JP2010158345A - Intervertebral spacer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an intervertebral spacer, prevented from biting into a vertebral body and smoothly causing bone union after insertion between the vertebrae. <P>SOLUTION: This intervertebral spacer 1 includes a cylindrical outer frame member 2, the interior of which is filled with a bone prosthetic material A to be held in the direction of thickness and inserted between the vertebrae. The outer frame member 2 has circumferential tensile strength to limit the circumferential expansion of the bone prosthetic material A when load is applied to the bone prosthetic material A while having smaller compressive strength in the direction of thickness than the bone prosthetic material A. The outer frame member 2 having a lower compressive strength is used so that even when load is applied to the bone prosthetic material A, the shape of the bone prosthetic material A can be retained. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an intervertebral spacer.

As a treatment method for spinal cord diseases such as cervical spondylosis and intervertebral disc herniation that develops when the spinal cord is compressed, after removing the intervertebral disc where pressure is applied and decompressing the spinal cord, a spacer is inserted between the vertebrae from which the intervertebral disc has been removed However, a method for holding the spine in an appropriate position is used.
Autologous bones or artificial bones collected from the human body are housed as transplanted bones inside the spacers, and these bones fuse together after the intervertebral grafts to achieve healing. Since these grafted bones alone cannot withstand the load between the vertebrae, the periphery is covered and reinforced by an outer frame made of titanium or resin having a higher compressive strength than the grafted bone (for example, Patent Documents). 1 and Patent Document 2).

Japanese Patent No. 3839055 Special table 2007-512874 gazette

However, there is a problem that such an outer frame having a high compressive strength gradually bites into the end plate of the vertebral body when a load from the vertebral body is continuously applied. Further, there is an inconvenience that when the X-ray observation is performed after the operation, the outer frame is shaded and the operation part cannot be observed accurately.
In addition, the material with high compressive strength is difficult to unite, and if the wall thickness of the outer frame is increased to increase the compressive strength of the outer frame, the amount of transplanted bone that can be filled inside and the contact area of the transplanted bone and vertebral body Cannot be secured sufficiently. As a result, there is an inconvenience that bone fusion with the vertebral body of the spacer cannot be sufficiently achieved and healing is delayed.

  The present invention has been made in view of the above-described circumstances, and an object of the present invention is to provide an intervertebral spacer capable of preventing bite into a vertebral body and smoothly healing bone after intervertebral insertion.

In order to achieve the above object, the present invention provides the following means.
The present invention includes a cylindrical outer frame member that is filled with a bone prosthetic material and is inserted between vertebrae in the thickness direction, and the outer frame member is inserted in the thickness direction into the bone prosthetic material. An intervertebral spacer having a circumferential tensile strength capable of restricting radial expansion of the bone prosthetic material when a load is applied to the bone prosthetic material in the intervertebral space while having a smaller compressive strength To do.

According to the present invention, when the intervertebral spacer is press-fitted into the intervertebral disc from which the intervertebral disc has been previously removed, the intervertebral body can be held at an appropriate size and the position of the vertebral body can be stabilized.
In this case, if a load in the thickness direction is applied to the outer frame member and the bone prosthetic material between the vertebrae, the bone prosthetic material has higher compressive strength than the outer frame member. The outer frame member is pressed radially outward. Since the outer frame member has a tensile strength that can withstand this pressing force, the expansion of the bone grafting material is limited and the shape thereof is held in the outer frame member.

  That is, according to the present invention, the outer frame member has a circumferential strength that can limit the expansion of the bone prosthetic material, so that the bone prosthetic material between the vertebrae even when the compressive strength in the thickness direction of the outer frame member is low. The shape of is retained. Thereby, since the outer frame member does not have a compressive strength that resists the load from the vertebral body, it is possible to prevent the outer frame member from biting into the vertebral body.

  In addition, the structure of the outer frame member and the use of materials that are difficult to unite bone such as metal, which have been used to increase the compressive strength, become unnecessary. Therefore, the wall thickness of the outer frame member is formed thin, and a material that is easy for bone fusion is used for the outer frame member. As a result, the amount of the bone filling material to be filled and the contact area between the bone filling material and the vertebral body can be sufficiently secured, and the bone filling material can be smoothly fused with the vertebral body. Bone fusion can also be achieved in the member.

