Set for treating a bone fracture

Abstract

The invention relates to a set (1) for treating a bone fracture, in particular for treating a femoral neck fracture, comprising: an intermedullary nail (2) having an opening (6) with a first opening region (61) for receiving a bone screw (3) and a second opening region (62) for receiving an adjusting and / or fixing screw (4) for the bone screw (3), the first opening region (61) being connected to the second opening region (62) in a transition region (63); as well as an optionally multi-part sleeve (5) and a plurality of drill wires (7). In order to be able to make corrections when a drill wire (7) for the bone screw (3) is placed too high or too low, according to the invention the opening (6) of the intermedullary nail (2) in the transition region (63) is larger than an outer diameter of a drill wire (7).

Description

[0001] Set for treating a bone fracture

[0002] The invention relates to a set for treating a bone fracture, in particular for treating a femoral neck fracture, comprising an intermedullary nail with an opening having a first opening region for receiving a bone screw and a second opening region for receiving an adjustment and / or fixation screw for the bone screw, wherein the first opening region is connected to the second opening region in a transition region, as well as an optionally multi-part sleeve and a plurality of drill wires.

[0003] Femoral neck fractures are relatively common bone fractures that particularly affect older patients. Treating femoral neck fractures in older people is challenging for several reasons: Firstly, the broken femoral head fragment must be correctly positioned in relation to the separated femur for good healing. Healing takes several weeks, and over this time the forces acting on the broken bone pieces, for example from surrounding muscles, can change significantly. Correct alignment of the separated bone pieces during surgery is therefore very important, but at the same time is complex due to several variables. Secondly, the bone structure in older people is often significantly poorer than in young people, which can make it difficult to anchor bone screws in the femoral head.

[0004] A large number of different devices for treating femoral neck fractures are known from the prior art. For example, plate solutions are known in which a plate is screwed onto the femur and further screws are passed through the plate to anchor the femoral head. Devices that work with an intramedullary nail are also often used today. The intramedullary nail is driven into the medullary canal of the femur and has at least one proximal opening through which a bone screw can be passed. The bone screw is then screwed into the femoral head. If necessary, the desired compression can be applied in order to use the bone screw to fix the femoral head or femoral head.To move the neck fragment towards the base of the femoral neck and thus align the two broken bone pieces together and, if necessary, also exert a certain pressing force. Devices have already been developed for this purpose which enable this with relatively fine adjustment. These devices usually use two screws: a bone screw which is anchored in the femoral head and an adjustment and / or fixation screw for the bone screw; one or more distal screws are also provided for distal locking. The function of the adjustment and / or fixation screw can vary depending on the device. In most cases, the adjustment and / or fixation screw can interact with the bone screw in such a way that the paired arrangement of the two screws initially prevents rotation of the femoral head.Advanced devices are also known which enable control of the force to be applied in a lateral direction and / or, if appropriate, also permit lateral mobility of the bone screw within certain limits during the healing process. US Pat. No. 7,527,627 B2, for example, describes a system with which compression can be achieved using a paired arrangement of a bone screw and an adjustment and / or fixation screw. DE 202022 002 403 U, for example, discloses a device for treating a femoral neck fracture, wherein a paired arrangement of a bone screw and an adjustment and / or fixation screw creates a situation in which lateral play for the bone screw can be adjusted during the healing process while simultaneously providing rotational blockage.

[0005] State-of-the-art devices with an intermedullary nail and a bone screw (“lag screw”) as well as an adjustment and / or fixation screw (“set screw”) thus offer the possibility of effectively dealing with forces and relative movements. The procedure for arranging such devices is generally as follows: First, the intramedullary nail or intermedullary nail is inserted into the medullary cavity of the femur. Suitable targeting modules are used for this purpose, with which the intramedullary nail can be moved inside the bone. A sleeve is then connected to the targeting module. The sleeve usually runs at an angle to the inserted intermedullary nail, which, when inserted, runs roughly along the axis of the leg. The tissue is then opened through an incision through the sleeve.Additional sleeve components, namely tissue protection sleeves, can then be inserted into the sleeve to gain free access to the bone through the tissue. Drill wires are then inserted into the sleeve and tissue protection sleeves. The drill wires serve as guides for a drill. The drill can then be used to drill appropriate holes to accommodate the bone screw as well as the adjustment and / or fixation screw. The bone screw is then inserted first and, if necessary after a compression step, is locked in a rotationally stable manner with the adjustment and / or fixation screw by moving the bone screw and thus the femoral head laterally. Optionally with the option of a predefined lateral movement of the bone screw during the healing process.

