How Does Race-Training Influence the Ultrastructural Characteristic of the Equine Proximal Phalangeal Sagittal Groove?

Introduction: In racehorses, proximal phalanx (PP) sagittal fractures are common injuries without a confirmed pathogenesis. We hypothesized that microstructural proximal bone characteristics of the PP would vary significantly according to anatomical location, race-training history and injury status.

Materials and Methods: The proximal aspect of PPs from three groups of horses (contralateral fracture [CF], raced control [RC], and unraced control [UC]) were imaged with microcomputed tomography (μCT) at 15 μm isotropic voxel resolution. Subchondral (SCB) and trabecular (TBB) bone volumes of interest (VOI) at the medial fovea, sagittal groove, and lateral fovea at 25% (dorsal), 50% (middle), and 75% (palmar) of the distance from dorsal to palmar were analyzed. The standard μCT bone parameters were calculated. Analysis of variance (ANOVA) and Friedman’s test were used to compare VOIs within and between each group.

Results: Within the SCB of CF and RC, TBMD of the middle region was significantly higher compared with the dorsal and palmar regions. Within the CF group, central region TP was lower than the medial region. Between groups, TBMD, and TbTh was significantly greater in the CF TBB compared with the RC group in the dorsal and middle regions. Specifically, the 50% medial VOI had greater SCB and TBB TBMD in the CF compared with the RC group.

Discussion/Conclusion: The PSG region adapts to race-training by site-specific increases in bone density, which appear to be greater in the contralateral to fracture group, which is consistent with the underlying pathophysiology of the majority of fractures in the TB racehorse.

Acknowledgment: Horserace Betting Levy Board.