WO2021090039A1

WO2021090039A1 - Spinal implant for intervertebral fusion

Info

Publication number: WO2021090039A1
Application number: PCT/HU2020/050051
Authority: WO
Inventors: Gergely BODON; György FALK; Tamás KIRÁLY; Dávid LUKÁCS
Original assignee: Bodon Gergely; Falk Gyoergy; Kiraly Tamas; Lukacs David
Priority date: 2019-11-04
Filing date: 2020-11-03
Publication date: 2021-05-14
Also published as: HUP1900374A1

Abstract

Implant cage which can be inserted surgically between two vertebrae and comprises a substantially oblong-shaped body and a frame (33) having two sides (13, 14) and at least one intermediate supporting wall (15) and a top (11) and a bottom (12) fixed to the frame (33), wherein the said top (11) and the bottom (12) of the cage (10) have respective convex shapes that follow the shape of the end surfaces of the adjacent vertebrae, and the height of the frame (33) and of the support wall (15) follow the convex shape, and on the top (11) and the bottom (12) a high number of gaps (21, 22) are provided that open to the interior of the frame (33) that facilitate ossification and bone ingrowths into the cage (10), and the gaps (21, 22) extend in transverse direction directly under each other between respective parallel ribs separated by narrow spacing. The different types of cages can be used as cervical, thoracic, lumbar and lumbosacral implants.

Description

Spinal implant for intervertebral fusion

The invention relates to a cage which can be inserted surgically between two vertebrae and comprises a substantially oblong-shaped body and a frame, that has two side-walls and at least one supporting wall in between that define together at least two internal hollow partitions and the cage comprises furthermore an anatomically designed top and a bottom covering sheet being fixed to the frame. Embodiments of the invention can be used to fuse cervical, thoracic and lumbar, vertebrae and also to perform fusion and the lumbosacral junction.

The invention relates also to a fixing arrangement for a cervical cage with an associated supporting plate.

US patent 7,112,222 B2 describes and implant arrangement which can be used primarily as a lumbar implant cage. The main emphasis at this design was how the implant cage can be coupled to the adjacent vertebrae following its insertion therefore the cage was realized without having any top and bottom plates, wherein the adjacent vertebrae contacted only the edges of the frame of the cage.

Such a design required necessarily the use of great wall thicknesses of the frame that had knurled upper and lower edges with wedge-like ribs to prevent displacement of the cage. Additionally, at the top and bottom of the central supporting wall of the cage respective planar recesses were provided to receive respective connection sheets of a separate support plate.

Following the placement of the cage the arrangement allows a temporary connec tion between the support plate and the cage by means of the sheets and then the cage can still be adjusted to a slight extent, and by a subsequent insertion of specially designed screws into prefabricated bores in the tabs of the support plate the arrangement is fixed to the vertebrae adjacent to the implant, fixing the position of the cage.

The load represented by the adjacent vertebrae is transmitted to the cage on comparatively small surfaces that results in high local pressures that might cause bone deformation. There can be a real need for the distribution of the force along larger surface areas. The hollow inner space of the cage is closed without having any access thereto and the discovery of any possible blood rests coming from the spinal channel or of other tissues and their removal is not possible. In case of the cervical spine, the spinal canal could not be visualized after cage implantation and thus tissue debris and bleeding from the spinal canal could cause compression of the spinal cord.

In case of using implant cages it has a primary importance that at a time following the surgery a required bone growth takes place that can stabilize the relative position of the adjacent vertebrae for a long period. The long-term goal of cage implantation is to reach bony fusion of the adjacent segments with the help of bone ingrowth into the cage.

Usual practice at the cervical spine is to add an anterior plate after insertion of the cage to enhance segmental stability. As the cages are not connected to the plate, after midline insertion of the cage it is difficult to place the unconstrained plate also aligned in the midline.

The task of the present invention is to provide an implant cage which is free from the above outlined drawbacks and its insertion and use is not difficult, furthermore the filling of the cavities with bone granulates or bone substitutes can be resolved and the design facilitates ossification.

A further task regarding the cervical cage is to allow the discovery and removal of tissues that have accidentally penetrated into the spinal canal during the insertion of the cage into the intervertebral space.

A still further task is to provide in case of cervical vertebral implants an improved cage and an associated anterior plate.

For solving these tasks an implant cage has been provided designed as defined in the attached claims, and furthermore an arrangement for a cervical anterior plate has also been provided that can be used together with such improved cage and also defined in the claims.

According to different spinal regions three different embodiments have been provided.

The invention will now be described in connection with preferable embodiments thereof, in which reference will be made to the accompanying drawings. In the drawing: Fig. 1 shows the perspective view of the implant cage according to the invention projected slightly from above and from the left side;

Fig. 2 is the perspective view of the implant cage shown in Fig. 1 projected from below and from the left; Fig. 3 is the front view of the implant cage of Fig. 1;

Fig. 4 is the rear view of the implant cage of Fig. 1;

Fig. 5 is the top view of the implant cage of Fig. 1;

Fig. 6 is the bottom view of the implant cage of Fig. 1;

Fig. 7 is the perspective view of the implant cage shown in Fig. 1 projected slightly from a side;

Fig. 8 is the front view of a vertebra fixing plate;

Fig. 9 is the rear view of the anterior cervical plate shown in Fig. 8;

Fig. 10 is the side view of the anterior cervical plate shown in Fig. 8;

Fig. 11 is the front view of an assembled cervical cage and plate arrangement; Fig. 12 is the side view of the arrangement shown in Fig. 11;

Fig 13 is the top view of the arrangement shown in Fig. 11;

Fig. 14 is a view similar to Fig. 12 that shows also the screws used for the fixing;

Fig. 15 is a top sectional view taken in the central plane of the implant cage;

Fig. 16 is similar to Fig. 14 being a section taken in the central plane of the plate; Fig. 17 is the rear view of the arrangement shown in Fig. 14;

Fig. 18 is the front view of the arrangement shown in Fig. 14;

Fig. 19 shows the perspective view of the cage designed for the lumbosacral junction;

Figs. 20a, 20b and 20c are three embodiments of the thoracic and lumbar implant cages;

Figs. 21a, 21b and 21c are exploded views of three embodiments with different applications;

Figs. 22a, 22b and 22c are top views of three embodiments with different applications; and Fig. 23 illustrates the mapping of the fitting surface of a cervical vertebra to a cage by its characteristic points. First the embodiment of the vertebral implant cage according to the invention will be described with reference to Figs. 1 to 18 which is used as a cervical vertebral implant cage and also includes the fixing plate associated with the cage.

In Figs. 1 to 6 the design of the cervical vertebral implant cage 10 is shown. The cage 10 is a spatial body with specific shape and its introduction requires illustration from several views. The cervical cage is used after the surgical removal of the intervertebral disk for keeping the distance and for maintaining the continuity and loadability of the spinal column. The cage 10 has a more or less oblong like shape and has top 11, bottom 12 and left and right sides 13 and 14. These four members do not have exact planar shapes and they do not extend parallel to each other as they narrow in backward direction. In the drawing it can be observed that the top 11 and the bottom 12 have slightly convex shapes which try to follow the shape of the end plates of the adjacent vertebrae, more exactly they are shaped as negatives of these end plates, and therefore the shapes of the top 11 and the bottom 12 are different. The attribute "convex" indicates that the height of these plates is the greatest in the central zone and slightly decreases towards the sides i.e. they are concave when viewed from inside.

The cage 10 has a hollow interior space which is divided by a central support wall 15 into two halves 16, 17 and the cage 10 is open both at the front and the back. The two sides 13, 14 and the central support wall 15 together with connection members are united to form a common frame 33 that determine the loadability of the cage 10. The top 11 and the bottom 12 are separate elements coupled to the frame 33 (see Fig. 21a).

The width of the central support wall 15 decreases gradually from the front to the back which can be seen in Figs. 5 and 6 and it is provided at the front with a bore 18 that has an internal thread around which the central support wall 15 is wider, takes at the front a substantially cylindrical shape limited at the two sides with respective vertical planar surfaces 19, 20.

The two sides 13, 14 are mirror symmetrical and they diverge from the bottom toward their top because the top 11 is slightly wider than the bottom 12.

The central supporting wall 15 has multiple tasks. Its primary goal is to resist compression forces acting on the top 11 and bottom 12, besides it increases rigidity and overall strength of cage 10. The threaded bore 18 allows for connection with the inserting tool, placement and fine adjustment of cage 10, and finally it enables the connection of a holding plate 50 shown in Figs. 8 and 9 to the cage 10. The two lateral planar surfaces 19, 20 provide quick guidance and support to the holding plate 50 when being connected to the cage 10.

On the top 11 and bottom 12 of the cage 10 a plurality of transversal parallel gaps 21, 22 are provided kept together by a frame. The gaps are defined by spaced ribs 23, 24 wherein the spacing corresponds to the width of the gaps 21, 22. In the present description the term "transversal" designates a direction normal to the sides 13, 14. With respect to the outer surfaces of the ribs 23, 24 towards the interior of the cage 10 sunken spaced parallel rods 25, 26 are connected with the ribs 23, 24 which extend normal to the ribs 23, 24 and from forward to backward when viewed from the cage 10 (see Figs. 5 and 6). Between the gaps 21, 22 defined by the ribs 23, 24 and the rods 25, 26 that are bridging the ribs 23, 24 a high number of rectangular openings are formed which make it possible that from the vertebrae held by the cage 10 bones can grow into the openings and there they can get combined with bone granulates or bone substitute placed in the interior cavity of the cage 10 at the final stage of the surgery.

This design ensures also that the top 11 and the bottom 12 of the cage 10 have the required rigidity and stability to resist the load without deformation which will act thereon whereas the presence of the holes assists the bone ingrowth. Additionally, the convex shape of the top 11 and the bottom 12 fits better to the shape of the vertebrae to be connected by the cage 10. The position of the cage 10 is further facilitated by the presence of a spike 27 provided at the central part of the top 11 that has the shape of a pyramid with the top facing upward, and two further similar spikes 28, 29 formed at the sides of the front edge of the bottom 12 having tops facing downward.

A further characteristic to the design of the cage 10 is that in both sides 13, 14 respective large openings 30, 31 are provided with preferably oval shapes, and in the connection line of these openings in the central support wall 15 there is a comparatively large circular opening 32 (Fig. 7).

The two hollow half spaces 16, 17 provided in the interior of the cage 10, and the two lateral openings 30, 31 and the opening 32 made in the central support wall 15 enable the visual control of the spinal canal behaving the cage 10. A further advantage lies in that the aforementioned openings 30, 31 and 32 can fall in a line during insertion of the cage 10 and on the lateral X-ray picture make up an "silhouette of an eye", ruling out malposition of the cage.

Reference will be made now to Figs. 8 to 10 in which the front, rear and side views of the support plate 50 are shown. The task of the support plate 50 is the fixing and stabilizing the vertebrae directly adjacent to the cage 10 as well as of the cage 10. The scale used in these figures differs from those used in Figs. 1 to 7, and the plate 50 has a flat, nearly rectangular body that has a central part 51, respective bending zones 52, 53 at the lower and upper ends of the central part 51 and support tabs 54 and 55 connected to the bending zones 52, 53. The central part 51 has the task of fixing the cage 10 and its width is slightly smaller than the width of the cage 10 but greater than the width of the central support wall 15. In the middle of the central part 51 a larger countersunk head bore 56 is provided and diagonally and obliquely outward from it there are two smaller bores 57, 58. In the central bore 56 that has a countersunk head design a screw 59 can be inserted that has a specially designed head shown in the sectional views of Figs. 15 and 15, and it can be driven into the threaded bore 18 made in the central support wall 15. The screw 59 has preferably a Phillips head. In the bores 57, 58 securing bolts 60, 61 can be inserted sown in Figs. 11 and 18 that have a cut on their heads. After the screw 59 has been appropriately inserted and fastened into the threaded bore 18 then the securing bolts should be inserted in respective angular positions into their associated bores 57, 58 that the cuts fit to the straight line defined by the cross-line of the head of the screw 59, whereby the screw 59 has been simply secured against being turned. Such a screw securing design is regarded as usual in applications in spinal surgery.

