DE29710979U1 - Implant for fixing bone parts and tool for this implant - Google Patents

Description

IMPLANT FOR FIXING BONE PARTS AND TOOL FOR THIS IMPLANT

The invention relates to an implant for the relative fixation of bone parts, in particular for spinal fixation, with anchoring elements that can be inserted into each bone part and are connected via a detachable ball clamp connection to a bearing body, which on the one hand has a cup-shaped receptacle for a spherical end of an anchoring element and on the other hand has a bearing recess for a connecting rod, and with a clamping element on the bearing body, which in the tensioned state presses the connecting rod into the bearing recess and thereby fixes it relative to the bearing body and which thereby tensions the connecting rod directly or indirectly against the spherical end of the anchoring element and thereby presses it into the cup-shaped receptacle and clamps it relative to the bearing body.

Such an implant is known, for example, from DE 43 07 576 Cl.

It can be used to fix different bone parts relative to each other, in particular

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use such an implant to fix adjacent vertebrae of the spine. The spherical connection of an anchoring element that can be inserted into the bone part with a bearing body allows the bearing body to be positioned differently relative to the bone part, so that the bearing bodies in adjacent bones can be aligned with each other in such a way that they can be permanently and firmly aligned relative to each other using connecting rods.

In the known device, the ball clamp connection is secured by pressing the connecting rod against a pressure body via a nut-shaped clamping element, which in turn secures the spherical end of the anchoring element. The connecting rod is located directly above the spherical end of the anchoring element, so this is no longer accessible from the outside after the connecting rod has been inserted.

Although the known implant can be used variably, the achievable stiffening of adjacent bearing bodies is limited, since the bearing bodies are connected via a single connecting rod. There is a risk that the bearing bodies can twist against each other around the longitudinal axis of the connecting rod.

It is the object of the invention to design a generic implant in such a way that it is suitable for safely absorbing large forces while maintaining a structurally simple structure, so that the risk is reduced

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that the bearing bodies fixed relative to each other change in their position.

This object is achieved according to the invention in an implant of the type described at the outset in that a bearing recess for a connecting rod is arranged in the bearing body on both sides of the cup-shaped receptacle. This makes it possible to connect the bearing bodies to one another via two connecting rods, and this reliably excludes, for example, a rotation of the bearing bodies about the longitudinal axis of a connecting rod. In this way, significantly higher fixation stability can be achieved.

It is already known to use devices for spinal fixation in which bearing bodies are connected to one another by two connecting rods, but the anchoring body is not connected to the bearing body in an articulated manner, so that variable adaptation to anatomical conditions is not possible (WO 96/29016).

In a preferred embodiment of the invention, the distance between the bearing recesses is so large that there is free access between them to the spherical end of the anchoring element. Such a design makes it possible to reach the spherical end of the anchoring element even after the connecting rods have been inserted into the bearing recesses, so that the anchoring element can be inserted into the bone, even though the connecting rods

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be already inserted. It is therefore possible to align the bearing bodies of the individual bone parts relative to each other by inserting the connecting rods and only then to fully insert the anchoring elements in the bone parts, for example by finally screwing them in.

It is advantageous if a common clamping element is provided for both connecting pieces, in particular this clamping element can be a nut.

It is advantageous if the bearing recess is a longitudinal groove where the longitudinal grooves preferably run parallel to each other.

If the spherical end of the anchoring element according to a preferred embodiment protrudes slightly into the cross-section of the bearing recess, the connecting rod accommodated in this bearing recess can lie directly on the spherical end of the anchoring element and thereby fixes the spherical end for a clamping connection when the clamping element is tensioned. This means that the connecting rod is fixed in a three-point support in the bearing recess, namely once on the spherical end of the anchoring element, secondly on the clamping element and finally in the bearing recess.

In a preferred embodiment, it is provided that the bearing body is plate-shaped. This makes it possible to place the bearing body flatly on the bone part to be fixed, the bearing body

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has the function of a conventional bone plate.

It is advantageous if the bearing body has protruding tips on its underside facing away from the bearing recesses. These dig into the bone part to be fixed and lead to additional fixation of the bearing body relative to this bone part.

The tips can be inserted into the bearing body, for example in the form of pins, but it is also possible that the tips are formed in one piece with the bearing body.

In a preferred embodiment, the bearing body has an externally threaded sleeve between the bearing recesses, which is connected to the pan-shaped receptacle and onto which the clamping element can be screwed. This results in a very compact structural unit that can already be pre-assembled and is therefore easy to handle.

