Measurement device for total knee arthroplasty

Abstract

A measuring device (1) according to one embodiment comprises: a base (2) that is disposed in front of a knee joint; a tibial paddle (4) having a first contact surface (40) and fixed to the base (2); a femoral paddle (5) having a second contact surface (50) and attached to the base (2) so that the femoral paddle (5) is movable in a direction orthogonal to the first contact surface (40); and a distance display unit (11) that displays the distance between the first contact surface (40) and the second contact surface (50). The measuring device (1) further comprises a femoral attachment (7) attachable to and detachable from the femoral paddle (5). The femoral attachment (7) includes a reproduction part (71) having a shape corresponding to a portion that covers a distal end resection surface of a distal femur in a femoral component of a knee joint prosthesis. The reproduction part (71) has a third contact surface (70) that is brought into contact with the distal end resection surface of the distal femur in a right angle bending orientation.

Description

Technical Field

[0001] The present invention relates to a measuring device used in total knee arthroplasty.

Background Art

[0002] In total knee arthroplasty (TKA), the proximal part of the tibia and the distal part of the femur are resected, and the tibial component and the femoral component of the artificial knee joint are respectively attached to the resected proximal part of the tibia and the distal part of the femur. Various devices are used in total knee arthroplasty.

[0003] For example, Patent Document 1 discloses a measuring device (referred to as a "surgical instrument" in Patent Document 1) used in total knee arthroplasty. In total knee arthroplasty, more specifically, the proximal end of the proximal part of the tibia is resected, and the distal end, the front end, and the rear end of the distal part of the femur are resected. In addition, an anterior inclined surface is formed between the distal resection surface and the front resection surface, and a posterior inclined surface is formed between the distal resection surface and the rear resection surface. A general femoral component has a U-shaped shape in side view so as to cover the distal resection surface, the anterior inclined surface, the front resection surface, the posterior inclined surface, and the rear resection surface of the distal part of the femur, and the tibial component is installed on the proximal resection surface of the proximal part of the tibia and supports the femoral component. It has a plate-shaped support part (usually a laminate of a resin plate having a pair of concave curved surfaces for receiving the medial and lateral condyles and a metallic plate), and a stem or a keel that extends downward from the support part and is embedded in the tibia (these are integrally formed with the metallic plate of the support part).

[0004] The measuring device disclosed in Patent Document 1 measures the distance between the proximal resection surface of the proximal part of the tibia and the distal resection surface of the distal part of the femur in the extended position and the distance between the proximal resection surface of the proximal part of the tibia and the rear resection surface of the distal part of the femur in the right-angle flexion position before the tibial component and the femoral component are attached.

[0005] Specifically, the measuring device disclosed in Patent Document 1 includes a base disposed in front of the knee joint, a locking plate fixed to the base via an arm, and a support plate facing the locking plate. The locking plate is brought into contact with the proximal end resection surface of the proximal tibia, and the support plate is brought into contact with the distal end resection surface in the extended position of the distal femur or the posterior end resection surface in the right angle flexion position.

[0006] The support plate is attached to the base so as to be movable in a direction orthogonal to the locking plate. The measuring device includes a ratchet mechanism that switches whether to allow only the movement of the support plate away from the locking plate or to allow movement in both directions. By holding the support plate at an appropriate position by the ratchet mechanism, the distance between the resection surfaces (the distance between the proximal end resection surface of the proximal tibia and the distal end resection surface of the distal femur in the extended position, and the distance between the proximal end resection surface of the proximal tibia and the posterior end resection surface of the distal femur in the right angle flexion position) can be measured in a state where appropriate tension is applied to soft tissues such as ligaments.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0008] As a method for adjusting the soft tissue balance in the extended position and the right-angle flexion position of the knee joint, there is a method of adjusting the resection position of the rear end of the distal part of the femur after resection of the distal end of the distal part of the femur. Specifically, first, measure the distance between the distal resection surface of the distal part of the femur and the proximal resection surface of the proximal part of the tibia in the extended position under appropriate soft tissue tension, and then measure the distance between the rear end of the distal part of the femur and the proximal resection surface of the proximal part of the tibia under appropriate soft tissue tension in the right-angle flexion position. Then, based on the distances measured in the extended position and the right-angle flexion position, determine the resection position of the rear end of the distal part of the femur. As a procedure, the distal end of the distal part of the femur is resected in advance. However, compared with before resection or after installation of the femoral component, due to the space generated after resection, the tension of the soft tissue attached to the patella in the right-angle flexion position changes, and the distance between the rear end of the distal part of the femur and the proximal resection surface of the proximal part of the tibia may vary.

[0009] Therefore, an object of the present invention is to provide a measuring device for total knee arthroplasty that can more accurately measure the distance between the proximal resection surface of the proximal part of the tibia and the rear end of the distal part of the femur in the right-angle flexion position while suppressing the influence of resection of the distal end even when the distal end of the distal part of the femur is resected and the rear end is not resected.

Means for Solving the Problems

[0010] In order to solve the above problems, the present invention provides a measuring device used in total knee arthroplasty, comprising: a base disposed in front of the knee joint; a tibial paddle fixed to the base and having a first contact surface that is brought into contact with the proximal resection surface of the proximal tibia; a femoral paddle attached to the base so as to be movable in a direction orthogonal to the first contact surface and having a second contact surface that is brought into contact with the rear end of the distal femur in the fully flexed position; a ratchet mechanism that can be switched to allow only the femoral paddle to move away from the tibial paddle or to allow bidirectional movement; a femoral attachment that is detachable from the femoral paddle and has a third contact surface that is brought into contact with the distal resection surface of the distal femur in the fully flexed position; and a distance display unit that displays the distance between the first contact surface and the second contact surface. The femoral attachment includes a reproduction portion having a shape corresponding to a portion that covers the distal resection surface of the distal femur in the femoral component of the artificial knee joint, and the reproduction portion has the third contact surface. A measuring device for total knee arthroplasty is provided.

[0011] According to the above configuration, since the distance between the first contact surface of the tibial paddle and the second contact surface of the femoral paddle is displayed by the distance display unit, if the first contact surface is brought into contact with the proximal resection surface of the proximal tibia and the second contact surface is brought into contact with the rear end of the distal femur in the fully flexed position, the distance between the proximal resection surface of the proximal tibia and the rear end of the distal femur can be measured. Moreover, if the femoral paddle is held at an appropriate position by the ratchet mechanism, the distance between the proximal resection surface of the proximal tibia and the rear end of the distal femur can be measured in a state where appropriate tension is applied to soft tissues such as ligaments.

