JP2006136470A - Prosthetic hip joint, cup and surgical instrument for installation - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce a possibility of a neck part of a stem coming into contact with the edge of a cup by contriving the shape of the cup and to prevent luxation of a bone head caused by the contact. <P>SOLUTION: The subject prosthetic hip joint is constituted of the cup 11 being mountable on the acetabulum of the pelvis and having a recessed inner wall, the stem 13 being mountable on the medullary cavity of the femur, and the bone head 12 fixed to the upper end of the stem 13 and having a spherical surface sliding along the cup inner wall. The cup 11 is provided with a low wall part 2 having the inner wall height L1 and a high wall part 3 having the inner wall height L2 higher than L1 using the rotation center of the head bone 12 as a reference, and the high wall part 3 is positioned in the low-order direction of the hip joint. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an artificial hip joint for replacing a hip joint portion of a human body, a cup for an artificial hip joint, and an installation surgical instrument for mounting the cup on an acetabulum of a pelvis.

  Artificial hip joints are widely used as a final treatment method for hip joint diseases.

  FIG. 14 is an explanatory diagram showing a situation where a typical artificial hip joint is installed at a hip joint site. The hip prosthesis is composed of a cup that is embedded in the acetabular acetabulum of the pelvis, a stem that is embedded in the medullary cavity of the femur, and a bone head that is attached to the tip of the stem and slides against the inner wall of the cup.

  Some cups are made of ultra-high molecular weight polyethylene and are fixed by bone cement, and after the metal outer shell is fixed in the acetabulum with a screw or the like, it is fixed in the cup. There are various types, such as those made of ultra high molecular weight polyethylene, or an integral type of ultra high molecular weight polyethylene that is screwed into a female screw dug into the acetabulum with a dedicated instrument.

  Among the problems that occur after this hip replacement surgery, dislocation is one of the serious problems. The situation where dislocation occurs is shown in FIGS. When the positional relationship between the edge 5 of the cup 11 and the neck 14 of the stem is within the normal range as shown in FIG. 15, no problem occurs, but when the foot is moved greatly, as shown in FIG. Furthermore, when the stem neck portion 14 moves to a position where it contacts the edge 5 of the cup 11 and the foot is further moved, the bone head 12 gets over the wall 1 of the cup 11 and dislocated as shown in FIG. It falls into such a situation.

  The angle at which the edge 5 of the cup 11 and the neck 14 of the stem can be moved without contact (oscillation angle) is greater than the angle at which a normal person can normally move in conventional products. This is due to the narrowness, and various ideas have been made to widen the oscillation angle.

  For example, (1) a technique for reducing the diameter of the neck 14 of the stem as shown in FIG. 18, (2) a technique for increasing the diameter of the bone head 12 as shown in FIG. 19, and (3) a technique shown in FIG. As described above, attempts have been made to reduce the distance between the rotation center 4 of the bone head 12 and the end surface of the cup 11 in the cup 11, that is, to arrange the entire bone head toward the outer side. It hasn't been done yet.

  As for the method (1), it is difficult to secure a diameter at the neck portion that can withstand a load that is said to be five times the weight of the patient. As for method (2), increasing the bone head diameter reduces the thickness of the polyethylene portion of the cup 11 and increases the risk of increasing the amount of wear of the polyethylene. Regarding method (3), the possibility of contact with the cup edge is reduced, but the distance until the bone head is completely dislocated is reduced, and the resistance to dislocation is weakened. Moreover, in order to install each member of the artificial hip joint thus designed in an ideal position in the human body, a very high technique is required, and the dislocation prevention effect has not been enhanced.

  Therefore, it is unavoidable that the neck of the stem comes into contact with the edge of the cup. As disclosed in Japanese Patent Laid-Open No. 59-192365, when the stem is further rotated after contact, the head of the cup is It has been proposed to form an inner wall shape of the cup with a wall in a direction in which the head of the head tries to get over so as not to get over the edge.

