JPH10305043A - Bone fixer and production thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To quickly treat bone fracture while preventing the deviation of bone fixing part by composing a bone fixer of a stick body which has anchor parts at the top end and rear end parts and generates fixing power by shortening an axial length and increasing a diameter length based on temperature changes. SOLUTION: A bone fixer 1 is formed from a stick body 8 having a full length of about 10 to 80 mm and an axial diameter of about 1 to 6 mm, and trapezoidal screws 3 and 2 with peak height of about 0.1 to 3.0 mm are formed at preceding and following ends while being equally shaped and positioned. A driver driving part is provided at the following end. A bone fixer inserting hole is formed on a bone. The bone fixer 1, which retains warmth lower than 37 deg.C, preferably, lower than 25 deg.C, is inserted into the bone fixer inserting hole formed on the bone while using a driver so that the central axial line of the stick body 8 can be spread over a bone fracture part. Then, the axial length of the bone fixer 1 is shortened by heating caused by a body temperature, the diameter length is increased, and the bone fixer is fixed. This stick body 8 is formed from orientated plastic such as polyglycol acid. Thus, pressure provided at the time of fixture is kept for a long time and deviation is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bone fixation device used for internal fixation of broken bones and for internal fixation of bone fragments during osteotomy and bone transplantation.

[0002]

2. Description of the Related Art Conventionally, in orthopedic surgery and oral surgery, bone fracture fixation at the time of bone fracture treatment or osteoarthritis osteotomy and bone grafting to a bone tumor tissue curettage has been performed.
Bone fasteners such as bone screws, plates, wires, and internal nails have been commonly used. Fracture treatments can be divided into external fixation, which is well-known for casting, and internal fixation, in which the fracture is surgically opened. The point is that exercise becomes possible later and early. The shape and usage of such bone anchors are described in the Manual of Internal Fixation (M.E.
Müller et al., 1991, 3rd edition Springer
FAIRLAK), internal fixation of small fractures (co-authored by U. Heim and K. M. Pfeiffer, 1989, issued by Springer Verlag Tokyo Co., Ltd.), ASTF
(564-85, F543-82, F336-82, F
453-76), and based on past detailed demonstration experience, the material and shape of a bone fixation device that exhibits sufficient fixation to various parts of the bone and damage state and does not hinder healing , Usage is set. Generally, these bone anchors are made of a stainless steel alloy or a titanium alloy, and by strongly pressing the two bone fragments, the displacement of the bone fragments is prevented, and a good bone healing is obtained. .

However, in the case of a fragile bone or a fracture of an osteoporosis patient, it is impossible to strongly compress the bone in view of bone strength and bone mass. Furthermore, even in the case of a fracture of a healthy person, the fixing force obtained at the time of surgery does not last until the fracture healing time due to creep deformation of the bone. Also,
These metal bone anchors must be removed as much as possible after the fracture has healed. This is because the metal fastener has a very high elasticity compared to the bone tissue, so there is a problem that the stress transmitted to the bone is absorbed by the fastener and the bone tissue around the inner fastener becomes weak. is there. In addition, there is a possibility that the problem of inflammatory reaction due to metal allergy or that when the bone fixation material detaches from the bone and strays, the surrounding soft tissue may be damaged. The operation of removing the bone fastener from the body is called nail extraction, but it is particularly difficult to remove a deep part such as a hip joint because the operation is performed by re-opening a site where the tissue is complicated. Further, depending on the surgical site, there is a risk that the nerve bundle or the vascular system may be damaged, and furthermore, performing a nail extraction procedure imposes a great mental burden on the patient. Therefore, the determination as to whether or not to perform the nailing operation is determined based on the situation of the healing disorder due to the bone fastener and the uncomfortable feeling of the patient and the difficulty of the nailing operation. For this reason, in recent years, bone fixation devices made of biodegradable plastics such as polyglycolic acid, polydioxanone, and polylactic acid, which do not require nail removal, have been clinically applied.However, since sufficient fixation force cannot be obtained, adaptation is not possible. Limited.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to continuously apply a compressive force to a bone fixation portion and to reduce the clearance between the bone fixation device and the bone tissue, thereby displacing the bone fixation portion. It is an object of the present invention to provide a bone fixation device and a fixation system capable of preventing the occurrence of a fracture and quickly and favorably healing the fracture. Further, to provide a biodegradable bone fastener that does not require nail removal,
Another object of the present invention is to provide a bone fixing device capable of defining a compression force applied to a bone fixing portion.

