Bottom loaded pedicle screw
A pedicle screw includes a tulip head, a rod seat, a screw shank, and a retainer collar. The tulip head has 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. The upper and lower openings form a single cavity extending through the tulip head from a top end to the bottom end. The rod seat is disposed within the cavity of the tulip head and engages a stop extending inwardly from an interior wall of the cavity. The screw shank has a thread disposed along a length of the screw shank and a connector positioned at an upper end. The retainer collar has a pass through aperture, an expansion slit, and is disposed about the connector of the screw shank. Other embodiments are described and claimed.
1. 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;
engaging the rod seat against a stop that extends inwardly from an interior wall of the cavity, wherein the stop is disposed between the lower opening and the upper opening of the cavity;
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 comprises 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.
2. The method of claim 1 , wherein the annular retainer collar has a pass-through aperture disposed there through with an inner diameter that is less than an outer diameter of the connector of the screw shank.
3. The method of claim 1 , wherein the locking ring is a portion of wire of a spool of wire; and
wherein inserting the locking ring comprises: (i) continuously feeding the portion of wire from the spool of wire into and through the retention groove inlet of the tulip head, and (ii) severing the portion of wire from a remainder of wire of the spool of wire.
4. The method of claim 3 , wherein severing the portion of wire comprises severing the portion of wire from the remainder of wire of the spool of wire at one of outside the tulip head, within the retention groove inlet of the tulip head, or within the retention groove of the cavity of the tulip head.
5. The method of claim 1 , wherein slideably positioning the annular retainer collar comprises slideably positioning the annular retainer collar about the shank collar of the screw shank prior to inserting the screw shank into the lower opening of the cavity of the tulip head to engage the connector of the screw shank with the shank mating face of the rod seat.
6. The method of claim 1 , wherein the annular retainer collar includes a collar body having an anti-rotation tab extending from the collar body; and
wherein slideably positioning the annular retainer collar further comprises slideably positioning the annular retainer collar about the shank collar of the screw shank such that the anti-rotation tab is received within an anti-rotation socket of the cavity.
7. The method of claim 1 , wherein the tulip head comprises a pair of opposing arms that define a U-shaped channel;
wherein the rod seat comprises a rod mating face opposite the shank mating face, the rod mating face is configured to accommodate a geometry of an elongated member; and the method further comprising:
inserting the elongated member into the U-shaped channel of the tulip head such that the elongated member contacts the rod mating face of the rod seat.
8. The method of claim 7 , wherein the cavity of the tulip head has internal threads disposed within the interior wall and adjacent to the upper opening; and the method further comprising:
threading a compression member into the internal threads of the cavity to contact and secure the elongated member.
9. The method of claim 8 , wherein the compression member is one of an externally threaded set screw or an externally threaded plug.
10. The method of claim 8 , further comprising clamping the connector of the screw shank between the shank mating face of the rod seat and a connector mating surface of the annular retainer collar.
11. The method of claim 10 , wherein clamping the connector of the screw shank between the shank mating face of the rod seat and the connector mating surface of the annular retainer collar comprises tightening the compression member to advance the elongated member in a direction against the rod mating face of the rod seat such that the shank mating face of the rod seat engages the connector of the screw shank.
12. 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 comprises (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.
13. The method of claim 12 , wherein the annular retainer collar has a pass-through aperture disposed there through with an inner diameter that is less than an outer diameter of the connector of the screw shank.
14. The method of claim 12 , wherein the locking ring is a portion of wire of a spool of wire; and
wherein inserting the locking ring comprises: (i) continuously feeding the portion of wire from the spool of wire into and through the retention groove inlet of the tulip head, and (ii) severing the portion of wire from a remainder of wire of the spool of wire.
15. The method of claim 14 , wherein severing the portion of wire comprises severing the portion of wire from the remainder of wire of the spool of wire at one of outside the tulip head, within the retention groove inlet of the tulip head, or within the retention groove of the cavity of the tulip head.
16. The method of claim 12 , wherein slideably positioning the annular retainer collar comprises slideably positioning the annular retainer collar about the shank collar of the screw shank prior to inserting the screw shank into the lower opening of the cavity of the tulip head to engage the connector of the screw shank with the shank mating face of the rod seat.
17. The method of claim 12 , wherein the tulip head comprises a pair of opposing arms that define a U-shaped channel;
wherein the rod seat comprises a rod mating face opposite the shank mating face, the rod mating face is configured to accommodate a geometry of an elongated member; and the method further comprising:
inserting the elongated member into the U-shaped channel of the tulip head such that the elongated member contacts the rod mating face of the rod seat.
18. The method of claim 17 , the method further comprising threading a compression member into the internal threads of the cavity to contact and secure the elongated member.
19. The method of claim 18 , further comprising clamping the connector of the screw shank between the shank mating face of the rod seat and a connector mating surface of the annular retainer collar.
20. The method of claim 19 , wherein clamping the connector of the screw shank between the shank mating face of the rod seat and the connector mating surface of the annular retainer collar comprises tightening the compression member to advance the elongated member in a direction against the rod mating face of the rod seat such that the shank mating face of the rod seat engages the connector of the screw shank.