From the central part 51 of the support plate 50 at both sides' respective flexible tabs 62, 63 extend out in posterior direction towards the cage 10 which are spaced and dimensioned to flank the two planar surfaces 19, 20 provided at the sides of the central support wall 15, whereby the support plate 50 and the cage 10 get connected.

The middle region of the central part 51 of the support plate 50 which holds the sunken bore 56 is slightly deeper than its outer parts, and the boundary lines of the deeper portion can be seen in the Figures 8 and 18.

At the bending zones 52, 53 the support plate 50 has decreased thickness which makes possible that during the surgery the surgeon can bend the planes of the two outer support tabs 54, 55 into the required angular positions as it is needed by the anatomy of the two adjacent vertebrae. As a result of the bending the parts of the support plate 50 fit better to the front surfaces of the upper and lower vertebral bodies, whereby the distance between the vertebrae and the support plate 50 will be shorter that results in a more solid fixation.

The support tabs 54, 55 are slightly wider than the central part 51, they have rounded corners and respective pairs of bores 64, 65 and 66, 67 are provided through them. The axes of these bores 64 to 67 are not normal to the planes of the surrounding support tabs 54, 55 but with respect to the tabs they are slightly inclined in inward direction in order that the screws required for the connection with the vertebrae can be inserted in the optimum angles. In the support plate 50 vertical slots 72, 73 (see Figs. 8 and 9) are provided which serve only the decrease of the weight.

The material of the support plate 50 does not differ from that of known similar support plates its design is however basically different. In connection with Figs.11 to 18 it will be shown how can the cage 10 be inserted and connected with the support plate 50. During surgery in the space formed between two vertebrae in the place of the removed intervertebral disk the implant cage 10 is inserted by an appropriate tool. To this step a positioning tool should be temporarily driven in the threaded bore 18 that enable the position adjustment of the cage 10. Thereafter through the openings 16 and 17 the visual control of the spinal canal is possible after the implantation of the cage 10, also granulated bone or bone- substitute can be inserted into the hollow interior of the cage 10.

The support plate 50 is connected to the cage 10 that it is attached to the cage 10 from the front, whereas the two projecting tabs 62, 63 will flank the two planar surfaces 19, 20 at both sides of the central support wall 15. The tabs 62, 63 are guided and slide inwardly along these surfaces whereby between the cage 10 and the support plate 50 a temporary but definite connection will be established. At this phase the fine position adjustment of the assembly is still possible. Then the screw 59 with the countersunk head is introduced through the bore 56 into the oppositely positioned threaded bore 18 but the screw 59 will not be fastened tightly at this position.

The two outer support tabs 54, 55 of the support plate 50 have been bent in the expected final angular position then special screws 68, 69, 70 and 70 designed for fixing in bones are screwed in the previously prepared bores then after fastening these screws 68 to 70 the central screw 59 can also be fastened, and in this position the two securing bolts 60, 61 are used to secure this fixed position of the screw 59 permanently. In the sectional views of Figs. 13 and 15 the cage 10 can be observed as being connected with the support plate 50. This position will be obtained only at the site of the surgery.

Following the description of the cervical vertebral implant cage 10 another embo diment will be described which can be used for fusion of the lumbosacral junction cage 80 (see Fig. 19). In human beings there are typically five lumbar vertebrae (Ll-5) and the sacrum is also comprised of five fused melted vertebrae (Sl-5). This implant cage 80 is used to replace the disc between the vertebrae L5-S1, also the lumbosacral junction.

