Device for treating a bone fracture with dynamization control

Abstract

The invention relates to a device (1) for treating a bone fracture, in particular a proximal femoral fracture, comprising an elongate intramedullary nail (3) having a first opening (31), which intersects a longitudinal axis (X) of the intramedullary nail (3), and a second opening (32), which runs substantially along the longitudinal axis (X) of the intramedullary nail (3), a locking element (4), which can be introduced into the second opening (32) in the intramedullary nail (3), and a sliding element (2) that can be inserted through the first opening (31) and has a groove (21) in which the locking element (4) engages in order to limit a movement of the sliding element (2). According to the invention, in order to effectively control a movement of the sliding element (2), in particular a bone screw, during a healing process, the groove (21) in the sliding element (2) has at least one step (24) between a medial stop (22) and a lateral stop (23).

Description

[0001] Device for treating a bone fracture with dynamic control

[0002] The invention relates to a device for treating a bone fracture, in particular a proximal femur fracture, comprising an elongated intramedullary nail with a first opening that intersects a longitudinal axis of the intramedullary nail and a second opening that extends substantially along the longitudinal axis of the intramedullary nail, and a locking element that can be inserted into the second opening of the intramedullary nail, as well as a sliding element that can be inserted through the first opening and that has a groove in which the locking element engages to limit movement of the sliding element.

[0003] Proximal femur fractures are relatively complex bone fractures that occur frequently, especially in older individuals, due to age-related decline in bone quality, as well as generally reduced mobility and muscle mass. The often demanding physical conditions associated with such fractures, and the surgical treatment of a proximal femur fracture itself, present exceptionally challenging conditions for their management.

[0004] Various devices have been developed for treating bone fractures in the proximal femur, some of which are relatively simple in design. Typically, an intramedullary nail is used, which has openings running perpendicular to its longitudinal axis. The nail is inserted into the medullary canal of the femur. A bone screw is then inserted through the first opening of the intramedullary nail and anchored in the femoral head. This fixes the femoral head relative to the femur at the fracture site. Additional screws may be placed distally to further secure the intramedullary nail. With these simple devices, to put it simply, everything remains as it was after the operation. The healing process begins and completes with this fixed position.

[0005] The healing process of a femur fracture is also associated with changes, for example, in the surrounding muscles, which are not in their natural position due to the fracture. Thus, the conditions in the fracture area change during the healing process. The simple devices described above do not offer a way to address this. To tackle this, the aforementioned simple devices have been further developed, particularly to allow for compression of the separated bone fragments during surgery, but also to permit some lateral movement of the bone screw inserted into the femoral head. This ensures that the device is not completely rigidly fixed during the healing process, but rather retains a degree of flexibility. As a result, the anatomical conditions can adjust more effectively to their original position during the healing process.Various devices are known for this purpose, including those employing a combination of screws: a bone screw that engages the femoral head and an adjusting screw, which may also engage the femoral head but is primarily designed to define the bone screw's range of motion through interaction with it. If the bone screw has a groove into which an adjusting screw, which is not perfectly parallel and is also guided through a first opening, engages, rotational movement of the bone screw and thus of the associated femoral head is initially prevented. Simultaneously, the groove can be designed such that the bone screw can move in a predetermined manner in a lateral direction up to a final position determined by the adjusting screw.Thus, with rotational stability of the bone screw and therefore of the femoral head, a certain degree of lateral mobility, and possibly also medial mobility, is possible for the femoral head. In other words, such a device allows flexibility during the healing process but prevents unwanted movements such as rotation of the femoral head.

[0006] Rotational stability and a predetermined range of motion in the lateral and, if necessary, medial direction can be achieved even more simply in the further developed devices by having the bone screw itself have a groove and a locking element inserted through an opening running along a longitudinal axis of the intramedullary nail, so that the bone screw is only displaceable between a medial end of the groove and a lateral end of the groove relative to the intramedullary nail. This is a significantly simpler embodiment that provides not only rotational stability but also the desired flexibility. However, a disadvantage is that the same flexibility or range of motion is always available for individuals of different constitutions. Therefore, it is not yet possible to adequately adapt to the individual needs of a patient undergoing surgery.

[0007] 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 the device can be used for persons with different anatomical conditions, while at the same time still allowing the desired rotational stability and a possibility of movement, especially in the lateral direction.

[0008] This problem is solved if, in a device of the type mentioned above, the groove of the sliding element has at least one step between a medial stop and a lateral stop.

