Kit for building a cage for spondylodesis and method therefor

A modular kit and/or method buildings a cage for spondylodesis, wherein the kit and/or method comprises at least two plates, wherein the plates comprise a biocompatible material and each comprise a planar structure and a plurality of pins projecting from the planar structure of the plates, wherein the pins each comprise at least one latching element, wherein the pins are elastically deformable and are arranged sufficiently close to each other on the planar structure such that pressing planar structures studded with pins of several plates onto each other causes the latching elements of different plates to snap into each other, wherein at least two of the at least two plates comprise a recess with a diameter of at least 5 mm.

This application claims priority of German Patent Application No. 10 2015 110 202.1, filed on Jun. 25, 2016, and Canadian Patent Application No. 2,932,795, filed on Jun. 9, 2016, their entire contents of which are incorporated herein by reference.

The invention relates to a modular kit for building a cage for spondylodesis. The invention also relates to a method for producing such a cage as well as a cage for spondylodesis.

Accordingly, the subject of the invention is also a cage for spondylodesis of vertebral bodies with adjustable height and a method for producing cages with adjustable height.

Spondylodesis (vertebral fusion) is used to stiffen two or more vertebral bodies in the cervical, thoracic and lumbar spine. Spondylodesis (vertebral fusion) is used for unstable breakages of vertebral bodies, congenital (inborn) scoliosis and spondylolisthesis. Here, two or more vertebral bodies which lie one on top of the other are joined together with the aid of bolts, plates and rods. Cages are inserted into the intervertebral space, which create a distance between the vertebral bodies which lie one on top of the other, thus avoiding compression of the spinal cord and the nerves which emanate from it. Further, the cages serve to transmit force between the vertebral bodies. The cages usually contain an open axial hollow chamber. This hollow chamber can for example be filled with bone replacement material such as calcium phosphates, or also with autologous cancellous bone (Aaron R Cutler A. R., et. al.: Comparison of polyetheretherketone cages with femoral cortical bone allograft as a single-piece interbody spacer in transforaminal lumbar interbody fusion. J. of Neurosurgery. Spine 5, No. 6 (2006): 534-539.). Bone tissue between the vertebral bodies can grow into this hollow chamber, so that the vertebral bodies are connected via the newly formed bone. For the clinical success of the cages, it is essential that the physiologically correct distance between the vertebral bodies is maintained through the height of the cages used. As a result, a situation wherein the cages are too high or too low must be avoided at all costs. It is therefore standard procedure for manufacturers to offer cages of different heights. As an alternative, cages are also known in which the height of the cage can be individually adjusted. Examples of these are patent applications US 2014/358 235 A1, CA 2 846 793 A1, CA 2 845 613 A1 and US 2014/207 238 A1. These cages are mechanically sophisticated and have a relatively complex structure. Furthermore, due to their complex structure they are relatively costly and not easy to handle.

The object of the invention is thus to overcome the disadvantages of the prior art. In particular, a mechanically stable cage is to be developed the height of which can be adjusted in a highly simple manner without the use of technical aids. The cage to be developed should contain no complex levers and/or bolt systems. Furthermore, the cage should be as porous as possible in order to guarantee a bony consolidation of the cage. Additionally, the cage must be biocompatible. The cage should also form a porous body with a stable form, have open porosity and be mechanically stable. The porosity and the size of the pores should here be sufficient and suitable for the human bone of a patient treated with the cage can grow into the pores of the cage.

The objects according to invention are achieved by a modular kit for building a cage for spondylodesis, the kit comprising at least two plates, wherein the plates consist of a biocompatible material and each comprising a planar structure and a plurality of pins projecting from the planar structure of the plates, wherein the pins each comprise at least one latching element, wherein the pins are deformable elastically and are arranged sufficiently close to each other on the planar structure such that pressing the planar structures studded with pins of several plates onto each other causes the latching elements of different plates to snap into each other, wherein at least two of the at least two plates comprise a recess with a diameter of at least 5 mm.

Preferably, it can be provided that the at least two plates consist of a biocompatible plastic, a biocompatible metal and/or a biocompatible metal alloy. Biocompatible metals and biocompatible metal alloys are preferred according to the invention in order to produce the plates of the kit from them.

Preferably, all of the at least two plates comprise a recess with a diameter of at least 5 mm.

When they snap into each other, the latching elements of the pins of the plates grip into latching elements of pins of adjacent plates in such a manner that the plates can no longer be separated from each other, but also can no longer be moved towards each other by the plates being further pressed together. The latching elements can be formed by hooks, grooves, undercuts, snap-in elements and/or counter snap-in elements.

The term “planar” is used with reference to planar bodies and bodies derived from planar bodies, which are respectively formed by a closed or perforated plate-like base body. Perforated planar structures are here preferred for the plates to be connected to the vertebral bodies, since due to this perforation or due to the pores formed by the perforation, bone tissue can grow into the plates. It is very particularly advantageous and preferred according to the invention when one perforation or one pore is arranged alongside each pin. Then, after several plates have snapped into place, two porous base areas form for connection to the vertebral bodies, which when suitable material such as tantalum is selected are osteoconductive.

When pressure acts on the plates of the kit which are touching each other, according to the invention these form a mechanically stable connection.

With kits according to the invention it can be provided that the plates which are snapped into each other form a cage consisting of plates which are snapped into each other with at least one open axial hollow chamber, wherein the hollow chamber has a diameter of at least 5 mm, wherein preferably the plates which are snapped into each other form a cage consisting of plates which are snapped into each other with two open axial hollow chambers, wherein the two hollow chambers have a diameter of at least 5 mm respectively.

As a result, the interior of the cage is formed by the at least one open axial hollow chamber. The bone can grow through the at least one open axial hollow chamber, so that the two vertebral bodies can grow together.

Further it can be provided that each of the at least two plates comprises a recess with a diameter of at least 5 mm, wherein preferably at least one open axial hollow chamber of the cage produced from the plates can be created with the recesses of the at least two plates.

As a result, due to the fact that the at least two plates lie on top of each other and snap into each other, the recesses can be arranged in relation to each other that they lie one on top of the other, so that the recesses that lie one on top of the other form the at least one open axial hollow chamber into which the bone of the two adjacent vertebral bodies can grow.

With the invention it is also recommended that the wall of the at least one open axial hollow chamber of a cage formed from the at least two plates which are snapped into each other and/or the boundaries of the recesses of the at least two plates are filled with autologous bone material.

As a result, autologous bone growth is supported so that the bone of the patient can more easily and quickly grow through the recesses or the at least one open axial hollow chamber.

With one advancement it is recommended that the plates which are snapped into each other form a porous cage consisting of plates which are snapped into each other, preferably an open-pore cage made of plates which are snapped into each other.

As a result, the bone can grow at least in some areas into the pores of the cage formed by the plates. Furthermore, it is recommended with the invention that the pores of the open-pore cage made of several plates are interconnecting and osteoconductive, wherein preferably the pores have a free profile of between 0.1 mm and 1 mm, particularly preferably between 0.25 mm and 0.9 mm. This ensures that the bone can grow together well with the pores of the cage produced from the kit. The side walls of the cage which project outwards can according to the invention be completed by a closed wall. For this purpose, on the at least two plates, a circumferential edge can be provided which when snapped into an adjacent plate creates a form-fit completion with the edge of the adjacent plate, thus forming the closed wall.

With preferred kits, it can be provided according to the invention that the modular kit for building a cage for spondylodesis has an adjustable height and for this purpose preferably comprises three plates so that different heights can be set through the optional use of one inner plate or of several inner plates.

As a result, a cage with different heights is made possible which is particularly easy to construct from the kit. The kit can thus be variably used for different patient requirements and adapted to the anatomical conditions.

With a further development, it can also be provided that the at least two plates comprise a completing circumferential edge, so that the plates which are snapped into each other form a cage with a wall that is closed to the outside, wherein preferably, the edges are interlocked.

As a result, it is possible to prevent the material exiting outwards from the interior of the cage that has been produced.

