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Report

Teaser, summary, work performed and final results

Periodic Reporting for period 2 - CYBERLEGs Plus Plus (The CYBERnetic LowEr-Limb CoGnitive Ortho-prosthesis Plus Plus)

Teaser

Summary

Lower-limb loss is a disabling condition affecting health and quality of life, particularly in older persons. Universal to all developed countries the main factors influencing the amount of lower-limb amputations are the high prevalence of atherosclerosis and dysvascular diseases and the overall increase of life span. Over the past century, the growth of the older population has resulted mostly from a general increase in the overall population and from major declines in the leading causes of mortality all around the world. With regard to European Countries, improved survival at older ages and low birth rate have resulted in Europe having the oldest populations in the world, with almost one European citizen out of four projected to be aged 65 years or older by 2030. As a consequence, prevalence and incidence rates of age-related diseases are expected to increase in the years to come.

A person with a dysvascular transfemoral amputation usually walks more slowly than before but expends much more energy because it takes a much greater effort to walk after amputation. Moreover we know that energetic, cognitive and stability challenges are not fully overcome by any artificial passive or active transfemoral prosthesis in the current state of the art. These factors and the lack of confidence in the prosthetic devices lead most of the amputees to prefer wheelchair to prostheses, with a deep impact on the health status, on the social inclusion and on the independence of the amputee in daily living activities.

The global goal of the CYBERLEGs Plus Plus (CLs++) project is to validate the technical and economic viability of the powered robotic ortho-prosthesis developed within the framework of the FP7-ICT-CYBERLEGs project as a means to enhance/restore the mobility of transfemoral amputees and to enable them to perform locomotion tasks such as ground-level walking, walking up and down slopes, climbing/descending stairs, standing up, sitting down and turning in scenarios of real life. Restored mobility will allow amputees to perform physical activity thus counteracting physical decline and improving the overall health status and quality of life.
The CYBERLEGs ortho-prosthesis is a modular, multi-degree of freedom cognitive robotic system constituted of an active artificial leg for the functional replacement of the amputated limb, and a wearable active orthosis for assisting the movement of hips, and knee and ankle joints of the contralateral limb.

Work performed

During the first thirty months of the project, the CYBERLEGs Plus Plus team addressed the improvement of the FP7 CYBERLEGs prototypes by means of the design and development of two generations (namely 1st- and 2nd-generation) of the following devices:
- a new Active Transfemoral Prosthesis (ATP), improving the FP7 CYBERLEGs Î²-prosthesis; this device is able to operate autonomously and to adapt to user intentions, actively helping the amputee in motor tasks such as walking, ascending and descending stairs, or sitting and standing;
- a new Active Pelvis Orthosis (APO), improving the CYBERLEGs Î²-APO; this device is able to operate autonomously and to adapt to user intentions, actively helping in motor tasks such as walking, ascending and descending stairs, or sitting and standing with hip joint assistance in flexion and extension;
- a new Active Knee Orthosis, improving the FP7 CYBERLEGs KAFO, for the assistance of knee flexion and extension of the contralateral limb; the Active Knee Orthosis operates as an optional additive module of the Active Pelvis Orthosis;
- a new Wearable Sensory Apparatus that comprises a pair of instrumented shoes endowed with pressure-sensitive insoles and a set of Inertial Measurement Units that can be attached to body segments in order to monitor userâ€™s movements and allow an estimation of his motor intentions;
- a new Bidirectional Interface, a non-invasive, portable device that comprises a control board and a belt with a series of wearable vibrotactile stimulation units to be worn around the waist; the Bidirectional Interface improves the intuitiveness of the CYBERLEGs prototypes by providing discrete stimulations that are expected to enhance a more physiological gait pattern;
- new Intention Detection algorithms for the Active Pelvis Orthosis and the Active Transfemoral Prosthesis; these classification methods for intended movement recognition use data coming from the Wearable Sensory Apparatus to pre-emptively identify different motor tasks in order to effectively provide assistance and to accordingly move the prosthesis;
- an updated version of the Fall Risk Mitigation control strategy, mediated by the Active Pelvis Orthosis, meant to assist users when multidirectional slippages are detected.
In addition to the activities of design and development, a thorough experimental validation of the developed prototypes was carried out. In particular, two clinical studies were carried out to evaluate the 1st-generation CLs++ APO and ATP, at VUB and FDG clinical centers. Clinical studies involved two so-called main protocols, which focused on the evaluation of the CLs++ ATP and APO (in terms of clinical outcomes and technical performance) and different ancillary protocols, which evaluated specific modules independently (i.e. the sensory feedback, the APO augmented feedback, the fall risk mitigation strategy for the APO, the ATP bioinspired controllers). Furthermore, during the clinical activities, data from 15 subjects have been used to carry out an initial economic viability assessment of the developed CLs++ technologies.

Final results

The expected progress beyond the state of the art of CYBERLEGs Plus Plus project is articulated on mostly four points:
- development of highly efficient and light-weighted powered prosthesis and orthoses;
- a miniaturized wearable sensory apparatus which will enable highly accurate and intuitive algorithms to decode user intention detection and combine them with bio-inspired walking assistive strategies;
- the integration of fall-risk mitigation strategies in the control of the CLs++ ortho-prosthesis modules; this strategies will work based on the â€œassist-as-neededâ€ strategy in order to take advantage of the intrinsic capability of a power exoskeleton to modify the dynamics of the user only if it is required to promote her/his balance recovery;
- a bidirectional interface based on vibrotactile stimulations will be used to improve the gait pattern of CLs++ users.
Increased mobility of dysvascular transfemoral amputees through CYBERLEGs Plus Plus is expected to have a positive impact on the quality of life of transfemoral amputees with limited ambulation abilities, most of whom do not use their prosthesis on a regular basis, or do not use it at all, and, accordingly, suffer from the devastating consequences of physical inactivity. CYBERLEGs Plus Plus will have an impact also within the healthcare domain, by influencing both the rehabilitation phase, where the device could support a more efficient training, and the after-rehabilitation phase, where the use of the device would support higher mobility and thus more activity of the user.