An In Vitro Investigation of the Effect of Curve Running on Equine Distal Limb Tendon Strain

Abstract

Reasons for performing studyHorses run on curves during training and competition, and are often trotted in circles to assist lameness diagnosis. The effects of moving on a curve on tendon strain in the distal limb are not known.ObjectivesTo investigate the effect of curve running on the tendons and ligaments of the equine distal limb.Study designControlled experimental study.MethodsCadaver forelimbs from 6 Thoroughbred horses were loaded on a forceplate using a hydraulic ram. Limbs were loaded to 17–33 N/kg on a flat surface and with medial and lateral wooden wedges under the hoof to simulate curve running with the limb being on the inside and outside of a curve, respectively. Tendon length was measured for the superficial and deep digital flexor tendons (SDFT and DDFT), accessory ligament of the DDFT (ALDDFT), the suspensory ligament body (SL) and the medial and lateral suspensory ligament branches (SBM and SBL) using motion capture. A mixed effects model was used for data analysis.ResultsUnder most loading conditions SL was under most strain and DDFT least. For a medial 15° wedge SDFT was under 0.4% greater load than SL (P = 0.04). SBM was under 0.48% greater strain than SBL with a lateral 20° wedge (P = 0.01), and SBL was under 1.37% greater strain than SBM with a medial 20° wedge (P<0.01).ConclusionsCurve running leads to increasing and asymmetrical strain on the suspensory ligament branches. This difference is unlikely to be sufficient to cause injury, but may assist lameness diagnosis.Ethical animal research: Research ethics committee oversight not currently required by this conference: the study was performed on material collected at an abattoir. Source of funding: R. Parkes is undertaking a PhD funded by the Horserace Betting Levy Board. Competing interests: None declared.