Tuesday, September 8, 2015

Active range of shoulder motion - objective measurement with the Kinect

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

These authors demonstrated the practicality of using an inexpensive, validated, commercially available infrared position sensor, the Kinect, for the observer-independent recording of the active ranges of motion of patients' shoulders. This device - familiar to computer gamers - does not require the application of sensors or markers to the patient and functions well in the clothed subject.

When mounted to a wheeled frame along with a laptop computer, the Kinect can be easily moved from one examination room to another. 

The Kinect outputs numerical data that can also be represented as a stick figure. The device measures the angles between the arm (A) and the trunk (T), automatically correcting for the patient leaning to one side or the other.

In 10 control subjects, they compared Kinect motion measurements to measurements made on standardized anteroposterior and lateral photographs taken concurrently. The Kinect measurements strongly agreed with photographic measurements. 

In 51 patients, they correlated active motion with the ability to perform the functions of the Simple Shoulder Test (SST). 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.

Comment: The shoulder's ability to participate in sports and activities of daily living depends on its active range of motion. Because of inter-observer variability, range of motion measurements with a goniometer are of limited utility in rigorously assessing limitation of motion and the effectiveness of treatment. The use of an objective system for the observer-independent measurement of active shoulder motion - such as the Kinect - holds promise for clarifying the indications for and the results of therapeutic interventions designed to improve shoulder function and for the comparison of results among surgeon-scientists.