Influence of radiographically detectable orthopedic changes on racing performance in standardbred trotters.

The tarsocrural, metacarpophalangeal, and metatarsophalangeal joints of 753 Standardbred yearlings were radiographed. On the basis of radiographic findings, the horses were allotted into 4 groups. Group-1 horses had osteochondrosis in the tarsocrural joints. Group-2 horses had palmar/plantar bony fragments in the metacarpo- and metatarsophalangeal joints. Group-3 horses had radiographic changes in the metacarpo- and metatarsophalangeal joint region, such as bony fragments located at the dorsoproximal end of the proximal phalanx, osteochondrosis of the sagittal ridge of the third metacarpus/metatarsus, ununited proximoplantar tuberosity of the proximal phalanx, or nonarticular, osteolytic and productive changes in the proximal sesamoid bones. Group-4 horses did not have radiographic changes. The number of race starts and race earnings (categorized) of the horses in groups 1, 2, and 3 were compared with those of the horses in group 4, using a multivariate regression analysis. Horses in groups 1, 2, and 3 had significantly fewer starts and somewhat lower earnings compared with the horses in group 4.