I'm trying to understand what the difference is. Isn't that just a type of sliding genio procedure?
A slide is usually an angled cut where the bone is
slid onto itself and some
bone contact remains. There is some shortening of the chin with a 'forward' slide to project outwards. There is some elongation to the chin with backward slide BUT with loss of forward projection.
Although one can still make an angled cut to DROP DOWN the chin, as to not actually slide it BACKWARDS a spacer block or graft needs to be buttressed between where it was cut. Buttress materials can vary, eg. bone from spine of pelvis, calcium hydroxy appatite blocks, sometimes porex...something where the cut and SEPARATED bone segments have contact with something else.
However, some docs might elect to do the sliding (backwards) genio to elongate and then compensate with lost forward projection with a chin implant overlay.