JPH084607B2 - Artificial disc - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an artificial intervertebral disc used for treating diseases such as herniated intervertebral disc and damage to the spine due to an accident.

[Conventional technology]

As shown in FIG. 7, the spine of the human body is composed of hard vertebral bodies 1 arranged in a row and a cartilage intervertebral disc 2 connecting vertically adjacent vertebral bodies 1. When the above-mentioned spine disease or damage is severe, surgical treatment is performed by removing all or part of the vertebral body 1 and the intervertebral disc 2 by incision surgery, and implanting autologous bone or artificial vertebral body in the portion. It is being appreciated.

As such an artificial vertebral body, conventionally, as shown in FIGS. 8 and 9, an alumina ceramic molded into a substantially disk shape or a rectangular parallelepiped shape is used.
In addition, recently, known bioactive ceramic materials having an apatite crystal phase, materials obtained by blending high density polyethylene or methacrylate resins, and the like have been used.

[Problems to be Solved by the Invention]

However, all of these artificial vertebral bodies are merely used as spacers that fill the gaps and support the load when the intervertebral disc or the like is excised, and are not as flexible as the original intervertebral disc. Therefore, it is difficult to follow the movement of the human body, and an excessive load often damages the treatment area or its peripheral portion again, which is a problem.

The present invention has been made in view of such circumstances,
It is an object of the present invention to provide a flexible artificial intervertebral disc that can sufficiently follow the movement of the human body.

[Means for solving the problem]

In order to achieve the above-mentioned object, the artificial intervertebral disc of the present invention is substantially cylindrical or prismatic in its entirety, and its upper region and lower region are made of a biocompatible polymer elastic material as a base. It is formed of a composition in which powder is dispersed and contained, and a central region sandwiched between the upper region and the lower region is formed of only the polymeric elastic material.

[Action]

That is, in the present invention, the conventional artificial vertebral body is a hard block-shaped one, whereas the whole is made into a substantially cylindrical body or a substantially prismatic body, and the upper region and the lower region thereof are made of a biocompatible material. It is formed by a composition in which a bioactive ceramic powder is dispersed and contained in a base of a molecular elastic material, and an intermediate region sandwiched between the upper region and the lower region is formed only by the polymeric elastic material. is there. Therefore, if the upper end surface and the lower end surface of this artificial disc are joined to the vertebral body in the living body, the bioactive ceramic powder dispersedly contained in this portion is chemically joined to the vertebral body in the living body to make the artificial intervertebral disc. Are integrally connected between the vertebral bodies. Since the intermediate region of the artificial intervertebral disc is made of only a polymeric elastic material and has elasticity, the upper and lower ceramics-containing regions freely rotate about this intermediate region. Therefore, the artificial intervertebral disc flexibly moves in accordance with the forward bending, backward bending, etc., so that the entire spine moves smoothly and no excessive load is applied. Also, by appropriately selecting the overall shape and hardness of the polymeric elastic material, it is possible to provide an artificial intervertebral disc that fits the person while checking the physique of the patient and the balance with other spinal functions. You can
You can give detailed treatment.

 Next, the present invention will be described in detail.

The artificial intervertebral disc of the present invention is formed into a cylindrical body 10 as a whole, for example, as shown in FIG. The upper region A and the lower region B of the columnar body 10 are formed by a composition in which the biocompatible polymer elastic material 11 is used as a base and the bioactive ceramic powder 12 is dispersed and contained therein. ing. Further, the central region C sandwiched between the upper region A and the lower region B is formed only by the polymeric elastic material 11.

