IMPLANT, ESPECIALLY SPINAL IMPLANT

Description

[0001] The invention relates to an implant, in particular a spinal implant, in the form of a multi-part connecting device serving to couple a fastening element, in particular a pedicle screw, to a connecting element, in particular a connecting rod of a spinal support, with a first part in the form of a saddle having a receptacle for a part of the fastening element and a second part in the form of a tulip having a receptacle for the connecting element in an axially upper region and surrounding the receptacle of the saddle in an axially lower region, wherein in an assembled state of the saddle already mounted in the tulip in a predetermined orientation, said saddle is axially displaceable in the tulip,in order to be able to receive the part of the fastening element in a receiving position when displaced towards the upper area and to no longer be able to release the received part of the fastening element in a holding position when displaced towards the lower area, wherein an axial guide for the axial displaceability has a projection area on the radially outer side of the saddle which engages in a recess area on the radially inner side of the tulip, the end areas of which are spaced apart from one another by at least 30° when viewed azimuthally, and has an axial lock which blocks the axial emergence of the projection area from the recess area in the direction of the upper area.

[0002] Such implants are known, in particular as spinal implants for a spinal support system, and are described, for example, in US 9,486,246 B2. Put simply, it involves connecting two or more vertebrae via a spinal support. For this purpose, a pedicle screw is screwed into a vertebra in a known manner and connected via an implant of the type mentioned above with, for example, a connecting rod in a rigid coupling, with other vertebrae in turn being coupled to this connecting rod via pedicle screws via identical or similar implants in the form of connecting devices. This rigid coupling is based on the above-mentioned holding position, in which an axial force is exerted which pushes the saddle against the sleeve-like tulip, which is achieved by means of a locking screw which can be screwed into the tulip and which acts directly on the saddle or indirectly via the connecting rod when screwed in, with, for example,A conical design of both the lower area of ​​the tulip and the receiving area of ​​the saddle creates a clamping force on the pedicle screw head and thus a rigid coupling between the pedicle screw and the connecting rod.

[0003] To insert the pedicle screw into the connecting device, the saddle can be axially moved from the holding position into a receiving position. This provides more radial space for the receiving area of ​​the saddle to expand, and in this position, the head of the pedicle screw can be gripped by the saddle's receptacle, for example, by clipping it on. In the receiving position, the axial orientation of the pedicle screw relative to that of the connecting device can still be freely adjusted within certain limits (polyaxial connection), even in the holding position, as long as excessive axial forces are not yet exerted. This design allows for efficient use of the connecting device, and the surgeon can achieve the correct positioning of all components of the spinal support under the given conditions before final fixation.

[0004] As an axial guide, a projection on the saddle is provided in the above-mentioned US 9,486,246 B2, which engages in a recess in the tulip. The projection is designed in the form of a rotating nose in order to fit the saddle to the tulip for the deployed state. In this case, cuts between the side walls of the tulip, often U-shaped, and a support area of ​​the saddle for the connecting rod, also U-shaped, are oriented to each other in the assembled state, so that the connecting rod, on the one hand, passes through the U-shaped opening of the tulip and, on the other hand, rests on the U-shaped support of the saddle. Since, in use, the pedicle screw, for example,The axial lock is also provided for the connection of the tulip through a lower opening in the tulip and received by the saddle. This reliably prevents the saddle from axially protruding upwards from the tulip. In the above-mentioned prior art, this is achieved by a shoulder delimiting the recess, against which the projection / rotating lug of the saddle abuts. To prepare such a connecting device for use, the rotating lug is inserted axially into the tulip, starting from an orientation of the saddle rotated by 90° relative to the operating state, and then screwed from this rotated orientation into the recess of the tulip.

[0005] US 2010 / 0145394 A1 teaches a pedicle screw with limited pivoting within a plane in a tulip. EP 2 286 748 A1 teaches a simple assembly of an implant, according to which the pedicle screw and then the saddle are inserted from above into the tulip of the implant.

