Methodology and validity of assessing kinematics of the thoracolumbar vertebral column in horses on the basis of skin-fixated markers

Objective-To determine the validity of using skin-fixated markers to assess kinematics of the thoracolumbar vertebral column in horses. Animals-5 Dutch Warmblood horses without abnormalities of the vertebral col umn. Procedure-Kinematics of T6, T10, T13, T17, L1, L3, L5, S3, and both tuber c oxae were determined by use of bone-fixated and skin-fixated markers. Three -dimensional coordinate data were collected while horses were walking and t rotting on a treadmill. Angular motion patterns were calculated and compare d on the basis of 2-dimensional analysis of data from skin-fixated markers and 3-dimensional analysis of data from bone-fixated markers. Results-Flexion-extension of thoracolumbar vertebrae and axial rotation of the sacrum were satisfactorily determined at both the walk and trot, using skin-fixated markers. Data from skin-fixated markers were accurate for dete rmining lateral bending at the walk in the midthoracic and lower lumbar por tion of the vertebral column only. However, at the trot, data from skin-fix ated markers were valid for determining lateral bending for all thoracolumb ar vertebrae. Conclusions and Clinical Relevance-Caution should be taken when interpretin g data obtained by use of skin-fixated markers on lateral bending motions d uring the walk in horses. For determination of other rotations at the walk and all rotations at the trot, use of skin-fixated markers allows valid cal culations of kinematics of the vertebral column. Understanding to what exte nt movements of skin-fixated markers reflect true vertebral motion is a com pulsory step in developing noninvasive methods for diagnosing abnormalities of the vertebral column and related musculature in horses.