Abstract
BackgroundRobotic exoskeletons are increasingly being used in objective and quantitative assessment of upper limb (UL) movements. A set of instrumental indices computed during robot-assisted reaching tasks with the Armeo®Spring has been proven to assess UL functionality. The aim of this study was to test the construct validity of this indices-based UL assessment when used with patients who have had a stroke.MethodsForty-four 45- to 79-year-old stroke patients with a Wolf Motor Function Test ability score (WMFT-FAS) ranging from 10 to 75 and a Motricity Index (MI) ranging from 14 to 33 at shoulder and elbow were enrolled, thus covering a wide range of impairments. Residual UL function was assessed by both the WMFT-FAS and the WMFT-TIME, as well as by a set of 9 numerical indices assessing movement accuracy, velocity and smoothness computed from a 3D endpoint trajectory obtained during the “Vertical Capture” task of the Armeo®Spring device. To explore which variables better represented motor control deficits, the Mann-Whitney U Test was used to compare patients’ indices to those obtained from 25 healthy individuals. To explore the inner relationships between indices and construct validity in assessing accuracy, velocity and smoothness, a factor analysis was carried out. To verify the indices concurrent validity, they were compared to both WMFT-FAS and WMFT-TIME by the Spearman’s correlation coefficient.ResultsSeven indices of stroke subjects were significantly different from those of healthy controls, with effect sizes in the range 0.35–0.74. Factor analysis confirmed that specific subsets of indices belonged to the domains of accuracy, velocity and smoothness (discriminant validity). One accuracy index, both velocity indices and two smoothness indices were significantly correlated with WMFT-FAS and WMFT-TIME (|rho| = 0.31–0.50) (concurrent validity). One index for each of the assessed movement domains was proven to have construct validity (discriminant and concurrent) and was selected. Moreover, the indices were able to detect differences in accuracy, velocity and/or smoothness in patients with the same WMFT level.ConclusionsThe proposed index-based UL assessment can be used to integrate and support clinical evaluation of UL function in stroke patients.
Highlights
Robotic exoskeletons are increasingly being used in objective and quantitative assessment of upper limb (UL) movements
Ability of indices to distinguish between stroke patients and healthy subjects The mean values of indices in the sample are presented in Table 3, along with the corresponding normal reference values
Values of instrumental indices used to assess upper limb reaching motion (10th – 90th percentile range) in healthy subjects (N = 25) and the sample of stroke patients enrolled in this study (N = 44)
Summary
Robotic exoskeletons are increasingly being used in objective and quantitative assessment of upper limb (UL) movements. With respect to the International Classification of Functioning, Disability and Health (ICF), [10] the FMA only deals with the body function domain, while the WMFT is classified in terms of ICF categories as an Activity Scale, as it measures changes in functional activities [11] These tests have proven their reliability [12] and validity [13,14,15] when assessing UL function in stroke patients, despite some minor limitations [16,17,18], such as equipment needs, time of execution, training requirements and the lack of sensitivity to subtle changes in motor performance throughout the rehabilitation process
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