Modular elbow

Abstract

A modular elbow prothesis includes a humeral component, an ulnar component and three bearing components. The ulnar component includes a stem for implantation in the intramedullary canal of an ulna and a body including a slot. Two of the three bearing components include flanges that mate with the slot of the ulnar component. The humeral component includes a stem for implantation in the intramedullary canal of the humerus and two arms extending from one end of the stem. An opening is formed in each arm and in two of the three bearing components. The modular elbow may be used in an unconstrained mode by attaching one bearing component to the ulnar component and the other to the humeral component by inserting a pin through the openings in the arms and the bearing component. The two bearing components are then placed adjacent each other such that they articulate about their bearing surfaces. Alternatively, the prosthesis can be utilized in a constrained mode by positioning the flange of the third bearing component in the slot on the ulnar component and positioning the third bearing component between the arms of the humeral component and inserting a pin through the openings in the arms of the third component. In one embodiment, two of the bearing surfaces are configured to permit axial rotation without becoming disengaged.

What is claimed is:  
     
         1 . A prosthetic elbow, including: 
 an ulnar component having a stem with a first end adapted to fit within the medullary canal of an ulna and a second end;    a first bearing component adapted to engage the ulnar component;    a humeral component having a stem with a first end adapted to fit within the medullary canal of a humerus; and    a second bearing component having a spherical surface, the second bearing component being adapted to engage the humeral component and mate with the first bearing component so as to be held in place by the soft tissues of the elbow,    wherein said second bearing component is releasably coupled to said humeral component.    
     
     
         2 . A prosthetic elbow according to  claim 1 , wherein the spherical surface of the second bearing component mates with the first bearing component.  
     
     
         3 . A prosthetic elbow according to  claim 1 , wherein the ulnar component includes a slot and the first bearing component includes a flange configured to mate with the slot.  
     
     
         4 . A prosthetic elbow according to  claim 1 , wherein the first bearing component includes a spherical surface.  
     
     
         5 . A prosthetic elbow according to  claim 4 , wherein the spherical surface of the first bearing component mates with the spherical surface of the second bearing component.  
     
     
         6 . A prosthetic elbow according to  claim 1 , wherein the ulnar component further has a ridge configured to inhibit rotation of the ulnar component relative to the ulna when the ulnar component is located within the medullary canal of the ulna.  
     
     
         7 . A prosthetic elbow according to  claim 1 , wherein the humeral component further includes at least one ear configured to inhibit rotation of the humeral component relative to the humerus when the humeral component is located within the medullary canal of the humerus.  
     
     
         8 . A prosthetic elbow according to  claim 1 , wherein the first bearing component further includes a nubbin which contacts at least a portion of the ulnar component.  
     
     
         9 . A prosthetic elbow according to  claim 8 , wherein the ulnar component further includes an opening defined therein for engaging the nubbin.  
     
     
         10 . A prosthetic elbow according to  claim 8 , wherein the ulnar component further includes a sloped notch defined therein for guiding the nubbin during coupling of the first bearing component to the ulnar component.  
     
     
         11 . A prosthetic elbow, comprising: 
 a humeral component;    an ulnar component; and    a plurality of bearings for providing axial rotation of the ulnar component relative to the humeral component,    wherein said plurality of bearings includes a first bearing component and a second bearing component which contact each other,    wherein said first bearing component is releasably coupled to said ulnar component, and    wherein said second bearing component is releasably coupled to said humeral component.    
     
     
         12 . A prosthetic elbow according to  claim 11 , wherein at least one of the bearings has a spherical bearing surface.  
     
     
         13 . A prosthetic elbow according to  claim 12 , wherein the spherical bearing surface mates with a bearing surface of another of the plurality of bearings.  
     
     
         14 . A prosthetic elbow according to  claim 11 , wherein at least two of the bearings have a spherical surface.  
     
     
         15 . A prosthetic elbow according to  claim 14 , wherein a spherical bearing surface of one bearing mates with a spherical bearing surface of another bearing.  
     
     
         16 . A prosthetic elbow according to  claim 11 , wherein the bearings provide at least two degrees of freedom.  
     
     
         17 . A prosthetic elbow according to  claim 11 , wherein the bearings provide at least three degrees of freedom.  
     
     
         18 . An elbow prosthesis, comprising: 
 an ulnar component;    a humeral component; and    means for providing axial rotation of the ulnar component with respect to the humeral component,    wherein said axial rotation providing means includes a first bearing component and a second bearing component which contact each other,    wherein said first bearing component is releasably coupled to said ulnar component, and    wherein said second bearing component is releasably coupled to said humeral component.    
     
     
         19 . The elbow prosthesis according to  claim 18 , wherein the means for providing axial rotation includes a bearing component having a spherical bearing surface.  
     
     
         20 . The elbow prosthesis according to  claim 18 , wherein the means for providing axial rotation includes two spherical bearing surfaces configured to mate with one another.  
     
     
         21 . An elbow prosthesis, comprising: 
 an ulnar component;    a humeral component; and    means for providing at least three degrees of freedom between the ulnar and humeral components,    wherein said three degrees of freedom providing means includes a first bearing component and a second bearing component which contact each other,    wherein said first bearing component is releasably coupled to said ulnar component, and    wherein said second bearing component is releasably coupled to said humeral component.    
     
     
         22 . The elbow prosthesis according to  claim 21 , wherein the means for providing at least three degrees of freedom includes a bearing having a spherical surface.  
     
     
         23 . The elbow prosthesis according to  claim 21 , wherein the means for providing at least three degrees of freedom includes a first bearing component having a spherical bearing surface and a second bearing component having a spherical bearing surface configured to mate with the spherical bearing surface of the first bearing component.