KINEMATICS OF THE EQUINE BACK - A METHOD TO STUDY THE THORACOLUMBAR FLEXION-EXTENSION MOVEMENTS AT THE TROT

This study was conducted to evaluate a method for quantifying the flex ion-extension movements: of the back of horses trotting on a track in the conditions of the clinical lameness examination. Using a 3-D kinem atic analysis system, the successive positions of four markers placed at regular intervals between the withers and the tuber sacrale were re corded. To isolate the: flexion-extension movements of the back, the p ositions of these four markers were recomputed in a trunk-related co-o rdinate system of the horse. Then, for each frame, the equation of the third-order polynomial that best fitted the position of the four mark ers was determined. Using these equations, it was then possible to int erpolate the vertical displacement of any point situated between the w ither's and the tuber sacrale. The accuracy of this method was evaluat ed using three additional markers placed between the four previous one s. The vertical displacements of these three markers were recorded and compared to the interpolated displacements provided by this method. T he results showed that the experimental and interpolated values did no t present any statistical difference except in the lumbar region. In t his region, the general shape of the vertical displacement curve was c onserved but magnified by 17 %. This study showed that despite the wea kness of the range of the flexion-extension movements of the equine ba ck at trot, these movements can be quantified with reliability. This m ethod was then used on a lame horse. The results obtained demonstrated the usefulness of this method to study the flexion-extension movement s of horses suffering from various locomotor disorders. (C) Inra/Elsev ier, Paris.