JPS5841855B2 - internal knee prosthesis device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an endoprosthetic vessel osteosynthesis device, and more particularly to a device for the knee joint.

Work on the hip joint has shown that there is a close relationship between the shape of the articulating surfaces, the load distribution between these surfaces, and the pattern of degeneration seen in the population.

The basic characteristics of the hip joint are that the contact area shows a slight discrepancy that allows it to grow with increasing loads, and at large loads, when all the useful cartilage on the acetabulum come into contact, the thickness of the cartilage increases. The distribution appears to be such that a state of uniform pressure is obtained (Ninis Greenwald (A-S
・The transmission of loads through the human hip joint, by John Greenwald and J.J.
of ioadthrough the bum
an hip joint)” Geo Biomechanics, April 1971, pp. 507-528).

A similar shape design is discussed in the elbow joint, which appears as an important feature of human and animal joint design (Geo.
Double Good Fellow (J.W.Good f.
e 11 ow) and P.G.
``The pattern of maturation in the articular cartilage of the JMM joint'' by John Bullough.
ing in the articular cart
ilage of the eibow joint)”
Geo Bone and Joint Surgery Publishing, 1967, Volume 493, P. Barrow, J.D. Prue Gutsudfellow-1, and Geo. O'Connor, "The Relation between Degeneration and Load Contact in the Human Hip." betw
eendegenerative changes a
nd 1 oad bear”ing in the
human hip)” Shei Bone and Joint Surge Lily Published 1973 55B, 746
roll).

However, the knee joint is an exception to this general rule insofar as the interarticular cartilage cannot play a significant role in load transfer.

The work leading to the idea of the present invention has shown that this is indeed the case and that in loaded conditions the interarticular cartilage transmits a significant proportion of the load.

The tendency of the femur to push the facet cartilage radially outward is resisted by circumferential tension in the facet cartilage.

It is reasonable to assume that the ideal prosthetic device reproduces the normal pattern of physiological ranges, modes of motion, axes of motion, and load contacts of natural joints.

The kinematics and axes of the human knee are complex, variable, and dependent at any given location on the shape of the articulating surfaces and the direction and magnitude of the tension created in the associated muscles and ligaments. do.

The ideal prosthesis is therefore considered to be one that reproduces the shape of the relevant surfaces as precisely as possible, interferes as little as possible with the continuous functioning of the muscles and ligaments, and at the same time maintains a sufficiently uniform distribution of the loads. be able to.

Previously proposed knee joints used in medical practice have shown that this ideal is not achievable.

Early proposals included hinge devices that constrained movement to a single pivot about a single axis.

Such hinge devices in each case led to unacceptable failure rates.

Recent proposals include two parts connected to the femur and tibia, respectively, and held in place by muscles and ligaments, to eliminate hinge device failure and create a more vital condition. I'm here.

However, these recent proposals face contradictory requirements such as:

That is, the alignment of the engaging surfaces of the parts with uniform load distribution provides little freedom for variations in the mode of motion and axis of motion, while any mismatch between the surfaces to meet the motion requirements is inevitable. The surface contact area is reduced and/or changed, resulting in an unfavorable load distribution.

It is an object of the present invention to reduce these difficulties by providing a device which allows one to come closer to achieving the ideal.

To this end, the present invention provides a femoral head component adapted to be secured to the femur and having a generally convexly curved articulating contact surface, and a femoral head component adapted to be secured to the tibia. a tibial head component having an articulating contact surface that is relatively planar and relatively flat compared to the contact surfaces of said components; an interarticular cartilage component having two articulating contact surfaces having individual shapes.

When using this configuration of the invention, the femoral and tibial components are arranged such that the joint surfaces of these components face each other;
An interarticular cartilage component is affixed to the femur and tibia, respectively, and is positioned therebetween, with its joint contact surfaces respectively engaging the surfaces of said components.

The array result looks like this:

(1) The femoral and interarticular cartilage components and the interarticular cartilage and tibial components are capable of independent relative movement due to the complementary nature of the two pairs of engaged surfaces.

In particular, the femoral and interarticular cartilage components can rotate relative to each other about three orthogonal axes, and the interarticular cartilage and tibial components can rotate around two orthogonal axes.
They are capable of mutual sliding in two associated axes and mutually rotatable about a third axis.

