JP2011139785A - Nail insertion type artificial knee joint - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To insert a nail for fracture treatment without detaching an artificial joint when fracture is caused after artificial joint replacement. <P>SOLUTION: In the artificial knee joint in which a tibia side member mounted on the bone end of the tibia and a thigh bone side member mounted on the bone end of the thigh bone are rollably combined, a box is protruded on the inner surface of the thigh bone side member, and in the box, a nail insertion hole is formed through which the nail can be unrotatably inserted from the outer surface to the thigh bone, when the thigh bone side member is bent backward relative to the tibia side member. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a nail insertion type artificial knee joint in which a nail for fracture treatment can be inserted without removing the artificial knee joint when a femur fractures after the knee joint is replaced with an artificial knee joint. .

  Artificial joint replacement has been applied to joint diseases represented by osteoarthritis, rheumatoid arthritis and the like for the purpose of reducing pain, reconstructing joint function, and correcting distortion. This artificial joint has been replaced with various joints, the most common being the knee joint. After replacing a knee prosthesis with a knee disease, there are restrictions on daily activities, but activity within a range that does not involve intense exercise is guaranteed, and in this sense, as a means to improve the quality of life Useful.

  However, since most of the patients to whom this is applied are elderly, there are problems that are not caused by artificial knee joints. A typical example is a fall while walking. When an elderly person falls, there is a risk of fracture, and when attention is paid to the lower limbs, the frequency of occurrence of epicondylar fractures and diaphyseal fractures is very high. These fractures naturally occur even after replacement of the knee prosthesis.

  The basis of the fracture treatment is to fix the fracture site, and the same applies to the femoral epicondyle fracture and diaphyseal fracture. In general, fracture sites are fixed by inserting a nail (pin) into the medullary cavity through the fracture site, and fixing the nail with a screw from the diaphysis, and a plate with the fracture site sandwiched around the cortical bone. There is an external fixation method in which the plate is fixed to the cortical bone with a screw, but the internal fixation method has fewer movement restrictions and the fixation becomes stronger and the healing is faster. For this reason, many internal fixation methods are employed.

  If an internal fixation method is applied to a femoral epicondyle fracture or a diaphyseal fracture, the nail cannot be inserted if the femoral side member of the artificial knee joint that has already been replaced becomes an obstacle. Therefore, it is necessary to remove the femoral side member once, insert a nail, and then mount the artificial knee joint again after the fracture has healed.

  The artificial knee joint is a pair of a femoral side member attached to the femur and a tibia side member attached to the tibia. Among these, as the femoral side member, Patent Documents 1 and 2 As shown, it has a substantially C shape in a side view with a medial condyle and a lateral condyle on the outer surface (distal side). Then, the inner surface (proximal side) is attached to the distal end of the femur, but over time, bone grows at the distal end and is sufficiently fixed to the inner surface. Therefore, exfoliating this is a loss because it destroys normal bone tissue and imposes a great burden on the patient.

JP 2002-028170 A JP 2003-230582 A

  The problem to be solved by the present invention is to make it possible to insert a nail without removing the artificial knee joint when the femur fractures after replacing the artificial knee joint.

  Under the above-described problems, the present invention provides a knee prosthesis according to claim 1 in which the tibial side member attached to the tibial end and the femoral side member attached to the femoral end are combined in a rollable manner. At the joint, when a box is protruded from the inner surface of the femoral side member and the femoral side member is bent backward with respect to the tibial side member, the nail can be inserted into the femur from the outer surface of the joint so as not to rotate. A nail insertion type artificial knee joint characterized by forming a nail insertion hole is provided.

  In this configuration, the key groove is formed in the nail insertion hole described in claim 2 and the key that can be fitted into the key groove is provided in the nail, and the key-provided portion and nail described in claim 3 The means in which the insertion hole has a tapered shape with a small diameter at the top, the head of the nail described in claim 4 is made a polygon having a diameter larger than the trunk diameter, and the nail insertion hole has a shape corresponding to the shape of the head. Provided is a means in which a counterbore hole into which the head can be depressed is provided.

  According to the first aspect of the present invention, it is possible to insert a nail by using the box when a fracture occurs, and it is necessary to remove the femoral side member. There is no. Therefore, normal bone tissue is not destroyed and the burden on the patient is not so great. In addition, since the inserted nail cannot be rotated (autorotated), even if it is stopped with a screw, an excessive load is not applied and stable fixing can be performed. According to the means of claim 2, the nail rotation inhibiting mechanism is simple, and according to the means of claim 3, the fitting between the nail insertion hole and the nail becomes tight, leading to prevention of loosening and rotation inhibition. According to the means of claim 4, a further rotation suppression function can be provided.

