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.
What Is S-M Distance?
S-M Distance measures the surface path length from a skin entry point (S-point) to the midline plane. The measurement follows the surface of the volume rather than a straight line through space, giving a more realistic sense of approach depth. The result is displayed in millimeters (mm).Requirements
S-M Distance is calculated automatically when both of the following are present:- At least one S-point (skin entry marker created via Skin Detection)
- A defined Midline plane (see Midline Tool)
Where the Distance Appears
The S-M distance for each S-point is shown in the right panel next to the corresponding S-point entry. If multiple S-points exist, each displays its own distance to the midline.Path Visualization
The surface path used for the measurement is drawn on the 3D volume as a colored line connecting the S-point to the nearest midline crossing. This lets you visually verify the path and confirm it follows the anatomy as expected.Comparing Approach Distances
When multiple arrows and S-points are placed on different sides or levels, S-M distances can be compared side by side in the panel. This makes it straightforward to assess which approach is shorter or more symmetric.| S-point | S-M Distance |
|---|---|
| S1 (Left L4) | 42 mm |
| S2 (Right L4) | 38 mm |
S-M Distance updates automatically when the midline or S-point position changes. No manual recalculation is required.