EP1720492A1

EP1720492A1 - Cervical intervertebral disc prosthesis with anti-luxation means, and instrument

Info

Publication number: EP1720492A1
Application number: EP05715518A
Authority: EP
Inventors: Helmut D. Link; Arnold Keller
Original assignee: Cervitech Inc
Current assignee: Cervitech Inc
Priority date: 2004-03-05
Filing date: 2005-02-24
Publication date: 2006-11-15
Also published as: KR20070015136A; CA2556579A1; JP2007526053A; AU2005220016A1; ZA200607693B; US20080027550A1; BRPI0507340A; RU2006134961A; IL177491A0; WO2005084589A1; EP1570813A1; RU2372054C2; CN1953722A

Abstract

The invention relates to a cervical intervertebral prosthesis comprising a lower anchoring plate and an upper anchoring plate (11, 12) with a prosthesis core (10) arranged thereinbetween for the creation of an articulated connection. The anchoring plates (11, 12) are embodied, with the anchoring plate surface thereof, in such a way as to rest on adjacent vertebral bodies. According to the invention, at least one anchoring plate surface (11, 12) comprises a rib-type projection (18) which can be used to engage with the vertebral body in a positively-locking manner. The invention also relates to an instrument comprising a handle, a shaft and a head part containing a evacuating element which can be sunk thereinto, for the production of a corresponding recess in the vertebral body. The protection of the cervical intervertebral disk prosthesis against an accidental movement can thus be essentially improved. The medullary canal running along the rear edge of the vertebral column is thus protected from damage.

Description

CERVICAL DISC PROSTHESIS WITH UXATIONAL SECURITY AND INSTRUMENTS

The invention relates to a cervical intervertebral prosthesis comprising a lower and an upper anchoring plate and an interposed prosthesis core, which forms an articulated connection between the anchoring plates, and an instrument for implanting such a prosthesis.

Intervertebral prostheses that are intended for implantation in the cervical area of the spine must be positioned extremely precisely in this area due to the small dimensions of the spine. The prosthesis must not inadvertently shift in its bone anchoring after implantation. Even with a slight shift of prosthetic parts dorsally, there is a risk that spinal nerves are affected. It is therefore very important to securely fix the intervertebral prosthesis in place in its implanted place. However, this is particularly difficult in the area of the cervical spine, since there is little space available due to the small dimensions. It is known (WO-A-030 75 803) to provide the anchoring plates of the intervertebral prostheses with a flange at their ventral edge and to fasten this to the vertebral body by means of screws. In order to have sufficient connection security, the screws and the flange must have dimensions that are difficult to reconcile with the difficult implantation conditions in the area of the cervical spine. This difficulty is bypassed another construction (WO-A-030 75 804), which provides a shortened flange without screw fastening for securing against slipping dorsally and a toothed surface of the anchoring plates as securing against slipping ventrally. This construction is well suited for implantation under the cramped conditions in the cervical spine. Under certain conditions, an increase in connection security is desirable.

It is also known to provide self-tapping ribs running in the anterior or posterior (AP) direction in addition to the teeth (WO 03/075804). These automatically press into the end surface of the vertebral body. This does not secure against unwanted movement in the AP direction. Due to the self-tapping property, the rib introduces considerable forces into the anchoring plates, some of which also act in the horizontal direction. This increases the risk of incorrect positioning. A similar prosthesis is known from US-A-6,517,580.

It is also known to provide protruding bolts on the surface of the anchoring plate facing the vertebral bodies for better anchoring of the prosthesis on the vertebral bodies. The preparation of corresponding recesses in the vertebral body for receiving the bolts is difficult. It does not succeed with the required accuracy, so the prosthesis often has play. It is also known to arrange a spherical cap-like elevation on the surface of the anchoring plate (US-A-2001/0016773). Due to their rounded shape, a sufficient locking effect cannot be achieved. Furthermore, an intervertebral prosthesis is known (DE-U-203 11 400), which on the surface of the anchoring facing the vertebral bodies has anchoring projections. This prosthesis is of another type without articulations, instead it has spherical articular surfaces directly on the anchoring plates. The force application is very concentrated, so that it has to be absorbed by the anchoring projections.

The invention is based on the object of increasing the security of a cervical intervertebral prosthesis while maintaining good implantability.

