Equine proximal phalanx bone properties during growth

Abstract

Fatigue is the most common cause of fractures in racing horses. Bone adaptation can be driven by mechanical loading, and exercise during youth has been shown to have life long benefits for bone health. However, normal development must be characterized in order to evaluate the effect of exercise during post-natal skeletal development. Three Standardbred trotting colts were longitudinally CT scanned between 2 and 12 months old. Finite-element models were constructed of the left forelimb proximal phalanx (P1) bone and used to simulate the loading during quiet standing. Changes in mineral density and bone area fraction in the distal, diaphysis, and proximal regions were evaluated. The diaphysis of the P1 maintained constant strain energy density (SED) during growth, indicating adaptation to the standing condition. The proximal region experienced the most changes in mineral density and bone area fraction in the medial quadrant, which is the quadrant most loaded when young horses graze. The data presented provides a benchmark of normal growth trajectories that can be used to evaluate the effect of training regimens during growth.