JP2852780B2 - Artificial head and method of manufacturing the same - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an artificial head which is replaced as a substitute when the head of a femur is damaged due to, for example, a fracture or osteoarthritis, and a method of manufacturing the same. About.

(Prior Art) Conventionally, in this type of artificial head, when the head and the stem are of a split type, they are usually integrated as follows.

First, a tip portion of a stem (hereinafter, also simply referred to as “tip portion”) formed with the same taper with respect to a tapered hole portion (hereinafter, also simply referred to as “hole portion”) provided in a head ball.
Is fitted. After that, a weak impact is applied to the top of the head of the head to firmly fit, fix, and integrate.

Therefore, in this case, the load (mainly weight) received by the top of the head of the head is supported at the tapered fitting portion.

By the way, in the above-mentioned conventional technique, when the stem is taperedly fitted to the head cap, a gap of about 3 mm is formed between the lower part of the hole and the tip of the stem. This gap is used to properly maintain the taper fitting by absorbing a processing error due to the necessity in processing the hole.

(Problem to be Solved by the Invention) In the conventional artificial head, a load applied to the top of the head of the replaced patient due to the presence of the above-mentioned space is:
The bottom of the hole and the tip of the stem are not supported in a so-called butt-joined state, but are supported in a tapered fitting portion. Therefore, in this case, the distal end of the stem is deeply pushed into the bottom of the hole in the head of the head, and at the same time, has an effect of expanding the area around the hole outward by the so-called wedge effect. For this reason, a tensile stress along the circumferential direction is generated in this portion by the internal pressure received by the taper fitting. In addition, a tensile stress accompanying bending in a shape that is pushed outward is also generated inside the gap along the periphery. Moreover, such tensile stress increases in proportion to the increase in the load, and remains as a residual stress due to the pushing of the stem even after unloading. Especially when walking or exercising like jumping,
The tensile stress when an impact load that is several times as large as the static load acts is extremely large.

Therefore, it can be said that this structure is suitable when the head cap is made of a metal material having a large tensile strength. It has the disadvantage of being easy and therefore dangerous and unsuitable.

In order to secure the strength by increasing the thickness of the head cap, the head cap itself becomes large, and the applicable range of patients is limited. On the other hand, since the wall thickness cannot be increased for a small diameter head ball, the strength is insufficient and the ball cannot be used.

As a countermeasure against this, it is considered that the voids may be filled with a filler, but a rational means for sealing the filler at the time of fitting has not yet been developed. For example, in the case of filling the filling material by a syringe method, a part of the filling material drips, so that the gap cannot be filled without a gap or adheres to the tapered surface of the stem, resulting in poor fitting. In practice, the task is considered difficult.

In view of the above-mentioned problems to be solved, the present invention uses a material with a low tensile strength such as ceramics for the headcap by preventing the stem from being pushed in after replacement and suppressing the occurrence of tensile stress in the headcap. Another object of the present invention is to obtain an artificial head having sufficient strength and to provide a rational manufacturing method thereof.

(Means for Solving the Problems) In order to achieve the above object, the present invention integrates a hole formed in a caput ball by fitting a distal end of a tapered stem to the hole. A buckling occurs when integrated, and a sleeve-like container containing a hardening filler is interposed in a portion between the bottom of the hole and the tip. It is.

And, as the manufacturing method, the head of the head and the stem, the tip of the stem formed into a tapered shape with respect to the hole provided in the head of the head, the bottom of the hole and the tip of the stem In keeping the gap between the fitting and the integration, at the site between the bottom of the hole and the tip, a sleeve-like container containing a hardening filler is interposed, Fit the tip to the hole under the condition,
Then, an external force is applied to buckle the sleeve-shaped container, the gap is filled with the filler, and the filler is hardened to integrate the head ball and the stem.

