Preliminary report into the function of the shoulder using a novel imaging and motion capture approach.

This research investigates how the shoulder blade moves in horses during different gaits through a new imagining technique. The study found that shoulder blade motion helped absorb shock from locomotion impact and contribute to stride economy, yet it did not increase with speed, implying potential detriments on pigs’ breathing.

Objectives, Assumptions and Methodology

• The research intended to discern and document the movement of the horse’s shoulder blade (or scapula) during different types of movement (or gaits) through a newly devised imaging technique.
• Previously, due to the shoulder blade being obscured by layers of muscle and skin, its movements were simply modeled as a pivot during locomotion, essentially dismissing any translational motion.
• To counter this assumption, the researchers tracked the ripple of movement in the horse’s shoulder blade using an array of markers. This approach allowed them to monitor the sliding motion of the scapula with locomotion, providing a numerically quantified record.

Results and Observations

• From the gathered data, they found that there were minor differences in recorded interstride variability. Despite varying stride lengths, the limit of scapula movement deviated by less than 5 mm in the gaits examined.
• They observed scapula sliding of up to 80 mm in the plane of progression (front-to-back) but found that the stride length seemed to be extended by rotation of the scapula within the same plane.
• This rotational flexion-extension was most prominent in trotting and showed negligible difference between the canter and walk.
• They also found significant sliding in a dorsal-ventral direction (top-to-bottom), which varied with the type of gait, both in magnitude and timing, potentially acting as a shock absorption mechanism.
• In the canter gait, despite expectations, the scapula didn’t slide as much. This was related to a lateral positioning of the scapula which led to an increased impact on the ribcage.

Conclusions and Implications

• The research concluded that there’s an assumption that scapula-thoracic sliding increases stride length and hence improves locomotor speed economically. They found that the extra motion of the scapula appeared to absorb shocks from forelimb impact and maintain locomotion economy. However, speed was not amplified with these movements.
• Interestingly, the tension produced by these movements might have adverse effects on the horse’s ventilation system.