A sliding genioplasty is the autologous alternative to using a chin implant. It is done far less frequently than using implants for chin augmentation, and it should be, but it does have a defined role for lower facial augmentation. It is indicated for large chin movements which standard implants can not achieve, for young patients who need large amounts of chin augmentation and for existing chin implants that have developed complications.
A sliding genioplasty involves a bone cut below the anterior tooth roots and mental foramen which is done at various angles depending on the type of dimensional bone movement needed. As the bone moves forward it is important to appreciate that the labiomental fold will not move with it. The labiomental fold or groove, which is situated about 1/3 the distance from the lower lip to the bottom of the chin, is a fixed structure that is reflective of the attachment of the mentalis muscle to the chin bone over the incisor tooth roots. Its deepest part correlates to the depth of the vestibule on the inside of the lower lip.
As the chin bone comes forward with a sliding genioplasty, the labiomental fold ‘stays behind’. Thus it will get deeper with horizontal chin bone movements. This is due to the now ‘step’ shape of the chin which allows the lower part of the labiomental fold to stay where it is but the chin tissue beneath moves forward. One historic effort to deal with the deepening labiomental fold effect in a sliding genioplasty is to graft the step of the osteotomy. Many materials have been advocated and used but the hydroxyapatite block graft is one of the most historic. They have long been used in maxillofacial surgery as an interpositional or onlay graft which offers excellent biocompatibility due to its inorganic mineral content and interconnected material porosity.
A carved hydroxyapatite block to fill the step of a sliding genioplasty is an excellent graft choice. Its benefits are when the sliding genioplasty movement is significant, usually 10mms or greater where a large bone step is created. Part of the bone is covered in the midline by the fixation plate but the hydroxyapatite block is placed on top of it regardless. Bone will grow around the fixation plate and into the block.
Grafting the bone step of the sliding genioplasty is not the complete cure for preventing the deepening or for the treatment of the deep labiomental fold. It does, however, have some benefit and is a simple and uncomplicated adjunct to the procedure.
Dr. Barry Eppley
Indianapolis, Indiana