Computed tomographic observations of short incomplete parasagittal fractures of the proximal phalanx in Thoroughbred racehorses

Summary Background Short incomplete parasagittal fractures of the proximal phalanx are common injuries described in racehorses and also horses not used for racing. Computed tomographic (CT) features have been described in horses not used for racing, but not in a racehorse population. Objectives To describe CT features of short incomplete parasagittal fractures of the proximal phalanx in a group of Thoroughbred racehorses. Study design Retrospective observational study. Methods CT images of 59 Thoroughbred racehorses diagnosed with 60 short incomplete parasagittal fractures of the proximal phalanx examined between January 2014 and February 2023 were reviewed retrospectively. Horse signalment and clinical features were retrieved from hospital records. Results 50/60 fractures were dorsally biased unicortical fractures. Mean proximodistal fracture extension in forelimbs (13.6 mm ± 3.4) was less than in hindlimbs (17.4 mm ± 4.4) ( p = 0.0019). There was no difference in fracture extension in the proximodistal direction according to age or gender. Fractures in 2‐year‐olds were shorter in dorsopalmar/−plantar direction (17.4 mm ± 6.3) than in 3‐year‐olds and older horses (21.7 mm ± 7.4) ( p = 0.015). Periosteal new bone was present in 91.2% of fractures and endosteal new bone in 75%. Main limitations Conclusions from this study can only confidently be applied to similar populations of racing Thoroughbred horses. Conclusion Short incomplete parasagittal fractures of the proximal phalanx in Thoroughbred racehorses most commonly involve only the dorsal cortex and adjacent subchondral and cancellous bone. The distribution of fracture configurations differs from that described in horses not used for racing.