Intramedullary tibial alignment system

Abstract

The present invention relates to an intramedullary tibial alignment system (1) having an alignment rod (3), a tibial resection guide (4), and a tibial alignment jig (5), wherein the tibial alignment jig (5) has a slide rail (6), a casing (8) slidably receiving the slide rail (6) and attached to the alignment rod (3), and a user adjustment element (9) rotatably held by the alignment rod (3) and operatively connected to the casing (8) by a link element (22) such that rotation is converted into a pivotal movement, wherein the user adjustment element (9) and the alignment rod (3) are adapted to interlock with each other at a plurality of rotational positions of the user adjustment element (9), the plurality of rotational positions corresponding to different orientations of the alignment rod (3) according to the pivotal movement of the alignment rod (3).

Description

Technical Field

[0001] The present invention relates to arthroplasty, particularly knee arthroplasty and total knee arthroplasty. More specifically, the present invention relates to an apparatus that enables a surgeon to efficiently and accurately excise the proximal portion of the tibia before placing a prosthesis on the proximal portion of the tibia. In particular, the present invention relates to an intramedullary tibial alignment system.

Background Art

[0002] The knee joint enables the human leg to bend or articulate during movement. At the knee, the lower bone (tibia) meets the upper bone (femur). Proximally at the knee, the femur has two projections known as femoral condyles. The femoral condyles engage with fibrocartilage at the upper end of the tibia. The knee joint is held together by ligaments, capsules, muscles, and tendons. Four ligaments are particularly prominent in the knee structure, with one ligament on each side of the knee and two ligaments located centrally. Of the centrally located ligaments, one ligament faces forward and one faces backward. The patella or kneecap is a bone fragment supported in front of the knee joint. Functionally, the kneecap acts as a shield.

[0003] The knee joint can be rendered nearly or completely inoperable by long-term severe use, disease, or trauma. The best treatment is often total replacement (arthroplasty). During total knee arthroplasty, the femoral and tibial surfaces joined at the knee are completely replaced. The first step in this process is the removal of the condylar surface and the underlying portion. The distal end of the femur is excised to provide clearance for the femoral prosthesis component. Similarly, the proximal portion of the tibia is excised to provide a relatively flat surface for the tibial prosthesis component.

[0004] A person's weight moves from the head of the femur near the hip joint to the ankle. When femoral and tibial prosthetic devices are installed, proper alignment of the knee must be maintained to allow proper transfer of the weight to continue. For the prosthesis to function properly, the femoral and tibial surfaces resulting from these resections must be accurately aligned. Also, these surfaces must be separated by an appropriate distance so that the planned prosthesis fits and functions properly.

[0005] Previously, alignment of the tibial resection guide before surgical resection has been done by using a long, straight metal rod. One end of the metal rod is aligned with the center of the femoral head. The other end is aligned with the center of the ankle. The center of the femoral head is determined from an x-ray or, less preferably, by establishing a point located three finger breadths medial to the anterior superior iliac spine. When aligned, the rod should bisect the center of the knee component and be generally perpendicular to the tibial and femoral resection planes. Arthritic knees can have varus or valgus deformities, and corresponding bone defects or gaps.

[0006] These resected surfaces with exposed defects may not be suitable for supporting the replacement prosthesis. Currently, the surgeon places an artificial organ device on the resected bone with an exposed defect and fills the defect under the component with, for example, bone cement or a spacer, or removes the defect or gap and must resect the tibia further away from the knee to insert a thicker prosthetic component. When the surgeon performs further resection, a tibial resection guide is needed to ensure that the resected portion is the correct shape and size.

[0007] For example, U.S. Patent Application Publication No. 2009 / 264890 (A1) discloses a tibial alignment system for aligning a proximal tibial resection cutting instrument, the tibial alignment system having an alignment rod, a tibial resection guide, and a tibial alignment jig for orienting the tibial resection guide relative to the alignment rod and thus relative to the tibia, the tibial alignment jig having a slide rail adapted to be connected to the head of the tibia at its proximal end portion and a casing that slidably receives the slide rail along a slide axis. SUMMARY OF THE INVENTION

[0008] Accordingly, an intramedullary tibial alignment system may be needed that enables a surgeon to quickly and efficiently align a tibial resection guide so that an implanted prosthesis fits and functions correctly. In particular, an intramedullary tibial alignment system may be needed that enables more accurate adjustment of the position and orientation of the tibial resection guide.

