Effect of sedation on fore- and hindlimb lameness evaluation using body-mounted inertial sensors

Diagnostic analgesia is an integral part of equine lameness examinations, but is challenging to perform in uncooperative horses. Using sedation to facilitate this might, because of analgesic and ataxia-inducing effects, interfere with lameness evaluation.

To evaluate whether sedation with low-dose xylazine would alter lameness amplitude as measured by body-mounted inertial sensors.

Controlled experiment.

Forty-four horses were randomly split into 2 groups. Lameness was measured using body-mounted inertial sensors before and after injection of xylazine (0.3 mg/kg bwt) or saline. Sedation was measured at 5, 20 and 60 min following treatment, and lameness evaluations were performed before (Time 0) and at 20 and 60 min after treatment. Forelimb lameness was determined by measuring the vector sum of mean head height maximum and minimum differences between all right and left forelimb strides (n>25) collected with the horse trotting in a straight line. Hindlimb lameness amplitude was determined by measuring mean pelvic height maximum and minimum differences between right and left hindlimb strides. Numbers of horses staying the same, improving or worsening were compared between groups at each time interval.

There were no significant differences in head or pelvic movement asymmetry between xylazine and saline treatment groups. However, a few horses with forelimb lameness in the xylazine treatment group showed a large decrease in head movement asymmetry (decrease in forelimb lameness) at 60 min following sedation.

Low-dose sedation with xylazine may be used without the concern of potential lameness-masking effects for hindlimb lameness evaluation, but caution should be used in some horses with forelimb lameness of mild severity. The Summary is available in German - see Supporting information.