Balancer device

Abstract

To provide a balancer device with excellent maneuverability, preventing a center of gravity from easily deviating to a knee joint.SOLUTION: A balancer device 1 includes a tibia mounting part 3 fixed to a device body part 5, a femur attachment part 4 disposed between the tibia mounting part 3 and a distal end of the femur, a movable part 60 to which the femur attachment part 4 is connected and that is movable relative to the device body part 5, and a movement mechanism 6 being operated from the outside by an operating tool such as a hexagonal wrench to move the movable part 60, where a sizer 7 is detachably attached to the movable part 60 by magnetic force.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a balancer device. [Background technology]

[0002] Conventionally, in orthopedic surgical procedures such as total knee replacement, a ligament balancing device known as a balancer device for balancing the ligaments around a patient's knee joint may be used. As such a ligament balancing device, an orthopedic surgical instrument system is known that includes a balancer instrument having a tibial attachment part and a femoral attachment part movable relative to the tibial attachment part, a distraction instrument having an operating function for moving the femoral attachment part relative to the tibial attachment part, and a femoral sizing instrument for measuring the size of the femur as information required for surgery, and in which the distraction instrument or the femoral sizing instrument can be integrally assembled to the balancer instrument (see, for example, Patent Document 1).

[0003] The distraction device included in the orthopedic device system described in Patent Document 1 is detachable from the balancer device, and is structured to include a link mechanism in which a fixed arm and a movable arm that rises and falls relative to the fixed arm engage with a part of the balancer device, and the distraction device and the balancer device are linked to each other with the fixed arm. By manually gripping an operating lever included in the distraction device, the movable arm rises relative to the fixed arm, and the femoral attachment part of the balancer device moves in a direction away from the tibial attachment part. In addition, the femoral sizing device is separate from the balancer device and the distraction device, and is attached to the upper part of the balancer device, which is connected to the movable arm, by a fastener such as a magnet or a screw. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special table 2022-526360 Summary of the Invention [Problem to be solved by the invention]

[0005] In the above-mentioned conventional orthopedic surgical instrument system, the distraction instrument for moving the femoral attachment portion of the balancer instrument relative to the tibial attachment portion is provided with a link mechanism assembled to the balancer instrument, and although the structure is complex, large, and heavy, the user must either hold the orthopedic surgical instrument system to maintain a predetermined tension between the tibia and femur during surgery, or remove the distraction instrument from the balancer instrument.

[0006] In this case, the balancer device with the distraction device attached is heavy and the center of gravity is biased toward the user, and the distraction device needs to be repeatedly attached and detached as the surgery progresses. Therefore, the bias of the center of gravity of the distraction device and / or the user's human error can impair the accuracy of applying tension to the knee joint, and the position of the balancer device relative to the human body can shift from the correct position.

[0007] If the position of the balancer device relative to the human body deviates from the correct position, the position of the femur sizing instrument relative to the balancer device will also deviate from the correct position, which may result in inaccurate measurements.

[0008] The present invention has been made in consideration of the above-mentioned problems, and an object of the present invention is to provide a balancer device which is less likely to cause deviation of the center of gravity relative to the knee joint and is easy to operate. [Means for solving the problem]

