JPS5841055B2 - Jinkohizakansetsouchi - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to artificial knee replacement devices, and more particularly to intracorporeal knee prosthesis or knee joint replacement devices.

Traditional knee replacement devices are usually mechanical hinges that have a single axis of rotation and a long stem that is placed within the bone marrow to secure the femur and tibia.

While it is recognized that such conventional knee joint replacement devices have been used with advantage in many applications, they have suffered from various drawbacks.

Their disadvantages are the relatively restricted and unnatural movements due to the mechanical hinges compared to the joints of the human body, and the ligaments of the joints (ligames) to apply the articulation device.
nt) and a large amount of bone must be removed, and the medullary canal (medullary canal)
) requires drilling a relatively deep hole.

More recently, articulating devices have been proposed that consist of separate femoral and tibial components.These femoral and tibial components are said to be connected by a pivot axis or linkage similar to a mechanical hinge. Rather, it is held in bearing engagement by the body's joint capsule.

Although such articulation devices offer some improvements over earlier hinge types, they still must suffer from some of the drawbacks mentioned above in use.

It is an object of the present invention to provide an intracorporeal knee prosthesis that is a further improvement over the recently proposed joint devices mentioned above.

To this end, according to the invention, the knee joint replacement device consists of a femoral or lower component and a tibial or upper component, said lower component having an elongated saddle shape. The joint load-bearing surface of the joint is curved inwardly toward its rear, and has a ball shape projecting upward from one end, and the lower component is fixed to the top of the tibia in an anteroposterior position with the ball shape facing backwards. and a base for the upper component, the upper component having a socket-shaped joint load-bearing surface, the socket-shaped joint load-bearing surface being essentially symmetrical to the saddle shape and ball shape of the lower component. The socket has a complementary relationship, but has a larger curvature than the curvature along the saddle shape, so that the outer side of the socket shape is fixed to the bottom of the femur.

In use of the joint replacement device of the present invention, the longitudinal axis of the saddle shape is placed along the anterior-posterior axis of the knee joint with the ball shape or pommel positioned posteriorly.

Special placement of the femoral and tibial components is when:

That is, when the surface portions in a complementary relationship between the above-mentioned components are in a position where the joint flexion action is zero in mutual bearing engagement, and the joint flexion action increases and the pommel is in bearing engagement. That's when it became like that.

Such a change in bearing engagement is made possible by the mutual divergence of the longitudinal shapes.

The advantages obtained from the above-described shape of the joint replacement device of the present invention are as follows.

That is, fixation of the articular device is simplified by reducing the need for bone removal and deep penetration into the medullary canal.

More recently proposed conventional joint replacement devices have been designed to replace the femoral and tibial skulls with convex and concave bearing members, respectively.

The joint substitute device of the present invention has the above-mentioned general geometry reversed, and the femoral and tibia components are connected to the intercondylar notch of the human femur.
ar notch of a femur) and 1nter-condylar tubercle of the tibia.
cles of a tibia).
) to reduce the need for removal.

Another advantage is that the anatomical structure of the femoral and tibial components is similar to that of the human body, so fixation of these components requires cement to fill the cast without penetrating the bone marrow. It can be used.

Yet another advantage derived from the joint substitute device of the present invention is that in changing the bearing engagement of the joint flexion action, it can slide and move between appropriate longitudinal shapes that simulate the shape of the human knee joint. A rotational movement is performed.

This will be discussed further later.

The saddle shape is also preferably as follows.

That is, the lateral shape of the saddles, at their opposite ends to the pommel, is approximately complementary at their pair of corresponding ends; It gradually widens towards the end of the area.

When the femoral and tibial components of this preferred shape are engaged between their complementary ends, rotational movement relative to each other is not possible, but longitudinal movement is possible.

Such a single rotational performance is similar to that of a normal knee joint in a position of zero joint flexion action, when rotation about the longitudinal axis of the foot is prohibited so that it can be easily stabilized in an upright position. handle.

When the alignment of the femoral and tibial components first changes in joint flexion, the longitudinal extension of the bearing surface shape slides and transfers the bearing engagement between the non-complementary ends of the bearing surfaces. and the lateral extent of the bearing surface shape is such that the final bearing engagement occurs between the pommel.

In this last case, the surface parts of the pommel engage in a ball-and-socket manner and are subject to the previously inhibited relative rotational movement.

In practice, this additional rotational movement begins when the femoral and tibial components are in the above-mentioned position, and the rotational movement increases towards full engagement of the papillae.

This corresponds to the increased rotational capacity of the normal knee joint, and such full joint flexion facilitates the ability of the foot to flex to accommodate various seated and other non-upright positions. approach and reduce the torsional stress associated with such a position.

