Anterior cervical plate

Abstract

An anterior cervical plate (10) with receiving openings (12, 12*) for bone screws is described. To give the anterior cervical plate with locking option for inserted bone screws an optimized anatomical design to reduce swallowing difficulties and tissue irritation, the cervical plate (10) with a normal thickness DN, i.e., the raw thickness of the plate without machined surfaces, tapers at least at its cranial end section (AE) starting at a distance AK from a cranial edge (60), for which the following applies: 0.5 × DN ≤ AK ≤ 3 × DN, preferably 1 × DN ≤ AK ≤ 2.5 × DN Based on a Cartesian coordinate system with an X-axis in the longitudinal direction, a Y-axis in the transverse direction, and a Z-axis in the thickness direction of the plate (10) in the direction of its thickness extension up to an edge-side rounding section (RA) at 25% to 80% of the normal thickness DN. The tapering of the anterior cervical plate in the transverse direction is achieved by a rounding starting from approximately the center of the bores to the end of the plate.

Description

Technical field

[0001] The present disclosure relates to an anterior cervical plate with at least one locking element for a bone screw inserted therein. Such systems are used for mono- and multi-segmental stabilization of the cervical spine.

[0002] Several cervical plate systems are available on the market, differing, among other things, in their locking mechanisms for the bone screws used. Such plate systems are already marketed by the applicant under the name Quintex and, for example, by companies such as Bricon (under the name Shark CP Pro), Zimmer (Trinica), Medtronic (Zevo), Stryker (Ozark), Biomet (Maxan), DePuy Synthes (Skyline), Globus Medical (Assure), Nuvasive (C360), and Biomed (Quantum).

[0003] The cervical plate system according to US 8,906,077 B2 or EP 2 217 163 B1 uses a locking element in conjunction with a separate fixing element.

[0004] In the system according to US 7909,859 B2, the screws are secured against loosening by means of clamps.

[0005] The system according to US 8,500,737 B2 uses either a snap ring that slides in a longitudinal guide or a sliding plate to secure the inserted bone screw.

[0006] The cervical plate known from document US 10,492,836 B2 is equipped with a locking mechanism in the form of a wing nut, which is secured to the cervical plate by means of a clamping nut inserted from the rear of the cervical plate. A similar locking element is used in the system according to US 8,480,717 B2.

[0007] A screw locking system according to DE 202 21 560 U1 uses a washer with an elongated hole that can be moved on the underside of the screw head in question.

[0008] The locking system according to US 8,778,001 B2 provides locking plates that are held in place by spring-loaded spreader legs in an undercut groove of the cervical plate.

[0009] The plate system according to US 8,747,441 B2 uses spring-loaded C-rings or slotted rings as locking elements, which are received in a corresponding groove in the cervical plate.

[0010] The locking mechanism according to US 8,702,766 B2 uses a rotatable plate body per screw with a radially and circumferentially projecting spring arm, at the distal end of which a claw body is located. When the plate body is rotated, the claw body is forced into an undercut guide groove in the plate by bending deformation of the spring arm, and snaps into a recess in the plate upon reaching the locking position. This design requires a greater plate thickness due to the undercut.

[0011] The cervical plate system according to US11,166,755 B2 secures two adjacent bone screws by means of spring rings that snap over the respective screw head and can be expanded with an adjusting screw located laterally between adjacent screw holes.

[0012] In the generic cervical plate system known from document EP 1 737 365 B1, the locking element for the screws is formed by a spring plate which is received in a longitudinal guide.

[0013] Conventional cervical plates, which are typically equipped with a locking system, must be manufactured with a thickness that allows for the secure and unobtrusive integration of the locking components. The thickness of the cervical plate cannot be arbitrarily reduced, partly because the plate must be securely gripped by handling instruments attached to it during insertion. It has been observed that such known cervical plates, which are generally formed from slightly rounded rectangular plates, cause swallowing difficulties once inserted.

[0014] The application is based on the task of creating an anterior cervical plate with a locking option for inserted bone screws, which, while maintaining sufficient stability and good handling during insertion of the plate, can better prevent swallowing difficulties.

