Counter rotational layering of ePTFE to improve mechanical properties of a prosthesis
View Patent ↗A prosthesis, and method for forming same, are provided which includes expanded polytetrafluoroethylene (ePTFE) tubes having angularly offset node and fibril configurations. Also, the node and fibril configurations are angularly offset from the longitudinal axes of the respective tubes, providing resistance against failure in the longitudinal direction.
1. A composite prosthesis comprising:
a first seamless extruded ePTFE tube having a node and fibril structure;
a second seamless extruded ePTFE tube positioned concentrically about said first ePTFE tube, the second seamless extruded ePTFE tube having a node and fibril structure; and
only one of said first and second ePTFE tubes being in a helically twisted state oriented in a first rotational direction, and having been twisted from an initial untwisted state to said helically twisted state,
wherein the node and fibril structure of said first seamless tube is angularly offset from the node and fibril structure of the second ePTFE tube.
2. A composite prosthesis of claim 1 wherein each of said tubes defines a longitudinal axis and said node and fibril structure of one of said first and second tube is angularly offset from said longitudinal axis.
3. A composite prosthesis of claim 1 wherein each of said first and second tubes are in a helically twisted state oriented in different rotational directions.
4. A composite prosthesis of claim 1 further including a stent positioned between said first and second tubes.
5. A composite prosthesis of claim 1 further including a polymer layer positioned between said first and second tubes.
6. A composite prosthesis of claim 1 wherein at least a portion of said prosthesis is impregnated with at least one of a therapeutic and pharmacological substance.
7. A composite prosthesis of claim 1 wherein said first tube is fixed to said second tube.
8. A composite prosthesis of claim 7 wherein said first and second tubes are fixed by sintering.
9. A composite prosthesis of claim 1 wherein one of said first and second tubes is in a helically twisted state oriented in clockwise direction about a longitudinal axis of the graft and the other of the first and second tubes is in a helically twisted state oriented in counter-clockwise direction about the longitudinal axis of the graft.
10. A prosthesis comprising:
a first seamless extruded ePTFE tube having a node and fibril structure;
a second seamless extruded ePTFE tube positioned concentrically about said first ePTFE tube, the second seamless extruded ePTFE tube having a node and fibril structure; and
one of said first and second seamless extruded ePTFE tubes being in a helically twisted state with a first amount of twisting and having been twisted from an initial untwisted state,
the other of said first and second seamless extruded ePTFE tubes not having said first amount of twisting,
wherein the node and fibril structure of said first seamless extruded ePTFE tube is angularly offset from the node and fibril structure of the second seamless extruded ePTFE tube.
11. The prosthesis of claim 10 wherein the other of said first and second seamless extruded ePTFE tubes is in a helically twisted state with a second amount of twisting different from said first amount and having been twisted from an initial untwisted state.
12. The prosthesis of claim 11 wherein one of said first and second seamless extruded ePTFE tubes is twisted in a clockwise direction and the other of said first and second seamless extruded ePTFE tubes is twisted in a counterclockwise direction.
13. The prosthesis of claim 10 wherein the other of said first and second seamless extruded ePTFE tubes is not twisted.