It is advantageous if the spherical end of the anchoring element has a non-circular central opening, for example a hexagon socket, as a holder for a turning tool.

The anchoring element can basically be designed in any way, but it is particularly advantageous if the anchoring element is a bone screw.

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This can be hollow so that bone material remains inside after screwing in. It is particularly advantageous if the bone screw has perforated wall areas through which the bone material can grow after the bone screw has been inserted.

It is also advantageous if the spherical end is detachably connected to the rest of the anchoring element. This not only makes it possible to insert the anchoring element into the bone in advance and only then to attach the spherical end, but it is also possible to remove the spherical end at a later point in time when the implant is to be removed, whereby the rest of the anchoring element can then remain in the bone.

In particular, the spherical end can be screwed into the rest of the anchoring element.

To screw in the anchoring element, it is advantageous to provide a turning tool which is characterized by the fact that it has a spherical head whose cross-section is so non-circular that it can be inserted into the non-circular central opening in the anchoring element with play, so that insertion is possible at different angles, but that when the tool is rotated in the central opening it has a positive fit on the non-circular cross-section of the central opening. For example, the turning tool can have a spherical head which is reworked to be hexagonal in cross-section.

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so that it can be inserted into a hexagon socket in the spherical end of the anchoring element. If the longitudinal axis of the hexagon socket is inclined relative to the longitudinal axis of the turning tool, the spherical head can still be inserted into the central opening of the spherical end due to the existing play, and when the turning tool is turned, the hexagonally reworked spherical head rests against the inner surfaces of the hexagon and enables the anchoring element to be turned.

It is also advantageous if a tool is provided for inserting the described implant, which is characterized in that it comprises a sleeve that can be inserted or screwed into the externally threaded sleeve. By inserting the sleeve into the externally threaded sleeve, it is possible to position the bearing body using a suitable instrument, while at the same time positioning the bone part to which the bearing body is attached. For example, it is possible to change the distance between two bearing bodies by inserting the sleeves inserted into the bearing bodies in a distractor known per se, which then adjusts the distance between the two sleeves parallel to itself.

In a preferred embodiment, it can further be provided that a screw-in sleeve is placed on the sleeve, which can be moved longitudinally thereon and rotated relative to it, and which has a

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positive-locking receptacle for the clamping element and an engagement surface for a turning tool in an area above it. The clamping element can be screwed onto the bearing body using this screw-in sleeve, while retaining the sleeve inserted into the bearing body, which then serves as a guide for the screw-in sleeve. The screw-in sleeve is rotated using a turning tool, for example a wrench, which can be placed on the engagement surface.

It is advantageous if the screw-in sleeve is shorter than the sleeve that can be inserted into the externally threaded sleeve, so that the latter protrudes beyond the screw-in sleeve. A distractor can then be attached to this protruding area, for example, in order to change the distance between bearing bodies relative to one another.

It is also advantageous that a turning tool can be inserted through the sleeve inserted into the bearing body, with which the anchoring element can also be turned when the sleeve is inserted into the bearing body and if the screw-in sleeve is also arranged on the bearing body. This means that the anchoring element can be finally screwed in with the distractor in place, and it is then also possible to tighten the clamping element by operating the screw-in sleeve with the distractor in place and the turning tool for the anchoring element still inserted. In this way, all processes can be carried out independently of one another and, if necessary, simultaneously.

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The following description of preferred embodiments of the invention serves to explain in more detail in conjunction with the drawing. They show:

Figure 1: a perspective view of two vertebral bodies when inserting an anchoring element with bearing body when screwing in the anchoring element or when placing a screw-in sleeve on the inserted anchoring element;

Figure 2: a longitudinal sectional view of a screwed-in anchoring element with bearing body and mounted insertion tools;

Figure 3: a view similar to Figure 1 with anchoring elements inserted with connecting rods and a distractor attached;

Figure 4: a view similar to Figure 3 with a turning tool inserted for the final screwing in of an anchoring element and with a turning tool for turning a screw-in sleeve;

Figure 5: a longitudinal sectional view of an anchoring element inserted into the bone with bearing body and clamped connecting rods;

Figure 6: a view similar to Figure 5 of a modified embodiment of an anchoring element with bearing body and

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Figure 7: a perspective view of the anchoring element of Figure 6 in the inserted state.

The implant shown in the drawing is explained below using the example of a spinal fixation system, i.e. a system in which the vertebrae of the spine are fixed relative to one another. It goes without saying, however, that the implant can also be used to attach to other bones and bone parts in the body that need to be fixed relative to one another, for example after a bone fracture.

