SURGICAL INSTRUMENTS

Description

[0001] The invention relates to a surgical instrument for use in knee replacement surgery.

[0002] The use of orthopedic prostheses as artificial replacements for damaged or worn-out natural bone structures is common medical practice. Hip and knee replacement surgeries, in particular, are now part of the standard repertoire of surgical orthopedics.

[0003] In total knee arthroplasty (TKA), worn or otherwise impaired joint surfaces of the femur and / or tibia due to disease or accident are replaced with a knee joint prosthesis. Such knee joint prostheses typically consist of a femoral component, which is implanted at the distal end of the femur, and a tibial component, which is implanted at the proximal end of the tibia. To ensure proper function of the artificial joint replacement, the said components must be positioned as precisely as possible in terms of their position and orientation in relation to the patient's anatomy and their body axes. Otherwise, an unsatisfactory result for the patient is to be expected. There are different surgical approaches regarding the positioning of the components.

[0004] An approach known as mechanical alignment, which has been the most widely used to date, involves determining the position and alignment of the artificial joint axes of the knee joint prosthesis in a mechanically ideal manner, without taking into account any orthopedic malalignments of the patient. The longitudinal axis of the tibia often serves as the reference axis for alignment and positioning. Clinical studies have shown that the mechanical alignment approach can lead to a perceived unnatural function of the artificial knee joint.

[0005] Another approach is known as kinematic alignment (hereinafter also abbreviated as KA). In this procedure, the femoral and tibial components are positioned taking into account any orthopedic malalignments of the patient. The goal is to restore the patient's natural, potentially malaligned, joint alignment. Clinical studies have shown that the kinematic alignment approach is often associated with improved patient satisfaction. In particular, patients perceive the function of the artificial knee joint as more natural.

[0006] The aim of further improving patient satisfaction is accompanied by a fundamental need for surgical instruments that are as precise, easy to use and cost-effective as possible for the implementation of KA.

[0007] The present invention relates to such a surgical instrument, specifically to a surgical instrument for positioning a tibial cutting block on the proximal tibia. Such instruments are also referred to as tibia transfer tools and allow the transfer of a varus / valgus alignment (hereinafter referred to as V / V alignment) already established on the femur side to the tibia. Various such instruments are known from the prior art.

[0008] For example, GB 2558543 A discloses an instrument with an extension arm. The extension arm can be attached at one end to a femoral reference component. The reference component defines, in particular, the V / V alignment. The V / V alignment can be transferred to the proximal tibia using the extension arm. The length of the extension arm defines a proximodistal position of the tibial cutting block and thus of the proximal tibial cut (hereinafter referred to as the tibial cut height). The transfer takes place under extension, i.e., with the leg straight.

[0009] Another instrument is known from US 2019 / 0336141 A1 and can be attached at one end to a 4-1 femoral cutting block and the other end to a tibial cutting block. The known instrument features a type of linear guide for adjusting the tibial cutting height. The transfer is performed under flexion, i.e., with the leg bent.

[0010] From US 10,709,458 B1, further transfer tools are known that allow a transfer in extension or flexion.

[0011] The document US 2015 / 045801 A1 discloses another surgical instrument for use in knee replacement surgery.

[0012] The object of the invention is to provide a surgical instrument which offers advantages over the prior art and in particular enables improved positioning of the tibial cutting block starting from a reference component fixed on the femur side.

[0013] This object is achieved by providing a surgical instrument having the features of claim 1.

