Device for treating a bone fracture with a telescopic bone screw

Abstract

The invention relates to a device (1) for treating a bone fracture, in particular a proximal femoral fracture, comprising a base (2), for fastening to a femur, as well as at least one bone screw (4) and an adjustment screw (5), wherein the base (2) has an opening (6) through which the bone screw (4) can be guided in order to be fastened in a femoral head and which receives the adjustment screw (5), wherein the bone screw (4) is in particular slidably mounted in the opening (6), and wherein the adjustment screw (5) is designed to predetermine, in the fastened state, in particular a maximum lateral sliding of the bone screw (4). According to the invention, in order to allow a targeted lateral movement of the femoral head without moving a lateral end of the bone screw (4), the bone screw (4) comprises a first bone screw part (41) and a second bone screw part (42), wherein the bone screw parts (41, 42) can be shifted relative to one another to change a bone screw length (L).

Description

[0001] Device for treating a bone fracture with a telescopic bone screw

[0002] The invention relates to a device for treating a bone fracture, in particular a proximal femur fracture, comprising a base for attachment to a femur, as well as at least one bone screw and an adjusting screw, wherein the base has an opening through which the bone screw can be guided to be fixed in a femoral head, and which receives the adjusting screw, wherein the bone screw is in particular slidably mounted in the opening and wherein the adjusting screw is arranged to predetermine, in particular a maximum, lateral sliding of the bone screw in the fixed state.

[0003] Fractures of the proximal femur are regularly considered challenging to treat. This is often due, in particular, to the fact that such fractures tend to occur in older people, and the bone structure is no longer optimal due to the patient's age. Furthermore, healing processes take longer in advanced age.

[0004] When treating a proximal femur fracture, it is important to consider that the surrounding muscles are no longer optimally positioned due to the fracture. During the healing process, the forces acting on the fracture site can therefore change. To address this, devices for treating proximal femur fractures have been developed that allow movement of the femoral head during the healing process. This promotes a more dynamic healing process. A base, such as an intramedullary nail or a plate attached laterally to the femur, is typically used for this purpose. The base has an opening into which a bone screw can be inserted or through which it can be passed. The bone screw fixes the femoral head and slides within this opening.To prevent lateral slippage of the bone screw and rotation of the femoral head, an adjusting screw is also provided. The adjusting screw is designed to engage, for example, in a groove on the bone screw. This prevents the bone screw, and consequently the femoral head, from twisting, resulting in rotational stability. Furthermore, the adjusting screw is designed to limit lateral movement of the bone screw, for example, with a stop or by having the aforementioned groove taper laterally, so that the bone screw can only move laterally within a predetermined range. This range can be, for example, 5 mm to 15 mm. Thus, depending on the given anatomical conditions and tailored to the specific fracture, a certain degree of lateral play of the bone screw can be predefined.As a result, during the healing process, the femoral head can move laterally, given rotational stability, if acting forces require or force this.

[0005] Although state-of-the-art devices allow for lateral movement of the bone screw and thus of the femoral head, transforming a static healing device into a dynamic one, the disadvantage is that lateral movement of the bone screw by, for example, 15 mm results in a noticeable change in the tissue, which is unpleasant for the patient and ultimately leads to altered conditions during the ongoing healing process.

[0006] This is where the invention comes in. The object of the invention is to eliminate or at least reduce the disadvantages of the prior art explained above.

[0007] This problem is solved if, in a device of the type mentioned above, the bone screw comprises a first bone screw part and a second bone screw part, wherein the bone screw parts are displaceable relative to each other by changing the length of the bone screw. In particular, it can be provided that the first bone screw part and the second bone screw part are displaceable relative to each other when the first bone screw part is fixed in a fixed state by shortening the length of the bone screw.

[0008] With a device according to the invention, the advantage is achieved that, in the fixed state of the device, i.e., when the first bone screw part engages in a femoral head, only the first bone screw part needs to be moved to allow lateral sliding in the base and thus also lateral movement of the femoral head. Movement of the first bone screw part is independent of movement of the second bone screw part. In other words, the first bone screw part, together with the femoral head, can slide laterally while the second bone screw part remains unchanged in position. Lateral movement of the second bone screw part is prevented by the adjusting screw, for example, by the adjusting screw having a suitable stop that blocks lateral movement of the second bone screw part.

