JP2004166802A - Artificial knee joint - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an artificial knee joint smoothly bent to a high bending angle by guiding a winding angle corresponding to the bending angle in the artificial knee joint constituted to make a thighbone component to roll and slide on a tibia component. <P>SOLUTION: The thighbone component 1 is formed by connecting mutually rear parts of a pair of condyloid projecting members 2a and 2b laterally provided at some interval apart therefrom with a cam 3. The tibia component 11 is formed with a spine 4 and, at least, a guide surface out of mutual guide surfaces 3a and 4s where the cam 3 and the spine 4 contact with each other when the bending angle of the knee joint increases, is formed by twisting. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an artificial knee joint used to restore a knee joint that has been highly deformed due to rheumatoid arthritis, osteoarthritis or the like or a joint that has been destroyed due to a traffic accident or disaster to a normal function. .
[0002]
[Prior art]
Conventionally, as shown in FIG. 6, the distal portion of the femur A and the proximal portion of the tibia B of the knee joint deformed or destroyed due to a disease or an accident are cut, and the femoral component 1 and the tibia component 11 are cut. An artificial knee joint replacement operation in which each is inserted and fixed is performed. In order to reproduce a normal joint motion of a person, the lower surface of the femoral component 1 is contacted with the upper surface (referred to as “joint surface”) 12 of the tibial component 11. An artificial knee joint having a structure in which the convex portion 8 can be bent by rolling and / or sliding has been used (a general-purpose product).
[0003]
By the way, the artificial knee joint currently used in Japan accounts for nearly 95% of those developed in Europe and the United States (for example, see Patent Literatures 1 to 3). Since it was developed with an emphasis on the bending angle (bending angle in the front-rear direction) necessary for the life in which it was used, there were many cases where only a bending angle of up to about 120 degrees could be obtained clinically.
[0004]
However, Japanese elderly people and the like often sit on a daily basis, and therefore, an artificial knee joint capable of bending at an angle of 150 degrees or more is desired.
[0005]
In addition, in the actual living knee joint, at the time of bending, rotation in the horizontal direction with respect to the joint surface (referred to as “rotation”) also occurs at the same time, and the rotation angle corresponding to the bending angle is induced, so that it can be bent smoothly. Things. In order to realize more natural and smooth bending at a high bending angle of 150 degrees or more, it is desirable to secure a rotation angle of 10 degrees or more.
[0006]
The artificial joint disclosed in Patent Document 4 (see FIGS. 7 and 8) is proposed to realize a high bending angle of 160 degrees (conventional example 1). As shown in FIG. 7, the femoral component 1 that constitutes this artificial joint has a pair of condylar protrusion members 2a and 2b spaced horizontally (horizontally) at a predetermined interval 9 (not shown), as in the general-purpose product. Direction), and these rear portions 6 are connected to each other by a connecting member (referred to as a “cam”) 3 to form an integral body. The convex portion 7 is formed so as to be wound around the portion 5. On the other hand, as shown in FIG. 8, the tibial component 11 has a joint surface 12 and a projection (referred to as “spine”) 4 similarly to the general-purpose product. As a result, as shown in FIG. 8, even when the bending angle exceeds 130 degrees, the cam 3 is in contact with and supported by the spine 4, while the convex portion 7 slides while smoothly contacting the joint surface 12. Therefore, a high bending angle up to 160 degrees can be obtained without the femoral component 1 falling off from the tibial component 11.
[0007]
However, in the proposed artificial joint, rotation is not considered at all, and only bending in the front-back direction is possible. When performing such an artificial joint that can only bend, for a case in which the soft tissue including the ligaments is healthy to some extent, the rotation by the soft tissue can be somewhat secured and the flexion can be secured to some extent. In cases where the tissue condition is poor, rotation is unlikely to occur and there is room for improvement in terms of bending.