It is a perspective view of the femur side member of the knee prosthesis according to the present invention. 1 is a side view of an artificial knee joint according to the present invention. It is a cross-sectional side view of the artificial knee joint according to the present invention. It is a cross-sectional rear view of the artificial knee joint according to the present invention.

  1 is a perspective view of a femoral side member of an artificial knee joint according to the present invention, and FIG. 2 is a combination of a femoral side member and a tibial side member. FIG. 3 is a sectional side view showing a state where a nail is inserted into the femur, and FIG. 4 is a sectional rear view showing a state where the nail is inserted into the femur. The artificial knee joint is composed of a combination of the femoral side member 1 and the tibial side member 2, which can slide and rotate (roll) with respect to each other, and can extend and bend the knee.

  Among these, the femoral side member 1 is made of a biocompatible material such as a titanium alloy, a cobalt chromium molybdenum alloy, or medical ceramics, and is formed in a substantially semicircular shape when viewed from the side, that is, a substantially C shape. The semicircular inner surface 3 is formed in a polygonal shape (a pentagon in this example), and is provided with a cove-shaped missing portion 4 opened at the rear end at the center, and the outer periphery of the cross section is substantially semicircular on both sides. A condyle 5 and a lateral condyle 6 are formed.

  The femoral bone member 1 is attached to the epiphysis of the femur 7, and the distal end of the femur 7 is cut in accordance with the shape of the inner surface 3, and the osteotomy surface is attached in close contact with the inner surface 3. To do. At this time, the bones grown with the inner surface 3 being porous are filled in the meantime to enhance the fixing property. Further, bone cement may be interposed between the distal end and the distal end.

  In contrast, the tibial member 2 includes a joint plate 8 that receives the femoral member 1 and a base plate 10 that is attached to the tibia 9 and supports the joint plate 8. Among these, the joint plate 8 is made of a medical resin material such as ultra high molecular weight polyethylene, and an inner joint surface 11 that receives the inner condyle 5 and an outer joint surface 12 that receives the outer condyle 6 are formed on the upper surface. The lower surface is the joint surface portion 13. In this case, the medial joint surface 11 and the lateral joint surface 12 have a cross-sectional shape that matches the outer surface shape of the medial condyle 5 and the lateral condyle 6, followed by a strip shape. And the lateral condyle 6 are received with a high joint fitting surface ratio.

  The base plate 10 is made of a biocompatible material such as metal or ceramics, like the femoral side member 1, and has a support portion 14 that receives the joint surface portion 13 at the top. The attachment of the base plate 10 to the tibia 9 is the same as that of the femoral side member 1, and the proximal end of the tibia 9 is cut flat and the lower surface of the support portion 14 is along the cut surface. At this time, a stem 15 is protruded from the lower surface of the support portion 14 and the stem 15 is inserted into the tibia 9 to strengthen the fixation. When the joint plate 8 is superimposed on the pace plate 10 in this state from above, the tibial member 2 is configured.

  In the above knee prosthesis, the medial and lateral condyles 5 and 6 roll on the medial and lateral joint surfaces 11 and 12 as the knee is extended and flexed. On the other hand, the tip of the tibia 9 rotates inwardly), and the extension is set to rotate outwardly. Further, the femoral side member 1 is provided to be inclined outward with respect to the tibial side member 2. This is because the knee joint of a living body is the same. In the former, it plays mainly by guiding the medial and lateral joint surfaces 11 and 12 in that direction, and in the latter, the diameter of the medial condyle 5 is achieved. Is made smaller than the diameter of the lateral condyle 6. In addition, bending is allowed at about 0 to 160 ° with respect to the femur 7 of the tibia 9 like a living body knee.

  Next, in the present invention, a box 16 is formed in the middle of the inner surface 3 of the femoral side member 1 so as to protrude upward from the missing portion 4 at the center position or slightly forward position, and a nail insertion hole is formed in the box 16. 17 is formed. Along with this, the distal end of the femur 7 needs to be shaped into a shape that can accommodate the box 16. The nail insertion hole 17 of this example is formed with a counterbore hole 17a having a polygonal shape (generally a quadrangle) at the lower end, followed by a taper in which the diameter is smaller than the diameter of the counterbore hole 17a and the upper part is narrowed. A hole 17b is formed. Further, a key groove 18 is carved in the tapered hole 17b upward and downward.

