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A

Automated Interpretation and Degree of Evidence (AIDE)

Interpretation assistance is offered at the bottom of the report.

The strength of evidence reported is based on whether the TDH/VS, Diff Max pelvis or Diff Min pelvis is outside of the reference range for that measure and the stride to stride variability (SD). 

Indications of severity are based on a general range of amplitude of lameness, with levels increasing from “very mild”, “mild”, “mild/moderate”, “moderate”, and “moderate/severe”.  

The timing of the asymmetry is also noted in the AIDE. 



C

Compensatory Lameness Patterns

Law of Sides 

Ipsilateral suggests 1º hind limb lameness - THIS IS TRUE!!!!! WATCH OUT

  • Compensatory FL can be of any type (impact, midstance, push off)

Contralateral suggests 1º forelimb lameness - This is partly true…  

Most Common

  • Compensatory contralateral HL decreased push off 

Less Common

  • Compensatory contralateral HL decreased push off and ipsilateral HL decreased impact
  • Compensatory ipsilateral HL decreased impact (note: this pattern could also be indicative of primary hind)

D

Diff Max Head

the difference in maximum head height that occurs before RF weight bearing compared to before LF weight bearing. Ref range: -6.0 to +6.0 mm

  • Measured in mm and reported as a mean value of all strides.
  • Diff Max Head determines timing of asymmetry (depending on sign of Diff Min Head).
  • Diff Max Head = Max height of head before RF weight bearing minus (-) max height of head before LF weight bearing. 

Diff Max Pelvis

the difference in maximum pelvis height that occurs before RH weight bearing compared to before LH weight bearing. Ref range: -3.0 to +3.0 mm

  • Measured in mm and reported as a mean value of all strides. 
  • RH asymmetries are assigned (+) values. LH asymmetries are assigned (-) values.  Elevated Diff Max (either + or -) correlates to a push off lameness in the hind limb. 
  • Diff Max Pelvis = Max height of pelvis before RH weight bearing minus (-) max height of pelvis before LH weight bearing.



Diff Min Head

the difference in minimum head height that occurs during RF mid stance compared to during LF mid stance. Ref range: -6.0 to +6.0 mm 

  • Measured in mm and reported as a mean value of all strides. 
  • Diff Min Head determines side of asymmetry (positive value = RF, negative value = LF). 
  • Diff Min Head = Min height of head during RF mid-stance minus (-) min height of head during LF mid-stance.

Diff Min Pelvis

the difference in minimum pelvis height that occurs during RH mid stance compared to during LH mid stance.Ref range: -3.0 to +3.0 mm

  • Measured in mm and reported as a mean value of all strides. 
  • RH asymmetries are assigned (+) values.  LH asymmetries are assigned (-) values.  Elevated Diff Min (either + or -) correlates to an impact lameness in the hind limb.
  • Diff Min Pelvis = Min height of pelvis during RH mid-stance minus (-) min height of pelvis during LH mid-stance 

H

Hard Surface

If the foot does not create a depression or a divot in the ground, the surface should be considered hard.  Hard preset surfaces = asphalt, concrete, packed dirt, gravel/stone, wood, frozen, treadmill, hard synthetic, hard (generic).



Head Sensor

The head sensor device contains an accelerometer that tracks vertical head acceleration.



I

Indications of Severity

Indications of severity are based on a general range of amplitude of lameness, with levels increasing from “very mild”, “mild”, “mild/moderate”, “moderate”, and “moderate/severe”.

  • “no” evidence: lameness measure is within reference range (see note**)
  • “strong” evidence: Reported when the standard deviation is less than 50% of the mean Diff Min head (since Diff Min Head determines the side of forelimb lameness, it is the more important measure to assess for variability); or Mean Diff Min and/or Diff Max pelvis. 
  • “moderate” evidence: Reported when the SD is between 50 and 120% of the mean.
  • “weak” evidence: Reported when the standard deviation is greater than 120% of the mean.

**The veterinarian should keep in mind that the severities are a range, and should not be used to compare two trials for consistency of amplitude (such as in establishing a stable baseline between two trials) or to assess change in amplitude (such as before and after a block, or change over time).



L

Lameness Metrics

quantitative data from the collected trial. Calculated lameness metrics include 1) mean values of Diff Max head, Diff Min head, Diff Max pelvis and Diff Min pelvis; 2) standard deviations for each respective mean Diff Max and Diff Min;  3) Total Diff Head (mean vector sum) of the forelimb data; and 4) The Q Score for both forelimb and hind limb data. 



P

Pelvic Sensor

The pelvic sensor device contains an accelerometer that tracks vertical pelvic acceleration.



