JP5419490B2 - Artificial knee joint - Google Patents

Description

  The present invention relates to an artificial knee joint, and more particularly to an artificial knee joint that can control the rotational resistance of the knee joint according to the bending angle. This artificial joint has high stability in the front-rear direction and can reduce local wear on the post.

  When the knee joint is highly deformed due to osteoarthritis of the knee or rheumatoid arthritis, replacement surgery for an artificial knee joint is performed to restore normal function.

  The artificial knee joint includes a femoral component fixed to the distal end of the femur and a tibial component fixed to the proximal end of the tibia (for example, Patent Documents 1 to 3). The tibial component is composed of a metal, ceramic, or resin tibial tray that is directly fixed to the tibia, and a resin tibial plate that is fixed to the upper surface of the tibial tray and contacts the femoral component.

  When the knee joint is bent, the femoral component rotates while sliding on the surface of the tibial plate. At this time, an anterior force acts on the femoral component. Therefore, when the cruciate ligament is excised, there is a possibility of dislocation of the knee joint, in particular, the femoral component may be dislocated forward.

  In addition, it has been confirmed clinically that a normal knee joint rotates slightly externally in an extended to slightly bent position, and performs a large external rotation in deep bending. This is presumably because the cruciate ligament plays a major role in suppressing excessive rotation in the extended to slightly bent position. Therefore, when the cruciate ligament is excised, there is a possibility that the rotation direction is slightly bent and unstable in the rotation direction.

In order to prevent the dislocation of the femoral component in the forward direction at the time of knee joint flexion, in Patent Document 1, a cam is provided at the rear end of the femoral component and between the medial condyle and the lateral condyle, And a post projecting upward. When the knee joint is bent, the cam contacts the posterior surface of the post to prevent the femoral component from moving forward.
Moreover, in order to reduce the swaying property in the rotation direction at the time of extension to slight bending, the fact that the opening between the femoral condyles and the post interfere with each other in the rotation direction is used.

However, in Patent Document 1, since the load from the femoral component is concentrated on the post at the time of bending, the post may be significantly worn locally to be deformed or damaged.
At the same time, even in deep flexion, the opening between the femoral condyles and the post interfere with each other at a small rotation angle, so that a large rotation cannot be expected.

In order to solve the problems of rotational freedom and wear in the cam-post structure of Patent Document 1, in the knee prosthesis disclosed in Patent Documents 2 and 3, the rear end of the femoral component and the medial and lateral condyles Is provided with a convex sliding surface, and a concave sliding surface is provided at the center of the rear part of the tibial component. When the knee joint is bent, the convex sliding surface contacts the concave sliding surface to prevent the femoral component from moving forward. Moreover, since the load from the femoral component at the time of bending is widely distributed over the concave sliding surface, local wear of the concave sliding surface can be suppressed.
However, when the tension of the ligament cannot be adjusted properly, the resistance force in the front-rear direction and the rotation direction in the extension to the slight bending position is relatively small, and there is a fear that the front-rear direction and the rotation direction are not stable.

US Pat. No. 4,298,992 Japanese Patent No. 2981917 International Publication No. 2007/116232 Pamphlet

  Among patients who have undergone knee replacement, patients who have excised ligaments (especially cruciate ligaments) have low stability in the anterior and posterior directions of the knee joint and in the rotational direction. Therefore, when the ligament tension of the knee joint cannot be properly adjusted, the femoral component may not be stabilized in the anteroposterior direction and the rotation direction. Therefore, it is desirable that the knee prosthesis be stable in the front-rear direction and the rotation direction in the extended to lightly bent positions. On the other hand, in deep bending, it is desirable that the artificial knee joint has a large degree of freedom of rotation. That is, the artificial knee joint is required to simultaneously achieve these contradictory characteristics. Furthermore, it is also necessary to ensure wear resistance to the post.

  The knee prosthesis disclosed in Patent Document 1 has stability in the extended to light bending position and stability in the front-rear direction, but is inferior in resistance to abnormal wear of the post and has a large rotation necessary for deep bending. There is no freedom. In addition, the artificial knee joints disclosed in Patent Documents 2 and 3 have a relatively small resistance in the anteroposterior direction and the rotational direction when the ligament tension of the knee joint cannot be adjusted appropriately, so that the stretched to slightly bent position In this case, there is a risk that the rotation direction will not be stable.

  Therefore, the present invention has a high stability in both the front and rear direction and the rotation direction even when the ligament tension of the knee joint cannot be adjusted properly in the extended to slightly bent position. It is an object of the present invention to provide an artificial knee joint capable of realizing the above-mentioned, that is, an artificial knee joint capable of controlling the rotation by the bending angle. It is another object of the present invention to provide an artificial knee joint having high resistance to post wear.

  An artificial knee joint of the present invention is an artificial knee joint comprising a femoral component fixed to the distal end of the femur and a tibial plate fixed to the proximal end of the tibia and slidably receiving the femoral component. The femoral component has a medial condyle and a lateral condyle, and an opening and a posterior end of the medial condyle and the lateral condyle are connected between the medial condyle and the lateral condyle; An elliptical spherical sliding portion that slides with respect to the tibial plate when the knee joint is bent, and the tibial plate includes a medial fistula that receives the medial condyle and a lateral fossa that receives the lateral condyle. A spine that moves between the opening in the front-rear direction corresponding to the bending / extending operation of the knee joint between the inner and outer fossa and that contacts the elliptical spherical sliding portion when the knee joint is bent; , Constituting the rear surface of the spine, the elliptical spherical sliding part A concave sliding surface slidably receive, is formed, the width of the oval-spherical sliding portion, an artificial knee joint, characterized in that widens toward the rear end from said opening.

