TREATMENTS

Total knee replacement

Total knee replacement has become one of the most common procedures carried out on the knee joint. It is used in joints that have become stiff and painful and significantly damaged from arthritis which results in increasing pain, loss of mobility and loss of function in the joint. The number of total knee replacements performed is almost the same as that for hip replacements in the United Kingdom. The overall results of total knee replacement have improved significantly over the years with over a 90% success rate over ten years.

Whilst there are many different types of knee replacement, the overall design is similar. The aim is to re-line the damaged surface of the joint using a plate placed into the shinbone which is made either of titanium or cobalt chrome alloy and a carved sleeve of metal which is placed over the lower end of the thighbone, again usually made of cobalt chrome alloy. The space between the two metal inserts is filled with high density polyethylene which is resistant to wear but decreases the amount of friction between the two metal plates. The components of the knee replacement may be fixed into position using a cement or, in some cases, are pressed into position and then the fixation occurs using a biological method.

Pre-operative Assessment

The patient is seen by the orthopaedic surgeon and a decision made using the clinical findings and x-rays as to whether a total knee replacement is required. The main indication for surgery is pain, but other reasons such as deformity may influence the decision. Once the decision has been made the patient is assessed in the pre-admission clinic with regard to their general health and post-operative requirements.

The patient then comes into hospital, usually the day before surgery, and undergoes the procedure which takes about one to two hours. The patient requires either a full general anaesthetic or a spinal anaesthetic in which the lower part of the body is numbed by injection into the spine. At operation the most important features of the procedure are accurate bone cuts which are made using specialised jigs and also fixation of the prosthesis. In the United Kingdom most patients do not have replacement of the kneecap with a high density plastic button but there are indications where this is necessary. This should be discussed with your surgeon pre-operatively.

Post-Operative Management

Following the operation the patient is rested for 24 hours after which he starts to bend the knee on a machine (CPM) and is usually able to get out of bed and start walking either using a frame or crutches. Over the following week the patient slowly increases the amount of knee flexion and the amount he is able to walk so that by seven to ten days afterwards, the patient is able to walk reasonable distances on sticks and is able to walk up and down stairs. The patient should be fully independent before leaving hospital.

The post-operative management is usually under the care of the physiotherapists and the surgeons and after discharge from hospital, physiotherapy is continued as an outpatient for a varying amount of time up to three months. The patient would be expected to increase his activity in the post-operative period and also the amount of movement in the knee. Depending on the surgical advice, the patient will be seen at intervals following the procedure to check on progress and to check that the prosthesis is not causing problems.

Possible Problems

The longevity of the prosthesis is difficult to predict. There are many factors associated with longevity. The main complication post-operatively is that of infection. In such cases the patient will develop a temperature, possibly with rigors and inflammation and redness of the wound in the early stages, or in later stages stiffness and pain. If infection is suspected various investigations are carried out and if the diagnosis is confirmed, the patient will require removal of the prosthesis and a period of rest for the knee before reinsertion of the prosthesis. At worst the knee may require stiffening but this is very unusual. Other complications include deep venous thrombosis and in order to prevent this happening the knee and leg are mobilised very early and support stockings used. Various other ways of preventing DVTs are chosen by individual surgeons and again this could be discussed with your surgeon.