Low profile pedicle screw and rod assembly
A pedicle screw and rod assembly is provided which has a low profile in the final assembled position. The pedicle screw includes a screw having a threaded portion and a head portion. A tulip is positioned on the head portion of the screw. A fastener assembly is coupled to the tulip and positioned to retain the tulip on the head portion. A rod retainer member is positioned inside the tulip and grips the rod, to hold it in position relative to the tulip assembly and pedicle screw. The top of rod retaining member is approximately equal in height to, or lower than the rod itself. This provides a low profile pedicle screw and rod assembly since the rod itself will normally be the uppermost member of the completed assembly.
1. A pedicle screw and rod assembly for securing a rod, comprising:
a screw having a threaded portion and a head portion; a tulip positioned on the head portion of the screw, the tulip being configured to couple the rod, the tulip including at least one side orifice providing access to an inner cavity of the tulip;
a fastener assembly associated with the tulip, the fastener assembly being positioned adjacent the head portion of the screw in direct contact therewith to retain the tulip assembly on the screw;
a rod retaining member coupled to the tulip, between the fastener assembly and the tulip the rod retaining member having a ripping region for holding the rod in a fixed position relative to the tulip, the gripping region defining at least in part a substantially circular shape, the gripping region being positioned such that a top most portion of the rod retaining member and the fastener assembly are defined by heights that are less than the height of the top most portion of the rod and the substantially circular shape defined by the gripping region when the rod is coupled in the gripping region such that a portion of the rod and the substantially circular shape defined by the gripping region extends outwardly from the top-most portion of the rod retaining member when the rod retaining member is in a fully engaged position; and
an engaging tab on the fastener that couples the fastener to the rod retaining member to couple the rod retaining member to the tulip, the engaging tab being accessible through the side orifice of the tulip.
2. The pedicle screw and rod assembly of claim 1 , further comprising:
an engagement tool including an outer housing configured to engage an outer wall of the tulip; and
at least one protrusion extending from an inner wall of the outer housing, the at least one protrusion being sized to enter the side orifice and release the engagement tab from interfering with the rod retaining member.
3. The pedicle screw and rod assembly of claim 1 , wherein the fastener assembly is in direct contact with both the head portion of the screw and the rod retaining member.
4. A pedicle screw system comprising:
a screw having threads and a head;
a tulip coupled to the screw;
a fastener internal to the tulip and positioned to couple the tulip to the screw;
a rod retaining assembly that retains a rod, the rod retaining assembly having a substantial portion of the rod retaining assembly internal to the tulip; and an engaging tab on the fastener that couples the fastener to the rod retaining member to couple the rod retaining member to the tulip, the engaging tab being accessible through a side orifice of the tulip
wherein the fastener is positioned between the rod retaining assembly and the screw; and
wherein the rod is retained within the rod retaining assembly such that a topmost portion of the rod extends above an outer top surface of said tulip, a top surface of the fastener, and a top surface of the rod retaining assembly when the rod retaining assembly is in a fully engaged position.
5. The pedicle screw system according to claim 4 , wherein the top most portion of the rod retaining assembly is approximately at the same height as the top most portion of the tulip assembly.
6. The pedicle screw system according to claim 4 , wherein the rod retaining assembly includes at least one split that permits the diameter of the rod retainer assembly to vary from a first, large diameter to a second, small diameter.
7. The pedicle screw system according to claim 4 , wherein the fastener includes at least one split that permits the diameter of the fastener to vary from a first, large diameter to a second, small diameter.
8. The pedicle screw system of claim 4 , wherein the rod retaining assembly defines a recess on a bottom surface thereof, at least a portion of the fastener being insertable into the recess.