[0014] The surgical instrument according to the invention comprises: a first fastening device, which is designed for detachable fastening to a reference component attached to a distal femur, a second fastening device, which is spaced distally from the first fastening device and is designed for detachable fastening to a tibial cutting block for guiding the cut on a proximal tibia, a circular arc guide, which is connected at one end to the first fastening device and at the other end to the second fastening device and by means of which the second fastening device is guided linearly relative to the first fastening device in a sagittal guide plane along a circular arc-shaped longitudinally extended guide path, a first linear guide, by means of which the circular arc guide is connected at one end to the first fastening device and is guided relative to the same in the guide plane along an anteroposteriorguided linearly along an elongated first guideway, and a second linear guide, by means of which the second fastening device is connected at the other end to the circular arc guide and is guided linearly relative to the latter in the guide plane along an anteroposteriorly elongated second guideway. The surgical instrument according to the invention allows improved positioning of the tibial cutting block. The improved positioning is achieved by an interaction of the circular arc guide, the first linear guide, and the second linear guide. During use of the surgical instrument, the first fastening device is detachably attached to the reference component attached on the femur side, and the tibial cutting block is detachably attached to the second fastening device. The reference component is, for example, a distal femoral cutting block for distal cutting guidance on the femur or the like. Neither the reference component norThe tibial cutting block are components of the surgical instrument according to the invention. The circular arc guide allows a guided circular arc-shaped movement of the second fastening device relative to the first fastening device. During use of the surgical instrument, the circular arc guide consequently allows a correspondingly guided relative movement of the tibial cutting block with respect to the femoral reference component. This allows the inclination of the tibial cutting block to be adjusted in the guide plane. The guide plane is sagittally aligned and thus extends anteroposteriorly and proximodistal. This inclination is also referred to as the posterior or anterior slope. The adjustability of the inclination of the tibial cutting block (hereinafter referred to as slope) allows, on the one hand, adaptation to preoperatively determined parameters. On the other hand, an actually predominant flexion or extension position of the leg can be achieved through the mobility of theThe circular arc guide is movable relative to the first fastening device along the first guideway. This allows the anteroposterior position of the circular arc guideway in relation to the first fastening device - and thus the reference component - to be changed and adapted to the patient's anatomy. Ideally, the position of the circular arc guideway is adjusted such that its circle center lies on the mechanical tibial axis. This ensures that an adjustment of the slope does not simultaneously lead to an unwanted change in the proximodistal position of the tibial cutting block and thus the tibial cutting height. The second fastening device is movable relative to the circular arc guide along the second guideway. This ensures that the anteroposterior position of the second fastening device - and thusthat of the tibial cutting block - can be adapted to the patient's anatomy, in particular the size of the tibia, without any unwanted change in the anteroposterior position of the circular guideway.

[0015] The position and direction terms used in this description refer to the patient's body, in particular their femur, and are to be understood according to their usual anatomical meaning. Consequently, "anterior" means front or in front, "posterior" means back or behind, "medial" means inner or inside, "lateral" means outer or outside, "proximal" means toward the body's center, and "distal" means away from the body's center. Furthermore, "proximodistal" means along, preferably parallel to, a proximal-distal axis, "anteroposterior" means along, preferably parallel to, an anterior-posterior axis, and "mediolateral" means along, preferably parallel to, a medial-lateral axis. These axes are orthogonal to each other and can, of course, be set in relation to X, Y, and Z axes unrelated to the patient's anatomy.For example, the proximal-distal axis can alternatively be referred to as the X-axis. The medial-lateral axis can be referred to as the Y-axis. The anterior-posterior axis can be referred to as the Z-axis. For clarity and simplicity of terminology, the aforementioned anatomical position and direction terms will be used primarily below.

[0016] In an embodiment of the invention, an alignment rod is provided and configured for alignment on an anterior edge of the tibia, wherein the alignment rod is pivotally mounted on the second fastening device at one end relative to the second fastening device about a pivot axis oriented orthogonally to the guide plane. The alignment rod allows referencing on said anterior edge, which can also be referred to as the anterior tibial edge. The slope (anterior or posterior inclination of the tibial incision) is often determined preoperatively in relation to the anterior tibial edge. The alignment rod allows easy control of the slope in relation to the anterior tibial edge. The alignment rod is elongated between a first end and a second end. The first end is pivotally mounted on the second fastening device. The second end is distally facing away from the second fastening device.

[0017] In a further embodiment of the invention, a first display device is provided and configured to display a first angular position of the second fastening device in relation to the circular guideway, and / or a second display device is provided and configured to display a second angular position of the alignment rod in relation to the pivot axis. The first display device serves to display the relative sagittal inclination between the first fastening device and the second fastening device. When the surgical instrument is in use - with the first fastening device attached to the femur and the tibial cutting block attached to the second fastening device - the first display device displays the slope of the tibial cutting block and thus also of the tibial cut. The second display device serves to display a relative sagittal inclination between the alignment rod and the second fastening device.When using the surgical instrument, a deviation in the flexion / extension position can be determined using the second display device. The determined deviation can subsequently be compensated for by adjusting the slope accordingly. For this purpose, the slope is initially set to 0°. This can be achieved by moving the second fastening device along the circular, longitudinal guideway. The alignment rod can then be aligned parallel to the anterior edge of the tibia. The resulting second angular position is displayed using the second display device. The first angular position can then be corrected by the value of the second angular position. This results in an actual slope of 0°, regardless of any deviation from the exact extension. The slope can subsequently be adjusted again to a preoperatively determined value.Preferably, the first display device is a scale attached to the circular arc guide. Preferably, the second display device is a scale arranged on the alignment rod and / or the second fastening device. The scales preferably each have a reading mark and graduations for indicating and / or reading the respective angular position. Alternatively, it is conceivable that the first angular position and / or the second angular position are detected and digitally displayed using suitable sensors. Accordingly, the first display device and / or the second display device can also be designed as a display.

