Digital Analysis And Anatomical Studies On The Reduction Malarplasty With L-shaped Osteotomy

Objective1. The Reduction Malarplasty with L-shaped Osteotomy has been widely used in clinical practice for nearly20years, but research on this is very rare.In our exploratory study, we aimed at the following aspects:2. To compare the morphology changes of the craniofacial structures before and after the Reduction malarplasty with L-shaped osteotomy, based on measurements and analysis of the three-dimensional CT imaging and submentovertex view radiograph.3. To establish three dimensional finite element model of the Reduction Malarplasty with L-shaped Osteotemy, and to explore biomechanical characteristics of the surgery.4. To evaluate the extent of the sensory function of the zygomatic facial area affected by the surgery.5. To study the anatomy relationships among the nerves and blood supplies which related with the zygomaticofacial foramen.Methods1. Preoperative and postoperative CT data of24patients who received the Reduction Malarplasty with L-shaped Osteotomy were measured and analyzed to find the morphology changes of the craniofacial structures with the three-dimensional selected points method and the three-dimensional registration method.2. Based on the cephalometrics principles, we designed and manufactured a cephalometer chair for submentovertex view radiograph positioning.3. Preoperative and postoperative submentovertex view cephalometric radiographs of17patients who received the Reduction Malarplasty with L-shaped Osteotomy were measured and Image processed to compare the morphology changes of the craniofacial structures.4. Followed by the three dimensional reconstruction and L-shaped osteotemy simulation remeshing, and material properties assignment, the3D finite element model of the Reduction Malarplasty with L-shaped Osteotemy was established, which were based2patients’ CT data. The FEA model was carried out biomechanical analysis under the load of simulated zygomatic pressure.5. The sensation measurements and surveys were done to the34patients preoperative and postoperative10days respectively, to assess the changes of the sensory function in zygomaticfacial area.6.26dry skull specimens and6fresh skull specimens were respectively anatomical studied to find the Reduction Malarplasty with L-shaped Osteotomy related structures connections and distribution characteristics, which is like the zygomatic foramen, zygomaticofacial nerve, zygomaticotemporal nerve, infraorbital nerve, temporal branch and zygomatic branch of facial nerve, zygomaticofacial artery etc.Results1. By using the three-dimensional selected points method measurement, significant differences were found in five indicators before and after the Reduction Malarplasty with L-shaped Osteotomy, and they were:the distance between the bilateral zygomatic process (zp-zp), the distance between the bilateral midpoint of the zp and zy (mpy-mpy), the bilateral distance from zygomatic process to porion (po-zp), the zygomatic process angle (∠n-zp-po), and the zygomaticofrontal index (zp-zp/ft-ft).2. By using the three-dimensional registration method measurement, a common trend of morphology changes of the craniofacial structures was showed:the maximum difference was located just outside of the zygomaticomaxillary suture; from this area to the superolateral area, the difference was gradually decreases like a series of concentric circles. Till the root of the zygomatic arch, the difference decreases to the tolerance.3. By using the submentovertex view cephalometric radiographs,significant differences were found in five pairs of indicators before and after the Reduction Malarplasty with L-shaped Osteotomy, and they were:the distance from the Most forward point of the zygomatic body to the X-axis distance (3-X), the distance from the zygomatic process point to the X-axis (4-X), the distance from the zygomatic process point to the Y-axis(4-Y), the distance from the midpoint of the zygomatic process point and the zygionto to the Y-axis (5-Y), the zygomatic process root angle: the angle between the line connected with the zygomatic process point to the point of the root of the zygomatic arch and the X-axis (∠4-7-X).4. By using Image processing and analysis of the two-dimensional image of the submentovertex radiographs, a common trend of change was showed:the variable starting from the middle of the zygomatic arch, gradually increasing to the anterior part, and to the zygomatic process, the change reaches the maximum, and then to the anterior area,it gradually decreases. The postoperative zygomatic contour tends to be more smooth, and its degree of bending is reduced compared with the preoperative ones.5. Through the application of digital technology, the use of three-dimensional CT data synthesis clear two-dimensional submentovertex radiographs image. There is no obviously significant difference in the measurement data obtained with the same cephalometric from the two kinds of submentovertex radiographs images.6. The two3D finite element models were established. The deformation analysis revealed that:from the root of the zygomatic arch to the anterior of the zygomatic body, the inward displacement gradually increasing;the maximum amount of displacement were on the zygomatic osteotomy end vertex. Stress analysis revealed that:a single independent stress was concentrated in the root of the zygomatic arch area.7. From the sensation measurements and surveys, there is no significant changes were found preoperative and postoperative10days in the zygomaticfacial area.8. There were complicate relationship among the zygomaticofacial nerve and the zygomaticotemporal nerve, infraorbital nerve, facial nerve. There were communications between the ones adjacent each other.9. The out-bone segment of the zygomatic facial artery is divided into a deep branch and superficial branch:the deep branch close and beyond the periosteum, towards the rear along the zygomatic arch; the superficial branch were closely accompany with the branch of the zygomaticofacial nerve. 10. The zygomaticofacial artery and the zygomaticotemporal artery originate from the anterior branch of the deep temporal artery of the maxillary artery in Chinese people.Conclusion1. Significant craniofacial morphology changes can be found post the Reduction Malarplasty with L-shaped Osteotomy:the changes of the protrution and width of the zygomatic body were the most obvious, the inward displacement of the anterior and middle part of the zygomatic arch were also very obvious. But the root of the zygomatic arch almost remained stable, and there is no significant changes on their width.2. The submentovertex radiographs cephalometric and image processing methods can meet the general needs of the clinical diagnosis, treatment and the follow-up of the ordinary cosmetic surgery of the zygomatic complex.3. Pressing the zygoma in the Reduction Malarplasty with L-shaped Osteotemy can lead to an expected greenstick fracture just on the root of the zygomatic arch, which result in an inward and lower deformation.4. The Reduction Malarplasty with L-shaped Osteotomy is usually not cause significant impact on patients’zygomaticofacial sensation function.5. The Zygomaticofacial nerve has very complicate communication and adjacent relationship with the infraorbital nerve, the zygomaticotemporal nerve, and the facial nerve. They may have some compensatory function for the zygomaticofacial nerve. The facial nerve maybe play a significant role of sensory function in the zygomaticfacial and the infraorbital area.