KR100458639B1 - Cemented stem for hip joint arthroplastry - Google Patents

Abstract

According to the present invention, the front surface and the rear surface, respectively proximal to the outside of the front projection and the proximal portion formed with the rear projection; A distal portion extending vertically downward from the proximal portion; A neck extending upwardly at an angle from the proximal portion at an angle; And a truncated cone portion formed at an end of the neck portion. A cement stem for an artificial hip joint is provided.

Description

Cemented stem for hip joint arthroplastry

The present invention relates to a cement stem for an artificial hip, and more particularly, to a stem inserted with cement in the femur of the hip joint.

The hip joint is a joint that connects the femur of the human body and the acetabular pelvis. The hip joint may be damaged by pathological causes such as tuberculosis, diseases, and the like, and artificial hip joint devices may be applied through surgery to repair the hip joint. Typically, hip joint devices consist of a stem and a cup. Stems and cups are made of alloys such as titanium, which are harmless to humans, for example. The stem of the artificial hip appliance is inserted into the femur and fixed, and the cup is fixed to the acetabular pelvis. At the end of the stem a sphere formed of a ceramic material or a metal material is fixed, and in the cup a corresponding hemisphere capable of receiving and rotating the sphere is fitted and the corresponding hemisphere is made of ceramic material or polymer polyethylene.

The femur of the human body is composed of cortical bones forming the structure of the outer cortex and cortical bones existing inside the cortical bones. Cortical bone is a very hard tissue, while reticulum is a relatively soft spongy tissue. In practice, the stem of the artificial hip appliance is inserted into the cortical bone to dig into the reticular bone. The cement stem often has a cross-sectional shape that can be fixed by the wedge action on the cortical bone. That is, the cross section of the stem has a quadrangular shape as a whole so that the stem is fixed by the wedge action in the interior of the cortical bone which is almost cylindrical. In addition, blades may be formed on the sides of the stem to assist in the wedge action of the stem and to prevent the stem from rotating in the cortical bone.

On the other hand, the device for artificial hip joint may be applied with cement. Cement is injected together when pushing the stem into the femur to enhance the bond between the femur and stem.

U.S. Pat.No. 5,314,493, on the other hand, discloses a stem for use in a device for hip arthroplasty according to the prior art, which is inserted into the femur together with cement. The stem disclosed herein has the problem that when the cement is inserted into the femur together with the cement, the cement mantle is not properly distributed in the femur. That is, although the distribution of the cement mantle is optimized by providing a centralizer at the end of the stem, there is a problem in that the thickness of the cement mantle for a specific portion of the femur cannot be increased. Therefore, there is a problem that the supply of cement to the portion where the thickness of the cement mantle should be larger is not easy because the rigidity of the bone is relatively weak.

The present invention has been made to solve the above problems, it is an object of the present invention to provide an improved cement type stem for artificial hip joint that can be applied with cement.

1 is a front view of the cement stem for artificial hip joint according to the present invention.

2 is a side view of FIG. 1;

3A-3E are cross-sectional views of each part of FIG. 1.

<Brief Description of Major Codes in Drawings>

11. Stem 12. Proximal

13. Distal 14. Neck

15. Frustrated Cone 17. Anterior Projection

25. Rear protrusion

In order to achieve the above object, according to the present invention, the front surface and the rear surface, respectively proximal portion formed with a front projection and a rear projection close to the outside; A distal portion extending vertically downward from the proximal portion; A neck extending upwardly at an angle from the proximal portion at an angle; And a truncated cone portion formed at an end of the neck portion.

According to one feature of the invention, the front and rear projections, respectively, the lower the protrusion height as the proximal portion approaches the distal portion.

According to another feature of the invention, the distal portion is formed by double tapering.

According to another feature of the invention, the proximal and distal sections are formed in a rectangular shape as a whole, and the corners of the rectangle are rounded.

According to another feature of the invention, the inner surface of the proximal portion is formed as a curved portion having a radius of curvature of 87 to 93 mm.

According to another feature of the present invention, there is further provided a semi-collar made by forming a step in the downward direction in a portion of the proximal portion extending from the neck portion to the proximal portion.

According to another feature of the invention, the cross section of the neck is formed in an oval shape.

According to another feature of the invention, the neck and the truncated cone extending therefrom are inclined at an angle of 127 to 133 degrees with respect to the portion extending from the proximal portion to the distal portion.

According to another feature of the invention, the outer surface of the neck portion and a portion of the proximal portion proximate the neck portion are high polished.

Hereinafter, the present invention will be described in more detail with reference to an embodiment shown in the accompanying drawings.

1 is a front view of a stem for a hip prosthesis according to the present invention.