The solution according to the invention lies in an instrument for implanting a cervical intervertebral prosthesis according to claim 1. It also lies in a cervical intervertebral prosthesis with the features of claim 13. The invention extends further to a method according to claim 20. Advantageous further developments are the subject of the dependent Expectations.

An instrument according to the invention for implanting a cervical intervertebral prosthesis of the type mentioned at the beginning comprises a handle, a stem and a head piece at an end remote from the handle, the dimensions of which are selected such that it can be inserted into the space created for accommodating the intervertebral prosthesis, wherein the

Headpiece has a clearing element for creating a recess in the cranial-caudal direction and an actuating device is provided for the clearing element, which between a rest position in which it is sunk in the headpiece and a working position in which it projects transversely to the handle from the headpiece , is flexible. The headpiece of the instrument can be pushed to the intended implantation site, which was prepared in a manner known per se. The clearing element is in its rest position, in which it is sunk in the head piece, so the headpiece can be advanced to the intended implantation site without difficulty. Reaching the correct position is expediently verified by X-ray checks. For this purpose, it can be expedient to provide separate x-ray marks on the head piece. In order to create a recess on the end face of the vertebral body, into which a rib-like projection arranged on the anchoring plate of the intervertebral prosthesis can positively engage, the broaching element is moved into its working position. The recess can then be created by actuating the clearing element. To remove the instrument, the clearing element can then be brought back into its retracted rest position. The clearing element can be extended on one or both sides. The invention thus provides an instrument for implanting the intervertebral prosthesis according to the invention, which can be easily pushed onto the intended implantation site and in this position creates recesses for the positive reception of the projections in the vertebral body.

The headpiece can also be designed as a broach (rasp with transverse teeth), as is used to create an implant bed by removing bone in the vertebral bodies in the anterior / posterior direction, or as a trial prosthesis with which the size and position of the later can be checked under X-ray control implanting prosthesis.

The clearing element is expediently a knife disk. It preferably has at least one pair of cutting fins which are offset over the circumference. In the rest position, the cutting fins are in such a position that they do not protrude from the head piece. If the knife disc is rotated by the actuating element, the cutting fins protrude from the head piece perpendicular to the direction of the Stems out of the cranial / caudal surfaces of the head piece and thus engage in the adjacent vertebral body when the head piece is inserted. The recess is then created by moving the knife disc. It is advisable to arrange the cutting fins of a pair exactly opposite on the knife disc. It can thereby be achieved that the recess in both adjacent vertebral bodies can be produced in the same cutting process. This ensures that the recesses are aligned. In addition, no horizontal forces act on the head piece. However, it can also be provided that the cutting fins are not arranged exactly opposite one another, but are offset by a certain angle which is dimensioned such that when the knife disc is rotated out of its rest position, a cutting fin first comes into contact with one of the two adjacent vertebral bodies and a recess cuts in it, and only when this cutting fin has worked into this vertebral body does the other cutting fin emerge from the opposite cranial / caudal surface of the head piece and cut into the other of the two vertebral bodies. This has the advantage that the forces required for actuation are lower, since it is not cut into both vertebrae at the same time, but one after the other.

In order to avoid easier cutting and breaking out of bone material, it is advisable to provide cutting fins with different heights. They are arranged in such a way that when moving from the rest position the cutting fin with the lower height protrudes first and cuts into the vertebral body and then the cutting fin with the higher height. It goes without saying that more than two cutting fins of different heights can also be provided. In order to be able to cut into both adjacent vertebral bodies at the same time, the cutting fins are Licher height suitably arranged in pairs opposite one another.

However, other types of clearing elements can also be provided. In another embodiment, it is designed as a drill. A thrust / screw drive is expediently provided for actuation. Several drills can also be provided, expediently at least two drills arranged transversely to the handle are provided.

The clearing element preferably has a movable axis of rotation. This enables simple actuation by means of a rotatable shaft.

The clearing element is expediently displaceable along a guide, so that a slot can be milled.

The actuating element preferably comprises a handle and a transmission shaft. Such manual actuation keeps the instrument simple and enables the surgeon to move the clearing element as he feels. It has proven useful to provide the actuating element with an index device which marks the rest position. This enables the surgeon to ensure that the broaching element is in its rest position before inserting or pulling out the instrument. However, manual actuation is not mandatory; a rotary drive coupling can also be provided for motor actuation.

