A MODEL OF THE HORSE DIGIT – RELIABILITY AND COMPARISON WITH IN-VIVO EXPERIMENTS

Abstract

INTRODUCTION: The aim of this study was to develop a model for the calculation of the moments, muscle and tendon forces, and joint forces of the 3 joints of the digit and to compare the muscle/tendon forces with the values of in-vivo experiments of Jansen et al. (1993). METHODS: All analyses were made with the software HORSE-FOOT (Animal Biomechanics Research Group). This program serves for the inverse-dynamic quasi-static calculation of moments, muscle and tendon forces, and joint forces and stresses of the 3 articulations (coffin, pastern, and fetlock joints) of the horse foot. Basic data are: 1) ground reaction forces during motion (amount, direction and position), 2) joint angles during motion (gait cycle), and 3) morphological details (attachments of tendons and ligaments, geometry of tendon deviations and joint surfaces, hoof shape, rotation centers). 1) & 2) are taken from literature sources (Becker, 1996), 3) from own studies (dissections, marking of ligaments and tendons with wires, radiographs). RESULTS: The muscle and tendon forces (relative to body weight) during walking amounted up to: interosseous - 1 - 1.5, superfic. flex. tendon - 0.75 - 1, deep flex. tendon - 0.75 - 1 (deep flex. muscle - 0.23 - 0.5, deep check ligament - 0.5 - 1). These results were completely comparable with the results of Jansen et al. (1993). The joint forces (relative to body weight) amounted up to: fetlock joint - 3, pastern joint - 2.5 - 3, prox. sesamoids - 2 - 2.5, coffin joint - 1, navicular bone - 0.5 - 1. CONCLUSIONS: The comparability and reliability of the model results in comparison with the in-vivo results clearly show that in-vivo experiments are no longer necessary and can completely be replaced by model calculations. The introduced model can be used for any muscle and joint force calculation of the horse digit. This model provides reliable mechanical data on all structures, which otherwise could only be obtained by means of experimental methods such as inserting strain gauges into tendons, which of course cannot be used for routine diagnostics. Furthermore, the effects of morphological variability can be defined biomechanically, and predictions concerning the mechanical purpose of treatment strategies can be made. REFERENCES: Jansen, M. O., van den Bogert, A. J., Riemersma, D. J., Schamhardt, H. C. (1993). In Vivo Tendon Forces in the Forelimb of Ponies at the Walk, Validated by Ground Reaction Force Measurements. Acta Anat. 146, 162-167. Becker, C. K. (1996). Function and dysfunction of the accessory ligament. Utrecht.