I believe a genioplasty can increase chin width, although it's not very commonly used. If the hardware used to secure the bone is placed laterally, then it will lead to a widening... I'm not sure this would be cosmetically pleasing though. Alternatively you can use bone grafts, harvested from another site such as the hip. You can bring the chin forward as with a standard genioplasty, then cut the osteotomy segment in half and move each laterally, leaving a gap for the placement of the harvested graft. I've never spoke to anyone who has had it done, but I hear it is possible.
