Biomechanical integrity of hydroxyapatite/poly-l-lactide fixation system in mandibular body reconstruction with deep circumflex iliac artery free flap

The mechanical integrity of a deep circumflex iliac artery (DCIA) free flap connected to the remaining mandible after a segmental mandibulectomy directly influences the reconstructive surgery prognosis. This study aimed to assess the biomechanical integrity of fixation systems on the reconstruction site. The mechanical properties of mini-plate and screw fixations in two different materials, namely titanium (Ti) and hydroxyapatite/poly-L-lactide (HA-PLLA), were simulated using finite element analysis. Each end of the free flap was fixed with three mini-plates, a total of six mini-plates at the midline and the anterior to the coronoid process with 35 screws. The masticatory loading increment effect on peak von Mises stress (PVMS) distribution, size of fixation deformation, principal stresses on bones, and a gap opening size were taken into account for each material's pros and cons evaluation. Based on the comprehensive evaluation, the Ti fixation system presented superior performance immediately after surgery. However, the Ti fixation system's superiority was diminishing over time, and eventually, the differences became marginal at 12-months postop. This study's results imply the clinical indications of the HA-PLLA fixation system with the DCIA free flap during mandibular reconstructive surgery.