A sliding genioplasty is an effective multidimensional chin reshaping procedure. Because it alters the bone along the inferior border through a pedicle bone flap repositioning, the profile of the chin bone is changed. This profile change is commonly called the bony stepoff, which is most evident in significant forward advancements…although it occurs with any type of chin bone movement.
While the repositioned bone in a sliding genioplasty has a negligible incidence of non-union or bone healing problems, this does not mean that its full shape is restored. There will be bone gaps and contour changes that result. Almost all of these will have some minor aesthetic consequence. For example the sagittal effect of the bony step off is the collapse of the overlying soft tissue into it, potentially creating a deeper labiomental fold or lip tightness due to the soft tissue contracture into it.
While the ideal method to treatise contour changes from a sliding genioplasty is an autologous bone graft, this is not practical or desired by almost all patients. As a result surgeons have placed a wide variety of materials into these defects from synthetic implants to hydroxyapatite granules. I think as a general rule implant materials should probably be avoided as the goal should be partial or complete bone defect restoration.
A very obtainable and logical onlay and interpositional graft material to use is allogeneic or tissue bank bone grafts. Available in blocks and crushed chips they have proven to be effective gap fillers and I have yet to see an infection with their use. In moderate sliding genioplasty movements the corticocancellous chips can restore the bone contour adequately. Their particulated nature makes them easily adaptable to fill in any type of bone gap/defect. I typically mix them with antibiotic solutions to create more of a putty composition which molds into defects better.
In more major movements chin movements, either forward or vertically, a solid allogeneic bone block provides a stouter bone fill that is a complement to the bone fixation used. Bone blocks are not as easily adaptable to bone defects and usually require some shaping to do so. They can also be mixed with bone chips if desired to fill in and around the bone block.
While bone edges and defects do remodel to some degree after a sliding genioplasty, there is no reason to not help that process be better than it might naturally be. Rather than implants of any material or shape, tissue bank bone graft materials offer a biologic boost to the healing bone with a negligible risk of infection/rejection.
Dr. Barry Eppley