Sliding genioplasty step off?

Small horizontal advancements with a minimally angulated bone cut have a low risk of any significant step-off deformity.

The sliding genioplasty can be designed in a few ways; but the 'cut' in the bone will create a change in the contour 'until' the bone heals and 'remodels'. Typically, it will remodel smooth and without 'notching'. However, that also depends upon the 3D movements of the chin. Most importantly, some of us use thin strips of gortex or other methods to ensure a smooth contour on the sides and in the 'front' /ledge' area. Talk to the surgeon about it.