ZA200506743B

ZA200506743B - Intramedullary nail

Info

Publication number: ZA200506743B
Application number: ZA200506743A
Authority: ZA
Inventors: Andre Schlienger; Markus Buettler; Peter Senn
Original assignee: Synthes Ag
Priority date: 2005-08-23
Filing date: 2005-08-23
Publication date: 2006-05-31

Description

1972/ALLG. 20.3.2003

English translation of the International Patent Application No. PCT/CH03/00184 “Intramedullary nail” in the name of Synthes AG Chur

Intramedullary nail

The invention relates to an intramedullary nail in accordance with the generic term of

Patent Claim 1, specifically for the distal tibia.

The state of the art already includes intramedullary nails that have two intersecting cross holes at the same height, so that the same intramedullary nail can be used both for a right and for a left tubular bone.

The disadvantages of this prior known arrangement is that the two (or even more) holes intersect and their axis of intersection lies on the longitudinal axis of the nail, with the result that a relatively large quantity of material is taken from the cross section of the intramedullary nail, which in turn leads to considerable mechanical weakening of the intramedullary nail at this point.

The invention is intended to remedy this situation. The invention is based on the problem of creating an intramedullary nail with two (or more) intersecting cross holes that has improved mechanical strength compared to the state of the art described above, but which does not require the size of the cross section of the intramedullary nail to be increased.

The invention solves the specified task by providing an intramedullary nail having the features of Claim 1.

One variation of this invention is that the cylinder axes of the two mutually penetrating drill cylinders meet at an intersection point P which is at a distance d > 0 from the longitudinal axis. The distance d relative to the diameter D of the intramedullary nail is advantageously in the range 0.0001 D < d < 0.6000 D, preferably in the range of 0.2 D

<d<05D.

One further variation is that the cylinder axes of the two mutually penetrating drill cylinders are slanted and have as shortest distance the length x > 0. The length x in this system should be less than half the total of the two diameters of the mutually penetrating drill cylinders to enable the two dri cylinders to be penetrated. The section

S of the length x representing the shortest distance between the two slanted cylinder axes can run parallel or at an angle to the longitudinal axis and have a shortest distance y > 0. The distance y is advantageously less than D/2, but greater than 0.4 D.

In a further embodiment, the cylinder axes of the two mutually penetrating drill cylinders lie in a level orthogonal to the longitudinal axis.

In another embodiment, the cylinder axes of the two mutually penetrating drill cylinders are in contrast in one level that is penetrated by the longitudinal axis at an angle a, wherein 0° < a < 60° and preferably 0° < a < 30°. The advantage of this slanted arrangement compared to the orthogonal arrangement is to be found in the potentially longer bearing length of the screw to be inserted into the drill cylinder, which leads to greater stability. A further advantage is improved fracture treatment.

In a further embodiment, the cylinder axes of the two mutually penetrating drill cylinders intersect at an angle B, wherein 30° < 3 < 90°, and preferably 50° < B < 80°. Selection of the ideal angle will lead to optimisation of the wall thickness of the intramedullary nail.

In a preferred embodiment, the mutually penetrating drill cylinders are provided with two separate entrance points into the intramedullary nail, but only one common exit from the intramedullary nail. The advantage of this system compared to one with 4 openings is that this system has less material loss, i.e. greater strength of the intramedullary nail.

The diameter Dg of the mutually penetrating drill cylinders advantageously measures at most 0.6 times, but preferably at most 0.5 times of D.

In a further embodiment, the intramedullary nail is provided with a longitudinal hole coaxial to the central longitudinal axis. The bigger the diameter is of this hollow relative to the diameters of the drill cylinders, the greater can be the angle between the mutually penetrating cross holes, without any impairment to the cross section area of the intramedullary nail, i.e. without any lessening of the strength of the intramedullary nail.

The invention and refinements of the invention are described in more detail in the following on the basis of partially schematic illustrations of several embodiments.

Fig. 1 shows a front and rear view of the intramedullary nail with two intersecting cross holes;

Fig. 2 shows a front view of the intramedullary nail with a schematic, perspective view of the drill cylinders;

Fig. 3 shows an orthogonal cross section through the intramedullary nail according to

Fig. 2 in the range of the intersecting cross holes; and

Fig. 4 shows a schematic perspective view of two mutually penetrating drill cylinders with slanted cylinder axes.

The intramedullary nail illustrated in figures 1 to 3 is provided with a distal end 2 suitable for insertion in the medullary space of a tubular bone, a proximal end 3, a central longitudinal axis 4 and two cross holes 5 with a hole axis 6, each of which defines a virtual drill cylinder 8 with a cylinder axis 9 corresponding to the hole axis 6 of the defining cross hole 5. The intramedullary nail has generally a constant diameter D and a longitudinal hole 10 coaxial to the central longitudinal axis 4.

