Disclosed is a device comprising at least one intervertebral implant (3) and at least one plate (4,5) that is to be connected to the intervertebral implant (3) and an adjacent spine (21-23). The intervertebral implant (3) is connected to at least two spaced-apart plates (4,5). One end of both plates (4,5) respectively forms a fixable joint along with the intervertebral implant (3). Preferably, at least one of the plates (5,4) is embodied in a Z-shaped or L-shaped manner. The inventive device provides for great adaptability to the anatomic characteristics of the spinal column and a modular structure while the number of parts is kept small.

The invention relates to a device for spondylodesis and in particular to a device for anterior intersomatic spondylodesis of the cervical spine, with at least one intervertebral implant, and with at least one connecting plate which is to be connected to the intervertebral implant and to an adjacent vertebra.

Spondylodesis is understood as surgical stiffening or blocking of a portion of the spinal column. For this purpose, in the traditional method, use is made of bone or of a bone replacement material which is inserted between the vertebral bodies, so-called intersomatic spondylodesis, or applied across the rear elements of the vertebrae, so-called dorsal spondylodesis. Over the course of time, this results in the creation of an osseous bridge which connects the vertebrae in such a way that they are no longer able to move relative to one another. To allow ossification to take place, it is necessary for the relevant portion of the spinal column to be immobilized. This is achieved by means of suitable implants. These can be connected to the intervertebral implant or can be fitted independently of the latter.

Indications for spondylodesis include pain, spinal cord compression, nerve root compression and defective posture which are not able to be influenced by conservative therapeutic measures. Pain may in principle radiate from all pathologically altered structures of the spinal column. Narrowing of the spinal canal or of the intervertebral foramina is mainly responsible for the development of spinal cord compression or nerve root compression. By performing a surgical procedure, the pathological defects are eliminated and the stability of the spinal column is restored by the spondylodesis.

Since intersomatic spondylodesis always involves the reaming out of intervertebral disks, and this impairs the stability of the spinal column, this stability always has to be restored. This can be done, for example, using pressure-resistant bone chips which are taken from the patient, so-called autogenous bone chips, and are inserted between the vertebral bodies. Since the load-bearing capacity of such chips is often uncertain, and since their availability is limited, and since in addition the morbidity caused by collecting samples of bone chips may be considerable, the use of autogenous bone chips is increasingly being replaced by the use of intervertebral implants, also called cages, made from exogenous materials.

An intervertebral implant functions as a pressure-absorbing spacer which stabilizes the spondylodesis, secures the adjustability of the vertebral bodies relative to one another and ensures that a solid osseous bridge forms between the adjacent vertebral bodies. Bones or bone replacement material filled into the intervertebral implants and/or applied around them form a matrix for the new bone formation. The stability of the spondylodesis is crucial for the ossification process. Movements occurring within the spondylodesis delay or prevent its osseous consolidation.

Many intervertebral implants connected to vertebrae by a plate have been disclosed in the prior art.

For example, U.S. Pat. No. 6,235,059 B discloses a device with an intervertebral implant with which two vertebrae can be stabilized on one another. A plate with two arms is secured on the intervertebral implant and is connected in a rigid or pivotable manner to said intervertebral implant. Each arm has a continuous hole through which a bone screw can be screwed into the corresponding vertebral body. Adaptation to the particular anatomical circumstances, and in particular to the sagittal curvature, is very limited in this case. The intervertebral implant can only be connected to the adjacent vertebrae.

WO 00/24343 discloses a device with an intervertebral implant which has windings about the circumference and can be screwed in the manner of a screw in between the vertebrae. A wing-shaped plate with two arms is secured on a front end of the intervertebral implant. It is secured here in such a way that the plate can be moved in order to adapt to the anatomical circumstances. The two arms of the plate each have an oblong hole for receiving a bone screw. In this device too, the intervertebral implant can be connected only to the adjacent vertebrae. The adaptability to the anatomical circumstances is very limited.

FR 2 727 005 discloses a device with several intervertebral implants which are connected to one another by a common band. The band has holes for securing the band and in each case an intervertebral implant and holes for receiving a bone screw. It is true that several intervertebral implants can be connected to one another with this device, but the adaptability to the anatomical circumstances is also very limited here. To ensure such adaptability, different bands would have to be made available in this case. The distances between the intervertebral implants is predetermined.

