1. A dynamic spine stabilization device comprising: a bone anchor having a housing; a cavity in the housing coaxial with the bone anchor; a deflectable post received in the cavity; the deflectable post having a retainer at a distal end and a mount at a proximal end; the retainer being secured in a pocket of the cavity of the housing such that the deflectable post may pivot and rotate about a longitudinal axis of the deflectable post; and a spring positioned in the cavity of the housing between the post and the housing such that pivoting of the post away from a position in which the longitudinal axis of the post is coaxial with the bone anchor causes compression of the spring and such that the spring applies a force upon the post pushing the post towards a position in which the longitudinal axis of the post is coaxial with the bone anchor.
1. A dynamic spine stabilization device comprising: a bone anchor having a housing; a cavity in the housing coaxial with the bone anchor; a deflectable post received in the cavity; the deflectable post having a retainer at a distal end and a mount at a proximal end; the retainer being secured in a pocket of the cavity of the housing such that the deflectable post may pivot and rotate about a longitudinal axis of the deflectable post; and a spring positioned in the cavity of the housing between the post and the housing such that pivoting of the post away from a position in which the longitudinal axis of the post is coaxial with the bone anchor causes compression of the spring and such that the spring applies a force upon the post pushing the post towards a position in which the longitudinal axis of the post is coaxial with the bone anchor. 13. The device of claim 1 , wherein said spring has an isotropic deflection profile.