3D printable implants: the future of meniscus repair?

Meniscus repair with 3D printed cartilage

To demonstrate how their 3-D-printable, cartilage-mimicking material might work, the researchers used a $300 3D printer to create custom menisci for a model of a knee. Photo credit: Feichen Yang

Coming soon – print your own knee? Sounds ludicrous, we know, but the worlds of 3D printing and medical science have been skirting around each other for a few years now. There have already been examples of 3D printing being used to create exact moulds of body parts (such as the scalp), but the latest development from Duke University in North Carolina is interesting for those suffering from a common knee injury.

According to a report issued last month, a $300 3D printer has been used at the university to create custom-built menisci for a model of a knee – and if things go to plan, it may not be too long before knee surgeons will be able to print replacement, custom-fitted artificial cartilage, cutting the costs and time or certain knee surgeries at a stroke.

The importance of the menisci

The meniscus is a vital part of the knee. A rubbery, crescent-shaped disc, situated between the thigh and shin bones, their main roles are to cushion the stress that the knees endure during the simple mechanics of walking and running, and help steady the knee by balancing the weight you put on it. In other words, it’s a part of the knee that you don’t notice until something goes wrong with it, and that ‘something’ is usually a meniscal tear.

The meniscus is a vital part of the knee. A rubbery, crescent-shaped disc, situated between the thigh and shin bones, their main roles are to cushion the stress that the knees endure during the simple mechanics of walking and running, and help steady the knee by balancing the weight you put on it. In other words, it’s a part of the knee that you don’t notice until something goes wrong with it, and that ‘something’ is usually a meniscal tear.

A meniscal tear can be caused by many factors: it can happen when you twist or turn your knee, usually when the foot is planted while the knee is bent. It can happen when you lift a heavy item. It can happen during the rigours of sports participation. And sometimes, amongst older people, it can even happen while you’re going about your day-to-day routine, menisci tend to wear over time.

The knock-on effect of a meniscus tear depends on the severity of the tear. A minor tear can result in slight pain and swelling for a couple of weeks. A moderate tear can cause a greater intensity of pain and swelling, along with knee stiffness and difficulty in bending. A severe tear can not only result in pieces of the meniscus getting caught in the joint space (causing the knee to lock and catch, but the knee can also give way without warning.

Coming soon: cartilage from a cartridge?

While replacement surgery for meniscus repair is available (and has been for over 20 years), it’s still a very uncommon procedure, mainly because it depends on the use of healthy cartilage tissue taken from a cadaver and an extremely strict criteria that patients must meet before they’re even considered for treatment. So it goes without saying that the possibility of being able to map out and print millimetre-perfect copies of bespoke menisci could revolutionise knee surgery.

But before we all start rushing out for 3D printers, it’s worth pointing out that while the actual models of the menisci can be printed out, the actual printing materials are not yet up to par. The current gels being used in the printing process are currently not as strong or as hard-wearing as natural cartilage, and it’ll be a while before they match the durability and elasticity of the real thing. But this is one development well worth keeping tabs on.