[0018] In a further embodiment of the invention, the circular arc guide has at least one curved guide rod and a guide receptacle in which the guide rod is slidably guided, wherein the guide receptacle is connected to the first linear guide and the guide rod to the second linear guide, or vice versa. The guide rod is essentially elongated proximodistal and - with respect to a mediolateral viewing direction - is curved posteriorly concavely and / or anteriorly convexly. The curvature of the guide rod and / or the guide receptacle defines the elongated circular arc-shaped guide path. The same applies analogously to the guide receptacle. To avoid unwanted rotation about the longitudinal axis of the guide rod, the guide rod preferably has a non-rotationally symmetrical cross-section. The same applies analogously to the guide receptacle in which the guide rod is accommodated.In one embodiment, the guide receptacle is connected to the first linear guide, and the guide rod is connected to the second linear guide. In another embodiment, the guide rod is connected to the first linear guide, and the guide receptacle is connected to the second linear guide.

[0019] In a further embodiment of the invention, the guide receptacle is connected to the first linear guide and has a guide element, in particular a cylinder element or a cylinder receptacle, thereof, and / or the guide rod is connected to the second linear guide and has a guide element, in particular a sliding block or a sliding slot, thereof. The guide receptacle is fixedly and / or relatively immovably connected to said guide element of the first linear guide. In one embodiment, the guide element of the first linear guide is a cylinder element, in a further embodiment a cylinder receptacle in which the cylinder element is guided so as to be slidable along the first guide track. The guide rod is fixedly and / or relatively immovably connected to said guide element of the second linear guide.In one embodiment, the guide element of the second linear guide is a sliding block, in another embodiment it is a sliding slot in which the sliding block is guided so as to slide along the second guideway.

[0020] In a further embodiment of the invention, the first linear guide is a cylinder guide and has at least one anteroposteriorly elongated cylinder element and a cylinder receptacle in which the cylinder element is slidably guided. The longitudinal extent of the cylinder element and / or the cylinder receptacle defines the first guideway. The cylinder guide enables slidable relative displacement of the circular arc guide with respect to the first fastening device and thus - when the surgical instrument is in use - with respect to the reference component. This embodiment of the first linear guide is particularly robust and precise. To prevent unwanted rotation about the longitudinal axis of the cylinder element and / or the cylinder receptacle, the cylinder element preferably has a non-rotationally symmetrical cross-section. The same preferably applies analogously to the cylinder receptacle.Alternatively, the cylinder element and / or the cylinder receptacle can have a circular cross-section. To prevent unwanted rotation around the longitudinal axis in this case, the cylinder guide preferably has two cylinder elements and cylinder receptacles arranged at a mediolateral distance.

[0021] In a further embodiment of the invention, the cylinder element is immovably connected to the first fastening device, and the cylinder receptacle is immovably connected to the circular arc guide, preferably its guide receptacle. This further simplifies the design of the surgical instrument.

[0022] In a further embodiment of the invention, the second linear guide is a sliding guide and has a sliding block and an anteroposteriorly elongated slot in which the sliding block is slidably received. The slot defines the second guideway. Since the second linear guide is movable along the circular guideway together with the second fastening device, the orientation of the elongated slot naturally changes accordingly. The orientation of the slot is at least substantially anteroposterior, independent of the position of the second fastening device along the circular guideway.

[0023] In a further embodiment of the invention, the sliding block is immovably connected to the circular arc guide, preferably its guide rod, and the sliding block slot is formed on the second fastening device. This further simplifies the construction of the surgical instrument. Preferably, the sliding block is arranged and / or formed on an end of the guide rod facing away from the first fastening device. Preferably, the sliding block is integrally formed on said end of the guide rod.

[0024] In a further embodiment of the invention, the first fastening device has at least one plug-in element which is designed for detachable mating with a complementary reference geometry of the reference component. This allows the first fastening device to be detachably attached to the reference component in a particularly simple manner. In one embodiment, the reference component is a distal femoral cutting block which is designed to receive and guide a saw blade when making a distal femoral cut. For this purpose, the femoral cutting block has at least one receiving slot for said saw blade. Preferably, the at least one plug-in element is designed for insertion into the guide slot. In this embodiment, the guide slot forms the complementary reference geometry.

[0025] In a further embodiment of the invention, the second fastening device has a base body on which a fastening element, which is designed for releasable fastening to a fastening section of the tibial cutting block provided for this purpose, a guide element of the second linear guide, preferably its slotted guide, and the alignment rod are arranged. This results in a further simplified structure of the surgical instrument. The fastening element is designed differently in different embodiments and can, for example, be a clamping, locking, plug-in and / or snap-in element for releasable fastening to the tibial cutting block. In one embodiment, the fastening element is displaceable relative to the base body between a fastening position and a release position.In the fastening position, the second fastening device and the tibial cutting block are releasably connected to one another by means of the fastening element. In the release position, the second fastening device is released from the tibial cutting block, and vice versa. The alignment rod is mounted on the base body so that it can pivot relatively about the pivot axis. If a second display device for displaying a second angular position of the alignment rod with respect to the pivot axis is present according to one of the preceding embodiments, it is preferably arranged as a scale on the base body and / or the alignment rod.

