Changes in mineralised tissue at the site of origin of condylar fracture are present before athletic training in Thoroughbred horses.
OBJECTIVE
To show that changes are present at the site of origin of metacarpal condylar fracture in young Thoroughbred horses before they enter race training.


METHODS
Bone slices, 2 mm thick, in three mediolateral planes through the centre of rotation of the metacarpo-phalangeal joint (MCPJ) of both distal third metacarpal bones (Mc3) of 12 Thoroughbred horses aged 17 months, were imaged using point-projection digital X-ray imaging (muXR).


RESULTS
In some horses, linear or ovoid radiolucency was found in articular calcified cartilage (ACC) and subchondral bone of the palmaro-distal aspect of the sagittal groove, exactly at the site of more advanced stages of condylar fatigue fracture. An incidental finding was ovoid radiolucency in the apex of the dorso-distal aspect of the sagittal ridge, with or without fragmentation or disturbance of the subchondral mineralised tissue line, resembling equine osteochondrosis.


CONCLUSIONS
The findings imply that the aetiology of condylar fatigue fracture in young Thoroughbred horses includes abnormality in development of the bone and joint that is present before athletic activity occurs.
National Research Centre for Growth and Development, Institute of Veterinary, Animal and Biomedical Sciences, Massey University, Private Bag 11222, Palmerston North 4442, New Zealand. e.c.firth@massey.ac.nz
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D000222:Adaptation, Physiological; D000818:Animals; D016723:Bone Remodeling / Q000502:physiology; D002113:Calcification, Physiologic / Q000502:physiology*; D005552:Forelimb / Q000000981:diagnostic imaging* / Q000293:injuries; D050723:Fractures, Bone / Q000209:etiology / Q000662:veterinary*; D015775:Fractures, Stress / Q000000981:diagnostic imaging / Q000209:etiology / Q000662:veterinary; D006736:Horses / Q000502:physiology*; D008663:Metacarpus / Q000033:anatomy & histology / Q000293:injuries / Q000502:physiology; D010805:Physical Conditioning, Animal / Q000502:physiology*; D011859:Radiography