Femur prosthetic stem with back grasping

Femur prosthetic hollow stem having a length, the hollow stem comprising:

• a sidewall and a cavity;
• the sidewall having an interior surface defining the cavity and an opposing exterior surface;
• the sidewall comprising a base and two wings, each wing having a free edge, wherein each free edge is convexly curved in a lengthwise direction along the length of the stem;
• wherein the interior surface of the base has a profile extending in a lengthwise direction along the length of the stem from a proximal end of the cavity to a distal end of the cavity, the profile comprising a first convex curve segment adjacent to the proximal end, a second convex curve segment adjacent to the distal end, and a concave curve segment in-between the first convex curve segment and the second convex curve segment wherein the hollow stem is characterized in that a radius of curvature of the stem is constant, so that a surgeon can insert the stem in a femur bone with a movement of constant curvature.