[0026] In a further embodiment of the invention, a fixing device is provided and configured to fix the mobility of the circular guide. By means of the fixing device, the second fastening device can be fixed immovably along the circular guideway relative to the first fastening device. This counteracts any unintentional displacement of the second fastening device along the circular guideway. During use of the surgical instrument, the fixing device counteracts any unintentional adjustment of the slope. The fixing device acts in a form-fitting and / or force-fitting manner between different components and / or sections of the circular guideway. If the circular guideway has a guide rod and a guide receptacle, said components can be fixed relative to one another by means of the fixing device.

[0027] The invention also relates to a surgical instrument system comprising a surgical instrument according to the preceding description, a reference component releasably attached to the first fastening device of the surgical instrument, and a tibial cutting block releasably attached to the second fastening device of the surgical instrument.

[0028] Further advantages and features of the invention emerge from the claims and from the following description of a preferred embodiment of the invention, which is illustrated by the drawings. Fig. 1 shows a schematic side view of an embodiment of a surgical instrument according to the invention in an intraoperative situation, in which the surgical instrument is detachably attached at one end to a distal femoral cutting block and at the other end to a proximal tibial cutting block, Fig. 2 shows a schematic perspective view of the Fig. 1 shown intraoperative situation, Fig. 3 a further schematic perspective view of the Fig. 1 and 2 shown intraoperative situation, Fig. 4 a further representation of the intraoperative situation in a schematic side view and Fig. 5 a schematic side view of the surgical instrument in a further intraoperative situation in which the tibial cutting block is aligned in a sagittally inclined manner by means of the surgical instrument.

[0029] According to the Fig. 1 to 5A surgical instrument 1 is intended for use in a knee replacement operation. The surgical instrument 1 can also be referred to as a transfer tool or tibia transfer tool and serves for the referenced positioning of a tibial cutting block 700 on a proximal tibia T. A distal femoral cutting block 600 already positioned on a distal femur F serves as a reference for the position of the tibial cutting block 700. The femoral cutting block 600 and the tibial cutting block 700 are not part of the surgical instrument 1. The surgical instrument 1 can be detachably connected, on the one hand, to the femoral cutting block 600 and, on the other hand, to the tibial cutting block 700 in a manner described in more detail below. The surgical instrument 1, together with the two cutting blocks 600, 700, forms a surgical instrument system 10.

[0030] The surgical instrument 1 has a first fastening device 100, a second fastening device 200, a circular arc guide 300, a first linear guide 400 and a second linear guide 500.

[0031] The first fastening device 100 is configured for releasable attachment to the distal femoral cutting block 600. The femoral cutting block 600 serves as a reference component for referencing the position and orientation of the tibial cutting block 700.

[0032] The second fastening device 200 is spaced distally from the first fastening device 100 and is configured for releasable attachment to the tibial cutting block 700.

[0033] The circular guide 300 is connected at one end to the first fastening device 100 and at the other end to the second fastening device 200. The connections are respectively direct or indirect. The circular guide 300 is connected at one end to the first fastening device 100 by means of the first linear guide 400. The other end of the circular guide 300 is connected to the second fastening device 200 by means of the second linear guide 500. The circular guide 300 has a circularly arcuate, longitudinally extending guide path C. The circularly arcuate guide path C (hereinafter also referred to as the circular guide path) is arranged in a guide plane E. The guide plane E runs proximodistal and anteroposterior. The guide plane E is a sagittal plane. The circular guide 300 allows guided relative mobility between the second fastening device 200 and the first fastening device 100.The second fastening device 200 is guided linearly relative to the first fastening device 100 along the circular guide path C. The second fastening device 200 performs a rotation and / or pivoting movement around a center point M of the circular guide path C. The center point M is spaced posteriorly from the circular guide path C. In other words, the circular guide path C is curved concavely posteriorly and convexly anteriorly. The center point M can be positioned relative to the patient's joint axes, specifically to the tibia axis (without reference numeral), in a manner described in more detail below.

[0034] The first linear guide 400 is connected at one end to the first fastening device 100 and at the other end to the circular guide 300. The first linear guide 400 establishes a relatively movable connection between the first fastening device 100 and the circular guide 300. The first linear guide 400 has a first guideway L1. The first guideway L1 is longitudinally extended anteroposteriorly and is arranged in the guide plane E and / or offset parallel to it. The first guideway L1 is longitudinally straight.