[0009] This object is solved by the intramedullary tibial alignment system according to claim 1. Further advantageous developments of the invention are made with respect to the subject matter of the respective dependent claims.

[0010] The intramedullary tibial alignment system described herein may be applied to total knee replacement, which is a surgical procedure in which flat and / or curved surfaces must be created in or on the bone to enable proper attachment or implantation of an orthopedic device. In total knee replacement, a series of flat and / or curved surfaces, or "resections," are created to enable attachment of an orthopedic device or other device to the femur, tibia, and / or patella.

[0011] To meet the above requirements, the intramedullary tibial alignment system according to claim 1 is proposed. The intramedullary tibial alignment system is for aligning a tibial resection cutting instrument.

[0012] The intramedullary tibial alignment system according to the present invention has an alignment rod for individually adjusting the alignment system to the tibia. The intramedullary tibial alignment system further has a tibial resection guide (also called a cutting block) for guiding a separate (external, not belonging to the system) cutting instrument at the correct position and inclination with respect to the tibia, and this cutting guide is connected to, or connectable to, the proximal end portion of the alignment rod. Preferably, such an alignment rod is a telescopic extension bar that is adjustable for the tibias of individual patients of various different lengths.

[0013] The intramedullary tibial alignment system also has a tibial alignment jig for orienting the tibial resection guide with respect to the tibia. The tibial alignment jig is connected to the alignment rod in the vicinity of the tibial resection guide. The tibial alignment jig has a slide rail adapted to be connected to the head of the tibia at its proximal end portion. The tibial alignment jig has a casing that slidably receives the distal end portion of the slide rail. The casing is attached to the alignment rod via a pivot axis (extending perpendicular to the rod) such that the alignment rod and the slide rail are maintained pivotable relative to each other about the pivot axis.

[0014] According to the present invention, the tibial alignment jig further comprises a user adjustment element, for example a vernier adjustment element, and the user adjustment element is rotatably held on the alignment rod such that rotation of the user adjustment element with respect to the alignment rod is converted into a pivoting movement of the alignment rod with respect to the slide rail, and is preferably functionally connected to the casing by a link element. The user adjustment element and the alignment rod are adapted to cooperate with each other at a plurality of rotational positions of the user adjustment element, and the plurality of rotational positions correspond to different orientations of the alignment rod with respect to the tibia according to the pivoting movement of the alignment rod.

[0015] In other words, according to the present invention, an intramedullary alignment system comprising a (telescopic) rod / bar is provided, and a cutting block for guiding a separate cutting instrument (saw) is connected to the proximal end portion of the rod. Further, an inclination adjustment device (alignment jig) is provided at the proximal end of the rod (proximal to the cutting block) for adjusting the angle / inclination of the cutting block with respect to the tibia.

[0016] For this purpose, the inclination adjustment device comprises a cantilever arm (slide rail) adapted such that its proximal end portion is fixed to the tibia, in particular to the head of the tibia, and its distal end portion is supported within or on a casing / bracket such that it is slidable in its longitudinal direction. The casing / bracket is pivotally held at the proximal end portion of the rod (proximal to the cutting block) via a pivot axis oriented perpendicular to the longitudinal axis of the rod. Thus, the rod is pivotable about the pivot axis with respect to the cantilever arm, thereby changing the angle / orientation with respect to the tibia.

[0017] According to the present invention, it is intended to implement user adjustment means / elements / mechanisms adapted to provide fine adjustment of the inclination of the rod (and thus the cutting block) with respect to the tibia. Preferably, the user adjustment element may have a knob shape or a knob-shaped portion for providing a grip to the user while turning the user adjustment element. In other words, for this purpose, a manually operable rotating knob / sleeve / bolt is provided, which is rotatably supported / held / attached to the alignment rod (preferably parallel to the rod). The rotating sleeve is functionally connected to the casing (preferably within the casing) such that rotation of the rotating sleeve about its longitudinal axis is converted into a pivoting movement of the casing about the pivot axis.