[0009] The various aspects of the present invention are as follows. [Aspect 1] a tibial attachment part fixed to the device main body and positioned on the proximal end side of the tibia; a femur attachment part positioned on the distal end side of the femur; a movable part to which the femur attachment part is connected and which is movable relative to the device main body part to change the distance between the femur attachment part and the tibial attachment part; and a moving mechanism for moving the movable part, the moving mechanism having a moving operated part operated by an operating tool outside the device for moving the femur attachment part in a direction away from the tibial attachment part, a restricting mechanism for restricting movement of the femur attachment part in a direction approaching the tibial attachment part, and a release mechanism for releasing the restriction, the sizer being releasably attached to the movable part by magnetic force. [Aspect 2] The balancing device according to aspect 1, wherein the operating tool is a hexagonal wrench, a star driver, a Phillips head screwdriver, or a flat head screwdriver. [Aspect 3] The balancer device according to aspect 1, wherein the sizer has a base portion of a main body member having a holding portion, the holding portion having the magnetic force. [Aspect 4] 2. The balancer device according to claim 1, wherein the movement mechanism includes a rack-and-pinion mechanism. [Aspect 5] The balancer device according to claim 1, wherein the regulating mechanism includes a plurality of regulating teeth formed on the movable portion, and a regulating piece provided on the device main body and engaging with the regulating teeth. [Aspect 6] 6. The balancer device according to claim 5, wherein the holding portion is provided at a position vertically and horizontally offset from the regulating mechanism. [Aspect 7] The balancer device of claim 1, wherein the magnetic force that attaches the sizer to the movable part has an adhesive force that can hold the sizer in a predetermined position relative to the movable part against vibrations that occur when the movable part is moved. [Aspect 8] The balancer device according to aspect 1, wherein one of the movable part or the sizer is provided with a convex part, and the other of the movable part or the sizer is provided with a concave part that engages with the convex part. Effect of the Invention

[0010] According to the present invention, it is possible to provide a balancer device in which the center of gravity of the balancer device is less likely to become misaligned with respect to the knee joint, and tension can be applied to the knee joint more accurately. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a perspective view showing a balancer device according to an embodiment of the present invention. [Diagram 2] 13 is a side view showing the state in which the balancer device is disposed by inserting a balancer between the resected tibia and femur. FIG. [Diagram 3] FIG. 2 is a vertical cross-sectional view of the balancer. [Figure 4] FIG. 13 is a perspective view showing a state in which the balancer and the sizer are separated, as viewed from the rear side. [Diagram 5] FIG. 13 is a perspective view showing a state in which the balancer and the sizer are separated, as viewed from the front side. [Figure 6] FIG. 2 is a front view showing the balancer device of the present embodiment. [Figure 7] FIG. 2 is a rear view showing the balancer device of the present embodiment. [Figure 8] FIG. 2 is a plan view showing the balancer device of the present embodiment. [Figure 9] FIG. 2 is a bottom view showing the balancer device of the present embodiment. [Figure 10] FIG. 2 is a right side view showing the balancer device of the present embodiment. [Figure 11] FIG. 2 is a left side view showing the balancer device of the present embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] As described in detail below, a balancer device according to an embodiment of the present invention is used between the femur and the tibia to install an artificial knee joint, and is equipped with a sizer for measuring the size of the femur, and includes a device main body, a tibial attachment part fixed to the device main body and arranged on the proximal end side of the tibia, a femur attachment part arranged on the distal end side of the femur, a movable part to which the femur attachment part is connected and which is arranged to be movable relative to the device main body to change the distance from the tibial attachment part, and a moving mechanism for moving the movable part, the moving mechanism including a moving operated part operated by an operating tool outside the device for moving the femur attachment part in a direction away from the tibial attachment part, a restricting mechanism for restricting movement of the femur attachment part in a direction approaching the tibial attachment part, and a release mechanism for releasing the restriction, and the sizer is releasably attached to the movable part by magnetic force. According to such a balancer device, the moving mechanism for moving the movable part connected to the femoral attachment part to change the distance between the femoral attachment part and the tibial attachment part is operated by an operating tool outside the device, so there is no need to provide the balancer device with an operating part for moving the movable part. This makes it possible to reduce the weight of the balancer device as a whole, making it easier for the user to hold the balancer device in a predetermined position. This makes it difficult for the center of gravity of the balancer device to become misaligned with respect to the knee joint during surgery, making the procedure easier and enabling accurate size measurement of the femur using a sizer.

[0013] In addition, in this embodiment, the sizer is attached by magnetic force, which allows for a lightweight attachment structure and is easy to attach and detach manually, resulting in excellent operability. In other words, combined with the weight reduction of the balancer device due to the movement mechanism being operated by an external operating tool, even if the balancer device is held by hand, the position of the entire balancer device is unlikely to shift relative to the knee joint, and therefore accurate position measurement by the sizer can be performed.

[0014] ==== Implementation form ==== DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A balancer device according to an embodiment of the present invention will now be described with reference to the drawings.

