EP2709545A1

EP2709545A1 - Bone plate

Info

Publication number: EP2709545A1
Application number: EP12722713.0A
Authority: EP
Inventors: Dietmar Wolter
Original assignee: Individual
Current assignee: WOLTER, DIETMAR
Priority date: 2011-05-17
Filing date: 2012-05-16
Publication date: 2014-03-26
Also published as: US20140330320A1; WO2012156453A1

Abstract

The application relates to a bone plate with a through-hole (14) that extends from an upper face (15) of the bone plate to a bone-side lower face (16) thereof. A lip (17) is formed in the through-hole (14), protrudes from the interior surface (18) of the through-hole (14) and extends in the circumferential direction of the through-hole (14). The lip (17) has a plurality of circumferential portions in which the lip surface (19) directed towards the upper face (15) of the bone plate is designed as an inclined surface (21, 22) that slopes in the circumferential direction, wherein the lip surface (19) has a front inclination face (21) and a rear inclination face (22), and wherein the front inclination face (21) and the rear inclination face (22) have an opposite inclination in the circumferential direction. The bone plate has the advantage that a bone screw (31) can easily cut into the lip.

Description

bone plate

The invention relates to a bone plate having a through hole extending from an upper side to a bone-side underside of the bone plate. In the through-hole, a lip is formed protruding from the circumferential surface of the through-hole and extending in the circumferential direction of the through-hole. Such bone plates are designed to be connected to a bone. For example, they can be used to stabilize a bone after a break. This is done by positioning the bone plate so that it extends across the fracture site and then attaching it to the bone fragments. The fracture is thereby immobilized and the bone can heal. The bone plate may also serve other purposes and, for example, be an element of an endoprosthesis to be connected to a bone.

To attach the bone plate to the bone, a bone screw is inserted into the through hole, which is threaded both on the shaft and on the head. The shaft of the screw penetrates the bone material so far that the head of the screw passes into the through hole of the bone plate. The head of the bone screw be is dimensioned so that its outer diameter is greater than the smallest diameter of the lip. As the bone screw is screwed in further, the lip is deformed so that a thread connection is formed between the head screw head and the lip in the through hole of the bone screw. By having a threaded connection between the shaft of the bone screw and the bone material as well as between the head of the screw and the bone plate, a secure connection is made between the bone plate and the bone. Since the threaded connection between the head of the bone screw and the bone plate is formed only when screwing the bone screw by a forming process, it is not necessary to screw the bone screw at a certain predetermined angle in the bone plate. Rather, the angle can be freely selected within certain limits. This gives the surgeon a high degree of flexibility during the operation. With the previous lips, which extend uniformly in the circumferential direction of the through-hole, the thread on the head of the bone screw strikes the lip at an acute angle. Bs there is a risk that the thread first slides along the surface of the lip before the forming process begins and the thread engages the lip. The plate can thereby be displaced prior to forming the threaded connection, which can lead to tension forces between the bone plate and the bone screw. Such tension forces can delay the healing of the bone.

The invention is based on the object to present a bone plate, in which the risk that unwanted Forces on the bones act, is diminished. Based on the above-mentioned prior art, the object is achieved with the features of the independent claim. Advantageous embodiments can be found in the subclaims.

According to the invention, the lip has a plurality of peripheral portions in which the lip surface facing the top of the bone plate is formed as a circumferentially inclined slope surface, the lip surface having a front slope surface and a rear slope surface and the front slope surface and the rear slope surface Slope surface have an opposite slope in the circumferential direction.

First, some terms are explained. A lip refers to a region in which the material thickness is reduced compared to the material thickness of the bone plate. The lip protrudes from the lateral surface of the through-hole in the direction of the center of the through-hole. The lip can taper from the lateral surface towards the center. Also included are embodiments in which this is not the case, and in which, for example, the lip near the center has the same material thickness as near the lateral surface. The lip has a longitudinal extent along the circumference of the through-hole. The lip has a lip surface facing the top of the bone plate and a lip surface facing toward the bottom of the bone plate, each having a circumferential extent and a radial extent. The underside of the bone plate rests on the bone when the bone plate is inserted. When the lip surface has a circumferentially inclined slope surface, a movement following the slope surface circumferentially has a component up toward the top of the bone plate or a component down toward the bottom of the bone plate.

The lip preferably extends without interruption over the entire circumference of the through-hole. The sloping surfaces are then formed in sections of the lip. This means that the lip continues circumferentially on both sides of the slope surface. In particular, a section of the lip adjoins on both sides of the inclination surface, in which the lip surface has no inclination in the circumferential direction.

The bone plate according to the invention has the advantage that the first contact takes place at a less acute angle when the head thread of the screw strikes the sloping surface. The less acute angle reduces the risk of the thread sliding along the lip surface instead of cutting into the lip and reshaping it. The threaded connection between the bone screw and the bone plate is thus formed in exactly the position that the bone plate at the first

Has engagement of the thread in the lip. Bs thus takes place before forming the threaded connection no displacement of the bone plate. Undesirable tension forces between the bone plate, the bone screw and the bone are thereby avoided.

The lip comprises a front inclination surface and a rear inclination surface whose inclination in the circumferential direction is opposite. The front slope surface is a slope surface that points in the direction of the thread of an associated bone screw. The first contact between the thread on the head of the bone screw and the lip will thus take place on a front slope surface and not on a rearward slope surface.

In order to increase the likelihood that the first contact between the head thread and the lip takes place at a front inclination surface, the lip surface may be provided with a plurality of front inclination surfaces. For example, the lip surface may have at least three front inclined surfaces, preferably at least six front inclined surfaces. Regularly is between each of the two front sloping surfaces a backward

Inclined surface arranged so that the number of front inclination surfaces equal to the number of rear inclination surfaces. For the engagement of the head thread in the lip, it is advantageous if the head thread meets at an angle in the order of 90 ° to the front inclination surface. The likelihood that the head thread slides along the lip surface before the procedure takes place is then lowest. This can be achieved by having the front slope surface a greater pitch than the rearward slope surface. Slope refers to the angle that inclines the inclination surface in the circumferential direction with the horizontal. For example, the slope of the front slope surface may be between 60 ° and 90 °. The slope of the rear slope surface may for example be between 20 ° and 60 °. The probability that the first contact between the head thread and the lip takes place on the slope surface can be further increased by the slope surface having a large height extent. The height refers to the distance from the bottom of the bone plate to the top of the bone plate. The inclination surface preferably extends over at least 30%, more preferably over at least 50%, more preferably over at least 70% of the thickness of the bone plate.

The lip surface can be even. In alternative embodiments, the lower lip surface may also be provided with sloping surfaces. The number of slope surfaces on the lip surface may correspond to the number of slope surfaces on the lip surface. Preferably, in each case a slope surface on the lip underside is aligned substantially parallel to a slope surface on the lip underside. This has the advantage that the head thread has to displace only a little material of the lip in the first procedure before the head thread emerges from the lip again. Thus, a lip can be produced whose thickness is substantially constant in the circumferential direction and which extends in a wave-like manner over the circumference of the passage hole.

The bone plate with the lip in the through hole may be formed integrally. Alternatively, it is possible for a region surrounding the through-hole to be inserted into the bone plate in the form of an inlay. The inlay with the lip can first be formed as a separate part and then connected to the bone plate. To facilitate the forming of the threaded connection, the Inlay made of a softer material than the bone plate.

Optionally, to allow the surgeon to use conventional bone screws whose head is not threaded, the peripheral surface of the through-hole above the lip may be flared outwardly. This area of the lateral surface can then form a counter surface for a conventional screw head. In cross-section, the expansion may for example have the shape of a circle segment.

The invention also relates to a system of such a bone plate and a bone screw. The bone screw has a head thread adapted to reshape the lip in the through hole to form a threaded connection. In order to allow a secure attachment to the bone, the bone plate usually has a plurality of through holes. Accordingly, the system can also include a plurality of bone screws.