[0012] Incidentally, when excising the proximal part of the tibia and the distal part of the femur, it is necessary to retract the patella and the like (the patella and soft tissues such as the patellar tendon and quadriceps tendon attached thereto) to the inner or outer side of the knee joint. After excising the distal end of the distal part of the femur, if the patella and the like are returned to their original positions with the distal resection surface exposed in the right-angle flexion position, the soft tissues attached to the patella will be in a loose state. On the other hand, in the above configuration, since the femoral attachment that can be attached to and detached from the femoral paddle includes a reproduction part having a shape that partially corresponds to the femoral component where the femoral attachment is to be installed, when the third contact surface of the reproduction part of the femoral attachment is brought into contact with the distal resection surface of the distal part of the femur with the femoral attachment attached to the femoral paddle, appropriate tension can be applied to the soft tissues attached to the patella when the patella and the like are returned to their original positions. That is, the distance between the proximal resection surface of the proximal part of the tibia and the rear end of the distal part of the femur can be measured under the same conditions as after the future femoral component is installed. In other words, even when the distal end of the distal part of the femur is excised and the rear end is not excised, the measurement of the distance between the proximal resection surface of the proximal part of the tibia and the rear end of the distal part of the femur in the right-angle flexion position can be performed more accurately while suppressing the influence of the excision of the distal end.

[0013] Furthermore, in a state where the femoral attachment is removed from the femoral paddle, if the first contact surface is brought into contact with the proximal resection surface of the proximal part of the tibia and the second contact surface is brought into contact with the distal resection surface of the distal part of the femur in the extended position, the distance between the proximal resection surface of the proximal part of the tibia and the distal resection surface of the distal part of the femur can be measured.

[0014] The femoral attachment may be attached to the femoral paddle so as to be movable in the anterior-posterior direction of the knee joint. According to this configuration, by moving the femoral attachment in a state where the third contact surface of the femoral attachment is in contact with the distal end resection surface of the distal part of the femur in the right-angle flexion position, the relative position between the proximal part of the tibia and the distal part of the femur in the anterior-posterior direction of the knee joint can be adjusted. Thereby, when measuring the distance between the proximal end resection surface of the proximal part of the tibia and the rear end of the distal part of the femur, the relative position between the proximal part of the tibia and the distal part of the femur in the anterior-posterior direction of the knee joint can be made to coincide with the ideal relative position after the artificial knee joint is installed.

[0015] The femoral paddle is divided into a first femoral paddle and a second femoral paddle arranged in the medial-lateral direction of the knee joint, and the first femoral paddle and the second femoral paddle are attached to the base so as to be movable independently of each other in a direction orthogonal to the first contact surface, and the distance display unit may display the distance between the first contact surface and the second contact surface for each of the first femoral paddle and the second femoral paddle. According to this configuration, when the positions of the rear ends are different between the medial condyle and the lateral condyle of the distal part of the femur in the right-angle flexion position, both the distance from the proximal end resection surface of the proximal part of the tibia to the rear end of the medial condyle and the distance from the proximal end resection surface of the proximal part of the tibia to the rear end of the lateral condyle can be measured. Also, when the positions of the distal end resection surfaces are different between the medial condyle and the lateral condyle of the distal part of the femur in the extended position, both the distance from the proximal end resection surface of the proximal part of the tibia to the distal end resection surface of the medial condyle and the distance from the proximal end resection surface of the proximal part of the tibia to the distal end resection surface of the lateral condyle can be measured.

[0016] Alternatively, the femur paddle may be swingable about a swing axis extending in the anteroposterior direction of the knee joint, and the distance display unit may display the distance between the first contact surface and the second contact surface on a perpendicular line to the first contact surface and passing through the swing center of the femur paddle. According to this configuration, when the positions of the medial and lateral condyles at the distal end of the femur are different in the right-angle flexion position, the femur paddle can be brought into contact with both the posterior end of the medial condyle and the posterior end of the lateral condyle. Also, before resection of the distal end of the distal part of the femur, when the positions of the medial and lateral condyles at the distal end of the distal part of the femur are different in the extended position, the femur paddle can be brought into contact with both the distal end of the medial condyle and the distal end of the lateral condyle. Further, when the space between the proximal part of the tibia and the distal part of the femur is widened after resection of the distal end or the posterior end of the distal part of the femur to apply appropriate tension to the soft tissue, even if the distal end resection surface or the posterior end resection surface of the distal part of the femur is inclined with respect to the proximal end resection surface of the proximal part of the tibia, the femur paddle can be brought into surface contact with the distal end resection surface.

[0017] The tibia paddle includes a first paddle portion having the first contact surface and a first arm portion extending from the first paddle portion toward the base. The femur paddle includes a second paddle portion having the second contact surface, a first base portion located above the base, and a second arm portion extending from the second paddle portion toward the first base portion. The femur attachment includes a second base portion located above the base and a third arm portion extending from the reproduction portion toward the second base portion. When one of the medial and lateral directions of the knee joint is defined as the first direction and the other is defined as the second direction, the first arm portion is shifted toward the first direction from the center of the first paddle portion, the second arm portion is shifted toward the first direction from the center of the second paddle portion, and the third arm portion may be shifted toward the first direction from the center of the reproduction portion. According to this configuration, space can be secured on the sides of the first to third arm portions, and during distance measurement, the patella or the like that has been retracted to the inside or outside of the knee joint when the proximal part of the tibia and the distal part of the femur are resected can be returned to this space.

[0018] The above-described measuring device for total knee arthroplasty may further include a femur sizing device that is detachable from the femur paddle and is used to measure the size of the distal femur at the right-angle flexion position and to determine the resection position of the front end and the resection position of the rear end of the distal femur. According to this configuration, it is possible to measure the size of the distal femur and determine the mounting position of the femoral component while maintaining the relative position between the proximal tibia and the distal femur at an appropriate position that reproduces the physiological state in which appropriate tension is applied to the soft tissue.

