1. A spinal rod anchoring system comprising: a rod adapted to extend along a spine of a patient; a first rod anchor adapted to be fixed to a vertebra of the spine, the first rod anchor receiving the rod such that the rod is secured against substantial lateral translation relative to the first rod anchor and the rod is allowed to slide axially relative to the first rod anchor through a first pivot point and to change in pitch and yaw about the first pivot point while substantially limiting roll of the rod relative to the first rod anchor; a housing forming a receptacle portion having a substantially concave inner surface and a protrusion extending inwardly from the concave inner surface; and a sleeve slidably receiving the rod, the sleeve having a substantially convex mating surface mating with the concave inner surface, the sleeve having a circumferential groove in the convex mating surface mating with the protrusion in the concave inner surface of the housing such that the sleeve is adapted to rotate relative to the housing to change in pitch and yaw relative to the housing while being substantially prevented from changing in roll relative to the housing.
2. The system of claim 1 , wherein the housing and the sleeve are adapted to substantially inhibit roll relative to one another.