Bipolar Hip Replacement

What Is Bipolar Hip Replacement?

Bipolar hip replacement is just one of several types of hip replacement a person may undergo. There are partial hip replacements and total hip replacements, and categories within each. The type of hip replacement a person may have done depends partially on the extent of damage that has occurred in the hip joint, the person's age, and the person's anticipated activity level over the next several years. Some hip replacement types are longer lasting than others, and the different types have differing recovery periods. In other words, all hip replacements are not the same.

The Hip Joint - Before getting into the specifics of the bipolar hip replacement, it may be helpful to look into the mechanics of the hip, and why a replacement is sometimes needed. The hip consists of a ball and socket joint, the largest in the body, together with muscles, tendons, and ligaments, all of which keep the joint and affected bones in place. There are two bones making up a joint. In most cases, the ends of the two bones, held in tight proximity to one another, such as in the elbows, fingers, or knees, make up a joint. In the hip joint, the end of only one bone, the femur, is involved. The other bone is the pelvic bone, and the joint consists of the upper end of the femur and a socket in the pelvic bone. The socket is called the acetabulum. The surface of the socket is the acetabular surface.

Wear And Tear - The upper end of the femur, the bone of the upper leg, has a spherical or ball-like shape. In a healthy hip joint, the femur head fits nicely inside the acetabulum, held in place by muscles, tendons, and ligaments, and lubricated so that the two surfaces slide against one another without the two bones actually touching. The hip joint, like all joints, is subjected to a certain amount of wear and tear. In fact the hip is subjected to a great deal of potential wear and tear because of the pressure brought about by our body weight. Over time, the end of the femur may begin to wear, and the acetabular surface may begin to wear as well. Bone fragments can accelerate the process, causing discomfort or pain as the two surfaces soon begin grinding together. At some point in time, the pain or discomfort may become so great, that a hip replacement is in order. If the situation becomes severe enough, a person can begin to experience difficulty in walking or bending over.

Unipolar And Bipolar - In some hip replacement procedures, bone is not actually replaced with a prosthetic device, but the ball of the femur is resurfaced, or the acetabular cavity is resurfaced, or both. When this is not a realistic solution, the ball, or tip of the femur may be replaced. If only part of the femur, or a part of the acetabulum (pelvis) is replaced, it is called a unipolar hip replacement. If both parts are partially replaced, it is called a bipolar hip replacement.

What Is Involved - When a person receives a bipolar hip replacement, what happens is this. The acetabular cavity, or socket, is reamed out to make it slightly larger. A shell is then placed in the cavity. This shell, often constructed from a metallic compound, becomes the new socket surface. The ball end of the femur is removed and replaced by a ball and stem. The stem, often made from titanium, is inserted into the femur. The stem is usually porous so that the bone in the femur will eventually fuse with it. A second socket is placed in the acetabular cavity, and the ball and stem is placed in this new socket. The ball and socket are now completely artificial, though the remainder of the femur, at least 90% of it, has not been affected by the procedure.

Quick Recovery - When installing the new ball and socket, incisions are made in such a way as to bypass muscle tissue, so muscles are not cut into more than is absolutely necessary during the procedure, and recovery is therefore quite rapid. For the most part, only bone tissue has been replaced by prosthetics, and the muscles, ligaments, and tendons remain intact.

In some case, where the tip of the femur can be saved, or the acetabular surface is not badly eroded, new surfaces are preferable to a bipolar replacement, as the former procedure is preferable for young and active people. Older patients often benefit more from the bipolar hip replacement, as their mountain climbing and skiing days are often behind them, though they can still continue on, leading an active life.