Finite element analysis of type B condylar head fractures and osteosynthesis using two positional screws

Abstract

Objective: The aim of this study was to explore the cause of type B condylar head fracture after parasymphyseal impact, and evaluate the biomechanics of osteosynthesis using two positional screws for the repair of this type of fractures.

Methods: A finite element model of the mandible was created, and a parasymphyseal impact was simulated using Mimics 10.01 and Abaqus 6.10 software. The type B condylar head fracture was simulated in the right condyle using a mimics simulation cut with polyplane module according to the analyzed results together with clinical experience, and the left condyle was used as a control. Two positional screws were used for rigid internal fixation of the fracture. von Mises stress distributions in the condyles and screws were analyzed.

Results: The von Mises stress generated in parasymphyseal trauma simulation showed a significant concentration in the sagittal direction of the condyle. In two-positional-screw osteosynthesis of the condylar head fractures, stress concentration appeared within the screws in the gap area between the two fractured segments and the area around the screw head. A small amount of stress was distributed in the screw holes and on the posterior surfaces of both segments. The von Mises stress was negligible in the fractured sagittal surfaces.

Conclusion: It is reasonable to attribute the cause of type B condylar head fracture to the anatomical features of the condyle. The biomechanics of two-positional-screw osteosynthesis revealed that the stress can transmit through the screws to the medial fragments, and the stresses on both sagittal fractured surfaces are minimal.

Keywords: Biomechanics; Condylar head fracture; Elastic modulus; Rigid internal fixation; Stability.