[0015] In total knee replacement surgery, first, the patient's knee is bent at 90 degrees, the skin of the knee is incised, the diseased femur and the damaged part of the tibia are resected, and an artificial joint implant is placed between the resected femur and tibia. The artificial knee joint implant has a tibial component provided in the resected part at the proximal end of the tibia, a femoral component provided in the resected part of the femur, and an insert interposed between the tibial component and the femoral component. There may also be a patella component used to replace the joint surface of the patella.

[0016] As shown in FIG. 1, the balancer device 1 comprises a balancer body 2 for expanding the space between the tibia and femur to reproduce ligament tension, and a sizer 7 used to determine the size of the femoral component is provided on the upper part of the balancer body 2 so as to be removable.

[0017] For example, the balancer device 1 can be inserted between a femur F from which a damaged portion has been resected (hereinafter referred to as the femur after resection) and a tibia T from which a damaged portion has been resected (hereinafter referred to as the tibia after resection) as shown in Fig. 2 to check a dimension that serves as a guide for an appropriate thickness of an insert to be inserted between a tibial component and a femoral component, and measure the distance therebetween. On the other hand, the sizer 7 is used to measure the size of the femur and select an appropriate femoral component (including a femoral trial).

[0018] In the following explanation, the up-down direction in the figure where the distance between the tibia T (FIG. 2) and femur F (FIG. 2) changes after resection, measured by the balancer device 1, is referred to as the "up-down direction", the inside of the patient's knee is simply referred to as the "inside", the outside of the knee is simply referred to as the "outside", the direction to the left and right of the patient is referred to as the "inside-outside direction" according to each knee, and the direction to the front or back as seen from the practitioner's side is referred to as the "depth direction". The directions will be specified and explained as the up-down direction, in-outside direction, depth direction, etc. for each part of the balancer device 1, and for each member constituting the balancer device 1, whether in a standalone state or when assembled as the balancer device 1.

[0019] As shown in Figures 1 and 2, the balancer main body 2 is used between the femur F and the tibia T, and is equipped with a plate- or tray-shaped tibial attachment portion 3 that is positioned on the proximal end side of the tibia T and abuts against the tibia T after resection, a plate- or tray-shaped femur attachment portion 4 that is positioned between the tibial attachment portion 3 and the distal end of the femur F and abuts against the femur F after resection, a device main body portion 5 to which the tibial attachment portion 3 is fixed, and a moving mechanism 6 that moves the femur attachment portion 4.

[0020] The balancer body 2, whether used in a left knee artificial knee joint replacement surgery or a right knee artificial knee joint replacement surgery, is positioned so that the tibia attachment part 3 and the femur attachment part 4 protrude further back than the device body part 5. The sizer 7 is positioned on the device body part 5 in front of the tibia attachment part 3 and the femur attachment part 4.

[0021] In the following explanation, the balancer device 1 in which a sizer 7 is attached to the balancer body 2 for left knee surgery shown in Fig. 1 will be taken as an example for explanation. Note that the balancer body 2 for right knee surgery is partially reversed in the inward and outward directions from the balancer body 2 for left knee surgery, but the configuration is the same.

[0022] As shown in Figures 1 and 3, the device body 5 has a through hole 5a through which the main part of the movable part 60, which is movable in the vertical direction relative to the device body 5, is inserted in the vertical direction, and the device body 5 has a tube part 5b that is intended to be positioned in the center in the inner and outer directions during surgery. The lower side of the tube part 5b has a substantially circular outer shape in horizontal cross section, while the upper side has a substantially rectangular outer shape in horizontal cross section. As shown in Figure 1, a slit 5c is formed in the vertical direction on the front surface of the upper side of the tube part 5b.

[0023] The slit 5c is connected to the insertion hole 5a, and the edge forming the slit 5c serves as a guide for the movable part 60 that is inserted into the insertion hole 5a and moves up and down. The device main body 5 also has an upper extension part 5d that extends from the top of the tube part 5b to the rear side, and the tibia attachment part 3 is attached to the rear end of the upper extension part 5d.

