Hybrid cannulated orthopedic screws
The disclosure relates to medical devices and methods of manufacturing medical devices. An orthopedic screw includes an inner core member having a head having a first outer diameter, a tip having a second outer diameter, and a body extending between the head and the tip and having a third outer diameter that is less than the first outer diameter and the second outer diameter. An outer body member is disposed circumferentially around the body of the inner core member and defines an outer body member external thread. The tip of the inner core member can define an inner core member external thread that forms an interrupted thread with the outer body member external thread.
1. An orthopedic screw, comprising:
an inner core member defining a head having a first outer diameter, a tip having a second outer diameter, the tip defining an inner core member external thread having a first flange width, and a body extending between the head and the tip and having an inner core member outer surface that defines a circumferential recess having a third outer diameter that is less than the first outer diameter and the second outer diameter, the first flange having a first flange first side, a first flange second side, and a first flange crest, the first flange width comprising a thickness of the first flange from the first flange first side to the first flange second side at the first flange crest; and
an outer body member disposed circumferentially around the body and within the circumferential recess, the outer body member having an outer body member outer surface, the outer body member defining an outer body member external thread having a second flange width that is different from the first flange width and that is constant along a majority of an axial length of the outer body member, the second flange having a second flange first side, a second flange second side, and a second flange crest, the second flange width comprising a thickness of the second flange from the second flange first side to the second flange second side at the second flange crest;
wherein the inner core member external thread and the outer body member external thread lie on the same helical plane and cooperatively define an interrupted thread having an interruption that comprises an absence of at least part of a complete revolution of the interrupted thread along each of the inner core member outer surface and the outer body member outer surface adjacent a distal circumferential contact interface between the inner core member and the outer body member;
wherein the outer body member outer surface is flush with a portion of the inner core member outer surface.
2. The orthopedic screw of claim 1 , wherein the inner core member defines a distal recess wall that partially bounds the circumferential recess; and
wherein the outer body member defines a distal engaging surface that is in sealing contact with the distal recess wall to form the distal circumferential contact interface between the inner core member and the outer body member.
3. The orthopedic screw of claim 2 , wherein the distal engaging surface is free of the outer body member external thread.
4. The orthopedic screw of claim 3 , wherein the distal recess wall is free of the inner core member external thread.
5. The orthopedic screw of claim 4 , wherein the interruption is disposed at the distal circumferential contact interface between the inner core member and the outer body member.
6. The orthopedic screw of claim 1 , wherein the inner core member external thread has an inner core member external thread outer diameter and the outer body member external thread has an outer body member external thread outer diameter that is the same as the inner core member external thread outer diameter.
7. The orthopedic screw of claim 1 , wherein the inner core member external thread has an inner core member external thread outer diameter and the outer body member external thread has an outer body member external thread outer diameter that is different from the inner core member external thread outer diameter.
8. The orthopedic screw of claim 1 , wherein the first flange width is greater than the second flange width.
9. The orthopedic screw of claim 8 , wherein the first flange width is between about 1.1 times the second flange width and about 1.001 times the second flange width.
10. The orthopedic screw of claim 8 , wherein the first flange width is between about 1.1 times the second flange width and about 1.01 times the second flange width.
11. The orthopedic screw of claim 8 , wherein the first flange width is about 1.01 times the second flange width.
12. The orthopedic screw of claim 8 , wherein the first flange width is greater than about 1.01 times the second flange width.
13. The orthopedic screw of claim 1 , wherein the inner core member is anodized.
14. The orthopedic screw of claim 13 , wherein the inner core member comprises a titanium alloy.
15. The orthopedic screw of claim 14 , wherein the outer body member comprises PEEK.
16. The orthopedic screw of claim 14 , wherein the outer body member comprises a carbon fiber reinforced polymer.
17. The orthopedic screw of claim 16 , wherein the outer body member comprises CFR PEEK.