According to the invention, in the case of a cervical intervertebral prosthesis, it comprises a lower and an upper anchoring plate, each of which is designed with an anchoring plate surface for contacting an adjacent vertebral body, and an interposed prosthesis core, which forms an articulated connection between the anchoring plates, provided that at least one of the two anchoring plate surfaces to the vertebral body has a rib-like projection for positive engagement in the vertebral body.

The invention is based on the idea of using the rib-like projection according to the invention to achieve a form-fitting mounting of the base or anchoring plate on the vertebral body. The projection engaging in the vertebral body prevents undesired displacement of the anchoring plate with respect to the vertebral body. Dislocation of the cervical intervertebral prosthesis as a whole can thereby be avoided. It has been shown that the protrusion engaging in the vertebral body in a form-fitting manner so firmly anchors the intervertebral prosthesis to the vertebral body that subluxation in the sense of emigration to the dorsal is not to be feared. It goes without saying that the projection can not only prevent an undesired movement in the dorsal direction, but also in the opposite direction to the ventral direction. The operational safety of the intervertebral prosthesis provided with the projection according to the invention is thereby increased considerably.

The shape of the projection is in itself arbitrary. It is particularly important that the form-fitting engagement of the projection in the vertebral body is designed as an undercut in the AP direction of insertion of the intervertebral prosthesis into the space between the adjacent vertebral bodies. It has proven useful to design the projection as a rib. It is preferably arranged in a plane parallel to the ventral and dorsal edge of the anchoring plate. In the implanted state, the rib is thus at right angles to the AP direction, which means that there is an undesirable shift opposed the greatest possible resistance. It may be appropriate to make the upper edge of the rib convex. A curvature diameter of 3 to 10 mm has proven itself. The insertion of the anchoring plate with its projection into its position on the vertebral body is simplified because the anchoring plate can find its position due to the convex shape. In addition, the convex, rounded design has the advantage that corners protruding into the vertebral body are avoided. This counteracts the risk of undesired peak loads in the corner area. Finally, the convex, ideally circular section-shaped design of the rib also has the advantage that the congruent recess in the vertebral body can easily be produced with a corresponding rotating cutting tool.

In another expedient embodiment, the projection is divided into two or more segments with a gap in between. However, with multiple segments, it is not essential that each be in its own

Recess engages. A slot in which the segments arranged in one plane engage can equally well be provided as the recess for the positive engagement.

The projection is preferably arranged outside an edge region of the anchoring plate surface. An edge region is understood to mean the outer sector of the anchoring plate surfaces, which takes up about 1/10 of the total anchoring plate surface. In this area, the risk of the projection breaking away from the positive engagement in the vertebral body under high loads is reduced. The vertebral body is of greater strength at its edge regions, in particular in the ventral and dorsal edge, than in the region in between. Placing the protrusion in the anterior or post-serior The area would have the disadvantage, however, that the recess for the positive reception of the projection would have to be formed in a hard and brittle area of the vertebral body. There is a risk of bone fragments splintering. It has been shown that an arrangement of the protrusion offset somewhat dorsally, preferably in a range between 3/5 and 3/4 of the extension in the AP direction, provides both a high power transmission possibility and also safely and without risk of splintering to implant. animals is.

The protrusion may have a height of 0.3 to 5.0 mm, preferably 1.0 to 3.0 mm, above the level of the anchor plate surface. If this is provided with a toothing, which is advantageous for further increasing the security of the connection, the level of the anchoring plate surface is defined by the upper edge of the toothing. The projection is advantageously tapered towards the top. A self-centering effect can thus be achieved when inserting the anchoring plate on the vertebral body. Smaller inaccuracies can be compensated for in this way. The implantation is simplified.

