Prosthetic joint

Abstract

A prosthetic joint has a central axis and includes: (a) a first member of rigid material and including a body having a cantilevered perimeter flange extending therefrom, the flange defining a wear-resistant, concave first contact surface having a protruding rim and a recessed central portion; and (b) a second member of rigid material with a wear-resistant, convex second contact surface. The first and second contact surfaces bear directly against each other so as to transfer axial and lateral loads from one of the members to the other, while allowing pivoting motion between the two members. The flange is shaped and sized so as to deform elastically and permit the first contact surface to conform in an irregular shape to the second contact surface when the joint is placed under a predetermined load.

1 . A prosthetic joint having a central axis, comprising:
 (a) a first member comprising a rigid material and including a body having a cantilevered perimeter flange extending therefrom, the flange defining a wear-resistant, concave first contact surface having a protruding rim and a recessed central portion; and   (b) a second member comprising a rigid material with a wear-resistant, convex second contact surface;   (c) where the first and second contact surfaces bear directly against each other so as to transfer axial and lateral loads from one of the members to the other, while allowing pivoting motion between the two members; and   (d) wherein the flange is shaped and sized so as to deform elastically and permit the first contact surface to conform in an irregular shape to the second contact surface when the joint is placed under a predetermined load.   
     
     
         2 . The prosthetic joint of  claim 1  wherein the flange has a saddle shape with ends which are elevated relative to the central axis. 
     
     
         3 . The prosthetic joint of  claim 1  in which at least one of the members is bone-implantable. 
     
     
         4 . The prosthetic joint of  claim 1  wherein the rim has a curved cross-sectional shape. 
     
     
         5 . The prosthetic joint of  claim 1 , wherein the rim has a substantially conical surface. 
     
     
         6 . The prosthetic joint of  claim 1  wherein the rim has a free shape defining a first contact area with the second contact surface and a loaded shape defining a second contact area with the second contact surface which is substantially larger than the first contact area. 
     
     
         7 . The prosthetic joint of  claim 1  wherein the contact surfaces comprise a ceramic material, a metal, or a combination thereof. 
     
     
         8 . The prosthetic joint of  claim 1  wherein the first contact surface includes more than one protruding rim, with a circumferential relief area defined between adjacent rims. 
     
     
         9 . The prosthetic joint of  claim 1 , where the flange is sized so as to permit elastic deflection of the flange while limiting stresses in the flange to less than the endurance limit of the material from which the flange is constructed, when an external load in the range of about 0 to 300 lbs. is applied to the joint. 
     
     
         10 . The prosthetic joint of  claim 1  wherein the body includes a peripheral wall and the perimeter flange extends radially inward from a peripheral wall. 
     
     
         11 . The prosthetic joint of  claim 1 , wherein an initial curvature of the rim before use is different from an initial curvature of the second contact surface. 
     
     
         12 . The prosthetic joint of  claim 1  where the curvatures of the rim and the second contact surface are configured to produce a constantly diminishing wear characteristic when in use. 
     
     
         13 . The prosthetic joint of  claim 1  wherein at least one of the surfaces includes a wear-resistant thin film or coating. 
     
     
         14 . A method of making a prosthetic joint, comprising:
 (a) providing a joint according to  claim 1 , wherein an initial curvature of the rim before use is different from an initial curvature of the second contact surface;   (b) assembling the first and second members and placing them under load such that the rim defines a contact band with the second contact surface, the contact band having an initial width resulting in an initial contact stress level greater than a preselected level;   (c) subjecting the joint to movement cycles under load during a wear-in process so as to cause wear in the contact band; and   (d) terminating the wear-in process when the contact band has increased to a post wear-in width resulting in a contact stress level less than the preselected level.   
     
     
         15 . The method of  claim 14  wherein the wear is substantially uniform around the entire periphery of the contact band. 
     
     
         16 . A prosthetic joint, comprising:
 (a) a first member comprising a rigid material and including a body having a cantilevered perimeter flange disposed at a first end thereof, the first end of the body and the flange cooperatively defining a wear-resistant, concave first contact surface having a protruding rim and a recessed central portion;   (b) a second member comprising a rigid material and including a body having a cantilevered perimeter flange disposed at a first end thereof, the first end of the body and the flange cooperatively defining a wear-resistant, concave second contact surface having a protruding rim and a recessed central portion; and   (c) a third member comprising a rigid material positioned between the first and second members, the third member having a double convex shape defining opposed wear-resistant third and fourth contact surfaces;   (d) wherein the first and second contact surfaces bear against the third and fourth contact surfaces, respectively, so as to transfer load from the first member to the second member, through the third member, while allowing pivoting motion between the first and second members;   (e) wherein the flanges are shaped so as to deform elastically and permit the first and second contact surfaces to conform to the third and fourth contact surfaces, respectively, when the joint is placed under a predetermined load.   
     
     
         17 . A prosthetic joint, comprising:
 (a) a first member comprising a rigid material, the first member defining a wear-resistant, concave first contact surface with a protruding rim and a recessed central portion;   (b) a second member comprising a rigid material with a wear-resistant, convex second contact surface;   (c) where the first and second contact surfaces bear directly against each other so as to transfer load from one member to the other while allowing pivoting motion between the two members; and   (d) wherein one of the two members is hollow and shaped so as to deform elastically and permit the associated contact surface to conform to the other contact surface when the joint is placed under a predetermined load.   
     
     
         18 . The prosthetic joint of  claim 17  wherein the first member comprises a disk-like base and a cup which are interconnected by a peripheral wall, where an interior cavity is defined between the base and the cup. 
     
     
         19 . The prosthetic joint of  claim 17 , wherein an interior cavity of the hollow member is filled with a resilient nonmetallic material.