Longitudinal Bone Implant

Abstract

The invention relates to a longitudinal bone implant with a substantially circular cross-sectional profile, comprising a front section having a front end and a shaft section having a rear end, wherein the front section comprises at least three longitudinal groove-like cut-outs extending in the axial direction of the front section and opening towards the front end of the implant, circumferentially alternating with at least three longitudinal, radially protruding ribs extending in an axial direction, wherein the ribs have an increased cross-sectional width in the section radially more distant to the central longitudinal axis of the implant as compared to the width in a section radially closer to the central longitudinal axis of the implant. Furthermore, the invention relates to uses of the implant and methods that employ the implant.

Claims

1. A longitudinal bone implant with a substantially circular cross-sectional profile, comprising a non-threaded front section having a front end and a shaft section having a rear end, wherein the front section comprises, at least three longitudinal groove-like cut-outs extending in axial direction of the front section and opening towards the front end of the implant, circumferentially alternating with at least three longitudinal, radially protruding ribs extending in axial direction, wherein the ribs have an increased cross-sectional width in a section radially more distant to the central longitudinal axis of the implant as compared to the width in a section radially closer to the central longitudinal axis of the implant.

2. The implant of claim 1, wherein the groove-like cut-outs are configured radially opposite to the ribs.

3. The implant of claim 1, wherein the ribs are cross-sectional substantially T-formed.

4. The implant of claim 1, wherein the edges at the front end of the implant are configured as cutting edges.

5. The implant of claim 1, wherein the protruding end of the ribs comprises convex outer surfaces directed in radial direction and/or the ribs comprise concave surfaces directed towards the longitudinal groove-like cut-outs.

6. The implant of claim 5, wherein the front end of the convex surface of the ribs comprises cut-outs configured to decrease the width of the front edges of the ribs and/or wherein the groove-like cut-outs are chamfered towards the front edge of the implant.

7. The implant of claim 1, wherein the groove-like cut-outs taper off towards the shaft of the implant.

8. The implant of claim 1, wherein the groove-like cut-outs taper off towards the shaft over the entire length of the groove-like cut-outs.

9. The implant of claim 1, wherein the groove-like cut-outs comprises a middle section between a front section of the cut-out and a shaft directed end section, wherein the middle section tapers-off linearly towards the shaft and the shaft directed end section tapers-off concavely towards the shaft.

10. The implant of claim 1, wherein the groove-like cut-outs comprises an un-tapered middle section between a front section of the cut-out and a shaft directed tapered section end section, wherein the bottom of the cut-out in said middle section is parallelly aligned with the longitudinal axis of the implant, and the shaft directed end section tapers-off towards the shaft

11. The implant of claim 1, wherein the implant comprises a cannulation along the longitudinal axis of the implant opening to the front and the rear end of the implant.

12. The implant of claim 1, wherein the surface of the shaft comprises at least one notch extending in axial direction.

13. The implant of claim 1, wherein the diameter of the front section of the implant, as defined by the radially protruding ribs, is smaller than the diameter of the shaft of the implant.

14. A method comprising the implantation of an implant of claim 1 into the femur, wherein one groove-like cut-out is directed into cranial direction upon implantation.

15. An assembly comprising the implant of claim 1 assembled into an intramedullary nail.

16. The implant of claim 12, wherein the notch is facing into the same direction as one of the cut-out.

Description

[0053] In the following, embodiments of the implant according to the present invention are explained in reference to the attached drawings, wherein

[0054] FIG. 1 shows an implant according to the present invention in lateral view partially from the front;

[0055] FIG. 2 shows an implant according to the present invention in a lateral view, partially from the rear;

[0056] FIG. 3 shows the front section of the implant according to the invention in a front/side view;

[0057] FIG. 4 shows an implant according to the present invention in a front view;

[0058] FIG. 5 shows a cross-section through the front part of the implant according to the lo invention comprising ribs and cut-outs;

[0059] FIG. 6 shows a longitudinal section through the front part of an implant according to the invention, comprising a groove-like cut-out with a linearly tapering section;

[0060] FIG. 7 shows a longitudinal section through the front part of an implant according to the invention, comprising a groove-like cut-out with an untapered section; and

[0061] FIG. 8 shows a longitudinal section through an entire implant according to the present invention, wherein the groove-like cut-outs comprise openings.

[0062] In FIGS. 1 to 8, a longitudinal bone implant 1 with a substantially circular cross-section profile, comprising a front section 10 having a front end 11 and a shaft section 30 having a rear end 31, wherein the front section 10 comprises at least three longitudinal groove-like cut-outs 12 extending in the axial direction of the front section 10 and opening towards the front end 11 of the implant, circumferentially alternating with at least three longitudinal protruding ribs 13 extending in an axial direction is shown. The embodiments exemplified in the figures all have a configuration wherein the groove-like cut-outs 12 are configured radially opposite to the ribs 13.

[0063] The substantially circular cross-sectional profile of the implant corresponds to the view along the longitudinal axis of the implant, which is for example depicted in FIG. 4.

[0064] As shown in FIG. 5, the ribs 13 in the front section 10 of the implant may have an increased cross-sectional width (W1) in a section radially more distant to the central longitudinal axis of the implant, as compared to the width (W2) in a section radially closer to the central longitudinal axis of the implant. Furthermore, the ribs 13 may comprise a third section, radially even closer to the central longitudinal axis, as compared to the second section, which may have a greater cross-sectional width (W3) as compared to the second section. The embodiment shown in FIG. 5 encompasses ribs which are cross-sectionally substantially T-formed, wherein the base of the T is directed towards the longitudinal axis 40 of the implant.

