Conformity of the Actual to the Planned Result in Orthognathic Surgery

Virtual surgical planning has facilitated preoperative planning, splint accuracy, and intraoperative efficiency in orthognathic surgery. The translation of the virtual surgical plan to the actual result has not been adequately examined. The authors examined the conformity of the virtual surgical plan to the postoperative result. They hypothesize that the greatest conformity exists in the anteroposterior dimensions.

The authors examined patients who underwent Le Fort I maxillary advancement, bilateral sagittal split osteotomy, and genioplasty. The preoperative virtual surgical planning file and postoperative cone beam computed tomographic scan were registered in Mimics using unchanged landmarks. The conformity to the virtual surgical plan was quantified using linear and angular measurements between bone surface landmarks. Results were compared using t tests, with p < 0.05 considered statistically significant RESULTS:: One hundred patients who underwent Le Fort I maxillary advancement, bilateral sagittal split osteotomy, and genioplasty were included. Three-dimensional analysis showed significant differences between the plan and outcome for the following landmarks: A point (y, p = 0.04; z, p = 0.04), B point (y, p = 0.02; z, p = 0.02), pogonion (y, p = 0.04), menton (x, p = 0.02; y, p = 0.01; z, p = 0.03), and anterior nasal spine (x, p = 0.04; y, p = 0.04; z, p = 0.01). Angular measurements sella-nasion-A point, sella-nasion-B point, and A point-nasion-B point were not statistically different.

There is a high degree of conformity comparing the orthognathic virtual surgical plan to the actual postoperative result. However, some incongruency is seen vertically (maxilla) and sagittally (mandible, chin). Departures of the actual position compared with the plan could be the result of condylar position changes, osteotomy locations, aesthetic intraoperative decisions, and/or play in the system.