JP4678867B2 - Artificial finger joint - Google Patents

Description

  The present invention relates to an artificial finger joint that is replaced by a finger joint represented by a metacarpophalangeal joint (MP joint) formed between a metacarpal bone and a proximal phalanx.

  When the finger joint function is lost due to rheumatism or trauma, replacement with an artificial finger joint is performed. The flexion and extension of the living finger joint is controlled by a soft tissue composed of a ligament or a tendon such as a palmar plate existing on the palm side, an extensor tendon existing on the back side, and a collateral ligament existing on both sides. Looking at the movement of this biofinger joint, when the metacarpal bone and the proximal phalanx are extended (extension position), the latter can bend in the left-right direction with respect to the former. It is what is done. In the extended position, the palmar plate, extensor tendon, and collateral ligament are balanced, thereby causing side sway.

  When the proximal phalanx is bent with respect to the metacarpal bone (bending position), the lateral swayability is regulated. This is because the radius of curvature of the metacarpal bone head is larger on the bent side, and when the bent position is taken, the collateral ligament is tense due to the difference in the radius of curvature. Is supposed to be regulated. Therefore, it is preferable that the artificial finger joint behaves the same as the living finger joint.

  However, in rheumatic patients and the like that have to be replaced with artificial finger joints, the bone head, the joint surface, and the soft tissue constituting the joint are damaged, and the above-mentioned movement of the living finger joint is often impossible. In many cases, it is said that subluxation occurs due to the volar displacement that causes the joint surface to slide down when not in a fully extended position and in a bent position. This movement is caused by the long-term familiarity of joints and soft tissues, and it is very difficult to reduce the movement to normal finger joints simply by replacing them with artificial finger joints.

Conventionally, various artificial finger joints such as those shown in, for example, the following Patent Document 1 have been proposed, but these are considered to be palm-side displacement in a bent position, although lateral sway properties are ensured. It was not what I did. For this reason, the patient's satisfaction was low because it was merely acquired joint function and far from the movement of the living finger joint.
Japanese Patent Laid-Open No. 09-038122

  The problem to be solved by the present invention is an artificial finger joint that can bend and stretch by the movement of the soft tissue peculiar to the above-mentioned rheumatic patients, that is, ensuring the lateral swayability in the extended position and the lateral swayability in the bent position. In addition to restricting, in addition, when bending, dislocation is prevented and a certain amount of palm side displacement is allowed.

Under the above problems, the present invention provides a metacarpal member having a head formed at the tip of a stem inserted into the metacarpal bone according to claim 1 and a head at the tip of the stem inserted into the proximal phalanx. In an artificial finger joint composed of a proximal phalanx member having a socket that can be bent and received from the extended position to the bent position, the socket is opened on the head side and does not exceed the maximum outer diameter of the head In addition to making it a weak semi-cylindrical body, a window that penetrates up and down is formed behind the head, the center top and bottom of the socket are attached to the outer periphery of the head, and the space between the window and the window increases as the bend enters into the window during bending. The present invention provides an artificial finger joint characterized by being gradually reduced to an angle that becomes zero when bent by 90 ° .

Further, according to the present invention, in the artificial finger joint described above, the head is a rugby ball-shaped cylindrical body in which the head extends in the left-right direction, and the socket has a C-shaped side view in which the socket is received. In addition, the present invention provides means that is a strong semi-cylindrical body whose corner exceeds the maximum outer diameter of the head, and means that is formed in a tapered shape in which the lateral width of the corner becomes narrower toward the tip.

According to the first aspect of the present invention, since there is a certain amount of play in the bending of the head and the socket, the palm side displacement due to the movement unique to the soft tissue of a rheumatic patient or the like is possible, but the dislocation is not reached . Further, the lateral swayability is ensured by making the socket a weak semi-cylinder with the head side opened. When bending, the corners enter the window, and gradually limit as the bending angle increases due to the gradual decrease of the gap between the corners and the window and zero at the time of 90 ° bending, and are restricted at the bending position. In addition, since the corners follow the outer periphery of the head, the head is highly retained by the socket, enabling smooth rotation. Of course, when bending, the corners go into the window, so no dislocation occurs.

  Further, according to the means of claim 2, the contact area is increased, the pressure is reduced, the durability is increased, the head is rubbed with respect to the socket, and the lateral swaying property is also increased. In addition, the above-described relationship between the corner and the gap between the windows can be easily realized by adopting the means of claim 3.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a plan view of a palm with the palm side facing down by applying the artificial finger joint of the present invention, FIG. 2 is a partial sectional plan view of the artificial finger joint, and FIG. 3 is a sectional side view. The finger joint includes a metacarpal member 2 attached to the distal end of the metacarpal bone 1 and a proximal phalanx member 4 attached to the proximal end of the proximal phalanx 3. In this example, the artificial finger joint is applied to the middle finger joint for the sake of simplicity, but it may be applied to any or all of the other finger, ring finger, and little finger joints. Needless to say.

