Device for the osteosynthetic treatment of bone fractures, especially patella fractures

Abstract

Device for the osteosynthetic treatment of bone fractures, in particular patella fractures, with a plate (1) which has a plurality of star-shaped cavities (4), each extending in the radial direction of the plate (1) from an open end (5) on the radially outer edge of the plate (1) to an opposite end which is closer to the center (6) of the plate (1) than the open end, and a plurality of arms (18, 19, 20, 21), each having two legs (22, 24, 25, 26, 27) arranged at an angle to one another, wherein the arms (18, 19, 20, 21) are radially continuously movable relative to the plate (1) after the one leg (22) has been received in the cavities (4) and can be releasably held in place in their respective position on the plate (1) by means of fastening means, characterized in that the arms (18, 19, 20, 21) are each individually detachably connectable to the plate (1) and independently movable relative to the plate (1), the arms (18, 19, 20,21) and the plate (1) each have at least one through-opening (13, 14, 16), and the fastening means have a plurality of screws (15, 17, 31) by means of which each arm (18, 19, 20, 21) can be detachably connected to the plate (1) and to at least one bone fragment, or the plate (1) can be detachably connected to at least one bone fragment.

Description

[0001] The invention relates to a device for the osteosynthetic treatment of bone fractures, in particular patella fractures, with a plate which has a plurality of star-shaped cavities, each of which extends in the radial direction of the plate from an open end at the outer edge of the plate to an opposite end which is closer to the center of the plate than the open end, and a plurality of arms, each of which has two legs arranged at an angle to one another, wherein the arms are radially continuously movable relative to the plate after the one leg has been received in the cavities and can be releasably held in place on the plate in their respective position by means of fastening means.

[0002] Such a device is known from CN 211325502U. In this device, intended for the treatment of patella fractures, the radially inner ends of one leg of all arms are each firmly connected to one end of a wire, the other end of which is firmly connected to a roller rotatably mounted in a central cavity of the plate, which can be rotated by means of a rotating part projecting axially beyond the plate. By rotating the roller in one direction, the wires are wound up on the roller, whereby all arms are simultaneously pulled radially inward and the other legs of the arms exert a uniform radial compression pressure on the patella fragments. The arms can be releasably fixed in their respective radial position relative to the plate by screws acting on the plate and one leg of the arm.After loosening these screws and unwinding the wires by rotating the roller in the opposite direction, the pressure exerted by the arms on the patella is released, allowing the device to be removed from the patella. The disadvantage of this approach is that the compression pressure exerted by the arms on the patella fragments can cause a displacement of the fragments, which can adversely affect fracture healing and postoperative patella mobility, and / or excessive compression of adjacent fragments, which can impair interfragmentary blood flow.

[0003] CN 111616786A also discloses a device for treating patella fractures. This device comprises a disc-shaped, flat ring with several screw holes distributed circumferentially and a number of band-shaped arms extending from the plate in a star shape, depending on the number and course of the fracture lines. The arms can be plastically deformed with the fingers to adapt to the shape of the surface of the fragmented patella. Each of the arms has several screw holes distributed along its length, into each of which the threaded head of an angle-stable screw can be screwed at a variable angle relative to the arm.One of the angle-stable screws can be screwed into the screw hole formed at the radially inner end of the arms. This screw's shaft, which is also threaded, screws into a screw hole in the ring, thereby releasably connecting the ring and the or each arm. The screws screwed into the other screw holes in the arms have their threaded shafts screwed into the respective bone fragment, thereby releasably connecting the or each arm to the respective bone fragment. The disc-shaped ring, the band-shaped arms, and the screws are made of a medical-grade titanium alloy. Plastic deformation of the band-shaped arms with the fingers is not suitable for precisely reuniting the fragments and preserving the interfragmentary blood flow and nerve structure in the case of a dislocated patella fracture.