[0024] The moving mechanism 6 is configured between the device main body 5 and the movable part 60, and is configured to be movable upward or downward along the penetrating direction of the insertion hole 5a while guiding the movable part 60 into the insertion hole 5a of the device main body 5 by manually operating it from outside the device using an operating tool such as a hex wrench, star driver, Phillips screwdriver, or flat head screwdriver that is separate from the balancer device 1.

[0025] The movable part 60 has a shaft-like part 60a extending in the vertical direction and movably inserted into the insertion hole 5a of the cylindrical part 5b, and a movable part upper part 60b integrally provided on the upper part of the shaft-like part 60a and the lower surface of which can be placed on the cylindrical part 5b. As shown in Fig. 3, the moving mechanism 6 has a rack 61 provided on a part of the outer side part of the shaft upper part 60a of the movable part 60, a pinion 62 provided so as to prevent vertical movement with respect to the device main body part 5 and allow only rotation and engage with a part of the rack 61, and a regulating mechanism 63 that regulates the descent of the movable part 60 that has moved upward. That is, the moving mechanism 6 has a rack and pinion mechanism.

[0026] The upper movable part 60b of the movable part 60 has an arm part 60c extending to the rear side, and the femur attachment part 4 is attached to the tip of the arm part 60c. The femur attachment part 4 is rotatable about an axis that protrudes in the depth direction from the tip of the arm part 60c.

[0027] As shown in Fig. 4, the femur attachment part 4 is provided with an angle indicating part 4a which extends from the inside of the femur attachment part 4 towards the movable part 60 and swings integrally with the femur attachment part 4 to indicate the swing angle. A long hole is formed in the movable part upper part 60b of the movable part 60 so that the tip of the angle indicating part 4a can be visually observed moving up and down, and a swing angle display part 60d is provided so that the swing angle of the femur attachment part 4 can be known by reading the scale displayed at the position of the angle support part 4a from the front side as shown in Fig. 1.

[0028] As shown in FIG. 3, the regulating mechanism 63 includes a plurality of regulating teeth 60e formed on the inner side of the shaft-shaped portion 60a of the movable portion 60, and a regulating piece 64a provided on the device main body portion 5 and engaging with the regulating teeth 60e.

[0029] As shown in FIG. 1, the side surface on the front side of the movable part 60 is provided with a planar protruding part 60f, whose upper part protrudes from approximately the center in the vertical direction to the front side to form a flat surface. The planar protruding part 60f is configured to be disposed in a slit 5c provided on the front side surface of the device main body part 5 with the shaft-shaped part 60a inserted into the insertion hole 5a. The width of the planar protruding part 60f in the inner and outer directions is formed slightly narrower than the width of the slit 5c in the inner and outer directions, and the planar protruding part 60f is guided by the slit 5c when the movable part 60 moves up and down, so that the movable part 60 can move up and down in a more stable state. As shown in FIG. 3, the movable part 60 has an elongated guide groove 60i along the longitudinal direction of the shaft-shaped part 60a, and the cylindrical part 5b has a protrusion 5e protruding into the insertion hole 5a. With the protrusion 5e accommodated in the guide groove 60i in advance, the movable part 60 moves up and down while being restricted from rotating in the circumferential direction.

[0030] Furthermore, the planar protruding portion 60f is provided with a scale 60g that is visible to the user of the balancer device 1. This scale 60g indicates the vertical height positions of the tibia attachment portion 3 and the femur attachment portion 4 when the movable part upper portion 60b is placed on the cylindrical portion 5b and the lower surface of the movable part upper portion 60b is in contact with the upper surface of the cylindrical portion 5b. Therefore, when the movable part 60 is raised, it indicates the distance from the contact point between the tibia attachment portion 3 and the resected tibia T to the contact point between the femur attachment portion 4 and the femur F.

