JPH1085231A - Bone joint pin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a biodegradable absorbable bone joint pin that has a sufficient locking force to eliminate the fear of being unlocked from a pin hole or a marrow hole in a bone junction and further increase the strength of the pin while giving bondability to living bones. SOLUTION: In an approximately cylindrical bone joint pin A made from a biodegradable absorbable polymer, taper face parts 1 that taper toward one axial end and stepped parts 2 are formed alternately on the outer peripheral surface of the pin A. Since the outer peripheral end of each stepped part 2 bites into the inner surface of a pin hole or a marrow hole, the pin is held locked, with the locking force increased. The bone joint pin may be approximately prism-shaped, and inclined faces that slope diagonally inwards toward one axial end and stepped parts may be formed alternately on one of the outside surfaces of the pin. The strength of the pin is increased depending on the orientations of drawing and compression, and bioceramic powder is contained in the pin so that the pin can be given bondability to living bones.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a biodegradable and resorbable osteosynthesis pin.

[0002]

2. Description of the Related Art Conventionally, osteosynthesis pins made of metal or ceramic have been frequently used. However, since such an osteosynthesis pin has a much higher elastic modulus than that of a living bone, there is a problem that the strength of the surrounding bone is reduced by a phenomenon of stress protection after healing. In particular, since a metal osteosynthesis pin may adversely affect a living body due to elution of metal ions, it is necessary to perform a reoperation to remove the pin from the body as soon as a fracture or the like is healed. There is.

Under these circumstances, osteosynthesis pins made of biodegradable and absorbable polylactic acid, which do not require reoperation, have recently been developed and are receiving attention.

However, these osteosynthesis pins are merely round bar-shaped pins or round bar-shaped pins having a dish-shaped head at one end, so that the following problems occur. there were.

[0005]

That is, when the above-mentioned round bar-shaped osteosynthesis pin is inserted into the pin insertion hole formed in the fractured portion, the pin does not catch on the inner surface of the pin insertion hole and is easily slipped. There is a drawback of poor power. Therefore, when a force in the separating direction acts on the osteosynthesis site joined by the osteosynthesis pin, the osteosynthesis site may be loosened or misaligned, or in extreme cases, the osteosynthesis pin may fall out of the pin insertion hole and be removed. There was a risk that the joints would separate.

[0006] Such a problem does not occur so much with a screw for osteosynthesis having a large fixing force. However, in the case of a screw, since a screw cutting process is required, a long and thin screw suitable for joining a small broken bone fragment is used. Difficult to manufacture.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a biodegradable bioabsorbable material which has a sufficient fixing force and has no risk of falling out of a pin insertion hole at an osteosynthesis site. It is to provide an osteosynthesis pin. And
Desirably, the purpose of the present invention is to significantly improve the strength of the osteosynthesis pin, and to further increase the fixing force by imparting bonding to living bone.

[0008]

In order to achieve the above object, an osteosynthesis pin according to claims 1 to 12 of the present invention has the following features.

More specifically, the osteosynthesis pin according to the first aspect is a substantially columnar osteosynthesis pin made of a biodegradable and absorbable polymer, and has a tapered tapered outer peripheral surface toward one end in the axial direction. The surface portion and the step portion are alternately formed.

[0010] The osteosynthesis pin according to claim 2 is a substantially prismatic osteosynthesis pin made of a biodegradable and absorbable polymer, and has at least one outer surface inclined obliquely inward toward one end in the axial direction. The slope portion and the step portion are formed alternately.

According to a third aspect of the present invention, there is provided the osteosynthesis pin according to the first or second aspect, wherein a head is formed at the other end in the axial direction.

The osteosynthesis pin according to claim 4 is a substantially columnar osteosynthesis pin made of a biodegradable and absorbable polymer, and is disposed on the outer peripheral surface at one axial end from the center of the pin and at one axial end. A tapered surface portion and a step portion which are tapered toward the other end are formed alternately, and a tapered surface portion which is tapered toward the other end in the axial direction from the center of the pin to the outer peripheral surface at the other end in the axial direction. And step portions are alternately formed.

The osteosynthesis pin according to claim 5 is a substantially prismatic osteosynthesis pin made of a biodegradable and absorbable polymer, and has at least one outer surface at one axial end from the center of the pin.
A slope portion inclined obliquely inward toward one end in the axial direction,
Step portions are alternately formed, and at least one outer surface at the other end in the axial direction from the center of the pin has a slope portion inclined obliquely inward toward the other end in the axial direction, and a step portion. It is characterized by being formed alternately.

According to a sixth aspect of the present invention, there is provided the osteosynthesis pin according to any one of the first to fifth aspects, wherein the width of the step is 0.1 to 1.0 mm, and the interval between the steps is zero. .
It is characterized in that it is 5 to 3.0 mm.

The osteosynthesis pin according to claim 7 is the osteosynthesis pin according to any one of claims 1 to 6, wherein the osteosynthesis pin is stretched in the axial direction, and the molecular chains or crystals of the biodegradable and absorbable polymer are oriented in the axial direction. It is characterized by doing.

The osteosynthesis pin according to claim 8 is compressed in the osteosynthesis pin according to any one of claims 1 to 6,
The molecular chains or crystals of the biodegradable and absorbable polymer are obliquely oriented from the periphery toward the central axis of the osteosynthesis pin or an axis parallel thereto.

