Inertial measurement units are comparable to motion capture for measuring intersegmental spinal angular velocities in horses.

Overview

• This study evaluates whether inertial measurement units (IMUs) can accurately measure spinal motion in horses compared with the traditional marker-based motion capture systems.
• Results show that IMUs provide comparable data to motion capture systems for intersegmental spinal angular velocities, suggesting IMUs are a valid alternative for clinical and field use.

Study Purpose and Background

• The research aimed to compare spinal movement data obtained from IMUs and a marker-based motion-capture system in horses to determine if IMUs are an accurate alternative.
• Marker-based motion capture is a precise laboratory technique for tracking motion but requires complex equipment and controlled environments.
• IMUs are small, portable devices equipped with accelerometers and gyroscopes that measure angular velocities and accelerations, and can be used in field settings.
• Validating IMUs against the gold standard motion-capture system would allow for practical, non-laboratory assessment of equine spinal movement.

Methods

• Four horses were fitted with custom marker clusters that included a 3D-printed base to secure the IMU. This ensured that the IMU and motion capture markers recorded from the exact same anatomical spot and orientation.
• A total of 3,737 paired time points across 37 gait cycles were collected, providing extensive data for comparison.
• Data focused on intersegmental angular velocities of the spine, analyzed across three different planes of motion (likely sagittal, frontal, and transverse planes).
• Statistical analyses included Bland-Altman analysis to assess any systematic bias between the two methods, and intraclass correlation coefficients (ICCs) to evaluate the agreement level.

Results

• The Bland-Altman analysis showed no significant systematic bias between IMU and motion capture measurements, suggesting that the two methods are consistent with one another.
• Intraclass correlation coefficients revealed:
  • Excellent agreement (r = 0.964 to 0.991) in 7 of 9 comparisons.
  • Good agreement (r = 0.854 and 0.875) in the remaining 2 comparisons.
• These strong ICC values indicate that IMU-derived measurements correlate closely with the motion capture data.

Conclusions and Implications

• IMUs can reliably measure intersegmental spinal angular velocities in horses, comparable to data from sophisticated marker-based systems.
• This validates the use of IMUs as a practical and portable alternative to motion capture for assessing topline function and spinal motion.
• IMUs enable evaluations outside of specialized laboratories, extending their use to clinical environments and field settings where motion capture systems are impractical.
• This advancement can improve monitoring of spinal health, performance, and rehabilitation in equine medicine using accessible technology.