What does an artificial hip joint consist of?

In the case of a total endoprosthesis, a hip socket is also placed into the hip bone in addition to a femoral head in the thigh bone.

Prof. Dufek: A complete artificial hip replacements consists

1. of a acetabulum/socket. This acetabulum/socket is anchored in the pelvis. It is made for instance from a metal shell and is lined on the inside with plastic or ceramic.

2. of a femoral head. This head or ball moves about in the socket. To keep its position when exposed to stresses, the prosthesis head sits on a long stem which is anchored in the thigh bone. The stem is made from metal and the head either from metal or porcelain.

If the complete joint is replaced your doctor will speak about a total endoprosthesis (TEP), a total joint replacement within the body. Sometimes only the femoral head or only the acetabulum/socket is replaced. This is called a partial prosthesis.

What anchorage system is the right one for me?

Prof. Dufek: There are two options for anchorage in the hip bone:

• The use of so-called bone cement, a plastic similar to acrylic glass, with which the prostheses is "cast" in the bone.
• So-called cementless anchorage. The good fit thus achieved firmly clamps the prosthesis in the bone in the first instance. Then the bone grows into the surface of the prosthesis achieving long-term stability.

Both anchorage methods (the cemented and cementless method) have advantages and disadvantages. Cemented anchorage can loosen the prosthesis after some years because of the ageing processes in the cement. Also abrasion particles from the plastic acetabulum/socket can play a part in the loosening process. A requirement for cementless anchorage is a bone substance which is tolerated well by the bone bed. It is often the choice for younger patients. The surgeon makes the decision during surgery when he can directly evaluate the quality of the bone.

When should someone have a hip joint operation?

Prof. Dufek: The decision for an operation is not an easy one. However if there is severe pain and considerable restriction in mobility and daily life is severely impaired, it is often advisable to have an operation. In particular chronic pain when resting and at night is an indication of a disease that should be treated.

A joint replacement can make work and every day life considerably easier. Should you give an operation consideration, your doctor will examine all the general risks and risks particular to you. He should advise you in depth on this topic.

If you already have hip arthritis how can a joint replacement be avoided?

Prof. Dufek: An operation which reconstructs the surfaces of your joints, i.e. repairs them, can postpone an artificial joint replacement or even the use of a prosthesis. Axial corrections in the joint or cartilage plasties also delay the use of prostheses. A good supplement is treatment with hyaluronic acid. This is injected directly into the affected joint. The product acts as a lubricant and therefore reduces not only friction but also inflammation. A positive side effect is the reduction of pain.

What risks are there with a joint replacement operation?

Prof. Dufek: An artificial joint is a foreign body. This however is usually well tolerated. Often there is low blood supply around the prosthesis. If you have poor immunity or you belong to a risk group, then there is an increased risk of infection.

The following count as belonging to a risk group

• Diabetics
• Patients who are older than 75 or 80 years of age
• patients who have previously had an operation
• People suffering from rheumatism
• Patients with arterial circulation disorders.

During a medical consultation the various risks are discussed with you and it is established whether you are at greater risk. Other risks could be thrombosis, intolerance to medication or damage to the surrounding structures (vessels, nerves, bones, or muscles).

How long does a joint replacement operation last and how long will I have to stay in hospital?

Prof. Dufek: How long an operation lasts depends absolutely on the type and scope of the operation. It will usually last around 1 hour. Your stay on the ward in hospital will be between a week and 10 days. Better implants and gentler operation techniques also ensure a shorter duration of stay during follow-up treatment - known as rehabilitation. In earlier times this was 6 weeks but today only 3 weeks are necessary. Most patients can therefore manage their everyday activities on their own after about 5 weeks.

How great is the friction between the articulating components of the prosthesis?

Prof. Dufek: Femoral head and acetabulum, the articulating prostheses components linked to one another, are usually made of metal, ceramic or polyethylene. These materials ensure low friction even with extremely small amounts of abrasion. Nevertheless after many years this abrasion is of relevance because it can accumulate between the bone and the prosthesis parts encouraging disintegration of bone and eventually loosening of the prosthesis. A solution to this in the case of hip replacements is to use ceramic on ceramic bearing surfaces. These total prostheses are resistant to wear and are a biologically well-tolerated combination, which unfortunately industry offers at a high cost.

Does the artificial joint feel like a type of foreign body after the operation?

Prof. Dufek: Every artificial joint is initially a foreign body, but anatomical reconstruction is more and more successful. The feeling of something different very quickly goes away. The real advantages of a pain-free joint that works properly is what matters most.

How long does an artificial hip joint last?

Prof. Dufek: Loosening usually occurs nowadays only after 15 to 20 years whereas in earlier times joints had to be replaced often only after 10 years. However there can be exceptions in individual cases.