BONE IMPLANT HAVING AN OFFSET IN THE INJECTION CHANNEL AND IMPLANTATION TOOL THEREFOR

Abstract

A bone implant includes a shank for arrangement in a bone and a head arranged proximally on the shank and having a tool receiver for an implantation tool. The shank has a longitudinal axis. A continuous injection channel for injection of bone connection material is formed in the shank and has a proximal inlet opening for bone connection material on the side of the tool receiver. The wall of the shank surrounding the injection channel has a radial offset with respect to the longitudinal axis on the side of the proximal inlet opening. An implantation instrument for a bone implant includes an injection cannula having an inner channel having a longitudinal axis for injection of bone connection material. The inner channel has a distal outlet opening for bone connection material. A wall of the injection cannula surrounding the inner channel has a radial offset with respect to the longitudinal axis.

Claims

1. A bone implant comprising a distal implant shank formed for being embedded in a bone, and a proximal implant head having a tool receiver for an implantation tool, from which an injection channel for injecting a bone connection material extends into the implant shank and forms a predetermined injection channel diameter, wherein the injection channel comprises a proximal inlet opening and a wall surrounding the injection channel, and wherein the wall, starting from the tool receiver, comprises a radial offset machined in the wall of the injection channel, the radial offset extending radially outwards with respect to the predetermined injection channel diameter proximally and distally relative to the radial offset.

2. The bone implant according to claim 1, wherein the radial offset is formed by at least one step or shoulder machined in the wall of the injection channel and/or is formed so as to circumferentially extend in a circumferential direction at least in sections.

3. The bone implant according to claim 1, wherein the radial offset is formed by an undercut machined in the wall of the injection channel.

4. The bone implant according to claim 1, wherein the radial offset is formed in an area of the wall which is spaced from the proximal inlet opening of the injection channel at least by about 0.5 mm and at most about 10 mm.

5. The bone implant according to claim 1, wherein the radial offset in a radial direction amounts to between about 0.1 mm to 3 mm.

6. The bone implant according to claim 1, wherein the bone implant is a bone screw, the implant head is formed as a ball head, and the tool receiver is configured for receiving a screw-driving tool, wherein the proximal inlet opening is formed in a distal boundary surface of the tool receiver.

7. The bone implant according to claim 1, wherein the tool receiver comprises a connection structure for a detachable connection with an injection cannula for injection of bone connection material, and/or the tool receiver comprises an engagement contour for an implantation tool by which the bone implant is implanted during an implantation.

8. An implantation instrument for a bone implant according to claim 1, the implantation instrument comprising an injection cannula including an inner channel having a longitudinal axis for injection of bone connection material and a second wall surrounding the inner channel, wherein the inner channel comprises a distal outlet opening for bone connection material and has a predetermined inner channel diameter, wherein the second wall of the injection cannula has a second radial offset with respect to the longitudinal axis, the second radial offset starting from the distal outlet opening and being machined in the second wall of the inner channel, the second radial offset extending radially outwards with respect to the predetermined inner channel diameter proximally and distally relative to the second radial offset.

9. The implantation instrument according to claim 8, wherein the second radial offset of the injection cannula is formed by at least one step or shoulder machined in the second wall of the inner channel and/or is formed so as to circumferentially extend in the circumferential direction at least in sections.

10. The implantation instrument according to claim 8, wherein the second radial offset of the injection cannula is formed by a second undercut machined in the second wall of the inner channel.

11. The implantation instrument according to claim 8, wherein the second radial offset of the injection cannula is formed in an area of the second wall which is spaced from the distal outlet opening at least by about 0.5 mm and at most about 10 mm.

12. The implantation instrument according to claim 8, wherein the injection cannula comprises a connection structure for a detachable connection with the tool receiver of the bone implant.

13. The implantation instrument according to claim 8, wherein the injection cannula is designed as an implantation tool and comprises a tool contour matched with the tool receiver.