[0005]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above problems, and as a result, have found the following present invention. (1) A bone made of a stretch-oriented plastic material, characterized in that a rod body having an anchor portion at a leading end and a trailing end generates a fixing force by shortening an axial length and increasing a radial length by a temperature change. Fixture. (2) The axial length is 1-2 due to a temperature change from 0 ° C. to 37 ° C.
0.1% reduction by 0% reduction and 1-10% increase in diameter
The bone fastener according to the above (1), wherein the bone fastener generates a fixing force of 0 kgf / mm ² . (3) The axial length is 1 due to the temperature change from 25 ° C to 37 ° C.
10-5% reduction by 10% reduction and 1-5% increase in diameter
The bone fastener according to the above (1) or (2), wherein the bone fastener generates a fixing force of gf / mm ² . (4) The above-mentioned (1) to (1), wherein the stretch-oriented plastic is made of at least one kind of biodegradable plastic of polyglycolic acid, polydioxanone, polylactic acid, polyhydroxybutyric acid, and polyhydroxyvaleric acid. The bone fastener according to 3).

(5) The above-mentioned (1) wherein the leading end and the trailing end anchor portions have the same shape and the same phase thread shape.
The bone fastener according to any one of (1) to (4). (6) The bone fixation device according to any one of (1) to (5), wherein the bone fixation device has a hollow structure having at least one open end. (7) A molded body made of an unstretched plastic material is inserted into a metal tube and stretched together at a temperature lower than a predetermined temperature at the time of use. A bone fixation device made of a stretch-oriented plastic material, wherein the bone fixation device returns to a shape similar to that of the unstretched shape. (8) A molded body made of an unstretched plastic material is inserted into a metal tube and stretched together at a temperature lower than a predetermined temperature during use, and is unstretched by heating to a predetermined temperature during use. A method for producing a bone fixation device made of a stretched oriented plastic material, characterized in that the bone fixation device returns to a shape at the time of stretching or a shape close to that at the time of unstretching.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The stretch oriented plastic used in the present invention is not particularly limited as long as it has stretch orientation.
Non-biodegradable materials can be used depending on the purpose and application,
Taking into account the fact that postoperative nail removal is unnecessary, biodegradable ones are preferred. Also, a combination of these may be used. The non-biodegradable plastic is not particularly limited as long as it is harmless to the human body, and examples thereof include polyethylene, polyamide, and polyurethane. The biodegradable plastic is not particularly limited as long as it has a small inflammatory reaction at the time of implantation into a living body, but is preferably polyglycolic acid, polydioxanone, polylactic acid that is decomposed and absorbed in the body.
Preferred are polyhydroxybutyric acid, polyhydroxyvaleric acid, and the like. In addition, bioabsorbable materials such as calcium phosphate, magnesium phosphate, hydroxyapatite, and calcium carbonate, or biodegradable plastics to which salts which do not cause a problem even if they remain in the body may be used. Further, as other additives, glass fiber, carbon fiber and the like can be added.

The plastic material used in the present invention is:
The material must be capable of being oriented by stretching. Heating the oriented plastic material shortens it in the direction of the orientation axis and uses the heat shrinkage phenomenon in which the diameter increases in the direction perpendicular to the orientation axis.However, if a conventional stretching method is used, plastic It is very difficult to impart such properties to materials. Therefore, as a result of our efforts, we inserted the unstretched plastic molded product into a metal pipe such as aluminum, brass, copper, etc., stretched it together, and applied appropriate heat treatment as needed, so that the heat shrinkage phenomenon, The inventors succeeded in obtaining a stretch-oriented plastic material characterized by being shortened in the axial direction by heating and increased in the radial direction.

