7. An implantable spine stabilization device comprising: an elongated bone anchor having a distal end and a proximal end and a longitudinal axis; a deflectable post having a distal end and a proximal end and coaxially aligned with the longitudinal axis of the anchor; a joint which secures the distal end of the post to the proximal end of the bone anchor such that the deflectable post may pivot relative to the bone anchor; a tubular extension of the bone anchor which extends over a portion of the deflectable post; and a compliant member disposed between the distal portion of the deflectable post and the tubular extension of the bone anchor whereby the compliant member biases the deflectable post into alignment with the bone anchor with the compliant member being shaped to control deflection of the deflectable post from alignment with the longitudinal axis of the bone anchor.
7. An implantable spine stabilization device comprising: an elongated bone anchor having a distal end and a proximal end and a longitudinal axis; a deflectable post having a distal end and a proximal end and coaxially aligned with the longitudinal axis of the anchor; a joint which secures the distal end of the post to the proximal end of the bone anchor such that the deflectable post may pivot relative to the bone anchor; a tubular extension of the bone anchor which extends over a portion of the deflectable post; and a compliant member disposed between the distal portion of the deflectable post and the tubular extension of the bone anchor whereby the compliant member biases the deflectable post into alignment with the bone anchor with the compliant member being shaped to control deflection of the deflectable post from alignment with the longitudinal axis of the bone anchor. 8. The dynamic pedicle screw of claim 7 , wherein: said tubular extension is associated with a limit surface positioned to contact the deflectable post after a predetermined amount of deflection of the deflectable post away from alignment with the longitudinal axis of the bone anchor; and wherein the compliant member comprises a surface relief to prevent the compliant member from being pinched between the deflectable post and the limit surface.