[0018] Preferably, a locking mechanism can be provided. The locking mechanism may be adapted to lock and unlock the rotational movement between the alignment rod and the user adjustment element (in a fine adjustment manner). The locking mechanism may include a release element fixed to the user adjustment element, preferably a snap hook, and an engagement element fixed to the alignment rod, preferably a snap slot. The release element engages with the engagement element in the locked position.

[0019] More preferably, the locking mechanism may include a plurality of engagement elements each forming a locking position. The plurality of engagement elements may preferably be spaced apart from each other in the circumferential direction of the alignment rod. The circumferential direction of the alignment rod corresponds to the circumferential direction of the user adjustment element. More preferably, the plurality of engagement elements may be spaced apart from each other such that two adjacent locking positions generate a stepwise, more preferably 1°-step rotational movement between the alignment rod and the slide rail without interruption. That is, by rotating the user adjustment element from one locking position to an adjacent locking position, a rotational movement is caused that corresponds to a 1° change in the orientation of the tibial resection guide relative to the tibia in the sagittal view. That is, the rotational movement corresponds to the posterior tilt of the resection. In other words, a locking mechanism (preferably manually operable) may be provided between the rotating sleeve / bolt and a rod that is divided into or includes a plurality of locking positions spaced apart from each other in the rotational direction of the rotating sleeve / bolt. In a preferred embodiment of the present invention, the circumferential distance between two adjacent locking positions is defined to generate a 1° rotation of the rod relative to the cantilever arm. Thus, the rotational movement can smoothly adjust the posterior tibial slope. More preferably, the user adjustment element may include a scale indicating the adjusted inclination corresponding to the selected locking position.

[0020] In a particularly preferred embodiment according to the present invention, the release element may comprise a button on the periphery of the user adjustment element, and the button is manually pressed by the user to release the lock mechanism, preferably to disengage the engagement at one of the locked positions, and is adapted to allow the user adjustment element to be rotated clockwise or counterclockwise in the circumferential direction of the alignment rod. That is, the lock mechanism is manually releasably engaged. Therefore, unintentional adjustment can be avoided.

[0021] More preferably, the lock mechanism may be designed to provide an adjustment ability of an orientation of at least 0° to 7°. In a preferred embodiment, the lock mechanism may comprise a limit stop that limits the adjustment ability of the rotation of the user adjustment element, and thus the adjustable inclination may be within a predetermined range, particularly within a predetermined range corresponding to an inclination of 0° to 7°.

[0022] In a preferred embodiment according to the present invention, the casing may comprise a slide guide slot for slidably receiving a slide rail along a slide axis, and the slide axis is the longitudinal direction / axis of the slide rail. For example, the slide guide slot may be a through hole that penetrates the casing in the slide direction / along the slide axis. Thereby, a compact configuration can be achieved. For example, the slide guide slot may have a rectangular cross section (in a plane perpendicular to the slide axis) that eliminates any degree of freedom of the slide rail with respect to the casing except for relative movement in the slide direction. In other words, the casing, particularly the slide guide slot, provides a linear bearing / unidirectional bearing for the slide rail.

[0023] Preferably, the slide rail may include a hole through which an alignment rod, which is elongated along the slide axis, passes. The elongated hole may be designed to allow for a maximum swiveling movement of the alignment rod relative to the casing and / or to allow for a maximum sliding movement of the slide rail relative to the casing while remaining attached to the casing. Thus, the sliding ability is not hindered by the alignment rod, and the swiveling ability is not hindered by the slide rail.

[0024] In a preferred embodiment of the present invention, the casing may include a swivel element that pivotally attaches the casing to the alignment rod via a swivel axis, the swivel axis being perpendicular to the rotation axis and perpendicular to the slide axis. Since the axes (swivel axis, slide axis, rotation axis) are perpendicular to each other, they can be adjusted to any orientation. Preferably, the swivel element may be in contact with the circumferential surface of the user adjustment element (or alignment rod). In this way, the swiveling movement can be guided and controlled. Preferably, the swivel element may be fixed to the casing, particularly inside the casing, and extend towards the circumferential surface of the user adjustment element. More preferably, the swivel element may be formed by two (first) pins, the longitudinal axis of each pin coinciding with the swivel axis, and the pins being arranged on opposite sides in the circumferential direction of the user adjustment element.

