Measurement of lumbar spine range of movement and coupled motion using inertial sensors - a protocol validity study.

Measurement of spinal lumbar range of movement is useful in clinical examination of the spine and for monitoring changes in spinal movement characteristics of individuals over time, particularly in the research context. As the spine exhibits six degrees of movement, three dimensional measurements provide additional information that could benefit the study of spinal conditions. Inertial measurement systems present an innovative method of spinal motion measurement. These systems are small and portable, and of low cost compared to laboratory based three dimensional measurement systems such as electromagnetic and opto-electronic systems. The present study aimed to validate the use of inertial measurement systems in three dimensional spinal range of movement measurement using an electromagnetic tracking system as a reference. Twenty-six healthy participants had their lumbar spine range of movement measured using both an inertial measurement system and an electromagnetic tracking system. Measurements taken by the inertial measurement system were found to be highly correlated with the electromagnetic tracking system (overall regression R(2) 0.999, p < 0.005). Measurements showed strong agreement (mean differences between -0.81° and 1.26°) and produced no significant difference from the electromagnetic tracking system (paired t-test p > 0.05). The ranges of movement measured were also highly comparable to those reported in the literature. Inertial measurement systems that consist of triaxial gyroscopes, accelerometers and magnetometers are concluded to be valid tools for three dimensional spinal range of movement measurement within or outside of the laboratory settings due to their cost, size and portability.