WO2006066992A1

WO2006066992A1 - Implant for bone or cartillage replacement, with fixing element

Info

Publication number: WO2006066992A1
Application number: PCT/EP2005/055661
Authority: WO
Inventors: Werner Hermann; Klaus Matzen
Original assignee: Werner Hermann; Klaus Matzen
Priority date: 2004-12-22
Filing date: 2005-10-31
Publication date: 2006-06-29
Also published as: EP1674053A1

Abstract

Implant for replacing at least a part of a bone or cartilage of a patient. The implant (10) comprises an implant body (40) and a fixing arrangement with at least one fixing element (50). The fixing element (50) can be brought from a neutral position into a working position, whereby it moves cuttingly through a bone adjacent to the implant body. In the working position the fixing element (50) has intruded the bone. The fixing arrangement comprises an actuator (60). The actuator (60) is movingly coupled with the fixing element (50) and it is adjustable between a passive position in which the fixing element assumes a neutral position and an active position in which the fixing element (50) assumes a working position.

Description

H11-0017P-WO PCT

IMPLANT FOR BONE OR CARTILAGE REPLACEMENT, WITH FIXING ELEMENT

The invention concerns an implant according to the preamble of claim 1.

Implants take the place of damaged or missing bone parts, bones, cartilage parts or cartilage.

Implants of the kind initially mentioned are for instance intervertebral disc implants or intervertebral disc replacements, respectively, and are as such referred to as ,,Cage", but other applications are also possible where an implant is fixedly connected to a planar bone area. In this case implants are inserted as replacement of an intervertebral disc or as part thereof between two vertebrae of the spinal column and fixed to one or both of the adjacent vertebrae of the spinal column. Coπventioπal implants used as intervertebral disc replacements have different shapes. Known are for instance implants that consist of an implant body and a fixing arrangement. The fixing arrangement can be brought from a passive position, which it takes on before and during the application into a patient, into an active position in which it fixes the implant body in its definitive position. Hereby a screw is used as fixing arrangement of fixing element, which is screwed into an adjacent vertebra of the spinal column during the application of the intervertebral disc replacement.

Using a screw as fixing element has several disadvantages. It is unfavorable that due to the screwing into the bone of the spinal column relatively much of the bone material has to be removed, which in itself is undesirable and brings along the danger that bone chips remain in the torso. If the implant has to be removed at a later point in time, for instance because it does not show the desired effect or causes complaints, the loosening of the screw is very difficult. Furthermore, the removed screw leaves behind at least for some time a screw hole in the bone in the adjacency of which no further fixing element of a new implant can be fixed.

It is thus regarded to be an object of the invention to propose an implant of the kind initially mentioned, which allows the disadvantages of the prior art to be avoided.

According to the invention this object is achieved by the features of claim 1. Advantageous improvements of the new implant are covered by the depended claims. Consequently, the new implant comprises an implant body and a fixing arrangement. The fixing arrangement comprises at least one fixing element and an actuator for the fixing element. The actuator is movingly coupled with the fixing element and it is adjustable between a passive position and an active position. When the actuator is in its passive position, the fixing element takes on a neutral position. If the actuator is brought into an active position, then the fixing element gets into a working position in which it acts upon the adjacent bone.

Preferably, the whole fixing arrangement, but at least the fixing element, form an integral part of the implant body.

It turned out to be advantageous to design the fixing element as lamella with a lamella surface. The lamella comprises at least one cutting edge. The cutting edge moves forward when moving the fixing element and thereby cuts itself into the bone until the fixing element, or the lamella, has reached the final position in the bone.

It is particularly advantageous to move the fixing element designed as lamella by means of a rotation about an axis. In such an arrangement the lamella prefera- bly has a first cutting edge moving forward when the fixing element is moved by rotation in the direction of its working position, and a second cutting edge moving forward when the fixing element is moved by rotation in the reverse direction into its passive position, either because it was rotated too far or because the whole implant is to be removed.

The fixing arrangement may comprise several fixing elements that can be brought into interaction with the same bone. Hereby, discrete fixing elements can be adjustable by separate or common actuators. The actuators preferably comprise a tapered section in order to shift the fixing element when adjusting the actuator. In particular, the actuator can be a setting screw that comprises a tapered section.

It turned out to be advantageous to provide securing elements to secure the actuator directly or indirectly in its definitive active position, or the fixing elements in their working position.

The implant may comprise further identical or similar fixing arrangements, the fixing element of which is intended to act upon a further adjacent bone or bone part. Due to this, the implant can be fixed between two subsequent bones, for instance as intervertebral disc replacement between two subsequent vertebrae of the spinal column.