[0009] The first part of the bone screw is advantageously designed to have a lateral piston extension that can slide into the bone screw section. This allows the bone screw to shorten while maintaining its outer diameter.

[0010] In general, according to the invention, the overall length of the bone screw decreases when the bone screw parts move relative to each other. The piston process can be round in cross-section with respect to the longitudinal axis of the bone screw. However, a non-round shape, for example oval or elliptical, is preferred, with a corresponding inner surface on the second bone screw part. This provides a rotational locking mechanism to prevent rotation, with the piston process sliding in the cylindrical cavity of the second bone screw part.

[0011] The bone screw components can be designed to be loosely inserted into one another. The bone screw can consist of only two parts: the first and second bone screw components. When in use or fixed, the assembled bone screw is held laterally by the adjusting screw, which blocks lateral movement of the second bone screw component, for example, by means of a stop against which the second component rests. The first bone screw component is connected to the femoral head. Both bone screw components can then slide within predetermined limits, namely until a gap between them is closed. This primarily concerns lateral movement of the first bone screw component along with the femoral head attached to it.Medial movement of the second bone screw part is possible, but irrelevant for the healing process.

[0012] The first part of the bone screw typically has an external thread at one medial end. This external thread allows the first part of the bone screw to engage with the femoral head. For this purpose, a suitable hole is first drilled in the femoral head. The first part of the bone screw can then be fixed in the femoral head.

[0013] The first part of the bone screw is preferably tapered at one lateral end. This tapered design allows the first part to slide into a recess in the second part of the bone screw. The second part of the bone screw remains stationary, thus shortening the length of the bone screw.

[0014] In particular, to ensure rotational stability of the bone screw and thus prevent rotation of the femoral head, it is preferably provided that the first part of the bone screw has at least one groove on its outer surface, which is designed such that the adjusting screw can engage in it. For this purpose, the adjusting screw can be positioned at a slight angle of more than 0° to 5° relative to a longitudinal axis of the bone screw. The adjusting screw then engages slightly obliquely in the groove of the bone screw. This prevents any pivoting movement of the bone screw and thus also of the femoral head, despite possible sliding.

[0015] The first part of the bone screw can have at least two grooves on its outer surface, preferably lying in a plane that encloses a longitudinal axis of the bone screw. It is also possible for the bone screw to have even more grooves, for example, three or four. This may facilitate adjustment during the operation.

[0016] It is particularly preferred that the first bone screw part has a laterally narrowed, especially tapered, piston-shaped projection at its end, which engages with the second bone screw part, and that in the adjacent area of ​​the first bone screw part, the outer diameter of the first bone screw part corresponds to the outer diameter of the second bone screw part. This results in a bone screw with a constant diameter at the transition between the first and second bone screw parts when fully retracted, ensuring uniformity. Although not required, as previously described, the first bone screw part may be connected to the second bone screw part by a locking element.This locking element can prove particularly useful during surgery, as the two bone screw parts are then inseparable. In the simplest embodiment, however, the device does without a locking element and consists only of two bone screw parts that can be loosely inserted into one another. To prevent the two bone screw parts from coming loose during surgery when the bone screw has already been inserted but the adjusting screw has not, the bone screw is held in position until the adjusting screw is secured, for example, with a screwdriver that is locked against rotation. Once the adjusting screw is secured, the screwdriver can then be released.Due to the lateral fixation of the first bone screw part in the femoral head and the blockage of the second bone screw part with respect to lateral displacement by the adjusting screw, the bone screw can no longer fall apart into its individual parts during the healing process.

[0017] The base can be formed as a plate, but preferably the base is formed as an intramedullary nail.

[0018] In one variant, a screw can be incorporated, and the first bone screw component has a stop surface for the screw, with the screw being connected to the second bone screw component. In this variant, the screw and its connection to the second bone screw component provide an additional function: the possibility of lateral compression. When assembling the two bone screw components, the intended screw is first guided past the stop surface with its shaft and screwed into the second bone screw component. The device is then ready for use. When treating a fracture, the second bone screw component engages with a femoral head and is thus fixed in place. If the screw is simultaneously in contact with the stop surface, the second bone screw component, along with the femoral head, can be pulled laterally by turning the screw.This allows for adjustment and the application of desired compression. Any potential lateral gliding during a later stage of healing is not affected.