Generally, plastic stretched by a normal operation is elastically deformed immediately after starting stretching and almost completely returns to its original length, but does not return to its original length more than a certain length after being stretched beyond a certain length. Has nature. In other words, when stretched to such an extent that it does not completely return to its original state, the plastic molecules can maintain their shape with residual strain inside. Such properties are observed to a greater or lesser extent in any plastic. Such residual strain can be released by heating, but the temperature at which it can be released depends on the thermal properties of the plastic, and the degree of deformation at the time of release depends on the magnitude of the strain held inside the molded article. That is easy to imagine. First, the glass transition temperature Tg is an important factor for thermal properties. When the plastic is non-crystalline, at temperatures higher than the glass transition temperature, the molecules of the plastic are relatively mobile and the internal residual strain is easily eliminated. Therefore, it is difficult to leave a large residual strain in a stretching operation at a temperature above Tg. On the other hand, non-crystalline materials, such as acrylic and polystyrene, are hard at Tg or higher, are easily broken when stress is concentrated, and are often brittle, and are stretched by applying a large residual strain in a normal stretching operation at Tg or lower. It is difficult.

On the other hand, in the stretching method of the present invention, plastic is inserted into a metal pipe capable of being plastically deformed with a higher elastic modulus than plastic, and the plastic is stretched through deformation when the metal pipe is pulled down through a die.
The stretching force is hardly applied to the plastic, and the compression force transmitted to the outer surface of the plastic through the inner wall of the metal pipe is mainly stretched in the axial direction of pulling down.
Further, since the compressive force is transmitted as a surface pressure from the inner surface of the metal pipe, it is difficult for the stress to concentrate on a part of the stretched plastic molded product, and as a result, it is difficult for the plastic molded product to be damaged. As a result, T
By drawing a brittle resin such as polystyrene or acrylic at less than g, large residual strain can be accumulated in the molded product. On the other hand, general drawing of a highly crystalline plastic with a low degree of crystallinity is a method often used when producing a high-strength drawn yarn, drawn rod, or drawn film. At this time, the T
g or less, it is expected that the same effect as that of the present invention can be provided.However, since the temperature control after melt molding becomes more difficult as the thickness of the molded product becomes larger, the purpose of the present invention is to improve the intraosseous fixation device. Stable molding involves difficulties. If the temperature is maintained at Tg or more after stretching, the residual strain is naturally eliminated due to the progress of crystallization, and the fixture of the present invention cannot be used.

If the plastic to be stretched is highly crystallized, the method according to the invention is effective. As described above, it is difficult to obtain a relatively large molded product of crystalline plastic in a low crystalline state, but a high crystalline state has an advantage that it can be molded relatively easily and stably. Tg of such high crystallinity plastic
In the case of stretching in the following, it is clear that it is difficult to generate a large residual strain by stretching by a normal stretching operation from the point of brittleness similar to the case of the amorphous plastic, and the stretching method of the present invention is Obviously it is very effective.

On the other hand, when the crystalline plastic is stretched at a temperature of Tg or more, it can be expected that a large degree of crystallinity can produce a large strain due to a three-dimensional interaction of crystal parts. In other words, in such a high crystallinity plastic, even at a temperature higher than Tg, the elimination of the residual strain due to the molecular motion in the non-crystalline region is sterically hindered by the arrangement of the crystal region in which the molecular motion is difficult. As expected, for example, polyhydroxybutyric acid, which is known to have a very high crystallinity at room temperature (usually a crystallinity of 70 to 80% at room temperature, Tg = 0 ° C.), is also famous for being very brittle. As can be seen, it is almost impossible with a normal stretching method. However, according to the stretching method using the metal pipe of the present invention, such a hard and brittle material having a high degree of crystallinity can be stretched while leaving a large residual strain, and a stretch-oriented molded product suitable for the fixture of the present invention. Can be given. The residual strain is a residual strain that can be eliminated by deforming a molded product at a temperature higher than a stored temperature, preferably near a human body temperature.

That is, the stretch-oriented plastic material used in the present invention is characterized in that it shrinks in the axial direction and expands in the radial direction due to a change in temperature. Such properties are different from normal elasticity. Ordinary elasticity means that the shape at a constant temperature is generated by external pressure or tension regardless of the temperature change. It is characterized by contracting in the axial direction and expanding in the radial direction. It should be noted that the bone fastener of the present application may have both such characteristics and ordinary elasticity.

