JP2001037792A - Artificial hip joint - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an artificial hip joint having a stem which adapts itself well to the intrinsic physique and skeleton of Orientals and the Japanese and allows the stable fixation of the stem without using cement. SOLUTION: A build-up part, forward build-up part and outer build-up part 4b are disposed on the front side and lateral side direction of the femur on the outer peripheral surface of a region near the neck part of the femur of the stem 3. The front width ML on the distal end aide of the stem 3 is made smaller than a lateral width AP.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an artificial joint for prosthesis of a human joint, and more particularly to an artificial hip joint for prosthesis of a hip joint, and more particularly, to an artificial hip joint having a cementless prosthesis stem.

[0002]

2. Description of the Related Art As shown schematically in FIG. 4 (a), a human hip joint is a portion connecting a femur F and a pelvis P, and has a spherical head B at the end of the femur F. The other has an acetabulum P1 of the pelvis P, and the head B and the acetabulum P1 function as a joint by being combined like a ball and socket.

[0003] As a treatment in the event that the hip joint becomes malfunctioned for some reason, the head B of the femur F is treated.
Is cut off along the line AA, the marine bone F2 at the upper end is removed from the intramedullary cavity F1, and fatty tissue (not shown) at the back is removed. Also, if necessary, the acetabular P1 is shaped,
Thereafter, as shown in FIG. 4B, the artificial hip joint 20 is implanted.

[0004] The artificial hip joint 20 includes a femoral stem 21 (hereinafter abbreviated as a stem) to be implanted into the femur. The stem 21 is implanted to maintain a painless joint of the hip joint. 21 for intramedullary cavity F
It is important that it is firmly fixed to 1. Conventionally, there have been roughly the following two methods for fixing the stem 21.

[0005] The first method is a method using an osteosynthesis agent (cement having little toxic component to a living body) C which adheres to the stem 21 and the wall of the intramedullary cavity F1. The stem 21 used in this method includes a stem 21 along the longitudinal direction.
It is a shape that is curved in the direction that becomes the posterior side of the femur when wearing it, or a shape that is straight and tapered toward the lower end, and the horizontal cross-sectional shape of the lower end is circular or square. Had become. However, this method of using cement usually resulted in a uniform distribution of the mechanical load in the short term, a reduction in the relative movement between the stem 21 and the bone, etc., but in the long term, There was a risk of necrosis of adjacent bones due to the toxicity of the cement itself, and loosening due to lack of elasticity.

Therefore, in order to avoid these problems, the stem 21 is inserted into the medullary cavity F1 without using cement (without cement).
The method of press-fitting and fixing inside is adopted. This is the second method, in which a porous surface is provided on the stem 21 using this method, and the shape of the stem 21 and the medullary cavity are increased in order to strengthen the adhesion between the porous surface and the wall of the intramedullary cavity F1. Design attempts have been made in Europe and the United States to approximate the shape of F1 as much as possible.

Japanese Patent Application Laid-Open No. Sho 60-41963 is an invention relating to such a design improvement. In this invention, as shown in FIG. 5, a stem 31 is provided with a porous material in a region near the neck provided at one end. It has a surface 32 and has a curved shape slightly backward along the longitudinal direction (R direction / direction of the posterior side of the femur when the stem 31 is attached).
Further, as shown in FIG.
The side width AP is larger than the front width ML.

Further, as shown in FIG.
In the invention of No. 049 as well, the stem 41 is provided with a porous surface 42 in the proximal region of the neck of the femur as shown in FIG. 6, and has a shape slightly curved (R direction) along the longitudinal direction. Further, as shown in the horizontal cross section of the other end in FIG. 3C, the side width AP is larger than the front width ML, and further, as shown in FIG. Is the horizontal axis when the direction extending laterally outward (in the OS direction / facing laterally outward of the hip joint F) and laterally inward (in the IS direction / facing laterally inward of the hip joint F. The direction toward the crotch side) is defined as the axis ax. The cross-sectional shape is non-linearly symmetric with respect to the axis ax.

[0009]

However, all of the above-mentioned conventional artificial hip joints for fixing the stem without cement have been developed in Europe and the United States, and have been created based on the physique and skeleton of Westerners. Although suitable for human skeletons, Orientals, including Japanese, have unique physique and skeletal characteristics, so they were not necessarily suitable for Orientals.