The osteosynthesis pin according to claim 9 is compressed in the osteosynthesis pin according to any one of claims 1 to 6,
The molecular chains or crystals of the biodegradable and absorbable polymer are obliquely oriented from both sides toward a plane that bisects the osteosynthesis pin in a direction perpendicular to the axial direction or a plane parallel thereto. And

According to a tenth aspect of the present invention, there is provided the osteosynthesis pin according to any one of the first to ninth aspects, wherein the bioceramic powder is contained at a uniform concentration.

An osteosynthesis pin according to an eleventh aspect is the osteosynthesis pin according to the tenth aspect, wherein the bioceramic powder has a uniform concentration of 10 to 60% by weight.

According to a twelfth aspect of the present invention, there is provided an osteosynthesis pin according to any one of the first to eleventh aspects, wherein the entire pin is curved.

Next, the operation of these osteosynthesis pins will be described.

A pin insertion hole having a diameter slightly smaller than the maximum diameter (outer diameter of the step) of the osteosynthesis pin according to the first aspect is drilled in the fracture part. As the osteosynthesis pin is pressed into the insertion hole, the tapered surface of the osteosynthesis pin elastically pushes and expands the pin insertion hole toward one axial end of the osteosynthesis pin. Pressing work can be performed. Then, when the press-fitting of the osteosynthesis pin is completed, the pin insertion hole returns to the original state, so that the outer peripheral end of the step portion of the osteosynthesis pin bites into the inner surface of the pin insertion hole. When the osteosynthesis pin is bitten in this way, even if a force in the pullout direction (a force from one axial end to the other end) acts on the osteosynthesis pin, the outer peripheral end of the step portion and the inner surface of the pin insertion hole are strongly slid. Since the dynamic resistance is large, the osteosynthesis pin is prevented from coming off, and the osteosynthesis site can be firmly fixed.

The osteosynthesis pin is made of a biodegradable and absorbable polymer. The inner diameter of the step is the narrowest. Can be cut relatively easily at the inner diameter portion of.

The osteosynthesis pin made of such a biodegradable and absorbable polymer is hydrolyzed by contact with a body fluid in a living body, and is finally absorbed in the living body. Needless to say.

In the osteosynthesis pin according to the second aspect of the invention, at least one outer surface is formed with a slope portion inclined inwardly toward one end in the axial direction and a step portion, which are alternately formed. The pin can be relatively easily press-fitted while pushing and expanding the pin insertion hole at the slope. When the press-fitting is completed, the tip of the step portion bites into the inner surface of the pin insertion hole, so that even if a force in the removal direction acts, the tip does not come out of the pin insertion hole, and the osteosynthesis site can be firmly fixed. . Then, similarly to the osteosynthesis pin of the first aspect, it can be cut relatively easily at the stepped portion, and is eventually decomposed, absorbed and disappeared in the living body.

The osteosynthesis pin of the third aspect can be easily driven into the pin insertion hole by hitting the head formed at the other end in the axial direction. Further, the head can be inserted into a pin insertion hole provided in a narrow portion by sandwiching the head with a jig.

In the osteosynthesis pin according to a fourth aspect of the present invention, a tapered surface portion formed on the outer peripheral surface at one end in the axial direction from the center of the pin is tapered toward one end in the axial direction. Since the tapered surface formed on the outer peripheral surface at the other end in the direction is tapered toward the other end in the axial direction, the medullary hole or the pin of one bone that has fractured one end in the axial direction from the center of the pin It is relatively easy to press-fit into the insertion hole, and the other end in the axial direction from the center of the pin can be relatively easily press-fitted into the medullary hole or pin insertion hole of the other bone, and the fracture can be joined. When joined in this manner, the outer peripheral end of the stepped portion cuts into the inner surface of the medullary canal or the pin insertion hole from both the center and one end of the osteosynthesis pin and the other end from the center to prevent the bone from coming out. It can be firmly fixed without loosening or displacement at the joint.

In the osteosynthesis pin according to the fifth aspect, a slope formed on at least one outer side at one end in the axial direction from the center of the pin is inclined obliquely inward toward one end in the axial direction. Since the slope portion formed on at least one outer surface at the other end in the axial direction is inclined obliquely inward toward the other end in the axial direction, the fracture portion is joined in the same manner as the osteosynthesis pin according to claim 4. As a result, the tip of the step portion bites into the inner surface of the pin insertion hole or the medullary hole and is prevented from coming out, so that it can be firmly fixed.

When the width of the step portion is 0.1 to 1.0 mm as in the osteosynthesis pin of the sixth aspect, the step portion has a good bite into the inner surface of the pin insertion hole and is caught in the exit direction (sliding). Resistance) is increased, so that the slip-out preventing action is improved, and if the gap between the step portions is 0.5 to 3 mm, the number of step portions per 1 cm of the osteosynthesis pin is 20 to
It is about 3 and a large sliding resistance in the exit direction can be obtained, so that the exit prevention action is further improved. If the width of the difference portion is less than 0.1 mm, the bite is insufficient, and it is difficult to sufficiently prevent the osteosynthesis pin from coming off. Conversely, even if the width of the gap is larger than 1.0 mm, the degree of bite hardly changes, and rather a partial gap is formed between the inner surface of the pin insertion hole and the osteosynthesis pin. Absent. On the other hand, if the distance between the step portions is larger than 3 mm, the sliding resistance decreases because the number of step portions decreases, and conversely, if the distance between the step portions becomes smaller than 0.5 mm, the bite of the individual step portions worsens and the sliding resistance decreases. Is also undesirably reduced.