Further, it can be provided within the scope of the present invention that at least one group of the at least two plates, preferably at least one group of the at least four plates, are of the same shape with regard to the form of the planar structure or are essentially of the same shape, so that they can be stacked one on top of the other and/or snapped into each other in a form-fit manner in the direction vertical to the planar structures.

As a result, with the kit, a cage can be produced from the kit which is variable in terms of height but which is clearly formed in terms of its circumference.

Here, it can be provided that at least two groups of the at least two plates, preferably at least two groups of the at least four plates, are of the same shape with regard to the form of the planar structure or are essentially of the same shape, so that they can be stacked one on top of the other and/or snapped into each other in a form-fit manner in the direction vertical to the planar structures, wherein the at least two groups comprise different geometries as regards the planes of the planar structures.

As a result, with the kit, a plurality of different cages can be constructed for different anatomical conditions.

Further, it can be provided that at least two outer plates of the at least two plates which are provided for direct connection with the vertebral bodies are osteoconductive due to pores in the planar structures and/or the planar structures comprise an attachment surface without pins, which is designed to be placed against the vertebral bodies, wherein preferably the attachment surface comprises peaks or naps for connecting the plates to the bone of the vertebral bodies.

The peaks or naps can be pressed into the bones of the vertebral bodies. Alternatively or in addition, eyelets or bore holes can be provided in the planar structure of the at least two outer plates, through which the at least two outer plates can be bolted or otherwise connected (e.g. with nails) to a vertebral body. Even when both sides of the at least two plates comprise pins, sharp tips can be provided for attachment to the bone surface, for which purpose the pins should protrude with the latching elements. With embodiments with sharp tips, a plate can be anchored by driving the sharp tips into the bone tissue of the vertebral body. Building on this, further plates from the kit can then be applied and snapped in.

Outer plates of this type can be used for direct planar attachment on the bone. With the eyelets or bore holes, it is possible to bolt the plate onto the bone tissue and to apply as many further plates from the kit as required and then to snap them in. As a result, three-dimensional cages with variable heights can be constructed in a load-bearing manner.

According to the invention, the pores are preferably rounded off, in particular they do not comprise any sharp-edged contours. In a particularly preferred manner, the pores in the planar structure of the plate have a free profile of between 0.25 mm and 1 mm, particularly preferred between 0.3 mm and 0.9 mm.

Due to the pores, the cage produced from the plates of the kit can be attached to the adjacent vertebral bodies in a particularly stable manner.

According to a preferred embodiment of the kit according to the invention, it can be provided that at least three plates are provided, with at least one inner plate and at least one outer plate, wherein one inner plate and in addition at least one outer plate respectively always form a planar group, wherein each outer plate comprises a recess so that this outer plate encloses in a form-fit manner the inner plate of the same planar group or a different outer plate of the same planar group on the plane of the planar structures.

As a result, cages with different cross sections can be produced using the kit.

Furthermore, it can be provided that the planar structure of at least one of the plates, in particular of at least one inner plate, has a gradient in the thickness, wherein preferably, the area with the greatest thickness is maximum 100% thicker than the area with the least thickness.

Due to a kit of this type, curved or inclined cages can also be produced, with which the positions of the vertebral bodies can be adapted to each other, or taken into account.

Further, it is recommended that on one planar structure of at least one plate, preferably on the planar structures of the outer plates, at least two positioning aids, in particular positioning pins, are provided, wherein with the positioning aids the orientation of the plates to be joined together in relation to each other is specified.

This ensures that the plates can only be joined together in the desired orientation. As a result, the degree of possibility of misuse is reduced.

Preferably, it can be provided that the latching elements are mushrooms, hooks, undercuts, snap-in elements and/or counter snap-in elements.

These latching elements are particularly well suited for a mutual snapped-in connection. Textile connections such as hook and loop connections with easily deformable fibres are by contrast unsuitable according to the invention since with these, no dimensionally stable, pressure-resistant cages can be constructed for spondylodesis.

With one advancement it is recommended that the distance between the latching elements and the planar structure of the at least two plates is between 0.3 mm and 2 mm, preferably between 0.5 mm and 1 mm.

As a result, a sufficiently stable snapped-in connection is achieved between the latching elements, and at the same time sufficient bending of the pins is made possible in order to connect the latching elements.

According to an advancement of the invention it can be provided that at least one of the at least one latching elements per pin has a truncated cone shape, wherein the longitudinal axes of the pins form the longitudinal axes of the cones and wherein the sheath of the cones points towards the outer side that faces away from the planar structure of the at least one plate.

As a result, the at least two plates can be connected in particularly stable manner by means of the latching elements shaped as truncated cones. Moreover, said shaping prevents surrounding soft tissue and bone tissue from being injured following implantation of the cage.

Moreover, the invention can provide at least one of the at least one latching elements per pin is designed in the form of a hook and/or as a mushroom head.

The hooks and/or the mushroom heads provide for stable and non-detachable connection of the plates to each other. If the latching elements are mushroom head-shaped, they can possess, for example, a collar at the mushroom head edge provided in the direction of the planar structure such that hook-shaped latching elements of other plates can engage this thus generated undercut, whereby an irreversible, non-detachable interlocked or snapped-in connection between the plates is produced. It is also feasible, and preferred according to the invention, that at least one plate contains various latching elements or various pins with different latching elements. Accordingly, a plate can simultaneously possess hooks and mushroom heads as latching elements, both on the same pin and on different pins.

In a preferred embodiment, the latching elements are provided as mushroom heads. In a particularly preferred embodiment, the mushroom heads are shaped appropriately such that the mushroom heads comprise a conical undercut on the side facing the surface of the respective planar structure. As a result, hook-shaped snap-in elements can be interlocked irreversibly and non-detachably with said mushroom heads. If the shapes of the undercuts and of the mushroom heads match properly, further propulsion of the mushroom heads can be prevented so that the mushroom heads snap into the undercuts.

According to a preferred advancement, it can be provided that the pins between the planar structure of the at least two plates and at least one of the at least one latching elements contain a circumferential groove as a counter-latching means, into which latching elements of other plates can snap, preferably snapping into place in such a manner that no further movement of the latching elements along the pins is possible.

This also enables a particularly stable connection between the plates.

Particularly advantageous kits can provide that the at least one plate is made from biocompatible plastic, stainless steel, titanium, a titanium alloy, tantalum, a tantalum alloy or composites of said materials.

Said materials are particularly well-suited for medical purposes and can be used to attain the suitable elastic properties of the pins. It is preferred, according to the invention, to produce plates consisting of metal or metal alloys by selective laser sintering or by melting with electron beams, preferably by a 3D printing method.

The biocompatible plastic material can be biodegradable. Polylactides, polyglycolides, polycaprolactones and polyester formed from different a-hydroxy carboxylic acids can be used for this purpose. Conceivable non-biodegradable plastic materials include polyamides, polyimides, polyetherketone, and polysulfone. Plates made of these non-biodegradable and biodegradable plastic materials can be produced by selective laser sintering.

According to a preferred embodiment of the present invention, it is recommended that adjacent pins which are arranged on the same side of a first plate of the at least two plates are of such a distance from each other that following an elastic deformation due to a snapped-in connection with a latching element of one second plate of the at least two plates, the pins of the first plate enable at least two snapped-in connections with at least two further latching elements of the second plate, and preferably enable at least three snapped-in connections with three further latching elements of the second plate.

Due to multiple snapped-in connections of the plates, a particularly stable cage can be formed from the plates in the kit.

It can also be provided that the at least two plates are filled with inorganic or organic particular bone replacement material and/or autologous or also allogenic cancellous bone.

In this manner, healing of the bone and the connection between the cage and the bone of the vertebral bodies can be accelerated.

Further, the invention can provide that the at least two plates are coated with one or more pharmaceutical agents from the groups of antibiotics, bisphosphonates, steroids, non-steroidal anti-inflammatory drugs, growth factors, and cytostatic agents.

As a result, the cage has a pharmacological effect that contributes to the healing of the patient treated with the cage. Preferred agents from the group of antibiotics are, in particular, gentamicin, tobramycin, amikacin, vancomycin, teicoplanin, clindamycin, and daptomycin.

