Impact of race training on volumetric bone mineral density and its spatial distribution in the distal epiphysis of the third metatarsal bone of 2-year-old horses.

The aim of the study was to use spatial and multiple correspondence analysis (MCA) to describe and compare the regional proportion and spatial pattern of volumetric bone mineral density (BMDv) values within loaded regions of the plantar metatarsal epiphysis of young horses in race training. A single 2 mm transverse peripheral quantitative computed tomography 'slice', 10 mm proximal from the distal limit of the sagittal ridge of the distal metatarsal epiphysis was obtained from 14 2-year-old Thoroughbred fillies (7 exercised and 7 controls). Six regions of interest were generated and examined for relative BMDv using MCA. The spatial distribution of BMDv was statistically examined at two sites loaded by the proximal sesamoid bones using geographical information software. The BMDv response was focal with distinct regional differences in relation to load. Deposition of new bone within existing high density bone contributed to a greater bone fraction and the distinct profile of clusters of uniformly distributed high density bone as well as a lower proportion of lower density bone in exercised horses. The MCA and spatial analysis provided statistical techniques to quantify and describe non-invasively the exercise induced changes in bone that had previously been described using microradiography of thin slices and by block-face imaging. These statistical techniques may prove useful in quantifying spatial patterns of response to load.
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