If the wear of the cartilage in a joint is too advanced and conservative measures no longer make the symptoms bearable, quality of life is significantly restricted.
Joint replacement, i.e. implanting a prosthesis in the joint, should then be carried out as a last resort. These operations are mainly performed on the hip and knee, but are also possible on the shoulder or on small joints such as finger joints.
Hip prosthesis
There are different types of artificial hip joints. The aim of every first operation is to preserve as much of the patient’s own bone as possible and to restore the original anatomy as far as possible. The artificial hip joint known as the uncemented hip endoprosthesis is the most commonly used worldwide. There is very long experience with this type, and excellent function can be predicted in most cases. The artificial joint is fitted precisely into the pelvic bone and the thigh bone. Both the socket and the femoral head are replaced. If bone is weakened (osteoporosis), the joints can also be anchored securely with bone cement. To implant a new hip joint, the surgeon needs access to the joint, i.e. an incision past or through the muscles to reach the joint. Three approaches are common in Germany:
The lateral approach: the most commonly used in Germany. Its advantage is a good view of the joint during the operation. Its disadvantage is that the partly detached middle gluteal muscle has to heal back on, which takes about 6 weeks.
The posterior approach: also a very common approach. Its disadvantages are also the healing of the muscles and a slightly higher risk of the ball dislocating from the socket compared with the other approaches.
The minimally invasive approach: here the surgeon reaches the hip joint in front of the middle gluteal muscle. No muscle has to be detached, which makes this the gentlest approach. Its disadvantage is a slightly restricted view during the operation. Its main advantage is that full weight-bearing is possible relatively quickly.
The advantage of the minimally invasive approach lies in the first few weeks; in the long term, results show no difference between the approaches.
Knee prosthesis
If the cartilage surfaces are so badly worn that in places bone rubs on bone, an artificial knee joint is necessary. The aim is to replace worn and destroyed joint surfaces with a new, smooth surface. The new surfaces are not connected to each other; this function continues to be performed by the outer and inner ligaments and partly by the posterior cruciate ligament.
There are different types of artificial knee joints. In a partial knee replacement (unicompartmental or “sled” prosthesis), only part of the diseased joint surface is replaced. In a total knee replacement, the entire diseased joint surface of the bone is removed. The artificial joints can be cemented, partly cemented or uncemented.
Another aim of knee surgery is to straighten the leg axis. Many patients have developed bow legs or sometimes knock knees because of osteoarthritis. This can be corrected in the same operation.
Joint replacement and sport
People with a joint prosthesis do not have to give up regular sporting activity. On the contrary, measured strain promotes bone formation and thus the anchoring of the artificial joint. It also improves coordination and muscular stability. This keeps the joints mobile, which in turn reduces the risk of accidents. However, a few points should be considered for the artificial joint in order not to take unnecessary risks.
The following general conditions should be met:
- Operation more than 6 months ago
- Good mobility
- Walking without a limp
- Stable muscles and ligaments
- X-ray check
- Stable cardiovascular condition
Sport is not allowed if the prosthesis has loosened or if there is an infection.
Competitive sport is generally not advisable with a joint prosthesis.
People with a hip prosthesis should avoid strong twisting, rapid changes of direction and crossing their legs.
Patients with a knee prosthesis should avoid strong impact loads and rapid changes of direction.