[0009] By dividing the provided groove with at least one step, the device can be used by individuals with significantly different anatomical proportions. The step can be designed with a vertical first surface and a horizontal second surface adjoining it. In this case, the first and second surfaces form an angle of 90°. Alternatively, the first surface and the adjoining second surface of a step can form a different angle and / or not run parallel or perpendicular to a longitudinal axis of the sliding element. In the latter case, inclined steps result. If multiple steps are provided, they can be designed with identical first and second surfaces. With a rectangular cross-section, the steps can be joined in such a way that the height of the second surface of each step increases within the groove.Such a step-like increase in height preferably runs from the lateral stop to the medial stop.

[0010] Subdividing the groove with at least one step, preferably several steps, creates a local segmentation of the groove. This local segmentation allows the sliding element, in conjunction with the locking element, to travel only certain distances, specifically between a medial stop and a lateral stop. If multiple steps are provided, the distance along which the sliding element can move depends on how far the locking element is positioned relative to the sliding element via the second opening. If the locking element is positioned only so slightly that it reaches only a maximum medial stop and a maximum lateral stop of the provided groove, the sliding element can move completely freely, just as if there were no steps, medially or laterally.If the locking element is positioned further against the sliding element, the maximum range of motion is determined by how quickly or slowly the sliding element engages the locking element with its step(s). For example, the locking element may be inserted into the intramedullary nail, or positioned against the sliding element, to such an extent that the sliding element can move through two steps before an initial blockage occurs, either medially or laterally. Alternatively, the locking element may be inserted into the intramedullary nail to such an extent that movement is only possible along the longitudinal extension of a single step or a portion thereof. The sliding element is thus freely gliding between two end positions. These end positions are determined by the medial stop and / or the lateral stop and / or at least one step.

[0011] The locking element preferably has a rigid pin at its end that engages in the groove. The movement of the sliding element is then determined solely by the relative position of the rigid pin in the groove. This allows for a simple design of the device, and in particular, no rotatable elements are required; specifically, the pin is not rotatably mounted but rather held in a positionally stable manner at the engaging end of the locking element. The sliding element can then slide freely between a medial and a lateral end position.

[0012] In principle, any number of steps can be provided. Usually, the steps are identical in a side view along the groove, although this is not mandatory. Generally, it is sufficient to have two steps, preferably two to four, along the groove.

[0013] Although the steps are preferably identical in design, for example, as steps of the same height or in the form of a sawtooth profile with teeth of equal height, it is also possible for the steps to be designed differently. A combination of different step geometries is also possible. In side view, the steps can be designed with a groove in cross-section featuring alternating straight sections. In the case of a conventional step or staircase, this means that horizontal and vertical sections of the step alternate. In the case of a sawtooth-like structure, correspondingly angled sections, relative to a longitudinal axis of the sliding element, alternate. It is also possible for the steps to have curved sections.Curved sections can be particularly useful for very fine adjustments regarding the maximum lateral deflection of a sliding element, such as a bone screw. While lateral movement is permissible in terms of distance, it requires increasingly greater force along that distance. For this purpose, the locking element is, for example, spring-mounted. This allows the femoral head to be adjusted so that it only moves laterally as far as it is capable of doing so. In other words, such a cam guide in the groove allows the femoral head to move laterally (or, if necessary, medially, depending on the positioning of the guide or step) only as far as is physically possible.

[0014] Preferably, at least one step, or optionally several steps, are integrated into the groove. This means that the at least one or more steps are fixed in position. In this case, the sliding element can, for example, be a single piece. The steps are rigidly arranged. However, it is also possible to additionally provide a spring element in the groove, which holds a step slidably mounted in the groove against any movement of the femoral head. The spring can then be used to adjust the degree of lateral or, if applicable, medial deflection of the sliding element. However, it is generally preferred that the sliding element be a single piece to ensure a simple design.

[0015] The sliding element can be a bone screw. The bone screw can be specifically designed for intervention in a femoral head. In principle, the sliding element can be separate from the bone screw and secured in a first opening within the intramedullary nail, its movement restricted by the locking element. Simultaneously, the sliding element can interact with the bone screw, engaging in an elongated indentation or recess on the outer surface of the bone screw. This ultimately prevents rotation of the bone screw and also limits its movement both medially and laterally, as this is then linked to the movement of the sliding element. However, it is particularly preferred that the sliding element itself be a bone screw. This allows the bone screw to perform multiple functions.Firstly, the bone screw is anchored in the femoral head, ensuring its stability during the healing process. Secondly, rotational stability is provided by the provided groove and its interaction with the locking element. Finally, the design according to the invention also allows for excellent adjustability of movement, making it adaptable to individual anatomical conditions.

