Written by: PROFESSOR ALI GHOZ
Published: 25/01/2019 | Updated: 09/05/2019
Edited by: NICHOLAS HOWLEY
There are lots of ways to replace a knee – but which is best? Should you have a
partial or full knee replacement? Are robotic techniques and 3-D printed
replacements worth the extra cost? We asked expert orthopaedic
surgeon Professor Ali Ghoz:
What are the main types of knee replacement surgery?
When we talk about the types of knee replacement surgery, we’re mainly talking
about how much of the knee is being replaced. Knee replacement can be
classed as partial or total, and partial knee replacement can be further divided
into one component or two component replacements.
Many people ask about “3-D printed” knee replacements, and “robot-assisted”
knee replacements. These are best thought of as techniques to help us perform a
successful well aligned knee replacement. But the first decision has to be either
to have a partial or full knee replacement.
Which type of surgery is better?
The most preferable from a functional point of view is a partial knee replacement
involving just one component (often known as unicompartmental knee
replacement). It’s less invasive and the functional outcome is better – it will feel
like almost like a more normal knee. This is because we only replace the
damaged side of the knee and preserve the rest of the knee’s biomechanics and
ligaments. In contrast, bicompartmental and full knee replacements tend to
result in a knee that doesn’t feel quite natural.
However, not everyone can have a partial knee replacement. Your ligaments have
to be intact, the damage must only be in one part of the knee, and the bone
quality needs to be good. Finally, associated deformities are likely require a total
knee replacement rather than a partial knee replacement.
Should I have a 3D-printed knee replacement?
The aim of a 3D printed knee is to create a knee that fits the patient – after all,
some people will have small knees, and other people bigger knees.
The printing is carried out as part of the preoperative planning process. A 3D
scan of the knee is made and the customised knee replacement is then printed.
The idea of making the knee to fit the patient exactly is intuitively attractive, and
many people believe it is likely to last longer and result in fewer complications.
However, so far nobody has been able to show there is a long-term difference in
outcomes compared to the use of a standard knee replacement.
Should I choose a clinic which offers robot-assisted surgery?
With robotic assistance, we can achieve a better alignment with our implants,
and this is clear on the X-rays we look at. All procedures are carried out by a
surgeon who is trained in performing knee replacements using the robot.
Generally, robot-assisted surgery results in less postoperatie pain and an earlier
return home. However, as with the use of 3-D printed knee replacements, there is
still no clear evidence that this changes outcomes in the long term.
What should I expect after surgery?
It’s normal for your knee replacement to have a minor “click” or “clunk” –
especially after full replacement. This tends to get better in time – but there may
always be some clicking between the metal and plastic in your knee. 1 in 5
people who has a knee replacement will always have some pain in the knee.
There might be some stiffness in the knee and the scar can have some associated
numbness. A patient with a knee replacement may have difficult kneeling after
the operation. The knee replacement side always feels warmer than the native
side. There is usually some permanent swelling around the knee replacement.
The scar can be a bit sensitive and tender. It takes a full year to get used to a knee
replacement.
You should also seek medical advice if you experience:
• unexplained severe pain
• episodes of the knee giving way
• any signs of infection, such as leakage
• any signs of loosening
How long does a knee replacement last?
The average knee replacement lasts around 10-15 years.
95% of total knee replacements survive for about 10-13 years, whereas partial
knee replacement have a shorter life span (8-10 years). This is usually because of
the deterioration of arthritis, and replacement with a full knee replacement is
necessary the second time around.
The lifespan of knee replacements has improved in recent years. This is because
materials have improved and the way we sterilise implants have changed. In
modern knee replacements we tend to use high-strength plastic inserts,
ceramicised oxinium, and customised implants.
Finally, the way we cement the join to the bone has changed. Cemented knee
replacements survive longer and have fewer complications than uncemented
knee replacements
The drive is ultimately to make the implanting of the knee perfect. The materials
we now use certainly make a difference, but it remains to be seen whether
techniques such as robotic assistance or 3D printing will improve outcomes and
satisfaction rates in knee replacement patients.