In this specification, “becomes wider from the opening toward the rear end” means that the width of the elliptical spherical sliding portion is “always” or “continuously” wider from the opening toward the rear end. This includes a case where the width is partially constant while going from the opening toward the rear end, but wide as a whole. In other words, “becomes wider from the opening toward the rear end” means that the width of the elliptical spherical sliding portion does not become narrower from the opening toward the rear end.
In the present specification, the “elliptical spherical sliding part” is a sliding part having a curved surface of an elliptical spherical body as a sliding surface, and may include all or a part of the elliptical spherical body.
In addition, the “elliptical sphere” in this specification includes not only an elliptical three-dimensional object having a long axis and a single axis but also a true sphere.

In the knee prosthesis according to the present invention, the width of the elliptical spherical sliding portion becomes wider from the opening toward the rear end. Therefore, when the bending angle of the knee joint is increased, the width of the elliptical spherical sliding portion relative to the width of the spine is also increased. growing. That is, when the bending angle of the knee joint is increased, the degree of freedom in the rotation direction of the elliptical spherical sliding portion is increased. Therefore, the knee prosthesis of the present invention can control the limitation of rotation of the knee joint according to the bending angle.
In the knee prosthesis of the present invention, when the knee joint is bent, the spine comes into contact with the elliptical sliding portion, so that the stability in the rotation direction can be improved.

1 is a schematic perspective view at the time of extension of an artificial knee joint according to Embodiment 1. FIG. FIG. 2 is a schematic exploded view of the knee prosthesis according to the first embodiment. 3A is a schematic cross-sectional view taken along the line α-α in FIG. 1, and FIG. 3B is a schematic cross-sectional view when the knee prosthesis in FIG. 3A is bent at 90 °. 4A to 4E are schematic cross-sectional views at various bending angles of the knee prosthesis according to the first embodiment. 5A to 5E are schematic front views at various bending angles of the knee prosthesis according to the first embodiment. 6A to 6E are schematic perspective views at various bending angles of the artificial knee joint according to Embodiment 1. FIG. 7A to 7C are schematic perspective views for explaining external rotation at various bending angles of the artificial knee joint according to Embodiment 1. FIG. FIGS. 8A to 8F are schematic cross-sectional views of modifications of the knee prosthesis according to the first embodiment. FIG. 9 is a schematic perspective view of the distal end of the osteotomized femur. 10A to 10C are schematic cross-sectional views at various bending angles of the knee prosthesis according to the first embodiment. 11A to 11C are schematic perspective views at various bending angles of a conventional artificial knee joint. 12 (a) to 12 (c) are schematic perspective views of various conventional knee prostheses at various bending angles. FIG. 13A is a schematic sectional view of the knee prosthesis according to Embodiment 1, and FIG. 13B is an exploded view of the knee prosthesis shown in FIG. 14A to 14C are schematic cross-sectional views at various bending angles of the artificial knee joint according to the first embodiment. FIG. 15 is a schematic perspective view of a tibial plate used in an artificial knee joint according to the second embodiment. FIG. 16A is a schematic cross-sectional view when the artificial knee joint according to Embodiment 2 is bent at 150 °. FIG. 16B is a schematic perspective view for explaining the external rotation when the artificial knee joint of the comparative example is bent at 150 °. FIG. 17 is an enlarged view of the rear end sliding surface (portion I in FIG. 15) of the tibial plate used in the knee prosthesis according to the second embodiment. FIG. 18 is a schematic top view of a tibial plate used in the knee prosthesis according to the second embodiment. FIG. 19 is a schematic top view of a tibial plate used in the knee prosthesis according to the second embodiment. FIG. 20 is an enlarged view of the rear end portion (part II in FIG. 15) of the medial fossa of the tibial plate used in the knee prosthesis according to the second embodiment. FIG. 21A is a schematic cross-sectional view taken along the line YY of FIG. 15, and FIG. 21B is a schematic cross-sectional view taken along the line ZZ of FIG. 22 is a schematic cross-sectional view taken along line YY of FIG. 23A and 23B are schematic cross-sectional views when the artificial knee joint according to Embodiment 2 is bent at 150 °. FIG. 24 is a schematic perspective view of a tibial plate used in the knee prosthesis according to the second embodiment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following description, terms indicating specific directions and positions (for example, “up”, “down”, “right”, “left” and other terms including those terms) are used as necessary. . The use of these terms is to facilitate understanding of the invention with reference to the drawings, and the technical scope of the present invention is not limited by the meaning of these terms. Moreover, the part of the same code | symbol which appears in several drawing shows the same part or member.

<Embodiment 1>
1 and 2 show an artificial knee joint 1 according to the present embodiment.
The knee prosthesis 1 includes a femoral component 20 that is secured to the distal end of the femur and a tibial plate 10 that is secured to the proximal end of the tibia.

  The femoral component 20 includes a medial condyle 21 and a lateral condyle 22. Between the medial condyle 21 and the lateral condyle 22, an opening 23 and an elliptical spherical sliding portion 24 that connects the rear ends of the medial condyle 21 and the lateral condyle 22 are formed.

  The tibial plate 10 is fixed to the proximal end of the tibia via a metal tibial tray (not shown). The tibial plate 10 includes an inner pit 11 and an outer pit 12. A spine 13 and a concave sliding surface 14 constituting the rear surface of the spine 13 are formed between the inner pit 11 and the outer pit 12.

  When the knee prosthesis 1 is constructed from the femoral component 20 and the tibial plate 10, the medial condyle 21 of the femoral component 20 is disposed on the medial fovea 11 of the tibial plate 10, and above the lateral fossa 12 of the tibial plate 10. The lateral condyle 22 of the femoral component 20 is placed on the Also, the spine 13 of the tibial plate 10 is inserted into the opening 23 of the femoral component 20.

  When the knee prosthesis 1 is extended and bent, the medial condyle 21 and the lateral condyle 22 slide in the front-rear direction with respect to the medial fossa 11 and the lateral fossa 12. In accordance with the operation, the spine 13 also moves in the front-rear direction in the opening 23 (FIGS. 3A and 3B).

