Background

Our team has recently returned from a trip to Reboocon Bionics, where the first UK amputee was fitted with the motorised Intuy Knee microprocessor knee (MPK). Reboocon is a small prosthetic manufacturing company based in Delft, the Netherlands. The small team lead by Shiqian Wang, have developed a powered prosthetic knee that is already making a difference to the daily lives of amputees across France, Germany, Belgium, Russia & China. Mr Wang has a successful background in design & manufacturing powered joints for exoskeletal robotic suits for individuals with spinal cord injuries. His latest design (the ILK) has been in development since 2016, the motorised external knee joint offers active propulsion and active swing with sophisticated software to make this a state-of-the-art intuitive prosthesis.  

The prescription of powered prostheses is not a new concept to the team at Pace Rehabilitation who have been successfully prescribing powered prostheses such as the Ossur Power knee and the Empower foot (previously the BiOM) to their clients for the last decade. Pace was the first UK prosthetic provider to prescribe the Power knee by Ossur. The Power knee has just been rereleased worldwide following a redesign, the new knee offers improved symmetry, more natural gait, and increased participation in daily activities.   

Intuy Knee

The Intuy is a single axis motorised knee joint that generates an impressive kilowatt of power, the knee is suitable for knee disarticulation, trans femoral and hip disarticulation amputees up to 125kgs with activity levels K2-K4.  The Intuy is suitable for use with unilateral and bilateral amputees potentially offering a significant reduction in energy expenditure for amputees with multiple limb loss.  The unit is weatherproof and has ample battery life with up to 63km of walking after a 2-hour charge, a clever design feature regenerates power to the battery during the braking phase. The build height is slightly less at 255mm than other MPK’s on the market making it suitable for longer residual limbs, knee disarticulation and presentations when prosthetic build height is a challenge.  

Gait

The Intuy is a default stance knee joint which means it provides a variable resistance to stop the knee from collapsing during stance phase making it a safe knee for walking. During swing phase the Intuy offers a motorised active flexion and extension aimed at reducing the high levels energy expenditure that above the knee amputees experience when walking. This can enable the user to walk further or wear their prosthesis for longer periods during the day, many patients on powered prostheses report feeling less tired and irritable towards the end of the day. The powered knee extension also makes walking through terrain such as long grass and snow more efficient and safer. The sophisticated software allows the knee to fully extend in standing but introduces a default 4 degree of stance flexion during walking, this mimics the human gait cycle which primarily offers shock absorption at heel strike but secondly makes the gait cycle appear more natural and symmetrical, this concept was first introduced as the optimised physiological gait (OPG) feature in the Ottobock in the Genium prosthesis, the combination of the stance flexion and powered knee flexion/extension arguably offers the most technically advanced prosthesis on the market for walking.

The intuitive software adjusts in real time to walking speed to keep the swing phase flexion extension symmetrical to the intact limb offering a natural feeling and symmetry gait pattern.

Sitting, standing, ramp & stair ascent

The Intuy offers a variable resistance when sitting, this allows the user to load both legs when sitting reducing the over reliance on the intact limb. Unlike other MPK’s the resistance remains throughout its full range of motion. When standing from a sitting position the software recognises the early loading movement pattern and provides an assistive extension to aid standing once again reducing the over reliance on the intact limb. During ramp ascent the active swing & extension propulsion provides confidence and reduced energy expenditure to the user, it recognises the change in gait characteristics and reduces the active flexion and increases the extension to provide confidence that the foot will be in position for the next step.

The stair ascent feature of the Intuy is the most impressive design feature of this prosthesis, it showcases the mechanical and electrical software intelligence of this MPK. Unlike other MPK joints that require unnatural movement patterns to activate the stair ascent feature the Intuy recognises the natural movement patterns. Stair ascent mode is activated when the intact limb lifts the rest of the body on the first step. The Intuy flexes when lifted from the ground placing the prosthetic foot in the correct position to be placed on the next step. Once the prosthetic foot is placed on the step the Intuy provides an active extension propulsion to lift the user onto the next step. This continues until the last step when the ILK recognised the change in movement patterns that indicate the user is at the top of the stairs. The Intuy then switches back to normal walking function in real time allowing the user to walk away with a natural gait pattern.

Cycling

The cycling mode is automatically activated when the software recognises the movement patterns of the user climbing onto the bike and when getting off the bike, the device automatically switches back to walking as well.

The Process

During the trip to Delft Prosthetists Jamie Gillespie, Ian Talbot and Physiotherapist Kat Sizer received the training required to enable Pace client Craig Evans to be the first UK amputee to be fitted with the Intuy prosthesis.

Craig is a 35-year-old right transfemoral amputee following a traumatic accident 7 years ago. Within a couple of hours of being fitted with the Intuy Craig was confidently ascending steep ramps & stairs leg over leg, something he hasn’t achieved since becoming an amputee. Further therapy input would build on this confidence until the features of the Intuy would become second nature.

The certification process for the Intuy is a competency-based system that has three levels of qualification, basic, pro & master. Each level requires you to build on previous levels of experience and pass an examination. The basic qualification lasts for 3 months, and the pro & master certification lasts for 1 year.

Conclusion

The Intuy is an exciting advancement in the MPK market, the intuitive software combined with the mechanical power make it a desirable prospect for an everyday prosthesis. It has potential benefits around energy expenditure, enhanced gait biomechanics, and superior function when ascending ramps and stairs. For a powered unit the Intuy was surprisingly quiet and almost unnoticeable for most of the time during the day this can be an important factor as the noise from other powered prostheses can draw unwanted attention for the user. In the longer-term improvements in symmetry are known to reduce the risk associated with overuse injuries and arthritis on the intact side and the body as a whole. With a new powered prosthetic foot due for release in the near future Reboocon are a company helping to power ahead the prosthetic market.