[0065] In the embodiments shown in FIGS. 1 to 8, the protruding ends of the ribs, thus the ends of the ribs opposite to the longitudinal axis of the implant, comprise convex outer surfaces 14 directed in the radial direction. The convex outer surfaces of the ribs all substantially align with a circle having the longitudinal axis 40 of the implant in its center, which is, for example, schematically shown in FIGS. 4 and 5. Furthermore, the ribs comprise concave surfaces 15 directed towards the longitudinal groove-like cut-outs.

[0066] In a preferred embodiment of the implant according to the invention, the edges at the front end 10 of the implant may preferably be configured to minimize the surface area of the implant directed into outward axial direction. Therefore, as shown in FIG. 3, the front end of the convex surfaces of the ribs 13 comprise cut-outs 16 configured to decrease the width of the front edges of the ribs 13. Furthermore, the groove-like cut-outs 12 may comprise chamfered sections 17 towards the front edge of the implant.

[0067] In some embodiments of the invention, the groove-like cut-outs 12 comprised in the front section 10 may taper off towards the shaft section 30 of the implant, as, for example, shown in FIGS. 6 and 7. When the groove-like cut-outs 12 taper off towards the shaft section, the distance D1 in the longitudinal cross-section of the implant between the bottom of the groove-like cut-outs and the central longitudinal axis 40 increases. The implant shown in FIG. 6 exhibits cut-outs with a section 21 that tapers off linearly and a section 22 that tapers off concavely. The implant shown in FIG. 7 exhibits cut-outs with an untapered section 23 and a section 22 that tapers off concavely.

[0068] In the embodiments shown in FIGS. 1 to 8, the implant according to the invention comprises a cannulation 41 along the longitudinal axis 40 of the implant opening to the front 11 and the rear end 31 of the implant. In the embodiment of the implant shown in FIG. 8, the bottom of the groove-like cut-outs 12 comprises openings 42 which connect the void of the cut-outs with the cannulation 41.

[0069] As shown in FIGS. 1, 2 and 8, the shaft section 30 of the implant according to the present invention may comprise a notch 43 in the surface of the shaft section 30 for restricting rotation of the implant in relation to a second implant. In the depicted embodiments, the notch 43 is phasing into the same direction as one of the groove-like cut-outs 12 of the front section 10 of the implant.

[0070] As shown in FIGS. 1, 2 and 8, the implant may preferably furthermore comprise an intermediate section 50 between the front section 10 and the shaft section 30 with a diameter tapering from the diameter of the front section 10 to the diameter of the shaft section 30. As shown, for example, in FIG. 2, the rear end 31 of the shaft section 30 of the implant may be configured and dimensioned for attachment of an insertion device that facilitates the handling of the implant during the implantation procedure. For example, the rear end 31 of the shaft section may have a recess 32. The embodiments shown in FIGS. 2 and 8 furthermore comprise two threads 33, 34, wherein the thread 33 directed to the front end of the implant has a smaller diameter when the thread 34 directed to the rear end 31 of the implant. The two threads may run in opposite directions.

[0071] The implant, its uses and the methods according to the present invention, as described above and exemplified in the figures, surprisingly solve the problem underlying the invention and provide significant advantages over the prior art.

[0072] The front section of the implant comprising ribs alternating with groove-like cut-outs has a minimal cross-sectional area. Thus, when the front end of the implant is driven into a bone, the volume of a spongiosa which is displaced by the implant is minimized. This minimized spongiosa displacement is advantageously combined with a high stability, especially bending stability, of the ribs in the implant of the present invention. Furthermore, the forces for insertion of the implant into the bone are reduced. Advantageously, the implant can be implanted into a bone with a groove-like cut-out facing into the direction from which the highest mechanical force is exerted onto the implant. Thereby, only little spongiosa is displaced in the direction from which the force is applied, which enables an optimized transfer of the mechanical force from the bone to the implant.

[0073] When the implant is used for the treatment of femur fractures, one groove-like cut-out may be directed in the cranial direction, which advantageously preserves spongiosa material in the area that bears the highest mechanical forces, and thus advantageously enables optimized force distribution and bone preservation.

[0074] Especially the substantially T-formed ribs provide a high bending stability while requiring only little material. Furthermore, although the above-described design of the front part of the implant reduces spongiosa displacement upon insertion of the device into the bone, the ribbed structure of the front section of the implant advantageously provides a high rotational stability of the implant in the bone.

[0075] The implant according to the present invention advantageously provides a maximal support area in radial projection and therefore generally minimizes the pressure exerted from the bone structure onto the implant and thus relieves the spongiosa and the implant. The structure of the front section comprising ribs and cut-outs according to the present invention, furthermore advantageously increases the total contact area of the implant that engages with the bone. Thus, the friction between the implant and the bone structure is increased and consequently the backing out of the implant from the bone is advantageously prevented. In addition, the tapered sections of the cut-outs advantageously cause a densification of the spongiosa, which leads to an improved stability of the implant in the bone.

[0076] Surprisingly, when comparing the stability of a bone implant according to the present invention, comprising a front section with groove like cut-outs, with state of the art helical blade implants, it was found that implant according to the invention exhibited a higher stability in an artificial bone model. While exertion of high forces on implants according to the invention inserted into a cellular rigid polyurethane foam only induced a slight migration, the same force induced a cutting-out of the helical blades from the test material.

[0077] Furthermore, the cutting edges at the front of the implant advantageously decrease the forces required for insertion of the implant into the bone.