Bone stress in the horse forelimb during locomotion at different gaits: a comparison of two experimental methods.

The research article investigates how the bones in a horse’s forelimb respond to stress during movement at different gaits. Two separate experimental methods were used with the conclusions varying more for the results concerning the metacarpus than the radius.

Objective of the Research

• The research was aimed at determining the longitudinal stresses present in various parts of a horse’s forelimb during movement at different speeds (gaits).

Approach and Methods Used in the Research

• The researchers used two independent methods to analyze the stress on the horse forelimb. One involved the usage of rosette strain gauges to measure the in vivo bone strain during locomotion, and the other method used a film/force plate analysis.
• The film/force plate analysis involved capturing the horse’s forelimb position as it moved over a force plate. This method relies on accurate limb segment orientation relative to ground reaction force and computational calculations.

Comparison and Findings between the Two Methods

• The results obtained from both methods regarding the radius – one of the main bones in the horse’s leg – were more consistent when compared to the results for the metacarpus (another important bone in a horse’s leg).
• The disparity in results from the metacarpus might have been caused by the simplicity of the biomechanical model used in the film/force method, which may have neglected certain influential factors like the force exerted by sesamoids on the distal end of the metacarpus.
• Both methods revealed that the cranial cortex of the radius undergoes tension, while its caudal cortex undergoes compression. The film/force method suggested sagittal bending in the metacarpus, resulting in palmar cortex compression and dorsal cortex tension. However, in vivo bone strain measurements suggested axial compression in the metacarpus.
• Peak stress according to the film/force analysis was 1.5-2 times and 2-3 times greater than those of the in vivo strain recording for the radius and metacarpus respectively.

Implications and Conclusions of the Research

• The measurements made from in vivo bone strain recordings showed a consistent loading regime on each bone, even as the gait of the horse changed. This information is significant as it implies that these bones have an ability to economically use tissue for supporting the applied dynamic loads.
• The research found the peak stress values measured from the radius were significantly higher than those of the metacarpus at constant speed. However, during acceleration and deceleration, peak stress in the metacarpus rose dramatically, while that in the radius remained constant.

In conclusion, the study highlighted the value of accurate and comprehensive computational models in movement studies, the complexity of equine biomechanics, and the influence of movement speed and direction changes on equine bone stress.