  In the following description, the direction, position, and angle of the metacarpal bone member 2 and the proximal phalanx member 4 may be referred to, but these extend the proximal phalange 3 with respect to the metacarpal bone 1. The state is based on the state where the palm side is facing down and parallel to the ground. Therefore, the upper side is the upper side, the palm side is the lower side, the right and left or the side is the horizontal direction, and the bending and stretching of the metacarpal bone 1 and the proximal phalanx 3 are performed in the vertical direction. In addition, expressions such as front and rear, front and rear, and head may be used, but this is toward the counterpart member (for example, the proximal phalange member 4 in the case of the metacarpal member 2).

  The metacarpal bone member 2 is made of a biocompatible metal such as a Co—Cr—Mo alloy, and a stem 5 to be inserted into the medullary cavity of the distal end of the metacarpal bone 1 is formed in the tail, and the head (tip) ) With a head 6 formed thereon. The head 6 of this example is a rugby ball-shaped cylindrical body whose axis extends in the left-right direction, but may be a straight cylindrical body. The stem 5 is formed in a curved shape that warps upward along the shape of the medullary cavity of the metacarpal bone 1. Further, a window 7 penetrating vertically is formed in the stem 5 behind the head 6. Note that the thickness of the upper and lower portions of the stem 5 in the portion where the window 7 is formed is thinner than the other portions.

  The proximal phalanx member 4 is made of medical ultra-high molecular polyethylene or the like, and a stem 8 to be inserted into the medullary cavity at the proximal end of the proximal phalanx 3 is formed at the tail, and the head 6 is moved up and down at the head. The socket 9 is formed so as to be pivotably received. Therefore, the socket 9 takes a shape along the outer shape of the head 6. However, since the head 6 bends and stretches from the extended position to the bent position, the tip is missing so that the stem 5 does not interfere during this time. It is a weak half-cylinder (open). Here, the weak semi-cylindrical body means that the protrusion of the socket 9 on the circumferential side with respect to the head 6 does not exceed the maximum outer diameter of the head 6, and is to ensure lateral swayability. Furthermore, the stem 8 is also formed in a curved shape that warps upward along the shape of the medullary cavity of the proximal phalanx 3.

  And the corner | angular 10 which protrudes toward the tip (head 6 side) is formed in the upper and lower sides of the socket 9. The corner 10 has a width smaller than the left and right width of the socket 9, but the vertical distance is narrowed along the outer periphery of the head 6 toward the tip. Therefore, the socket 9 is a strong semi-cylindrical body having a substantially C shape in a side view. Here, the strong semi-cylindrical body means that the protrusion on the circumferential side with respect to the head 6 at the corner 10 exceeds the maximum outer diameter of the head 6, and is to secure a certain degree of strong holding force.

The corner 10 is not inserted into the window 7 when the head 6 and the socket 9 are in the extended position, is intended to be inserted into the window 7 when start bending, lateral width of the corner 10 at this time, the window 7 is set to be smaller than the left-right interval and has a gap between them. However, this gap is set so as to decrease as the bending angle increases, and accordingly, the corner 10 is formed in a tapered shape that becomes thinner toward the tip.

  In addition, the head 6 and the socket 9 are fitted with a certain amount of backlash. This backlash is achieved by making the outer diameter of the head 6 smaller than the inner diameter of the socket 9, and in this example, this diameter difference is set to about 0.5 to 1.0 mm. In addition to the fact that the socket 9 has a weak half-cylinder shape, this backlash ensures the lateral swaying of the head 6 and the socket 9 in the extended position. While allowing the palm-side displacement, which is the movement of the knuckle of the fingers, to some extent, it has the effect of not reaching dislocation. If the head 6 is in the shape of a rugby ball, the swinging motion is possible, and the lateral swinging property is further enhanced.

  By the way, the head 6 and the socket 9 can be fitted by inserting the head 6 into the socket 9 from the lateral direction. At this time, the vertical distance between the corners 10 is smaller than the diameter of the head 6, but insertion can be easily performed by making the thickness of the stem 7 where the window 7 is formed thinner than this. Become. Further, the head 6 may be inserted from the front surface of the socket 9. At this time, the tip of the corner 10 has to be opened up and down, but since the corner 10 is formed of resin, it can be easily deformed and inserted. Thus, having a plurality of fitting methods means that there is a high degree of freedom in surgery.

