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. 11. The spine stabilization device of claim 7 , wherein: said compliant member is a polymer disc having an outer diameter sized to fit within the tubular extension and a central aperture sized to receive the deflectable post; and wherein the compliant member is shaped to prevent the compliant member from being pinched between the deflectable post and the tubular extension.