JPH10146353A - Artificial knee joint - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable high bending, and enhance stability and durability of a knee by slidably arranging a bearing insert between a thighbone component and a tibia component, and specifying a shape or the like of this bearing insert. SOLUTION: An artificial knee joint is composed of a thighbone component 1, a tibia component 5 and an integral bearing insert 6 on which an upper surface presents a recessed surface and an under surface presents a projecting surface and which is composed of polyethylene. In this case, the bearing insert 6 is formed so that a line connecting the upper ends of the bearing insert 6 in the longitudinal direction is inclined backward at an angle of about 1 deg. to 25 deg. to a surface vertical to the central axis of the tibia component 5, and in its upper surface, the whole is formed as a recessed surface having a radius of curvature of about 20mm to 1000mm. On the other hand, the thighbone component 1 is formed so that both branch parts branched off so as to stride over the recessed surface in a depth of the recessed part not less than about 10mm are supported by the integral bearing insert 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an artificial knee joint, and more particularly, to an artificial knee joint capable of high bending and having stability and durability of the knee.

[0002] Knee replacement is one of the most effective treatments for destructive knee joint disorders. Conventionally, there is an artificial knee joint capable of high flexion described in Japanese Patent Publication No. 5-72823. In the fully flexed state, as shown in the schematic diagram of FIG. Tibial component 5 and patella component 1 made of plastic such as polyethylene
0, the anterior upright portion 1 of the femoral component
a, the lower surface 1b and the sliding surface of the rear standing portion 1c each have a gentle curved contour. 2 is a fixing peg for fixing the femoral component 1 to the femur. On the other hand, the tibial component 5 has a concave surface 5a for sliding the femoral component 1, and is fixed to the tibia (not shown) by the stem.

[0003] In the artificial knee joint disclosed in the above-mentioned publication, the femoral component 1 has a concave surface 1d at the center of the lower surface serving as a sliding surface with the patella. By specifying this shape, the movement of the prosthetic joint in bending is determined. The maximum width has been increased.
It is then described that the shape and dimensions of the prosthesis component are such that the tension of the quadriceps is approximately equal to the tension in the natural joint throughout the flexion of the prosthetic joint.

[0004] Further, although not aimed at high bending, a knee joint part having a shape substantially similar to that of FIG. 2 is also known from Japanese Patent Publication No. 3-195550.

[0005] The knee performs not only a simple hinge movement but also an axial rotation and a rolling movement in the front-rear direction. In particular, when bending the knee, a rollback motion in which the contact surface of the femur and the tibia and the rotation axis move backward are indispensable for the high bending of the knee.

[0006] Considering that the oriental lifestyle requires a large flexion such as a near-seat flexion at the knee joint, an alumina femoral component and a titanium alloy tibial component having polyethylene fixed on its upper surface. Thus, an artificial knee joint is formed by using such a method, and a sliding surface between these components is designed to be highly bendable. However, in this method, there is a concern that the stress applied to the polyethylene at the time of high bending is increased, so that the wear is promoted.

[0007]

Therefore, conventionally,
In addition to being capable of high flexion, no knee prosthesis has been devised which achieves knee stability and which overcomes the problem of wear of polyethylene and which is durable. The inventor has
In order to improve the reliability and function of the artificial knee joint, the following inventions were developed, focusing on the fact that it is necessary to reduce the wear of polyethylene and the like used for the sliding parts when the knee bending angle increases. did.

[0008]

SUMMARY OF THE INVENTION A first aspect of the present invention is a thigh fixed to a distal part of a femur, the sliding surface comprising a front standing portion, a lower portion, and a rear standing portion, each of which forms a gentle curved surface. A bone component having a concave portion serving as a sliding surface with the patella or the patella component in the lower center portion,
With a femoral component made of insert metal, fixed to the tibia proximally, with a concave upper surface, a tibial component made of insert metal, a concave upper surface, a convex lower surface, and an integral bearing insert made of polyethylene. A knee joint prosthesis, wherein the bearing insert is slidably mounted between the femoral component and the tibial component with respect to the components, the bearing insert being located substantially at the center of the tibial component. The line connecting the upper end of the bearing insert in the front-rear direction to the plane perpendicular to the central axis of the tibial component
The bearing insert is inclined rearward so as to form an angle of 25 ° from, and the upper surface of the bearing insert is entirely concave with a radius of curvature of 20 mm to 1000 mm, and the femoral component is An artificial knee joint having a depth of 10 mm or more, wherein both branch portions branched so as to straddle a concave surface sliding with the patella or the patella component are supported by the integral bearing insert; A second aspect of the invention is a femoral component comprising a front standing portion, a lower portion, and a rear standing portion, each of which has a gentle curved surface, and which is fixed to a distal portion of a femur. A concave portion serving as a sliding surface for the patella or the patella component; a femoral component made of insert metal; A knee prosthesis comprising a tibial component having a flat top surface and made of insert metal; a concave top surface and a flat bottom surface and an integral bearing insert made of polyethylene; The bearing insert is slidably mounted between the femoral component and the tibial component relative to the components and ties the upper end of the bearing insert longitudinally to a plane perpendicular to the central axis of the tibial component. The lines are inclined rearward so that the lines make an angle of 1 ° to 25 ° rearward, and the upper surface of the bearing insert is generally 20 mm to 1000
mm, wherein the femoral component has a depth of 10 mm or more, and the bifurcation bifurcated so as to straddle a patella or a concave surface that slides with the patella component. An artificial knee joint supported by a bearing insert. Hereinafter, the present invention will be described in detail.

