| This study was performed to test whether two-dimensional (2D) and three-dimensional (3D) kinematic, ground reaction force (GRF) and 2D inverse dynamic analysis could identify differences between sound horses and horses with mild tarsal joint lameness. Hypotheses tested were that kinematic and kinetic profiles of horses with distal tarsal synovitis differ from those of sound horses, and that the tarsal joint complex undergoes 3D motion. Four sound horses were selected on the basis of clinical evaluation, radiography and nuclear scintigraphy. Gait analysis was performed for the sound condition, after which synovitis was induced by injecting endotoxin into the right distal intertarsal and tarsometatarsal joints. Gait analysis was repeated 24–30 hours later for the lame condition. Independent t-tests were performed to identify differences between the variables in the two conditions. In the sound condition, tarsal joint ranges of motion were 12.12° ± 0.96 and 44.67° ± 1.90 during stance and swing, respectively. The peak vertical force on the hind limb was 9.05 ± 0.40 N/kg. During stance, the tarsal joint power profile showed two cycles of elastic energy storage and release on the extensor aspect, which was a mechanism for minimizing energy expenditure at the trot. During swing, the tarsal joint power profiles showed two bursts of energy generation, on the flexor aspect in early swing then on the extensor aspect in late swing. After synovitis induction, tarsal joint range of motion during stance decreased by 2.20° ± 1.28. Peak vertical force and vertical impulse decreased by 0.31 ± 0.18 N/kg and 0.05 ± 0.03 Ns/kg. The mechanical deficits at the tarsal joint included a trend toward a decrease in energy absorption during early stance, and a decrease in energy generation during push off. During swing, there was a trend toward a decrease in tarsal positive net joint energy. There was no compensatory increase in energy generation from the other joints within the lame hind limb. The contralateral hind limb showed a trend toward an increase in peak vertical force of 0.17 ± 0.13 N/kg and increase in positive power at the coxofemoral joint during early swing. Vertical impulse in the contralateral forelimb decreased by 0.05 ± 0.02 Ns/kg. It was found that the tarsal joint complex showed 3D rotational and translational motions. In the sound condition, the tarsal joint complex was flexed, abducted and internally rotated, and translated in cranial, lateral and proximal directions during stance. The motions during swing were similar to those during stance, except that the joint externally rotated. (Abstract shortened by UMI.)... |
