Measuring a Distance
To measure a linear distance in a 2D or a 3D viewer:
Click Measure on the menu bar.
Click 
Distance. Alternatively, press [M].
Click the first point.
Notes
Right-click to cancel.
For a measurement on a 2D image that has not been calibrated, the calibration starts.
If the tip or the shoulder point of an implant is clicked, the measurement will be linked to that implant. When moving the implant, the linked measurement is updated.
Click the second point.
The point-to-point measurement is shown in the viewer and added to the smart panel 
Visibility tab. To edit the distance measurement, drag the control points. The value is updated accordingly.
Note
When an existing measurement is moved to the tip or shoulder point of an implant, it becomes a linked measurement.