Spinal Mechanics

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Three Pole Sacroiliac Theory

Observe figures A, B, and C below. The sacroiliac facets are shown to illustrate the ‘Three Pole’ theory. The sacral facets are colored in green and the iliac facets in red.  Each ‘pole’ causes the sacral facets to overlap their perimeter and cause a state of semi-dislocation. Notice that the sacral facet surface slides up and down and takes and no account of the bony ridge running along the middle.   


















Nutation Sacroiliac Theory

This theory fairs no better than the “Three Pole” theory. In fact it roughly describes the same sacral facet semi-dislocation. Observe figures  D and E below. Again this theory takes no account of the bony ridge running along the middle.  

The Three Pole Sacroiliac Theory

The Three Pole Sacroiliac Theory

The Three Pole Sacroiliac Theory

A

B

C

Three Pole’ and ‘Nutation’ Sacroiliac Theories

D

E

The Nutation Sacroiliac Theory

The Nutation Sacroiliac Theory

Upper Pole

Middle Pole

Lower Pole

Point of pivot

Point of pivot

Which is the best theory, the Nutation or Three pole sacroiliac theory?  

The answer is that both theories should be considered as examples of how the sacroiliac joints lesion rather than articulate.

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