The material forming taking place during the forming of the threaded connection should as far as possible not be associated with chip abrasion. Experiments have shown that the chip wear is kept low when the screw head is a conical

Has lateral surface and the angle which encloses the lateral surface with the screw axis is between 19 ° and 28 °. The invention will now be described by way of example with reference to the accompanying drawings by way of advantageous embodiments. Show it: 1 shows a view from above of a bone plate according to the invention;

2 shows a section through FIG. 1 along the line I-I FIG. 3 shows an enlarged view of the detail A from FIG.

1;

Fig. 4 is a view in the direction of arrow B in Figure 3, wherein the cylindrical lateral surface of the through-hole is projected into the plane.

Fig. 5 is the view of Fig. 4 in another embodiment of the invention;

Fig. 6: the view of Figure 4 in a further Ausfüh approximately form of the invention.

FIG. 7 shows the view from FIG. 2 in another embodiment of the invention; FIG.

8 shows a bone screw intended for the bone plate according to the invention; and

Fig. 9: The view of Fig. 2 in a further Ausfüh approximately form of the invention. According to FIGS. 1 and 2, a bone plate according to the invention has six through-holes 14, which extend from an upper side 15 of the bone plate to a lower side 16 of the bone plate. In each through hole 14, a lip 17 is formed, which protrudes from the lateral surface 18 toward the center of the through hole 14.

The lip 17 is a continuous lip which extends uninterrupted over the entire circumference of the through-hole. The lip 17 has a lip surface 19 pointing to the upper side 15 of the bone plate and a lower lip surface 20 pointing to the lower side 16 of the bone plate.

The bone plate is intended to be placed with the bottom 16 on a bone, so that the bones plate extends over a break point of the bone away. After the bone is reduced to the correct position, the bone plate is connected to the bone fragments. The bone is then fixed in this position and can heal.

Bone screws 31, as shown in FIG. 8, are used to connect the bone plate to the bone. The bone screws 31 have a shaft 27 which is provided with a bone thread 28, and a screw head 29, whose outer surface has a head thread 30 with a smaller pitch. The lateral surface of the screw head 29 encloses an angle of 25 ° with the screw axis. The bone screw is screwed into the bone until the screw head 29 penetrates into the through hole 14. In this case, the angle that includes the bone screw with the axis of the through hole between about 0 ° and 15 ° can be freely selected. When the bone screw is now further screwed in, the head thread 30 of the bone screw 31 comes into engagement with the lip 17. The lip 17 is deformed and a threaded connection is formed between the head 29 of the bone screw 31 and the lip 17. To facilitate the formation of the threaded connection, the bone screw 31 may be made of a harder material than the bone plate. For example, the bone plate may be made of pure titanium while the bone screw 31 is made of titanium alloy TiA16V4. The lip 17 is, as indicated in Fig. 3 by radial lines, on the lip top 19 equipped with a wave-shaped structure. In Fig. 3 are the areas in which the lip surface 19 in the circumferential direction a great slope has, characterized by closely adjacent lines. If one thus moves in the circumferential direction on the lip surface 19 transversely to the closely spaced lines, this is a movement with which one moves away from or approaches the top side 15 of the bone plate. Thus, the closely spaced lines characterize the slope surfaces on the lip surface 19.

In Fig. 3, a lip surface 19 is shown with four front slope surfaces 21 and four rear slope surfaces 22. Moving in Fig. 3 in a clockwise direction along a front inclined surface 21, one moves upward in the direction of the top 15 of the bone plate. The slope of the rearward sloping surfaces 22 is reversed. Moving in Fig. 3 in a clockwise direction along a rear inclined surface 22, so you move down and away from the top 15 of the bone plate. Between the front inclination surfaces 21 and the rear inclination surfaces 22 there is a region in each case in which the lip surface 19 has no incline, ie is oriented parallel to the horizontal.