Advantages of the Invention

[0019] According to the present invention, it is possible to measure the distance between the proximal resection surface of the proximal tibia and the rear end of the distal femur at the right-angle flexion position. Note that even with the measuring device disclosed in Patent Document 1, if the measuring device is used after the proximal tibia has been resected and before the distal femur has been resected, it is possible to measure the distance between the proximal resection surface of the proximal tibia and the rear end of the distal femur at the right-angle flexion position. However, by using the measuring device of the present invention, more accurate measurement can be performed than by using the measuring device disclosed in Patent Document 1.

Brief Description of the Drawings

[0020]

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Mode for Carrying Out the Invention

[0021] (First Embodiment) Fig. 1 shows a measurement device 1 for total knee arthroplasty according to the first embodiment of the present invention. This measurement device 1 is used for total knee arthroplasty.

[0022] Specifically, the measuring device 1 includes a base 2 disposed in front of the knee joint, a tibial paddle 4 fixed to the base 2, and a femoral paddle 5 facing the tibial paddle 4. The measuring device 1 also includes a femoral attachment 7 shown in FIG. 8 and a femoral sizer 8 shown in FIG. 10.

[0023] As shown in FIGS. 6 and 7, the tibial paddle 4 and the femoral paddle 5 are inserted between the proximal part 91 of the tibia and the distal part 95 of the femur. Hereinafter, for convenience of explanation, as shown in FIGS. 1 to 5, the axial direction of the tibia is the vertical direction, the medial-lateral direction of the knee joint is the left-right direction (the lower right side in FIG. 1 is the left side, and the upper left side in FIG. 1 is the right side), and the anterior-posterior direction of the knee joint perpendicular to the axial direction of the tibia is also simply referred to as the anterior-posterior direction.

[0024] When the measuring device 1 is used, the proximal end of the proximal part 91 of the tibia and the distal end of the distal part 95 of the femur are resected before that. The measuring device 1 measures the distance between the distal resection surface 96 of the distal part 95 of the femur and the proximal resection surface 92 of the proximal part 91 of the tibia in the extended position as shown in FIG. 6, and measures the distance between the rear end 97 of the distal part 95 of the femur and the proximal resection surface 92 of the proximal part 91 of the tibia in the right-angle flexion position as shown in FIG. 7. It should be noted that it is also possible to use the measuring device 1 after the resection of the proximal end of the proximal part 91 of the tibia and before the resection of the distal end of the distal part 95 of the femur. Alternatively, it is also possible to measure the distance between the rear resection surface of the distal part 95 of the femur and the proximal resection surface 92 of the proximal part 91 of the tibia in the right-angle flexion position using the measuring device 1 after the resection of the rear end 97 of the distal part 95 of the femur.

[0025] The tibial paddle 4 has a first contact surface 40 that is brought into contact with the proximal resection surface 92 of the proximal part 91 of the tibia. The vertical direction is also the direction perpendicular to the first contact surface 40. The femoral paddle 5 has a second contact surface 50 that is brought into contact with the distal resection surface 96 of the distal part 95 of the femur in the extended position and is brought into contact with the rear end 97 of the distal part 95 of the femur in the right-angle flexion position.

[0026] As shown in FIG. 2, the base 2 is substantially plate-shaped and orthogonal to the front-rear direction, and has a first main surface 2a facing rearward, a second main surface 2b facing forward, a pair of side surfaces facing left and right, and a pair of end surfaces facing upward and downward. The tibial paddle 4 extends rearward from the upper portion of the first main surface 2a of the base 2.

[0027] The base 2 is provided with a pair of through holes 22 and 23 that penetrate the base 2 in the vertical direction at positions spaced apart in the left-right direction. Further, on the second main surface 2b of the base 2, a pair of grooves 24 and 25 that extend in the vertical direction from the upper end surface to the lower end surface are provided at positions spaced apart in the left-right direction.

[0028] Furthermore, a pair of support pieces 21 protrude from both side surfaces of the base 2 in opposite directions. Each support piece 21 has a flat upper surface orthogonal to the vertical direction, and the upper surface of the right support piece 21 is connected to the right side surface of the groove 24, and the upper surface of the left support piece 21 is connected to the left side surface of the groove 25.

[0029] The tibial paddle 4 includes a first paddle portion 41 having a first contact surface 40 and a first arm portion 42 that extends from the first paddle portion 41 toward the base 2. The first arm portion 42 is parallel to the front-rear direction and is connected to the upper portion of the first main surface 2a of the base 2. On the other hand, with respect to the first paddle portion 41, the first arm portion 42 is shifted to the right of the center of the first paddle portion 41.

[0030] The femoral paddle 5 is attached to the base 2 so as to be movable in the vertical direction. The femoral paddle 5 includes a second paddle portion 51 having a second contact surface 50, a first base portion 53 located above the base 2, and a second arm portion 52 that extends from the second paddle portion 51 toward the first base portion 53. The second arm portion 52 is parallel to the front-rear direction and is shifted to the right of the center of the second paddle portion 51 in the same manner as the first arm portion 42 of the tibial paddle 4. That is, the second arm portion 52 is located directly above the first arm portion 42.

[0031] In this embodiment, as shown in FIG. 4, the femur paddle 5 is divided into a first femur paddle 5A and a second femur paddle 5B arranged in the left-right direction. Therefore, the second contact surface 50 is also divided into contact surfaces 50A and 50B, the second paddle portion 51 is also divided into paddle portions 51A and 51B, the second arm portion 52 is also divided into arm portions 52A and 52B, and the first base portion 53 is also divided into base portions 53A and 53B. However, the femur paddle 5 may be an integral one formed by the first femur paddle 5A and the second femur paddle 5B.

[0032] The first femur paddle 5A and the second femur paddle 5B are attached to the base 2 so as to be independently movable in the vertical direction. More specifically, a rod 54A having a circular cross-section extends downward from the base portion 53A of the first femur paddle 5A, and the first femur paddle 5A can slide with respect to the base 2 by inserting the rod 54A into the through-hole 22 of the base 2. Similarly, a rod 54B having a circular cross-section extends downward from the base portion 53B of the second femur paddle 5B, and the second femur paddle 5B can slide with respect to the base 2 by inserting the rod 54B into the through-hole 23 of the base 2.