[0015] This problem is solved with an anterior cervical plate according to claim 1. Accordingly, the cervical plate, with a substantially constant normal thickness DN (i.e., the raw thickness of the plate without machined surfaces), is machined at least at its cranial end section at a distance AK from a cranial edge edge, for which the following applies: 0.5×DN≤AK≤3×DN, preferably 1×DN≤AK≤2.5×DN Based on a Cartesian coordinate system with an x-axis in the longitudinal direction, a y-axis in the transverse direction and a z-axis in the thickness direction of the plate, the plate tapers in the direction of its thickness extension to a rounded section at the edge in the x-direction, to 25% to 80% of the normal thickness DN, where the normal thickness of the plate can be in a range between 1 and 3 mm. This taper is superimposed on a further taper of the anterior cervical plate in the transverse direction, which is formed by a rounding starting from a central area of ​​the edge-side receiving openings to the plate end, i.e. to the edge of the plate.

[0016] According to the new design, the cervical plate, at least in its cranial end region, is given a new shape: a geometrically flattened and rounded form at the ends of the plate. This ensures that tissue can glide over it with minimal resistance. This effectively prevents postoperative swallowing difficulties without weakening the stabilizing function for the vertebral bodies outside the end region.

[0017] It is an additional advantage if the anterior cervical plate features an undercut instrument interface in a central area. This design allows a surgical insertion instrument for the plate to be inserted into this interface without protruding beyond the plate's edge. This effectively prevents the surgical instrument from colliding with bone or other areas of the wound. Simultaneously, this instrument interface offers the additional benefit of accommodating a pin for the temporary fixation of the cervical plate to the vertebral bodies, thus facilitating easier alignment of the plate on the patient.

[0018] The new design of the cervical plate can be further supported if it is to be equipped with functional surfaces for receiving a locking device for inserted screws, provided that the functional surfaces are limited to at least one bore for receiving a bearing pin of at least one locking disc that can be pivoted by hand.

[0019] The stability of the cervical plate becomes particularly high in areas outside its end sections if the diameter of a bore for receiving the bearing pin for the axis of rotation of a locking body is limited to values ​​in the range between 1.2 and 3.5 mm.

[0020] The undercut instrument interface can be formed and produced particularly easily if it is shaped like a keyhole and opens onto a window that is already regularly formed in the cervical plate, which further facilitates the insertion of the surgical instrument.

[0021] If the cervical plate tapers in the cranial end section in the direction of the Z-axis, i.e. in the thickness direction, initially in a slightly arc-shaped manner and starting with an edge that is essentially in the middle of the end section, then the tissue-protecting function can be optimally adapted via the position of the edge.

[0022] The following schematic drawings describe exemplary embodiments of the new anterior cervical plate in more detail. They show: Brief description of the characters Fig. 1. A perspective view of a cervical plate from below; Fig. 2 a perspective view of the cervical plate of the Fig. 1 from the top; Fig. 3 the enlarged perspective view of an end section of the cervical plate according to Fig. 1 and Fig. 2; Fig. 4 a longitudinal sectional view of a cervical plate, somewhat modified with respect to the openings formed in it, in the area of ​​its cranial end section; Fig. 5 a partially broken side view of the cervical plate according to Fig. 4; Fig. 6. Top view of a cervical plate modified with respect to its segments; Fig. 7 the side view of the cervical plate according to Fig. 6; and Fig. 8 the view of the cervical plate according to Fig. 6 from the bottom Description of the exemplary implementations

[0023] The following are examples of embodiments of the present disclosure based on the accompanying figures. First embodiment

[0024] In the Fig. Figures 1 to 3 show a first embodiment of an anterior cervical plate 10. The cervical plate 10 is symmetrical to a Fig. 1 schematically drawn plane of symmetry ES and has 6 approximately circular receiving openings 12 for bone screws not shown in detail and one window 14 per segment. To describe the geometry of the cervical plate 10, a Cartesian coordinate system with axes X, Y and Z is used, which is shown in the figures, in which the X-axis extends in the longitudinal direction, the Y-axis in the transverse direction and the Z-axis in the thickness direction of the cervical plate 10.

[0025] The contact surfaces for the heads of the bone screws are not described in detail; they are preferably designed to consist of a spherical surface or a spherical surface in combination with a conical surface, thus allowing the use of both angularly restricted (constrained) and angularly variable screws. The cervical plate 10 shown is therefore a so-called two-segment hybrid plate, in which translational screw slippage is prevented.

