Romiumeter: An Open-Source Inertial Measurement Unit-Based Goniometer for Range of Motion Measurements

Range of motion (ROM) serves as a crucial metric for assessing movement impairments. Traditionally, clinicians use goniometers to measure the ROM, but this method relies on the clinicians skill, in particular for difficult joints such as the shoulder and neck joints. Recent studies have explored the use of wearable inertial measurement units (IMUs) as an alternative. IMUs exhibit excellent agreement with goniometers, but the lack of affordable, accessible, and clinically validated tools remains an issue. This paper introduces the Romiumeter, a single IMU-based device designed to measure the ROM of the neck and shoulder movements. To validate its accuracy, the Romiumeter was tested on 34 asymptomatic individuals for shoulder and neck movements, using an optical motion capture system as the ground truth. The device demonstrated good accuracy, with a maximum absolute error of less than 5{degrees} with moderate to good reliable measurements(inter-rater reliability: 0.69 - 0.87 and intra-rater reliability: 0.76 - 0.87). Additionally, the Romiumeter underwent validation for different algorithms, including the complementary and Madgwick filters. Interestingly, no significant differences were found between the algorithms. Overall, the Romiumeter provides reliable measurements for assessing shoulder and neck ROM in asymptomatic individuals.