Other features of the preferred geometry of the joint substitute of the present invention, interrelated geometry features for varying the rotational performance to simulate a normal knee joint, include: This means that the bearing contact area is much larger at the complementary bearing surface area than at the bearing area of the saddle advisor.

This is consistent with an appropriate positioning of the articulating device for the zero position of joint flexion action and for its increasing position, respectively.

This is because bearing loads occur most frequently in the above-mentioned positions of zero joint flexion action and in positions of increasing thereof, ie during walking and in relatively small ranges from zero joint flexion action.

Therefore, the present articulation device has a large bearing contact area when bearing loads are most frequent.

This, of course, takes into account the issue of wear of the joint replacement device.

The above-mentioned and other features of the invention will be made clear in the description of embodiments with reference to the drawings.

The femoral or upper component and the tibial or lower component are generally designated 1 in the drawings.
and 2, having joint load-bearing surfaces designated 3 and 4, respectively.

Although each of these bearing surfaces has a similarly complex shape, I believe that their overall shape can best be described as a ball-shaped or pommel saddle.

The femoral component 1 has a concave or saddle shape, and the tibial component 2 has the opposite shape, that is, a substantially convex shape.

The bearing surfaces 3 and 4 are very similar at their corresponding ends opposite the pommel and have approximately complementary extents in their longitudinal and transverse shape.

Such a relationship is based on one aspect of reference to the drawings, namely the shape of the longitudinal center portion between the positions 3a and 3b of the bearing surface 3 shown in FIG. 5 and the corresponding bearing surface 3 shown in FIG. It will be understood from a comparison with the shape of the longitudinal center portion between the positions 4a and 4b of 4.

This relationship also applies from other points of view, namely, the lateral shape portion 4c of the bearing surface 4 shown in the front view of FIG. It can also be understood by comparing with part 3c.

However, with respect to the mutual arrangement between the bearing surfaces 3 and 4, although the anterior ends of the femoral and tibial components engage in a complementary manner, such complementary tightness is limited to the extent that these components are It gradually separates and disappears.

Such a state of separation occurs from the position 3b in the shape of the longitudinally intermediate portion of the bearing surface 3 to the pommel portion 3 shown in FIG.
This can be understood by comparing the transition part up to d and the corresponding transition part shown in FIG. Good morning.

The transition of the bearing surface 3 has a greater curvature than the transition of the bearing surface 4.

Such a state of separation can also be understood by comparing the lateral shape 4e of the bearing surface 4 shown in FIG. 10 with the corresponding shape 3e of the bearing surface 3 shown in FIG.

The shape 3e is wider than the shape 4c except for the pommel portion 4d.

A comparison of the longitudinal shapes as described above can be facilitated by showing the two positions of the tibial component, shown in phantom lines in FIG.

In fact, those two positions are such that the joint flexion performance is approximately 1100.

As mentioned in the introduction, the configuration of the described embodiments, insofar as discussed, is as follows.

That is, the complementary portions of the bearing surfaces have relatively large contact areas and are engaged such that only a single relative rotational movement is possible in their common longitudinal direction.

As such rotational motion increases, the bearing surfaces become subject to relative sliding motion, and as the bearing engagement transitions to the pommel, lateral freedom occurs and further relative rotational motion in the horizontal plane occurs. It becomes like a monkey.

This last bearing engagement is essentially a ball-and-socket joint, but is laterally limited by the mutually opposed sides of the two bearing surfaces.

This bearing surface interaction is similar to that of the human knee joint, and the bearing surface can be shaped more specifically as shown to simulate more detailed functions of the knee joint. .

For example, movement of the knee joint in the vertical plane consists only of sliding, limiting changes in the center of rotation.

Since such movement is simulated in the embodiment, the trajectory of the center of rotation is limited and approximates that typical of a human knee joint.

This is achieved in an embodiment by forming an intermediate portion in the shape of the longitudinal center of the bearing surface on the femoral side,
This femoral bearing surface has a certain meaningful curvature relative to its shape, which is shaped like a typical human head on the femoral side, and the corresponding tibial bearing surface. The shape is formed into a widened shape.

The ends of the bearing surfaces are flared sections 3f and 4f, respectively, along their lateral circumference, which have a bearing action at their front ends and which have zero bending action. They have a nearly complementary relationship in order to better distribute the bearing load caused by the initial bending action starting from the position.

In practice, such flange portions are arranged in longitudinally central portions such that they are engaged on at least one side or the other over the entire range of flexural action, as shown in the examples. It can be formed in a similar manner in terms of shape and function.

However, the engagement towards the rearward end essentially serves to provide stability with the flap acting in an all-trigger manner rather than to increase bearing load capacity.

Such effects do not prevent rotational performance in the horizontal plane.

Next, we will discuss the problem of fixation of the knee joint.