  This wall is usually oriented posteriorly or posteriorly upward in the joint, but when this type of cup actually removed by dislocation is observed, the stem neck contact mark is left on this wall. Many cases are seen. That is, if the installation direction of the wall is not appropriate, it is estimated that this wall may act as a fulcrum when the stem neck part becomes a lever and the bone head is about to come off.

  FIG. 21 is a perspective view showing an example of a conventional artificial hip joint. FIG. 22A is a vertical sectional view showing an example of a conventional cup, and FIG. 22B shows a front view thereof. Here, a state where the artificial hip joint is attached as the left foot hip joint is shown, and the cup is described as an example of a type fixed with bone cement.

  The artificial hip joint includes a cup 11, a stem 13, a bone head 12, and the like. As shown in FIG. 22A, the cup 11 has a low wall portion 2 having an inner wall height L1 and a high wall portion 3 having an inner wall height L2 larger than L1 with reference to the rotation center 4 of the bone head 12. And the high wall portion 3 is positioned behind the hip joint as shown in FIG. Therefore, as in Japanese Patent Laid-Open No. 59-192365, when the neck portion 14 of the stem 13 becomes a lever and the bone head 12 is about to come off, the high wall portion 3 acts as a fulcrum and may be dislocated. Get higher.

JP 59-192365 A Special table 2003-526455 gazette Japanese Patent No. 3075686

  An object of the present invention is to devise a cup shape, to eliminate as much as possible the possibility that the neck of the stem contacts the edge of the cup, and to prevent the dislocation of the bone head caused by the contact, and It is to provide a cup for an artificial hip joint.

  Another object of the present invention is to provide a surgical instrument for installation for mounting such a cup on the acetabulum of the pelvis.

  The present inventors have invented a new shape acetabular cup by measuring the three-dimensional range of motion that can be taken by normal hip joint movement, and tracing the trajectory of the femoral stem neck movement to reach it. The effect was confirmed.

  In the description of the present invention, parameters for expressing the body movement direction and angle are defined.

  As shown in FIG. 4, when a leg is moved forward from a normal standing state as a reference, this is called bending, and the moved angle is called bending angle. On the other hand, when the foot is moved backward, this is called extension and the angle is called extension angle. Further, when the foot is moved from the normal standing state to the left and right direction, this is called abduction, and the angle is called abduction angle. When moving in the opposite direction, this is called adduction and the angle is called adduction angle. In addition, when the foot is held upright and moved so that the toe of the foot is opened outward, this is called external rotation, and the angle is called external rotation angle. On the other hand, when moving the toe to close inward, this is called internal rotation, and that angle is called internal rotation.

  The actual hip movement is not limited to these six directions, but all movements can be described as a combination of these six directions. For example, the state of the femur in a Japanese-style toilet, which is a limb position where dislocation occurs frequently, is an internal rotation of 20 degrees to 25 degrees after bending 90 degrees or more.

  The present inventors have a range in which the hip joint can normally move by bending an external rotation, an internal rotation, an abduction, or an adduction after bending a certain angle from the normal standing state of the normal human hip joint. Was measured. The results were as shown below (Table 1).

  Next, the movement of the stem neck to these positions is traced, and the wall height of the inner wall of the cup with the maximum height within which this stem neck does not contact the cup edge. I decided. As a result, a cup having a shape as shown in FIG. 2 was devised. This is a type of polyethylene cup that is secured to the acetabulum by bone cement. As described in Japanese Patent Application Laid-Open No. 59-192365 and Japanese Translation of PCT International Publication No. 2003-526455, the configuration in which the height of the wall is changed and the high wall is arranged in a direction in which the head of the bone tries to get over at the time of dislocation is as follows. Although it is known, the direction of the high wall is supposed to be directed rearward or rearward and upper, and the configuration directed toward the lowerward inner direction is proposed for the first time by the present invention.

