A digit alignment device for kinematic analysis of the thumb and index finger

Department of Biomedical Engineering, Cleveland Clinic, Cleveland, OH 44195, United States.
Gait & posture (Impact Factor: 2.75). 05/2012; 36(3):643-5. DOI: 10.1016/j.gaitpost.2012.04.012
Source: PubMed


Kinematic analysis of the digits using optical motion capture systems relies on defining accurate coordinate systems for the individual segments. Limitations of previous digit kinematic protocols include marker placement errors, marker occlusion and superimposition, and skin movement artifact. The purpose of this study was to develop a protocol utilizing a digit alignment device (DAD) and nail marker clusters to overcome these limitations. Ten subjects underwent 10 static calibration trials for validation. The orientation of the thumb distal phalange relative to the index finger distal phalange was described using Euler angles of pitch(x), yaw(y'), and roll(z''). The digit calibration protocol demonstrated high accuracy (0.5°, 1.9° and 2.2° for x, y', z'') and precision (1.4°, 2.3° and 3.1° for x, y', z''). The developed protocol provided convenient identification of transformations that determine anatomically relevant coordinate systems for the distal phalanges of the digits. The potential of utilizing this protocol as a standardized tool for digit kinematics was demonstrated using a dynamic task of precision pinching.

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Available from: Zhilei Shen
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    • "Using the aligned 3-D coordinate system defined for each digit segment as described by (Shen, 214 Mondello et al. 2012), angle rotations describing the relative orientation of the finger-pads were 215 calculated as order-dependent (X-Y-Z) Euler angles as described in (Nataraj and Li 2013). These 216 three Euler angle rotations represent the distal-orientation-coordination-angles (DOCA) of the distal 217 thumb segment relative to the distal index finger segment and are denoted as Pitch-Yaw-Roll. "
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    ABSTRACT: Purpose: This study investigated novel kinematic performance parameters to understand regulation by visual feedback (VF) of the reaching hand on the grasp and transport components during the reach-to-pinch maneuver. Conventional metrics often signify discrete movement features to postulate sensory-based control effects (e.g., time for maximum velocity to signify feedback delay). The presented metrics of this study were devised to characterize relative vision-based control of the sub-movements across the entire maneuver. Methods: Movement performance was assessed according to reduced variability and increased efficiency of kinematic trajectories. Variability was calculated as the standard deviation about the observed mean trajectory for a given subject and VF condition across kinematic derivatives for sub-movements of inter-pad grasp (distance between thumb and index finger-pads; relative orientation of finger-pads) and transport (distance traversed by wrist). A Markov analysis then examined the probabilistic effect of VF on which movement component exhibited higher variability over phases of the complete maneuver. Jerk-based metrics of smoothness (minimal jerk) and energy (integrated jerk-squared) were applied to indicate total movement efficiency with VF. Results/discussion: The reductions in grasp variability metrics with VF were significantly greater (p<.05) compared to transport for velocity, acceleration, and jerk, suggesting separate control pathways for each component. The Markov analysis indicated that VF preferentially regulates grasp over transport when continuous control is modeled probabilistically during the movement. Efficiency measures demonstrated VF to be more integral for early motor planning of grasp than transport in producing greater increases in smoothness and trajectory adjustments (i.e., jerk-energy) early compared to late in the movement cycle. Conclusions: These findings demonstrate the greater regulation by VF on kinematic performance of grasp compared to transport and how particular features of this relativistic control occur continually over the maneuver. Utilizing the advanced performance metrics presented in this study facilitated characterization of VF effects continuously across the entire movement in corroborating the notion of separate control pathways for each component.
    Full-text · Article · Jun 2014 · Human Movement Science
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    • ") B) Calibration using a digit alignment device (Shen, Mondello et al. 2012) C) Subject with arm-support cyclically performing 2-sec cycle of precision pinch movement (markers not shown) D) Aligned axes about which relative rotation of distal thumb with respect to distal index finger defines DOCA. Note: Origin of axes located at respective " nail-point " estimated from the respective nail marker-cluster. "
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    ABSTRACT: Carpal tunnel syndrome (CTS) can adversely affect fine motor control of the hand. Precision pinch between the thumb and index finger requires coordinated movements of these digits for reliable task performance. We examined the impairment upon precision pinch function affected by CTS during digit movement and digit contact. Eleven CTS subjects and 11 able-bodied (ABL) controls donned markers for motion capture of the thumb and index finger during precision pinch movement (PPM). Subjects were instructed to repetitively execute the PPM task, and performance was assessed by range of movement, variability of the movement trajectory, and precision of digit contact. The CTS group demonstrated shorter path-length of digit endpoints and greater variability in inter-pad distance and most joint angles across the PPM movement. Subjects with CTS also showed lack of precision in contact points on the digit-pads and relative orientation of the digits at contact. Carpal tunnel syndrome impairs the ability to perform precision pinch across the movement and at digit-contact. The findings may serve to identify deficits in manual dexterity for functional evaluation of CTS. © 2014 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.
    Full-text · Article · Jun 2014 · Journal of Orthopaedic Research
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    • "LEFT: Markers utilized for motion tracking and computing digit kinematics [13] RIGHT: Calibration using a digit alignment device [14]. "
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    ABSTRACT: Carpal tunnel syndrome (CTS) compromises fine sensorimotor function during activities of daily living. Reach-to-pinch for a small object requires not only dexterity of the grasping digits, but also coordinated transport of the hand to the target. This study examined the effects of CTS on the kinematic performance of reach-to-pinch maneuver. Eleven CTS subjects and 11 able-bodied (ABL) controls donned markers for motion capture of the hand, thumb and index finger during reach-to-pinch. Subjects were presented with a virtual target they could see without seeing their reaching upper-extremity. Subjects were instructed to reach to and grasp a virtual object as accurately and precisely as possible. Performance was assessed by variability of the movement trajectories of the digits and hand, the accuracy relative to the target, and precision of pinch contact over repetitive trials. The CTS group demonstrated significantly increased movement variability in inter-pad distance, joint angles, and transport of the hand compared to ABL controls (p<0.01). CTS subjects also exhibited reductions in accuracy (41%) and precision (33%) of their pinch contact location (p<0.05). CTS adversely affects the ability to execute the reach-to-pinch maneuver. Reduced performance was shown in terms of increased variability for both grasp and transport and the ability to locate the grasping digits relative to a target-object. These performance indices could be used for diagnostic and evaluative purposes of CTS.
    Full-text · Article · Mar 2014 · PLoS ONE
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