Ball and shaft of joint prothesis

Abstract

A prosthesis for replacement of a ball and socket joint in the human body. The prosthetic components comprise a plurality of separate parts which may be inserted through a hole in the femur of the patient and assembled and attached to the prepared acetabulum of the hip bone to form a cup-shaped first shell in a minimally invasive surgical procedure. A cup may be passed through the hole in the femur and attached to the first shell to form a socket portion of the joint. The prosthesis may comprise a shaft having a first end with a ball formed thereon that is inserted in the hole through the femur so that the ball engages the cup for movement therein.

1 . A joint prosthesis, comprising: 
 An implant comprising a neck joining a ball to a body of the implant and a flange extending spirally from an outer cylindrical surface of the body such that the spiral flange extends into a bone and increases the contact area between the implant and the bone, when the implant is threaded into the bone, wherein the implant has a cylindrical axis extending along the cylindrical axis of the outer cylindrical surface and through the ball of the implant.    
   
   
       2 . The joint prosthesis of  claim 1 , wherein a plurality of channels are formed in the implant such that holes on the outer cylindrical surface are in the fluid communication with a channel capable of delivering a cement between the outer cylindrical surface and the bone.  
   
   
       3 . The joint prosthesis of  claim 1 , wherein an end of the implant opposite of the ball is dome-shaped.  
   
   
       4 . The joint prosthesis of  claim 1 , further comprising a socket capable of receiving the ball of the implant in a cup of the socket.  
   
   
       5 . The joint prosthesis of  claim 4 , wherein the socket comprises a shell and the cup is fixedly supported by the shell, and the shell is capable of being fixed to a bone structure in the body of a patient undergoing joint replacement surgery without fully opening and exposing the hip joint.  
   
   
       6 . The joint prosthesis of  claim 5 , wherein the shell is comprised of a plurality of separate segments, each having a concave arcuate surface such that the concave surface for supporting the cup is assembled by joining the concave arcuate surfaces of each of the plurality of separate segments.  
   
   
       7 . The joint prosthesis of  claim 6 , wherein a plurality of the plurality of separate segments have an interlocking member capable of interlocking with an interlocking member of a neighboring interlocking member, when assembled to form the shell.  
   
   
       8 . The joint prosthesis of  claim 7 , wherein a key segment has a wedge and two femal interlocking members each of the two femal interlocking members being capable of engaging a male interlocking member of each of its two nearest neighboring segments, and the wedge locks the plurality of segments together.  
   
   
       9 . The joint prosthesis of  claim 6 , further comprising a base having at least one ridge extending from the base and a fastener for fastening the base to the bone structure in the body of the patient, and a plurality of the plurality of segments each have a groove capable of pivotally engaging the at least one ridge of the base during assembly of the shell.  
   
   
       10 . The joint prosthesis of  claim 5 , wherein the ball and the shell, when assembled to form the socket, define an outwardly facing surface opposite of a surface of the socket facing the bone structure, and the outwardly facing surface is nonplanar.  
   
   
       11 . The joint prosthesis of  claim 10 , wherein the nonplanar outwardly facing surface is arranged such that the implant has a range of motion greater than the range of motion of an implant having a planar outwardly facing surface.  
   
   
       12 . A joint prosthesis comprising: 
 a segmented shell having an interior surface,    a second shell fixedly retained within said interior surface of said segmented shell;    a cup, said cup having an exterior surface and an interior surface, said exterior surface of said cup being sized and configured to be fixedly retained in said second shell, and    a shaft having a first end and a second end, said first end of said shaft having a ball formed thereon that is received by said cup for movement therein, wherein the segmented shell comprises:    a base; and    a plurality of segments, each segment, of said plurality of segments, having a first end, a second end and a pair of opposing sides extending therebetween, each first end of each said segment, of said plurality of segments, pivotally engaging said base such that each side of each said segment, of said plurality of segments, is adjacent one of said sides of another one of said plurality of segments, each segment, of said plurality of segments, being longitudinally and transversely arcuate, such that when each segment, of said plurality of segments, is aligned with adjacent segments thereto, said plurality of segments form a cup-shaped shell.    
   
   
       13 . A joint prosthesis as in  claim 12 , wherein said base has a ridge formed thereon and each segment, of said plurality of segments, has a groove proximal one end of each segment capable of pivotally engaging said base.  
   
   
       14 . A joint prosthesis as in  claim 12 , wherein said second shell is formed from a polymer and the polymer adheres to the surface of the segmented shell.  
   
   
       15 . A joint prosthesis comprising: 
 a first segmented shell having an interior surface comprised of a plurality of separate segments;    a second segmented shell supported by the first segmented shell, the second shell being comprised of another plurality of separate segments;    a cup, the cup having an exterior surface and an interior surface, said exterior surface of said cup being sized and configured to be fixedly retained in the second segmented shell, and a shaft having a first end and a second end, the first end of the shaft having a ball that is received by the cup.    
   
   
       16 . A joint prosthesis as in  claim 15 , wherein the shaft has at least one channel passing through a body of the shaft such that the at least one channel extends from an opening in the second end of the shaft through the body to an opening in the neck.  
   
   
       17 . A joint prosthesis as in  claim 16 , wherein the shaft has a plurality of channels, and at least two channels are in fluid flow communication.  
   
   
       18 . A joint prosthesis as in  claim 15 , wherein the shaft has at least one longitudinally extending side wall and a groove formed in said side wall proximal the second end of the shaft, and a U-shaped shield has a bottom and a pair of legs extending outwardly from the bottom, the bottom being received in the groove such that the pair of legs extend outwardly form the shaft.  
   
   
       19 . A joint prosthesis as in  claim 15 , wherein the shaft has a flange extending spirally from an outer cylindrical surface of the shaft.  
   
   
       20 . A joint prosthesis as in  claim 12 , wherein the shaft has a flange extending spirally from an outer cylindrical surface of the shaft.