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Knee replacements have been carried out in the UK since the 1970s, with approximately 80,000 performed every year in England and Wales. This includes both total and partial knee arthroplasty (joint replacement) where either the whole knee or one side of the knee is removed and fitted with a prosthesis (artificial joint part). These operations are for people who have problems such as severe arthritis, injury or deformity in the knee joint, which cause pain and greatly impact mobility and quality of life.
On the whole, these are successful procedures, and many patients have good outcomes. However, the new joint parts do not last forever, and this is where knee revision surgery comes in. If the new joint fails, a second surgery is required to ‘revise’ the joint: taking out any old or dysfunctional prostheses, clearing any debris or inflamed tissues (known as debridement) and creating a new joint replacement. Without further complications, most successfully-replaced knee joints can be expected to last around 20 years before needing to be replaced again, however, this is greatly dependent on the age and activity level of its recipient. Overall, long-term follow-up of patients receiving knee replacements showed that only 3.9% required revision of the joint within 10 years, rising to 10.3% requiring revision by 20 years. However, in younger individuals (around 50 years old), the rate rose to 35% needing a second surgery. Overall revision rates for the UK are below 5%.
The challenge with revision surgery is that, because the joint has already been operated on, the procedure is generally very difficult to carry out, is associated with a higher rate of complications, and is often not quite as good as the original replacement. As such, knee revision surgery is a highly skilled procedure, requiring both expert opinion and experienced hands to complete successfully.
In addition to general wear and tear and age of the new joint, there are several other complications (normal risks of having any joint replacement), which, although occur rarely, are important indications for the need of revision surgery. These are described below. Usually, when a knee joint requires revision it is due to a number of contributing factors leading to the failure of the implant.
When an artificial joint part is put into place, it is secured by one of two methods. The first is using cemented parts, where a specially designed medical cement is used to fix the joint part in place. The second method uses joint parts that are particularly designed to allow the bone to grow into them, securing them in place. Both methods are shown to be effective, however, in some individuals, there is still loosening of one or more of the new joint parts which can result in both pain and reduced joint function.
This is more likely to occur with increasing age and use of the implant, however, factors such as very high-impact activity or being overweight can accelerate this process and increase the likelihood of it happening. Sometimes, a phenomenon known as ‘osteolysis’ may also occur. This is where the bone itself around the implant begins to degenerate, resulting in loosening. The National Joint Registry shows that in 2017, half of the knee revisions in the UK were as a result of ‘aseptic loosening’ of the joint implants (loosening of the implant without infection).
Whilst infection is a complication to consider in any invasive medical procedure, there are several types of infection that are particularly troublesome in the context of joint prostheses. Following the initial risk of infection from the stay in the hospital and the surgery itself, joint implants can become infected over the coming years. This results in pain, redness, swelling and sometimes even dislodging of the joint implants themselves, causing the new joint to fail.
In particular cases, a joint ‘wash out’ and exchange of the spacer part of the implant between the thigh and shin bone can be performed, without the need for removal and replacement of the fixed parts of the joint; this can be sufficient to treat the infection. However, in many cases, a ‘staged revision’ is required. This involves removal of all the joint implant parts and debridement (surgical removal) of infected tissues, followed by a rest period and course of strong antibiotics, before having a second operation to put in a new joint once the infection is clear.
The knee joint has six main ‘soft tissue’ elements that stabilise the joint. Two of these, the menisci (pads of cartilage which sit on top of the shin bone, cushioning the thigh bone on top), are removed as part of the joint replacement. The remaining four elements are ligaments (collateral and cruciate ligaments) that run between the thigh and shin bones providing support and stability to the joint. In order to get access to that joint space during replacement surgery, these ligaments can often become slightly damaged. This is usually managed well with appropriate physiotherapy and rehabilitation after the surgery, but in a few cases the ligaments are either too damaged or do not heal. This results in an unstable joint that may ‘give way’, swell and cause pain. Knee revision surgery can restore this stability and balance to the knee to maximise function.
Joint stiffness is a major issue following knee joint replacement and is initially targeted with graded physiotherapy. However, it remains that some patients experience severe stiffness in the affected joint, resulting in major restrictions in the range of movement, which can be severely disabling. Following the failure of physiotherapy to alleviate stiffening of the joint, manipulation under general anaesthetic can be effective. This involves going to sleep under a general anaesthetic so you won’t feel anything, then the surgeon will move the knee around freely, breaking down any of the scar tissue that has built up around the joint. This is often a successful procedure and, whilst still carries the risks associated with anaesthetic, solves the problem without the need for another surgical intervention. Following this, surgical revision of the joint has also been shown to increase the range of movement and improve outcomes overall. Although this also carries the increased risks associated with revision knee surgery, data suggests that, as only 5% of knee revisions are carried out as a result of ongoing joint stiffness, physiotherapy and manipulation under anaesthetic are effective strategies to manage this.
Often when adults get older, bones can weaken as part of the natural ageing process or from ‘osteoporosis’ (where bones become more brittle). Additionally, when a prosthetic joint implant is fitted into a bone, that part of the bone can become weaker than normal, meaning that the bone is more prone to breaks or fractures around the implant. Unfortunately, if the bone surrounding the implant becomes fractured, this means that there is nothing anchoring the implant and it will become unstable. This presents a scenario that is more complicated than a simple bone fracture, as the replaced joint must also be taken into account. In these cases, a larger operation to both stabilise and fix the fracture, as well as replace the artificial joint parts, is carried out to provide optimal long-term outcomes for the joint.
Steps to prepare for knee revision surgery are fairly similar to those for initial knee replacement surgery. The main difference is that, if you are undergoing a revision procedure, it is likely that this is because of problems with the current artificial joint, which is probably causing pain. Moving around on a painful joint is hard at the best of times, but keeping mobile and building up the muscle around the joint after the operation is not only essential but will also enhance recovery.
Here are seven quick tips to consider when preparing for knee revision surgery:
As mentioned previously, knee revision surgery confers a higher level of risk and complication to initial knee replacements, as the joint has already been operated on. This means that revision surgery is longer and more complex, however, as with the original operation, every precaution to minimise risk will be taken, and your consultant will use their medical judgement and experience to weigh up the risks versus benefits of the procedure to advise you.
Risks of revision knee surgery include:
Here is some advice from one of our top consultant orthopaedic surgeons, Mr Matthew Hearth, who has a special interest in hip and knee replacements, including revision surgery:
‘My name is Matthew Hearth and I am a Consultant Orthopaedic Surgeon. My specialist interest is Lower Limb Joint reconstruction. As such one of the operations I perform is revision total knee replacement.