Hip replacement: types and complications

Total hip replacement surgery involves the replacement of the hip joint by an implant, i.e. by a prosthesis. It consists of a femoral component or stem and an acetabular component or cup. Both components are articulated with a head applied to the femoral stem and an insert in the cup.

Types of hip replacements

Depending on the implant fixation system to the bone, prostheses can be cemented (fixed with methyl methacrylate), uncured or biological, or, hybrid (one cemented component and another not). There are excellent results with different techniques. The decision of the fixation system is made by the orthopaedic surgeon with the criterion usually based on the quality of the bone.

Generally, at the femoral level, hip implants are used that are not cemented in men up to 75 years old and in women until the age of 70 years. At the acetabular level, uncemented hip implants are usually used in most cases.

There are countries, such as the United States, where almost all implants are uncured and others, such as the United Kingdom, where a majority of cases are cemented regardless of the age or bone quality of the patient.

Another important difference to know is the friction pair, which refers to the materials that will contact during the mobility of the hip. Perhaps, this is where most progress has been made in the improvement of friction surfaces, which can be metal, ceramic or polyethylene.

• The friction pair that has been used for the longest time  is the metal / polyethylene. Currently, polyethylene prostheses are better manufactured, more resistant to wear (highly crosslinked beams) and some include antioxidants like vitamin E to lengthen their duration. Its long-term problems are known and detected early on.

• The ceramic / ceramic friction pair have also been used for a long time but the problems that some implants presented years ago (noises or ruptures of material) as well as their price means their use is less common now. It seems to be the pair of friction with less wear, but is less tolerant to errors in surgical technique.

• The ceramic / polyethylene friction pair is a combination of the above and is a good choice.

• The metal / metal friction pair, with a good implant and a perfect technique, give good results but currently, its use is discouraged because of the seriousness of problems that have arisen with these types of implants in the past few years.

The most important factor for the correct functioning of a hip replacement, as well as for duration of more than 10-15 years, is its correct implantation. It is difficult to qualify if certain sports activities can alter the duration of the prosthesis, but it would be advisable to avoid impact sports.

Hip replacement complications

The most serious complication that can occur in a hip replacement is infection that can be acute or chronic. An acute infection can occur in the immediate postoperative period or after years due to an infection in another region of the body. Chronic infection may also occur, which does not have an explicit symptomatology, but may cause a painful prosthesis or loosening of the prosthesis.

Another of the most feared complications is dislocation. The most frequent cause is usually the poor orientation of the components, although there are other causes such as trauma, neurological problems or wear of components, among others.

Specialists believe that the patient should be informed about the different options and their pros and cons, but the decision of the implant must be the responsibility of the orthopaedic surgeon. The patient can choose the surgeon.