Flexible bone implant
Examples of devices and methods for stabilizing a fracture in a bone include a body having an elongate distal portion having an outer surface defining a screw thread and an elongate proximal portion having a non-threaded outer surface.
1. A bone implant comprising an elongate body having a distal portion and a proximal portion spaced longitudinally relative to a longitudinal axis, wherein:
the proximal portion comprises:
a non-threaded outer surface; and
a fully-bounded transverse bore passing through the proximal portion from a first fully-bounded opening in the non-threaded outer surface to a second fully-bounded opening in the non-threaded outer surface; and
the distal portion comprises a helical distal thread formed thereon, the helical distal thread having a major diameter, a minor diameter, and a pitch, the helical distal thread being operable to bend as it is threaded into a bone to follow a curved path, the helical distal thread having a bending stiffness lesser than a bending stiffness of the proximal portion,
wherein a ratio of a bending stiffness of the proximal portion to the bending stiffness of the distal portion is in the range of 2:1 to 20:1.
2. The bone implant of claim 1 wherein the torque required to turn the distal thread into a bone to follow a threaded curved path having a radius of curvature of 50 mm is less than 5 inch-lbs.
3. The bone implant of claim 1 wherein a diameter of the non-threaded outer surface is greater than or equal to the major diameter of the helical distal thread.
4. The bone implant of claim 1 wherein the proximal portion has a length measured from a proximal end to a proximal start of the distal thread, the proximal portion having a maximum diameter, the maximum diameter being uniform over at least one-fourth of the proximal portion length.
5. The bone implant of claim 4 further comprising a driver engaging feature formed at the proximal end for engaging a driver in torque transmitting relationship, the driver engaging feature having a maximum dimension normal to the longitudinal axis that is less than or equal to the maximum diameter.
6. The bone implant of claim 1 further comprising a helical proximal thread formed on the proximal portion.
7. The bone implant of claim 6 further comprising a mid-portion between the distal thread and the helical proximal thread, wherein the helical proximal thread has a helical proximal thread major diameter and a helical proximal thread minor diameter;
wherein the helical proximal thread minor diameter is equal to an outer diameter of the mid-portion; and
the outer diameter of the mid-portion is greater than or equal to the major diameter of the helical distal thread.
8. The bone implant of claim 1 wherein the proximal portion comprises a first material harder than a second material of which the distal portion is comprised.
9. The bone implant of claim 8 wherein the distal thread comprises a polymer.
10. The bone implant of claim 9 wherein the proximal portion comprises a metal.
11. The bone implant of claim 9 wherein the distal thread comprises a resorbable polymer.
12. The bone implant of claim 9 wherein the proximal portion comprises a reinforced polymer.
13. The bone implant of claim 1 wherein major diameter is less than 4.0 mm and a ratio of the major diameter to the minor diameter is greater than 1.7.
14. The bone implant of claim 1 wherein a ratio of the major diameter to the pitch is less than 2.0.
15. The bone implant of claim 1 wherein a ratio of the minor diameter to the pitch is less than 1.0.
16. The bone implant of claim 1 , wherein the minor diameter of the helical distal thread is uninterrupted along an entire length of the helical distal thread.
17. The bone implant of claim 1 , further comprising a mid-portion between the proximal portion and the distal portion, the mid-portion comprising a mid-portion non-threaded outer surface;
wherein the non-threaded outer surface of the proximal portion and the mid-portion non-threaded outer surface, combined, have a first length, along the longitudinal axis that is greater than a second length of the helical distal thread, along the longitudinal axis.
18. A bone implant comprising an elongate body having a distal portion and a proximal portion spaced longitudinally relative to a longitudinal axis, wherein:
the distal portion comprises a helical distal thread formed thereon, the helical distal thread having a major diameter, a minor diameter, and a pitch, the helical distal thread being operable to bend as it is threaded into a bone to follow a curved path, the helical distal thread having a bending stiffness lesser than a bending stiffness of the proximal portion;
a ratio of a bending stiffness of the proximal portion to the bending stiffness of the distal portion is in the range of 2:1 to 20:1; and
the minor diameter of the helical distal thread is uninterrupted along an entire length of the helical distal thread.
19. A bone implant comprising an elongate body having a distal portion, a proximal portion, and a mid-portion spaced longitudinally relative to a longitudinal axis, wherein:
the proximal portion comprises a non-threaded outer surface;
the mid-portion is between the proximal portion and the distal portion and comprises a mid-portion non-threaded outer surface; and
the distal portion comprises a helical distal thread formed thereon, the helical distal thread having a major diameter, a minor diameter, and a pitch, the helical distal thread being operable to bend as it is threaded into a bone to follow a curved path, the helical distal thread having a bending stiffness lesser than a bending stiffness of the proximal portion;
wherein:
the non-threaded outer surface of the proximal portion and the mid-portion non-threaded outer surface, combined, have a first length, along the longitudinal axis that is greater than a second length of the helical distal thread, along the longitudinal axis, and
a ratio of a bending stiffness of the proximal portion to the bending stiffness of the distal portion is in the range of 2:1 to 20:1.