Patent Application
20100298946
Not applicable.
1. Technical Field
The present invention relates generally to an artificial knee joint which can replace a natural knee joint. More specifically, this invention is directed to an artificial knee joint having a femur joint member which is attached to an end portion of the femur near the tibia, and a tibia joint member which is attached to an end portion of the tibia near the femur, wherein the artificial knee joint evenly disperses the stress of both the femur joint member and the tibia joint member regardless of the kind of knee movement by enlarging the contact surface between the femur joint member and the tibia joint member. Especially, the artificial knee joint classifies the curvatures of the femur and tibia joint members according to the degree of rotation so as to enlarge the contact area in any state, thus effectively dispersing the stress caused by the repeated load. The tibia joint member includes a bearing member near the contact portion with the femur joint member, thus forming the curvature of the bearing member corresponding to the curvature of the femur joint member.
2. Background Art
Among the many joints in the body, the knee joint is the junction between the tibia and the femur. Because of the wearing of the knee joint, the aging of the bone tissue and accidents, the number of patients for whom recovery is impossible is gradually increasing. The knee joint is the joint which is located between the lower end of the femur, the upper end of the tibia, and the back of the patella, and functions to bend the leg backwards at the knee.
The back of the patella is covered by cartilage 4 mm to 6 mm thick. The patella moves up and down along the articular surface which is in front of the end portion of a thighbone (the femur) while the knee is bent or stretched (at the patellofemoral joint), thus improving the knee stretching force of the musculus quadriceps femoris. Pressure acting on the patellofemoral joint when a person walks on a flat ground is equal to half of his or her weight. When a person goes up the stairs, a force which is 3 times as great as his or her weight acts on the patellofemoral joint. Further, when a person sitting in a squatting position stands up, a force which is 8 times as great as his or her weight acts on the patellofemoral joint. An articular capsule extends from the edge of the lower end of the femur to the edge of the upper end of the tibia. In addition to the above components, the inner and outer collateral ligaments, the cruciate ligaments of knee in the articular capsule, and other strong ligaments strengthen the connection of the bones and limit the moving direction and range of the bones.
The symptoms that appear when the meniscus of the knee joint is damaged will now be described. Here, the meniscus of the knee joint is the cartilaginous tissue which is located between the femur and the tibia forming the knee joint. The meniscus is positioned between the articular cartilage to absorb shocks acting on the knee joint, supply nutrients to the articular cartilage, provide the joint with stability, allow the knee joint to move smoothly, and transmit the load imposed by the weight.
Generally, the meniscus includes a medial meniscus and a lateral meniscus. As for Europeans and Americans, the medial meniscus is larger in size and smaller in mobility than the lateral meniscus, so that the medial meniscus is easily damaged. However, it is known the lateral meniscus of Koreans is more heavily damaged than is the medial meniscus.
The damage to the meniscus is one type of damage frequently occurring in knee joints. The meniscus is frequently damaged during athletic sports, mountain climbing or daily life. This easily occurs when the bent knee is rotated, that is, when torsional force is applied to the knee joint. When excessive external force acts on the knee joint, a cruciate ligament or collateral ligament may be damaged and the tibia may be fractured.
Most symptoms of disease taking place in the patella do not reveal any noteworthy external injury, and are caused by structural and functional disorders of the patellofemoral joint. When the leg is bent abnormally outward or the foot is bent excessively outward, excessive force is repeatedly exerted on the patellofemoral joint, thus leading to the malacia of the articular cartilage. Even when the knee joint is not used for a lengthy period of time, the musculus quadriceps femoris may become weak, thus causing damage to the patella.
When there are structural disorders of the patellofemoral joint, it is possible to wear an orthosis to stabilize the patella. Meanwhile, when the damage to the patellofemoral joint is severe, surgical procedures may be performed to replace the damaged joint with an artificial knee joint.
Recently, a surgical procedure for replacing a patient's joint which has been so severely damaged that it is impossible to recover with an artificial joint has been widely performed. Metal, ceramic or polyethylene is used for the motion part of the artificial joint, thus providing superior mechanical characteristics, reducing the coefficient of friction, and enhancing biocompatibility. Generally, the artificial knee joint includes a femur part, a tibia part, and a bearing part which is provided between the femur part and the tibia part and corresponds to cartilage. Here, the femur part and the tibia part are most commonly made of a metal alloy, while the cartilage part is made of polyethylene or the like. The tibia part is secured by an insertion part which is inserted into an end of the tibia near the knee joint. The insertion part is attached to the marrow of the tibia. However, if a load is repetitively applied to the knee joint, it is difficult for the artificial knee joint to achieve a sufficient effect, because of its structural defects. The femur part and the tibia part may be damaged by the continuous imposition of a load. Especially should the bearing part be broken, big problems occur.
Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide an artificial knee joint including a plurality of flexions in a femur joint member, in which the curvatures of the femur joint member and a bearing member are adjusted to evenly distribute the stress, thus imparting a contact portion when the knee moves with a larger contact area, therefore dispersing the stress.
Another object of the present invention is to provide an artificial knee joint including a plurality of flexions in a femur joint member, in which the femur joint member and a bearing member have corresponding curvature when seen from the front, because horizontal rotation may occur at the contact portion of a femur and a tibia, and the femur joint member and the bearing member have circular curvature so as to allow knee movement to be more smoothly and easily performed, thus preventing the concentration of stress and dispersing the stress when leaning to one side.
A further object of the present invention is to provide an artificial knee joint including a plurality of flexions in a femur joint member, in which the femur joint member has various curvatures when seen from the side, thus allowing the knee to be smoothly rotated and bent, enabling the knee to be bent at a larger angle, and preventing the femur from becoming separated from the tibia.
Yet another object of the present invention is to provide an artificial knee joint including a plurality of flexions in a femur joint member, which enlarges a contact area between the upper portion of a bearing member and a lower portion of the femur joint member, thus evenly dispersing stress caused by load acting in a direction from an upper position to a lower position, therefore improving the durability of the femur joint member, the bearing member, and the tibia joint member, and providing more stable movement to a patient who underwent a surgical procedure.
Still another object of the present invention is to provide an artificial knee joint including a plurality of flexions in a femur joint member, which adjusts the curvature of the side of the lower portion of the femur joint member, thus allowing the knee to be more naturally bent forward or backward, permitting the load to be evenly transmitted, and dispersing stress.
Another object of the present invention is to provide an artificial knee joint including a plurality of flexions in a femur joint member, which adjusts the curvature of the front of the lower portion of the femur joint member, thus dispersing stress at the site where the load is concentrated, because one side of the femur joint member is lifted up and a large load acts on only one side when the knee is slightly rotated leftward or rightward.
In order to accomplish the above objects, the present invention provides an artificial knee joint including flexions in a femur joint member, having a femur joint member attached to an end portion of a femur, a tibia joint member attached to an end portion of a tibia, and a bearing member positioned between the femur joint member and the tibia joint member, wherein the femur joint member comprises a contact portion which is in contact with the bearing member so as to disperse stress, and the contact portion comprises side flexions having various curvature radii so that a contact surface between the femur joint member and the bearing member is large when viewed from a side.
According to an aspect of the invention, the side flexions may include a first side flexion, a second side flexion and a third side flexion, the second side flexion being connected to the third side flexion, the first side flexion being connected to the second side flexion, curvature radii being reduced from the third side flexion to the first side flexion.
In another aspect of the invention, the contact portion of the femur joint member may further include a front flexion having a gently curved surface so as to provide a large contact area between the contact portion of the femur joint member and the bearing member, when viewed from a front, thus dispersing stress.
In yet another aspect of the invention, the bearing member may include a depressed portion having curvature which substantially corresponds to curvature of the side flexions of the contact portion of the femur joint member, thus increasing the contact area and dispersing stress.
In still another aspect of the invention, the bearing member may include a concave portion having curvature which substantially corresponds to curvature of the front flexion of the contact portion of the femur joint member, thus increasing the contact area and dispersing stress.
In yet another aspect of the invention, the bearing member may further include a front projecting part which is projected from a front portion of the bearing member to a predetermined height, and a rear projecting part which is projected from a rear portion of the bearing member to a predetermined height, thus preventing the femur joint member from being dislocated from the bearing member.
In still another aspect of the invention, the artificial knee joint may include a contact portion making contact with a bearing member so as to disperse stress, the contact portion including side flexions having various curvature radii so that a contact surface between the femur joint member and the bearing member is large when viewed from a side, the side flexions including a first side flexion, a second side flexion and a third side flexion, the second side flexion being connected to the third side flexion, the first side flexion being connected to the second side flexion, curvature radii being reduced from the third side flexion to the first side flexion.
In yet another aspect of the invention, the artificial knee joint may further include a front flexion having a gently curved surface so as to provide a large contact area between the contact portion of the femur joint member and the bearing member, when viewed from a front, thus dispersing stress.
