Femoral prosthesis employing a small ceramic ball

Abstract

The disclosure relates to a femoral prosthesis consisting of a metal rod having a male frustoconical end portion and a femoral head, or ceramic ball, having a frustoconical blind recess, assembled by means of a conical sleeve fitment. The ceramic ball is formed of material having an improved flexion breakage modulus and an improved elasticity modulus.

We claim:  
     
       1. A femoral prosthesis comprising: 
       a metal rod comprising a first end adapted to be implanted in a femur and a second frustoconical end having a total angle greater than 4°,  
       a ceramic femoral head comprising a substantially spherical body with an outer surface having a diameter which is not more than 26   22 . 22 mm and made of a ceramic materialtetragonal zirconia having a mean grain size not more than 1 micrometer, and a 3 points flexion breakage modulus better than 920 MPa and an elastically modulus greater than 220 GPa ,  
       a blind-ended recess being provided in said body and comprising an inwardly converging frustoconical shaped recess having a total angle substantially the same as said total angle of said frustoconical end of said metal rod, said frustoconical shaped recess intersecting said outer surface of said body in a circle having an entrance diameter between about 8 and about 14 mm,  
       said frustoconical end of said metal rod being force-fitted in said blind-ended recess, said prosthesis having a rupture load of between  82  kN and  120  kN.  
     
     
       2. A femoral prosthesis according to  claim 1 , wherein said ceramic material comprises stabilized dense zirconia. 
     
     
       3. A femoral prosthesis according to  claim 2 , wherein said ceramic material contains at least 95%, by weight, of ZrO 2 . 
     
     
       4. A femoral prosthesis according to  claim 1 , wherein said ceramic material is a Hot Isostatic Pressing sintered material. 
     
     
       5. A femoral prosthesis according to  claim 1 , wherein said body has a specific mass at least equal to 98% of the theoretical density of said ceramic material. 
     
     
       6. A femoral prosthesis according to  claim 5 , wherein said ceramic material has a 3 points flexion breakage modulus greater than 1600 MPa. 
     
     
       7. A femoral prosthesis according to  claim 1 , wherein said entrance diameter is between about 10 and about 11 mm. 
     
     
       8. A femoral prosthesis according to  claim 7 , wherein said entrance diameter is substantially 10 mm. 
     
     
       9. A femoral prosthesis according to  claim 1 , wherein said total angles of said frustoconical end and said frustoconical shaped recess are at least equal to 6°. 
     
     
       10. A femoral prosthesis according to  claim 9 , wherein said total angles are about 10°. 
     
     
       11. A femoral prosthesis according to  claim 1 , wherein said body of said ceramic femoral head has a diameter which is at least about 22.22 mm. 
     
     
       12. A femoral prosthesis according to  claim 1 , wherein said frustoconical end and the surfaces defining said blind-ended recess are only in contact along an inner portion thereof, said frustoconical end and said blind-ended recess being out of contact near said outer surface of said femoral head. 
     
     
       13. A femoral prosthesis according to  claim 2 , wherein said ceramic material is a Hot Isostatic Pressing sintered material. 
     
     
       14. A femoral prosthesis according to  claim 2 , wherein said ceramic material has a specific mass of at least 6 g/cu.cm. 
     
     
       15. A femoral prosthesis according to  claim 2 , wherein said entrance diameter is between about 10 and about 11 mm. 
     
     
       16. A femoral prosthesis according to  claim 2 , wherein said total angles of said frustoconical end and said frustoconical shaped recess are at least 6°. 
     
     
       17. A femoral prosthesis according to  claim 16 , wherein said total angles are about 10°. 
     
     
       18. A femoral prosthesis according to  claim 2 , wherein said body of said ceramic femoral head has a diameter which is at least about 22.22 mm. 
     
     
       19. A femoral prosthesis according to  claim 18 , wherein said entrance diameter is about 10 mm and said total angles of said frustoconical end and said frustoconical shaped recess are about 10°. 
     
     
       20. A femoral prosthesis according to  claim 18 , wherein said ceramic material is Hot Isostatic Pressing sintered. 
     
     
       21. A femoral prosthesis according to  claim 18 , wherein the surface defining said blind-ended recess and said frustoconical end are out of contact near said outer surface of said femoral head.