Screw with interface for an anterior cervical plate

Abstract

A screw with an interface to a screwdriving tool for use with an anterior cervical plate is described, comprising a first functional section (50A) for transmitting the screwdriving torque and a second functional section (50S) for the self-locking function of the screw on the screwdriving tool. To provide the interface with improved robustness and functionality, the functional sections (50A, 50S) are arranged and dimensioned such that the use of one function precludes any stress on at least one other function.

Description

Technical field

[0001] The invention relates to a screw with an interface for an anterior cervical plate.

[0002] Cervical plate systems already exist, for example the applicant's Quintex system, in which the screws used are designed to form a dual-function interface when used with a corresponding screwdriver: a self-locking function and a screw-in function. With this known screwdriver, both the clamping and the torque transmission between the screw and screwdriver occur at the star-shaped drive of the interface. The clamping surfaces are thus also used and stressed during the screwing and unscrewing process.

[0003] Furthermore, a Hexalobe screwdriver with a slotted elastic functional end is known, for example, from document US2018 / 0280067 A1. However, the slotted elastic functional end potentially loses its clamping function due to deformation, and the tool must be replaced prematurely.

[0004] Document CN 217366057 U discloses a surgical screwdriver with a holding mechanism that requires various moving components, which negatively impacts both the cost-effectiveness of manufacturing and the strength of the components.

[0005] Finally, document GB 2 377 641 A discloses a screwdriver in which the holding function is provided by a slotted and radially compressible metal ring inserted in a circumferential groove of the screwdriver. The holding function is thus limited to linear contact, which is why the star-shaped profile must also be used to position the screw.

[0006] The innovation is based on the task of creating a screw with an interface for an anterior cervical plate, characterized by improved robustness and functionality.

[0007] This problem is solved by the features of claim 1.

[0008] According to the innovation, the functional sections are arranged and dimensioned in such a way that the use of one function precludes any stress on at least one other function. The functional elements relevant to the functional sections can thus be designed as independent elements, with the result that the individual functions can be optimized individually and independently of one another with regard to strength and functionality.

[0009] It is particularly advantageous if the self-holding function on the tool is formed by a clamping section that allows the screw to be aligned coaxially with the tool's axis without stressing the torque transmission section. The clamping mechanism completely relieves the torque transmission section, thereby improving the durability of the interface components and simultaneously making screw insertion safer, as the clamping section can be designed to be particularly robust. Since the torque is transmitted via the torque transmission section, tightening the screw does not significantly increase the clamping force, allowing the tool to be easily removed from the screw after insertion.

[0010] The screw is particularly stable when its clamping section is formed by a recess axially adjacent to the functional section for transmitting the screw torque. This recess allows the screw to be clamped to the tool's clamping section. When the screw is placed on the tool, usually a screwdriver, it clamps securely and axially aligned onto the clamping section. This allows the screw to be inserted into the wound and positioned against the bone. The screw is then tightened by turning the screwdriver, with the torque now being transmitted to the screw via the functional section for transmitting the screw torque, typically a star-shaped profile. Because the screw is held by the clamping section, tightening the screw does not affect its clamping position on the screwdriver.The direction of the screw can be adjusted by tilting the screwdriver. The length of the engagement in the screw is then crucial.

[0011] The self-holding function can be used particularly effectively when the clamping section has an axial length in the range between 0.25 and 1.5 x D, where D represents the larger diameter of the clamping section.

[0012] It has been shown that the design of the multifunctional interface readily allows the screw with interface to be equipped with an additional functional section for actuating a locking element of the screw, without deviating from the concept of decoupled design of all functional sections. In this case, it is only necessary to provide a bore in the screw, axially adjacent to the functional section for the self-holding function, into which an actuating section of the tool for the locking element can be inserted with clearance.

[0013] The screw with interface becomes particularly robust and inexpensive to manufacture when the clamping section of the screw is formed by a self-locking clamping cone that can be brought into a mate engagement with an external conical section of the tool. The design of the clamping cone depends, among other things, on the material pairing between the screw and the tool. It has been found that the cone angle is advantageously in the range of 1 to 15°, preferably between 1 and 5°, and particularly preferably between 2 and 4°.

[0014] If the cone angle of the clamping cone is toleranced during manufacturing so that it always bears the largest diameter when the tool is inserted, it is ensured that the screw is always aligned coaxially to the axis of the tool without play.

[0015] As an alternative to the clamping cone, the clamping section of the screw can be formed by a cylindrical or conical recess into which an elastic element provided on the tool can be pressed for clamping with the screw.

[0016] Advantageous embodiments of the tool belonging to the interface are the subject of claims 11 to 16.

