The theory behind cementless stems is that over time, bone will grow and attach itself to the stem, making the stem "part of" the femur. Cementless stems usually have a porous coating or Hydroxyapatite (also known as HA)over part or all of the stem, providing a rough surface for bone to grow onto. Below is a chart of commonly used stems, and the location of the porous coating.

Cementless stems are a good choice for patients who have good bone structure in their femur and show potential for generating more bone mass in the femur over time.

The procedure for installing cementless stems is similar to that of cemented stems, but obviously without the cement. The femur is reamed (meaning the center of the bone is drilled out) and the uncemented stem is inserted into the femur. Over time, the bone will grow into the femoral component, securing it in place.