Smartphones are being used in a variety of practice settings to measure joint range of motion (ROM). A number of factors can affect the validity of the measurements generated. However, there are no studies examining smartphone-based goniometer applications focusing on measurement variability and error arising from the electromechanical properties of the device being used.
To examine the concurrent validity and interrater reliability of 2 goniometric mobile applications (Goniometer Records, Goniometer Pro), an inclinometer, and a universal goniometer (UG).
Nonexperimental, descriptive validation study.
3 physical therapists having an average of 25 y of experience.
Main Outcome Measures:
Three standardized angles (acute, right, obtuse) were constructed to replicate the movement of a hinge joint in the human body. Angular changes were measured and compared across 3 raters who used 3 different devices (UG, inclinometer, and 2 goniometric apps installed on 3 different smartphones: Apple iPhone 5, LG Android, and Samsung SIII Android). Intraclass correlation coefficients (ICCs) and Bland-Altman plots were used to examine interrater reliability and concurrent validity.
Interrater reliability for each of the smartphone apps, inclinometer and UG were excellent (ICC = .995–1.000). Concurrent validity was also good (ICC = .998–.999). Based on the Bland-Altman plots, the means of the differences between the devices were low (range = –0.4° to 1.2°).
This study identifies the error inherent in measurement that is independent of patient factors and due to the smartphone, the installed apps, and examiner skill. Less than 2° of measurement variability was attributable to those factors alone. The data suggest that 3 smartphones with the 2 installed apps are a viable substitute for using a UG or an inclinometer when measuring angular changes that typically occur when examining ROM and demonstrate the capacity of multiple examiners to accurately use smartphone-based goniometers.
Wellmon, D. Gulick, and Paterson are with the Inst for Physical Therapy Education, Widener University, Chester, PA. C. Gulick is with the Dept of Kinesiology, California State University at Fullerton, Fullerton, CA.