Biomechanics in Ataxic Horses
Authors:Kristie Conde, Holly Greene, Jacqueline Lee, Anam Noormohamed, Krista Page, Katherine Steffen
Mentor:Yvette Nout, Assistant Professor - Equine Sciences, California State Polytechnic University Pomona
Hypothesis: The objective for this study is to simulate ataxia in horses through drug administration, and use detailed quantifiable gait analysis to create a new, more objective grading scale for ataxia in horses.
Rationale: Ataxia is defined as gross loss of coordination of the limbs. In horses ataxia is seen mostly due to impaired proprioceptive abilities as a result of neurologic disease. The severity of ataxia is graded on a scale from 0 (neurologically normal) to 5 (recumbency with the inability to stand without assistance). The correct assessment of ataxia in horses is critical to diagnostics, treatment, and evaluation of response to treatment. However, this grading scale is somewhat subjective.
Methods: For this study we used 4 adult Arabian horses, assessed before and after administration of 2 doses of xylazine. Physiological data were collected at baseline and 5, 10, 20, 30, 45, and 60 minutes after xylazine administration. Gait analysis took place between 5 – 10 min after xylazine and included: kinematic data collected on the Sato equine high-speed treadmill (Flat and Decline – 10%), accelerometer data collected simultaneously, and kinetic data collected while horses were standing on a Kistler Instruments force plate.
Results: After administration of xylazine horses had a reduced heart rate, head height, lip tone, and developed ataxia. Data analysis shows an increased stride duration and stride length, decreased stride frequency, and increased side-to-side movement of the hind quarters following xylazine administration. Preliminary data suggests that increased postural sway can be determined in horses after xylazine administration, through quantification of the range of center of pressure measurements.
Principal Conclusions: We can successfully induce ataxia in horses using xylazine and we have determined numerous quantifiable gait parameters that are affected by sedation. Future work includes development of a scale incorporating these parameters and validation in clinically ataxic animals.