25. A spine implant comprising: an anchor adapted to be inserted into the bone of a patient; an anchor head having a deflection guide cavity, the deflection guide cavity having a deflection guide cavity wall, a central axis, and a deflection guide cavity opening; a deflection rod having a distal end secured within said deflection guide cavity and a proximal end extending out of the deflection guide cavity opening; wherein the spine implant is configured such that said deflection rod is resiliently held in alignment with the central axis of the deflection guide cavity; wherein, with the deflection rod aligned with a central axis of the deflection guide cavity, there exists a gap between the deflection guide cavity wall and the deflection rod at the deflection guide cavity opening which gap diminishes in size towards the distal end of the deflection rod; and wherein the proximal end of the deflection rod can resiliently deflect in response to a load applied to the proximal end of the deflection rod and wherein contact between the deflection rod and the deflection guide cavity wall limits deflection of the deflection rod.
25. A spine implant comprising: an anchor adapted to be inserted into the bone of a patient; an anchor head having a deflection guide cavity, the deflection guide cavity having a deflection guide cavity wall, a central axis, and a deflection guide cavity opening; a deflection rod having a distal end secured within said deflection guide cavity and a proximal end extending out of the deflection guide cavity opening; wherein the spine implant is configured such that said deflection rod is resiliently held in alignment with the central axis of the deflection guide cavity; wherein, with the deflection rod aligned with a central axis of the deflection guide cavity, there exists a gap between the deflection guide cavity wall and the deflection rod at the deflection guide cavity opening which gap diminishes in size towards the distal end of the deflection rod; and wherein the proximal end of the deflection rod can resiliently deflect in response to a load applied to the proximal end of the deflection rod and wherein contact between the deflection rod and the deflection guide cavity wall limits deflection of the deflection rod. 31. The implant of claim 25 , wherein the proximal end of the deflection rod can resiliently deflect in response to a load applied to the proximal end of the deflection rod by bending of the deflection rod in response to a load applied to the proximal end of said deflection rod.