Clinical perspectives on equine back kinematics

Abstract Back pain and dysfunction are important reasons for impaired performance in sport horses. Earlier studies have developed a clinical tool, the infrared-based automated gait analysis system, to objectively evaluate the function of the equine back. The aim of this thesis was to test its ability to differentiate horses with back pain from clinically sound horses. Additional aims were to evaluate the effect of local anaesthesia and weighted boots, respectively, on the movement of the back in asymptomatic horses. In all studies, the kinematics of the back were recorded at 240 Hz at walk and trot on a treadmill. Range of movement and symmetry of movement were derived from angular movement pattern data in Backkin®. In study I, the back kinematics of twelve horses with clinical back pain and dysfunction were measured and compared to the same parameters in 33 clinically sound horses in regular training and competition. In study II, a crossing-over study, ten clinically sound horses were measured before and after injections with mepivacaine and injections with sodium chloride around the interspinous spaces between T16 and L2. In study III, a lactic acid solution was injected into the left m. longissimus dorsi of eight clinically sound horses. The movement of the back was measured before the injections and on five occasions during the week subsequent to the injections. In study IV, a crossing-over study, eight clinically sound horses in regular training and competition were measured with and without weighted boots on the forelimbs and hind limbs, respectively. In conclusion, the results show that the infrared-based automated gait analysis technique can differentiate horses with back dysfunction from horses with normal back movements, and that this technique can be used to evaluate a specific, localized change in movement in a patient with clinical back pain. It has also been shown that local anaesthesia affects the back movement in asymptomatic horses, and that weighted boots on the limbs affect the movement of the back in clinically sound horses. Suggestions for future items to be studied are bilateral back pain and longterm follow-ups of back patients after treatment