[0019] It is advantageous for the first part of the bone screw to have a tapered section that encompasses the stop surface. This results in a structurally simple design for the first part of the bone screw and provides a stop surface for the screw head. The stop surface can extend the entire circumference of the first part of the bone screw, although this is not mandatory. A fully continuous stop surface can be easily created using a machining operation. The stop surface and the inner free diameter of the tapered section are matched to the screw being inserted, and vice versa.

[0020] The screw head is preferably designed to rest against the inner surface of the first bone screw section and slide within it until the screw head reaches the stop surface. An inner free diameter of the tapered section can be designed such that the unthreaded portion of the screw adjoining the screw head has a corresponding outer diameter. This, in conjunction with the screw head resting against the inner surface of the first bone screw section, ensures good guidance of the screw.

[0021] For connecting the screw to the second bone screw part, it is advantageous if the second bone screw part has an internal thread that interacts with an external thread of the screw.

[0022] The screw is typically connected to the second bone screw part in such a way that the screw slides with the second bone screw part. As explained, this design variant thus offers multifunctionality, since in addition to sliding, targeted lateral movement of the second bone screw part via the screw is also possible.

[0023] To ensure proper guidance of the slidingly mounted parts, it can also be provided that an outer surface of the second bone screw part rests against an inner surface of the first bone screw part. Further features, advantages, and effects of the invention will become apparent from the exemplary embodiments described below. The drawings referred to therein show:

[0024] Fig. 1 shows a section through a device according to the invention in a first state; Fig. 2 shows a section through a device according to the invention in a second state; Fig. 3 shows a first perspective view of a device according to the invention in a first state;

[0025] Fig. 4 shows a second perspective view of a device according to the invention in a first state;

[0026] Fig. 5 shows a perspective view of a device according to the invention in a second state;

[0027] Fig. 6 shows a variant of a device according to the invention.

[0028] Figure 1 shows a device 1 according to the invention. The device 1 comprises a base 2, which in the exemplary embodiment according to Figures 1 to 5 is designed as an intramedullary nail 3. The intramedullary nail 3 is typically an intramedullary nail that can be inserted into a femur. The intramedullary nail 3 is elongated and has an opening 6. Furthermore, the intramedullary nail 3 has another opening 8 distally. This further opening 8 serves to receive a distal screw with which the intramedullary nail 3 is fixed distally in the femur. Several distal openings 8 can also be provided.

[0029] The opening 6 accommodates a bone screw 4 and an adjusting screw 5. The opening 6 is designed such that the bone screw 4 is slidably mounted within it. The bone screw 4 can slide within the opening 6. For this purpose, the inner surface of the opening 6 is smooth in the area of ​​the bone screw 4, allowing the bone screw 4 to slide as soon as it comes into contact with the inner surface of the opening 6.

[0030] The bone screw 4 is designed in two parts, but can also include a safety element, which will be explained in more detail later, if required. The bone screw 4 comprises a first bone screw part 41, which interacts with a second bone screw part 42. The first bone screw part 41 is designed to be inserted into a femoral head. For this purpose, the first bone screw part 41 has an external thread 45 in the region of a medial end 44. This external thread 45 engages in a femoral head (not shown). For this purpose, a suitable bore is drilled in the femoral head, for example, a guide wire, around which a bore is then drilled using a suitable drill. The bone screw 4 is then inserted into the bore to anchor the first bone screw part 41 in the femoral head.

[0031] At an opposite, lateral end 46, the first bone screw part 41 is tapered. In the embodiment according to Figs. 1 to 5, this tapered shape can be designed such that the first bone screw part 41 has a tapered piston process 43. An outer diameter D1 of the first bone screw part is wider than the tapered area with the piston process 43.

