The sliding genioplasty is a well known chin reshaping procedure that has its origins in the weak chin were advancement of the bone was needed. In this more straightforward application wire ligatures were originally used to hold the cut bone into its new position. Such wire ligature fixation was replaced with more rigid forms using plates and screws now for the past three decades. Some of that has been due to the development of very use friendly plate and screw systems, the improved stability that they provide and that bony genioplasties today are much more aesthetically ‘complex’ for some patients that just moving the chin bone forward.
Today two basic forms of genioplasty bone fixation techniques are used, a plate and screws or lag screws only. The former constitutes the majority seen because of its easier application. Lag screw fixation is less popular as it is more technique sensitive. Both fixation methods will work, as defined by the bone healing, but each has their own advantages and potential disadvantages.
In the November 2021 issue of the Plastic and Reconstructive Surgery journal an interesting technique article on this topic was published entitled ‘Osseous Genioplasty: Prevention of Witch’s Chin Deformity with No-Degloving Technique’ In this paper the authors compared traditional stair step plate fixation with that of lag screw fixation in fifty (50) consecutive patients with equal numbers in each fixation group. They looked at a variety of postoperative measures including advancement, vertical height, complications, presence of witch’s chin, surgeon’s assessment and patient surveys. The relevant differences between the two groups came down to a higher incidence of witch’s chin in the stair step plate fixation group and better patient satisfaction scores in the lag screw fixation group.
The premise of this paper is that lag screw fixation can be done with less soft tissue stripping which leads to less risk of postoperative chin soft tissue sagging. While this premise seems simple and straightforward, it is not. One observation I have made over decades of doing this procedure is that most surgeons way over deglove the soft tissues to perform the procedure. It simply isn’t necessary to do so. One should create the same exposure to do either lag screw or plate fixation. Surgeons should be doing a ‘less invasive’ bony genioplasty if they are willing to make the effort and learn how to do it with more of a tunnel technique. Just because it is done intraorally with no visible external scar shouldn’t be a license to widely strip off a lot of soft tissue simply because the view is better. Then the risk of soft tissue ptosis, with the exception of setback genioplasties (which shouldn’t be done anyway), is virtually eliminated.
The problem that I have always seen with lag screw fixation of the chin and undoubtably why it is not more widely used is that control of the position of the mobilized chin segment is not as dimensionally versatile. In the end what counts is what is the exact 2D positioning of the chin (projection and height changes) compared to the superior stable chin segment that is needed to achieve the aesthetic effect the patient desires. Too often I see patients for genioplasty revision with lag screw fixation where it is clear getting the mobilized chin segmented lagged to the superior chin segment took precedence over what was a better aesthetic chin position. Because of the angled bone cut the chin has been brought forward and vertically shortened, often unfavorably so. Using lag screw fixation is more challenging, and even potentially limiting, when significant vertical lengthening of the chin is needed.
Like all adjunctive surgical techniques, of which bone fixation devices are, their effectiveness is multifactorial. But they are to easy to isolate and quantitate because they can be radiographically seen. Whether their postoperative visibility always tells the full story is less clear.
Dr. Barry Eppley