[0004] CN 216628671U discloses an elliptical curved plate made of steel or a titanium alloy for the osteosynthetic treatment of patella fractures, wherein the plate has a central region provided with a central through-opening and a plurality of peripheral regions spaced apart in the circumferential direction and connected to the central region by radial connecting struts arranged in a star shape, which peripheral regions are connected to one another by connecting struts extending in the circumferential direction and each have a through-opening, wherein the through-openings in the central region and in the peripheral regions can be occupied by angle-stable screws which can be screwed with their heads into the through-openings and with their shafts into the fragments of the patella.This device is one-piece and rigid, so it is not possible to move dislocated fragments of the patella back to their original position by applying centripetal forces to restore the anatomical shape of the patella.

[0005] The object of the invention is to further develop the device mentioned at the outset for the osteosynthetic treatment of bone fractures, in particular patella fractures, in such a way that it can be easily adapted to all fracture types with different fracture courses and in this way enables individual repositioning of the individual fracture components with retention of these and the development of interfragmentary compression.

[0006] The object of the invention is achieved in that the arms are each individually detachably connectable to the plate and independently movable relative to the plate, the arms and the plate each have at least one through-opening, and the fastening means have a plurality of screws by means of which each arm is detachably connectable to the plate and to at least one bone fragment or the plate is detachably connectable to at least one bone fragment.

[0007] The advantage of the device according to the invention is that it allows flexible attachment to the bone fragments in such a way that, depending on the number, shape, and position of the bone fragments, it can be attached to the bone fragments either as a unit comprising a plate and the final number of arms in one step or in parts in several steps. When the device is attached in parts, the plate can be fixed to one or more bone fragments with screws in a first step and then, in one or more further steps, the arms can be fixed to the plate and the bone fragment(s) with further screws by applying more or less strong pressure. The device according to the invention therefore corresponds to a multi-part kit or modular structure that can be detachably attached to the bone fragments in one or more steps.

[0008] Advantageous further developments of the device according to the invention emerge from the dependent claims.

[0009] The device according to the invention is particularly advantageous if the plate has at least one multi-part through-opening in the region of each cavity, which through-opening comprises a plurality of partial openings, of which at least one partial opening is located in a first wall section of the plate bounding the respective cavity from above, and another partial opening is located in a second wall section of the plate bounding the respective cavity from below, wherein the other partial opening is slit-shaped and extends in the radial direction of the plate. This makes it possible to align the plate together with an arm on a bone fragment and to removably attach it with a screw which, if necessary, runs at an angle other than perpendicular in the radial direction relative to the arm and the plate in order to thereby introduce the screw into the bone fragment outside of a fracture line.The slit-shaped partial opening not only allows for variable angle screw positioning in the radial direction of the arm and the plate, but also reduces the plate's contact surface on the anterior surface of the patella. Reducing the plate's contact surface on the anterior surface of the patella results in a smaller contact area between the osteosynthesis material and the bone, thus reducing perfusion compromise and thus improving bone healing.

[0010] It is further advantageous if at least one further partial opening is located in the first wall section of the plate, wherein the or each further partial opening and the one partial opening are spaced apart from each other in the radial direction of the plate. This allows another screw to penetrate the plate and the arm at a different location and be screwed into the bone fragment, so that the screw penetrates the bone fragment outside of a fracture line.

[0011] Preferably, the plate also has at least one through-opening in the third wall sections extending circumferentially between the star-shaped cavities. This allows the plate to be releasably connected directly to a bone fragment even outside the area of ​​the cavities and the arms displaceably mounted therein, in order to increase the stability between the plate and the bone fragment and ensure the relative positioning of the bone fragments.

[0012] Preferably, one leg of the arms each has a through-opening in the form of an elongated hole which extends in the longitudinal direction of one leg and, after receiving the one leg in the respective cavity, is arranged between the at least one partial opening in the first wall section and the other partial opening in the second wall section, wherein the screw passing through the other partial opening also projects through the elongated hole in one leg of the respective arm and is in threaded engagement with a wall surface delimiting the elongated hole, by means of which the arm is held relative to the plate.This makes it possible to lock the arm or each arm in any position relative to the plate by means of the screw passing through the plate and through the elongated hole in the arm and to further fix the bone fragment itself relative to the plate and the respective arm by penetrating it, whereby only the length of the elongated hole in the arm limits the area within which the arm can assume any number of positions relative to the plate.

