Radiographic evaluation of sclerosis of the third carpal bone associated with exercise and the development of lameness in Standardbred racehorses.
BACKGROUND
Sclerosis of the third carpal bone is a common radiographic finding in both lame and sound racehorses, but there are no guidelines correlating degree of sclerosis and incidence of lameness.


OBJECTIVE
To develop a protocol for describing subchondral bone sclerosis in C3 on dorsoproximal-dorsodistal oblique (DPr-DDiO) radiographs of the carpus and to correlate these changes with exercise history and carpal lameness.


METHODS
One hundred and six Standardbreds entering their first year of training (exercise group) and 7 age-matched Standardbreds at pasture (controls) were examined at approximately 3 month intervals over 12-18 months. Examinations consisted of lameness evaluation and carpal radiographs (DPr-DDiO and flexed lateromedial projections). A grading system (very mild, mild, moderate and severe) for C3 sclerosis seen on the DPr-DDiO radiograph was developed that utilised a combination of the criteria of trabecular thickening (trabecular score; TS) and total percent area of the C3 radial facet affected (TAA).


RESULTS
Exercise group horses showed significant increase in TS and TAA throughout training compared to control horses. Middle carpal joint lameness developed in 32/106 (30%) exercise group horses and none of the control horses. Incidence of middle carpal joint (MCJ) lameness was lower in horses with mild (2/30, 6.7%) than moderate (10/32, 31.2%) and severe (20/44, 45.4%) sclerosis throughout training.


CONCLUSIONS
Horses with higher grades of sclerosis, as defined by this novel grading system, were more likely to develop MCJ lameness at some point of training. The proposed grading system gave a quantitative assessment of radiographic sclerosis that could then be used to correlate increasing severity of sclerosis with increasing incidences of lameness.


CONCLUSIONS
These results serve as a basis for further investigation into determining the degree of C3 sclerosis at which pathological changes and lameness can be expected.
Hopper
B J
BJ
Division of Veterinary and Biomedical Sciences, School of Veterinary Clinical Science, Murdoch University Veterinary Hospital, Murdoch Drive, Murdoch, Western Australia 6150, Australia.
Steel
C
C
Richardson
J L
JL
Alexander
G R
GR
Robertson
I D
ID
D000818:Animals; D002348:Carpal Bones / Q000000981:diagnostic imaging* / Q000473:pathology; D016022:Case-Control Studies; D005260:Female; D006734:Horse Diseases / Q000000981:diagnostic imaging* / Q000209:etiology / Q000473:pathology; D006736:Horses; D007794:Lameness, Animal / Q000000981:diagnostic imaging* / Q000209:etiology / Q000473:pathology; D008297:Male; D010805:Physical Conditioning, Animal; D011859:Radiography; D012598:Sclerosis / Q000000981:diagnostic imaging / Q000473:pathology / Q000662:veterinary; D012720:Severity of Illness Index