The implant essentially comprises three parts, namely a bearing body 1 and a bone screw 2 connected to the bearing body 1 via a ball joint, as well as two connecting rods 3 for producing a rigid connection between two bearing bodies 1, which are attached to bone parts that are to be fixed relative to one another.

The bone screw 2 of the embodiment shown in Figures 1 to 5 is designed as a hollow screw and for this purpose has a hollow cylinder 4 with a thread 5 running on the outer shell and openings 6 arranged between the adjacent threads. A threaded ring 9 is screwed into a head 8 of the hollow cylinder 4, which is provided with an internal thread 7, which in turn has an internal thread 10, and a connecting part 11 is screwed into this internal thread 10, which

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protrudes from the threaded ring 9 with a spherical end 12. This spherical end is cut off at the top 13, in this area a central opening 14 with a hexagonal cross section enters the spherical end 12, which is located in a threaded blind hole

15 with a smaller diameter. The opening with the hexagonal cross-section thus forms a hexagon socket that extends approximately to the center of the spherical end 12.

The bearing body 1 is designed as a bone plate 16, it has a central through-opening 17, which at its lower end has the shape of a cup-shaped bearing ring 18 that narrows from top to bottom, while it merges upwards into an externally threaded sleeve 19, which extends upwards from the bone plate

16 protrudes. On both sides of this external thread sleeve 19, two groove-shaped bearing receptacles 20 run parallel to one another, the cross-section of which is limited in the shape of a circular arc and which, on their side facing the external thread sleeve 19, penetrate into the interior of the external thread sleeve 19. In this area, the wall of the external thread sleeve 19 has an opening 21 which is arranged directly above the pan-shaped bearing ring 18.

On the outside of the groove-shaped bearing receptacles 20, pins 23 are inserted into openings 22 of the bone plate 16, with a pointed end 24 protruding downwards from the bone plate 16, while the ends 25 protruding upwards from the bone plate 16 directly follow the contour of the groove-shaped bearing receptacles 20.

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Connect the ger holders 20 and continue them (Figure 5).

The bearing body 1 and the bone screw 2 are connected to one another by a ball joint. To do this, the connecting part 11 is pushed through the externally threaded sleeve 19 from above until the spherical end 12 is received in the cup-shaped bearing ring 18. The internal thread 10 of the threaded ring 9 is then screwed onto the connecting part 11, if necessary already together with the hollow cylinder 4.

The spherical end 12 of the connecting part 11 inserted in the bearing ring 18 in this way projects slightly through the openings 21 into the two bearing receptacles 20 (Figure 5).

A connecting rod 3 is inserted into each of these bearing receptacles 20, the outer diameter of which is dimensioned such that the connecting rod 3 rests on the one hand against the spherical end 12 entering the bearing receptacle 20 and on the other hand against the bearing receptacle 20 itself.

A clamping element in the form of a nut 27 is screwed onto the external thread 26 of the external thread sleeve 19, which rests with its underside on the top of the connecting rods 3 inserted into the bearing holder 20 and, when tightened, presses the connecting rods 3 strongly against both the spherical end 12 of the connecting part 11 and against the side wall of the bearing holder 20. This means that the connecting

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rods 3 are fixed immovably relative to the bearing body 1, but at the same time the spherical end 12 is also clamped immovably in the bearing ring 18.

An elongated sleeve 29 can be inserted into the external thread sleeve 19 in a form-fitting manner, which thus practically forms an extension of the external thread sleeve 19. A screw-in sleeve 30 is placed onto this sleeve 29, which is overall shorter than the sleeve 29 and which is guided on the screw-in sleeve 30 in a longitudinal direction freely displaceable and freely rotatable. The screw-in sleeve 30 has a receptacle 31 for the nut 27 at its lower end, which is received in the receptacle 31 in a form-fitting manner, and on the top a nut-shaped engagement surface 32 for a wrench 33 (Figure 4).

The sleeve 29 protrudes from the screw-in sleeve 30 with its section 34 facing away from the bearing body 1, and this section 34 serves as an engagement surface for a distractor 35 of a known design (Figure 3), which essentially has two parts 36, 37 that can be moved relative to one another, each of which can be plugged onto a section 34 of a sleeve 29 of a bearing body 1 and which can be moved parallel to one another by a suitable drive, for example a spindle drive 38, in such a way that the distance between the two sleeves 29 on which the distractor 35 is placed is also changed.

