Prosthetic hip implants

Abstract

Prosthetic hip stems and acetabular cups for use in prosthetic hip joints. The hip stem may include a core having a stem portion and a neck portion, a polymer matrix layer substantially covering the stem portion of the core, and a porous metal layer substantially covering the polymer matrix layer. The polymer matrix layer connects the core and the porous metal layer and provides a stiffness for the hip stem which more closely mimics the stiffness of bone than do known hip stems. The hip stems and acetabular cups additionally include a number of improvements adapted for more optimized results with certain types of patient anatomy, such as the anatomy of female patients, for example.

1 . A prosthetic hip stem comprising:
 a stem portion having a proximal end and a distal end; and   a distal end fixation mechanism operable between a first condition wherein said distal end of said stem portion has a first width with respect to at least one of a medial/lateral plane and an anterior/posterior plane of said stem portion and a second condition wherein said distal end of said stem portion has a second width with respect to at least one of said medial/lateral plane and said anterior/posterior plane, said second width greater than said first width.   
     
     
         2 . The hip stem of  claim 1 , wherein said distal end fixation mechanism comprises at least one expansion point in said stem portion defining radially expandable portions of said stem portion, wherein when said stem portion is in said first condition, said radially expandable portions are substantially non-expanded and when said stem portion is in said second condition, said radially expandable portions are at least partially expanded. 
     
     
         3 . The hip stem of  claim 1 , wherein said distal end fixation mechanism comprises an expandable structure and at least one passage in said stem portion, wherein upon insertion of a filler substance through said at least one passage, said filler substance expands said expandable structure, wherein when said stem portion is in said first condition, said expandable structure is substantially empty, and when said stem portion is in said second condition, said expandable structure is at least partially expanded by presence of said filler substance therewithin. 
     
     
         4 . An acetabular cup comprising:
 a liner including a substantially hemispherical bearing surface;   a porous metal cup portion; and   an intermediate layer disposed between said liner and said porous metal cup portion, said intermediate layer formed of a polymer matrix.   
     
     
         5 . A prosthetic hip stem comprising:
 a proximal portion and a distal portion;   an inner core;   a porous metal outer layer; and   an elongated cavity formed in said distal portion, wherein said distal portion is flexible.   
     
     
         6 . The hip stem of  claim 5 , wherein said proximal portion is between 30 mm and 45 mm in length, and said distal portion is between 100 mm and 135 mm in length. 
     
     
         7 . The hip stem of  claim 5 , wherein said proximal portion includes lateral and medial sides which are substantially complementary radiused. 
     
     
         8 . The hip stem of  claim 5 , wherein said proximal portion includes anterior and posterior sides which each flare outwardly as same approach a proximal end of said hip stem. 
     
     
         9 . The hip stem of  claim 5 , wherein said distal portion includes a distal end having a width of between 10 mm and 18 mm in the posterior/anterior dimension and a width of between 11 mm and 19 mm in the medial/lateral dimension.