When the molecular chains or crystals of the biodegradable and absorbable polymer are oriented in the axial direction as in the osteosynthesis pin according to claim 7, the strength is higher than that of the non-oriented osteosynthesis pin. (Particularly, bending strength, etc.) is improved. However, since the osteosynthesis pin has a large anisotropy in the molecular chain (crystal) orientation between the axial direction and the direction perpendicular thereto, it is difficult to generally improve the strength against external forces in various directions. .

On the other hand, the molecular chain or crystal of the biodegradable and absorbable polymer which is compressed like the osteosynthesis pin according to claim 8 is directed from the periphery toward the central axis of the osteosynthesis pin or an axis parallel thereto. The oblique orientation not only increases the density and surface hardness than non-oriented osteosynthesis pins or stretch-oriented osteosynthesis pins, but also increases the molecular chains between the axial direction and the direction perpendicular to this. Since the anisotropy of the (crystal) orientation is reduced, the strength against external forces in various directions is significantly improved as a whole, in combination with the fact that the material becomes dense by compression. In particular, in the osteosynthesis pin, in a cross section perpendicular to the axial direction, molecular chains (crystals) take a radial arrangement around the central axis or an axis parallel to the central axis, so that the torsional strength is remarkably improved. .

The osteosynthesis pin according to claim 9 is also compressed, so that the density and surface hardness are improved, and the molecular chains or crystals of the biodegradable and absorbable polymer make the osteosynthesis pin perpendicular to its axial direction. Since it is obliquely oriented from both sides toward a plane bisecting in the direction or a plane parallel thereto, the anisotropy of the molecular chain (crystal) orientation is small, and the strength against external force in various directions is generally higher. Significantly improved.

When the bioceramic powder is contained in a uniform concentration as in the osteosynthesis pin of the tenth aspect, the bioceramic powder pins the bone tissue with the hydrolysis of the biodegradable and absorbable polymer. To guide formation inside,
In a relatively short time, the osteosynthesis pin is combined with the living bone, and the fixing force is further improved. Finally, the entire osteosynthesis pin is replaced by living bone and disappears.

When the bioceramics powder is contained, the concentration is 10 to 10 as in the osteosynthesis pin according to the eleventh aspect.
It is desirable to set the content within the range of 60% by weight, and if it is less than 10% by weight, the ability to form and induce bone tissue by the bioceramics powder becomes insufficient. It will be difficult to do so. on the other hand,
When the content is more than 60% by weight, the hardness of the osteosynthesis pin 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.

Further, if the whole pin is curved as in the osteosynthesis pin according to the twelfth aspect, the sliding resistance when press-fitting into the pin insertion hole or the medullary canal further increases, so that the osteosynthesis pin comes out further. It becomes difficult.

[0036]

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 an osteosynthesis pin A according to an embodiment of the present invention, and FIG. 2 is a conceptual view showing an orientation state of molecular chains (crystals) in a longitudinal section of the osteosynthesis pin A.

The osteosynthesis pin A is a substantially cylindrical pin made of a biodegradable and absorbable polymer, and is formed by cutting the outer peripheral surface thereof so as to be moved toward one axial end (the lower end in the figure). The tapered surface portion 1 of the constriction and the flange-shaped step portion 2 are alternately formed. The step 2 forms a surface substantially perpendicular to the axial direction, and the step has a width of 0.1 to 1.0 mm as described later.

The biodegradable polymer of the material includes:
All high molecular weight strength and toughness, non-toxic, crystalline thermoplastic polymers that are absorbed in vivo by hydrolysis can be used, and among them, the initial viscosity average molecular weight is preferably 100,000 to 700,000, Particularly preferred are about 150,000 to 600,000 polylactic acid, lactic acid-glycolic acid copolymer, lactic acid-caprolactone copolymer and the like, and these are used alone or in combination of two or more. 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.

As shown in FIG. 2, the osteosynthesis pin A is stretched in the direction of the axis L before cutting, and the molecular chain (crystal) M of the biodegradable and absorbable polymer is oriented in the direction of the axis L. .
Therefore, as compared with a non-oriented osteosynthesis pin, the bending strength, the bending elastic modulus, and the like are improved, and the strength is almost the same as that of a living bone. The stretching magnification is about 2 to 10 times, preferably 2
It is preferable to adjust to about 5 times, and if it is less than 2 times, the orientation of the molecular chain (crystal) M is insufficient, and if it exceeds 5 times, the polymer becomes fibrillated, and if it exceeds 10 times, the polymer becomes fibrillated. Instead, the strength is reduced.

In the present invention, the molecular chain (crystal) orientation by stretching as described above is not essential, and a non-stretched, non-oriented osteosynthesis pin may be used. In addition, the above osteosynthesis pin A
Is cut, but if the surface is roughened by such cutting or other means, there is an advantage that the rate of hydrolysis in a living body becomes moderate.

