Measurement of active shoulder motion using the Kinect, a commercially available infrared position detection system

Abstract

Background: The shoulder's ability to participate in sports and activities of daily living depends on its active range of motion. Clinical goniometry is of limited utility in rigorously assessing limitation of motion and the effectiveness of treatment. We sought to determine (1) whether a validated position-sensing tool, the Kinect, can enable the objective clinical measurement of shoulder motion and (2) the degree to which active range of motion correlates with patient self-assessed shoulder function. Methods: In 10 control subjects, we compared Kinect motion measurements to measurements made on standardized anteroposterior and lateral photographs taken concurrently. In 51 patients, we correlated active motion with the ability to perform the functions of the Simple Shoulder Test (SST). Results: In controls, Kinect measurements strongly agreed with photographic measurements. In patients, the total SST score was strongly correlated with the range of active abduction. The ability to perform each of the individual SST functions was strongly correlated with active motion. The active motion in well-functioning patient shoulders averaged 155° ± 22° abduction, 159° ± 14° flexion, 76° ± 18° external rotation in abduction, -59° ± 25° internal rotation in abduction, and -3.3 ± 3.7 inches of cross-body adduction, values similar to the control shoulders. Use of the Kinect system was practical in clinical examination rooms, requiring <5 minutes to document the 5 motions in both shoulders. Discussion: The Kinect provides a clinically practical method for objectively measuring active shoulder motion. Active motion was an important determinant of patient-assessed shoulder function.