Is a standalone inertial measurement unit accurate and precise enough for quantification of movement symmetry in the horse?

The research article studies the accuracy and precision of standalone, low-cost inertial measurement units (IMUs) in measuring movement symmetry in horses, specifically for orthopaedic deficits. The study compared the results with an established gait analysis system and concluded that the standalone IMUs provide sufficient precision but have scope for improvement.

Understanding Inertial Measurement Units (IMUs)

• IMUs are devices that measure and report a body’s specific force, angular rate and orientation. These devices are important for motion tracking applications and can facilitate large-scale studies into identifying minimal important differences (MID) for orthopaedic deficits in horses.
• The research investigates a standalone 6 degree-of-freedom IMU which is a low-cost solution compared to more expensive, fully-equipped gait analysis systems.

Understanding the Study Design

• The study was conducted on six horses for two anatomical landmarks: sacrum (the base of the spine) and sternum.
• The symmetry measures used were the symmetry index (SI), the difference between minima (MinDiff) and the difference between maxima (MaxDiff), are calculated from vertical displacement.

Results and Interpretation

• The Limits of Agreement (LoA), which indicate how well the standalone IMU matches the established system, calculated for the sacrum were ± 0.095 for SI, ± 6.6 mm for MinDiff and ± 4.3 mm for MaxDiff. For the sternum, the LoA values were ± 0.088 for SI, ± 5.0 mm for MinDiff and ± 4.2 mm for MaxDiff.
• When compared to reference data from mildly lame horses, the SI values were deemed accurate enough, indicating that the standalone IMU performs with sufficient precision in measuring symmetry index.
• However, the MinDiff and MaxDiff values were less favorable, suggesting that the standalone IMU’s performance in accurately measuring these parameters could be improved.

Conclusions and Future Works

• The study finds that standalone IMUs could provide a cheaper and fairly accurate alternative to established gait analysis systems for studying orthopaedic deficits in horses.
• However, they recommend that future studies should investigate specific calibration and processing algorithms that could further improve the performance of standalone IMUs.