[0032] The second bone screw part 42 is designed to receive a lateral end of the first bone screw part 41. If, as shown in Figures 1 to 5, a narrowed piston process 43 is provided, this piston process 43 engages with its outer surface on an inner surface of the second bone screw part 42. An outer diameter D2 of the second bone screw part 42 corresponds essentially to an outer diameter D2 of the first bone screw part 41 in the region that connects to the narrowed piston process 43. An outer diameter of the piston process 43 corresponds to an inner diameter of the second bone screw part 42, so that the piston process 43 slides on an inner surface of the first bone screw part 42. The piston process 43 can be round or oval. An inner surface of the second bone screw part 42 is designed accordingly.

[0033] The first bone screw part 41 has two grooves 47. The adjusting screw 5 can engage in one of these grooves 47. The adjusting screw 5 has an external thread 51 that interacts with an internal thread of the opening 6. In other words, the opening 6 is smooth in the area of ​​the bone screw 4, but threaded in the area of ​​the adjusting screw 5. The adjusting screw 5 can be secured against rotation by a pin 9. The external thread 51 of the adjusting screw 5 engages in one of the grooves 47 of the first bone screw part 41. This secures the bone screw 4, and thus also a femoral head, against rotation. However, lateral movement of the first bone screw part 4 and the femoral head attached to it is possible because the external thread 51 of the adjusting screw 5 allows for movement up to a predetermined play S.The first bone screw part 41 is not blocked in the area of ​​a gap L1 between the first bone screw part 41 and the second bone screw part 42. However, lateral movement of the first bone screw part 41 is only possible until either the clearance S or the gap L1 is closed. Ideally, the clearance S is exactly the same length as the gap L1, resulting in a double stop. The second bone screw part 42 is secured against lateral displacement by the adjusting screw 5 via a stop 7. Thus, the second bone screw part 42, which also interacts with the external thread 51 via a corresponding groove, could theoretically move medially, but this would require corresponding forces. However, as far as lateral movement is concerned, it is prevented by the stop 7 of the adjusting screw 5 by blocking it.

[0034] Fig. 2 shows a second state in which the first bone screw part 41 has moved along the possible play S or gap L1 towards the second bone screw part 42. This exhausts the lateral displacement; the first bone screw part 41, and thus also the femoral head, can no longer move laterally. The maximum lateral movement can therefore be predetermined via the play S and the gap L1. A particular advantage of the two-part design is that tensile and compressive forces can be effectively absorbed. In principle, it would be conceivable to simply make the bone screw 4 shorter and allow it to move until it reaches a stop on the adjusting screw 5. However, in this case, the tensile and compressive forces and the bending moments would be distributed much more inhomogeneously. The solution according to the invention ensures a balanced force transmission.

[0035] Figures 3 and 4 show the first state according to Figure 1 in perspective view. Figure 5 shows the second state according to Figure 1, also in perspective view. Figure 6 schematically illustrates a variant of a device 1 according to the invention. The device 1 again comprises a bone screw 4 with a first bone screw part 41 and a second bone screw part 42, as well as an adjusting screw 5. An intramedullary nail 3 has an opening 6 through which both the bone screw 4 and the adjusting screw 5 are guided. To achieve additional functionality, in this variant the first bone screw part 41 is formed internally with a taper 10, which, facing laterally, defines a stop surface 9 for a screw 8. The taper 10 has a free inner diameter that is smaller than the free inner diameter of the first bone screw part 1 in general.In principle, the first bone screw part 41 can be approximately cylindrical in shape. The second bone screw part 42 is connected to the screw 8. For this purpose, the screw 8 has a suitable external thread, and the second bone screw part 42 has a corresponding internal thread that interacts with the external thread of the screw 8. This makes it possible to connect the screw 8 to the second bone screw part 42 as shown. The second bone screw part 42 has an outer diameter at a medial end that corresponds to the outer diameter of the first bone screw part 41, so that a continuous surface is formed when the gap 11 shown in Fig. 6 is bridged. The second bone screw part 42 is formed with a step towards a lateral end, at which the outer diameter decreases. The outer diameter can be as shown in Fig.6 is designed such that the outer surface of the second bone screw part 42 rests against an inner surface of the first bone screw part 41 in this area and is thus guided stably along a straight line during lateral sliding. The distance 11 defines a maximum lateral sliding of the second bone screw part 42 along with the screw connected to it. For this purpose, the tapering is positioned in the first bone screw part 41, viewed in the lateral direction, so far that even when a maximum lateral position is reached and the distance 11 is closed, the head of the screw 8 does not protrude beyond a lateral end of the first bone screw part 41 when viewed in the lateral direction.The first bone screw part 41 is fixed by the adjusting screw 5, which can be designed at its end with a collar as shown. This collar engages in a groove of the first bone screw part 41, preventing the first bone screw part 41 from sliding in the opening 6. The multiple functions of the device 1 according to Fig. 6 result from the interaction of the screw 8 with the second bone screw part 42. If the second bone screw part 42 is inserted into a femoral head and the situation is as shown in Fig. 6 with a gap 11, the femoral head can be pulled laterally by turning the screw 8. As long as the gap 11 is not completely closed by appropriate compression, the second bone screw part 42, along with the screw on one side and the femoral head on the other, can slide laterally during the healing process.Device 1 thus offers the possibility of optimally treating a fracture.

