Fixation Methods for Mandibular Advancement and Their Effects on Temporomandibular Joint: A Finite Element Analysis Study

Abstract

Objectives: Bilateral sagittal split osteotomy (BSSO) is a common surgical procedure to correct dentofacial deformities that involve the mandible. Usually bicortical bone fixation screw or miniplates with monocortical bone fixation screw were used to gain stability after BSSO. On the other hand, the use of resorbable screw materials had been reported. In this study, our aim is to determine first stress distribution values at the temporomandibular joint (TMJ) and second displacement amounts of each mandibular bone segment.

Methods: A three-dimensional virtual mesh model of the mandible was constructed. Then, BSSO with 9 mm advancement was simulated using the finite element model (FEM). Fixation between each mandibular segment was also virtually performed using seven different combinations of fixation materials, as follows: miniplate only (M), miniplate and a titanium bicortical bone fixation screw (H), miniplate and a resorbable bicortical bone fixation screw (HR), 3 L-shaped titanium bicortical bone fixation screws (L), 3 L-shaped resorbable bicortical bone fixation screws (LR), 3 inverted L-shaped titanium bicortical bone fixation screws (IL), and 3 inverted L-shaped resorbable bicortical bone fixation screws (ILR).

Results: At 9 mm advancement, the biggest stress values at the anterior area TMJ was seen at M fixation and LR fixation at posterior TMJ. The minimum stress values on anterior TMJ were seen at L fixation and M fixation at posterior TMJ. Minimum displacement was seen in IL method. It was followed by L, H, HR, M, ILR, and LR, respectively.

Conclusion: According to our results, bicortical screw fixation was associated with more stress on the condyle. In terms of total stress value, especially LR and ILR lead to higher amounts.

Figure 1

Illustrations of seven different fixation techniques used in this study. Rightmost panel: white rings show the locations of the insertion areas of the screws.

Figure 2

Example of fixation method with the highest stress value recorded at the posterior area of TMJ: LR fixation and stress values at both areas of TMJ.

Figure 3

Example of fixation method with the lowest stress value recorded at the anterior area of TMJ: L fixation and stress values at both areas of TMJ.

Figure 4

Example of fixation method with the greatest stress value ratio of posterior to anterior area of TMJ: IL fixation and stress values at both areas of TMJ.

Figure 5

Exemplary comparison of the maximum stress values with total relapse values at the mandibular segments.