The relatively low hoof accelerations, vibrations, and peak GRFs associated with the synthetic surface evaluated in the present study indicated that synthetic surfaces have potential for injury reduction in Thoroughbred racehorses. However, because of the unique material properties and different nature of individual dirt, synthetic, and turf racetrack surfaces, extending the results of this study to encompass all track surfaces should be done with caution.

Fractured PSBs had adapted to high loading but had focal evidence of excessive remodeling and porosity that likely predisposed the horses to complete fracture and catastrophic injury. Detection of focal injury before complete fracture provides an opportunity for prevention of catastrophic injury. Development of diagnostic imaging methods to assess porosity of PSBs may help to identify at-risk horses and allow for modifications of training and racing schedules to reduce the incidence of PSB fracture in Thoroughbred racehorses.

The LCP system is more likely than LC-DCP and DCP systems, with neutrally positioned screws, to maintain a planned interfragmentary gap, although gap strains range from 0% to 15% across the 2 mm gap during a trot load.

Background Proximal sesamoid bone (PSB) fracture is the most common fatal injury in Thoroughbred (TB) racehorses in the United States. Epidemiological and pathological evidence indicates PSB fracture is likely the acute culmination of a chronic stress‐related process. However, the aetiopathogenesis of PSB fracture is poorly understood. Objective To characterise bone abnormalities that precede PSB fracture. Study design Two retrospective case‐control groups of PSBs from TB racehorses with, and without, unilateral biaxial PSB fracture. Methods Proximal sesamoid bones were harvested post‐mortem from TB racehorses subjected to euthanasia for unilateral biaxial PSB fracture (cases) or causes unrelated to PSB fracture (controls) while racing or training. The fractured medial PSB (FX‐PSB) and contralateral intact medial PSB (CLI‐PSB) from racehorses that sustained PSB fracture, and an intact medial PSB (CTRL‐PSB) from racehorses that did not have a PSB fracture were collected as case and control specimens. Study 1 distributions of morphological features were compared among case and control groups using visual examination, photographs, radiographs and histology of whole PSBs and serial sagittal sections (10 FX‐PSB, 10 CLI‐PSB and 10 CTRL‐PSB). Study 2 local bone volume fraction and mineral densities were compared among case and control PSBs using microcomputed tomography (9 FX‐PSB, 9 CLI‐PSB and 9 CTRL‐PSB). Results A focal subchondral lesion characterised by colocalised focal discoloration, radiolucency, osteopenia, low tissue mineral density and a surrounding region of dense cancellous bone was identified in most case horses but not in controls. This subchondral lesion was found in a slightly abaxial mid‐body location and was bilaterally present in most case horses. Main limitations The post‐mortem samples may not represent the spectrum of abnormalities that occur throughout the development of the subchondral lesion. Lateral PSBs were not examined, so their contribution to biaxial PSB fracture pathogenesis is unknown. Conclusion Abaxial subchondral lesions are consistent with pre‐existing injury and likely associated with PSB fracture.

T and RI fissure-fracture patterns show morphologic differences and likely arise from different supraphysiologic loading. Medial compartment disease is not homogenous and pattern recognition may assist further investigation of etiopathogenesis.