Heraeus Medical

Anaesthesia

The operation can be performed under a general or local anaesthetic (epidural). A local anaesthetic has less effect on the patient's general condition than a general anaesthetic. For this reason many knee prosthesis operations are performed with a local anaesthetic nowadays. The method used depends on a number of individual factors – the decision is reached and information provided during the preoperative discussion with the anaesthetist. The entire procedure normally takes between 60 and 120 minutes.

Start of the operation

Once the anaesthetic has taken effect, the patient is moved into the supine position on the operating table. The leg to be operated on is then disinfected and covered with sterile drapes. In addition, a blood pressure cuff is fitted round the thigh and inflated, thus preventing any substantial bleeding during surgery.

Now the surgeon performs a gently curved skin incision about 20 cm – 30 cm long at the front of the knee. The tissue underneath is pushed aside along with the kneecap, thus exposing the knee joint. The surgeon now has a good view of all the parts of the knee joint.

Question: What is the difference between standard and minimally invasive surgical techniques?: The length of the surgical incision varies from case to case and with standard knee prosthesis operations it is between 20 cm and 30 cm. This provides the surgeon with an excellent view of the site of the operation but on the down side the healing phase takes longer as a greater amount of tissue must heal. Consequently, over the last few years minimally invasive surgical techniques have been developed increasingly. The skin incision with such methods is not only shorter (10 cm to 12 cm) but the operation is also particularly atraumatic for all the other structures such as the muscles and ligaments. This means the healing phase is shorter. However, this surgical method is not suitable for all patients. Consult your attending doctor.

Preparation of the joint surfaces

With the knee joint bent at right angles the surgeon now removes the anterior cruciate ligament, the menisci and the damaged cartilage remnants from the femoral condyle and the tibial plateau. The posterior cruciate ligament is retained if possible, as are the collateral ligaments, which are vital for knee joint stability.

With the aid of high-precision sawing templates the femoral condyle, tibial plateau and, if necessary, the back of the kneecap, are prepared in such a way that the prosthesis components fit perfectly. In doing so the surgeon can also correct any leg axis malalignments.

Before the surgeon fixes the artificial prosthesis components inside the joint he uses trial prostheses. This way he can check whether the prosthesis will be secure, whether the size of the prosthesis will fit and whether the prosthesis will provide stability and mobility.

Femoral condyle replacement

Then the femoral component is secured, in many cases by using bone cement.