Hip replacement

What is a hip replacement?

Hip replacement, is an operation to replace a hip joint with an artificial (‘ prosthetic’) hip joint. It is a common procedure and effectively relieves pain and restores mobility.

Why might a hip joint need to be replaced?

The hip is the joint that connects the thigh bone (the femur) to the pelvis. The hip joint is what is known as a ‘ball and socket’ type of joint. The upper end (head) of the femur is rounded and smooth so that it fits into a hollow cup in the pelvis. This arrangement gives the upper leg the very wide range of movement needed to walk, run, climb and jump.

The hip is a ‘synovial’ joint, meaning that it is enclosed by a ‘capsule’. The space within the capsule is filled with fluid, which allows the two bone surfaces to move smoothly over each other. The bone surfaces are also covered by a smooth substance called ‘cartilage’ to aid this movement.

There are many reasons why a hip joint may need to be replaced. However, by far the most common reason for hip replacement is joint damage due to arthritis. There are two major forms of arthritis, which are fully described in another factsheet. Rheumatoid arthritis is an inflammation of the joints that tends to affect women in early to middle age. Osteoarthritis is ‘wear and tear’ of the joint and most commonly affects the joints of elderly people. Both of these conditions can lead to destruction of the hip joint which results in pain and loss of mobility of the joint.

The hip joint may also need to be replaced after injury. In older people particularly, the head of the femur can be fractured in an accident and it may not be possible to repair surgically.

A less common reason is death of the head of the femur. This may be from a number of causes, including sickle cell disease, trauma, excessive use of steroids and rare genetic conditions.

What happens during a hip joint replacement?

The replacement joint is an artificial version of the natural ball and socket joint. It has two separate components. The lower part is usually made of metal and is a shaft with the ball part of the joint at the top. The other part of the artificial joint is the socket which fits into the pelvis and this can be made of either metal or a special type of plastic.

There are many different types of prosthetic hip joint, made of different materials and in different shapes. Improvements are being made all the time to strengthen and to perfect these artificial joints. The surgeon performing the operation will choose the type of replacement joint he or she feels is most appropriate for your condition and build.

During a hip replacement operation, the surgeon first cuts through the skin and parts the muscle to get to the hip joint. The femur is then separated from its cup in the pelvis.

The rounded head of the femur is then removed and replaced with the artificial substitute. The natural socket in the pelvis is opened out and the artificial socket inserted. Both parts of the artificial hip joint are strongly bonded to the normal bone using a special glue rather like cement.

The ball and socket are then re- united and the muscles and ligaments repaired. Any final repairs to tissues are then made and the incisions closed.

What are the preparations for a hip replacement?

The hip replacement operation is carried out under general anaesthetic. This means you may be asked to visit the hospital one to two weeks before the date of your surgery, to have a preoperative interview with a nurse and / or the anaesthetist. They will ask you questions about your current and past health, and will need to know about any allergies you may have, medications you are taking (including over the counter products or vitamin supplements), previous surgery, whether you smoke or take street drugs, and how much alcohol you use. You may also be given a physical examination, during which your heart and lungs will be checked to make sure it is safe for you to have an anaesthetic. You may be given routine laboratory tests, such as urinalysis (tests of your urine), chest x- rays, or complete blood cell counts, as well as a hip x- ray. These should reveal potential problems that might complicate the surgery if not detected and treated early. No testing may be necessary if you are in good health and younger than age 65, but each clinic may have different requirements.

Please answer all questions completely and honestly as they are asked only for your own wellbeing, so that your surgery can be planned as carefully as possible. If you are unsure of the names of any medications, bring them with you. You will be told whether or not to stop any medications at this preoperative clinic visit. For example, if you are taking aspirin-containing medicines or anticoagulants, they may need to be temporarily withdrawn or reduced in dose for two weeks before the procedure. If you can, try to stop smoking at least six to eight weeks prior to surgery.

What are the possible complications?

Hip replacement is usually very successful and can lead to an enormous improvement in quality of life. The operation can relieve constant severe pain and make it possible for people who had become virtually immobile to get about comparatively easily.

One potentially serious complication is for the new joint to become infected. For this reason you will be given antibiotics when you have the operation and for a short time afterwards. If an artificial joint does become infected, it may have to be replaced.

Surgery on the leg combined with immobility after the operation increases your chances of getting a blood clot in one of the veins in the leg (venous thrombosis). For this reason you will be given injections of heparin, a substance that helps prevent clots.

Eventually, the artificial joint may need to be replaced, usually after about 10 years. The weakest point is the glue used to bond the artificial parts to the bone. Sometimes the bond can gradually loosen with time. If the joint becomes loose, surgery to repair it is necessary. However, constant research and development is leading to rapid advances in the design of artificial joints and methods of uniting them to the pelvis and femur.

How long will I stay in hospital?

The joint remains unstable for 1 or 2 weeks after the operation. The length of time you will stay in hospital will therefore depend very much on your progress and mobilisation in hospital, as well as your age and general health and how you are set up to manage at home. Mobilisation as early as is safely possible after the operation is generally recommended. Your progress should be discussed with your doctors, nurses and physiotherapists.

What happens after a hip replacement?

The joint and the muscles need time to settle down after the operation as at first the joint can easily become dislocated. You will be advised on how to go about mobilising yourself by your physiotherapist and on how best to sleep so as not to put undue strain on the newly replaced joint. The main point is to take things gently and enjoy your new- found freedom of movement.