That is, even if the shape of the stem is curved slightly backward along the longitudinal direction, or if the horizontal cross-sectional shape of the region near the neck of the femur is non-linear,
Since the shape in the medullary cavity of the oriental thigh was not so, the degree of adhesion between the stem and the inner wall of the medullary cavity was not high.

In an extreme case, the fixation supportability is reduced due to a decrease in the occupancy of the stem in the medullary cavity and a decrease in the adherence to the bone,
As a result, there have been cases where micromotion of the stem occurs, causing joint pain due to poor sliding between the head and the acetabulum. In addition, when the load stress is concentrated on a local site due to a decrease in the area in contact with the bone, the bone of the portion subjected to the stress concentration may absorb and contract, and as a result, there is insufficient support for stable support of the stem. In some cases, bone loss had to be reduced to a level, which necessitated a revision procedure (re-implantation of a new stem with bone adhesive).

[0012] Because of the above situation, the stem shape is adapted to the physique and skeletal characteristics inherent to the Oriental people, and more reliable.
It has been desired to develop a hip prosthesis that enables safe prosthesis.

[0013]

In order to solve the above-mentioned problems, the present inventors have used materials for surgery of about 100 cases of a chanley-type stem using cement, and have developed a hip deformity which required hip arthroplasty. The following radiographic measurement was performed from the case.

Postoperative simple X in the case of Changlei type stem replacement
Trace the stem outline, cement mantle layer (outline) and femur outline in the front and side images of the radiograph, obtain the magnification of the X-ray with reference to the size of the head, and use this magnification to scale the image to actual size. Reduced to In the reduced trace drawing, the midpoint of the cement layer was determined at the middle position of the Changlei stem and the tip end position of the stem, and a straight line obtained by connecting these was used as a reference line. Along this reference line, the stem length is divided into ten equal parts, and points 1, 2, 3, ... 11 are defined, and the distance to the cement mantle layer end on a line orthogonal to the reference line at each of these points. Was measured.

The following dimensions were obtained as a result of the measurement.

[0016] The average of these distance values was determined.

Next, the shape of the stem is examined using a CT scan photograph of the femur, the most average shape is derived, and the design drawing and three-dimensional modeling of the stem are performed using the numerical values of the X-ray photograph measurement as a reference for sizing. Created.

The hip prosthesis of the present invention is a stem having an optimal shape based on the stem designed by the above procedure, and is made of a metal stem which is inserted and fixed in the medullary cavity of a human femur. And a head prosthesis attached to the neck provided at one end of the stem, wherein the stem is located on the outer peripheral surface of the proximal region of the neck of the femur in the frontal and lateral directions of the femur. It has a raised part, and the front width of the distal end side of the stem is smaller than the side width.

[0019]

Next, the present invention will be described in detail with reference to the accompanying drawings.

FIGS. 1 to 3 show one embodiment of a hip prosthesis 1 according to the present invention, 2 is a head cap, and 3 is a stem. The material of each member is a high strength ceramic for living body such as alumina or zirconia in which the above-mentioned head ball 2 is produced by a known method, and the living body such as a titanium alloy or stainless metal produced by a known method. It is a safe metal material.

The stem 3 has an anterior surface 3a, a posterior surface 3b, a lateral outer surface 3c, and a lateral inner surface 3d in correspondence with the body direction. It is a part facing the rear side, the lateral outside, and the lateral inside. FIG. 1 is a front view in which the front surface 3a is the front, and FIG.
FIG. 3 is a side view with the lateral outer surface 3c as a front face, and FIG.
3A is a cross-sectional view taken along line XX of FIG. 1, and FIG. 3B is a cross-sectional view taken along YY line in FIG.

As is well known, said stem 3 is adapted to be placed in the medullary canal of a human femur F, the proximal neck region 4, the middle region 5 and the distal region of the femur. 6, and a neck 7 extending outside the medullary cavity in close proximity to the acetabulum (not shown). In the figure, the neck 7 is inserted into the medullary cavity of the femur F indicated by a dashed line. The distal region 6 and the intermediate region 5 are fitted together and cooperate with the acetabulum via the head ball 2 carried on the neck 7.

As shown in FIG. 1, the proximal neck region 4 of the femur includes an outer ridge 4a formed by raising the lateral outer surface 3c.
And, as shown in FIG. 2, a front protruding portion 4b formed by protruding the front surface 3a. Furthermore, as shown in FIG. 3 (a), it is preferable that the horizontal cross-sectional shape is generally a line-symmetric shape such that the rear surface 3b and the front surface 3a approach from the lateral outer surface 3c to the lateral inner surface 3d. That is, laterally outward (OS direction / facing laterally outward of hip joint F) and laterally inward (IS
Orientation / facing outward of the hip joint F. When the direction extending to the crotch side is set as the axis ax, the horizontal cross-sectional shape is made to be line-symmetric with respect to the axis ax.