EP 0 179 695 A discloses an intervertebral implant on which eyelets are formed, with which eyelets the implant can be screwed securely onto adjacent vertebrae. Here once again, the adaptability to anatomical circumstances is very limited. In particular, it is generally not possible in this case to fit the bone screws into the vertebral body at the desired location. Moreover, only two vertebrae can be connected with one intervertebral implant.

U.S. Pat. No. 5,360,430 discloses an intervertebral implant which completely or partially replaces a vertebra, is secured by plates to the upper and lower vertebrae, and permits a certain unsprung or sprung mobility between these vertebrae.

U.S. Pat. No. 5,443,515 likewise discloses an implant intended to replace a vertebral body. It is made of tantalum foam.

Because of the considerable anatomical variations existing between individuals and also caused by disease, in particular the anatomical variations in the cervical spine, stabilization of intervertebral implants with conventional plates necessitates a large range of plates of different lengths and with different distances between their holes. The length of the plates is dependent on the position of the upper and lower end holes. If, in the case of multi-level spondylodesis, the plates are secured only on the end vertebrae, there is a danger that the plates will tear off at one end vertebra. It is therefore advisable also to fix the plates by screws to the vertebral bodies lying between the end vertebrae. However, the screw holes provided for this purpose in conventional plates do not always lie exactly in a way that allows the screws in question to be fitted correctly into the vertebral bodies lying between the end vertebrae. In addition, when using different plate types, only one screw can be secured in each case in the vertebral body.

The object of the invention is to make available a device of this type which can be optimally adapted to the particular anatomical circumstances.

In a device of the generic type, the object is achieved by the fact that the intervertebral implant is connected to two plates which are arranged at a distance from one another, one end of each of the two plates forming a fixable joint together with the intervertebral implant. The two plates connected to the intervertebral implant can be moved independently of one another in several degrees of freedom and can be fixed at a stable angle in a desired end position. An important advantage of the device according to the invention is that it is also possible to perform multi-level spondylodesis, with adjacent intervertebral implants being able to be connected directly to one another. This affords an especially high degree of stability and thus of reliability. The intervertebral implants and the plates thus form a particularly stable unit. Different sizes of intervertebral implants can also be combined and can be connected to one another at stable angles by different plates. In particular, adaptation to different curvatures of the spinal column and to different distances between intervertebral implants and vertebrae is also possible. The invention is particularly suitable for plates which are not plastically deformable and are made, for example, of titanium or a composite material.

The device is especially suitable for spondylodesis of the cervical spine. It is recommended in this case to secure the spondylodesis with plates fixed to the anterior face of the cervical vertebral bodies. A modular system in particular is possible, which is advantageous both in terms of production and also in practice. The adaptability can be achieved with a surprisingly small range of individual parts.

According to a development of the invention, at least one plate is Z-shaped or L-shaped. A particularly high degree of adaptability and a particularly stable connection is possible with such plates. Z-shaped plates are suitable in particular for connecting adjacent intervertebral implants and, consequently, for stabilizing three vertebrae. Such Z-shaped plates can be anchored in a central area for example with two bone screws. L-shaped plates likewise permit securing of such plates with two bone screws. In the same way, more than three vertebrae or more than two intervertebral implants can be connected to one another. Also suitable as implant bridges are rectilinear plates which are secured by fixable joints to the intervertebral implants and by bone screws to the vertebral bodies lying between intervertebral implants. A configuration is also conceivable in which two intervertebral implants are fixed to one another not directly by a connecting plate (implant bridge), but indirectly via the vertebral bodies lying between the two intervertebral implants. For this purpose, short plates are provided which are secured by fixable joints to the respective intervertebral implant and by bone screws to the vertebral body, in which case the plate arranged on the upper intervertebral implant is directed downward and the plate arranged on the lower intervertebral implant is directed upward such that the plate ends with the bone screws lie alongside one another on the middle vertebra. In this way, each of the two intervertebral implants is then connected to the middle vertebra by a plate and at least one bone screw.

The invention also relates to a kit for producing a device as claimed in claim1.