[0014] The temperature of the process of inserting the unstretched plastic molded body into a metal tube made of aluminum, brass, copper or the like when obtaining a stretch-oriented plastic material and stretching it together is not particularly limited, but is not more than 37 ° C. Preferably, the temperature should be 10 ° C. or less. The bone fastener of the present invention is formed by cutting or press-molding the obtained stretch-oriented plastic material. The temperature at the time of cutting and press-molding is not particularly limited, but is not more than 37 ° C, preferably 10 ° C. It is good if it is below ° C. In the case of press molding, the temperature at the time of taking out from the mold is not particularly limited. However, if the temperature is 37 ° C. or lower, preferably 10 ° C. or lower, the temperature during molding may be lower than the melting point of the material used. Absent.

[0015] The shape of the anchor portion of the bone fastener of the present invention is as follows.
There is no particular limitation, and for example, by adopting a screw shape, the entire bone fixing device can be embedded in the bone, and it can be applied to fixation of a fracture near a joint. Further, damage to the screw head due to stress concentration, which is expected when a commercially available bone screw is formed, can be avoided. The shape of the anchor portion of the bone anchor that can be buried in the bone is not limited to this.

In the bone fixing device of the present invention, since the shaft length is shortened and the shaft diameter is increased by heating by body temperature, a compressive force is continuously applied to the bone fixing portion to reduce the clearance with the bone tissue. This is a bone fixation device that enables stable bone fixation for a period until bone fusion, which could not be achieved with biodegradable bone screws such as commercially available metal bone screws and polylactic acid bone screws. The bone fixation device of the present invention, when heated to a body temperature, that is, around 37 ° C., causes a reduction in shaft length and an increase in shaft diameter sufficient for bone fragment fixation. But,
When a pressing force needs to be immediately applied to the bone fixing part, the time required for fixing can be reduced by heating using a heater or the like. The bone fixation device of the present invention can control the compression force applied to the bone fixation portion by setting the material, stretching ratio, diameter length, shaft length, and preheating (temperature, time). Fixation according to the bone properties of the tissue becomes possible.

Hereinafter, the shape and usage of a typical example of the bone anchor of the present invention will be described. The shape of the bone anchor of the present invention is not limited to this. Figures 1 and 2
Shows an example of the bone anchor according to the third aspect. The bone fastener 1 of the present invention has a total length of 10 to 80 mm and a shaft diameter of 1 mm.
A leading end side trapezoidal screw 3 and a trailing end trapezoidal screw 2 having a peak height of 0.1 to 3.0 mm are formed at the leading end and the trailing end of the rod body 8 having a shape and a phase, respectively, at the leading end and the trailing end. At the trailing end, a driver fitting portion 4 is provided for inserting the present bone fastener into the bone. Here, the thread shape is not particularly limited, and may be a square screw, a triangular screw, a round screw, a current bone screw shape, or the like. Also, the thread width and pitch of the screw thread are not particularly limited, and are determined by factors such as the trabecular bone on the fixed bone side, bone density, and bone properties. Further, in FIG. 2, the screwdriver fitting portion has a minus driver shape, but a plus screwdriver shape, a concave hexagonal shape, a convex hexagonal shape, or any other shape that can apply a rotational force to the shaft of the bone fastener of the present invention. However, there is no particular limitation.

Next, an actual bone fixing method will be described.
After the bone fragments to be fixed are anatomically reduced, a bone fastener insertion hole 10 is prepared as shown in FIG. 3 by using a drill and a tap adapted to the bone fastener of the present invention. 37 ° C or less,
The bone fastener, preferably stored at 25 ° C. or lower, is
Is inserted into the bone using a screwdriver so that the central shaft of the is straddling the fracture line. FIG. 4 shows the state immediately after the insertion of the bone fastener. FIG. 5 shows the bone fixing part in a state where the axial length of the bone fixing tool is shortened by heating by body temperature. Good fixability can be obtained by the intricate surface 9 of the bone fragments.

