14. A spinal stabilization device comprising: a centering rod having a first end, a second end and a flexible section connecting the first end and the second end; wherein said centering rod is made of a super-elastic metal; a ball-rod including at least a partial ball-shaped retainer and a rod; a first bore extending along a longitudinal axis of the ball-rod and opening through the ball-shaped retainer opposite the rod, wherein the first end of the centering rod is received in the first bore; a housing extending from a threaded bone anchor; a socket within the housing, wherein the socket at least partially encloses the ball-shaped retainer to form a ball-joint; a channel extending from the socket out of the housing, wherein the rod of the ball-rod extends through the channel out of the housing; wherein the channel comprises a frusto-conical surface positioned to contact the rod after an amount of deflection of the rod from center of the channel; a second bore in the housing extending from the socket opposite the channel, wherein the second end of the centering rod is received in the second bore; and whereby deflection of the ball-rod bends the flexible section of the centering rod and the centering rod exerts a restoring force to center the rod of the ball-rod within the channel.
14. A spinal stabilization device comprising: a centering rod having a first end, a second end and a flexible section connecting the first end and the second end; wherein said centering rod is made of a super-elastic metal; a ball-rod including at least a partial ball-shaped retainer and a rod; a first bore extending along a longitudinal axis of the ball-rod and opening through the ball-shaped retainer opposite the rod, wherein the first end of the centering rod is received in the first bore; a housing extending from a threaded bone anchor; a socket within the housing, wherein the socket at least partially encloses the ball-shaped retainer to form a ball-joint; a channel extending from the socket out of the housing, wherein the rod of the ball-rod extends through the channel out of the housing; wherein the channel comprises a frusto-conical surface positioned to contact the rod after an amount of deflection of the rod from center of the channel; a second bore in the housing extending from the socket opposite the channel, wherein the second end of the centering rod is received in the second bore; and whereby deflection of the ball-rod bends the flexible section of the centering rod and the centering rod exerts a restoring force to center the rod of the ball-rod within the channel. 15. The spine stabilization device of claim 14 , wherein said rod and said ball-shaped retainer are made in one piece.