The resulting capacity for relative motion between the femoral and tibial components is therefore extensive and can include rotation, sliding, torsion, and combinations thereof, as found in the knee joint.

(2) The generally convex and relatively flat shapes of the contact surfaces of the femoral and tibial components can sufficiently reproduce the natural shapes of the natural femoral and tibial heads, resulting in joint stabilization. The complete interplay between the surface geometry and the forces in the surrounding muscles and ligaments is life-like, controlling the

(3) The complementary nature of the engaging surfaces of the parts is such that a relatively uniform distribution of surface pressure is obtained at all locations of these parts.

(4) The interphalangeal cartilage component has a complementary convex-concave shape on the engaged femoral-interarticular cartilage component surface and a relatively flat complementary shape on the engaged interarticular cartilage-tibial component surface. Because of this, it is trapped between the femoral and tibial components.

Although the formation of the present invention from the initial concept allows for a wide variety of foreseeable and advantageous shapes to fall within the more general scope of the present invention, the foregoing results are consistent with the formation of an engaged femoral and interarticular cartilage contact. It is shown that the surfaces can result from a relatively simple shape of the invention, where the surfaces are partially spherical in shape and the contact surfaces of the engaged interarticular cartilage and tibial components are flat.

Next, the present invention will be explained with reference to the drawings.

FIGS. 1 and 2 show a bicond-ylar device consisting of two sets of parts used for replacement of the lateral and medial heads of the joint and the interarticular cartilage, respectively.

The two parts are the same, and for convenience of explanation, only one set of structures will be described.

In related sets, the femoral, tibial, and interarticular cartilage parts are designated with reference numerals 10, 20, and 30, respectively.

Shown in dotted outline in FIGS. 1 and 2 are the distal portion 40 of the femur and the proximal end portion 50 of the tibia.

The femoral component consists of a contact body 11 generally in the form of a longitudinally curved strip, the convex surface of which forms a partially spherical surface 12 to serve as an articulating contact surface.

The concave surface of the body 11 serves as an anchoring surface 13 suitable for anchoring to the femur according to existing techniques, such that the surface 12 acts as a substitute for the femoral surface.

In the present invention, this fixation is performed using an acrylic bone cement, and for this purpose the surface is formed with one or more integrally formed internal porous rods 14 projecting therefrom. , and the surface 13 is provided with grooves.

The tibial component 20 consists of a D-shaped plate-shaped contact body 21 of uniform thickness throughout.

One surface of body 21 forms a flat surface 22 that serves as an articulating contact surface.

The other surface of the body 21 serves as an anchoring surface 23 that is secured to the tibia according to techniques similar to those for the femoral component, and the surface 22 serves as a tibial head surface substitute.

For this purpose, the surface 23 is formed with one or more integrally formed internal porous rods 24 projecting therefrom.

The interarticular cartilage component 30 has a circular disc-shaped contact body 31
Take from.

One surface of this body serves as an articulating contact surface 32 that engages surface 12 of the femoral component.
It is formed into a concave, partially spherical shape with the same radius.

The other surface of body 31 is flat to serve as an articulating contact surface for engaging surface 22 of the tibial component.

In using these components, the femoral and tibial components are secured to the femur and tibia at suitably prepared locations, and the interarticular cartilage components are then engaged therebetween.

The entire surgical procedure does not involve any special matters.

The reason for this is that these surgeries are based on the so-called "polycentric" technique devised by Gunstone.
This is because the procedure may be similar to the surgery already developed for existing bipedicular knee joint devices such as the ``Ric'' device.

A first advantage of the illustrated device arises from the first three results mentioned above.

That is, while natural joint motions are closely mimicked without significant distortion of natural accommodation and stabilization mechanisms,
At the same time a uniform distribution of surface pressure is maintained throughout the device.

Unless the shape of the contacting surfaces of the parts accurately reproduces the natural skull shape, the respective overall positional relationships between these shapes for a given operating state of the muscles and ligaments during the flexion-extension cycle will vary. There is a difference.

However, these differences are extremely small;
This was confirmed by cadaver tests, which demonstrated the well-known characteristics of natural joint motion.

