An Investigation of the Effect of Irradiation on the Biomechanical Properties of Fibular Grafts

Abstract

Irradiation of fibular grafts for jaw reconstruction following mandibulectomy can be associated with increased graft failure and implant instability. The objective of this study is to investigate the effect of isolated irradiation on the biomechanical properties of ex-vivo porcine fibula grafts. It was hypothesized that the isolated irradiation (without biological response) will not significantly influence the biomechanical properties of the fibular grafts. Forty porcine fibular grafts (n=20 irradiated and n=20 nonirradiated) were obtained. The irradiated group was subjected to a single dose of 60Gy of irradiation with cesium 137. Both groups underwent 3-point bending tests with cyclic loading for 1500 cycles (50 to 500N at 2Hz) followed by push to failure. Rate of damage (mm/s), stiffness (N/mm), modulus of elasticity (MPa), maximum load (N), maximum displacement (mm), and maximum stress (MPa) were compared between the 2 groups using independent t tests (P<.05). No significant differences were found between the irradiated and nonirradiated groups for any of the biomechanical parameters (all P values > 0.05). The results of this study support our hypothesis that even high levels of isolated irradiation do not significantly affect the biomechanical properties of fibular bone grafts. This work allows us to exclude acute structural changes in the bone due to irradiation as a possible factor leading to bone/implant instability following jaw reconstruction with fibular grafts. Further studies need to be conducted to better understand the range of factors that may lead to implant instability, including the biological response after radiation therapy.