When the implant body and, as the case may be, the at least one fixing element has a structured outer surface, the growing into the torso of a patient, respectively the growing of body substances around the implant components is promoted. Implant bodies, the fixing element of which has structured outer surfaces, however, are more difficult to mount and disassemble. The structuring of the outer surface of the implant body as such should be such that the removal of an implant does not pose too many problems. One or more of those surfaces that face adjacent bones or bone parts may for instance comprise grooves as structuring of the implant body. If lamellas serving as fixing elements are employed, these grooves run in the mounted condition preferably across the direction of the lamella surfaces.

In order to give the implant body the optimum design, it may have different heights which are chosen according to the actual local distance of the adjacent bones when mounted. Typically, the implant body has cavities and openings. Since the implant body often consists of a material having a higher specific density than bones or cartilages, such cavities or openings can provide for a reduction of weight. Furthermore, they facilitate the tight connection of the implant with substance of the body in that newly formed substance grows around the implant and also into the cavities.

It is desirable in certain cases to configure the connection between two bones or bone parts by an implant to be flexible. For this purpose, the implant body can be split into a first outer implant body part and a second outer implant body part, between which an intermediate implant body part is situated and relative to which the outer parts are moveable in mounted condition, this movement, however, being limited. For this, at least one plane of the opposing surfaces of the outer part and the intermediate part can be convex from the outside, and pref- erably the other plane concave from the outside, so that a ball-joint like arrangement is obtained. Further, the intermediate part can be elastic when mounted.

In the following the invention is described in detail in connection with embodi- ments and by means of reference to the drawings. In the context of this embodiment the implant is a disk replacement and the non-schematic figures can essentially be considered to be drawn to scale for this application or at least in proportions that can be realized. Numerical values given are reference points only and real values may considerably deviate from these values, whereby the size of the patient also plays a role. It is, however, explicitly mentioned that the invention is under no circumstances limited to disk replacements or the replacement of cartilage substance. Shown are:

Fig. 1 an implant, according to the invention, designed as a disk replacement between two subsequent vertebrae, viewed from the side in a strongly simplified, schematized representation; Fig. 2 an implant, according to the invention, designed as a disk replacement, viewed from the side;

Fig. 3A the implant body, from the side, of the implant shown in Fig.

2;

Fig. 3B the implant body, from above and below, of the implant shown in Fig. 2;

Fig. 4A the fixing element of the implant shown in Fig. 2 from above;

Fig. 4B the fixing element shown in Fig. 4A from the side;

Fig. 4C the fixing element shown in Fig. 5A and 5B from the front;

Fig. 4D the fixing element shown in Fig. 4A and 4B from behind;

Fig. 5A the actuator of the implant shown in Fig. 2, viewed from the side of the patient;

Fig. 5B the actuator shown in Fig. 5A in a sideview of the actuator;

Fig. 5C a cut along the line C-C of the Fig. 5B; and

Fig. 6 an implant body divided in several parts. It is to be said in advance that in the description following below the expressions above, below, left, right, in front and behind - if nothing else is mentioned - relate to the position of an implant serving as disk replacement after its insertion into the torso of a patient standing upright, or the torso of a patient standing up- right, respectively. Identical and similar elements, which essentially have the same function, are designated in the different figures with the same reference numbers. Certain obviously recognizable details are not described.

Fig. 1 shows an implant 10 which is arranged but not yet fixed between to bone parts 1, 2. The bone parts 1 and 2 are subsequent vertebrae and the implant 10 is a disk replacement. As is generally known, the spinal column is differently bent forward or backward depending in the position and in general the distance between subsequent vertebrae is not constant. This fact is taken into account in that the implant 10 does not have a constant height.

In Fig. 2 an implant 10 is shown which is designed as disk replacement. One such implant 10 can replace a whole disk or a part of a disk. The implant 10 comprises an implant body 40, which is shown in the Fig. 3A and 3B, furthermore a fixing element 50, which is shown in the Fig. 4A to 4D, and furthermore an actuator 60, which is shown in the Fig. 5A to 5C.

The actual implant body 40 is box like. It has a front face 40.1, a back face 40.2 and two side faces 40.3. In the present embodiment the front face 40.1 is parallel to the back face 40.2 and the two side faces 40.3 are parallel with respect to each other, but this parallel arrangement is not mandatory. Furthermore, the implant body 10 comprises a top face 40.4 and a bottom face 40.5. The top face 40.4 and the bottom face 40.5 are not parallel, but they taper towards each other from the back to the front, essentially conical, although they can taper in a different manner or they can be parallel as well. Depending on the altitude within the spinal column of a patient the front face 40.1 and the back face 40.2 can be exchanged so that the top face 40.4 and the bottom face 40.5 diverge from each other from the front to the back.

