femoral prosthesis 34 comprising ball 36 which is connected to stem 38 by neck 40 stem 38 mates with sleeve 46 by means of complementary locking tapers not shown on the outside of the stem and the inside of the sleeve a pin 42 through stem 38 may be used to engage slots 44 of sleeve 46 to establish angular orientation of neck 40 relative to the femur bone in which sleeve 46 has been implanted torque and longitudinal forces between stem 38 and sleeve 46 are transmitted through the locking taper however the prosthesis is implanted using standard surgical techniques by for example preparing the patient 39 s femoral bone to receive the distal portion 56 of stem 38 and threading sleeve 46 into the prepared proximal femur using an appropriate driving and aligning instrument which engages sleeve 46 by its internal taper and by slots 44 lastly stem 38 is driven into the complementary locking taper of sleeve 46 in accordance with the invention sleeve 46 includes threaded columns 48 and porous columns 50 as with the acetabular cup of fig1 4 threaded columns 48 provide initial mechanical fixation of the prosthesis while porous coated columns 50 provide long term fixation by means of bone ingrowth and remodeling as discussed above.