BIORESORBABLE IMPLANTS MADE OF EXTRUDED POWDER WITH VARYING CHEMICAL COMPOSITION

Abstract

The invention relates to a powder mixture for producing an alloy, a powder metallurgy process for producing a material, a material, and a medical implant made from it.

Claims

1. A powder mixture for production of an alloy by powder metallurgy, the powder mixture comprising: a first metal powder selected from the group consisting of magnesium, aluminum, zinc, calcium, and iron; at least one second metal powder different from the first metal powder, the at least one second metal powder selected from the group consisting of magnesium, aluminum, zinc, calcium, and iron; at least one metal salt powder; and optionally at least one powder of a bioresorbable, eutectic metal alloy.

2. The powder mixture according to claim 1, wherein the first metal powder is magnesium.

3. The powder mixture according to claim 1, wherein the at least one metal salt powder is selected from the group consisting of magnesium hydrogen phosphate, magnesium carbonate, calcium phosphate, tricalcium phosphate, calcium carbonate, calcium hydroxide, calcium fluoride, lithium stearate, calcium stearate, magnesium stearate, zinc pyrophosphate, and zinc carbonate.

4. The powder mixture according to claim 1, wherein the first metal powder has a proportion of 40-95 weight %, the second metal powder a proportion of 2-60 weight %, the metal salt powder a proportion of 4-15 weight %, and the powder made of a bioresorbable metal alloy a proportion of 0-25 weight %, all components adding up to 100 weight %.

5. The powder mixture according to claim 1, wherein the particles of the first metal powder have a particle size of <45 m.

6. A powder metallurgy process for producing a material from a bioresorbable alloy, the process comprising the steps of: preparing the powder mixture according to claim 1; pressing the powder mixture to produce a semi-finished product; hot working the semi-finished product to produce a material made of a bioresorbable alloy.

7. The process according to claim 6, wherein the step of hot working the semi-finished product is done by extrusion.

8. The process according to claim 6, wherein the powder mixture is pressed, with a pressure in the range from 1 kPa to 20 kPa, into the semi-finished product.

9. The process according to claim 6, wherein the semi-finished product is heated to a temperature in the range from 200 C. to 500 C. during the hot working.

10. The process according to claim 6, wherein the material made of the bioresorbable alloy is shaped into a medical implant.

11. A material produced by the process according to claim 6.

12. A bioresorbable medical implant that is produced according to claim 10.

13. A bioresorbable medical implant whose base body and surface are polymer-free, porous, and active ingredient-eluting.

14. The implant according to claim 13, wherein at least one active ingredient is located in the pores of the surface of the implant.

15. The implant according to claim 14, the implant being selected from the group consisting of an intramedullary nail, a bone plate, a vascular implant, and a stent.

Description

DETAILED DESCRIPTION

[0077] The discussion below is intended to explain other features and advantages of this invention on the basis of individual embodiments or examples of the invention.

Example 1

[0078] A powder mixture made of 10.98 g pure Al (99.9%) and 89.02 g pure Mg (99.9%) is weighed out and homogenized in a ball mill at 3,000 rpm. To these 100 g of powder, 10 g of another powder mixture are added. This powder mixture consists of 5.00 g of tricalcium phosphate and 5.00 g of zinc pyrophosphate. This second powder mixture was previously homogenized under the same conditions. This powder mixture that now consists of 4 components is filled into a hollow cylindrical pressing device which has a diameter of 5.00 mm and a depth of at least 26 mm. The bottom of this hollow cylinder is tightly closed by a suitable device. The filling height of the powder mixture is about 10 mm. Following that, a slightly undersized die with a diameter of 4.99 mm is introduced, and the powder mixture is pressed at room temperature and a pressure force of about 3 kN. This reduces the original 10 mm height of packing of the powder mixture to about 6 mm. After the bottom of the hollow cylinder is opened, it is now possible to press the pressed preform out using the same die. This cylindrical blank is then processed into a hollow cylinder by shaping processes that involve machining. The resulting inside diameter is 1.6 mm. In the next step, this hollow cylinder is put on a hard metal die whose outside diameter is about 1.58 mm. The hard metal die with the blank put on it is pushed so that it is centered into a matrix that has been preheated (e.g., by means of induction) to 280 C., and the blank is shaped, with a pressure force of about 5 kN, into a miniature tube. This tube with outside diameters between 2.0 and 3.00 mm can then undergo further processing to shape it into a wide range of absorbable implants such as cannulated Kirschner wires, surgical screws, or stents for coronary but also peripheral applications. The degradation time of such implants is between 2 months and 18 months, depending on the wall thickness profile.

Example 2

[0079] A powder mixture made of 47.04 g pure Zn (99.9%) and 52.96 g pure Mg (99.9%) is weighed out and homogenized in a ball mill at 3,000 rpm. The further steps are the same as in example 1, except that the temperature used is 325 C. and the pressure force is 7 kN.

Example 3

[0080] A powder mixture made of 47.04 g pure Fe (99.9%) and 52.96 g pure Mg (99.9%) is weighed out and homogenized in a ball mill at 3,000 rpm. To these 100 g of powder, 10 g of another powder mixture are added. This powder mixture consists of 5.00 g of calcium fluoride and 5.00 g of zinc pyrophosphate. This third powder mixture was previously homogenized under the same conditions. This powder mixture that now consists of 4 components is filled into a hollow cylindrical pressing device which has a diameter of 5.00 mm and a depth of at least 26 mm. The bottom of this hollow cylinder is tightly closed by a suitable device. The filling height of the powder mixture is about 10 mm. Following that, a slightly undersized die with a diameter of 4.99 mm is introduced, and the powder mixture is pressed at room temperature and a pressure force of about 3 kN. This reduces the original 10 mm height of packing of the powder mixture to about 7 mm. After the bottom of the hollow cylinder is opened, it is now possible to press the pressed preform out using the same die. This cylindrical blank then undergoes machining processes to shape it into a hollow cylinder. The resulting inside diameter is 1.6 mm. In the next step, this cylindrical blank is put on a hard metal die whose outside diameter is about 1.58 mm. The hard metal die with the blank put on it is pushed so that it is centered into a matrix that has been preheated (e.g., by means of induction) to 420 C., and the blank is shaped, with a pressure force of about 7 kN, into a miniature tube. This tube test with outside diameters between 2.0 and 3.00 mm can then undergo further processes to shape it into a wide range of absorbable implants such as cannulated Kirschner wires, surgical screws, or stents for coronary but also peripheral applications. The degradation time of such implants is between 2 months and 18 months, depending on the wall thickness profile.

Example 4

[0081] A powder mixture made of 47.04 g pure Zn (99.9%) and 52.96 g pure Mg (99.9%) is weighed out and homogenized in a ball mill at 3,000 rpm. To these 100 g of powder, 10 g of another powder mixture are added. This powder mixture consists of 5.00 g of calcium fluoride and 5.00 g of magnesium carbonate. This second powder mixture was previously homogenized under the same conditions. The further steps are the same as in example 1, except that the temperature used is 325 C. and the pressure force is 7 kN.