[0013] It is advantageous if the wall surface delimiting the elongated hole has opposing sections in the width direction of the elongated hole, which are surface sections of at least one insert integrated into one leg, which is softer than the screw penetrating the elongated hole, wherein the thread of the screw, which is preferably made of titanium or a titanium alloy, penetrates the surface of the insert.

[0014] Preferably, the other leg of at least one arm has the shape of an inverted T or a straight or angled band, with the other leg having one or more through-holes at its free end, through which a corresponding number of screws can be inserted. This makes it possible to releasably and preferably angularly connect the arms to the bone fragments at the lateral edges of the bone fragments, and to push the bone fragments in a radial direction without stressing or even damaging lateral tissue structures.

[0015] The other leg of at least one arm can also be shaped like a curved hook and have one or more points at its free end. This variant is advantageous when the bone fragment to be held with the arm is very small or has a tapered end, leaving insufficient space to screw a screw into this bone fragment. The curved hook of the other leg then grips the bone fragment like a claw.

[0016] Preferably, at least one of the screws is a locking screw having a thread on the head of the screw and a thread on the shank of the screw.

[0017] It is also advantageous if the plate and / or the or each arm is made of metal, in particular titanium or a titanium alloy, or of plastic, in particular polyetheretherketone.

[0018] The modular design of the device according to the invention makes it possible, depending on the fracture pattern, to use only one arm or several identical or different continuously movable arms on the plate and in the best possible position for osteosynthesis and, in addition, to occupy one or more positions on the plate not occupied by continuously movable arms with an arm or arms which, instead of an elongated hole, have or have a round screw hole which is axially aligned with a round screw hole in the plate, so that the additional arm or arms can only be firmly connected to the plate and the respective bone fragment if the screw hole in the plate and the screw hole in the additional arm or arms are axially aligned one above the other and the screw is screwed into both axially aligned screw holes and the respective bone fragment.Both the screw hole in the plate and the screw hole in the additional arm can be provided with a pre-cut thread into which the thread of the screw engages when screwed in. The use of this additional arm or these additional arms, which can only assume a predetermined fixed position relative to the plate, increases the stability of the connection between the device and the bone fragments. Outside the cavities, the plate has additional through-openings in any number and arrangement through which screws can be passed and through which the plate can be detachably connected to bone fragments. All through-openings that can be passed through screws enable an angularly stable connection between the plate and the respective addressed bone fragment thanks to a thread structure in the through-opening that corresponds to the screw head.

[0019] The invention will be described in more detail below using an exemplary embodiment with reference to the accompanying drawings. In the drawings: Fig. 1 a side view of a device for the osteosynthetic treatment of bone fractures, in particular patella fractures, according to the invention; Fig. 2 a view of the Fig. 1 shown device from below; Fig. 3 a perspective view of the Fig. 1 shown device from obliquely above; Fig. 4 a perspective view of the Fig. 1 shown device from below; Fig. 5A a view of the Fig. 1 shown device from above; Fig. 5B is a sectional view of the Fig. 1 shown device along the line AA in Fig. 5A, wherein the arms 18 and 19 are each shown partly in section and partly in elevation; Fig. 6A - 6D perspective views of the various Fig. 1 device used arms without the corresponding plate and without the corresponding screws; Fig. Figure 7A is a schematic representation of a fragmented patella in which the fracture conforms to a particular pattern in which a single fracture line runs vertically medially in the patella and, as a result, two fragments are formed, one of which is significantly larger than the other; Fig. 7B is a plan view of a device according to the invention in use in the Fig. 7A, the device being adapted to treat this fracture pattern; Fig. Figure 8A is a schematic representation of another fragmented patella in which the fracture conforms to a different pattern in which one fracture line runs transversely and another fracture line runs vertically, forming three approximately equal-sized fragments; Fig. 8B is a plan view of a device according to the invention in use in the Fig. 8A, the device being adapted to treat this fracture pattern; Fig. 9A is a schematic representation of a multi-fragmented patella in which the fracture conforms to a further pattern in which multiple transverse fracture lines and multiple longitudinal fracture lines together form five different sized fragments; and Fig. 9B is a plan view of a device according to the invention in use in the Fig. 9A, the device being configured to treat this fracture pattern.

[0020] As can be seen from the drawings, a device for the osteosynthetic treatment of bone fractures, in particular patella fractures, comprises a circular, curved plate 1, wherein the side 3 facing the convex front side of a fragmented patella 2a, 2b or 2c during use of the device, which is also referred to here as the "underside 3" of the plate 1, is designed in a bowl-shaped concave manner in order to be able to fit precisely against the convex front side of the patella 2a, 2b or 2c during use of the device. The plate 1 has six star-shaped cavities 4 ( Fig. 4, Fig. 5), which each extend in the radial direction from an open end 5 at the edge of the plate 1 to an opposite end near the center 6 of the plate 1, are T-shaped in cross-section, and which enclose a constant opening angle ω of 60° between each two adjacent cavities 4. The plate 1 has, in the region of each cavity 4, a through-opening comprising three partial openings 7, 8 and 9, wherein the partial openings 7 and 8 are located at a radial distance from one another in a first wall section 10 of the plate 1 that delimits the respective cavity 4 from above, and the partial opening 9 is located in a second wall section 11 of the plate 1 that delimits the respective cavity 4 from below. The partial opening 9 is slit-shaped and extends in the radial direction of the plate 1. In the example shown, the two partial openings 7, 8 have a round cross-sectional shape; however, they can also have an oval cross-sectional shape.The first wall section 10 of the plate 1, which delimits the respective cavity 4 from above, has an outer surface extending in the radial direction of the plate 1, which is convexly curved in the circumferential direction of the plate 1, whereby the first wall section 10 obtains a high bending strength.

[0021] The plate 1 has in the third wall sections 12 extending between two adjacent cavities 4 two through openings 13, 14 arranged at a radial distance from each other and in its center 6 a further through opening 16. In the case of the Fig. In the example of the device shown in Figures 1 to 5, some of the through holes 13 are fitted with screws 15 and the through hole 16 is fitted with a screw 17.

[0022] The number and selection of the through holes 13, 14, and 16, which are filled with screws 15 and 17, depend on the fracture pattern of the fragmented patella to be treated during use of the device and are accordingly different for different fracture patterns. Fig. The number and selection of through holes 13, 14 and 16 occupied by screws 15 and 17 shown in Figures 1 to 5 are therefore to be understood as only one of several examples, some of which are shown in the Fig. 7B, Fig. 8B and Fig. 9B and explained in more detail below.

[0023] The device further comprises a plurality of arms 18, 19, 20 and 21 which are Fig. 6A, Fig. 6B, Fig. 6C and Fig. 6D. Each of these arms has two legs 22, 24, 25, 26, 27, 28 arranged at an angle to one another, of which one leg 22 is identical in shape and size and each has a through-opening in the form of an elongated hole 23 extending in the longitudinal direction of one leg 22. The other legs 24, 25, 26, and 27 of the arms 18, 19, 20, and 21 have different shapes as follows:

[0024] The other leg 24 of arm 18 has the shape of a straight band and a screw hole 28 at its free end; the other leg 25 of arm 19 has the shape of an inverted T and three adjacent screw holes 28 in the free end of the other leg 25 forming the crossbar of the inverted T. The other leg 26 of arm 20 has the shape of an angular band and three adjacent screw holes 28 in the free end of the other leg 26 forming the base of the angular band, and the other leg 27 of arm 21 has the shape of an inwardly bent hook with two spread tips 29 at its free end. Each arm 18, 19, 20, 21 has a recess 30 on its other leg, near the one leg, into which a surgical tool such as a repositioning forceps can be inserted during use of the device. The recess 30 can be a notch.The end sections of the other legs 25 and 26, which have the three adjacent screw holes 28, are bent inwards so that they can fit precisely against the curved outer side edge of the respective bone fragment when the device is in use.

