title: Development and application of stereo camera-based upper extremity workspace evaluation in patients with neuromuscular diseases.
abstract: BACKGROUND
  The 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.
  
  
  RESULTS
  A 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
  The 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.
authors.affiliation: University of California at Berkeley College of Engineering, Department of Electrical Engineering and Computer Science, Berkeley, California, United States of America. gregorij@eecs.berkeley.edu
authors.forename: Gregorij
authors.initials: G
authors.lastname: Kurillo
authors.forename: Jay J
authors.initials: JJ
authors.lastname: Han
authors.forename: Richard T
authors.initials: RT
authors.lastname: Abresch
authors.forename: Alina
authors.initials: A
authors.lastname: Nicorici
authors.forename: Posu
authors.initials: P
authors.lastname: Yan
authors.forename: Ruzena
authors.initials: R
authors.lastname: Bajcsy
mesh_terms: D000328:Adult; D000368:Aged; D000465:Algorithms; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009068:Movement; D009468:Neuromuscular Diseases / Q000503:physiopathology*; D010781:Photography / Q000295:instrumentation*; D016059:Range of Motion, Articular / Q000502:physiology; D058998:Remote Sensing Technology / Q000295:instrumentation*; D034941:Upper Extremity / Q000502:physiology*