[0025] In a preferred embodiment of the present invention, the user adjustment element may include a swivel guide groove on the circumferential surface of the user adjustment element that receives a link member. The link member may be fixed inside the casing and extend towards the swivel guide groove. The swivel guide groove may be designed to cause a relative movement of the casing relative to the user adjustment element when the user adjustment element is rotated. Preferably, the longitudinal axis of the link member coincides with the slide axis, i.e., it is axially parallel to the slide axis. Thus, it is possible to achieve a conversion between the rotation of the user adjustment element relative to the alignment rod and the swiveling movement of the alignment rod relative to the slide rail. This has the advantage of easily adjusting the posterior tibial slope by rotating the user adjustment element.

[0026] In other words, the pivoting function can be achieved by a link member fixed inside the casing so as to extend towards the circumferential surface of the rotating sleeve / bolt, and the rotating sleeve / bolt is provided with a guide slot which receives / slidably holds the free end of the link member, where the guide slot extends in the circumferential direction of the rotating sleeve / bolt and is designed to pull and / or draw the link member when the rotating sleeve / bolt is rotated (manually), and thus is designed to pull the casing towards / away from the rotating sleeve / rod.

[0027] In a preferred embodiment, the pivoting guide groove has a depth that preferably increases or decreases continuously along its circumferential extension. By changing the depth of the pivoting guide groove, the link member is pulled towards / away from the alignment rod and the user adjustment element, i.e., approaches or moves away from the user adjustment element (thus causing the alignment rod to pivot). In an alternative preferred embodiment, the pivoting guide groove may preferably have a helical shape with a constant pitch. That is, the spherical axis (of the link member) connects with the helical groove guiding the link member to cause a pivoting motion. For example, the length of the groove can be limited to less than half of the circumferential length of the cylindrical support. In particular, the length may be limited to the angle / inclination adjusted according to the tibial resection guide.

[0028] In a preferred embodiment of the present invention, a fastening element may be provided for rotatably attaching the user adjustment element to the alignment rod. The user adjustment element may comprise a groove on its circumferential surface for receiving the fastening element fixed to the alignment rod. The groove rotatably supports the alignment rod and the user adjustment element relative to each other. The groove may be arranged in a plane perpendicular to the axis of rotation. For example, the fastening element may be formed by one or more (second) pins, the longitudinal axis of each pin being perpendicular to the axis of rotation, and the pins being spaced apart from each other in the circumferential direction of the user adjustment element (and the alignment rod), more preferably at equal distances. The groove is formed in the circumferential direction. Thus, relative rotational ability can be provided while preventing any other relative movement between the alignment rod and the user adjustment element, such as translational movement along the axis of rotation.

[0029] In a preferred embodiment of the present invention, the alignment rod may be an extensible telescopic bar with adjustable length. Thus, the alignment rod may be adapted to the length of the patient's individual tibia. Further, the selected angle can be verified by means of a telescopic alignment rod extending from the end of the adjustment. In an alternative preferred embodiment of the present invention, the alignment rod and the user adjustment element may each form a through hole extending along the longitudinal direction of the alignment rod, i.e., the direction of rotation, the through hole being adapted to receive a (separate) extra-medullary check rod. Thus, the selected angle can be verified using an extra-medullary check rod passing through the system. Thus, the verification is more accurate than a system with an extra-medullary check rod provided outside the system.

[0030] Preferably, a tibial adjustment housing may be provided, the tibial adjustment housing holding an alignment rod and connecting the alignment rod to a tibial alignment jig with a tibial resection guide. More preferably, the tibial adjustment housing may be slidably attached to the alignment rod along a rotation axis. As a result, the tibial adjustment housing enables the tibial resection guide to move in the direction of the alignment rod. Thus, the tilt and shift movements of the tibial resection guide can be achieved by an intramedullary tibial alignment system as described herein.

