The Biomechanical Properties of A Modified Distraction Device Used in Mandibular Distraction Osteogenesis for Craniofacial Microsomia Patients: A Simulation Finite Element Analysis Study.

Objective: Finite element analysis (FEA) of the biomechanical properties of the modified extraoral distractor device used in the mandibular distraction of craniofacial microsomia patients.

Materials and methods: Finite element analysis (FEA) models of 5 patients under 2 working conditions, the instance when the distractor is activated and when the distractor participates in mastication, were included in the current study. To conduct the FEA, load boundary conditions (35.6 N on the distractor for the first working condition and 50 N on the unoperated side, 100 N and 200 N on both sides for the second working condition) were applied. Besides, constraint boundary conditions and contact conditions were also applied.

Results: With 5 or 3 bioabsorbable screws fixing the upper fixing plate, the maximal displacement of the mandible was <3 mm and the maximal stress distributed on distractor and bioabsorbable screws was less than the yield strength of corresponding materials under the 2 working conditions when setting 50 N on the unoperated side and 100 N on both sides for the second working condition. However, when setting 200 N on both sides for the second working condition, the maximal displacement of the mandible slightly increased, and stress distributed on distractor and bioabsorbable screws exceeded the yield strength of corresponding materials in some patients.

Conclusion: In most cases, both 5 and 3 poly-L-lactic acidscrews could firmly fix the distractor on the mandible without plastic deformation, although the situation would be different when the mastication force was too powerful.