How the operation is carried out
Once you've been anaesthetised, the surgeon removes the existing hip joint completely. The upper part of the thigh bone (femur) is removed and the natural socket for the head of the femur is hollowed out.
A socket is fitted into the hollow in the pelvis. A short, angled metal shaft (the stem) with a smooth ball on its upper end (to fit into the socket) is placed into the hollow of the thigh bone. The cup and the stem may be pressed into place or fixed with acrylic cement.
Metal-on-metal hip resurfacing is carried out in a similar way. The main difference is that less of the bone is removed from the femur as only the joint surfaces are replaced with metal inserts.
The prosthetic parts can be cemented or uncemented:
- cemented parts are secured to healthy bone using acrylic cement
- uncemented parts are made from material that has a rough surface; this allows the bone to grow on to it, holding it in place
Most prosthetic parts are produced using high-density polythene for the socket, titanium alloys for the shaft and sometimes a separate ball made of an alloy of cobalt, chromium and molybdenum.
Some surgeons use a metal ball and socket and in some cases ceramic parts are used, which don't wear as quickly as plastic.
There have been recent reports about metal-on-metal hip replacements causing complications. Read our metal-on-metal implant advice Q&A.
The hip replacement operation has become a routine procedure. However, as with all surgery, it carries a degree of risk. Read about the risks of hip replacement surgery.
Choosing your prosthesis
There are more than 60 different types of implant or prosthesis. However, the options are usually limited to around four or five. Your surgeon can advise you on the type they think would suit you best.
The National Institute for Health and Care Excellence (NICE) only recommends prostheses known to have a 95% chance of lasting at least 10 years. Your surgeon will also be able to discuss any concerns you have regarding metal-on-metal replacements.
The National Joint Registry (NJR), which collects details on total hip replacement operations from hospitals in England and Wales, can help you to identify the best performing implants and the most effective type of surgery.
Minimally invasive hip replacement
In conventional hip replacement, a relatively large cut of 20-30cm (8-12 inches) is made in the skin above the hip, for the surgeon to gain access to the hip joint.
A new technique, called minimally invasive hip replacement, uses a smaller cut of around 10cm (4 inches). Specially designed instruments are then passed through the incision to perform the surgery.
Minimally invasive hip replacement appears to be as safe and effective as conventional surgery, with the added benefit of causing less post-operative pain.
However, access to this type of specialised treatment is limited and will probably involve waiting much longer for treatment.
NICE has more information on minimally invasive total hip replacement.