[0031] In other words, the present invention relates to an intramedullary tibial alignment system that enables easy adjustment of the posterior tilt from 0° to 7° in 1° increments before performing tibial resection during total knee arthroplasty. Adjusting the posterior tilt enables management of knee flexion. Intramedullary tibial alignment typically has the drawback that it cannot adjust and lock the angle of the posterior tilt and has only some fixed angles. The intramedullary system may be able to position the tibial cutting guide required for tibial resection, where the tibial intramedullary system may be for reference. Further, the system may be able to orient the cutting guide support by unlocking and turning a button. This orientation may be 0° to 7° in 1° increments in the sagittal plane (posterior tilt). The posterior tilt may be between 0° and 7°, which are the two maximum and minimum positions. In particular, the system may enable adjustment and locking of the angle, which does not take up much space. In other words, the slide rail may enable connection to the intramedullary axis and displacement of the system. The angulation from 0° to 7° is managed by rotation of the system around the axis in conjunction with a slide nut. This rotation may be generated by operation of a button. In fact, the rotation of the button may generate the angulation of the system depending on the connection between the ball shaft and the helical groove of the cylindrical support. The required angle can be locked according to, for example, the spring portion of the release button that fits into eight specific grooves (0° to 7°) of the support, and thereafter, the angle of the system cannot be changed without the user's operation on the release button. The new angle can only be selected by pressing the release button and turning the button until it reaches the appropriate groove. In other words, the button may be referred to as a rotary knob as described above. In parallel with all adjustments and / or at the end of all adjustments, the system provides the possibility of verifying the selected angle with an external cortical check, including passing an alignment rod through. Since the rod passes through the system, the system is more accurate than a system with a shift where the rod is outside the mechanism. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The present invention will be described in more detail below based on preferred embodiments with reference to the drawings. The drawings are of a schematic nature and are intended to improve the understanding of the present invention. Identical elements are referred to by the same reference numerals.

[0033]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

DETAILED DESCRIPTION OF THE INVENTION

[0034] Figs. 1 to 5 show a preferred embodiment of an intramedullary tibial alignment system 1 (hereinafter referred to as the alignment system 1) according to the present invention. The alignment system 1 is for aligning a (tibial resection) cutting instrument with respect to the tibia 2. The alignment system 1 guides the adjustment of the tibial resection cutting instrument in order to achieve a desired posterior tilt of the resection of the tibia 2.

[0035] The alignment system 1 has an alignment rod / alignment pipe 3 for individually adjusting the alignment system 1 with respect to the tibia 2. The alignment system 1 has a tibial resection guide 4 for guiding the cutting instrument. The tibial resection guide 4 is connected to the tip (lower end) of the alignment rod 3. The alignment system 1 has a tibial alignment jig 5 for orienting the tibial resection guide 4 with respect to the tibia 2. The tibial alignment jig 5 statically fixes the alignment rod 3 to the patient's tibia 2. The tibial alignment jig 5 is connected to the alignment rod 3 proximal (above in Fig. 1) to the tibial resection guide 4.

[0036] The tibial alignment jig 5 has a slide rail 6. The slide rail 6 is adapted to be connected to the head of the tibia 2 at its proximal end portion. The slide rail 6 is insertable into the tibia 2, particularly the tibial head, or is connected to an adjustable slide rail fixture 7 for an element on the inner side of the tibia 2. Alternatively, the slide rail fixture 7 is a stylus, providing precise positioning of the slide rail 6 and thus the tibial alignment jig 5.

[0037] The tibial alignment jig 5 has a casing 8. The casing 8 slidably receives the slide rail 6 (at its distal end) along a slide axis S. The slide axis S coincides with the longitudinal axis of the slide rail 6. The casing 8 is attached to the alignment rod 3 via a pivot axis P such that the alignment rod 3 and the slide rail 6 are pivotally held relative to each other. The pivot axis P is perpendicular to the slide axis S.

[0038] The tibial alignment jig 5 has a user adjustment element 9. The user adjustment element 9 is rotatably held about a rotation axis R by the alignment rod 3. The rotation axis R coincides with the longitudinal axis of the alignment rod 3. The rotation axis R is perpendicular to the slide axis S. The rotation axis R is perpendicular to the pivot axis P. The user adjustment element 9 is functionally connected to the casing 9 such that rotation of the user adjustment element 9 relative to the alignment rod 3 is converted into a pivoting movement of the alignment rod 3 relative to the slide rail 6. This conversion of movement will be described below with reference to FIG. 2.

