Its size is not and cannot be reduced by compression as shown in the cut. A displaced vertebra, one whose articular surfaces are separated, enlarges the foramina, therefore, does not occlude the opening, does not pinch, compress or squeeze the outgoing nerves as they pass through the intervertebral foramina. The spinal nerves and their branches may be impinged upon or against, or stretched because of displaced vertebra, but not pinched. Impinged nerves from narrowing of the foramina. The author here refers to nerves being pinched, not impinged.
Constriction is a condition of being narrowed by a binding force applied around a tubular orifice.
A morbid contraction of a passageway, any hollow tube of the body. Constriction and stricture mean one and the same. Illustrate stricture on board, contracture of nerve tissue, inflammation because of increased combustion of oxygen. Compression is to press together, to make more compact, to reduce in volume, to make narrower in one direction. A concussion is a shaking, a jarring, an agitation, or a shock caused by a collision.