JP2000166937A - In-vivo decomposition absorptive screw - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an in-vivo decomposition absorptive screw which allows the secure and deep screwing down of a rotating means to the last without the chipping of a hole for insertion of the rotating means and without cracking and crushing the rotating means. SOLUTION: The screw 1 consisting of an in-vivo decomposition absorptive polymer is constituted by forming an oblong or elliptic hole 1c for insertion of the rotating means on its central line 1 from the top end face of a screw head 1a toward the front end side of the screw. The hole 1c for the insertion of the rotating means is formed to an oblong or elliptic hole shape to avoid the concentration of the rotating force of the rotating means, by which the rotating force is dispersedly acted on the hole and the chipping and cracking are prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biodegradable and absorptive screw which is suitably used for fixing and fixing a fractured portion and for reconstructing and fixing tendons and ligaments.

[0002]

2. Description of the Related Art Conventionally, metal or ceramic screws have been used for fixing joints of fractures and reconstructing and fixing tendons and ligaments. However, since these screws have a high elastic modulus, there are problems such as a decrease in the strength of the surrounding bone, and in particular, metal screws may harm the living body due to elution of metal ions, so that fractures and the like are caused. When healed, he had to re-operate to remove it from the body early.

[0003] Under such circumstances, a screw made of a biodegradable and absorbable polymer which does not require reoperation is developed. However, this biodegradable absorptive screw has a cross groove and a hexagonal wrench hole formed on the screw head like a conventional screw, and is screwed with a Phillips screwdriver or hexagonal wrench. was there.

[0004]

That is, when a plus screwdriver or a hexagonal wrench is inserted into a cross groove or a hexagonal wrench hole of the screw head, and the biodegradable and absorptive screw is screwed into a living bone or the like while applying a rotating force. Since the rotational force tends to concentrate on the corners of the cross groove or hexagon wrench hole, the cross groove or hexagon wrench hole may be chipped, cracked, or crushed, and the screw may not be able to be screwed deeply to the end. .

[0005] The present invention has been made in view of such a problem, and an object of the present invention is to ensure that the hole into which the rotating tool is inserted is not broken, broken, or crushed, and that the hole is firmly completed. To provide a biodegradable and absorbable screw that can be screwed deeply.

[0006]

In order to achieve the above object, a screw made of a biodegradable absorbent polymer of the present invention has an oblong or elliptical hole for inserting a rotating tool on its central axis. It is characterized by being formed from the upper end surface of the screw head toward the screw tip.

[0007] This screw uses a dedicated rotating tool whose tip has an oval or elliptical cross section, and the tip of the rotating tool is inserted into a hole for inserting the rotating tool of the screw, thereby producing a rotational force. It is screwed into the living bone etc. while adding, but as described above, the hole for inserting the rotating tool is an oval or elliptical hole and does not have a corner where the rotational force is concentrated, Because the rotating force acts on the inner surface of the hole,
The screw can be screwed firmly and deeply to the end without chipping or cracking during the screwing operation.

[0008] The screw screwed into the living bone or the like as described above is subjected to hydrolysis of the biodegradable and absorptive polymer from the surface by contact with the body fluid, and is eventually absorbed into the living body and disappears. Therefore, unlike a metal screw, it is not necessary to perform another operation and remove the patient from the body, so that the patient's pain and economic burden are reduced.

[0009]

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 front view of a biodegradable and absorptive screw according to an embodiment of the present invention, FIG. 2 is a plan view of the screw, FIG. 3 is a longitudinal sectional view of the screw, and FIG. It is an explanatory view of a use example.

The screw 1 is made of a biodegradable and absorbable polymer, and is an interference screw used for reconstructing and fixing tendons and ligaments.

That is, the head 1a of the screw 1 is formed in a substantially hemispherical shape, and the diameter of the head 1a and the outer diameter of the screw thread 1b are substantially the same. And the screw thread 1 of the screw 1
The top of b is cut to form a flat surface. In particular, the top of the thread 1b near the tip of the screw is greatly cut to reduce the outer diameter, and the top of the screw is formed on the inner surface of the hole formed in the joint bone or the like. The flat surface of the part has a screw shape that can be screwed deeply and smoothly into the hole while being pressed against it.