Next, an example in which a heater is used for heating in the present invention will be described. FIGS. 6 and 7 show a bone fastener 1 ′ in which a rod 8 ′ is formed in a hollow shape and a heater insertion hole 11 is provided. The heater insertion hole is desirably along the axis of the bone fastener, and its diameter is preferably smaller than a value obtained by subtracting 1.0 mm from the axis diameter of the bone fastener, but not particularly limited thereto. The heater insertion hole 11 must be made so that the heater can be inserted from the trailing end 21 of the bone fastener, but the depth is sufficient up to the rear end 22 of the leading end anchor portion. It can be shorter or longer. Also,
It may be penetrated. FIG. 6 shows a state in which the leading end side anchor portion is longer than the trailing end 22.

At this time, the temperature of the heater is suitably in the range of 40 to 80 ° C., but is not particularly limited to this temperature, and may be lower than the melting point of the plastic material as the bone fixing material. The heating operation can also move the heater up and down or rotate. Further, the heater used here is not particularly limited to a heating wire, and ultrasonic vibration may be used as long as heat energy is transmitted to the bone fixing material.

Hereinafter, examples will be shown to specifically illustrate the bone fastener of the present invention. (Example 1) It was confirmed that the bone fixing device of the present invention can generate a tensile force at the time of fixing a bone, and further, whether the generated tensile force can be adjusted. An experiment was conducted to Double and four
Double drawn polyhydroxybutyric acid rod at room temperature (25 ° C)
After standing for a period of time, the body was heated to body temperature (37 ° C.), and the generated tensile force was measured using a universal tensile tester. as a result,
0.42 kgf / mm ^{2 for} 2x drawn polyhydroxybutyrate rod
In the 4-fold stretched polyhydroxybutyric acid rod, a tensile force of 1.05 kgf / mm ² was generated. The 4-fold stretched polyhydroxybutyric acid rod was able to generate 2.5 times the tensile force of the 2-fold stretched polyhydroxybutyrate rod.

Example 2 A 3.5-mm 4-fold drawn polyhydroxybutyric acid rod was cut at 4 ° C., and FIG.
A polyhydroxybutyric acid bone fastener (main body 12 and nut 16) having the shape described in No. 9 was produced. 5 mm at both ends of the bone fastener body is a metric screw (M3.5 male screw).
A 5 mm thick cancellous bone block was prepared from bovine bones frozen and stored within 4 hours after sacrifice. Two cancellous bone blocks were fixed using a commercially available stainless steel bone screw and the above-mentioned polyhydroxybutyric acid bone fixing device, immersed in a 37 ° C constant temperature bath, and the compression force applied to the bone fixing portion was measured over time. . FIG. 10 shows a state of being fixed to the inter-bone fragment compression force measuring device. After the elapse of 40 hours, the compression force was relaxed to 5 kgf, and a change in the compression force applied to the bone fixing portion was confirmed. Three hours later, the compression force was further reduced to 3 kgf, and a change in the compression force applied to the bone fixation portion was confirmed.

FIG. 11 is a line graph showing the results of the experiment. In stainless steel bone screw fixation, the compression force obtained at the time of fixation decreases with time, and once a sudden decrease in compression force occurs, the compression force does not increase. However, when the bone fastener of the present invention was used, it was confirmed that the compressive force increased to a constant value over time and continued to maintain that value. Further, it was confirmed that even when the compression force suddenly decreased, the compression force increased again.

(Example 3) A bone fixation device shown in FIGS. 6 and 7 was prepared using a 4 × drawn polyhydroxybutyric acid rod having a diameter of 4.5 mm, heated by a heater (80 ° C.), and fixed. The time required was measured. As a result, the time required for bone fragment fixation was reduced from 1 hour to 1 minute by performing heating with a heater.

[0025]

The bone fixation device according to the present invention can reduce the length of the shaft and increase the diameter of the shaft at the temperature (37 ° C.) at the time of fixing the bone fragments.
It is possible to maintain the compression force generated between the bone fragments for a long time and to reduce the clearance with the bone tissue as compared with the metal bone screw fixation. These are effective to fix firmly so that the bone fixation part does not shift,
As a result, rapid and good bone healing is obtained. Furthermore, by setting the stretching ratio, the shaft diameter, and the like, it is possible to adjust the compression force generated between the bone fragments, and when performing fracture fixation of a fragile bone or an osteoporosis patient, to a degree that does not cause bone destruction. Fracture fixation can be performed with a specified force.

