"So you've really got two fixations here. You've got the press fit and then you actually have the bone ingrowth into the device to lock it in."" Doctor Thomas P. Sculco, Surgeon-in-Chief at the Hospital for Special Surgery in New York, demonstrates how the hip prosthesis attaches to the femur.

Dr. Sculco:



So the bone itself and the surrounding surface of the implant then actually grow into these little surfaces.



Fixation of the device is twofold. Both on this side and this side. And the fixation is first what I can press-fit. And basically what that means is that we channel out the femur bone. And then when I drive this into the bone, it takes on that configuration. The bone is absolutely tight against it, so you get a press-fit. And then the bone itself and the surrounding surface of the implant then actually grows in to these little surfaces. And thats where the actual secondary stability comes from. So you really got two fixations here. You got the press-fit... press-fit here where it contacts there, and then you actually got the bone ingrowth into the device to lock it in. So they tend to be very very tight.