Claims

Patent claims 1. Device (1) for treating a bone fracture, in particular a proximal femur fracture, comprising a base (2) for attachment to a femur, as well as at least one bone screw (4) and an adjusting screw (5), wherein the base (2) has an opening (6) through which the bone screw (4) can be guided to be attached in a femoral head, and which receives the adjusting screw (5), wherein the bone screw (4) is in particular slidably mounted in the opening (6) and wherein the adjusting screw (5) is arranged to predetermine, in particular a maximum, lateral sliding of the bone screw (4) in the attached state, characterized in that the bone screw (4) comprises a first bone screw part (41) and a second bone screw part (42), wherein the bone screw parts (41, 42) are displaceable relative to each other by changing a bone screw length (L).

2. Device (1) according to claim 1 , characterized in that the first bone screw part (41) and the second bone screw part (42) are displaceable relative to each other in a fixed state of the first bone screw part (41) by shortening the bone screw length (L).

3. Device (1) according to claim 1 or 2, characterized in that the first bone screw part (41) has a lateral piston process (43) which can slide into the second bone screw part (42), wherein the piston process (43) is not round in cross-section to the longitudinal axis of the bone screw, in particular oval or elliptical, and an inner surface of the second bone screw part is formed accordingly.

4. Device (1) according to one of claims 1 to 3, characterized in that the first bone screw part (41) has an external thread (45) at a medial end (44).

5. Device (1) according to one of claims 1 to 4, characterized in that the first bone screw part (41) is narrowed, in particular tapered, at a lateral end (46).

6. Device (1) according to one of claims 1 to 5, characterized in that the first bone screw part (41) has at least one groove (47) on its outer side, which is arranged such that the adjusting screw (5) can engage in it.

7. Device (1) according to one of claims 1 to 6, characterized in that the first bone screw part (41) has at least two grooves (47) on its outer side, which preferably lie in a plane.

8. Device (1) according to one of claims 1 to 7, characterized in that the bone screw part (41) has a narrowed, in particular tapered, piston process (43) at its lateral end, which engages in the second bone screw part (42), and that in the adjoining region (4) of the first bone screw part (41) an outer diameter (D1) of the first bone screw part (41) corresponds to an outer diameter (D2) of the second bone screw part (42).

9. Device (1) according to one of claims 1 to 8, characterized in that the first bone screw part (41) is connected to the second bone screw part (42) via a locking element.

10. Device (1) according to one of claims 1 to 9, characterized in that the base (2) is designed as an intramedullary nail (3).

11. Device (1) according to claim 1 or 2, characterized in that a screw (8) is provided and the first bone screw part (41) has a stop surface (9) for the screw (8) and the screw (8) is connected to the second bone screw part (42).

12. Device (1) according to claim 11 , characterized in that a tapered section (10) is formed in the first bone screw part (41) which comprises the stop surface (9).

13. Device (1) according to claim 11 or 12, characterized in that the second bone screw part (42) has an internal thread which interacts with an external thread of the screw (8).

14. Device (1) according to any one of claims 11 to 13, characterized in that the screw (8) is connected to the second bone screw part (42) such that the screw (8) slides with the second bone screw part (42).

15. Device (1) according to one of claims 11 to 14, characterized in that an outer surface (10) of the second bone screw part (42) abuts an inner surface of the first bone screw part (41).

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