Bottom loaded pedicle screw

A method of assembling a pedicle screw, the method comprising:

• inserting a rod seat into a lower opening of a cavity of a tulip head, wherein the lower opening of the cavity is disposed at a bottom end of the tulip head, and wherein the cavity has an upper opening disposed at a top end of the tulip head and internal threads disposed within an interior wall of the cavity adjacent to the upper opening;
• engaging the rod seat against a stop that extends 90° inwardly from the interior wall of the cavity, wherein the stop is disposed between the lower opening and the upper opening of the cavity and is separate from the internal threads;
• inserting a screw shank into the lower opening of the cavity of the tulip head such that a connector of the screw shank engages a shank mating face of the rod seat, wherein the connector is positioned at an upper end of the screw shank;
• slideably positioning an annular retainer collar about a shank collar of the screw shank, the shank collar disposed between the connector of the screw shank and a thread of the screw shank, wherein the annular retainer collar comprising (i) a collar body having an anti-rotation tab extending from the collar body and configured to mate with a corresponding anti-rotation socket of the cavity when the annular retainer collar is positioned about the shank collar and the connector of the screw shank is engaged with the shank mating face and (ii) a locking ring groove disposed within an outer surface of the annular retainer collar that aligns with a retention groove disposed within the interior wall of the cavity when the annular retainer collar is positioned about the shank collar and the connector of the screw shank is engaged with the shank mating face;
• and
• inserting a locking ring into a retention groove inlet disposed within an exterior surface of the tulip head and into the locking ring groove of the annular retainer collar and the retention groove of the cavity.