The invention is explained below with reference to the drawing, in which advantageous exemplary embodiments are shown. Show it:

1 shows a perspective view of an exemplary embodiment of a cervical prosthesis according to the invention;

FIG. 2 shows a view from the posterior of the cervical prosthesis according to FIG. 1; 3 shows a posterior-cranial view;

4 shows a view of the posterior end of an exemplary embodiment for an instrument according to the invention;

5 shows a sectional view through a head piece of the instrument according to FIG. 4;

6 is a sectional view of an alternative embodiment of an instrument;

7 the instrument according to the invention in a perspective view obliquely from behind;

8 shows an enlarged illustration of the head piece of the instrument;

9 is a plan view of the instrument according to the invention;

10 shows a schematic view of two adjacent vertebral bodies between which a cervical prosthesis according to the invention is to be implanted;

11 shows a schematic view of the two vertebral bodies according to FIG. 9 when preparing the implantation site;

FIG. 12 shows a further grading of the preparation according to FIG. 10; and

Fig. 13 the cervical prosthesis implanted between the adjacent vertebrae. The exemplary embodiment shown in FIGS. 1 to 3 is a cervical prosthesis according to the invention, which is provided with the reference number 1 in its entirety. It is intended for implantation in the space between two adjacent vertebral bodies of the cervical spine (see FIG. 13).

The cervical prosthesis 1 consists of an upper end plate 11 and a lower end plate 12 with a sliding core 10 arranged between them. The cervical prosthesis 1 is intended for implantation in the space between two adjacent vertebrae of a person's cervical spine. The upper anchoring plate 11 is attached to the underside of the cranial vertebra and the lower anchoring plate 12 is attached to the upper side of the caudal vertebra. The anchoring plates 11, 12 consist of hard, resistant material, in particular titanium or another biocompatible material. Preferably, at least the surfaces of the anchoring plates 11, 12 which are used to abut the adjacent vertebral bodies are provided with a coating which requires bone growth, for example hydroxylapatite. The prosthesis core 10 is made of polyethylene or another low-friction and sufficiently wear-resistant plastic. The prosthesis core 10 is firmly, if detachably, connected to the lower anchoring plate 12. An undercut edge strip 14 on the anterior side (on the left in FIG. 1) of the lower anchoring plate 12 serves for connection, into which the prosthesis core provided with a complementary groove can be inserted. In its inserted position, the prosthesis core 10 is secured by means of a plate 15. The upper side of the prosthesis core 10 and the lower side of the upper anchoring plate 11 form cooperating, complementary sliding surfaces, which are preferably designed spherically. The anchoring plates 11, 12 are provided on their anterior edge with an edge designed as a flange, which projects cranially in the upper anchoring plate 11 and caudally in the lower anchoring plate 12. The posterior side (on the right in FIG. 1) of the back of the flange 16 has a stop surface for the ventral edge of the vertebral body. In order to prevent the anchoring plates 11, 12 from protruding ventrally and thereby possibly causing irritation of internal organs, the ventral edge of the vertebral bodies is preferably machined in such a way that a recess is formed into which the flange 16 of the anchoring plates 11, 12 is sunk. The anterior edge of the flange 16 is preferably rounded in order to ensure that the flange 16 bears securely against the vertebral body. This is also accompanied by a certain protection against undesired lateral displacements. In order that too much material does not have to be removed from the vertebral bodies for the recessed arrangement of the flange 16, its dimensions are expediently small. In particular, it should only have a small height above the upper side of the anchoring plate 11 or below the lower edge of the anchoring plate 12. It should be between 0.5 and 2 mm, preferably between 0.8 and 1.3 mm. Relative to the size of the intervertebral prosthesis, the height should measure approximately 0.5 to 2/10 of the total dimension in the anterior / posterior direction (AP direction).

The upper sides of the anchoring plates 11, 12 are provided with teeth 17 over most of their area. They are sawtooth-shaped, the steeper flank pointing anterior to the flange 16 and the less steep flank pointing posteriorly. The steep flank of the teeth 17 preferably forms an angle of 70 to 90 degrees with the plane of the anchoring plates 11, 12. The teeth 17 are designed so that they are oriented transversely to the AP direction. Because of this orientation, the teeth 17 exert a force acting posteriorly on the intermediate cervical prosthesis 1 and thus prevent an undesired displacement of the cervical prosthesis 1 anteriorly. The flange 16 in turn secures the cervical prosthesis 1 against posterior movement. As a result, the cervical prosthesis is secured against undesired movement in both directions.