[0006] US 2018 / 0014862 A1 discloses a variant in which the saddle is inserted into the tulip from below. In US 2017 / 0086895 A1, the bottom opening of the tulip is also designed for axial insertion of the saddle from below. In the variant disclosed in US 2015 / 0230829 A1, projections of the saddle, which are aligned with the U-shaped channel for rod insertion, engage with recesses in the tulip, which are aligned with the U-shaped channel for rod insertion.

[0007] EP 3 158 957 A1 discloses an implant which, according to the assembly of saddle and tulip, is designed similarly to the above-mentioned US 9,486,246 B2.

[0008] The invention is based on the object of improving an implant in the form of a connecting device of the type mentioned above, in particular with regard to its reliability.

[0009] This object is achieved by the invention by an implant having the features of claim 1.

[0010] Advantageous developments of the invention are the subject of the dependent claims.

[0011] The implant has a rotation lock that prevents the projection area from rotating into the recess area and, in the assembled state, prevents the projection area from rotating out of the recess area.

[0012] Thus, the invention departs from the teaching of the aforementioned US Pat. No. 9,486,246 B2 by preventing the inward and outward rotation of the rotating lug provided therein. Within the scope of the invention, it has been discovered that, with the inventive design, increased positional stability of the tulip and saddle is achieved, and consequently, increased positional stability of the entire spinal support relying on it. This has a particularly positive effect when the spinal support is worn for extended periods of time, thus potentially avoiding premature readjustment, which is unpleasant for the wearer.

[0013] The explanations given above regarding polyaxial coupling, receiving position, and holding position also apply to the present invention. This means that in use, i.e. during implantation, the connecting device can be placed in the assembled state onto the head of a polyaxial screw, wherein in preferred variants a receiving area of ​​the saddle is clipped onto the screw head (in the receiving position). If the screw and tulip are then pushed in different directions (holding position), the lower area of ​​the saddle strikes the lower area of ​​the sleeve-like tulip, preventing the pedicle screw from escaping axially from the lower opening of the tulip. However, rotating the head in the receptacle is still possible, which is equivalent to pivoting the tulip relative to the pedicle screw (polyaxial adjustment option).Only when, for example, the connecting rod inserted into the tulip / saddle is firmly coupled using a locking screw, does the clamping force of the interaction between the tulip and the saddle ensure that the screw head is firmly clamped and thus that there is a rigid coupling between the pedicle screw and the connecting rod of the spinal support.

[0014] The projection region preferably rises from a wall-like saddle region, which is itself flat and curved, in particular circular in cross-section relative to the axial direction. In a particularly preferred embodiment, the arc length between the azimuthal end regions of the projection region is several times, in particular at least twice, preferably at least three times, in particular at least four times longer than a dimension of the projection region in the axial direction.

[0015] In a particularly preferred embodiment, two such axial guides are provided, in particular offset by 180°, particularly in a symmetrical arrangement. Both axial guides, together with their end regions, ensure that the saddle is guided in the tulip at least in areas that, viewed in cross-section, are distributed like the end points of an "X," whose center passes through the axial axis and whose top-bottom direction is rotated by 90° relative to the position of the connecting rod.

[0016] According to the invention, the tulip has two azimuthally spaced side walls in the upper region, between which the receptacle for the connecting element is located. A recessed area of ​​the axial guide is arranged in each of the side walls. These side walls are preferably also arcuate, in particular circular, when viewed in cross-section.

[0017] Preferably, a thread is provided on the inside of the side walls for screwing in a locking screw, by means of which an axial force can be exerted on the saddle, particularly via the connecting element. However, designs with external threads on the side walls of the tulip and the use of a screw cap are also conceivable.

[0018] According to the invention, the saddle has, on the side facing away from its receptacle, two walls arranged in the predetermined orientation corresponding to the side walls, each supporting a projection region of a respective axial guide. Between these walls, a free space is also formed, preferably U-shaped in axial section, which, when aligned with a corresponding free space in the tulip, can form a receiving channel for the connecting rod.