[0017] If the tool has three axially staggered functional sections whose radial extent decreases towards the tool tip, wherein the largest functional section for transmitting the screw torque is formed by a star profile and the smallest functional section for actuating a locking element is formed by a polygonal profile, the tool can be used particularly economically as a multi-functional tool, whereby even when actuating the locking element, it is excluded that the functions of other functional sections are used.

[0018] If the polygonal profile used to actuate the locking element is spherical, a greater tilting of the tool is permitted.

[0019] The functional section for the self-holding function of the screw can be formed on the tool by an elastic element that can be clamped over a surface area against a recess in the screw to be actuated. The elastic element can be attached to the tool or be an integral part of the tool.

[0020] Preferably, the elastic element is formed from a stainless steel for surgical instruments according to DIN EN ISO 7153-1, such as with the designation 1.4123, or from a plastic element made of POM (polyoxymethylene), PEI (polyetherimide) or PEEK (polyetheretherketone) plastic.

[0021] The following schematic drawings describe exemplary implementations of the innovation. Brief description of the characters Fig. 1. Top view of an anterior cervical plate with locking elements for inserted screws; Fig. 2 a sectional view of a screw with tool inserted; Fig. 3 a perspective view of a cervical plate with a locking element during adjustment; Fig. 4. In enlarged view, a tool as part of the new interface; Fig. 5, Fig. 6 and Fig. 7 sections through the different functional sections of the tool according to Fig. 4; Fig. 8 a sectional view of the screw as part of the new interface; Fig. 9 the front view of the screw according to Fig. 8; and Fig. 10 a side view of a modified tool as part of a modified interface. First embodiment

[0022] In Fig. Figure 1 shows an anterior cervical plate 10 with six approximately circular receiving openings 12 for bone screws (not shown) and a locking mechanism for inserted bone screws that are screwed into a vertebral body and press the cervical plate against the vertebral body. In addition to the essentially circular receiving openings 12, the cervical plate 10 also has two windows 14. The bearing surfaces for the heads of the bone screws are not described in detail; however, they are preferably designed to consist of 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 screw slippage is prevented.

[0023] In a manner known per se, the cervical plate 10 is pre-curved longitudinally and slightly convex transversely to conform as closely as possible to the shape of the cervical spine. A special feature of the cervical plate 10 is that it is equipped with a locking mechanism for the bone screws that are inserted and screwed into the cervical vertebrae.

[0024] The locking mechanism is designed such that a locking body 16 can be moved from a position leaving a receiving opening 12 freely accessible 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 prevented from any movement that would loosen the screw seat, thus preventing the screws from migrating out of the cervical plate 10.

[0025] 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 an axis of rotation A16 that is substantially perpendicular to the cervical plate 10. The disk 16 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 and lying in the plane of the disk. This support section 20 is disengaged by rotating the disk 16 through a predetermined angle of rotation. Fig. 1 shows the open position snapping into a detent position that locks the bone screws.

[0026] The rotatability of the disks 16 is provided by a bearing journal (not shown in detail) which is received with clearance in a bore of the cervical plate 10 and riveted to the cervical plate 10.

[0027] To provide the locking mechanism integrated into the cervical plate system, the support section 20 interacts with a locking pin 30 mounted on the cervical plate 10. When the disc 16 is rotated, the locking pin deforms the support section 20 before it reaches the locking position, and the disc 16 snaps into the locking position of a locking recess 32. The disc 16 can be moved in and out of the snapping position, while simultaneously ensuring that the operator can feel the engagement of the locking position. The locking state is thus clearly identifiable both haptically and visually.

[0028] Only manual force is required to rotate the disc, so it is sufficient to provide a small-diameter polygonal recess 42 or another screw engagement profile in the disc and the bearing journal for the engagement of a tool, usually a screwdriver. The wrench size of the screw engagement profile can be less than 2 mm, for example 1.5 mm.

[0029] The above description thus shows that 10 tools are required for inserting a cervical plate, with which a) the setting of the screws, b) the screwing in of the screws and c) locking the screws This is made possible. A self-holding function is required for setting the screws, a screw torque transmission function for screwing them in, and a multi-sided drive function for locking and unlocking.

[0030] According to the innovation, these functions are achieved by a screw 50 with a multifunctional interface, i.e., by the interaction of a component integrated into the Fig. 2 to 7 of the multi-tool 60 shown with a modified version in Fig. 2 and Fig. The screw shown in 8 is 50.

[0031] The screw 50 has, axially and in diameter or inner width decreasing from a screw head 52, a drive functional section 50A, a self-holding functional section 50S and a locking functional section 50V. The drive functional section 50A is formed by a star profile recess, the self-holding functional section 50S by an internal conical surface forming a clamping section with a large diameter D and a small diameter d, and the locking functional section 50V by a blind hole.