The device1shown inFIGS. 1 to 4comprises two intervertebral implants3which, according toFIGS. 10 and 11, are each inserted into the intervertebral disk space between adjacent vertebrae21,22and22,23, respectively, of a spinal column24. The vertebrae21to23are here in particular vertebrae of the cervical spine, reference number26designating the anterior face of the cervical spine. The esophagus and major blood vessels (not shown here) lie to the left inFIG. 10in front of the anterior face.

The two intervertebral implants3are made of metal, in particular titanium, or of a suitable plastic and constitute intersomatic and pressure-absorbing bodies. They each have a recess20which opens to the outside and serves to receive bone or a bone replacement material. The patient's bone grows through the recesses20so that an osseous bridge forms between the adjacent vertebrae21,22and22,23, respectively. The vertebrae21,22and23can thus be firmly connected to one another.

The two intervertebral implants3are firmly connected to one another by a Z-shaped plate5. According toFIG. 2, this plate5has two arms5aand5band also a central area5cextending transversely with respect to these. The two arms5aand5bare preferably of identical design, so that the plate5is rotationally symmetrical in relation to a center point P. At a free end of each of the two arms5athere is a hemispherical depression27with a centrally extending through-opening17. These hemispherical depressions27and the through-openings17in each case receive a ball-head screw7which is screwed via a threaded shank12into a bore13of an intervertebral implant3. The ball-head screws7each have a head9with a tool socket8and a likewise hemispherical underside10. Arranged between the shank12and the head9there is a neck11whose diameter is smaller than that of the shank12and of the through-opening28. The hemispherical underside10bears on the hemispherical depression27. When the two screws12are firmly screwed into the respective intervertebral implant3, the plate5is fixed at its two free ends securely on the respective intervertebral implant3by clamping. The clamping faces are formed by a hemispherical surface15and a likewise hemispherical surface14of the corresponding intervertebral implant3. If the two ball-head screws7are not screwed in fully, the two connections of the plate5to the intervertebral implant3each form a kind of ball joint, in each case permitting movements in several degrees of freedom at both attachment points.

The plate5and the two intervertebral implants3can thus be moved relative to one another and, in each desired position, these parts can be connected to one another at a stable angle by tightening of the screws7. After the ball-head screws7have been tightened, the two intervertebral implants3and the Z-shaped plate5form a stable unit. If necessary, the screws7can be loosened at any time and, in this way, the movable state can be restored.

Arranged on each of the two intervertebral implants3there is in each case a further plate4which is preferably L-shaped or corner-shaped. These plates4each have two arms4a and4b, which may be identical or different. The arm4a has, on its underside, a spherical joint part18with a spherical inner face16and a likewise hemispherical outer face15. The joint part18has a through-opening17. The joint part18sits in a hemispherical depression14of the corresponding intervertebral implant3. To secure the plate4on the corresponding intervertebral implant3, a ball-head screw7is fitted from above into the joint part18, in the same way as for securing the Z-shaped plate5, and is screwed into the bore13of the corresponding intervertebral implant3. InFIGS. 1-3, these screws7have been omitted for the sake of clarity. Before the screw7is tightened, the corresponding plate4can be moved, by virtue of the ball-joint connection, and adapted to the anatomical circumstances. When the optimal position is reached, the corresponding screws7are tightened and the plates4are in this way fixed at a stable angle in relation to the corresponding intervertebral implant3.

In the arm4b,the two plates4each have two through-openings19which are arranged at a distance from one another and which each serve to receive a bone screw25, as is shown diagrammatically inFIG. 7. Such bone screws25are known per se. The connection can be made with a stable angle by using a screw in accordance with WO 01/30251 or alternatively can also be made movable. With these screws25, the two plates4are secured in the corresponding vertebral body21,23. These bone screws25should lie as far as possible at the center of the corresponding vertebral body21,23. Otherwise, their fit could be adversely affected. Moreover, these screws should not penetrate into a healthy intervertebral disk, and, in addition, the arms4bshould not touch a healthy intervertebral disk. This would lead to destruction or degeneration of the intervertebral disks concerned. By virtue of the adjustability of the plates4, it is now possible to orient them in such a way that the screws, as has been explained above, can be screwed at suitable positions into the vertebral bodies21,23. Likewise, it is in this way possible to ensure that the arms4bdo not touch an intervertebral disk.

