Composite porous material for bone replacement and method of its manufacture

 

(57) Abstract:

The invention relates to medicine and can be used for the manufacture of bone prostheses and reconstructive surgery. Composite porous material includes a fibrous reinforcing the Foundation and the matrix, reinforcing the base is made in the form of a frame containing the vertically mounted rods and horizontal layers, each of which is formed by rods, and the rods are formed of carbon fibers and a matrix made of pyrocarbon. The rods of each layer is oriented relative to the rods next and previous layers at an angle of 60o. A method of making a porous composite material includes forming the reinforcing substrate in the form of a frame in layers of rods formed from carbon fibers, directing them in each layer are parallel relative to each other, and then into the vertical channels introduce additional rods, and the matrix is formed by deposition of pyrocarbon from a gaseous environment containing at least one hydrocarbon, at a temperature above the temperature of its decomposition to changes in the mass of material not less than 3 times. Carbon composite parity compatibility and electrical conductivity. 2 C. and 7 C.p. f-crystals, 1 Il.

The invention relates to medicine and can be used for the manufacture of bone prostheses and reconstructive surgery.

Currently, for the manufacture of implants and replacement of bone defects in reconstructive surgery are used metals and alloys, polymers and ceramics, as well as bioactive calcium phosphate glass and glass ceramics. The advantage of the latter is the similarity of their chemical and mineralogical compositions composition of bones. However, these artificial bioactive materials in its structure and texture hardly correspond bone tissues, another disadvantage is the brittleness and poor mechanical machinability, which greatly complicates the accurate adjustment of the implants to living bone.

Known bioactive microporous material for bone surgery, containing hydroxyapatite, Salomatina and a blowing agent. As stellamarisa use neutral aluminosilicate glass, and as the pore-forming - carbonates of magnesium and calcium (RF Patent 2053737).

Known material made of a mixture of hydroxyapatite, the matrix glass and preobrazheniyu 700-1000oC. the Porosity of the finished product depends on the ratio of components of the mixture, sintering and foaming and changes in the range of 5-80%. Bending strength of a material depends on its porosity and is in the range from 10 to 60 MPa. To produce a material with increased strength in the initial mixture is injected reinforcing fibers. From the obtained material machining by cutting, drilling, grinding, etc. are made endoprostheses and implants.

The known material is fragile and poorly machinable, which greatly complicates the accurate adjustment of the implants to living bone.

The present invention is directed to the creation of a carbon composite porous material, combining chemical and thermal resistance, high structural strength, biocompatibility and electrical conductivity.

To ensure the technical result in the composite porous material including fibrous reinforcing the Foundation and the matrix, reinforcing the base is made in the form of a frame containing the vertically mounted rods and horizontal layers, each of which is formed by rods, and the rods form the additional rods next and previous layers at an angle of 60o.

The material contains pores of a size of 100-1000 μm, and the proportion of these pores in the material is equal to not less than 5 vol.%, with a total porosity of no more than about 20. %. The limit of the compressive strength of the material is not less than 50 MPa, the density is 1.6-1.7 g/cm3. Mass fraction of reinforcing substrate in the mass matrix is not less than 0.4. A method of making a porous composite material includes forming the reinforcing substrate in the form of a frame in layers of rods formed from carbon fibers, directing them and each layer in parallel relative to each other, and then into the vertical channels introduce additional rods, and the matrix is formed by deposition of pyrocarbon from a gaseous environment containing at least one hydrocarbon, at a temperature above the temperature of its decomposition to changes in the mass of material not less than 3 times.

The rods forming the layer, set parallel to each other and at an angle of 60orelative to the rods of the previous and subsequent layers. In each layer, the rods have a distance of not less than the diameter of the rod.

Pyrocarbon precipitated in the medium, at least one hydrocarbon group containing azzaretti possible deposition of natural gas at 750-950oC.

The essence of the invention include 2 - material and method, is that the molded structure of the carbon rods in the form of a frame connected pyrocarbon matrix in a single carbon material without damaging the integrity of the structure and contains many regularly spaced pores.

