cause: insufficient downward growth of posterior maxillacure: bimaxillary rotation advancement with downgraft of post. maxilla.
why?as far as i know segmental leforts are mainly used to widen or shorten the maxilla. if you just want to rotate the entire thing and drop it down, you don't need to cut into pieces.
I think the OP thinks multiple chunks are taken out vertically. It's just one wedge-shaped slice of bone removed, AFAIK.