JPH0329650A - Artificial joint - Google Patents

Abstract

PURPOSE:To firmly fasten both members by forming a circular grooves with a tape along the inner circumferential wall of a back metal opening end section, thereby engaging a tapered snap ring which presses the end face of an inner cup to the depth side of the back metal, with the circular groove. CONSTITUTION:The condyle section of an artificial bone 2 is coupled in the recessed section 14 of an inner cut 12 provided for the inner side of a back metal 11. The inner circumferential wall at the opening periphery section of the back metal 11 is formed with a tapered circular groove 11b. A tapered snap ring 20, which presses the end face 12A of the inner cup 12 to the depth side of the back metal 11, is engaged with the circular groove 11b. Namely, the back metal 11 which constitutes the mortar cover of an artificial joint can simply be mounted on and/or demounted from the inner cup 12 again and again. Moreover, when both of them is once connected, it is firmly fastened against the direction that either of them comes out, and against the direction of rotation. This can prevent the joint from being rattled and also from coming off from one side, thereby eliminating dislocation between the artificial bone and the mortar cover.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an artificial joint that is attached to a patient, and in particular, an artificial joint that maintains strong joints between members even during long-term use.
Moreover, each component is related to an artificial joint that can continue to maintain its posture and condition when applied. Although an artificial joint applied to a hip joint will be described below, the scope of application of the present invention is not interpreted as being limited to this example.

[Prior Art] FIG. 4 is a schematic explanatory diagram showing the hip joint portion of a human body, in which the head A of the femur A is rotatably fitted into the acetabulum B1 of the pubic bone B. If the femoral head has to be removed due to injury or disease, the portion surrounded by the chain line R is removed and an artificial joint as shown in Figure 5.6 is used instead.

The artificial joint is formed by an artificial bone 2 (a portion of which is shown by the broken line in FIG. 5) that is joined to the remainder of the femur A, and an acetabulum 1 that is attached to the acetabulum B side, and is shaped into the acetabulum M1. The bone head 2a of the artificial bone 2 is fitted into the central recess 14, and the acetabulum 1 is
and the artificial bone 2 are fitted together so that they can freely rotate with each other.

When using such an artificial bone, in a case where the acetabulum M1 is fixed to the remaining acetabone by the growth of the living bone without using bone cement, the acetabulum M1 is the inner c height of the metal back metal 11. A cup fitted with an inner cup 12 made of a strong synthetic resin (for example, ultra-high-density, high-molecular-weight polyethylene) is commonly used. When attaching this mortar M1 to the human body, first, the back metal 11 is initially fixed to the remaining bone with screws 13, and then the inner cup 12 is
is fitted inside the back metal 11. In order to fix the back metal 11 and the inner cup 12 during this fitting process, in the example shown in FIG. A structure is adopted in which a circumferential groove formed along the inner cup 12 is engaged with the protrusion 11a to prevent the inner cup 12 from coming off. As another example of the slip-out prevention structure, a circumferential groove is formed along the inner circumferential wall of the back metal 11 on the opening side, and a snap elastically engages with the circumferential groove on the outer circumferential side of the inner cup 12. It is also possible to employ a structure in which a piece is provided in a protruding manner and both members engage with each other.

[Problems to be Solved by the Invention] However, in the mortar M1 as shown in FIG. 5, once the inner cup 12 is fitted into the back metal 11, it is difficult to remove it again. After attaching the back metal 11 with the screws 13, it is normal to practice to test whether the inner cup 12 fits properly. Alternatively, when it becomes necessary to change to an inner cup 12 with a different size recess 14 during a reoperation, there is a problem in that special removal tools must be prepared in advance and extensive removal work is required. Furthermore, since the engagement structure of the circumferential groove and the protrusion 11a (or the snap piece) is adopted for fitting the back metal 11 and the inner cup 12, large stress is concentratedly applied to this engagement part. This tends to damage the inner cup 12, and furthermore, the protrusions 11a and the like may wear out due to long-term use, resulting in rattling between the back metal 11 and the inner cup 12. In addition, as shown in Fig. 5.6, if a flat part +2a is formed on the inner cup 12J) to prevent dislocation of the artificial bone 2, the flat part +2a is always located at the rear of the human body. However, in the above engagement structure, the inner cup 12 easily rotates around the axis relative to the back metal 11, and the artificial bone 2 may dislocate. There was also the problem of high sex.

Therefore, the present inventors conducted research with the aim of providing an artificial joint that has a structure in which the back metal and inner cup can be easily attached and detached, and also has an acetabulum that allows these two components to be extremely firmly fixed over long periods of use. Through repeated efforts, the present invention was completed.