The top face 40.4 as well as the bottom face 40.5 are not even, but they exhibit a structure 40.6, which in the present embodiment has the shape of parallel grooves. But differently natured structures are possible, too. The grooves of the structure 40.6 are, if the implant 10 is implanted in a patient, oriented across the longitudinal middle plane of the patient.

The implant body 40 comprises several cavities or cutouts, namely two vertical cavities 40.7 on the side which essentially receive the fixing element 50, as well as one vertical cavity 40.8 in the middle that is vertical, too. The implant body 40 further comprises a horizontal drilling 40.9, which extends between the side faces 40.3, for receiving the actuator 60. The implant body 40 further comprises a vertical drilling 40.10 for receiving a pin 42, which is intended to serve as securing element for the actuator 60.1 in its active position. Even further drillings, in Fig. 3A left of the drilling 40.9, serve as access for an implant tool, that is for a tool required for holding the implant 10 during the implanting. The drillings are only necessary for the actual implanting process.

The implant body 40 exhibits on its side face 40.3, which faces upwards in Fig. 2, an arrow 40.11 with a marking ,,LOCK". The arrow 40.11 and the marking ,,LOCK" indicate in which direction the actuator 60.1 has to be turned in order to rotate the fixing element 50 from its passive position into its working position. The implant body 40 exhibits on the side face 40.3 as well which faces upwards in Fig. 2 a body marking 40.12. This body marking 40.12 is intended to interact with an actuator marking 60.2 on the actuator 60 and when the actuator marking 60.2 is aligned with the body marking 40.12, the fixing element 50 has assumed its extreme position.

Also several body markings can be provided which designate together with the actuator marking 60.2 starting from the passive position differently far protruding positions of the fixing element 50. This is interesting, because the fixing element 50 not necessarily has to or can be brought into its extreme working position to fix the implant body 40. The markings can be applied by laser, for in- stance.

The fixing element 50 exhibits an intermediate part 50.1, which here has a square cross-section, in which a central drilling 50.2 is provided being intended for receiving the actuator 60, as illustrated in the Fig. 4A - 4D. A lamella-shaped extension 50.4 projects away from any of the two opposing faces of the intermediate part 50.1. These lamellas 50.4 form the actually active area of the fixing element 50. Each lamella 50.4 exhibits a cutting edge 50.5. The lamellas 50.4 can be identically shaped so that the fixing element 50 in the view according to Fig. 4B is symmetric with regard to the center, but an identical shape is not compellingly necessarily. The fixing element 40 may instead of two lamellas also just comprise one lamella or also more than two lamellas.

Fig. 4B shows the fixing element 50 in its passive position from the side. The extensions or lamellas, respectively, hereby would be situated inside the side cavi- ties 40.7 of the implant body 40. If one now moves the fixing element 50 towards its working position, in that one rotates it counter-clockwise in the direction of the arrow Al, the lamellas 50.4 are due to this are rotated out of the cavities 40.7. Their cutting edges 50.5 during this movement are running ahead and cut themselves into the abutting bone parts 1, 2, or the vertebra, or through the later, respectively. The fixing element 50 has reached its extreme position if it was turned by 90°. In other embodiment smaller maximum angles of rotation can be provided.

Each of the lamellas 50.4 may also exhibit a second cutting edge 50.6. This cutting edge is running behind when fixing the implant body 40, that is when rotating the fixing element 50 in the direction of the arrow A2 according to Fig. 4B and hereby has no function. First the fixing element 50 has to be brought into its passive position, however, if the implant 10 is to be removed from the patient. Since the cut caused by the fixing element 50 during the implanting of the implant 10 has gradually filled with newly formed bone substance, a new cut has to be generated. This is done by the further cutting edge 50.6 while the fixing ele- ment 50 is rotated clockwise, that is according to Fig. 4B in the direction of the arrow A2.

The actuator 60.1 by means of which the fixing element 50 is adjustable, is illustrated in Fig. 5A through 5C. The actuator 60.1 is a setting screw or bolt with a hexagon socket exhibiting an actuator marking 60.2, a screw shaft 60.4 at which the fixing element 50, respectively several fixing elements are fixed with a mutal distance, and a front end range 60.5 being intended to interact with the pin 42.