[0032] In contrast, the screwdriver-shaped tool 60 also has three functional sections, decreasing in axial direction and in diameter or outer width: a drive functional section 60A, a self-holding functional section 60S, and a locking functional section 60V. The drive functional section 60A is formed by a star profile, the self-holding functional section 60S by an external cone forming a clamping section, and the locking functional section 60V by a hexagon whose profile corresponds to that of the polygonal recess 42 (see Fig. 1) corresponds to disc 16.

[0033] The clamping section of screw 50 is formed by a self-locking clamping cone, which can be brought into a mate engagement with a clamping section of the tool designed as an external cone, such that the cone surfaces always contact at their largest diameter, ensuring that the clamping cone, when tool 50 is inserted, always bears the load at its largest diameter. This can be ensured by appropriate tolerance specifications during the manufacturing of the cone surfaces.

[0034] The clamping cone has a cone angle WK that depends on the material pairing between screw 50 and tool 60 (see Fig. 8), which is in the range of 1 to 15°, preferably between 1 and 5°, particularly preferably between 2 and 4°. For a titanium alloy for the screw 50 and for instrument steel for the screwdriver 60, a cone angle of 3° for the inner cone of the screw 50 and a cone angle of 5°20' for the outer cone of the screwdriver are preferably selected.

[0035] The self-retaining functional section 50S of the screw preferably has an axial length LA in the range between 0.25 and 1.5 x D, where D is the large diameter D of the inner cone forming the self-retaining functional section 50S. For a cervical plate with a plate thickness of, for example, 2 mm, the self-retaining functional section 50S of the screw 50 has a diameter of 2 mm and an axial length LA of 1.7 mm.

[0036] This design results in a screw 50 with an interface to a screw tool 60 for use with an anterior cervical plate, in which the functional sections 50A, 50S and 50V of the screw and the functional sections 60A, 60S and 60V of the tool are arranged and dimensioned in such a way that when using one of these functions, a stress on at least one further function is excluded.

[0037] For when the screw 50 is first placed on the tool 60 in the configuration as a screwdriver, it clamps with the self-holding functional section 50S in the configuration as a clamping section on the self-holding functional section 60S of the tool, which is designed as an outer cone, whereby it is aligned coaxially to the tool 60 and the axis A60 of the tool 60 coincides with the axis A50 of the screw 50 (see Fig. 2) This allows the screw to be inserted into the wound with good guidance and positioned against the bone.

[0038] Because the self-holding functional sections 50S and 60S clamp the screw and tool together in a coaxial alignment, the drive functional sections 50A and 60A are not stressed during this phase. Since the locking functional section 50V fits into the larger diameter blind hole of screw 50, it is also not stressed.

[0039] The screw 50 is then tightened by turning the screwdriver, whereby the torque is transmitted to the screw 50 via the star-shaped profile of the drive function section 60A. The screw continues to be held by the conical clamping surface, and the tightening action has no effect on the clamping of the screw on the screwdriver. The direction of the screw can be adjusted by tilting the screwdriver; this is determined by the length of engagement of the tool in the screw, which is the sum of the axial lengths of the drive function sections 50A and 60A and the self-holding function sections 50S and 60S.

[0040] When all screws 50 are inserted into the cervical plate 10 and screwed to the cervical spine, the tool 60 can be removed from the screw 50 and inserted into the polygonal recess 42 with the locking functional section 60V to pivot the locking bodies 16 into the locking state. Second embodiment

[0041] Fig.Figure 10 shows a further embodiment of the interface according to the invention based on the design of the tool 160. The tool 160 again has three axially staggered functional sections, i.e., a drive functional section 160A, a self-holding functional section 160S, and a locking functional section 160V. The drive functional section 160A is essentially identical to the drive functional section 60A described above. In contrast to the first embodiment, the self-holding functional section 160S, which forms a clamping section for the screw, is formed by an elastic element 80 that can be pressed into a cylindrical or conical recess in the associated screw, which represents the self-holding functional section, in order to clamp the screw coaxially and preferably over a surface with the tool.

[0042] In the illustrated embodiment, the elastic element is connected to the drive functional section 160A, e.g., integrally molded or permanently bonded to it. In this case, the elastic element 80 is made of a stainless steel for surgical instruments according to DIN EN ISO 7153-1, such as with the designation 1.4123, or a plastic element made of POM (polyoxymethylene), PEI (polyetherimide), or PEEK (polyetheretherketone) plastic.

[0043] The elastic element can also be formed by a coating or a sleeve.

