JP3687897B2 - Artificial ankle - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an artificial ankle joint.
[0002]
[Prior art]
When an ankle joint is highly damaged due to rheumatism, osteoarthritis or the like, it is replaced with an artificial ankle joint like other joints. However, the ankle joint is a load joint that takes up most of its weight, and in addition, since both rolling and sliding under high loads are required, unique functions are required.
[0003]
The following artificial ankle joints are currently used. The first is disclosed in Japanese Patent Publication No. 60-43136, and is provided with a columnar portion having a curvature in the front-rear direction and mounted on the talus, and slidably mounted on the columnar portion in the front-rear direction. The cylinder itself is called a cylindrical type that includes a tibial component that can move in parallel in the left-right direction and is attached to the tibia. As for the ankle joint, the talus and tibia must be able to bend and extend in the front-rear and left-right directions. However, there is a risk that dislocation occurs due to the easy movement in the left-right direction.
[0004]
Therefore, Japanese Utility Model Publication No. 62-32021 proposes a conical type in which the movement in the left-right direction is restricted and only the sliding movement in the front-rear direction is performed. However, in this case, the movement is excessively restrained, and even if a slight external force such as a slight trauma after replacement is applied, there is a concern that loosening may occur.
[0005]
[Problems to be solved by the invention]
By the way, dislocation occurs if the back-and-forth movement is allowed without limitation. However, in the above-described previous example, no effective means for restricting this is provided. In addition, the function required for the ankle joint requires rotation that allows the talus to turn around the bone axis of the tibia in addition to the above-described longitudinal and lateral flexion and extension. However, if it is attempted to rotate with the preceding example, the sliding contact surfaces of the opposing components will be lifted, and a large resistance will be generated, which is practically impossible.
[0006]
Furthermore, it is also a condition that an ankle joint can be easily operated like other artificial joints. Although an appropriate excision area and operation method are set with great care before surgery, it may differ in the actual situation and may not always be optimally set. In addition, it may become different from the first set because it is familiar with the living body after surgery. In particular, subsidence is a serious problem, as the talus component deviates from the cortical bone of the talus and falls into the cancellous bone. If this happens, it will not be able to perform its full function, and may require re-operation when it is severe. The present invention eliminates the above-mentioned drawbacks.
[0007]
[Means for Solving the Problems]
Under the above object, the present invention is a prosthetic ankle joint is replaced by ankle, the ankle prosthesis is, have a curvature in the longitudinal direction, and a cylindrical portion which has a concave groove recessed central a talar component that is attached to the talus is provided on the upper surface, Ri slidably mounting in the longitudinal direction on the cylindrical portion, the intermediate component upper surface is formed in a concave shape having a relatively large radius of curvature to the deepest point of the center And a tibial component mounted on the upper surface of the intermediate component so as to be slidable in the front-rear and left-right directions and attached to the tibia.
[0008]
A necessary and sufficient configuration for the artificial ankle joint of the present invention is an intermediate component that is allowed to move back and forth with respect to the talus component, and a tibial component that is allowed to move back and forth and slightly to the left and right with respect to the intermediate component. . That is, while the conventional artificial ankle joint is composed of two components, the present invention is characterized in that it is composed of three components. The three components are advantageous in that the three components, particularly the intermediate component, can absorb the deviation from the first set due to the fact that the optimal set cannot be made during the operation and the familiarity after the operation.
[0009]
In this case, the longitudinal movement of the tibial component relative to the intermediate component is guided by a guide mechanism that slightly allows lateral movement, and if a stopper mechanism that restricts the longitudinal movement beyond a certain range is provided in the guide mechanism, Unrestricted left-right movement is restricted, preventing dislocation. Furthermore, if the planar shape of the columnar part that forms the talar component is a trapezoid that narrows forward and backward, it will be along the excised shape of the talus, and the entire circumference will rest on the cortical bone evenly. Sinking can be prevented.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1 is a side sectional view of the artificial ankle joint according to the present invention, FIG. 2 is a rear sectional view, FIG. 3 is an AA sectional view of FIG. 2, and FIG. 4 is a talus component constituting the artificial ankle joint. FIG. 5 is a plan view, FIG. 6 is a perspective view of an intermediate component, and FIG. 7 is a perspective view of a tibial component. In the foot bone, the tibia 2 is present on the talus 1 and the two are joined. The face forms a joint. In the artificial ankle joint of the present invention, the talus component 3 is mounted on the talus 1, and the tibial component 5 is mounted on the tibia 2 with the intermediate component 4 interposed therebetween, and these three members constitute the joint portion. Become.
[0011]
Of these components, the talus component 3 includes a columnar portion 6 having a curvature that faces in the front-rear direction when mounted on the talus 1, and a stem 7 that protrudes from the lower surface of the columnar portion 6. The stem 7 is inserted into the medullary cavity when it is attached to the talus 1 to strengthen the fixation. In this case, the columnar portion 6 has a concave shape with a concave center when viewed from the front, and has a trapezoidal shape that is narrow before and after when viewed from above. The concave shape is that the intermediate component 4 placed thereon does not shift to the left and right, and the trapezoidal shape is that the proximal end of the talus 1 is shaped flat when mounted, In addition, the cylindrical portion 6 is placed on the entire cortical bone 1 a at the periphery of the talus 1.
[0012]
The intermediate component 4 has an overall flat plate body 8 whose bottom surface has a curvature that follows the curvature of the cylindrical portion 6. In this example, the upper surface has a relatively large radius of curvature with the center as the deepest point. The groove 9 is formed on both the left and right side surfaces. When the intermediate component 4 is placed on the talus component 3, the intermediate component 4 can rotate back and forth along its curvature with respect to the talus component 3. The grooves 9 on the left and right side surfaces are necessary for a stopper mechanism described later, and in this example, the front and rear ends have shallow bottoms. The concave shape of the upper surface enables sliding and turning of the tibial component 5 mounted on the upper and lower sides and the left and right, and at the same time, exerts a self-centering function that helps returning to the deepest point. Even if the irregularities on the upper surface of the intermediate component 4 and the bottom surface of the tibial component 5 are opposite to those described above, the self-centering function is exhibited, and even if it is flat, a load is applied. To do.
[0013]
The tibial component 5 has a substantially flat body 10 whose bottom surface is placed on the upper surface of the intermediate component 4, and a stem 11 is protruded from the upper surface. And the protrusion part 12 which penetrates into the groove | channel 9 of the intermediate | middle component 4 is formed in the right-and-left both sides | surfaces. In this case, the protrusion 12 is formed in the center portion with the front and rear ends omitted, and the tip of the protruding inward direction does not reach the bottom of the groove 9 (having a certain gap), and It is deeper than the shallow bottom portions at the front and rear ends (FIG. 3). Further, the thickness of the protrusion 12 is set to be considerably narrower than the width of the groove 9, and the vertical wall portion at the base of the protrusion 12 is set to be wider than the left and right width of the intermediate component 4 (with a certain gap). Have).
[0014]
Thereby, when the tibial component 5 moves back and forth on the intermediate component 4, the protrusion 12 and the groove 9 constitute a guide mechanism and move without blurring from side to side. In addition, when the sliding contact surface of the tibial component 5 and the intermediate component 4 is formed as an uneven surface having the deepest point at the center, the projecting portion 12 also moves upward when the tibial component 5 moves. This can be dealt with because the thickness of the protrusion 12 is set to be considerably narrower than the width of the groove 9.
[0015]
Further, the protrusion 12 and the shallow portion of the groove 9 constitute a stopper mechanism, and even if the tibial component 5 moves on the intermediate component 4 in the front-rear direction, its movement is restricted within a certain range that does not dislocation. It has come to be. In this case, the protrusion 12 cannot be inserted into the groove 9, but if one or both of the tibial component 5 and the intermediate component 4 are made of a material that can be elastically deformed, the protrusion 12 can be pushed to a certain extent. This becomes possible (so-called snap-in). In addition, the tibial component 5 can be slightly slid and rotated in the left-right direction with respect to the intermediate component 4 by maintaining the relationship between the protrusion 12 and the groove 9 described above. Even in this case, when the vertical wall portion of the base of the protrusion 12 hits the left and right end surfaces of the intermediate component 4, further movement is restricted, and when the tip of the protrusion 10 hits the bottom of the groove 9, further rotation is restricted. Dislocation is prevented.
