Fig 1.
Principles of single-splint two-jaw orthognathic surgery.
Both maxilla and mandible are completely osteotomized, fixed in the final dental splint and moved as a united “maxillo-mandibular complex” (MMC) to the desired position. The maxillary segment is then referred to as the Le Fort I segment, and the mandible consists of two proximal (ramus) segments and one distal segment bearing the dental arch and the neurovascular bundle after osteotomy. The rotation movements are described as pitch, roll and yaw, en-bloc linear horizontal movements as left and right shifts or advancements and setbacks in the antero-posterior direction, and en-bloc linear vertical movements as extrusion and intrusion according to the movement in relation to the skull base.
Fig 2.
In the first step, the patient’s initial preoperative Cone-Beam Computer Tomography (CBCT) defines Position0. After segmentation, the conventional orthodontic 2D plan is transferred into the 3D simulation and recorded as Position1. The transferred plan is then adjusted for roll, midline, pitch, yaw, and genioplasty positions by the surgical team, and the resulting 3D simulation is noted as Position2. The changes in each parameter from Position1 to Position2 are recorded and evaluated.
Fig 3.
Visualization of the three positions in sample patient #25 (Table 1).
Isolated cleft palate patient. From left to right frontal, left lateral, right lateral and basal views are shown of the same position. Subfigures A-D show the initial Position0, Subfigures E-H the result of the 2D plan translation into the 3D environment and Subfigures I-L the adjusted Position2 in the 3D plan agreed upon by the orthodontists and the surgical team. Note the severe bony collision in the right ramus area of this patient in Subfigures E and G and the subsequent large bony gap in the left ramus area. Through counterclockwise yaw rotation the collision and overall asymmetry were resolved (Subfigures H and L, E and I). The genioplasty position was altered by shortening the chin segment, thus reducing the patient’s facial height (Subfigures I-L).
Fig 4.
Visualization of the three positions in sample patient #29 (Table 1).
Bilateral cleft lip/palate patient. From left to right frontal, left lateral, right lateral and basal views are shown of the same position. Subfigures A-D show the initial Position0, Subfigures E-H the result of the 2D plan translation into 3D environment and Subfigures I-L the adjusted Position2 in 3D simulation agreed upon by the orthodontists and the surgical team. Bony collisions were not seen in this patient, but a yaw correction of 2° counterclockwise seen from basal Subfigures H to L was implemented.
Fig 5.
English (Fig 5a) and Chinese (Fig 5b) versions of the OQLQ questionnaire measuring the patient’s dentofacial deformity in relation to their quality of life. It consists of a 4-point scale ranging from “bothers you a little” (score 1) to “bothers you a lot” (score 4). If the patient did not feel impaired by the subject (“does not apply, does not bother me”), it was rated as N/A or 0 points. Ranging from 0 to 88, lower OQLQ scores indicate better and higher score indicate poorer quality of life. The 22 items cover 4 topics: facial esthetics (items 1, 7, 10, 11, and 14 scoring 0 to 20), oral function (items 2–6 scoring 0 to 20), awareness of dentofacial esthetics (items 8, 9, 12, and 13) scoring 0 to 16), and social aspects of dentofacial deformity (items 15–22 scoring 0 to 32) [30].
Fig 6.
Pie chart of patients with different amounts of position changes.
According to the changes from Position1 (2D planning) to Position2 (3D simulation), 5 (16.7%) patients underwent no change, 6 (20.0%) had a change in one, 16 (53.3%) had a change in two, 1 (3.3%) had a change in three and 2 (6.7%) had a change in four parameters (Fig 4). 26 (83.3%) patients underwent the procedure with at least one modification of the initial 2D planning, while 16.7% had no changes from the 2D plan.
Fig 7.
Frequency of parameter changes in the patients.
Most frequently changed parameter was yaw rotation (19 patients, 63.3%), followed by midline adjustment (11 patients, 36.7%), roll rotation (9 patients, 33.3%), genioplasty position (6 patients, 20.0%) and pitch rotation (3 patients, 10.0%). Of the 11 patients that had a modification of the midline from 2D to 3D planning, 6 (45.5%) had a movement over 2 mm, 5 (45.5%) between 1 to 2 mm, and 1(9.0%) under 1 mm.
Table 1.
Patient information and 2D cephalometry plan for orthognathic surgery.
Table 2.
Parameter changes from 2D planning to 3D simulation in the CL/P subgroups.
Table 3.
Total and subitem OQLQ scores in the unilateral cleft lip/palate, bilateral cleft lip palate and isolated cleft palate group.
Fig 8.
Position analysis of the Le Fort I segment of sample patient #29 (Table 1).
Bilateral cleft lip/palate patient. The 3D position of the Le Fort I segment in relation to the superior fixed part of the maxilla is recorded in both lateral and piriform areas to facilitate proper positioning of the MMC during surgery. Midline shifts in the patient’s right lateral pillar and impaction of the left piriform aperture (Fig 5a) are noted as well as the different amounts of advancement or setback in both left and right lateral and piriform levels (Fig 5b). This information is the result of the 3D alternation of the MMC and helps to transfer the results of 3D simulation into the surgical setting.