Device for applying a tensile force to a bone screw, and set comprising same

Abstract

The invention relates to a device (1) for applying a tensile force to a bone screw (6) displaceably mounted in a bone nail (5). According to the invention, in order to easily apply a defined compression force to the bone screw (6), the device (1) comprises an elongate pin (2) having a first end (21) and a second end (22), wherein the pin (2) is designed to be inserted in an opening (51) in the bone nail (5) while the pin (2) is freely rotatable, and the device (1) has a driver (3) for an adjusting means (4) connected to the bone screw (6), wherein the driver (3) can be fastened to the pin (2) and comprises a receptacle (32) for the adjusting means (4), such that the adjusting means (4) can be moved, in particular laterally, by rotation of the inserted pin (2).

Description

[0001] Device for applying a tensile force to a bone screw and set with this

[0002] The invention relates to a device for applying a tensile force to a bone screw displaceably mounted in a bone nail.

[0003] Today, a combination of an intramedullary nail and bone screws is often used to treat femoral neck fractures. The intramedullary nail is inserted into the femoral shaft and has an opening at an angle to the nail's longitudinal axis. This opening is designed so that a bone screw can first be inserted at an angle to the nail's longitudinal axis and screwed into a femoral head, thereby fixing the femoral head for healing. The opening in the intramedullary nail also provides space for a second screw, which can be designed as an adjusting and / or fixation screw that interacts with the bone screw.In this regard, various designs are known from the prior art, with many of the different variants having in common that the opening in the intramedullary nail is designed such that both the bone screw and the adjustment and fixation screw are positioned in this opening and the bone screw and the adjustment and fixation screw touch, or at least can touch, each other. The adjustment and fixation screw can be used to move the bone screw laterally in order to align the femoral head with the fractured femoral neck and, if necessary, to apply a desired compression force. Furthermore, the bone screw can be secured in a desired position with the adjustment and fixation screw to prevent lateral displacement.

[0004] Treating a femoral neck fracture is a challenging task, especially since such fractures primarily occur in older individuals, who often lack optimal bone mass. During surgery, it may be necessary to determine that the bone screw needs to be tightened further into the femoral head even after the bone screw and the adjustment and / or fixation screw have been secured. This then requires the adjustment and / or fixation screw to be removed first. This not only involves increased effort and is a source of error, but also prolongs the operation.

[0005] This is where the invention comes in. The object of the invention is to further develop a device of the type mentioned above in such a way that a well-regulated compression force can be applied to the bone screw, while at the same time allowing the bone screw already secured in the femoral head to be further tightened without great effort, if necessary.

[0006] This object is achieved if, in a device of the type mentioned at the outset, the device comprises an elongated pin with a first end and a second end, wherein the pin is designed to be inserted into an opening in the bone nail while the pin is freely rotatable, and in that the device has a driver for an adjusting means connected to the bone screw, wherein the driver can be fastened to the pin and comprises a receptacle for the adjusting means, so that the adjusting means can be moved, in particular laterally, by rotation of the inserted pin.

[0007] One advantage achieved with a device according to the invention is that the device is very simply constructed, yet still allows a well-defined force to be applied to the bone screw. For this purpose, the device comprises a combination of two units: The first unit is an elongated pin with a first end and a second end, wherein the pin is designed to be inserted into an opening in the bone nail while allowing free rotation of the pin. The pin can thus be inserted into the opening in the bone nail while remaining freely rotatable. As a second unit, the device comprises a driver that can be releasably attached to the pin. The driver has a receptacle for the adjusting means, which is designed such that the receptacle entrains the adjusting means when the pin rotates.When the receptacle moves the adjusting device in a lateral direction when the pin rotates, the bone screw, to which the adjusting device is releasably attached, is pulled in a lateral direction. This can close a gap between the femoral head and femoral neck in the area of ​​the fracture. It is also possible, however, to apply a precisely defined compression force. Conversely, it is also possible to move the bone screw medially when the pin rotates in the opposite direction, which may also be necessary under certain circumstances. Typically, however, a lateral displacement occurs in order to define a fracture gap or apply a desired compression force in the area of ​​the fracture. The adjusting device is designed to interact with the receptacle of the driver, so that the driver moves the adjusting device with it when the driver moves along the pin.For this purpose, the adjusting element can be elongated, with a different diameter, or designed in another suitable manner to allow the driver to engage. If both lateral and medial movement of the adjusting element is required, the driver can be attached to the adjusting element between two stops, allowing lateral or medial movement of the adjusting element depending on the direction of rotation of the pin.