As illustrated in Fig. 3, the drill cylinders 8 of the two cross holes 5 penetrate each other, wherein the cylinder axes 9 of the two mutually penetrating drill cylinders 8 intersect at point P, which is at a distance d = 0.4 D from the longitudinal axis 4. In other words, the point P does not lie on the longitudinal axis 4 of the intramedullary nail.

The mutually penetrating drill cylinders 8 are provided with two separate entrance points in the intramedullary nail 1, but only one common exit from the intramedullary nail 1.

The cylinder axes 9 of the two mutually penetrating drill cylinders 8 are placed in a level orthogonal to the longitudinal axis 4, corresponding to the plane of projection of Fig. 3.

The cylinder axes 9 of the two mutually penetrating drill cylinders 8 can, however, also be in one level, which is penetrated by the longitudinal axis 4 at a defined angle a (Fig. 2).

In the illustrated example, the cylinder axes 9 of the two mutually penetrating drill cylinders 8 intersect at an angle & of 60°.

The diameter Dg of the mutually penetrating drill cylinders 8 measures in the illustrated example 0.3 times D.

As illustrated in Fig. 4, the cylinder axes 9 of the two mutually penetrating drill cylinders 8 in an alternative embodiment can also run in slanted direction and have a shortest distance 11 of the defined length x, which is smaller than half the total of the two diameters of the mutually penetrating drill cylinders 8. The section S of the length x representing the shortest distance 11 between the two slanted cylinder axes 9 runs in the illustrated example parallel to the longitudinal axis 4 and has a shortest distance y > 0. The section S can, however, also run slanted in relation to the longitudinal axis 4. The distance y is in the range of D/2>y > 0.4 D.

Claims

Patent claims

1. Intramedullary nail (1) with A) a distal end (2) suitable for insertion into the medullary space, wherein the segment of the intramedullary nail (1) facing the distal end (2) has a diameter D: B) a proximal end (3); C) acentral longitudinal axis (4); and D) several cross holes (5) with a hole axis (6), each of which defines a virtual drill cylinder (8) with a cylinder axis (9) corresponding to the hole axis (6) of the defining cross hole (5), wherein E) the drill cylinders (8) of at least two cross holes (5) penetrate each other, characterised in that F) the cylinder axes (9) of the two mutually penetrating drill cylinders (8) have no common intersection point P on the longitudinal axis (4).

2. Intramedullary nail (1) according to Claim 1, characterised in that the cylinder axes (9) of the two mutually penetrating drill cylinders (8) intersect at an intersection point P, which is at a distance d > 0 from the longitudinal axis (4).

3. Intramedullary nail (1) according to Claim 1, characterised in that the cylinder axes (9) of the two mutually penetrating drill cylinders (8) are slanted and have a shortest distance (11) of length x > 0.

4. Intramedullary nail (1) according to Claim 3, characterised in that the length x is less than half the total of the two diameters of the mutually penetrating drill cylinders (8).

5. Intrameduliary nail (1) according to Claim 3 or Claim 4, characterised in that section S of the length x representing the shortest distance (11) between the two slanted cylinder axes (9) runs parallel or at an angle to the longitudinal axis (4) and has a shortest distance y > 0.

6. Intramedullary nail (1) according to Claim 5, characterised in that the distance y is less than D/2.

7. Intramedullary nail (1) according to Claim 5 or Claim 6, characterised in that the distance y is greater than 0.4 D.

8. Intramedulilary nail (1) according to one of the claims 1 or 2, characterised in that the cylinder axes (9) of the two mutually penetrating drill cylinders (8) lie in a level orthogonal to the longitudinal axis (4).

9. Intramedullary nail (1) according to one of the claims 1 or 2, characterised in that the cylinder axes (9) of the two mutually penetrating drill cylinders (8) lie in a level that is penetrated by the longitudinal axis (4) at an angle a, wherein 0° < a < 60° and preferably 0° < a < 30° gilt.

10. Intramedullary nail (1) according to one of the claims 1, 2, 8 or 9, characterised in that the cylinder axes (9) of the two mutually penetrating drill cylinders (8) intersect at an angle 3, wherein 30° < 8 < 90°, and preferably 50° < 3 < 80°.

11. Intramedullary nail (1) according to one of the claims 1, 2, 8, 9 or 10, characterised in that the distance d relative to the diameter D lies in the range 0.0001 D < d < 0.6000 D, preferably in the range 0.2 D <d < 0.5 D.

12. Intramedullary nail (1) according to one of the claims 1 to 11, characterised in that the mutually penetrating drill cylinders (8) are provided with two separate entrance points into the intramedullary nail (1), but only one common exit from the intramedullary nail (1).

13. intramedullary nail (1) according to one of the claims 1 to 12, characterised in that the diameter Dg of the mutually penetrating drill cylinders (8) measures at most 0.6 times, and preferably at most 0.5 times D.

14. Intramedullary nail (1) according to one of the claims 1 to 13, characterised in that jt is provided with a longitudinal hole (10) coaxial to the central longitudinal axis (4).