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Documentation Index

Fetch the complete documentation index at: https://docs.spine.altician.com/llms.txt

Use this file to discover all available pages before exploring further.

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What Is the Midline?

The midline is a reference plane representing the body’s central axis — the line that divides the body into left and right halves. Once defined, it serves as a fixed reference for measurements and visual orientation.

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Defining the Midline

The midline is defined by drawing reference lines in two separate viewports (for example, one in the axial view and one in the coronal view). This two-point definition gives the plane full 3D orientation.
  1. Select the Midline tool from the toolbar.
  2. In the first viewport, click to draw a line along the center of the anatomy.
  3. Switch to a second viewport and draw a second reference line.
  4. The midline plane is calculated and displayed automatically.
For best accuracy, use bony landmarks (such as the spinous processes) as guides when drawing midline lines.

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Midline Display

Once defined, the midline appears as a translucent plane overlaid on the 3D volume. It is visible in both the main viewport and the Scouter viewport.

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Toggle Midline Visibility

Click the eye icon next to Midline in the right panel to show or hide the plane. Hiding the midline does not delete it — it remains defined and can be shown again at any time.

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Midline as a Measurement Reference

The midline is used automatically in the S-M Distance measurement, which calculates the surface path from a skin entry point to the midline. See S-M Distance for details.
The midline is a user-defined reference plane. It is not detected automatically from the anatomy — take care to draw the lines accurately along the intended central axis.