When significant lengthening of the chin is needed the opening wedge bony genioplasty is the best procedure to do so. In this procedure the chin bone is cut with a horizontal osteotomy and down fractured. The desired vertical lengthening is then set by the application of a fixation plate c reating a bony gap between the two bone segments. The downfractured chin segment, contrary to the perception of some, is not a free floating piece of bone. It remains as a live bone segment due to the attachments of the soft tissues to its inferior and lingual sides of the bone.
While the down fractured chin bone remains alive the gap between the two bone segments will not fill in with bone as it heals. The interpositional gap is too big for the bone to jump across it. It has no substrate or lattice to which it can attach and be helped to walk across with new bone. For this reason I always placed a bone graft between the segments which should help recreate a bony union across the gap underneath the fixation plate. While the patient’s own bone may be ideal no patient wants a harvest site. Thus I use a cadaveric or allogeneic corticocancellous bone block which can be shaped to fit into the size and shape of the gap. Shaping of such a a bone graft its done with a reciprocating saw. This allows for good bone contact particularly in the central two-thirds of the gap.
While placing such a bone graft is sound biologically his well does it create bone healing across bone gaps of significant size? (10 to 15 mms) Having seen numerous vertical lengthening bony genioplasties progress onto other jaw surgeries (custom jawline implants) I have had the opportunity to assess the bone healing from the 3D CT scan necessary for the implant design. At one year after placement considerable bone healing is consistently seen particularly in the central 2/3 s of the gap. (where the graft actually is) The graft reaches out to the very end of the osteotomy cut as it narrows down considerably in size.
Even in extremely large vertical chin lengthening (18 to 2omms) significant bone graft healing is seen across much of a very large bone gap.
The use of a cadaveric bone graft in vertical lengthening genioplastiues avoid a bomb graft harvest and provides a structural lattice for osteocytes to cross between the two bone segments and encourages new bone formation.
Dr. Barry Eppley
World-Renowned Plastic Surgeon