That is, the artificial hip joint according to the present invention can be attached to the acetabulum of the pelvis, and has a cup having a concave inner wall,
A stem that can be attached to the medullary cavity of the femur;
A bone head with a spherical surface that is fixed to the upper end of the stem and slides along the inner wall of the cup;
The cup is provided with a low wall portion having an inner wall height L1 and a high wall portion having an inner wall height L2 larger than L1, with reference to the rotation center of the bone head,
The high wall portion is positioned in a lower direction of the hip joint.

  In the present invention, the angular position at which the high wall portion changes to the low wall portion is preferably in the range of 35 ° to 80 ° and in the range of −35 ° to −80 ° with respect to the lower direction of the hip joint.

  Moreover, in this invention, it is preferable that the inner wall height L2 of a high wall part exists in the range of 0.5 mm-8.0 mm.

  Moreover, in this invention, it is preferable that the inner wall height L1 of a low wall part exists in the range of 0 mm-3.0 mm.

The cup for an artificial hip joint according to the present invention can be mounted on the acetabulum of the pelvis and has a concave inner wall for storing a spherical bone head,
With reference to the rotational center of the head, a low wall portion having an inner wall height L1 and a high wall portion having an inner wall height L2 larger than L1 are provided.
A pair of pin insertion holes is formed on a line that intersects the symmetric center line of the high wall portion substantially perpendicularly.

Moreover, the surgical instrument for installation according to the present invention is for mounting the cup on the acetabulum of the pelvis,
A rod for operation;
A plate attached to the front end of the rod,
It is provided on a line intersecting substantially perpendicular to the longitudinal direction of the rod, and includes a pair of cup holding pins protruding from the lower surface of the plate.

  According to the present invention, the cup is provided with a low wall portion and a high wall portion, and the high wall portion is positioned in the lower direction of the hip joint, thereby ensuring a movable range similar to that of a normal human hip joint and the neck of the stem. The possibility that the part contacts the edge of the cup can be eliminated as much as possible. As a result, the dislocation of the bone head due to contact can be prevented.

  FIG. 1 is a perspective view showing an example of an artificial hip joint according to the present invention. FIG. 2 is a perspective view showing an example of a cup according to the present invention. FIG. 3A shows a vertical sectional view of the cup, and FIG. 3B shows a front view thereof. Here, a state where the artificial hip joint is attached as the left foot hip joint is shown, and the cup is described as an example of a type fixed with bone cement.

  The artificial hip joint includes a cup 11, a stem 13, a bone head 12, and the like.

  The cup 11 is made of a polymer material having wear resistance and corrosion resistance, such as ultra high molecular weight polyethylene, and has a concave inner wall 1 for housing the bone head 12 and a dome shape so that it can be attached to the acetabulum of the pelvis. Equipped with external walls. You may provide the outer wall of the cup 11 with the groove | channel and the unevenness | corrugation for improving the bond strength with bone cement. FIG. 2 shows an example in which a conical flange extending from the circumferential edge of the outer wall to the pelvis side is provided. However, in FIG. 3, the flange is not shown for easy understanding. .

  The stem 13 is formed of a material having high strength and corrosion resistance, such as a metal or an alloy. The root of the stem 13 has a shape that can be attached to the medullary cavity of the femur. A tapered neck portion 14 for fixing the bone head 12 is provided at the upper end of the stem 13.

  The bone head 12 is formed of a ceramic material or metal material having high strength and corrosion resistance, and has a spherical surface that slides along the inner wall of the cup 11. An insertion hole for inserting and fixing the neck portion 14 of the stem 13 is provided in a part of the spherical surface.

  In the present embodiment, as shown in FIG. 3A, the cup 11 has a low wall portion 2 having an inner wall height L1 and an inner wall height L2 larger than L1 with reference to the rotation center 4 of the bone head 12. The high wall part 3 which has is provided.

  The inner wall 1 of the cup 11 has a hemispherical portion having a radius that matches the spherical radius of the bone head 12.

