Fryette’s Laws Teaching Tool

This teaching tool uses spherical cams to help visualize the coupled biomechanical movements that occur in the lumbar and thoracic spine during movement. See here for video and assembly sequence: https://youtu.be/jYGLIR5nwPY

“Fryette’s Laws” are a set of guiding principles used by physiotherapists and practitioners of osteopathic medicine to discriminate between dysfunctions in the axial skeleton. The coupled movements can be tricky to visualize, and especially difficult to explain to patients.
In this model, the central vertebrae represents the spine in neutral and demonstrates the first principle:

“Principle I: When the spine is in neutral, sidebending to one side will be accompanied by horizontal rotation to the opposite side.”

The front and back vertebrae represent the spine in flexion and extension respectively. These vertebrae demonstrate the second principle:

“Principle II: When the spine is in a flexed or extended position (non-neutral), sidebending to one side