JP5473130B2 - Artificial hip joint - Google Patents

Description

  The present invention relates to an artificial hip joint that relieves an impact when walking, standing up or jumping down in an artificial hip joint composed of metal-to-metal.

  The hip joint is a structure in which the femoral head at the tip of the femur is rotatably fitted in the acetabulum of the pelvis, allowing the femur to rotate (bend and stretch) when a person moves, and from the femur It plays the role of distributing the transmitted load to the pelvis and mitigating impact. If the hip joint is normal, you can walk, stand up, jump off and sit down smoothly, but if the hip joint cannot function smoothly due to illness or trauma, it can be used as an artificial hip joint. I have to rely on it.

  The artificial hip joint is fitted with a metal outer cup that is fixed to the pelvis and has a hemispherical recess, and is rotatably fitted in the recess of the outer cup. The inner cup made of ultra-high molecular weight polyethylene resin and the metallic spherical femoral head (spherical head) formed at the tip of the femoral stem fixed to the femur were fitted to allow for precession. There are three-piece ones and two-piece ones in which the spherical head is directly inserted into the recess of the outer cup.

  The former is called a metal-to-resin mold (Non-Patent Document 1), and has a characteristic that the resin relaxes the impact on the hip joint. The same applies to the hip joint of a living body, and soft tissue or the like existing in the joint portion plays a role of impact relaxation. However, in this type, wear of the polyethylene resin becomes a problem, and when wear progresses, a gap is generated in the structure between the inner cup and the spherical head that are in close contact with each other at the sliding contact portion. If this gap becomes large, the spherical head may come off the inner cup and cause dislocation. In addition, when the abrasion powder is dispersed in the body and diffused into the blood due to abrasion, the predatory action of macrophages proceeds, and eventually, osteolysis is caused and re-operation is required.

  For this reason, Patent Document 1 proposes the use of carbon fiber reinforced polyetheretherketone as a material having better wear resistance than ultrahigh molecular weight polyethylene resin. Patent Document 2 also proposes a method in which the end portion of the socket is wrapped so that the abrasion powder remains locally and does not diffuse. However, since there is no change in using polyethylene resin, more or less wear problems arise.

  On the other hand, the latter is referred to as a metal-to-metal type and is expected to be an artificial hip joint that eliminates the drawbacks of the polyethylene structure due to its low wear, and its use has increased in recent years (Non-Patent Document 2). However, since this type of metal is in direct contact with the metal, it lacks the ability to relieve the impact during movement such as walking or standing up, and has the problem of causing great pain to the body. Therefore, the characteristic required for this type is how to reduce the impact.

  A ceramic with less wear may be used instead of a metal, but since the ceramic is also a hard material, it has the same problem in terms of reducing the impact. In Patent Document 1 described above, a proposal has been proposed in which a resin liner is provided on the cup surface in anticipation of an impact mitigating action in ceramic. Furthermore, Patent Document 3 also proposes that a resin liner be attached to the head. However, all of them use a resin material, and it is inevitable that the problem of dislocation due to wear or wear powder occurs as in the case of ultrahigh molecular weight polyethylene.

JP 2008-054788 A JP 2004-024868 A Special table 2007-536948 gazette

Kurtz SM Muratoglu OK, Evans M, Edidin AA. Advances in the processing, sterilization, amd switching of ultra-high molecular weight polyethylene for total joint arthroplasty Biomaterials 1990; 20: 1659-1685 Duncan Dowson, DSc, Cath Hardaker, Msc, Magnus Flett, MSc, and Graham H.A.hipjoint simulator study of the performance of Metal-on-Metal joint.The Journal of Arthroplasty Vol.19 No.8 Suppl.3 2004

  As a result of examining various improvement measures in order to overcome the problem of lack of impact relaxation in a metal-to-metal artificial hip joint having excellent wear resistance, the present inventors have instead used an organic polymer resin. By using a novel means, the inventors have invented an artificial hip joint that exerts an impact relaxation action.

  Under the above-mentioned problems, the present invention is a metal product that is inserted into the acetabulum according to claim 1, the outer surface is cut obliquely downward at approximately 45 °, and a cylindrical recess is formed above the cut surface. Fitted to the outer cup and the cylindrical recess of the outer cup so as to be able to swivel and slide, the lower outer surface is cut obliquely downward at approximately 45 °, and the femoral head is fitted to allow for precession movement facing the cut surface. It is an artificial hip joint consisting of a cylindrical metal inner sleeve with a substantially hemispherical recess formed, and a clearance is secured between the outer cup and the inner sleeve, and an impact relaxation material is interposed in this clearance. A prosthetic hip joint is provided.

