Robotic Rigor: Validity of the Kinarm End-Point Robot Visually Guided Reaching Test in Multiple Sclerosis

Abstract

Objective: To determine whether robotic metrics: (1) correlate with the Nine-Hole Peg Test (9HPT; good convergent validity); and (2) differentiate between those self-reporting "some hand problems" versus "no hand problems" (good criterion validity).

Design: Cross-sectional validation analyses.

Setting: Rehabilitation research laboratory located within a hospital.

Participants: People with multiple sclerosis self-reporting "some" (n=21; mean age, 52.52±10.69 y; females, n=16; disease duration, 18.81±10.38 y) versus "no" (n=21; age, 51.24±12.73 y; females, n=14; disease duration, 17.71±10.16 y) hand problems.

Main outcome measures: We assessed hand function using the criterion standard 9HPT and robotic testing. Robotic outcomes included an overall task score, as well as 2 movement planning (ie, reaction time and initial direction angle) and 2 movement correction (ie, movement time and path length ratio) spatiotemporal values. We identified participants reporting "some" versus "no" hand problems via the Multiple Sclerosis Impact Scale-29. We analyzed our nonparametric data using a Mann-Whitney U test and Spearman rank-order correlation.

Results: Those reporting "some hand problems" included more right-handed individuals (P=.038); otherwise, the 2 groups were characteristically similar. Visually guided reaching task score and movement planning but not movement correction spatiotemporal values demonstrated moderate correlations with 9HPT for both the dominant (reaction time: r=0.489, P=.001; initial direction angle: r=0.429, P=.005) and nondominant (reaction time: r=0.521, P<.001; initial direction angle: r=0.321, P=.038) side. Further, reaction time, but not 9HPT or any other robotic outcome, differentiated between the 2 groups (P=.036); those reporting "no hand problems" moved faster (ie, dominant side: 0.2810 [0.2605-0.3215] vs 0.3400 [0.2735-0.3725] s).

Conclusions: Robotic test metrics demonstrated modest criterion and convergent validity in multiple sclerosis, with reaction time being the most compelling. When looking beyond the task score, spatiotemporal robotic measures may help discern subtle multiple sclerosis-related hand problems. Movement planning spatiotemporal values appear more meaningful than movement correction and could prove fruitful as the target for future intervention strategies.

Keywords: Multiple sclerosis; Reaction time; Upper-limb; hand; motor; reaching; rehabilitation; robotics; validation.

Graphical abstract

Fig 1

Kinarm End-Point VGR Test. (A) Kinarm End-Point Lab. (B) Screenshot of the VGR test with all peripheral targets illuminated. Note that only 1 peripheral target illuminates during an actual trial.

Fig 2

Graphical description of spatiotemporal values for the Kinarm End-Point VGR Test. (A) Illustrates initial direction angle and path length ratio, where: green (d) = actual hand path while reaching from the central (white) to the peripheral target (red); white (l) = shortest possible hand path while reaching from the central to the peripheral target; a° = initial direction angle; and d/l = path length ratio. (B) Illustrates the reaction and movement time phases relative to hand speed and test completion time. Table 1 provides an objective description of each spatiotemporal value.

Fig 3

Kinarm End-Point VGR task score and movement planning spatiotemporal values (ie, reaction time and initial direction angle) are significantly associated with 9HPT time on the dominant (A) and nondominant (B) side.

Fig 4

Kinarm End-Point VGR mean reaction time of the dominant but not the nondominant hand is significantly different between the 2 groups (ie, none vs some hand problems).