[0019] To achieve the assembly state, the saddle is inserted into the tulip from above, i.e. from the axially upper area (i.e. the side facing away from the holder for the part of the fastening element), in the axial direction of the axial guide (axial entry from above).

[0020] According to the invention, the walls of the saddle have an elastic flexibility that allows the saddle to enter the tulip axially, overcoming the axial lock, and prevents radially inward bending during assembly. This facilitates axial assembly without predominantly plastic deformation of the components.

[0021] In a practical design, the thread has a notch on one or both side walls to facilitate axial insertion of the saddle into the tulip. This facilitates axial insertion while maintaining a compact design in terms of radial dimensions.

[0022] Furthermore, it is preferred that the azimuthal end regions of one or both projection regions be spaced apart by at least 36°, in particular at least 42°. This further increases the guiding stability of the axial guide.

[0023] In a practical embodiment, the recessed area(s) have / have a shape that is complementary to the shape of the projection area, either in a section orthogonal to the axial direction, either in certain areas or as a whole. This prevents jamming during axial displacement.

[0024] In a further advantageous embodiment, one or both projection regions are continuous in cross-section orthogonal to the axial direction and are formed, in particular, as a crescent-shaped projection. This facilitates precision accuracy during the manufacture of the saddle.

[0025] Furthermore, it is expediently provided that one or both projection areas form a particularly substantially rectangular step upwards, viewed in axial section, and / or a blunt step downwards. This ensures low transverse forces while maintaining the intended axial lock, yet allows for easier overcoming of the axial lock when establishing the assembly state.

[0026] In a suitable embodiment, the walls of the saddle have on their inner side a holding bearing, in particular a thread, which serves to decouple an elongated instrument, which instrument serves to release the fastening element by axially holding the saddle in the receiving position with part of the fastening element received in its receptacle.

[0027] With regard to the saddle receptacle, it is preferably provided that it is a receptacle that holds the head of a pedicle screw, particularly by means of elastic clipping, and in particular encompasses beyond a region of the maximum head diameter. This ensures simplified handling when the coupling between the screw and the connecting device is not yet rigid.

[0028] A further component of the connecting device can be a locking screw, in particular a one-piece one, with a thread designed to match the thread of the side walls.

[0029] Furthermore, the invention also provides protection for an implant set comprising at least one connecting rod, in particular of round cross-section, at least two pedicle screws and at least two implants according to one of the aforementioned aspects in the assembled state, into which the heads of the pedicle screws can be inserted through an opening at the end of the lower region of the tulip and can be received by the seat of the saddle.

[0030] Such an implant set may also include an instrument having a thread designed to match the thread of the walls of the saddle for holding the saddle in the receiving position relative to the tulip.

[0031] Further features, details and advantages of the invention will become apparent from the following description of the invention with reference to the accompanying figures, of which Fig. 1 shows a saddle in a tulip in a partially different representation, Fig. 2 a sectional view of a lower area of ​​the arrangement of Fig. 1 with the pedicle screw held, Fig. 3 is a view of the shape of the saddle's protrusion areas in an azimuthal plane, Fig. 4 shows a notch in a threaded section, Fig. 5 shows intermediate stages of an axial assembly in perspective view, front view and in axial section, and Fig. 6 shows a different design of protrusion areas than those in Fig. 3 shown shows.

[0032] Fig. 1 outlines the basic structure of a part of a connecting device to be implanted, namely a combination of a tulip 1 and a saddle 2 arranged in the tulip 1. In the illustration of Fig. 1 The right half of the image shows a front view, the left half of the image is further divided into an elevation view in the right area to the left of the axial axis X of the connecting device, and a sectional view on the far left of the image area.

