Changes on radiographs at Thoroughbred yearling sales: Prevalence and significance

Examination of Thoroughbred yearlings at public auction is a special form of prepurchase examination since the clinician cannot be as thorough as in clinical situations. Yearlings are purchased based on visual and limited physical examinations and evaluation of presale radiographs and upper respiratory tract endoscopic examination. The prevalence and clinical relevance of radiographic changes has been the subject of our recent publications and a summary of our results is presented here. Radiographic changes were most common in the fetlock joints and 1127 forelimb and 1102 hindlimb fetlock radiographic series were examined. Flattened areas of the distal palmar aspect of the distal articular surface of the third metacarpal bone (McIII) were found in 41% of yearlings and had neither an effect on performance nor caused the subsequent development of clinical problems. Flattening (10%) or radiolucency (17%) of the dorsal aspect of the distal sagittal ridge of McIII was common and had no effect of these 2 parameters. Thirty of 1130 yearlings that had complete carpal radiographic examinations had signs of dorsal medial middle carpal disease. The presence of dorsal medial middle carpal joint lesions affected the horse’s ability to start a race and increased the incidence of clinical problems. The most common finding on carpal radiographs was circular radiolucencies in the ulnar carpal bone but the presence of this finding neither affected the ability to start nor was associated with clinical problems. Forty-eight of 1101 yearlings with complete tarsal radiographic examinations had concavity or fragmentation of the cranial intermediate ridge of the distal tibia, but there was no effect on racing performance. The changes most commonly observed in the distal tarsal joints were the presence of osteophytes or enthesophytes involving the distal intertarsal or tarsometatarsal joints. The presence of osteophytes or enthesophytes involving the distal intertarsal or tarsometatarsal joints were the only changes significantly associated with starting a race, but the effect was small. There were 600 yearlings with stifle radiographs, but in only 170 of them could the medial femoral condyle and proximal tibia be evaluated. Thirty-four yearlings had defects with or without fragments on the lateral trochlear ridge of the femur and there were no significant associations with any outcome except that they were more likely to have surgical treatment.