According to the present invention, in the above artificial hip joint, the impact relaxation material described in claim 2 is a coil spring, and the pocket is recessed in the upper end of the inner sleeve , and the lower end of the coil spring is placed in the pocket. The means accommodated in the apparatus, the means described in claim 4, wherein the lower end of the coil spring is fixed to the inner sleeve, the means described in claim 5, wherein the shock absorbing material is a disc spring, and the shock relaxation described in claim 6. The means in which the material is a pair of magnets attached to the outer cup and the inner sleeve with the same poles facing each other, wherein the inner sleeve has one or more holes communicating the substantially hemispherical recess and the gap. Providing means to be formed.

  According to the first aspect of the present invention, since the impact relaxation material is interposed between the outer cup and the inner sleeve, the impact is generated when a person moves or when a large load is momentarily applied to the hip joint portion. Absorbs and relaxes. Therefore, the burden on the body (hip joint), pain and discomfort are eased, and more natural behavior is guaranteed. This also reduces damage to the hip prosthesis itself, and further, the occurrence of loosening, stabilizes the life of the hip prosthesis for a long period of time, and removes the patient who is mentally and physically burdened. Reduce re-surgical situations.

  In this case, as a specific example of the impact relaxation material, there is a coil spring according to claim 2, which has an advantage that a spring having a desired spring constant can be manufactured at low cost. According to the third aspect of the present invention, there is an advantage that the free length can be increased and the degree of freedom of design is increased. According to the fourth aspect of the present invention, there is an advantage that the stability of the coil spring is improved and the inner sleeve is allowed to turn when the coil spring is expanded and contracted, thereby further reducing the impact. According to the disc spring of claim 5 and the magnet of claim 6, there is an advantage that the accommodation space is small. According to the seventh aspect, the body fluid accumulated in the gap can be supplied as a lubricant to the sliding surface of the femoral head.

It is a disassembled perspective view of the artificial hip joint which concerns on this invention. It is principal part sectional drawing of the state which installed the artificial hip joint which concerns on this invention in the acetabulum. It is principal part sectional drawing which shows the other example of the state which installed the artificial hip joint which concerns on this invention in the acetabulum. It is principal part sectional drawing which shows the other example of the state which installed the artificial hip joint which concerns on this invention in the acetabulum. It is principal part sectional drawing which shows the other example of the state which installed the artificial hip joint which concerns on this invention in the acetabulum. It is principal part sectional drawing which shows the other example of the state which installed the artificial hip joint which concerns on this invention in the acetabulum.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is an exploded perspective view of an artificial hip joint according to the present invention. This artificial hip joint includes an outer cup 2 to be inserted into the acetabulum 1, an inner sleeve 3 to be fitted to the outer cup 2, and an inner sleeve. 3 and a femoral stem 4 inserted into the femur. Among these, the outer cup 2 has a hemispherical shape in principle, and is fixedly attached to the shaped acetabulum 1 with bone cement or screw nails. The outer surface of the outer cup 2 viewed from the acetabulum 1 is cut obliquely downward at approximately 45 °, and a cylindrical recess 6 is formed above the cut surface 5. The cylindrical recess 6 is formed between the outer surface of the outer cup 2 and leaving some meat. The outer cup 2 is made of a biocompatible metal such as a Co—Cr—Mo alloy or a titanium alloy.

  The inner sleeve 3 has a cylindrical body whose outer shape is fitted into the cylindrical recess 6 of the outer cup 2, and the lower outer surface is cut obliquely downward at approximately 45 ° like the outer cup 3, and faces the cut surface 7. A substantially hemispherical recess 8 is formed. It is a normal state that the lower end of the inner sleeve 3 is inserted until it is flush with the cut surface 5 of the outer cup 2, but at this time, between this state and the upper end of the cylindrical recess 6 of the outer cup 2. Has a gap 9. The inner sleeve 3 has a gap of about 1 mm at the maximum with respect to the cylindrical recess 5 and can freely turn and slide. The inner sleeve 3 is also made of a biocompatible metal similar to the arter cup 2.