[0039] The user adjustment element 9 and the alignment rod 3 are adapted to engage with each other at a plurality of rotational / locking positions of the user adjustment element 9. The plurality of rotational positions correspond to a plurality of different orientations of the alignment rod 3 in accordance with the pivoting movement of the alignment rod 3, i.e., to a plurality of different posterior resection inclinations with respect to the tibia 2 guided by the alignment system 1. In FIG. 1, the alignment system 1 is aligned such that inclinations of 0° (left side) and 7° (right side) with respect to the tibia 2 can be achieved by resection.

[0040] The alignment system 1 has a tibial adjustment housing 10. The tibial adjustment housing 10 is connected to the distal end of the alignment rod 3. The tibial adjustment housing 10 is connected to the alignment rod 3 distally of the tibial alignment jig 5. The tibial adjustment housing 10 connects the alignment rod 3 to the tibial resection guide 4. The tibial adjustment housing 10 is slidably attached to the alignment rod 3 slidable along / parallel to the axis of rotation R.

[0041] FIGS. 2 to 4 show the tibial adjustment jig 5 in detail. The user adjustment element 9 comprises a (lower / distal) cylindrical support portion 11 and an (upper / proximal) knob portion 12. The knob portion 12 is adapted to be contacted / handled by the user in order to adjust the alignment system 1. The cylindrical support portion 11 and the knob portion 12 are fixed by a screw 13 engaging with the cylindrical support portion 11 and the knob portion 12. The cylindrical support portion 11 and the knob portion 12 are immovable relative to each other.

[0042] The alignment system 1 has a locking mechanism adapted to lock and unlock the rotational movement between the alignment rod 3 and the user adjustment element 9. The locking mechanism comprises a release element 14 and an engagement element 15. The release element 14 is fixed to the user adjustment element 9. The engagement element 12 is fixed to the alignment rod 3. The release element 14 and the engagement element 15 are engaged in the locked position. The locking mechanism comprises a plurality of engagement elements 15 each forming a locked position. The plurality of engagement elements 15 are spaced apart from each other such that two adjacent locked positions produce a stepwise, more preferably a 1° step-by-step pivoting movement between the alignment rod 3 and the slide rail. The release element 14 comprises a button 16 on the circumference of the user adjustment element 9. The button 16 is adapted to be manually pressed by the user to unlock the locking mechanism and to allow the user to rotate the user adjustment element 9 clockwise or counterclockwise in the circumferential direction with respect to the alignment rod 3. Without pressing the button 16, the user cannot rotate the user adjustment element 9 in either direction. The locking mechanism will be described in detail with reference to FIG. 5.

[0043] The casing 8 comprises a slide guide slot 17. The slide guide slot 17 slidably receives / supports the slide rail 6 along the slide axis S. The slide guide slot 17 is formed as a through hole. The slide guide slot 17 has a rectangular cross-section when viewed perpendicular to the slide axis S. The slide guide slot 17 guides the slide rail 6 in one direction.

[0044] The slide rail 6 is received in the slide guide slot 17. The slide rail 6 comprises an elongated hole 18. The hole 18 is elongated along the slide axis S. The alignment rod 3 (or an element fixed to the alignment rod 3) passes through the hole 18 independently of the (slide) position of the slide rail 6 along the slide axis S or independently of the (pivot) position of the alignment rod 3 via the pivot axis P.

[0045] The casing 8 is provided with a swivel element 19. The swivel element 19 pivotally attaches the casing 8 to the alignment rod 3 via a swivel axis P. The swivel element 19 contacts the circumferential surface of the user adjustment element 9 (here a cylindrical support 11). The swivel element 19 is fixed to the casing 8. The swivel element 19 is proximal / above the slide guide slot 17. The swivel element 19 is fixed inside the casing 8 so as to extend towards the circumferential surface of the user adjustment element 9. The swivel element 19 passes through the hole 20 of the alignment rod 3. The swivel element 19 is formed by two (first) pins. The longitudinal axes of the pins respectively coincide with the swivel axis P. The pins are arranged on sides facing each other in the circumferential direction of the user adjustment element 9.