[0008]
On the other hand, Patent Literature 5 discloses an artificial knee joint as shown in FIG. 9 (conventional example 2). Like the conventional example 1, the femoral component 1 and the tibial component 11 are used. However, unlike the conventional example 1, the spine and the cam are not used. Among the pair of concave portions 12a and 12b provided on the joint surface 12 of the tibial component 11, the curvature of a significant portion of one concave portion 12a and the pair of condylar members 2a and 2b constituting the femoral component 1 The curvature of the significant portion of the convex portion 8a of the condylar projection member 2a that is in contact with the concave portion 12a is substantially equal to the curvature of the significant portion of the other concave portion 12b. By making the curvature smaller than the significant portion of the convex part 8b of the condylar projection member 2b (in other words, making it smoother), the convex part 8a of one condylar projection member 2a fits into the former concave surface part 12a. With this as a fulcrum, the other condylar projection member 2b can rotate in the horizontal direction, that is, can rotate. However, the purpose of this artificial knee joint is to secure a required rotation angle within a relatively small range of bending angle during walking, and cannot be applied to a high bending angle. Further, the rotation angle is not induced according to the bending angle.
[0009]
[Patent Document 1]
JP-B-61-50625 [Patent Document 2]
JP-B-62-36696 [Patent Document 3]
Japanese Patent Publication No. 2-45456 [Patent Document 4]
JP-A-11-313845 [Patent Document 5]
US Patent No. 5,219,362
[Problems to be solved by the invention]
In view of the above situation, an object of the present invention is to provide an artificial knee joint capable of smoothly bending to a high bending angle by inducing a rotation angle corresponding to the bending angle.
[0011]
[Means for Solving the Problems]
The invention of claim 1 is directed to an artificial knee joint including a femoral component mounted on a distal portion of a femur and a tibial component mounted on a proximal portion of a tibia, in which a change in the bending angle of the artificial knee joint is prevented. An artificial knee joint configured such that the rotation angle of the artificial knee joint changes correspondingly.
[0012]
According to a second aspect of the present invention, there is provided an artificial knee joint including a femoral component mounted on a distal portion of a femur and a tibial component mounted on a proximal portion of a tibia, wherein the femoral components are spaced from each other. And a coupling member having a generally forwardly directed guide surface for coupling the posterior portions of the pair of condylar members to each other, wherein the tibial component comprises A pair of concave portions on which the convex portion of the condylar protrusion member slides and / or rolls, and is formed so as to be fitted into a space between the pair of condylar protrusion members and to be movable in the longitudinal direction of the space. A projection having a guide surface that is directed substantially rearward, and when the bending angle of the artificial knee joint changes, the position of the contact portion of the guide surface between the protrusion and the coupling member changes, The artificial knee joint Is rotation angle is configured knee joint so as to change.
[0013]
The invention according to claim 3 is the artificial knee joint according to claim 2, wherein at least one of the guide surface of the coupling member and the guide surface of the protrusion has a twisted shape.
[0014]
[Action]
In the following, in order to facilitate understanding of the relative movement and positional relationship between the femoral component and the tibial component, the tibial component is assumed to be fixed with its joint surface horizontal, and only the femoral component Will be described as being bent or rotated.
[0015]
Since the artificial knee joint of the present invention is configured so that the rotation angle of the artificial knee joint changes in response to the change in the bending angle, the rotation angle is induced in accordance with the bending angle, and smooth bending is possible. Become.
[0016]
For example, if the angle of rotation of the artificial knee joint is changed by changing the position of the contact portion of the guide surface between the projection and the coupling member when the bending angle changes, the bending angle can be changed. The rotation angle is guided in accordance with the rotation angle, thereby enabling smooth bending.
[0017]
Also, for example, if the guide surface of the coupling member is formed into a twisted shape, when the bending angle is changed, the guide member comes into contact with the guide surface of the projection corresponding to the amount of change in the bending angle. As the position in the height direction of the contact portion of the guide surface of the coupling member moves, the horizontal position of the contact portion also moves, and the femoral component is moved horizontally with respect to the tibia component by the amount of movement in the horizontal direction. Rotate (rotate) in the direction (joint surface direction). Therefore, a rotation angle corresponding to the bending angle occurs.
[0018]
In the above description, it is apparent that the same operation and effect can be obtained even if the guide surface of the projection is formed in a twisted shape instead of the guide surface of the coupling member.
[0019]
Further, in the above, if both the guide surface of the coupling member and the guide surface of the protrusion are formed in a twisted shape, a rotation angle corresponding to the bending angle is generated by the same operation as described above, and both of them are formed. The degree of twisting of the guide surfaces can be reduced as compared with the case where each is twisted alone, so that concentrated stress generated between the femoral component and the tibia component is dispersed to the coupling member and the protrusion, and each component The fatigue life is extended.