  A spherical femoral head (spherical head) 10 is fitted into the substantially hemispherical recess 10 of the inner sleeve 3 so as to be capable of precession movement (three-dimensional rotational movement similar to a kneading rasp). 11 to the femoral stem 4 which is inserted into the femur. The femoral stem 4 including the spherical head 10 is also made of the above-described biocompatible metal.

  In the present invention, the impact relaxation material 12 is interposed between the cylindrical recess 6 of the outer cup 2 and the inner sleeve 3. In this example, a coil spring 12 a is shown as the impact relaxation material 12, and this is loaded in the gap 9 described above. In this case, the lower end of the coil spring 12a is fixed to the upper end of the inner sleeve 3 at three points on the circumference, but may be free (the upper end is free). When the gap 9 is small, the pocket 13 is recessed on the upper surface of the inner sleeve 3, and the lower end of the coil spring 12a is accommodated therein. This is to stabilize the posture of the coil spring 12a and to increase the degree of freedom in spring design.

  As described above, when a person moves, the spherical head 10 exhibits a hip joint function similar to that of a living body hip by freely performing precession in the substantially hemispherical concave portion 8 of the inner sleeve 3. In addition, according to the present invention, when a load in the vertical direction is applied to the hip joint, the inner sleeve 3 rises through the coil spring 12a in the cylindrical recess 6 of the outer cup 2 to alleviate the impact. In general, force is transmitted from one point to another, but it is said that a large impact means that this force is large, the degree of attenuation of the force is small, and the transmission time is short. Yes.

The load applied to the hip joint is said to be 3 × 10 ³ N when walking and 4 × 10 ³ N when standing upright, and if this load transmission time is lengthened, the load will be attenuated and the impact will be reduced. it can. If the impact on the hip joint can be alleviated, the burden on each part of the human body including the hip joint can be reduced, and pain and discomfort can be removed. The artificial hip joint according to the present invention makes this possible by using an impact relaxation material.

  The mode of impact mitigation by the coil spring 12a is to contract itself and delay transmission, but the elastic force of the coil spring 12a contributes to it. In addition, when the coil spring 12a contracts, the outer diameter is enormous and the body itself turns, but if the lower end of the coil spring 12a is fixed to the inner sleeve 3, the inner sleeve 3 rises while turning. This also contributes to transmission time delay (impact mitigation). In this case, the inner sleeve 3 and the cylindrical recess 6 have the above-described gap to facilitate turning.

The inventors of the present invention tested whether or not the coil spring relieves shock in a similar situation using an 858 MiniBionix tester manufactured by MTS, USA. A coil spring having a diameter of 10 mm, a number of turns of 2 to 3, and a spring constant of 240 N / mm is used. The coil spring is inserted into a cylindrical space having a diameter of 43 mm and a length of 5 mm. The coil spring was contracted by pushing with a load of 3 × 10 ³ N in 3 seconds. The result is to attenuate load of 3 × 10 ³ N to 2.3 × 10 ³ N, transmission time could be delayed until 1.2 seconds. From this, it was possible to confirm the impact relaxation effect of this coil spring, and to prove the significance of applying this to an artificial hip joint.

In the case of the present invention, it becomes a problem how much the degree of relaxation by the impact relaxation material 12 is set. However, when a load of 3 × 10 ³ N is applied during walking, the coil spring 12 has already contracted somewhat. Can be said to be suitable. This is because a living hip joint also exhibits this phenomenon. When a load of 4 × 10 ³ N when suddenly rising is applied, it can be assumed that the coil spring 12a is in a substantially contracted state. On the other hand, if the spring constant of the coil spring 12a is too high, a strong sense of incongruity will occur in the installer. In this respect, the coil spring 12a is considered to have a spring constant of about 4 × 10 ³ N / 3 mm, a winding number of 2 to 4, and a diameter of about 35 to 40 mm. When an excessively strong load is applied, the coil spring 12a becomes a rigid body that does not contract any more as the windings come into contact with each other, and exhibits a kind of stopper action.

  By the way, when the dimensions and the like of the outer cup 2 and the inner sleeve 3 described above are described, the outer cup 2 has a substantially hemispherical shape with a diameter of 50 to 60 mm, and the outer surface side is 40 to 50 ° from the horizontal. A cylindrical recess 6 having a long side of 37.1 mm, a short side of 6.5 mm, and a diameter of 43 mm is formed. The inner sleeve 3 has a cylindrical body with a diameter of 42.9 mm (the gap with the cylindrical recess 6 is 1 mm), and the lower end is cut at an angle of 40 to 50 ° from the horizontal. A substantially hemispherical recess 8 having a diameter of 31 mm is formed. The inner sleeve 3 has a long side of 33 mm and a short side of 1.5 mm, and has a gap 9 of 5 mm between the upper part of the cylindrical recess 6 of the outer cup 2.

