Knee Replacement: The Facts

Benefits
The main reason for any patient having a knee replacement performed is to rid them of their arthritic pain. In doing so unless multiple joints are affected by arthritis, this should lead to an improvement in an individual’s mobility and quality of life.

History
In 1860, to relieve the pain of roughened, osteoarthritic joint surfaces rubbing on one another it was suggested that a variety of materials could be interposed, including pig bladder!! By 1940, a metallic femoral surface was inserted in the USA and in the late 1950’s an acrylic upper tibial spacer was also tried.

By the 1960’s and early 1970’s a combination of metal and plastics were inserted with bone cement and in parallel with these designs, inter-linked "hinged" prostheses were also developed. This was the beginning of Total Knee Arthroplasty Surgery (TKA).

These early models did not fully take into consideration the mechanics of the knee, which has a rotatory motion rather than simple "hinging" and led to loosening and failure.

Modern generation knee replacements rely on resurfacing the worn out joint surface whilst preserving the patient's own ligaments to allow the replacement to move as close as is possible to a normal knee joint.

Occasionally realignment operations such as an osteotomy may avoid the need for a total knee arthroplasty (whole knee joint) and on occasions if only one part of the knee joint is severely worn then uni-compartmental or patello femoral replacement surgery is recommended rather than TKA.

Indications
The main reasons for having a knee replacement are osteoarthritis, (wear and tear), of the knee joint limiting the patients’ quality of life due to pain and loss of independence and mobility. Sometimes ‘knee replacements’ are also performed for inflammatory arthritis, (such as rheumatoid arthritis) and for fractures and less commonly for cancer.

The operation normally takes 1 - 2 hours with most patients being in hospital for approximately 5-7 days.

Illustration of a Normal Knee. Please click here to enlarge this image. Illustration of a Diseased Knee. Please click here to enlarge this image.
Please click the illustrations above to enlarge them.

Illustration of a Replaced Knee. Please click here to enlarge this image.
Illustration of a Replaced Knee.
Please click here to enlarge the image.

Implant Design
Image of AGC Knee Prosthesis. Click to enlarge image.Mr Charnley uses a cemented knee replacement in which the lower thigh bone, (femur), is replaced by a metal surface inserted over the end of the bone with antibiotic loaded bone cement. This cement acts as a "grout". The upper tibia (shin bone) is resurfaced with a combined high density plastic and metal surface and the back of the patella (knee cap) is resurfaced with a high density plastic button.

Mr Charnley routinely uses a knee replacement called the AGC (Anatomic Graduated Condylar, image right) which was designed by Dr Merrill Ritter, past president of the American Hip and Knee Society. The design has been available for over fifteen years and world-wide is probably the most successful in multi-centre studies from Europe and the USA.

Mr Charnley and his team like to follow up the knee replacements performed by his "firm" on a regular basis and some patients are entered into a patient satisfaction audit of the AGC knee.

Uni-compartmental knee replacement has been successfully performed by surgeons in Oxford and other centres. This is a partial replacement of the knee where the arthritis is limited to the inner aspect of the knee and in patients who have no ligament damage or weakness. Certain patients therefore with early arthritis in this area may successfully undergo this lesser procedure.

uni-compartmental_knee_replacement.jpg (17276 bytes)
Uni-Compartmental Knee Replacement Implant

Complications
The overall success rate of a TKA is 95% plus, but there are some complications you must be aware of:

The average life span of all knee designs is about a decade.

As with any operation there are acknowledged risks. Most patients are worried about their anaesthetic but modern day anaesthesia is extremely successful with rarely patients not waking up after their anaesthetic, (perhaps a 1 in a million risk). Patients over 80 may have medical problems which may add additional peri-operative medical risks such as strokes and heart attacks.

Other risks associated with the surgery itself are infection from bacterial organisms and to reduce this Mr Charnley uses antibiotics around the time of surgery as well as using bone cement with antibiotics in it. There is still a chance of one or two patients in every hundred having this complication. Wound healing can also occasionally be delayed with such a complication.

Blood clots in the legs and on the lungs (thrombo-embolism) is also reported in particular in those patients who smoke. There is a remote chance of damage to the nerves and arteries around the knee (less than 1 in 100), more so with those knees that have had previous surgery or are of a rather abnormal shape.

Finally, we are sometimes asked if the operation went wrong - could a patient lose their leg following a replacement. This does sadly happen if there is severe overwhelming infection or major damage to the blood supply or all the nerves. The chances of this happening are remote possibly one in five or six thousand.

The Post-Operative Period
Your knee surgery will be performed by an experienced team of surgeons, nurses, physiotherapists and occupational therapists. The whole team will try and help you get over the post-operative period with advice about do’s and don’ts. You will normally be sent home on a pair of crutches once you are safe and not before. The team are happy to give additional information regarding return to work, driving and sexual intercourse.

Training
Mr Charnley and his surgical team perform on average 1 knee replacement per week. The majority of the surgery is performed by Mr Charnley himself but also by experienced staff grade surgeons and higher surgical trainees. These latter surgeons will have all been personally trained and supervised by Mr Charnley and by other knee surgeons on their training rotation.

Finally Mr Charnley is happy to try and explain any aspects of the surgery including the risks or complications before the operation.

All illustrations on this page are acknowledged and are supplied for patient information by Schering-Plough/Doctor Direct Ltd.

This page was last updated on 04/Mar/2012