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

Condylar stress fracture of the third metacarpal/metatarsal bone (MC3/MT3) in Thoroughbred racehorses is a common catastrophic injury, putting racehorse and jockey safety 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 process of repair by remodeling in the condylar parasagittal grooves (PSG). Standing computed tomography (sCT) is a practical screening tool for detection of fatigue-induced structural changes, but the clinical interpretation remains subjective. The goal of this study was to develop and validate a sCT-based subject-specific finite element analysis (FEA) pipeline for virtual mechanical testing of the distal MC3. Twelve (n=12) MC3 condyles with available ex vivo strain were selected. Half of the specimens were used for tuning of the Young’s modulus in fatigue sites, and the other half to examine validity of the pipeline for prediction of PSG strain. The tuned model improved 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 is expected to assist clinicians with interpretation of sCT-detectable structural changes and ultimately condylar fracture risk assessment.