[0006] Although state-of-the-art devices with an intermedullary nail and a bone screw as well as an adjusting and / or fixation screw offer very good adjustment options with regard to healing, one very crucial point has not yet been addressed: the exact determination of the position of the bone screw. The bone screw is essentially already fixed by the first inserted drill wire, which later guides the drill, whose hole is created in the femoral head and in turn fixes the bone screw medially and caudally / cranially as well as in rotation. If the drill wire is incorrectly placed caudally / cranially, this will have an impact right up to the positioning of the bone screw. Although possible incorrect positioning of a drill wire can be detected using imaging techniques during the operation, there are no or insufficient options for correction.In general, the current technique for corrective surgery often involves removing the drill wire, moving the implant freehand using a targeting module, and drilling again. This can often result in the drill wire being deflected into pre-existing drill channels, resulting in imprecise positioning for subsequent surgical steps. If the drill wire remains in the wrong position, optimal conditions for subsequent healing are not achieved, as the load-bearing bone screw connected to the femoral head is not optimally positioned.

[0007] This is where the invention comes in. The object of the invention is to further develop a set of the type mentioned above in such a way that the drill wire for the bone screw can still be correctly inserted during surgery with minimal effort if the first drill wire, intended for the bone screw, is incorrectly positioned. This object is achieved if, in a set of the type mentioned above, the opening of the intermedullary nail in the transition area is larger than the outer diameter of a drill wire.

[0008] A particular advantage achieved with the invention is that the drill wire for guiding a drill for a hole for a bone screw can still be correctly inserted even if a first drill wire has already been inserted which would have been intended for the bone screw but is positioned too far proximal or too far distal. Since the opening in which both the bone screw and the adjusting and / or fixation screw are accommodated in the intermedullary nail is designed such that there is a continuous opening with a first opening area and a second opening area, wherein the transition area is larger than the outer diameter of a drill wire, the intermedullary nail or intramedullary nail together with the associated targeting module can be moved depending on the desired correction so that the next drill wire to be inserted can be inserted in a position correct for the bone screw.This allows for easy correction both cranially and caudally. If, for example, the first drill wire, intended for the bone screw, is positioned too far distally, the intermedullary nail can be lifted upwards so that the first drill wire is no longer inserted superiorly but inferiorly, thus becoming the drill wire for laying out the drill hole for the adjustment and / or fixation screw. A second drill wire can then be placed above or superior to this drill wire to define the drill hole for the bone screw. A similar correction can be made if the first drill wire is placed too far proximally. In this case, the second drill wire is first inserted below, i.e. inferiorly. This second drill wire is then no longer used to lay out a drill hole for the adjustment and / or fixation screw, but now for the bone screw.After removing the superiorly positioned drill wire, the intermedullary nail can then be moved again, this time distally. This places the second drill wire, which was previously positioned inferiorly, superiorly and can therefore define a hole for the bone screw. The inferior drill wire can then be inserted below it, which is used to define the hole for the adjustment and / or fixation screw. The position of a drill wire and other parts of the set for treating a bone fracture is checked during surgery using imaging techniques. This allows the position of a drill wire to be identified and corrected if it is not in the optimal position. The correction options both cranially and caudally are opened up in the manner explained by the special design of the transition area of ​​the opening relative to the outer diameter of the respective drill wire.

[0009] Typically, the first opening area has a larger free inner diameter than the second opening area. This is because the bone screw is usually significantly stronger than the non-load-bearing adjustment and / or fixation screw. The first opening area can lie in front of or along the leg axis above the second opening area in the proximal-to-distal direction, although the reverse is also possible. It is also possible for the bone screw and the adjustment and / or fixation screw to lie in a plane that intersects the vertical leg axis perpendicularly or at a certain angle. In this case, correction does not occur upwards or downwards, but to the left or right, or a combination of both.In general, a correction can be performed in the plane in which the intermedullary nail is movable with a fixed drill wire, thus also planes that run normal or oblique to the leg axis or the femur.