[0016] At least one step can restrict movement of the sliding element in a lateral direction. The same applies to movement in a medial direction, meaning the locking element restricts movement of the sliding element in a medial direction. Both of these points are particularly relevant when the locking element interacts directly with a bone screw. If a bone screw is provided that interacts directly with the locking element, no further sliding elements are required. The device then essentially consists of the intramedullary nail, a bone screw, and the locking element, which can be a single or multi-part component, as well as optionally additional screws for distal fixation of the intramedullary nail.

[0017] In another aspect, the invention relates to a set comprising a device according to the invention and locking elements of different lengths.

[0018] Such a set offers the advantage that the concept according to the invention can be implemented with particular sensitivity. By providing several locking elements of different lengths, and in conjunction with the stepped design along the groove between the medial and lateral stops of the sliding element, particularly a bone screw, a range of motion between a lateral and a medial position can be very effectively defined. While movement between these positions could also be controlled, for example, by screwing or rotating a locking element to a different depth, it is generally more advantageous for physicians to have a single arrangement in which the locking element is moved completely distally within the intramedullary nail. This achieves a final position that represents an optimal state.To avoid further considerations in this regard, the set is easily designed by using locking elements of varying lengths. These locking elements can then be inserted until they reach an end contact with the intramedullary nail. This end position is then the final position. The length of the locking element determines the medial and / or lateral movement of the sliding element, and in particular of the bone screw that constitutes the sliding element. For example, if four stair-like steps are planned, different length locking elements can be used to adjust whether one, two, or three steps can be bridged during sliding. The possibility of maximum movement between the medial and lateral stops is maintained when the locking element is adjusted accordingly.

[0019] The locking element can be formed in a single piece. Advantageously, the locking element has a rigidly arranged pin at its end. This pin is designed to engage in the groove of the sliding element. The locking element can be helical and is designed to be releasably screwed into the intramedullary nail. The locking element is preferably screwed in until it reaches the end position of an internal thread of the intramedullary nail. The groove can be tapered in a top view, either medially or laterally.

[0020] Further features, advantages, and effects of the invention will become apparent from the exemplary embodiments described below. The drawings referenced therein show:

[0021] Fig. 1 schematic representations of the functioning of a device according to the prior art;

[0022] Fig. 2 schematic representations of the operation of a further device according to the prior art; Fig. 3 schematic representations of the operation of a device according to the invention in a first variant;

[0023] Fig. 4 schematic representations of the functioning of a device according to the invention in a second variant;

[0024] Fig. 5 shows a top view of a stepped groove of a device according to the invention;

[0025] Fig. 6 shows a top view of a further stepped groove of a device according to the invention; Fig. 7 shows a cross-section through a device according to the invention;

[0026] Fig. 8 shows a top view of the device according to Fig. 7;

[0027] Fig. 9 shows a section through the bone screw from Fig. 7;

[0028] Fig. 10 shows a side view of the bone screw from Fig. 7 and Fig. 9.

[0029] Figure 1 shows a prior art device 1. The device 1 comprises an elongated intramedullary nail 3. The intramedullary nail 3 is shown in Figure 1, as well as in the following, in a highly schematic form for the purpose of illustrating the function of the device 1. In practice, the intramedullary nail 3 is designed as an elongated intramedullary nail, which is surgically inserted into the medullary canal of a femur. The intramedullary nail 3 has a first opening 31 that intersects a longitudinal axis X of the intramedullary nail 3. The first opening 31 is designed such that a sliding element 2 can be received in it. The sliding element 2 can be any implant or implant component; however, it is usually a bone screw that is inserted into the intramedullary nail 3 through the first opening 31 and secured in a femoral head.The bone screw can thus be used to fix the femoral head in the case of a femoral neck fracture.

[0030] The sliding element 2 has a groove 21 on its outer surface. The groove 21 has a medial stop 22 and a lateral stop 23. The groove 21 is longitudinally oriented and extends essentially in the direction of a longitudinal axis Y of the sliding element 2. The sliding element 2, in particular a bone screw, can be inserted into the first opening 31 as shown in Fig. 1 such that the sliding element 2 runs essentially perpendicular to the longitudinal axis X of the intramedullary nail 3. However, other arrangements are also possible. Usually, the sliding element, in particular a bone screw, is positioned obliquely to the longitudinal axis X of the intramedullary nail 3, which is essentially determined by the first opening 31.