[0035] The second linear guide 500 is connected at one end to the circular arc guide 300 and at the other end to the second fastening device 200. The second linear guide 500 establishes a relatively movable connection between the circular arc guide 300 and the second fastening device 200. The second linear guide 500 has a second guideway L2. The second guideway L2 is straight in length. The second guideway L2 is arranged in the guide plane E and / or offset parallel to it. In the Fig. 1 In the intraoperative situation shown, the second guideway L2 is parallel to the first guideway L1 and thus extends anteroposteriorly. The orientation of the second guideway L2 in the embodiment shown depends on the position of the second fastening device 200 along the circular guideway C.

[0036] Through the interaction of the circular arc guide 300, the first linear guide 400 and the second linear guide 500, the tibial cutting block 700 can be positioned on the tibia T in a manner improved compared to the prior art, starting from the positioned femoral cutting block 600. Firstly, the sagittal inclination of the tibial cutting block 700 can be adjusted in a manner described in more detail without unintentionally influencing the so-called tibial cutting height. The sagittal inclination is also referred to as the slope. The tibial cutting block 700 is positioned in extension, i.e. with the leg and / or knee joint extended. In extension, the femur F and the tibia T form an angle of 180°. Using the surgical instrument 1, deviations from the exact extension position can be taken into account when adjusting the slope.

[0037] Before going into further details of the function of the surgical instrument 1 and its use, the further structure of the surgical instrument 1 will first be explained in detail.

[0038] In the embodiment shown, the first fastening device 100 has a plug-in element 101, which is designed for detachable connection to a reference geometry of the femoral cutting block 600. The femoral cutting block 600 serves to make a distal femoral cut and can also be referred to as a femoral saw block or distal femur cutting jig. The design and function of the femoral cutting block 600 are generally known to those skilled in the art. The femoral cutting block 600 has a guide slot 601, which in this case serves as a reference geometry. The guide slot 601 is designed to receive and guide a medical saw blade for distal resection of the femur F and is usually aligned parallel to a distal condylar line of the femur F within the framework of the kinematic alignment approach.The plug-in element 101 can be inserted into the guide slot 601 of the femoral cutting block 600 to fasten the surgical instrument 1. Such a state is illustrated in FIG. Fig. 1 to 5 shown. For this purpose, the plug-in element 101 is dimensionally matched to the guide slot 601. In the inserted state, the plug-in element 101 is held in the guide slot 601 in a form-fitting manner mediolaterally, proximodistally, and posteriorly. To release the fastening, the plug-in element 101 can be pulled out of the guide slot 601 anteriorly.

[0039] In the embodiment shown, the first linear guide 400 is a cylinder guide Z and has at least one cylinder element 401 extending longitudinally along the first guideway and a cylinder receptacle 402 extending longitudinally coaxially therewith. The cylinder element 401 is slidably received in the cylinder receptacle 402 along the first guideway L1.

[0040] In the present case, the cylinder element 401 is fixedly and / or (relatively) immovably connected to the first fastening device 100, more precisely: its plug-in element 101. The cylinder receptacle 402 is fixedly and / or (relatively) immovably connected to the circular arc guide 300. In an embodiment not shown in the figures, a reverse arrangement is provided.

[0041] The cylinder element 401 and the cylinder receptacle 402 each have a circular-cylindrical cross-section. To counteract unwanted rotation of the cylinder guide Z about its longitudinal axis, a further cylinder element 401' and a further cylinder receptacle 402' are provided in the present case. The further cylinder element 401' and the further cylinder receptacle 402' are arranged at a medial distance from the cylinder element 401 and the cylinder receptacle 402. Otherwise, their function and design are identical. Further explanations of the further cylinder element 401' and the further cylinder receptacle 402' are therefore unnecessary. In an embodiment not shown in the figures, the cylinder guide does not have rotationally asymmetrical cross-sections to counteract unwanted rotation about the first guideway.

[0042] In the embodiment shown, the circular arc guide 300 has a curved guide rod 301 and a complementarily curved guide receptacle 302. The guide rod 301 is slidably received in the guide receptacle 302 along the circular guide path C.

[0043] In the embodiment shown, the guide receptacle 302 is fixedly and / or immovably connected to the first fastening device 100 with respect to the circular guide path C. In contrast, the guide rod 301 is movable relative to the first fastening device 100 with respect to the circular guide path C. Both the guide rod 301 and the guide receptacle 302 are movable relative to the first fastening device 100 with respect to the first guide path L1.

[0044] In the embodiment shown, the guide receptacle 302 has a U-shaped cross-section with mediolaterally opposing legs 3021, 3022. The legs 3021, 3022 can also be referred to as lateral leg 3021 and medial leg 3022. The guide rod 301 is held mediolaterally in a form-fitting manner between the two legs 3021, 3022. In the embodiment shown, the guide receptacles 402, 402' of the cylinder guide Z are fixedly and / or immovably connected to the guide receptacle 302. In the present case, the guide receptacle 302 and the two cylinder receptacles 402, 402' form a common, one-piece component.