Further it can be provided that the pins are arranged in rows of three or more pins respectively and that between said three or more rows a strip of unoccupied surface of the planar structure remains, or that a grouped or nest-shaped arrangement of pins with latching elements is provided.

As a result, space is provided for the deformation of the pins with the latching elements for the snapped-in connection.

Further it can be provided that the pins of the at least two plates extend vertically or at an angle of between 60° and 90°, preferably at an angle of between 80° and 90°, from the planar structures of the at least two plates.

As a result, it is achieved that the plates can later be particularly easily connected to each other. Moreover, this achieves an even load-bearing capacity of the cage.

According to a preferred embodiment of the present invention, it can be provided that the kit comprises at least two outer plates for connection with the vertebral bodies and at least one inner plate for setting the height of the cage to be built, wherein each of the at least one inner plate comprises pins with latching elements on both sides of the planar structure, and preferably the at least two outer plates comprise pins with latching elements only on one side of the planar structure.

As a result, the height of the cage to be built can be set in a particularly simple manner by omitting or adding inner plates.

It is also recommended that the latching elements are provided on the sheath surface of the pins.

Thus a stable connection can be achieved between the pins and thus between the plates.

Preferred kits according to the invention can provide that plates pressed into each other irreversibly interlock and/or snap into each other.

As a result, it is ensured that the plates of the fully formed cage do not detach from the cage.

With an advancement of the present invention, it is recommended that the at least two plates without the projecting pins or the planar structure of the plates have a thickness of maximum 2 mm, preferably a thickness of between 0.25 mm and 1.5 mm, and in a particularly preferred manner, a thickness of between 0.5 mm and 1.5 mm.

The thickness of the at least two plates or of the planar structure can also be described as the thickness of the plates or planar structure, and is the dimension of the plate without the pins, which is arranged vertical to the planar structure of the plate. As a result, it is achieved that the plates can either be sufficiently strongly bent or deformed in order to be adjusted to the treatment situation, or that different construction heights of the cage can be achieved with just a few plates through the use of plates of differing thickness.

Furthermore, it can be provided that the at least two plates are produced using a generative 3D printing method.

This enables the plates and thus the cage to be produced at a low cost.

It can also be provided that two latching elements are arranged in sequence on the sheath surface of the pins, and in a particularly preferred manner, three latching elements are arranged in sequence on the sheath surface of the pins.

By this means, it is possible to snap in plates at different distances from each other. As a result, greater flexibility is achieved when forming the cage. However, here it is difficult to achieve the necessary stability of the cage vertical to the plane of the planar structure.

It can also be provided that the at least one plate is designed in the form of a surface with rounded corners, preferably in a kidney shape.

Through this forming, the plates and the cages produced from them are particularly well adjusted to the vertebral bodies to be treated.

Further, it can be provided that continuous pores are contained in the planar structure of the at least two plates, wherein the depth of the pores vertical to the planar structure of the at least two plates is at least 0.25 mm, preferably at least 0.4 mm.

As a result, it can be ensured that the pores are stably enclosed by the bone and with a uniform shape. The plates thus recreate cancellous tissue that corresponds to a normal bone structure, and can grow together well with said bone structure and thus with the vertebral bodies.

It can also be provided that the at least one plate is plastically or elastically deformable in the planar structure.

As a result, the at least one plate can be particularly easy adapted to different treatment situations.

The objectives that form the basis of the present invention are also attained by means of a method for producing a cage for spondylodesis with a kit of the type according to the invention, in which several plates are pressed against each other, wherein the plates snap into each other and form the cage.

With this method, it can also be provided that the pins with the latching elements of the at least two plates are brought into contact with each other and that subsequently, by pressing the plates against each other, the pins with the latching elements snap into each other.

When pressure acts on the plates of the kit that are touching each other, according to the invention, said plates then form a mechanically stable connection.

With one advancement, it is recommended that no, one or several inner plates are inserted between two outer plates depending on the thickness desired of the cage to be produced, wherein the plates are snapped into each other by being pressed on top of each other and as a result are firmly connected to each other.

The objectives that form the basis of the invention are further attained by means of a cage for spondylodesis constructed of at least two plates from a kit according to the invention and/or produced using a method according to the invention.

Finally, the objectives that form the basis of the present invention were also attained through the use of such a cage for spondylodesis in accident surgery, orthopaedics or veterinary medicine.

The invention is based on the surprising finding that plates that mechanically snap into each other can be used as components of a kit for producing a cage for spondylodesis. Here, the plates can be arranged in layers, wherein the cage thus formed is rigid and non-compressible after the desired three-dimensional structure has been formed without chemical hardening reactions, such as radical polymerisations or a complex mechanism for stable setting of the height being necessary. The plates are preferably flexible in a limited scope and can thus be brought into the correct form, and snap into each other through pressure and in so doing are connected to each other. When the formed plates snap into each other, the plates stabilise among each other, so that the three-dimensional cage that is created is rigid and dimensionally stable. When the plates are connected to each other by being pressed on top of each other from different directions and with sufficient force, it can be ensured that a sufficient number of interlocking connections and snap-in connections ensue that the cage produced is dimensionally stable and able to withstand mechanical loads. Due to a suitable form and size of the plates, a cage is thus formed which is sufficiently mechanically stable for medical use and that can be appropriately designed for the form of treatment situation. The bone can preferably grow into pores provided in the cage that is connected through pressure and thus form a permanent connection with the cage. Through at least one open axial hollow chamber in the cage, the bone can grow together originating from the vertebral bodies and rigidify the joint of the vertebral bodies.

Surprisingly, it was found that the plates of the kit according to the invention can be attached to the vertebral bodies in layers and through simple manual compression or with the aid of a tappet be hardened to form a homogeneous body with the individual layers (or plates) forming a snapped-in connection. A hardening of the cage according to the invention is enabled through simple compression of plates that lie in contact with each other over the surfaces. A load-bearing connection of two vertebral bodies is possible with the planar material according to the invention (i.e. the plates of the kit according to the invention).

Mechanically interlocking systems following the design principles of hook and loop fasteners have been known for several decades. The principle of the hook and loop fastener was first described by de Mestral in CH 295 638 A. Said principle has been developed further and is put to use in a wide range of reversibly closing hook and loop closures. Exemplary refinements are described in the publications DE 1 610 318 A1, DE 1 625 396 A1, U.S. Pat. Nos. 5,077,870 A, and 4,290,174 A.

Within the scope of the present invention, it was surprisingly found that such systems or such functional principles can be used for the construction of cages for spondylodesis, or are transferable to plates for the production of cages for spondylodesis. Here, it can be advantageous for the cages that connections of such a type do not close tightly, but that intermediate chambers remain as an open-pore structure. The interconnecting pores that are formed in the cage as a result can grow together with the bone and thus generate a stable connection between the bone and the cage. For this purpose, it must be ensured that the pores in the plates have a sufficiently free profile. The pores are described as osteoconductive when the bone can grow into the pores and thus connect with the cage formed from the plates.

The invention is thus based on the idea that a cage consisting of at least one distal and one proximal plate can be compiled, wherein between the plates, depending on the desired height of the cage, one or more intermediate plates can be inserted. The connection between the plates is achieved through “burdock type” snap-in connections of latching elements, which are arranged on the surface of the plates. The plates can be connected to each other by the medical user simply by pressing them together axially.

An exemplary embodiment of the present invention, and one which is particularly preferred according to the invention, is a cage with adjustable height which is compiled of at least two plates, in which on at least one side, three or more elastically deformable pins are arranged which on one pin end have at least one latching element respectively, and wherein the at least three or more pins respectively of the distal plate, the proximal plate and the intermediate plates are positioned so closely to each other that when there is contact with the pins of the plates that each lie in contact with each other, said pins interlock under the effect of the pressure and form a cage that is pressure-resistant in the axial direction.

The structure of the plates is designed in such a manner that when the plates are pressed together, plates that come into contact with each other irreversibly snap into each other and form a cage consisting of plates that have snapped into each other.

