Method and system for fabricating artificial bone implants

Abstract

A process for making bone implants from calcium phosphate powders is disclosed. This process involves selectively fusing layers of calcium powders that have been coated or mixed with polymer binders. The calcium powder mixture may be foamed into layers and the polymer fused with a laser. Complex three-dimensional geometrical shapes can be automatically replicated or modified using this approach.

What is claimed is:  
     
         1 . A method for making an implant, comprising the steps of: 
 (a) forming a mixture of a calcium phosphate and a polymer binder; and    (b) selectively fusing the polymer binder to form an implant.    
     
     
         2 . The method of  claim 1 , wherein the mixture comprises a plurality of agglomerated polymer-coated calcium phosphate particles.  
     
     
         3 . The method of  claim 2 , wherein the polymer-coated particles are formed by spray drying an aqueous mixture of the calcium phosphate and the polymer binder.  
     
     
         4 . The method of  claim 1 , further comprising the steps of infiltrating and thermally sintering the implant.  
     
     
         5 . The method of  claim 4 , wherein the implant is infiltrated with a calcium phosphate solution.  
     
     
         6 . The method of  claim 1 , further comprising the step of thermally sintering the implant.  
     
     
         7 . The method of  claim 6 , further comprising the steps of infiltrating and again thermally sintering the implant.  
     
     
         8 . The method of  claim 7 , wherein the implant is infiltrated with a calcium phosphate solution.  
     
     
         9 . The method of  claim 1 , wherein the polymer binder is selectively fused with a laser beam.  
     
     
         10 . The method of  claim 9 , wherein the polymer binder is selectively fused to replicate a desired geometrical shape.  
     
     
         11 . The method of  claim 9 , wherein the polymer binder is selectively fused to form a desired geometrical shape.  
     
     
         12 . The method of  claim 10  or  claim 11 , wherein the desired geometrical shape is communicated to the laser beam by a computer.  
     
     
         13 . The method of  claim 12 , wherein the desired geometrical shape is obtained from computed tomographic data.  
     
     
         14 . The method of  claim 12 , wherein the desired geometrical shape is obtained from computer aided design software data.  
     
     
         15 . The method of  claim 1 , wherein the calcium phosphate is prepared by reacting aqueous solutions of hydroxyapatite and phosphoric acid.  
     
     
         16 . The method of  claim 1 , wherein the calcium phosphate is selected from the group consisting of: 
 calcium metaphosphate, calcium pyrophosphate, calcium phosphate with from about 25 to about 45 percent by weight calcium oxide, and calcium phosphate with from about 0.5 to about 2 percent by weight sodium oxide.    
     
     
         17 . The method of  claim 1 , wherein the calcium phosphate comprises calcium metaphosphate.  
     
     
         18 . The method of  claim 1 , wherein the calcium phosphate has a mean particle size of from about 5 to about 100 microns.  
     
     
         19 . The method of  claim 1 , wherein the calcium phosphate has a mean particle size of from about 30 to about 50 microns.  
     
     
         20 . The method of  claim 1 , wherein the polymer binder has the following properties: 
 (a) a T g  of between about 40° C. and about 100° C.; and    (b) a melt flow index of between about 1 and about 50 g/10 minutes at 200° C. and 75 psi extrusion pressure.    
     
     
         21 . The method of  claim 20 , wherein the polymer binder comprises a homopolymer, copolymer, or terpolymer of methyl methacrylate.  
     
     
         22 . The method of  claim 21 , wherein the polymer binder comprises a poly(methyl methacrylate-co-n-butyl methacrylate) copolymer.  
     
     
         23 . The implant produced in accordance with the method of  claim 1 .  
     
     
         24 . The implant produced in accordance with the method of  claim 9 .  
     
     
         25 . A method for making an implant, comprising the steps of: 
 (a) forming a mixture of a calcium phosphate and a polymer binder;    (b) forming a layer of the mixture;    (c) selectively fusing the polymer binder; and    (d) repeating steps (b) and (c) a desired number of times to form a plurality of layers, wherein each layer is fused to adjacent layers to form an implant.    
     
     
         26 . The method of  claim 25 , wherein the thickness of each layer is from about 3 to about 12 thousandths of an inch.  
     
     
         27 . The method of  claim 25 , wherein the implant has a mean pore size of from about 100 to about 300 microns.  
     
     
         28 . The method of  claim 25 , wherein the implant has a relative density of from about 50 to about 80%.  
     
     
         29 . The implant produced in accordance with the method of  claim 25 .  
     
     
         30 . A system for making an implant, comprising: 
 (a) a mixture of a calcium phosphate and a polymer binder; and    (b) means for selectively fusing the polymer binder to form an implant.    
     
     
         31 . The system of  claim 30 , further comprising means for forming layers of the mixture.  
     
     
         32 . The system of  claim 30  or  31 , wherein the fusing means comprise a laser beam.  
     
     
         33 . The system of  claim 30 , further comprising means for controlling the fusing means to form the implant in a desired geometrical shape.  
     
     
         34 . The system of  claim 33 , wherein the controlling means comprise computed tomographic data.  
     
     
         35 . The system of  claim 33 , wherein the controlling means comprise computer aided design software.