[0045] The guide rod 301 is bent longitudinally between a proximal end and a distal end (each without reference symbol). The proximal end is slidably held in the guide receptacle 302. The distal end is connected to the second fastening device 200 by means of the second linear guide 500 for relative movement along the second guide path L2.

[0046] In the present case, the circular arc guide 300 also has a fixing device 303, which is designed to fix the mobility of the circular arc guide 300. By means of the fixing device 300, the relative mobility between the guide rod 301 and the guide receptacle 302 can be selectively fixed and released. The fixing device 303 thus counteracts any unwanted relative movement along the circular guide path C. The fixing device 303 effects a releasable force-locking and / or form-locking connection between the guide rod 301 and the guide receptacle 302. For example, the fixing device 303 can cause the legs 3021, 3022 to be braced relative to the guide rod 301. For this purpose, the fixing device 302 can have a screw, clamp, box, or other mechanism. Further details regarding the function and structure of the fixing device 303 are not essential to the present invention.A more detailed explanation of the fixing device 303 is therefore considered unnecessary.

[0047] Furthermore, the circular guide 300 in the present case has a first display device A1. In the embodiment shown, the first display device A1 is a scale with unspecified graduations, which in this case are attached to the guide rod 301. A distal front edge of the guide receptacle 302, unspecified, can serve as a reading mark. During a relative movement between the guide rod 301 and the guide receptacle 302, the reading mark moves along the graduations. The first display device A1 thus indicates a relative position between the guide rod 301 and the guide receptacle 302 with respect to the circular guide path C. During use of the surgical instrument 1, the first display device A1 thus indicates a first angular position α1 of the second fastening device 200—and thus also of the tibial cutting block 700—with respect to the circular guide path C.In other words, the first display device A1 serves to display the sagittal inclination, ie the slope, of the tibial cutting block 700.

[0048] The second linear guide 500 is a sliding guide K in the embodiment shown. The sliding guide K has a sliding block 501 (see in particular Fig. 3 ) and a link slot 502. The link slot 502 extends longitudinally along the second guide track L2. The link block 501 is held in the link slot 502 so as to slide along the second guide track L2.

[0049] In the embodiment shown, the sliding block 501 is fixedly and / or (relatively) immovably connected to the circular arc guide 300. The sliding block slot 502 is fixedly and / or (relatively) immovably connected to the second fastening device 200. In particular, the sliding block 502 is fixedly connected to the distal end (no reference symbol) of the guide rod 301. The sliding block slot 502 is open at one end, at its anterior end (no reference symbol). The sliding block 501 can be inserted into the sliding block slot 502 through the open end and removed from the sliding block. This allows, in particular, easy disassembly and reassembly of the surgical instrument 1, for example, for cleaning, sterilization, or the like.

[0050] In the embodiment shown, the second fastening device 200 has a base body 201. The guide slot 502 is formed on the base body 201 in the present case. For the actual fastening of the tibial cutting block 700 to the second fastening device 200, the latter has a fastening element 202. The fastening element 202 interacts releasably in a force-fitting and / or form-fitting manner with a section of the tibial cutting block 700 provided for this purpose. In the present case, the fastening element 202 is mounted on the base body 201 between a fastening position and a release position relative to the latter. In the fastening position, the tibial cutting block 700 is releasably connected to the base body 201 by means of the fastening element 202. In the release position, the tibial cutting block 700 is released relative to the base body 201 and vice versa.

[0051] In the embodiment shown, the surgical instrument additionally comprises an alignment rod 800. The alignment rod 800 is configured for alignment with an anterior edge V of the tibia T. The anterior edge V can also be referred to as the anterior edge of the tibia. The alignment rod 800 is mounted at one end on the second fastening device 200 so as to be pivotable relative to the second fastening device 200 about a pivot axis S oriented orthogonal to the guide plane E. In the embodiment shown, the alignment rod 800 is mounted on the base body 201. The alignment rod 800 is elongated between a proximal end 801 and a distal end 802 (not shown in detail). The pivotable mounting allows the alignment rod 800 to be aligned in the guide plane E and / or parallel to the same.As a result, the alignment rod 800 can be aligned parallel to the tibial anterior edge V, in particular for controlling the position of the tibial cutting block 700 and / or for controlling the extension position of the tibia T. The specific function of the alignment rod 800 will be explained in more detail below.