[0031] The movement and restriction of the movable part 60 relative to the device main body 5 will be described in detail. As shown in FIG. 3, the rack 61 engages with a pinion 62 provided at the lower end of the tube 5b of the device main body 5. The pinion 62 is provided at the lower end of the tube 5b, and is provided in a space communicating with the insertion hole 5a so as to be rotatable about an axis along the depth direction. As shown in FIG. 1, the axis of the pinion 62 is provided with a hexagonal hole 62a penetrating in the depth direction. The tip of an operating tool such as a hexagonal wrench operated from the outside of the tube 5b is inserted into the hexagonal hole 62a, and the pinion 62 can be rotated by rotating the operating tool. Here, the hexagonal hole 62a that can rotate the pinion 62 corresponds to the moving operated part in the present invention. When a star driver, a flat head driver, or a Phillips head driver is used as the operating tool, a star-shaped recess, a flat head recess, or a Phillips head recess can be provided instead of the hexagonal hole 62a.

[0032] As shown in Fig. 3, the restricting mechanism 63 allows the movable part 60 to move upward relative to the device body 5, but restricts only the downward movement. The restricting mechanism 63 is provided on the upper side of the cylindrical part 5b, and is configured such that a restricting member 64 having a restricting piece 64a that engages with a restricting tooth 60e provided on the shaft-shaped part is biased outward by a spring 65, so that the restricting piece 64a engages with the restricting tooth 60e. The restricting member 64 has a restricting release part 64b that is integral with the restricting piece 64a and protrudes outward from the cylindrical part 5b. On the other hand, when a user presses the restricting release part 64b inward, the restricting member 64 moves inward against the biasing force of the spring 65, and the engagement between the restricting piece 64a and the restricting tooth 60e is released.

[0033] More specifically, the outer side of the regulating piece 64a, i.e., the side of the regulating piece 64a that engages with the regulating tooth 60e, is provided with a plurality of claws 64c, each having a horizontal upper surface and a downwardly inclined lower surface. The regulating tooth 60e has a downwardly inclined upper surface and a horizontal lower surface, each having a plurality of grooves 60h arranged vertically.

[0034] As shown in Figure 3, in the regulating mechanism 63, with the lower surface of the movable part upper part 60b facing the upper surface of the tubular part 5b, the claw 64c of the regulating piece 64a biased by the spring 65 is inserted into the groove 60h of the regulating tooth 60e, so that the horizontal surface of the claw 64c of the regulating piece 64a faces the horizontal surface of the groove 60h of the regulating tooth 60e and the inclined surface of the claw 64c of the regulating piece 64a faces the inclined surface of the groove 60h of the regulating tooth 60e, thereby regulating the downward movement of the movable part 60.

[0035] As shown in Fig. 5, by turning the hexagonal wrench 9 inserted into the hexagonal hole 62a, the pinion 62 in Fig. 3 rotates. When the movable part 60 is pushed up by the pinion 62, the inclined surface of the groove 60h of the regulating tooth 60e rises and presses the inclined surface of the claw 64c upward, so that the regulating piece 64a moves inward while moving along the inclined surface against the biasing force of the spring 65.

[0036] Then, when the claw 64c comes out of the groove 60h, it is inserted into the next lower groove 60h by the biasing force of the spring 65. That is, the movement of the movable part 60 in the upward direction is permitted, but the movement of the movable part 60 in the downward direction is restricted, and it becomes possible to hold the position of the movable part 60 by the pitch of the restricting teeth 60e. For this reason, it is desirable to make the pitch of the restricting teeth 60e coincide with the scale 60g of the flat protruding part 60f.

[0037] Next, the sizer 7 will be described. As shown in Fig. 2, the sizer 7 is used with the tibia T and the femur F bent at 90 degrees. The sizer 7 has a sizer body member 70 having a femur contact surface 70a that contacts a femur cut surface Fa that is a vertical plane formed by resecting the front side (distal end) of the femur F, an elevation member 71 that is provided so as to be movable up and down relative to the sizer body member 70, and a stylus 72 that engages with an upper portion of the elevation member 71 and indicates the position of the femur F.

[0038] As shown in FIG. 1, the sizer main body member 70 has a main body standing portion 70b that is elongated in the vertical direction and has a roughly rectangular parallelepiped shape, a plate-like abutment plate portion 70c that extends on both sides of the main body standing portion 70b, and a base portion 70d that is positioned on the arm portion 60c of the movable portion 60.