The polymeric elastic material serving as the base of the composition forming the upper region A and the lower region B is required to have biocompatibility and a certain elasticity, for example, silicone rubber for living body or urethane for living body. Rubber or the like is used. Further, foamed silicone resin or foamed urethane resin, which is given elasticity by foaming, may be used. The hardness (JIS A) of these polymeric elastic materials is preferably in the range of 10 to 50 degrees. If the hardness is less than 10 degrees, it is too soft to be embedded in the middle of the spine, and this portion is easily deformed by the load and protrudes in the anteroposterior and lateral directions, which is not suitable because it presses the nerve tissue. On the contrary, if the hardness exceeds 50 degrees, the artificial intervertebral disc obtained because it is too hard loses flexibility,
It is not easy to use.

Further, the ceramic powder 12 dispersedly contained in the polymer elastic material 11 in the upper region A and the lower region B of the columnar body 10 has a bioactivity that chemically binds to bone and becomes inseparable. It must be present and is made from a bioactive ceramic material. Examples of the ceramic material include hydroxyapatite, bioglass, glass ceramics and the like. Of these, apatite-wollastonite-containing ceramics, which is a crystallized glass, is suitable.

The artificial intervertebral disc of the present invention can be manufactured, for example, as follows using the biocompatible polymer elastic material 11 and the bioactive ceramics powder 12. That is,
First, an uncrosslinked biocompatible polymer elastic material liquid and the bioactive ceramic powder 12 are mixed, filled in a disk-shaped mold and cured to prepare two ceramic powder-containing disks. Next, the above-mentioned two discs are fitted into both end faces of the cylindrical mold, and in that state, the uncrosslinked polymer elastic material liquid is filled into the mold. Then, by curing, a cylindrical body 10 having a three-layer structure as shown in FIG. 1 can be obtained. Further, the ceramic powder 12 is evenly laid on the bottom of the mold, and the polymer elastic material liquid is filled from above, and the ceramic powder 12 is evenly placed on the top of the polymer elastic material liquid,
It can also be manufactured by setting the mold in that state and curing it.

In the above-mentioned manufacturing method, the mixed composition of the biocompatible polymer elastic material 11 and the bioactive ceramic powder 12 forming the upper region A and the lower region B of the cylindrical body 10 is the same as the polymer elastic material 11. It is preferable to set the powder 12 to be contained in an amount of 30 to 80% by volume. If it is less than 30% by volume, the amount of the ceramic powder 12 exposed on the upper surface and the lower surface of the columnar body 10 tends to be small and the joint with the vertebral body in vivo tends to be weak. This is because the proportion of the polymer elastic material 11 having a function as a binder for binding the powders 12 is too small, and the moldability and shape retention of this portion tend to deteriorate.

Further, in the artificial intervertebral disc of the present invention, the total thickness, or the thickness of the upper region A and the lower region B containing the bioactive ceramics powder 12 depends on the physical constitution of the patient and the balance with other spinal functions. Can be set individually. For example, as shown in FIG. 2, the outer peripheral surface of the central region of the substantially columnar body 10 may be recessed into a concave shape so that the entire body can be bent in a dogleg shape, or conversely, as shown in FIG. As shown, a convex roundness may be provided to show a strong resistance against a load applied in the vertical direction.

Further, projections (or streak-shaped grooves) 10a as shown in FIG. 4 may be formed on the upper surface and the lower surface of the cylindrical body 10. By doing so, the joint area between the vertebral body (see FIG. 7) and the artificial intervertebral disc increases when it is implanted in the living body, and the artificial intervertebral disc is firmly fixed.

Further, the artificial intervertebral disc may be set in a cross-sectional shape in which one side of a circle is crushed, as shown in FIG. 5, imitating an actual spine.

The overall shape is not limited to the columnar shape, and can be formed into an appropriate shape such as a quadrangular prism.

 Next, examples will be described.

[Examples 1 to 7] Using the materials shown in the table below, the first method was performed according to the above production method.
An artificial disc as shown in the figure was created. Then, among the seven types of artificial intervertebral discs thus obtained, the compression spring characteristics were measured for the samples of Examples 1 to 3 by compressing the sample at a test speed of 1 mm / min. The result is shown in FIG.