(Operation) With the above configuration, the head cap and the stem are butt-joined at the bottom of the hole of the head cap and the tip of the stem via the hardened filler. This allows
After replacement with the patient, the load is less likely to act at the tapered fitting site, and is substantially transmitted directly to the distal end of the stem via the filler. That is, since the distal end of the stem is not further pushed into the head cap, the generation of excessive tensile stress is effectively prevented. As a result, substantially only a compressive stress is generated in the head cap, so that a material having a low tensile strength such as ceramics can be used regardless of the diameter.

Also, since the filler is interposed in the state of being accommodated in the sleeve-shaped container, the filling operation can be simplified, and furthermore, when interposed, it is possible to prevent the filler from dripping and attaching to the tapered surface to cause a poor fitting. It is valid.

Further, since the sleeve-shaped container is buckled by applying an external force (in some cases, the deformation is not buckling, but is referred to as buckling in the present specification), the gap is substantially evenly distributed by the filler. It is effective to integrate the head cap and the stem in a tightly contacted state without any gap.

Thus, an artificial head having excellent strength can be rationally manufactured even if a material having a low tensile strength such as ceramic is used for the head of the head.

(Example)-Example 1-A first example of the present invention will be described in detail with reference to Figs. 1 to 4.

In the figure, reference numeral 1 denotes an artificial head replaced with a hip joint,
The stem 2 and the head 3 are integrally formed as described below.

That is, the stem 2 has a base end 4 formed in a square shape.
And a distal end portion 5 formed on the base end portion 4 and connected to each other in the shape of a tapered truncated cone.

On the other hand, the head cap 3 has a substantially spherical shape, has an opening at the lower center, and has a hole 6 formed with the same taper as the tip 5 of the stem 2. However, when the distal end portion 5 of the stem 2 is fitted, a predetermined gap S is maintained between the distal end surface 7 and the bottom surface 9 of the bottom portion 8 of the hole portion 6 when the distal end portion 5 of the stem 2 is fitted. It is large. The recess 11 formed along the peripheral edge of the bottom surface 9 of the hole 6 is a so-called relief groove in the drilling of the hole 6.

Reference numeral 12 denotes a sleeve-shaped container having an outer diameter substantially equal to the outer diameter of the distal end surface 7 of the stem 2 and formed in a substantially cylindrical shape. Then, in a state where the hardening filler 13 is accommodated inside, it is interposed between the bottom surface 9 of the hole and the tip end surface 7 of the stem. However, this sleeve-shaped container 12
Are buckled and interposed in a state where the tip portion 5 is fitted into the hole portion 6 and is integrated.

The sleeve-shaped container 12 in this example is made of a titanium alloy, and has a length (height) slightly larger than the thickness (height) of the gap S before buckling (deformation). In addition, a thin portion 15 is formed by recessing an annular groove 14 having a substantially arc-shaped cross section with respect to the outer periphery of the intermediate portion in the up-down direction, so that the portion is easily buckled at the time of fitting. In this example, the thickness of the thin portion 15 before buckling is set to 0.07 mm.

Next, a method of integrating the stem 2 and the head 3 in this example will be described in detail.

First, prior to fitting the distal end 5 of the stem 2 into the hole 6 of the head 3, a portion between the bottom 8 and the distal end 5 of the hole 6, in this example, the distal end surface 7 of the stem 2. On the other hand, the sleeve-shaped container 12 is placed concentrically.

Next, an appropriate amount of the curable filler 13 is injected up to the upper end surface of the sleeve-like container 12 (see FIGS. 2 and 3). In this example, the filler 13 uses bone cement. However, any filler that is hard after curing and harmless to the human body, such as an epoxy resin, can be appropriately selected and used.

Then, in this state, the distal end 5 of the stem 2 is inserted into the hole 6 of the head ball 3. Thereafter, a slight impact is applied to the top 16 of the head 3 by a hammer or the like. In this way, the stem 2 and the head ball 3 are tightly tapered,
The sleeve-like container 12 is deformed in such a manner that the difference between the original length and the length of the gap S is substantially compressed by the buckling at the thin portion 15, and is crushed. At the same time, the filler 13 fills the void S,
It adheres closely to the bottom surface 9 of the hole 6 of the head ball 3 and the distal end surface 7 of the stem 2 and is cured under this condition.

