Three-Dimensional Imaging and Histopathological Features of Third Metacarpal/Tarsal Parasagittal Groove and Proximal Phalanx Sagittal Groove Fissures in Thoroughbred Horses.
Authors: Lin Szu-Ting, Foote Alastair K, Bolas Nicholas M, Peter Vanessa G, Pokora Rachel, Patrick Hayley, Sargan David R, Murray Rachel C
Journal: Animals : an open access journal from MDPI
Summary
Early detection of fissuring in the parasagittal groove of the third metacarpal/tarsal bone and sagittal groove of the proximal phalanx could allow intervention before catastrophic fracture, yet characterising these lesions has proven challenging. Researchers examined 33 cadaver limbs using cone-beam CT, fan-beam CT, and low-field MRI, comparing imaging findings against microscopic examination of 291 anatomical locations to establish diagnostic accuracy and describe imaging features. Cone-beam CT demonstrated the highest sensitivity (88.5%) but lower specificity (61.3%), whilst fan-beam CT offered better specificity (72.3%) with comparable sensitivity (84.1%); MRI was less sensitive (43.6%) but highly specific (85.2%), appearing as subchondral hypo- or hyperintense defects rather than the linear defects visible on CT. Fissures identified on CT correlated with histopathological evidence of fatigue injury, including subchondral bone sclerosis, microcracks, and collapse, validating that these imaging findings represent genuine pathological changes rather than imaging artefacts. For practitioners, this suggests that CT—particularly cone-beam where available—offers superior detection of early fissuring lesions, supporting its use in pre-fracture screening programmes and lameness investigations in high-risk athletes, although clinicians should anticipate some false positives and consider MRI's higher specificity when confirmatory imaging is needed.
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Practical Takeaways
- •CBCT is the most sensitive imaging modality for detecting early fissures that may progress to fracture; consider CBCT over other modalities when early detection is clinically important
- •Fissure presence on CT imaging indicates fatigue-type bone injury at the microscopic level, suggesting these are genuine pathological lesions worth monitoring rather than incidental findings
- •MRI has low sensitivity for fissure detection despite good specificity; rely on CT-based imaging as primary diagnostic tool for this condition in clinical practice
Key Findings
- •CBCT demonstrated highest sensitivity (88.5%) for fissure detection compared to FBCT (84.1%) and MRI (43.6%)
- •CT-identified fissures were significantly associated with histopathological evidence of subchondral bone sclerosis, microcracks, and collapse
- •Four distinct imaging feature types were characterised on CT imaging, ranging from hypoattenuating linear defects to subchondral irregularity
- •Microscopic examination identified fissures in 114 of 291 anatomical locations (39.2%), indicating fissures are a common finding in cadaver specimens