JP3223346B2 - Osteosynthesis screw washers - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention is used for fixing a fractured part with an osteosynthesis screw, or for joining and fixing the osteotomized bones with an osteosynthesis screw after an osteotomy. The present invention relates to a biodegradable and absorbable osteosynthesis screw washer.

[0002]

2. Description of the Related Art Conventionally, as one method for joining and fixing a fractured portion, a tapped hole is formed in the fractured portion, and a metal or ceramic osteosynthesis screw is screwed into the tapped hole to join and fix the fractured portion. The method has been adopted.

Recently, an osteosynthesis screw made of biodegradable and absorbable polylactic acid, which does not require surgery for removal from a living body after healing, has been increasing in place of the above-mentioned osteosynthesis screw.

[0004]

However, depending on the type of living bone, there is a range from hard to soft bone, and even the same single bone has different hardness depending on the site. And relatively soft. Therefore, when the osteosynthesis screw is screwed into a relatively soft fracture as described above, as shown in FIG. 18, the head 1a of the osteosynthesis screw 1 is embedded in the bone fragment 2 of the fracture, and the screw is screwed. There is a problem that it is difficult to press and fix the bone fragments 2 with the head 1a.

The present invention has been made in view of the above problems, and has as its object to prevent the head of an osteosynthesis screw from being embedded in a bone and sufficiently tighten and fix a fractured portion. An object of the present invention is to provide a washer for an osteosynthesis screw which can perform a surgery for removing a fracture from a living body after healing a fracture. Then, it is desirable to significantly improve the strength of the washer, and to further provide the washer with connectivity to a living bone.

[0006]

In order to achieve the above object, a washer for an osteosynthesis screw according to the present invention has the following features.

That is, a washer for an osteosynthesis screw according to claim 1 of the present invention is a washer made of a biodegradable and absorbable polymer having a through hole formed at the center thereof for inserting a shaft portion of the osteosynthesis screw, 3. The osteosynthesis screw according to claim 2, wherein the molecular chains or crystals of the biodegradable and absorbable polymer that are compressed are obliquely oriented from the periphery toward the central axis of the washer or an axis parallel to the washer. The washer is a washer made of a biodegradable and absorbable polymer in which a through hole for inserting the shaft of the osteosynthesis screw is formed at the center, and is compressed, and the molecular chain or crystal of the biodegradable and absorbable polymer is used as the washer. The osteosynthesis screw washer according to claim 3, characterized in that it is obliquely oriented from both sides toward a plane including the central axis or a plane parallel thereto. A washer made of a biodegradable and absorbable polymer having an insertion hole through which a shaft portion of a joining screw is inserted, wherein the washer is compressed and a molecular chain or a crystal of the biodegradable and absorbable polymer bisects the washer in a thickness direction. Characterized in that it is obliquely oriented from both the upper and lower sides toward the surface to be parallel to this surface, the washer for the osteosynthesis screw according to claim 4, in the washer according to any one of claims 1 to 3, A washer for an osteosynthesis screw according to claim 5 is characterized in that a tapered countersunk portion is formed at the periphery of the insertion hole. The body is uniformly contained in the whole washer. The washer for an osteosynthesis screw according to claim 6 is the washer according to claim 5, wherein Concentration of the box powder is characterized in that 10 to 60% by weight.

[0008]

[0009]

[0010]

[0011]

[0012]

[0013]

[0014]

[0015]

Next, the operation of these osteosynthesis screw washers (hereinafter simply referred to as washers) will be described.

When the shaft of the osteosynthesis screw is inserted into the through hole of the washer according to the first aspect and the shaft of the screw is screwed into a tap hole formed in a fractured part or a bone cut part, the head of the screw becomes washer. , The pressing force (tightening force) of the screw head is distributed and transmitted to the entire washer, and the entire washer uniformly presses a fractured portion or a bone cut portion over a wide range. Therefore, unlike the case where the osteosynthesis screw is screwed in without using a washer, the pressing force of the screw head does not concentrate in a narrow range, so that the screw head together with the washer is inserted into the bone of the fracture or osteotomy. Without being implanted, the fractured portion is evenly pressed by the entire washer as described above, and is securely fixed.

When the fracture or bone cut is fixed as described above, the washer is made of a biodegradable and absorbable polymer. The screw head is fixed while maintaining practical strength for several months until healing, but after healing, further hydrolysis proceeds and it is gradually decomposed into small pieces, and finally all are completely decomposed Is absorbed into the body. Therefore,
By joining and fixing a fracture or bone cut using a biodegradable and absorbable osteosynthesis screw and this washer, there is no need to perform an operation to remove the screw or washer from the body after healing, so the pain and economy of reoperation The burden on the target can be eliminated.