  4, 5, and 6 show a state when the knee prosthesis 1 of the present embodiment is bent from 0 ° to 150 °.

(1) Bending angle 0 ° (during extension): FIGS. 4 (a), 5 (a), 6 (a)
The spine 13 is inserted into the opening 23 of the artificial knee joint 1 during extension. The oval spherical sliding portion 24 is not in contact with the concave sliding surface 14, and the medial condyle 21 and lateral condyle 22 of the tibial plate 10 and the medial fossa 11 and lateral fossa 12 of the femoral component 20 are in contact with each other. ing.

(2) Bending angle 45 °: FIG. 4 (b), FIG. 5 (b), FIG. 6 (b)
The medial condyle 21 and the lateral condyle 22 slide in the forward direction with respect to the medial fossa 11 and the lateral fossa 12, and accordingly, the spine 13 moves backward in the opening 23. When bent to a bending angle of 45 °, the oval spherical sliding portion 24 formed at the rear ends of the medial condyle 21 and the lateral condyle 22 contacts the rear surface (concave sliding surface 14) of the spine 13. Since the width of the opening 23 is close to the width of the spine 13, the movement of the spine 13 is limited to 0 ° to 15 ° within the opening 23.

(3) Bending angle 90 °: FIG. 4 (c), FIG. 5 (c), FIG. 6 (c)
Since the spine 13 supports the front side of the elliptical spherical sliding portion 24, the dislocation of the femoral component 20 in the forward direction is prevented.
Further, the spine 13 is detached from the opening 23. Thereby, there is no restriction | limiting of the movement of the spine 13 by the opening 23, and it transfers to the rotation limitation of an elliptical spherical sliding part. Accordingly, the femoral component 20 can be rotated from 0 ° to 20 ° (FIG. 7A).

(4) Bending angle 120 °: FIGS. 4 (d), 5 (d), 6 (d),
The elliptical spherical sliding portion 24 slides with respect to the concave sliding surface 14. Further, when the oval spherical sliding portion 24 rotates in the outward direction, the femoral component 20 can be externally rotated by 0 ° to 25 ° (15) (FIG. 7B).

(5) Bending angle 150 °: FIGS. 4 (e), 5 (e), and 6 (e)
The elliptical spherical sliding portion 24 slides further with respect to the concave sliding surface 14. The femoral component 20 can rotate outwardly by 0 ° to 35 ° (FIG. 7C).

As described above, as the bending angle of the knee prosthesis 1 increases, the femoral component 20 can rotate more with respect to the tibial plate 10. The external rotation possible angle is determined by the relationship between the width 13 w of the spine 13 and the width 24 w of the elliptical spherical sliding portion 24.
In particular, it is preferable that the width 24w of the oval-spherical sliding portion 24 is widened toward the rear end. The external rotation state is the same as that of a natural knee joint (the external rotation angle is small at the time of light flexion, and the external rotation at the time of deep flexion). Can be realized (FIGS. 5C to 5E and FIGS. 7A to 7C). The relationship between the width 24w of the oval spherical sliding portion 24 and the external rotation angle will be described in detail below.

  At a bending angle of 90 ° (FIG. 5C), the width 24 w of the elliptical spherical sliding portion 24 is slightly wider than the width 13 w of the spine 13. for that reason. The angle at which the elliptical spherical sliding portion 24 can rotate on the rear surface of the spine 13 (concave sliding surface 14) is also slight (0 ° to about 20 °). That is, the femoral component 20 can also be externally rotated in an angle range of, for example, 0 ° to about 20 ° (FIG. 7A).

  When the bending angle is 120 ° (FIG. 5D), the width 24 w of the oval spherical sliding portion 24 with respect to the width 13 w of the spine 13 becomes wide. Therefore, the angle range in which the elliptical spherical sliding portion 24 can rotate is widened (for example, 0 ° to about 25 °). Therefore, the femoral component 20 can also be externally rotated in an angle range of, for example, 0 ° to about 25 ° (FIG. 7B).

  When the bending angle is 150 ° (FIG. 5E), the width 24w of the oval spherical sliding portion 24 with respect to the width 13w of the spine 13 is further increased. Therefore, the angle range in which the elliptical spherical sliding portion 24 can rotate is further widened (for example, 0 ° to 35 °). Therefore, the femoral component 20 can also be externally rotated in an angle range of 0 ° to 35 °, for example (FIG. 7B).

  As described above, when the width 24w of the oval-spherical sliding portion 24 becomes wider toward the rear end, it is possible to limit the external rotation at the time of slight bending and to improve the stability of the knee joint, and to increase the bending angle. Accordingly, the range of the external rotation angle can be expanded, and a large external rotation angle (for example, an external rotation angle of 25 ° to 35 ° at a bending angle of 135 ° or more) can be realized during deep bending. Therefore, the artificial knee joint 1 that functions in the same manner as a natural knee joint can be obtained.

  As shown in FIGS. 5 and 6, between the inner surface of the spine 13 and the inner fovea 11 (that is, the inner side surface of the spine 13) and between the outer surface of the spine 13 and the outer fovea 12 (of the spine 13). The outer side surface) is preferably a smooth curved surface. Thereby, when the femoral component 20 slides back and forth and when the femoral component 20 rotates, the surface between the medial condyle 21 and the lateral condyle 22 of the femoral component 20 and the side surface of the spine 13. The pressure is lowered, and the wear of the spine 13 can be suppressed. It is further preferable that the edge of the opening 23 of the femoral component 20 (in particular, the edge extending in the front-rear direction) is a curved surface having substantially the same curvature as the inner side surface and the outer side surface of the spine 13.

