Uncoated biodegradable corrosion resistant bone implants

Patent metadata

Field	Value
Publication number	US-10954587-B2
Application number	US-201815933688-A
Country	US
Kind code	B2
Filing date	Mar 23, 2018
Priority date	Jun 26, 2012
Publication date	Mar 23, 2021
Grant date	Mar 23, 2021

Abstract

A preferred embodiment is an uncoated, biodegradable corrosion resistant bone implant. The implant includes a body being uncoated and lacking any protective polymer, metallic or ceramic coating, the body being shaped to fix to a bone and/or bone fragment. The body is formed of a magnesium alloy. The magnesium alloy includes from high-purity vacuum distilled magnesium containing impurities, which promote electrochemical potential differences and/or the formation of precipitations and/or intermetallic phases. The impurities are such that the body has a strength of >275 MPa, and a ratio yield point of <0.8, wherein the difference between strength and yield point is >50 MPa.

First claim

The invention claimed is:

1. An uncoated, biodegradable corrosion resistant bone implant comprising
a body being uncoated and lacking any protective polymer, metallic or ceramic coating, the body being shaped to fix to a bone or bone fragment;
the body being a magnesium alloy comprising 0.1 to 1.6% by weight of Zn, 0.001 to 0.5% by weight of Ca, with the rest being high-purity vacuum distilled magnesium containing impurities in a total amount of no more than 0.005% by weight of Fe, Si, Mn, Co, Ni, Cu, Al, Zr and P, wherein the content of Zr impurity is no more than 0.0003% by weight, and wherein the alloy contains elements selected from the group of rare earths with the atomic number 21, 39, 57 to 71 and 89 to 103 in a total amount of no more than 0.002% by weight;
wherein a ratio of the content of Zn to the content of Ca is no more than 3, wherein the alloy contains an intermetallic phase of one or both of Ca 2 Mg 6 Zn 3 and Mg 2 Ca in a volume fraction of up to 2% whereby the intermetallic phase has an anti-corrosion effect, and wherein the body has a tensile strength of >275 MPa, and a ratio yield point of <0.8.

2. The bone implant of claim 1 , wherein the body is shaped as a screw, plate, wire or pin.

3. The bone implant of claim 1 , wherein the alloy does not contain an intermetallic phase MgZn.

4. The bone implant of claim 1 , wherein the content of Ca is 0.2 to 0.45% by weight, and the alloy contains the intermetallic phase Mg 2 Ca.

5. The bone implant of claim 1 , wherein a ratio of the content of Zn to the content of Ca is no more than 1.

6. The bone implant of claim 1 , wherein individual impurities contributing to the total sum of the impurities are present in the following amounts in % by weight: Fe ≤0.0005; Si ≤0.0005; Mn ≤0.0005; Co ≤0.0002; Ni ≤0.0002; Cu ≤0.0002; Al ≤0.001; Zr ≤0.0003; P ≤0.0001.

7. The bone implant of claim 1 , wherein a combination of the impurity elements Fe, Si, Mn, Co, Ni, Cu and Al totals no more than 0.004% by weight, the content of Al is no more than 0.001% by weight, and/or the content of Zr is no more than 0.0003% by weight.

8. The bone implant of claim 1 , wherein individual elements from the group of rare earths total no more than 0.001% by weight.

9. The bone implant of claim 1 , wherein the alloy has a fine-grain microstructure with a grain size of no more than 5.0 μm without considerable electrochemical potential differences between the individual matrix phases.

10. The bone implant of claim 1 , wherein the intermetallic phase is as noble as the matrix phase or less noble than the matrix phase.

11. The bone implant of claim 1 , having precipitates with a size of no more than 2.0 μm and are distributed dispersely at the grain boundaries or inside the grain.

12. The bone implant of claim 1 , wherein a combination of the impurity elements Fe, Si, Mn, Co, Ni, Cu and Al totals no more than 0.001% by weight, the content of Al is no more than 0.001% by weight, and/or the content of Zr is no more than 0.0001% by weight.

13. The bone implant of claim 1 , wherein individual elements from the group of rare earths total no more than 0.0003% by weight.

14. The bone implant of claim 1 , wherein individual elements from the group of rare earths total no more than 0.0001% by weight.

15. The bone implant of claim 1 , wherein the alloy has a fine-grain microstructure with a grain size of no more than 3.0 μm without considerable electrochemical potential differences between the individual matrix phases.

16. The bone implant of claim 1 , wherein the alloy has a fine-grain microstructure with a grain size of no more than 1.0 μm.

17. An uncoated, biodegradable corrosion resistant bone implant comprising
a body being uncoated and lacking any protective polymer, metallic or ceramic coating, the body being shaped to fix to a bone or bone fragment;
the body being a magnesium alloy comprising 0.1 to 1.6% by weight of Zn, 0.001 to 0.5% by weight of Ca, with the rest being high-purity vacuum distilled magnesium containing impurities in a total amount of no more than 0.005% by weight of Fe, Si, Mn, Co, Ni, Cu, Al, Zr and P, wherein the content of Zr impurity is no more than 0.0003% by weight, and wherein the alloy contains elements selected from the group of rare earths with the atomic number 21, 39, 57 to 71 and 89 to 103 in a total amount of no more than 0.002% by weight;
wherein a ration of the content of Zn to the content of Ca is no more than 3, wherein the alloy contains an intermetallic phase of one or both of Ca 2 Mg 6 Zn 3 and Mg 2 Ca in a volume fraction of up to 2% whereby the metallic phase has an anti-corrosion effect, and wherein the body has a tensile strength of >300 MPa, a yield point of >225 MPa, and a ratio yield point of <0.75, wherein the difference between tensile strength and yield point is >100 MPa.

Assignees

• Biotronik Ag

Inventors

• Mueller Heinz
• Uggowitzer Peter
• Loeffler Joerg

Classifications

• C22C23/04

  with zinc or cadmium as the next major constituent · CPC title

• C22F1/06 Primary

  of magnesium or alloys based thereon · CPC title