Racehorse Injury Biomechanics

Overview

The metacarpophalangeal joint (MCPJ) represents a common injury site for racehorses. These injuries tend to be caused by repetitive stress injuries over time, rather than as the result of an acute traumatic event such as a race accident. This project aimed to better understand stress and strain distributions within the MCPJ by using Simpleware software to process CT scans and generate meshes for musculoskeletal modelling in OpenSim and Finite Element (FE) analysis in Abaqus®. The accuracy of this model has enabled researchers to improve their knowledge of MCPJ injury and develop better treatments of fractures.

Characteristics:

  • 3D FE model from CT images
  • Segmentation of bone and ligament in Simpleware ScanIP
  • Placement of landmarks for musculoskeletal modelling in ScanIP
  • Generation of surface and volume meshes in Simpleware +FE
  • Surface mesh used as part of a musculoskeletal modelling analysis in OpenSim
  • Export of FE mesh to Abaqus/Explicit with OpenSim loads for stress and strain distribution analysis

Thanks to

JD Wheat Veterinary Orthopedic Research Laboratory, University of California, Davis: 
M. Hardisty • T. Garcia

Image Processing & Mesh Generation

A model of the equine MCPJ was generated by importing CT scans of the in vivo joint into Simpleware ScanIP. Image data was then processed using semi-automated tools to obtain Regions of Interest (ROI’s). The proximal sesamoid bone complex (composed of the medial and lateral proximal sesamoid bones (PSB)), as well as the intersesamoid ligament and the third metacarpal (MC3 bone) were individually segmented. Landmark points were also created for the model using intuitive measurement tools. Surface meshes and volume meshes were then automatically generated from segmented image data using Simpleware +FE for export to OpenSim and Abaqus/Explicit.

Musculoskeletal Modelling in OpenSim

The surface meshes and landmarks generated in Simpleware software were used to carry out musculoskeletal analysis in OpenSim. Kinematic data of racehorses galloping was combined with the subject-specific MCPJ model to help calculate boundary and initial conditions (position, orientation, ligament, tendon and joint reaction loads). The surfaces created in Simpleware software were capable of registering each bone individually to the reference frame of the OpenSim model.

FE Analysis in Abaqus/Explicit

The volume mesh generated in Simpleware FE was exported to Abaqus/Explicit with the subject-specific load cases obtained from OpenSim. Strain and stress distribution analysis was then carried out to evaluate the effect of galloping on the MCPJ. Initial results indicated that these distributions within the MCPJ were consistent with clinical observation of failure and sites of bone remodeling. The results of the subject-specific analysis has applications to predicting and treating fractures before they occur, reducing race death rates and costs.