21. A spine stabilization device comprising: a first element; a second element; and a self-centering joint connecting the first element and the second element; wherein the self-centering joint includes, a housing having a socket; a retainer received in the socket such that the retainer is deflectable relative to the housing; and a centering rod having an inner core and an outer sheath, the centering rod received partially within retainer and partially within the housing; and whereby deflection of the retainer bends the centering rod and the centering rod exerts a restoring force on the retainer.
21. A spine stabilization device comprising: a first element; a second element; and a self-centering joint connecting the first element and the second element; wherein the self-centering joint includes, a housing having a socket; a retainer received in the socket such that the retainer is deflectable relative to the housing; and a centering rod having an inner core and an outer sheath, the centering rod received partially within retainer and partially within the housing; and whereby deflection of the retainer bends the centering rod and the centering rod exerts a restoring force on the retainer. 24. The spine stabilization device of claim 21 , wherein said outer sheath of said centering rod is made of PEEK.