Quantitative evaluation of the remodeling response of the proximal sesamoid bones to training-related stimuli in Thoroughbreds.

This study investigates how the bones of young Thoroughbred horses change in response to different types of training. Horses were divided into four groups each subjected to distinct training environments and regimes, and their proximal sesamoid bones were analyzed after five months.

Study Design and Execution

• The research involved 8 untrained 2-year-old Thoroughbred horses. These horses were put into one of four groups, with two horses in each. Each group represented different training variables. Group 1 (control) was untrained and allowed to roam in pasture. Group 2 had a modified classically trained routine on a dirt track. Group 3 were classically trained on a dirt track, while Group 4 were classically trained on a wood chip track.
• During the training, all horses were given fluorochromic bone labels every 28 days. After 5 months of training, all of the horses were euthanized and their Proximal Sesamoid Bones (PSB) were removed for further analysis.
• A computerized image analysis and epifluorescent microscopy were used to perform histomorphometric analysis on midsagittal bone sections which were 85 to 95 microns thick. Various parameters were measured at different points in each specimen.

Results and Interpretation

• Data were pooled to allow comparison by training group and by region. It was found that PSBs from horses who trained on dirt tracks (groups 2 and 3) had significantly less porous properties and greater trabecular width compared to the control group. This indicates that this type of training results in stronger and denser bones.
• The PSB from all the trained groups had significantly larger mineralizing surfaces than the control group specimens. This means that the bone was actively growing and hardening in response to training stimulus.
• The fractional mineralizing surface in bones from horses trained on dirt tracks showed a quick and robust response from the endosteal surface of the PSB, indicating effective bone remodeling upon such training.
• Overall, the study showed that different training styles and regimes had significant impacts on the morphometric properties of PSB in Thoroughbred horses. This can provide insights into suitable training regimes for optimal bone health in these animals.