[0019]

[0020]

The washer of the first aspect, wherein the molecular chain (crystal) of the biodegradable and absorbable polymer is obliquely oriented from the periphery toward the central axis of the washer or an axis parallel thereto. , Not only the density and surface hardness are improved compared to non-oriented or stretch-oriented washers, but also the anisotropy of molecular chain (crystal) orientation between the direction of the central axis and the direction perpendicular thereto is small. Therefore, the strength against external forces in various directions is greatly improved as a whole, in combination with the fact that the compression becomes dense. In particular, in the washer, in a cross section perpendicular to the central axis, the molecular chain (crystal) takes a radial arrangement around the central axis or an axis parallel to the central axis, so that the torsional strength is remarkably improved. Therefore, when the osteosynthesis screw is screwed in, even if a rotational force or a torsional force acts on the washer due to sliding friction with the screw head or the like, the washer does not have to be damaged.

Further, the washer of the second aspect is also compressed, and the molecular chains (crystals) of the biodegradable and absorbable polymer are obliquely oriented from both sides toward a plane including the central axis of the washer or a plane parallel thereto. Therefore, the anisotropy of the molecular chain (crystal) orientation between the direction of the plane and the direction perpendicular thereto is small, and combined with the fact that it is dense by compression,
The strength against external forces in various directions is greatly improved as a whole.

Further, the washer of the third aspect is also compressed, and the molecular chains (crystals) of the biodegradable and absorbable polymer are inclined obliquely from both upper and lower sides toward a plane bisecting in the thickness direction of the washer or a plane parallel thereto. Molecular chains (crystals)
The anisotropy of the orientation is small, the material is dense and the strength is greatly improved overall.

Further, in the washer according to the fourth aspect, since the tapered shank is formed on the periphery of the insertion hole, when the osteosynthesis screw is screwed, the head of the screw comes into surface contact with the shank. As a result, the stability (sitting) is improved, and the pressing force of the screw head is evenly distributed and transmitted to the entire washer, so that the fractured portion or the bone cut portion can be pressed and fixed more uniformly. When the bioceramic powder is uniformly contained in the entire washer as in the washer of claim 5, the bioceramic powder induces bone tissue into the washer as the biodegradable and absorbable polymer is hydrolyzed. In order to form the washer, the washer is combined with the living bone and fixed within a relatively short period of time. Finally, the entire washer is replaced by living bone and disappears.

Preferably, the concentration of the bioceramics powder is set in the range of 10 to 60% by weight, as in the washer of claim 6. If it is less than 10% by weight, the ability of the bioceramics powder to induce and form bone tissue is obtained. Is insufficient, and it is difficult to bond with living bone in a short period of time. On the other hand, when the content is more than 60% by weight, the hardness of the washer is improved, but the inherent toughness of the biodegradable and absorbable polymer is impaired and the polymer becomes brittle, so that the polymer is easily broken or chipped.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a perspective view showing a washer A according to an embodiment of the present invention, and FIG. 2 is a vertical sectional view of the washer A taken along line XX.

The washer A is made of a biodegradable and absorbable polymer, and has the shape of a circular donut plate having a circular insertion hole 3 formed at the center for inserting the shaft of the osteosynthesis screw. The specific dimensions of the washer are as follows: the inner diameter (diameter of the insertion hole) is about 1.5 to 8 mm, the outer diameter is about 4 to 15 mm, and the thickness is It is desirable to set it to about 3 mm.

As the biodegradable absorbent polymer of the material, any crystalline thermoplastic polymer which is high molecular weight, has high strength and toughness, is non-toxic and can be absorbed into the living body by hydrolysis can be used. Among them, polylactic acid having an initial viscosity average molecular weight of 100,000 to 700,000, preferably about 150,000 to 600,000, a lactic acid-glycolic acid copolymer, a lactic acid-caprolactone copolymer, and the like are particularly suitable. Alternatively, two or more kinds are used in combination. The above-mentioned polylactic acid is a polymer whose safety in vivo has already been proven, and since it is a crystalline and linear polymer, it is necessary to improve the strength by stretching orientation and compression orientation as described later. Can be.

A tapered countersunk portion 3a is formed on the upper surface of the washer A at the periphery of the insertion hole 3 to a depth approximately half the thickness of the washer A. When such a seating portion 3a is formed, as shown in FIG. 3, when the shaft portion of the osteosynthesis screw 1 is screwed into a tap hole (not shown) formed in the fracture portion to join the fracture portion, the screw is screwed. The lower surface of the head 1a is in surface contact with the seating portion 3a and is stable (sitting)
This has the advantage that the pressing force (tightening force) of the screw head 1a is evenly distributed and transmitted to the entire washer A, so that the fractured portion can be uniformly pressed and fixed by the entire washer A.

It is desirable that the taper angle of the countersunk portion 3a be substantially the same as the taper angle of the lower surface of the screw head 1a. In many cases, the lower surface of the portion is formed in a substantially spherical shape having a small curvature, so that if the taper angle with respect to the central axis of the facing portion 3a is set to about 30 to 75 °, in most cases, surface contact or surface contact is achieved. It becomes a close state, and the stability (sitting) improves.

