Hip fractures can result in life-threatening complications, such as blood clots that originate in the deep veins of the legs. These blockages can then travel to the heart or to the lungs, where they can cause strokes or pulmonary embolisms. Depending on the type and severity of a hip fracture, a full or partial replacement of the joint may be necessary. It is important to weigh the gravity of hip replacement prostheses options when considering treatment.
Cemented
Cemented hip prostheses use an epoxy cement to fasten a metal implant to the bone. There are two bones involved in the ball and socket configuration that makes up the hip joint: The head of the femur forms the ball, and the socket is formed by a structure called the acetabulum of the pelvis.
Hip replacement involves removal of the damaged area of the femoral head, according to the American Academy of Orthopaedic Surgeons. This is replaced with a prosthetic metal "stem" that is inserted flush with the surface of the femur. The "ball," made of metal or ceramic, may be already attached, or may be a separate piece that is then attached to the stem.
The acetabulum is cleaned and enlarged, then fitted with a shell made of metal or polyethylene. Then the ball is inserted into the socket. Both of the prosthetic elements, the ball and the socket, are bound to the bone with cement, most commonly an acrylic polymer that is known as polymethylmethacrylate.
Non-cemented
Another surgical option for hip replacement involves the use of textured surface coatings that encourage bone to grow into the surface of the implant. Orthogate, the Internet Society of Orthopaedic Surgery and Trauma, notes that it is this tightly conforming fit that holds the femoral stem in place, like a nail driven into a hole. This type of prosthesis requires extremely precise placement by the surgeon to ensure that the shape of the prosthetic surface matches that of the bone.
Unlike cemented hip replacements, which allow for almost immediate weight bearing, non-cemented prostheses may require the use of crutches or a walker until the bone becomes firmly attached to the implant.
Sometimes a hip replacement may involve a hybrid of both cemented and non-cemented elements. In other cases, replacement may be an option for only one part of the joint, most commonly the femoral head, while the other is left intact.
Internal Fixation
For hip fractures that are less severe, the Merck Manual of Health and Aging notes that metal pins may suffice in keeping the hip joint functional, a process called internal fixation. This type of prosthesis can involve the placement of metal pins through the femoral neck to stabilize it. Fractures that affect the trochanters, bony processes to which the muscles of the buttocks and legs attach, may be repaired using compression screws and metal plates, thus stabilizing the bone while salvaging the individual's own joint.