FIG. 3 is an explanatory view of one use state of the osteosynthesis pin A. The fractured portion of the living bone 6 is slightly smaller than the maximum diameter of the osteosynthesis pin A (the outer diameter of the stepped flange 2). A pin insertion hole (not shown) having a hole diameter is pierced, and the osteosynthesis pin A is pressed into the pin insertion hole from one end (lower end) in the axial direction to fix the fracture portion.

When the fracture portion is joined with the osteosynthesis pin A in this manner, when the osteosynthesis pin A is press-fitted, the tapered surface portion 1 tapered toward one axial end (lower end) forms the pin insertion hole. The osteosynthesis pin A can be press-fitted relatively easily because it is elastically pushed and expanded, and when the press-in is completed, the pin insertion hole returns to its original state. The outer peripheral end of the stepped portion 2 is cut into the inner surface of the pin insertion hole. Therefore, even if the force X in the pull-out direction acts on the osteosynthesis pin A, the osteosynthesis pin A is simple because the outer peripheral end of the flanged step portion 2 and the inner surface of the pin insertion hole are strongly caught and the sliding resistance is large. The fractured part can be securely joined and fixed. Then, for several months until the fracture is healed, there is little decrease in strength due to hydrolysis of the biodegradable and absorbable polymer.
Keeps the osteosynthesis site fixed while maintaining the practical strength. After the healing, the hydrolysis proceeds further and all of the osteosynthesis is absorbed into the living body, and is finally replaced with the living bone.

In order to effectively prevent the osteosynthesis pin A from slipping out of the pin insertion hole by increasing the sliding resistance of the osteosynthesis pin A, as shown in FIG. ~
It is desirable to set the range of 1.0 mm and to set the interval P between the flange-shaped step portions 2 to 0.5 to 3 mm.
The reason has already been described in detail, and thus will not be described.

If the inner diameter of the flanged step portion 2 is the thinnest like the osteosynthesis pin A, the osteosynthesis pin A
In the case where the total length is longer than the length required for osteosynthesis, it can be cut relatively easily at the inner diameter portion of the flange-shaped stepped portion 2.

The osteosynthesis pin A as described above is manufactured, for example, by the following method.

First, the biodegradable and absorbable polymer of the material is heated and melted at a temperature higher than its melting temperature and lower than its decomposition temperature.
Extruded into a cylindrical shape. Then, the columnar molded body is heated to 60 to 160 ° C. and uniaxially stretched in the axial direction at a magnification of about 2 to 10 times, and the outer peripheral surface of the stretched cylindrical molded body is cut and tapered. When the face portions 1 and the flange-shaped step portions 2 are alternately formed, the osteosynthesis pin A is obtained.

In the above manufacturing method, if the stretching step is omitted and the melt-extruded columnar molded body is cut,
An unstretched, non-oriented osteosynthesis pin is obtained.

FIG. 4 is a side view of an osteosynthesis pin B according to another embodiment of the present invention.

The osteosynthesis pin B has a dish-shaped head 3 formed at the other axial end (upper end in the figure). Other configurations are the same as those of the osteosynthesis pin A described above, and therefore, the same reference numerals are given to the same portions in FIG. 4 and the description will be omitted.

The osteosynthesis pin B having the head 3 thus formed
Can be easily driven into the pin insertion hole by hitting the head 3 with a hammer or the like, and can be fixed without loosening.
In addition, since the head 3 can be grasped by the jig, the insertion of the osteosynthesis pin B at a site where there is only a narrow space can be easily performed by using a jig or the like having a small taper.

FIG. 5 is a perspective view of an osteosynthesis pin C according to still another embodiment of the present invention.

This osteosynthesis pin C is a substantially prismatic osteosynthesis pin made of a biodegradable and absorbable polymer. The entire outer surface is cut into a prism by cutting or the like, and the opposing outer surfaces on both sides are further cut. By performing a cutting process, a slope portion 4 that is inclined obliquely inward toward one axial end (the lower end in the figure);
It is formed by alternately connecting rectangular step portions 5.

The width W of the rectangular step 5 is set to 0.1 to
In addition to the setting of 1.0 mm, the mutual interval P of the rectangular step portions 5 is set to 0.5 to 3 mm to increase the sliding resistance in the exit direction when the osteosynthesis pin C is pressed into the pin insertion hole. .

As in the case of the osteosynthesis pins A and B, before the cutting process, about 2 to 10 times, preferably 2 to 5 times in the axial direction.
By stretching about twice, the molecular chains (crystals) are oriented in the axial direction to improve the strength.

In the osteosynthesis pin C of this embodiment, the inclined surface 4 and the rectangular step 5 are formed on the outer surfaces on both sides facing each other, but at least one outer surface is cut to form the inclined surface 4.
If the rectangular step portions 5 are alternately formed, a desired osteosynthesis pin that is difficult to come out is obtained.

Such a substantially prismatic osteosynthesis pin C is formed by melt-extruding a biodegradable and absorbable polymer into a plate, stretching this plate-like molded body in a uniaxial direction, and then stretching the plate along the stretching direction. It can be manufactured by cutting into a column shape and cutting the outer surface. Alternatively, the biodegradable and absorbable polymer may be melt-extruded into a prism shape from the beginning, uniaxially stretched, and then the outer surface may be cut to produce the polymer.

FIG. 6 is a side view showing an osteosynthesis pin D according to still another embodiment of the present invention.