[0020]
Further, of the pair of concave portions, the curvature of the significant portion of one concave portion is substantially equal to the curvature of the significant portion of the convex portion of the condylar member in contact with the concave portion, and the other concave portion has a significant curvature. By making the curvature of the significant portion smaller than the curvature of the significant portion of the convex portion of the condylar member in contact with the concave portion, the convex portion of one condylar member fits into the former concave portion. With this as a fulcrum, the other condylar member can slide on the latter concave surface, so that the rotation is performed more smoothly.
[0021]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of an artificial knee joint according to the present invention will be described with reference to the drawings.
[0022]
FIG. 1 is a perspective view of an artificial knee joint according to an embodiment of the present invention. 2 to 4 are diagrams for explaining the operation state of the artificial knee joint according to the embodiment of the present invention. FIG. 2 shows a state where the bending angle is 0 degree, FIG. 3 shows a state where the bending angle is 90 degrees, and FIG. Show. Each of FIGS. 2A to 4A is a cross-sectional view obtained by joining an AA section above the joint surface 12 in FIG. 1 and a CC section below the joint surface 12 in FIG. 1, and FIG. A section above the surface 12 is a BB section, and a section below the joint surface 12 is a section of a DD section.
[0023]
In FIG. 1, the artificial joint of the present invention comprises a femoral component 1 and a tibial component 11. The femoral component 1 forms a patella by connecting a pair of condylar projection members 2a, 2b provided laterally (horizontally) at a fixed interval 9 to each other by integrally joining their front parts together, The rear portions of each other are connected by a cam 3 as a connecting member. On the other hand, the tibial component 11 has a joint surface 12 formed with a pair of concave portions 12a and 12b and a spine 4 which is a projection. The spine 4 is fitted into the space 9 of the femoral component, and It is used in a state where the respective convex portions 8a, 8b of the respective condylar projection members 2a, 2b are in contact with the respective portions 12a, 12b.
[0024]
The width (horizontal direction) of the space 9 is slightly wider than the width of the protrusion 4 so that the spine 4 inserted in the space 9 can freely move in the front-rear direction according to the bending of the knee joint. The length of the space portion at the interval 9 in the front-rear direction (longitudinal direction) is longer than the length of the protrusion 4 in the front-rear direction (ie, the length of the skirt) at the height level of the joint surface 12.
[0025]
The guide surface 4 s of the spine 4, which is directed substantially rearward, is not a symmetrical shape but a twisted shape, for example, a cutting line when the guide surface 4 s is horizontally cut from the lower end (hem) of the spine 4. It is formed in such a shape that it rotates counterclockwise as viewed from above as it approaches the upper end (top).
[0026]
Alternatively, instead of the guide surface 4 s of the spine 4 having a twisted shape, the guide surface 3 s of the cam 3 over substantially the entire circumference may have a twisted shape instead of a symmetric shape. In order to form the guide surface 3 s in a twisted shape, for example, a cam which is obtained by bending a central axis of a cylinder laid sideways may be used. Alternatively, the center axis of the cam 3 may be straight in the left-right direction, the right and left diameters of the cam 3 may be changed, and the cam 3 may be formed in a truncated cone shape and twisted.
[0027]
Alternatively, as shown in FIG. 1, it is more preferable that both the guide surface 4 s of the spine 4 and the guide surface 3 s of the cam 3 have a twisted shape, so that a further turning angle can be obtained.
[0028]
First, in order to make the guide surface 4s of the spine 4 twisted, as shown in FIG. 2, the guide surface 4s of the spine 4 has a right side (inside) at the upper portion (proximal portion) on the left side (inside). It is preferable that the right side (inside) is located behind the left side (outside) in the lower part (distal part). Note that only one of the upper part (proximal part) and the lower part (distal part) may have the above positional relationship. Next, in order to form the guide surface 3s of the cam 3 into a twisted shape, as shown in FIG. 2, the guide surface 3s of the cam 3 has an upper portion (proximal portion) and a lower portion (distal portion). It is preferable that the right and left sides (inside and outside) are located at substantially equal positions in the front-rear direction, and that the right (inside) radius is smaller than the left (outside) radius.
[0029]
In general, rotation of the knee is performed with the inside of the femur and the tibia as the axis (outside rotation). However, the present invention does not limit the control of the rotation to only the external rotation. By appropriately designing the shapes of the cam 3 and the spine 4, the internal rotation in which the inside of the femur and the tibia are rotated around the outside is performed. Can also be controlled.