That is, the femoral component rotates with only a slight translational motion relative to the tibial component during initial extension, and the femoral component rotates with increasing anterior translation of the interarticular cartilage component during further extension. Continuing rotation, the axis of femoral-tibial rotation moves posteriorly into the femur, the latter translation being accompanied by a lateral rotation near full extension, so that the tibia forms the so-called screw home. home
) movements, such as twisting about the longitudinal axis of the leg relative to the femur.

The opposite order of this action occurs during flexion. Although these operating sequences involve relative rotation, sliding and twisting between the femur and tibia, the parts of the device undergo only sliding movements under uniform pressure distribution.

Another advantage is therefore that there are no undue dynamic stresses in the parts that could lead to additive wear.

Other advantages arise from the interarticular cartilage component.

This part can be easily replaced by simple surgery due to wear.

Other advantages are that the joint parts are made of plastic material and the other parts are made of metal, the intermediate material provides the well-known low friction properties, the fixed parts are inherently stable, and long-term wear is more easily replaced. It is obtained by occurring in the parts that can be produced.

Other advantages arising from the interarticular cartilage component are that it is available in a range of different thicknesses and allows the surgeon to properly tension the capsule from this range, especially to avoid undue loosening, and for patients with clubfoot or valgus feet. Correct the deformation of.

Another advantage of the illustrated device is that the surgeon is relieved of the requirement to position the femoral and interarticular cartilage components in a defined relationship when fixating the femoral and interarticular cartilage components.

This requirement typically arises with existing equipment.

However, the interarticular cartilage of the device of the present invention acts as a self-adjusting intermediate that accommodates different positional relationships between the other two parts.

Although the invention has been described with particular reference to the illustrated embodiments, the invention is not limited thereto.

It is preferred to apply the invention to a double cephalic device configuration.

The reason is that this shape offers particular advantages in the ability to retain the cruciate ligament and does not require the inherent requirement of separating the patella for component fixation.

However, in this configuration the device may be modified from the illustrated embodiment.

One such modification is illustrated in FIG. 3, which shows a deformed tibial and interarticular cartilage component.

The modification includes providing a mushroom-shaped projection 25 entirely from the central region of the contact surface 22 of the knee bone component.

This protrusion engages the lower notch recess 34 of the interarticular cartilage component.

The mouth of the recess has a diameter significantly larger than the diameter of the base of the projection and slightly smaller than the diameter of the head of the projection.

Engagement of the protrusion and recess involves a snap action, after which the relative sliding movement occurs in all directions of surfaces 22 and 33 until the limit imposed by the abutment of the protrusion and the side walls of the recess. can occur.

Preferably, the projections and the recesses have equal depths with respect to the flat surfaces at their respective free ends and bottoms;
The surfaces are parallel to surfaces 22 and 33, and the former surface engages when the latter surface engages as well.

Although the interarticular cartilage component of embodiments such as those of FIGS. 1 and 2 can be held properly between two other components, the modification of FIG. 3 compromises the ability to perform the desired movements. Improve stability without any problems.

The preferred sliding engagement between the projection and the recess maintains and actually slightly increases the contact area between the tibial and interarticular cartilage components relative to FIGS. 1 and 2.

A similar stabilizing arrangement can be achieved between the interarticular cartilage and the femoral component by using protrusions from surface 32 and slot-like recesses in surface 12.

The stability of the interarticular cartilage component is increased by elongating the component into an oval shape in plan view.

The curved contact area with the femoral component, which is the fundamental cause of entrapment of the interarticular cartilage component, is increased.

In use, this elongation is preferably maintained in a generally anteroposteriorly expanding manner, and to this end, the extension at 26 in FIG.
It is appropriate to provide the tibial component with a raised sidewall, as shown in FIG.

Increased lateral stability may be provided in the bifemoral head device of the present invention by mutually slanting the interface between the tibial surface 22 and the interarticular cartilage surface 33 laterally.

This can be done by providing an appropriately sloped point in the tibia for a uniform thickness tibial component, but generally wedge-shaped tibial components are provided for use where they are commonly placed. You can also do that.

The proposed configuration of the bifrontal device is not limited to any particular fixation technique or use of special materials.