A cage according to the invention consists for example of

a) A distal (outer) plate on the proximal side of which three or more elastically deformable pins are arranged, which on one pin end respectively have at least one latching element

b) A proximal (outer) plate, on the proximal side of which three or more elastically deformable pins are arranged, which on one pin end respectively have at least one latching element

c) One or more intermediate plates (inner plates), on the distal and proximal side of which three or more elastically deformable pins are arranged respectively, which on one pin end respectively have at least one latching element, and

d) Wherein the three or more pins respectively of the distal plate, the proximal plate and the intermediate plates are positioned so closely to each other that when the pins come into contact with the plates which each lie in contact with the other, said pins interlock under the effect of the pressure and form a cage that is pressure-resistant in the axial direction.

It is very particularly advantageous when alongside each pin with a latching element a perforation is arranged in the plates, which causes an open porous body to be formed following the snap-in connection of several plates, which when suitable material is selected, such as tantalum, is osteoconductive.

According to the invention it can be provided that the at least two plates, in particular the proximal plate, the distal plate and the intermediate plates, are formed in a ring shape or an elliptical ring shape, or in the shape of two rings that lie in contact with each other. This means that in the at least one axial hollow chamber of the cages, common bone replacement materials such as tricalcium phosphate, or also autologous bone material, can be used. As a result, a bony through-structure of the cage is facilitated.

It is advantageous when the at least two plates, in particular the proximal plate, the distal plate and the intermediate plates, contain perforations that have a diameter in the range of 300 μm to 3000 μm. These perforations permit bone tissue to grow in.

According to the invention, an exemplary method is furthermore provided for producing a cage for spondylodesis. This method is characterised by the fact that between two outer plates (the distal plate and the proximal plate), depending on the desired height of the cage, one or more intermediate plates are arranged, and the plates are pressed against each other so that the latching elements of the plates interlock and a connection between the plates is formed through the form-fit connection of the latching elements. With the method, the plates are advantageously laid one on top of the other in such a manner that the outer edges of the plates are arranged flush over each other.

FIGS. 1 to 5show a first embodiment of the present invention, withFIG. 1showing a schematic perspective view onto a cage according to the invention which is constructed from five plates1,2from a kit according to the invention,FIG. 2shows a schematic perspective view onto two of the plates1,2according toFIG. 1which are not snapped-in to each other,FIG. 3shows a schematic cross-sectional view through the five snapped-in plates1,2of the cage according toFIG. 1,FIG. 4shows an enlarged representation of a schematic cross-sectional view through the five snapped-in plates1,2of the cage according toFIG. 1, andFIG. 5shows a schematic cross-sectional view through the two plates according toFIG. 2which are not snapped in.

The kit comprises at least two outer plates1, which are provided to be fixed to vertebral bodies of the spine (not shown), and comprises several middle or inner plates2, which can be inserted in between the outer plates1for setting the height of the cage. The plates1,2consist of an elastic biocompatible plastic material or of stainless steel, titanium, a titanium alloy, tantalum, a tantalum alloy, but can also be fabricated from composites of said materials. The plates1,2are manufactured by a CAM procedure (CAM—computer-aided manufacturing) and/or a 3D printing procedure, for example by selective laser melting, or SLM. Other rapid prototyping methods and/or computer-aided generative production methods can also be used for producing the plates1,2, such as, for example, Fused Layer Modeling/Manufacturing (FLM), Fused Deposition Modeling (FDM), Laminated Object Modelling (LOM) of plastic films, Layer Laminated Manufacturing (LLM) of plastic films, Electron Beam Melting (EBM) of plastic materials or metals, Multi Jet Modeling (MJM) of plastic materials, Selective Laser Sintering (SLS) of plastic materials or metals, Stereolithography (STL or SLA) of plastic materials, polishing or multi-axes milling procedures or Digital Light Processing (DLP) of photopolymerising liquid plastic materials.

The plates1,2respectively comprise a plate-shaped planar structure3, which bears all the plates1,2and connects them. The planar structure3can be flexible and elastically deformable to a limited degree, so that other surfaces can also be formed as planes with the planar structure3, so that the plates1,2can to a small degree be adapted to the form of the vertebral bodies. From the planar structures3, with each plate1,2, a plurality of pins4extend which stand up vertically from the plane of the planar structures3.

InFIGS. 1 to 5, two different types of plates1,2are shown, namely outer plates1, which comprise a flat underside and with which the pins4only extend on one side of the planar structures3originating from the planar structure3, and secondly, middle plates2and/or inner plates2, with which the pins4extend originating from both sides of the planar structure3. With a completed cage (seeFIGS. 1, 3 and 4), the plates1,2are arranged in a sandwich-like manner in relation to each other, wherein the outer plates1form the two covering surfaces and the inner plates2are arranged between the outer plates1. The outer plates1can be affixed lying over a large surface on the vertebral bodies to be treated. For this purpose, eyelets (not shown) can be provided in the planar structure3, so that the outer plates1can be bolted onto the vertebral bodies, or on the side of the planar structure3without pins4, peaks (not shown) can be provided which are inserted into the bone of the vertebral bodies. The inner plates2can however theoretically also be affixed to the vertebral bodies to be treated, albeit with a lesser contact surface, so that theoretically, the outer plates1can be omitted.

On the otherwise cylindrical pins4, on the ends of the pins4positioned opposite the planar structures3, mushrooms5are provided as latching elements5. The mushrooms5are rounded outwards (pointing away from the planar structure3) and form spherical segments. However, other roundings are also possible, such as elliptical segments. On the side oriented towards the planar structure3, the mushrooms5form a planar engagement surface, which are suitable for interlocking and snapping in with other mushrooms5on engaging plates1,2.

In the pins4, grooves6are provided as counter snap-in elements adjacent to the mushrooms5and/or to the engagement surfaces, into which the mushrooms5of adjacent plates1,2can engage and/or snap in. For this purpose, edges of the grooves6which face towards the planar structure3have a rounded shape, so that the mushrooms5can fit and/or snap in well to the grooves6. The shape of the grooves6corresponds to a negative of the shape of the surface of the mushrooms5, so that said mushrooms can come into contact along a line in one of the grooves6. The mushrooms5thus form latching elements5and the grooves6form the matching counter snap-in elements6. A further pushing in of the plates1,2following the snap-in connection is prevented by this structure.

In this relation,FIGS. 3 and 4show a schematic cross-sectional view onto plates1,2of the kit according to the invention which are snapped in to each other via the mushrooms5.

In the planar structure3of the outer plates1, a plurality of continuous pores7is arranged between the pins4, which create an open porosity of the cage on the contact surface to the vertebral bodies in a direction vertical to the planar structures3. As a result, the bone of the vertebral bodies can grow together more easily with the outer plates1of the cage.

The pins4with the mushrooms5can be arranged in groups and/or islands of pins4and/or mushrooms5(not shown inFIGS. 1 to 5). As a result, pins4arranged on the edge of the groups and/or islands are easier to bend outwards when the mushrooms5of another plate1,2are pressed on. Thus the plates1,2are easier to connect to each other, since the elastic deformations of the pins4do not hinder each other when the mushrooms5are snapped into the grooves6.

In order to construct a cage according to the invention with the aid of a kit according to the invention, the plates1,2are preferably provided in contact with each other, but are not interlocked or snapped in to each other, so that thus the mushrooms5of the pins4of adjacent plates1,2do not yet engage in each other. Additionally, the plates1,2can be provided moistened with a fluid. The fluid preferably contains at least one pharmaceutically active substance which is suitable for combating an infection or stimulating bone growth. Alternatively or in addition, the plates1,2can be coated with a pharmaceutically active substance of this type.

The cage can be formed by pressing the plates1,2into each other via their surfaces. As a result, the plates1,2snap into each other and the cage is rigidified in the desired form. Prior to or during this process, the plates1,2can be deformed through a slight elastic deformation of the planar structures3and adapted to the treatment situation. After snapping into at least one further (usually then also deformed) inner plate2, the two plates1,2thus connected to each other stabilise mutually, so that the selected form is rigidified.

The plates1,2can here snap into each other when the mushrooms5elastically deform the pins4of connected plates1,2and through the elastic resilience of the pins4, the mushrooms5and/or the edges of the mushrooms5press into the grooves6and as a result limit the movement of adjacent plates1,2away from the planar structure3(seeFIGS. 3 and 4). Due to the adapted form of the grooves6to the mushrooms5, a further movement of the mushrooms5is blocked, in particular when a large number of mushrooms5is snapped into a large number of grooves6.

Preferably, the dimensions of the mushrooms5, the thickness of the planar structure3, the shape of the grooves6and the length of the pins4between the planar structure3and the mushrooms5are coordinated with each other in such a manner that when the plates1,2are connected the surfaces of the mushrooms5facing away from the planar structure3are in contact with the surface of the grooves6of adjacent plates1,2and/or when the plates1,2are connected, the engagement areas of the mushrooms5come into contact with the engagement areas of the mushrooms5of the adjacent plates1,2. As a result, it is achieved that the connected plates1,2are not and/or not without a great force effect able to move against each other.

The grooves6also prevent the engagement areas or the opposite upper sides of the caps of the mushrooms5from completely covering the pores7. In order for the recesses7to be even less covered by the mushrooms5, the recesses7can comprise several slits (not shown) which are distributed over the extent of the recesses7.

The completed cage comprises two open axial hollow chambers8, which are created by positioning the plates1,2one on top of the other, in which suitably fitting recesses9are provided. The open axial hollow chambers8and thus the recesses9serve to ensure that bones from the vertebral bodies can grow through them. For this purpose, the surfaces of the open axial hollow chambers8and of the recesses9are filled with autologous bone replacement material and, if desired, are additionally coated with a substance which promotes bone growth. The free profile of the recesses9and of the open axial chambers8totals approximately 10 mm, but at least 5 mm, so that the bone of the vertebral bodies can grow in well. The open axial hollow chambers8thus form the interior of the cage.

In order to ensure that the open axial hollow chambers8are uniform and that the outer form of the cage is even, the plates1,2must be snapped in onto each other flush and/or so that they fit. In order to facilitate this, four positioning pins10respectively are provided as positioning aids10on the planar structures3of the outer plates1. Accordingly, in addition the inner plates2comprise four matching bore holes in the planar structures3so that the positioning pins10are inserted through said bore holes when the plates1,2snap into each other and thus specify the orientation and position of the inner plates2relative to the outer plate1. As a result, it can be ensured that the plates1,2are placed onto each other flush and/or in such a manner that they fit. The plates1,2all have the same shape in relation to the plane of the planar structures3, so that they can be laid one on top of the other in such a manner that they fit. With the embodiment shown inFIGS. 1 to 5, the length of the positioning pins10is selected precisely so that it reaches only through the bore hole of the adjacent plate2. However, it would easily be possible to provide longer positioning pins10which extend through the bore holes of further plates1,2. Equally, the positioning pins10could also be provided on an inner plate2and bore holes could be provided in the outer plates1. The positioning pins10could then also end in peaks which are inserted into the vertebral body and affixed there. Equally, with this variant (not shown), the positioning pins10can extend vertically from the planar structure3in both directions.

FIGS. 6 to 12show a second embodiment of the present invention, wherebyFIG. 6shows a schematic perspective view onto a second cage according to the invention, which is constructed of four plates11,12from a second kit according to the invention,FIG. 7shows a schematic perspective view of the cage according toFIG. 6in the state as used in the patient,FIG. 8shows a schematic cross-sectional view through the four snapped-in plates11,12of the cage according toFIG. 6,FIG. 9shows an enlarged representation of a schematic cross-sectional view through two snapped-in plates11,12from the kit according toFIGS. 6 to 8,FIG. 10shows a schematic perspective view onto an outer plate11according to one ofFIGS. 6 to 9,FIG. 11shows an enlargement of a partial area A inFIG. 10, andFIG. 12shows a schematic perspective view onto one of the inner plates12according to one ofFIGS. 6 to 9.

The kit comprises at least two outer plates11, which are provided for affixing to dorsal vertebral bodies17(seeFIG. 7), and comprises several middle or inner plates12which can be inserted between the outer plates11in order to set the height of the cage. The plates11,12consist of an elastic biocompatible plastic material or stainless steel, titanium, a titanium alloy, tantalum, a tantalum alloy or composites of said materials. The plates11,12are produced using a CAM method (Computer-Aided Manufacturing) and/or using a 3D printing method, for example with selective laser melting, or SLM. Other rapid prototyping methods and/or computer-aided generative production methods can also be used for producing the plates11,12, such as, for example, Fused Layer Modeling/Manufacturing (FLM), Fused Deposition Modeling (FDM), Laminated Object Modelling (LOM) of plastic films, Layer Laminated Manufacturing (LLM) of plastic films, Electron Beam Melting (EBM) of plastic materials or metals, Multi Jet Modeling (MJM) of plastic materials, Selective Laser Sintering (SLS) of plastic materials or metals, Stereolithography (STL or SLA) of plastic materials, polishing or multi-axes milling procedures or Digital Light Processing (DLP) of photopolymerising liquid plastic materials.

The plates11,12respectively comprise a plate-shaped planar structure13, which bears all the plates11,12and connects them. The planar structure13can be flexible and elastically deformable to a limited degree, so that other surfaces can also be formed as planes with the planar structure13, so that the plates11,12can to a small degree be adapted to the form of the vertebral bodies. From the planar structures13, with each plate11,12, a plurality of pins14extends which stand up vertically from the plane of the planar structures13.

InFIGS. 6 to 12, two different types of plates11,12are shown, namely outer plates11, which comprise a flat underside and with which the pins14only extend on one side of the planar structures13originating from the planar structure13, and secondly, middle plates12and/or inner plates12, with which the pins14extend originating from both sides of the planar structure13. With a completed cage (seeFIGS. 6, 7 and 8), the plates11,12are arranged in a sandwich-like manner in relation to each other, wherein the outer plates11form the two covering surfaces and the inner plates12are arranged between the outer plates11. The outer plates11can be affixed lying over a large surface on the vertebral bodies17to be treated. For this purpose, eyelets (not shown) can be provided in the planar structure13, so that the outer plates11can be bolted onto the vertebral bodies17, or on the side of the planar structure13without pins14, peaks (not shown) can be provided which are inserted into the bone of the vertebral bodies17. The inner plates12can however theoretically also be affixed to the vertebral bodies to be treated, albeit with a lesser contact surface, so that theoretically, the outer plates11can be omitted.

On the otherwise cylindrical pins14, on the ends of the pins14positioned opposite the planar structures13, mushrooms15are provided as latching elements15. The mushrooms15are rounded outwards (pointing away from the planar structure13) and form spherical segments. However, other roundings are also possible, such as elliptical segments. On the side oriented towards the planar structure13, the mushrooms15form a planar engagement surface, which are suitable for interlocking and snapping in with other mushrooms15on engaging plates11,12.

In the pins14, grooves16are provided as counter snap-in elements adjacent to the mushrooms15and/or to the engagement surfaces, into which the mushrooms15of adjacent plates11,12can engage and/or snap in. For this purpose, edges of the grooves16which face towards the planar structure13have a rounded shape, so that the mushrooms15can fit and/or snap in well to the grooves16. The shape of the grooves16corresponds to a negative of the shape of the surface of the mushrooms15, so that said mushrooms can come into contact along a line in one of the grooves16. The mushrooms15thus form latching elements15and the grooves16form the matching counter snap-in elements16. A further pushing in of the plates11,12following the snap-in connection is prevented by this structure.

In this relation,FIGS. 8 and 9show a schematic cross-sectional view onto plates11,12of the kit according to the invention which are snapped in to each other via the mushrooms15. No pores are arranged in the planar structure13, in contrast to the first exemplary embodiment.