In order to improve the securing effect and to protect against subluxation, a rib projecting towards the cranial or caudal is arranged on the surface of the anchoring plates 11, 12. It is oriented parallel to the teeth 17 transversely to the AP direction. Its top is designed as an arc segment. The thickness of the rib 18 is preferably constant over the entire height, but it can also taper towards the top. A self-tapping function is not provided. The rib 18 is firmly connected to the respective anchoring plate 11, 12 by welding or brazing. However, it can also be provided that the anchoring plate 11, 12 and the rib 18 are each made from one piece.

If the ligamentous apparatus holding the vertebral bodies together is weakened and there is a risk that the pressure exerted by the vertebral bodies on the cervical prosthesis 1 is low, it may be advisable to rib 18 with an opening 19, as shown by the broken line in FIG. 2 is shown. The opening 19 allows bone material to grow through this opening 19 after the implantation of the anchoring plates in the respective vertebral body. The anchoring plate is thus fixed to the vertebral body in such a way that it cannot stand out from the vertebral body. The rib 18 has a height of 1.5 mm. As already stated, it should not be self-tapping. It is therefore necessary to make a corresponding recess in the corresponding intervertebral surfaces when preparing the implantation site. The instrument shown in FIGS. 3 to 9 is used for this. The instrument as a whole is designated by reference number 2. It comprises a handle 40, a stem 50 and a head piece 60. The head piece 60 functions as a test piece and has the contour and the dimensions of the cervical prosthesis 1 to be implanted. A flange 66 corresponding to the flange 16 of the cervical prosthesis 1 is provided on the anterior edge of the head piece 60. The instrument can thus serve as a trial gauge for the cervical prosthesis 1 to be implanted.

A knife disk 7 is arranged in the head piece 60 as a clearing element. For this purpose, the head piece 60 has a slot 65 which extends over the entire height of the head piece from the top 63 to the bottom of the head piece 60. The knife disc is designed as a double finned knife with two pairs of opposing fins. The first pair of fins are pre-cutting fins 72, each of which has a cutting edge which acts in the circumferential direction. The second pair of fins are two main cutting fins 71 which lie opposite one another and have a cutting edge which points in the same direction as the pre-cutting fins 72, but which is angularly set back in the cutting direction by an amount of approximately 35 degrees. The

Knife disk 7 has a square drive opening 73 in its center.

On the handle 40, a transmission shaft 51 is arranged in a T-shape, which is designed as a hollow cylinder Handle 50 leads into the head piece 60. At its end remote from the handle 40, the transmission shaft 51 is provided with a driver square 52. The transmission shaft 51 is guided on the stem 50 so as to be rotatable and longitudinally movable. An indexing device 45, 46 is arranged on the handle-side end of the handle 50. It comprises a recess 45 on the edge of the stem 50 and a marking pin 46 on the handle-side end of the transmission shaft 51. In a rest position, the handle 40 is rotated with the transmission shaft 51 and pushed into the stem 50 such that the marking pin 46 lies in the recess 45 , To move the handle 40 in its working position, the handle 40 with the transmission shaft 51 is pulled away from the edge of the stem 50 until the marking pin 46 is free of the recess 45 and the handle 40 can be rotated with the transmission shaft 51. The driver square 52 at the end of the transmission shaft 51 remote from the handle is designed as a square, at least over the distance over which the handle must be pulled to free the marking pin 46 from the recess 45. This ensures that the square always extends over the area of the slot 65 of the head piece 60, regardless of whether the handle 40 is in its rest position or in its twisted working position.

The functioning of the knife disk 7 is shown in more detail in FIG. 4. In Fig. 4 a the rest position is shown. The knife disc 7 is in the position in which it is also shown in FIG. 3. The cutting fins 71, 72 are sunk. In this rest position, the instrument can be inserted into or removed from the implantation space. 4 b and c show working positions. To reach this position, the handle 40 is pulled out so far that the marking pen 46 is free of the recess 45 on the stem 50. The handle 40 can then be moved in the direction in which the cutting edges of the cutting fins 71, 72 point. The cutting fins 71, 72 move on a circular path due to the rotation of the knife disk 7. First, the pre-cutting fins 72 leave the slot 65 of the head piece 60 and cut a first, low slot in the adjacent surface of the vertebral body. The pre-cutting fins are designed so that they break through the comparatively hard edge of the vertebral body. The main cutting fins 71 then move out of the slot 65 and cut a larger slot in the bone material of the vertebral body which is softer than the edge. The rotation takes place so far that the cutting fins 71 start again on the opposite side, in the FIGS