Said adjustability of the plates4allows them to be adapted to the different curves and shapes of the anterior face26of the cervical spine. This is even possible when intervertebral implants3as desired do not protrude from the anterior face26. The intervertebral implants3ought not to protrude from the anterior face26because they could then cause damage to the structures situated in front of the cervical spine24, in particular the esophagus and major blood vessels.

With the ball-head screws7tightened, the two plates4thus each connect an intervertebral implant3to a vertebral body21,22and22,23at a stable angle. The plate5connects the two intervertebral implants3to one another at a stable angle. In the central and transversely extending area5c,the plate5also has two through-openings6which each receive a bone screw25, these bone screws25being screwed into the central vertebral body22and thus anchoring the plate5on this central vertebral body22. Here too, an angularly stable or movable connection is possible between plate4and bone screw25.

According toFIGS. 4 and 5, the two plates4and the plate5can lie in one plane. Because of said joint connections, however, a plane arrangement of this kind is not essential. For example, the two plates4can be pivoted upward or downward, according to the double arrows29inFIG. 4, independently of one another and in a comparatively wide range. These two plates4can also be pivoted independently of one another according to double arrows29to31inFIGS. 2,4,5and6.

By virtue of the ball-joint connections, however, other movements and degrees of freedom are also possible here. Thus, in particular the pivot movement indicated by the double arrow31inFIG. 5is available. Each possible position can be fixed by tightening of the corresponding ball-head screw7. In this way, as has been explained above, optimal adaptation to the particular anatomical circumstances is possible.

FIG. 6shows a device2according to the invention, which only has one intervertebral implant3and two L-shaped or corner-shaped plates4. As has already been explained above, the plates4are each secured with a ball-head screw7on the intervertebral implant3. As has been explained above, the connection is in the manner of a ball joint. As has been explained above, the two plates4can likewise be moved before the two screws7are tightened. Only one of the two ball-head screws7is shown inFIG. 6. In the embodiment shown, the two plates4are of identical design. However, the plates4can also be different, for example of different lengths. They do not necessarily have to be L-shaped or corner-shaped, and instead can also be rectilinear elongate plates. This applies also to the plates4of the device1. The device2is used to connect two adjacent vertebrae21,22and22,23. Of course, several such devices2can be fitted on a spinal column24. However, the corresponding intervertebral implants3are then only interconnected across intermediate vertebrae. A direct connection, as in the device1, is thus not present here.

The plates4and5and the intervertebral implants3are preferably made of a suitable plastic, for example of a fiber-reinforced plastic. Such plastics are known per se and have the important advantage that they are transparent to X-rays. With such materials, it is also possible to produce very stable plates4and5which also have a high degree of flexural rigidity. It is thus possible to minimize movements within the spondylodesis and, consequently, the risk of a sometimes serious secondary dislocation of the implant. In principle, however, the plates4and5can also be made of another material, for example of titanium.

A device is also possible (not shown here) with more than two intervertebral implants3which are connected directly to one another by a corresponding number of Z-shaped plates5. For example, such a device can comprise three intervertebral implants3connected to one another by two Z-shaped plates5. An L-shaped plate4is then also secured on each of the two outer intervertebral implants.

FIG. 7shows an embodiment of a device according to the invention which has two L-shaped plates4and a rectilinear plate32. At each of its ends, the long plate32is connected to an intervertebral implant3via a ball-head screw7. The connections to the intervertebral implants3are joints which have a polyaxial mobility and can be fixed by tightening of the screws7. The configuration of the long and rectilinear plate32can be seen inFIG. 9.

FIG. 8also shows a comparatively short plate33which can receive a ball-head screw7and a bone screw25and which can be used in particular according toFIG. 13.

A method for stiffening a portion of a spinal column with the device according to the invention is explained in detail below.

After suitable exposure of the portion of the spinal column that is to be stiffened, the affected intervertebral disk is reamed out. By means of a suitable instrument, the reamed intervertebral disk space is widened and enlarged. A suitable intervertebral implant3is now chosen and is inserted into the reamed intervertebral disk space, where it is wedged between the adjacent vertebrae. If appropriate, a further intervertebral disk is reamed out and a further intervertebral implant3is inserted.