The osteosynthesis pin D is a substantially columnar osteosynthesis pin made of a biodegradable and absorbable polymer, the outer peripheral surface of which is cut, and one end (lower end) in the axial direction from the center of the pin. Has a tapered surface portion 1a tapered toward the one end (lower end) and a stepped portion 2 in the form of a collar, which are alternately formed, and the other end (upper end) in the axial direction from the center of the pin. Tapered surface portions 1b tapering toward the end (upper end side) and step portions 2 having a flange shape are alternately formed.

The width, pitch interval, molecular chain (crystal) orientation, and the like of the flanged step portion 2 of the osteosynthesis pin D are the same as those of the above-described osteosynthesis pin A, and a description thereof will be omitted.

This osteosynthesis pin D is, as shown in FIG.
By press-fitting one end of the bone from the center of the pin into the medullary canal or pin insertion hole of one bone 6a having a fracture, and pressing the other end from the center of the pin into the medullary canal or pin insertion hole of the other bone 6b,
It is to join the fractured part, and when joined in this way,
At both the one end side and the other end side of the osteosynthesis pin D, the outer peripheral end of the flange-shaped stepped portion 2 bites into the inner surface of the medullary canal or the pin insertion hole and is prevented from coming out, so that the osteosynthesis site becomes loose or misaligned. It becomes possible to fix firmly without.

FIG. 8 is a side view showing an osteosynthesis pin E according to still another embodiment of the present invention.

The osteosynthesis pin E is a curved cylindrical osteosynthesis pin made of a biodegradable and absorbable polymer.
Its outer peripheral surface is machined, in the axial L ₁ direction end side curved from the pin center portion (lower end side), and the tapered surface portion 1a of the tapered-off toward the axis L ₁ direction one end side, a flange-shaped step portion 2 are formed alternately in the axial L ₁ direction other end side (upper side) from the pin center portion, and the tapered surface portion 1b of the tapered-off toward the other axis L ₁ direction end side, a flange-shaped step Part 2
Are formed alternately.

Similarly to the above-mentioned osteosynthesis pin D, this osteosynthesis pin E is press-fitted into one medullary cavity having one end fractured from the center of the pin, and the other end from the center of the pin to the other bone marrow. The fractured portion is joined by press-fitting into a hole or the like, so that the flange-shaped stepped portion 2 is prevented from coming off by biting at the tip thereof and can be firmly fixed.

In particular, since the osteosynthesis pin E is curved as a whole, it has a greater effect of preventing the osteosynthesis pin from slipping out than a straight osteosynthesis pin, and is also used when joining a curved bone such as a rib. Is very convenient.

[0066] From the viewpoint of improving the effect of preventing escape, it is preferable to set the radius of curvature of the bone pin E (curved radius of curvature of the axis L ₁₎ in the range of 20 to 200 mm. If the radius of curvature is larger than 200 mm, it is difficult to significantly improve the slip-out preventing effect, and if the radius of curvature is smaller than 20 mm, it is difficult to press into the medullary canal or the pin insertion hole. When joining ribs or the like, it is desirable that the radius of curvature is approximately the same as that of the ribs in advance.

The osteosynthesis pin E is formed by bending a columnar molded body of a biodegradable and absorbable polymer to a predetermined radius of curvature.
It can be manufactured by cutting the outer peripheral surface.

FIG. 9 is a conceptual diagram showing the orientation of molecular chains (crystals) in a longitudinal section of a osteosynthesis pin F according to still another embodiment of the present invention, and FIG. It is a conceptual diagram which shows the orientation state of (crystal).

The shape of the osteosynthesis pin F is the same as the shape of the osteosynthesis pin A described above. By cutting the outer peripheral surface, the tapered surface portion is tapered toward one end (lower end) in the axial direction. 1 and flange-shaped steps 2 are formed alternately.

However, this osteosynthesis pin F is compressed before cutting, and as shown in FIG. 9, the molecular chains (crystals) M of the biodegradable and absorbable polymer move from the periphery toward the central axis L of the osteosynthesis pin. The molecular chains (crystals) M are in a radially oriented state around the central axis L in the cross section as shown in FIG. Therefore, compared with the non-oriented osteosynthesis pin or the uniaxially oriented osteosynthesis pin A by stretching, the density and the surface hardness are large, and the molecular chains between the direction of the central axis L and the direction perpendicular to this direction ( Since the anisotropy of the crystal) orientation is small, the strength against external force in various directions is generally improved in combination with the fact that the material becomes dense by compression. Strength is increasing.

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 it is less than 0 °, the improvement of the anisotropy of the molecular chain (crystal) orientation becomes insufficient, and if it exceeds 60 °, the production is not easy and cracks and the like tend to occur. A more preferred range of the orientation angle is 10 to 35 °.

In this osteosynthesis pin F, the molecular chain (crystal) M
Are oriented obliquely downward from the periphery toward the central axis L. However, even if they are oriented obliquely downward from the periphery toward an eccentric axis parallel to the central axis L, almost the same strength improving effect can be obtained. Can be

The osteosynthesis pin F as described above is manufactured, for example, by the following method.