Thus, the head 3 and the stem 2 are integrally fixed via the filler 13 (FIG. 1). As a result, the load acting on the head ball 3 is transmitted as it is to the distal end surface 7 of the stem 2 via the bottom surface 9 of the hole 6 and the filler 13 as a compressive force. Therefore, the stem 2 is not further pushed into the hole 6, and the generation of tensile stress in the area around the hole 6 and the peripheral edge of the gap S is effectively prevented.

Therefore, a material having a small tensile strength, such as a ceramic material, can be used also for a head ball having a small diameter (for example, φ22 mm or less).

In addition, as a ceramic applicable to the head ball 3, in addition to alumina ceramic, zirconia, silicon nitride, silicon carbide, sialon, or a composite thereof can be exemplified. Incidentally, for the stem 2, a titanium alloy, a cobalt chromium alloy, stainless steel, high carbon steel, or the like is used.

In this example, a titanium alloy is exemplified as the material of the sleeve-shaped container 12.In addition, a cobalt chromium alloy, stainless steel, and even a metal material having high corrosion resistance such as aluminum and easily causing plastic deformation can be used. Resin materials such as high-density polyethylene, polyacetal, 6-nylon, and Teflon can also be appropriately selected and used.

The shape of the sleeve-shaped container is the same as that described above.
Or a U-shaped section provided on the outer periphery (see FIGS. 4 (b) and (c)).
It is not limited to these. Head ball 3 and stem 2
Is fitted and buckled when subjected to a weak impact, and if it is possible to obtain the desired deformation, it is possible to use a material having an appropriate shape such as, for example, a U-shaped cross section. it can. The thickness (t) of the thin portion 15 is
Although it depends on the material, about 0.03 to 0.8 mm is appropriate for practical use. If it is too thin, it will be difficult to manufacture it. If it is too thick, it may not buckle even if an impact force is applied.

-Example 2-Next, a second example of the artificial head of the present invention will be described with reference to Figs. 5 to 7. However, this embodiment can be said to be a modification of the first embodiment, and therefore the description will be made focusing on the differences, and the same portions will be denoted by the same reference numerals and description thereof will be appropriately omitted.

That is, in the present example, the sleeve-like container 12 containing the filler 13 and interposed between the bottom 8 of the hole 6 of the head 3 and the tip 5 of the stem 2 Along the periphery of the surface 7, it is formed to stand integrally.

Therefore, every time the filler 13 is injected, the step of mounting the sleeve-shaped container 12 at a predetermined position on the distal end surface 7 of the stem is not required. Moreover, since the sleeve-shaped container 12 does not shift sideways when the filler 13 is injected or when the stem 2 is inserted into or fixed to the head cap 3, the fitting can be performed easily and stably.

When the stem 2 is inserted into the head cap 3 and an impact is applied to the head cap 3, the thin portion 15 buckles and is integrated. In this example, as a result of the sleeve-shaped container 12 being formed integrally with the stem 2, they are made of the same material.
However, the sleeve-shaped container 12 may be made of a different material, and the lower end portion may be integrated with the stem surface at the distal end surface 7 thereof.

-Example 3-Next, a third example of the artificial bone head of the present invention will be described with reference to Figs. 8 to 10. However, this embodiment is also a modification of the first embodiment, like the previous embodiment, and therefore, the same portions are denoted by the same reference characters and description thereof will not be repeated.

The sleeve-shaped container 12 in this embodiment has an inner diameter at the lower end slightly larger than the outer diameter of the distal end surface 7 of the stem 2. Then, it is fitted to the outer peripheral edge of the distal end face 7 of the stem 2 via the lower end. That is, the sleeve-shaped container 12 of this example has the same outer diameter and the same cylindrical shape, the upper end of the inner diameter is stepped and thick, and the lower end is the thin portion 15 so as to be easily buckled (the second end). As shown in FIG. 10 (a)), the stem 2 is fitted to the outer periphery of the distal end surface 7 of the stem 2 via the thin portion 15.