[0033] As shown in FIG. 3, a tooth surface 54a that repeats unevenness in the vertical direction is formed on the left side portion of the rod 54A of the first femur paddle 5A. On the other hand, as shown in FIG. 2, an operation shaft 31 that extends in the front-rear direction to the left of the through-hole 22 is rotatably held on the base 2. The operation shaft 31 is operated by a user such as a doctor.

[0034] As shown in FIG. 5, a pinion 33 that meshes with the tooth surface 54a is provided on the operation shaft 31. Therefore, when the operation shaft 31 is operated, the first femur paddle 5A moves in the vertical direction by an amount corresponding to the operation amount (rotation amount).

[0035] Similarly, as shown in FIG. 3, on the left side portion of the rod 54B of the second femoral paddle 5B, a tooth surface 54b that repeats concavities and convexities in the vertical direction is formed. On the other hand, as shown in FIG. 2, on the base 2, an operation shaft 32 that extends in the front-rear direction to the left of the through hole 23 is rotatably held. The operation shaft 32 is operated by a user such as a doctor.

[0036] As shown in FIG. 5, the operation shaft 32 is provided with a pinion 34 that meshes with the tooth surface 54b. Therefore, when the operation shaft 32 is operated, the second femoral paddle 5B moves in the vertical direction by an amount corresponding to the operation amount (rotation amount).

[0037] Furthermore, the measuring device 1 includes a ratchet mechanism 6 that switches whether to allow only the movement of the femoral paddle 5 in a direction away from the tibial paddle 4 (i.e., upward) or to allow movement in both directions (i.e., upward and downward), and a distance display unit 11 that displays the distance between the first contact surface 40 and the second contact surface 50.

[0038] As described above, since the femoral paddle 5 is divided into the first femoral paddle 5A and the second femoral paddle 5B, the ratchet mechanism 6 includes a first ratchet mechanism 6A for the first femoral paddle 5A and a second ratchet mechanism 6B for the second femoral paddle 5B. Similarly, the distance display unit 11 also includes a first distance display unit 11A for the first femoral paddle 5A and a second distance display unit 11B for the second femoral paddle 5B. That is, the distance display unit 11 displays the distance between the first contact surface 40 and the second contact surface 50 (contact surface 50A or contact surface 50B) for each of the first femoral paddle 5A and the second femoral paddle 5B.

[0039] The first ratchet mechanism 6A is composed of a column 55A provided on the first femoral paddle 5A, a ratchet lever 61 (see FIG. 2) swingably attached to the base 2, and a spring 63 that biases the ratchet lever 61. However, the configuration of the first ratchet mechanism 6A is not limited to this and can be appropriately changed.

[0040] As shown in FIG. 3, the column 55A is located in front of the rod 54A and extends downward from the base 53A of the first femoral paddle 5A. The column 55A has a rectangular cross-section and fits into a groove 24 provided on the second main surface 2b of the base 2. A tooth surface 55a that repeats irregularities in the vertical direction is formed on the right side surface of the column 55A.

[0041] The ratchet lever 61 is disposed above the right support piece 21 and is attached to the base 2 via a pin that extends in the front-rear direction in the vicinity of the groove 24. The ratchet lever 61 includes an operation portion that extends rightward from the pin and a hook portion that extends upward from the pin and engages with the tooth surface 55a at the tip.

[0042] The spring 63 described above is disposed between the operation portion of the ratchet lever 61 and the support piece 21, and biases the ratchet lever 61 in a direction in which the engagement state between the hook portion and the tooth surface 55a is maintained. With such a structure, only upward movement of the first femoral paddle 5A is possible when the operation portion is not operated, and when the operation portion is operated to release the engagement state between the hook portion and the tooth surface 55a, upward and downward movement of the first femoral paddle 5A becomes possible.

[0043] Similarly, the second ratchet mechanism 6B includes a column 55B provided on the second femoral paddle 5B, a ratchet lever 62 (see FIG. 2) swingably attached to the base 2, and a spring 64 that biases the ratchet lever 61. However, the configuration of the second ratchet mechanism 6B is not limited to this and can be changed as appropriate.

[0044] As shown in FIG. 3, the column 55B is located in front of the rod 54B and extends downward from the base 53B of the second femoral paddle 5B. The column 55B has a rectangular cross-section and fits into a groove 25 provided on the second main surface 2b of the base 2. A tooth surface 55b that repeats irregularities in the vertical direction is formed on the left side surface of the column 55B.

[0045] The ratchet lever 62 is disposed above the left support piece 21 and is attached to the base 2 via a pin extending in the front-rear direction in the vicinity of the groove 25. The ratchet lever 62 includes an operation part extending leftward from the pin and a hook part extending upward from the pin and engaging with the tooth surface 55b at the tip.

[0046] The above-described spring 64 is disposed between the operation part of the ratchet lever 62 and the support piece 21, and biases the ratchet lever 62 in a direction in which the engagement state between the hook part and the tooth surface 55b is maintained. With such a structure, only the upward movement of the second femur paddle 5B is possible when the operation part is not operated, and when the operation part is operated to release the engagement state between the hook part and the tooth surface 55b, the upward and downward movements of the second femur paddle 5B become possible.

[0047] As shown in FIG. 3, a scale 14 regarding the distance from the first contact surface 40 to the contact surface 50A is formed on the front surface of the column 55A provided on the first femur paddle 5A. On the other hand, as shown in FIG. 2, a mark 12 indicating the current position of the contact surface 50A is formed on the second main surface 2b of the base 2. These scale 14 and mark 12 constitute a first distance display part 11A that displays the distance between the first contact surface 40 and the contact surface 50A.

[0048] Similarly, a scale 15 regarding the distance from the first contact surface 40 to the contact surface 50B is formed on the front surface of the column 55B of the second femur paddle 5B. On the other hand, a mark 13 indicating the current position of the contact surface 50B is formed on the second main surface 2b of the base 2. These scale 15 and mark 13 constitute a second distance display part 11B that displays the distance between the first contact surface 40 and the contact surface 50B.