The depth of the countersunk portion 3a is approximately 1/2 of the thickness of the washer A, but may be shallower or deeper than that. And the entire inner surface of the insertion hole 3 may be widened upward and tapered. Forming the seating portion 3a deep in this manner has an advantage that the protrusion dimension of the screw head 1a can be reduced. If the seating portion 3a is too shallow, the contact area with the lower surface of the screw head 1a is reduced and the stability is reduced. Therefore, it is desirable to form the washer A deeper than １ ／ of the thickness. Also, when the countersunk portion 3a is not provided, when the osteosynthesis screw 1 is screwed in at an angle, only one side of the screw head 1a may come into contact with the washer A and the pressing force may be reduced. Cost.

Such a washer A can be manufactured by various methods such as cutting the biodegradable and absorbable polymer after melt injection molding or melt extrusion molding. It is desirable that the entire surface of the manufactured washer is roughened by cutting or other means. Such a roughening treatment has an advantage that the rate of hydrolysis in a living body becomes appropriate.

The shaft of the biodegradable and absorbable osteosynthesis screw 1 is inserted through the insertion hole 3 of the washer A as described above.
As shown in FIG. 3, when the shaft of the screw 1 is screwed into a tap hole (not shown) formed in the living bone of the fracture, the screw head 1a faces the seating portion 3a at the periphery of the insertion hole 3 of the washer A. In the contact state, it is stably pressed and locked, and the screw head 1
The pressing force (clamping force) of “a” is evenly distributed and transmitted to the entire washer A, and the whole washer A uniformly presses the bone fragments 2 of the fractured part. Therefore, unlike the case where the osteosynthesis screw is screwed in without interposing a washer, the pressing force of the screw head does not concentrate in a narrow range, so that the screw head 1a is embedded in the living bone together with the washer A. As described above, the bone fragments 2 of the fractured portion are evenly pressed by the entire washer A and securely fixed.

When the fracture is bonded and fixed as described above, the washer A made of the biodegradable and absorbable polymer comes into contact with the body fluid in the living body and hydrolysis proceeds from the surface, but it takes several months until the fracture heals. While maintaining the practical strength, there is no cracking or chipping. Then, after healing, the hydrolysis proceeds further, and the washer A is decomposed into small pieces, and finally all of the washer is completely decomposed and absorbed into the living body. Similarly, the biodegradable and resorbable osteosynthesis screw 1 is finally completely decomposed and absorbed into the living body. Therefore, it is not necessary to perform an operation to remove the screw or washer from the body after healing, so that the pain and the economic burden of the reoperation can be reduced.

FIG. 4 is a plan view of a washer B according to another embodiment of the present invention, and FIG. 5 is a plan view of a washer C according to still another embodiment of the present invention.

Each of these washers B and C is made of a biodegradable and absorbable polymer.
It has an oval plate shape having a circular insertion hole 3 for inserting the shaft of the osteosynthesis screw at the center, and a circular countersunk portion 3a is formed at the periphery of the insertion hole 3. The washer C is formed in an oval plate shape having an oval insertion hole 30 at the center. As described above, the washer of the present invention is not limited to the circular donut plate shape such as the above-mentioned washer A, but is not limited to the elliptical plate shape such as the washer B, the oval plate shape such as the washer C, and the like, and the oval plate shape. It can be configured in various shapes such as a rectangular plate shape, and the shape of the insertion hole is not limited to a circle, but may be various shapes such as an oval shape such as the insertion hole of the washer C, and other shapes such as an oval shape and an oval shape. It can be formed into a shape. If the insertion hole is oval or elliptical, the position of the shaft of the osteosynthesis screw 1 can be moved within the oval or elliptical range, and the washer can be moved to the left or right according to the condition of the fracture. There is an advantage that the washer can be located at the most suitable position.

FIG. 6 is a conceptual diagram showing an orientation state of molecular chains (crystals) in a longitudinal section of a washer D according to still another embodiment of the present invention, and FIG. 7 is a molecular chain (crystals) in a transverse section of the washer D. FIG. 3 is a conceptual diagram showing an orientation state of the liquid crystal.

This washer D has a circular insertion hole 3 formed at the center similarly to the above-mentioned washer A, and a tapered seating portion 3a which extends upward at the periphery of the insertion hole 3 has a thickness of 1/100 of the thickness of the washer. 2 is a circular donut plate shaped washer formed to a depth of 2.

