Stress Distribution and Displacement of Craniofacial Structures Following Rapid Maxillary Expansion in Different Types of Cleft Palate: A Three-Dimensional FEM Study

Three-dimensional finite element analysis on stress distribution after different palatoplasty and levator veli palatini muscle reconstruction

OBJECTIVES

To establish a three-dimensional finite element model of the upper palate, pharyngeal cavity, and levator veli palatini muscle in patients with unilateral complete cleft palate, simulate two surgical procedures that the two-flap method and Furlow reverse double Z method, observe the stress distribution of the upper palate soft tissue and changes in pharyngeal cavity area after different surgical methods, and verify the accuracy of the model by reconstructing and measuring the levator veli palatini muscle.

MATERIALS AND METHODS

Mimics, Geomagic, Ansys, and Hypermesh were applied to establish three-dimensional finite element models of the pharyngeal cavity, upper palate, and levator veli palatini muscle in patients with unilateral complete cleft palate. The parameters including length, angle, and cross-sectional area of the levator veli palatini muscle etc. were measured in Mimics, and two surgical procedures that two-flap method and Furlow reverse double Z method were simulated in Ansys, and the area of pharyngeal cavity was measured by hypermesh.

RESULTS

A three-dimensional finite element model of the upper palate, pharyngeal cavity, and bilateral levator veli palatini muscle was established in patients with unilateral complete cleft palate ; The concept of horizontal projection characteristics of the palatal dome was applied to the finite element simulation of cleft palate surgery, vividly simulating the displacement and elastic stretching of the two flap method and Furlow reverse double Z method during the surgical process; The areas with the highest stress in the two-flap method and Furlow reverse double Z method both occur in the hard soft palate junction area; In resting state, as measured, the two flap method can narrow the pharyngeal cavity area by 50.9%, while the Furlow reverse double Z method can narrow the pharyngeal cavity area by 65.4%; The measurement results of the levator veli palatini muscle showed no significant difference compared to previous studies, confirming the accuracy of the model.

CONCLUSIONS

The finite element method was used to establish a model to simulate the surgical procedure, which is effective and reliable. The area with the highest postoperative stress for both methods is the hard soft palate junction area, and the stress of the Furlow reverse double Z method is lower than that of the two-flap method. The anatomical conditions of pharyngeal cavity of Furlow reverse double Z method are better than that of two-flap method in the resting state.

CLINICAL RELEVANCE

This article uses three-dimensional finite element method to simulate the commonly used two-flap method and Furlow reverse double Z method in clinical cleft palate surgery, and analyzes the stress distribution characteristics and changes in pharyngeal cavity area of the two surgical methods, in order to provide a theoretical basis for the surgeon to choose the surgical method and reduce the occurrence of complications.

A Three-Dimensional Finite Element Analysis of Displacement and Stress Distributions of Unilateral and Bilateral Cleft Lips by Using Developed Pre-Surgical Treatment Architecture

Cleft lips and cleft palates are the most common birth defects in newborns. Pre-surgical correction of unilateral and bilateral cleft lips and palates has been the subject of interest of many previous works. This condition has necessitated the evolution of many surgical and non-surgical techniques to mitigate the problem of this deformity in children. In this study, we proposed a new architecture that can be used instead of the conventional pre-surgical treatment. The proposed architecture has mechanical and electronic parts. This architecture was adopted to apply external stress to the cleft bones and cleft edges using an airbag that is located in the mechanical part. The amount of air in the airbag can be controlled by an available control unit in the electronic part. The effect of external stress on the cleft bones and the cleft edges was analyzed by using the finite element analysis (FEA) method. The FEA study aimed to analyze the displacement, amount of tensile and compressive forces, and Von Mises stress distributions on the cleft bones, cleft edges, nasal septum, and superior alveolar part of the maxillary jaw of unilateral and bilateral cleft models during pre-surgical treatment with the novel architecture. The results show that displacement and stress affected the clefts of both models. Displacement had a significant effect of gradually bringing the clefts closer to each other and returning them to the posterior. The analysis also investigated the effects of stress on the cleft bone and cleft edge. It was found from the results that the stresses helped to bring the incisions closer to the most appropriate position for plastic surgeons. The results prove that the positive and negative X-displacements move in the opposite direction, which means that the cleft edges gradually converge toward each other. Moreover, the negative Z-displacement affected the movement of cleft bones and cleft edges from outside to inside and gradually returned them to a suitable position. The findings show that the proposed architecture can be contributed to the pre-surgical treatment of the unilateral and bilateral clefts as an alternative to the traditional method.