Elsevier

Gait & Posture

Volume 39, Issue 2, February 2014, Pages 827-830
Gait & Posture

Short Communication
Implementation of a markerless motion analysis method to quantify hyperkinesis in males with fragile X syndrome

https://doi.org/10.1016/j.gaitpost.2013.10.017Get rights and content

Highlights

  • Use of a markerless motion analysis system to quantify hyperkinesis.

  • Outcome variables track travel distance of limb segments relative to body COM.

  • Outcome variables discriminate normal from FXS cohort.

  • Outcome variables correlate with clinical rating scales for hyperkinesis.

Abstract

Hyperactive behavior – and implicitly, motion – in Fragile X syndrome (FXS) has been historically described using behavioral rating scales. While rating scales are the current standard outcome measures used in clinical research, they have limitations including their qualitative nature and subjectivity. The advent of new motion capture technologies has provided the opportunity to develop quantitative methods for measuring hyperactive motion. The hypotheses for this study were that a novel markerless motion analysis method (1) can quantitatively measure kinematic parameters, (2) can differentiate the level of hyperkinesis between control and FXS populations, and (3) will correlate with blind-reviewer synchronous video-capture methods and behavioral rating scale scores. Twenty young males (7-control, 13-FXS; ages 9–32) were studied using a standardized protocol in a markerless motion analysis suite. Behavioral scale questionnaires were filled out by parents and those scores were correlated with motion parameters (frequency and total traveled distance) of body segments during 30 s of story listening while standing in the observation space. The markerless system was able to track subjects and the two populations displayed significantly different quantities of motion, with larger amounts of motion in the FXS group (p < 0.05). Pearson's correlation coefficients between frequency counts obtained from the markerless system and rater-based video capture were between 0.969 and 0.996 (p < 0.001). Significant correlations between rating scale scores and motion parameters ranged from 0.462  r  0.568 (p  0.040). These results suggest feasibility and validity of a markerless system as a non-invasive method able to quantify motion in individuals with hyperkinesis.

Introduction

Fragile X syndrome (FXS) is the most common inherited cause of intellectual disability and the most common known genetic cause of autism [1]. It is associated with increased motor activity (hyperkinesis) that includes hyperactivity with increased body and limb movement and motor stereotypies (repetitive, non-goal directed movement patterns). Hyperactivity has been quantified in rodent models using open field tests to measure locomotor activity of the animal in a defined space [2]. An equivalent quantitative method does not exist for humans. Current outcome tools used when investigating pharmaceutical (or other therapy) effects on hyperkinesis typically use parent/guardian rating scales [3], [4]. These scales are the present gold standard for use in clinical trials research [5] and have validity and reliability [6], [7]. However, they are not ideal because they are qualitative, inherently subjective, unable to detect small increments of behavioral changes, and prone to floor and/or ceiling effects. Traditional state of the art marker based motion analysis approaches to analyze hyperkinetic behaviors have not been reported in the FXS or autism literature, but they would likely have considerable limitations in this developmentally disabled population. Marker placement requires an expert spending a considerable amount of time with marker application and a subject who understands, does not object to removing clothing, and is cooperative with the instructions for motion analysis. A subject population with FXS and/or autism is expected to be non cooperative with the tedious marker application process due to behavioral issues including tactile defensiveness, anxiety, and lack of tolerability and understanding of the procedure. The above limitations in quantifying hyperkinesis and stereotypies, in combination with the critical need to quantify these core behavioral features of FXS and autism for efficacy research provided the impetus for the present study.

Motion analysis is used in several fields of medical practice, including orthopedics, sports medicine, rehabilitation, and neurology. Accurate description of body kinematics is typically achieved with the use of reflective markers placed on anatomical landmarks to track limb, head and trunk position. Only recently have technological advances in image-recognition algorithms allowed development of systems robust enough to be used in clinical, sports and occupational biomechanics [8], [9], [10], [11]. The objective of this study was to determine the feasibility of using markerless motion technology to quantify motor activity (specifically body mass center and limb segment movement) in young males with and without FXS. Our hypotheses are that a markerless motion analysis system will provide quantitative measures of hyperkinesis observed clinically in subjects with FXS, differentiate levels of motor activity between controls and those with FXS, and motion parameters of hyperkinesis will correlate with both video-captured and clinical hyperactivity rating scale scores. Ultimately, we anticipate that this quantitative system will serve as a model for markerless motion measurement in hyperkinetic disorders.

Section snippets

Materials and methods

The markerless motion capture system (Biostage, Organic Motion, New York, NY) acquired motion with fourteen video cameras mounted in a self-contained observation space bound by three reflective-canvas walls measuring with a footprint of 3.5 m × 4.9 m and a wall height of 2.5 m (Fig. 1a). This system has been reported to have high correlation factors with a traditional marker-based system (VICON™) for kinematic gait variables [12]. The 3D motion data was analyzed using The MotionMonitor®

Results

FXS subjects showed a large amount of movement in the Biostage. Fig. 1b and c show skeleton views of representative subjects from both experimental groups as viewed on the Motion Monitor's interface. Arm and foot travel distances, were significantly greater in the FXS group compared to controls (p = 0.038 and 0.011, respectively, Fig. 2). The distance traveled by the body COM was greater in the FXS (3.3 ± 4.0 m) versus control (1.1 ± 0.5 m) groups. Due to the variable activity pattern within the FXS

Discussion

Kinematic assessment of body segments could be useful for future interventional studies attempting to quantify changes in hyperkinesis in patients with hyperkinetic disorders. This study is the first to attempt measurement of kinematic parameters obtained from a markerless motion capture system and correlate these measurements with scores on video-capture methodology and behavioral rating scales in persons with FXS, a condition associated with hyperkinesis. The results obtained are encouraging

Conflict of interest statement

None of the authors have financial or other conflicts of interest in regards to this research.

Acknowledgements

This study was supported by a pilot grant from the FRAXA Research Foundation (PI: Berry-Kravis). The authors also thank Mr. Robert Trombley from the Motion Analysis Lab at Rush University for his expert assistance with the motion analysis routines. Further, we would like to thank Renee Kawecki, Chris Ferrigno, Gary Farkas, and Samir Chabra for their assistance with video analysis.

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