However, the above-mentioned washer A is neither compressed nor stretched, and is a molecule (crystal) of a biodegradable and absorbable polymer.
Is unoriented, whereas this washer D is compressed,
As shown in FIG. 6, the molecular chains (crystals) M of the biodegradable and absorbable polymer are oriented obliquely downward from the periphery toward the central axis L of the washer D, and as shown in FIG. The chain (crystal) M is in a radially oriented state around the central axis L. Therefore, the density and surface hardness are larger than those of the non-oriented washer A and the uniaxially oriented washer G and H described later, and the molecular chains between the direction of the central axis L and the direction perpendicular thereto. (crystal)
Since the anisotropy of the orientation is small, the strength against external force in various directions is greatly improved as a whole, in combination with the fact that it is dense by compression. Strength is increasing. Therefore, when the osteosynthesis screw 1 is screwed in and tightened, even if a rotational force or a torsional force acts on the washer D due to sliding friction with the screw head 1a, the washer D does not have to be damaged.

The orientation angle of the molecular chain (crystal) M with respect to the central axis L is preferably adjusted within a range of 10 to 60 °.
If the angle is less than 10 °, the improvement of the anisotropy of the molecular chain (crystal) orientation becomes insufficient, and if it exceeds 60 °, the production is not easy,
Cracks and the like easily occur. A more preferred range of the orientation angle is 10 to 35 °.

In this washer D, the molecular chains (crystals) M are oriented obliquely downward from the periphery toward the central axis L, but may be oriented obliquely upward from the periphery toward the central axis L. Further, even when the molecular chains (crystals) are oriented obliquely downward or obliquely upward from the periphery toward a parallel axis deviated from the central axis L, almost the same strength improving effect can be obtained.

The washer D as described above is manufactured, for example, by the following method.

First, a biodegradable and absorbable polymer as a material is melt-extruded at a temperature equal to or higher than its melting temperature and equal to or lower than its decomposition temperature to produce a cylindrical billet. A molding die 4 as shown in FIG. 8, that is, a large-diameter cylindrical housing cavity 4a having a large cross-sectional opening area and a small-diameter cylindrical bottomed molding cavity 4c having a small cross-sectional opening area are formed. Between the narrowed portion 4b, the inner peripheral surface of which is a tapered surface with a constriction
The coaxially provided molding die 4 is used, the billet 5 is accommodated in the accommodation cavity 4a, and the pressurizing male mold 4 is
By d, the billet 5 is continuously or intermittently press-filled into the molding cavity 4c as shown in FIG. 9 at a temperature at which the biodegradable and absorbable polymer can be crystallized (above the glass transition temperature and below the melting temperature).

With such press-fitting, when the billet 5 passes through the constricted portion 4b, a large shear force is generated between the billet 5 and the tapered surface due to frictional resistance. MD) and lateral (TD) external force, the molecular chains (crystals) are compressed while being oriented obliquely downward from the periphery toward the center axis Lm of the mold 4 (in other words, the center axis of the billet 5). And crystallization proceeds. Then, even after filling into the molding cavity 4c, the inner surface and the bottom surface of the molding cavity 4c receive a back pressure and are fixed while maintaining the molecular chain (crystal) orientation and the compressed state, thereby forming a columnar compression orientation. A molded body 50 is obtained.

Then, the compression-oriented molded body 50 is taken out from the molding die 4 and is cut into a circle having a thickness corresponding to the thickness of the washer as shown in FIG.
The washer D can be obtained by cutting the circularly cut disk 500 to have a constant outer diameter and forming the circular insertion hole 3 and the countersunk portion 3a. In this case, if the countersunk portion 3a is formed from the upper surface of the disc 500, the molecular chain (crystal) M becomes a washer oriented obliquely downward from the periphery toward the central axis L, and the countersink portion 3a is formed of the disc 500. If it is formed from the lower surface, it becomes a washer in which the molecular chains (crystals) M are oriented obliquely upward from the periphery toward the central axis L.

In the above-described manufacturing method, the orientation angle of the molecular chain (crystal) with respect to the center axis Lm of the molding die 4 is determined by the inclination angle θ of the tapered surface of the narrowed portion 4b and the opening area between the housing cavity 4a and the molding cavity 4c. Therefore, it is desirable to adjust the orientation angle of the molecular chain (crystal) to the above-mentioned range of 10 to 60 ° by changing the ratio between the inclination angle θ and the opening area. In this case, the opening area between the housing cavity 4a and the molding cavity 4c is set such that the deformation ratio (cross-sectional area of the billet 5 / cross-sectional area of the compression-oriented molded body 50) is substantially in the range of 1.5 to 6.0. Ratio 1.5
It is desirable to change within the range of -6.0. If the deformation ratio is less than 1.5, a compression-oriented molded product having insufficient molecular chain (crystal) orientation is obtained, and if it exceeds 6.0, the orientation becomes excessive and a fibrillated compression-oriented molded product is obtained.

