Page 186 - Adams and Stashak's Lameness in Horses, 7th Edition

152 Chapter 2

In contrast, on hard surfaces, torso tilt is the primary with both subjective and objective lameness evaluation.
and most significant factor creating asymmetric head Some of the variable movement can be removed when
VetBooks.ir impact‐type forelimb (less head fall on the inside fore­ that extract and discard random movement, and pre­
using objective measurement methods with algorithms
and pelvic vertical movement, so an inside forelimb
sumably this is done also subjectively, and collecting
limb) and an inside hindlimb impact (less pelvic fall) and
pushoff (less pelvic rise) lameness are frequently seen data on higher numbers of multiple contiguous strides
and should not be unexpected (Figure 2.145). can mitigate some of the negative consequences of high
Surfaces with characteristics that are intermediate stride‐by‐stride variability. However, stride‐by‐stride
between hard and soft may have hybrid vertical head and variability can be noticeably reduced with mild seda­
pelvic height asymmetries. However, certain asymmetric tion, increasing the consistency of measurement and
movements are abnormal regardless of direction or sur­ confidence in interpretation. Also, most studies have
face characteristics. Impact‐type lameness on the outside shown that mild sedation, although it may significantly
forelimb or pushoff‐type forelimb lameness on the inside affect limb movement parameters (e.g. stride length)
forelimb should not be expected on any surface. Impact‐ sometimes used to assess lameness, does not as a rule
type lameness on the outside hindlimb should also not be artificially lower amplitude of head vertical movement
seen in any direction or on any type of surface. asymmetry, and does not artificially lower amplitude of
VPM asymmetry, as might be expected if sedation
caused significant orthopedic analgesia. 3,15,61 Some pro­
Evaluation of Lameness with Sedation
tocols tested include 0.1–0.3 mg/kg xylazine and
Examination of the horse in motion for lameness is 0.025 mg/kg acepromazine. The author also believes
more complicated in anxious and misbehaving horses. that mild sedation in anxious or misbehaving horses
Random movement of the head, frequent and abortive allows are more thorough and particular limb and torso
gait transitions from trot to canter, rearing, jumping, palpation. Of course, mild sedation may also facilitate
attempting to bite the handler, all of these behaviors blocking procedures in some horses. There are some cir­
make it more difficult to detect small asymmetries (mild cumstances of lameness evaluation (prepurchase exami­
lameness) in vertical head and pelvic movement. Also, nation, substance use before competition, owner
anxiety of the horse may mask the display of lameness. preference) that do not allow the use of mild sedation,
Lameness amplitude will vary more from stride to stride but if possible the clinician can mildly sedate without
and confidence in results is sacrificed. This is a problem adversely affecting blocking results.

Forelimb Assessment
60 60
RF pushoff RF impact RF pushoff RF impact
40 40
Diff Max Head
20 –7.9 mm Mean 11.7mm 20
Diff Min (mm) 0 9.9mm Diff Min Head 8.1mm Diff Min (mm) 0
SD

7.6mm
–20
7.1mm
SD
6.1mm Mean –2.7mm –20
–40 Total Diff Head (Vector Sum) –40
LF impact LF pushoff LF impact LF pushoff
10.9 mm 12.1 mm
–60 –60
–60 –40 –20 0 20 40 60 Strides Assessed –60 –40 –20 0 20 40 60
Diff Max (mm) 36 69 Diff Max (mm)
Hindlimb Assessment
Left Hind Lameness Right Hind Lameness Left Hind Lameness Right Hind Lameness
–30 Pushoff Pushoff 30 30 30
– Diff Max (mm) –20 20 + Diff Max (mm) Diff Max Pelvis – Diff Max (mm) 20 Pushoff Pushoff 20 + Diff Max (mm)
–10
10
3.2mm
4.3mm
SD:
3.3mm Mean: –5.6 mm 10 10
0 0 0 0
Diff Min Pelvis 3.9mm 10 10
– Diff Min (mm) –20 Impact Impact 20 + Diff Min (mm) 4.3mm SD: 7.0mm – Diff Min (mm) 20 Impact Impact 20 + Diff Min (mm)
–10
–10.8 mm
10
Mean:
Strides Assessed
–30
0 20 40 60 0 20 40 60 30 71 74 –30 0 20 40 60 0 20 40 60 30
Stride Stride Stride Stride
Figure 2.144. Lameness Locator® report of a non‐lame horse lunging on a soft sand surface. Outside forelimb pushoff lameness, outside
hindlimb pushoff lameness, and inside hindlimb impact lameness are measured.