“Abnormalities in vascular channel appearance within the proximal sesamoid bone (PSB) are the most common findings in Thoroughbred yearling presale radiographs and are often evaluated on radiographs of adult racehorses. Despite this, their pathogenesis and clinical significance are poorly understood, and associations with racing performance are inconsistent.” This was the summary provided on the article “Associations between the radiographic appearance of vascular channels in proximal sesamoid bones, their microstructural characteristics and past racing performance in Thoroughbreds” that was authored by Lloyd, K.A.; Ayodele, B.A.; Hitchens, P.L.; Beck, C.; Mackie, E.J.; Whitton, R.C.
This cross-sectional study investigated the clinical significance of radiographic changes in proximal sesamoid bone (PSB) vascular channel morphology, or “sesamoiditis.”
The paired PSBs were isolated from the forelimbs of Thoroughbreds undergoing post-mortem examination. This included yearlings in pre-training, mature horses in race training and those resting from training or those that had retired from racing in the last 12 months. Each PSB was radiographed and assigned a vascular channel grade using previously published and novel grading systems. The sesamoids were then separated and individual whole bones were imaged with microcomputed tomography (µCT); an imaging modality that allows assessment of bone microstructure in three dimensions. Associations between radiographic, µCT and performance variables were investigated with uni- and multi-variable generalized linear models.
One hundred and eighteen PSBs were collected from 59 horses aged between 16 months and 12 years. Nine horses were resting from training and 50 were in race training at the time of death. All PSBs had at least one vascular channel observed on µCT originating from the abaxial border; 63.6% (75/118) of which were observed radiographically. Proximal sesamoid bones with a higher bone volume fraction and wider channel diameter on µCT were more likely to have vascular channels identified on radiographs. Greater radiographic channel number and diameter were associated with fewer career placings.
No association was found between any variable and the horse being subjected to euthanasia due to catastrophic fracture.
Bottom line: This study suggests that more radiographic channels and greater channel diameter are associated with poorer measures of past performance.
