Page 184 - Adams and Stashak's Lameness in Horses, 7th Edition

150 Chapter 2

Quantification of Asymmetry Quantification of Asymmetry
Stride Rate: 1.5 Strides Assessed (fore/hind): 29/29 Stride Rate: 1.8 Strides Assessed (fore/hind): 36/36
Hindlimb Strides
Hindlimb Strides
Forelimb Strides
Forelimb Strides
VetBooks.ir 60 40 Right Fore Lameness –30 Left Hind Lameness Right Hind Lameness 30 60 40 Right Fore Lameness –30 Left Hind Lameness Right Hind Lameness 30
Pushoff
Pushoff
Pushoff
Pushoff
Midstance
Midstance
–20
20
20
–20
20 Pushoff Impact – Diff Max (mm) –10 10 + Diff Max (mm) 20 Pushoff Impact – Diff Max (mm) –10 10 + Diff Max (mm)
Diff Min (mm) 0 0 0 Diff Min (mm) 0 0 0
–20 –10 10 –20 –10 10
Pushoff Impact Pushoff
Impact
–40 Midstance – Diff Min (mm) –20 20 + Diff Min (mm) –40 Midstance – Diff Min (mm) –20 20 + Diff Min (mm)
Left Fore Lameness Left Fore Lameness
–60 –30 Impact Impact 30 –60 –30 Impact Impact 30
–60 –40 –20 0 20 40 60 0 10 20 30 0 10 20 30 –60 –40 –20 0 20 40 60 0 10 20 30 0 10 20 30
Diff Max (mm) Stride Stride Diff Max (mm) Stride Stride
Lameness Metrics Lameness Metrics
Thresholds for Max/Min Head: ±6 mm Thresholds for Max/Min Pelvis: ±3 mm Thresholds for Max/Min Head: ±6 mm Thresholds for Max/Min Pelvis: ±3 mm
Diff Max Head: Mean: 3.4 mm SD: 7.3 mm Diff Max Pelvis: Mean: –12.9 mm SD: 4.1 mm Diff Max Head: Mean: –90.3 mm SD: 32.7 mm Diff Max Pelvis: Mean: 12.2 mm SD: 13.4 mm
Diff Min Head: Mean: 35.6 mm SD: 10.0 mm Diff Min Pelvis: Mean: 11.3 mm SD: 4.4 mm Diff Min Head: Mean: –74.3 mm SD: 37.6 mm Diff Min Pelvis: Mean: –39.8 mm SD: 24.1 mm
Threshold for Total Diff Head: 8.5 mm Threshold for Total Diff Head: 8.5 mm
Total Diff Head (Vector Sum): 35.7 mm Total Diff Head (Vector Sum): 116.9 mm
Q Score (fore): R 35.7 Mid Q Score (hind): L 12.9 Push / R 11.3 Imp Q Score (fore): L 116.9 Imp Q Score (hind): R 12.2 Push / L 39.8 Imp
Figure 2.142. Lameness Locator® reports of multiple limb tion of this type of multiple limb lameness is the second part of the
lameness. Left report: Left hindlimb pushoff, right hindlimb impact, law of sides, or primary forelimb lameness with compensatory
and right forelimb lameness. Right report: Right hindlimb pushoff, contralateral hindlimb pushoff lameness and ipsilateral hindlimb
left hindlimb impact, and left forelimb lameness. The best explana- impact lameness.
Hindlimb Assessment
Left Hind Lameness Right Hind Lameness Left Hind Lameness Right Hind Lameness
–30 Pushoff Pushoff 30 Thre sholds for Mean Diff Max/Min 30 Pushoff Pushoff 30
–Diff Max (mm) –20 20 +Diff Max (mm) Diff Max Pelvis –Diff Max (mm) 20 20 +Diff Max (mm)
±3mm
10
10
10
–10
–9.1mm
SD:
9.3 mm
3.0mm Mean: –23.7 mm
0 0 0 0
Diff Min Pelvis –15.9 mm 10 10
10
–10
–Diff Min (mm) –20 Impact Impact 20 +Diff Min (mm) 4.9mm SD: 11.1mm –Diff Min (mm) 20 Impact Impact 20 +Diff Min (mm)
–16.5mm
Mean:
Strides Assessed
–30
0 2 4 6 8 0 2 4 6 8 30 8 9 30 0 5 10 0 5 10 30
Stride Stride Stride Stride
Figure 2.143. Lameness Locator® reports of before (left) and hindlimb flexion test. Eight strides were collected as baseline before
after (right) left hindlimb flexion. Absolute value of Diff Max Pelvis flexion and nine strides were collected after flexion.
increases from |−9.1| to |−23.7| mm. This is a strong positive left
tests by trotting the horse off in one direction only. or negative, believing the lameness to be unchanged
Therefore, a baseline trot off in one direction without when in fact it is greater or lesser than before block.
flexion should be collected as baseline before flexion. A desire for observing improvement in lameness after
A positive response to flexion is then ascertained by blocking is made stronger late in the day, after several
simply comparing the amplitude of the lameness values blocks have been applied with no improvement, and
for that limb before and after flexion (Figure 2.143). It especially in horses that are difficult or dangerous to
is interesting that most hindlimb flexion tests are associ­ block. On the other hand, partial improvements in lame­
ated with an increase in Diff Max Pelvis, but not Diff ness, or a change in the timing of lameness, may be mis­
Min Pelvis, or a decrease in hindlimb propulsion and taken for no effect. Objective measurements reduce these
not in a decrease in hindlimb impact. 43,67 In one study a potential mistakes. Also, intraindividual (between horse)
minimum increase in Diff Max Pelvis of about 4.5 mm variation in lameness has been shown to be less than
indicated a positive flexion test. 43 interindividual (within horse) variation of lameness;
therefore smaller changes in amplitude of lameness and
a quantitative percent improvement can be confirmed.
Evaluation of Lameness Before and After Blocking
Lameness Locator® calculates percent improvement
One of the most useful applications of using body‐ in lameness in two ways: (1) returning the amplitude of
mounted inertial sensors is to more precisely and accu­ asymmetry (i.e. lameness) down to perfect mean sym­
rately evaluate the effect of blocking for reducing metric movement and (2) returning the amplitude of
lameness. 56,64–66,69 This protects against the bias inherent lameness to within the reference range of asymmetry
in unblinded subjective evaluation. Bias can be positive, where even experts, performing full lameness evalua­
believing the lameness to be improved but in reality not, tions, do not conclude that the horse is “lame.” The first