[0026] In a manner known per se, the cervical plate 10 is pre-bent longitudinally with a normal thickness DN measured in the Z-direction, i.e. a thickness measured on the blank without any machining surfaces (as shown in the diagram). Fig. 1 and Fig. 2) and - as can be seen from the sectional view according to Fig. 5 recognizable - slightly curved in the transverse direction in order to conform as closely as possible to the shape of the cervical spine.

[0027] The cervical plate 10 is equipped with a locking mechanism for the bone screws that are inserted and screwed into the cervical vertebrae. This locking mechanism prevents the bone screws from migrating out of the plate.

[0028] The locking mechanism is designed such that a locking body 16 consists of a Fig. 2 shown, a receiving opening 12 can be brought into a locking position in which the screw head lying in the receiving opening 12 is at least partially covered by the locking body 16 and thus the migration of the screw is prevented.

[0029] In the illustrated embodiment, three locking elements 16 are provided, each associated with two adjacent receiving openings 12 and each arranged substantially centrally between two adjacent receiving openings 12. Each locking element 16 is formed by a thin disk 16 rotatably fixed to the anterior cervical plate 10 about a rotation axis A16 that is substantially perpendicular to the cervical plate 10. This disk has at least one locking arm 18-1 and 18-2 angularly distributed around its circumference and a support section 20 extending about a specific central angle. This support section 20 is disengaged by rotating the disk 16 through a predetermined angle of rotation. Fig. The open position shown in section 2 snaps into a locking position that secures the bone screws.

[0030] The rotatability of the disk 16 is provided by a hollow bearing journal 22, preferably formed integrally with the disk 16, which fits with clearance in a bore 24 (see Fig. 3) is received in the cervical plate 10 and riveted therein on the underside of the plate 10. The locking element, in the form of a disc 16 with a hollow bearing pin 22, which has a multi-sided recess 42, e.g., an internal hexagonal recess for an actuating tool, e.g., a screwdriver, is cannulated in this way, which can be used to pull the bearing pin 22 as a guide for a temporary fixation pin to fix the cervical plate 10 to the spine.

[0031] The dimensions of disc 16 are chosen so that they only minimally increase the overall thickness of the cervical plate system. For example, the thickness D16 (see Fig. 4) of the disc 16 in the case that the normal thickness DN of the cervical plate 10 is between 1.5 and 2.5 mm, in the range between 0.25 and 0.75 mm.

[0032] In this case, the diameter D22 of the bearing journal 22 is in the range between 1.2 and 3.5 mm.

[0033] A special feature of the locking mechanism is that it incorporates a detent mechanism. For this purpose, the support section 20 interacts with a detent pin 30 mounted on the cervical plate 10, which, when the disc 16 is rotated, deforms the support section 20 before it reaches the detent position, and thus before the disc 16 snaps into the detent position.

[0034] Another special feature of the anterior cervical plate is that the cervical plate 10 is connected to a Fig. The normal thickness DN, as designated in section 4, tapers in a special way at least at its cranial end section AE in the direction of the Z-axis, i.e., in its thickness extension. The tapering of the anterior cervical plate in the transverse direction occurs via a rounding starting from approximately the middle of the openings 12 or bores to the end of the plate. Thus, the plate decreases continuously at its ends in both width and thickness. This tapering begins for the thickness at a distance AK (see Fig. 2 and Fig. 4) from a cranial edge 60, where the distance AK is: 0.5×DN≤AK≤3×DN, preferably 1×DN≤AK≤2.5×DN

[0035] The thickness of the cervical plate 10 tapers – as is best seen in the Fig. Figure 4 shows the following: in the longitudinal direction, i.e., along the X-direction, such that at a rounded section RA at the edge, which comprises between 10 and 30% of the cranial end section, the thickness is only 25% to 80% of the normal thickness DN. This thickness is in Fig. 4, denoted by DRA. The tapered cross-section, viewed in a longitudinal section, i.e., in a section through a mid-plane of the plate parallel to the X-axis, is in Fig. 3 is marked with coarse hatching; the tapered surface extending in the direction of the Y-axis, i.e., in the transverse direction, is marked with finer hatching.

