Advances in prosthetic knee technology

An interview with Alastair Ward conducted by April Cashin-Garbutt, MA (Cantab)

How do microprocessor-controlled prosthetic knees differ from traditional prosthetic knees?

These prosthetics are a big change from traditional models. The knees are designed with a programmable computer that is built in to the joint. This battery powered technology continuously controls both the swing and the stance phase of the prosthetic through real time data that the computer receives from its built-in sensors. This means that the knee can actively think for itself and adapt based on the information it is receiving.

In what ways do patients benefit from microprocessor-controlled prosthetic knees?

Using current systems available on the NHS, amputees often struggle when walking on different surfaces, particularly on slopes and uneven terrain. With microprocessor-controlled knees, amputees benefit from stability on different terrains, slopes and steps, as well as being able to walk more naturally and efficiently at either single or varying speeds. This means that users can walk without the fear of stumbling or falling, as their prosthesis will continuously adapt to the terrain around them.

Are there any downsides or limitations to this new technology at the moment?

There are always downsides and limitations to any technology. In general, however, these devices are very good. Lifelike cosmetic appearance can still present an issue for some amputees but these days many choose to wear custom covers or display the technology itself. As manufacturers, there is a lot more work goes into making the knees look less medical in nature than was perhaps previously the case.

How does the technology work?

Prosthetics devices such as Blatchford’s Orion 3 adapt hydraulic resistance in real time, to provide the wearer with support when moving in any environment or standing still. This model also has stumble recovery technology, ensuring that the knee remains stable should the user falter.

As well as this, knee flexion during the swing of the leg forward varies according to walking speed. With microprocessor pneumatic swing control, the limb controls heel rise across a range of walking speeds for a more natural swing. A pneumatic system allows for a ‘spring’ that can be varied by electronically adjusting a valve in real-time. This allows it to walk as naturally at low speeds as it can at higher speeds.

At the same time, the on-board computer is also tasked with switching off the hydraulic standing resistance at just the right time, making it easy to initiate swing phase whilst being as safe as possible for the user.

Basically, the computer can’t be ‘tricked’ into switching off the stability as easily as a purely mechanical system can. In combination, all of this helps to save energy whilst remaining as safe as possible at all times.

In what countries are microprocessor-controlled prosthetic knees currently available?

Microprocessor-controlled knees are readily available in many countries including Germany, the US, Scandinavia and Italy for example.

Strictly they are available nearly anywhere, but it is mainly insurance based systems where they are routinely supplied.

In the UK, the technology was previously only available as part of specific trials, to military amputees from recent and historical conflicts, through private clinics or in Scotland, where they have approached provision differently.

Can you please give an overview of the recent announcement from NHS England on the funding available?

NHS England recently announced the decision to routinely commission ten new specialised treatments based on advice from the service’s clinical priorities advisory group, which assessed the relative priority of investing in a new range of specialised treatments and interventions. This took into account revised prices submitted by some manufacturers since the provisional investment decision were published in July.

One of the ten items approved for funding, a decision that was made following consideration by NHS England’s Specialised Services Commissioning Committee, is microprocessor-controlled knees.

What will the NHS funding mean for the development of this technology?

The decision to make microprocessor knees readily available to NHS patients will act as a catalyst to accelerate the development of even more advanced technologies, improving patients’ lives further.

Previously, the technology was only accessible to a small market, hindering developer’s potential to grow and expand. Now that the treatment will be available on the Health Service, the number of people who require these devices has suddenly become far broader. This will provide a much larger user group who can shape the future of the devices.

To ensure developers of prosthetic devices stand out to the NHS as a natural choice, companies will need to make sure that the product on offer provides users with the best functionality possible, whilst also proving to be the best value for money.

This battle within the prosthesis market is only going to increase the pace of development of these limbs, helping create better devices that will benefit all in the future. There are already some highly advanced prosthesis available, and the industry will continue to search for ways to create even more advanced microprocessor-controlled knees in the future.

How will this technology add value to both the NHS and patients?

For patients, the technology eliminates the risk of amputees falling or injuring themselves when walking or changing environments, providing users with the confidence and stability needed to move without fear. Such benefits not only make a huge difference to patient safety and quality of life; they also reduce the lifelong care needs of amputees.

Patients wearing microprocessor-controlled limbs are less likely to injure themselves thanks to the advanced technology and this has the potential to reduce costs associated with patient care and waiting times at clinics. If fewer amputees have to visit GPs or hospital wards due to prosthetic issues or injuries, NHS time and money can be spent on other areas, while patients will spend less time and money going to and from hospitals to treat any issues they may have.

What do you think the future holds for prosthetic knee technology? What advances are in the pipeline?

The next generation of devices will aim to also provide muscle like power back to the patient. There are devices that aim to do this currently but control system limitations, cost and current battery technology limit their usefulness.

Further advances in materials, battery technology, manufacturing techniques, and things like implanted sensor control technology will all contribute to limbs that may not necessarily get lighter, but will be more intelligent with more complexity whilst keeping them at a weight that is practical.

Where can readers find more information?

Further information is available including what designs are available and the benefits of the technology, as well as the NHS’s decision to fund the technology, in the document prepared by the health service.

Information around specific models available, such as Orion 3, is usually best found on company websites, where you can find some added context on the benefits of the technology can be seen.

About Alastair Ward

Alastair Ward graduated from Salford University in 2000 with a first-class BSc (Hons) degree in Prosthetics Orthotics. Having worked as a Prosthetist in Sheffield’s Northern General Hospital for six years, he joined Blatchford’s Products division in 2006.

Over the last ten years he has been actively involved in new product development, as well as his education and training role and has accrued a vast wealth of experience of the fitting of Endolite devices to the end users. In particular, this has allowed him to develop expertise in the understanding, fitting, and setup Biomimetic Hydraulic Ankle and Microprocessor technologies such as Echelon, Elan, Linx and Orion 3.