[0016]
The above artificial ankle joint is attached to the talus 1 and the tibia 2 by surgery. First, the talus component 3 is mounted by excising the proximal end of the talus 1 and shaping it flat, placing the column 6 on it and inserting the stem 7 into the medullary cavity (if necessary, bone cement or the like is also used) To do). At this time, since the planar shape of the cylindrical portion 6 is narrowed forward and backward in accordance with the planar shape of the shaped talar 1, the cylindrical portion 6 is uniformly placed on the hard cortical bone 1 a and subduction is avoided.
[0017]
Similarly, the distal end of the tibia 2 is also cut out flat, and the top surface of the tibial component 5 is applied thereto and the stem 11 is inserted into the medullary cavity and fixed (the bone cement or the like may be used as described above). the same). Then, when the intermediate component 4 is fitted into this and the lower surface thereof is aligned with the upper surface of the talar component 3, the mounting is completed. Therefore, it can be said that when the talar component 3 and the tibial component 5 are mounted, a space corresponding to the thickness of the intermediate component 4 is vacant and mounting is easy. In this case, the excision allowance of the talus 1 and the tibia 2 is performed according to the thickness of the artificial ankle joint composed of three components and set to the same height as the living joint. However, the final height adjustment at this time is The thickness of the intermediate component 4 is adjusted.
[0018]
As described above, the joint between the talus and tibia is replaced with the artificial ankle joint. When the ankle joint is replaced with such an artificial ankle joint, the talus and tibia can be moved slightly to the left and right and rotated with the forward and backward rotation as the main movement, and can move close to a living ankle joint. These movements are movements with less resistance because the three components make their own judgments and move appropriately. For smooth movement, the talus and tibial components are preferably made of a biocompatible metal or ceramic material (in this example, a Co-Cr-Mo alloy is used), and the intermediate component is slippery with them. Ultra high molecular weight polyethylene with good compatibility is suitable.
[0019]
【The invention's effect】
As described above, the artificial ankle joint according to the present invention is made of three components including a talus component fixed to the talus, a tibial component fixed to the tibia, and an intermediate component interposed therebetween. First of all, even if it cannot be optimally set for some reason at the time of surgery, or if it is different from the first set after adapting to the living body, this deviation is absorbed by 3 components, especially the intermediate component, There is an advantage that does not lead to non-conformity. Secondly, in addition to forward and backward rotation, left and right movements and rotations are also possible, so that it can move close to a living ankle joint, and this movement is the cooperation of the three parties, so the movement is smooth Do not put excessive burden on ligaments and tendons.
[Brief description of the drawings]
FIG. 1 is a side sectional view showing a state in which an artificial ankle joint according to an embodiment of the present invention is mounted.
FIG. 2 is a rear cross-sectional view of a state where an artificial ankle joint according to an example of the present invention is mounted.
3 is a cross-sectional view taken along line AA in FIG.
FIG. 4 is a perspective view of a talar component illustrating an example of the present invention.
FIG. 5 is a plan view of a talar component illustrating an example of the present invention.
FIG. 6 is a perspective view of an intermediate component showing an example of the present invention.
FIG. 7 is a perspective view of a tibial component illustrating an example of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Talar 2 Tibial 3 Talar component 4 Intermediate component 5 Tibial component

Claims (5)

Talar an artificial ankle joint which is substituted in the ankle, the ankle prosthesis is to be mounted have a curvature in the longitudinal direction, and a cylindrical portion which has a concave groove recessed central talus provided on the upper surface components and, Ri slidably mounting in the longitudinal direction on the cylindrical portion, an upper surface and an intermediate component which is formed in a concave shape having a relatively large radius of curvature to the deepest point of the center, before and after on the upper surface of the intermediate component And a tibial component that is slidable in the left-right direction and is attached to the tibia.   The artificial ankle joint according to claim 1, wherein the tibial component is moved back and forth with respect to the intermediate component by a guide mechanism that slightly allows left and right movement, and the guide mechanism is provided with a stopper mechanism that restricts back and forth movement beyond a certain range. .   The artificial ankle joint according to claim 1 or 2, wherein the tibial compote is allowed to rotate in a plane with respect to the intermediate component.   The artificial ankle joint according to any one of claims 1 to 3, wherein the planar shape of the columnar portion of the talar component is a trapezoid that narrows forward and backward.   The artificial ankle joint according to any one of claims 1 to 4, wherein the talus component and the tibial component are made of biocompatible metal or ceramic, and the intermediate component is made of ultrahigh molecular weight polyethylene.

Images