[0010] The sleeve is preferably designed for inserting the bone screw and the adjustment and / or fixation screw, wherein the area for the bone screw borders on an area for the adjustment and / or fixation screw, wherein a free diameter of the sleeve or parts thereof in a boundary area between the bone screw and the adjustment and / or fixation screw is larger than an outer diameter of a drill wire. This allows the rest of the set as a whole to be moved smoothly around an already fixed drill wire. The sleeve can be designed in several parts with an outer sleeve part and inner tissue protection sleeves which are received in the outer sleeve part. The inner tissue protection sleeves can be designed with slots facing one another.This makes it possible, similar to the opening in the intermedullary nail, for the sleeve to be moved around the already fixed first drill wire in such a way that the first drill wire can become the drill wire for the adjustment and / or fixation screw and the second drill wire can then define the exact positioning for the bone screw.

[0011] The inner tissue protection sleeves can be elongated and have a U-shape in cross-section along a longitudinal axis, with open areas of the tissue protection sleeves facing each other. This ensures that a drill wire already fixed in the femoral head can be easily shifted from superior to inferior or vice versa by moving the remaining set relative to the fixed drill wire. Open, U-shaped tissue protection sleeves allow this to be done easily. At the same time, the necessary protection for the tissue and unobstructed access for surgery are provided.

[0012] It is particularly preferred that the sleeve or parts thereof, in particular the tissue protection sleeves, are formed with holes, wherein the holes are preferably arranged along a straight line between a medial end and a lateral end. The holes are arranged laterally on the tissue protection sleeve or parts thereof, for example internal tissue protection sleeves. By arranging them along a straight line, the position of a drill wire can be detected using imaging techniques. By arranging them along a straight line, the remaining set can be aligned to the straight drill wire such that the corresponding straight lines of the holes and the drill wire coincide. The second inserted drill wire is then automatically aligned parallel to the first inserted drill wire.

[0013] For easier handling, the set includes a targeting module. The targeting module can be used to move the intermedullary nail. The targeting module is designed to connect to the intermedullary nail at one end. The targeting module is designed to accommodate the sleeve at the opposite, lateral end.

[0014] The intermedullary nail can have one or more additional openings distally to accommodate screws for distal fixation of the bone nail. The set advantageously includes two drill wires of identical design. Since the set is designed so that the two drill wires can be swapped functionally, contrary to the original plan (the drill wire for defining the drill hole for the bone screw becomes the drill wire for defining the drill hole for the adjustment and / or fixation screw, and vice versa), it is advisable that the drill wires be identical to achieve the desired flexibility.

[0015] It can also be particularly advantageous for the set to comprise a correction sleeve for a plurality of drill wires, wherein the correction sleeve has a plurality of passages for receiving the drill wires and wherein the distance between the passages is smaller than the distance between a center of the first opening region and a center of the second opening region. With such a correction sleeve, which is preferably also releasably attached laterally to the target module, minor corrections can be made, for example if a drill wire is set slightly too high. In this case, the correction sleeve can be pushed over the set drill wire and then provides the basis for inserting a next drill wire slightly inferiorly. For this purpose, the passages of the correction sleeve are spaced accordingly close together.For example, the passages of the correction sleeve can be spaced apart from each other by less than 5 mm, in particular less than 3 mm, for example less than 2.5 mm.

[0016] A method for correcting an incorrectly placed first drill wire, in particular a first drill wire placed too far proximally or too far distally, wherein an intermedullary nail is inserted in the method, wherein a bone screw is guided through the intermedullary nail and fixed in a femoral head, wherein an adjustment and / or fixation screw is preferably provided for a rotation block and / or for determining a lateral movement possibility or restriction for the bone screw, comprises the following steps:

[0017] - Determining the position of a drill wire, particularly inserted in a femoral head, for determining a drill hole for a bone screw, particularly by means of an imaging procedure during an operation;

[0018] - if necessary, removing one of several, in particular two, drill wires; - moving an intermedullary nail around the fixed drill wire for the bone screw so that the fixed drill wire defines a position of a drill hole for the bone screw.

[0019] In these process steps, a set according to the invention can be used in particular, which is advantageously suitable for carrying out such a process.

[0020] This procedure offers the advantage of allowing corrections to be made both cranially and caudally during the operation if it is determined that the drill wire was incorrectly inserted to determine the position of the bone screw. Using a correction sleeve also allows for minor, but in individual cases important, corrections. The procedure and its individual steps are explained in detail below in exemplary embodiments.