The crystallinity of the compression-oriented molded body 50 is as follows:
It is desirable to control the opening area ratio between the housing cavity 4a and the molding cavity 4c, the press-in temperature, the pressure, the press-in speed, and the like of the billet 5 so as to be adjusted in the range of 30 to 60%. The washer D obtained by slicing the compression-oriented molded body 50 having the crystallinity adjusted as described above and performing cutting processing has a well-balanced ratio of a crystal phase and an amorphous phase, and improves strength and hardness by the crystal phase. In addition, since the flexibility of the amorphous phase is well matched, there is no brittleness as in the case of only the crystalline phase, and there is no weak property with no strength as in the case of the amorphous phase alone. Therefore, the washer D has toughness and has a sufficiently high overall strength.

Further, in the above-described manufacturing method, a billet 4 in which the inclination angle of the tapered surface of the narrowed portion 4b is gradually changed over the entire circumference of the tapered surface or at an arbitrary portion is used, and the billet is formed in the same manner as described above. 5 is press-filled to obtain a cylindrical compression-oriented molded body 50 in which molecular chains (crystals) M are oriented obliquely downward from the periphery toward an eccentric axis parallel to the central axis L. Cut 50 into slices,
If the insertion hole 3 and the counterbore 3a are formed by cutting, a compressed washer in which the molecular chain (crystal) M is oriented obliquely downward or obliquely upward from the periphery toward an axis parallel to the central axis L of the washer. Can be obtained.

FIG. 11 is a conceptual diagram showing the orientation of molecular chains (crystals) in a longitudinal section of a washer E according to still another embodiment of the present invention, and FIG. 12 is a molecular chain (crystal) in a transverse section of the washer E. FIG. 3 is a conceptual diagram showing an orientation state of the liquid crystal.

The washer E has the same shape as that of the washer C, and has an oval insertion hole 30 formed at the center thereof. It is an oval plate-shaped washer formed to a depth of の of the thickness, but is compressed like the washer D described above. However, the orientation state of the molecular chain (crystal) M of the biodegradable and absorbable polymer is different from that of the washer D described above.

[0052] That is, in the washer E, are oriented from the left and right sides toward the face P ₁ obliquely downward that includes the center axis of the molecular chain (crystal) M is the washer E as shown in FIG. 11, FIG. 12 in a state of molecular chains (crystals) M is oriented toward the left and right sides to face P ₁ in cross section as shown. Therefore, the or washer A non-oriented, washer G uniaxial stretching and orientation to be described later, compared to H, large density and surface hardness, also, the molecular chains between the direction perpendicular to the direction of the surface P ₁ Since the anisotropy of the (crystal) orientation is small, the strength against external forces in various directions is generally improved in combination with the fact that the material becomes dense by compression.

Such a washer E can be manufactured by, for example, the following method in which the manufacturing method of the washer D is slightly changed.

First, a biodegradable and absorbable polymer as a material is melt-extruded to produce a thick plate-shaped billet. And
As a molding die, between the wide rectangular accommodating cavity having a large cross-sectional opening area and the narrow rectangular bottomed cavity having a small cross-sectional opening area, inner surfaces on both sides (on both long sides facing each other). Using a molding die with a constricted portion with an inclined surface having the same inclination angle, the above-mentioned billet is accommodated in the accommodation cavity, and the billet is press-fitted into the molding cavity with a male mold for pressurization. I do.

When press-fitting is performed in this manner, the billet is subjected to shearing force by the inclined surfaces on the inner surfaces of both sides of the narrowed portion, and the molecular chains (crystals) are directed from both sides toward the surface bisecting the width in the same manner as described above. A compressed rectangular oriented molded article is obtained which is compressed while being oriented diagonally downward and crystallized. Then, by cutting the compression-oriented molded body in a direction perpendicular to the axial direction thereof and punching or cutting the periphery into an oval shape, and cutting the oval insertion hole 30 and the countersunk portion 3a, molecular chains (crystals) washer E is obtained oriented from both sides obliquely towards the plane P ₁ including the center axis line. In that case, as in the case of the washer D, and the orientation angle of the molecular chain (crystal) M to the surface P ₁ is adjusted to 10 to 60 °, the degree of crystallinity 3
It is desirable to adjust to 0 to 60%. In addition, sitting part 3
By cutting a from the upper or lower surface, molecular chains (crystals)
Is oriented obliquely downward or obliquely upward as in the case of the washer D.

When a thick plate-like billet is press-filled in the same manner as described above using a mold having different inclination angles of the inclined surfaces on both sides of the narrowed portion, the molecules are moved toward a displaced surface parallel to the central axis. Since a plate-shaped compression-oriented molded product in which chains (crystals) are obliquely oriented from both sides is obtained, if this is cut and punched or cut to form the insertion hole 30 and the countersunk portion 3a, the molecular chains (crystals) can be obtained. Can be obtained obliquely oriented from both sides toward a deflected surface parallel to the central axis of the washer.