[0046] The user adjustment element 9 is provided with a swivel guide groove 21 on the circumferential surface of the user adjustment element 9. The swivel guide groove 21 houses a link member 22. The link member 22 functionally connects the casing 8 and the alignment rod 3. The link member 22 is fixed inside the casing 8 and extends towards the swivel guide groove 21. The link member 22 is proximal / above the slide guide slot 17. The swivel guide groove 21 is designed to cause relative movement of the casing 8 with respect to the user adjustment element 9 when the user adjustment element 9 is rotated. For example, the casing 8 can be pulled / attracted to or away from the user adjustment element 9. The link member 22 is formed as a screw or a (spherical) pin. The link member 22 passes through the hole 23 of the alignment rod 3. The hole 23 is formed elongated along the rotation axis R. The swivel guide groove 21 is spiral. That is, the swivel guide groove 21 is inclined with respect to the circumferential direction, and when the spherical axis of the link member 22 is guided circumferentially within the swivel guide groove 21, it causes relative movement of the casing 8 with respect to the user adjustment element 9. Alternatively, the swivel guide groove 21 can have a depth that increases or decreases (consistently) along its circumferential extension to cause relative movement of the casing 8 with respect to the user adjustment element 9. The circumferential extension of the swivel guide groove 21 can provide a limit stop for the rotational movement of the user adjustment element 5 with respect to the alignment rod 3.

[0047] The alignment system 1 comprises a fastening element 24. The fastening element 24 rotatably attaches a user adjustment element 9 to the alignment rod 3 along a rotation axis R. The fastening element 24 is fixed to the alignment rod 3 (the fastening element 24 engages with a hole 25 of the alignment rod 3). The fastening element 24 is formed by a plurality of (second) pins, here three second pins. The longitudinal axes of the pins are perpendicular to the rotation axis R. The pins are spaced apart in the circumferential direction of the user adjustment element 9. The pins are equidistantly spaced from each other. The user adjustment element 9 comprises a groove 26 extending in a plane perpendicular to the rotation axis R on the circumferential surface of the user adjustment element 9. The groove 26 is formed in the circumferential direction. The groove 26 receives the fastening element 26 (pin).

[0048] The tibial alignment jig 2 comprises a through hole 27 passing through the alignment system 1. The through hole 27 extends in coincidence / parallel with the rotation axis R. The through hole 27 is adapted to receive / accommodate a separate extra-medullary check rod 28 (see FIG. 1) for verifying the adjusted inclination of the alignment rod 3 with respect to the tibia 2. Alternatively, the alignment rod 3 can be formed by a telescopic extension bar with an adjustable length. The portion of the bar extending proximally from the tibial alignment jig 2 can be used as an extra-medullary check rod.

[0049] Figure 5 shows the visual mechanism in detail. The release element 14 is formed as or has a snap-fit hook. The engagement element 15 is formed as or has a snap-fit slot. The snap-fit slot is formed on the inner (circumferential) side surface of the alignment rod 3 (or an element fixed to the alignment rod 3). The snap-fit hook extends towards the inner (circumferential) side surface of the alignment rod 3 and engages with one of the snap-fit slots (plural if applicable) in the locked / locking position. When the button 16 is pushed radially inward (e.g., against the force of a spring), the snap fit between the hook and the slot is released, thereby enabling the user to turn the user adjustment element 9. The snap-fit slots are circumferentially spaced apart on the alignment rod 3. The circumferential distance between adjacent locked positions generates a defined step of the pivoting movement between the alignment rod 3 and the slide rail 6, and thus between the tibia 2.