Referring to the drawings, the stem 11 extends upwardly at a predetermined angle with respect to the proximal portion 12, the distal portion 13 extending downward from the proximal portion 12 in a linear direction, and the proximal portion 12. A neck 14 and a truncated cone 15 formed at the end of the neck 14 are provided. As can be seen in the figure, the part of the stem extending from the proximal part 12 to the distal part 13 is tapered, and this taper extension is the part inserted into the femur of the human body. In addition, the ceramic cone (not shown) is fitted to the truncated cone portion 15.

In practice, when the stem 11 is inserted into the femur, the portion indicated by reference numeral 21 corresponds to the inner side between the two legs and the reference numeral 20 corresponds to the outer side. Thus, the front surface of the proximal portion 12 shown in the drawing faces the front of the human body, and the portion not shown in the drawing is the rear surface.

A protruding portion 17 is formed on the front surface near the outer side 20 of the proximal portion 12, and a protruding portion is formed near the outer side 20 on the rear surface. The protrusion 17 of the front surface and the protrusion of the rear surface are symmetrical. This can be easily understood through the cross-sectional view shown in FIG. 3A. The protrusion 17 is formed close to the outside over the longitudinal direction of the proximal portion 12 as shown in the figure.

The protrusion 17 serves to increase the pressure of the cement into the femur bone when the stem 11 is inserted into the femur. That is, the pressure of the femur portion facing the inner side 21 helps to form a better cement mantle. The protrusion 17 serves to push the cement toward the inner side 21 in the inner space of the femur so that the cement thickness of the corresponding portion can be thickened. This protrusion 17 forms an important feature in the present invention.

In addition, the longitudinal portion extending from the proximal portion 12 to the distal portion 13 and the longitudinal portion extending from the proximal portion 12 to the truncated cone 15 form a predetermined angle. For example, the center position in the proximal portion 12 is indicated by the reference numeral 18, a line extending from the point through the center of the distal portion 13, and the center point of the truncated cone portion 15 from the point 18. The line extending towards 19 is at an angle of about 127 to 133 degrees. This angle is a suitable angle in consideration of the shape of the femur and pelvis and at the same time when the cement is applied together, it is possible to achieve a more stable fixation when the stem 11 is inserted into the femur. In particular, this angle contributes to anatomical restoration in the elderly patients who use a lot of cement stems.

On the other hand, a curved surface 23 is formed inside the proximal portion 12, and the radius of curvature of the curved surface 23 is about 87 to 93 mm. This radius of curvature is also adapted in consideration of the anatomical shape of the femur and the application of cement, which forms another feature of the present invention. 1, the inner and outer surfaces of the distal portion 13 are tapered at an angle of α, which is preferably about 4 to 7 degrees.

Reference numeral 8 denotes the length of the lever arm extending from the center of the distal portion 12 to the center of the truncated cone 15. The length of the lever arm 8 should be as large as possible because the larger the length of the lever arm, the more effective the length of the muscle can be used. As described above, when the line extending from the point 18 toward the center point 19 of the truncated cone 15 forms an angle of about 127 to 133 degrees, the length 8 of the lever arm is anatomically anatomical. It is possible to restore most effectively to the same offset within the allowable range (ie the distance between the vertical line passing through point 18 and the vertical line passing through point 19).

Designated by reference numeral 9 is a groove formed at the top of the distal portion 12. The groove 9 is a groove for inserting the end of a tool (not shown) used during the procedure. By inserting and pressing a tool into the groove 9, the stem 11 can enter the intramedullary canal of the femur.

2 is a right side view of FIG. 1.

Referring to the drawings, the front protrusion 17 and the rear protrusion 25 are formed symmetrically in front of and behind the stem 11. On the other hand, as seen in FIG. 2, the front and rear surfaces of the distal portion 13 are tapered at an angle of β, and β is preferably about 1 to 5 degrees. Consequently, the distal portion 13 is doubled by the taper angle α of the distal portion 13 in the front view shown in FIG. 1 and the taper angle β of the distal portion 13 in the right side view shown in FIG. It can be understood that the taper. This double tapered cross-sectional structure allows the stem to acquire a clamping force by acting as a wedge in the cement in the bone marrow cavity. It also serves to reduce the stress toward the downward direction of the femur. On the other hand, the cross-sectional edge of the stem is rounded, thereby preventing the stem from rotating in the bone marrow as a wedge, and at the same time, the rounded cross-section suppresses the possibility of fracture of cement or the like.

Referring back to FIG. 1, the neck portion 14 has a smaller cross-sectional area than the truncated cone portion 15. The small cross section of the neck portion 14 is for facilitating the procedure when the stem 11 is removed from the femur. That is, when the neck 14 is gripped using a tool, it is relatively easy to remove the stem 11. It is preferable that the neck portion 14 is actually elliptical in cross section. The elliptical cross section enhances the strength of the neck 14. In addition, when the acetabular cup and stem are mutually articulated, the neck portion 14 comes into contact with the edge of the acetabular cup, thereby increasing the range of articulation. The truncated cone portion 15 extends from the neck portion 14 and is a portion to be fitted into a ceramic or metal sphere not shown.

