Equine superficial digital flexor tendon force and axial speed of sound: a calibration method under clinical conditions.

This research article presents a study on developing and testing a simple calibration procedure for non-invasively evaluating force in horse tendons during locomotion using Axial Speed of Sound (SOS) measurements, with focus on superficial digital flexor tendons. This method eliminates the need for direct measurement of the ground reaction force, a process that normally involves expensive and complex equipment.

Background of the Research

• The method of non-invasively evaluating equine tendon force during movement is a current practice. It uses axial speed of sound (SOS) measurements to estimate the tendon force.
• A particular focus of this method has been on the superficial digital flexor tendons (SDFTs) of horses due to this tendon’s critical role in equine locomotion and susceptibility to injury.
• The current calibration procedure that converts SOS into force values involves the use of a nonlinear relationship between the SOS and tendon force, which can be approximated by a logarithmic curve.
• This involves trotting the horse on a hard, flat surface like asphalt, and taking SOS measurements which are then transformed into force values.

Issues with the Existing Procedure

• The current calibration method hinges on the assumption that the tendon force represents approximately 76% of the limb force at mid-stance, which is a point in the stride when the metacarpus (part of the horse’s leg) is almost vertical. This is a finding from previous in vitro studies.
• However, this method requires the direct measurement of the ground reaction force (GRFz). To measure this, it needs an instrumented shoe – a device that is not only complex to utilize but can also be expensive.

Objective of the Study

• The study set out to develop a simpler calibration procedure that does not require the direct measurement of the GRFz.
• The authors aimed to test this new calibration method and compare it with the existing calibration procedure that uses a dynamometric horseshoe.
• The goal was to implement this new method to compare the SDFT force when a horse performs two different exercises commonly required during clinical examinations: an uphill trot and a downhill trot.