Development and Application of Stereo Camera-Based Upper Extremity Workspace Evaluation in Patients with Neuromuscular Diseases

Abstract

BackgroundThe concept of reachable workspace is closely tied to upper limb joint range of motion and functional capability. Currently, no practical and cost-effective methods are available in clinical and research settings to provide arm-function evaluation using an individual’s three-dimensional (3D) reachable workspace. A method to intuitively display and effectively analyze reachable workspace would not only complement traditional upper limb functional assessments, but also provide an innovative approach to quantify and monitor upper limb function.Methodology/Principal FindingsA simple stereo camera-based reachable workspace acquisition system combined with customized 3D workspace analysis algorithm was developed and compared against a sub-millimeter motion capture system. The stereo camera-based system was robust, with minimal loss of data points, and with the average hand trajectory error of about 40 mm, which resulted to ∼5% error of the total arm distance. As a proof-of-concept, a pilot study was undertaken with healthy individuals (n = 20) and a select group of patients with various neuromuscular diseases and varying degrees of shoulder girdle weakness (n = 9). The workspace envelope surface areas generated from the 3D hand trajectory captured by the stereo camera were compared. Normalization of acquired reachable workspace surface areas to the surface area of the unit hemi-sphere allowed comparison between subjects. The healthy group’s relative surface areas were 0.618±0.09 and 0.552±0.092 (right and left), while the surface areas for the individuals with neuromuscular diseases ranged from 0.03 and 0.09 (the most severely affected individual) to 0.62 and 0.50 (very mildly affected individual). Neuromuscular patients with severe arm weakness demonstrated movement largely limited to the ipsilateral lower quadrant of their reachable workspace.Conclusions/SignificanceThe findings indicate that the proposed stereo camera-based reachable workspace analysis system is capable of distinguishing individuals with varying degrees of proximal upper limb functional impairments.

Validity, Reliability, and Sensitivity of a 3D Vision Sensor-based Upper Extremity Reachable Workspace Evaluation in Neuromuscular Diseases

“…In this paper, we follow up on the previously published work16 by evaluating the validity, reliability, and sensitivity of the developed methodology and the outcome measurement. The results support discriminant validity of the developed methodology and outcome measure by demonstrating significant difference in the total reachable workspace RSA between healthy able-bodied controls and patients with NMDs.…”

“…Recently, an innovative method to measure and graphically reconstruct an individual’s upper extremity 3D reachable workspace using a low-cost single stereo camera sensor system was developed by the study investigators 16. The results showed that a single stereo camera system was capable of capturing and reconstructing 3D reachable workspace that was robust, fast, with minimal loss of data points when compared against full-scale motion analysis system simultaneously.…”

Novel Ergonomic Postural Assessment Method (NERPA) Using Product-Process Computer Aided Engineering for Ergonomic Workplace Design

“…Different applications and developments concerning the use of 3D simulation tools for the evaluation of workstations can be read in the scientific literature, successfully describing the use of these tools for the design and improvement of workstations [6–9]. In addition, different studies associate the improvement of ergonomics with quality and productivity improvement [10–13].…”

Optimal design for individualised passive assistance

“…Genetic algorithms have been used to set the parameters of the exoskeleton to maximize the range of motion [5]. Recently, clinical reachable workspace metrics have been developed to quantify an individual's range of motion using a Kinect camera [15,10]. In the controls community, there are various methods to compute the reachable set of a dynamical system which include: Hamilton-Jacobi Methods [20], support function methods [8], sum-of-squares programming [24,26], and occupation measures [19].…”