Locomotion in the Horse: A Procedure for Computing the Internal Forces in the Digit

Abstract

SUMMARY A procedure has been developed to determine the internal forces in the digit of the horse. This procedure is based on an analytical model of the digit which employs a number of assumptions and idealizations of the functional anatomy. The model can be used to compute forces in the deep flexor tendon, combined forces in the suspensory ligament and the superficial flexor tendon, force on the metacarpus at the fetlock joint, force on P2 at the coffin joint, and force of the deep flexor tendon on the navicular bone. Input data needed for the model are external forces between the hoof and the ground, configuration of the digit during the support phase of gait, and internal geometry of the digit. External forces are obtained by means of a force platform, digit configuration (kinematics) by means of high-speed cinefilms, and digit geometry from radiographs. The procedure can be used to provide estimates of the mechanical effects of limb conformation, type of activity, working surface, and trauma or disease. These estimates can be compared with those of normal populations for purposes of diagnosis or prognosis. The values obtained for internal forces depend directly on the measured external force and its point of application with respect to the hoof. It has been found that the measurement of both horizontal and vertical components of hoof force is required for determining force magnitudes and for determining the point of application accurately.