P.2.4 Upper extremity reachable workspace evaluation in DMD using Kinect

Abstract

There is a lack of outcome measures evaluating upper extremity function in Duchenne Muscular Dystrophy (DMD) and a need to develop a quantitative low-cost method to evaluate upper extremity function in clinical trials. We developed a 3D reachable workspace tool to quantify joint mobility within the patient’s functional space. Reachable workspace is defined as all points relative to the torso an individual can reach by moving their hands, and its envelope is defined by the encompassing surface area. Reachable workspace is associated with functional upper limb status and is applicable in evaluating patients with DMD, where weakness and dysfunction stems from early involvement of shoulder girdle muscles. We developed a system based on the Microsoft Kinect to capture upper-limb movement during a specially devised workspace protocol. We are able to fit spherical surface data to the hand trajectory. The resulting envelope is quantified as a surface area using 3D surface plots projected to anatomical body planes. Surface area is normalized to the unit of the hemisphere of hand movement to facilitate comparison between individuals. We collected data in 8 pediatric subjects with DMD aged 6–13 years (mean: 9.4 ± 2.5 years). All subjects were able to follow the movement protocol for assessment of the reachable workspace. Average normalized surface area for the dominant side was 0.749 (SD: 0.063) with a minimal area of 0.627 obtained in an 11 year-old. Maximal area of 0.883 was obtained in another 11-year old subject with milder phenotype. Performance of the same movement protocol in a healthy control boy showed normalized surface area of 0.884, and in the adult control group ( n = 10), the average normalized surface area reached 0.679 (SD: 0.090). To increase the sensitivity to detect subtle weakness we measured the workspace with loading condition (500 g wrist weight). Further studies will examine reliability, accuracy and correlation with traditional functional outcome measures.