[0021] Further features, advantages, and effects of the invention will become apparent from the following exemplary embodiments. The exemplary embodiments show:

[0022] Fig. 1a a side view of a set for supplying a bone structure;

[0023] Fig. 1b a section in the area of ​​an intermedullary nail in Fig. 1a;

[0024] Fig. 1c shows a cross-section of the tissue protection sleeves of the set in Fig. 1a;

[0025] Fig. 2 to Fig. 6 illustrations of a correction process for a drill wire that has been set too deep;

[0026] Fig. 7 to Fig. 13 a correction process when a drill wire is set too high;

[0027] Fig. 14 a correction sleeve;

[0028] Fig. 15 to Fig. 23 a correction of a drill wire using a lateral correction sleeve;

[0029] Fig. 24 an intermedullary nail in an inserted state with bone screw and adjustment and / or fixation screw.

[0030] Fig. 1a to Fig. 1c show a set 1 according to the invention in a side view (Fig. 1a) and in two sections (Fig. 1b and Fig. 1c). The set 1 comprises an intermedullary nail 2, which is not yet fully visible in Fig. 1a to Fig. 1c and is located in a femur. The intermedullary nail 2 is connected to a targeting module 11. For this purpose, the targeting module 11 is designed such that it can be connected to the intermedullary nail 2 at a medial end 9 and vice versa. This connection is detachable. The targeting module 11 can be used to move and position the intermedullary nail 2 in the femur.

[0031] Furthermore, the set 1 comprises a sleeve 5. The sleeve 5 has an outer sleeve part 51 and tissue protection sleeves 52, 53 located on the inside. The sleeve 5 is inserted into a receptacle for the sleeve 5 at a lateral end 10 of the target module 11. The sleeve 5 is provided in particular because the two tissue protection sleeves 52, 53 are positioned slightly converging (approximately 0.5° to 3°) towards one another. In particular, if the two tissue protection sleeves 52, 53 are guided parallel, they can also be received directly on the target module 11. In this case, the sleeve part 51 can be omitted and the sleeve 5 is formed by the two tissue protection sleeves 52, 53 or, if necessary, just one of the tissue protection sleeves 52, 53.

[0032] As can be seen in Fig. 1a, a drill wire 7 is inserted into the set 1. For the introduction and guidance of the drill wire 7, a suitable, laterally arranged guide sleeve 12 is provided, which is inserted into the sleeve part 51 of the sleeve 5. The drill wire 7, as well as other drill wires 7 that are used when using the set 1, generally have a constant outer diameter along a longitudinal extent of a drill wire 7. Only at a first end of a drill wire 7, which is driven into a femoral head, is there a variation in the diameter due to a thread. As can be seen in the section in Fig. 1b, the intermedullary nail 2 has an opening 6 with a first opening region 61 and a second opening region 62. A transition region 63 is located between the first opening region 61 and the second opening region 62.The first opening area 61 is generally smooth on an inner side and accommodates a bone screw 3 (shown later). The bone screw 3 is thus generally mounted so as to be displaceable in the intermedullary nail 2, since the first opening area 61 is thread-free. The second opening area 62 is designed for an adjusting and / or fixing screw 4 and has an internal thread for receiving and securing this adjusting and / or fixing screw 4, which is formed with a corresponding external thread. The adjusting and / or fixing screw 4 interacts with the bone screw 3 to adjust a maximum lateral deflection of the bone screw 3 during a healing process. Typical ranges of motion for the bone screw 3 range from 0 mm to 15 mm, in particular from 0 mm to 10 mm.

[0033] As can be seen from Fig. 1b, the transition region 63 between the first opening region 61 and the second opening region 62 is designed such that it is wide enough for the drill wire 7 to pass from the first opening region 61 into the second opening region 62 when the intermedullary nail 2 is displaced. In other words, an outer diameter of the drill wire 7 is smaller than a free diameter of the opening 6 in the transition region 63. Since the drill wire 7 is already fastened in the femoral head, the drill wire 7 can only pass from the first opening region 61 into the second opening region 62 by displacing the intermedullary nail 2.Should the situation be reversed, i.e. the drill wire 7 is located in the second opening area 62, it is also possible, conversely, that by linearly displacing the intermedullary nail 2 the drill wire 7 is initially located in the second opening area 62 and then, after displacing the intermedullary nail 2, in the first opening area 61.