Further, by implanting the artificial intervertebral discs of Examples 1 to 7 in a cadaver specimen, anterior flexibility, posterior flexibility, axial twistability,
Lateral flexibility was measured and compared with that of the actual intervertebral disc to evaluate the quality of movement.

The results are shown in the table below. As a control example, the conventional apatite artificial vertebral body shown in FIG. 8 is prepared,
The same evaluation as above was performed, and the results are also shown in the table below.

From the above results, it can be seen that the products of the Examples all exhibit good spring compressibility and have excellent flexibility as compared with the control product.

〔The invention's effect〕

As described above, the artificial intervertebral disc of the present invention is a substantially columnar body or a substantially prismatic body as a whole, and the upper region and the lower region thereof are made to contain the bioactive ceramic powder dispersed and contained in the biocompatible polymer elastic material. Since it is formed of a composition, and the intermediate region is formed only of the above-mentioned polymeric elastic material, if the upper end surface and the lower end surface of this artificial intervertebral disc are joined to a vertebral body in vivo, the ceramics dispersedly contained in this portion The powder chemically bonds with the vertebral bodies in the body to integrally bond the artificial intervertebral disc between the vertebral bodies. Since the intermediate region of the artificial intervertebral disc is made of only a polymeric elastic material and has elasticity, the upper and lower ceramics-containing regions freely rotate about this intermediate region. Therefore,
This artificial intervertebral disc moves flexibly according to the forward bending, backward bending, etc., so that the entire spine moves smoothly and no excessive load is applied. Also, by appropriately selecting the overall shape and hardness of the polymeric elastic material, it is possible to provide an artificial intervertebral disc that fits the person while checking the physique of the patient and the balance with other spinal functions. It is possible and can give detailed treatment.

[Brief description of drawings]

1 is a longitudinal sectional view showing an embodiment of the present invention, FIG. 2 is a perspective view showing another embodiment, FIG. 3 is a perspective view showing still another embodiment, and FIG. 4 is another embodiment. 5 is a vertical sectional view showing an example.
FIG. 7 is a plan view showing a modified example of the cylindrical body, FIG. 6 is a diagram showing the compression spring characteristic of the embodiment product, FIG. 7 is a partial perspective view showing the constitution of the spine, FIGS. 8 and 9 Each of the drawings is a perspective view showing an example of a conventional product. 10 …… Cylindrical body, 11 …… Polymer elastic material, 12 …… Ceramics powder, A …… Upper area, B …… Lower area, C ……
Intermediate area

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Hiroaki Ishikawa 3-12-10 Momiji Tainan, Atsubetsu-ku, Sapporo, Hokkaido (72) Inventor Takehiro Shibuya 2-41-7, Motomiya, Otsu City, Shiga Prefecture Inventor Masataka Takagi 626, Kogoji Temple, Notogawa-cho, Kanzaki-gun, Shiga Prefecture (72) Inventor Yukio Sakuraba 3600 Amagatsu, Komaki-shi, Aichi Prefecture, Toyama Rubber Industry Co., Ltd. (72) Kiyoshi Baba, Komaki-shi, Aichi Prefecture Tsu 3600 Tokai Rubber Industry Co., Ltd. (56) Reference JP-A-2-215461 (JP, A)

Claims (3)

[Claims] 1. A composition having a substantially columnar shape or a substantially prismatic shape as a whole, the upper region and the lower region of which are made of a biocompatible polymer elastic material as a base and in which a bioactive ceramic powder is dispersed and contained. An artificial intervertebral disc, characterized in that the central region sandwiched between the upper region and the lower region is formed of only the biocompatible polymeric elastic material. 2. The artificial intervertebral disc according to claim 1, wherein the bioactive ceramic powder is bioactive glass or bioactive crystallized glass. 3. The artificial intervertebral disc according to claim 1, wherein the biocompatible polymeric elastic material is urethane rubber or silicone rubber.