  Referring to FIG. 3 again, in the illustrated knee prosthesis 1, the elliptical spherical sliding portion 24 is not in contact with the tibial plate 10 when the knee prosthesis 1 is extended. When the knee prosthesis 1 is bent (for example, at a bending angle of 90 °), the oval spherical sliding portion 24 comes into contact with the concave sliding surface 14 (FIG. 3B). The oval spherical sliding portion 24 is slidable with respect to the concave sliding surface 14.

Further, the dimensional shape and the like of the artificial knee joint can be changed so that the bending angle at which the elliptical spherical sliding portion 24 and the concave sliding surface 14 come into contact is 90 ° or less.
For example, as shown in FIGS. 8A to 8F, the artificial knee joint 1 according to the present invention includes an artificial knee joint 1 in which the oval spherical sliding portion 24 and the concave sliding surface 14 are in contact with each other at a bending angle of 0 °. Contains. In the artificial knee joint shown in this figure, the elliptical spherical sliding portion 24 and the tibial plate 10 are in contact with each other in the entire range of the bending angle of 0 ° to 150 °. In addition, it is preferable that the bending angle which the elliptical spherical sliding part 24 and the concave sliding surface 14 contact exists in the range of 0-90 degrees. If the elliptical spherical sliding portion 24 and the concave sliding surface 14 do not contact each other up to a bending angle exceeding 90 °, it is not preferable because the stability of the artificial knee joint 1 becomes too low.

As shown in FIG. 3 (a), the artificial knee joint 1 of the present embodiment has a top portion 13t of the spine 13 from when the knee joint is extended (flexion angle 0 °) to deep flexion (flexion angle 135 °). It is at a position higher than the lowest point of the oval spherical sliding portion 24. (This can be expressed as “JD> 0” by using “jumping distance JD”, which will be described later.) Therefore, when the femoral component 20 is about to dislocate forward, the elliptical spherical sliding portion 24 moves to the spine 13. To touch. Therefore, the femoral component 20 can be prevented from dislocation in the forward direction.

In order to more effectively suppress the dislocation of the femoral component 20 in the anterior direction, the top portion 13t of the spine 13 is at a position higher than the lowest point of the elliptical spherical sliding portion 24 by about 1 mm or more (JD > 1 mm) is more preferred.

  When the artificial knee joint 1 is bent, the oval spherical sliding portion 24 comes into contact with the rear surface (concave sliding surface 14) of the spine 13 (FIG. 3B). Although a forward force is applied to the femoral component 20, since the oval spherical sliding portion 24 is in contact with the spine 13, the dislocation of the femoral component 20 in the forward direction hardly occurs.

  In the knee prosthesis 1 using the tibial plate 10 having the spine 13, the spine 13 is inserted from the opening 23 of the femoral component 20 and the inside of the femoral component 20 (region where the distal end of the femur is fixed). Protrusively. Therefore, it is necessary to form a space 92 for accommodating the spine 13 at the distal end 91 of the femur 90 so that the spine 13 does not contact the femur 90 as shown in FIG. The space 92 is formed between the medial condyle and the lateral condyle of the femur 90 (between the condyles) and extends in the anteroposterior direction.

  In order to keep the strength of the femur 90 high, it is preferable to reduce the amount of osteotomy. For this purpose, it is desirable to reduce the amount of protrusion of the spine 13 protruding inside the femoral component 20 and to narrow the space 92 for accommodating the spine 13. On the other hand, if the protruding amount of the spine 13 is reduced, the femoral component 20 is easily dislocated in the forward direction. The ease of dislocation of the femoral component 20 can be known from the jumping distance.

  Jumping distance is the “height” of the obstacle that must be overcome when the femoral component 20 is dislocated forward. In the knee prosthesis 1 of the present invention, the jumping distance corresponds to the difference in height between the lowest point of the elliptical spherical sliding portion 24 and the apex 13t of the spine 13.

A specific example of the jumping distance JD will be described with reference to FIG.
In the knee prosthesis 1 shown in FIG. 10A, the position of the top portion 13 t of the spine 13 is higher than the position of the lowest point (corresponding to the lower end 24 b in this figure) of the oval spherical sliding portion 24. Thus, when there is an obstacle that must be overcome when the femoral component 20 is dislocated, the jumping distance JD takes a positive value (JD> 0) (this is referred to as “positive jumping distance”). "). The absolute value of the jumping distance (referred to as “the magnitude of the jumping distance”) is equal to the difference in height between the top portion 13 t of the spine 13 and the lower end 24 b of the elliptical spherical sliding portion 24.

As is apparent from FIG. 10B, the artificial knee joint 1 at a bending angle of 90 ° also has a positive jumping distance JD. Further, the difference between the top portion 13t of the spine 13 and the lowest point of the elliptical spherical sliding portion 24 is larger than the difference in FIG. Therefore, the size of the jumping distance JD in FIG. 10B is larger than that in FIG. As the jumping distance JD is larger, the femoral component 20 is less likely to dislocation in the anterior direction. Therefore, the femoral component 20 is less likely to dislocation at a bending angle of 90 ° than at a bending angle of 0 °.
In the knee prosthesis, the deep flexion tends to dislocate the femoral component 20 in the anterior direction when the flexion is low. Since the artificial knee joint 1 of the present invention has a large jumping distance in deep flexion, dislocation of the femoral component 20 in deep flexion can be effectively suppressed.

  Further, as shown in FIG. 10C, the artificial knee joint 1 at a bending angle of 150 ° also has a positive jumping distance. And the magnitude | size of the jumping distance of the artificial knee joint 1 of FIG.10 (c) is equivalent to or more than the thing of FIG.10 (b). Therefore, at the bending angle of 150 °, the femoral component 20 is less likely to dislocation than the bending angle of 90 ° or more.

