Abstract

Background: Low back pain is the leading cause of disability worldwide. Subjective assessments are often used to assess extent of functional limitations and treatment response. However, these measures have poor sensitivity and are influenced by the patient’s perception of their condition. Currently, there are no objective tools to effectively assess the extent of an individual’s functional disability and inform clinical decision-making.
Objective: The purpose of this study was to evaluate the reliability of a wearable motion system based on Inertial Measurement Unit (IMU) sensors for use in quantifying low back function.
Methods: Low back motion assessments were conducted by 3 novice raters on 20 participants using an IMU-based motion system. These assessments were conducted over 3 days with 2 days of rest in between tests. A total of 37 kinematic parameters were extracted from the low back motion assessment in all three anatomical planes. Intra-rater and inter-rater reliability were assessed using Intraclass Correlation Coefficients (ICCs) calculated from repeated measures, mixed-effects regression models.
Results: Lumbar spine-specific kinematic parameters showed moderate to excellent reliability across all kinematic parameters. The ICC values ranged between 0.84-0.93 for intra-rater reliability and 0.66 - 0.83 for inter-rater reliability. In particular, velocity measures showed higher reliabilities than other kinematic variables.
Conclusion: The IMU-based wearable motion system is a valid and reliable tool to objectively assess low back function. This study demonstrated that lumbar spine-specific kinematic metrics have the potential to provide good, repeatable metrics to assess clinical function over time.

Keywords:Low back disorder; Reliability; Intra-rater; Inter-rater; Wearables; Lumbar function