Distances between the intervertebral implant3or intervertebral implants3and suitable positions for the bone screws are now determined. In the case of two intervertebral implants3, the distance between these is also measured. Suitable plates4and if appropriate5are selected according to these distances are fitted loosely on the intervertebral implant3or on the intervertebral implants. The plates4are chosen such that they do not touch adjacent intervertebral disks, as can be seen inFIGS. 7 and 8. The loosely fitted plates4and5are now placed on the vertebrae and fixed with bone screws25. The plates4and if appropriate5are now connected firmly to the intervertebral implant3or intervertebral implants by tightening of the screws7.

FIGS. 10 and 11show three vertebrae21to23which are connected to one another by a device according to the invention. As can be seen, the plate5connects two intervertebral implants3to one another and is additionally connected to the vertebra22by bone screws25. If only two vertebrae are connected to one another, the device2according toFIG. 6is used, in which a Z-shaped plate5is not provided.

FIGS. 11-15show five of the possible embodiments of the device according to the invention with which two or more vertebrae can be connected to one another. InFIGS. 11 to 15, the cervical spine is seen from the front and inFIG. 10it is seen from the side.

FIG. 14shows a connection of two vertebrae with the aid of two L-shaped plates4and one intervertebral implant3. The L-shaped plates4are each secured to the vertebral bodies by two bone screws25and to the intervertebral implant3by in each case one ball-head screw7.

FIG. 11shows a connection of three vertebrae21-23. The intervertebral implants3are connected directly to one another by an implant bridge. The latter consists in this case of a Z-shaped plate5. The Z-shaped plate5is secured to the body of the central vertebra22by two bone screws25.

FIG. 10shows a view of a cervical spine from the -side, with the device according to the invention fromFIG. 11bearing on the anterior of the cervical vertebral bodies.

FIG. 12shows a connection of four vertebral bodies, rectilinear plates32forming the implant bridge to the intervertebral implants3. Each rectilinear plate32is secured by a bone screw25to the vertebral bodies lying below the plate32in question.

In the illustrative embodiment according toFIG. 13, three intervertebral implants3are connected to one another not directly by implant bridges, but indirectly via the vertebral bodies lying between two respective intervertebral implants3, by means of short plates33being secured on the intervertebral implants3and on the vertebral bodies lying between these.

FIG. 15shows a connection of four vertebrae, with Z-shaped plates5again forming the implant bridges to intervertebral implants3. The Z-shaped plates5are each secured by two bone screws25to the vertebral body located below the respective plate. The connection to the upper vertebra and lower vertebra is effected in the manner described forFIG. 14. The connection is in this case produced exclusively with Z-shaped plates5.

An important advantage of the invention is that the implant according to the invention, by virtue of the articulated cage-plate connections, a range of plates of different lengths and intervertebral implants of different sizes (heights) can be precisely adapted to the individual and sometimes very different anatomical circumstances, in particular the anterior face of the cervical spine. The latter may be plane, more or less convex or even concave or can be alternately convex or concave from vertebra to vertebra. The cervical spine, seen from the front, may also be slightly crooked or twisted slightly about the longitudinal axis. All of this can be compensated by the free mobility of the plates.

The present invention is concerned not only with stable connections between the implants and with stable connections between the end vertebrae of the spinal column portion stiffened with the aid of the device, but above all with the complete adaptability of the device to the respective anatomical circumstances (curvatures, dimension ratios, irregularities). This adaptability is especially important on the cervical spine, because the implants must not protrude from the anterior face of the cervical spine. They must not be thicker than 2 mm to at most 3 mm and they have to bear well on the vertebral bodies. Otherwise, there is a danger of a serious complication arising, for example if structures lying near the anterior face of the cervical spine, such as the esophagus and blood vessels, become eroded over the course of time.

Our device is distinguished by its low profile, i.e. by a low overall height.

The adaptability of the device according to the invention is due in particular tothe lockable ball joints, each with three degrees of freedoma range of plates of different lengths (both L-shaped plates and Z-shaped plates)a range of intervertebral implants of different sizes.

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