The pins14with the mushrooms15can be arranged in groups and/or islands of pins14and/or mushrooms15(not shown inFIGS. 1 to 5). As a result, pins14arranged on the edge of the groups and/or islands are easier to bend outwards when the mushrooms15of another plate11,12are pressed on. Thus the plates11,12are easier to connect to each other, since the elastic deformations of the pins14do not hinder each other when the mushrooms15are snapped into the grooves16.

In order to construct a cage according to the invention with the aid of a kit according to the invention, the plates11,12are preferably provided in contact with each other, but are not interlocked or snapped in to each other, so that thus the mushrooms15of the pins14of adjacent plates11,12do not yet engage in each other. Additionally, the plates11,12can be provided moistened with a fluid. The fluid preferably contains at least one pharmaceutically active substance which is suitable for combating an infection or stimulating bone growth. Alternatively or in addition, the plates11,12can be coated with a pharmaceutically active substance of this type.

The cage can be formed by pressing the plates11,12into each other via their surfaces. As a result, the plates11,12snap into each other and the cage is rigidified in the desired form. Prior to or during this process, the plates11,12can be deformed through a slight elastic deformation of the planar structures13and adapted to the treatment situation. After snapping into at least one further (usually then equally deformed) inner plate12, the two plates11,12thus connected to each other stabilise mutually, so that the selected form is rigidified.

The plates11,12can here snap into each other when the mushrooms15elastically deform the pins14of connected plates11,12and through the elastic resilience of the pins14, the mushrooms15and/or the edges of the mushrooms15press into the grooves16and as a result limit the movement of adjacent plates11,12away from the planar structure13(seeFIGS. 8 and 9). Due to the adapted form of the grooves16to the mushrooms15, a further movement of the mushrooms15is blocked, in particular when a large number of mushrooms5is snapped into a large number of grooves16.

Preferably, the dimensions of the mushrooms15, the thickness of the planar structure13, the shape of the grooves16and the length of the pins14between the planar structure13and the mushrooms15are coordinated with each other in such a manner that when the plates11,12are connected the surfaces of the mushrooms15facing away from the planar structure13are in contact with the surface of the grooves16of adjacent plates11,12and/or when the plates11,12are connected, the engagement areas of the mushrooms15come into contact with the engagement areas of the mushrooms15of the adjacent plates11,12. As a result, it is achieved that the connected plates11,12are not and/or not without a great force effect able to move against each other.

The completed cage comprises two open axial hollow chambers18, which are created by positioning the plates11,12one on top of the other, in which suitably fitting recesses19which are provided. The open axial hollow chambers18and thus the recesses19serve to ensure that bones from the vertebral bodies17can grow through them. For this purpose, the surfaces of the open axial hollow chambers18and of the recesses19are filled with autologous bone replacement material and, if desired, are additionally coated with a substance which promotes bone growth. The free profile of the recesses19and of the open axial chambers18totals approximately 12 mm, but at least 5 mm, so that the bone of the vertebral bodies can grow in well. The open axial hollow chambers18thus form the interior of the cage.

In order to ensure that the open axial hollow chambers18are uniform and that the outer form of the cage is even, the plates11,12must be snapped in onto each other flush and/or so that they fit. In order to facilitate this, in the same way as with the first exemplary embodiment positioning pins (not shown) can be provided as positioning aids. The plates11,12all have the same shape in relation to the plane of the planar structures13, so that they can be laid one on top of the other in such a manner that they fit.

FIG. 13shows a schematic side view onto five interlocked plates21,22, which form a third cage according to the invention. The cage is constructed in the same way as one of the first two exemplary embodiments. In contrast to these exemplary embodiments, on the planar structures (not shown inFIG. 13) of the outer plates21and the inner plates22, edges27are provided which run around on the outside. The edges27are in contact with each other in such a manner that they interlock when the plates21,22are snapped into each other. As a result, the cage is closed to the outside, so that autologous bone material cannot penetrate outwards from the interior of the cage. The cage can be designed to be open-pore in the interior through pores in the plates21,22, so that the bones can grow through well without materials for this purpose being able to penetrate outwards from the interior of the cage.

FIG. 14shows a schematic perspective detailed view onto two interlocked hooks55(left) and two hooks55that are not interlocked (right) as parts of plates from a fourth kit according to the invention

The structure of the complete plates for this purpose is completed in the same way as the plates according to one of the previous exemplary embodiments, wherein instead of mushrooms, the hooks55are provided to connect the plates.

On the otherwise cylindrical pins54, on the ends of the pins54positioned opposite the planar structures53, hooks55are provided as latching elements55. The hooks55are rounded outwards (pointing away from the planar structure53) and form parts of spherical surfaces. However, other roundings are also possible, such as elliptical segments. On the side oriented towards the planar structure53, the hooks55form undercuts, which are suitable for interlocking or snapping in with other hooks55on engaging plates.

The pins54are thinner and/or formed with a smaller profile (as grooves) in the area adjacent to the hooks55and/or to the undercuts of the hooks55. The hooks55of adjacent plates can more easily engage and/or snap into the thinner areas.

With the present fourth embodiment, only hooks55are provided as latching elements55. In order to build a cage according to the invention, the plates are used lying in contact with each other but not interlocked or snapped into each other, so that thus, the hooks55of the pins54of adjacent plates do not yet engage with each other. Additionally, the plates can be provided moistened with a fluid. The fluid preferably contains at least one pharmaceutically active substance which is suitable for combating an infection or stimulating bone growth. Alternatively or in addition, the plates can be coated with a pharmaceutically active substance of this type.

The cage can be formed by pressing the plates into each other via their surfaces. As a result, the plates interlock or snap into each other and the cage is rigidified in the desired shape.

Here, the plates connect in such a manner that free intermediate chambers remain between the plates that are connected to each other in the area of the pins54and the hooks55, so that the cage formed from the plates is open-pore in the directions parallel to the plane of the plates. The plates have a profile and/or a thickness of approximately 5 mm, so that the remaining pores comprise a free profile in the range of approximately 0.5 mm. This profile is sufficient to enable bone material to develop and/or to grow into the pores. The cage with its open pores can thus be described as osteoconductive. The cage formed from the plates is therefore well suited for connection to the vertebral bodies.

The plates should be firmly pressed into each other so that the cage is dimensionally stable. The plates can here snap into each other in a first step whereby the hooks55elastically deform the pins54of connected plates and through the elastic resilience of the pins54, the hooks55and/or peaks of the hooks55press into each other and as a result restrict the movement of adjacent plates away from the planar structure53. It is thus achieved that the connected plates cannot be moved against each other without being deformed.

The fourth embodiment according toFIG. 14therefore primarily differs from the embodiment according toFIGS. 1 to 12in that hooks55are provided as latching elements55.

FIG. 15shows a schematic perspective view onto sections of two plates61,62which are not interlocked, of a fifth kit according to the invention, andFIG. 16shows three schematic views of sections of two plates (according toFIG. 15) which are connected to each other from the fifth kit A) as a top view onto the upper side, B) in a side view, C) in a cross-sectional view along section B-B according toFIG. 16A).

The plates61,62consist of a biocompatible metal, in particular of stainless steel, titanium or a titanium alloy, tantalum or a tantalum alloy, although they can also be made of an elastic biocompatible plastic material or a composite of such materials. The plates61,62are produced using a CAM method and/or a 3D printing method, for example using selective electron beam melting (EBM). Other rapid prototyping methods and/or computer-supported generative production methods can also be used to produce the plates61,62.

The plates61,62respectively comprise a plate-shaped planar structure63, which bears all the plates61,62and connects them. The planar structure63is elastically deformable, so that other surfaces can also be formed as planes with the planar structure63. From the planar structures63, with each plate61,62, a plurality of pins64extend which stand up vertically from the plane of the planar structures63. In the planar structure63, a plurality of continuous pores67is arranged between the pins64, which, when the plates61,62are connected to each other to form a cage, can create an open porosity of the cage in a direction vertical to the planar structures63when the adjacent plates61,62are not in contact, thus covering the pores67.