  As can be seen from FIG. 10, in the knee prosthesis 1 of the present invention, the jumping distance is positive from low flexion to deep flexion, so that dislocation of the femoral component 20 can be suppressed in both low flexion and deep flexion. Furthermore, since the jumping distance in the deep flexion is large, the dislocation of the femoral component 20 in the deep flexion can be effectively suppressed.

  In the conventional knee prosthesis 1P as shown in FIG. 11, the lowest point of the cam 240P of the femoral component 200P is higher than the apex 130Pt of the spine 130P at a bending angle of 0 ° (FIG. 11A) ( That is, it has a negative jumping distance JD (JD <0). Therefore, dislocation of the femoral component 200P cannot be suppressed.

  At the bending angles of 90 ° (FIG. 11B) and 150 ° (FIG. 11C), the artificial knee joint 1P has a positive jumping distance JD and can suppress the dislocation of the femoral component 200P. However, it is necessary to increase the height of the spine 130 in order to effectively suppress the dislocation of the femoral component 200 in the forward direction by increasing the jumping distance JD, so that the spine 130P is accommodated. The space 920P becomes wider.

Further, in another conventional knee prosthesis 1Q as shown in FIG. 12, the bending angle is 0 ° (FIG. 12A), the bending angle is 90 ° (FIG. 12B), and the bending angle is 150 ° (FIG. 12C). All of)) have a positive jumping distance JD.
However, the magnitude of the jumping distance at the bending angle of 150 ° is too small. Therefore, there is a risk of dislocation of the femoral component 200Q during deep flexion.
Further, since the action point O is near the top of the spine 130Q (low strength), the spine 130Q is easily damaged.

On the other hand, as shown in FIG. 10, in the artificial knee joint 1 of the present invention, the elliptical spherical sliding portion 24 sinks into a low position (concave sliding surface 14) of the spine 13. Even if it is lowered, a sufficiently large jumping distance JD can be secured.
And since the height of the spine 13 is low, the space 92 for the spine 13 can be made very narrow compared to the conventional case.

  As described above, the artificial knee joint 1 of the present invention supports the elliptical spherical sliding portion 24 of the femoral component 20 with the rear surface (concave sliding surface 14) of the spine 13 at the time of bending, thereby increasing the height of the spine 13. Even if the height is kept low, the jumping distance can be made sufficiently large. Therefore, dislocation of the femoral component 20 in the forward direction can be effectively suppressed while reducing the amount of osteotomy of the femur 90.

  Further, as is clear by comparing FIGS. 10 (b) to 10 (c) with FIGS. 11 (b) to 11 (c) and FIGS. 12 (b) to 12 (c), the femoral components 20, 200P, 200Q The thicknesses of the spines 13, 130P, and 130Q receiving the operating point O are completely different. The spine 13 of the present embodiment is two to three times thicker than the conventional spines 130P and 130Q. Therefore, the spine 13 of the present embodiment is not easily damaged even when subjected to a large stress F.

In particular, in a bending position with a bending angle of 90 ° or more, the position in the height direction of the action point O between the elliptical spherical sliding portion 24 and the 14-concave sliding surface is the height T ₀ of the bottom of the outer fovea 12 and the outer side. Preferably, it is between a height T _2/3 at a position 2/3 of the height T ₁ of the top 13t of the spine 13 measured from the bottom of the fovea 12. Here, the “bottom part of the outer fovea 12” refers to the lowest part of the outer fovea 12.
Since the thickness of the spine 13 is thick between the bottom height T ₀ and the height T _2/3 , the spine 13 is not easily damaged even when receiving a large stress F from the action point O.

  Further, as illustrated in detail in FIG. 13, it is desirable that at least a part of the oval spherical sliding portion 24 of the femoral component 20 protrudes outward from the lateral condyle 22. In FIG. 13, the oval spherical sliding portion 24 protrudes outward from the lateral condyle 22 by a dimension A in the rearward direction and a dimension B at the upper end. If the elliptical spherical sliding part 24 protrudes outward from the lateral condyle 22 as shown in the figure, the elliptical spherical sliding part 24 can sink into a lower position (concave sliding surface 14) of the spine 13. The jumping distance JD can be made larger and the position of the action point O can be made lower.

  As shown in FIG. 14, even when the bending angle of the artificial knee joint 1 is 90 ° or more, the action point O is at the same height as the outer fovea 12 or at a position lower than the outer fovea 12. Therefore, a large jumping distance JD can be secured, and it can be seen that the femoral component 20 is difficult to dislocate in the anterior direction even with deep flexion. Moreover, since the thickness of the spine 13 that supports the stress F is also thick, it can be seen that the spine 13 is not easily damaged even when deep bending is repeated.

<Embodiment 2>
The artificial knee joint 1 of the present embodiment further facilitates external rotation during bending. The shape of the edge portion on the rear end side of the tibial plate 10 is different from that of the first embodiment. Other configurations are the same as those in the first embodiment.

  In the present embodiment, the tibial plate 10 is preferably provided with a rear end sliding surface at the rear end side edge of the outer fossa 12 in order to promote external rotation during deep bending.

In the present embodiment, as shown in FIG. 15, the rear end portion of the outer fossa 12 of the tibial plate 10 is preferably chamfered by a flat surface or a curved surface. This chamfered surface forms a rear end sliding surface (rear end sliding curved surface 12c or rear end sliding plane 12p).
In the present specification, the “rear end sliding curved surface 12c” includes all curved rear end sliding surfaces. As will be described later, the rear end sliding surface is a surface on which the outer condyle 22 of the femoral component 20 slides. Therefore, in order to stably slide the lateral condyle 22, the rear end sliding curved surface 12c is preferably a concave curved surface.
Further, in this specification, the “rear end sliding plane 12p” includes all planar rear end sliding surfaces.

  Hereinafter, the rear end sliding surface 12c of the present invention will be described mainly by exemplifying the rear end sliding curved surface 12c. Unless otherwise specified, “rear end sliding curved surface 12c” can be read as “rear end sliding plane 12p”.

