Three-dimensional carpal kinematics of trotting horses

Reasons for performing study: Descriptions of 3D kinematics assist in understanding joint function and dysfunction, and are an essential step toward 3D inverse dynamic analysis. Objectives: To measure 3D carpal joint motion during trotting. Methods: Three-dimensional trajectories of bone-fixed markers on the radius and third metacarpus of the right forelimb of 3 healthy horses were recorded at 120 Hz using a 6-camera analysis system. Joint kinematics were calculated in terms of helical angles between the 2 segments using a spatial attitude method. Results: All horses showed carpal extension and internal rotation of the metacarpus relative to the radius as the carpus assumed the close-packed position. In late stance, the carpus began a cycle of flexion that continued through midswing, accompanied by a small cycle of internal rotation. The direction of abduction/adduction varied between horses. The predominant rotational movement was flexion/extension, which showed a range of motion of 15 +/- 6* in stance and 76 +/- 13degrees in swing. Conclusions: Carpal motions were generally similar between horses with the exception of abduction/adduction. Potential relevance: Knowledge of carpal joint motion should assist in understanding the pathogenesis of carpal injuries. However, it seems probable that real differences exist between individuals; therefore, further investigations of the effect of conformation on carpal motion should be performed in a much larger population of horses.