Method for preparing non-toxic porous implant of polylactic acid for building of long bone defects

FIELD: medicine.

SUBSTANCE: invention refers to medicine, particularly traumatology and orthopedics, and can find application in treating false joints of long bones. What is described is a method for preparing a non-toxic porous implant of polylactic acid with controlled pore size for building of long bone defects involving melting the polylactic acid granules in a melting pot immersed in thermally stable oil with porogen presented by sodium chloride crystals 100-250 nm to be washed out by aqueous solutions of antiseptics. The implant is prepared with no toxic solvents added and has a pre-set pore diameter.

EFFECT: improved efficiency of the method.


The invention relates to medicine and can be used, in particular, in trauma and orthopaedic practice for full reparation of defects bones when diastasis up to 2-2,5 cm, in particular during the formation of the defect after resection of false joints of long bones. Upon the occurrence of traumatic defects or other situations associated with the planned resection of the pathological part of this bone, one of the promising methods is the replacement of bone defect biodegradiruemym implant.

Of the proposed methods recently drew the attention of the manufacturer of the implant from polylactic acid. The advantage of this material is reactively living tissues, hypoallergenic, long enough degradation, absence of toxic products during enzymatic depolymerization in tissues (lactic acid enters the Krebs cycle).

Requirements implant:

It must be porous (pore Diameter of 100-200 nm (Cima, L.G., Vacanti, J.P., Vacanti, C., et al. Tissue engineering by cell transplantation using degradable polymer substrates. J. Biomech. Eng. Str, 143, 1991), the pores must be connected, which promotes germination of granulation tissue, migration of fibroblasts by transforming them into osteoblasts on the walls of the pores of the matrix and subsequent biodegradation.

Following the venture is the event of obtaining a porous material of polylactic acid:

- Leaching of the particles of the evaporated or lyophilized polymer solution (A.G. Mikos, and other Preparation and characterization of polylactic acid foams. Polymer, No. 35, page 1035, 1994), in which dissolve the polymer in an appropriate organic solvent (xylene, chloroform, methylene chloride), then added to a solution of the corresponding particles of porogen, insoluble in this solvent (soluble salts and others), then remove the organic solvent and remove particles of porogen by dissolving in a polar solvent (water and others). The advantage of this method is that when using 70% of porogen by weight relative to the weight of the polymer formed pores are highly interconnected. The use of toxic organic solvents with a probability of incomplete removal of their porous structure material is a disadvantage of this method.

The foaming gas under high or ultra high pressure (Novel approach to fabricate porous sponges of poly(-lactic-co-glycolic acid) without the use of organic solvents. David J. Mooney, Daniel F. Baldwin, Nam P. Suh, Joseph P. Vacanti and Robert Langer. Biomaterials Volume 17, Issue 14, July 1996, Pages 1417-1422), requires a long time and/or equipment to create a high-pressure neutral gas.

- Phase separation, spinodal decomposition or emulsification followed by lyophilization, uses toxic organic high-molecular solvents (naphtha is in, phenol, 1,4-dioxane) or, using the techniques of emulsification and subsequent cryolipolysis obtained pore size usually does not exceed 10-30 nm, which negatively affects the dynamics of biodegradation of the polymer matrix in vivo and does not promote migration of cells into the pores of the matrix.

- Casting and after making porogen in the melt, where as porogen use gelatin - biologically reinerton substance complex protein structure (Cima, L.G., Vacanti, J.P., Vacanti, C., et al. Tissue engineering by cell transplantation using degradable polymer substrates. J. Biomech. Eng. Str, 143, 1991. Thomson, Robert C.1; Yaszemski, Michael J.2; Powers, John M.3; Mikos, Antonios G. Journal of Biomaterials Science, Polymer Edition, Volume 7, Number 1, 1996, p.23-38)having antigenic activity.

The objective of the invention is to develop methods of obtaining porous implant of polylactic acid without the use of toxic solvents with a given diameter of pores connected.

The problem is solved in that in the method of obtaining non-toxic porous implant made of polylactic acid for replacement of defects of the long bones, including the melting of the granules polylactic acid in a metal crucible with the addition of porogen, as porogen use crystals of salt the size of 100-250 nm, followed by washing in distilled water with the addition of antiseptics, while the immersed in a heated heat-resistant mineral oil.

The method is as follows.

Take a sample of pellets of polylactic acid in the amount of 30 grams of salt crystals in the amount of 15 grams, the size of the crystals of 100-250 nm, placed in a stainless steel crucible. The crucible is heated to a temperature transition of the polymer to a viscous state (185-190C). Heat transfer to the crucible from the heating element of an electric furnace with thermostat is performed by immersion of the crucible in a heat-resistant mineral oil. Temperature control is immersed in mineral oil sensor of the electronic thermometer. Upon reaching the desired temperature (~190C) and viscosity of the contents of the crucible mechanically stirred until a homogeneous state. The resulting mass is put in a cylindrical or other configuration of the metal mold and cool it. Then, after cooling, salt remove from the finished implant by means of washing with aqueous solutions of antiseptics.

The proposed method for obtaining highly porous implant of polylactic acid allows to obtain non-toxic implant, easy to use, does not require complicated hardware design.

The method allows evenly without combustion to melt granules of the polymer and to obtain a porous material with controlled pore size, dependent on the particle size of porogen, with a predictable degree of interconnectivity of the pores, not zag is ananny organic solvents.

The method of obtaining non-toxic porous implant made of polylactic acid for replacement of bone defects in long bones, including the melting of the granules polylactic acid in a metal crucible, immersed in a heat-resistant mineral oil, with the addition of porogen, characterized in that as porogen use crystals of salt the size of 100-250 nm, followed by washing them with aqueous solutions of antiseptics.


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