How parts in cutting-edge Linx prosthetic replicate unconscious work of the leg

When we walk, our knees and ankles work in tandem to ensure balance and stability.

Prosthetics company Blatchford – which has been making artificial limbs since the 19th century – used cutting-edge technology to replicate that in Linx, the world’s first integrated limb system.

The system allows the artificial knee and foot to communicate with each other in both directions, giving the user a more normal gait across all types of terrain, providing much greater confidence and freedom. Linx won the Royal Academy of Engineering’s MacRobert Award in 2016.

Socket

Socket interface and interface to the ground are both fundamental to comfort. A good socket fit allows the most effective use of the prosthetic limb. The interface to the ground is governed by the prosthetic foot. The hydraulic technology used has been proven to improve the peak loading and overall comfort.

Wearability also depends on the reliability and support of the prosthetic limb in different activities. With automatic detection of different activities and appropriate control strategies (such as for walking down a ramp), Linx supports the wearer so they don’t need to think about the terrain and can focus on their daily activities.

Materials

The materials used to create Linx need to be lightweight and to have high structural strength to withstand daily use. They include metals such as aluminium, stainless steel and titanium, as well as composites such as carbon fibre.

Sensors 

Linx uses a network of integrated sensors across the knee and foot that act like human nerves, continuously collecting data on the user, their activity, the environment and the terrain around them. The central computer uses this data to adapt the limb’s ankle and knee responses to the situation. This integrated and coordinated limb response ensures fast adjustment times and easy navigation of slopes and steps, allowing the user to think about where they are going, rather than how they are going to get there.

The future

The intelligence and capabilities of prostheses are improving every day. Further integration and control of the prosthesis through connectivity to the residual limb will soon allow the users to control their prosthetic limbs in much the same way as they would a natural leg.

“The prosthetic limbs of the future will surely enable further Paralympics records to be broken and victories won,” says Blatchford. “But they must also enable amputees to live their lives independently and without barriers, every day, as well as when performing at their best. Linx is a step towards that goal.”