Abstract:

BACKGROUND: Segmental defect of mandible is often caused by tumor, trauma and other reasons. Simultaneous mandibular defect by vascularized fibular flap is the most important repair method at present. It is not only useful for the reconstruction with titanium plates, but also useful for small titanium plates for fixation. Clinical retrospective studies have shown that there is no significant difference in postoperative complication rate between patients with the two fixation methods, but relevant biomechanics studies are still lacking at present.

OBJECTIVE: The three-dimensional finite element analysis was used to analyze the stress distribution and stability on mandibular segmental defects simulated fibular flaps grafted with reconstruction plates and miniplates fixation.

METHODS: A healthy adult male with complete dentition was selected for CT scan and data were input into the computer to reconstruct the mandible and dentition model. Three types of 3D models were built for mandibular defects dependent on Jewer’s classification, including models H (loss of lateral mandible, mandibular angle, ascending branch of mandible, and condyles), L (loss of unilateral mandible) and C (loss of bilateral mandible chin). Mechanical distribution features and stability of fixation with reconstruction plates and miniplates were comparatively studied after fibular repair of mandibular segmental defects.

RESULTS AND CONCLUSION: (1) The stress graphs showed that stress was mostly higher in surrounding areas of normal mandibles such as condyle, condylar neck, mandibular angle, molar and titanium screws. In particular, the stress was highest near mandibular angles. (2) For type-H defect, the great stress was generated near the mandibular angles when mandible was reconstructed with reconstruction plate, and the stress value was 185 MPa. The stress values approximately ranged from 117 to 135 MPa on type-H and type-L defects with miniplates. The maximum stress of fibula block was less than 30.4 MPa, and the maximum stress of titanium nail was 56.2 MPa. (3) The relative displacements approximately varied between 15 μm and 18 μm on the fracture sides after repair with type-H and type-L defects with miniplates and reconstruction plates. Almost no relative displacement was generated on the fracture sides after type-C mandibular defects. (4) Both titanium reconstruction plates and titanium miniplates could meet biomechanical requirements for fibular repair of H, C, and L defects.

Key words: mandibular defect, mandibular reconstruction, fibular flaps, finite element analysis, biomechanics, reconstruction plate, miniplate, stress, stability, relative displacement