Biomechanical comparison of plate materials and designs for subcondylar fracture fixation: An in silico assessment

The fixation of common mandibular subcondylar fractures is associated with a high complication rate, and the decision of a suitable plate design and material still remains a challenge. Computational models have been developed and verified for understanding mandibular fracture fixation, but most of the investigation has been limited to a simplified model, single force and evaluation of plate-only designs. Using finite elements, we analysed the fracture stability with five materials - Nitinol, Magnesium alloys, two types of Titanium alloys (Ti-6Al-4V and Ti-29Nb-13Ta-4.6Zr) and Stainless Steel 316L, for four types of fixation plate designs. The soft tissues such as periodontal ligament, were included and molar clenching tasks were considered for accurately mimicking the physiological mastication cycle. The maximum principal tensile strain in the mandible was found to be decreasing with an increase in stiffness for most of the cases, except for the trapezoid and strut plates. We attribute the differences between trapezoid/strut and double mini/lambda to the presence of an additional screw near the sigmoid notch in the proximal segment in case of double mini and lambda plates. As the mandible reconstructed with double mini plates had the least interfragmentary gap, the double mini plate was deemed as the most suitable design. The results such as a lower von Mises stress in plates (compared to yield strength) indicated that the anchorage provided by titanium alloys (Ti-6Al-4V and TNTZ) is sufficient for load bearing.