How do these replacement hips mimic the movement of normal hip joints?
The hip acts as a ball-and-socket joint within the body. A hip socket works by forming a cup around the ball of the upper thighbone, or femur. When the original joint becomes damaged and unusable, this ball-and-socket joint is replaced with a prosthetic joint made of metal and plastic. The process of replacement, known as arthroplasty, involves removing the part of the thighbone that connects to the pelvis.
An artificial hip provides a new ball for the femur bone, which is usually made of the lightweight plastic polyethylene. The replacement pelvic socket is composed of the same material. The upper thighbone joint is originally made of tough and sleek articular cartilage that allows the joint to function without incurring damage, so a replacement joint must mimic this action.
The new joint is made of strong and sturdy metals that contain little to no iron – such as chromium or cobalt – so rust is minimal or nonexistent.
1. Femoral head – The head of the thighbone (femur) is replaced with a prosthetic part, usually made of the lightweight plastic polyethylene.
2. Femur – A cobalt-chrome or titanium prosthesis replaces the femur and attaches to the new femoral head.
3. Pelvis – A plastic socket is placed in the cup of the pelvis, into which the replacement femoral head slots.
4. Movement – The metallic joint will move like a normal hip, although it may take some time for the patient to adjust.