In the said invention, the said tensile strength of the said outer frame member is good also as being 15 Mpa or more.
By doing so, the outer frame member has sufficient resistance to the radial expansion of the bone grafting material against the load in the cervical vertebra, and can prevent the bone grafting material from scattering between the cervical vertebrae and maintain its shape. it can. That is, the intervertebral spacer can stably support the vertebral body between the cervical vertebrae.

Moreover, in the said invention, the said tensile strength of the said outer frame member is good also as being 40 Mpa or more.
By doing so, the outer frame member can maintain the shape of the bone prosthetic material against the load on the lumbar vertebra, and thus the intervertebral spacer can stably support the vertebral body between the lumbar vertebrae.

Moreover, in the said invention, the said bone grafting material is good also as being a porous body which has (beta) -tricalcium phosphate ((beta) -TCP) as a main component.
In this way, when the bone grafting material contacts the vertebral body and blood or cells penetrate into the bone grafting material from the surrounding tissue through the hole, β-TCP is replaced with autologous bone, and the intervertebral disc Autogenous ossification can be achieved in the intervertebral space from which the vertebrae have been removed.

Moreover, in the said invention, it is good also as the inner peripheral surface of the said outer frame member being formed so that a diameter size may become large gradually toward each end surface in the end surface vicinity.
By doing so, the contact area between the bone grafting material and the end plate of the vertebral body can be increased, and the bone healing of the bone grafting material can be further accelerated.

Moreover, in the said invention, the said outer frame member is good also as including PEEK (polyethyl ether ketone), PE (polyethylene), PP (polypropylene), or PU (polyurethane).
By doing in this way, bone fusion with a vertebral body can be made easy, giving sufficient tensile strength of the peripheral direction to an outer frame member.

  According to the present invention, it is possible to prevent the vertebral body from being bitten and to smoothly fuse bones after intervertebral insertion.

It is a whole block diagram which shows the intervertebral spacer which concerns on one Embodiment of this invention. It is a figure explaining the usage method of the intervertebral spacer of FIG. 1, (a) When inserting between vertebrae, (b) The state at the time of fixing between vertebrae is shown.

An intervertebral spacer 1 according to an embodiment of the present invention will be described below with reference to FIGS. 1 and 2.
As shown in FIG. 1, the intervertebral spacer 1 according to the present embodiment includes a cylindrical outer frame member 2 and is filled with a bone grafting material A.

The outer frame member 2 is formed so that the inner surface gradually increases in diameter toward each end surface in the vicinity of the end surface. The outer frame member 2 is made of, for example, a highly biocompatible resin, specifically, PEEK, PE, PP, or PU.
As the bone grafting material A, for example, a β-TCP porous body having a compressive strength of about 10 MPa is used. β-TCP is replaced with autologous bone over time by being brought into contact with surrounding tissues in the body.

Further, the outer frame member 2 has a compressive strength in the thickness direction smaller than that of the bone grafting material A. Further, the outer frame member 2 has a tensile strength in the circumferential direction large enough to limit the outward expansion of the bone prosthetic material A due to the application of a thickness direction load in the intervertebral B.
Accordingly, when a load is applied to the intervertebral spacer 1 in the intervertebral space B, the bone prosthetic material A having a higher compressive strength tries to expand outward in the radial direction under the load, and the outer frame member 2 is moved outward in the radial direction. Press toward. Since the outer frame member 2 has a tensile strength sufficient to withstand this pressing force, the bone prosthetic material A is restricted from expanding and the shape is held in the outer frame member 2.

When the intervertebral spacer 1 is inserted between the cervical vertebrae, the outer frame member 2 has a circumferential tensile strength of 15 MPa or more. When the tensile strength in the circumferential direction of the outer frame member 2 is less than 15 MPa, the outer frame member 2 has sufficient resistance against the radially outward pressing force of the bone grafting material A when a load is applied between the cervical vertebrae. I can't expect it.
When the intervertebral spacer 1 is inserted between lumbar vertebrae, the outer frame member 2 has a tensile strength in the circumferential direction of 40 MPa or more.

