thoracic spinal joints articulate. As an example, if the thoracic joints articulated as per Fryette’s theory (see photograph to the right) we, as humans would not be able to breath efficiently. This is because the ribs must stay in parallel for us to breath correctly. So you cannot have a theory that states that they side-bend and rotate.


A working spinal theory must take obvious factors like this into account, along with how each joint integrates with the articulations of the rest of the spine and sacroiliac. This is what John Bayliss’s synergetic spinal theories are all about.  That is why his work is such a huge breakthrough.


If you do not know how the spine articulates, your chances of fixing it when it goes wrong are considerably reduced.





Fryettes Laws

Fryettes theory on the thoracic spine.

If thoracic joints articulated as Fryette described, there would be forced displacement of the ribs. This would seriously hinder the breathing mechanism. However, this is a common lesion found in the thoracic joints.