When the above-described implants 10 are used as disk replacements, the disks can be fully or partially replaced to thereby reduce or prevent patient's complaints, the maneuverability, however, being partially impaired. This loss can be reduced if the implant bodies 40 are designed appropriately, as shown in Fig. 6 in connection with an example. For this purpose the implant body 40 is divided into a first outer implant body part 44 and a second outer implant body part 46. Therebetween an intermediate implant body part 48 is situated, with respect to which the outer implant body parts 44, 46 are moveable in a limited range when being mounted. For this, at least one plane of the opposing surfaces of the outer part and the intermediate part can be convex from the outside, and preferably the other plane concave from the outside, so that a ball-joint like arrangement is obtained. The intermediate implant body part 48 can also be elastic.

Beneath others, titanium, chromium-cobalt alloy, peel or ceramics such as alu- minum oxide or zircon oxide is suited a material for implants according to the invention.

Claims

CIaims

1. Implant (10) for replacing at least a part of a bone or cartilage of a patient, comprising - an implant body (40) and

- a fixing arrangement with at least one fixing element (50) which is moveable from a neutral position into a working position and which is intended to intrude in its working position into a bone (1, 2) adjacent to the implant body (40), characterized in that, the fixing arrangement exhibits an actuator (60) being

- movingly coupled with the fixing element (50), and

- adjustable between

- a passive position, in which the fixing element (50) assumes its neutral position, and

- an active position, in which the fixing element (50) assumes its working position.

2. Implant (10) according to claim 1, characterized in that, the fixing element (50) is shaped a lamella (50.4), with at least one lamella surface, which comprises a cutting edge (50.5) being intended to run ahead when moving the fixing element (50) to cuttingly intrude into the bone (1, 2).

3. Implant (10) according to claim 2, characterized in that, the lamella (50.4) comprising fixing element (50) is rotatable by a rotation about an axis which is essentially perpendicularly oriented with respect to the surface of the lamella (50.4).

4. Implant (10) according to one of the claims 1 to 3, characterized in that, the fixing arrangement comprises at least two fixing elements (50) which can be made to intrude into the same bone (1, 2).

5. Implant (10) according to claim 4, characterized in that, the two fixing elements (50) are adjustable by means of the same actuator (60).

6. Implant (10) according to one of the claims 1 to 5, characterized in that, the actuator (60) comprises a setting screw.

7. Implant (10) according to one of the claims 1 to 6, characterized in that, the actuator (60) comprises an eccentric arrangement by means of which the fixing element (50) is moveable.

8. Implant (10) according to one of the claims 1 to 7, characterized in that, the implant body (40) and the actuator (60) comprise markings (40.11,

60.2), whose relative position shows the position of the fixing element (50).

9. Implant (10) according to one of the claims 1 to 8, characterized in that, it comprises at least one securing element (42), to secure the at least one fixing element (50) directly or indirectly in its working position.

10. Implant (10) according to one of the claims 1 to 9, characterized in that, it comprises a further fixing arrangement whose at least one fixing element is intended to intrude into a further abutting bone.

11. Implant (10) according to one of the claims 1 to 10, characterized in that, the implant body (40) and, if any the at least one fixing element (50) exhibit an outer surface with a structure (40.6).

12. Implant (10) according to one of the claims 1 to 11, characterized in that, the implant body (40) comprises on the top face (40.4) and/or bottom face (40.5) facing the abutting bone (1, 2) a structure, for instance with grooves running in the mounted state preferably across the direction of the lamellas (50.4).

13. Implant (10) according to one of the claims 1 to 12, characterized in that, the heights of the implant body (40) corresponds to the local distance of those bones (1, 2) which are in the mounted state adjacent to the implant.

14. Implant (10) according to one of the claims 1 to 13, characterized in that, the implant body (40) exhibits cavities or cutouts (40.8).

15. Implant (10) according to claim 1, characterized in that, the implant body (40) is divided into a first outer implant body (44) and a second outer implant body (46) between which an intermediate implant body (48) is situated, with respect to which the outer implant bodies (44, 46) are moveable within limits in the mounted state.

16. Implant (10) according to claim 15, characterized in that, from opposing surfaces of an outer implant body (44, 46) and the intermediate implant body (48) at least one surface is convex from the outside and preferably the other surface is concave from the outside.

17. Implant (10) according to one of the claims 15 to 16, characterized in that, the intermediate implant body (48) is elastic.

18. Implant (10) according to one of the claims 15 to 17, characterized in that, it is a spinal column disk implant replacing at least a part of a spinal col- umn disk and the abutting bones are subsequent vertebrae.