[0036] In the Fig. 4 and Fig. Figure 5 shows the geometry of the shaping of the cranial end section in detail.

[0037] The cervical plate, which has a small normal thickness in the range between 1.5 and 2.5 mm, tapers starting at a distance AE from the edge 60, i.e. in the embodiment according to Fig. 4 approximately in the region of the cranial receiving opening 12*, initially slightly curved to a first edge 62, which lies essentially in the middle of the end section AE. The distance of the first edge 62 from the edge section RA is in Fig. 4 is labelled A62 and lies in the range between 0.1 and 0.55 x AK.

[0038] From there, the thickness of the plate decreases in the X-direction, i.e., in the longitudinal direction, preferably linearly, until at a second straight edge 63 the rounded section RA is reached with a thickness DRA that is only 25 to 80% of the normal thickness DN (see Fig. 4, in which the reference lines shown with dashed lines lie on the lower and upper surfaces of the plate) of the cervical plate 10. This linear progression up to the rounding section RA is in Fig. 4 indicated by the tangent T.

[0039] The tapering of the terminal section of the cervical plate 10 in the direction of the Y-axis, i.e., in the transverse direction, i.e., the decrease in the width of the plate, is—as can best be seen from the Fig. 1 and Fig. 2 is evident - formed by a fillet 64, for example with a radius R. The fillet 64 thus overlaps with the reduction in thickness in the direction of the X-axis, i.e., in the longitudinal direction. The end of the plate is formed by combining the two radii R of the fillets 64 with a third, larger radius RZ (see Fig. 3) are connected, resulting in a slightly convex curved edge 60. The radius of curvature RZ of the edge 60 is a multiple of the radius R of the fillet 64. As shown, both the width (ΔY) and the thickness (ΔZ) of the plate decrease in the longitudinal direction. In the transverse direction, i.e., in the direction of the Y-axis, the fillet with radii R and RZ extends to the median plane EM of the plate, which overlaps with the taper directed in the Z-direction along the X-axis.

[0040] The functional surfaces required on the cervical plate 10 for mounting the locking device for inserted screws, i.e., the locking body 16 in the configuration of the discs with a bearing pin 22, are limited to the bore 24 for receiving the bearing pin 22. It has been found that the diameter of the bore 24 for receiving the bearing pin 22 can be in the range between 1.2 and 3.5 mm.

[0041] The cervical plate 10 features additional provisions for handling the plate with a surgical insertion instrument that minimizes mechanical stress. For this purpose, the plate 10 has an undercut instrument interface 70 in a central area, through which the cervical plate 10 can be connected to a surgical insertion instrument. This has the advantage that the insertion instrument no longer protrudes beyond the edge of the cervical plate, thus preventing collisions between the instrument and bone. Simultaneously, recesses in the instrument interface 70 can be used for inserting temporary fixation pins, which facilitate simple and precise alignment of the cervical plate on the cervical spine.

[0042] As in Fig. 1 and Fig. As shown in Figure 2, the undercut instrument interface 70 is keyhole-shaped and open to a window 14 of the cervical plate 10. Second embodiment

[0043] In the Fig. Figures 6 to 8 show another embodiment of the cervical plate, which has reference numeral 110. The cranial and dorsal end sections, as well as the locking devices, are designed in the same way as in the embodiment of the Fig. Steps 1 to 5 are completed, so a description is unnecessary.

[0044] The cervical plate 110 is designed as a hybrid 5-segment plate. Accordingly, two instrument interfaces 170 can be formed at a central window 114.

[0045] Of course, variations of the described embodiments are possible without abandoning the basic idea of ​​the innovation.

[0046] The design is equally suitable for anterior cervical plates prepared for constrained fixations and for so-called dynamic plates for dynamic fixations. The term "constrained" refers to limited stability / stiffness of the connection between the plate and screw, while "dynamic" refers to mobility (rotational and / or translational) between the screw and plate.