First, the biodegradable and absorbable polymer of the material is melt-extruded to form a cylindrical billet 8. And
A molding die 7 as shown in FIG. 11, that is, a large-diameter cylindrical housing cavity 7a having a large cross-sectional opening area, and a small-diameter cylindrical bottomed cavity 7 having a small cross-sectional opening area.
a molding die 7 coaxially provided with a constricted portion 7b whose inner peripheral surface is a tapered surface with a downward constriction, and accommodates the billet 8 in its accommodation cavity 7a. As shown in FIG. 12, the billet 8 is continuously or intermittently press-filled into the molding cavity 7c at a temperature at which the biodegradable and absorbable polymer can be crystallized (above the glass transition temperature and below the melting temperature) by the pressing male mold 7d. I do.

When the billet 8 passes through the constricted portion 7b, a large shear force due to frictional resistance is generated between the billet 8 and the tapered surface when the billet 8 passes through the narrowed portion 7b. MD) and lateral force (TD), the molecular chains (crystals) are compressed while being oriented obliquely downward from the periphery toward the central axis Lm of the mold 7 (in other words, the central axis of the billet 8). And crystallization proceeds. Then, even after filling in the molding cavity 7c, the inner surface and the bottom surface of the molding cavity 7c 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 80 is obtained.

When the compression-oriented molded body 80 is taken out of the molding die 7 and the outer peripheral surface thereof is finally cut to form the tapered surface portion 1 and the flange-shaped step portion 2 alternately, the osteosynthesis pin F
Is obtained.

In the above manufacturing method, the center axis L of the molding die 7
The orientation angle of the molecular chain (crystal) with respect to m is approximately determined by the inclination angle θ of the tapered surface of the narrowed portion 7b and the ratio of the opening area between the receiving cavity 7a and the molding cavity 7c. 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 area ratio. In this case, the opening area between the housing cavity 7a and the molding cavity 7c is set so that the deformation ratio (cross-sectional area of the billet 8 / cross-sectional area of the compression-oriented molded body 80) 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-orientation molded product 80 is as follows:
It is desirable to control the opening area ratio between the housing cavity 7a and the molding cavity 7c, the press-fitting temperature, the pressure, the press-fitting speed, and the like of the billet 8 so as to be adjusted in the range of 30 to 60%. The osteosynthesis pin F obtained by cutting the compression-oriented molded body 80 having the crystallinity adjusted in this manner.
Has a good balance of the ratio of the crystalline phase and the amorphous phase, and the improvement in strength and hardness by the crystalline phase and the flexibility by the amorphous phase are well coordinated. There is no weak property without strength as in the case of only an amorphous phase. Therefore, the osteosynthesis pin F which is tough and has a sufficiently high strength overall is obtained.

Further, in the above-described manufacturing method, a billet 7 was used in the same manner as described above by using a molding die 7 in which the inclination angle of the tapered surface of the narrowed portion 7b was gradually changed over the entire circumference of the tapered surface or at an arbitrary portion. 8 is press-filled to obtain a columnar compression-oriented molded body 80 in which molecular chains (crystals) are oriented obliquely downward from the periphery toward an eccentric axis parallel to the central axis. If the outer peripheral surface is cut to form the tapered surface portion 1 and the flange-shaped step portion 2 alternately, the compressed osteosynthesis pin in which the molecular chains (crystals) are obliquely oriented from the periphery toward an axis parallel to the central axis. Can be obtained.

In the above-mentioned manufacturing method, a throttle portion having four inclined surfaces is coaxially provided between the rectangular cylindrical receiving cavity having a large opening area and the rectangular cylindrical forming cavity having a small opening area. When the billet obtained by melting and molding the biodegradable and absorbable polymer into a prismatic shape is housed in the housing cavity using the mold provided in the above, and the mold cavity is press-filled, the molecular chains (crystals) move toward the central axis. From which a prismatic compression-oriented molded body oriented diagonally downward is obtained,
If this compression-oriented molded body is cut to form a slope portion 4 and a rectangular step portion 5 on at least one outer surface thereof, it has the shape of FIG. 5 and the molecular chains (crystals) are aligned with the central axis. A substantially prismatic osteosynthesis pin that is obliquely oriented from the periphery toward the outside and has a high strength and is difficult to come out can be obtained.

FIG. 13 is a conceptual diagram showing the orientation of molecular chains (crystals) in a longitudinal section of an osteosynthesis pin G according to still another embodiment of the present invention, and FIG. It is a conceptual diagram which shows the orientation state of (crystal).

The osteosynthesis pin G is a substantially prismatic pin similar to the osteosynthesis pin C described above, but is compressed before cutting, and the molecular chain (crystal) M of the biodegradable and absorbable polymer is
The osteosynthesis pin G is obliquely oriented from both sides toward a surface N bisecting in a direction perpendicular to its axial direction. for that reason,
Compared to non-oriented osteosynthesis pins and uniaxially oriented osteosynthesis pins by stretching, the density and surface hardness are high, and the anisotropy of molecular chain (crystal) orientation is small, so that they become dense by compression. In combination with this, the strength against external forces in various directions is generally improved.

The osteosynthesis pin G is manufactured, for example, by the following method.

First, a biodegradable and absorbable polymer as a material is melt-extruded to form 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 having a constricted portion with an inclined surface having the same inclination angle, the above-mentioned billet is accommodated in its accommodation cavity, and the temperature at which the billet can be crystallized by a male mold for pressurization. And press-fit into the molding cavity.

