Next-Generation Scaffold-Based Implants for Mandibular Reconstructions: Patient-Specific Design, Computational Modelling and Experimentation

Abstract

Surgeons perform fibula free flap transplantation to reconstruct a critical-sized segmental defect in the human mandible. However, being able to restore the original shape of the mandible becomes problematic due to the anatomical shape mismatch between the fibula and mandible. This thesis undertakes the research and development of a tissue-engineered scaffold implant that is 3D printed to match the defect shape. The scaffold is not only load-bearing but its porous structure supports bone ingrowth.

A current challenge in bone tissue engineering is to create favourable biomechanical conditions for bone ingrowth by mechanically stimulating the scaffold to initiate bone apposition. This thesis combines computed tomographic (CT)-based finite element (FE) modelling with multiobjective optimisation to determine the optimal height and angle to place a titanium fixation plate on a scaffold-based reconstructed human mandible so as to enhance bone ingrowth, structural strength, and structural stiffness of the scaffold-host bone construct.

Animal models (in silico, in vitro, and in vivo) are used for the research, development, test, and evaluation of bone implant prototypes. This thesis combines in silico CT-based FE modelling with in vitro mechanical testing to (i) inversely characterise the Young’s modulus of cortical bone in an intact in vitro sheep mandible and (ii) validate the in silico FE model of this sheep mandible after its bilateral reconstruction with two scaffold devices. This in silico FE model is combined with computational fluid dynamics modelling and multiobjective optimisation to determine the optimal design of the Schwarz P-surface unit cell geometry of the implant so as to enhance appositional mechanical stimulus and permeability to facilitate interstitial fluid flow through the scaffold.

In summary, this thesis demonstrates advances in computational modelling, experimentation, and design optimisation of scaffold-based mandibular bone reconstruction devices.