[0049] As shown in Fig. 6, in the extended position, if the first contact surface 40 is brought into contact with the proximal end resection surface 92 of the proximal tibia 91 and the second contact surface 50 is brought into contact with the distal end resection surface 96 of the distal femur 95, the distance between the proximal end resection surface 92 of the proximal tibia 91 and the distal end resection surface 96 of the distal femur 95 can be measured. In this embodiment, since the femoral paddle 5 is divided into a first femoral paddle 5A and a second femoral paddle 5B, when the positions of the distal end resection surfaces 96 at the medial and lateral condyles of the distal femur 95 are different, both the distance from the proximal end resection surface 92 of the proximal tibia 91 to the distal end resection surface 96 of the medial condyle and the distance from the proximal end resection surface 92 of the proximal tibia 91 to the distal end resection surface 96 of the lateral condyle can be measured.

[0050] Moreover, if the femoral paddle 5 is held at an appropriate position by the ratchet mechanism 6, the distance between the proximal end resection surface 92 of the proximal tibia 91 and the distal end resection surface 96 of the distal femur 95 can be measured in a state where appropriate tension is applied to soft tissues such as ligaments.

[0051] As shown in Fig. 7, in the right-angle flexion position, if the first contact surface 40 is brought into contact with the proximal end resection surface 92 of the proximal tibia 91 and the second contact surface 50 is brought into contact with the rear end 97 of the distal femur 95, the distance between the proximal end resection surface 92 of the proximal tibia 91 and the rear end 97 of the distal femur 95 can be measured. In this embodiment, since the femoral paddle 5 is divided into a first femoral paddle 5A and a second femoral paddle 5B, when the positions of the rear ends 97 at the medial and lateral condyles of the distal femur 95 are different, both the distance from the proximal end resection surface 92 of the proximal tibia 91 to the rear end 97 of the medial condyle and the distance from the proximal end resection surface 92 of the proximal tibia 91 to the rear end 97 of the lateral condyle can be measured.

[0052] Moreover, if the femoral paddle 5 is held at an appropriate position by the ratchet mechanism 6, the distance between the proximal end resection surface 92 of the proximal tibia 91 and the rear end 97 of the distal femur 95 can be measured in a state where appropriate tension is applied to soft tissues such as ligaments.

[0053] Next, with reference to FIG. 8, the femoral attachment 7 will be described. As shown in FIG. 9, the femoral attachment 7 is used when measuring the distance between the proximal resection surface 92 of the proximal tibia 91 and the rear end 97 of the distal femur 95 in the right-angle flexion position.

[0054] The femoral attachment 7 includes a reproduction part 71 having a shape corresponding to the part covering the distal resection surface 96 of the distal femur 95 in the femoral component of the artificial knee joint (that is, a shape that physiologically restores the resected part of the distal femur 95), a second base part 73 located above the base 2, and a third arm part 72 extending from the reproduction part 71 toward the second base part 73. The reproduction part 71 has a third contact surface 70 that is brought into contact with the distal resection surface 96 of the distal femur 95 in the right-angle flexion position.

[0055] More specifically, the reproduction part 71 includes a medial condyle part and a lateral condyle part that are spaced apart from each other in the left-right direction, and a connecting part that connects the medial condyle part and the lateral condyle part. In the present embodiment, the rear surfaces of the medial condyle part, the lateral condyle part, and the connecting part are located on the same plane and constitute the third contact surface 70.

[0056] The third arm part 72 is parallel to the front-rear direction and is shifted to the right of the center of the reproduction part 71. In the present embodiment, the third arm part 72 is located directly above the arm part 52A of the first femoral paddle 5A. The second base part 73 is located directly above the base 53A of the first femoral paddle 5A.

[0057] The femoral attachment 7 is configured to be detachable from the femoral paddle 5. In the present embodiment, the femoral attachment 7 is detachable from the first femoral paddle 5A. Further, in the present embodiment, the femoral attachment 7 is attached to the first femoral paddle 5A so as to be movable in the front-rear direction.

[0058] Specifically, a groove 56 with a trapezoidal cross-section extending in the front-rear direction is provided on the upper surface of the base 53A of the first femoral paddle 5A. On the other hand, a rail portion 74 extending in the front-rear direction and fitting into the groove 56 is provided on the second base 73 of the femoral attachment 7. By fitting the rail portion 74 into the groove 56, the femoral attachment 7 can slide relative to the first femoral paddle 5A.

[0059] Further, a screw hole penetrating the second base 73 in the vertical direction is provided in the second base 73, and a set screw 76 is screwed into this screw hole. By rotating the set screw 76 and pressing the tip of the set screw 76 against the bottom of the groove 56, the relative position of the femoral attachment 7 with respect to the first femoral paddle 5A can be fixed.

[0060] Furthermore, a scale 75 regarding the relative position of the femoral attachment 7 with respect to the first femoral paddle 5A is formed on the upper surface of the second base 73. On the other hand, as shown in FIG. 3, a pillar 57 protruding upward from the left end of the base 53A is provided on the base 53A of the first femoral paddle 5A. The upper surface of the pillar 57 is located on the same plane as the upper surface of the second base 73 of the femoral attachment 7 when the femoral attachment 7 is attached to the first femoral paddle 5A. A mark 58 indicating the current position of the femoral attachment 7 is formed on the upper surface of the pillar 57.

[0061] When excising the proximal tibia 91 and the distal femur 95, it is necessary to retract the patella etc. (the patella and soft tissues such as the patellar tendon and quadriceps tendon attached thereto) to the inner or outer side of the knee joint. If the patella etc. are returned to their original positions with the distal resection surface 96 of the distal femur 95 exposed in the right-angle flexion position, the soft tissues attached to the patella will be in a loose state.

[0062] In contrast, in the present embodiment, since the femur attachment 7 that is detachable from the femur paddle 5 includes a reproduction part 71 having a shape that partially corresponds to the femur component where the femur attachment 7 is to be installed, as shown in FIG. 9, when the reproduction part 71 of the femur attachment 7 is brought into contact with the distal end resection surface 96 of the distal part 95 of the femur with the femur attachment 7 attached to the femur paddle 5, appropriate tension can be applied to the soft tissue attached to the patella when the patella and the like are returned to their original positions. That is, the distance between the proximal end resection surface 92 of the proximal part 91 of the tibia and the rear end 97 of the distal part 95 of the femur can be measured under the same conditions as after the future installation of the femur component. In other words, the measurement of the distance between the proximal end resection surface 92 of the proximal part 91 of the tibia and the rear end 97 of the distal part 95 of the femur in the right angle flexion position can be performed more accurately while suppressing the influence of the resection of the distal end even in a state where the distal end of the distal part 95 of the femur is resected and the rear end 97 is not resected.

