Original Research Accuracy Quantification of the Reverse Engineering and High-Order Finite Element Analysis of Equine MC3 Forelimb Saeed Mouloodi a, b, * , Hadi Rahmanpanah c , Colin Burvill a , Helen M.S. Davies b a Department of Mechanical Engineering, The University of Melbourne, Melbourne, Australia b Department of Veterinary Biosciences, The University of Melbourne, Melbourne, Australia c Department of Mechanical Engineering, Sharif University of Technology, Tehran, Iran article info Article history: Received 7 March 2019 Received in revised form 8 April 2019 Accepted 8 April 2019 Available online 26 April 2019 Keywords: Reverse engineering Error of reconstructed geometry Adaptive mesh refinement Convergence and error analysis Finite element analysis (FEA) Equine third metacarpal bone (MC3) abstract Shape is a key factor in influencing mechanical responses of bones. Considered to be smart viscoelastic and inhomogeneous materials, bones are stimulated to change shape (model and remodel) when they experience changes in the compressive strain distribution. Using reverse engineering techniques via computer-aided design (CAD) is crucial to create a virtual environment to investigate the significance of shape in biomechanical engineering. Nonetheless, data are lacking to quantify the accuracy of generated models and to address errors in finite element analysis (FEA). In the present study, reverse engineering through extrapolating cross-sectional slices was used to reconstruct the diaphysis of 15 equine third metacarpal bones (MC3). The reconstructed geometry was aligned with, and compared against, computed tomographyebased models (reference models) of these bones and then the error map of the generated surfaces was plotted. The minimum error of reconstructed geometry was found to be þ0.135 mm and -0.185 mm (0.407 mm ± 0.235, P > .05 and 0.563 mm ± 0.369, P > .05 for outside [convex] and inside [concave] surface position, respectively). Minor reconstructed surface error was observed on the dorsal cortex (0.216 mm ± 0.07, P > .05) for the outside surface and 0.185 mm ± 0.13, P > .05 for the inside surface. In addition, a displacement-based error estimation was used on 10 MC3 to identify poorly shaped elements in FEA, and the relations of finite element convergence analysis were used to present a framework for minimizing stress and strain errors in FEA. Finite element analysis errors of 3%e5% provided in the literature are unfortunate. Our proposed model, which presents an accurate FEA (error of 0.12%) in the smallest number of iterations possible, will assist future investigators to maximize FEA accuracy without the current runtime penalty. © 2019 Elsevier Inc. All rights reserved. 1. Introduction Bones are mainly responsible for withstanding and absorbing applied loads. To predict bone fracture and failure, and to investi- gate reasons for such incidents, comprehensive insight into the responses of bones to loading is crucial. Identifying the strains and stresses to which bones are exposed will assist in elucidating the reasons for fractures and locating their most likely sites. Bones are complex both in their material characteristics and their shape but respond in similar ways to external loads throughout the animal kingdom [1]. Clearly, a large bone that shows a relatively restricted range of normal movements would provide the best chance to develop a model to investigate the normal responses of bones to loading. Horses are large animals with large, elongated, and simplified forelimb bones that are apparently well-adapted for exercise at high speeds. Hence, considerable forces can be exerted on their forelimb bones. These forces are believed to be involved in different kinds of injuries and incidents, and most disastrous in- juries in racing horses worldwide are associated with forelimb in- juries, especially failures of the third metacarpal bone (MC3) [2e8]. The third metacarpal bone forms an essential part of the lower forelimb in withstanding loads [9]. Furthermore, due to its large size, minimal muscle attachments, and relatively simple move- ments, the MC3 is a unique long bone that can assist in investi- gating the responses of bones when they are exposed to forces. Animal welfare/ethical statement: No ethical permission was sought as no animal was euthanised for the purposes of this study. Conflict of interest statement: The authors have no conflict of interest to declare. * Corresponding author at: Departments of Mechanical Engineering and Veteri- nary Biosciences, The University of Melbourne, Melbourne, Australia. E-mail address: saeed.mouloodi@unimelb.edu.au (S. Mouloodi). Contents lists available at ScienceDirect Journal of Equine Veterinary Science journal homepage: www.j-evs.com https://doi.org/10.1016/j.jevs.2019.04.004 0737-0806/© 2019 Elsevier Inc. All rights reserved. Journal of Equine Veterinary Science 78 (2019) 94e106