[0033] With respect to the axial axis X, the tulip 1 forms a sleeve-shaped part with an upper end 11 and a lower end 12. Starting from the upper end 11, a channel with direction Y perpendicular to the plane of the paper is formed through a U-shaped recess in the part of the sleeve wall facing the viewer and facing away from him. Fig. 1 formed. As Fig. 1 and Fig. 5a As is immediately apparent, the side walls 18L, 18R arranged laterally on both sides of the U-shaped recess (seen transversely to the direction Y of the channel) comprise the recess area 14 of the axial guide. Fig. 1 connecting rod, not shown, which connects in a manner known to the person skilled in the art several connecting devices of the type shown, which in turn are also Fig. 1 pedicle screws (not shown). The connecting rod can be inserted laterally (in the Y direction) or from above along the axial direction X. The rod is fixed to the connecting device via a clamping screw (not shown), such as a grub screw, which is screwed into the internal thread 13 formed in the upper area of ​​the tulip 1.

[0034] The saddle 2 also has a U-shaped recess in its upper area, which forms a channel which is in the Fig. 1 shown position intended for use runs parallel to the channel of the tulip 1.

[0035] In the Fig. 1 In the assembly position shown, ready for use, the saddle 2 is axially displaceable in the tulip 1 by means of an axial guide. For this purpose, a recess 14 is formed in the side walls 18L, 18R remaining in the upper region due to the U-shaped cutout of the tulip 1, approximately halfway up the height of the tulip 1, which is delimited in the axial direction downwards by a shoulder 15 and in the axial direction upwards by a shoulder 16. A projection 24 is guided in the recess 14, which is arranged in the upper region of the saddle 2 on the radially outer side of the upper saddle wall 28L. It can be seen that the saddle 2 is made of the Fig. 1 In the relative position shown relative to the tulip 1, it is axially upwardly displaceable relative to it until the upper end 26 of the projection 24 strikes the shoulder 16. In this way, an axial lock is provided which prevents further displacement of the saddle 2 in the tulip 1 towards its upper end 11. The same axial guide is found on the right side on the second wall 18R.

[0036] In its lower area, the saddle 2 is formed in the form of a basket-like receptacle, with holding sections 22 separated from each other by gaps 21. The basket-like receptacle can ( Fig. 2 ) receive the head 32 of a pedicle screw 3. If, for example, a pedicle screw 3 has already been screwed into a vertebra, the tulip 1 with the saddle 2 located therein can be slipped onto the screw head 32. In doing so, the saddle 2 initially moves upwards in the tulip 1. As soon as the saddle 2, with its maximum radial dimension in the lower area, reaches the area (indicated by the dashed line ZM) in which the tulip 1 has a larger inner diameter than at the lower end 12 due to an inner curvature, the holding sections 22 can bend elastically radially outwards, receive the screw head 32 like a clip and, with the screw head 32 received, engage over it beyond an area of ​​the maximum screw head diameter.

[0037] In this position, which is known to the person skilled in the art, the orientation of the screw axis relative to the axial axis X can be pivoted from a parallel position in any spatial direction by a certain angle (polyaxial coupling before the rigid fixation between pedicle screw 3 and connecting device).

[0038] According to a mechanism also known from the art, the ultimately desired rigid coupling between the connecting device consisting of tulip 1 and saddle 2 and the pedicle screw 3 is achieved in that the clamping screw screwed into the thread 13 presses the saddle 2 in the tulip 1 downwards via the connecting rod, until, due to the particularly conical narrowing of the opening of the tulip 1 in the lower area towards the lower end 12, the holding sections 22 are pushed radially inwards and hold the screw ever more tightly until the rigid coupling (conical clamping), which is achieved by screwing the screw (not shown) into the thread 13.It is understood that if the screw is already slightly tightened but not yet fully tightened, a favorable situation arises for the implanting surgeon in that he can still change the relative position between the screw and tulip 1 by applying targeted force, but no unintentional change in the position occurs.