[0052] In the embodiment shown, a second display device A2 is assigned to the alignment rod 800. The second display device A2 is configured to display a second angular position α2 of the alignment rod 800 relative to the pivot axis S. In the present case, the second display device A2 is a scale with multiple graduations (without reference symbols). The graduations are attached to the second fastening device 200, more precisely, its base body 201. A reading mark (not shown in detail) is also provided, which can also be formed, for example, by the alignment rod 800 itself.

[0053] An exemplary use of the surgical instrument 1 for positioning the tibial cutting block 700 is explained below.

[0054] Positioning is carried out starting from a configuration in which the distal femoral cutting block 600 is already fixed to the distal femur F in a manner known to those skilled in the art. This means that the already fixed femoral cutting block 600 serves as a reference. The guide slot 601 extends mediolaterally and anteroposteriorly. A rotational alignment of the guide slot 601 with respect to an anteroposterior axis specifies a varus / valgus alignment of the distal femoral cut to be made. In the present case, it is assumed that the varus / valgus alignment is 0°. The guide slot 601 is therefore oriented parallel to a distal condylar line of the distal femur F. By means of the surgical instrument 1, in particular a varus / valgus alignment already performed on the femur side can be transferred to the tibial cutting block 700, more precisely: its guide slot 701.

[0055] For this purpose, the tibial cutting block 700 is first detachably fastened to the second fastening device 200 in the manner described above. The surgical instrument 1 is then referenced on the femur side together with the tibial cutting block 700 fastened to the same. For this purpose, the first fastening device 100 is detachably fastened to the femur cutting block 600 already fixed on the femur side. This is done in the manner described above, ie the plug-in element 101 is inserted posteriorly into the guide slot 601. This results in the Fig. 1 to 4 configuration shown.

[0056] In this (exemplary) configuration, an exact extension is present, in which the femur F and the tibia T form an angle of 180°. Starting from such (complete) extension, the sagittal inclination of the guide slot 701 is adjusted as follows: First, the center point M of the circular arc guide 300 is positioned to match the patient's anatomy. This positioning is achieved using the first linear guide 400. When the circular arc guide 300 is displaced along the first guide track L1 in the posterior direction, the center point M moves posteriorly. Conversely, an anteriorly directed relative movement of the circular arc guide 300 relative to the first fastening device 100 - and thus the femoral cutting block 600 - causes an anterior displacement of the center point M. It is understood that the plug-in element 101 always remains inserted into the guide slot 601.Ideally, the center point M is positioned centrally on a (mechanical) tibial axis (not shown in detail). Such positioning of the center point M prevents an adjustment of the inclination of the tibial cutting block 700 from simultaneously causing an unwanted change in the proximodistal position relative to the tibia (tibial cutting height).

[0057] After the center point M has been positioned via the previously described adjustment of the first linear guide 400, the tibial cutting block 700 is positioned anteriorly against the tibia T. The second linear guide 500 ensures that the position is always as required. The tibial cutting block 700 can be raised or lowered to adapt to the prevailing dimensions of the tibia T by displacing the second fastening device 200 along the second guide axis L2.

[0058] In a further step, the actual adjustment of the sagittal inclination of the guide slot 701, ie the slope, takes place. Fig. 1 to 4 the slope is 0°, so that the guide slot 701 of the tibial cutting block 700 is aligned plane-parallel to the guide slot 601 of the femoral cutting block 600. The first angular position α1 ( Fig. 1 ) represents the aforementioned slope. The slope can be adjusted using the circular guide 300. The set value can be read off the first display device A1. The previously positioned center point M on the tibial axis does not change the tibial cutting height.

[0059] The alignment rod 800 serves, on the one hand, to control full extension. With full extension and parallel alignment of the alignment rod 800 to the anterior tibial edge V, the second angular position α2 is 0°.

[0060] The alignment rod 800, together with the two display devices A1, A2, also enables flexion / extension correction. If there is no exact extension, this can be determined using the alignment rod 800 and the second display device A2 and compensated by adjusting the slope on the second display device A1 accordingly. For explanation, reference is made below to the Fig. 5 The exemplary situation presented is discussed.

[0061] In the Fig. 5In the situation shown, there is no exact extension. Instead, the tibia T is angled by an angle α3 relative to the femur F. The surgical instrument 1 allows the angle α3 to be taken into account when setting the slope. For this purpose, the surgical instrument 1, together with the tibial cutting block 700, is first connected to the already fixed femoral cutting block 600 in the manner described above. The circular arc guide 300 is then adjusted such that the display device A1 displays a first angular position α1, which represents a slope of 0°. The actual slope in this case is not 0° due to the existing flexion. The angle α3 is then determined by aligning the alignment rod 800 parallel to the anterior tibial edge V. The angle α3 can be read off the second display device A2. The corresponding angle is then set on the circular arc guide 300.This ensures that the guide slot 701 is set orthogonal to the anterior tibial edge V and thus at a slope of 0°, despite the deviation from the exact extension position. Starting from this (basic) setting, further adjustment of the slope can be made by appropriately relocating the circular guide 300.

