Feasibility of using the Leap Motion Controller to administer conventional motor tests: a proof-of-concept study

Abstract

Although upper-limb movement impairments are common, the primary tools for assessing and tracking impairments in clinical settings are limited. Markerless motion capture (MMC) technology has the potential to provide a large amount of quantitative, objective movement data in routine clinical use. Many past studies have focused on whether MMC are sufficiently accurate. However, another necessary step is to create meaningful clinical tests that can be administered via MMC in a robust manner. Four conventional upper-limb motor tests common in clinical assessments (visually guided movement, finger tapping, postural tremor, and reaction time) were modified so they can be administered via a particular MMC sensor, the Leap Motion Controller (LMC). In this proof-of-concept study, we administered these modified tests to 100 healthy subjects and present here the successes and challenges we encountered. Subjects generally found the LMC and the graphical user interfaces of the tests easy to use. The LMC recorded movement with sufficiently high sampling rate (>106 samples/s), and the rate of LMC malfunctions (mainly jumps in time or space) was low, so only 1.9% of data was discarded. However, administration of the tests also revealed some significant weaknesses. The visually guided movement test was easily implemented with the LMC; the modified reaction time test worked reasonably well with the LMC but is likely more easily implemented with other existing technologies; and the modified tremor and finger tapping tests did not work well because of the limited bandwidth of the LMC. Our findings highlight the need to develop and evaluate motor tests specifically suited for MMC. The real strength of MMC may not be in replicating conventional tests but rather in administering new tests or testing conditions not possible with conventional clinical tests or other technologies.

Administering Movement Assessments via Markerless Motion Capture Provides New Normative Values Over Clinical Tests

“…Complete details of the development of the MMC-mediated tests are described in Kincaid, Johnson & Charles (2023) [15]. Brie y, we scrutinized a variety of motor assessments associated with various movement-related disorders and identi ed the motor tests that were 1) most widely used, 2) most adaptable to LMC technology, and 3) most easily administered via the LMC.…”

“…Administration of the modi ed and conventional tests were conducted according to established protocols. Each modi ed test is described fully in previous work [15] and condensed in Table 1, but we also provide a brief summary of each test here.…”

“…Raw position data from the LMC (position/orientation of the ngertips/palm/dowels) were processed as follows (for details, see Kincaid et al [15]). Since the raw data were sampled at a variable sampling rate, raw data from all tests (except the reaction time test) were resampled at a constant rate of 100 samples per second.…”

“…More speci cally, gaps in time greater than 50ms, jumps in position of more than 30 mm, and movements less than 20 samples long were agged as invalid and excluded from the analysis. These threshold values were chosen after a thorough visual inspection of the data [15]. After this processing, we extracted a number of measures for each test (Table 2).…”

“…Another necessary step in preparing MMC-mediated motor batteries for clinical use is to establish test norms (the range of test results of neurotypical, healthy participants against which the results of impaired subjects can be evaluated) and compare these norms to those of similar conventional tests. The purpose of this study was to establish test norms for our recently developed MMC-mediated tests [15] as well as an additional MMC-mediated balance test, and to compare these norms to those of the conventional tests on which the MMC-mediated tests were based.…”