1. Introduction
In the Global Burden of Diseases, Injuries and Risk Factors (GBD) study conducted in 2016, it was estimated that between the years 1990 and 2016 the number of people affected by Parkinson’s disease (PD) doubled worldwide, with an incidence rate of 8 to 18 people per 100,000 per year [
1]. PD is defined as a chronic, neurodegenerative movement disorder, whose most characteristic motor symptoms are resting tremor, rigidity, and bradykinesia. Resting tremor is characterized by a prominent involuntary, rhythmic muscle movement in the distal upper limb (UL) at a frequency of about 4 to 6 Hz. Rigidity is an increased resistance to passive movement. The third most characteristic symptom is bradykinesia, characterized by slow movement and difficulty planning, initiating, and carrying out a movement [
2]. Other non-motor symptoms such as sleep problems, constipation, anxiety, depression and fatigue may also appear [
3]
The motor and non-motor symptoms of PD have negative repercussions on the quality of life and functionality of people with the disease. The burden of motor symptoms and impairment of some activities of daily living (ADLs), such as eating, hygiene and clothing, related to alterations in functional mobility, has been identified as one of the major predictors of quality of life with this disease [
4,
5,
6].
Following the perspective of the International Classification of Functioning and Disability (ICF) of the World Health Organization (WHO), three interconnected levels of human functioning are differentiated: (1) Body functions and structures, physiological and psychological functions, and bodily and anatomical impairments; (2) Limitations in the performance of activities; and (3) Restrictions in participation in daily life [
7,
8]. The progression of PD leads to alterations in body function, limited performance of ADLs and increased dependence, while reducing quality of life [
4,
8,
9,
10].
As the disease progresses, the worsening of symptoms, such as tremor, rigidity and bradykinesia, leads to a deterioration of manual dexterity, which translates to a greater difficulty in performing some ADLs. The most commonly reported basic self-care activities affected by PD symptoms are bathing/showering, dressing, and grooming/personal hygiene. Other instrumental activities of daily living that are affected are driving, preparing food, shopping, and writing [
11]. Therefore, the presence of these symptoms is closely related to a poorer quality of life [
5,
12].
The treatment of PD is mainly based on the administration of levodopa, whose efficacy decreases over time and can produce side effects such as motor fluctuations, dyskinesias and dopaminergic dysregulation syndrome. The onset of the disease and the variety of possible symptoms makes it difficult to design a therapeutic regimen for the treatment of the disease. So far, approved therapies have focused on compensatory approaches aimed at treating clinical symptoms. However, the current research is focused on delaying or halting disease progression and not only on temporary symptomatic relief. Currently, all therapies are directed toward ameliorating motor deficits by increasing dopamine, but unfortunately, this loses efficacy over time as dopaminergic neurodegeneration progresses, with symptoms worsening in the long-term. Therefore, new non-pharmacological therapies need to be assessed [
13,
14,
15].
There are several non-pharmacological therapies design to reduce functional impairments of this disease and, although evidence of their efficacy is increasing, there is still a limited number of studies on them and on the necessary intervention doses [
16,
17]. New non-pharmacological therapies that can be easily implemented can complement pharmacological treatment in order to improve the patients’ functional mobility and quality of life. In this regard, the dynamic elastomeric fabric orthoses (DEFO,
Figure 1) may be a suitable candidate for reducing motor symptoms and improving functional movement and quality of life in patients with PD. These types of devices were developed by dynamic movement orthoses
®, led by clinical orthopedist and managing director Martin Matthews. They are custom-designed devices for the user’s limbs or other parts of his/her body. Through the application of traction forces, they bring the limb into a better biomechanical alignment, while allowing and guiding movement. The elastic fabric promotes the extension of fingers and wrist, the stability of the thumb and the supination or pronation of the forearm. In addition, due to the localized compression of the soft tissues and the stimulation of the dermal and proprioceptive receptors, it is possible to regulate motor activity, avoiding atrophy and muscle rigidity, improving the patient’s quality of life [
18,
19]. These orthoses, compared to other orthopedic devices, have demonstrated better tolerance and high user satisfaction [
20,
21,
22].
This type of device has been effective in children with cerebral palsy (CP). In the study conducted by Pavão et al., the use, by children with CP, of a vest made of this material showed better postural stability when performing a manual reaching activity [
23], and in another study, it showed improved balance, postural control, and manual dexterity [
24]. On the other hand, wearing these devices on the foot and ankle improved balance and walking speed in multiple sclerosis [
25,
26], and pain and function in patients suffering with complex regional pain syndrome (CRPS) [
16]. Stroke has been the condition in which the use of this UL orthosis has been most investigated, and several studies have shown positive effects on strength, manual dexterity, and UL functionality, which need to be confirmed in studies with larger sample sizes [
27,
28].