14. An implantation system comprising: a bone implant comprising a distal implant shank formed for being embedded in a bone, and a proximal implant head having a tool receiver for an implantation tool, from which an injection channel for injecting a bone connection material extends into the implant shank and forms a predetermined injection channel diameter, wherein the injection channel comprises a proximal inlet opening and a wall surrounding the injection channel, and wherein the wall, starting from the tool receiver, comprises a radial offset machined in the wall of the injection channel, the radial offset extending radially outwards with respect to the predetermined injection channel diameter proximally and distally relative to the radial offset; and an implantation instrument comprising a injection cannula including an inner channel having a longitudinal axis for injection of bone connection material and a second wall surrounding the inner channel, wherein the inner channel comprises a distal outlet opening for bone connection material and has a predetermined inner channel diameter, wherein the second wall of the injection cannula has a second radial offset with respect to the longitudinal axis, the second radial offset starting from the distal outlet opening and being machined in the second wall of the inner channel, the second radial offset extending radially outwards with respect to the predetermined inner channel diameter proximally and distally relative to the second radial offset.

Description

BRIEF DESCRIPTION OF THE DRAWING FIGURES

[0028] Further features and advantages of the present invention will be apparent from the following exemplary and non-limiting description of the invention on the base of a pedicle screw system as an example for a bone screw system with the aid of Figures. These Figures are of schematic nature only and merely serve the understanding of the invention. In the Figures:

[0029] FIG. 1 shows in a sectional view along the longitudinal axes A and B portions of an implant according to a first embodiment of the invention in the form of a pedicle screw comprising an implantation instrument according to a first embodiment of the invention in operative engagement,

[0030] FIG. 2 shows an embodiment similar to FIG. 1 in a perspective view,

[0031] FIG. 3 shows in a sectional view along the longitudinal axes A and B portions of an implant according to a second embodiment of the invention in the form of a pedicle screw comprising an implantation instrument according to a second embodiment of the invention in operative engagement,

[0032] FIG. 4 shows an embodiment of FIG. 3 in a perspective view, and

[0033] FIG. 5 shows the embodiment of FIGS. 1 and 2 with an implantation instrument that is not illustrated in cross-section.

DETAILED DESCRIPTION

[0034] The present description of the invention on the base of the Figures is made with reference to a pedicle screw 1. However, the invention relates in particular to a bone screw. The term pedicle screw is to be understood as being directed to a bone screw, and vice versa.

[0035] The pedicle screw 1 has a longitudinal axis A and comprises a screw shank 2 extending in its axial direction and including a male thread 3 or bone thread 3. Formed on the proximal end of the screw shank 2 is a ball-shaped screw head 4 which for its part carries a receiving sleeve 5, also referred to as a tulip 5, so as to be able to be positioned by swiveling due to its ball shape. The tulip 5 has an essentially U-shaped design comprising opposing wall portions 6, 7, which are generally referred to as sleeve flanks, and an intermediate gap 8 extending in the radial direction and defining a receiving space for a longitudinal beam or web which is not shown in the Figures. The tulip 5 is provided with a female thread 9 extending in axial direction, into which a (not shown) clamping screw (sets crew) can be screwed after insertion of the longitudinal beam in the tulip 5, in order to clamp and fix it.

[0036] Formed in the screw shank 2 of the pedicle screw 1 is an injection channel 10 which is oriented in the direction of the longitudinal axis A and (not identifiable in the Figures) extends substantially along the entire length of the screw shank 2. The injection channel 10 comprises a proximal inlet opening 11 at the head-side end and one or more outlet openings at the distal end of the shank 2 and/or distributed over the screw shank 2. By means of the implantation instrument 12 illustrated in part in the Figures bone connection material or bone cement is conveyed through the injection channel 10 to the outlet openings of the pedicle screw 1 which is placed/screwed into a bone, which material emerges from these and cements the pedicle screw 1 in place in the bone.