The tool for inserting the implant further comprises a turning tool 39 with a shaft 40 with a

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a handle 41 at one end and a ball head 42 at the other end, which is reworked so that it has a hexagonal cross-section. The dimensions are chosen so that the ball head 42 can enter the hexagon socket area of the opening 14 with play, this also allows the ball head 42 to enter when the shaft 40 is inclined relative to the bone screw 2. Nevertheless, a positive connection can be made when the turning tool 39 is turned relative to the bone screw 2.

To insert the implant described, a receiving channel for the bone screw 2 is first machined into the bone in a known manner. The bone screw 2 is screwed into this bone channel together with a bearing body to which it is captively connected. This screwing can be done with the rotary tool 39 or, if necessary, with a normal polygonal wrench that is inserted in the direction of the bone screw. This screwing process is not carried out completely, but only to the extent that the pointed end 24 of the pins 23 does not yet penetrate into the bone 43. The same procedure is followed for a second bone that is to be rigidly connected to the first bone.

After this partial screwing in of the bone screws 2, the sleeve 29 and the screw-in sleeve 30 are placed on the bearing body 1 in the manner described. For the sake of completeness, it should be noted that this placement can of course also take place at the beginning of the screwing-in process, in which case

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To screw in the bone screw 2, a turning tool with a shaft must be used that extends through the sleeve 29, as shown in Figure 1 on the posterior vertebral body. In the example shown there, only the sleeve 29 is put on for screwing in, the screw-in sleeve 30 is only put on after it has been partially screwed on (front vertebra in Figure 1).

When bone screws 2 with bearing bodies 1 are inserted into the vertebral bodies to be connected in this way, two connecting rods 3 are then inserted into the bearing receptacles 20, as is clear from the illustration in Figure 3. These can be temporarily secured using the nut 27, whereby the nut 27, which is located in the receptacle 31 and is put on when the screw-in sleeve 30 is put on, is only loosely screwed on and not yet tightened, so that the bearing body 1 can still pivot relative to the bone screw 2, and the connecting rods 3 can also still be moved.

The distractor 35 is then placed on the sections 34 of the sleeves 29 that protrude beyond the screw-in sleeve 30 and is adjusted so that the sleeves 29 and thus the bearing bodies 1 and the bones holding them are at the correct distance from one another.

Once this is achieved, the bone screws 2 are fully screwed into the bone 43 using the turning tool 39, which is

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Sleeve 29 is inserted through and its ball head 42 is inserted into the opening 14. As described, an effective rotary connection is also possible if the longitudinal axis of the shaft 42 and the longitudinal axis of the bone screw enclose an angle with each other.

It is advantageous to screw in the bone screws 2 of both bones approximately evenly, if necessary by alternately applying the turning tool 39.

As soon as the bone plates 16 are completely screwed in, they are securely fixed to the bone 43, since the pointed ends 24 of the tips 23 dig into the bone material (Figure 5).

The implant is finally fixed by turning the screw-in sleeve 30 using the wrench 33 (Figure 4), whereby both the connecting rods 3 in the bearing body 1 and the spherical end 12 in the bearing ring 18 are tightened.

When this has been achieved for both bearing bodies, the distractor 35, the sleeves 29 with the screw-in sleeves 30 and the turning tool 39 are removed, and only the implant remains in the body, which permanently and securely connects the adjacent bones 43 to one another via two parallel connecting rods 3.

After the healing process is complete, the implant can be largely removed again. All you have to do is open the nut 27 and remove the connecting rods 3, then the connecting part can be

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11 can be unscrewed from the bone screw in the manner described, so that the connection part can then be removed and, using a suitable tool, the bearing body 1 can also be removed. The bone screw remaining in the bone can be closed with a suitable plug.

The embodiment of Figures 6 and 7 largely corresponds to that of Figures 1 to 5, corresponding parts therefore bear the same reference numerals.

In contrast to the embodiment of Figures 1 and 5, the embodiment of Figures and 7 lacks pins 23 inserted into the bone plate 16; instead, pointed projections 44 projecting downwards are integrally formed on the bone plate 16.

A further difference can be seen in the fact that the central opening, which is hexagonal in cross-section, is not connected to a threaded blind hole 15, but rather to a conical blind hole 45. The turning tool 39, with which the bone screw 2 can be screwed into the bone 43, in this case penetrates into the hexagonal opening by means of a hexagonal section 46 and into the conical blind hole 45 with a conical section 47 adjoining the hexagonal section 46. The hollow screw can be screwed in both directions using this turning tool.

A further difference compared to the embodiment of Figures 1 to 5 is that the

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External thread sleeve 19 additionally has an internal thread 48, into which the elongated sleeve 29 can be screwed by means of an external thread 49.

