Article
Validation of a Hybrid Exoskeleton for Upper Limb
Rehabilitation. A Preliminary Study
Isabel-María Alguacil-Diego
1
, Alicia Cuesta-Gómez
1
, Aldo-Francisco Contreras-González
2
,
David Pont-Esteban
2
, David Cantalejo-Escobar
2
, Miguel Ángel Sánchez-Urán
2,3
and Manuel Ferre
2,
*
Citation: Alguacil-Diego, I.-M.;
Cuesta-Gómez, A.;
Contreras-González, A.-F.;
Pont-Esteban, D.; Cantalejo-Escobar,
D.; Sánchez-Urán, M.Á.; Ferre, M.
Validation of a Hybrid Exoskeleton
for Upper Limb Rehabilitation. A
Preliminary Study. Sensors 2021, 21,
7342. https://doi.org/10.3390/
s21217342
Academic Editors: Xiaochun Cheng
and Daming Shi
Received: 30 September 2021
Accepted: 1 November 2021
Published: 4 November 2021
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4.0/).
1
Physiotherapy, Occupational Therapy, Physical Medicine and Rehabilitation Department, Universidad Rey
Juan Carlos, Campus de Alcorcón, Av. de Atenas, s/n, 28922 Alcorcón, Spain;
isabel.alguacil@urjc.es (I.-M.A.-D.); alicia.cuesta@urjc.es (A.C.-G.)
2
Centro de Automática y Robótica (CAR) UPM-CSIC, ETS Ingenieros Industriales, Universidad Politécnica de
Madrid, Calle de José Gutiérrez Abascal, 2, 28006 Madrid, Spain; af.contreras@alumnos.upm.es (A.-F.C.-G.);
david.pont@upm.es (D.P.-E.); david.cantalejo@upm.es (D.C.-E.);
miguelangel.sanchezuran@upm.es (M.Á.S.-U.)
3
ETS Ingeniería y Diseño Industrial, Universidad Politécnica de Madrid, Ronda de Valencia, 3,
28012 Madrid, Spain
* Correspondence: m.ferre@upm.es
Abstract:
Recovery of therapeutic or functional ambulatory capacity in patients with rotator cuff
injury is a primary goal of rehabilitation. Wearable powered exoskeletons allow patients to perform
repetitive practice with large movements to maximize recovery, even immediately after the acute
event. The aim of this paper is to describe the usability, acceptability and acceptance of a hybrid
exoskeleton for upper-limb passive rehabilitation using the System Usability Scale (SUS) question-
naire. This equipment, called ExoFlex, is defined as a hybrid exoskeleton since it is made up of rigid
and soft components. The exoskeleton mechanical description is presented along with its control
system and the way motion is structured in rehabilitation sessions. Seven patients (six women and
one man) have participated in the evaluation of this equipment, which are in the range of 50 to
79 years old. Preliminary evidence of the acceptance and usability by both patients and clinicians
are very promising, obtaining an average score of 80.71 in the SUS test, as well as good results in a
questionnaire that evaluates the clinicians’ perceived usability of ExoFlex.
Keywords: rehabilitation; upper-limb; exoskeleton; robot
1. Introduction
Alterations of the musculoskeletal system are one of the conditions of greater medical
consultation at different levels of health care, and within these, shoulder pain occupies an
important place, also causing considerable functional disability to perform activities of
daily life [
1
]. The rehabilitation programs for pathologies of trauma origin at the level of
the upper limb have as common objectives the increase of the joint range to promote the
highest level of functionality of the patients.
In some pathologies of traumatic origin such as rotator cuff tendinopathy or frozen
shoulder, recovery of functional capacity must begin early. Though, in others, such as
fractures, dislocations and arthroplasties, it is important to respect an initial period of
immobilization, which helps recovery, reduces pain and edema, helps consolidation and
prevents radiological deformities [
2
]. After this period of immobilization, it is necessary to
restore the patient’s functionality using various techniques such as kinesitherapy as soon as
possible because of complications such as joint stiffness, muscle atrophy, bone degradation
and both capsular and ligamentous retraction, which the immobilization produces [
3
].
However, it is not always possible to meet these demands for early and intensive care,
especially in the current situation due to the COVID-19 epidemic, where the time to start
treatments has been increased due to the limitation/restriction of the number of patients
Sensors 2021, 21, 7342. https://doi.org/10.3390/s21217342 https://www.mdpi.com/journal/sensors
