An intramedullary nail comprising a central axis and a transverse borehole, provided with an insert which can be introduced into the transverse borehole, said insert also containing a longitudinal slit.
1. An intramedullary nail, comprising:
a central axis;
at least one transverse bore extending across the central axis, having a length, a transverse axis, and a cross-sectional profile F with maximum dimension “a” in the direction of the central axis and a maximum dimension “b” perpendicular thereto; and
an insert having a length, a longitudinal axis, and a longitudinal slot, the insert being insertable into the transverse bore and essentially congruent with the transverse bore, the longitudinal slot being configured so that the insert is press-fit into the transverse bore to prevent the insert from falling out of the transverse bore.
2. The intramedullary nail of claim 1 , wherein the length of the insert is substantially the same as the length of the transverse bore.
3. The intramedullary nail of claim 1 , wherein the outside of the insert is at least partially threaded.
4. The intramedullary nail of claim 1 , wherein the longitudinal slot extends along the entire length of the insert.
5. The intramedullary nail of claim 1 , wherein the insert has several longitudinal slots, each longitudinal slot extending along only part of the length of the insert.
6. The intramedullary nail of claim 5 , wherein the longitudinal slots are offset from each other.
7. The intramedullary nail of claim 5 , wherein the longitudinal slots are arranged axially one above the other.
8. The intramedullary nail of claim 1 , wherein the intramedullary nail is made of a material M having a tensile strength F 2 , a compressive strength F d , a density ρ 2 and a modulus of elasticity E, and wherein the insert is made of a material m which has a lower modulus of elasticity e<E than the material M.
9. The intramedullary nail of claim 8 , wherein e<0.8 E.
10. The intramedullary nail of claim 9 , wherein e<0.7 E.
11. The intramedullary nail of claim 1 , wherein the insert comprises a coaxial bore coaxial with its longitudinal axis.
12. The intramedullary nail of claim 11 , wherein the longitudinal slot communicates with the coaxial bore.
13. The intramedullary nail of claim 1 , wherein the transverse bore is unthreaded.
14. The intramedullary nail of claim 1 , wherein the transverse bore has a smooth inner surface.
15. The intramedullary nail of claim 8 , wherein the material m is a biocompatible plastic, preferably a polyethylene or a high-molecular-weight polyethylene (HMWPE).
16. The intramedullary nail of claim 15 , wherein the plastic is a bioabsorbable polymer or copolymer.
17. The intramedullary nail of claim 16 , wherein the plastic is a polyactide.
18. The intramedullary nail of claim 1 , wherein the transverse bore is a substantially circular bore, such that dimensions “a” and “b” of cross-sectional profile F are substantially equal.
19. The intramedullary nail of claim 1 , wherein the transverse bore is an elongated bore, such that dimensions “a” and “ab” of cross-sectional profile F are not equal.
20. The intramedullary nail of claim 8 , wherein the material m has a lower density ρ 1 than the density ρ 2 of the material M.
21. The intramedullary nail of claim 20 , wherein ρ 1 <0.8 ρ 2 .
22. The intramedullary nail of claim 1 , comprising a locking screw or a locking pin insertable into the transverse bore through the insert, the shaft thereof having a diameter “d” which obeys the conditions a>d<b.
23. The intramedullary nail of claim 1 , wherein the transverse bore widens toward the surface of the nail, in the form of a conical section.
24. The intramedullary nail of claim 1 , further comprising a locking screw having a shaft and an outside thread, the outside thread having a diameter “d” such that a>d<b.
25. The intramedullary nail of claim 24 , wherein “d” is at least 5% smaller than the smaller of “a” and “b.”
26. The intramedullary nail of claim 23 , wherein the insert consists of a pin with a conically enlarged head.
27. An intramedullary nail, comprising:
a central axis;
a central bore coaxial with the central axis;
at least one transverse bore extending across the central axis, having a length and a transverse axis; and
an insert insertable into the transverse bore, consisting of a pin having a central bore and one or more conical enlargements which are able to engage the nail in the form of a click closure, one conical enlargements engaging the central bore.
28. The intramedullary nail of claim 27 , wherein one of the one or more conical enlargements engages a conical cavity in the nail.