High mechanical properties of the material resulting from the features of the obtained patterns together with biocompatibility and good machinability provided through the use of carbon allow the use of material for the manufacture of prostheses and implants, bones and joints.

In the drawing in schematic form the structure of a reinforcing frame made of carbon fiber.

For forming a reinforcing carcass use of fibrous reinforcing elements are rods made of carbon fibers oriented along the axis of the rod, which provides the most complete implementation of the modulus carbon fiber without damaging its structure. For receiving the rods, in particular, you can use pultrusion, comprising the following stages:

- impregnated carbon fibers p is through the die plate to obtain the desired cross section of the rod;

curing of the binder.

Optimal conditions for production of carbon fiber reinforcing elements determined by varying the concentration of the PVA solution, the oven temperature curing, the speed of passage of the wire harnesses through the spunbond unit. The main monitoring value is the strength of the elements in three-point bending with a base definition of 100 mm

Of carbon fibers, formed into rods, assemble in layers frame on the graphite mandrel. At the first stage of Assembly in the holes around the perimeter of the mandrel installed elements-rods vertically, then assemble horizontal layers, setting the rods in the layer parallel relative to each other and at an angle of 60owith respect to the terminals of the previous and subsequent layers. After laying horizontal layers at the desired height of the resulting end-to-end channels install additional rods. Collected in this way the frame shown in the drawing, where 1 is the rods in horizontal layers, 2 - vertical rods, 3 - graphite mandrel. Further, the frame of rods formed from carbon fibres are placed in a reactor, and in an environment of gaseous hydrocarbons (hydrocarbons) at a temperature higher than the Noah matrix. Low molecular weight hydrocarbons - methane, ethane, acetylene, propane, benzene, etc. and their mixtures, such as natural gas at a specified temperature, usually in the range of 550-1200oWith that can come in a heterogeneous chemical reaction of decomposition according to the scheme:

< / BR>
The reaction of 1 in the pores of a carbon fiber frame provides for the formation of pyrocarbon matrix. For a process you can use a reactor made of stainless steel 18CR10NITI. The heating is carried out through a graphite rod or plate by passing electric current. The plant is equipped with means for the supply, regulation and measurement of gas flow. At the end of the process, the mandrel is removed.

As a result of implementation of the described method were made of carbon composite materials with a porosity of 5% and higher, which can be adjusted.

Basic physical and mechanical properties of the obtained composite material was determined by the following methods:

1. Determination of apparent density and open porosity - GOST 474.4-81.

2. Determination of ultimate strength in compression OST 3-4579-80.

3. Determination of tensile strength and modulus of elasticity in static 3-point shevarash the requirements of GOST 7855-74.

The invention can be illustrated by the following example.

An example of manufacturing of the material.

Reinforcing rods with a diameter of 1.3 mm, formed of three carbon fiber bundles brand Chis - 5000 ultronia using a tie - PVA, collected in the framework as follows:

1. On the graphite mandrel is installed vertically along its perimeter holes in the rod guide.

2. In the horizontal plane on the frame, perpendicular to the rails, put the rods at a distance of 1.3 mm from each other, parallel to each other.

3. The next layer is formed on the first stacking rods at the same distance from each other, parallel to each other, at an angle of 60oto the terminals of the first layer.

4. The next layer is formed on the second stacking rods at the same distance from each other, parallel to each other, at an angle of 60oto the terminals of the second layer and so on, the desired height of material receiving, stacking the desired number of layers.

5. Formed in the vertical channels of the frame to install additional rods, seeking to maximize the density of the skeleton.

6. The formation of the pyrocarbon matrix proizvoda.

Properties of the obtained material, including those described in the example:

Porosity,% vol. - 3-20

The tensile strength in bending, MPa - 50-130

The modulus of elasticity, GPA - 30-40

Resistivity, OSM - 1,610-2< / BR>
High mechanical properties of the inventive composite material and manufacturability of mechanical processing can be used as implants and prostheses during operations on bones and joints.

The porosity of such materials is more important, because the presence of pores allows bone tissue to grow into the implant or prosthesis that provides direct contact with the last bone (without connective tissue layer).