[0037] The ball-shaped screw head 4 comprises a central tool receiver 13 in the form of a recess. As can be clearly seen in particular in FIG. 5, the tool receiver 13 comprises an engagement contour 14 designed as a Torx socket for a correspondingly shaped tool contour 15 of the implantation instrument 12. Furthermore, as shown in FIGS. 1 and 3, the tool receiver 13 has formed therein a connection contour 16, here in the form of a female thread 16, which superimposes with the engagement contour 14. The female thread 16 serves for a screwing engagement with a connection structure 17 of the implantation instrument 12, here in the form of a male thread 17 with mating design.

[0038] FIGS. 1 and 3 show that the implantation instrument 12 comprises an injection cannula 18 having a longitudinal axis B. In said injection cannula, an inner channel 19 is formed along the longitudinal axis B, which at the distal end of the injection cannula 18 has a distal outlet opening 20. The inner channel's 19 opposite end, which is not illustrated in the Figures, is fluidically connected to a reservoir or container for bone connection material. The inner channel 19 serves to convey bone connection material from said reservoir to the outlet opening 20, and from the latter via the proximal inlet opening 11 into the injection channel 10 of the pedicle screw 1.

[0039] To this end, the implantation instrument 12 can be coupled to the pedicle screw 1 in the manner described in the following: Via the female thread 16 and the male thread 17, the implantation tool 12 is placed and retained in the tool receiver 13 of the screw head 4 such that the inner channel 19 and the injection channel 10 form a flow path from the cement reservoir to the (not shown) outlet openings of the pedicle screw 1, which flow path is tight towards outside for the bone connection material. With such an intended arrangement of the instrument 12 in the tool receiver 13, also the engagement contour 14 of the pedicle screw 1 engages the tool contour 15 of the implantation instrument 12 in such a manner that the pedicle screw 1 can be screwed into a bone with the implantation instrument 12. When the intended end position of the pedicle screw 1 is reached, bone connection material is introduced via the injection cannula. Said material flows through the inner channel 19 and the injection channel 10 to the outlet openings of the pedicle screw 1 and out of these into cavities present between the pedicle screw 1 and the bone substance. After a certain period of time, the material is at least partially hardened and solidified so that the implantation instrument 12 can be detached from the pedicle screw 1 and removed therefrom.

[0040] To this end, the female thread 16 and the male thread 17 are simply unscrewed, whereby the instrument 12 and its injection cannula 18 are removed from the screw head in axial direction. In this process, the inventive design of the channels 10, 19 comprising an offset comes into effect. With the embodiment of FIGS. 1 and 2, a female thread 22 is machined in the injection channel 10 in the wall 21 in an area adjoining the proximal inlet opening 11, said female thread forming an offset or several offsets. In the embodiment of FIGS. 3 and 4, an undercut 23 is machined in the wall 21 of the injection channel 10. FIGS. 1 to 4 show that the wall 24 of the inner channel 19 of the injection cannula 18 has an offset as well, here in each case in the form of an undercut 25. An alternative is represented by a female thread which is not illustrated in the Figures.

[0041] Any bone connection material which is present in the channels 10, 19, see for instance in FIG. 5, penetrates into the screw threads of the female thread 22 or into the undercuts 23, 25 in the course of the injection process and hardens there. It could be said that the offset of the channels 10, 19 in the form of the female thread 22 or the undercuts 23, 25 is casted in the bone connection material, the latter hardening in said shape. Due to the positive fit with the corresponding offset, the material cannot be positioned in the direction of the respective longitudinal axis A or B. Upon removing the implantation instrument 12 in axial direction away from the pedicle screw 1, the bone connection material which is present within the channels 10, 19 will break or shear off in a (predetermined breaking) area 26 situated between the two undercuts 23 and 25 or between the undercut 25 and the female thread. This ensures that hardened bone connection material breaks off as close as possible to the proximal inlet opening 11 of the channel 10 in the pedicle screw 1 or the outlet opening 20 of the channel 19 in the injection cannula 18 and does not protrude too far.

[0042] In above embodiment, the injection cannula 18 is part of the implantation tool 12. The injection cannula 18 may also be a separate component that can be screwed into the pedicle screw 1 and likewise is provided with an undercut 25 or radial offset.