[Brief description of the drawings]

FIG. 1 is a side view of an example of a bone fastener of the present invention.

FIG. 2 is a top view (view from the trailing end) of an example of the bone fastener of the present invention.

FIG. 3 shows a schematic view of fixing a bone fragment using the bone fixing device of the present invention (showing a state before the bone is fixed).

FIG. 4 shows a schematic view of fixation of a bone fragment using the bone fixation device of the present invention (a state immediately after the fixation device is inserted).

FIG. 5 is a schematic view showing fixation of a bone fragment using the bone fixation device of the present invention (showing a state after heating by body temperature).

FIG. 6 is a side sectional view of an example of the bone fastener of the present invention having a heater insertion hole.

FIG. 7 is a top view (view from the trailing end) of an example of the bone fastener of the present invention having a heater insertion hole.

FIG. 8 is a side view of a bone fastener (main body) used in Example 2.

FIG. 9 is a side sectional view of a bone fastener (nut) used in Example 2.

FIG. 10 is a schematic view of a device for measuring inter-fragment compression force fixed to bone fragments used in Example 2.

FIG. 11 is a line graph showing the results of Example 2.

[Brief description of reference numerals]

1, 1 ': bone fixing tool, 2, 2': trailing end trapezoidal screw,
3, 3 ': leading end side trapezoidal screw, 4, 4': screwdriver fitting portion, 5: bone side anchor portion, 6: bone fragment A, 7: bone fragment B, 8, 8 ': rod, 9: bone Uneven surface between pieces,
10: Bone fixture insertion hole, 11: Heater insertion hole, 1
2: Bone fixing device (main body) provided in Example 2, 13: Central shaft portion, 14: Trailing end anchor portion, 15: Leading end anchor portion, 16: Bone fixing device (nut) provided in Example 2 ,
17: screw groove, 18: pressure sensor, 19: cemented iron plate, 20: cancellous bone block, 21: heater insertion port, 22;

Claims (8)

[Claims] 1. A stretch-oriented plastic material comprising a rod body having an anchor portion at a leading end and a trailing end, wherein a shaft length is reduced by a temperature change and a fixing force is generated by increasing a diameter length. Become a bone anchor. 2. A change in temperature from 0 ° C. to 37 ° C. reduces the axial length by 1 to 20% and increases the diameter by 1 to 10%, thereby increasing the axial length by 0.1 to 10%.
Bone fixation device, according to claim 1, characterized in that to produce a clamping force of 1 to 10 kgf / mm ^2. 3. A change in temperature from 25.degree. C. to 37.degree. C. reduces the axial length by 1 to 10% and increases the diameter by 1 to 5%.
3. The bone fastener according to claim 1, wherein the bone fastener has a fixing force of 1 to 5 kgf / mm ² . 4. The stretch-oriented plastic is made of at least one biodegradable plastic of polyglycolic acid, polydioxanone, polylactic acid, polyhydroxybutyric acid, and polyhydroxyvaleric acid. 4. The bone fastener according to 3. 5. The bone anchor according to claim 1, wherein said leading end and trailing end anchors have the same shape and the same phase thread shape. 6. The bone fixation device according to claim 1, wherein the bone fixation device has a hollow structure having at least one open end. 7. A molded article made of an unstretched plastic material is inserted into a metal tube and stretched together at a temperature lower than a predetermined temperature during use, and is heated to a predetermined temperature during use. A bone fixation device made of a stretch-oriented plastic material, which returns to a shape at the time of stretching or a shape close to that at the time of unstretching. 8. A method in which a molded body made of an unstretched plastic material is inserted into a metal tube and stretched together at a temperature lower than a predetermined temperature during use. A method for producing a bone fastener made of a stretched oriented plastic material, wherein the bone fastener returns to an unstretched shape or a shape close to the unstretched state.