Similarly to the insertion of the cervical cage 10 the cage 80 for the lumbosacral junction is also inserted following removal of the disc from the anterior direction, therefore the functional parts and their shapes are similar. A substantial difference lies in that in case of cage 80, there is no need for the support plates 50 used and described in connection with the previous cervical cage, but instead of the plate three special screws 81a, 81b and 82 are used which are large compared to the size of the cage 80 and the screws 81a and 81b extend out in an inclined position from the top of the cage 80 slightly backwards and upwards while the screw 82 extends our from the bottom of the cage 80 and it is inclined in rearward direction.

The essential similarity of the cage 80 with the cervical cage 10 can be observed in Fig. 19. The cage 80 has a rigid frame 83 (Fig. 21b) which is divided by a pair of substantially vertical sides 86, 87 and a central support wall 88 into two space halves 88,89, and on the frame 83 respective top 84 and bottom 85 are fitted.

Similarly to the openings 30, 31 on the sides of the cage 10 on the sides 86, 87 of the cage 80 there are respective oval openings of which in Fig. 19 only one opening 91 can be seen. In the central line of the oval openings a circular opening is provided in the central support wall 88 which is covered in the drawing. The role of these transversal openings is the same as in the previous embodiments, i.e. the lateral X-ray picture makes up an "silhouette of an eye", ruling out malposition of the cage.

In Fig. 21b it can be seen that the upper part of the frame 83 has a reinforced structure because of the presence of the large screws 81a, 81b, and the size of the openings above the half spaces 89, 90 is smaller. The design of the top 84 and the bottom 85 is the same as that of the top 11 and bottom 12 shown in the previous embodiment, however, the size dimensions are proportionally larger which can be seen by the comparison of Figs. 21b and 21a. The ribs, the transversal rods and the gaps formed between them are not indicated separately, but in Fig. 22c the ribbed structure and the gaps between the ribs can be well observed. The role of such structure is significant both from the point of view of ossification and the loadability.

The curved upper and lower surfaces of the cage 80 and their sizes fit to the shape and size of the vertebrae connected thereby. Figs. 21 and 22 illustrate in proportional scale the relative size of the three embodiments of the invention.

Reference is made now to Figs. 20a, 20b and 20c in which a third embodiment of the present invention is shown in three versions. This embodiment is used as a thoracic or lumbar implant cage 100 after the disc has been opened and removed from lateral direction and being inserted in the gap left after the disc was removed. The three versions of the dorsal lumbar implant cage 100 have similar shapes and functional parts.

Owing to the greater load and width the cage 100 does not have a single central support wall but it has three intermediate support walls 101, 102 and 103 and two sides 104, 105 which divide the hollow interior into four chambers. The cage 100 has frame 106 that can be well observed in Fig. 21c. It can also be observed in this Fig. 21c that in the side 105 (the other side is covered) three openings are provided of which only the middle opening 107 is circular and in front and behind of it respective openings 108, 109 are provided which have half-moon like shapes, and at places corresponding to these openings the intermediate support walls 101, 102 and 103 have similar openings trough which the interior of the chambers can be observed by laterally directed X-ray examina tions.

In the exploded view of Fig. 21c it can be seen that the cage 100 has also ribbed top 110 and bottom 111 which have identical design and function as mentioned in the previous embodiments. It can be seen in Fig. 20 that on the top 110 a pair of spikes 112 are provided which have the task of fixing the position of the cage 100 after its insertion until fusion takes place.

In Figs. 20a, 20b and 20c it is demonstrated that depending on the anatomy of the patient the shape of the cage 100 can change and its height can be symmetric (Fig. 20a) or asymmetric (Fig. 20c) but its height can be the same in the two sides but deceases in rearward direction (Fig. 20b).

In the following the common properties which are true for all the three embodiments will be mentioned.

Owing to the strict tolerance expectations and their complex geometry the cages 10, 80 ad 100 can be manufactured primarily by 3D printing technique. Because of the required high loadability expectations instead of titanium with commercial purity the use of Ti6AI4V alloy is preferred. Cages made of this alloy have good mechanical stability, loadability, good corrosion resistance and favorable bio-compatibility.