[0063] Moreover, in the present embodiment, the first arm part 42 of the tibia paddle 4 is shifted to the right of the center of the first paddle part 41, the second arm part 52 of the femur paddle 5 is shifted to the right of the center of the second paddle part 51, and the third arm part 72 of the femur attachment 7 is shifted to the right of the center of the reproduction part 71. For this reason, a space can be secured on the sides of the first to third arm parts 42, 52, 72, and when measuring the distance, the patella and the like that have been retracted to the inner or outer side of the knee joint when the proximal part 91 of the tibia and the distal part 95 of the femur are resected can be returned to this space.

[0064] Furthermore, in the present embodiment, since the femoral attachment is movable in the front - rear direction, by moving the femoral attachment 7 with the third contact surface 70 of the femoral attachment 7 in contact with the distal resection surface 96 of the distal part 95 of the femur in the right - angle flexion position, the relative position between the proximal part 91 of the tibia and the distal part 95 of the femur in the front - rear direction of the knee joint can be adjusted. Thereby, when measuring the distance between the proximal resection surface 92 of the proximal part 91 of the tibia and the rear end 97 of the distal part 95 of the femur, the relative position between the proximal part 91 of the tibia and the distal part 95 of the femur in the front - rear direction of the knee joint can be made to coincide with the ideal relative position after the artificial knee joint is installed.

[0065] Next, with reference to FIG. 10, the femoral sizing jig 8 will be described. As shown in FIG. 12, the femoral sizing jig 8 is for measuring the size of the distal part 95 of the femur in the right - angle flexion position. Also, the femoral sizing jig 8 is for determining the resection position of the front end and the resection position of the rear end 97 of the distal part 95 of the femur.

[0066] When resected the front end and the rear end 97 of the distal part 95 of the femur, for example, a femoral cutting guide 88 as shown in FIGS. 11(a) and (b) is used. The femoral cutting guide 88 is provided with a plurality of slits 88b - 88e for guiding a saw for resection. Also, the femoral cutting guide 88 is provided with a pair of positioning pins 88a.

[0067] The femoral sizing jig 8 includes a measurement and positioning part 81 having a contact surface that can be brought into contact with the distal resection surface 96 of the distal part 95 of the femur in the right - angle flexion position, a third base part 83 located above the base 2, and a fourth arm part 82 extending from the measurement and positioning part 81 toward the third base part 83. The measurement and positioning part 81 is provided with a pair of through - holes 81a having the same pitch as the positioning pins 88a of the femoral cutting guide 88. Through these through - holes 81a, positioning holes are machined in the distal resection surface 96. Instead of forming the positioning holes, pins, screws or nails may be driven into the distal resection surface 96. In this case, the femoral cutting guide 88 is provided with positioning holes.

[0068] The fourth arm portion 82 is parallel to the front-rear direction and is shifted to the right of the center of the measurement / positioning portion 81. In the present embodiment, the fourth arm portion 82 is located directly above the arm portion 52A of the first thigh paddle 5A. The third base portion 83 is located directly above the base portion 53A of the first thigh paddle 5A.

[0069] The thigh sizing device 8 is configured to be detachable from the thigh paddle 5. In the present embodiment, the thigh sizing device 8 is detachable from the first thigh paddle 5A. Further, in the present embodiment, the thigh sizing device 8 is attached to the first thigh paddle 5A so as to be movable in the front-rear direction.

[0070] Specifically, the third base portion 83 of the thigh sizing device 8 is provided with a rail portion 84 extending in the front-rear direction and fitting into a groove 56 provided on the upper surface of the base portion 53A of the first thigh paddle 5A. By fitting the rail portion 84 into the groove 56, the thigh sizing device 8 can slide relative to the first thigh paddle 5A.

[0071] Further, the third base portion 83 is provided with a screw hole penetrating the third base portion 83 in the vertical direction, and a set screw 86 is screwed into this screw hole. By rotating the set screw 86 and pressing the tip of the set screw 86 against the bottom of the groove 56, the relative position of the thigh sizing device 8 with respect to the first thigh paddle 5A can be fixed.

[0072] Furthermore, a scale 85 regarding the relative position of the thigh sizing device 8 with respect to the first thigh paddle 5A is formed on the upper surface of the third base portion 83. On the other hand, when the thigh sizing device 8 is attached to the first thigh paddle 5A, the upper surface of the column 57 provided on the base portion 53A of the first thigh paddle 5A is located on the same plane as the upper surface of the third base portion 83 of the thigh sizing device 8, and a mark 58 (see FIG. 3) formed on the upper surface of the column 57 indicates the current position of the thigh sizing device 8.

[0073] By using such a femur sizing device 8, it is possible to measure the size of the distal femur portion 95 and determine the attachment position of the femur component while maintaining the relative position between the proximal tibia portion 91 and the distal femur portion 95 at an appropriate position that reproduces the physiological state in which appropriate tension is applied to the soft tissue. However, the measuring device 1 may not include the femur sizing device 8.

[0074] (Second Embodiment) Figs. 13 to 15 show a measuring device 1A for total knee arthroplasty according to the second embodiment of the present invention (Figs. 14 and 15 are views in a state where the femur attachment 7 is removed). In the present embodiment and the third embodiment described later, the same reference numerals are given to the same components as those in the first embodiment, and redundant descriptions are omitted.

[0075] The measuring device 1A includes a base 2, a tibia paddle 4, a femur paddle 5, a ratchet mechanism 6, and a femur attachment 7, similar to the measuring device 1 of the first embodiment. The measuring device 1A may include the femur sizing device 8 shown in Fig. 10.

[0076] In the present embodiment, instead of the femur paddle 5 being divided into a first femur paddle 5A and a second femur paddle 5B, it is swingable about a swing axis extending in the front-rear direction. Therefore, when the positions of the inner condyle and the outer condyle at the rear end are different in the right-angle flexion position of the distal femur portion 95, the femur paddle 5 can be brought into contact with both the rear end of the inner condyle and the rear end of the outer condyle. Further, when the space between the proximal tibia portion 91 and the distal femur portion 95 is widened in the right-angle flexion position after resection of the rear end 97 of the distal femur portion 95 to apply appropriate tension to the soft tissue, even if the rear end resection surface of the distal femur portion 95 is inclined with respect to the proximal end resection surface 92 of the proximal tibia portion 91, the femur paddle 5 can be brought into surface contact with the rear end resection surface.

