Verification of skin-based markers for 3-dimensional kinematic analysis of the equine tarsal joint.

This research article investigates the potential of using skin-based markers for 3D analysis of motion in a complex joint, the tarsal joint. The study finds that with appropriate correction for skin movement, these markers can accurately measure the joint’s 3D motion, offering a less invasive alternative to the bone pin technique traditionally used.

Objective of the Research

• The main objective of the research was to assess the feasibility and accuracy of using skin-based markers for 3D analysis of tarsal joint motion in horses. This study aimed to provide a less invasive alternative to the commonly used bone pin technique.

Methods employed

• The researchers attached retroreflective markers on the horses’ tibial (shinbone) and metatarsal (midfoot bone) segments.
• The motion of these markers was automatically tracked as the horse moved at a trot.
• They then used 3D skin correction algorithms to adjust the data for skin displacement. The researchers then compared 3D motions derived from the corrected and uncorrected skin movements with data from a past study that used bone-fixed markers, utilizing correlation, root mean square errors (RMS), and shape agreement (SA) of the curves.

Results and Findings

• The study found that the root mean square errors (a measure of the differences between the predicted and observed data) between the bone-fixed markers and corrected skin displacement were smaller compared to those between bone-fixed markers and uncorrected skin displacement.
• The correlation coefficients (indicating how closely the data sets match each other) were also higher between bone-fixed markers and corrected skin displacement than between bone-fixed markers and uncorrected skin displacement.
• Shape agreement (which assesses the similarity of the shape of two curves) was generally good or fair for all motions except for internal/external rotation and medial/lateral translation.

Conclusion

• The findings suggest that with appropriate adjustments for skin movement, skin markers could provide a valid way to measure tarsal 3D motions (flexion/extension, abduction/adduction, cranial/caudal translation, and proximal/distal translation).
• This approach could offer a less invasive and more user-friendly method for kinematic studies, potentially broadening their usage beyond the research laboratory and allowing for analysis and comparison of information between horses during different movement phases.