Validity of a low-cost inertial measurement unit for the assessment of range and quality of movement of cervical and thoracic spine

Background and aims: Patients with spinal pain frequently consult clinical practice because of movement impairments and decreased motor control, which can be challenging to assess in a clinical setting. Inertial measurement sensors may provide an opportunity for developing reliable, affordable, and simple methods for detecting and monitoring spine motion in a clinical context. This study aimed to examine the validity and reliability of an inertial sensor with a 3D camera system for measuring range of motion (ROM) and quality of movement (QOM) in single-plane neck and trunk motions.

Methods: Thirty-three healthy, pain-free individuals took part in the study. Each participant performed neck (cervical flexion, extension, and lateral flexion) and trunk (thoracic flexion, extension, rotation, and lateral flexion) movements, which were recorded simultaneously using a 3D camera system and an inertial measuring unit (MOTI, Aalborg, Denmark). For ROM and QOM (quantified as the jerk index), agreement and consistency were assessed using intraclass correlation coefficients (ICC3.1), mean bias, and Bland-Altman plots.

Results: The reliability of ROM was excellent for all movements (ICC3.1 between 0.91 and 1.00) and good to excellent for QOM (ICC3.1 between 0.84 to 0.95). The average bias for all motions was less than the minimum acceptable difference between devices (0.1-0.8°). According to the Bland-Altman plot, MOTI measured higher ROM and QOM than the 3D camera system for all neck and trunk motions.

Conclusions: This study showed that MOTI was a reliable and valid method for assessing ROM and QOM for neck and trunk motions in experimental and clinical settings.