Abstract
Stroke, the third leading cause of global disability, poses significant challenges to healthcare systems worldwide. Addressing the restoration of impaired hand functions is crucial, especially amid healthcare workforce shortages. While robotic-assisted therapy shows promise, cost and healthcare community concerns hinder the adoption of hand exoskeletons. However, recent advancements in soft robotics and digital fabrication, particularly 3D printing, have sparked renewed interest in this area. This review article offers a thorough exploration of the current landscape of soft hand exoskeletons, emphasizing recent advancements and alternative designs. It surveys previous reviews in the field and examines relevant aspects of hand anatomy pertinent to wearable rehabilitation devices. Furthermore, the article investigates the design requirements for soft hand exoskeletons and provides a detailed review of various soft exoskeleton gloves, categorized based on their design principles. The discussion encompasses simulation-supported methods, affordability considerations, and future research directions. This review aims to benefit researchers, clinicians, and stakeholders by disseminating the latest advances in soft hand exoskeleton technology, ultimately enhancing stroke rehabilitation outcomes and patient care.
1. Introduction
Strokes are the second leading cause of death worldwide [1,2,3]. These events, which consist of the sudden death of some brain cells due to lack of oxygen when blood flow is lost due to blockage or rupture of an artery [4,5], are also the third cause of permanent disability and one of the main causes of dementia and depression [6,7]. The occurrence of strokes is subject to different risk factors [8,9]. Diseases such as hypertension and diabetes, along with habits such as smoking, are considered modifiable risk factors, that is, factors susceptible to prevention. Other risk factors are not preventable, such as atrial fibrillation and transient ischemic attacks, which are presumed to be of genetic origin [10].
Globally, 70% of strokes and 87% of deaths related to these events occur in low- and middle-income countries [11]. Over the past four decades, the incidence of stroke in low- and middle-income countries has increased by more than 100%. During these decades, its incidence has decreased by 42% in high-income countries. On average, this event occurs 15 years earlier and causes more deaths for people living in low- and middle-income countries when compared to those in high-income countries. Strokes mainly affect people at the peak of their productive lives [12], and despite its enormous impact on the socio-economic development of countries, this growing crisis has received very little attention to date.
Recent neurological research indicates that impaired motor skills of stroke patients can be improved and possibly restored through repetitive, task-oriented training [13,14,15,16,17]. This is due to a property of the human brain known as neuroplasticity or the ability of the brain to reorganize itself by establishing new neural connections [18,19]. On this basis, the use of automatic devices has been implemented to help therapists increase the intensity of treatments, produce multisensory stimulation, and reduce costs during their work [20,21,22,23,24,25]. This new concept dates to the early 1990s with a new family of robotic machines called “haptic interfaces”. These mechanical devices were designed to interact with the human being, guiding the upper limb towards passive and active assisted mobilization, assisting in some movement tasks through biofeedback systems, and measuring kinematic changes and dynamics in motion. However, there is no consensus on the metrics or devices used to treat motor function deficiencies through neuroplasticity [26,27]. Additionally, recovery success relies heavily on a patient’s ability to attend therapy, which can be deterred by the frequency, duration, or cost of the therapy [28]. In this way, robotic therapy could represent a standard and successful complement to rehabilitation programs, improve patient access, and increase compliance and subsequent outcomes of rehabilitation efforts.
Despite the multiple designs reviewed in the last decade [29], there is no clinical evidence of the superiority of robotic training over traditional therapy. However, this procedure can complement traditional therapy processes [30]. In contrast, soft robots have the potential to overcome the limitations that are present in rigid robots. This design paradigm, inspired by the behavior and structure of living things, seems to be more compatible with rehabilitation activities due to increased versatility and compliance [31,32].
In addition, the solutions proposed, under the appropriate portability parameters, would have the potential to support the patient in the execution of activities of daily living, increasing their level of independence, mental health, and the well-being of their family nucleus.
The purpose of this work is to present a comparative review of the most recent rehabilitation hand exoskeletons based on soft actuators. This comparison is based on two main criteria: (i) the complexity of the manufacturing process and (ii) the resulting adaptability to the patient’s anatomy in rehabilitation environments.
This review also wants to motivate future designers to work in interdisciplinary solutions, taking into consideration multiple initiatives related to the implementation of makerspaces within the facilities of healthcare institutions, enabling the high reception and adoption of digital fabrication methods in society, and specifically, in healthcare [33,34,35,36,37,38]. […]
TBI Rehabilitation 