As shown in FIGS. 2 and 3, a large oblong hole 1c for inserting a rotating tool is provided on the center axis L of the screw 1 from the upper end surface of the screw head 1a toward the tip of the screw. The hole 1c
A small perfect circular through hole 1d penetrating from the lower end to the screw tip is formed on the central axis L. This through-hole 1d is a hole for inserting a guide rod when the ligament is reconstructed and fixed.

In the screw 1, an oval hole 1c is formed as a hole for inserting a rotating tool, but an oval hole may be formed.

The biodegradable and absorbable polymer used as the material of the screw 1 has an initial viscosity average molecular weight of 15
Polylactic acid (poly-L-lactic acid, poly-D-lactic acid, poly-L / D) of about 10,000 to 600,000, preferably about 200,000 to 550,000
-Lactic acid), lactic acid-glycolic acid copolymer, and the like, and particularly those containing about 10 to 60% by weight of bioceramic powder such as hydroxyapatite are more preferably used. When the screw 1 of the biodegradable and absorbable polymer containing the bioceramics powder is screwed into living bone, the bioceramics powder removes the biological calcium phosphate and bone tissue from the surface layer of the screw 1 with hydrolysis from the screw surface. Since the screw 1 is deposited or conductively formed, there is an advantage that the screw 1 is not loosened due to the connection with the living bone in a relatively short period of time.

The screw 1 may be formed by melt-forming a biodegradable and absorbable polymer and cutting the molded body, or by further uniaxially stretching the molded body and then cutting the molded body.
Alternatively, it is manufactured by further forging or compressing the molded body in a cold state, followed by cutting. In particular, when cold forging or compression molding is performed before cutting a molded body of a biodegradable and absorbable polymer, the molecular chains of the polymer, its aggregation domains, clusters, crystals, etc., along many reference axes having different axial directions. Thus, there is an advantage that the screw 1 can be manufactured which is dense, has little strength anisotropy, and has high strength against external force and twisting force in various directions.

The interference screw 1 as described above is suitably used for reconstructing and fixing tendons and ligaments. For example, when a tendon is implanted in a knee joint between a femur and a tibia and reconstructed, holes 2a and 3a are made in the femur 2 and the tibia 3, respectively, as shown in FIG. , 4 are passed through the holes 2a, 3a. Then, one of the interference screws 1 is screwed into the hole 2a of the femur 2 to fix the graft bone piece 4 at one end of the tendon graft 5 to the inner surface of the hole 2a.
While taking appropriate slack, the other interference screw 1 is screwed into the hole 3a of the tibia 3 to fix the grafted bone piece 4 at the other end of the transplanted tendon 5 by crimping, so that the tendon is transplanted and reconstructed. In that case, the holes 2a, 3
Tapping may be applied to a in advance.

The above interference screw 1
Is carried out by using a dedicated rotating tool having a tip part having an oval cross section as a rotating tool, and inserting the tip part into a hole 1c for inserting a rotating tool of the screw head 1a and rotating the screw. However, as described above, since the rotating tool insertion hole 1c is an oval hole and does not have a corner where the rotating force is concentrated, the rotating force is dispersed on the inner surface of the hole 1c. Will work. Therefore, the hole 1c can be firmly and deeply screwed to the end without chipping or cracking during the screwing operation. The screw thread 1b of the screw 1 is screwed without being crushed by the inner surface of the hole 1c because the crest is a flat surface, so that the bone graft 4 can be pressed and fixed.

The screw 1 screwed into the holes 2a and 3a of the femur and the tibia as described above makes the hydrolysis of the biodegradable and absorbable polymer proceed from the surface by contact with the body fluid,
The necessary strength is maintained until the bone grafts 4 and 4 are completely bonded to the femur 2 and the tibia 3, but after that, the hydrolysis proceeds further to be broken down into small pieces, and eventually absorbed into the living body. Disappear. Therefore, unlike a conventional metal screw, it is not necessary to perform another operation and take it out of the body, so that pain and economic burden on the patient can be reduced.

If the screw 1 contains bioceramic powder, as described above, calcium phosphate and bone tissue of a living body are deposited or conductively formed on the screw surface layer by the bioceramic powder, as described above. Since the femur 2 or the tibia 3, the screw 1, and the bone graft 4 are combined and integrated within a relatively short period of time, the bone graft 4 can be more reliably fixed.