[0025] In order to detachably connect the arms 18, 19, 20 and 21 to the plate 1, one of the legs 22 of the arms is each pushed individually into the cavities 4 through its open end 5, so that they are mounted in the cavities 4 between the wall sections 10 and 11 of the plate 1 so as to be continuously displaceable in the radial direction of the plate 1, wherein the elongated hole 23 in the respective one leg 22 of the arms 18, 19, 20 and 21 is in register with the slot-shaped partial opening 9 in the second wall section 11 of the plate 1 and in register with the partial opening 7 in the first wall section 10 of the plate 1 and, with a correspondingly large insertion depth of the arm in the cavity 4, also in register with the partial opening 8 in the first wall section 10 of the plate 1.If the arms 18, 19, 20 and 21 are each in the desired position relative to the plate 1, the arms and the plate 1 are releasably fastened to one another by means of angle-stable screws 31 which are guided through the partial openings 7 and / or 8 in the first wall sections 10 of the plate 1 and through the elongated holes 23 in one of the legs 22 of the arms, wherein they penetrate with their thread on the head into the wall of the partial openings 7 and / or 8 in the first wall sections 10 of the plate 1 and with their thread on the shaft into the opposite edges of the elongated holes 23 in one of the legs 22 of the arms to form a threaded engagement which releasably connects the arms 18, 19, 20 and 21 and the plate 1. In order to enable the threaded engagement between the screws 31 and the edges of the elongated holes 23, the opposite edges of the elongated holes 23 are spaced from each other by a distance that is less than the diameter of the screws 31.

[0026] To facilitate the penetration of the thread of the screws 31 into the edges of the elongated holes 23, the edges of the elongated holes 23 can be the surfaces of one or more integrated inserts made of a softer material than that of the screws 31. The screws 31 protrude with a small lateral clearance through the slot-shaped partial openings 9 in the second wall sections 11 of the plate 1. This makes it possible to vary the angle of the screws 31 and, in particular, the longitudinal direction of the slot-shaped partial opening 9 relative to the plate 1, so that the screws 31 can always be screwed into the bone fragments outside of fracture lines.

[0027] When using the device for the osteosynthetic treatment of a patella fracture, the screws 15, 17, and 31 protruding from the underside of plate 1 engage the bone fragments and hold them firmly relative to plate 1. They are brought together precisely and in a way that protects the vessels and joints, allowing them to heal together without problems, by the radial pressure exerted by the other legs of arms 18, 19, 20, and 21 on the outer lateral edges of the bone fragments. This pressure is generated manually and / or with a suitable tool, such as reduction forceps, by medical personnel when positioning the device on the fragmented patella. Screws can also be inserted laterally into the bone fragments through the screw holes 28 in the other legs 24, 25, and 27 to hold the fragment structure in a reduced position and maintain the generated interfragmentary compression.All or at least some of the screws that are inserted into the bone fragments are angle-stable screws that also have a thread on the head of the screw in order to hold the bone fragments in their desired position relative to the plate 1.

[0028] It is understood that the Fig. The number and arrangement of arms and screws shown in Figures 1 to 5 A and 5 B is only an example, as more or fewer arms and screws can be used in a different arrangement than shown if this is medically better for the particular patella fracture to be treated. Furthermore, it is understood that the Fig. The shapes of the other legs 24, 25, 26, and 27 of the arms 18, 19, 20, and 21 shown in Figures 6A to 6D can also be replaced by other shapes. For example, the shape of the other leg 26 could be replaced by a shape in which the foot points in the opposite direction, and the other leg 27 could alternatively be formed with a hook that has only one point or no points at all. Furthermore, the number of screw holes 28 can also vary.

