Measurement and analysis of equine radial hoof strain and lower forelimb motion

Strain within the hoof capsule is unknown and difficult to estimate and limited information is available on motion of all the distal joints of the forelimb. Consequently, how impact is attenuated in the hoof, distal joints and suspensory system is still not fully understood. This study aims to develop instrumentation capable of measuring internal hoof strain in conjunction with a method of recording the three dimensional (31)) kinematics of the joints of the distal. forelimb. Instrumented plugs were developed and validated and radial strain was measured in equine hooves at the dorsum together with lower forelimb kinernatics and kinetics during in vitro simulations of walking. 3D kinematics were recorded from the lower forelimb of 4 ponies at the walk using non-invasive cluster markers and the Calibrated Anatomical Systems Technique. Soft tissue artefacts using this method were assessed in vitro. Relationships between radial strain and locomotion were investigated. Tensile radial strain is predominant in normal hooves at the dorsum with magnitudes in the region of 500 pE in the stratum medium at midstance during simulated walking. Compression was recorded in the hoof strata of limbs with chronic laminitis. Radial strain was moderately correlated with proximal interphalangeal joint (PIPJ) flexion (r = -. 519). Large reductions in radial strain were found in simulated impact and heel lift positions. As the PIPJ flexes at impact passive loading of the deep digital flexor tendon (DDFT) due to weight bearing is more gradual, so direct radial stress in the stratum me&m is reduced. Radial stress in the stratum medium is also reduced as a proportion of the ground reaction forces are redirected through the heels. This vital role needs further investigation in vivo with improved non-invasive technique