  The low wall portion 2 refers to a portion from the edge of the hemispherical portion to the edge portion 5 inclined at the cup end surface, and the inner wall height L1 of the low wall portion 2 is the edge plane of the hemispherical portion including the rotation center 4. To the edge 5 in terms of distance.

  The high wall portion 3 refers to a portion from the edge of the hemispherical portion to the raised portion of the cup end surface, and the inner wall height L2 of the high wall portion 3 is a raised portion from the edge plane of the hemispherical portion including the rotation center 4. Defined by distance.

  As shown in FIG. 1, the high wall portion 3 is positioned in the longitudinal direction of the stem 13 in the normal position, that is, in the lower direction of the hip joint. With such a configuration, it is possible to reduce the possibility that the neck portion of the stem contacts the edge portion of the cup while ensuring a movable range similar to that of a normal human hip joint.

  In determining the position θ at which the height changes from the high wall portion 3 to the low wall portion 2, it is necessary to satisfy both prevention of dislocation and securing a sufficient movable range. First, from the viewpoint of preventing dislocation, the most frequent dislocation posture is when an internal rotation is performed after bending at a certain angle.

  Therefore, after taking a bent position at a certain angle, the stem neck was moved in the internal rotation direction until it contacted the edge of the cup, and the contact position at that time was measured. This is because a high wall is required in the direction opposite to the contact position. The results are as shown below (Table 2), and the contact positions at the respective angles are shown in FIG.

  It should be noted that the movement in the internal rotation direction from the initial bending of less than 50 ° does not need to be taken into consideration because there is little practical risk of dislocation. Further, the bending position of 120 ° or more is an extreme posture and it is not necessary to consider this.

  From this result, it can be seen that from the viewpoint of preventing dislocation, it is optimal that θ is in the range of 35 ° to 80 ° with respect to the lower direction of the hip joint. By disposing the high wall portion 3 in this direction, the floating limit of the bone head, which was only the same height as the low wall portion 2 in the conventional shape, is expanded to the height L2 of the high wall portion 3. As a result, even if the neck portion 14 reaches an extreme internal rotation enough to come into contact with the cup edge 5, a high wall is formed on the distal inner side in which the bone head 12 tends to come out at that time. Therefore, the effect of preventing dislocation is exhibited.

  Here, as shown in FIG. 5, the height change position θ on the rear side has been examined. Similarly, with respect to the height change position on the front side, θ is from −35 ° on the basis of the lower direction of the hip joint. It can be seen that it is optimal to be in the range of −80 °.

  On the other hand, from the viewpoint of securing a sufficient movable range, how the limits of extension angle, abduction angle, inversion angle, internal rotation angle, and external rotation angle after 0 ° bending change when θ is changed We examined what to do. The results are shown in FIG.

  Note that the abduction angle and the internal rotation angle are not shown for the sake of simplification of explanation because there is no change in the numbers within the scope of the present investigation and the results are not affected. First, extension of 35 ° or more is sufficient for practical use, and there was no problem in the scope of this study. Further, the inward angle is required to be 30 ° or more, and it can be said that there is no problem in the scope of this study. On the other hand, the external rotation angle needs to be 40 ° or more, and for that purpose, θ needs to be in the range of 0 ° to 90 °. As the value of θ that satisfies both the prevention of dislocation and the securing of a sufficient movable range, 35 ° to 80 ° was obtained in the present invention.

  Next, when determining the height L <b> 2 of the high wall portion 3, it is necessary to keep the height so as not to contact even when the neck portion 14 of the stem 13 moves in the direction of the high wall portion 3. The parameters considered at this time are the internal rotation angle and external rotation angle after bending by 30 °, and as described above, the internal rotation angle should be 35 ° or more and the external rotation angle should be 53 ° or more. FIG. 7 shows the result of studying the internal rotation angle and external rotation angle after 30 ° bending after changing the height L2 of the high wall portion 3.

