Modifying Kinect placement to improve upper limb joint angle measurement accuracy.

STUDY DESIGN: Repeated measures.

INTRODUCTION: The Kinect (Microsoft, Redmond, WA) is widely used for telerehabilitation applications including rehabilitation games and assessment.

PURPOSE OF THE STUDY: To determine effects of the Kinect location relative to a person on measurement accuracy of upper limb joint angles.

METHODS: Kinect error was computed as difference in the upper limb joint range of motion (ROM) during target reaching motion, from the Kinect vs 3D Investigator Motion Capture System (NDI, Waterloo, Ontario, Canada), and compared across 9 Kinect locations.

RESULTS: The ROM error was the least when the Kinect was elevated 45° in front of the subject, tilted toward the subject. This error was 54% less than the conventional location in front of a person without elevation and tilting. The ROM error was the largest when the Kinect was located 60° contralateral to the moving arm, at the shoulder height, facing the subject. The ROM error was the least for the shoulder elevation and largest for the wrist angle.

DISCUSSION: Accuracy of the Kinect sensor for detecting upper limb joint ROM depends on its location relative to a person.

CONCLUSION: This information facilitates implementation of Kinect-based upper limb rehabilitation applications with adequate accuracy.

LEVEL OF EVIDENCE: 3b.