  The rear end sliding curved surface 12 c is a surface for sliding with the lateral condyle 22 of the femoral component 20, similarly to the lateral fossa 12. The lateral fossa 12 is a surface on which the lateral condyle 22 slides before the lateral condyle 22 is subluxed. The posterior end sliding curved surface 12c is a surface on which the outer condyle 22 slides after the outer condyle 22 is subluxed (in FIG. 15, the outer condyle 22 is the surface of the outer fossa 12 and the posterior end sliding curved surface 12c. The sliding route 12x when sliding on is shown).

  In the present specification, “subluxation” means that the lateral condyle 22 or the medial condyle 21 of the femoral component 20 detaches backward from the lateral fossa 12 or the medial fossa 11 of the tibial plate 10. Subluxation of the lateral condyle 22 brings the relative movement of the femoral component 20 and the tibial plate 10 closer to a healthy knee joint movement (external rotation of the femur). Therefore, the tibial plate 10 has the rear end sliding curved surface 12c, so that the tension balance of the ligament of the knee can be made close to a healthy knee joint, and deep bending similar to a natural knee joint is possible. To do.

Providing the rear end sliding curved surface 12c on the tibial plate 10 not only provides a sliding surface after the lateral condyle 22 is subluxed, but also promotes the subluxation of the lateral condyle 22.
The femoral component 20 rolls over the tibial plate 10 due to flexion of the knee joint. When the artificial knee joint 1 is deeply bent, the lateral condyle 22 or the medial condyle 21 of the femoral component 20 is sub-dislocated from the lateral fossa 12 or the medial fossa 11 of the tibial plate 10. At this time, if the rear end sliding curved surface 12 c is formed at the rear end of the outer fossa 12, the outer condyle 22 is subluxed before the inner condyle 21. The artificial knee joint 1 according to the present embodiment can easily achieve deep flexion by promoting subluxation.

  When the lateral condyle 22 is subluxed from the lateral fossa 12, the knee prosthesis 1 is unstable compared to a state where the subluxation is not performed. In the knee prosthesis 1 according to the present embodiment, when the lateral condyle 22 is subluxed, the oval spherical sliding portion 24 is in contact with the concave sliding surface 14 of the tibial plate 10. It is advantageous to make it. In addition, after the lateral condyle 22 is subluxed, the femoral component 20 can be stably rotated around the elliptical spherical sliding portion 24 (see FIG. 16A). Further, by externally turning the elliptical spherical sliding portion 24 as a fulcrum, the external rotation is smooth and the resistance to external rotation (for example, resistance at the time of subluxation) is small.

  16 (a) shows the artificial knee joint 1 having the rear end sliding curved surface 12c, and FIG. 16 (b) shows a rear end sliding plane 12p that is not directed inward and rearward as a comparative example. A prosthetic knee joint 1 'is shown. The artificial knee joint 1 shown in FIG. 16A can smoothly rotate outward.

In the present embodiment, it is preferable that the rear end sliding curved surface 12c is oriented inward and rearward.
Here, the “direction of the rear end sliding curved surface 12c” will be described in detail with reference to FIG.

FIG. 17 is an enlarged view of the rear end sliding curved surface 12c (part I in FIG. 15) of the outer fovea 12.
FIG. 17 illustrates the direction of the normal line (normal vector N) of the trailing end sliding curved surface 12c at an arbitrary measurement point P. In this specification, the “direction of the rear end sliding curved surface 12 c” is the direction of the normal vector N. Note that "normal vector N" as discussed herein, one of the two normal vectors that can be drawn with respect to the rear end sliding curved surface 12c, with the normal vector comprising an upward component N _S is there.

In Figure 17, first, to decompose the normal vector N in the horizontal component N _H was projected upward component N _S and the horizontal plane H, then the horizontal component N _H and an inner direction component N _m and rear direction component N _P Has been broken down. Using these component marks, “the rear end sliding curved surface 12c is oriented inward and rearward” means that the horizontal component _NH of the normal vector N of the rear end sliding curved surface 12c is the inner direction component N. and _m, is to include a backward component N _P.

  When a force is applied to the posterior end sliding curved surface 12c as shown in FIG. 17 by the outer condyle 22 of the femoral component 20, the drag force is in a direction perpendicular to the posterior end sliding curved surface 12c (matching the direction of the normal vector N). Will occur. This drag force exerts a force in the medial posterior direction on the lateral condyle 22. Therefore, the lateral condyle 22 is easy to move toward the medial posterior direction. That is, the external rotation of the lateral condyle 22 is promoted.

  Further, when the lateral condyle 22 is subluxed and the lateral condyle 22 is rotated outwardly, the lateral condyle 22 is supported by the rear end sliding curved surface 12c, so that smooth external rotation is realized.

  Thus, the rear end sliding curved surface 12c is oriented inwardly and rearwardly, so that the external rotation after the outer condyle 22 is sub-dislocated is promoted and smoothly rotated externally.

  As shown in FIGS. 18 and 19, the sliding route 12x of the outer condyle 22 sliding on the rear end sliding surface (the rear end sliding curved surface 12c or the rear end sliding plane 12p) can be approximated as an arc. 18 and 19, the arc of the sliding route 12 x is depicted as an arc having a radius R with the center O of the concave sliding surface 14 as the center.

18 and 19 show horizontal components N _{H1 to} N _H3 of the normal vector N of the rear end sliding curved surface 12c at arbitrary points (points P _{1 to} P ₃ ) on the sliding route 12x. Yes. The horizontal components N _{1 to} N ₃ illustrated in FIGS. 18 and 19 are all directed toward the inner rear side.

In FIG. 18, all three horizontal components N _{H1 to} N _H3 are directed in the same direction. That is, the rear end sliding surface in FIG. 18 is a rear end sliding plane 12p formed of a flat surface, and faces almost the same direction at any position.