As described above, the present invention can accomplish the following effects by the above-mentioned technical solutions and the construction and operation to be mentioned later.
According to the present invention, it is advantageous in that the curvatures of the femur joint member and a bearing member are adjusted to evenly distribute the stress, thus imparting a contact portion when the knee moves with a larger contact area, therefore dispersing the stress.
The present invention is advantageous in that the femur joint member has various curvatures when seen from the side, thus allowing the knee to be smoothly rotated and bent, enabling the knee to be bent at a larger angle, and preventing the femur from becoming separated from the tibia.
The present invention is advantageous in that the femur joint member and a bearing member have corresponding curvature when seen from the front, because horizontal rotation may occur at the contact portion of a femur and a tibia, and the femur joint member and the bearing member have circular curvature so as to allow knee movement to be more smoothly and easily performed, thus preventing the concentration of stress and dispersing the stress when leaning to one side.
The present invention is advantageous in that a contact area between the upper portion of a bearing member and a lower portion of the femur joint member is enlarged, thus evenly dispersing stress caused by load acting in a direction from an upper position to a lower position, therefore improving the durability of the femur joint member, the bearing member, and the tibia joint member, and providing more stable movement to a patient who underwent a surgical procedure.
The present invention is advantageous in that the curvature of the lower portion of a femur joint member is adjusted, so that a contact area with the upper portion of a tibia joint member or a bearing member is enlarged, thus dispersing stress, therefore preventing an artificial knee joint from being broken by a load, and increasing the durability and life-span of the artificial knee joint.
The present invention is advantageous in that the curvature of the lower portion of a femur joint member is adjusted, thus dispersing stress concentrated when the knee is greatly rotated and the load is thereby transmitted in various directions, therefore reducing the wear caused by friction, and realizing a sturdy artificial knee joint.
Various embodiments of the present invention will now be discussed with reference to the appended drawings. It is appreciated that these drawings depict only typical embodiments of the invention and are therefore not to be considered limiting of its scope.
Hereinafter, an artificial knee joint including a plurality of flexions in a femur joint member according to the preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.
Referring to
The femur joint member 100 has a “U” shape and is made of a biocompatible material. The upper portion of the femur joint member 100 has a part for receiving the femur 1, and the lower portion thereof has a curved surface which has various curvatures and approximates a spherical shape. The femur joint member 100 includes a femur receiving part 110 and a locking protrusion 150. Part of the femur is cut, so that it is received by the femur receiving part of the femur joint member 100. The locking protrusion 150 couples the femur more firmly to the femur receiving part 110. Further, the femur joint member 100 has on its lower surface curved contact portions which are in contact with the bearing member 500 that will be described below, and a depressed portion 170 which is concavely formed between the contact portions.
The femur receiving part 110 is positioned at the interior of the upper portion of the femur joint member 100, and is firmly coupled to the incision surface of the lower portion of the femur. Preferably, the femur receiving part 110 has a rough surface or is made of a porous material so as to be firmly coupled to the femur.
The locking protrusion 150 extends upwards from the femur receiving part 110 to be inserted into the femur 1, and has the shape of a screw. More preferably, the locking protrusion 150 has a locking part which is shaped to be inserted into the femur and firmly grip the bone tissue of the femur.
The contact portions are the important part of the present invention. When the femur moves while making contact with concave portions 510 of the bearing member 500, the contact portions are preferably shaped to maximally enlarge the contact area, thus naturally dispersing stress. Here, the curvature of the contact portion when seen from the side is different from that of the contact portion when seen from the front. The different curvatures enable natural movement even when the knee joint moves forward and backward, and increases the contact area, thus dispersing stress. Further, when the knee joint is slightly abducted leftward or rightward or one contact portion is slightly lifted, a large stress is concentrated on the other contact portion. In this case, the different curvatures increase the contact area so as to disperse stress. When seen from the side, the contact portion includes a first side flexion 131, a second side flexion 132, and a third side flexion 133. Meanwhile, when seen from the front, the contact portion includes a front flexion 137.