By press-filling as described above, a plate-shaped compression-orientation molded body in which molecular chains (crystals) are oriented obliquely downward from both sides toward a plane bisected in the thickness direction is obtained. By cutting and cutting, the above osteosynthesis pin G
Can be obtained. In this case, similarly to the osteosynthesis pin F, it is desirable to adjust the orientation angle of the molecular chain (crystal) to 10 to 60 ° and to adjust the crystallinity to 30 to 60%.

When the molds are similarly press-filled using molds having different slope angles on both sides of the narrowed portion, the molecular chains (crystals) are shifted toward the plane displaced parallel to the bisecting plane in the thickness direction. A plate-shaped compression-orientation compact that is obliquely oriented from both sides can be obtained. If this is cut into a prism and cut, the molecular chains (crystals) will be oblique from both sides toward a plane parallel to the bisecting plane. A substantially prismatic osteosynthesis pin that is oriented can be obtained.

FIG. 15 is a partial sectional view of an osteosynthesis pin H according to still another embodiment of the present invention.

The osteosynthesis pin H is a substantially columnar osteosynthesis pin made of a biodegradable and absorbable polymer containing a bioceramic powder 9 at a uniform concentration. A tapered surface portion 1 and a flange-shaped step portion 2 which are tapered toward one end (lower end) in the axial direction are formed alternately. Then, similarly to the osteosynthesis pin F described above, the molecular chains (crystals) are oriented obliquely downward from the periphery toward the central axis L of the osteosynthesis pin by compression before cutting, thereby improving the density and surface hardness. The strength against external forces in various directions is improved as a whole.

The bioceramics powder 9 is contained for the purpose of imparting bonding property to living bone to the osteosynthesis pin H, and is also exposed on the outer peripheral surface by cutting.

Preferred bioceramic powders 9 include sintered hydroxyapatite having bioactivity on the surface, bioglass or crystallized glass for living body, wet-type hydroxyapatite which can be absorbed in vivo, 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.

When the fracture portion is joined and fixed using such an osteosynthesis pin H, the apparent hydrolysis of the biodegradable and absorbable polymer containing the bioceramic powder 9 is accelerated, and the bioceramic powder 9 Since the bone activity is rapidly induced and formed on the outer peripheral surface by bioactivity, the osteosynthesis pin H is firmly connected to the living bone in a short period of time, and the fixing force is greatly improved. The concentration of the bioceramic powder 9 is preferably in the range of 10 to 60% by weight. 10
If the content is less than 10% by weight, the ability to form and induce bone tissue by the bioceramics powder 9 becomes insufficient, so that it becomes difficult to firmly bind to the living bone in a short period of time to improve the fixation force.
On the other hand, if the content is more than 60% by weight, although the hardness of the osteosynthesis pin is improved, the inherent toughness of the biodegradable and absorbable polymer is impaired, and the polymer becomes brittle and easily breaks or breaks. Therefore, this osteosynthesis pin H
Maintains sufficient practical strength for several months necessary for healing, and has almost no risk of breakage. After the healing, the hydrolysis proceeds, and finally the entire osteosynthesis pin H is replaced by living bone and disappears.

The osteosynthesis pin H 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 and absorbable polymer is added to a solution of the biodegradable and absorbable 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 billet containing the bioceramics powder 9 uniformly is obtained by melt molding, for example, extrusion molding or press molding using the granules.

Next, this billet is housed in the housing cavity 7a of the molding die 7 shown in FIG. 11, and the billet is press-filled into the molding cavity 7c with the male mold 7d for pressurization as described above, whereby the molecular A columnar compression-oriented molded body in which chains (crystals) are oriented obliquely downward from the periphery toward the central axis is obtained. The osteosynthesis pin H is obtained by cutting the outer peripheral surface of the compression-oriented molded body so that the tapered surface portions 1 and the flange-shaped step portions 2 are alternately formed.

Although the osteosynthesis pin H is a substantially cylindrical pin, a substantially prismatic osteosynthesis pin can also be manufactured by a method substantially similar to the above. That is, a prismatic billet is produced by melt molding into a prismatic extruded product or by cutting a thick plate-like extruded product into a prismatic shape. And
The billet is housed in the housing cavity of the mold having the above-described square cylindrical housing cavity and the molding cavity, and a prismatic compression-oriented molded body is produced by press-fitting and filling the molding cavity. If the slope 4 and the rectangular step 5 are formed on at least one outer surface by cutting, the bioceramics powder is uniformly contained, and the molecular chains (crystals) are oriented obliquely from the periphery toward the central axis. It is possible to obtain a substantially prismatic osteosynthesis pin H which does not easily come off.

[0097]

As is clear from the above description, the osteosynthesis pin of the present invention can be inserted into a pin insertion hole formed in a fractured part of a living bone or into a medullary cavity to join the fractured part. Since it does not fall out of the medullary canal, it can be fixed securely at the osteosynthesis site without loosening or displacement, and if it is too long, it can be cut relatively easily at the stepped portion, Since it is decomposable and absorptive, there is a remarkable effect that reoperation for removing from the living body is unnecessary.

[0098] The osteosynthesis pin in which the molecular chains (crystals) are oriented by stretching has improved strength, and in particular, the osteosynthesis pin in which a specific molecular chain (crystal) orientation is given by compression has the molecular chains (crystals). ) Since the anisotropy of the orientation is small and the material is dense due to compression, the strength against various directions of forces is significantly improved as a whole.