In a knee joint having high flexion, the sliding of the femoral component and the tibial component using polyethylene or the like due to the roll-back motion requires the conventional structure to move between the former convex surface and the latter flat surface. Since the contact is made and the contact is made with a small contact area, polyethylene is liable to wear and fatigue. For this purpose, in the present invention, a bearing insert made of polyethylene is slidably interposed between the femoral component and the tibial component with respect to both components. Therefore, when the stress applied to the bearing insert increases and the contact position between the femoral component and the bearing insert and the rotation axis move backward in the high bending state of the knee of about 150 to 170 °, the bearing insert slides backward. And the stress applied to the bearing insert decreases accordingly. Next, when the bending angle decreases from the maximum bending angle (about 170 °), a phenomenon in the opposite direction occurs, and the bearing insert moves forward and returns to the original position.

In order to smooth the movement of the bearing insert when sliding between the femoral component and the tibial component as described above, it is preferable to employ the following configurations. That is, the entire upper surface of the bearing insert is a concave surface having a radius of curvature of 20 to 1000 mm, and the rearward inclination angle of the bearing insert is determined by moving the upper end of the bearing insert back and forth with respect to a plane perpendicular to the central axis of the tibia component. The line connecting the directions must be inclined backward by 1 ° to 25 °. The posterior standing portion of the femoral component has large bulges. A deep dent that forms a sliding surface with the patella or the patella component is formed in the center of the lower surface of the femoral component.

[0011]

FIG. 1 shows an embodiment of the artificial knee joint according to the first invention.
This will be described with reference to FIG. The patella is not shown,
Also, the patella component 10 (see FIG. 2) can be an element of a knee prosthesis. In FIG. 1, 3 is a femur, 4 is a tibia, and 6 is a bearing insert. The bearing insert 6 is made of polyethylene and is slidably sandwiched between the femoral component 1 and the tibial component 5, each made of implant metal. In the upright position shown in FIG. 1, the femoral component 1 pushes the bearing insert 6 slightly back on the inclined surface of the tibial component 5. On the other hand, in FIGS. 3 to 5 schematically showing the bending of the knee, the knee is 90 to 130 ° (FIG.
With bending in the range of 5), the frictional force from the femoral component 1 causes the bearing insert 6 to slide slightly forward on the upper surface of the tibial component 5 to a position where the tension of the collateral ligament 13 of the knee is relieved. To reach. Similar sliding occurs in the case of the tibial component 5 and the bearing insert 6 that slide on a flat surface (not shown).

The upper surface of the bearing insert 6 shown in FIG. 1 has a concave surface in which one or more circular arcs having a radius of curvature of 20 mm to 1000 mm are smoothly connected. Therefore, when an axial load due to weight is applied to the bearing insert 6, the knee moves to a stable position, and stable walking can be performed even when the surrounding tissue is weak. Here, the femoral component 1 and the bearing insert 6 have a radius of curvature of less than 20 mm or more than 1000 mm.
And the contact area becomes small. The preferred radius of curvature is 20 to 100 mm.

Further, the inclined arrangement of the bearing insert 6 is determined as follows. In FIG. 7, the line aa is the central axis of the tibial component 5. cc is a plane perpendicular to the central axis of the tibial component. b
The -b line is a line connecting the upper end of the bearing insert 6 back and forth. In the first invention shown in FIG. 7A, when the bearing insert 6 is located substantially at the center of the tibial component 5, the angle (α) formed by the line bb with respect to the cc plane is set to 1 downward. ２５25 °. Also,
In the case of the second invention shown in FIG. 7B, the angle (α) is lowered by 1 to 25 ° regardless of the position of the bearing insert.
become.