[0029] The variability of the device resulting from the invention and its flexibility in treating different fracture patterns are illustrated by the illustrations in the Fig. 7A, Fig. 7B, Fig. 8A, Fig. 8B, Fig. 9A, Fig. 9B even clearer: At the Fig. 7A, in which only a single fracture line runs vertically medially, and the fragment to the right of the fracture line in the drawing is considerably smaller than the fragment to the left of the fracture line, Fig. 7B a device for use in which the plate 1 is used in combination with only one arm 19 and all screws 15 and 31 used releasably connect the plate 1 and the arm 19 only to the larger fragment.

[0030] At the Fig. In the fracture of the patella 2 b shown in Figure 8A, three fragments have been created, for the compression and stabilization of which a device is used, in which, as shown in Fig. 8B, the plate 1 is used in combination with two arms 19 and 20, and in which the screws 15 and 31 used engage in all three fragments and detachably connect them to the plate 1 and the arms 19 and 20.

[0031] At the Fig. In the multifragmentary fracture of the patella 2c shown in Figure 9A, a total of five fragments (2d, 2e, 2f, 2g, 2h) have developed. For the treatment of this fracture pattern, a device is used in which, as shown in Fig. As can be seen in Figure 9B, the plate 1 is combined with two identical arms 20, 20 and a third arm 19, and the three arms 19, 20, 20 are attached to three fragments 2d, 2e, 2f of the five fragments, while the fourth fragment 2g and the fifth fragment 2h are detachably connected to the plate 1 without arms and only with screws 15 and 17. The three arms 19, 20, 20 are detachably attached to the first three fragments 2d, 2e, 2f together with the plate 1 by means of screws 31. QUOTES CONTAINED IN THE DESCRIPTION

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

[0000] CN 211325502U

[0002] CN 111616786A

[0003] CN 216628671U

[0004]

