Wireless inertial measurement unit-based methods for measuring lumbopelvic-hip range of motion are valid compared with optical motion capture as golden standard

BACKGROUND: Lumbopelvic-hip motions in the sagittal plane are critical in distinguishing between individuals with Low Back Pain (LBP) and healthy counterparts. Assessment of these motions involves evaluation of the range of motion, timing, coordination, alignment, and functional performance. Traditional, golden standard devices, like optical motion capture systems, are costly and limited to lab settings. Alternatively, Inertial Measurement Units (IMUs) potentially offer an affordable solution that allows movement assessment in daily life.

METHODS: This cross-sectional study compares two IMU-based measurement methods (2 versus 3 sensors) with optical motion capture to assess the sagittal lumbopelvic-hip range of motion (RoM) during extension and flexion motions in individuals with nonspecific chronic LBP and healthy controls. The primary objective was to establish the clinimetric measurement accuracy of IMU-based methods by assessing their concurrent validity with optical motion capture. Secondary aims included assessment time differences and measurement errors.

FINDINGS: Strong positive correlations were shown between optical motion capture and both IMU-based measurement methods for flexion and extension RoM and the measurement timing. Minimal measurement errors were observed. For measuring both RoM and timing of measuring RoM, the IMU method with 3 sensors showed slightly better accuracy than the IMU method with 2 sensors.

INTERPRETATION: This cross-sectional study successfully established the clinimetric measurement validity and accuracy of IMU-based methods in assessing lumbopelvic-hip mobility in individuals with nonspecific low back pain and healthy controls. Revised Sentence: Based on our findings, low-cost IMU-based methods can be validly utilized in both daily clinical practice and clinical research for the assessment of lumbopelvic-hip motion.