Hereinafter, the embodiment of the first invention in which the upper surface of the tibial component and the lower surface of the bearing insert are curved will be described with reference to FIGS. It should be understood that the present invention can be applied to the invention except for this shape and the like. Further, as shown in FIGS. 5 and 6, when the bending angle is increased from 130 ° to 170 °, the contact position between the femoral component 1 and the bearing insert 6 moves to the posterior surface of the latter because the rollback motion occurs. . At this time, the bearing insert 6 slidably sandwiched between the components 1 and 5 moves backward on the tibial component 5 with the rollback movement. With this movement, the bearing insert 6 is rubbed by the two components 1, 5, but the wear caused by this is significantly less and almost negligible than the wear when the stress is locally high on the surface of the fixed insert. It is about.

In addition, in the present invention, the rear standing portion 1c (FIG. 8) of the femoral component 1 is provided with a swelling so that the femoral component 1 and the bearing insert 6 can be provided even at a high bending position of 150 to 170 °.
And a smooth sliding surface can be maintained.

In order to reduce the pressure between the patella component 10 and the femoral component at the time of high bending shown in FIG. 9, the depth of the sliding surface of the femoral component 1 with the patella component 10 is set to 10 mm or more. It is necessary. FIG. 10 is a view showing a preferred embodiment of the femoral component 1 and shows that a sliding surface 1e with a deep patella of d = 15 mm or more is formed in the center of the lower part 1b.

Next, the shape of the bearing insert of the first invention will be described with reference to FIGS. 11 (plan view), FIG. 12 (sectional view taken along line aa), and FIG. 13 (sectional view taken along line bb). The bearing insert 6 has a sliding concave surface 6 for guiding sliding of the branches 1f and 1g (FIG. 10) of the femoral component 1.
a, 6c (hereinafter referred to as “sliding guides”). The radius of curvature of the sliding guide portions 6a and 6c is the same as the radius of curvature of the branch portions 1f and 1g sliding on the mating member, as shown in FIG.
13, the contact areas of these (6a, 6c, 1f, 1g) are large, and the wear of polyethylene during sliding is reduced.

It is possible to provide two bearing inserts by making the sliding guides 6a and 6c independent members, but the two bearing inserts are only slightly difficult to install by surgery. However, there is a risk of falling off after installation and lack of stability. Therefore, in the first invention, the sliding guide portions 6a, 6c are mutually restricted during sliding. Specifically, FIG.
Preferred are monoliths as shown in FIGS. However, the weight is not limited to those shown in these figures, and it is also possible to reduce the weight by a method such as making a hole in the intermediate portion 6b or shortening the length L (FIG. 11).

Further, the tibial component 5 shown in FIG. 15 which is a cross-sectional view taken along the line cc of FIG. 14 and FIG.
b and stopper 5 for preventing bearing insert from falling off
c is formed. These sliding surfaces 5a are curved in the front-rear direction (AP) and in the lateral direction, and the respective radii of curvature substantially coincide with those of the bearing insert. Less.

The provision of the bearing insert as described above makes it possible for the artificial knee joint of the present invention to be highly bent, and in the case of high bending, the swelling of the rear standing portion 1c (FIG. 8) is required for the bearing insert to come off. Is effectively prevented, but by extending the stopper 5c (FIGS. 14 and 15) upward on both sides, it is possible to prevent the bearing insert from moving largely in the lateral direction and to more reliably prevent the bearing insert from falling off. Although not shown in FIGS. 14 and 15,
The width (W) of the bearing insert is determined to be sufficiently smaller than the distance between the stoppers 5c, thereby enabling sliding between them. Further, in FIG. 14, the stopper 5c is curved inward, but may be formed linearly.

FIGS. 16 and 17 show an embodiment of the second invention in which the upper surface of the tibial component and the lower surface of the bearing insert are flat, and show an embodiment in which a structure for preventing the bearing insert 6 from falling off is added. FIG. 16 shows a tibial component 5 having the structure of FIG.
Is formed with a laterally protruding portion for guiding the sliding of.
That is, the upper end of the extension stopper 5c extending upward from both side surfaces of the tibial component 5 is extended inward to form the projection 5d. On the other hand bearing insert 6
Has a groove 6e formed in the side surface as shown in FIG. 17, and extends in a length direction (a direction perpendicular to the paper surface). Since the protrusion 5d of the tibial component 5 is engaged with the groove 6e of the bearing insert 6 as shown in FIG. 17, the sliding of the bearing insert 6 is guided by the groove 6e and the protrusion 5d, and Detachment is prevented. Detachment prevention structures 5c, 5 shown in FIGS.
Naturally, d and 6e can be provided in the artificial knee joint of the first invention.