[0008] Another advantage of the device according to the invention is that the pin can be quickly inserted and removed, allowing the bone screw to be quickly tightened if necessary. Only when an optimal result has been achieved with regard to the femoral head can an adjusting and / or fixation screw, or a purely fixating screw, be inserted into the opening of the bone nail, usually a so-called intramedullary nail, instead of the pin. This allows the operation to be completed quickly even if it becomes apparent that the bone screw needs to be screwed further into the femoral head.

[0009] Preferably, the pin is tapered at the first end. With a tapered design, the pin can be inserted into the opening of the bone nail until the pin abuts the bone nail and can no longer be moved in the medial direction. Inserting the pin into the bone nail also serves to provide support for the pin when the nail rotates. The pin can have a widened stop following a tapered area at the first end. This ensures that the pin can be inserted into the bone nail and its opening with a certain length or a certain projection. The opening of the bone nail can be designed with a thread in the area into which the pin is inserted for the adjustment and fixation screw to be inserted later. However, the pin is preferably designed to be thread-free at the first end, preferably up to the stop.An outer surface of the pin at the first end is thus smooth. This smooth surface can extend, in particular, all the way to the stop. This smooth surface allows the pin to rotate within the opening. In the tapered area, the pin is designed with a diameter that roughly corresponds to that of the opening of the bone nail in this area. This is usually a circular arc-shaped part of the opening, which is connected to another circular part of the opening for the bone screw.

[0010] The pin may be formed with a cone at the first end, wherein the cone extends in the medial direction and is tapered in this direction.

[0011] This allows the pin to be positioned more easily in the opening of the intramedullary nail. A section of the pin with a constant diameter can then be connected to the cone before the stop.

[0012] It is advantageous if the pin has an external thread between the first end and the second end. This external thread can be provided in order to be able to detachably fasten the driver to the pin. The driver can then be easily screwed onto the pin. The external thread is arranged closer to the second end of the pin than to the first end of the pin, since the pin should not be excessively long. The external thread is advantageously located between the first end and the second end of the pin in a quarter of the longitudinal extent of the pin, adjacent to the second end. In other words, the external thread can be positioned close to the second end of the pin.

[0013] The driver preferably has an internal thread that interacts with the external thread of the pin. The driver can thus be easily screwed onto the pin. Furthermore, the combination of an external thread of the pin has the advantage that, in a manner to be explained below, a compression force can be applied relatively easily to a bone screw connected to an adjusting device.

[0014] The driver's receptacle is advantageously ring-shaped. This allows for easy insertion of the adjusting device. In particular, the ring-shaped receptacle can be provided with a slot. This makes it possible to attach the driver to the adjusting device even when both the adjusting device and the pin are already positioned in the bone nail.

[0015] The annular receptacle is usually designed as an elongated hole. When the driver is attached, the longitudinal axis of the elongated hole runs parallel to the longitudinal axis of the pin.

[0016] The pin can be constructed in several parts, but is preferably made in one piece. Common materials such as steel can be used for the pin. The driver can also be constructed in several parts. It is possible for the driver to have a threaded part which is positioned on the pin. A receiving part can then be provided separately and fastened to the adjusting means, after which the threaded part and the receiving part are connected to one another. It is also possible for the driver to be constructed in several parts, with a threaded part on the pin and a receiving part permanently fastened to the adjusting means or being part thereof, with the threaded part and the receiving part being connected to one another when required. However, it is preferably provided that the driver is also constructed in one piece. In this case, the device can consist of a one-piece pin and a one-piece driver.

[0017] In a further aspect, the invention relates to a set for the lateral displacement of a bone screw fastened in a bone nail, comprising a device according to the invention and an adjusting means for the bone screw, wherein the adjusting means is elongated and has a widened proximal end as a stop for receiving the driver. With a corresponding set, a desired compression force can be applied particularly easily to a bone screw that is connected to the adjusting means. Furthermore, it is also possible for the bone screw in a femoral head to be corrected in a simple manner by merely separating the device according to the invention, after which a desired correction can be carried out.

[0018] If, in addition to lateral displacement of the adjusting device and thus of the bone screw, medial displacement of the adjusting device is also required, an additional stop for the driver can be provided on the adjusting device. In this context, a locking mechanism can also be provided for connecting the driver to the adjusting device, ensuring that they remain securely connected during rotation of the pin. For this purpose, a click connection between the adjusting device and the driver holder can be provided, for example.