[0044] In further contrast to the first embodiment, the locking functional section 160V is formed by a polygonal profile 90, which is spherical in order to allow tilted insertion onto the polygonal recess 42 of the locking body 16.

[0045] The innovation thus creates a screw with an interface to a screwdriving tool for use with an anterior cervical plate, comprising a first functional section for transmitting the screw torque and a second functional section for the self-locking function of the screw on the screwdriving tool. To equip the interface with improved robustness and functionality, the functional sections are arranged and dimensioned in such a way that the use of one function prevents any stress on at least one other function. Reference symbol list 10 cervical plate 12 absorption breakthroughs 14 windows 16 discs A16 pivot axis 18-1, 18-2 locking arms 20 Support section 30 locking pins 32 Resting recess 42 Multi-sided recess 42 50 screws A50 axle of 50 50A drive functional section 50S self-holding function section 52 screw heads 50V locking functional section 60 tools A60 axle of 60 60A drive functional section 60S self-holding function section 60V locking functional section 80 elastic element 90 multi-sided profile WK Angle D, D* diameter LA axial length 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 2018 / 0280067 A1

[0003] CN 217366057 U

[0004] GB 2 377 641 A

[0005]

Claims

[1] Screw with interface to a screwdriving tool for use with an anterior cervical plate, comprising a first functional section for transmitting the screwdriving torque and a second functional section for the self-holding function of the screw on the screwdriving tool, characterized by , that the functional sections (50A, 50S, 50V, 60A, 60S, 60V) are arranged and dimensioned in such a way that when one function is used, a stress on at least one other function is excluded. [2] Screw with interface according to claim 1, characterized by , that the functional section (50S) for the self-holding function on the tool (50) is formed by a clamping section with which the screw (50) can be aligned coaxially to the axis (A60) of the tool (60) without loading the functional section (50A) for the transmission of the screw torque. [3] Screw with interface according to claim 2, characterized by, that the clamping section (50S) of the screw (50) is formed by a recess axially adjoining the functional section (50A) for the transmission of the screw torque, via which the screw (50) can be clamped with a clamping section (60S) of the tool (60). [4] Screw with interface according to claim 3, characterized by , that the clamping section (50S) has an axial length (LA) which is in the range between 0.25 and 1.5 x D, where D is the diameter of the clamping section (50S). [5] Screw with interface according to one of claims 1 to 4, characterized by a further functional section (50V) for receiving a locking functional section (60V) of a tool (60). [6] Screw according to claim 5, characterized by, that the further functional section (50V) is formed by a bore axially adjoining the functional section (50S) for the self-holding function, into which an actuating section (60V) of the tool (60) for the locking element (16) can immerse with clearance. [7] Screw with interface according to one of claims 3 to 6, characterized by , that the clamping section (50S) of the screw (50) is formed by a self-locking clamping cone which can be brought into fit engagement with an outer cone section of the tool (60). [8] Screw with interface according to claim 7, characterized by that the clamping cone has a cone angle (WK) in the range of 1 to 15°, preferably between 1 and 5°, particularly preferably between 2 and 4°, depending on the material pairing between screw and tool. [9] Screw with interface according to claim 8, characterized by, that the cone angle of the clamping cone is toleranced during manufacturing so that it basically has the largest diameter when the tool (50) is inserted. [10] Screw with interface according to one of claims 3 to 6, characterized by , that the clamping section of the screw is formed by a cylindrical or conical recess into which an elastic element (80) provided on the tool (60) can be pressed for clamping with the screw (50). [11] Tool for an interface according to any one of claims 1 to 10. [12] Tool according to claim 11, comprising three axially staggered functional sections (60A, 60S, 60V) whose radial extent decreases towards the tool tip, wherein the largest functional section (60A) for transmitting the screw torque is formed by a star profile and the smallest functional section (60V) for actuating a locking element (16) is formed by a polygonal profile. [13] Tool according to claim 12, characterized by , that the polygonal profile (90) is spherically shaped. [14] Tool according to claim 11 or 12, characterized by , that between the functional section (60A) for transmitting the screw torque and the functional section (60V) for actuating a locking element (16) a functional section (60S) for the self-holding function of the screw (50S) is arranged. [15] Tool according to claim 14, characterized by , that the functional section (60S) for the self-holding function of the screw (50S) is formed by an elastic element (80) which can be clamped over a surface with a recess of the screw to be actuated. [16] Tool according to claim 15, characterized by, that the elastic element (80) is formed of a stainless steel for surgical instruments according to DIN EN ISO 7153-1, such as with the designation 1.4123, or a plastic element made of POM (polyoxymethylene), PEI (polyetherimide) or PEEK (polyetheretherketone) plastic.

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