FIG. 13 is a conceptual diagram showing the orientation of molecular chains (crystals) in a longitudinal section of a washer F according to still another embodiment of the present invention, and FIG. 14 is a molecular chain (crystals) in a transverse section of the washer F. FIG. 3 is a conceptual diagram showing an orientation state of the liquid crystal.

The washer F has a circular insertion hole 3 in the center.
And a circular donut plate-shaped washer in which a tapered countersunk portion 3a is formed on the periphery of the insertion hole 3 so as to extend upward to a depth of 厚 み of the thickness of the washer. Compressed. However, the orientation state of the molecular chains (crystals) M of the biodegradable and absorbable polymer is different from those of the washers D and E.

[0059] That is, in the washer F, are oriented obliquely from upper and lower sides towards the bisecting plane P ₂ of the molecular chain (crystal) M is a washer F in the thickness direction as shown in FIG. 13, FIG. As shown in FIG. 14, molecular chains (crystals) M are arranged in parallel in one direction (right direction in the figure) in the cross section. Therefore, and said washer A non-oriented, washer G uniaxial stretching and orientation to be described later, compared to H, large density and surface hardness, also, the molecular chains between the direction perpendicular to the direction of the surface P ₂ Since the anisotropy of the (crystal) orientation is small, the strength against external forces in various directions is generally improved in combination with the fact that the material becomes dense by compression.

Such a washer F can be manufactured by, for example, the following method which is almost the same as the method of manufacturing the washer E.

First, a biodegradable and absorbable polymer as a material is melt-extruded to form a thick plate-shaped billet. And
Although the width of the housing cavity and the molding cavity is reduced as the molding die, substantially the same mold as that used for the washer E is used, and the billet is press-fitted into the molding cavity. With this press-filling, since a thin plate-like compression orientation molding body towards the plane P ₂ that bisects the thickness direction molecular chains (crystals) are oriented from both sides obliquely downward is obtained, the plate-like A washer F can be obtained by punching or cutting the compression-oriented molded body into a disk shape and forming the insertion hole 3 and the countersunk portion 3a in the disk. In that case, the washer D, as in the case of E, molecular chains (crystals) for bisecting plane P ₂ M
Is adjusted to 10 to 60 °, and the crystallinity is adjusted to 30 to 6
It is desirable to adjust to 0%.

When a mold having different inclination angles of the inclined surfaces on both sides of the narrowed portion is used, the molecular chains (crystals) are shifted toward the plane displaced parallel to the bisecting plane P _{2 in} the thickness direction of the washer. Washers oriented obliquely from both upper and lower sides can be obtained.

FIG. 15 is a conceptual diagram showing the orientation of molecular chains (crystals) in a longitudinal section of a washer G according to still another embodiment of the present invention, and FIG. 16 is a washer according to yet another embodiment of the present invention. It is a conceptual diagram which shows the orientation state of the molecular chain (crystal) in the longitudinal cross section of H.

Each of these washers G and H has a circular insertion hole 3 formed in the center, and a counterbore 3 is formed around the periphery of the insertion hole 3.
This is a circular donut plate-shaped washer provided with a, and has the same shape as the aforementioned washers A, D, F and the like.

However, the washer G in FIG. 15 is stretched in the thickness direction, and the molecular chain (crystal) M of the biodegradable and absorbable polymer is oriented in the stretching direction (thickness direction).
The washer H in FIG. 16 is stretched in one direction (right direction in the figure) perpendicular to the thickness direction, and the molecular chain (crystal) M of the biodegradable and absorbable polymer is stretched in one direction (one direction perpendicular to the thickness direction).
In that they are oriented in the same manner as the aforementioned washers A, D, and F.

As described above, the washers G and H in which the molecular chains (crystals) M are oriented in the stretching direction by the stretching in the thickness direction or the stretching in one direction perpendicular to the thickness direction are converted into the unoriented washers A. Although the strength is improved to some extent as compared with the washer D, E, F, which is compression-oriented, the strength and strength are improved.
Density, surface hardness, etc. are inferior. In addition, since these washers G and H have large anisotropy of molecular chain (crystal) orientation between the stretching direction and the direction perpendicular to the stretching direction, they generally improve the strength against external force in various directions. Is also difficult. However, it can be improved to the same degree as that of a living bone by stretching.

The stretching ratio of the washers G and H should be adjusted to about 2 to 10 times, preferably about 2 to 5 times. If it is less than 2 times, the orientation of the molecular chains (crystals) M becomes insufficient, and If it exceeds twice, fibrillation of the polymer proceeds, and if it exceeds 10 times, the polymer fibrillates, and the strength is rather reduced.

The above washers G and H can be manufactured, for example, by the following method.

As for the washer G, first, a biodegradable and absorbable polymer as a material is heated and melted at a temperature not lower than its melting temperature but not higher than its decomposition temperature and is extruded into a cylindrical shape. After heating to ℃, the film is uniaxially stretched in the axial direction at a magnification of about 2 to 10 times, preferably about 2 to 5 times.
Then, the stretched columnar molded body is cut into a ring having a thickness corresponding to the thickness of the washer, and the cut disk is cut to form a circular insertion hole 3 and a countersunk portion 3a. Can be manufactured.

