Papers of the Week

Evaluation of diagnostic anaesthesia during equine lameness examination requires comparison of complex movement patterns and can be influenced by expectation bias. There is limited research about how changes in movement asymmetries after successful analgesia are affected by different exercise conditions. Movement asymmetry of head, withers and pelvis was quantified in N=31 horses undergoing forelimb or hindlimb diagnostic anaesthesia. Evaluation on a straight line and a circle was performed with subjective diagnostic anaesthesia outcome and quantitative changes recorded. Mixed linear models (P<0.05) analysed the differences in movement asymmetry before/after diagnostic anaesthesia – random factor: horse, fixed factors: surface (soft, hard), direction (straight, inside, outside, inside-outside average), diagnostic anaesthesia outcome (negative, partially positive, positive) and two-way interactions. Forelimb diagnostic anaesthesia influenced primary movement asymmetry (all head and withers parameters) and compensatory movement asymmetry (two pelvic parameters) either individually (p≤0.009) or in interaction with surface (p≤0.03). Hindlimb diagnostic anaesthesia influenced primary movement asymmetry (all pelvic parameters) and compensatory movement asymmetry (two head and two withers parameters) either individually (p≤0.04) or in interaction with surface (p≤0.01;) or direction (p≤0.006). Direction was also significant individually for two pelvic parameters (p≤0.04). Changes in primary movement asymmetries after partially positive or positive outcome indicated improvement in the blocked limb. Compensatory changes were mostly in agreement with the 'law of sides'. The changes were more pronounced on the hard surface for hindlimb lameness and on the soft surface for forelimb lameness. Withers asymmetry showed distinct patterns for forelimb and hindlimb lameness potentially aiding clinical decision making.