Claims

[1] Device for the osteosynthetic treatment of bone fractures, in particular patellar fractures, comprising a plate (1) having several star-shaped cavities (4) extending radially from an open end (5) at the radial outer edge of the plate (1) to an opposite end closer to the center (6) of the plate (1) than the open end, and several arms (18, 19, 20, 21) each having two legs (22, 24, 25, 26, 27) arranged at an angle to each other, wherein the arms (18, 19, 20, 21) are radially stepless and movable relative to the plate (1) after the inclusion of one leg (22) in the cavities (4) and can be detachably held in their respective position on the plate (1) by means of fastening means, characterized by, that the arms (18, 19, 20, 21) can each be detachably connected to the plate (1) individually and can be moved independently of each other relative to the plate (1), that the arms (18, 19, 20, 21) and the plate (1) each have at least one through-hole (13, 14, 16), and that the fastening means have several screws (15, 17, 31) by means of which each arm (18, 19, 20, 21) can be detachably connected to the plate (1) and to at least one bone fragment or the plate (1) can be detachably connected to at least one bone fragment. [2] Device according to claim 1, characterized by, that the plate (1) has at least one multi-part through-opening in the area of ​​each cavity (4), comprising several partial openings (7, 8, 9), of which at least one partial opening (7) is located in a first wall section (10) of the plate (1) bounding the respective cavity (4) from above, and another partial opening (9) is located in a second wall section (11) of the plate (1) bounding the respective cavity (4) from below, wherein the other partial opening (9) is slot-shaped and extends in the radial direction of the plate (1). [3] Device according to claim 2, characterized by , that at least one further partial opening (8) is located in the first wall section (10) of the plate (1), wherein the or each further partial opening (8) and the one partial opening (7) are spaced apart in the radial direction of the plate (1). [4] Device according to claim 2, characterized by, that at least one partial opening (7) has a round or oval cross-sectional shape. [5] Device according to claim 3, characterized by that one partial opening (7) and / or the or each further partial opening (8) has a round or oval cross-sectional shape. [6] Device according to any one of the preceding claims, characterized by , that the plate (1) has at least one through opening (13, 14) in the third wall sections (12) extending circumferentially between the star-shaped cavities (4). [7] Device according to any one of claims 1 to 5, characterized by , that the plate (1) has at least two passage openings (13, 14) in the third wall sections (12) extending circumferentially between the star-shaped cavities (4), which are spaced apart from each other in the radial direction of the plate (1). [8] Device according to claim 6 or 7, characterized by, that the or each passage opening (13, 14, 16) has a round or oval cross-sectional shape. [9] Device according to any one of the preceding claims, characterized by , that the plate (1) is circular on its outer circumference and slightly curved towards the center. [10] Device according to any one of the preceding claims, characterized by , that the plate (1) has in its middle (6) a through-opening (16) through which a screw (17) can be inserted for the detachable connection of the plate (1) with a bone fragment. [11] Device according to any one of the preceding claims, characterized by , that the plate (1) has six cavities (4), of which two adjacent cavities (4) enclose a constant opening angle ω of 60° between them. [12] Device according to any one of the preceding claims, characterized by , that each cavity (4) has a substantially T-shaped cross-section. [13] Device according to any one of claims 2 to 12, characterized by , that each first wall section (10) of the plate (1) which bounds the respective cavity (4) from above has on its outer side facing away from the respective cavity (4) a surface extending in the radial direction of the plate (1) and convexly curved in the circumferential direction of the plate (1). [14] Device according to any one of claims 2 to 13, characterized by, that each leg (22) of the arms (18, 19, 20, 21) has a through-opening in the form of an elongated hole (23) extending longitudinally along one leg (22) and, after one leg (22) has been inserted into the respective cavity (4), is arranged between the at least one partial opening (7) in the first wall section (10) and the other partial opening (9) in the second wall section (11), wherein the screw (31) passing through the at least one partial opening (7) and the other partial opening (9) also projects through the elongated hole (23) in one leg (22) of the respective arm (18, 19, 20, 21) and engages in a threaded connection with a wall surface bounding the elongated hole (23), by which the arm (18, 19, 20, 21) is held relative to the plate (1). [15] Device according to claim 14, characterized by, that the elongated hole (23) of one leg (22) of the arms (18, 19, 20, 21) has a width that is smaller than the diameter of the respective screw (31) passing through the elongated hole (23). [16] Device according to claim 14 or 15, characterized by , that the wall surface bounding the elongated hole (23) has sections opposite each other in the width direction of the elongated hole (23), which are surface sections of at least one insert integrated into one leg (22) that is softer than the screw (31) passing through the elongated hole (23), wherein the thread of the screw (31) penetrates the surface of the insert. [17] Device according to any one of the preceding claims, characterized by, that the other leg (24, 25, 26, 27) of at least one arm (18, 19, 20, 21) has the shape of an inverted T or of a straight or angled band, wherein the other leg (24, 25, 26, 27) has at its free end one or more through-holes forming screw holes (28) which can be penetrated by a corresponding number of screws. [18] Device according to any one of claims 1 to 16, characterized by , that the other leg (27) of at least one arm (21) has the shape of an inwardly curved hook and has one or more points (29) at its free end. [19] Device according to claim 17, characterized by , that the leg (25) of the at least one arm (19), which has the shape of an inverted T, is bent inwards towards the edge of the plate at its terminal sections pointing away from each other. [20] Device according to claim 17, characterized by, that the leg (26) of the at least one arm (20), which has the form of an angled band, is bent inwards towards the edge of the plate at its foot formed at the free end. [21] Device according to any one of the preceding claims, characterized by , that each arm (18, 19, 20, 21) has a depression (30) or a raised area for the insertion of a surgical instrument, in particular a reduction forceps, wherein the depression (30) or the raised area is radially spaced from the edge of the plate (1) when one leg (22) of the respective arm (18, 19, 20, 21) is received in the respective cavity (4) of the plate (1). [22] Device according to any one of the preceding claims, characterized by , that at least one of the screws (15, 17, 31) is an angle-stable screw which has a thread on the head of the screw. [23] Device according to claim 22, characterized by, that in addition to at least one angle-stable screw (15, 17, 31) at least one screw without threads on the head is used. [24] Device according to any one of the preceding claims, characterized by , that the plate (1) and / or the or each arm (18, 19, 20, 21) is made of metal, in particular titanium or a titanium alloy, or of plastic, in particular polyetheretherketone.

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