appear more severe), and sometimes subtractive, thus masking a true lameness (or
making an existing lameness appear less severe).
When the rider is performing a ‘sitting trot’ the results are quite variable. About 1/3 of
the horses look the same as trotting in a straight line without the rider, about 1/3
seem to be less lame with the rider, and about 1/3 seem to be more lame with the
rider. However, with the rider performing a ‘rising trot’ (posting on the outside limb),
it is very common for the horse to appear to be lamer on the opposite side, both in
the forelimb and in the hind limb, with the most dramatic effect on the push-off
component of the opposite hind limb. These horses frequently appear to push off
less on the inside hind limb, even if the horse did not have a lameness in this limb to
begin with. These asymmetries could also mask a true lameness. For example, in
a horse that has a push-off type lameness in the right hind limb, going to the left with
the rider posting on the right forelimb, could cause the appearance of a left hind limb
push-off lameness, which could obscure the real right hind limb push-off lameness.
When the rider is posting on the outside limb, he/she is rising in the saddle and
shifting weight forward when the inside forelimb is on the ground. If the horse had a
true inside forelimb lameness, this could exacerbate the expression of lameness.
Using Lameness Locator® to assess response to regional analgesia
Assessing the response to regional analgesia as a decrease in lameness from
baseline is relatively straight forward using body-mounted inertial sensors. A
positive response to a nerve block is based upon finding a change in the
measurement of lameness that is outside the 95% confidence interval for
repeatability for the lameness measurement variables, which is +/- 6 mm for
DIFFMINHEAD and DIFFMAXHEAD for forelimb lameness, and +/- 3 mm for
DIFFMINPELVIS and DIFFMAXPELVIS for hind limb lameness.
Conclusion
Thus, detection of lameness, though at times difficult, is a simple measurement
problem that is markedly facilitated and rendered more objective and reliable with the
use of inertial sensor technology. This is not to be confused with determination of
the importance of lameness, localization of the causative focus within the involved
limb or limbs, determining treatment most likely to be successful, and rendering an
accurate prognosis. These are complex problems that require careful consideration
by veterinarians experienced in lameness examinations. Objections to the use of
objective methods to detect and evaluate lameness in horses frequently stem from
the rather understandable tendency to think about lameness as a disease to be
diagnosed and treated, instead of the less common, but actually more correct,
thinking about lameness as what it actually is, which is a clinical sign.
Selected Bibliography
1.
2.
3.
4.
Arkell M, Archer RM, Guitian FJ, May SA. Evidence of bias affecting the interpretation of the results of local anesthetic
nerve blocks when assessing lameness in horses. Vet Rec 2006;159:346–349.
Buchner HHF, Salvelberg HHCM, Schamhardt HC, Barneveld A. Limb movement adaptations in horses with
experimentally induced fore- or hindlimb lameness. Equine Vet J 1996;28: 63–70.
Buchner HHF, Savelberg HCCM, Schamhardt HC, et al. Head and trunk movement adaptations in horses with
experimentally induced fore or hindlimb lameness. Equine Vet J 1996; 28:71–76.
Buchner HHF. Limb movement pattern in forelimb and hindlimb lameness. Proceedings Am Assoc Equine Pract
2005;51: 128–133.
Proceedings
of
the
South
African
Equine
Veterinary
Association
Congress
2016
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