When screwing the bone screw comes at a certain time, the first thread of the head thread in contact with the lip 17. Since the thread, as indicated in Fig. 4 at 23 approaches obliquely from above to the lip 17, there is a high probability that the first contact between the head thread and the lip 17 takes place in the region of a front inclined surface 21. The threading path is substantially perpendicular to the front slope surface 21 so that the thread can immediately cut into the lip 17 and deform it. If the conical screw head deeper in engages the lip 17, more material is displaced and the screw head penetrates into the area in which the lip 17 has a greater material thickness (see Fig. 2). It forms a threaded connection which extends over the entire circumference of the screw head.

In the embodiment of Fig. 4, the lip base is flat. In the alternative embodiment of FIG. 5, there are also on the lip base 20 inclination surfaces 24, 25 which are each aligned parallel to the inclined surfaces 21, 22 on the lip top 19. The indicated at 23 first thread of the head thread must then displace only a small amount of material after the first contact before it exits the lip again. For the surgeon this has the advantage that when penetrating the head thread into the lip 17 no great resistance is overcome.

In Fig. 6, a variant is shown in which the front slope surfaces 21 have a greater slope than the rear slope surfaces 22. The slope of the front slope surfaces is about 80 ° and the slope of the rear slope surfaces about 30 °. This has the advantage that even head threads with a small thread pitch substantially perpendicular to the front slope surface 21 meet.

Fig. 7 shows an embodiment in which an inlay 26 is inserted into the bone plate. The inlay 26 is made of a softer material than the bone plate and forms the lip 17 and the vicinity of the through hole 14. Unlike in FIG. 2, the lip 17 does not taper toward the center of the through hole 14, but the lip 17 has a constant material thickness. In Fig. 9, the man- telflache 18 above the lip 17 a widening 34, which has the shape of a circle segment in cross section. In this embodiment, there is optionally the possibility of using conventional bone screws whose head is free of a thread. The expansion 34 then forms a counter surface for a bone screw with a hemispherical head, so that the bone screw can be inserted at different angles in the through hole 14.

Claims

1. Bone plate having a through hole (14) extending from an upper side (15) to a bone-side underside (16) of the bone plate, wherein in the through hole (14) has a lip (17) is formed, from the lateral surface (18) of the through-hole (14) and extending in the circumferential direction of the through-hole (14), characterized in that the lip (17) has a plurality of peripheral sections in which the lip surface facing the upper side (15) of the bone plate (FIG. 19) is formed as a tilted inclined surface (21, 22) in the circumferential direction, wherein the lip surface (19) has a front inclined surface (21) and a rear inclined surface (22) and wherein the front inclined surface (21) and the rear inclined surface ( 22) have an opposite inclination in the circumferential direction. 2. Bone plate according to claim 1, characterized in that the lip surface (19) has at least three front inclined surfaces (21), preferably at least six front inclined surfaces (21). 3. Bone plate according to claim 1 or 2, characterized in that the slope of the front slope surface (21) is greater than the slope of the rear slope surface (22). 4. Bone plate according to claim 3, characterized in that the slope of the front slope surface (21) is between 60 ° and 90 ° and that the slope of the rearward slope surface (22) between 20 °

lies. 5. Bone plate according to one of claims 1 to 4, characterized in that the inclination surface (21, 22) has a height extent of at least 30%, preferably at least 50%, more preferably at least 70% of the thickness of the bone plate. 6. Bone plate according to one of claims 1 to 5, characterized in that the lip lower surface (20) is flat. 7. Bone plate according to one of claims 1 to 6, characterized in that the lip lower surface (20) inclination surfaces (24, 25) and that in each case a slope surface (24, 25) of the lip lower surface (20) substantially parallel to a slope surface (21 , 22) of the lip surface (19) is aligned. 8. Bone plate according to one of claims 1 to 7, characterized in that a through hole (14) surrounding area in the form of an inlay (26) is inserted into the bone plate. 9. A bone plate system according to any one of claims 1 to 8 and a bone screw (31), the bone screw (31) having a head thread (30) designed to reshape the lip (17) of the through hole (14). 10. System according to claim 9, characterized in that the bone screw (31) has a head (29) with a ke Has gel-shaped lateral surface and that the lateral surface with the screw axis forms an angle between 19 ° and 28 °.