THE USE OF INERTIAL SENSORS IN THE
DIAGNOSIS OF LAMENESS
Michael Schramme and Kevin Keegan*
VetAgro Sup, Campus Veterinaire de Lyon, Marcy L’Etoile, Rhones-Alpes, France
*University of Missouri-Columbia, College of Veterinary Medicine, Columbia, Missouri, USA
Introduction
Lameness is a clinical sign not a disease. A synonym is “limping” and it indicates
that the horse is moving in a way such that it does not load onto or push off a limb
normally. Although there may be different reasons why a horse would do this,
including a neurologic dysfunction or an anatomical defect, the most common cause
is the presence of pain in a limb or in the torso. If the pain is in one limb, or if the
pain in one limb is greater than in the other(s), a relative reduction of loading of that
limb results in asymmetric vertical movement of the torso. Other body and limb
movement alterations may occur with lameness, such as decreases in stride length
and joint angle range of motion during stance, or shape of hoof and limb flight
trajectories during swing. However, there is strong evidence that vertical movement
of the torso is the most sensitive indicator of lameness that provides all of the
information necessary to detect lameness and localize lameness to the correct
limb(s) (Buchner et al. 1996). No further information is needed.
Subjective evaluation of lameness by simple observation of the horse in motion at
the trot is the most common method of lameness detection, but the spatial and
temporal resolution of the human eye is limited. Small differences in vertical torso
movement resulting from unequal loading of limbs are not reliably detected,
especially as the horse moves away from the observer, or when the horse is moving
fast. The ability of veterinarians to detect asymmetric vertical movement of the tuber
coxae, for example, was estimated using computer simulations to be reliable only
when the asymmetry was greater than 25% of gross vertical movement. The
threshold between sound and lame is estimated to be less than half of this. This
clarifies why studies indicate that agreement between practitioners for evaluation of
mild to moderate lameness in horses is poor (Fuller et al. 2006; Hewetson et al.
2006; Keegan et al. 2010). One cannot agree on what one cannot see.
Methods of objective measurement with higher spatial and temporal resolution are
more sensitive for detecting lameness than the human eye. There are several
techniques that can serve to measure lameness objectively. Video-capture and
replay or computer-assisted kinematic analysis of gait, offer high temporal resolution,
but unless the horse is contained on a treadmill, both techniques suffer from limited
spatial resolution. Body-mounted inertial sensors have both high sampling frequency
and wireless transmission of measurement and are not restricted by a limited field of
view like treadmills. They currently offer the only technique allowing accurate and
sensitive objective evaluation of lameness in the field.
Proceedings
of
the
South
African
Equine
Veterinary
Association
Congress
2016
36