Random Error and Systematic Error of Shoulder Joint Rotation Range of Motion Measurement Using iPhone

Abstract

[Purpose] To clarify whether the measurements using the angle value measurement application equipped in iPhone as a standard feature showed the random and systematic error or not, this study compared between the measurements of shoulder joint rotation range of motion by iPhone and those by goniometer. [Participants and Methods] At the shoulder joint, the range of motion of external rotation and that of internal rotation were measured using iPhone and goniometer for 10 healthy male university students. [Results] The measurement by iPhone showed no systematic error. At the shoulder joint external rotation, measurement of range of motion using the iPhone showed that the value of MDC₉₅ was 4.5 degree, while at the shoulder joint internal rotation, the MDC₉₅ was 7.0 degree. [Conclusion] It was suggested that the iPhone application of tilt angle measurement is a tool that can measure the motion range of shoulder joint rotation.