The operation of the intervertebral spacer 1 thus configured will be described below.
In order to implant the intervertebral spacer 1 according to the present embodiment into the intervertebral B, as shown in FIG. 2A, the direction in which the adjacent vertebral body C is separated from the intervertebral B from which the intervertebral disc has been removed in advance. The intervertebral spacer 1 is press-fitted while being spread out. As a result, as shown in FIG. 2B, the intervertebral spacer 1 can be transplanted into the intervertebra B and the vertebral body C can be stabilized at a normal position.

  In this case, according to the present embodiment, the compressive strength of the outer frame member 2 and the bone grafting material A are both sufficiently smaller than the compressive strength of the vertebral body C. Therefore, even if the intervertebral spacer 1 is left in the body for a long time and the load from the vertebral body C continues to be applied, the outer frame member 2 can bite into the end plate of the vertebral body C or damage the vertebral body C. There is an advantage that it can be prevented.

Further, by configuring the outer frame member 2 so as not to require high compressive strength in the thickness direction, the outer frame member 2 is configured only with a material having high biocompatibility that has been difficult to use for the outer frame member 2 in the past. Can do. Thereby, also in the outer frame member 2, the bone fusion with the vertebral body C can be easily achieved.
Furthermore, the wall thickness of the outer frame member 2 is reduced, and the amount of the bone prosthetic material A filled therein and the contact area between the bone prosthetic material A and the vertebral body C are increased. As a result, the bone fusion between the intervertebral spacer 1 and the vertebral body C proceeds smoothly in the intervertebral B, and the healing of the surgical site can be accelerated.

Further, by using a β-TCP porous body as the bone grafting material A, autogenous bone formation can be achieved in the intervertebral disc B from which the intervertebral disc has been removed.
In addition, by making the outer frame member 2 in a shape with a wider opening area at the end face, the contact area between the bone prosthetic material A and the vertebral body C is further increased, and the bone healing of the bone prosthetic material A is accelerated. Can be achieved.

In the above embodiment, the bone grafting material A is β-TCP, but instead of this, hydroxyapatite (HAP), polymethylmethacrylate (PMMA), etc., which are conventionally used as bone grafting materials. Alternatively, a plurality of types may be filled at the same time.
Even in this case, the intervertebral spacer 1 and the vertebral body C can be smoothly united with each other while preventing the intervertebral spacer 1 from biting into the vertebral body C as in the above embodiment.

Moreover, in the said embodiment, although the shape of the outer frame member 2 decided to be a cylindrical shape, it may replace with this and may be an elliptical cylinder shape or a rectangular tube shape.
By doing so, the vertebral body C can be supported more stably by using the outer frame member 2 having a shape that more closely matches the size and shape of the intervertebra B into which the intervertebral spacer 1 is inserted.

1 Intervertebral spacer 2 Outer frame member A Bone filling material B Intervertebral C Vertebral body

Claims (6)

It is provided with a cylindrical outer frame member that is inserted between the vertebrae by being filled with bone filling material inside and sandwiched in the thickness direction,
While the outer frame member has a compressive strength smaller than that of the bone grafting material in the thickness direction, the bone grafting material expands in the radial direction when a load is applied to the bone grafting material between the vertebrae. Intervertebral spacer with restrictable circumferential tensile strength.   The intervertebral spacer according to claim 1, wherein the tensile strength of the outer frame member is 15 MPa or more.   The intervertebral spacer according to claim 2, wherein the tensile strength of the outer frame member is 40 MPa or more.   The intervertebral spacer according to any one of claims 1 to 3, wherein the bone grafting material is a porous body mainly composed of β-tricalcium phosphate.   The intervertebral spacer according to any one of claims 1 to 4, wherein an inner peripheral surface of the outer frame member is formed so that a diameter dimension gradually increases toward each end surface in the vicinity of the end surface.   The intervertebral spacer according to any one of claims 1 to 5, wherein the outer frame member includes PEEK, PE, PP, or PU.

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