Basic three-dimensional kinematics of the vertebral column of horses trotting on a treadmill

Objective-To determine movements of the vertebral column of horses during n ormal locomotion. Animals-5 young Dutch Warmblood horses that did not have signs of back prob lems or lameness. Procedure-Kinematics of 8 vertebrae (T6, T10, T13, T17, L1, L3, L5, and S3) and both tuber coxae were determined, using bone-fixated markers. Measurem ents were recorded when the horses were trotting on a treadmill at a consta nt speed of 4.0 m/s. Results-Flexion-extension and axial rotation were characterized by a double sinusoidal pattern of motion during 1 stride cycle, whereas lateral bendin g was characterized by 1 peak and 1 trough. Ranges of motion for all verteb rae were: flexion-extension, 2.8 degrees to 4.9 degrees; lateral bending, 1 .9 degrees to 3.6 degrees; axial rotation, 4.6 degrees to 5.8 degrees, exce pt for T10 and T13, where the amount of axial rotation decreased to 3.1 deg rees and 3.3 degrees, respectively. Conclusion and Clinical Relevance-During locomotion, 3 types of rotations a re evident in the thoracolumbar vertebrae. Regional differences are observe d in the shape and timing of the rotations. These differences are related t o actions of the limbs. The method described here for direct measurement of vertebral column motion provides insights into the complex movements of th e thoracolumbar portion of the vertebral column in trotting horses. Informa tion on normal kinematics is a prerequisite for a better understanding of a bnormal function of the vertebral column in horses.