RADIOGRAPHIC AND ARTHROSCOPIC FINDINGS ASSOCIATED WITH SUBCHONDRAL LUCENCY OF THE DISTAL RADIAL CARPAL BONE IN 71 HORSES

Case records and radiographs of 71 horses with subchondral lucency, wi thout radiographic evidence of fracture, located on the distal radial carpal bone were examined retrospectively. All horses had lameness and /or joint effusion referable to the carpus, Distal radial carpal bone subchondral lucency was found as a solitary lesion or as a lesion conc urrent and symmetric to a contralateral distal radial carpal bone chip fracture, The lesion appeared radiographically as a lucency or shadow on the distal dorsal margin of the radial carpal bone and was most ev ident on the flexed lateromedial and dorsolateral-palmaromedial obliqu e projections, Sixty-four joints in 55 horses underwent arthroscopic s urgery, Surgical findings included osteochondral fragmentation in 44 j oints, cartilage fragmentation with subchondral bone softening in 17 j oints and cartilage fraying in 3 joints, Corresponding third carpal bo ne lesions were observed in 18 joints and moderate to severe synovitis was present in 24 joints, Carpal bone subchondral radiolucency withou t a fracture fragment observed on radiographs indicated cartilage and bone damage, In some cases, small chip fractures (1-2 mm) were present within the cartilage debris examined at surgery, yet were not radiogr aphically visible, Follow-up information was obtained on 50 of the ope rated horses and 14 nonoperated horses, Forty (80%) of the surgically treated horses returned to racing, with 34 (68%) of these horses (20 o f 26 with subchondral lucency as a solitary lesion) racing at a level of competition equal to or better than the pre-injury level, Of the 14 horses which were not operated, 6 (42%) returned to racing of which o nly 2 (14%) raced at the same pre-injury level of competition, Radiogr aphic evidence of radial or intermediate carpal bone subchondral lucen cy is an indication of cartilage and bone damage which is best treated with arthroscopic surgery.