  From this, it is read that the height L2 of the high wall portion 3 is appropriate to be 8.0 mm or less. Further, it was concluded that the height of the high wall is meaningless at 0 mm in order to exert the effect of preventing dislocation, and that 0.5 mm to 8.0 mm is appropriate in the present invention.

  Next, a criterion for determining the height L1 of the low wall portion 2 that does not contact even when the neck portion 14 of the stem 13 moves in the direction of the low wall portion 2 is applied. FIG. 8 shows the results of studying the abduction angle, the inversion angle, the internal rotation angle, and the external rotation angle after 0 ° bending after changing the height L1 of the low wall portion 2.

  As shown above, the abduction angle should be 40 ° or more, the inversion angle should be 30 ° or more, the internal rotation angle should be 40 ° or more, and the external rotation angle should be 40 ° or more. It was found that the height was 0 mm to 3.0 mm.

  In actual clinical application, an appropriate size is selected in consideration of the risk of dislocation of the patient.

  FIG. 9 shows an example of a cup provided with an external thread on the outer wall, FIG. 9 (a) shows a vertical sectional view thereof, and FIG. 9 (b) shows a front view thereof. After threading the acetabulum of the pelvis to form a female screw, the cup with the male screw 6 shown in FIG. 9 is rotated against the acetabulum to complete fixation by screw connection.

  FIG. 10 shows an example of a cup using an outer shell, FIG. 10 (a) shows a vertical sectional view thereof, and FIG. 10 (b) shows a front view thereof. After temporarily fixing the metal outer shell 7 to the pelvis acetabulum with the screw 8, the cup shown in FIG. 10 is fixed in the outer shell 7 by fitting or driving.

  Although the cups shown in FIGS. 9 and 10 have different shapes for attaching to the acetabulum, the sliding portion and the wall shape in contact with the bone head are the same as those in FIG.

  Next, a surgical instrument for fixing the cup according to the present invention to the acetabulum will be described.

  FIG. 11 is a side view showing an example of a surgical instrument according to the present invention. Fig.12 (a) is a partial side view which shows the mounting state of a cup, and FIG.12 (b) is the partial front view.

  As shown in FIGS. 2 and 12B, the cup according to the present invention has a pair of pin insertion holes 25 formed on a line that intersects the symmetric center line of the high wall portion 3 substantially perpendicularly. .

  The surgical instrument according to the present invention is provided on an operation rod 21, a horseshoe-like plate attached to the tip of the rod 21 in a forward-downward manner, and a line that intersects the longitudinal direction of the rod 21 substantially perpendicularly. And a pair of cup holding pins 24 protruding from the lower surface of the plate.

  When the cup is fixed to the acetabulum 23, the cup is first mounted on the surgical instrument plate. At this time, the rotation direction of the cup is determined by inserting the cup holding pin 24 into the pin insertion hole 25 of the cup. Next, after applying the bone cement 22 to the acetabulum, with the cup attached, the upper handle of the surgical instrument is lowered while being held horizontally to fit the cup into the acetabulum. Thus, the high wall portion of the cup can be correctly positioned in the lower direction of the hip joint.

  Fig.13 (a) is a partial side view which shows the mounting state of the cup in the front-end | tip part of the conventional surgical instrument, FIG.13 (b) is the partial front view. In the conventional cup, four pin insertion holes 25 are formed so that the high wall portion faces rearward. The reason why there are four pin insertion holes 25 is because there is a distinction between right and left.

  As described above, according to the application of the present invention, the range of limb position restriction of a patient can be expanded and QOL (Quality of Life) can be improved, and the medical cost burden due to dislocation and its response can be greatly reduced.