[0034] For the sleeve 5, which can be composed of several parts, a change in the position of the drill wire 7 from a superior position to an inferior position and vice versa is also possible. As can be seen in Fig. 1c, the sleeve 5 in the exemplary embodiment comprises, in addition to the outer sleeve part 51, inner tissue protection sleeves 52, 53 which are elongated with longitudinal axes X, Y (Fig. 1a). The inner tissue protection sleeves 52, 53 are mounted in the outer sleeve part 51. The inner tissue protection sleeves 52, 53 are approximately U-shaped in the cross-section shown in Fig. 1c, with slots in the two inner tissue protection sleeves 52, 53 pointing towards each other.The two openings in the U-shaped profile of the two inner tissue protection sleeves 52, 53 are designed, similar to the opening regions 61, 62 of the opening 6 of the intermedullary nail 2, with a boundary region 54, so that the drill wire 7 can move from a superior position to an inferior position and vice versa when the intermedullary nail 2 is moved essentially linearly in the medullary canal. The design of the opening 6 in the transition region 63 and of the sleeve 5 with the inner tissue protection sleeves 52, 53, each with a transition region 63 or an opening of the inner tissue protection sleeves 52, 53, in such a way that a drill wire 7 can be guided from a superior position to an inferior position and vice versa, relative to the intermedullary nail 2, opens up a variety of possibilities for ad hoc correction during an operation.This is initially illustrated below for the case where a first drill wire 7, which is actually intended for a bone screw 3, is positioned too low. This is followed by an explanation of how a correction can be made for a drill wire 7 that is positioned too high for the bone screw 3.

[0035] Fig. 2 to Fig. 6 explain a corrective procedure when a first drill wire 7 for a bone screw 3 is inserted too far distally in the femoral head. This can be seen in Fig. 2. Guide sleeves 12 for the drill wire(s) 7, which are initially inserted into the sleeve 5, are then removed as shown in Fig. 3. This results in the situation shown in Fig. 3. The intermedullary nail 2 is then pushed proximally with the target module 11, as can be seen in Fig. 4. Subsequently, the guide sleeves 12 for the drill wire(s) 7 are again inserted as shown in Fig. 5. The second drill wire 7 can then be inserted. The position of the first drill wire 7 is thus reversed from superior to inferior.In other words, the initially inserted drill wire 7, whose incorrect positioning was recognized as being too far distal for the subsequent fixation of a bone screw 3, is not used as a drill wire 7 for the definition of a hole for the bone screw 3, but for the adjustment and / or fixation screw 4.

[0036] The correct positioning of the intermedullary nail 2 through the linear displacement is facilitated by the fact that the inner tissue protection sleeves 52, 53 have holes 8. The holes 8, which can be seen, for example, in Fig. 1a or Fig. 4, are arranged along a straight line for both inner tissue protection sleeves 52, 53. This makes it possible to see the location of the drill wire 7 using an imaging instrument, which is usually used during surgery, and to align the inner tissue protection sleeves 52, 53 accordingly so that the drill wire 7 is visible through the holes 8. This initially results in excellent alignment of the remaining set 1 with respect to the inserted drill wire 7. The additional attached drill wire 7 can then be inserted into the femoral head exactly parallel to the first drill wire 7.

[0037] Fig. 7 to Fig. 13 show a caudal correction. The correction proceeds similarly to a cranial correction, the difference being that a drill wire 7 is removed. Fig. 7 shows an initial situation with a drill wire 7 that has been drilled too high (usually a Kirschner wire or K-wire). According to Fig. 8, a second drill wire 7 or K-wire is inserted. The upper drill wire 7 is then removed according to Fig. 9 and, according to Fig. 10, the guide sleeves 12 for the drill wires 7 are then pulled out. After that, according to Fig. 11, the intermedullary nail 2 with the targeting module 11 can be pushed distally so that the drill wire 7 that was not removed migrates to the superior position. Thus, the originally lower, inferiorly arranged drill wire 7 for the adjustment and / or bone screw 4 is in the position intended for the bone screw 3. Subsequently, according to Fig. 12 and Fig.13 in particular a guide sleeve 12 for a further drilling wire 7 is set and this second drilling wire 7, which is now relevant for the adjusting and / or fixing screw 4, is set.

