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

Objective-To determine kinematic movements of the vertebral column of horse s during normal locomotion. Animals-5 Dutch Warmblood horses without apparent lameness or problems asso ciated with the vertebral column. Procedure-Kinematics of 8 vertebrae (T6, T10, T13, T17, L1, L3, L5, and S3) and both tuber coxae were determined, using bone-fixated markers. Horses w ere recorded while walking on a treadmill at a constant speed of 1.6 m/s. Results-Flexion-extension was characterized by 2 periods of extension and f lexion during 1 stride cycle, whereas lateral bending and axial rotation we re characterized by 1 peak and 1 trough. The range of motion for flexion-ex tension was fairly constant for vertebrae caudal to T10 (approximately 7 de grees). For lateral bending, the cranial thoracic vertebrae and segments in the pelvic region had the maximal amount of motion, with values of up to 5 .6 degrees. For vertebrae between T17 and L5, the amount of lateral bending decreased to < 4 degrees. The amount of axial rotation increased gradually from 4 degrees for T6 to 13 degrees for the tuber coxae. Conclusions-This direct measurement method provides 3-dimensional kinematic data for flexion-extension, lateral bending, and axial rotation of the tho racolumbar portion of the vertebral column of horses walking on a treadmill . Regional differences were observed in the magnitude and pattern of the ro tations. Understanding of the normal kinematics of the vertebral column in healthy horses is a prerequisite for a better understanding of abnormal fun ction.