[0031] To prevent the sliding element 2, in particular a bone screw, from moving freely between medial and lateral positions, for example during movement of the femoral head during the healing process, the sliding element 2 is locked with a locking element 4. For this purpose, the locking element 4 is inserted through a second opening 32, which extends along the longitudinal axis X of the intramedullary nail 3. According to the prior art, the locking element 4 can be positioned against the sliding element 2 in such a way that the latter cannot move. However, in further developed solutions according to the prior art, as schematically illustrated in Fig. 1, a certain degree of movement between medial and lateral positions is allowed via the groove 21, starting from a baseline position at the end of the operation during the healing process.For this purpose, the locking element 4 can have a projection at an engaging end, for example in the form of a pin, which lies in an opening defined by the groove 21. The sliding element 2, for example a bone screw, can then move between a medial stop 22 and a lateral stop 23 during the healing process. In particular, if the sliding element 2 is a bone screw, the femoral head, which is held by the bone screw, can thus move within predetermined limits, namely between the medial stop 22 and the lateral stop 23. This allows for a certain degree of dynamic movement during the healing process.

[0032] The situation is similar if the groove 21 in the sliding element 2, particularly of a bone screw, is designed with a slope, as shown in Fig. 2. In this case, too, a range of motion is defined between a medial stop 22 and a lateral stop 23. The exact range of motion then depends on the position of the bone screw or the sliding element 2 at the beginning of the healing process. A slope can also be provided to partially or completely compensate for an inclination of the sliding element 2 relative to the locking element 4, thus ensuring that the locking element always engages in the groove 21, even with a greater inclination (for example, an angle of 125° relative to the longitudinal axis X of the intramedullary nail 3).

[0033] However, devices 1 according to the prior art, as exemplified in Figs. 1 and 2, have the disadvantage that the standard devices 1 are not easily adaptable to specific anatomical conditions. Different individuals have different body structures, and the treatment of a femoral neck fracture varies from case to case, even when using the same device 1 and the same surgical technique. Therefore, the devices 1 shown in Figs. 1 and 2 must cover a wide range of possible anatomical conditions, which compromises individual patient adaptation.

[0034] This problem is addressed by a device 1 according to the invention. Fig. 3 shows a first embodiment of a device 1 according to the invention. Fig. 4 shows a second embodiment of a device 1 according to the invention. The general descriptions of the devices in Fig. 1 and Fig. 2 concerning the intramedullary nail 3, the sliding element 2 (in particular a bone screw), and the locking element also apply analogously to the devices 1 shown in Fig. 3 and Fig. 4, as well as to devices 1 according to the invention in general. In contrast to the prior art, it is now provided that at least one step 24, preferably several steps 24, are provided between the medial stop 22 of the groove 21 and the lateral stop 23 of the groove 21. These steps 24 further subdivide the groove 21.This allows the sliding element 2, in particular a bone screw, to be provided as usual, and the same surgical technique can be applied. Simultaneously, at least one step 24 in the groove 21 introduces further stops between the medial stop 22 and the lateral stop 23, so that even with a relatively long groove 21, the range of motion can be adjusted to the typically desired range of 0 mm to 20 mm. Due to this subdivision, this can be achieved with the same device 1 largely independent of the specific anatomy of a patient.

[0035] As shown in Fig. 3, the device 1 can, for example, have three steps 24, whereby movement in the lateral direction L or medial direction M between two steps 24 is possible if one end of the locking element 4 projects deeply enough into the groove 21. In the exemplary embodiment 24, the steps 24 are recessed in the groove 21, so that full movement between the medial stop 22 and the lateral stop 23 is still possible when the locking element 4 is arranged above the steps 24 but still projects into the groove 21. This can be the case in all embodiments of a device 1 according to the invention and regardless of the specific design of the steps 24. If desired, this also allows for full movement along the entire length of the groove 21, even with the finer adjustment.For this purpose, several locking elements of different lengths can be present in a set, so that a locking element of suitable length can be selected.

[0036] The latter also applies to the second embodiment shown in Fig. 4. In this case, there are also several steps 24 arranged in a stepped pattern. The range of motion is defined by one step if the locking element extends deeply enough into the groove 21. However, depending on the penetration depth of the locking element 4, the stepped design also allows the range of motion to extend over several steps 24.

[0037] The steps 24 can be designed in a sawtooth shape as in Fig. 3 or in a stepped shape as in Fig. 4; however, the concept according to the invention is not limited to this. Other step designs are also possible, for example, with a curved profile. It is advantageous if all steps 24 are identical, but hybrid designs are also possible. It is also possible for a sliding element to have several grooves 21, which are designed with different step 24 structures.