Explanation of reference numerals

[0050] 1 Intramedullary tibial alignment system 2 Tibia 3 Alignment rod 4 Tibial resection guide 5 Tibial alignment jig 6 Slide rail 7 Slide rail fixture 8 Casing 9 User adjustment element 10 Tibial adjustment housing 11 Cylindrical part 12 Knob part 13 Pin 14 Release element 15 Engagement element 16 Button 17 Slide guide slot 18 Elongated hole 19 Pivoting element 20 Hole 21 Pivoting guide groove 22 Link member 23 Elongated hole 24 Fastening element 25 Hole 26 grooves 27 through holes 28 check rods

Claims

1. An intramedullary tibial alignment system for aligning a proximal tibia resection cutting instrument, An alignment rod for individually adjusting the alignment system to the tibia, A tibia resection guide that guides the proximal tibia cutting instrument and is connected to the proximal end portion of the alignment rod, The intramedullary tibial alignment system having a tibial alignment jig that orients the tibia resection guide with respect to the tibia and is connected to the alignment rod proximal to the tibia resection guide, The tibial alignment jig has a slide rail adapted to be connected to the head of the tibia at a proximal end portion of the head of the tibia, and a casing that slidably receives the slide rail along a slide axis, The casing is attached to the alignment rod via a pivot axis such that the alignment rod and the slide rail are pivotally maintained with respect to each other, The tibial alignment jig further comprises a user adjustment element, the user adjustment element being rotatably held on the alignment rod about a rotation axis such that rotation of the user adjustment element with respect to the alignment rod is converted into a pivoting movement of the alignment rod with respect to the slide rail, and being functionally connected to the casing by a link element, the user adjustment element and the alignment rod being adapted to engage with each other at a plurality of rotational positions of the user adjustment element, the plurality of rotational positions corresponding to different orientations of the alignment rod according to the pivoting movement of the alignment rod. An intramedullary tibial alignment system characterized by that.

2. Characterized by a locking mechanism adapted to lock and unlock the rotational movement between the alignment rod and the user adjustment element, the locking mechanism comprising a release element fixed to the user adjustment element and an engagement element fixed to the alignment rod, the release element engaging with the engagement element in a locked position. The intramedullary tibial alignment system according to claim 1.

3. The locking mechanism includes a plurality of engaging elements each forming a locking position, and the plurality of engaging elements are spaced apart from each other. The intramedullary tibial alignment system according to claim 2.

4. The release element includes a button on the periphery of the user adjustment element, and the button is adapted to be manually pressed by the user to unlock the locking mechanism and to allow the user adjustment element to be rotated clockwise or counterclockwise in the circumferential direction of the alignment rod. The intramedullary tibial alignment system according to claim 2.

5. The casing includes a slide guide slot for slidably receiving the slide rail along the slide axis, and the slide axis is in the longitudinal direction of the slide rail. The intramedullary tibial alignment system according to claim 1.

6. The slide rail is elongated along the slide axis and includes a hole through which the alignment rod passes. The intramedullary tibial alignment system according to claim 5.

7. The casing includes a pivoting element for pivotally attaching the casing to the alignment rod via a pivot axis, the pivot axis being perpendicular to the rotation axis and perpendicular to the slide axis. The intramedullary tibial alignment system according to claim 1.

8. The user adjustment element includes a pivoting guide groove on the circumferential surface of the user adjustment element for receiving a link member, the link member being fixed inside the casing and extending towards the pivoting guide groove, and the pivoting guide groove being designed to cause relative movement of the casing with respect to the user adjustment element when the user adjustment element is rotated. The intramedullary tibial alignment system according to claim 1.

9. The intramedullary tibial alignment system according to claim 8, wherein the turning guide groove has a depth that increases or decreases along its circumferential extension portion, or the turning guide groove has a spiral shape.

10. The intramedullary tibial alignment system according to claim 1, comprising a fastening element for rotatably attaching the user adjustment element to the alignment rod along the rotation axis, the rotation axis being the longitudinal direction of the alignment rod, the user adjustment element comprising a groove extending in a plane perpendicular to the rotation axis on the circumferential surface of the user adjustment element, the groove receiving the fastening element fixed to the alignment rod.

11. The intramedullary tibial alignment system according to claim 1, wherein the alignment rod is an adjustable telescopic extension bar, or the alignment rod and the user adjustment element each form a through hole extending along the rotation axis, the through hole being adapted to receive an extracortical check rod.

12. The intramedullary tibial alignment system according to claim 1, characterized by a tibial adjustment housing that holds the alignment rod and connects the alignment rod to the tibial alignment jig provided with the tibial resection guide.

13. The intramedullary tibial alignment system according to claim 12, wherein the tibial adjustment housing is slidably attached to the alignment rod along the rotation axis.

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