Tuning and validation of a virtual mechanical testing pipeline for condylar stress fracture risk assessment in Thoroughbred racehorses.

Abstract

Condylar stress fracture of the third metacarpal/metatarsal bone (MC3/MT3) in Thoroughbred racehorses is a common catastrophic injury, putting both the racehorse and the jockey at risk. Microdamage forms in the distal MC3 and may result in strain elevation and higher risk of stress fracture, directly and through focal osteolysis resulting from the associated damage repair by remodelling in the condylar parasagittal grooves (PSG). Standing computed tomography (sCT) is a practical screening tool for detecting fatigue-induced structural changes, but clinical interpretation remains subjective. The goal of this study was to develop and validate an sCT-based, subject-specific finite element analysis pipeline for virtual mechanical testing of the distal MC3. Twelve (<i>n</i> = 12) MC3 condyles with available <i>ex vivo</i> strain were selected. Half of the specimens were used for tuning Young's modulus in fatigue sites, and the other half were used to evaluate the validity of the pipeline in predicting PSG strain. The tuned model improved the prediction of strain and predicted higher strain in bones with PSG lysis over the untuned model, which is an essential feature for a diagnostic screening tool. The presented pipeline can assist clinicians with the interpretation of sCT-detectable structural changes and, ultimately, with the assessment of condylar fracture risk in racing Thoroughbreds.