Standard and Custom made Total Knee Replacements (TKR)
The knee joint is the largest joint in the body. It is formed by the top end of the tibia (shin bone), the far end of the femur (thigh bone) and the under surface of the patella (knee cap). The surfaces of the bone are lined with articular cartilage which is composed of type II collagen and proteoglycans. The collagen is different to that associated with collagen filler injections.
Osteoarthritis of the knee is a common condition where the articular cartilage becomes damaged and irregular due to breakdown of the collagen fibres. There are a number of reasons why this can happen. Examples include age related ‘wear and tear’, chronic inflammatory disease, traumatic arthritis and some birth defects.
A normal knee An arthritic knee
The treatment options for knee osteoarthritis may include doing nothing, analgesia, activity modification, using walking aids, injections and a total knee replacement (TKR). The choice depends on the severity of osteoarthritis.
A TKR is an operation performed to replace the damaged knee joint. The procedure involves cutting the skin and putting a ‘cap’ on the far end of the Femur (Thigh bone) and the top end of the Tibia(Shin bone). A polyethylene liner is put into the middle. The under surface of the kneecap is also replaced with a polyethylene liner.
The aim of surgery is to eliminate the pain and stiffness experienced with arthritis.
A Total Knee Replacement
‘Pre-rehabilitation’ before surgery to strengthen muscles and improve range of motion may help early recovery and improve the outcomes following surgery.
The operation technique
There are many different types of knee replacement designs. Some surgeons advocate the use of robotic knee surgery. This involves using a robot to help make cuts on the bone rather than using standard mechanical equipment . There is no evidence to suggest significant benefit at present .
Another technology is the use of custom-made total knee replacements. This involves obtaining a scan of the knee and then manufacturing a custom knee replacement. Companies that manufacture such implants include Conformis and Symbios. Custom knee replacements may provide superior outcomes compared to standard total knee replacements.
Risk of Surgery
The knee replacement is a mechanical device. Approximately 80% of knee replacements are expected to survive 25 years; five percent may fail at 10 years. This means they require revision surgery, ‘re-doing the knee replacement’. It is likely that this figure improves over time because implants continue to improve in design.
The risks associated with undergoing a total knee replacement include infection, deep vein thrombosis and pulmonary embolism (blood clots), pain, stiffness, damage to nerves ( causing numbness or weakness which may be temporary or permanent ) and blood vessels. Other risks include the fracture of bone and persisting pain which may take 2 years to settle. 15% of patients remain unhappy beyond this time. Death is a rare complication.
There are also other risks related to anaesthetic. You will be asked to sign a consent form following a discussion of the risks.
What to expect on the day of surgery?
On the day of surgery , you will see the surgeon and anaesthetist . The anaesthetist will discuss anaesthetic options . These may include general or regional anaesthetic. The nurses will prepare you for the operation .
The surgical procedure takes approximately two hours. Near the end of the operation, the knee will be injected with local anaesthetic to reduce the pain. Afterwards, you will go to recovery. When you have safely recovered from the anaesthetic, you will be sent to the ward.
You will be given antibiotics at the time of surgery to prevent infection. These may be continued afterwards for several doses. You will be given blood thinners following surgery which will need to be continued following discharge.
After the operation
You will be encouraged to mobilise as soon as its safe following the surgery . This is to improve the blood flow and give you confidence . As the local anaesthetic wears off , you will experience an increase in pain . It is important that you take your pain killers regularly and continue to work on your exercises during this time . The pain will improve over time.
Length of stay in hospital
There is a general trend in reducing the length of stay in hospital following surgery. Some patients may go home on the same day or the day after . Some times discharge from hospital can be after 2-3 days .
How do I look after the knee following discharge?
You need to keep the wound dry and protected using a dressing until it has healed (about 2 weeks). Using a Tubigrip bandage and putting ice on it for 15 minutes every hour can help the swelling . The Tubigrip should be taken off at night . Advice will be given to you before discharge from the hospital . You will be given exercises before discharge.
It is important to plan for physiotherapy following discharge to help with improving the range of motion and strength of the knee.
Following the Discharge
The wound will be reviewed two weeks following surgery to ensure that it has healed without complication . If there are any concerns , it is important that the wound is seen by the surgeon. I would like to see you approximately six weeks following surgery to assess your progress. If you are doing well , you will be discharged.
Physiotherapy is important following discharge. This will be discussed with you.
Do not hesitate to contact me if you require further information.