JPH09253089A - Screw for bone fixation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To smoothly perform screwing-in and to prevent the occurrence of damage by constituting a screwing cross hole having R at the heat part of a screw for bone fixation composed of intracelom decomposing and absorbing materials. SOLUTION: A screw head part 1 is composed of a vertex face 4 and a seat face 5, communicated through an under-neck round part 6 to a cylindrical part 7 of a thin part 2 and further communicated to a screw part 3 composed of a screw thread 8 and a screw valley 9. Then, the screw head part 1 has a screwing cross hole 10 for a driver or the like and further, the R, namely, curved line is formed at an apex part 11 of cross and a line 12 connecting the mutually adjacent apex parts to each other. The curvature radius of R part is not limited and for the purpose of use not requiring any strength comparatively, the constitution just providing the curved line at its one part is available as well. Then, the materials constituting the screw are composed of intracelom decomposing and absorbing polymers and use polylactic acid, polyglycolic acid or the coplymer of polylactic acid and polyglycolic acid having the molecular weight of about several ten thousands to one million, for example.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing screw used for surgical treatment of bones such as joining, fixing and reinforcing fractured bones.

[0002]

2. Description of the Related Art Recently, for example, bone-fixing devices made of biodegradable and absorbable polymers such as polylactic acid, polyglycolic acid, and a copolymer of polylactic acid and polyglycolic acid have been put into practical use. . Since such a material is hydrolyzed in a living body, it has a feature that there is no need for re-operation after surgery like metal, ceramics, etc.
Various forms such as rods, nails and plates have been proposed. On the other hand, such a material is inferior in strength such as tension and bending, or elastic modulus as compared with metal, ceramics and the like, and therefore, as a means for improving this, for example, Japanese Patent Publication No. 3-63901 by the applicant, Japanese Patent Laid-Open No. Hei 3-63901. This is improved by the stretching technique disclosed in JP-A No. 5-168647 or by combining with a fibrous material made of an absorbent material as disclosed in JP-B-7-63504.

[0003]

DISCLOSURE OF THE INVENTION The present invention relates to a screw in the fixing tool, wherein smooth screwing and
The present invention provides a screw having a specially configured head that does not break. That is, for example, in the case of a screw having a hexagonally cut screwing hole, when a tool (such as a screwdriver) suitable for this is inserted and screwed in, the screw hole is cracked or damaged, and It had a defect that the corners of the inner surface of the hole were scraped off and spun freely. Further, the ordinary plus screw has the same drawback. Furthermore,
In addition to the above-mentioned phenomenon, the minus screw has a problem that an excessive force is required for screwing in because the force is not sufficiently transmitted. The above phenomenon is due to the fact that the material is a synthetic high-molecular polymer and that it requires a considerable force when screwed into bone, which is still solved in the strength improvement by stretching, compounding, etc. It was a difficult problem to solve. On the other hand, after being applied in this way, it is desirable that the substance be smoothly absorbed into the living body and disappear without remaining as a foreign substance for a certain period of time that requires its function, for example, after several weeks to several months have elapsed. However,
The hole-shaped one also has a problem that the decomposition is slow. The present invention provides a novel screw for fixing bones which eliminates the above-mentioned conventional drawbacks.

[0004]

DISCLOSURE OF THE INVENTION The present invention is a bone fixing screw made of a biodegradable and resorbable material, characterized in that a screw cross hole having an R is formed at the head of the screw. And a bone fixing screw. That is, according to the present invention, it is possible to form a round line on the top of the cross and a line connecting the tops adjacent to each other.
The feature is that the parts are configured, and with such a configuration, when screwing in, since there is no corner portion, the force is not dispersed and the force is not partially concentrated, so that smooth screwing is possible, As a result, the occurrence of breakage, collapse of shape, etc. is suppressed. Moreover, the area of the hole itself is larger than that of a linearly cut hole, so that the hole is easily disassembled.

[0005]

DETAILED DESCRIPTION OF THE INVENTION The configuration of the present invention will be described below with reference to the drawings. FIG. 1 is a front view of the screw of the present invention with a part cut away, and FIG. 2 is a view of the head of FIG. 1 seen from the A direction. In FIG. 1, 1 is a screw head, 2 is a screw shaft portion, and 3 is a screw portion. Further, the screw head 1 is composed of a top surface 4 and a seat surface 5, is connected to the cylindrical portion 7 of the shaft portion 2 via the under-neck rounded portion 6, and is further composed of a screw thread 8 and a screw trough 9. Continue to. In the structure of such a screw, the present invention has a cross hole 10 for screwing in by a screwdriver or the like, as shown in FIG.
An R, that is, a curved line is formed on a line 12 connecting adjacent peaks. The radius R is not limited to a corner, and is configured to disperse the force. Therefore, the radius of curvature is not particularly limited as long as it meets the purpose. . In addition, in an application that does not require relatively high strength, a configuration may be used in which only a part of the curve is provided. The material constituting the screw is made of a biodegradable and absorbable polymer, for example, polylactic acid having a molecular weight of about tens of thousands to millions, polyglycolic acid, a copolymer of polylactic acid and polyglycolic acid, etc. as a raw material, For example, by a technique disclosed in the above-mentioned Japanese Patent Laid-Open No. 5-168647 or the like, the rod-shaped material is formed by stretching or compounding it by a factor of 2 to 10 or more and using a lathe or the like. An example is shown in which a thread is formed by processing by an arbitrary technique such as using a rolling die or compression molding. Especially,
Since the formation of the threaded portion by rolling is the formation of a screw by compression, the strength of the threaded portion is high and effective.

[0006]

EFFECTS OF THE INVENTION The screw of the present invention constructed as described above is made of a biodegradable and absorbable polymer as a material, and eliminates the drawbacks such as smooth screwing and damage accompanying it in a special application of fixing bone by screwing. Further, since it has decomposability, it can be widely applied to the application as a screw having a new function in place of conventional metals and ceramics.

[Brief description of drawings]

FIG. 1 is a partially cutaway front view illustrating the present invention.

FIG. 2 is a view of FIG. 1 seen from the A direction.

[Explanation of symbols]

 1 screw head 2 screw shaft portion 3 screw portion 4 screw top surface 5 screw seat surface 6 rounded neck portion 7 cylindrical portion 8 screw thread 9 screw valley 10 cross hole 11 cross hole top 12 cross hole top and top R part to tie

Claims (1)

[Claims] 1. A bone fixing screw made of a biodegradable and absorbable material, wherein a screw cross hole having an R is formed at the head of the screw.