Therefore, as in the previous example, the sleeve-shaped container 12 is
It does not shift laterally when the filler is injected or when the stem 2 is inserted and fixed into the head 3, so that both are fitted in an easy and stable state, and integrated. can do. The sleeve-shaped container 12 in this example
Is set to a size that is slightly larger than the height of the gap S when the head is fitted to the stem 2 before buckling.

Thus, the head 3 is inserted into the stem 2 and the head 3
When the unit is integrated by applying an impact to
Are buckled and deformed so as to be greatly curved outwardly along the recess 11 (see FIG. 8).

To describe another embodiment of the sleeve-shaped container 12 in this embodiment, the one shown in FIG. 10 (b) is made cylindrical with the same inner diameter, and the upper end of the outer diameter is stepped and thick. The lower end is a thin portion 15. Needless to say, the upper portion may be formed with a stepped thick inner and outer diameter, and the lower end may be formed as a thin portion (not shown).

(Effects of the Invention) Since the present invention is configured as follows, it has the effects described below.

After the patient has been replaced, the head ball is virtually free from further pushing of the stem, thus effectively inhibiting the occurrence of tensile stress. Therefore, substantially, only a compressive stress is generated in the head ball due to the load acting on the distal end of the stem and being transmitted through the filler. As a result, materials with low tensile strength, such as conventional ceramics, could not be applied to small-diameter head spheres due to insufficient strength. However, according to the present invention, even if these materials were used, the diameter of the head was reduced. Irrespective of much, an artificial bone head with high strength can be obtained.

In addition, in the method for manufacturing an artificial bone head, the filling operation is simplified since the filler is interposed in a state of being accommodated in the sleeve-shaped container. In addition, when interposed, it is effective in preventing the occurrence of poor fitting due to dropping or sticking to the tapered surface.

Further, since the sleeve-like container is buckled by applying an external force, the voids are substantially evenly filled by the filler, and thus it is effective to integrate the head cap and the stem in a tightly contacted state. .

[Brief description of the drawings]

1 to 4 show a first embodiment of the artificial head according to the present invention. FIG. 1 is a partially cutaway longitudinal front view of the artificial head, and FIG. FIG. 3 is a partially omitted cross-sectional view showing a state in which a sleeve-like container containing a filler is placed on the distal end surface. FIG. 3 is an enlarged cross-sectional view of a portion A in FIG.
FIGS. 1A to 1C are enlarged sectional views showing the shape of the sleeve-like container in a state in which the filler is accommodated. 5 to 7 show a second embodiment of the present invention. FIG. 5 is a partially omitted longitudinal front view of the artificial bone head, and FIG. 6 is a front end of the stem. 7 is an enlarged sectional view of a portion B in FIG. FIGS. 8 to 10 show a third embodiment of the present invention. FIG. 8 is a partially omitted longitudinal front view of the artificial bone head, and FIG. A partially omitted longitudinal sectional view showing a state in which a sleeve-like container containing
10 (a) and (b) are enlarged sectional views showing the shape of the sleeve-shaped container. DESCRIPTION OF SYMBOLS 1 ... Artificial head, 2 ... Stem 3 ... Head ball, 5 ... Tip 6 ... Hole, 8 ... Bottom 12 ... Sleeve-shaped container 13 ... Filler S ... Void

Claims (2)

(57) [Claims] 1. A taper-shaped stem that is integrated by fitting a tip end portion of a tapered stem into a hole provided in a head ball, wherein buckling occurs when integrated. An artificial bone head in which a sleeve-like container containing a hardening filler is interposed between a bottom portion of the hole and a front end portion. 2. A tip of a stem formed in a tapered shape with respect to a hole provided in the head,
In a method in which a gap is held and fitted between the bottom of the hole and the tip of the stem and integrated, a portion between the bottom of the hole and the tip is hardened. A sleeve-like container accommodating a filler is interposed, and the tip is fitted into the hole in that state, and then an external force is applied to buckle the sleeve-like container, and the filler And filling the void with the filler, thereby curing the filler, thereby integrating the head and the stem with the stem.