Validity and Reliability of an Inertial Measurement Unit-based 3-Dimensional Angular Measurement of Cervical Range of Motion

Objective This study aimed to assess the reliability and validity of an inertial measurement unit (IMU)–based 3-dimensional (3D) angular measurement system for evaluating cervical range of motion. Methods Thirty-three healthy participants (21.9 ± 2.1 years; 162.0 ± 6.0 cm; 55.8 ± 9.0 kg; 21.2 ± 2.4 kg/m2) were evaluated. Kinematic data of the cervical joints were simultaneously obtained using the IMU 3D angular, goniometer, and photographic measurements during cervical flexion (0°, 30°, and 50°), extension (30°, 50°), side-bending (0°, 20°, 40°), and rotation (45°). Test–retest reliability was investigated in each measurement method. Concurrent validity was assessed with the direct comparison between the IMU 3D angular measurement and other methods. Results The IMU 3D angular measurement showed mostly good to high test–retest reliability with relatively small standard error of measurement and the minimal detectable change values. The concurrent validity of IMU 3D angular measurements in the cervical range of motion was mostly reasonable. However, the measurement bias between the 2 methods tended to be larger at the end range of each plane. Conclusion Using the IMU 3D angular measurement in cervical spine is recommended because of its mostly good to high reliability and reasonable validity. However, using the IMU 3D angular measurement at the end range of each plane should be carefully considered owing to the poorer validity.