Screw with an interface for an anterior cervical plate

Abstract

The invention relates to a screw with an interface to a screwing tool for use with an anterior cervical plate, comprising a first functional section (50A) for transmitting the screwing torque and a second functional section (50S) for the self-holding function of the screw on the screwing tool. In order to provide the interface with improved robustness and functionality, the functional sections (50A, 50S) are arranged and dimensioned in such a way that when a function is used, activation of at least one further function is excluded.

Description

[0001] Screw with interface for an anterior cervical plate Description

[0002] Technical field

[0003] The invention relates to a screw with an interface for an anterior cervical plate.

[0004] 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.

[0005] 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.

[0006] 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.

[0007] Finally, document GB 2 377 641 A discloses a screwdriver in which the holding function is provided by a groove in a circumferential groove of the screwdriver AE2097P-WQ-0003

[0008] 2 / 17 is provided by an inserted slotted and radially compressible metal ring. The holding function is thus limited to a linear contact, which is why the star-shaped profile must also be used to position the screw.

[0009] Document WO 2021 / 094567 A1 discloses an arrangement in which a screwdriver with a multi-sided profile interacts with a screw in such a way that it is difficult for the screw to unintentionally fall off the screwdriver. The multi-sided profile has pins projecting radially from its front end, for which an S-shaped groove profile is provided on the screw, extending into the inner recess of the screw's multi-sided profile. However, this design allows the screw to be held loosely and not in a straight position on the screwdriver.

[0010] 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.

[0011] This problem is solved by the features of claim 1.

[0012] 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.

[0013] 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 to the tool's axis without stressing the torque transmission section. The clamping mechanism completely relieves the torque transmission section, thus increasing the durability of the interface components AE2097P-WG-0003.

[0014] 3 / 17 improves the design and simultaneously makes handling the screw during insertion safer because the clamping section can be made particularly robust. Since the torque is transmitted via the torque transmission section, screwing in the screw does not result in a significant increase in clamping force, and thus the tool can be easily removed from the screw after insertion.

[0015] 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.

[0016] 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.

[0017] 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.

[0018] 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°.

[0019] 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.

[0020] 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.

[0021] Advantageous embodiments of the tool belonging to the interface are the subject of claims 11 to 16.

[0022] If the tool has three axially staggered functional sections whose radial extent decreases towards the tool tip, with the widest functional section for transmitting the screw torque being a star profile and the narrowest functional section for actuating a locking element being a polygonal profile, the tool can be used particularly economically as a multi-functional tool. This ensures that the functions of other functional sections are not affected when the locking element is actuated. If the polygonal profile used to actuate the locking element is spherical, a greater tilting of the tool is permitted.

[0023] 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.

[0024] 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.

[0025] The following schematic drawings describe exemplary implementations of the innovation.

[0026] Brief description of the characters

[0027] Fig. 1 shows the top view of an anterior cervical plate with locking elements for inserted screws;

[0028] Fig. 2 shows a sectional view of a screw with a tool inserted;

[0029] Fig. 3 shows a perspective view of a cervical plate with a locking element during adjustment;

[0030] Fig. 4 shows an enlarged view of a tool as part of the inventive interface;

[0031] Figs. 5, 6 and 7 show sections through the various functional sections of the tool according to Fig. 4; AE2097P-WQ-0003

[0032] 6 / 17

[0033] Fig. 8 shows a sectional view of the screw as part of the inventive interface;

[0034] Fig. 9 shows the front view of the screw according to Fig. 8; and

[0035] Fig. 10 shows a side view of a modified tool as part of a modified interface.

[0036] First embodiment

[0037] Figures 1 to 14 show 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.

[0038] 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.

[0039] 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.

[0040] In the illustrated embodiment, three locking elements 16 are provided, each assigned to 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 located 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. By rotating the disk 16 by a predetermined angle, the support section 20 snaps from the open position shown in Figure 1 into a detent position that locks the bone screws.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] The above description shows that 10 tools are required to insert a cervical plate, enabling a) setting the screws, b) tightening the screws, and c) locking the screws. A self-holding function is required for setting the screws, a torque transmission function for tightening them, and a multi-sided drive function for locking and unlocking them.