InFIGS. 15 and 16, two different types of plates61,62are shown, namely first, one outer plate61, which comprise a flat underside and with which the pins64only extend on one side of the planar structures63originating from the planar structure63, and secondly, inner plates62, with which the pins64extend originating from both sides of the planar structure63. The outer plates61are shown below inFIG. 15, inFIG. 16A) below (on the image plane), inFIG. 16B) below and inFIG. 16C) on the left. The inner plates61are shown on top inFIG. 15, inFIG. 16A) above (out of the image plane), inFIG. 16B) above and inFIG. 16C) on the right. The outer plates61can be affixed lying over a large surface on the vertebral bodies to be treated (not shown). The inner plates62can however also be affixed to the vertebral bodies to be treated, albeit with a lesser contact surface, so that theoretically, the outer plates61can be omitted.

On the otherwise cylindrical pins64, on the ends of the pins64positioned opposite the planar structures63, mushrooms65or groups of four hooks68respectively are provided as latching elements65,68. The mushrooms65are rounded outwards (pointing away from the planar structure63) and form spherical segments. However, other roundings are also possible, such as elliptical segments. The hooks68are rounded outwards likewise. On the side oriented towards the planar structure63, the mushrooms65form a planar engagement surface69, which are suitable for interlocking and snapping in with other mushrooms65and hooks68on engaging plates61,62. Accordingly, the hooks68form undercuts on the side oriented towards the planar structure63, which are suitable for interlocking and snapping in with other mushrooms65and hooks68of engaging plates61,62.

In the pins64, grooves66are provided as counter snap-in elements adjacent to the engagement surfaces69and adjacent to the hooks68, into which the mushrooms65and hooks68of adjacent plates61,62can engage and/or snap in. For this purpose, the grooves66, in contrast to the grooves66shown, but preferred according to the invention, can be formed as a negative of the shape of the curve of the mushrooms65and/or the hooks68, so that the mushrooms65and the hooks68fit well into the grooves66.

With the present fifth embodiment, mushrooms65and hooks68are provided as a mixture on the plates61,62as latching elements65,68, wherein two of eleven latching elements65,68are hooks68, and the remainder are mushrooms65. This can also be reversed, and the hooks68and mushrooms65can also be present in another mixture ratio.

In order to build a cage according to the invention, the plates61,62are used lying in contact with each other but not interlocked or snapped into each other (i.e. not as shown inFIG. 16), so that thus, the mushrooms65and hooks68of the pins64of adjacent plates61,62do not yet engage with each other. Additionally, the plates61,62can be provided moistened with a fluid. The fluid preferably contains at least one pharmaceutically active substance, in particular an autologous bone substance. Alternatively or in addition, the plates can be coated with a pharmaceutically active substance of this type.

The cage can be formed by pressing the plates61,62into each other via their surfaces. As a result, the plates61,62snap into each other and the cage is rigidified in the desired form. Prior to this process, the plates61,62can also be deformed through elastic deformation of the planar structures63and adapted to the treatment situation. After interlocking or snapping into at least one further plate61,62, the two plates61,62thus connected to each other stabilise mutually, so that the selected form is rigidified.

Here, the plates61,62connect in such a manner that free intermediate chambers remain between the plates61,62that are connected to each other in the area of the pins64, the mushrooms65, the hooks68and the grooves66, so that the cage formed from the plates61,62is open-pore in the directions parallel to the plane of the plates61,62. The plates61,62have a profile and/or a thickness of approximately 9 mm, so that the remaining pores67comprise a free profile in the range of approximately 0.9 mm. This profile is sufficient to enable bone material to develop and/or to grow into the pores67. The cage with its open pores67can thus be described as osteoconductive. The cage formed from the plates61,62is therefore well suited for connection to the vertebral bodies.

The plates61,62should be firmly pressed into each other so that the cage is dimensionally stable. The plates61,62can here snap into each other whereby the mushrooms65and hooks68elastically deform the pins64of connected plates61,62and through the elastic resilience of the pins64, the mushrooms65and hooks68and/or the edges of the mushrooms65and peaks of the hooks68press into the grooves66and as a result restrict the movement of adjacent plates61,62away from the planar structure63(seeFIG. 16). It is also possible that first the edges of the mushrooms65and/or the peaks of the hooks68plastically deform the pins64, the grooves66or the mushrooms65to a small degree and thus a snapped-in connection between the plates61,62occurs.

Preferably, the dimensions of the mushrooms65, of the hooks68, the thickness of the planar structure63, the shape of the grooves66and the length of the pins64between the planar structure63and the mushrooms65or hooks68are coordinated with each other in such a manner that when the plates61,62are connected the surfaces of the mushrooms65and hooks68facing away from the planar structure63are in contact with the surface of adjacent plates61,62and/or when the plates61,62are connected, the surfaces of the mushrooms65and hooks68facing away from the planar structure63are in contact on the engagement surface69of the mushrooms65and preferably along at least one line or particularly preferably in a planar manner on the grooves66of the pins64of the adjacent plate61,62. As a result, it is achieved that the connected plates61,62are not able to move against each other without being deformed.

The fifth embodiment according toFIGS. 15 and 16thus primarily differs from that according toFIGS. 1 to 5by the fact that hooks68are provided as latching elements68.

FIG. 17shows a schematic cross-sectional view through an outer plate of a sixth kit according to the invention (FIG. 17, above), and a schematic side view onto the outer plate of the sixth kit (FIG. 17, below). In this regard,FIG. 18shows an enlarged representation of a schematic cross-sectional view through two snapped-in plates of the sixth kit according toFIG. 17.

FIG. 19shows a schematic cross-sectional view through an outer plate of a seventh kit according to the invention (FIG. 19, above) and a schematic side view onto the outer plate of the seventh kit according to the invention (FIG. 19, below). In this regard,FIG. 20shows an enlarged representation of a schematic cross-sectional view through two snapped-in plates of the seventh kit according toFIG. 19.

FIG. 21shows a schematic cross-sectional view through an outer plate of an eighth kit according to the invention (FIG. 21, above) and a schematic side view onto the outer plate of the eighth kit according to the invention (FIG. 21, below). In this regard,FIG. 22shows an enlarged representation of a schematic cross-sectional view through two snapped-in plates of the eighth kit according toFIG. 21.

These three embodiments, six, seven and eight, are highly similar to each other, and can thus be described collectively below.

The kits comprise at least two outer plates71,81,91, which are provided for affixing to dorsal vertebral bodies, and which comprise several middle or inner plates72,82,92, which can be inserted between the outer plates71,81,91, in order to set the height of the cage. The plates71,72,81,82,91,92consist of an elastic biocompatible plastic material or stainless steel, titanium, a titanium alloy, tantalum, a tantalum alloy or composites of said materials. The plates71,72,81,82,91,92are produced using a CAM method (Computer-Aided Manufacturing) and/or using a 3D printing method, for example with selective laser melting, or SLM. Other rapid prototyping methods and/or computer-aided generative production methods can also be used for producing the plates71,72,81,82,91,92such as, for example, Fused Layer Modeling/Manufacturing (FLM), Fused Deposition Modeling (FDM), Laminated Object Modelling (LOM) of plastic films, Layer Laminated Manufacturing (LLM) of plastic films, Electron Beam Melting (EBM) of plastic materials or metals, Multi Jet Modeling (MJM) of plastic materials, Selective Laser Sintering (SLS) of plastic materials or metals, Stereolithography (STL or SLA) of plastic materials, polishing or multi-axes milling procedures or Digital Light Processing (DLP) of photopolymerising liquid plastic materials.

The plates71,72,81,82,91,92respectively comprise a plate-shaped planar structure73,83,93, which bears all the plates71,72,81,82,91,92and connects them. The planar structure73,83,93can be flexible and elastically deformable to a limited degree, so that other surfaces can also be formed as planes with the planar structure73,83,93, so that the plates71,72,81,82,91,92can to a small degree be adapted to the form of the vertebral bodies. From the planar structures73,83,93, with each plate71,72,81,82,91,92, a plurality of pins74,84,94extend which stand up vertically from the plane of the planar structures73,83,93.

