Modular polyaxial pedicle screw system
View Patent ↗There is provided a modular polyaxial pedicle screw assembly that includes various components which may be configured in various manners so as to provide different functionalities to the pedicle screw assembly. This advantageously decreases surgery time, reduces repetitive and tedious surgical steps, and allows for streamlining inventory of expensive medical equipment. In one embodiment, a pedicle screw assembly includes a pedicle screw, a rod holding element, a polyaxial insert, a rod, and a set screw. The pedicle screw includes a threaded shaft and a cap. The rod holding element includes a screw hole, an insert bearing area, a chamber, chamber walls, a saddle area, and a threading area. The insert is disposed within the chamber, and the insert defines a bearing surface, an upper surface, side walls and a receiving area. The insert is positioned within the chamber such that the insert bearing surface contacts the rod holding element insert bearing area; additionally the side walls of the insert can bear against the chamber walls. The pedicle screw is positioned so that the screw shaft passes through the screw hole of the rod holding element and the screw cap rests within the receiving area of the insert. The rod is disposed so as to rest on the upper surface of the insert; and the set screw, joined to the threading area of the rod holding element, secures the rod to the upper surface of the insert.
1. A polyaxial pedicle screw assembly comprising:
a polyaxial pedicle screw having a shaft and head;
a rod holding element that defines a screw hole opening, a curved bearing surface, a chamber, a saddle area, a cutaway area, a head seating surface, and a threading area;
a polyaxial insert disposed within the chamber, wherein the polyaxial insert defines a curved lower insert bearing surface, a screw head bearing surface defined in and extending upwardly from the curved lower insert bearing surface, and an upper surface, wherein the curved lower insert bearing surface has a curvature that is substantially the same as the curvature of the rod holding element curved bearing surface;
wherein the polyaxial insert is positioned within the chamber of the rod holding element such that the curved lower insert bearing surface of the polyaxial insert contacts the rod holding element curved bearing surface, and wherein the curved contact between the polyaxial insert and the rod holding element allows for pivoting motion of the polyaxial insert within the rod holding element;
wherein the polyaxial pedicle screw is disposed so that a threaded portion of the shaft passes through the screw hole opening, and the polyaxial pedicle screw head contacts the screw head bearing surface of the polyaxial insert;
a rod disposed to rest on the upper surface of the polyaxial insert; and
a set screw joined to the threading area of the rod holding element so as to secure the rod to the upper surface of the insert and to lock the polyaxial pedicle screw and rod holding element into a desired position.
2. The assembly according to claim 1 wherein the rod holding element further defines opposing notches and wherein the polyaxial insert further comprises opposing guide pins positioned such that the each guide pin fits within the a respective notch when the polyaxial insert is disposed in the chamber.
3. The assembly according to claim 2 , wherein polyaxial insert is configured to pivot within the rod holding element about an axis defined by the guide pins.
4. The assembly according to claim 2 wherein the guide pins are-substantially cylindrical in shape.
5. The assembly according to claim 4 wherein the guide pins are substantially cylindrical in shape whereby the polyaxial insert has freedom of movement in a plane.
6. The assembly according to claim 1 wherein the rod holding element further comprises a head seating surface disposed proximate to the screw hole, and wherein the polyaxial pedicle screw head contacts the head seating surface.
7. The assembly according to claim 1 wherein the polyaxial pedicle screw head further comprises surface structures.
8. The assembly according to claim 7 wherein the surface structures comprises ridges.
9. The assembly according to claim 1 further comprising a rod adapter connected to the set screw and wherein the rod adapter is disposed to engage with the rod.
10. The assembly according to claim 9 , wherein the rod holding element further defines opposing notches having a dovetail configuration, wherein the rod adapter has opposing tabs having a reciprocal dovetail configuration, wherein each notch is configured to receive a respective tab.
11. A medical kit comprising:
a polyaxial pedicle screw having a shaft and head;
a rod holding element that defines a screw hole, a curved bearing surface, a chamber, a saddle area, a cutaway area, a head seating surface, and a threading area;
a polyaxial insert that defines a curved lower insert bearing surface, a screw head bearing surface defined in and extending upwardly from the curved lower insert bearing surface, and an upper surface, wherein the curved lower insert bearing surface has a curvature that is substantially the same as the curvature of the rod holding element curved bearing surface;
a set screw; and
a rod adapter,
wherein the polyaxial pedicle screw is configured to be disposed within the rod holding element so that a threaded portion of the shaft passes through the screw hole of the rod holding element, and wherein the rod holding element further defines opposing notches having a dovetail configuration, wherein the rod adapter has opposing tabs having a reciprocal dovetail configuration, wherein each notch is configured to receive a respective tab.
12. The medical kit according to claim 11 further comprising a rod.
13. The medical kit according to claim 11 further comprising a uniplanar insert and a monoaxial insert.
14. The medical kit according to claim 11 further comprising at least two rods having different diameters.
15. A method of forming a polyaxial pedicle screw assembly comprising the steps of:
providing a polyaxial pedicle screw having a shaft and head;
providing a rod holding element having a screw hole and a curved bearing surface;
providing a polyaxial insert defining a curved lower insert bearing surface and a screw head bearing surface defined in and extending upwardly from the curved lower insert bearing surface;
positioning the polyaxial pedicle screw relative to the rod holding element such that a threaded portion of the shaft of the polyaxial pedicle screw passes through the screw hole of the rod holding element;
positioning the polyaxial insert such that the screw head bearing surface of the polyaxial insert contacts the head of the polyaxial pedicle screw, and such that the curved lower insert bearing surface of the polyaxial insert contacts the rod holding element curved bearing surface;
positioning a rod within the rod holding element; and
joining a set screw to the rod holding element.
16. The method according to claim 15 wherein the step of positioning a polyaxial insert further comprises positioning the polyaxial insert such that guide pins of the polyaxial insert fit within notches of the rod holding element.
17. The method according to claim 16 further comprising the step of rotating the insert relative to the rod holding element by rotating the polyaxial insert about an axis defined by the guide pins.
18. The method according to claim 15 further comprising adjusting the position of the polyaxial pedicle screw relative to the rod holding element by moving the screw head at the screw head bearing surface of the polyaxial insert.
19. The method according to claim 15 further comprising positioning a rod adapter around the rod.
20. The method according to claim 15 further comprising fixing the polyaxial pedicle screw, the polyaxial insert, and the rod holding element into a desired substantially immovable configuration.