Dip slot 65 of the head piece 60. If necessary, the process can be repeated. Due to the symmetrical design of the knife disc 7, the slots in the upper and lower vertebral bodies are cut simultaneously. If this is not desired to reduce the actuation forces, the fins can either be provided on one side only or they can be offset by an angle of 180 degrees arranged so that first a set of pre-cutting and main cutting fins 71, 72 rises from the slot 65, while the other only later in the

Rotation follows.

5 shows another exemplary embodiment of a clearing element. It is a combined drilling / milling device 8. It comprises two drills 82 which are arranged in the head piece 60 transversely to the direction of the handle 50. The drills 82 have cutting trains 81 in their lower section. In their upper section they are provided with an external thread 83. This is guided in a counter thread arranged fixed in the head piece 60 84. A driven gear 85 is arranged at the upper end of the drill 82. It meshes with a drive wheel 86, which in turn is driven by the transmission shaft 51 via an angular drive 87. The drive wheel 86 has a greater strength than the driven wheel 85. Its strength preferably corresponds to the intended drilling stroke, ie the depth of the recesses to be produced with the drills 82. A drill arrangement is arranged in mirror image on the opposite side. The drilling / milling device 8 works as follows. The transmission shaft 51 is rotated by means of a preferred mechanical drive, as a result of which the drive wheel 86 also rotates via the angular drive 87. In their rest position, the drills are in the position shown in FIG. 5, the driven wheel 85 engaging in the drive wheel 86 at its upper edge. The rotation of the drive wheel 86 also rotates the driven wheel 85, causing the drill 82 to rotate. Due to the rotational movement, the drill 82 screws with its thread 83 into the external thread 84, as a result of which the drill 82 is moved downward. The drill 82 thereby works its cutting lines 81 into the bone material of the vertebral body. Due to the downward thrust movement of the drill 82, the driven wheel 85 also moves downward, while it remains always in engagement with the drive wheel 86. For this purpose, the latter has a thickness that is at least as large as the stroke of the drill 82. Once the desired depth of the recesses has been reached, reversing the direction of rotation means that the drills 82 move back into their rest position.

In an alternative embodiment, the rib 18 can also be divided into segments 18 '(see FIG. 3). The segmentation has the advantage that the resulting side surfaces provide additional protection for the prosthesis against undesirable displacements in the transverse axis is prevented. The rib 18 can be divided into two or three segments 18 ', as indicated by the broken line in FIG. 3. To improve the hold on the vertebral body, it can be provided that the recess in the vertebral body for receiving the rib segments 18 'is not continuous, but also to segregate animals. More detailed explanations are given in relation to the drilling / milling device 8.

The method for implanting the prostheses according to the invention using the tool according to the invention can be represented as follows. In a first sight. The adjoining vertebral bodies into which the cervical prosthesis 1 is to be implanted are prepared for receiving a spreading device 91. This is done by attaching the legs 92, 93 of the expansion tool 91 to the anterior side of the two vertebrae by means of a screw fastening. The spreading tool 91 is angled in such a way that the immediate access area from the anterior to the interspace remains free. After the vertebrae have been spread to the intended distance, the intermediate space is prepared for receiving the cervical prosthesis 1. This is done by Ra ^~ umen of excess bone material to produce a suitable contact surface for the anchoring plates 11, 12 and for the flange 16 (see Fig. 10). After the implantation site has been prepared so far, the instrument 2 according to the invention is attached. The head piece 60 is pushed into the prepared intervertebral space. diarch

When the handle 40 is actuated, the knife disc 7 is actuated, the cutting fins 71, 72 cutting a receptacle for the rib 18 into the cranially and caudally adjacent vertebral body. Then the knife disk 7 is again brought into its rest position and the instrument 2 can be removed. to be pulled. The preparation is now complete. The cervical prosthesis 1 can now be inserted, with the vertebral bodies possibly being spread a little by means of the spreading tool 91 in order to have sufficient space for inserting the ribs 18 into the recesses. After removing the spreading tool 91, the implantation is complete.

