The use of a sliding genioplasty for chin reshaping dates back half a century and is the most recognized facial osteotomy procedure. Unlike jaw surgery which affects the tooth-bearing part of the jaw and introduces some restrictions with mouth opening, downfracturing the mandibular symphysis (chin) does not. The chin bone is the only true aesthetic component of the lower jaw which can be manipulated with no functional sequelae.
Repositioning of the downfractured chin segment into the desired chin position has is usually done by plate and screw fixation. While a few surgeons use the bicortical screw fixation technique, this is not nearly as versatile as the use of the standard chin step plate which offer greater and more predictable dimensional changes. While a variety of different sliding genioplasty plates exist, they all are fundamentally step configurations.
While applying the chin plate seems straightforward, there are application techniques that make it easier. Trying to apply the plate to the superior fixed bone segment first and then securing the downfractured chin segment to the stabilized plate seems like the logical approach, it is not. The downfractured chin segment rarely moves forward easily as it remains attached to the tongue and neck musculature. It is also a smaller segment of bone that is hard to get a good hold of it. As a result I find it better to apply the plate first to the downfractured chin segment. It can then be used as a handle to put the chin bone forward and get the superior holes of the plate up and in position in front of the superior chin segment.
This technique becomes a little harder the longer the horizontal plate length is. But putting the superior holes behind the superior chin segment on its lingual surface helps put the inferior holes in good alignment on the mobilized chin segment.
Dr. Barry Eppley