Bioabsorbable magnesium alloy with controlled multi-phase absorption
A bioabsorbable magnesium alloy for use in an orthopedic implant comprises magnesium, zinc in an amount of 0.5-4 weight percent, calcium in an amount of 0.1-1.5 weight percent, and manganese in an amount of up to 1.5 weight percent. The alloy exhibits a controlled, multi-phase absorption profile when exposed to physiological conditions, including an initial period of minimal degradation, followed by a steady-state phase, and concluding with an accelerated absorption phase. A method of manufacturing the alloy includes casting, solution treating, and extruding. An orthopedic implant device formed from the alloy comprises a body that exhibits the controlled, multi-phase absorption profile when implanted.
1 . A bioabsorbable magnesium alloy for use in an orthopedic implant, comprising:
magnesium;
zinc in an amount of 0.5-4 weight percent;
calcium in an amount of 0.2-10 weight percent; and
manganese in an amount of 0.5-1.0 weight percent;
wherein the alloy comprises a microstructure having a Mg 2 Ca phase and ternary intermetallic phases;
wherein the Mg 2 Ca phase comprises less than 1.0 wt % of the alloy;
wherein an average diameter of Mg 2 Ca phase precipitates is less than 200 nanometers (nm);
wherein the alloy forms a protective oxide layer when exposed to physiological conditions; and
wherein the alloy exhibits a controlled, multi-phase absorption profile when exposed to physiological conditions, the profile comprising an initial period of minimal degradation, followed by a steady-state phase, and concluding with an accelerated absorption phase.
2 . The bioabsorbable magnesium alloy of claim 1 , wherein the zinc is present in an amount of greater than 2 weight percent and less than or equal to 4 weight percent.
3 . The bioabsorbable magnesium alloy of claim 1 , wherein the calcium is present in an amount of 0.3-0.8 weight percent.
4 . The bioabsorbable magnesium alloy of claim 1 , wherein the manganese is present in an amount of 0.6-1.0 weight percent.
5 . The bioabsorbable magnesium alloy of claim 1 , wherein the initial period of minimal degradation lasts for 7-14 days, the steady-state phase extends from approximately 2 to 8 weeks post-implantation, and the accelerated absorption phase begins after 8-12 weeks.
6 . The bioabsorbable magnesium alloy of claim 1 , magnesium acts as an anodic phase and the ternary intermetallic phases acts as cathodic phases, and the alloy has an anode-to-cathode ratio of at least 20:1.
7 . A bioabsorbable magnesium alloy for use in an orthopedic implant, comprising:
magnesium;
zinc in an amount of 0.5-4 weight percent;
calcium in an amount of 0.2-1.0 weight percent; and
a third alloying element in an amount of 0.1-1.0 weight percent;
wherein the alloy comprises a microstructure having:
a ternary intermetallic phase with a volume fraction between 0.5% and 5%;
the ternary intermetallic phase having an average particle size between 50 nm and 500 nm; and
Mg 2 Ca phase present in a volume fraction of less than 1% with an average particle diameter of less than 200 nm;
wherein the alloy exhibits a controlled, multi-phase absorption profile when exposed to physiological conditions, the profile comprising an initial period of minimal degradation, followed by a steady-state phase, and concluding with an accelerated absorption phase.
8 . The bioabsorbable magnesium alloy of claim 7 , wherein the ternary intermetallic phase comprises Ca 2 Mg 6 Zn 3 .
9 . The bioabsorbable magnesium alloy of claim 7 , wherein the ternary intermetallic phase has a volume fraction between 1% and 3%.
10 . The bioabsorbable magnesium alloy of claim 7 , wherein the ternary intermetallic phase has an average particle size between 100 nm and 300 nm.
11 . The bioabsorbable magnesium alloy of claim 7 , wherein the Mg 2 Ca phase is present in a volume fraction of less than 0.5%.
12 . The bioabsorbable magnesium alloy of claim 7 , wherein the Mg 2 Ca phase has an average particle diameter of less than 100 nm.
13 . The bioabsorbable magnesium alloy of claim 7 , wherein the alloy forms a protective oxide layer when exposed to physiological conditions, the protective oxide layer having a thickness between 10 nm and 500 nm.
14 . An orthopedic implant device, comprising:
a body formed from a bioabsorbable magnesium alloy, the alloy comprising magnesium, 1-4 weight percent zinc, 0.2-1.0 weight percent calcium, and 0.3-1.0 weight percent manganese;
wherein the alloy comprises a microstructure having a lower amount of Mg 2 Ca phase relative to ternary intermetallic phases;
wherein the ternary intermetallic phases comprise Ca 2 Mg 6 Zn 3 and have a volume fraction between 0.5% and 5%,
wherein the alloy forms a protective oxide layer when exposed to physiological conditions, the protective oxide layer having a thickness between 10 nm and 500 nm; and
wherein the alloy exhibits a controlled, multi-phase absorption profile when exposed to physiological conditions, the profile comprising an initial period of minimal degradation, followed by a steady-state phase, and concluding with an accelerated absorption phase.
15 . The orthopedic implant device of claim 14 , wherein the zinc is present in an amount of 2-2.5 weight percent, the calcium is present in an amount of 0.8-1.0 weight percent, and the manganese is present in an amount of 0.6-1.0 weight percent.
16 . The orthopedic implant device of claim 14 , wherein the ternary intermetallic phases has an average particle size between 50 nm and 500 nm.
17 . The orthopedic implant device of claim 14 , wherein the Mg 2 Ca phase is present in a volume fraction of less than 0.5% with an average particle diameter of less than 100 nm.
18 . The orthopedic implant device of claim 17 , wherein the device is configured for use in maxillofacial trauma and reconstruction applications.