A total knee arthroplasty – also called total knee replacement – is a surgical procedure to treat severe knee pain caused by injury or a degenerative condition like osteoarthritis. It involves removing the damaged knee joint and replacing it with a prosthetic implant. Knee replacement surgery is one of the most successful of all surgical procedures, enabling people who’ve been in chronic pain to enjoy a full and active life once more.
How long do prosthetic implants last?
Over time, however, prosthetic implants can become worn and may need to be replaced. According to an article in The Lancet (16 February 2019), which analysed pooled registry data from 2882 articles, 82% of total knee replacements (TKR) and 70% of unicondylar knee replacements (UKR) in patients with osteoarthritis last 25 years.
A total knee replacement entails replacing the whole of the knee joint whereas with a unicondylar knee replacement only the damaged compartments of the knee are replaced, leaving the remainder intact.
What are implants made from?
Artificial knee joints come in four main types. The most common is metal on plastic, which consists of a metal femoral stem and a polyethylene plastic spacer attached to the tibial component.
Some types of implant have a ceramic femoral stem rather than a metal one. These may be used in patients with a sensitivity to nickel. Less common are implants made entirely of ceramic as there is a risk of squeaking when you walk, and implants made entirely of metal as there are concerns about the long-term risk of implant breakdown.
What is a revision total knee replacement?
If your knee replacement fails, your knee can start to become painful and swollen. It may feel stiff or unstable, making everyday activities difficult. If this happens you may need a revision total knee replacement, which is a second surgical procedure to remove some or all of the prosthetic implant and replace it.
Unfortunately, a revision knee replacement is a longer and more complex surgical procedure than a primary knee replacement which means there is a greater risk of complications like poor wound healing or infection. For this reason, orthopaedic surgeons generally recommend delaying primary total knee replacement surgery for as long as possible to minimise the chances of requiring a revision total knee replacement in the future.
Research study
A research study carried out at the University of Otago in Christchurch, New Zealand looked at the lifetime risk of needing revision surgery following a total knee replacement. Researchers wanted patients, particularly younger patients, to be able to make a more accurate assessment of risk by understanding the likelihood of requiring further surgery in the future.
They used the New Zealand Joint Registry database to obtain revision rates and mortality rates for all primary total knee replacements over an 18-year period between January 1999 and December 2016. Patients were stratified into age groups at the time of the initial surgery and the lifetime risk of revision surgery was calculated according to age, sex and American Society of Anesthesiologists (ASA) grade.
Overall, the 10-year survival rate for implants was 95.6%. The lifetime risk of requiring revision surgery was 22.4% in patients aged between 46 and 50 at the time of the initial surgery. This decreased linearly with increasing age. In patients aged between 90 and 95 at the time of the initial surgery there was only a 1.15% risk of revision. The higher a patient’s ASA grade, the greater the lifetime risk of requiring revision surgery.
Researchers identified the three most common reasons for needing revision surgery as: aseptic loosening of the implant causing the joint to become unstable; infection of the prosthetic, and unexplained pain. Young male patients aged between 46 and 50 at the time of their primary total knee replacement surgery are at greatest risk of needing revision replacement surgery in the future.
Total Knee Replacement – Dublin
If you are due to undergo a total knee replacement, talk to your surgeon about the risk of needing revision knee replacement surgery in the future. We discuss all potential risks and complications with patients scheduled to undergo total knee replacement surgery. If you would like specialist advice or to make an appointment, contact us.