InFIGS. 17 to 22, two different types of plates71,72,81,82,91,92are shown respectively, namely outer plates71,81,91, which comprise a flat underside and with which the pins74,84,94only extend on one side of the planar structures73,83,93originating from the planar structure73,83,93, and secondly, middle plates72,82,92and/or inner plates72,82,92, with which the pins74,84,94extend originating from both sides of the planar structure73,83,93. With a completed cage and/or with conjoined or snapped-in plates71,72,81,82,91,92(seeFIGS. 18, 20 and 22), the plates71,72,81,82,91,92are arranged in a sandwich-like manner in relation to each other, wherein the outer plates71,81,91form the two covering surfaces and the inner plates72,82,92are arranged between the outer plates71,81,91. The outer plates71,81,91can be affixed lying over a large surface on the vertebral bodies to be treated. For this purpose, eyelets (not shown) can be provided in the planar structure73,83,93, so that the outer plates71,81,91can be bolted onto the vertebral bodies, or on the side of the planar structure73,83,93without pins74,84,94, peaks (not shown) can be provided which are inserted into the bone of the vertebral bodies. The inner plates72,82,92can however theoretically also be affixed to the vertebral bodies to be treated, albeit with a lesser contact surface, so that theoretically, the outer plates71,81,91can be omitted.

On the otherwise cylindrical pins74,84,94, four mushrooms75,85,95are provided respectively as latching elements75,85,95. The mushrooms75,85,95on the peaks of the pins74,84,94are rounded outwards (pointing away from the planar structure73,83,93). With the sixth embodiment (FIGS. 17 and 18) and the seventh embodiment (FIGS. 19 and 20), the mushrooms75,85form spherical segments on the peaks of the pins74,84,94, while with the eleventh embodiment, the mushrooms95are somewhat more pointed on the peaks of the pins94. However, other roundings are also possible, such as elliptical segments. The mushrooms75,85,95which are arranged below the mushrooms75,85,95on the peak of the pins74,84,94, and which are thus arranged on the pins74,84,94between the planar structure73,83,93and the mushrooms75,85,95, and the mushrooms75,85,95which are arranged on the side of the pins74,84,94facing away from the planar structure73,83,93, have the shape of a truncated cone and/or are truncated cone-shaped. On the side oriented towards the planar structure73,83,93, the mushrooms75,85,95form a planar engagement surface79,89,99, which are suitable for interlocking and snapping in with other mushrooms75,85,95on engaging plates, or with recesses76,86,96of engaging plates. The pins94and the mushrooms95of the eighth embodiment (FIGS. 21 and 22) comprise a somewhat lesser diameter than those of the sixth and seventh embodiment, wherein the engagement surfaces99of the eighth embodiment are somewhat deeper and/or larger-area than the engagement surfaces79,89of the sixth and seventh embodiment.

In the pins74,84,94, and/or between the mushrooms75,85,95, grooves76,86,96are provided as counter snap-in elements76,86,96, into which the mushrooms75,85,95of adjacent plates71,72,81,82,91,92can engage and/or interlock or snap in. The mushrooms75,85,95thus form latching elements75,85,95and the grooves76,86,96form approximately matching counter snap-in elements76,86,96. With the sixth, seventh and eighth embodiment, the plates71,72,81,82,91,92can be pushed in further by pushing the pins74,84,94with the mushrooms75,85,95into and/or through the recesses73,83,93.

In this regard,FIGS. 18, 20 and 22show a schematic cross-sectional view onto the plates71,72,81,82,91,92of the kits according to the invention which are interlocked via the mushrooms75,85,95. In the planar structures73,83,93of the outer plates71,72,81,82,91,92, a plurality of continuous pores77,87,97is arranged between the pins74,84,94. The pores74,84,94create an open porosity of the cage on the contact surface to the vertebral bodies in a direction vertical to the planar structures73,83,93. As a result, the bone of the vertebral bodies can grow together more easily with the outer plates71,81,91of the cage.

The pins74,84,94are thinnest between the mushrooms75,85,95and the planar structures73,83,93, so that the pins74,84,94can most easily be bent over in the area of the connection to the planar structures73,83,93, and/or are easiest to move there, in order to enable the snap-in process or interlocking of the mushrooms75,85,95with the grooves76,86,96between the mushrooms75,85,95. In order to construct a cage according to the invention with the aid of a kit according to the invention, the plates71,72,81,82,91,92are preferably provided in contact with each other, but are not interlocked or snapped in to each other, so that thus the mushrooms75,85,95of the pins74,84,94of adjacent plates71,72,81,82,91,92do not yet engage in each other. Additionally, the plates71,72,81,82,91,92can be provided moistened with a fluid. The fluid preferably contains at least one pharmaceutically active substance which is suitable for combating an infection or stimulating bone growth. Alternatively or in addition, the plates71,72,81,82,91,92can be coated with a pharmaceutically active substance of this type.

The cage can be formed by pressing the plates71,72,81,82,91,92into each other via their surfaces. As a result, the plates71,72,81,82,91,92snap into each other and the cage is rigidified in the desired form. Prior to or during this process, the plates71,72,81,82,91,92can also be deformed through a slight elastic deformation of the planar structures73,83,93and adapted to the treatment situation. After snapping into at least one further (usually then also deformed) inner plate72,82,92, the two plates71,72,81,82,91,92thus connected to each other stabilise mutually, so that the selected form is rigidified.

The plates71,72,81,82,91,92can here snap into each other when the mushrooms75,85,95elastically deform the pins74,84,94of connected plates71,72,81,82,91,92and through the elastic resilience of the pins74,84,94, the mushrooms75,85,95and/or the edges of the mushrooms75,85,95press into the grooves76,86,96and as a result limit the movement of adjacent plates71,72,81,82,91,92away from the planar structure73,83,93(seeFIGS. 18, 20 and 22).

Here, the plates71,72,81,82,91,92connect in such a manner that free intermediate chambers remain between the plates71,72,81,82,91,92that are connected to each other in the area of the pins74,84,94the mushrooms75,85,95and the grooves76,86,96, so that the cage formed from the plates71,72,81,82,91,92is open-pore in the directions parallel to the plane of the plates71,72,81,82,91,92. The plates71,72,81,82,91,92have a profile and/or a thickness of between 0.25 mm and 1.5 mm. This profile is sufficient to enable bone material to develop and/or to grow into the pores77,87,97and between the plates71,72,81,82,91,92. The cage with its open pores77,87,97can thus be described as osteoconductive. The cage formed from the plates is therefore well suited for connection to the vertebral bodies.

The completed cage comprises two open axial hollow chambers (not shown), which are created by positioning the plates71,72,81,82,91,92one on top of the other, in which suitably fitting recesses are provided, which are however not shown inFIGS. 17 to 22. The axial hollow chambers and the recesses are structured in the same way as for the preceding exemplary embodiments. The open axial hollow chambers and thus the recesses serve to ensure that bones from the vertebral bodies can grow through them. For this purpose, the surfaces of the open axial hollow chambers and of the recesses are filled with autologous bone replacement material and, if desired, are additionally coated with a substance which promotes bone growth. The free profile of the recesses and of the open axial chambers totals approximately 12 mm, but at least 5 mm, so that the bone of the vertebral bodies can grow in well. The open axial hollow chambers thus form the interior of the cage.

In order to ensure that the open axial hollow chambers are uniform and that the outer form of the cage is even, the plates71,72,81,82,91,92must be snapped in onto each other flush and/or so that they fit. In order to facilitate this, in the same way as for the first exemplary embodiment, four positioning pins (not shown) respectively can be provided as positioning aids. The plates71,72,81,82,91,92all have the same shape in relation to the plane of the planar structure73,83,93, so that they can be are placed onto each other in such a manner that they fit.

The kits from all exemplary embodiments can also comprise more plates than those shown, and also groups of plates with different geometries, in order to design the kits as variably as possibly and in order to make them suitable for use in the treatment of different anatomical conditions.

The features of the invention disclosed in the preceding description and in the claims, figures, and exemplary embodiments, can be essential for the implementation of the various embodiments of the invention both alone and in its different combinations.

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