  According to the above configuration, in the fitting of the head 6 and the socket 9, the lateral swaying property is ensured even when bent, but this lateral swaying property is limited to a certain amount by the gap between the corner 10 and the window 7. Will be. Specifically, it is maximum when the head 6 and the socket 9 are extended by 180 ° (about ± 30 °), and becomes zero when the head 6 and the socket 9 are bent by 90 °. FIG. 4 is a developed view showing the gap between the head 6 and the socket 9. The left-right distance of the window 7 is constant at D, but the left-right width d of the corner 10 increases as the bending angle increases (as the root increases). In the bent position, the left-right width d and the left-right distance D are the same.

  Next, an operation for replacing the above artificial finger joint with a finger joint will be described. After making a transverse incision in the skin almost immediately above the knuckles, the extensor tendon is shifted to the side, and the joint capsule is longitudinally incised to expose the joint. Then, the metacarpal bone 1 and the proximal phalanx 3 are bent by 90 ° and the end of each bone is excised, then the medullary cavity is drilled in the direction of the bone axis, and the stems 5 and 8 are inserted and fixed with cement. . The state of resection at this time is such that the bottom surface of the head 6 is the end surface of the metacarpal bone 1 in the metacarpal member 2, and the outer end of the window 7 is the end surface of the metacarpal bone 3 in the metacarpal member 2. Set as follows.

  When the above treatment is completed, when the head 6 and the socket 9 are pressed strongly while being slightly extended, both are fitted and connected. Then, after the extensor tendon is returned to the upper surface of the metacarpal bone member and the joint capsule is sutured, the skin is sutured, and the operation is completed. It is also possible to insert the head 6 and the socket 9 into the affected part in this state by fitting them in advance. Thus, one of the features of this artificial finger joint is that surgery is easy and simple. In the above, if the rib 11 is formed on the stem 5 of the metacarpal bone member 2, the fixation with the metacarpal bone 1 is strengthened, and the surface of the stem 8 of the proximal articular bone member 4 is made of metal 12. If covered, adverse effects on the proximal phalanx 3 due to resin elution can be prevented.

  When the finger joint is replaced with the artificial finger joint described above, the proximal phalange 3 can bend and stretch from the extended position to the bent position with respect to the metacarpal bone 1. The member 4 has a maximum lateral swaying property with respect to the metacarpal bone member 2 and is restricted as the bending angle increases. Further, the dislocation is prevented by inserting the corner 10 into the window 7. On the other hand, in the bending position, the lateral swaying property is completely regulated, and in addition to this, if a certain amount of backlash is given to the rotation of the head 6 and the socket 9, it is peculiar to a rheumatic patient in the bending position. The movement on the palm side is also allowed to some extent (it does not lead to dislocation), and it is in line with the familiar movement for many years, making use of the tension force of the soft tissue so far, smooth bending and stretching it can. Therefore, the movement close to the living finger joint can be acquired, and the patient's quality life is improved.

  The above artificial joint is applied to four finger joints, but can be similarly applied to a thumb joint (MP joint, IP joint). Moreover, if it is a joint in which the function similar to a finger joint is calculated | required, it can apply also to the joint. Specifically, the proximal interphalangeal joint (PIP joint) and the distal interphalangeal joint (DIP joint) are the same, and it can also be applied to the wrist joint.

It is a partial cross section top view of the state which applied the artificial finger joint which concerns on this invention. It is a partial cross section top view of the artificial finger joint which concerns on this invention. It is a partial cross section side view of the artificial finger joint which concerns on this invention. It is an expanded view which shows the relationship between the angle | corner and window in the artificial finger joint which concerns on this invention.

DESCRIPTION OF SYMBOLS 1 metacarpal bone 2 metacarpal bone member 3 proximal phalanx 4 proximal phalanx member 5 stem of metacarpal bone 6 ヘ ッ ド head 7 窓 window 8 stem of proximal phalange member 9 ソ ケ ッ ト socket 10 角 corner 11 中Hand bone rib 12 Metal of proximal phalanx

Claims (3)

A metacarpal bone member with a head formed at the tip of the stem inserted into the metacarpal bone, and a head at the tip of the stem inserted into the proximal phalanx can be bent with backlash from the extended position to the bent position. In an artificial finger joint composed of a proximal phalanx member that forms a socket to receive, the socket is made into a weak half cylinder that opens on the head side and does not exceed the maximum outer diameter of the head, and a window that penetrates up and down behind the head The top and bottom of the socket are attached to the outer periphery of the head, and the angle with the window gradually decreases as it enters the window during bending and increases in bending, and becomes an angle that becomes zero when bent 90 °. Artificial finger joint. The head is a rugby ball-like cylinder extending in the left-right direction and the socket has a C-shaped side view for receiving it, and is a strong half-cylinder whose corner exceeds the maximum outer diameter of the head. Item 1. Artificial finger joint.   The artificial finger joint according to claim 1 or 2, wherein the left and right widths of the corners are tapered such that the width decreases toward the tip.