The non-bearing surface, ie the upper surface 5 of the femoral component, is a simplified form of that bearing surface and has a ridge 5a rising and extending from between two flared peripheral portions 5b.

The raised portion 5a is adapted to be fixed to the intercondylar notch of the femur.

The ridge 5a can be positioned in the desired position by slight removal of bone and can be firmly fixed by the use of acrylic or equivalent material filling the gap.

The general stepped shape of the raised portion 5a in the longitudinal direction is compatible with such fixing.

Even if the protuberance is of low shape, Figures 1 and 3
As shown in the figures, the studs 7 allow the femoral component to be tightened with a bonding material.

Such studs extend upwardly from the posterior portion of the flared portion 5b and are compatible with femoral configurations such as those described above, so long as the appropriate femoral component is conventionally molded or cast. Formation of the part is compatible with molding or molding.

In Figures 5 and 6, the proper direction of die cutting will be seen.

The flared portion 5b is adapted to be easily positioned in the desired position and is therefore shaped to match the shape of the adjacent femoral skull surface.

Therefore, there is no need to remove bone directly adjacent to the flared portion 5b, so that the flared portion is effectively positioned on the skull surface.

Similarly, there is no need for the flared portion to extend laterally across most of the skull surface.

The flared portion 5b works together with the bonding material to further strengthen the fixation of the femoral component.

The non-bearing surface, the lower surface 6 of the tibial component, is less similar to its bearing surface.

The downward surface 6 has a groove portion 6a extending in the longitudinal direction.
is provided.

This groove portion 6a is partially defined by two raised portions 6b extending longitudinally below the flared portion 4f and a web portion 6c extending over and below the raised portions 6b.

The groove portion 6a is located at the intercondylar tuberosity of the tibia.
-jar tubercles), and this notch is
It is grooved along its sides to receive the rib portion 6b.

In the fixation described above, a slight bone removal is required and the fixation is made by the use of a cement, preferably in the low form of a keyed ridge.

The web portion 6c is opened as indicated by the reference numeral 8, and the opening forms the bonding material into a rivet shape to further strengthen the fixation.

It will therefore be seen that there is no need to penetrate the medullary canal either deeply or shallowly for fixation.

The articulating device of the present invention can be made of plastic materials such as high-density polyethylene and metal materials such as chromium-cobalton alloys by commonly practiced and preferred methods; The combination can provide low friction and other beneficial features.

Regarding the use of such materials, the femoral and tibial components are preferably made of plastic material and metal, respectively.

Plastic materials can be used in relatively large thicknesses in the main bearing load area along the central longitudinal portion of the femoral component, as shown in FIG. can provide a suitably large strength to the pommel neck area of the tibial component.

[Brief explanation of the drawing]

1 to 6 show the femoral component of an embodiment according to the present invention, in which FIG. 1 is a side view, FIG. 2 is a front view, and FIG. 3 is a front view.
4 is a cross-sectional view taken along line 1-1, FIG. 5 is a longitudinal sectional view taken along line T, and FIG. 6 is a rear view. 7 to 10 show the tibial component of an embodiment according to the present invention, in which FIG. 7 is a side view, FIG. 8 is a front view, and FIG. 9 is a front view.
The figure is a bottom view and FIG. 10 is a rear view. 1...Female component, 2...Tibial component, 3.4...Bearing surface, 3d, 4d...
... Pommel part, 3f, 4f ... Flare portion, 5a ... Protuberance, 5b ... Flare portion, 6 ... Lower surface, 6a... Groove portion, 6b... Raised portion.

Claims (1)

[Scope of Claims] 1. A knee joint substitute device comprising a lower component and an upper component, the lower component having an elongated saddle-shaped joint load-bearing surface, and the lower component having an elongated saddle-shaped joint load-bearing surface. The load-bearing surface is curved inwardly toward its rear and has a ball shape projecting upwardly from one end, and a load-bearing surface for fixing the lower component to the top of the tibia in an anteroposterior position with the ball shape facing backwards. a base, the upper component having a socket-shaped joint load-bearing surface, the socket-shaped joint load-bearing surface being essentially complementary to the saddle and ball shapes of the lower component. However, the knee joint substitute device has a larger curvature than the curvature along the saddle shape, and has a shape such that the outer side of the socket shape is fixed to the bottom of the femur. 2. The knee joint replacement device according to item 1 above, wherein the socket shape of the upper component portion follows the saddle shape of the lower component portion and widens toward its rear end. 3. The knee joint replacement device according to paragraph 1, wherein each joint load-bearing surface of the lower and upper components comprises flared portions as lateral extensions along both sides thereof;
the flared portions of the lower and upper components always partially engage each other throughout the range of flexion;
A knee joint substitute device, which is characterized in that it acts in a similar manner.