Furthermore, the osteosynthesis pin containing the bioceramics powder has an effect that the osteosynthesis pin is combined with the living bone in a relatively short period of time and the fixing force is further improved.

[Brief description of the drawings]

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

FIG. 2 is a conceptual diagram showing an orientation state of molecular chains (crystals) in a longitudinal section of the osteosynthesis pin A.

FIG. 3 is an explanatory diagram of one usage example of the osteosynthesis pin A.

FIG. 4 is a side view of an osteosynthesis pin B according to another embodiment of the present invention.

FIG. 5 shows an osteosynthesis pin C according to still another embodiment of the present invention.
It is a perspective view of.

FIG. 6 shows an osteosynthesis pin D according to still another embodiment of the present invention.
FIG.

FIG. 7 is an explanatory diagram of one usage example of the osteosynthesis pin D.

FIG. 8 shows an osteosynthesis pin E according to still another embodiment of the present invention.
FIG.

FIG. 9 shows an osteosynthesis pin 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. 10 is a conceptual diagram showing an orientation state of molecular chains (crystals) in a cross section of the osteosynthesis pin F.

FIG. 11 is a cross-sectional view illustrating a method of manufacturing the osteosynthesis pin F and showing a billet housed in a housing cavity of a molding die.

FIG. 12 is a cross-sectional view illustrating a method of manufacturing the osteosynthesis pin F and showing a state where a billet is press-fitted into a molding cavity of a molding die.

FIG. 13 is a conceptual diagram showing an orientation state of molecular chains (crystals) in a longitudinal section of an osteosynthesis pin G according to still another embodiment of the present invention.

FIG. 14 is a conceptual diagram showing an orientation state of molecular chains (crystals) in a cross section of the osteosynthesis pin G.

FIG. 15 is a partial sectional view of an osteosynthesis pin H according to still another embodiment of the present invention.

[Explanation of symbols]

 A, B, C, D, E, F, G, H Osteosynthesis pins 1, 1a, 1b Tapered surface part 2 Flange-shaped step part 3 Head 4 Slope part 5 Rectangular step part 6 Living bone 9 Bioceramic powder Body L Central axis of osteosynthesis pin N Surface that bisects osteosynthesis pin in the direction perpendicular to the central axis M Molecular chain (crystal) P Spacing between step portions W Width of shear portion

Claims (12)

[Claims] 1. A substantially cylindrical osteosynthesis pin made of a biodegradable and absorbable polymer, wherein a tapered surface portion tapered toward one end in an axial direction and a step portion are alternately formed on an outer peripheral surface thereof. An osteosynthesis pin characterized by being formed. 2. A substantially prismatic osteosynthesis pin made of a biodegradable and absorbable polymer, wherein at least one outer surface of the pin has:
A slope portion inclined obliquely inward toward one end in the axial direction,
An osteosynthesis pin characterized in that step portions are alternately formed. 3. The osteosynthesis pin according to claim 1, wherein a head is formed at the other end in the axial direction. 4. A substantially cylindrical osteosynthesis pin made of a biodegradable and absorbable polymer, wherein the outer peripheral surface at one axial end from the center of the pin has a tapered taper toward one axial end. The surface portion and the step portion are formed alternately, and the tapered surface portion tapered toward the other end side in the axial direction and the step portion are alternately formed on the outer peripheral surface from the center of the pin to the other end in the axial direction. An osteosynthesis pin characterized by being formed in a osteosynthesis pin. 5. A substantially prismatic osteosynthesis pin made of a biodegradable and absorbable polymer, wherein at least one outer surface at one axial end from the center of the pin is obliquely inward toward one axial end. The slope portion and the step portion that are inclined to are formed alternately, and the slope that is inclined inward toward the other end in the axial direction on at least one outer surface at the other end in the axial direction from the center of the pin. An osteosynthesis pin, wherein the portions and the step portions are alternately formed. 6. The step portion has a width of 0.1 to 1.0 mm,
The osteosynthesis pin according to any one of claims 1 to 5, wherein an interval between the steps is 0.5 to 3.0 mm. 7. The osteosynthesis according to claim 1, wherein the osteosynthesis is stretched in the axial direction, and the molecular chains or crystals of the biodegradable and absorbable polymer are oriented in the axial direction. pin. 8. The method according to claim 1, wherein the molecular chains or crystals of the compressed bioerodible resorbable polymer are oriented obliquely from the periphery toward the central axis of the osteosynthesis pin or an axis parallel thereto. An osteosynthesis pin according to any one of claims 1 to 6. 9. The compressed, biodegradable and absorbable polymer molecular chains or crystals are inclined from both sides toward a plane bisecting or parallel to the osteosynthesis pin in a direction perpendicular to the axial direction thereof. The osteosynthesis pin according to any one of claims 1 to 6, wherein the osteosynthesis pin is oriented in a direction. 10. The osteosynthesis pin according to claim 1, wherein the bioceramic powder is contained at a uniform concentration. 11. The method according to claim 1, wherein the uniform concentration of the bioceramics powder is 10 to 60% by weight.
The osteosynthesis pin according to 0. 12. The osteosynthesis pin according to claim 1, wherein the entire pin is curved.