The hierarchy of stability and predictability in orthognathic surgery with rigid fixation: an update and extension

The Dentofacial Program at the University of North Carolina was begun in 1975 as a way to coordinate the evaluation and treatment of patients who needed orthodontics and orthognathic surgery, and as a way to facilitate research in this area. A research grant focused on the outcomes of orthognathic surgery at UNC, funded by the National Institute of Dental and Craniofacial Research, enters its 28th year in June 2007.This research project has resulted in more than 100 research papers in peer-reviewed journals, and about half that many invited contributions and book chapters. It became obvious by the 1990s that a major influence on the outcomes of orthognathic surgery was the amount and direction of surgical movement. A series of research papers that focused specifically on stability as related to the different surgical movements was summarized in 1996 in a paper outlining a hierarchy of stability related to surgical movements [1]. The purpose of this paper is to update the hierarchy by extending it to include treatment of asymmetries and provide further information with regard to long-term stability.The data base created through this project currently (February 2007) has records on 2264 patients who have had orthognathic surgery. Nearly twice that many have had initial records through the Dentofacial Program after they were referred for evaluation. Many of these were judged not to need surgery; the remainder did not accept it if it was recommended [2,3]. As of February 2007, at least one year follow-up is available for 1475 patients who did receive surgery, and five year or longer postsurgical follow-up is available for 507 patients.Stability has been evaluated primarily from lateral cephalometric radiographs, which for all our studies have been oriented with the SN line rotated down 6° anteriorly, a position that approximates natural head position and is more reproducible than the Frankfort plane. This horizontal line is used as the x axis, and a vertical plane perpe