[0022]

As described above, the present invention enables a higher flexion than conventional knee prostheses, and in particular, reduces the abrasion of polyethylene at the time of high flexion, thereby increasing the durability and stability of the knee. Can be more reliably increased.

[Brief description of the drawings]

FIG. 1 is a side view showing an example of an artificial knee joint of the present invention (first invention).

FIG. 2 is a view showing an example of a conventional artificial knee joint.

FIG. 3 is a view showing a 30 ° flexion position of the artificial knee joint of the present invention (first invention).

FIG. 4 is a view similar to FIG. 3, showing a 90 ° flexion position.

FIG. 5 is a view similar to FIG. 4, showing a 130 ° flexion position.

FIG. 6 is a view similar to FIG. 5, showing a 170 ° flexion position.

FIG. 7 is a diagram illustrating a form of a tibial component.

FIG. 8 is a side view showing another example of the artificial knee joint of the present invention (first invention).

FIG. 9 is a diagram illustrating sliding with a patella component in a 170 ° flexion position.

FIG. 10 is a side view and a front view of the artificial knee joint of the present invention (first invention).

FIG. 11 is a plan view showing a more preferred embodiment of the bearing insert of the present invention (first invention).

FIG. 12 is a sectional view taken along line aa of FIG. 11;

FIG. 13 is a sectional view taken along line bb of FIG. 11;

FIG. 14 is a plan view of the tibial component of the present invention (first invention).

FIG. 15 is a sectional view taken along line cc of FIG. 14;

FIG. 16 is a view of a tibial component used in the present invention (second invention) having a projection for guiding a bearing insert.

FIG. 17 is a view showing a combination of the tibial component of FIG. 16, the bearing insert of one embodiment of the present invention (second invention), and the femoral component of FIG. 10;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Femoral component 2 Fixation peg 3 Femur 4 Tibia 5 Tibia component 6 Bearing insert

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yoshiharu Asai 3-30-13 Hongo, Bunkyo-ku, Tokyo Mizuho Medical Industry Co., Ltd.

Claims (4)

[Claims] The sliding surfaces each form a gentle curved surface,
A femoral component comprising an anterior upright portion, a lower portion, and a posterior upright portion, and fixed to a distal femur,
The lower surface has a concave portion serving as a sliding surface for the patella or the patella component in the center of the lower surface, a femoral component made of insert metal, and a tibial component fixed to the tibia proximal to the tibia and having a concave upper surface and made of insert metal. An integral bearing insert made of polyethylene, the upper surface having a concave surface and the lower surface having a convex surface, wherein the bearing insert is located between the femoral component and the tibial component. When the bearing insert is positioned substantially at the center of the tibial component, a line connecting the upper end of the bearing insert in the front-rear direction with respect to a plane perpendicular to the central axis of the tibial component is posterior. Bearings at an angle of 1 ° to 25 ° The insert is inclined backward and the upper surface of the bearing insert is 20m
m is a concave surface having a radius of curvature of 1000 mm, and the femoral component has a depth of the concave portion of 10 mm or more, and the bifurcated portions are bifurcated so as to straddle a patella or a concave surface sliding with the patella component. An artificial knee joint supported by an integral bearing insert. 2. The sliding surfaces each form a gentle curved surface,
A femoral component comprising an anterior upright portion, a lower portion, and a posterior upright portion, and fixed to a distal femur,
The lower surface has a concave portion serving as a sliding surface with the patella or the patella component at the center of the lower surface, a femoral component made of insert metal, and a tibial component fixed to the tibia proximal to the upper surface and having a flat surface on the upper surface and made of insert metal. ,
An artificial knee joint having a concave upper surface, a flat lower surface, and an integral bearing insert made of polyethylene, the bearing insert being located between the femoral component and the tibial component. And is inclined rearward such that a line connecting the upper end of the bearing insert in the front-rear direction with respect to a plane perpendicular to the central axis of the tibial component forms an angle of 1 ° to 25 ° rearward. And the entire upper surface of the bearing insert is 20m
m is a concave surface having a radius of curvature of 1000 mm, and the femoral component has a depth of the concave portion of 10 mm or more, and the bifurcated portion is branched to straddle a patella or a concave surface that slides with the patella component. An artificial knee joint supported by an integral bearing insert. 3. The artificial knee joint according to claim 1, wherein an extension extending upward from both sides of the tibial component is formed. 4. The bearing insert has a longitudinal groove formed on an outer side surface thereof, and the extension extending upward from both side surfaces of the tibial component is engaged with the groove to slide the bearing insert. 2. A projecting portion for guiding movement is formed so as to protrude in a lateral direction.
4. The artificial knee joint according to any one of items 1 to 3.