Page 177 - Adams and Stashak's Lameness in Horses, 7th Edition

Examination for Lameness 143

to flexion tests and blocking (or other treatment) can be quadrant 1 (upper right) represent lameness in the right
quantified. Compensatory or multiple limb lameness forelimb during the first half of stance, from impact to
VetBooks.ir of impact and pushoff asymmetry in all four limbs. At lameness in the right forelimb during second half of
midstance; rays in quadrant 2 (upper left) represent
patterns can be determined by studying the distribution
stance, midstance to pushoff; rays in quadrant 3 (lower
the time of this writing, Lameness Locator® is being
used in >300 private practice and university veterinary left) represent lameness in the left forelimb during the
teaching hospital sites around the world. The Q® and first half of stance; and rays in quadrant 4 (lower right)
Lameness Locator® are sold only to licensed veterinar­ represent lameness in the left forelimb during the second
ians. Using data mining techniques on inertial sensor half of stance.
data from large numbers of cases with definitive diagno­ The lameness values provide a more quantitative
ses opens the possibility of determining likelihood of site description of the forelimb lameness. Forelimb lameness
of lameness within the limb derived from inertial sensor is quantified by calculation of the difference in maxi­
results. mum head position between left and right forelimb
strides (Diff Max Head) and the difference in minimum
head position between left and right forelimb strides
Measuring Forelimb Lameness
(Diff Min Head). Diff Max Head and Diff Min Head are
Forelimb lameness is reported in a graphical display calculated for every stride selected for analysis, and the
and by calculating lameness values (Figure 2.131). The mean and standard deviation over all strides are reported.
forelimb lameness display provides a qualitative descrip­ The signs of Diff Max Head and Diff Min Head deter­
tion of the forelimb lameness by representing each ana­ mine side and timing of lameness. The approximate ref­
lyzed stride as a single ray directed outward from the erence range for consideration of “lameness” for these
plot origin. Each ray on the plot is a stride. The length of values is ±6 mm. Because forelimb lameness results in a
the ray is representative of the amplitude of asymmetric combination of both differences in maximum and mini­
head motion for that stride. The direction of the ray on mum heights of the head, the total overall forelimb lame­
the plot represents the side and timing of lameness for ness is a calculated sum called Total Diff Head or Vector
that stride. Using polar coordinate terminology, rays in Sum (VS). Because Diff Max Head and Diff Min Head
take on both positive and negative values depending on
side and timing of lameness, the total amplitude of lame­
Forelimb Strides
ness is a vector sum of both measures. Thus,
2
60 VS = Diff min Head 2 Diff max Head . Since the
approximate reference ranges of Diff Max Head and
Right Fore Lameness Diff Min Head are ±6 mm, the approximate reference
40 Midstance 2 2
Pushoff Impact range of VS = 6 6 , or 8.5 mm. These reference
20 ranges are actually confidence intervals of the inertial
sensor measures that were determined experimentally in
Diff Min (mm) 0 a group of >125 horses evaluated for lameness subjec­
tively by at least three experienced veterinarians when
the average AAEP score was 0. Variation of lameness

dence, is assessed along with amplitude of lameness. The
–20 side and amplitude, which is related to strength of evi­
Pushoff AIDEs used in this system remind the user of the statisti­
cal nature of these reference ranges with language indi­
Impact
–40 Midstance cating weak or strong evidence and reminders to repeat
Left Fore Lameness trials when measures are within reference range. Some
horses with measures below these reference ranges, but
–60 highly consistent, may still have clinical disease. Clinically
–60 –40 –20 0 20 40 60
Diff Max (mm) relevant reference ranges may be higher or lower depend­
ing on intended use and specific clinical situation.
Lamene
When the lameness evaluation is restricted to rela­
Thresholds for Max/Min Head: ±6 mm tively slow speeds with the horse being led by a handler
Diff Max Head: Mean: 13.2 mm SD: 15.4mm restrained by a lead rope, the majority of forelimb lame­
Diff Min Head: Mean: 12.9mm SD: 8.3 mm ness is measured during the first half of stance (impact
Threshold for Total Diff Head: 8.5mm to midstance). This is likely because at slow speeds the
Total Diff Head (Vector Sum): 18.4mm horse primarily uses the forelimb as a strut with little
active forelimb pushoff.
Q Score (fore): R 18.4 lmp
Figure 2.131. Output of Lameness Locator® indicating right Measuring Hindlimb Lameness
forelimb impact lameness. Predominance of rays pointing in
quadrant 1 (upper right) have Diff Max Head and Diff Min Head > ref- Hindlimb lameness is reported in a graphical display
erence range of ±6 mm and Vector Sum or Total Diff Head > 8.5 mm. that depicts deficiency of right and left hindlimb impact
Standard deviations of Diff Min Head less than mean Diff Min Head (first half of stance) or pushoff (second half of stance;
indicating consistent right‐sided lameness. Figure 2.132).