Clinical Research Abstracts of the British Equine Veterinary Association Congress 2015.

This research was undertaken to validate a clinical method for measuring limb stiffness in horses, a key factor in healing for injuries to the Superficial Digital Flexor Tendon (SDFT). Findings show correlations between ground reaction force (GRF) and joint angle, as well as limb stiffness and the weight of the horse, thus supporting the method’s applicability in assessing tendon healing post injury.

Background

• Injuries to a horse’s Superficial Digital Flexor Tendon (SDFT) are common, and are more likely to recur due to changes in tendon stiffness.
• While stiffness in limbs can indicate the stiffness of the tendon post-injury, it is difficult to measure outside of kinematic analysis which can be challenging in a clinical setting.
• The authors developed a less complex, static system to monitor how well the SDFT is healing through goniometric measurements of limb stiffness.

Methodology

• The study was cross-sectional and involved two methods for assessing limb stiffness, following kinematic analysis and static measurements.
• First, stiffness indexes from the forelimbs of 6 horses were determined while walking, using kinematic analysis. Stiffness indices were then computed utilizing portable scales to record Ground Reaction Force (GRF), and an electrogoniometer for a metacarpophalangeal joint angle reading.
• The second method used a goniometer to measure limb stiffness indices in 11 horses, aged 2-20 years, which showed no clinical evidence of SDFT injury.
• The study then evaluated the correlation and agreement strength between the two measurement techniques, and associations between limb stiffness, weight, horse age, and the limb side (left or right).

Findings

• The researchers found strong positive correlations between GRF and joint angle (R(2) = 0.98) as well as between the static and kinematic methods (R = 0.78, P<0.01).
• A positive correlation was found between limb stiffness and the horse’s weight (R(2) = 0.85, P<0.01). However, no association was found with either the horse's age or the side of the limb (left or right).

Conclusion

• The study successfully validated the goniometric measurement of limb stiffness for use in a clinical setting.
• The strong positive correlation between limb stiffness and the weight of the horse could imply that a more ‘optimised limb spring’ is preferable for efficient locomotion. This could thus be a clinically relevant measure to assess running efficiency post tendon injury healing.
• No conflict of interest was declared, and all animal research was conducted ethically, with proper owner consent obtained.