[0038] For all embodiments, the locking element 4 is advantageously an elongated element, in particular a screw, which can be detachably fastened in the intramedullary nail 3 via the second opening 32. For this purpose, the locking element 4 has a suitable external thread and the intramedullary nail 3 has a suitable internal thread. In one embodiment, however, the locking element 4 can also be composed of multiple parts, particularly if the groove 21 is formed with curved tracks that rise from lateral to medial or vice versa. In this case, the locking element 4 can be formed from a pin with a spring and a screw-in element. The locking element 4 is also screwed into the intramedullary nail 3 via the screw-in element and is thus anchored in the intramedullary nail 3. Due to the spring, however, the pin is movably mounted.If the femoral head moves from medial to lateral within the implant, the pin abuts the curved step 24. This generally prevents further lateral movement of the femoral head, unless the movement of the femoral head overcomes the spring force acting on the pin. The spring force can thus be used to adjust any further movement of the femoral head, allowing for additional fine-tuning. This design is also possible with inclined steps 24.

[0039] Figures 5 and 6 show top views of a device according to the invention in the area of ​​the groove 21. The groove 21 has the aforementioned steps 24. According to Figure 5, the groove 21 can be configured with parallel longitudinal sides, but also, as shown in Figure 6, with conically tapered longitudinal side walls, so that movement can also be blocked by the longitudinal side walls.

[0040] Figures 7 and 8 show a practical embodiment of a device 1 according to the invention. The device 1 again comprises an intramedullary nail 3 and a sliding element 2 designed as a bone screw. The bone screw is shown separately in a section in Figure 9. Figure 10 shows a side view of the bone screw from Figure 9.

[0041] The intramedullary nail 3 has a first opening 31 through which the bone screw is guided. The first opening 31 provides distal space for receiving a further screw, namely an adjusting screw, if the bone screw is used in a different manner. This additional distal extension can therefore also be omitted. The bone screw runs obliquely to a longitudinal axis X of the intramedullary nail 3. An angle α can be approximately 110° to 145°, preferably 115° to 135°. Furthermore, the device 1 comprises a locking element 4, which is inserted through a second opening 32 of the intramedullary nail 3. The locking element 4 is detachably fastened in the second opening 32. In particular, this can be done by means of a screw connection.For this purpose, the locking element 4 has an external thread and the intramedullary nail 3 has an internal thread in the area of ​​the second opening 32, which corresponds to the external thread of the locking element 4.

[0042] The locking element 4 has a pin-shaped end. The pin has a semicircular cross-section at its end. In three dimensions, the pin can be shaped like a spherical shell at its end. The pin of the locking element 4 engages in a groove 21 of the bone screw, which is particularly visible in Fig. 10. The groove 21 is divided into several sections formed by steps 24. The locking element 4, which is inserted through the second opening 32 of the bone screw, can engage in these steps 24. This allows for rotational stability. Lateral movement within predetermined limits is possible along the medially first step 24 of the groove 21. Further steps 24 adjoin this. In the example according to Fig.7 The locking element 4 is positioned relative to the bone screw such that the bone screw is movable over the two lateral end steps 24, between a stop formed by one of the steps 24 (in the medial direction M) and a lateral stop 23 in the lateral direction L. The individual steps 24 are formed with different widths, which results from the cylindrical shape of the bone screw.

Claims

Patent claims 1. Device (1) for treating a bone fracture, in particular a proximal femur fracture, comprising an elongated intramedullary nail (3) with a first opening (31) that intersects a longitudinal axis (X) of the intramedullary nail (3) and a second opening (32) that extends substantially along the longitudinal axis (X) of the intramedullary nail (3), and a locking element (4) that can be inserted into the second opening (32) of the intramedullary nail (3), as well as a sliding element (2) that can be inserted through the first opening (31) and which has a groove (21) into which the locking element (4) engages to limit movement of the sliding element (2), characterized in that the groove (21) of the sliding element (2) has at least one step (24) between a medial stop (22) and a lateral stop (23).

2. Device (1) according to claim 1 , characterized in that several steps (24) are provided in the groove (21).

3. Device (1) according to claim 1 or 2, characterized in that at least two stages (24), preferably two to four stages (24), are provided.

4. Device (1) according to one of claims 1 to 3, characterized in that the sliding element (2) is a bone screw, which is designed in particular for engagement in a femoral head.

5. Device (1) according to one of claims 1 to 4, characterized in that the at least one stage (24) restricts movement of the sliding element (2) in the lateral direction (L).

6. Device (1) according to one of claims 1 to 5, characterized in that the locking element (4) restricts movement of the sliding element (2) in the medial direction (M).

7. Set comprising a device (1) according to one of claims 1 to 6 and locking elements (4) of different lengths.

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