It is a perspective view which shows an example of the artificial hip joint which concerns on this invention. It is a perspective view which shows an example of the cup which concerns on this invention. FIG. 3A shows a vertical sectional view of the cup, and FIG. 3B shows a front view thereof. It is explanatory drawing which shows the parameter for expressing a body and its motion direction. It is explanatory drawing which shows the angle range about the boundary of a high wall part and a low wall part. It is a graph which shows the relationship between the angle position of a high wall part, and a movable angle. It is a graph which shows the relationship between the inner wall height of a high wall part, and a movable angle. It is a graph which shows the relationship between the inner wall height of a low wall part, and a movable angle. The example of the cup which provided the external thread in the outer wall is shown, Fig.9 (a) shows the vertical sectional view, FIG.9 (b) shows the front view. The example of the cup using an outer shell is shown, Fig.10 (a) shows the vertical sectional view, FIG.10 (b) shows the front view. It is a side view which shows an example of the surgical instrument which concerns on this invention. Fig.12 (a) is a partial side view which shows the mounting state of a cup, and FIG.12 (b) is the partial front view. Fig.13 (a) is a partial side view which shows the mounting state of the cup in the front-end | tip part of the conventional surgical instrument, FIG.13 (b) is the partial front view. It is explanatory drawing which shows the condition which installed the typical artificial hip joint in the hip joint site | part. It is explanatory drawing which shows the condition of the dislocation generation | occurrence | production in an artificial hip joint. It is explanatory drawing which shows the condition of the dislocation generation | occurrence | production in an artificial hip joint. It is explanatory drawing which shows the condition of the dislocation generation | occurrence | production in an artificial hip joint. It is explanatory drawing which shows the increase effect of the oscillation angle by making the diameter of the neck part of a stem thin. It is explanatory drawing which shows the increase effect of the oscillation angle by enlarging the diameter of a bone head. It is explanatory drawing which shows the oscillation angle increase effect by arrange | positioning the distance of the rotation center of the bone head in a cup, and a cup end surface small, ie, the outer side. It is a perspective view which shows an example of the conventional artificial hip joint. FIG. 22A is a vertical sectional view showing an example of a conventional cup, and FIG. 22B shows a front view thereof.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inner wall 2 Low wall part 3 High wall part 4 Center of rotation 5 Edge part 6 Male screw 11 Cup 12 Bone head 13 Stem 14 Neck part 21 Rod 22 Bone cement 24 Cup holding pin 25 Pin insertion hole

Claims (6)

A cup that can be attached to the acetabulum of the pelvis and has a concave inner wall;
A stem that can be attached to the medullary cavity of the femur;
A bone head with a spherical surface that is fixed to the upper end of the stem and slides along the inner wall of the cup;
The cup is provided with a low wall portion having an inner wall height L1 and a high wall portion having an inner wall height L2 larger than L1, with reference to the rotation center of the bone head,
The artificial hip joint, wherein the high wall portion is positioned in a lower direction of the hip joint.   The angular position at which the high wall portion changes to the low wall portion is in a range of 35 ° to 80 ° and a range of -35 ° to -80 ° with respect to the lower direction of the hip joint. Artificial hip joint.   The artificial hip joint according to claim 1, wherein an inner wall height L2 of the high wall portion is in a range of 0.5 mm to 8.0 mm.   The artificial hip joint according to claim 1, wherein an inner wall height L1 of the low wall portion is in a range of 0 mm to 3.0 mm. A hip prosthesis cup that can be attached to the pelvic acetabulum and has a concave inner wall to house a spherical head,
With reference to the rotational center of the head, a low wall portion having an inner wall height L1 and a high wall portion having an inner wall height L2 larger than L1 are provided.
A cup, wherein a pair of pin insertion holes are formed on a line that intersects substantially perpendicularly to the symmetrical centerline of the high wall portion. A surgical instrument for installation for attaching the cup according to claim 5 to the acetabulum of the pelvis,
A rod for operation;
A plate attached to the front end of the rod,
An installation surgical instrument comprising a pair of cup holding pins provided on a line that intersects substantially perpendicularly to the longitudinal direction of the rod and protruding from the lower surface of the plate.

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