Bottom loaded pedicle screw

1. A pedicle screw comprising:

a tulip head having an upper opening disposed in a top end of the tulip head and a lower opening disposed in a bottom end of the tulip head opposite the upper opening, wherein:

the upper and lower openings form a single cavity extending through the tulip head from a top end to the bottom end, and

the cavity has an interior wall, internal threads disposed within the interior wall and adjacent to the upper opening, and a stop disposed between the lower opening and the upper opening, the stop extending 90° inwardly from the interior wall and separate from the internal threads;

a rod seat disposed within the cavity and engageable with the stop, the rod seat having a rod mating face, a shank mating face opposite the rod mating face, and a hole disposed through the rod mating face and shank mating face;

a screw shank having a thread disposed along a length of the screw shank and a connector positioned at an upper end of the screw shank;

a retainer collar having a collar body, a pass through aperture disposed through the collar body, an anti-rotation tab extending from the collar body, and a collar expansion split disposed within the collar body, wherein the retainer collar is disposed about the connector of the screw shank; and

wherein the cavity of the tulip head further includes an anti-rotation socket constructed to receive and engage the anti-rotation tab of the retainer collar.

2. The pedicle screw according to claim 1 , wherein:

the cavity of the tulip head has a retention groove disposed within the interior wall;

the stop is disposed between the retention groove and the upper opening; and

the retainer collar has a locking ring groove disposed within an outer surface of the collar body.

3. The pedicle screw according to claim 2 , further comprising a locking ring disposed within the retention groove and the locking ring groove.

4. The pedicle screw according to claim 3 , wherein the locking ring has a compression zone disposed therein such that when the compression zone is in its natural state it has the unloaded outer diameter (DO 1 ) and an unloaded inner diameter (DI 1 ), and wherein when the compression zone is reduced, the locking ring has a loaded outer diameter (DO 2 ) and a loaded inner diameter (DI 2 ).

5. The pedicle screw according to claim 3 , wherein the tulip head includes a retention groove inlet that is connected to the retention groove and extends to an exterior surface of the tulip head.

6. The pedicle screw according to claim 5 , wherein the locking ring is disposed in the retention groove inlet.

7. The pedicle screw according to claim 6 , wherein the locking ring is a wire fabricated from a material selected from a group consisting of metals, alloys, and composites.

8. A pedicle screw comprising:

a tulip head having an upper opening disposed in a top end of the tulip head and a lower opening disposed in a bottom end of the tulip head opposite the upper opening, wherein:

the upper and lower openings form a single cavity extending through the tulip head from a top end to the bottom end, and

the cavity has an interior wall, internal threads disposed within the interior wall and partially extending from the upper opening to the lower opening, a retention groove disposed within the interior wall, and a stop extending 90° inwardly from the interior wall, wherein the stop is disposed in a position closer to the lower opening than to the upper opening and is separate from the internal threads and the retention groove;

a rod seat disposed within the cavity and engageable with the stop, the rod seat having a rod mating face, a shank mating face opposite the rod mating face, and a hole disposed through the rod mating face and shank mating face;

a screw shank having a thread disposed along a length of the screw shank and a connector positioned at an upper end of the screw shank;

a retainer collar having a collar body, a pass through aperture disposed through the collar body, a locking ring groove disposed within an outer surface of the collar body, an anti-rotation tab extending from the collar body, and a collar expansion split disposed within the collar body, wherein the retainer collar is disposed about the connector of the screw shank;

a locking ring disposed within the retention groove and the locking ring groove; and

wherein the cavity of the tulip head further includes an anti-rotation socket constructed to receive and engage the anti-rotation tab of the retainer collar.

9. The pedicle screw according to claim 8 , wherein the locking ring has a compression zone disposed therein such that when the compression zone is in its natural state it has an unloaded outer diameter (DO 1 ) and an unloaded inner diameter (DI 1 ), and wherein when the compression zone is reduced, the locking ring has a loaded outer diameter (DO 2 ) and a loaded inner diameter (DI 2 ).

10. The pedicle screw according to claim 8 , wherein the tulip head includes a retention groove inlet that is connected to the retention groove and extends to an exterior surface of the tulip head.

11. The pedicle screw according to claim 10 , wherein the locking ring is disposed in the retention groove inlet.

12. The pedicle screw according to claim 11 , wherein the locking ring is a wire fabricated from a material selected from a group consisting of metals, alloys, and composites such that the wire forms an annular ring when disposed within the retention groove and locking ring groove.