Claims

1. Surgical instrument (1) for use in a knee joint replacement operation, having a first fastening device (100) which is configured for releasably fastening to a reference component (600) attached to a distal femur (F), a second fastening device (200) which is spaced apart distally from the first fastening device (100) and is configured for releasably fastening to a tibial cutting block (700) for cutting guidance on a proximal tibia (T), a circular arc guide (300) which is connected at one end to the first fastening device (100) and at the other end to the second fastening device (200) and by means of which the second fastening device (200) is linearly movable relative to the first fastening device (100) guided in a sagittal guide plane (E) along a guide path (C) which is elongate in the manner of a circular arc, a first linear guide (400), by means of which the circular arc guide (300) is connected at one end to the first fastening device (100) and is linearly movable relative thereto guided in the guide plane (E) along a first guide path (L1) which is elongate anteroposteriorly, and a second linear guide (500), by means of which the second fastening device (200) is connected at the other end to the circular arc guide (300) and is linearly movable relative thereto guided in the guide plane (E) along a second guide path (L2) which is elongate anteroposteriorly.

2. Surgical instrument (1) according to Claim 1, characterized in that an alignment rod (800) is present and is configured for aligning on an anterior edge (V) of the tibia (T), wherein the alignment rod (800) is mounted at one end on the second fastening device (200) so as to be pivotable relative to the second fastening device (200) about a pivot axis (S) oriented orthogonally to the guide plane (E).

3. Surgical instrument (1) according to Claim 1 or 2, characterized in that a first indicating device (A1) is present and is configured for indicating a first angular position (α1) of the second fastening device (200) with respect to the circular-arc-shaped guide path (C), and / or in that a second indicating device (A2) is present and is configured for indicating a second angular position (α2) of the alignment rod (800) with respect to the second pivot axis (S).

4. Surgical instrument (1) according to one of the preceding claims, characterized in that the circular arc guide (300) has at least one curved guide rod (301) and a guide receptacle (302) in which the guide rod (301) is accommodated in a slidably guided manner, wherein the guide receptacle (302) is connected to the first linear guide (400) and the guide rod (301) to the second linear guide (500), or vice versa.

5. Surgical instrument (1) according to Claim 4, characterized in that the guide receptacle (302) is connected to the first linear guide (400) and has a guide element, in particular a cylinder element (401) or a cylinder receptacle (402), of same, and / or in that the guide rod (301) is connected to the second linear guide (500) and has a guide element, in particular a slotted guide block (501) or a slotted guide slot (502) , of same.

6. Surgical instrument (1) according to one of the preceding claims, characterized in that the first linear guide (400) is a cylinder guide (Z) and has at least one cylinder element (401), which is elongate anteroposteriorly, and a cylinder receptacle (402) in which the cylinder element (401) is accommodated in a slidably guided manner.

7. Surgical instrument (1) according to Claim 6, characterized in that the cylinder element (401) is connected immovably to the first fastening device (100), and in that the cylinder receptacle (402) is connected immovably to the circular arc guide (300), preferably to the guide receptacle (302) thereof.

8. Surgical instrument (1) according to one of the preceding claims, characterized in that the second linear guide (500) is a slotted guide mechanism (K) and has a slotted guide block (501) and a slotted guide slot (502) which is elongate anteroposteriorly and in which the slotted guide block (501) is accommodated in a slidably guided manner.

9. Surgical instrument (1) according to Claim 8, characterized in that the slotted guide block (501) is connected immovably to the circular arc guide (300), preferably to the guide rod (301) thereof, and in that the slotted guide slot (502) is formed on the second fastening device (200).

10. Surgical instrument (1) according to one of the preceding claims, characterized in that the first fastening device (100) has at least one plug-in element (101) which is configured for releasably plugging together with a complementary reference geometry (601) of the reference component (600).

11. Surgical instrument (1) according to one of the preceding claims, characterized in that the second fastening device (200) has a main body (201) on which a fastening element (202), which is configured for releasably fastening to a fastening portion, provided for this purpose, of the tibial cutting block (700), a guide element of the second linear guide (500), preferably the slotted guide slot (502) thereof, and the alignment rod (800) are arranged.

12. Surgical instrument (1) according to one of the preceding claims, characterized in that a fixing device (303) is present and is configured for fixing the movability of the circular arc guide (300).

13. Surgical instrument system (10) with a surgical instrument (1) according to one of the preceding claims, a reference component (600), which is fastened releasably to the first fastening device (100) of the surgical instrument (1), and with a tibial cutting block (700), which is fastened releasably to the second fastening device (200) of the surgical instrument (1).