Bone substitute material

Abstract

A method of fabricating a bone substitute material comprises the steps of providing a foam material ( 3 ) having an open cell structure, distorting the shape of the foam material ( 3 ) and holding the material in a distorted shape, coating the walls of the cells of the foam material with a ceramic slip ( 5 ), removing the foam material, and sintering the ceramic slip to form a bone substitute material that is approximately a positive image of the distorted foam material ( 3 ). In another method, a granular bone material is formed from a multiplicity of pieces of foam that are not distorted.

1 - 19 . (canceled) 
     
     
         20 . A method of fabricating a granular bone substitute ozutcrial, the method comprising the steps of:
 providing a multiplicity of pieces of foam material having an open cell structure, each occupying a space of less than 1000 mm 3 ,   coating the walls of the cells of the pieces of foam material with a ceramic slip,   removing the foam material, and   sintering the ceramic slip to form a granular bone substitute aterial in which the granules are approximately positive images of the pieces of foam material.   
     
     
         21 . A method according to  claim 20 , in which the pieces of foam material have a maximum dimension of less than 12 mm. 
     
     
         22 . A method according to  claim 20 , in which the pieces of foam material are of irregular shape. 
     
     
         23 . A method according to  claim 20 , in which the pieces of foam material are approximately cubes. 
     
     
         24 . A method according to  claim 23 , in which the cubes have sides of length less than 8 mm. 
     
     
         25 . A method according to  claim 20 , in which the pieces of foam material are all of substantially the same size. 
     
     
         26 . A method according to  claim 20 , in which the pieces of foam material vary in size and/or shape. 
     
     
         27 . A method according to  claim 20 , further comprising the step of treating the granular sintered material to reduce the size of and/or alter the shapes of the granules. 
     
     
         28 . A method according to  claim 27 , in which the treating step comprises a milling step. 
     
     
         29 . A method according to  claim 28 , in which the milling step comprises ball milling. 
     
     
         30 . A method according to  claim 20 , in which the step of removing the foam material comprises heating the material. 
     
     
         31 . A method according to  claim 30 , in which the method comprises a first heating step in which the foam material is removed and a second, subsequent, heating step in which the ceramic slip is heated to a higher temperature and is sintered. 
     
     
         32 . A method according to  claim 20 , in which the step of coating the walls of the cells of the pieces of foam material with a ceramic slip includes the steps of immersing the pieces of foam material in the ceramic slip and draining some of the ceramic slip from the pieces of foam material. 
     
     
         33 . A method according to  claim 32 , in which the step of draining some of the ceramic slip from the pieces of foam material comprises the step of supporting the pieces of foam material on a perforated support surface. 
     
     
         34 . A method according to  claim 32 , in which the immersing and draining steps are repeated. 
     
     
         35 . A method according to  claim 20 , in which the pieces of foam material are mechanically compressed and then allowed to expand while they are immersed in the ceramic slip. 
     
     
         36 . A method according to  claim 20 , in which air is directed onto the coated foam material to inhibit the formation of closed cells. 
     
     
         37 . A method according to  claim 20 , in which the foam material is a polymeric foam material. 
     
     
         38 . A method according to  claim 20 , in which the granular bone substitute material has a macroporosity in the range of 40 to 70%. 
     
     
         39 . A method according to  claim 20 , in which more than half the macroporosity of the material is provided by pores having an equivalent diameter in the range of 150 to 450 μm. 
     
     
         40 . A granular bone substitute material comprising a multiplicity of granules of a porous sintered ceramic, each granule having approximately the form of a positive image of an open celled foam material the walls defining the cells within the granules being hollow and the granule occupying a space of less than 1000 mm 3 . 
     
     
         41 . A granular bone substitute material according to  claim 40 , in which the material has a macroporosity in the range of 40 to 70%. 
     
     
         42 . A granular bone substitute material according to  claim 40 , in which more than half of the macroporosity of the material is provided by pores having an equivalent diameter in the range of 150 to 450 μm. 
     
     
         43 . A granular bone substitute material according to  claim 40 , in which the material has a compressive modulus at a load of 500 N of more than 40 MPa. 
     
     
         44 . A granular bone substitute material according to  claim 40 , in which the granules have a maximum dimension of less than 12 mm. 
     
     
         45 . A granular bone substitute material according to  claim 40 , in which the granules are of irregular shape. 
     
     
         46 . A granular bone substitute material according to  claim 40 , in which the granules are approximately cubes. 
     
     
         47 . A granular bone substitute material according to  claim 46 , in which the cubes have sides of length less than 8 mm. 
     
     
         48 . A granular bone substitute material according to  claim 40 , in which the granules have rounded edges. 
     
     
         49 . A granular bone substitute material according to  claim 40 , in which the granules are all of substantially the same size. 
     
     
         50 . A granular bone substitute aterial according to  claim 40 , in which the granules vary in size and/or shape. 
     
     
         51 - 61 . (canceled)