From the material obtained according to the invention, were manufactured by sawing, drilling, grinding and other methods of mechanical treatment implants and implants, in particular for arthroplasty of the spine for anterior spinal fusion.

In terms of the experimental laboratory of the research Institute of Phthisiopulmonology were performed surgery on rabbits with implantation of various grades of carbon material in different parts of the femur (Epimetheus, epiphysis).

R is presumed to resorption, bone intact to the carbon material, the material is not conducive to the formation of connective tissue capsule on the border of the bone-implant. Close values of the elastic modulus of the obtained material and bone tissue allow the system when the load of work as a whole.

The inventive material is biologically more inert compared with plastics, ceramic materials and metals. It is important that the material can have different levels of properties (strength, stiffness, and others) depending on the structure and modes of reception, to combine the gradient - functional properties. High temperature for the material ensures the sterility of the samples, and chemical and thermal resistance to allow sterilizing material in a variety of ways.

Experimental study and clinical trial material according to the invention, were carried out to identify opportunities for replacement of bone defects, including replacement of the vertebral bodies, destroyed by tuberculosis, tumors and other pathological processes.

The studies found the optimal form of use of this material, developed technology, it is l inert to the bone, does not cause any negative reactions from the bone bed, firmly fixed in it, because the bone tissue of the host grows into the pores and cavities on the surface of the implant, intimately contacting it.

Long-term experimental studies, which lasted about 4 years, showed that in this period the implant is so firmly fixed in the bone that mechanical removal without Paloma this is impossible, and he is so durable that the sawing using a conventional cutters can not be. Therefore, the qualities of this material, due to inertia in relation to the tissues, the strength of fixation in bone and mechanical properties is an ideal material for replacement.

The clinical trial was the use of the proposed material for joint replacement and replacement of defects of the vertebral bodies with a length of 11 cm in 34 patients provided above diseases. When monitoring patients for up to 4 years any negative effects of this material was not observed. 2 patients had negative results of operations: in 1 case relating to technical error in the period of development of methods who came stabilization replaced with implants, spine, the restoration of the anatomical relations and functions.

To date, there are all the conditions for widespread production and use of the specified material, possessing, as it was found during testing, the advantages compared to previously known, including for development on its basis of various implants and implants, applicable in clinical practice.

1. Composite porous material for bone replacement, including fibrous reinforcing framework and matrix of pyrocarbon, characterized in that the reinforcing base is made in the form of a frame containing the vertically mounted rods and horizontal layers, each of which is formed by rods formed of carbon fibers oriented along the axis of the rods, for example, ultreia, the rods forming the layer are parallel relative to each other, and the rods of each layer is oriented relative to the rods next and previous layers at an angle of 60oWith the material contains pores of a size of 100-1000 microns.

2. The material under item 1, characterized in that its density is 1.6-1.7 g/cm3.

3. The material under item 1 or 2, characterized in that the Pori-1000 μm is not less than 5% of the volume of material.

5. Material according to any one of paragraphs. 1-4, characterized in that the mass fraction of the cage material is not less than 30%.

6. A method of manufacturing a composite porous material for bone replacement, including the formation of fibrous reinforcing substrate and the matrix by deposition of pyrocarbon from the gas environment containing hydrocarbon, characterized in that the reinforcing base is formed with a frame in layers of rods formed of carbon fibers oriented along the axis of the rods, for example, ultreia, directing them in each layer are parallel relative to each other at an angle of 60oWith respect to the terminals of the previous and subsequent layers, and after laying a specified number of layers formed in the vertical channels introduce additional rods, the matrix is formed by deposition of pyrocarbon from a gaseous environment containing at least one hydrocarbon, at a temperature above the temperature of its decomposition, to increase the weight of the material is not less than 3 times.

7. The method according to p. 6, characterized in that the rods in the layer have a distance of not less than the diameter of the rod.

8. The method according to p. 6 or 7, characterized in that the pyrocarbon acosado in the environment of at least one hydrocarbon group, containing acetylene, methane, propane, pentane, hexane, benzene and their derivatives, when 550-1200oC.

 

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