[0039] The contact plate portion 70c of the sizer main body member 70 extends from the rear side of both side surfaces of the main body erection portion 70b, and as shown in Fig. 4, the rear surfaces of the main body erection portion 70b and the contact plate portion 70c form a single connected plane, forming the femoral contact surface 70a that comes into contact with the femoral cut surface Fa. The main body erection portion 70b is provided with a vertical hole (not shown) extending vertically from the upper surface, and the main body erection portion 70b is provided with a vertically elongated hole 70e that is connected to the vertical hole and is vertically long so as to be visible from the front, and scales 70f are provided on both sides of the vertically elongated hole 70e.

[0040] The base 70d of the sizer body member 70 has a pedestal portion 70g provided under the main body erection portion 70b and the abutment plate portion 70c, and a holding portion 70h extended to the front side of the pedestal portion 70g. The pedestal portion 70g and the holding portion 70h are connected to each other at their lower surfaces to form a single plane, and are placed on the upper surface of the arm portion 60c of the movable portion 60, which forms a horizontal plane. The holding portion 70h has a magnetic force that interacts with the metal material of the arm portion 60c of the balancer body 2 to detachably attach the sizer 7 to the balancer body 2. The magnetic force may be provided on the arm portion 60c side of the movable portion 60, or may be provided on both, or may be obtained by fixing a magnet to at least one of the members.

[0041] Furthermore, in order to ensure the positioning of the sizer 7 relative to the balancer body 2, a convex portion may be provided on one of the movable part 60 (arm part 60c) or the sizer 7 (holding part 70h), and a concave portion that engages with the convex portion may be provided on the other of the movable part 60 (arm part 60c) or the sizer 7 (holding part 70h). This allows the sizer 7 to be reliably and detachably attached to a predetermined position relative to the balancer body 2 by positioning using the concave and convex portions in addition to the coupling using magnetic force.

[0042] The base portion 70g of the sizer body member 70 is provided with two through holes 70i that are spaced apart from each other in the inner and outer directions and penetrate the body standing portion 70b in the depth direction. In each through hole 70i, a pin is fixed to the femoral cutting surface Fa with the femoral contact surface 70a of the sizer body member 70 in contact with the femoral cutting surface Fa, and then the sizer body member 70 is removed with the pin left in place. The pin (not shown) serves as a guide for later setting a four-facet osteotomy block (not shown) for performing four-facet osteotomy of the femur.

[0043] The lifting member 71 of the sizer main body member 70 has, at its upper portion, a stylus engagement portion 71a that is substantially disk-shaped and engages with a stylus 72, as shown in Figs. 1 and 2, and has a lifting shaft portion 71b that is disposed vertically from the center of the underside of the stylus engagement portion 71a and is inserted into a vertical hole in the main body erection portion 70b. The lifting member 71 can move up and down with the lifting shaft portion 71b guided by the vertical hole. The lifting shaft portion 71b has a protrusion 71c that protrudes toward the front at substantially the center of the longitudinal portion, and the protrusion 71c is disposed in a vertically long hole 70e in the main body erection portion 70b, and moves up and down within the vertically long hole 70e when the lifting member 71 moves up and down.

[0044] 1 and 2, the stylus 72 has a flat stylus body 72a that is long in a predetermined direction, a thin, rod-shaped indicator 72b that extends from one end of the stylus body 72a, and a grip 72c that is provided at the other end of the stylus body 72a and is held by a user. A stylus slot 72d that extends along the longitudinal direction is provided in the stylus body 72a, and scales 72e are provided on both sides of the longitudinal portion of the stylus slot 72d.

[0045] The stylus 72 is engaged with a vertical shaft 71d provided on the stylus engagement portion 71a of the lifting member 71, the shaft 71d being inserted into the stylus long hole 72d. Therefore, the stylus 72 is provided so as to be movable in the longitudinal direction of the stylus long hole 72d and rotatable around the shaft 71d relative to the main body standing portion 70b into which the lifting shaft portion 71b of the lifting member 71 is inserted.

[0046] In the balancer device 1 having the above configuration, with the knee bent at about 90 degrees, the tibia mounting part 3 and the femur mounting part 4 of the balancer body 2 are inserted between the femur F and the resected tibia T. At this time, the femur mounting part 4 is lowered and is closest to the tibia mounting part 3 side.

