To analyze the stability of different internal fixation methods for zygomaticomaxillary complex fracture using finite element biomechanical analysis and to provide a quantitative basis for the option of optimal internal fixation methods.

One patient with zygomaticomaxillary complex ZMC fracture (Zingg B type) was enrolled from the Second Hospital of Dalian Medical University in October 2016.The zygomaticofrontal suture and the inferior orbital rim were fixed during the surgery, and the postoperative function was well recovered with no mouth opening restriction, diplopia or implant displacement, and had a symmetrical facial appearance.The preoperative orbital CT images were collected.The normal craniofacial bones finite element model (FEM/intact) was reconstructed through Mimics, Geomagic, Solidworks and Abaqus softwares based on the non-fractured side and verified.Based on the verified model, the segmentation and assembling was performed according to the fracture location, and the internal fixation models were established according to the methods of surgery, including fixed zygomaticofrontal suture model (FEM/ZFS), fixed inferior orbital rim model(FEM/IOR), fixed zygomaticofrontal suture and inferior orbital rim model (FEM/ZFS+ IOR), fixed ZFS and IOR and zygomaticomaxillary suture model (FEM/ZFS+ IOR+ ZMS). The masseter muscle strength was applied to the model.The stress and displacement were analyzed and the rotation angle of zygoma was calculated to compare the stability of different operative methods.The postoperative model (FEM/post) was established according to the actual operative method and was compared with FEM/ZFS+ IOR.This study protocol was approved by the Ethic Committee of The Second Hospital of Dalian Medical University (2020-33), and written informed consent was obtained from the subject before entering the study.

The established FEM/intact had a realistic appearance and good geometric similarity, and the validity and accuracy of model was verified.In the FEM/ZFS+ IOR and FEM/ZFS+ IOR+ ZMS, the maximal stress of the titanium plate was 396 MPa and 426 MPa, respectively, which was lower than the yield strength 483 MPa of pure titanium, and the maximal displacement of the fracture line was 0.10 mm and 0.06 mm, respectively, which was both≤0.1 mm, and the rotation angle of zygoma was both<2°.In the FEM/ZFS and FEM/IOR, the maximal stress of the titanium plate was 730 MPa and 501 MPa, respectively, which was higher than the yield strength of pure titanium; the maximal displacement of fracture line was 0.27 mm and 0.15 mm, respectively, which was >0.1 mm, and the rotation angle of zygoma was <2°.The results of FEM/post were consistent with those of FEM/ZFS+ IOR.

The finite element analysis can perform digital analysis and evaluation of the stability of different internal fixation methods before surgery, which is available for the selecting of the optimal fixation methods.Finite element analysis can provide an objective quantitative basis for the precise treatment of zygomaticomaxillary complex fractures.

Zygomatic fractures; Orbital fractures; Fracture fixation/internal; Biomechanics; Finite element analysis