Knowledge Base

Classify Toes

Interactive Footprint Measurements

Classification of toes is done in the Interactive Footprint Measurements. Toe classification of the hind paws (by measuring the Toe Spread, Intermediate Toe Spread, and Print Length) can be used to calculate the Sciatic Functional Index, Peroneal Functional Index, and Tibial Functional Index. The Sciatic Functional Index is commonly used as a tool for the evaluation of the recovery of the sciatic nerve.

You first need to label a paw print before you can classify its toes. You need the Interactive Footprint Measurements module to be able to classify toes.

Choose Acquire > Interactive Footprint Measurements.

In the Interactive Footprint Measurements, you can measure the following:

• Toe Spread – This is the distance between the first and fifth toe of a hind paw.
• Intermediate Toe Spread – This is the distance between the second and fourth toe of a hind paw.
• Manual Print Length – This is the distance between the third toe and the heel of a hind paw. This parameter is different from Print Length, which is the length (in the horizontal direction) of the complete print.
• Paw Angle Body Axis – This is the angle of the paw relative to the orientation of the body axis of the animal.
• Paw Angle Movement Vector – This is the angle of the paw relative to the direction of movement of the animal. The Movement Vector is a more accurate measure of the actual walking direction of the animal. The Movement Vector is calculated by performing linear regression of the center-of-gravity of the body contour in the current frame and in the three preceding frames.

Procedure

1. Choose Acquire > Interactive Footprint Measurements.
2. Under Trial Run Selection, select a classified trial and run from the list, or click the Previous/Next buttons to navigate to the trial and run you want to measure.
3. Under Footprint Type Selection, select the paw prints you want to display. By default, both hind paws are selected.
4. Click the paw you want to classify. The Footprint view displays a zoomed-in picture of the complete paw. The paw print consists of all frames of that paw, whereas the Body Axis view only shows the frame at Max Contact; therefore, the paw prints can be different. The Body Axis view shows the frame with the Max Contact of the corresponding paw with the body contour and body axis of the animal. It also shows the Movement Vector as a red arrow.
5. In the Footprint view, you can measure the following parameters:
   • Toe Spread – This is the distance between the first and fifth toe of the hind paw. To measure Toe Spread, click as close as possible to the center of the first toe, move the mouse cursor as close as possible to the center of the fifth toe and click, and next select Toe Spread from the menu.
   • Intermediate Toe Spread – This is the distance between the second and fourth toe of a hind paw. To measure the Intermediate Toe Spread, click as close as possible to the center of the second toe, move the mouse cursor as close as possible to the center of the fourth toe and click, and next select Intermediate Toe Spread.
   • Manual Print Length – This is the distance between the center of the third toe and the heel of a hind paw. To measure Print Length, click as close as possible to the center of the third toe, move the cursor as close as possible to the heel of the paw print and click, and next select Print Length from the menu. If your animals do not show the heels in the Footprint view, draw the line from the third toe to between the proximal pads because that is in the direction of the heel, and stop where the print ends. Be consistent with this definition across the animals. When you next measure the third parameter, it is automatically assigned the remaining label.
   • Paw Angle Body Axis – This is the smallest angle between the Print Length line and the white line representing the body axis of the animal as displayed in the Body Axis view.

Classify Runs

Paw Angle Movement Vector

The Paw Angle Movement Vector is the smallest angle between the Print Length line and the red line representing the direction of movement of the animal as displayed in the Body Axis view.

Classifying Paws and Toes

1. Under Parameters, select Show parameter values to display the values of the parameters.
2. Optionally, in the Body Axis view, you can change the orientation of the body axis by moving one of the sides of the body axis line to a new position. When you do this, the Paw Angle Body Axis, displayed under Parameters, is instantly updated.
3. Go back to the previous step to proceed with the next paw and repeat the steps for all paws you want to classify.
4. Under Functional Index Settings, select the experimental paw from the list for calculation of the Sciatic Functional Index.
5. Click OK when you are finished with classifying toes for the current run.

In the top view with all the paw prints, a print with classified toes has a green border, and a print with unclassified toes has a white border.

Correct Measurements

Remove a Measurement

In the Footprint view, click a line and select Remove.

Move a Line

Both in the Footprint and Body Axis view, click on one of the end points and drag it to the new position.

Classification Status Icons

In the Experiment Explorer, the following symbols allow you to check the classification status of trials and runs.

Trials

The check mark at the top indicates whether the trial is compliant. The check mark at the bottom indicates whether the trial contains classified runs.

Runs

The check mark at the bottom indicates whether the run has been classified.

• Orange check mark below the compliant trial check mark: Not all runs in this trial were completely classified.
• Green check mark below the non-compliant trial check mark: All runs in this trial were completely classified.
• One green check mark: This trial has both been completely acquired and classified.
• Orange check mark below the green compliant check mark (Run): The run has been partially classified.
• Green check mark below the green compliant check mark (Run): The run has been completely classified.

Source: CatWalk XT 11.0 Reference Manual - Classify Runs, Noldus Information Technology