[0047] Next, as shown in Fig. 5, a hexagonal wrench 9 is inserted into the hexagonal hole 62a to rotate the pinion 62, widening the gap between the tibia attachment part 3 and the femur attachment part 4. More specifically, a hexagonal wrench 9 is attached to the hexagonal hole 62a, and a torque driver 10 set to a desired torque is used to rotate the hexagonal hole 62a. When the torque driver 10 starts to rotate freely or reaches a desired torque value, the operation of turning the torque driver 10 is stopped. This operation brings the ligament into a state of being tensioned to a desired level. At this time, the descent of the femur attachment part 4 is restricted by the restricting mechanism 63, so the gap between the tibia attachment part 3 and the femur attachment part 4 is maintained.

[0048] After adjusting the distance between the tibial attachment portion 3 and the femoral attachment portion 4 so that the ligaments are at the desired tension, the scale 60g on the planar protrusion 60f of the movable portion 60 is read to determine a value that serves as an indication of the appropriate thickness of the insert in the artificial knee joint to be fitted to the patient.

[0049] Next, the sizer 7 is placed on the arm 60c of the device main body 5 and held by magnetic force. At this time, the femur contact surface 70a is placed in contact with the femur cut surface Fa. Also, the lifting member 71 is raised, and the pointing portion 72b of the stylus 72 is previously placed at a position higher than the femur F.

[0050] Next, the lifting member 71 is lowered to a position where the indication portion 72b of the stylus 72 contacts the upper portion of a predetermined position of the femur F. At this time, the stylus 72 is rotated and moved along the stylus long hole 72d to adjust the position of the indication portion 72b.

[0051] After adjusting the stylus 72 and performing sizing, a pin is inserted into the through hole 70i provided in the base portion 70g, and the sizer 7 is fixed to the femur F with the femoral abutment surface 70a of the sizer main body member 70 abutting against the femoral cut surface Fa.

[0052] Then, with the indicator 72b in contact with the femur F (FIG. 2), the scale 72e provided on both sides of the stylus long hole 72d of the stylus main body 72a, which is indicated by the center of the stylus engagement portion 71a of the lifting member 71, and the scale 70f provided on both sides of the vertical long hole 70e, which is indicated by the protrusion 71c provided on the lifting shaft portion 71b of the lifting member 71, are read. A pin is inserted into the through hole 70i, and based on the values ​​read, four-sided osteotomy of the femur is performed using a four-sided bone cutting block, and a femoral trial of an appropriate size is selected from multiple types of femoral trials prepared in ready-made sizes.

[0053] According to the balancer device 1 of this embodiment, the moving mechanism 6 for moving the movable part 60 connected to the femur attachment part 4 to change the distance between the femur attachment part 4 and the tibia attachment part 3 is operated by a hexagonal wrench 9 attached to a torque driver 10 outside the device, and therefore the balancer body 2 does not need to be provided with an operating part for moving the movable part 60. This makes it possible to reduce the weight and size of the balancer body 2 and the balancer device 1, and makes it easier for the user to hold the balancer body 2 and the balancer device 1 at a predetermined position. This eliminates the need to repeatedly attach and detach an operating part (the extension device of Patent Document 1) outside the device for moving the movable part 60 during surgery, and the balancer body 2 and the balancer device 1 are less likely to be displaced, so that tension can be applied more accurately to the knee joint, the femur F can be accurately measured, and a more appropriate femoral trial can be easily selected in a short time.

[0054] In addition, since the sizer 7 is attached to the balancer body 2 by magnetic force, the attachment structure is lighter than when bolts and nuts are used for fastening, and attachment and detachment are easier, resulting in better operability. In other words, it is possible to provide a lightweight balancer device 1 with excellent operability that is less likely to shift in position relative to the knee joint and allows for easy accurate measurement using the sizer 7.