[0077] In addition, when the femoral attachment 7 is removed from the femoral paddle 5, before resection of the distal end of the distal femur 95, if the positions of the medial and lateral condyles of the distal femur 95 are different at the distal end in the extended position, the femoral paddle 5 can be brought into contact with both the distal end of the medial condyle and the distal end of the lateral condyle. Further, when the soft tissue is appropriately tensioned by widening the space between the proximal tibia 91 and the distal femur 95 after resection of the distal end of the distal femur 95, even if the distal resection surface 96 of the distal femur 95 is inclined with respect to the proximal resection surface 92 of the proximal tibia 91, the femoral paddle 5 can be brought into surface contact with the distal resection surface 96.

[0078] Specifically, in the present embodiment, the femoral paddle 5 is attached to the base 2 via the elevating member 44 so as to be movable in the vertical direction. Further, the femoral paddle 5 is swingably held by the elevating member 44.

[0079] More specifically, in the present embodiment, the base 2 has a substantially rectangular parallelepiped shape that is long in the vertical direction. The first arm portion 42 of the tibial paddle 4 extends to the right side of the base 2, and a hanging portion 43 that hangs down along the right side surface of the base 2 is provided on the first arm portion 42. This hanging portion 43 is connected to the base 2.

[0080] The base 2 is provided with a through hole 27 that penetrates the base 2 in the vertical direction. Further, a groove 28 that extends in the vertical direction from the upper end surface to the lower end surface is provided on the second main surface 2b of the base 2. Furthermore, a support piece 26 projects leftward from the left side surface of the base 2. The support piece 26 has a flat upper surface that is orthogonal to the vertical direction, and the upper surface of the support piece 26 is connected to the left side surface of the groove 28.

[0081] The elevating member 44 includes a head 46 located above the base 2 and a rod 45 having a circular cross-section that extends downward from the head 46. By inserting the rod 45 into the through hole 27 of the base 2, the elevating member 44 is slidable with respect to the base 2.

[0082] The head 46 is provided with a channel that traverses the head 46 in the left - right direction. In other words, the head 46 includes a pair of opposing walls that oppose each other with the channel interposed therebetween in the front - rear direction.

[0083] The first base 53 of the femur paddle 5 extends from a position above the head 46 to a position beyond the first arm portion 42 of the tibia paddle 4. A rectangular slot extending in the left - right direction is provided in the left - hand portion of the first base 53, and the rear opposing wall of the head 46 is inserted into this slot. Further, the first base 53 is connected to the pair of opposing walls of the head 46 via a shaft 47 extending in the front - rear direction, whereby the femur paddle 5 can swing about the central axis of the shaft 47 as a swing axis.

[0084] On the left - hand portion of the rod 45, a tooth surface 45a that repeats concavities and convexities in the up - down direction is formed. On the other hand, on the base 2, an operation shaft 35 that extends in the front - rear direction to the left of the through - hole 27 is rotatably held. The operation shaft 35 is operated by a user such as a doctor.

[0085] A pinion 36 that meshes with the tooth surface 45a is provided on the operation shaft 35. For this reason, when the operation shaft 35 is operated, the elevating member 44 and the femur paddle 5 move in the up - down direction by an amount corresponding to the operation amount (rotation amount).

[0086] In the present embodiment, the ratchet mechanism 6 is composed of a column 67 provided on the elevating member 44, a ratchet lever 65 swingably attached to the base 2, and a spring 66 that biases the ratchet lever 65. However, the configuration of the ratchet mechanism 6 is not limited to this and can be appropriately changed.

[0087] The column 67 is located in front of the rod 45 and extends downward from the head 46 of the elevating member 44. The column 67 has a rectangular cross - section and fits into a groove 28 provided on the second main surface 2b of the base 2. A tooth surface 67a that repeats concavities and convexities in the up - down direction is formed on the left - hand surface of the column 67.

[0088] The ratchet lever 65 is disposed above the support piece 26 and is attached to the base 2 via a pin extending in the front-rear direction in the vicinity of the groove 28. The ratchet lever 65 includes an operating portion extending leftward from the pin and a hook portion extending upward from the pin and engaging with the tooth surface 67a at the tip.

[0089] The spring 66 is disposed between the operating portion of the ratchet lever 65 and the support piece 26, and biases the ratchet lever 65 in a direction in which the engagement state between the hook portion and the tooth surface 67a is maintained. With such a structure, only the upward movement of the lifting member 44 and the femur paddle 5 is possible when the operating portion is not operated. If the operating portion is operated to release the engagement state between the hook portion and the tooth surface 67a, the upward and downward movements of the lifting member 44 and the femur paddle 5 become possible.

[0090] Regarding the femur attachment 7, as described in the first embodiment, the rail portion 74 is fitted into the groove 56 provided in the first base portion 53 of the femur paddle 5, so that the femur attachment 7 is slidable with respect to the femur paddle 5. Note that the femur attachment 7 swings following the swing of the femur paddle 5.

[0091] Furthermore, the measuring device 1A includes a distance display portion 16 and an angle display portion 19. The distance display portion 11 displays the distance between the first contact surface 40 and the second contact surface 50 on a perpendicular line to the first contact surface 40 and passing through the swing center of the femur paddle 5.

[0092] As shown in FIG. 14, a scale 18 regarding the distance from the first contact surface 40 to the second contact surface 50 is formed on the front surface of the column 67 provided on the lifting member 44. On the other hand, a mark 17 indicating the current position of the second contact surface 50 is formed on the second main surface 2b of the base 2. These scale 18 and mark 17 constitute the distance display portion 16.

[0093] The angle display unit 19 displays the angle between the first contact surface 40 and the second contact surface 50 (hereinafter referred to as the "angle between paddles"). A scale plate 69 is provided on the opposing wall behind the head 46 of the elevating member 44, and a scale 69a related to the angle between paddles is formed on this scale plate 69. On the other hand, a needle 59 indicating the current angle of the second contact surface 50 is provided on the first base 53 of the femoral paddle 5. These scale 69a and needle 59 constitute the angle display unit 19.