[0047] The innovation thus creates an anterior cervical plate with receiving holes for bone screws and windows located between these receiving holes. To give the anterior cervical plate with locking option for inserted bone screws an optimized anatomical design to reduce swallowing difficulties and tissue irritation, the cervical plate tapers to a normal thickness DN (i.e., the raw thickness of the plate without machining surfaces), starting at least at its cranial end section at a distance AK from a cranial edge, for which the following applies: 0.5×DN≤AK≤3×DN, preferably 1×DN≤AK≤2.5×DN in the direction of its thickness extension up to an edge-side rounding section RA to 25% to 80% of the normal thickness DN. In addition, this tapering in the thickness direction is superimposed with a tapering in the transverse direction, which is formed by a rounding starting from a central area of ​​the edge-side receiving openings to the edge edge of the plate. Reference symbol list 10 cervical plate 12 absorption breakthroughs 14,114 windows 16 locking elements as discs D16 Thickness of 16 18-1, 18-2 locking arms 20 Support section 22 bearing journals 24 bore 30 locking pins 42 Multi-sided recess 60 edge 62 first edge A62 Distance of the edge 63 second edge 64 rounding 70, 170 Instrument interface DN Normal thickness AE End section AK distance RA rounding section DRA thickness of RA T tangent ES symmetry plane QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] US 8,906,077 B2

[0003] EP 2 217 163 B1

[0003] US 7909,859 B2

[0004] US 8,500,737 B2

[0005] US 10,492,836 B2

[0006] US 8,480,717 B2

[0006] DE 202 21 560 U1

[0007] US 8,778,001 B2

[0008] US 8,747,441 B2

[0009] US 8,702,766 B2

[0010] US 11,166,755 B2

[0011] EP 1 737 365 B1

[0012]

Claims

[1] Anterior cervical plate (10) with receiving holes (12) for bone screws and, if applicable, windows (12) located between the receiving holes (12), characterized by , that the cervical plate (10; 110) with a normal thickness DN, i.e. the raw thickness of the plate without machined surfaces, at least at its cranial end section (AE) starting at a distance AK from a cranial edge (60), for which the following applies: 0.5×DN≤AK≤3×DN, preferably 1×DN≤AK≤2.5×DN based on a Cartesian coordinate system with an X-axis in the longitudinal direction, a Y-axis in the transverse direction and a Z-axis in the thickness direction of the plate (10) tapers in the direction of its thickness extension to a marginal rounding section (RA) to 25% to 80% of the normal thickness DN, wherein this taper is superimposed on a further taper of the anterior cervical plate in the transverse direction, which is formed by a rounding (64) starting from a central area of ​​the marginal receiving openings to the edge of the plate. [2] Anterior cervical plate according to claim 1, characterized by , that the plate (10; 110) forms at least one undercut instrument interface (70; 170) in a central area. [3] Anterior cervical plate according to claim 1 or 2, with incorporated functional surfaces for receiving a locking device for inserted screws, characterized by, that the functional surfaces are limited to at least one bore (24) for receiving a bearing pin (22) or at least one locking disc (16) that can be pivoted by hand. [4] Anterior cervical plate according to claim 1, characterized by , that the normal thickness DN of the plate (10; 110) is in the range between 1.5 and 2.5 mm. [5] Anterior cervical plate according to claim 3 or 4, characterized by , that the diameter of the bore (24) for receiving the bearing journal (22) is in the range between 1.2 and 3.5 mm. [6] Anterior cervical plate according to any one of claims 2 to 5, characterized by , that the undercut instrument interface (70; 170) is keyhole-shaped and opens to a window (14; 114) of the cervical plate (10; 110). [7] Anterior cervical plate according to any one of claims 1 to 6, characterized by , that the tapering in the transverse direction is formed by a rounding (64) with a radius R. [8] Anterior cervical plate according to any one of claims 1 to 6, characterized by , that the tapering in the transverse direction is formed by a rounding (64) of at least two radii (R and RZ). [9] Anterior cervical plate according to any one of claims 1 to 7, characterized by , that the cervical plate (10) in the cranial end section tapers in a slightly arc-shaped manner in the thickness direction and, starting with an edge (62) which is essentially located in the middle of the end section (AE), tapers linearly to the rounding section (RA). [10] Anterior cervical plate according to any one of claims 1 to 8, characterized by the design as a hybrid plate for constrained restorations or as a dynamic plate for dynamic restorations.

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