[0039] As better seen in the upper left figure of Fig. 5 As can be seen in column a), the recess 14 is also limited in the azimuthal direction (direction of rotation in the YZ plane) and does not open towards the U-shaped notch between the side walls 18L and 18R. The projection area 24 of the saddle 2 is therefore, as in Fig. 5c and Fig. 1 visible, in the recess 14 in the respective side wall 18L, 18R. The rotation lock formed thereby prevents rotation of the saddle 2 in the tulip 1 with axial axis X as the axis of rotation from the Fig. 1 Conversely, saddle 2 could also be formed from a position opposite to that shown in Fig. 1 shown position rotated by 90° around the axial axis X does not fit into the position shown in Fig. 1 shown position, since the rotation lock acts in both directions with respect to the azimuthal direction. Therefore, the insertion / introduction of the saddle 2 into the tulip 1 cannot be carried out via the rotational movement as in the prior art. Rather, it is carried out from above along the axial axis X, as can be seen from Fig. 5a is recognizable.

[0040] The production of this in Fig. 1 shown operating condition, i.e. the assembly of the components saddle 2 and tulip 1 is carried out purely axially, as in Fig. 5 shown. Fig. 5 shows three different representations, from top to bottom in perspective view, front view and section view, the intermediate stages of such an assembly process. In the left illustration of Fig. 5a ) shows how saddle 2 is arranged above tulip 1 coaxially to the common axial axis X with aligned channels formed by the respective U-shaped recesses. Starting from this position, the saddle 2 is inserted axially through the opening on the upper side 11 of the tulip 1, initially essentially force- and deformation-free, until the Fig. 5b ) is reached. For this purpose, in the illustrated embodiment, a recess 13A is provided in the thread ribs of the thread 13. Furthermore, in this embodiment, the dimensional relationships in the radial direction are such that the projections 24 also at least partially use the space formed by the recesses 13A during axial insertion, in other words, the axial insertion would be more difficult without the recesses 13A. The recess 13A is shown in a section of a cross-section taken at the level of a thread rib of the thread 13 in Fig. 4 shown.

[0041] Based on the Fig. 5b ) shown position, further insertion without exerting too much force is no longer possible due to the axial lock 16, 26 described above. However, by then force-loaded insertion, the walls 18L, 18R are elastically pushed radially inwards until the resistance is overcome and the projection 24 can enter the recess 14 at the level of the shoulder 26 with elastic recovery of the walls 18L, 18R. The assembly position is then reached, which is shown in Fig. 5c ), which is essentially Fig. 1 corresponds.

[0042] In this embodiment ( Fig. 3 ), the azimuthal extension of the projections 24L, 24R is approximately 50°. Regardless of the exact shape of the projection 24, particularly in a central region between its end regions, it is preferred that the azimuthal end regions of the projection region have an azimuthal spacing in the regions described above in order to achieve the most stable guidance of the axial guide. For this purpose, the projection region could also be provided with a material accumulation offset closer to the azimuthal end regions, such as in Fig. 6 shown, more weight at the end areas 24'a, b, c, d than central 24'm.

[0043] As shown in the axial section in the enlarged lower illustration of Fig. 5b ), the lower surface 27 of the projection 24 and the upwardly facing surface 17 of the shoulder 16 are not orthogonal to the axial direction X, but rather conical, in order to facilitate overcoming the axial lock when establishing the assembly state. Viewed in axial section, the projection 24 can thus have a basic step shape, with an essentially 90° step for the upper surface 26 and an oblique step to the lower surface 27 (with a more or less obtuse angle).

[0044] Seen in cross section, it has a crescent-shaped design ( Fig. 3 ) of the projection areas is preferred, other designs are conceivable (e.g. Fig. 6 ), whereby, as explained above, a minimum azimuthal distance is to be maintained.