[0094] Also in this embodiment, similar to the first embodiment, it is possible to measure the distance between the proximal resection surface 92 of the proximal tibia 91 and the rear end 97 of the distal femur 95 under the same conditions as after the future attachment of the femoral component. Moreover, in this embodiment, since the angle between the paddles is displayed by the angle display unit 19, the step between them when the positions of the distal end or the distal resection surface 96 are different between the medial condyle and the lateral condyle of the distal femur 95, and the inclination of the distal resection surface 96 can be evaluated by the angle.

[0095] (Third Embodiment) Figs. 16 and 17 show a measuring device 1B for total knee arthroplasty according to the third embodiment of the present invention (Fig. 17 is a view in a state where the femoral attachment 7 is removed). The difference between the measuring device 1B of this embodiment and the measuring device 1A of the second embodiment is that in the measuring device 1A, the groove 56 swings following the femoral paddle, whereas in the measuring device 1B, the groove 56 is kept parallel to the first contact surface 40 even when the femoral paddle 5 swings. For this reason, the femoral attachment 7 held in the groove 56 is kept parallel to the proximal resection surface 92 of the proximal tibia 91. The measuring device 1B may include the femoral sizer 8 shown in Fig. 10, as described in the second embodiment.

[0096] Specifically, the length of the first base 53 of the femoral paddle 5 in the left - right direction is set shorter than that in the second embodiment, and a pendulum 56a is arranged to the right of the first base 53. And a groove 56 is provided in this pendulum 56a.

[0097] The pendulum 56a is connected to the first base portion 53 via a shaft 56d extending in the front-rear direction. Further, a link member 56b is disposed above the first base portion 53. The link member 56b is connected to the pendulum 56a via a shaft 56e extending in the front-rear direction and is connected to the head 46 of the elevating member 44 via a shaft 56c extending in the front-rear direction.

[0098] Also in this embodiment, similar to the first embodiment, it is possible to measure the distance between the proximal resection surface 92 of the proximal tibia 91 and the rear end 97 of the distal femur 95 under the same conditions as after the future femoral component is attached. Moreover, in this embodiment, the same effects as those of the second embodiment can also be obtained.

[0099] (Other Embodiments) The present invention is not limited to the above-described embodiments, and various modifications are possible without departing from the gist of the present invention.

[0100] For example, contrary to the above-described embodiment, the first arm portion 42 may be shifted to the left of the center of the first paddle portion 41. In this case, the second arm portion 52 is also shifted to the left of the center of the second paddle portion 51, and the third arm portion 72 is also shifted to the left of the center of the reproduction portion 71. Alternatively, depending on the surgical technique of total knee arthroplasty, the center of the first arm portion 42 may coincide with the center of the first paddle portion 41 in the left-right direction.

[0101] Further, the femoral paddle 5 may not be divided into two and may be immovable about a rocking axis extending in the front-rear direction of the knee joint.

Explanation of Reference Numerals

[0102] 1, 1A, 1B Measuring Device for Total Knee Arthroplasty 11 Distance Display Unit 2 Base 4 Tibial Paddle 40 First Contact Surface 41 First Paddle Portion 42 First Arm Portion 5 Femoral Paddle 5A Femoral paddle 1 5B Femoral paddle 2 50 Second contact surface 51 Second paddle part 52 Second arm part 53 First base 6 Ratchet mechanism 7 Femoral attachment 70 Third contact surface 71 Reproduction part 72 Third arm part 73 Second base 8 Femoral sizer 91 Proximal tibia 92 Proximal resection surface 95 Distal femur 96 Distal resection surface 97 Rear end

Claims

1. A measuring device used for total knee arthroplasty, comprising: a base disposed in front of the knee joint; a tibia paddle fixed to the base and having a first contact surface that contacts the proximal resection surface of the proximal part of the tibia; a femur paddle attached to the base so as to be movable in a direction orthogonal to the first contact surface, the femur paddle having a second contact surface that contacts the rear end of the distal part of the femur in the right-angle flexion position; a ratchet mechanism that can be switched to allow only the movement of the femur paddle away from the tibia paddle or to allow movement in both directions; a femur attachment that is detachable from the femur paddle and has a third contact surface that contacts the distal resection surface of the distal part of the femur in the right-angle flexion position; a distance display unit that displays the distance between the first contact surface and the second contact surface; The femur attachment includes a reproduction part having a shape corresponding to a part covering the distal resection surface of the distal part of the femur in the femur component of the artificial knee joint, and this reproduction part has the third contact surface. A measuring device for total knee arthroplasty.

2. The measuring device for total knee arthroplasty according to Claim 1, wherein the femur attachment is attached to the femur paddle so as to be movable in the front-rear direction of the knee joint.

3. The femur paddle is divided into a first femur paddle and a second femur paddle arranged in the medial-lateral direction of the knee joint, The first femur paddle and the second femur paddle are attached to the base so as to be movable independently of each other in a direction orthogonal to the first contact surface, The distance display unit displays the distance between the first contact surface and the second contact surface for each of the first femur paddle and the second femur paddle. The measuring device for total knee arthroplasty according to Claim 1 or 2.

4. The femur paddle is swingable around a swing axis extending in the front-rear direction of the knee joint, The distance display unit displays the distance between the first contact surface and the second contact surface on a perpendicular line to the first contact surface and passing through the swing center of the femur paddle. The measuring device for total knee arthroplasty according to Claim 1 or 2.

5. The tibia paddle includes a first paddle part having the first contact surface and a first arm part extending from the first paddle part toward the base. The femur paddle includes a second paddle portion having the second contact surface, a first base portion positioned above the base, and a second arm portion extending from the second paddle portion toward the first base portion. The femur attachment includes a second base portion positioned above the base, and a third arm portion extending from the reproduction portion toward the second base portion. When one of the medial-lateral directions of the knee joint is defined as the first direction and the other is defined as the second direction, the first arm portion is shifted in the first direction from the center of the first paddle portion. the second arm portion is shifted in the first direction from the center of the second paddle portion. the third arm portion is shifted in the first direction from the center of the reproduction portion. The measurement device for total knee arthroplasty according to claim 1 or 2. **Claim 6** The measurement device for total knee arthroplasty according to claim 1 or 2, further comprising a femur sizer that is detachable from the femur paddle for measuring the size of the distal portion of the femur in the right-angle flexion position, and for determining the resection position of the front end and the resection position of the rear end of the distal portion of the femur.

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