Multi-layer composite material bone screw
According to some embodiments of the invention there is provided a composite material bone screw comprising: a screw core comprising straight reinforcing fibers arranged along a longitudinal axis of the screw; a winding screw thread surrounding at least a portion of the screw core; a layer intermediate the screw core and the screw thread, the layer comprising reinforcing fibers helically wound in an opposite direction to a winding direction of the screw thread.
1. A composite material bone screw comprising:
a screw core comprising straight reinforcing fibers arranged along a longitudinal axis of said screw;
a winding screw thread surrounding at least a portion of said screw core;
a layer intermediate said screw core and said screw thread, said layer comprising reinforcing fibers helically wound in an opposite direction to a winding direction of said screw thread.
2. The screw according to claim 1 , wherein said screw thread comprises reinforcing fibers helically wound in the same direction as said winding direction of said screw thread.
3. The screw according to claim 1 , wherein said screw further comprises at least one of: a first layer comprising fibers wound at a pitch angle of between +30 to +60° relative to said longitudinal axis, and a second layer comprising fibers wound at a pitch angle of between −30 to −60° relative to said longitudinal axis.
4. The screw according to claim 3 , wherein said fibers of said first layer are wound at a pitch angle of +45° relative to said longitudinal axis.
5. The screw according to claim 3 , wherein said fibers of said second layer are wound at a pitch angle of −45° relative to said longitudinal axis.
6. The screw according to claim 3 , wherein said first and/or second layers are intermediate said core and said intermediate layer.
7. The screw according to claim 1 , wherein said screw further comprises a layer comprising radiopaque material in the form of powder distributed within said composite material.
8. The screw according to claim 7 , wherein said powder comprises gold.
9. The screw according to claim 7 , wherein said layer comprising radiopaque material is intermediate said intermediate layer and said thread.
10. The screw according to claim 1 , wherein said screw further comprises a layer comprising chopped reinforcing fibers, said fibers randomly dispersed at various directions.
11. The screw according to claim 10 , wherein said layer comprising randomly dispersed chopped reinforcing fibers fills at least a portion of a volume of said screw thread, said volume defined between a thread base region and a thread peak.
12. The screw according to claim 1 , further comprising a layer comprising randomly dispersed continuous elongated reinforcing fibers.
13. The screw according to claim 1 , further comprising a metallic outer surface layer having a thickness between 1 μm and 200 μm.
14. The screw according to claim 13 , wherein said metallic outer surface layer comprises titanium.
15. The screw according to claim 1 , wherein said screw core is cannulated.
16. The screw according to claim 15 , wherein said cannula is sized to receive a guide wire, comprising a diameter between 1 mm and 3.5 mm.
17. The screw according to claim 1 , wherein said composite material comprises PEEK and wherein said reinforcing fibers are formed of carbon.
18. The screw according to claim 1 , wherein said screw is fully radiolucent.
19. A method of manufacturing a composite material screw, comprising:
winding prepreg tapes over a mandrel;
molding said prepreg tapes comprising reinforcing fibers into a thread coil while on said mandrel;
removing said thread coil from said mandrel and placing said thread coil in a mold defining a cavity shaped according to the final screw;
adding prepreg tapes to the mold to form a core of said screw wherein said prepreg tapes of said core include reinforcing fibers arranged along a longitudinal axis of said core; and
compression molding said thread coil and said core to form said screw wherein said reinforcing fibers of said prepreg tapes of said thread coil are at an angle to said reinforcing fibers of said core.
20. The method according to claim 19 , further comprising placing an external metallic layer in said mold prior to said placing of said thread coil.
21. The method according to claim 19 , further comprising attaching an external metallic layer to said thread coil before placing in said mold.
22. The method according to claim 19 , further comprising placing a mandrel in said mold to produce a cannulation throughout said core of said screw.