My question is how can I rotate only humerus bone (blue part in 3D). Right
now it rotates as a whole.
My second question is; Is there a better way to segment humerus bone apart
from whole? Because scissors kind of change the shape of humerus bone and I
dont want it to change.
Segmenting the humerus from MR will be a challenge. Probably the best is to get familiar with the various tools in the Segment Editor and see what works best for you.
Once you have the segmentation you can apply rotations with the Transforms module:
If you apply a transform to a segmentation node, the transformation is applied to all segments. To transform a segment separately, create a new segmentation node and copy or move the segment that you want to move separately into the new segmentation node (use Segmentations module Copy/move segments function).
Scissors is intended for pre- and post-processing. For accurate delineation of a bone, I would suggest to use the manual “Paint” effect or semi-automatic “Grow from seeds” effect.