Tilt-Twist Method Using Inertial Sensors to Assess Spinal Posture During Gait

In the clinical context, the need to estimate spinal posture during gait is constantly growing. The most functional way to achieve this goal is first to model the rachis as a multibody structure with rigid segments and second to apply the tilt-twist method. Inertial Measurement Units (IMUs) are the suitable instrumentation to do this because they are portable, low cost, not invasive and free from laboratory constraints. The aim of this pilot study was the assessment of spinal angles by applying the tilt-twist method to IMUs data. A marker stereophotogrammetric system (Optitrack) was adopted as gold standard. Three IMUs (MTx Xsens) were positioned on C7, T12 and S1 vertebral levels. A young healthy subject performed a gait trial at a self-selected speed. Data analysis focused on rotation matrices obtained simultaneously from both the instrumentations. Post-processing algorithms identified movement values of flexion-extension and lateral bending from both IMUs and stereo-photogrammetric system. Comparison graph with the obtained angular patterns showed very similar trends for the three spinal segments. Inertial sensors are suitable to be used to assess spinal posture during gait.