The future of knee surgery lies in biological reconstruction
Things have come an awfully long way since arthroscopy – a minimally invasive surgical procedure on a joint – was first introduced to the UK back in the 1970s. There are now a number of specialist knee surgeons who are regularly undertaking major complex reconstructive surgery, with highly encouraging results.
As a knee surgeon, the most common thing I see is meniscal tears. The menisci are ‘shock absorbers’ and load sharers in the knee, and they sit in between the bones like two rubber washers. However, when subjected to the high compressive and shear forces in a knee joint, the menisci can, and often do tear, which can cause pain, clicking, catching, giving way, locking and swelling in the knee. If a meniscal tear is symptomatic then it is likely to need surgery, and unfortunately only a minority of meniscal tears are repairable. Generally, it is thought that only about 15% of meniscal tears are repairable. In my hands, I tend to repair about 33% of the meniscal tears that I see; but this is still just a minority, and even though I have a specialist interest in meniscal repair, a majority of tears still end up simply having to be trimmed.
In the past, patients with meniscal loss who were starting to develop premature degeneration in their knee were simply told to put up with the symptoms for as long as they could, with a view to them eventually ending up having a knee replacement when they were older (normally 50+). Nowadays, however, we do actually have very good potential surgical solutions for these patients, which we are now able to offer. The obvious thing if someone is developing problems in their knee due to loss of a meniscus is simply to replace the meniscus with a new one, and this is exactly what we are doing nowadays with meniscal transplantation. This involves taking a meniscal allograft from a donor and transplanting it into the patient’s knee.
The surgical procedure of meniscal transplantation is fairly major and complex, and it is only undertaken by a very small number of specialist knee surgeons in the UK. The rehab is very slow and restrictive but the results are highly encouraging, with a success rate in the region of about 85% at 5-year follow-up. This procedure is not perfect, and it will not reverse whatever articular cartilage wear and tear the patient might already have in their knee, but it is an awful lot better than just leaving the patient with nothing and just telling them to go on suffering until they’re bad enough for a knee replacement.
The other kind of cartilage in a knee joint is the articular cartilage, which is the smooth white shiny layer of tissue that covers the joint surfaces and that makes the surfaces smooth and low friction, to reduce wear and tear. If a patient loses a patch of articular cartilage in their knee then this will cause pain and swelling, and if there are loose chunks of cartilage then these may cause giving way or locking. Also, leaving patches of damaged articular cartilage in a joint will simply result in progression of the damage, which then becomes more widespread, likely flaking paint on a rusty gate. When there is widespread cartilage loss with bare bone exposed and with bone rubbing on bone, then this is ‘osteoarthritis’, and if the damage is severe enough then the patient might then be looking at artificial joint replacement surgery.
The problem with knee replacements in younger patients is that younger people do more, and hence the rate of wear and tear on the artificial joint will be faster, which means that it will wear out quicker and fail sooner. This means that younger patients are far more likely to end up having to undergo revision surgery, and revision knee replacement is even bigger and even harder than primary joint replacement surgery, with higher complication risks and a lower probability of a good outcome.
Therefore, if you’re a younger person and you’ve lost a meniscus and you’ve also got articular cartilage loss as well, then this is an extremely difficult issue to address. In this case, it is possible (and sensible) to replace both the meniscus and the articular cartilage at the same time – and this is what is referred to as a ‘Biological Knee Replacement’. Although this surgery is very complex, and something that is only undertaken currently by just a small handful of specialist knee surgeons in the UK, it can give very good results in appropriate carefully selected patients.
The future of knee surgery lies in this biological reconstruction, with allografts, with 3D printed biological scaffolds, with tissue engineering, growth factors and stem cells. What’s clear is that knee surgery in the future will be a very different thing from what it is currently, and one day doctors really will be growing new knees for patients. The future is set to be extremely exciting, which is why being at the forefront of modern knee surgery is not just a challenge, but an absolute passion!