[0030]
As described above, if at least one of the guide surfaces 3s and 4s has a twisted shape, the rotation is guided according to the bending. For example, as shown in FIGS. 2 to 4, when both the guide surfaces 3 s and 4 s are twisted, and the bending angle of the knee joint is 0 degree (FIG. 2), the cam 3 and the spine 4 Does not contact, the condylar members 2a and 2b are not displaced in the front-rear direction (δ = 0), and no rotation occurs. As the bending angle is increased, the cam 3 and the spine 4 eventually come into contact with each other at the respective guide surfaces (3s and 4s). However, since the guide surfaces 3s and 4s both have a twisted shape, As shown in FIGS. 3 (a) and 3 (b), the contact positions in the front-rear direction on the AA section and the BB section in FIG. 1 are different, and a deviation δ between the condylar projection members 2a and 2b in the front-rear direction occurs, and rotation is caused. It begins to occur (FIG. 3). When the bending angle further increases, the contact position moves upward, the amount of shift δ increases, and the rotation angle also increases (FIG. 4). In this way, rotation is induced according to the bending. In the case of FIGS. 2 to 4 described above, it is apparent that rotation is induced by the same mechanism as described above even if only one of the guide surfaces 3s and 4s is formed into a twisted shape and the other is formed into a symmetrical shape. It is. However, in order to generate the same degree of rotation as in the case where both of the above are twisted and the above both are twisted, the degree of twisting is compared with the case where both are twisted. It is necessary to increase the stress, and there is a possibility that the concentration of stress at the contact portion increases.
[0031]
The cross-sectional shapes of the cam 3 and the spine 4 are not limited to those shown in FIGS. 2 to 4, and any shape may be used as long as the turning angle is changed by changing the bending angle. It does not matter, but it is preferable that the shape is such that it can withstand the stress caused by the load. For example, the cross-sectional shape of the cam 3 may be an ellipse or the like in addition to the circular shape in FIGS. 2 to 4, and the cross-sectional shape of the spine 4 may be a substantially rectangular shape in addition to the substantially triangular shape as in FIGS. It may be.
[0032]
Further, the guide surfaces 3s and 4s are preferably formed to have a smooth surface shape without corners so as not to generate a concentrated load when they come into contact with each other and to reduce wear as much as possible.
[0033]
Also, as shown in FIG. 1, the convex portions 8a and 8b of the condylar projection members 2a and 2b are formed in spherical shapes so that the knee joint bends as smoothly as possible. 12a and 12b are also preferably spherical in order to minimize the wear without causing a concentrated load.
[0034]
Furthermore, the curvature of the significant portion of one of the concave portions (12a in FIG. 1) of the concave portions 12a and 12b is made substantially equal to the curvature of the significant portion of the convex portion (8a in FIG. 1) in contact with it, and It is preferable that the curvature of the significant portion of the concave portion (12b in FIG. 1) is smaller than the curvature of the significant portion of the convex portion (8b in FIG. 1) in contact with the concave portion (in other words, the curvature is gentle). Here, the “significant portion” means a portion where the convex portion 12a (or 12b) and the concave portion 8a (or 8b) can come into contact with each other within the range of the bending angle and the rotation angle of the artificial knee joint. As a result, the convex portion 8a fits into the concave portion 12a and serves as a fulcrum, while the convex portion 8b can slide in the front and rear direction inside the concave portion 12b, so that the rotation is performed more smoothly. The curvature of the significant portion of the concave portion 12b may be appropriately adjusted according to the combination with the shapes of the guide surfaces 3s and 4s so as to enable smoother rotation.
[0035]
Incidentally, the artificial knee joint according to the present invention, in consideration of biocompatibility, mechanical strength, abrasion resistance, etc., by a known processing method which is generally performed using a known material which is generally used in this field. It may be formed. That is, as a material, for example, a metal material such as titanium, a titanium alloy, stainless steel, a Co—Cr alloy, or a ceramic material, a synthetic resin material such as ultra-high molecular weight polyethylene, or the like is used, and the surfaces (convex portions 8a and 8b) of each member are used. Preferably, the concave portions 12a and 12b) are mirror-finished or polished.