  Incidentally, the diameter of the spherical head 11 is 31 mm, which is the same as the diameter of the substantially hemispherical concave portion 8 of the inner sleeve 3. In addition, the above dimension is an example, Comprising: Since it changes with physiques and age, it is not limited to this. In particular, the gap 9 between the cylindrical recess 6 of the outer cup 2 and the upper end of the inner sleeve 3 is suitable to be lengthened by devising processing (the formation of the pocket 13 is an example thereof). This is because the longer the gap 9 is, the greater the freedom of design of the impact relaxation material 12 and the spring.

  As the impact relaxation material 12, a disc spring or a magnet can be considered in addition to the above spring 12a. FIG. 3 shows an example of a disc spring 12b, and FIG. 4 shows an example of a magnet 12c. However, if the disc spring 12b, the length of the gap 9 is short, and if it is a magnet (permanent magnet) 12c, The whole can be made thin and the gap 9 may be further shortened. In the case of the magnet 12c, it is necessary to use two magnets to make the opposite surfaces repel each other, and the surface of the outer cup 2 that contacts the cylindrical recess 6 and the inner sleeve 3 is fixed with an adhesive or the like. It is necessary to keep. Of course, biocompatible metals are used for these materials as well.

  FIG. 5 is a cross-sectional view of the main part showing still another example. In this example, the inner sleeve 3 is formed with a hole 14 for communicating the substantially hemispherical recess 8 and the upper gap 9. is there. According to this, since the gap 9 is a gap, body fluid accumulates therein, but the hole 14 has an action of supplying this body fluid to the sliding surfaces of the femoral head 10 and the substantially hemispherical concave portion 8. Has the advantage of smooth movement. The number of holes 9 is not limited to one and may be plural.

  FIG. 6 is also a cross-sectional view of the main part showing still another example. In this example, the bulging portion 15 is formed by securing the meat around the extension of the cylindrical concave portion 6 of the outer cup 2. It is. According to this, the clearance gap 9 can be taken long, the spring constant of the coil spring 12a accommodated in the inside can be kept low, the impact transmission time can be further delayed, the uncomfortable feeling can be reduced, and the functionality can be improved. Even if such a bulging portion 15 is provided, the insertion can be performed by shaping the acetabulum 1 into a shape corresponding to this. In addition, the outer cup 2 and the acetabulum 1 are also contributed to enhancing the fixation.

DESCRIPTION OF SYMBOLS 1 Acetabulum 2 Outer cup 3 Inner sleeve 4 Femoral stem 5 Outer cup cut surface 6 Cylindrical recessed part 7 Inner sleeve cut surface 8 Substantially hemispherical recessed part 9 Gap 10 Femoral head 11 Neck 12 Impact relaxation material 12a Coil spring 12b Belleville spring 12c magnet 13 pocket 14 hole 15 bulge

Claims (7)

  Inserted into the acetabulum, the outer surface is cut obliquely downward at approximately 45 °, and a metal outer cup with a cylindrical recess formed upward from the cut surface, and can be swung and slid into the cylindrical recess of the outer cup A cylindrical metal inner sleeve having a substantially hemispherical recess that is fitted and is cut obliquely downward at a lower outer surface of approximately 45 ° and into which the femoral head is fitted so as to be capable of precession. An artificial hip joint comprising: an artificial hip joint comprising a space between an outer cup and an inner sleeve and an impact relaxation material interposed in the space.   The artificial hip joint according to claim 1, wherein the shock absorbing material is a coil spring.   The artificial hip joint according to claim 2, wherein a pocket is recessed in the upper end of the inner sleeve, and the lower end of the coil spring is accommodated in the pocket.   The artificial hip joint according to claim 2 or 3, wherein a lower end of the coil spring is fixed to the inner sleeve.   The artificial hip joint according to claim 1, wherein the shock absorbing material is a disc spring.   The artificial hip joint according to claim 1, wherein the shock absorbing material is a pair of magnets attached to the outer cup and the inner sleeve with the same poles facing each other. The artificial hip joint according to any one of claims 1 to 6, wherein one or more holes are formed in the inner sleeve so as to communicate the substantially hemispherical concave portion and the gap.