The knee prosthesis operation

In the course of a knee prosthesis implantation, various surgical steps must be performed. Since not every operation follows the same pattern, the decisive and most important steps of a knee prosthesis implantation are described below. The individual steps mentioned below do not claim to be complete nor are they listed chronologically.

They are only intended to show which steps can be expected in any case. The actual operation time is between 90 and 120 minutes. However, since there are always individual differences, deviations both upwards and downwards are quite possible.

The anesthesia is initiated.

The patient is “positioned” on the operating table in a supine position.
A blood pressure cuff is applied to the patient’s thigh in order to operate in the so-called tourniquet (bloodlessness).In addition to the fact that the patient loses less blood, the tourniquet used in knee prosthesis surgery also allows the surgeon a better view during the actual operation.
The leg to be operated on is washed sterile with disinfectant.
The assessment of the leg axis, the extent of movement and ligament stability.
Exposing the knee joint by means of a 20 cm long, anterior, straight skin incision.
Cutting the joint surfaces of the femur and tibial head using special instruments. This procedure varies from person to person, although there is a standardized procedure for this.
This technique must always be adapted to the individual circumstances.
Removal of the abraded cartilaginous surfaces, the meniscus remnants and the remains of the anterior cruciate ligament. If possible, an attempt is made during knee prosthesis surgery not to damage or remove the posterior cruciate ligament (previous damage, etc.). Protection of the lateral ligament apparatus (internal and external) has priority in every respect.
Insertion of the trial prosthesis.
In the course of this insertion, corrections may become necessary in the area of the surrounding soft tissue (ligamentous apparatus). If the knee prosthesis is found to have insufficient mobility or ligament stability, the above-mentioned corrections will be necessary. As a rule, these measures must be taken in case of leg axis malpositions (correction of the X-, respectively O – legs).
The original prosthesis is cemented in.
As a rule, work is started at the head of the tibia. Only then is cementing in the area of the femur carried out.
In order to avoid deeper bruising after the knee prosthesis operation, two so-called Redon drains should be used to close the wound. These drains lie directly in the wound and are usually removed after the third postoperative day.
This skin closure is done with the help of so-called skin clips, which are removed after 14 days.
After the actual operation the tourniquet is opened. Thorough hemostasis will (have to) be ensured.

The demands on the material of a knee prosthesis are high. It must withstand the stresses of everyday life and moderate sporting activity, be well tolerated and ensure friction-free use of the joint.

Decades of further development of the materials used today enable a long service life of 15-20 years with high load-bearing capacity and a comparably low complication rate. In Germany, approximately 150 000 total knee endoprostheses are performed annually. Frequently used are special metal alloys, such as the cobalt-chrome alloy, plastic polymers and ceramics. For patients with metal allergies, titanium prostheses can be used. Polyethylene, a thermoplastic, is the preferred material for replacing the sliding components of a prosthesis due to its high wear resistance and sliding properties.