As for the washer H, a biodegradable and absorbable polymer is melt-extruded into a plate shape, and is similarly uniaxially stretched. Then, the washer H can be manufactured by punching or cutting this stretched plate-like molded body into a disk shape and forming the insertion hole 3 and the countersunk portion 3a in the disk.

FIG. 17 is a longitudinal sectional view of a washer J according to still another embodiment of the present invention, and also shows the orientation of molecular chains (crystals).

The washer J has a circular insertion hole 3 in the center.
And a tapered seating portion 3a which expands upward at the periphery thereof.
And a circular donut plate-shaped washer provided with the bioceramics powder 6 uniformly. Then, the molecular chains (crystals) M of the biodegradable and absorbable polymer are obliquely orientated from the periphery toward the central axis L by compression to improve the density and surface hardness, and to increase the strength against external forces in various directions as a whole. Has been improved.

When the washer J containing the bioceramic powder 6 is hydrolyzed from the surface of the washer by contact with a body fluid in a living body, the bioactive bioceramic powder 6 is accordingly converted into a bone tissue. Is formed from the surface of the washer J into the inside thereof, so that the washer J is fixed to the living bone in a relatively short period of time.
Finally, the entire washer J is replaced with the living bone and disappears.

The concentration of the bioceramic powder 6 is as follows:
It is desirable to set it in the range of 10 to 60% by weight.
If the amount is less than 0% by weight, the ability of the bioceramics powder 6 to induce and form bone tissue is insufficient, so that it is difficult to bond with living bone in a short period of time. On the other hand, when the content is more than 60% by weight, the hardness of the washer J is improved, but the inherent toughness of the biodegradable and absorbable polymer is impaired and the polymer becomes brittle, so that the polymer is easily broken or chipped.

Preferred bioceramic powders 9 include sintered hydroxyapatite having surface bioactivity, bioglass or crystallized glass for living organisms, bioabsorbable wet hydroxyapatite, dicalcium phosphate, tricalcium phosphate. , Powders such as tetracalcium phosphate, octacalcium phosphate, calcite, diopsite,
These may be used alone or as a mixture of two or more. In particular, a powder of wet hydroxyapatite having a high ability to induce and form bone tissue is optimal. The bioceramic powder 9 preferably has a particle size of about 0.2 to 50 μm, and more preferably has a particle size of several μm to several tens μm.

The washer J as described above is manufactured, for example, by the following method.

First, a suspension of a bioceramic powder in a non-solvent of a biodegradable polymer is added to a solution of the biodegradable polymer in a solvent, and the mixture is stirred. Disperse the powder uniformly without agglomeration. Then, a non-solvent is further added with stirring to simultaneously precipitate the biodegradable and absorbable polymer and the bioceramic powder, which is filtered and dried, and the bioceramic powder having the bioceramic powder uniformly dispersed therein is uniformly dispersed therein. Obtain granules of the biodegradable and absorbable polymer.

Next, a cylindrical billet containing the bioceramics powder uniformly is obtained by melt molding, for example, extrusion molding or press molding using the granules. Then, this billet is housed in the housing cavity 4a of the molding die 3 shown in FIG. 8, and as described above, the billet is press-fitted into the molding cavity 4c with the male mold 4d for pressurization, whereby the molecular chain (crystal) is formed. Produces a columnar compression-oriented molded body oriented obliquely downward from the periphery toward the center axis, and cuts this into a ring to form the insertion hole 3 and the countersunk portion 3a.
Is manufactured.

[0079]

As is apparent from the above description, the washer of the present invention prevents the head of the osteosynthesis screw from being embedded in the bone of the fracture, and the pressing force (the tightening force) of the screw head. ) Is dispersed throughout the washer, and the entire washer can evenly press the fracture or osteotomy to securely join and fix it. In addition, since it is made of biodegradable and absorbable polymer,
The operation of removing the washer from the body after the fracture or osteotomy is healed becomes unnecessary, and a remarkable effect is obtained in that the pain and economic burden of reoperation can be eliminated.

Then, a specific molecular chain (crystal) is formed by compression.
Since the orientation is given, the density is increased, and the anisotropy of the molecular chain (crystal) orientation is reduced, the remarkable effect that the strength against forces in various directions is remarkably improved as a whole is exerted. In addition, the washer, which has a counterbore at the periphery of the insertion hole of the osteosynthesis screw, provides stability of the screw head (sitting).
Because of this, it is possible to fix fractures and bone cuts with a more even pressing force.Furthermore, the washer containing bioceramic powder is combined with the excellent effect of being fixed by bonding with living bone. Play.