FIG. 5 is a front view of a biodegradable and absorbable screw according to another embodiment of the present invention, FIG. 6 is a plan view of the screw, FIG. 7 is a partial longitudinal sectional view of the screw, and FIG. It is explanatory drawing of one usage example.

The screw 10 made of the biodegradable and absorbable polymer is an osteosynthesis screw used for bone fixation. The diameter of the screw head 10a is larger than the outer diameter of the screw thread 10b of the screw shaft. Is also quite large. Accordingly, when the screw 10 is screwed into the fractured part of the living bone 6 as shown in FIG. 8, the bone fragment 6a is pressed by the screw head 10a and can be firmly fixed to the living bone 6. Although the screw thread 10b of the screw 10 is formed over the entire length of the screw shaft part, the screw thread 10b may be formed only in a part extending from the middle of the screw shaft part to the tip.

As shown in FIGS. 6 and 7, an elliptical hole 10c for inserting a rotating tool is provided on the center axis L of the osteosynthesis screw 10 from the upper end surface of the screw head 10a to the screw tip side. It is formed toward. The hole 10c for inserting the rotating tool is not formed so deeply as the hole 1c for inserting the rotating tool of the screw 1, and the screw head 1
0c is formed so as to fall within the thickness range,
Further, the osteosynthesis screw 10 is not formed with a through hole through which the guide rod is inserted. Obviously, an oval hole may be formed as the hole 10c for inserting the rotating tool.

The biodegradable and absorbable polymer used as the material of the osteosynthesis screw 10 is the same as that of the screw 1 described above, and preferably contains bioceramics powder.

The screw 10 for osteosynthesis uses a dedicated rotating tool having a tip part having an elliptical cross section as a rotating tool, and the tip part is inserted into a hole 10c for inserting the rotating tool of the screw head 10a. As shown in FIG. 8, a hole is drilled and screwed into the fractured portion of the living bone 6 while being inserted and rotated.
The hole 10c for inserting the rotating tool of the screw 10 is also an oval hole having no corner where the rotational force is concentrated, and the rotational force is dispersed on the inner surface of the hole 10c. Therefore, the hole 10c can be screwed firmly and deeply to the end without chipping or cracking during the screwing operation.

As described above, the interference screw 1
Although the present invention has been described using the screw 10 for osteosynthesis as an example, the present invention is not limited to only these screws 1 and 10, and the biodegradable absorption used by being implanted in a living body is used. It can be applied to all types of screws.

[0027]

According to the biodegradable and absorptive screw of the present invention, the hole for inserting the rotating tool is an oval or elliptical hole having no corner where the rotational force concentrates. Because the hole acts on the inner surface of the body, the hole can be screwed firmly and deeply without breaking or cracking during the screwing operation. This has the effect that it is not necessary to perform surgery and take it out of the body.

[Brief description of the drawings]

FIG. 1 is a front view of a biodegradable absorbable screw (interference screw) according to an embodiment of the present invention.

FIG. 2 is a plan view of the screw.

FIG. 3 is a longitudinal sectional view of the screw.

FIG. 4 is an explanatory diagram of one usage example of the screw.

FIG. 5 is a front view of a biodegradable and absorbable screw (osteosynthesis screw) according to another embodiment of the present invention.

FIG. 6 is a plan view of the screw.

FIG. 7 is a partial vertical sectional view of the screw.

FIG. 8 is an explanatory view of one usage example of the screw.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Interference screw 10 Osteosynthesis screw 1a, 10a Screw head 1b, 10b Thread 1c, 10c Hole for inserting a rotating tool L Center axis

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4C060 LL13 LL15 4C081 AB03 AB04 AB18 AC03 BA15 BA16 BB07 BB08 BC02 CA171 CC08 CF032 DA01 DC13 4C097 AA03 AA07 AA21 BB01 BB04 BB05 BB09 CC01 CC05 CC14 DD02 DD07 FE08 MM01

Claims (1)

[Claims] 1. A screw made of a biodegradable and absorbable polymer, wherein an oval or elliptical hole for inserting a rotating tool is provided on a central axis of the screw from an upper end face of the screw head toward the tip end of the screw. A biodegradable and absorbable screw characterized by being formed by: