Press-on pedicle screw assembly
A tulip assembly configured to be coupled to a screw head having a first diameter includes a housing, wherein the housing defines an inner diameter configured to engage the first diameter of the screw head. The exemplary inner diameter of the housing being smaller than the first diameter of the screw head.
1. An implant assembly comprising:
a first pedicle screw comprising:
a first pedicle screw head having a first pedicle screw head diameter; and
a first pedicle screw elongate threaded portion coupled to and extending from the first pedicle screw head;
a second pedicle screw comprising:
a second pedicle screw head having a second pedicle screw head diameter; and
a second pedicle screw elongate threaded portion coupled to and extending from the second pedicle screw head;
a first tulip assembly having a first tulip assembly bore extending into the first tulip assembly, the first tulip assembly bore having a first tulip assembly bore first inner diameter defined by a first tulip assembly inner wall, the first tulip assembly bore first inner diameter being smaller than the first pedicle screw head diameter;
a second tulip assembly having a second tulip assembly bore extending into the second tulip assembly, the second tulip assembly bore having a second tulip assembly bore first inner diameter defined by a second tulip assembly inner wall, the second tulip assembly bore first inner diameter being smaller than the second pedicle screw head diameter; and
a rod connected to and extending between the first tulip assembly and the second tulip assembly.
2. The implant assembly of claim 1 , wherein the first tulip assembly, the second tulip assembly, and the rod are coupled prior to coupling of the first tulip assembly to the first pedicle screw and the second tulip assembly to the second pedicle screw.
3. The implant assembly of claim 1 , wherein the first tulip assembly, the second tulip assembly, and the rod are unitarily formed from a single piece of material.
4. The implant assembly of claim 1 , wherein at least one of the first tulip assembly bore and the second tulip assembly bore is at least substantially cylindrical.
5. The implant assembly of claim 1 , wherein the first tulip assembly bore permits head-first introduction of the first pedicle screw head into the first tulip assembly bore until a section having the first pedicle screw head diameter is within the first tulip assembly bore, thereby creating a compression fit between the first tulip assembly inner wall and the first pedicle screw head within the first tulip assembly bore due to the first pedicle screw head diameter being larger than the first tulip assembly bore first inner diameter.
6. The implant assembly of claim 5 , wherein the compression fit is capable of withstanding at least 200 pounds of removal force between the first tulip assembly and the first pedicle screw along an axis of the first tulip assembly bore without relative movement of the first pedicle screw head along the first tulip assembly bore.
7. The implant assembly of claim 5 , wherein the first tulip assembly is adapted to permit head-first introduction of the first pedicle screw head into the first tulip assembly bore to create the compression fit while at least a portion of the first pedicle screw elongate threaded portion is embedded in bone.
8. The implant assembly of claim 1 , wherein the first pedicle screw head comprises a truncated spherical shape.
9. The implant assembly of claim 1 , wherein the implant assembly comprises a material selected from at least one of a titanium alloy, a cobalt chrome alloy, and a nickel titanium alloy.
10. An implant assembly comprising:
a pedicle screw comprising a head having a head diameter and an elongate threaded portion coupled to and extending from the head; and
a tulip assembly comprising:
a housing defining a bore comprising:
an engagement orifice;
a shape that is at least substantially fixed; and
a first region inner diameter that is smaller than the head diameter of the pedicle screw;
wherein head-first introduction of the head of the pedicle screw through the engagement orifice and into the bore creates a compression fit between the housing and the head of the pedicle screw due to the head diameter of the pedicle screw being larger than the first region inner diameter.
11. The implant assembly of claim 10 , wherein the compression fit between the housing and the head of the pedicle screw is capable of withstanding at least 200 pounds of removal force between the tulip assembly and the pedicle screw along an axis of the bore without relative movement of the head of the pedicle screw along the bore.
12. The implant assembly of claim 10 , wherein the bore comprises a second region having a second region inner diameter that is smaller than the first region inner diameter, wherein the second region is configured to receive a tool to disengage the pedicle screw from the tulip assembly.
13. The implant assembly of claim 10 , wherein the engagement orifice is at least substantially circular and wherein an inner wall of the housing defines an at least substantially cylindrical portion of the bore extending into the housing from the engagement orifice.
14. The implant assembly of claim 10 , wherein the head of the pedicle screw comprises a truncated spherical shape.
15. The implant assembly of claim 10 , wherein the tulip assembly is connected to a rod, which in turn is coupled to an additional tulip assembly.
16. The implant assembly of claim 15 , wherein the rod is coupled to the tulip assembly and the additional tulip assembly prior to implantation of the implant assembly by introduction of a pedicle screw into the bore of the tulip assembly.
17. The implant assembly of claim 10 , wherein the housing comprises a material selected from at least one of a titanium alloy, a cobalt chrome alloy, and a nickel titanium alloy.
18. A method for affixing a press-on pedicle screw assembly to a spine, the method comprising:
inserting a first pedicle screw having a first pedicle screw head portion with a first pedicle screw head diameter into a first portion of a patient's spine;
inserting a second pedicle screw having a second pedicle screw head portion with a second pedicle screw head diameter into a second portion of the patient's spine;
obtaining a first tulip assembly having a first tulip housing defining a first tulip bore comprising:
a first tulip assembly engagement orifice;
a first tulip assembly shape that is at least substantially fixed; and
a first tulip assembly region inner diameter that is smaller than the first pedicle screw head diameter; and
applying a force between the first pedicle screw and the first tulip assembly whereby the first pedicle screw head portion is pressed into the first tulip bore, thereby creating a first compression fit between an inner wall of the first tulip housing and the first pedicle screw head portion.
19. The method as recited in claim 18 , further comprising:
obtaining a second tulip assembly having a second tulip housing defining a second tulip bore comprising:
a second tulip assembly engagement orifice;
a second tulip assembly shape that is at least substantially fixed; and
a second tulip assembly region inner diameter that is smaller than the second pedicle screw head diameter; and
applying a force between the second pedicle screw and the second tulip assembly whereby the second pedicle screw head portion is pressed into the second tulip bore, thereby creating a second compression fit between an inner wall of the second tulip housing and the second pedicle screw head portion.
20. The method as recited in claim 19 , further comprising connecting the first tulip assembly to the second tulip assembly via a rod before engaging the first tulip assembly to the first pedicle screw.