The spatial shape of the tops 11, 84 and 100 as well as of the bottoms 12, 85 and 111 of the cages were made in such a way that CT (computer tomography) scans were used for making models of the end surfaces of the concerned vertebra as standards for the given anatomy samples or templates. The tops and bottoms of the cages were made as the negatives of these samples.

For the standardization on the surfaces of vertebral models control points 121 shown in Fig. 23 were designated, in the exemplary case nine of such points, and the relative positions of these points determine the shape of the top and bottom surfaces of a cage with "optimum match". For the 3D printing these data should be taken into account as base data, and the basic parameters (width, height, lordosis, place of the bores) as well as the shape of the top and bottom plates of the cage can be modified or made to ideal shape by using the control points 21.

In case of specific needs (e.g. at scoliosis or asymmetric degeneration) asymmetric cages can also be made. This method enables the manufacture of personalized implants based on the CT recording of the given patient.

As described earlier, the top and bottom plates of the cage comprise mutually normal spaced prisms (ribs and rods) interconnected by a frame. The spacing is typically around 0.65 mm which allows for bone ingrowths. During the pressure acting on the bone this latter gets deformed and the thickness of the first row of prisms and the joining ribs extending in transversal direction provides an increased contact surface with the bone, decreasing the danger of subsidence of the cage. The end walls of the cage are reinforced by a frame that interconnect such walls with the frame of the cage, and the so designed framed structure makes the cage resistant against any rotational load that might appear during use.

The cervical and the cage for the lumbosacral junction 10 and 80 comprise a substantial thicker central support wall 15, 88 which is provided with a bore having an internal thread which can receive an insertion tool. Here the frame structure also includes the two side-walls that resist also horizontal load.

The openings provided on the sides and internal walls of the cage constitute a single opening when viewed on a lateral X-ray picture indicating that the position of the cage is appropriate.

The primary stability (i.e. the prevention of the displacement of the cage following the implantation until the bony fusion is reached) is provided by the press-fit insertion, the tension of the remaining bands and the spikes provided on the top and bottom of the cages.

Claims

Claims:

1. Implant cage (10, 80, 100) which can be inserted surgically between two vertebrae and comprises a substantially oblong-shaped body and a frame (33, 83, 106) having two sides (13, 14; 86, 87; 104, 105) and at least one intermediate supporting wall (15, 88, 102) defining together at least two internal hollows partitions (16, 17) and a top (11, 84, 110) and a bottom (12, 85, 111) being fixed to the frame (33, 83, 106) and being substantially normal to the supporting wall (15, 88, 102), characterized in that said top (11, 84, 110) and bottom (12, 85, 111) of the cage (10, 80, 100) have respective convex shapes that follow the shape of the end surfaces of the adjacent vertebrae, and the height of the frame (33, 83,106) and of the support wall (15, 88, 102) follow said convex shape, and on the top (11, 84, 110) and the bottom (12, 85, 111) a high number of gaps (21, 22) are provided that open to the interior of the frame (33, 83, 106) that facilitate ossification and bone ingrowths into the cage (10, 80, 100), wherein said gaps (21, 22) extend in transverse direction directly under each other between respective ribs sepa rated by narrow spacing.

2. The implant cage as claimed in claim 1, wherein said sides (13, 14, 86, 87; 104, 105) and said support wall (15, 88, 102) comprise respective openings (30, 31; 91; 107, 108, 109) which at least partially cover each other when viewed from the side and enable x-ray observation of the interior space.

3. The implant cage (10) as claimed in claims 1 or 2 for use as a cervical implant, the cage (10) comprises a single central support wall (15) provided with a frontal threaded bore (18), and the front portion of the sides of the central support wall (15) are limited by respective planar surfaces (19, 20) extending parallel to the sides (13, 14).

4. The implant cage as claimed in claim 3, wherein from said top (11) and bottom (12) at least one stabilizing spike (27, 28, 29) extends out from the cage (10) in the direction of the adjacent vertebra for temporarily stabilizing the position of the cage (10).