[0045] In accordance with the innovation, these functions are realized by a screw 50 with a multifunctional interface, i.e. by the interaction of a multifunctional tool 60 shown in Figures 2 to 7 with a screw 50 adapted to it and shown in Figures 2 and 8.

[0046] 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.

[0047] 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 section AE2097P-WQ-0003

[0048] 9 / 17

[0049] Functional section 60S is formed 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 Figure 1) of the disk 16.

[0050] 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.

[0051] The clamping cone has a cone angle WK (see Figure 8) that depends on the material pairing between screw 50 and tool 60 and is in the range of 1 to 15°, preferably between 1 and 5°, and particularly preferably between 2 and 4°. For a titanium alloy screw 50 and instrument steel 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.

[0052] 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.

[0053] This design results in a screw 50 with an interface to a screwdriving 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 such that when one of these functions is used, stress on at least one other function is excluded. AE2097P-WQ-0003

[0054] 10 / 17

[0055] When the screw 50 is first attached to the tool 60, configured as a screwdriver, it clamps onto the self-retaining functional section 60S of the tool, which is designed as an outer cone, using the self-retaining functional section 50S, configured as a clamping section. The screw 50 is aligned coaxially with the tool 60, and the axis A60 of the tool 60 coincides with the axis A50 of the screw 50 (see Figure 2). This allows the screw to be inserted into the wound with good guidance and positioned against the bone.

[0056] Because the self-holding functional sections 50S and 60S clamp the screw and tool together in a coaxially aligned manner, the drive functional sections 50A and 60A are not stressed during this phase. Because the locking functional section 50V fits into the larger diameter blind hole of screw 50, it is also not stressed.

[0057] 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.

[0058] 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.

[0059] Second embodiment 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.

[0060] 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 of a plastic element made of POM (polyoxymethylene), PEI (polyetherimide), or PEEK (polyetheretherketone) plastic.

[0061] The elastic element can also be formed by a coating or a sleeve.

[0062] 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.

[0063] 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.

[0064] Reference symbol list

[0065] 10 cervical plate

[0066] 12 absorption breakthroughs

[0067] 14 windows

[0068] 16 discs

[0069] A16 pivot axis

[0070] 18-1, 18-2 locking arms

[0071] 20 Support section

[0072] 30 locking pins

[0073] 32 Resting recess

[0074] 42 Multi-sided recess 42

[0075] 50 screws

[0076] A50 axle of 50

[0077] 50A drive functional section

[0078] 50S self-holding function section

[0079] 52 screw heads

[0080] 50V locking functional section

[0081] 60 tools

[0082] A60 axle of 60

[0083] 60A drive functional section

[0084] 60S self-holding function section

[0085] 60V locking functional section

[0086] 80 elastic element

[0087] 90 multi-sided profile

[0088] WK Angle D, D* Diameter

[0089] LA axial length

Claims

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 in that the functional sections (50A, 50S, 50V, 60A, 60S, 60V) are arranged and dimensioned such that when using one function, a stress on at least one further function is excluded.

2. Screw with interface according to claim 1, characterized in 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 in 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 in 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 in that the further functional section (50V) is formed by a bore axially adjoining the functional section (50S) for the self-holding function, into which with clearance an actuation section (60V) of the tool (60) for the locking element (16) can be immersed.

7. Screw with interface according to one of claims 3 to 6, characterized in that the clamping section (50S) of the screw (50) is formed by a self-locking clamping cone which can be brought into mate engagement with an outer cone section of the tool (60).

8. Screw with interface according to claim 7, characterized in 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°, which depends on the material pairing between screw and tool.

9. Screw with interface according to claim 8, characterized in that the cone angle of the clamping cone is toleranced during manufacturing such 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 in 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 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 in that the polygonal profile (90) is spherical.

14. Tool according to claim 11 or 12, characterized in that a functional section (60S) for the self-holding function of the screw (50S) is arranged between the functional section (60A) for transmitting the screw torque and the functional section (60V) for actuating a locking element (16).

15. Tool according to claim 14, characterized in 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 in 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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