Claims

claims

1. Instrument for implanting a cervical intervertebral prosthesis (1), which comprises two anchoring plates (11, 12) and a prosthesis core (10) arranged between them, with a handle (40), a stem (50) and a head piece (60) which is arranged at an end distant from the handle (40) and the dimensions of which are selected such that it can be inserted into the space created between the adjacent vertebral bodies for accommodating the intervertebral prosthesis (1), characterized in that the head piece (60) is inserted Has clearing element (7, 8) for creating a recess in the cranial-caudal direction in the vertebral bodies and an actuating device (40, 51, 52) for the clearing element (7, 8) is provided, which is between a rest position in which it is sunk in the head piece (60) and a working position in which it projects transversely to the handle (50) from the head piece (60) is movable.

2. Instrument according to claim 1, characterized in that the clearing element is a knife disc (7).

3. Instrument according to claim 2, characterized in that the knife disc (7) at least one pair above the Has circumferentially offset cutting fins (71, 72).

4. Instrument according to claim 3, characterized in that the cutting fins (71, 72) have different heights.

5. Instrument according to claim 3 or 4, characterized in that the cutting fins (71, 72) are arranged in pairs opposite one another.

6. Instrument according to claim 1, characterized in that the clearing element (8) is a drill (82).

7. Instrument according to claim 6, characterized in that a thrust / screw drive (85, 83, 84) for actuating the drill (82) is provided.

8. Instrument according to claim 6 or 7, characterized in that at least two drills (82) are arranged transversely to the handle (50). are arranged.

9. Instrument according to one of claims 6 to 8, characterized in that the clearing element (8) identifies a ball milling section.

10. Instrument according to one of claims 1 to 9, characterized in that the clearing element (8) along a guide (84) is longitudinally movable.

11. Instrument according to one of claims 1 to 10, characterized in that the actuating element comprises a handle (40) and a transmission shaft (51).

12. Instrument according to one of claims 1 to 11, characterized in that the actuating element has a rotary drive coupling.

13. Cervical intervertebral prosthesis comprising a lower and an upper anchoring plate (11, 12), which are each formed with an anchoring plate surface for contacting an adjacent vertebral body, and an interposed prosthesis Core (10), which forms an articulated connection between the anchoring plates (11, 12), characterized in that at least one of the two anchoring plate surfaces (11, 12) to the vertebral body has a rib-like projection (18) for positive engagement in the vertebral body transverse to the AP Direction.

14. Cervical intervertebral prosthesis according to claim 13, characterized in that the projection (18) is arranged outside an edge region of the anchoring plate surface (11, 12).

15. Cervical intervertebral prosthesis according to claim 14, characterized in that the projection is arranged offset posteriorly from the center, preferably in a range between 3/5 and 3/4 of the extension in the AP direction.

16. Cervical intervertebral prosthesis according to one of claims 13 to 15, characterized in that the projection (18) has a height of 0.3 to 5.0 mm, preferably 1.0 to 3.0 mm, above the level of the anchoring plate surface (11 , 12).

17. Cervical intervertebral prosthesis according to one of claims 13 to 16, characterized in that the projection (18) is a spherical section.

18. Cervical intervertebral prosthesis according to one of claims 13 to 17, characterized in that the projection (18) is divided into two or more segments (18 ') with a gap therebetween.

19. Cervical intervertebral prosthesis according to claim 18, characterized in that the segments (18 ') are designed like bolts.

20. A method for implanting an intervertebral prosthesis (1) with two cover plates (11, 12) and a prosthesis core (10) arranged therebetween, comprising the steps: a) spreading (91) from two adjacent vertebral bodies, b) machining (94) the end faces of the Vertebral body to create a receptacle for the cover plates (11, 12), c) inserting an instrument (2) with a head piece (60) and a cranial-caudal cattle device removable broaching element (7, 8) for creating a recess in the cranial / caudal direction in at least one end face, d) removing the instrument (2) and inserting the intervertebral prosthesis (1) on at least one surface of the cover plates (11 , 12) has a projection (18) which engages in the recess.

21. The method according to claim 20, characterized by using the instrument according to one of claims 1 to 12.

22. The method according to claim 20 or 21, characterized by

Use of the intervertebral prosthesis according to one of claims 13 to 19.