[Brief description of the drawings]

FIG. 1 is a perspective view of a washer A according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along line XX of FIG.

FIG. 3 is an explanatory diagram of one usage example of the washer A;

FIG. 4 is a plan view of a washer B according to another embodiment of the present invention.

FIG. 5 is a plan view of a washer C according to still another embodiment of the present invention.

FIG. 6 is a conceptual diagram showing an orientation state of molecular chains (crystals) in a longitudinal section of a washer D according to still another embodiment of the present invention.

FIG. 7 shows a molecular chain (crystal) in a cross section of the washer D.
FIG. 3 is a conceptual diagram showing an orientation state of the liquid crystal.

FIG. 8 is a sectional view illustrating a method of manufacturing the washer D and showing a state where a billet is housed in a housing cavity of a molding die.

FIG. 9 is a cross-sectional view illustrating a method of manufacturing the washer D and showing a state where a billet is press-fitted into a molding cavity of a molding die.

FIG. 10 is a perspective view for explaining a manufacturing method of the washer D and showing a state where a columnar compression-oriented molded body is cut into a circle.

FIG. 11 shows a washer E according to still another embodiment of the present invention.
FIG. 3 is a conceptual diagram showing an orientation state of a molecular chain (crystal) in a vertical cross section of FIG.

FIG. 12 is a conceptual diagram showing an orientation state of a molecular chain (crystal) in a cross section of the washer E.

FIG. 13 shows a washer F according to still another embodiment of the present invention.
FIG. 3 is a conceptual diagram showing an orientation state of a molecular chain (crystal) in a vertical cross section of FIG.

FIG. 14 is a conceptual diagram showing an orientation state of a molecular chain (crystal) in a cross section of the washer F.

FIG. 15 is a washer G according to still another embodiment of the present invention.
FIG. 3 is a conceptual diagram showing an orientation state of a molecular chain (crystal) in a vertical cross section of FIG.

FIG. 16 shows a washer H according to still another embodiment of the present invention.
FIG. 3 is a conceptual diagram showing an orientation state of a molecular chain (crystal) in a vertical cross section of FIG.

FIG. 17 shows a washer J according to still another embodiment of the present invention.
3 is a longitudinal sectional view of FIG. 1 and also shows an orientation state of molecular chains (crystals).

FIG. 18 is an explanatory view of a conventional method for joining a fractured portion by an osteosynthesis screw.

[Explanation of symbols]

A, B, C, D, E, F, G, H, J Washer for osteosynthesis screw 1 Osteosynthesis screw 1a Head of osteosynthesis screw 3, 30 Insertion hole 3a Countersunk part 6 Bioceramic powder L Washer Central axis P ₁ A plane containing the central axis of the washer P ₂ A plane that bisects the washer in the thickness direction M Molecular chain (crystal)

────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-7-184922 (JP, A) JP-A-5-3883 (JP, A) JP-A-7-178115 (JP, A) JP-A-5-178115 168647 (JP, A) JP-A-8-196616 (JP, A) JP-A-10-14935 (JP, A) JP-A-9-239758 (JP, A) JP-A-60-175912 (JP, U) WO 96/19336 (WO, A1) (58) Fields investigated (Int. Cl. ⁷ , DB name) A61B 17/56 A61L 27/00 B29C 43 / 00,55 / 00 F16B 39/00

Claims (6)

(57) [Claims] 1. A washer made of a biodegradable and absorbable polymer having an insertion hole for inserting a shaft portion of an osteosynthesis screw in the center, wherein the washer is compressed, and a molecular chain or a crystal of the biodegradable and absorbable polymer is formed. A washer for an osteosynthesis screw, which is obliquely oriented from the periphery toward a central axis of the washer or an axis parallel to the washer. 2. A washer made of a biodegradable and absorbable polymer in which a through hole for inserting a shaft portion of an osteosynthesis screw is formed in the center, wherein a molecular chain or a crystal of the biodegradable and absorbable polymer is compressed. A washer for an osteosynthesis screw, which is obliquely oriented from both sides toward a plane including a central axis of the washer or a plane parallel thereto. 3. A washer made of a biodegradable and absorbable polymer in which a through hole for inserting a shaft portion of an osteosynthesis screw is formed at the center, wherein a molecular chain or a crystal of the biodegradable and absorbable polymer is compressed. A washer for an osteosynthesis screw, characterized in that the washer is obliquely oriented from both upper and lower sides toward a plane that bisects the washer in the thickness direction or a plane parallel thereto. 4. A tapered seating portion is formed at a peripheral edge of the insertion hole.
The washer for an osteosynthesis screw according to any one of the above. 5. The washer for an osteosynthesis screw according to claim 1, wherein the bioceramic powder is uniformly contained in the entire washer. 6. The bioceramic powder content concentration is 1%.
The washer for an osteosynthesis screw according to claim 5, wherein the amount is 0 to 60% by weight.