'Rotational' Genioplasty to correct jaw (face) asymmetry ? What is it ?

Hi all, Having visited a surgeon recently about my facial asymmetry he conclude my mandible is off 'one incisor' to the left giving my mandible an asymmetric appearance . He gave me 2 options: 1. Mandibular osteotomy following 12 months of braces . 2. A rotational genioplasty which would correct 90% of my asymmetry. He said given my good bite he would personally go for the genioplasty. Can anyone tell me what a 'rotational genioplasty' is ? Apparently very few surgeons perform it. Thanks!