The side flexion will be described with reference to
Next, the front flexion 137 will be described with reference to
The tibia joint member 300 is fitted into and secured to the upper portion of the tibia in the typical artificial knee joint, is made of a biocompatible material, and supports the bearing member 500 which will be described below. Further, the tibia joint member may be formed in various types, and is typically classified into a mobile type and a fixed type according to the coupling relation between the tibia joint member and the bearing member. In the case of the mobile type tibia joint member, the bearing member 500 may rotate or move forward and backward on the tibia joint member 300, thus achieving the more natural movement of the knee joint. However, in the case of the fixed type tibia joint member, the bearing member 500 is fixed to the tibia joint member 300 so as not to be moved. The fixed type tibia joint member makes free movement difficult, but realizes stable movement owing to firm coupling. Thus, in the fixed type tibia joint member, the bearing member 500 may be integrated with the tibia joint member 300 into a single structure. In this case, it is natural that the effect realized by the bearing member 500 which is coupled to and makes contact with the femur joint member 100 be also achieved by the tibia joint member 300. Thus, the effect achieved by the components and operation of the bearing member 500 according to the present invention can be achieved by the tibia joint member 300. This falls within the scope of the present invention.
The bearing member 500 is provided between the femur joint member 100 and the tibia joint member 300 to serve as the cartilage of the human body. Thus, the bearing member 500 is preferably made of polyethylene unlike the material of the femur joint member and the tibia joint member. Polyethylene does not produce impurities when it wears, and does not generate heat due to friction, so that it withstands friction well, and has a smooth surface to permit natural frictional contact. The bearing member 500 includes the concave portions 510 which are provided on the upper portion of the bearing member and make contact with the contact portions of the femur joint member 100 when seen from the front. A convex portion 520 is provided between the concave portions 510. Front and rear projecting parts 530 and 540 are provided on opposite ends of the bearing member 500 when seen from the side. A depressed portion 550 is further included.
The concave portions 510 are portions which are provided on both sides of the artificial knee joint according to the present invention when viewing the bearing member 500 from the front. Friction occurs between the concave portions and the contact portions, when the concave portions are in contact with the contact portions of the femur joint member 100, so that the femur joint member 100 rotates. Thus, since the contact concentrates the load on the concave portions, it is necessary to maximize the contact area so as to prevent the concentration of stress. Therefore, the concave portion 510 preferably has curvature corresponding to the front flexion 137 of the femur joint member 100. Thereby, as described above, when the concave portions are slightly lifted leftwards or rightwards at the front flexions 137, contact occurs on only one side, so that the stress is concentrated on the contact side. However, owing to the increase in the contact area, the stress can be dispersed.
The convex portion 520 protrudes upwards between the concave portions 510 when viewing the bearing member 500 from the front, and corresponds to the depressed portion 170 of the femur joint member 100. However, it is not a contact portion but receives the patella which allows the knee to bend. Since the mechanism for bending the knee because of the patella and the ligaments is well known by those skilled in the art, a detailed description will be omitted from herein.
The front and rear projecting parts 530 and 540 are projected from the front and rear portions, when viewing the bearing member 500 from the side, to predetermined heights. Especially the front projecting part 530 prevents the femur joint member 100 from becoming separated from the bearing member 500 when a patient having the artificial knee joint of the present invention bends his or her knee at a large angle. The rear projecting part 540 prevents dislocation when the knee is bent at a large angle and rolled back, thus guaranteeing the stable movement of the knee joint.
When viewing the bearing member 500 from the side, the depressed portion 550 is the portion which is in contact with the first side flexion 131, the second side flexion 132 or the third side flexion 133 at the contact portion of the femur joint member 100. Consequently, it is preferable that the depressed portion have curvature corresponding to that of the side flexions of the femur joint member as described above. Thereby, more stable coupling is achieved, and a sufficient contact area is acquired, thus effectively dispersing the stress.
The operation and use of the artificial knee joint according to the preferred embodiment of the present invention will be described below in detail with reference to the accompanying drawings.
The operation of the artificial knee joint according to the present invention will be described with reference to
The operation of the artificial knee joint according to the present invention will be described with reference to
The stress dispersion effect using the side and front flexions of the contact portion included in the femur joint member 100 can be clearly understood through
As such, according to the present invention, the contact portion of the femur joint member 100 includes side and front flexions, and the depressed portion of the bearing member 500 which is in contact with the femur joint member is formed as the curved surface, thus effectively dispersing stress, therefore preventing damage to the femur joint member, the bearing member and the tibia joint member, improving durability, and prolonging its life-span. Consequently, a sturdy artificial knee joint is realized.
Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2008-0002239 | Jan 2008 | KR | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/KR2009/000100 | 1/8/2009 | WO | 00 | 8/12/2010 |