  The nail 19 is inserted into the nail insertion hole 17, and the nail 19 is formed in a polygonal head 19a that fits into the counterbore 17a at the lower end according to the shape of the nail hole 17 and the tapered hole 17b. A tapered portion 19b to be inserted is formed, and a tip portion 19c continues upward from the tapered portion 19b. Further, a key 20 that fits into the key groove 18 is provided in the taper portion 19b, and a plurality of retaining holes 21 into which fixing screws (not shown) can be screwed are formed in the tip portion 19c.

  Assuming that an epicondylar fracture has occurred in the femur 7 (22 is a fracture surface), first, the femur 7 is bent relatively backward by at least 90 ° to expose the medial and lateral condyles 5 and 6. In this state, the nail 19 can be inserted from the nail insertion hole 17 by shifting the patella (not shown). At this time, the head 19a of the nail 19 is completely submerged in the counterbore hole 17a so as not to look downward, and the key 20 is fitted into the key groove 18 so that it cannot be rotated. Of course, the distal end portion 19c of the nail 19 is inserted so as to pass through the fracture surface 22, and various types having different lengths of the distal end portion 19c according to the difference in the fracture location are prepared.

  Next, when the screw 23 is screwed into the stop hole 22 from the cortical bone (not shown), the operation is completed. At this time, since the nail 19 is not allowed to rotate, an excessive load is not applied to the screw 23, and there is no possibility that the nail 19 is broken, displaced, or detached. If the key 20 is provided, the taper hole 17b and the taper portion 19c are not necessarily required because there is no risk of rotation. However, if such a taper fitting is used, the fitting becomes tight and the loosening is prevented. There are advantages to doing. Further, if the taper fitting can be tightened, the rotation is suppressed by the fitting, so the key 20 may not be necessarily required.

  According to the above, it is a feature of the present invention that it is not necessary to remove the femoral side member 1 when inserting the nail 19 for fracture treatment. For this reason, the box 16 is only prepared for a fracture, and the nail 19 is not inserted if there is no fracture. In addition, forming the box 16 in the femoral member 1 increases the contact area with the distal end of the femur and contributes to strengthening of fixation. Conventionally, for the purpose of strengthening the fixing, a pin or the like inserted into the femur is provided on the inner surface 3, but the box 16 can be said to be an alternative.

  As described above, when the nail 19 for fracture treatment is inserted, it is not necessary to remove the femoral side member 1 because the inner surface 3 of the femoral side member 1 and the distal end of the femur 7 are formed with great effort. It can be said that it is not necessary to destroy the bone tissue of the patient, and it can be said to be a surgery with less physical burden on the patient. In addition, since the incision surface can be small, it is a minimally invasive operation with less burden on the patient.

  The above is an explanation of the case where the present invention is applied to the femoral side member of an artificial knee joint, but the present invention can be similarly applied to a tibial side member. Furthermore, the present invention is not limited to the knee joint, and can be applied to all joints as long as the joint can be bent to the extent that the joint portion is exposed from the joint surface. Specifically, an artificial elbow joint, a wrist joint, an ankle joint, a toe joint, etc. can be considered.

DESCRIPTION OF SYMBOLS 1 Femur side member 2 Tibial side member 3 Inner surface of femoral side member 4 Missing part 5 Inner condyle part 6 Outer condyle part 7 Femur 8 Joint plate 9 Tibial 10 Base plate 11 Inner joint surface 12 Outer joint surface 13 Joint surface part 14 Support Part 15 Stem 16 Box 17 Nail insertion hole 17a Counterbore hole 17b Taper hole 18 Key groove 19 Nail 19a Head 19b Head tapered part 19c Tip part 20 Key 21 Stop hole 22 Fracture surface 23 Screw

Claims (4)

  In an artificial knee joint in which a tibial side member attached to a tibial end and a femoral side member attached to a femoral end are combined in a rollable manner, a box is projected from the inner surface of the femoral side member. And a nail insertion type artificial knee joint having a nail insertion hole through which a nail can be inserted into the femur from the outer surface when the femoral side member is bent backward with respect to the tibial side member. .   The nail insertion type artificial knee joint according to claim 1, wherein a key groove is formed in the nail insertion hole, and a key that can be fitted into the key groove is provided in the nail.   The nail insertion type knee prosthesis according to claim 2, wherein the key portion and the nail insertion hole have a tapered shape with a narrow diameter at the top.   The nail insertion type according to any one of claims 1 to 3, wherein the head of the nail is formed into a polygon having a diameter larger than the body diameter, and a counterbore hole into which the head can be depressed according to the shape of the head is provided in the nail insertion hole. Artificial knee joint.