[0036]
In addition, when the artificial knee joint of the present invention is actually implanted and mounted in a patient, a method of bonding to the remaining living bone using a bone cement such as polymethyl methacrylate, or an artificial knee joint without using bone cement A known technique used for a conventional artificial knee joint may be appropriately adopted, such as a method of invading and fixing a living bone by making the surface uneven.
[0037]
【Example】
An artificial joint similar to the shape shown in FIG. 1 (both the cam 3 and the spine 4 are formed in a twisted shape, the concave surface 12a is substantially congruent with the convex surface 8a and a significant part of each other, and the concave surface 12b is gentler than the convex surface 8b. Are manufactured in three different sizes, and the bending angle is sequentially increased from 0 ° to 150 ° for each size, and the rotation angle at each bending angle is measured, and the angle between the bending angle and the rotation angle is measured. The relationship was determined, and the results are shown in FIG.
[0038]
As shown in FIG. 5, the artificial knee joint of each size (the broken lines a, b, and c in FIG. 5) does not rotate until the bending angle is about 70 degrees, but starts to rotate when the bending angle reaches about 90 degrees. Thereafter, as the bending angle increases, the rotation angle also increases, and at a bending angle of 150 degrees, a rotation angle of 18 to 22 degrees is obtained. At a high bending angle of 150 degrees or more, a more natural and smooth bending can be realized. It was confirmed that the above rotation angle could be secured.
[0039]
Note that the maximum bending angle required for general walking is about 60 degrees, and the rotation angle at that time is about 3 degrees. Therefore, it is preferable to control the rotation angle even in the range of the required bending angle during walking. However, if the cam keeps in contact with the spine, the risk of wear and breakage of the spine and breakage of the cam increases. For this reason, in this embodiment, the spine and the cam are not brought into contact with each other until the bending angle reaches about 70 degrees, so that no rotation occurs.
[0040]
【The invention's effect】
As described above, according to the present invention, it is possible to provide an artificial knee joint in which a rotation angle corresponding to a bending angle is induced and can be smoothly bent to a high bending angle of 150 degrees or more.
[Brief description of the drawings]
FIG. 1 is a perspective view of an artificial knee joint according to an embodiment of the present invention.
FIG. 2 is a diagram illustrating an operation state of the artificial knee joint according to the embodiment of the present invention at a flexion angle of 0 °.
FIG. 3 is a diagram illustrating an operation state of the artificial knee joint according to the embodiment of the present invention at a bending angle of 90 degrees.
FIG. 4 is a diagram illustrating an operation state of the artificial knee joint according to the embodiment of the present invention at a bending angle of 150 degrees.
FIG. 5 is a diagram showing a relationship between a bending angle and a rotation angle in the artificial knee joint of the example.
FIG. 6 is a diagram illustrating a state where an artificial knee joint is attached to a living body.
FIG. 7 is a side view of a femoral component of the knee prosthesis of Conventional Example 1.
FIG. 8 is a side view of the artificial knee joint of Conventional Example 1 at a bending angle of about 130 degrees.
FIG. 9 is a perspective view of an artificial knee joint of Conventional Example 2.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Femoral component 2a, 2b ... Condylar member 3 ... Connecting member (cam)
3s: guide surface 4: protrusion (spine)
4s guide surface 5 front part 6 rear part 7 convex part 8, 8a, 8b convex part 9 interval 11 tibial component 12 joint surface 12a, 12b concave part A femur B ... tibia

Claims (3)

An artificial knee joint comprising a femoral component mounted on a distal portion of a femur and a tibial component mounted on a proximal portion of a tibia, the artificial knee joint corresponding to a change in bending angle of the artificial knee joint Artificial knee joint that is configured to change the rotation angle of the knee. In a knee prosthesis consisting of a femoral component mounted on the distal part of the femur and a tibial component mounted on the proximal part of the tibia,
A coupling member having a pair of condylar members spaced apart from each other and a laterally provided condylar member; and With
The tibial component is inserted into a space between the pair of concave members on which the convex surface of each of the condylar members slides and / or rolls, and is movable in the longitudinal direction of the space. A projection having a guide surface directed substantially rearward,
When the bending angle of the artificial knee joint changes, the rotation angle of the artificial knee joint is changed by changing the position of the contact portion of the guide surface between the protrusion and the coupling member. Artificial knee joint. The artificial knee joint according to claim 2, wherein at least one of the guide surface of the coupling member and the guide surface of the protrusion has a twisted shape.

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