Otherwise, the implant according to Figures 6 and 7 can be used in the same way as the implant according to Figures 1 to 5.

Claims (22)

A 53 875 u AESCULAP AG & Co. KG u - 223 18 June 1997 - 19 - PROTECTION CLAIMS 1. Implant for the relative fixation of bone parts, in particular for spinal fixation, with anchoring elements that can be inserted into each bone part and are connected via a detachable ball clamp connection to a bearing body that has on the one hand a pan-shaped receptacle for a spherical end of an anchoring element and on the other hand a bearing recess for a connecting rod, and with a clamping element on the bearing body, which in the tensioned state presses the connecting rod into the bearing recess and thereby fixes it relative to the bearing body and which thereby clamps the connecting rod directly or indirectly against the spherical end of the anchoring element and thereby presses it into the pan-shaped receptacle and clamps it relative to the bearing body, characterized in that in the bearing body (1) on both sides of the pan-shaped receptacle (18) a bearing recess (20) for a connecting rod (3) is arranged. 2. Implant according to claim 1, characterized in that the distance between the bearing recesses (20) is so large that there remains free access to the spherical end (12) of the anchoring element (2) between them. A 53 875 u AESCULAP AG & Co. KG u - 223 18 June 1997 - 20 - 3. Implant according to claim 1 or 2, characterized in that a common clamping element (27) is provided for both connecting rods (3). 4. Implant according to one of the preceding claims, characterized in that the clamping element (27) is a nut. 5. Implant according to one of the preceding claims, characterized in that the bearing recess (20) is a longitudinal groove. 6. Implant according to claim 5, characterized in that the longitudinal grooves run parallel to each other. 7. Implant according to one of the preceding claims, characterized in that the spherical end (12) of the anchoring element (2) projects slightly into the cross section of the bearing recess (20). 8. Implant according to one of the preceding claims, characterized in that the bearing body (1) is plate-shaped. A 53 875 u AESCULAP AG & Co. KG u - 223 18 June 1997 - 21 - 9. Implant according to claim 8, characterized in that the bearing body (1) has protruding tips (23, 24; 44) on its underside facing away from the bearing recesses (20). 10. Implant according to claim 9, characterized in that the tips (23) are inserted into the bearing body (1). 11. Implant according to claim 9, characterized in that the tips (44) are formed in one piece with the bearing body (1). 12. Implant according to one of the preceding claims, characterized in that the bearing body (1) between the bearing recesses (20) carries an externally threaded sleeve (19) adjoining the pan-shaped receptacle (18), onto which the clamping element (27) can be screwed. 13. Implant according to one of the preceding claims, characterized in that the spherical end (12) of the anchoring element (2) has a non-circular central opening (14) as a receptacle for a turning tool (39). A 53 875 u AESCULAP AG & Co. KG u - 223 18 June 1997 - 22 - 14. Implant according to one of the preceding claims, characterized in that the anchoring element is a bone screw (2). 15. Implant according to claim 14, characterized in that the bone screw (2) is hollow. 16. Implant according to claim 15, characterized in that the bone screw (2) has perforated wall areas (6). 17. Implant according to one of the preceding claims, characterized in that the spherical end (12) is releasably connected to the remaining anchoring element (4). 18. Implant according to claim 17, characterized in that the spherical end (12) is screwed into the remaining anchoring element (4). 19. Turning tool for screwing in an anchoring element with a non-circular central opening in one end, in particular according to claim 13, characterized in that it has a spherical head (42) whose cross section is non-circular in such a way that it can be inserted with play into the non-circular central opening (14) in the anchoring element (2). A 53 875 u AESCULAP AG & Co. KG u - 223 18 June 1997 - 23 - can be guided so that it can be inserted at different angles, but that when the tool (39) is rotated in the central opening (14) it comes into positive contact with the non-circular cross-section of the central opening (14). 20. Tool for inserting an implant according to claim 12 and optionally according to claims 13 to 18, characterized in that it comprises a sleeve (29) that can be inserted or screwed into the externally threaded sleeve (19). 21. Tool according to claim 20, characterized in that a screw-in sleeve (30) is placed on the sleeve (29) and is longitudinally displaceable thereon and rotatable relative to the latter, which has a positive-locking receptacle (31) for the clamping element (27) at the lower end and an engagement surface (31) for a turning tool (33) in an area above it. 22. Tool according to claim 21, characterized in that the screw-in sleeve (30) is shorter than the sleeve (29) insertable into the externally threaded sleeve (19).