[0038] Fig. 14 shows a correction sleeve 13. The correction sleeve 13 has three openings 14 extending from lateral to medial. All three openings are identically constructed on the inside. The openings 14 serve to guide drill wires 7. The correction sleeve 13 can be attached or inserted laterally to the target module 1 or a sleeve part 51 already located therein. Minor mispositions of a drill wire 7 can be reliably corrected with the correction sleeve 13. This is illustrated below using Figs. 15 to 23.

[0039] According to Fig. 15, a drill wire 7 is drilled slightly too high and is already positioned in a femoral head. The K-wire sleeves or guide sleeves 12 are then removed according to Fig. 16. Subsequently, the correction sleeve 13 is inserted according to Fig. 17 without causing any displacement of the target module 11. The second K-wire is then drilled, as can be seen in Fig. 18. Subsequently, the upper drill wire 7 is removed according to Fig. 19 and the correction sleeve 13 is removed according to Fig. 20. The target module 11 can then be moved according to Fig. 21, the guide sleeves 12 can be inserted according to Fig. 22, and the second K-wire or drill wire 7 can be inserted according to Fig. 23. Due to the small distance between the passages 14 of the correction sleeve 13, very small corrections can be made in this way for a later perfect fit of a bone screw 3 as well as an adjustment and / or fixation screw 4. Fig.Finally, Figure 24 shows a situation in which the bone screw 3 together with the adjustment and / or fixation screw 4 are positioned together with an intermedullary nail 2 to enable healing of a femoral neck fracture.

[0040] A set 1 according to the invention allows corrections to be made during surgery for a femoral neck fracture if it is detected that a first drill wire 7 for a bone screw 3, which bears the predominant load during the healing process, is incorrectly positioned. This applies both if the drill wire 7 for the subsequent fixation of the bone screw 3 is positioned too far proximally and too far distally. Thus, both an ad-hoc correction in a caudal and cranial direction is possible.

Claims

Claims 1. Set (1) for treating a bone fracture, in particular for treating a femoral neck fracture, comprising an intermedullary nail (2) with an opening (6) with a first opening region (61) for receiving a bone screw (3) and a second opening region (62) for receiving an adjusting and / or fixing screw (4) for the bone screw (3), wherein the first opening region (61) is connected to the second opening region (62) in a transition region (63), as well as an optionally multi-part sleeve (5) and a plurality of drill wires (7), characterized in that the opening (6) of the intermedullary nail (2) in the transition region (63) is larger than an outer diameter of a drill wire (7).

2. Set (1) according to claim 1, characterized in that the first opening area (61) is formed with a larger free inner diameter than the second opening area (62).

3. Set (1) according to claim 1 or 2, characterized in that the sleeve (5) is designed for inserting the bone screw (3) and the adjusting and / or fixing screw (4), wherein an area for the bone screw (3) adjoins an area for the adjusting and / or fixing screw (4), wherein a free diameter of the sleeve (5) or parts thereof in a boundary area (54) of the bone screw (3) and the adjusting and / or fixing screw (4) is larger than an outer diameter of a drill wire (7).

4. Set (1) according to claim 3, characterized in that the sleeve (5) is formed in several parts with an outer sleeve part (51) and has inner tissue protection sleeves (52, 53) which are received in the outer sleeve part (51).

5. Set (1) according to claim 4, characterized in that the inner tissue protection sleeves (52, 53) are formed with slots facing each other.

6. Set (1) according to claim 5, characterized in that the inner tissue protection sleeves (52, 53) are elongated and in a cross section form a Longitudinal axis (X, Y) have a U-shape, with open areas of the tissue protection sleeves (52, 53) facing each other.

7. Set (1) according to one of claims 1 to 6, characterized in that the sleeve (5) or parts thereof, in particular the tissue protection sleeves (52, 53), are formed with holes (8), wherein the holes (8) are preferably arranged between a medial end (9) and a lateral end (10) along a straight line.

8. Set (1) according to one of claims 1 to 7, characterized in that the set (1) comprises a target module (11).

9. Set (1) according to one of claims 1 to 8, characterized in that the set (1) comprises two drilling wires (7) with identical design.

10. Set (1) according to one of claims 1 to 9, characterized in that the set (1) comprises a correction sleeve (13) for a plurality of drilling wires (7), wherein the correction sleeve (13) has a plurality of passages (14) for receiving the drilling wires (7) and wherein a distance between the passages (14) is smaller than a distance between a center of the first opening area (61) and a center of the second opening area (62).

Images