Claims

1. An implant formed as a multi-part connecting device for coupling a fastening element (3) to a connecting element, comprising: a first part (2) formed as a saddle (2) having a receptacle for a part of the fastening element; and a second part (1) formed as a tulip (1) which, in an axially upper region, has a receptacle for the connecting element and, in an axially lower region, surrounds the receptacle of the saddle (2), wherein the tulip (1) has, in the upper region, two azimuthally spaced side walls (18L, 18R), between which the receptacle for the connecting element sits, wherein, in an assembly state of the saddle (2) already mounted in a predefined orientation in the tulip (1), the saddle is movable axially (X) in the tulip (1) so that, when moved in the direction of the upper region, said saddle in a receiving position is able to receive the part of the fastening element, and so that, when moved in the direction of the lower region, said saddle in a holding position is no longer able to release the received part of the fastening element, wherein the fastening element is received in a polyaxial coupling and the implant is configured for receiving, in the saddle, the fastening element inserted through a lower opening of the tulip, wherein an axial guide (14, 24) that provides axial mobility comprises a projection region (24) on an outer face of the saddle (2), when viewed radially, which engages a recess region (14) on an inner face of the tulip (1), when viewed radially, wherein the saddle (2), on a face facing away from the receptacle, has two walls (28L, 28R) arranged in the predefined orientation corresponding to the side walls (18L, 18R) of the tulip, each wall bearing such a projection region, and wherein the azimuth spacing of the end regions of the projection region (24), when viewed azimuthally, is at least 30°, and wherein the axial guide also comprises an axial lock that blocks the projection region (24) against axially exiting the recess region (14) in the direction of the upper region; wherein the implant further comprises: a rotary lock that prevents the projection region (24) from rotationally entering the recess region (14) and, in the assembly state, prevents the projection region (24) from rotationally exiting the recess region (14); and wherein the tulip (1) and saddle (2) are configured to produce the assembly state by inserting the saddle (2) into the tulip (1) axially from above, when viewed in the axial direction of the axial guide and to this end the walls (28L, 28R) of the saddle (2) have an elastic resilience against radially inwardly directed bending, which allows the saddle (2) to enter the tulip (1) axially, overcoming the axial lock, when the assembly state is produced.

2. The implant according to claim 1, comprising two such axial guides, in particular axial guides arranged with a 180° offset.

3. The implant according to claim 1 or 2, comprising a thread (13), provided on the inner face of the side walls (18L, 18R), for screwing in a locking screw by means of which an axial force can be exerted on the saddle (2), in particular via the connecting element.

4. The implant according to one of claims 1 to 3, wherein the thread (13) has, on one or both side walls, a notch (13A) that facilitates axial entry of the saddle (2) into the tulip (1).

5. The implant according to one of claims 1 to 4, wherein the azimuthal spacing of the azimuthal end regions of one projection region or both projection regions is at least at least 36°, in particular at least 42°.

6. The implant according to one of the preceding claims, wherein the recess region(s), when viewed in a section orthogonal to an axial direction, has / have a shape that complements a shape of the projection region.

7. The implant according to claim 6, wherein one or both projection region(s), when viewed in a section orthogonal to the axial direction, is / are continuous and in particular is / are formed as a crescent-shaped projection.

8. The implant according to claim 7, wherein one or both projection region(s), when viewed in an axial section, forms / form, in an upward direction, an in particular substantially rectangular step and / or, in a downward direction, a reflex step.

9. The implant according to one of the preceding claims, wherein the walls of the saddle (2) have, on their inner face, a thread for coupling an elongate instrument, which instrument serves to release the fastening element by axially holding the saddle (2) in the receiving position while part of the fastening element is received in the receptacle of the saddle.

10. The implant according to one of the preceding claims, wherein the receptacle of the saddle (2) is a receptacle (22) that holds the head of a pedicle screw, in particular by means of elastic clipping, and in particular engages beyond a region of the maximum diameter of the head of the pedicle screw.

11. The implant according to one of the preceding claims, comprising a locking screw having a thread that matches the thread (13) of the side walls.

12. A spinal implant, formed by an implant according to one of the preceding claims, wherein the multi-part connecting device is used to couple a pedicle screw to a connecting rod of a spinal support.

13. An implant set comprising at least one connecting rod, which in particular has a round cross-section, at least two pedicle screws and at least two implants according to one of claims 1 to 12 in the assembly state, wherein the heads of the pedicle screws can be inserted into the tulip (1) through an opening at the end (12) of the lower region of the tulip (1) and can be received by the receptacle of the saddle (2).

14. The implant set according to claim 13, comprising an instrument having a thread matching the walls (28) of the saddle (2), for holding the saddle (2) in the receiving position relative to the tulip (1).