Scatter radiation effects of titanium osteosynthesis plates in mandibular reconstruction: An experimental 3D-printed phantom and cell culture study

Mandibular reconstruction with fibula free flaps commonly requires fixation using titanium osteosynthesis plates. In patients receiving adjuvant radiotherapy, scatter radiation effects from metallic hardware may alter dose distribution and affect biological responses, but systematic evidence remains limited. This experimental study examined the influence of plate geometry on scatter radiation and cell proliferation. A three-dimensional printed mandibular phantom, generated from patient CT data and combined with a water phantom, was used to simulate clinical irradiation conditions. Irradiation was performed with an Ethos linear accelerator, and dose modifications in the vicinity of different plate designs were analyzed. Human mesenchymal stromal cells (hMSC) and human umbilical vein endothelial cells (HUVEC) were irradiated under identical conditions, and proliferation was assessed using MTS assays. Distinct dose increases were detected anterior to the plates, with dose reductions in the shadowing region, depending on plate diameter and geometry. These physical changes correlated with significant differences in hMSC and HUVEC proliferation. The results indicate that osteosynthesis plate design affects both dosimetric distribution and cellular responses during radiotherapy. These findings suggest that reduced metal volume and specific plate geometries may contribute to lower local radiation perturbations and should be considered in reconstructive planning for patients undergoing adjuvant radiotherapy.