The results of arthroscopic surgery in the treatment of osteochondral
fragmentation of the proximodorsal aspect of the first phalanx and the
influence of other fetlock joint lesions on prognosis were evaluated
in 336 horses. Horses were classified as: 1) returning to previous use
at the same or higher class of performance; 2) returning to previous
use (regardless of class of performance); or 3) failing to return to p
revious use. Ninety-six horses (29%) had fragmentation alone; 140 hors
es (42%) had fragmentation and additional. fetlock lesions, and 100 ho
rses (29%) underwent concurrent carpal arthroscopy. Of the 100 horses
that underwent carpal arthroscopy, 63 had proximodorsal first phalanx
fragmentation alone and 37 had other fetlock lesions associated with t
he fragment. There was significant association between lesion type and
return to previous use for the Thoroughbred racehorse group. There wa
s also a significant association between lesion type and return to the
same or higher class of racing for the Thoroughbred racehorse group.
No significant association in return to previous use existed for raceh
orses vs. nonracehorses, Thoroughbred racehorses vs. Quarter Horse rac
ehorses, single vs. multiple joint involvement, and single vs multiple
fragmentation per joint. The Thoroughbred racehorses in this study we
re sensitive to additional fetlock or carpal lesions, as was exemplifi
ed by the significant effect lesion type had on outcome.