hip joint prostheses. There is the shortneck type which can be used when the neck of the femur is long and adequate. This type, which replaces the head only, has been made in acrylic plastic, stainless steel, or vitallium. Other models have been developed for use when there is a loss of the neck, either from absorption or from a fracture well down toward the trochanteric region. These prostheses are usually made of metal-occasionally in combination with some form of plastic material. Regardless of the type selected by the surgeon, every hip prosthesis should meet certain requirements. It should be constructed so that the stress and strain on it will be dis-