[Extreme chin advancement with tandem genioplasty].

Chin correction is an important procedure in orthognathic and facial plastic surgery. Whereas simple genioplasty can be easily performed by sliding or jumping osteotomies, extreme chin advancement, i.e., an advancement greater than 10 mm, requires the use of the double-step sliding technique. Independent of the fixation technique chosen these bony segments tend towards instability when being pedicled on the periosteum and the posterior muscle attachments. The traction force of the geniohyoid, genioglossus and digastric muscles is responsible for the instability of the advanced segments. To compensate for this muscle force a special double-step osteotomy was developed that combines the sliding and jumping osteotomy and allows the positioning of the pedicled basal chin segment in front of the mandible. Using this new tandem genioplasty, six cases of retrogenia with an advancement of 16 to 20 mm were corrected. The only complications in one case was mild wound dehiscence of the mucous membrane of the mandible's frontal vestibulum.