Since the skeleton of the femur F of an Oriental man has such a characteristic in the neck region 4 of the femur, the stem 3 is formed into a hollow intramedullary cavity as described later. Contributes to a glove fit (with a glove that fits perfectly in the hand) without substantially creating any gaps or voids with the internal contour of the glove. In addition, although the said stem 3 is provided with these said front protrusion parts 4b, also forward,
And it is not curved backward.

The proximal neck region 4 of the femur has a roughened surface 11 surrounding the stem 3. This rough surface 11
Is formed by applying a titanium material by a known thermal spraying method, and a hydroxyapatite coating 13 having a bone growth inducing action is deposited thereon by a similar known thermal spraying method. As a result, a double coating of the titanium sprayed rough surface 11 + the hydroxyapatite coating 13 is applied.

The above-mentioned double coating stimulates the bone when the stem 3 applies a load to the adjacent bone and compresses the bone, and together with the osteoinductive action of hydroxyapatite, the rough coating of the rough surface 11 having a large surface area into the unevenness. Induces bone growth.
This greatly contributes to fixing the surface of the stem 3 in the medullary cavity.

The hydroxyapatite coating 13 is
It is formed not only on the rough surface 11 but also from the whole region near the neck 4 of the femur to the intermediate region 5. this is,
This is a process for obtaining a stepwise bonding force with the bone. Among them, the double coating of the rough surface and the hydroxyapatite film 13 has the largest bonding force with the bone, and subsequently, the bonding force with the bone decreases in the order of the single coated portion of the hydroxyapatite film 13 alone and the non-coated portion. In this way, by applying the above-mentioned stepwise coating, the stem 3 gradually weakens in three steps from the end of the proximal neck region 4 to the end of the distal region 6 of the femur. It is devised as follows. Here, the reason why the bonding force with the bone is made stepwise is to prevent undesirable stress transmission from occurring due to the presence of the interface where the bonding force with the bone changes rapidly. The reason for increasing the bonding force between the proximal neck region 4 of the femur and the bone is to provide a sealing effect for preventing wear powder and the like from entering the medullary cavity from a gap between the bone and the bone. is there. Furthermore, the looseness of the connection between the distal region 6 and the bone is set so that excessive stress is not applied to the proximal neck region 4 of the femur due to the rocking motion about the deep part of the medullary cavity. It is.

Next, in the distal region 6, as shown in FIG. 3B, the front surface 3a and the rear surface 3b are narrower than the lateral outer surface 3c and the lateral inner surface 3d. Furthermore, it is preferable that the horizontal cross-sectional shape be an elliptical shape. By the way, the relationship between the side width AP> the front width ML is established for the magnitude of the side width AP and the front width ML of the stem 3. The distal region is shaped like this because the skeleton of the oriental femur generally has such characteristics, and as described above, the stem 3 has a hollow inner contour in the medullary cavity. This is to fit the glove between. In contrast, FIG.
Comparing the cross-sectional shape of the proximal neck region 5 of the femur shown in (a), in the proximal neck region 5 of the femur, the anterior surface 3a and the posterior surface 3b are wider than the lateral outer surface 3c and the lateral inner surface 3d. Therefore, the relationship of the side width AP <the front width ML is established. That is, the stem 3 has a sectional shape from the proximal region 4 to the distal region 6 of the femur along the axis extending from the side width AP <front width ML shown in FIG. As shown in FIG. 3B, the shape gradually changes to the shape of the side width AP> the front width ML.

The stem 3 having such a configuration is implanted in the femur F following resection of the cervical bone of the femur F and proper formation in the hollow medullary cavity into which the stem 3 is inserted. In the formation of the hollow medullary cavity, the lattice-like cancellous bone tissue portion near the end of the femur F is first resected with a suitable cutting instrument (not shown). Following such removal, a file having substantially the same shape as the stem 3 is applied into the hollow medullary cavity of the femur F.
The stem 3 is then removed from the femur F and the stem 3 is inserted into the thus formed hollow medullary cavity. The stem 3 is glove-fitted without substantially creating a gap or void between the inner contour of the hollow intramedullary canal without breaking or disturbing the newly formed contour by the file. To achieve a fit).

