COMPUTER-ASSISTED 3-DIMENSIONAL GAIT ANALYSIS OF AMPHOTERICIN-INDUCEDCARPAL LAMENESS IN HORSES

Motion of 6 clinically sound horses trotting at a speed of 4 m/s on a treadmill was captured by video cameras before and 9, 16, and 23 days after amphotericin-induced lameness to determine the quantitative vari ables of three-dimensional computer-assisted image analysis that objec tively describe carpal lameness. Amphotericin-B was used to induce lam eness, and phenylbutazone (2.2 mg/kg of body weight, PO, once) and but orphanol tartrate (0. 1 mg/kg im, q 6 h, to effect) were used to contr ol discomfort. Four 60-Hz cameras were symmetrically placed around the treadmill to capture 6 seconds of images from retroreflective spheres taped to the trotting horses. Images were transferred to a video-base d digitizer and a computer work station, where 4 files of two-dimensio nal data were reduced to 1 file of three-dimensional data. The effect of lameness on motion analyzed was assessed by use of two-way ANOVA. D ifferences between means were assessed, using the Student-Newman-Keul' s test (P less-than-or-equal-to 0.05). Head and withers excursions, (d orsal vertical displacement of head and withers targets, respectively) during the sound forelimb support phase were increased significantly during all lameness measurement periods, Head excursion, but not withe rs excursion, during the lame forelimb support phase, was decreased si gnificantly during all lameness measurement periods. Computer determin ations of stride length swing phase, stance phase, forelimb abduction, and carpal and fetlock ranges of motion did not consistently characte rize the lameness. It was concluded that three-dimensional computer-as sisted image analysis could be used for objective lameness evaluation in horses and that head and withers excursions were the most consisten t variables for assessing equine carpal lameness.