3D kinematics of the equine metacarpophalangeal joint at walk and trot.

This research analyzes the 3D movements of the metacarpophalangeal joint (MCP) in horses while walking and trotting, aiming to provide a better understanding of the biomechanics that could influence injury development in these animals.

Background

• The research is premised on the observation that the MCP joint and related soft tissues are susceptible to injury in sporting horses. This vulnerability is often analyzed through 2D analysis in the sagittal plane, but there’s been a lack of information on the 3D motions of the MCP joint, meaning its entire mechanics haven’t been fully studied.

Methodology

• The study collected 3D data on the MCP joint’s movement in healthy horses. To achieve this, researchers used eight infra-red cameras to record the movements at 120 Hz of marker triads (three-point markers) fixed rigidly to two bone structures in a horse’s right forelimb: the third metacarpus and proximal phalanx. The number of horses studied varied by the action: four horses at walk and six horses at a trot.
• The data obtained was then analyzed using singular-value decomposition and spatial attitude methods for kinematics. This allowed for the computation of helical angles between the two segments, providing a clearer picture of the MCP joint’s rotational movement.

Findings

• The researchers concluded that the MCP joint’s movements consist of flexion/extension, adduction/abduction, and axial rotation. Each movement varied in range, whether the horse was trotting or walking. Flexion/extension averaged from 62 degrees (+/- 7 degrees) at walk to 77 degrees (+/- 5 degrees) at trot. Adduction/abduction registered 13 degrees (+/- 7 degrees) at walk and 18 degrees (+/-7 degrees) at the trot. Finally, axial rotation totaled somewhere around 6 degrees (+/- 3 degrees) at walk and 9 degrees (+/- 5 degrees) at trot.
• The researchers also found that flexion/extension remained consistent in pattern and amplitude regardless of the horse or movement, and it appeared to be tied with adduction/abduction. In other words, a stance phase extension occurred with abduction, while a swing phase flexion was accompanied by adduction. Axial rotation, on the other hand, was always the smallest movement and its direction was unique to each horse, although it was uniform in each animal across both walking and trotting.