Next, the neck 7 has a tapered cylindrical shape and carries a head ball 2 described later.

The neck 7 extends outside the medullary cavity close to the acetabulum.

The head 2 has a spherical outer surface 2a and a tapered cylindrical hole 2b formed in the center axis direction. By strongly pressing the tip side of the neck portion 7 into the tapered hole 2b, the neck portion 7 is firmly fixed to the tip of the stem 3 and slides on the outer acetabulum with the outer surface 2a. As a result, the stem 3 including the head ball 2 cooperates with the acetabular part on the pelvis side as an artificial hip joint, and restores a healthy joint function.

When the acetabulum is in a healthy state, the head 2 slides with the living tissue on the surface of the acetabulum, but otherwise, it is implanted in the acetabulum by a known method. Slides with the socket (not shown).

Incidentally, it is necessary to carefully check the fitted state between the stem 3 and the internal contour of the hollow intramedullary canal when carefully implanting the artificial hip joint in the body. This is because removing and replacing a hip prosthesis implanted in the body would cause a great deal of pain to the patient.
Therefore, in actual hip arthroplasty, even if it is necessary to prepare a plurality of stems 3 of different sizes and use the one having a size different from the planned size while checking the above-mentioned fitted state. Prepare in advance so that you can respond quickly.

For example, the length of the stem 3 is changed every 5 mm, and the length of the neck 7 is changed every 1 mm.
A. E every 1mm: B, D, G 0.5m
m), and several types of stems 3 having different dimensions G for each 0.75 mm may be prepared in advance.

Although the embodiment of the present invention has been described with reference to the drawings, it is needless to say that the present invention is not limited to the above-described embodiment, and can take any form without departing from the object of the invention.

[0037]

The present invention provides an artificial joint comprising a metal stem inserted into and fixed in the medullary cavity of a human femur and a head ball attached to a neck provided at one end of the stem. In the above, the stem has a bulge in the front side and the lateral direction of the femur on the outer peripheral surface of the neck proximal region of the femur, and the front width at the distal end side of the stem is larger than the lateral width. The feature of being small is that the stem is well adapted to the Oriental skeleton. Thereby, a glove fit can be achieved without substantially creating a gap or void between the hollow inner contour of the medullary cavity.

Therefore, it is possible to safely implant an artificial hip joint without using cement for Oriental people.

[Brief description of the drawings]

FIG. 1 is a front view of an artificial hip joint according to an embodiment of the present invention.

FIG. 2 is a side view of the hip joint prosthesis of FIG. 1;

3A is a sectional view taken along line XX of FIG. 1, and FIG. 3B is a sectional view taken along YY of FIG.

4A is a partially cutaway view showing a state of a hip joint, and FIG. 2 is a partially cutaway view showing a state where an artificial hip joint is mounted on the hip joint.

5A and 5B show a conventional artificial hip joint stem, wherein FIG. 5A is a side view, and FIG. 5B is a cross-sectional view taken along line DD of FIG.

6A and 6B show a conventional artificial hip joint stem, wherein FIG. 6A is a side view, FIG. 6B is a cross-sectional view taken along line EE of FIG.
FIG. 7 is a sectional view taken along line GG of FIG.

[Explanation of symbols]

 Reference Signs List 1 artificial hip joint 2 head ball 2a outer surface 2b tapered hole 3 (femur) stem 3a front surface 3b rear surface 3c lateral outer surface 3d lateral inner surface 4 femoral neck proximal region 4a forward ridge 4b outward ridge 5 Intermediate region 6 Distal region 7 Neck 11 Rough surface 13 Hydroxyapatite coating ML Front width AP Side width

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4C081 AB05 CF032 CG03 CG05 DA01 DB07 DC03 4C097 AA03 BB01 BB09 CC05 CC06 DD07 DD09 DD10 SC01 SC04 SC06

Claims (3)

[Claims] 1. An artificial joint comprising a metal stem inserted and fixed in a medullary cavity of a human femur and a head ball attached to a neck provided at one end of the stem. Has a protruding portion on the outer peripheral surface of the proximal region of the neck of the femur in the anterior and lateral directions of the femur, and the front width at the distal end side of the stem is smaller than the lateral width. And artificial hip joint. 2. The hip joint prosthesis according to claim 1, wherein a horizontal cross-sectional shape of the stem near the neck of the femur is substantially line-symmetrical. 3. The artificial hip joint according to claim 1, wherein the stem has a rough outer surface in a region near the neck of the femur and is coated with hydroxyapatite.