Arthroscopic findings in the carpal joints of lame horses without radiographically visible abnormalities: 41 cases (1986-1991)

Abstract

Summary Arthroscopy was performed in 1 carpal joint unilaterally in 27 horses and either in 2 carpal joints unilaterally or 1 carpal joint bilaterally in 7 horses. All horses were lame, but the cause of lameness could not be determined from radiographs. Twenty-seven carpi did not have radiographically visible abnormalities; the remaining 14 had only mild to moderate lucency or sclerosis of the radial facet of the third carpal bone. The primary abnormalities identified during arthroscopy included a crush fracture of the third carpal bone (7 carpi), an incomplete fracture of the third carpal bone in the frontal plane (13 carpi), an incomplete fracture of the third carpal bone in the sagittal plane (1 carpus), a crush fracture of the radial carpal bone (1 carpus), a chip fracture of the intermediate carpal bone (1 carpus), damage to the articular cartilage of the third carpal bone (12 carpi), tearing or fraying of the medial palmar intercarpal ligament (4 carpi), and synovitis (2 carpi). All of the horses in this study were racehorses (29 Standardbreds and 5 Thoroughbreds), and race records were used to evaluate performance before and after surgery. Twenty-four of 34 horses raced preoperatively, and 25 of 34 raced postoperatively. Twenty-three of the 27 (85%) horses in which a single joint was examined raced postoperatively. Fifteen of these horses had an incomplete or crush fracture of the radial facet of the third carpal bone, and 13 raced postoperatively; 7 horses had full- or partial-thickness damage of cartilage of the third carpal bone, and all 7 raced postoperatively; 2 horses had partial or complete rupture of the medial palmar intercarpal ligament, and both raced postoperatively. Fifteen horses with either a frontal plane incomplete fracture, crush fracture, or full-thickness damage of cartilage of the third carpal bone in 1 carpus were treated by removing bone and cartilage from the dorsoproximal margin of the third carpal bone; 13 of these horses raced postoperatively. Both horses with incomplete frontal plane fractures of the third carpal bone repaired with screws raced postoperatively. Only 2 of 6 horses that underwent bilateral carpal arthroscopy raced postoperatively; 1 of these horses had bilateral partial tearing of the medial palmar intercarpal ligament; the other had bilateral frontal plane incomplete fractures of the radial facet of the third carpal bone. The remaining horse, in which both the radiocarpal and middle carpal joints were examined, did not race postoperatively Our results suggest that horses with lameness, the cause of which has been localized to the carpus, in which radiographs are not diagnostic are likely to have an underlying abnormality that can be effectively diagnosed and treated via arthroscopy. Arthroscopy allows the examiner to thoroughly explore the joint, make an accurate diagnosis, and make the best decision regarding treatment.