Implantable medical devices comprising bio-degradable alloys with enhanced degradation rates

Abstract

The invention provides medical devices comprising high-strength alloys which degrade over time in the body of a human or animal, at controlled degradation rates, without generating emboli and which have enhanced degradation due to the presence of a halogen component. In one embodiment the alloy is formed into a bone fixation device such as an anchor, screw, plate, support or rod. In another embodiment the alloy is formed into a tissue fastening device such as staple. In yet another embodiment, the alloy is formed into a dental implant or a stent.

1 . An implantable medical device comprising a biodegradable alloy, wherein the alloy is iron based and comprises an iron reactive component, wherein the alloy reacts with a bodily fluid when it is in contact with the fluid and wherein the degradation rate of the alloy when implanted in a biological subject is faster than the degradation rate of an alloy having the same composition as the said alloy except the absence of the iron reactive component. 
     
     
         2 . The implantable medical device of  claim 1 , wherein the iron reactive component has a boiling point above the melting temperature of an alloy having the same composition as the said alloy in  claim 1  except the absence of the iron reactive component. 
     
     
         3 . The implantable medical device of  claim 1 , wherein the iron reactive component is a halogen component. 
     
     
         4 . The implantable medical device of  claim 3 , wherein the halogen component is selected from chloride, fluoride, bromide and iodide. 
     
     
         5 . The implantable medical device of  claim 3 , wherein the halogen component is chloride or fluoride. 
     
     
         6 . The implantable medical device of  claim 3 , wherein the halogen component is provided as a salt. 
     
     
         7 . The implantable medical device of  claim 3 , wherein the halogen component is selected from sodium fluoride, sodium chloride, copper chloride, copper fluoride, magnesium chloride, silver chloride, calcium chloride, calcium fluoride and iron chloride. 
     
     
         8 . The implantable medical device of  claim 1 , wherein the iron reactive component is in a salt form with a boiling temperature of at least about 1600° C., at least about 1650° C., at least about 1700° C., at least about 1750° C., at least about 1800° C., at least about 1850° C., at least about 1900° C., at least about 1950° C., or at least about 2000° C. 
     
     
         9 . The implantable medical device of  claim 3 , wherein the halogen component is chlorine. 
     
     
         10 . The implantable device of  claim 1 , wherein the iron reactive component is equally dispersed within the alloy. 
     
     
         11 . The implantable device of  claim 1 , wherein the iron reactive component is dispersed on the surface of the alloy. 
     
     
         12 . The implantable medical device of  claim 1 , wherein the device degrades at a rate of about 1-2 mg per day per square inch when placed in purified water. 
     
     
         13 . The implantable medical device of  claim 1 , wherein the average grain size is about 0.5 microns to about 5.0 microns. 
     
     
         14 . The implantable medical device of  claim 1 , wherein the average grain size is stable at minimum recrystallization temperature of about 0.55 times the absolute melting temperature of the alloy. 
     
     
         15 . The implantable medical device of  claim 1 , wherein the implantable device is a bone screw, bone anchor, tissue staple, craniomaxillofacial reconstruction plate, fastener, reconstructive dental implant, or stent. 
     
     
         16 . The implantable medical device of  claim 1 , wherein the alloy comprises an austenite promoting component and a corrosion resisting component. 
     
     
         17 . The implantable medical device of  claim 1 , wherein the alloy contains between about 20% to 40% manganese. 
     
     
         18 . The implantable medical device of  claim 1 , wherein the alloy contains less than about 0.3% niobium. 
     
     
         19 . The implantable medical device of  claim 1 , wherein the alloy contains less than about 1% carbon. 
     
     
         20 . The implantable medical device of  claim 1 , wherein the biodegradable alloy comprises manganese and niobium. 
     
     
         21 . The implantable medical device of  claim 1 , wherein the biodegradable alloy comprises at least about 0.01% to about 0.1% non-metallic element. 
     
     
         22 . The implantable medical device of  claim 1 , wherein the biodegradable alloy comprises at least about 0.01% to about 0.1% carbon. 
     
     
         23 . The implantable medical device of  claim 1 , wherein the device is coated with a therapeutic agent. 
     
     
         24 . The implantable medical device of  claim 1 , wherein the device is coated with a biodegradable hydrogel. 
     
     
         25 . The implantable medical device of  claim 1 , wherein the device comprises a geometry that maximizes the surface to mass ratio. 
     
     
         26 . The implantable medical device of  claim 1 , wherein the device comprises a hollow opening or passageway. 
     
     
         27 . The implantable medical device of  claim 1 , wherein the concentration of the iron reactive component in the alloy is between about 1 ppm to about 500 ppm, between about 10 ppm to about 300 ppm, or between about 50 ppm to about 150 ppm. 
     
     
         28 . The implantable medical device of  claim 1 , wherein the concentration of the iron reactive component in the alloy is about 200 ppm, 
     
     
         29 . An implantable medical device of  claim 1 , wherein the biodegradable alloy is formed by:
 adding a gaseous iron reactive component during the melting process.   
     
     
         30 . The implantable medical device of  claim 29 , wherein the gaseous iron reactive component has a partial pressure of at least about 0.1 tor, at least about 0.2 tor, at least about 0.5 tor, at least about 0.8 tor, at least about 1 tor, at least about 2 tor, at least about 5 tor, at least about 10 tor, at least about 50 for or at least about 100 tor. 
     
     
         31 . The implantable medical device of  claim 29 , the iron reactive component is a halogen component. 
     
     
         32 . The implantable medical device of  claim 31 , wherein the halogen component is chlorine. 
     
     
         33 . The implantable medical device of  claim 29 , wherein the gaseous iron reactive component was added to mix with argon gas. 
     
     
         34 . The implantable medical device of  claim 33 , wherein the argon gas has a partial pressure of at least about 10 tor, at least about 20 tor, at least about 50 tor, at least about 80 tor, at least about 100 tor, at least about 150 tor, at least about 200 tor, at least about 250 tor, at least about 300 tor, or at least about 500 tor. 
     
     
         35 . A method of controlling the degradation rate of an implantable medical device of  claim 1  comprising a step of:
 modulating the concentration of the iron reactive component in the alloy. 
 
     
     
         36 . The method of  claim 35 , wherein the concentration of the iron reactive component in the alloy is between about 1 ppm to about 500 ppm, between about 10 ppm to about 300 ppm, or between about 50 ppm to about 150 ppm. 
     
     
         37 . The method of  claim 35 , wherein the concentration of the iron reactive component in the alloy is about 200 ppm.