Posterior spinal fixation screws

A bone screw comprising:

• a bone screw shank comprising a shank head;
• a receiver comprising a base having a cavity therewithin, the cavity configured to securely accept insertion of the shank head from a top of the receiver;
• a pair of arms extending upwardly from the base;
• and a rod channel defined between the pair of arms, wherein the base comprises a recess formed in a bottom surface thereof, wherein the base and the recess are shaped and sized to allow angulation of the bone screw shank relative to the receiver in a range of about 0 degrees to about 60 degrees in a first lateral direction and prevent angulation of greater than about 0 degrees in a second lateral direction opposite the first lateral direction;
• and
• a load ring configured to be top-loaded into the receiver subsequent to the insertion of the shank head, wherein the load ring comprises a pair of legs connected by two concave surfaces at its proximal side.

A bone screw comprising:

• a bone screw shank comprising a shank head;
• a receiver comprising a base having a cavity therewithin, the cavity configured to securely accept insertion of the shank head;
• a pair of arms extending upwardly from the base;
• and a rod channel defined between the pair of arms, wherein the base comprises a recess formed in a bottom surface thereof, wherein the base and the recess are shaped and sized to allow angulation of the bone screw shank relative to the receiver in a range of about 0 degrees to about 60 degrees in a first lateral direction and prevent angulation in a second lateral direction opposite the first lateral direction;
• and
• a load ring configured to be loaded into the receiver subsequent to the insertion of the shank head, wherein the load ring comprises a pair of legs connected by two concave surfaces at its proximal side.