Computer-Aided Surgical Simulation for Yaw Control of the Mandibular Condyle and Its Actual Application to Orthognathic Surgery: A One-Year Follow-Up Study

Abstract

Background: Favourable occlusal interdigitation and an optimized position of the mandibular condyle after surgery are essential for obtaining favourable results. The position of the condyle is determined during the operation. However, it is difficult to maintain the condyle’s original position post-surgery despite the efforts of the surgeons. Indeed, a degree of rotation of the condyle is unavoidable, since it is difficult to verify whether the condyle is positioned correctly during surgery. Purpose: To maximize contact between the bone segments, the condyle was rotated around the vertical axis using surgical simulations. We examined changes to the condyle-fossa relationship after comparing virtual surgery to actual surgery. Methods: From 2015 to 2017, 20 patients were diagnosed with skeletal malocclusion and participated in computer-aided surgical simulation before undergoing orthognathic surgery. In the simulation, the mandibular condyles were rotated around the vertical axis, and the proximal segments were fixed to the distal segments using a customized miniplate and positioning device during actual surgery. This study investigated the relationship between the condyle and fossa using cone-beam computed tomography for several different time periods (preoperative (T0), virtual surgery (Tv), postoperative three days (T1) and one year (T2)). Results: The coronal and sagittal view exhibited significant differences in the mean values between T1and T0, Tv, and T2 for all joint spaces. As a result of the distance, the mean value of T2 in both the superior joint space (JS) and the lateral JS was significantly higher than that of Tv. In contrast, the mean value of Tv in the medial JS was significantly higher than that of T2. Moreover, the mean value of T2 on the axial plane was significantly larger than the values of Tv and T1. The mean value of T0 was also significantly larger than those of Tv and T1, and the mean value of Tv was larger than that of T1. Although the condyle was rotated, it exhibited a tendency to return to its preoperative position. There was no statistically significant difference in functional evaluation between T0 and T2. Conclusion: Our method of using yaw control for the condyle during virtual surgery and transferring this technique to the actual surgery can improve the conventional surgical technique by positioning the proximal segment in a pre-planned position, thus achieving optimal results.

Comparison of Changes in the Condylar Volume and Morphology in Skeletal Class III Deformities Undergoing Orthognathic Surgery Using a Customized versus Conventional Miniplate: A Retrospective Analysis

“…In the CP group, plates were premade according to the preoperative 3D diagnosis and design ( Figure 2 and Figure 3 ). During OGS in the CP group, condyle positioning was performed using a customized plate and proximal segment positioning device [ 14 ], not the method used in the NCP group.…”

Application of optimized digital surgical guides in mandibular resection and reconstruction with vascularized fibula flaps

“…It has been proven that using a preformed reconstruction plate has many advantages relative to a manually bent plate in operation, such as fractures, tumor resection, orthodontic surgery, and implant surgery. [ 6 , 15 – 17 ] However, even experienced surgeons face difficulty in placing the preformed plate in the same position as its preoperative design because of unstable bone segments and the lack of effective stabilization after the tumorectomy stage. In this project, a specially designed reconstruction guide template solved the difficulty of placing the preformed titanium plate via determinations during preoperative virtual design.…”

“…Many studies have reported a high success rate of mandibular reconstruction with digital surgical techniques, including surgical navigation and 3-dimensional (3D) digital guide technology, [ 4 – 6 ] which have markedly improved the precision and minimally invasive performance of modern oral and maxillofacial surgery. For instance, using a reconstructed three-dimensional skull model to pre-bend the titanium plate could assist correction of mandibular defects to a certain extent and check the effect of bond repair.…”

Correction of Condylar Displacement of the Mandible Using Early Screw Removal following Patient-Customized Orthognathic Surgery

“…In our recent study, the condyle position was adjusted to establish the optimal relationship between the proximal and distal segments during mandibular virtual surgery. However, there were cases wherein the condyle–fossa relationship after the operation was not similar to that after the virtual surgery [ 19 ].…”