On the other hand, in FIG. 19, the three horizontal components N _{H1 to} N _H3 are directed in different directions. That is, the rear end sliding surface in FIG. 19 is a rear end sliding curved surface 12c formed of a curved surface. As shown in FIG. 19, it is preferable that the inward direction component of the horizontal component _NH increases as the point P is located rearward. Specifically, when the horizontal components N _H1 and N _H2 at each of the points P ₁ and P ₂ are compared, the point P ₂ is behind the point P ₁ , and therefore the horizontal component N _H2 is the horizontal component N _H1 . It is preferable that the inner direction component is larger than that (directed more in the inner direction).
As the lateral condyle 22 moves rearward (that is, the bending angle of the artificial knee joint 1 increases), the force for directing the lateral condyle 22 in the medial direction increases, and accordingly, the lateral condyle 22 also increases the external rotation angle. be able to.
As shown in FIG. 19, the horizontal components N _{1 to} N ₃ coincide with the tangential direction of the sliding route 12x at the points P _{1 to} P _3, but the present invention is not limited to this.

For comparison, the rear end portion of the medial fossa 11 of the tibial plate 10 will also be described.
When the artificial knee joint 1 is deeply bent, the rear end portion of the medial fossa 11 of the tibial plate 10 may contact the femoral component 20 or the femur. Therefore, it is preferable to chamfer the rear end portion of the inner cavity 11 with the flat surface 11p. (See FIG. 15). FIG. 20 shows an enlarged view of the plane 11p (part II in FIG. 15).
As can be seen from FIG. 20, the normal vector N ′ drawn to an arbitrary point P ′ on the plane 11p includes an upward component N _S ′ and a backward component N _P ′. However, the normal vector N ′ does not include the inner direction component N _m ′. That is, the plane 11p is directed rearward but is not directed rearwardly inside.

FIG. 21 (a), in the longitudinal direction through the lowest point of the outer fossa 12 (coincides with the position Q _2), is an end view of the tibial plate 10. FIG. 21B is an end view of the tibial plate 10 in the front-rear direction passing through the lowest point of the medial fossa 11.
As shown in FIGS. 21A and 21B, in the tibial plate 10 used in the artificial knee joint 1 of the present invention, the lateral fossa 12 and the medial fossa 11 are curved surfaces.

  In the present invention, it is preferable that the radius 12r of the posterior region 12PS of the outer pit 12 is larger than the radius 11r of the posterior region 11PS of the inner pit 11 (see FIGS. 21A and 21B).

In this specification, "back region 12PS outside fossa 12", is a region of the outer fossa 12 located behind the position _{Q 2} in FIG. 21 (a). In addition, "back region 11PS inner fossa 11" is a region of the inner fossa 11 located behind the position to _{Q 1} FIG 21 (b).
The “position Q ₂ ” of the lateral fossa 12 refers to the lowest position of the lateral condyle 22 (broken line in FIG. 21A) of the femoral component 20 when the artificial knee joint 1 is extended. This is the position in contact with the lateral fossa 12. Further, the “position Q ₁ ” of the medial fossa 11 means that the lowest position of the medial condyle 21 (broken line in FIG. 21B) of the femoral component 20 is the position of the tibial plate 10 when the artificial knee joint 1 is extended. This is the position in contact with the medial fossa 11.

  Further, in this specification, the “radius of the rear region 12PS of the outer fossa 12” is the radius of the rear region 12PS in the cross section of the outer fovea 12 in the front-rear direction (see FIG. 21A). Similarly, the “radius of the rear region 11PS of the inner fossa 11” is a radius of the rear region 11PS in the cross-section in the front-rear direction of the inner fossa 11 (see FIG. 21B).

When the radius 12r of the posterior region 12PS of the outer fossa 12 of the tibial plate 10 is larger than the radius 11r of the posterior region 11PS of the inner fossa 11 as shown in FIGS. The inclination of 12PS becomes gentler than the inclination of the rear region 11PS of the inner fovea 11. That is, when the heights of the medial fossa 11 and the lateral fossa 12 are made to coincide with each other in the vicinity of the center of the tibial plate 10 in the front-rear direction (for example, positions Q ₁ and Q ₂ ), the positions from the positions Q ₁ and Q ₂ toward the rear When moved equidistantly, the height of the outer fossa 12 is always lower than the height of the inner fovea 11. Therefore, when the femoral component 20 rolls back, the lateral condyle 22 is more easily moved backward than the medial condyle 21 of the femoral component 20. As a result, when rollback occurs, the lateral condyle 22 is more likely to be positioned posteriorly than the medial condyle 21, and the femoral component 20 is likely to rotate outward. Further, since the difference in height between the outer and inner pits 12 and 11 of the tibial plate 10 increases toward the rear, the bending at which the rollback proceeds further than the bending angle (for example, 90 °) at which the rollback starts to occur. An angle (for example, 135 °) is easier to externally rotate. By using such a tibial plate 10, it is possible to obtain an artificial knee joint that is easy to rotate externally by deep bending rather than mild bending.

In the outer fossa 12, the radius of the rear region 12PS is preferably larger than the radius of the front region 12AN. The radius of the rear region 11PS can be substantially equal to the radius of the front region 11AN, but the radius of the rear region 11PS is preferably larger than the radius of the front region 11AN. In this specification, "front region 12AN of the outer fossa 12" is an area in front of the position _{Q 2,} "front region 11AN of the inner fossa 11" is an area in front of the position _{Q 1.}

  As shown in FIG. 21A, it is preferable that a curved surface is formed between the lateral fossa 12 and the rear end sliding surface (the rear end sliding curved surface 12c or the rear end sliding flat surface 12p). When subluxing from the lateral fossa 12 to the rear end sliding surface, the impact on the artificial knee joint can be reduced.