[0019] Further features, advantages, and effects of the invention will become apparent from the following exemplary embodiment. Reference is made to the drawings, which show:

[0020] Fig. 1 shows a cross-sectional view of a device according to the invention, including instruments comprising an intramedullary nail, bone screw, adjusting means, and targeting module; Fig. 2 shows a further cross-sectional view similar to Fig. 1 with the driver released; Fig. 3 shows a device according to the invention;

[0021] Fig. 4 to Fig. 8 an instrumentation for the treatment of a femoral neck fracture including intramedullary nail and bone screw.

[0022] Fig. 1 shows a cross-section of a device 1 according to the invention, including instrumentation, for treating a femoral neck fracture. The instrumentation comprises a bone nail 5, a bone screw 6, and an aiming module 7. The device 1 according to the invention comprises a one-piece pin 2 and a one-piece driver 3. The pin 2 has a first end 21 and a second end 22. With regard to the treatment of a femoral neck fracture, the first end 21 is medial, while the second, opposite end 22 is lateral. In the region of the first end 21, the pin 2 has a (frusto-)conical tip that points in the medial direction M. This tip is followed by a region with a constant diameter, before this tapered region 23 transitions into a stop 24.The first end 21 of the pin 2 with the tapered cone, the adjoining tapered area 23 and the stop 24 is designed such that the pin 2 can be inserted into an opening 51 of the bone nail 5, usually an intramedullary nail. In the area adjacent to the cone, the pin 2 is thread-free on the outside and thus has a smooth surface. This allows the pin 2 to rotate freely in the opening 51 of the intramedullary nail, although the intramedullary nail has an internal thread in the area of ​​the opening 51, into which the pin 2 is inserted with the first end 21, which later receives an external thread of an adjustment and / or fixation screw. Adjacent to the stop 24, the pin 2 is initially designed with a constant outer diameter in the lateral direction L, which transitions into a wider outer diameter. In the area of ​​a last quarter in the lateral direction L, the pin 2 has an external thread 25.The external thread 25 can extend over approximately 5% to 20%, for example 7% to 18%, along a length of the pin 2. The extent of a length of the external thread 25 is dimensioned such that, in a manner to be explained below, a suitable compression force can be applied to a bone screw 6 by moving an adjusting means 4 connected thereto accordingly.

[0023] Furthermore, the device 1 comprises a driver 3 which has an internal thread 31. The driver 3, which is shown in detail in a perspective view as part of the device 1 in Fig. 3, firstly comprises a threaded part 33 with an internal thread 31. The driver 3 can be detachably connected to the pin 2 via the internal thread 31 by screwing the driver 3 onto the pin 2. The driver 3 furthermore has a receiving part 34 with a receptacle 32. The annular receptacle 32 is formed with an elongated hole and has a slot. A longitudinal axis of the receptacle 32 runs parallel to a longitudinal axis of the pin 2. Furthermore, the longitudinal axis of the receptacle 32 runs parallel to a longitudinal axis which extends through the opening which is surrounded by the internal thread 31 of the driver 3.

[0024] As can be seen in Fig. 1, the driver 3 with the receptacle 32 can be turned over so that the receptacle 32 comes into contact with the adjusting means 4. At the same time, the pin 2 is located in the opening of the bone nail 5, but can rotate freely in this opening because the pin 2 does not have an external thread in the region of the first end 21 that would engage with a corresponding internal thread 31 in the opening 51 of the intramedullary nail. Movement of the pin 2 in the medial direction M is prevented by the stop 24 of the pin 2, since this stop 24 comes into contact with the bone nail 5.

[0025] As can be seen from Fig. 2, the pin 2 together with the driver 3 can, in a state not connected to the adjusting means 4, even with the driver 3 attached to the adjusting means 4, be guided past a widened, in particular end-side, stop of the adjusting means 4 in the region of a proximal end 41. This is made possible by the driver 3 being sufficiently thin in that region of the threaded part 33 which is located at the maximum distance from the receiving part 34. The pin 2 can extend at a predetermined angle to the adjusting means 4 of less than 5°, in particular less than 2°. This angle is defined by the opening 51 and the engagement of the pin 2 therein.

[0026] The use of a device 1 according to the invention is illustrated in more detail in FIGS. 4 to 8. In FIG. 4, the device 1 comprising the pin 2 and the driver 3 has already been inserted into an opening 51 of the intramedullary nail or bone nail 5, but the driver 3 is not yet connected to the adjusting means 4 for the bone screw 6.