[0055] When the moving mechanism 6 moves the movable part 60 upward, vibration may occur in the regulating mechanism 63. The magnetic force that attaches the holding part 70h of the sizer 7 to the movable part 60 of the balancer body 2 can have an attractive force that can hold the holding part 70h of the sizer 7 at a predetermined position relative to the movable part 60 against this vibration. This can prevent the sizer 7 from falling off or moving from the movable part 60 when the movable part 60 moves. The magnet used as the magnetic source can preferably be a neodymium magnet. The magnet is disposed in the holding part 70h. At least the arm part 60c (balancer 2) and the holding part 70h (sizer 7) can preferably be made of stainless steel. The magnetic force for attaching the sizer 7 to the arm part 60c, i.e., the attractive force of the magnet (the force required to remove the sizer 7 from the arm part 60c), can be 3.0 to 5.0 kg, more preferably about 4.3 kg. Assuming this adsorption force, the weight of the balancer 2 is preferably 400 to 500 g, more preferably about 457 g, and the weight of the sizer 7 is preferably 200 to 300 g, more preferably about 237 g.

[0056] 1 and 3, the holding part 70h of the sizer 7 is attached to the arm part 60c at a position vertically and horizontally shifted from the regulating mechanism 63. Therefore, vibrations generated in the regulating mechanism 63 when the movable part 60 moves upward are less likely to affect the magnetic coupling between the holding part 70h and the arm part 60c.

[0057] Furthermore, the above-described embodiment is for the purpose of facilitating understanding of the present invention, and is not intended to limit the present invention. The present invention can be modified or improved without departing from the spirit of the present invention, and it goes without saying that the present invention includes equivalents thereof. [Industrial Applicability]

[0058] The present invention may be utilized in orthopaedic surgery to place an artificial knee joint. [Explanation of symbols]

[0059] 1 Balancer device 2. Balancer 3 Tibial attachment 4 Femoral attachment part 4a Angle indicator 5. Device main body 5a Insertion hole 5b Cylinder part 6 Moving mechanism 7 Sizer 9 Hexagonal wrench 10 Torque driver 60 Moving parts 60a Shaft-shaped part 60c Arm section 61 LACK 62 Pinion 62a hexagonal hole 63 Regulatory Mechanisms 64 Regulatory Members 70 Sizer body material 70d base 70g Base 71 Lifting member 72 Stylus 72b Instruction section F Femur Fa Femoral cut surface T tibia

Claims

1. A balancer device is used between a femur and a tibia to install an artificial knee joint, the balancer device having a sizer for measuring the size of the femur, A device main body, a tibial attachment portion fixed to the device body portion and disposed on a proximal end side of the tibia; a femoral attachment portion disposed on a distal end side of the femur; a movable section to which the femur attachment section is connected and which is movable relative to the device body section so as to change a distance between the femur attachment section and the tibia attachment section; A moving mechanism that moves the movable part; having The moving mechanism includes a moving operated portion that is operated by an operating tool outside the device to move the femur attachment portion in a direction away from the tibial attachment portion; a restricting mechanism that restricts movement of the femoral attachment portion in a direction toward the tibial attachment portion; A release mechanism for releasing the restriction; having A balancer device, wherein the sizer is removably attached to the movable part by magnetic force.

2. 2. The balancer device according to claim 1, wherein the operating tool is a hexagonal wrench, a star driver, a Phillips head screwdriver, or a flat head screwdriver.

3. 2. The balancer device according to claim 1, wherein the sizer has a base portion of a main body member having a holding portion, and the holding portion has the magnetic force.

4. 2. The balancer device according to claim 1, wherein the movement mechanism includes a rack and pinion mechanism.

5. 2. The balancer device according to claim 1, wherein the regulating mechanism includes a plurality of regulating teeth formed on the movable portion, and a regulating piece provided on the device body and engaging with the regulating teeth.

6. The balancer device according to claim 5, wherein the holding portion is provided at a position vertically and laterally offset from the regulating mechanism.

7. 2. The balancer device according to claim 1, wherein the magnetic force that attaches the sizer to the movable part has an attractive force that can hold the sizer in a predetermined position relative to the movable part against vibrations that occur when the movable part is moved.

8. 2. The balancer device according to claim 1, wherein a convex portion is provided on one of the movable portion or the sizer, and a concave portion that engages with the convex portion is provided on the other of the movable portion or the sizer.

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