Further, longitudinal cross-section through the lowest point of the outer fossa 12 (coincides with the position _{Q 2)} (FIG. 21 (a), the reference 22) at the rear end sliding surface (rear end sliding curved surface 12c or rear The length 12d in the front-rear direction of the sliding plane 12p) is preferably 1/5 or less of the length in the front-rear direction of the tibial plate 10. Thereby, the bending angle at which the lateral condyle 22 of the femoral component 20 is sub-dislocated from the lateral fossa 12 to the rear end sliding surface can be set within a relatively large bending angle range (for example, 90 ° to 150).

  Further, in the cross-section in the front-rear direction passing through the lowest point of the outer fossa 12 (see FIGS. 21A and 22), the inclination of the rear end sliding surface (the rear end sliding curved surface 12c or the rear end sliding plane 12p). The angle is preferably 20 ° or more. Here, the “inclination angle of the rear end sliding surface” means the rear end sliding surface when observed in a cross-section in the front-rear direction passing through the lowest point of the outer fossa 12 (FIGS. 21A and 22). Refers to the maximum tilt angle.

FIG. 23A shows an artificial knee joint 1 using a tibial plate 10 in which the inclination angle of the rear end sliding surface (for example, the rear end sliding curved surface 12c) is 20 ° or more (about 35 ° in this figure). is there. FIG. 23B shows the knee prosthesis 1 using the tibial plate 10 whose inclination angle of the rear end sliding surface is less than 20 degrees (in this figure, about 10 degrees).
When the femoral component 20 is bent at 150 °, in FIG. 23A, after subluxation, the contact range between the lateral condyle 22 of the femoral component 20 and the rear end sliding curved surface 12c of the tibial plate 10 is wide (surface). Contact). Therefore, the lateral condyle 22 can slide smoothly on the rear end sliding curved surface 12c. On the other hand, in FIG.23 (b), the lateral condyle 22 and the posterior edge part of the rear end sliding curved surface 12c are contacting.

  Thus, when the inclination angle of the rear end sliding curved surface 12c of the tibial plate 10 is 20 ° or more, the outer condyles 22 can be received by the surface of the rear end sliding curved surface 12c even if deep bending is performed. The femoral component 20 slides more smoothly.

  As shown in FIG. 24, the rear end sliding curved surface 12c is preferably formed in the range of an angle θ = 5 to 30 ° with the center O of the concave sliding surface 14 as the center. Thereby, the external rotation of the femoral component 20 is likely to occur within the range of the natural external rotation angle (5 to 30 °) of the knee.

  The artificial knee joint 1 according to the present embodiment can naturally rotate the femoral component 20 at the time of deep flexion. Therefore, even after replacement with the artificial knee joint 1, natural knee joint motion can be realized. it can.

DESCRIPTION OF SYMBOLS 1 Artificial knee joint 10 Tibial plate 11 Medial fossa 11p Resection surface of medial fossa 11r Radius of medial fossa 12 Outer fovea 12c Sliding curved surface of rear end 12p Sliding plane of rear end 12r Radius of back of external fossa 13 Spine 13t Top 14 Concave sliding surface 20 Femoral component 21 Medial condyle 22 Outer condyle 23 Opening 24 Ellipsoidal sliding part 24b Lower end of elliptical sliding part

Claims (8)

A knee prosthesis comprising: a femoral component secured to the distal end of the femur; and a tibial plate secured to the proximal end of the tibia and slidably receiving the femoral component;
The femoral component has a medial condyle and a lateral condyle;
Between the medial condyle and the lateral condyle,
An opening,
An oval spherical sliding part that connects the rear ends of the medial condyle and the lateral condyle and slides with respect to the tibial plate during knee flexion is formed,
The tibial plate comprises a medial fistula for receiving the medial condyle and a lateral fossa for receiving the lateral condyle;
Between the medial fossa and the lateral fossa,
A spine that moves in the front-rear direction corresponding to the bending / extending motion of the knee joint, and that contacts the elliptical spherical sliding portion when the knee joint is bent,
Forming a rear surface of the spine, and a concave sliding surface that slidably receives the elliptical spherical sliding portion; and
The width of the oval-spherical sliding portion, and Tsu a wider toward the rear end from said opening,
The tibial plate has a rear end sliding surface for sliding the outer condyles of the femoral component by chamfering the rear end of the outer fossa with a flat surface or a curved surface,
An artificial knee joint characterized in that the rear end sliding surface is oriented inward and rearward .   The rear end sliding surface includes a curved surface,
  The curved surface at the second point at a first point on the sliding route of the rear end sliding surface on which the outer condyle slides and a second point located behind the first point The artificial knee joint according to claim 1, wherein a horizontal component of the normal line is oriented in an inward direction with respect to a horizontal component of the normal line of the curved surface at the first point. The artificial knee joint according to claim 1, wherein the rear end sliding surface includes a concave curved surface. The artificial knee joint according to any one of claims 1 to 3, wherein a rear end portion of the medial fossa is chamfered by a plane directed rearward. The artificial part according to any one of claims 1 to 4 , wherein, at a bending angle of 0 ° to 150 °, a top portion of the spine is at a position higher than a lowest point of the elliptical spherical sliding portion. Knee joint. Between the inner fossa and the inner surface of the spine, and between the outer fossa and an outer surface of the spine, according to any one of claims 1 to 5, characterized in that it is a curved surface Artificial knee joint. In a bending position with a bending angle of 90 ° or more, the position in the height direction of the action point between the elliptical spherical sliding part and the concave sliding surface was measured from the height of the outer fossa bottom and the outer fossa bottom. The knee prosthesis according to any one of claims 1 to 6 , wherein the knee prosthesis is between 2/3 of the height of the top of the spine. The artificial knee joint according to any one of claims 1 to 7 , wherein at least a part of the oval spherical sliding portion protrudes outward from the lateral condyle.

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