5. The implant cage (80) as claimed in claims 1 or 2 for use as lumbosacral implant, the cage (80) comprises a single central support wall (88) which has two bores in the front part with respective upwardly inclined and diverging axes for receiving screws (81a, 81b) for fixing the cage (80) to the upper vertebra and a further bore with a downwardly and rearward inclined axis for receiving a screw (82) for fixing the cage (88) to the lower vertebra.

6. The implant cage (100) as claimed in claims 1 or 2 for use as a thoracic or lumbar implant, wherein in the interior space comprises three evenly spaced support walls (101, 102, 103), and on the sides (104, 105) and on said support walls (101, 102, 103) respective larger central openings (107) and beside it respective smaller openings (108, 109) are provided.

7. The implant cage (100) as claimed in claim 6, wherein from said top (110) and bottom (111) at least one stabilizing spike (112) extends out from the cage (100) in the direction of the adjacent vertebra for temporarily stabilizing the position of the cage (100).

8. A cervical vertebral fixing arrangement and associated implant cage (10) which can be inserted by surgery between two cervical vertebrae and comprises a substantially oblong-shaped body and a frame (33) having two sides (13, 14) and a central support wall (15) to which a support plate (50) can be attached by a releasable connection, and the support plate (50) has a central part (51) that can be connected to the cage (10) and from this central part (51) respective support tabs (54, 55) extend out towards the adjacent vertebrae, and bores (64, 65, 66, 67) are provided on these tabs (54, 55) for receiving special screws (68, 69, 70, 71) that can be inserted into said vertebrae, characterized in that the cage (10) has a top (11) and a bottom (12) both having respective convex shapes that follow the shape of the end surfaces of the adjacent vertebrae, and sides (13, 14) are substantially normal to these convex surfaces, and on the top (11) and the bottom (12) a high number of gaps (21, 22) are provided that extend to the interior of the cage (10) and facilitate ossification and bone ingrowths into the cage (10), and the central support wall (15) has a central threaded bore (18), and the front portion of the central support wall (15) is limited by parallel planar surfaces (19, 20) which are almost parallel with the sides (13, 14) of the cage (10), and from the two sides of the central part (51) two tabs (62, 63) extend out towards the cage (10) which are supported by said two planar surfaces (19, 20) of the central support wall (15) of the cage (10) when the support plate (50) is coupled to the cage (10), and at the central part (51) of the support plate (50) a bore (56) is provided which is in opposite position to the central bore (18) in the central support wall (15) into which a screw (59) can be inserted that connects the support plate (50) with the cage (10).

9. The arrangement as claimed in claim 8, wherein on the top (11) and the bottom (12) there are spaced transversal ribs (23, 24) interconnecting the sides, and the ribs (23, 24) are interconnected with spaced rods (25, 26) extending normal to the ribs (23, 24) which have respective outer surfaces lying more inside than the outer surfaces of the ribs (23, 24), and said gaps (21, 22) are constituted by the spacing between the ribs (23, 24) and the rods (25, 26).

10. The arrangement as claimed in claims 8 or 9, wherein said sides (13, 14) comp- rise respective large openings (30, 31) and said central support wall (15) comprises a further opening (32) which falls in the connection line between said large openings (30, 31).

11. The arrangement as claimed in any of claims 8 to 10, wherein from said top (11) and bottom (12) at least one stabilizing spike (27, 28, 29) extends out from the cage (10) in the direction of the adjacent vertebra for temporarily stabilizing the position of the cage (10).

12. The arrangement as claimed in any of claims 8 to 11, wherein at the central part (51) of the support plate (50) two further bores (57, 58) are provided into which respective securing bolts (60, 61) are inserted which prevent turning of said fixing screw (59).

13. The arrangement as claimed in any of claims 8 to 12, wherein the support plate (50) comprises between the central part (51) and the two support tabs (54, 55) respect ive zones (52, 53) that have decreased thickness.