Revision knee replacment: when is it necessary?
Autore:When exactly is a revision knee replacement required?
After undergoing total knee replacement, the vast majority of people are happy with the outcome and do not require more surgery. However, there are several particular circumstances when knee replacements may need to be redone. The most frequent reasons in descending order are:
- Loosening of the knee implant from the supporting bone
- Infection on or around the implant
- Instability
Loosening
Loosening occurs over time as the knee is put through normal use. Most commonly it is the Tibial component (the metal base plate that sits on top of the shin bone), that becomes loose. Either the component becomes loose from the bone cement in which it sits (known as de-bonding) or the bone cement securing the implant to the bone starts to loose its ‘grip’ on the bone around it.
Both problems classically cause ‘start- up pain’. This is when the first few walking steps after a period of rest are most painful, before the implant finds some temporary stability and the pain briefly improves.
Revision surgery is performed to remove the loose implant(s) and re-establish a solid fixation within the bone with new more specialist implants.
Infection
A knee replacement has no direct blood supply, therefore, the body’s immune system is not always able to identify and fight off bacteria that may settle in the joint. Despite the high level of care taken during the operation to minimise infection, rarely, some bacteria can still enter the joint.
Alternatively, infection elsewhere in the body such as in the urinary tract, teeth and gums or gut can travel to the knee joint via the blood stream.
Once established within the knee, infection can cause pain via loosening of the impants and sometimes damage to the tissues and bones of the knee. Revision surgery is required to remove the implants, clear the infection from around the joint and then place new components into the now sterile joint.
From time to time, after removing the infected joint, a temporary knee replacement is left in place and antibiotics are given via the vein, before the definitive reconstruction is performed.
Instability
One part of knee replacement surgery is placing the components into a persons knee in such a way as to recreate the natural movement and get a ‘feel’ of the knee for the individual patient. Occasionally this ideal target is not fully achieved and the knee may feel unstable to the person concerned.
Often instability is very subtle with people ‘not trusting’ the knee particularly during activities where the knee is bent e.g walking on inclines or stairs. In these scenarios, revision surgery may be needed to address these issues.