DEFOs have not yet been investigated in in a wide range of motor variables in PD. In the recent review, conducted by Son Nguyen, studies of different types of portable orthoses for UL tremor suppression were assessed, the majority being active orthoses (45%), followed by semi-active orthoses (35%), and passive orthoses (20%). All orthoses have proven to be effective in suppressing tremors, but several had inconveniencies such as being heavy and bulky, had not been evaluated in laboratory settings or were not yet commercially available [
29].
Although current orthoses have proven to be effective in suppressing tremor, their clinical or home use is still limited. This limited their clinical or home use for suppressing tremor. Given these former results and lack of studies in PD, our main objective was to analyze the efficacy of a lighter device for the UL, such as the DEFO, in motor variables, functional mobility and quality of life in PD.
4. Discussion
The aim of this study was to analyze the efficacy of the use of a DEFO for the UL on the functionality and quality of life of people with PD. The main findings of the present study are an immediate improvement after the implementation of the orthosis in the OFF and ON states of motor variables in the postural tremor task; only in the OFF state in the speed of rapid alternating movements and only in the ON state in the rhythm of hand movements and amplitude of rapid alternating movements. No differences were observed after two months of orthosis use in the improvement of functionality or in the quality of life of the patient with PD.
Neurological disorders, such as PD, are currently the leading source of disability in the world. The global burden of disease study estimated that the number of people with PD will double from about 7 million in 2015 to approximately 13 million in 2040. This estimation of the growth of the population with PD is worrying considering the amount of burden this disease carries for society [
45].
The neurodegenerative effects of PD lead to a loss of functional mobility in balance, postural stability and gait, decreasing independence in the performance of activities, and compromising their participation both at home and in the community [
6,
46,
47]. On the other hand, contextual factors such as age, the feeling of being a person with a disability, unemployment or perceived control are examples of personal and environmental factors that have a negative impact on the functional mobility and quality of life of the individual [
6,
7,
8,
47,
48].
There have been many advances in the knowledge of the etiopathogenesis and in the symptomatic treatment of PD in recent years. However, there are no effective neuroprotective or disease-modifying therapies that slow disease progression and improve functionality and quality of life without producing side effects on the patient [
5].
Due to the fact that pharmacological treatment loses its efficacy with the passage of time and produces side effects in the person and the lack of precise knowledge about the currently existing non-pharmacological therapies, it is necessary to implement new non-pharmacological therapies that allow an improvement in the functionality and quality of life of the patient [
16,
17].
All DEFOs are made in the same way, being able to be designed and adapted to the needs of the pathology and the user, so that they can be devices for UL, lower limbs or vest for the whole body. In diseases such as CP, different studies carried out with vests and meshes of these characteristics have demonstrated their efficacy on postural control, balance, walking speed, and manual dexterity [
23,
24,
49]. In the study conducted by Yasukawa et al., in which DEFOs were implemented for UL in two cases with CP with hemiplegia and brachial plexus palsy, improved limb alignment and improved functionality of the affected UL were observed [
18]. In the same way, they have also been effective in improving balance and walking speed in people with MS, as well as in improving pain and functionality of the lower limb in people with CRPS [
20,
25,
26]. In a single case study conducted by Watson et al., the beneficial functional effects of a lycra orthosis in a multiple sclerosis patient were equivocal [
50]. In another study of 16 patients with hemiparesis resulting from brain damage, the use of these devices showed a reduction in muscle tone and swelling, and improved wrist and finger movement [
51]. Although some studies have shown that the use of these devices in people with brain damage improve strength, manual dexterity, and UL functionality, there is a need for studies with larger sample sizes [
27,
28]. These results coincide with those observed in the present study, in the sense that the implementation of the orthosis showed improvements on motor aspects of UL such as resting tremor, rhythm of hand movements or speed of rapid alternating movements, assessed with Kinesia, leading to an improvement in manual dexterity. No differences were observed in PDQ-39 and UPDRS-III scores on quality of life and functionality after orthosis implementation. Regarding the use of orthoses for tremor reduction, the review by Fromee et al. showed that the implementation of orthoses had a positive effect on the reduction in involuntary movement, being a complementary device to medical treatment. However, these orthoses turn out to be difficult to handle and unattractive, so they often lead to rejection by the patient. Therefore, there is a need to design orthosis that combines a tremor suppression mechanism with a soft, compact, and lightweight suppression system that increases patient acceptance [
52]. Similarly in the review conducted by Mo et al., it was concluded that weight reduction in wearable orthosis for tremor reduction is an important research priority, as they have so far only been evaluated in patient cohorts or on the bench with simulated data and with very small samples, which may weaken the reliability of the data [
53].
These findings should be considered within the context of their strengths and limitations; the results show new information about the efficacy of this type of orthosis in patients with PD. On the other hand, the evaluations have been carried out in the “ON” and “OFF” state of the disease, which gives us information on its effect in the different states of the disease. This device has proven to be a non-pharmacological treatment that is easy to implement, with high adherence to treatment and without any type of contraindication. With respect to the limitations, the nature of the intervention was such that the participants and investigators of the initial evaluation were not blinded, and it has not been possible to ascertain whether the results have been maintained in the long term due to the limited duration of the study.