Ex vivoSimulation ofin vivostrain distributions in the equine metacarpus

Abstract

Summary The objective of this study was to examine several simple ex vivo loading conditions for the equine metacarpus, and to evaluate their ability to reproduce the mid‐diaphyseal bone surface strain distributions previously reported in vivo at the walk and trot. Distributed axial compressive loads, and 9 different axial compressive point loads at −7.5 kN and −15 kN were applied to metacarpal‐distal carpal bone preparations from 6 Thoroughbred horses, aged 1–5 years. The resulting dorsal, medial, palmar, and lateral mid‐diaphyseal bone surface axial and shear strains were compared with previously reported in vivo surface strain distributions using a root mean square error (RMSE) protocol. The effects of loading condition and load magnitude on RMSE were assessed with a mixed‐model analysis of variance. There were significant differences between loading conditions, and, in most cases, between load magnitudes, in the fit of the ex vivo to the in vivo strain distributions. In vivo mid‐diaphyseal bone surface strain distributions at the walk can be well approximated ex vivo by a distributed axial compressive load, or by a point load positioned 0.5 cm mediad to the sagittal midline, at −7.5 kN loads. In vivo mid‐diaphyseal bone surface strain distributions at the trot can be well approximated by the −15 kN loads applied to the same locations. These simplified loading conditions can be used in designing biologically relevant loading protocols for ex vivo mechanical testing studies, as well as in developing boundary conditions for finite element analysis. As such, these loading conditions may be considered as tools to be used as a means of replicating in vivo loading conditions during the intial design and testing stages in the development of fracture fixation devices, as well as in the theoretical mechanical analysis of the metacarpal structure.

Aging and loading rate effects on the mechanical behavior of equine bone

“…[2][3][4] It has even been shown to adapt locally to better manage biomechanical loads experienced within individual bones. 5,6 However, despite decades of research on the me-aging and Loading rate effects on the mechanical behavior of equine bone Robb M. Kulin, Fengchun Jiang, and Kenneth S. Vecchio chanical behavior of bone, how this structure interacts at its various levels to perform these functions is still poorly understood. This lack of complete understanding is partially due to the complex structure of the material, and is especially true under dynamic fracture conditions and with bone age.…”

Biomechanical investigation of the association between suspensory ligament injury and lateral condylar fracture in thoroughbred racehorses

“…In vitro loading was limited to a maximum of 5.6 kN to prevent complete suspensory ligament disruption observed at higher loads in some pilot tests of limbs with partially transected MBSL. Axial loads of 7.5 and 15 kN are representative of loads at the walk and trot, respectively 39 . Despite the restrictions on loading, we did identify that strain measurements increased significantly at each load level, suggesting that higher load levels simulating those reached in vivo during high‐speed exercise could be expected to amplify these strain changes.…”

Finite Element Analysis of Six Transcortical Pin Parameters and Their Effect on Bone–Pin Interface Stresses in the Equine Third Metacarpal Bone

“…To simulate walking, a 7500 N distributed axial compressive load was applied to the proximal surface of the bone. 24 The material properties of the bone and pins used for the models were based on previous studies and reference data obtained from metal suppliers for pins (►Table 1). [25][26][27][28] Free meshing algorithms were used and all models were meshed using solid quadratic tetrahedral elements (type C3D10I).…”