Comparing cervical range of motion, head repositioning accuracy and quality of movement using an inertial measurement unit and a 3d camra system

Background and aims: Neck pain is a common musculoskeletal condition where many develop persistent symptoms. Studies have demonstrated sensory-motor disturbances e.g altered range of motion (ROM), head repositioning accuracy (HRA) and quality of movement (QOM) in neck pain populations. 3D camera systems can be used to quantify human movement accurately, but this may not be applicable in a clinical setting. This study aimed to compare MOTI, a small digital inertial measurement unit connected to a smartphone via Bluetooth, to 3D motion recordings during head rotations.

Methods: Thirty healthy participants were recruited. Participants were seated on a chair, fixed with a chest strap to the backrest. Participants were blindfolded, wore noise protection earmuffs and a headband with both MOTI and markers for 3D motion recordings. Participants were asked to rotate through full cervical rotation from a neutral head position before returning to this position again. Movements were done in triplets, bilaterally. ROM, HRA and QOM were extracted from both systems and analysed using Pearson’s correlation coefficient, paired t-tests, and Bland-Altman plots.

Results: When comparing the two systems, excellent correlations were seen for ROM (r=0.99), HRA (r=0.77-0.82) and QOM (r=0.96-0.98). A systematic higher offset was seen for MOTI compared to 3D recordings when inspecting the Bland-Altman plots for both ROM (mean bias=-0.56±0.65°), HRA (mean bias=0.48±0.76°) and QOM (mean bias=-0.05±0.08 Log°/s3).

Conclusions: The results showed that the inertial measurement unit, MOTI, could accurately assess ROM, HRA and QOM and may be a promising new tool in clinical practice.