The present invention can be applied to devices other than double-headed tube devices.

In its simple form, the invention is applicable to devices having a single set of parts for the entire knee (such as the so-called Freeman-8wanson device).

The shape of the bicephalic bone is the so-called geomesoic (Ce om
While providing a slotted part structure for the retention of the cruciate ligament (such as an ed ic) device, it can be modified by forming some or all of the corresponding parts in one piece.

The contact surface of the femoral component can vary in curvature and (
It differs, at least in part, from what it articulates (such as the Freeman-Swanson device).

The engagement surfaces of the tibial and interarticular cartilage components do not necessarily have to be flat, but these surfaces are relatively flat compared to other engagement surfaces.

Although these changes do not necessarily result in the aforementioned benefits,
It is clearly possible to obtain advantages over comparable devices in the aforementioned devices.

Deformations can also be made by using elastic plastic materials on the interarticular cartilage component so that the interarticular cartilage component adapts to shape changes during articulation, particularly in the associated femoral surface.

Preferably, the elasticity is present in the longitudinal axis relative to the leg, i.e. perpendicular to the contact surface of the interarticular cartilage component, while the component constrains the radially outward component of the load like natural interarticular cartilage. relatively hard in the peripheral direction.

Such differential elasticity may be achieved with a peripherally fiber-reinforced plastic structure, such as silastic rubber within an annular member of nylon or other synthetic fibers.

Moreover, such interarticular cartilage components may find application only for the engagement between the natural femoral and tibial heads in the treatment of conditions such as those resulting from sports activities and those currently treated by so-called cartilage removal. good.

[Brief explanation of drawings]

1 and 2 are mutually perpendicular, schematic cross-sectional views of one embodiment of the invention in simple form; FIG. FIG. 3 is a schematic diagram showing a modification of the embodiment. 10...Femoral bone part, 20...Tibial bone part, 30...Interarticular cartilage part, 11...
・Contact body, 12... Spherical surface, 13...
...Fixed surface, 14...Internal porous frame, 21.
...Contact body, 22...Flat surface, 2
3... Fixed surface, 31... Contact body,
32...Contact surface.

Claims (1)

Claims: 1. A femoral head component adapted to be secured to the femur and having a generally convexly curved articulating contact surface, and adapted to be secured to the tibia; a tibial head component having an articulating contact surface that is relatively flat compared to a contact surface of said component, and an individual shape that is dorsodorsally oriented and substantially complementary to the articulating surfaces of said femoral and tibial components; an interarticular cartilage component having two articulating contact surfaces having a femoral head component and a tibial head component, the interarticular cartilage component being slidably disposed between the femoral head component and the tibial head component. , an internal knee prosthesis device characterized by: 2. The device of item 1, wherein the femoral component surface and the supplementary interarticular cartilage component surface are each partially spherical and shaped with equal radii of curvature. 3. The device of item 1 or 2 above, characterized in that the tibial component surface and the supplementary interarticular cartilage component surface are each flat. 4. The device of paragraphs 1, 2, or 3 above, wherein each of the femoral and tibial components has a unitary metal structure;
The device characterized in that the interarticular cartilage component has an integrally formed plastic material structure. 5. Apparatus according to any of the preceding claims, characterized in that each of said parts has two of said surfaces for respective positions in the lateral and central compartments of the knee joint. 6. The device of item 5, characterized in that at least the interarticular cartilage component is subdivided into two subdivisions for respective positions in the lateral and central sections of the knee joint. 7. In any of the preceding devices, one of the interarticular cartilage component and the femoral and tibial components has an integrally formed protrusion from a contact surface of one of such components; device, characterized in that it is connected by a recess in a contact surface of another of the objects, said protrusion being able to enter said recess and move laterally within said recess. 8. The device of item 7, wherein the projection projects from the tibial component and the recess is formed in the interarticular cartilage component. 9. The device of claim 8, wherein the projection is generally mushroom-shaped and the recess is a lower cutout to receive the projection by a snapping action. 10. The device of paragraph 1, wherein the interarticular cartilage component is made of an elastic plastics material and reinforced in the circumferential direction with respect to the two contact surfaces so as to reduce the elasticity of the component in a corresponding radial sense. A device characterized by: