Radiographic changes in Thoroughbred yearlings. Part 1: Prevalence at the time of the yearling sales

Abstract

Summary Reasons for performing study: Radiography in presale examinations of TB yearlings has become standard practice in recent years. Objectives: To describe the prevalence and distribution of radiographic changes in the fetlocks, carpi, tarsi, stifles and fore feet of Thoroughbred yearlings in central Kentucky when these joints were examined as part of routine pre‐ and post sale evaluations. Methods: Horses subjected to radiographs included the fore (n = 1127) and hind (n = 1102) fetlocks, carpi (n = 1130), tarsi (n = 1101), stifles (n = 660) and fore feet (n = 300). Radiographic changes were categorised by location and type of change present (e.g. lucency, fragment) for each series. Results: In the fore fetlocks 1.6% had fragmentation of the proximal dorsal first phalanx and 0.5% fragmentation of the proximal palmar aspect. In the hind fetlocks 5.9% had fragmentation at the plantar aspect and 3.3% fragmentation dorsally. Lucencies, fragments or loose bodies were detected at the dorsal aspect of the distal third metacarpus in 2.8% and, at the same location on the third metatarsus, 3.2%. Most yearlings (98%) had vascular channels in the proximal sesamoid bones and irregularvascular channels (>2 mm wide or with nonparallel sides) were more common (79%) than regular vascular channels (56%). The intermediate ridge of the distal tibia was the most common location for fragmentation in the tarsus (4.4%). Conclusions: While some radiographic changes, e.g. vascular channels in proximal sesamoid bones, are very common in Thoroughbred yearlings, others, e.g. fragmentation or subchondral lucency within joints are quite rare usually affecting less than 5% of the population. Potential relevance: Veterinarians should expect to find radiographic changes in Thoroughbreds presented for examination prior to the yearling sales. The rarity of some changes thought to affect soundness or racing performance will make further invesigation of these conditions in horses without clinical signs more difficult.

Radiographic changes in Thoroughbred yearlings in South Africa

“…Radiographic studies as part of a pre-purchase examination of yearlings at national yearling sales was initiated in Kentucky, USA, in 1993 with the repository system, a facility which allows the viewing of radiographs, coming into effect in 1996 14 . In New Zealand the repository system was 1st established in January 2003 at Karaka, Auckland 17 .…”

“…In New Zealand the repository system was 1st established in January 2003 at Karaka, Auckland 17 . In South Africa the 1st repository was opened at the 2007 National Yearling Sale in Germiston where over 300 sets of radiographs were lodged, while in the same year at the Keeneland National Yearlings sale in Kentucky, USA, 4700 sets of radiographs were lodged 14 .…”

“…Radiographic changes recorded from pre-purchase radiographs of Thoroughbred yearlings have been investigated in Thoroughbred populations around the world, not only in terms of the prevalence of specific radiographic changes but also the impact these changes have on the sale price and future racing career of the Thoroughbred 3,10,11,13,14,17,24 . The changes identified can either be classified as developmental or traumatic in origin.…”

“…Osteochondritis dissecans (OCD) is a developmental orthopaedic disease and most commonly manifests as sagittal ridge defects of the distal metacarpus, distal intermediate ridge defects of the tibia, trochlear ridge lesions in the tarsus and lesions in the stifle joint in the Thoroughbred yearling 10,11,13,14,17,24 . The most common traumatic radiographic lesions identified in the same studies are within the distal joints of the tarsus with the prevalence varying from 6.1 % to 31 % 9, 14,17 . Evidence has been found linking these degenerative changes of the distal joints of the tarsus to osteochondrosis in juvenile horses 1,27 .…”

Osteochondrosis-Related Gene Expression in Equine Leukocytes Differs among Affected Joints in Foals

“…The developmental orthopaedic disease osteochondrosis (OC) affects growing horses and severely compromise their athletic careers [1][2][3][4]. OC is considered a major cause of considerable economic losses in the horse breeding industry [5,6] with reported incidences ranging from 10% to 44% [6][7][8][9].…”