A Spinal Motion Measurement Protocol Utilizing Inertial Sensors Without Magnetometers.

This study presents an approach for instrumenting a spinal motion measurement protocol using two inertial measurement units (IMU)s affixed at the posterior pelvis and superior trunk. The accuracy of the inertial motion measurement instrumentation in tracking the relative orientation of the trunk with respect to the pelvis in three spinal motions (flexionextension, side bending, and rotation) is compared to that of a concurrent optical motion capture (mocap) system. Six healthy adults $(31.5 \pm 11.2$; 2 females) were recruited to perform the spinal motions. The results show minimal deviations of the IMU measurements from those of the mocap system (RMSE $\lt 2 \deg $, $\mathrm {r}\gt 0.84$ in all cases) and demonstrate the efficacy of the proposed instrumentation approach for spinal motion measurement.