User-centred assistive SystEm for arm Functions in neUromuscuLar subjects (USEFUL): a randomized controlled study

Abstract

Background: Upper limb assistive devices can compensate for muscular weakness and empower the user in the execution of daily activities. Multiple devices have been recently proposed but there is still a lack in the scientific comparison of their efficacy.

Methods: We conducted a cross-over multi-centric randomized controlled trial to assess the functional improvement at the upper limb level of two arms supports on 36 patients with muscular dystrophy. Participants tested a passive device (i.e., Wrex by Jaeco) and a semi-active solution for gravity compensation (i.e., Armon Ayura). We evaluated devices' effectiveness with an externally-assessed scale (i.e., Performance of the Upper Limb-PUL-module), a self-perceived scale (i.e., Abilhand questionnaire), and a usability scale (i.e., System Usability Scale). Friedman's test was used to assess significant functional gain for PUL module and Abilhand questionnaire. Moreover, PUL changes were compared by means of the Friedman's test.

Results: Most of the patients improved upper limb function with the use of arm supports (median PUL scores increase of 1-3 points). However, the effectiveness of each device was related to the level of residual ability of the end-user. Slightly impaired patients maintained the same independence without and with assistive devices, even if they reported reduced muscular fatigue for both devices. Moderately impaired patients enhanced their arm functionality with both devices, and they obtained higher improvements with the semi-active one (median PUL scores increase of 9 points). Finally, severely impaired subjects benefited only from the semi-active device (median PUL scores increase of 12 points). Inadequate strength was recognized as a barrier to passive devices. The usability, measured by the System Usability Scale, was evaluated by end-users "good" (70/100 points) for the passive, and "excellent" (80/100 points) for the semi-active device.

Conclusions: This study demonstrated that assistive devices can improve the quality of life of people suffering from muscular dystrophy. The use of passive devices, despite being low cost and easy to use, shows limitations in the efficacy of the assistance to daily tasks, limiting the assistance to a predefined horizontal plane. The addition of one active degree of freedom improves efficacy and usability especially for medium to severe patients. Further investigations are needed to increase the evidence on the effect of arm supports on quality of life and diseases' progression in subjects with degenerative disorders. Trial registration clinicaltrials.gov, NCT03127241, Registered 25th April 2017. The clinical trial was also registered as a post-market study at the Italian Ministry of Health.

Keywords: Exoskeleton; assistive device; neuromuscular disorders; upper limb.

Conflict of interest statement

The authors declare that they have no competing interests.

Figures

Fig. 1

Commercial arm supports tested. a Wrex Jaeco and b Armon Ayura

Fig. 2

Intervention. T0: baseline assessment without arm support; T1 A: assessment after the use of the first device (Device A); T1 B: assessment after the use of the second device (Device B); PUL Performance of Upper Limbs module, Abilhand Abilhand scale, SUS System Usability Scale

Fig. 3

Participant CONSORT flow chart

Fig. 4

Frequency histogram of MRC values at deltoid and biceps muscles for all participants. Green: slightly impaired subjects; yellow: moderately impaired subjects; red: severely impaired subjects

Fig. 5

PUL module results. a Reports raw total PUL values (on a scale 0–74 points) at T0, T1 with the semi-active device, and T1 with the passive one. Green circles, yellow squares, and red stars represent PUL scores of slightly impaired, moderately impaired, and severely impaired subjects respectively. Straight lines connect data from the same participant. Grey boxes identify interquartile ranges and the black lines highlight the median values. Asterisks indicate statistical differences (p-value<0.05) between groups, tested with Friedman’s and post hoc comparisons. b Reports Delta PUL values (i.e., the difference between T1, with the semi-active or passive device, and T0 PUL scores. Each data point is represented with the same marker and color code of a. The dashed black line indicates the zero delta value. Asterisk indicates a statistical difference between the two groups, as computed by means of Friedman’s test (p = 0.001015)

Fig. 6

Upper panels: PUL module results for the sub-groups analysis. a slightly impaired subjects; b moderately impaired subjects; c severely impaired subjects. Lower panels: Abilhand scores, expressed in logit, for the sub-groups analysis. One logit is the distance along the line of the variable that increases the odds of observing the event specified in the measurement model by a factor equal to Euler’s constant e. All logits are the same length with respect to this change in the odds of observing the indicative event. Higher scores represent higher perceived manual ability. d Slightly impaired subjects; e moderately impaired subjects; f severely impaired subjects. Green circles, yellow squares, and red stars represent PUL scores of slightly impaired, moderately impaired, and severely impaired subjects respectively. Straight lines connect data from the same participant. Grey boxes identify interquartile ranges and the black lines highlight the median values. Asterisks indicate statistical differences (p-value<0.05) between groups, tested with Friedman’s and post-hoc comparisons

Fig. 7

Responses to the final satisfaction questionnaire proposed to patients. Each row reports the number of responses for the three groups of patients (i.e., slightly, moderately, and severely impaired, 12 patients for each group). Black, dark grey, light grey, and white bars represent, respectively, the number of answers relative to the passive device, the semi-active device, both devices, and none