[0027] Fig. 5 shows the connection of the driver 3 to the adjusting means 4 in a situation otherwise unchanged compared to Fig. 4. This connects the pin 2 and the adjusting means 4, and thus indirectly also the bone screw 6. The bone screw 6 runs on the upper side of the pin 2 in the corresponding opening 51 of the intramedullary nail or bone nail 5. The bone screw 6 is freely displaceably mounted in the opening of the intramedullary nail or bone nail 5. This results from the fact that the bone screw 6 is smooth on the outside in this area and has no thread. The same applies to the intramedullary nail or bone nail 5.

[0028] Fig. 6 to Fig. 8 show various views after the pin 2 has been rotated clockwise using a suitable instrument that is applied to the end of the pin 2, namely at the lateral, second end 22. The rotation of the pin 2, which rests against the intramedullary nail or bone nail 5 with the stop 24, results in a forced guidance of the adjusting means 4 and thus also of the connected bone screw 6 in the lateral direction L. The further the pin 2 is moved clockwise, the further the bone screw 6 moves in the lateral direction L. This allows the bone screw 6 to be moved such that a gap between a femoral head and a femoral neck caused by a fracture is bridged. This can be done, for example, up to a position that is shown in two views in Fig. 6 and Fig. 7. The driver 3 can then be detached from the adjusting means 4 and the pin 2 together with the driver 3 can be removed.An adjustment and / or fixation screw can then be screwed into the opening 51 in order to fix the bone screw 6 in its lateral movement.

[0029] Should it become apparent during surgery that the bone screw 6 is not yet sufficiently screwed into the femoral head, this can be easily remedied by simply loosening the pin 2 with the driver 3 from the adjusting device 4 and then driving the bone screw 6 further into the femoral head with the adjusting device 4. Subsequently, the desired compression force can be applied by folding the driver 3 and thus the receptacle 32.

Claims

Patent claims 1. Device (1) for applying a tensile force to a bone screw (6) displaceably mounted in a bone nail (5), characterized in that the device (1) comprises an elongated pin (2) with a first end (21) and a second end (22), wherein the pin (2) is designed to be inserted into an opening (51) of the bone nail (5) while the pin (2) is freely rotatable, and in that the device (1) has a driver (3) for an adjusting means (4) connected to the bone screw (6), wherein the driver (3) is attachable to the pin (2) and comprises a receptacle (32) for the adjusting means (4), so that the adjusting means (4) is movable, in particular laterally, by rotation of the inserted pin (2).

2. Device (1) according to claim 1, characterized in that the pin (2) is tapered at the first end (21).

3. Device (1) according to claim 1 or 2, characterized in that the pin (2) has a widened stop (24) following a tapered region (23) at the first end (21).

4. Device (1) according to claim 2 or 3, characterized in that the pin (2) is designed to be thread-free at the first end, preferably up to the stop (24).

5. Device (1) according to one of claims 1 to 4, characterized in that the pin (2) has an external thread (25) between the first end (21) and the second end (22).

6. Device (1) according to claim 5, characterized in that the external thread (25) is arranged closer to the second end (22) of the pin (2) than to the first end (21) of the pin (2).

7. Device (1) according to claim 5 or 6, characterized in that the external thread (25) is located, with respect to a longitudinal extent of the pin (2), between the first end (21) and the second end (22) of the pin (2) in a quarter of the longitudinal extent adjoining the second end (22).

8. Device (1) according to one of claims 1 to 7, characterized in that the driver (3) comprises an internal thread (31) which cooperates with the external thread (25) of the pin (2).

9. Device (1) according to one of claims 1 to 8, characterized in that the receptacle (32) of the driver (3) is annular.

10. Device (1) according to claim 9, characterized in that the annular receptacle (32) is formed with a slot (33).

11. Device (1) according to claim 9 or 10, characterized in that the annular receptacle (32) is designed as an elongated hole.

12. Device (1) according to one of claims 1 to 10, characterized in that the pin (2) and / or the driver (3) are formed in one piece.

13. Set for the lateral displacement of a bone screw (6) fastened in a bone nail (5), comprising a device (1) according to one of claims 1 to 12 and an adjusting means (4) for a bone screw (6), wherein the adjusting means (4) is elongated and has a widened proximal end (41) as a stop for the receptacle (32) of the driver (3).

14. Set according to claim 13, characterized in that a securing means is provided for connecting the driver (3) to the adjusting means (4).

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