Femoral Hip Prosthesis and Method of Implantation

Abstract

Implants and methods are presented for surgically repairing a hip joint with a proximal femoral prosthesis that comprises femoral head component and a femoral stem component. The femoral stem component comprises a neck portion, a flange portion, a transitional body region and an elongated stem. The femur is prepared for implantation of the femoral hip prosthesis by resecting the proximal femur and reaming a symmetric intramedullary cavity in the femur. The femoral hip prosthesis is then inserted the on the resected femur and in the intramedullary cavity. The femoral hip prosthesis elastically deforms when loaded during use to apply dynamic compressive loads and displacement to the calcar region of the resected proximal femur.

1 . A prosthesis adapted for implantation against a resected surface on a proximal end of a femur and inside of an intramedullary cavity of the femur, the prosthesis comprising:
 a femoral head component comprising an external bearing surface and a femoral stem component comprising:
 a neck portion comprising a proximal portion, re-engageable with the femoral head component, and a distal neck body; 
 a flange portion distal and adjacent to the neck portion, the flange portion comprising a bottom surface; 
 a transitional body region adjacent to the bottom surface of the flange portion and extending from the distal neck body; and 
 an elongated stem portion extending distally from the transitional body region and having a longitudinal axis oriented at an acute angle from the bottom surface of the flange portion; 
 wherein the transitional body region shaped to flex such that, during a normal gait cycle, the bottom surface exerts a significant compressive load on the resected surface of the femur. 
   
     
     
         2 . A prosthesis as is  claim 1 , wherein the elongated stem portion comprises a uniform envelope with a substantially constant cross-sectional peripheral shape and size. 
     
     
         3 . A prosthesis as in  claim 1 , wherein the elongated stem portion comprises a proximal section having a cross sectional shape that is substantially consistent along a longitudinal length of the proximal section, wherein a minimum displacement between the bottom surface of the flange and the proximal section, measured normal to the bottom surface, is less than thirteen millimeters. 
     
     
         4 . A prosthesis as in  claim 1 , further comprising a rotation-restricting boss, extending from the bottom of the flange portion. 
     
     
         5 . A prosthesis as in  claim 2 , further comprising a rotation-restricting boss, extending from the bottom of the flange portion. 
     
     
         6 . A prosthesis as in  claim 5 , wherein the rotation restricting boss has an axis of protrusion with a boss axis origin near the bottom surface of the flange, the elongated stem also has a stem axis origin near the bottom of the flange, the boss axis origin and the stem axis origin are spaced apart by a length more than the maximum cross-section of the elongated stem portion. 
     
     
         7 . A prosthesis as in  claim 6 , wherein the axis of protrusion and the longitudinal axis are substantially parallel. 
     
     
         8 . A prosthesis as in  claim 6 , wherein the axis of protrusion and the longitudinal axis are not substantially parallel. 
     
     
         9 . A prosthesis as in  claim 6 , wherein the axis of protrusion is normal to the bottom surface of the flange portion. 
     
     
         10 . A prosthesis as in  claim 1 , wherein the elongated stem portion has a distal section with multiple longitudinal flutes, wherein the longitudinal flutes are aligned approximately parallel to the longitudinal axis. 
     
     
         13 . A prosthesis as in claim  12 , wherein the obtuse angle is between 100° and 170°. 
     
     
         14 . A prosthesis as in  claim 1 , wherein the neck portion has a first end and a second end, wherein the first end is connected to the flange portion and extends proximally therefrom and the second end is shaped to press-fit into the femoral head component. 
     
     
         15 . A prosthesis as in  claim 14 , wherein at least a portion of the outer surface of the femoral head component is hemispherical. 
     
     
         16 . A prosthesis as in clam  1 , wherein the acute angle ranges from 15° to 80°. 
     
     
         17 . A prosthesis as in  claim 2 , wherein the uniform envelope has a maximum cross-section area measured on a plane perpendicular to the longitudinal axis. 
     
     
         18 . A prosthesis adapted for implantation against a resected surface on a proximal end of a femur and inside of a cavity of the femur, comprising:
 a femoral head component comprising an external bearing; and   a femoral stem component comprising:
 a neck portion shaped to extend substantially outside the cavity of the femur, the neck portion having a proximal portion, engageable with the femoral head component, and a distal neck body; 
 a flange portion medially and distally projecting from the neck body, the flange portion comprising a bottom surface; 
 an elongated stem portion shaped to extend substantially inside the cavity of the femur and extending distally from the neck body and having a longitudal axis oriented at an acute angle from the bottom surface of the flange portion 
 wherein, distally of a medial tip of the flange, each cross sectional shape along substantially an entire length of the elongated stem portion is substantially radially. 
   
     
     
         19 . A prosthesis adapted for implantation against a resected surface on a proximal end of a femur and inside of a cavity of the femur, comprising:
 a femoral head component comprising an external bearing surface; and   a femoral stem component comprising:
 a neck portion shaped to extending substantially outside the cavity of the femur, the neck portion having a proximal portion, engageable with the femoral head component, and a distal neck body; 
 a flange portion medially and distally projecting from the neck body, the flange portion comprising a bottom surface; 
 an elongated stem portion shaped to extend substantially inside the cavity of the femur and extending distally from the neck body and having a longitudinal axis oriented at an acute angle from the bottom surface of the flange portion; 
 wherein, distally of a medial tip of the flange, substantially an entire length of the elongated stem portion circumscribed by a substantially cylindrical shape. 
   
     
     
         20 . A prosthesis as in  claim 1 , wherein the elongated stem portion comprises a proximal section having a cross sectional shape that is substantially consistent along a longitudinal length of the proximal section, wherein a minimum displacement between the bottom surface of the flange and the proximal section, measured normal to the bottom surface, is less than a maximum cross sectional width of the elongated stem portion, measured perpendicular to the longitudinal axis.