[Means for Solving the Problems] The present invention, which has achieved the above object, forms a tapered annular groove along the inner circumferential wall of the back metal opening, and the end surface of the inner cup is formed in the annular groove. The gist of this is that a tapered snap ring is engaged that presses the pack metal toward the inner side. [Operations and Embodiments] FIG. 1 is a cross-sectional explanatory diagram showing a typical embodiment of the present invention, and FIG. 2 is a bottom view of FIG. 1. A number of screw holes 16 are formed at appropriate positions in the hollow hemispherical back metal 11, and an inner cup 12 made of high-strength synthetic resin is fitted into the inside of the back metal 11. A recess 14 is formed in which the femoral head 2a of the artificial bone 2 is rotatably fitted. The back metal 11 and the inner cup 12 are fixed by the following engagement structure. That is, a tapered annular groove ttb is formed along the circumferential direction on the inner peripheral wall of the back metal 11 on the opening side, and the full width is gradually reduced toward the groove bottom side on the side wall of the annular groove ttb on the opening side. A tapered surface ttb is formed. The end surface 12A of the inner cup 12 on the opening side is the inner side wall 1 of the annular groove 1lb! The snap ring 20 is set to slightly protrude toward the opening side from b2, and is fitted into the annular groove itb, which expands elastically in the outer circumferential direction. A tapered surface 20a is formed along the circumferential direction on the end surface of the snap ring 20 that contacts the tapered surface 11bl, and the tapered surface 20a is formed in a direction in which the wall thickness of the snap ring 20 is temporarily thinned toward the outer circumferential side. The expansion force of the snap ring 20 applies a pressing force that causes the snap ring 20 itself to move along the Taber surface 1lb+ toward the opposite side of the opening end, thereby moving the inner cup 12 toward the back side of the back metal 11. The members 11 and 12 are pressed together so that no wobbling occurs between the two members 11 and 12.

The snap ring 20 is made of a highly corrosion-resistant and highly rigid metal material (such as stainless steel or Ti alloy) or a synthetic resin material. In order to facilitate the attachment and detachment of the snap ring 20, it is preferable to form holes 20c, 20c at the ends, as shown in FIG.
As a result, the snap ring 20 can be easily attached to and detached from the annular groove 1lb using a surgical tool such as a briar, and the back metal 11 and inner cup 12 can be easily fixed and removed any number of times. On the other hand, a notch groove 12b as shown in FIG. 3 is formed on the outer peripheral surface of the inner cup 12. back metal 1
A rotation prevention pin 21 that is disposed to penetrate through the thickness direction of 1.
The tip of the inner cup 12 engages with this notch to prevent rotation of the inner cup 12 about its axis. In the example shown above, three notched grooves 1 are formed on one anti-rotation pin 21 at intervals of about 10 degrees at a center angle around the axis.
Although the example in which grooves 2b are formed is shown, the number of grooves provided and the grooves provided are arbitrary as long as the grooves can be engaged with the rotation prevention pin 21. Also, the rotation prevention pin 21 is a screw. It is also possible to use well-known bolts, pins, etc. The notch groove 12b is preferably provided in a direction parallel to the axis of the inner cup 12, so that the notch groove acts as a guide groove to guide the back metal 11 into which the anti-rotation pin is inserted to the hip bone. The inner cup can be easily attached and detached even after it has been temporarily fixed. The above rotation prevention pin 21 allows the inner cup 12 to
The rotation of the femoral head 2a can be reliably prevented as shown in the figure.
With the acetabulum provided with the flat part 12a that prevents dislocation of the artificial bone 2, the extraction of the artificial bone 2 can be completely prevented. The cross-sectional shape of the snap ring 20 may be semi-elliptical or polygonal in addition to the illustrated example, and the end structure of the snap ring 20 is not limited to the illustrated example; It may be bent to make it easier to hold, or may be connected via a U-shaped spring.

[Effects of the Invention] Since the present invention is constructed as described above, the back metal and inner cup that constitute the acetabulum of the artificial joint can be easily attached and detached any number of times, and the above-mentioned two members can be connected once. When this happens, it is firmly fixed in the direction of withdrawal and rotation, and it is possible to reliably prevent rattling and withdrawal during long-term use, and there is no accident of dislocation of the artificial bone and the acetabulum.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional explanatory diagram showing a typical embodiment of the present invention, Fig. 2 is a bottom view of Fig. 1, Fig. 3 is a side view showing an example of an inner cup, and Fig. 4 is an example of a human hip joint. 5 is an explanatory diagram showing a conventional example, and FIG. 6 is an explanatory diagram showing a conventional example.
It is a cross-sectional view taken along the -Vl line. ! ... Acetabular side M2 ... Artificial bone 11 ... Back metal 12 ... Inner cup 13 ... Screw 14 ... Recessed part 15 ... Inclined part 2
0...Snap ring 21...Rotation prevention pin

Claims (2)

[Claims] (1) An artificial joint in which the head of an artificial bone is fitted into a recess of an inner cup disposed inside a back metal, in which a tapered annular groove is formed on the inner peripheral wall of the opening edge of the back metal. The artificial joint is characterized in that the annular groove is engaged with a tapered snap ring that presses the end surface of the inner cup toward the inner side of the back metal. (2) A pin for preventing rotation of the inner cup is inserted into the back metal, and a groove is formed in the outer circumference of the inner cup into which the tip of the pin for preventing rotation is inserted. The artificial joint according to (1).