R

Right Forelimb Sensor

The right forelimb sensor device contains a gyroscope that measures angular velocity in the sagittal plane. It is used as an event marker to determine right forelimb stance. It is also used to calculate a median stride rate.



S

Soft Surface

If the foot creates a depression or a divot in the ground, the surface should be considered soft.  Soft preset surfaces = loose sand, grass/turf, soft/deep, mud, soft synthetic, soft (generic). 



Stabilizing the Lameness

Following viewing the initial baseline straight evaluation, repeat the trial to confirm stability of lameness measurements! 

  1. When beginning an evaluation, it is advised to perform two straight line trials one after the other to confirm results, and, if lameness present, a stable lameness. 
  2. Horses fresh out of a stall or off of a trailer may not always show a stable lameness on the first evaluation.  
  3. There is also a small window of expected trial-to-trial variability. However, significantly different results between two trials are indicative of an unstable lameness. 
  4. If two trials back to back do not yield similar results in limb, timing, and amplitude, it is recommended to exercise the horse, such as lunging, for a few minutes and evaluate again. 

Stride Plot

the graphical representations of the trial data.



Stride-by-stride variability

the variability of the lameness measure (Diff Max Head, Diff Min Head, Diff Max Pelvis, Diff Min Pelvis) from stride to stride over the course of a single data collection trial. Stride-by-stride variability is assessed in the Lameness Locator® report by comparing the standard deviation to the absolute value of the mean for that measure. If the standard deviation is significantly greater than the mean (currently this is arbitrarily set at 120% of the mean), the confidence in, or strength of evidence for, lameness (in limb, amplitude and/or timing) is reduced.


T

The Quantification (Q) Score

the Q score is a summary of the side, timing and amplitude of the asymmetry. 

  • There is one Q score for forelimb and a combined Q score for hind limb (one for the pushoff component and one for the impact component). 
  • Note that Q Scores have no +/- sign.  The limb and timing in stride cycle is described directly – i.e. L/R (for Left or Right) and Imp/Mid/Push (for Impact, Midstance, or Pushoff) in forelimb and Imp or Push for hind limb.  
  • Q Scores do not assess variability. The user should still inspect lameness metric standard deviations (or the Trial AIDE statements) to understand the stride by stride consistency of asymmetry, which contributes to the overall evidence of lameness.

Total Diff Head (Vector Sum)

Can be considered the amplitude of total head movement asymmetry, taking into account both Diff Max and Diff Min of the head. 

As the side and timing of forelimb lameness is dependent upon both Diff Max Head and Diff Min Head, this single variable can be more easily used to estimate the overall level of forelimb lameness. 

Total Diff Head is the Vector Sum of the mean Diff Max and mean Diff Min values, and is calculated using Pythagorean Theorem (a2 + b2 = c2), where a is the value of Diff Max head, b is the value of Diff Min head, and c is Vector Sum. (a) is plotted on the X axis, (b) is plotted on the Y axis, and the hypotenuse that forms that triangle is the Vector Sum. Total Diff Head is indicated by the RED ray on the forelimb plot.

The Total Diff Head (Vector Sum) reference range is 0 to 8.5mm. The upper reference range value of 8.5 is derived from the VS calculation when Diff Max Head and Diff Min Head are at their upper reference range values of |6|.   62+62=VS2


Trial Metadata

Owner, horse, and trial specific data (including date, time and type of trial conducted).



Trial-to-trial variability

Trial-to-trial variability = the variability of the mean lameness measure between two trials. I.e. is the measure repeatable? Trial-to-trial variability is assessed by comparing the lameness measures between two trials and whether they are within the 95% confidence intervals of repeatability.  If a particular measure in two back-to-back trials is not within the 95% CI, then that lameness is not stable. 


“moderate” evidence

Reported when the standard deviation is between 50 and 120% of the mean.



“no” evidence

Lameness measure is within reference range. 

If asymmetry of head or pelvic movement is within reference range and the variability is very low, “weak or moderate evidence” of “very mild asymmetry” may be reported. Note that this is sub-threshold asymmetry, reported only as an alert to the veterinarian that very mild asymmetry with low variability is present. Only the veterinarian can confirm any asymmetry, above or below established reference ranges, as clinically significant lameness.



“strong” evidence

Reported when the standard deviation is less than 50% of the mean Diff Min head (since Diff Min Head determines the side of forelimb lameness, it is the more important measure to assess for variability); or Mean Diff Min and/or Diff Max pelvis. 


“weak” evidence

Reported when the standard deviation is greater than 120% of the mean.




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