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

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Abstract
Objective—To determine kinematic movements of the vertebral column of horses during normal locomotion.Animals—5 Dutch Warmblood horses without apparent lameness or problems associated 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 were 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 flexion during 1 stride cycle, whereas lateral bending and axial rotation were characterized by 1 peak and 1 trough. The range of motion for flexion-extension was fairly constant for vertebrae caudal to T10 (approximately 7°). 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°. For vertebrae between T17 and L5, the amount of lateral bending decreased to < 4°. The amount of axial rotation increased gradually from 4° for T6 to 13° for the tuber coxae.Conclusions—This direct measurement method provides 3-dimensional kinematic data for flexion-extension, lateral bending, and axial rotation of the thoracolumbar portion of the vertebral column of horses walking on a treadmill. Regional differences were observed in the magnitude and pattern of the rotations. Understanding of the normal kinematics of the vertebral column in healthy horses is a prerequisite for a better understanding of abnormal function. (Am J Vet Res2000;61:399–406)