Custom Knee Replacement

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.

Rehabilitation

Physiotherapy is important following discharge. This will be discussed with you.

Do not hesitate to contact me if you require further information.

Acknowledgements

https://commons.wikimedia.org/wiki/File:Osteoarthritis.jpg

https://en.wikipedia.org/wiki/User:Homerstrykercenterlibrary