Hip stem prosthesis with a porous collar to allow for bone ingrowth

Abstract

A femoral hip implant includes a first end, a second end, and a collar with a porous surface, all fabricated from a single piece of material. The entire area of the collar is porous, and the collar elastically deflects under load to promote bone ingrowth.

I claim: 
     
         1 . A bone implant apparatus comprising:
 a first end having a substantially smooth surface to inhibit bone ingrowth;   a second end extending from the first end in a non-coaxial fashion, the second end having a tapered shape and a surface, at least a portion of which comprises a porous surface to allow bone ingrowth; and   a collar located between the first end and the second end, the collar comprising a surface at least a portion of which comprises a porous surface to allow bone ingrowth into the collar.   
     
     
         2 . The bone implant apparatus of  claim 1 , wherein the first end, the second end, and the collar comprise a single piece of material. 
     
     
         3 . The bone implant apparatus of  claim 1 , wherein the entire surface area of the collar is porous. 
     
     
         4 . The bone implant apparatus of  claim 1 , wherein the collar further comprises a top surface and a bottom surface, both of which are porous. 
     
     
         5 . The bone implant apparatus of  claim 4 , wherein the top surface and the bottom surface of the collar are generally parallel. 
     
     
         6 . The bone implant apparatus of  claim 4 , wherein the portion of the surface of the second end comprising a porous surface extends along the top surface and the bottom surface of the collar. 
     
     
         7 . The bone implant apparatus of  claim 4 , wherein the bottom surface of the collar forms an angle with a longitudinal axis of the bone implant apparatus of from about 45 degrees to about 130 degrees. 
     
     
         8 . The bone implant apparatus of  claim 7 , wherein the bottom surface of the collar forms an angle with the longitudinal axis of the bone implant apparatus of about 110 degrees. 
     
     
         9 . The bone implant apparatus of  claim 1 , wherein the collar comprises a substantially semicircular projection from the second end of the bone implant apparatus in a direction substantially normal to the second end. 
     
     
         10 . The bone implant apparatus of  claim 1 , wherein at least a portion of the surface of the bone implant apparatus comprises a substantially smooth surface that restricts bone ingrowth. 
     
     
         11 . The bone implant apparatus of  claim 1 , wherein the collar elastically deflects under load to stimulate bone growth. 
     
     
         12 . The bone implant apparatus of  claim 11 , wherein the elastic deflection of the collar is between 0.004 inches and 0.02 inches when subjected to a load of 188 pounds. 
     
     
         13 . The bone implant apparatus of  claim 11 , wherein the elastic deflection of the collar is greater than 0.004 inches when subjected to a load of 188 pounds. 
     
     
         14 . The bone implant apparatus of  claim 1 , wherein the porous surfaces of the second end and the collar comprise a diamond cubic unit cell geometry. 
     
     
         15 . The bone implant apparatus of  claim 1 , wherein the bone implant apparatus is fabricated from a biocompatible material. 
     
     
         16 . The bone implant apparatus of  claim 1 , wherein the collar comprises a non-porous metal surface with a thickness of from about 0.005 inches to about 0.025 inches. 
     
     
         17 . The bone implant apparatus of  claim 1 , wherein the collar has a length of from about 12% to about 26% of a cross-sectional dimension of the second end of the implant. 
     
     
         18 . A method for total hip replacement, comprising:
 providing a femoral hip implant comprising a first end, the first end having a substantially smooth surface to inhibit bone ingrowth, a second end having a substantially tapered shape and extending from the first end in a non-coaxial fashion, at least a portion of which comprises a porous surface to allow bone ingrowth, and a collar located between the first end and the second end, at least a portion of the collar having a porous surface to allow bone ingrowth;   inserting the second end of the femoral hip implant into a femur; and   positioning the femoral hip implant to subside into the femur until the collar contacts the femur so that the porous surfaces of the second end and the collar are aligned with bone to allow bone ingrowth.   
     
     
         19 . The method of  claim 18 , wherein the collar of the femoral hip implant elastically deflects upon loading and unloading of the femoral hip implant. 
     
     
         20 . The method of  claim 19 , wherein the elastic deflection of the collar is between 0.004 inches and 0.02 inches when subjected to a load of 188 pounds. 
     
     
         21 . The method of  claim 19 , wherein the elastic deflection of the collar is greater than 0.004 inches when subjected to a load of 188 pounds. 
     
     
         22 . The method of  claim 18 , wherein the inserting of the femoral hip implant into the femur comprises press-fitting the femoral hip implant into the femur. 
     
     
         23 . The method of  claim 18 , wherein the first end, the second end, and the collar of the femoral hip implant comprise a single piece of material. 
     
     
         24 . The method of  claim 18 , wherein the collar comprises a substantially semicircular projection from the second end of the femoral hip implant in a direction generally normal to the second end of the femoral hip implant. 
     
     
         25 . The method of  claim 18 , wherein the entire surface area of the collar comprises a porous surface. 
     
     
         26 . The method of  claim 18 , wherein the porous surfaces of the second end and the collar comprise a diamond cubic unit cell geometry. 
     
     
         27 . The method of  claim 18 , wherein the bone implant apparatus is fabricated from a biocompatible material. 
     
     
         28 . A bone implant comprising:
 a proximal portion adapted for receiving a femoral head, the proximal portion being fabricated from a biocompatible material;   a distal portion having a generally tapered shape and extending distally from the proximal portion in a non-coaxial fashion, the distal portion comprising a femoral stem configured for press-fit insertion into a femur without the use of bone cement, the distal portion comprising a surface at least a portion of which is porous, the porosity of the porous surface of the distal portion comprising a diamond cubic unit cell geometry to allow bone ingrowth, the distal portion and the proximal portion comprising a single piece of material, the distal portion being fabricated from a biocompatible material;   a collar, the entire surface area of which is porous, the collar being generally disposed between the proximal portion and the distal portion, the collar being generally disposed about a proximal end of the distal portion, the collar comprising a generally semicircular projection, the collar comprising a top surface and a bottom surface, both of which are porous, the top surface and bottom surface being generally parallel, the porous surface of the collar integrally extending onto the surface of the distal portion, the porosity of the collar comprising a diamond cubic unit cell geometry to allow bone ingrowth, the collar elastically deflecting more than 0.004 inches under a load of 188 pounds, the collar, the proximal portion, and distal portion comprising a single piece of material, and the collar being fabricated from a biocompatible material.