A total hip prosthesis replaces the entire hip joint with manmade structures. The natural hip joint consists of the ball-shaped head of the leg bone, or femur, fitting inside a cup-shaped hollow, known as the acetabulum, in the bone of the pelvis. During everyday life, the hip joint has to bear a lot of weight and carry out a wide range of movements, and in older people the joint often becomes worn, in a condition known as osteoarthritis. When the resulting pain and reduced movement become too severe, a total hip prosthesis is sometimes required to replace the damaged joint. Conditions such as rheumatoid arthritis, where an autoimmune disease attacks the joints, and serious fractures of the hip, may also be treated using a total hip replacement.
There are a number of different techniques used by surgeons when replacing the hip with a total hip prosthesis. In the conventional form of total hip replacement, as well as replacing the acetabulum, the head of the femur is replaced, together with its supporting length of bone, known as the femoral neck. An alternative method, called a resurfacing total hip arthroplasty, only replaces the surface of the head of the femur, along with the acetabulum, and this is usually reserved for younger patients who have not lost too much bone. The hip resurfacing technique involves fitting a metal cap over the femoral head.
Also in younger patients, cement may not be used to fix the parts of the total hip prosthesis to surrounding bone. In this case, a special type of prosthetic hip is used with a bone-like or textured metal coating. This encourages nearby areas of bone to grow into it and fuse.
Conventional hip replacement surgery involves the use of large skin incisions to expose the hip joint, but more recent methods make use of hip arthroscopy. Arthroscopic techniques require only small cuts in the skin, as they use a slender viewing instrument to visualize the inside of the joint, and miniature surgical tools to carry out procedures. New variations of these methods are being developed all the time, but as yet they are not suitable for every patient who needs a total hip prosthesis.
The outlook following total hip replacement surgery is generally good, with most patients experiencing greater mobility and relief from pain. Complications such as infection are uncommon. The problem most frequently encountered is blood clots in the legs, and the use of blood-thinning medication, together with exercises and support stockings, can help to prevent clots from forming.
