Innovation & Entrepreneurship

Innovation & Entrepreneurship

Power prostheses: the incredible developments changing amputees’ lives


Kathryn Reilly talks to Saeed Zahedi, Technical Director of world-leading rehabilitation provider Blatchford Group about the increasing intelligence and capability of prostheses


Last year’s Paralympic Games were a testament to human strength, with more disabled athletes competing than ever before: 4,350 athletes from more than 160 countries took part in 22 different sports.  In many cases, the Games were also a celebration of medical technology. Wheelchairs have become lighter and more aerodynamic, and running blades for amputee athletes have become incredible works of engineering, using advanced materials and cutting edge design. Such development has translated into new records too. Team GB’s Jonnie Peacock ran the 100 metres in 10.8 seconds – just one second behind Usain Bolt’s record in the Olympics.

But it’s not just elite athletes who can benefit from such advances in medical technology. In England alone, there are currently around 45,000 people who rely on lower limb prostheses, with around 4,000 lower limb amputations carried out each year. For these people, simple tasks such as standing still can be a challenge, requiring significant energy and concentration to hold the leg steady, let alone to move at speed. Back pain is common, as an amputee is more likely to shift the balance of their weight to their sound side, increasing pressure on the spine and hips.

An innovator with history

Since 1890, Blatchford has designed, developed and manufactured prosthetic limbs to improve the day-to-day lives of amputees: from the first stabilised knee that allowed amputees from World War II to walk safely and securely, to the carbon fibre shin pioneered in the 1980s. And Blatchford’s prosthetic technology has included several firsts: the IP knee in the 1990s, which was the first commercial microprocessor-controlled knee; Elan, the first microprocessor-controlled hydraulic ankle in 2012 and most recently, Linx, the world’s first fully integrated above knee prosthesis. This year, Linx was awarded the UK’s premier engineering prize, the Royal Academy of Engineering’s MacRobert Award. Known for spotting the ‘next big thing’ in technology, every year the MacRobert Award is presented to the team behind the UK technology sector’s most exciting engineering innovation.

Linx is unique because it uses a network of sensors across both the knee and foot, which act like human nerves, continuously collecting data on the user, their activity, the environment and terrain around them. The central computer uses this data to predict and adapt the limb’s ankle and knee responses to the situation. This means the wearer can walk confidently, knowing that the limb will adjust appropriately and ensure support at all times. When a patient is first fitted with Linx, a prosthetist programmes the central computer by running through a self-calibration sequence so that the limb learns how its wearer naturally walks and adapts accordingly. This is done via a Bluetooth connection to a software app that shows in real time what the sensors are picking up as they detect the wearer’s natural speed and movements. A smart algorithm then programmes the limb automatically as the knee and the foot joints ‘talk’ to each other.

Linx also senses when the wearer comes to a standstill and automatically locks so that the wearer can relax, and maintain an even, balanced posture. It does this by using another algorithm to detect when the limb reaches a ‘steady state’ before increasing resistance to provide support as well as self-alignment. When the user wants to move again, the sensors allow Linx to unlock.

These adjustments make it easier to walk on a variety of terrains. If the wearer is walking down a slope, for example, the system recognises the angle from the sensors around the limb. It then increases the resistance provided by hydraulic dampers at the ankle to stop the energy being absorbed by the spring, which would cause it to propel the limb forward. Damping energy from the heel also allows some of the energy to be absorbed, while increasing resistance in the knee, which stops Linx from sinking forward too quickly. Overall, it gives the wearer a sense of stability and support.

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When walking uphill, the damping at the ankle may be increased to absorb some of the energy but reduced at the knee so the springs can produce the right level of energy to take a step upwards. The result is that the amputee feels like they are being assisted up the slope by the limb. The combination of these technologies has enabled a reduction in the amount of energy an above knee amputee needs to expend to compensate for the lost limb. The first microprocessor controlled knee reduced energy expended by 25 per cent. Adding a microprocessor to the ankle reduced the work done by a further 18 per cent, while integrating the control of both joints with a single processor in Linx reduced the hip power required by another 8 per cent. The amazing result is that, collectively, the energy expenditure by amputees is becoming closer to that of abled body person.

Immersive expertise

Blatchford is also a service provider, treating amputees, prosthetic and neuromuscular orthotic users in the UK and Norway. This direct access to user feedback and clinical staff is vital in informing future developments and innovations, in particular new technologies aimed at reducing the extra effort amputees have to make in order to manage their impairment and disability day-to-day.

Unfortunately, currently only a fraction of the tens of thousands of amputees in the UK will have access to the latest technology, as Linx requires a special case application within the NHS. As such, most Linx limbs in use today are benefiting amputees in the US, Germany and Norway, despite the fact that the prosthesis could result in a longer-term financial saving by reducing the need for secondary treatments required for back pain, arthritis, falls, and sound-side joint replacements.

But the future’s looking bright. Further integration and control of the prosthesis through nerve endings in the residual limb will soon allow the users to control their prosthetic limbs in much the same way that they would a natural leg. The prosthetic limbs of the future will surely enable further records to be broken and victories won. But they must also enable amputees to live their lives independently and without barriers, every day as well as when they want to perform at their very best.

About the author

Journalist and editor Kathryn Reilly has worked in consumer, contract and medical writing for more than 20 years.

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