12. A spine stabilization device comprising: a bone anchor having a distal end adapted to engage a bone; a housing at a proximal end of said bone anchor; a longitudinal bore in said housing; said bore being aligned with the bone anchor and having an open end and a closed end; a deflectable post having a proximal end, an elongated body and a distal end; the proximal end of said deflectable post extending from the open end of said longitudinal bore; a curved retainer at the distal end of the deflectable post; the curved retainer being received in the longitudinal bore; a fastener which secures the curved retainer in the longitudinal bore but allows the deflectable post to pivot relative to the bone anchor; and a spring positioned within the bore between the deflectable post and the housing such that the spring flexibly resists pivoting of the deflectable post towards the housing wherein pivoting of the deflectable post causes compression of the spring in a direction parallel to the axis of the longitudinal bore.
16. The spine stabilization device of claim 12 , wherein the spring comprises a first portion in contact with the deflectable post, a second portion in contact with the housing and a flexible portion between the first portion and the second portion which is elastically deformed by pivoting of the deflectable post towards the housing.