27. The spine stabilization device of claim 26 , wherein said inner core of said centering rod is made of a super-elastic metal and said outer sheath is made of a biocompatible polymer.
26. A spine stabilization device comprising: a bone anchor; a deflectable mount; and a self-centering joint connecting the bone anchor and the deflectable mount; wherein the self-centering joint includes, a housing having a socket; a retainer pivotably received in the socket; and a centering rod having an inner core and an outer sheath, the centering rod received partially within the retainer and partially within the housing; whereby deflection of the retainer bends the centering rod and the centering rod exerts a restoring force on the retainer.