In addition, a semi-collar 22 is formed to easily identify the insertion depth when inserting the stem 11 into the femur. The semi-collar 22 is formed by forming a step in the downward direction in a portion of the proximal portion 12 extending from the neck portion 14 to the proximal portion 12. If the semi-collar 22 is in contact with the inlet of the cut femur during the procedure, the operator can recognize the insertion depth thereby. Semi-collar 22 serves to improve the convenience of the procedure, while minimizing the stress transmitted to the bone by itself.

On the other hand, it is desirable that the entire surface of the stem be smooth and high polished. Surface treatment by high polishing prevents dissociation of bone marrow steel and cement. In particular, it is more desirable to high polish the portion, in order to prepare for the possibility that the ceramic hemisphere will contact the neck 14 and a portion of the proximal portion 12 adjacent thereto during operation of the hip prosthesis. Ceramic hemispheres (not shown) may generate particles at the friction surface if a portion of their surface contacts the neck 14 and the proximal portion 12 adjacent thereto during joint motion. Particles released by friction can penetrate into human tissue and have a negative effect. Therefore, high polishing of the surface of the stem which the ceramic hemisphere contacts with during the joint movement can minimize the generation of particles.

3A to 3E show each cross section of FIG. 1 in turn.

FIG. 3A shows a cross section taken along A-A in FIG. 1. It can be seen from the cross-section that the front projections 17 and the rear projections 25, which are formed in the front and rear surfaces of the proximal portion 12 and near the outer side 20, respectively, are formed.

3B is a cross-sectional view taken along the line B-B in FIG. 1, and FIG. 3C is a cross-sectional view taken along the line C-C in FIG. 1. It can be seen from these figures that the protruding height of each protrusion 17, 25 gradually decreases as it approaches the distal portion 13.

FIG. 3D illustrates a cross section taken along line D-D in FIG. 1, and FIG. 3E illustrates a cross section taken along line E-E in FIG. 1.

As can be seen from FIGS. 3a to 3e, the cross section of the stem 11 is generally rectangular as described above, with each corner of the rectangle being rounded. It will be appreciated that this rectangular cross section may be inserted in a wedge-bonded state in the cement in the femur with a circular cross section in its entirety to prevent rotation of the stem. The rounded corners of the rectangle prevent the sharp edges from destroying the cement when it is hardened.

The stem 11 preferably has the entire surface high polished, or at least a portion of the neck 14 and a portion of the proximal portion 12 proximate thereto.

The cement type stem for artificial hip according to the present invention has been adapted to the shape of the femur and has the advantage of increasing the pressure into the inside of the femur by the anterior and posterior protrusions formed in the proximal portion. In addition, by forming the cross-sectional area of the neck smaller than the cross-sectional area of the cone portion, it is possible to increase the range of motion during the joint movement to the acetabular cup. The stem is a double tapered shape with a rounded cross-sectional shape, which acts as a wedge in the bone marrow and prevents the destruction of the cement upon contact with the cement. In other words, the stress can be naturally transmitted to the femur. In addition, the semi-color was formed to increase the convenience of the procedure while minimizing the transfer of stress to the bone. On the other hand, it has been anatomically adapted by having an overall angle that can have a maximum lever arm length with respect to the same offset.

Although the present invention has been described with reference to one embodiment shown in the accompanying drawings, this is only illustrative, and it will be understood by those skilled in the art that various modifications and equivalent other embodiments are possible. Could be. Therefore, the true scope of protection of the present invention should be defined only by the appended claims.

Claims (9)

A proximal portion in which a front protrusion and a rear protrusion are formed on the front surface and the rear surface, respectively; A distal portion extending vertically downward from the proximal portion; A neck extending upwardly at an angle from the proximal portion at an angle; And, And a truncated cone portion formed at an end of the neck portion, The inner surface of the proximal portion is formed as a curved portion having a radius of curvature of 87 to 93 mm, The stem and the truncated cone extending therefrom are inclined at an angle of 127 to 133 degrees with respect to the portion extending from the proximal portion to the distal portion. The method of claim 1, And wherein each of the front protrusion and the rear protrusion has a lower protrusion height as the proximal portion approaches the distal portion. The method of claim 1, And said distal portion is formed by double tapering. The method of claim 1, And the proximal and distal cross sections are generally rectangular in shape, and the corners of the rectangle are rounded. delete The method of claim 1, And a semi-collar formed by forming a step in a downward direction in a portion of the proximal portion extending from the neck to the proximal portion. The method of claim 1, A stem for an artificial hip insertion instrument, characterized in that the cross section of the neck is formed in an elliptical shape. delete The method of claim 1, An outer surface of the neck and a portion of the proximal portion proximate to the neck are high polished.