Biomechanical characterization of custom-made dynamic implants fabricated by Electron Beam Melting for anterior chest wall reconstruction

Large thoracic defects need to be reconstructed to restore inner organs protection and normal ventilation. Early rigid implants have provided the stabilization of the ribcage; however, those have been associated with breathing restrictions. The evolution of additive manufacturing has enabled the production of 3D custom-made thoracic implants. This has led to case reports on reconstructions with these prostheses, particularly for large anterior resections. A novel design of thoracic implant with dynamic capacity has already been reported, with promising short-term outcomes. However, specific biomechanical studies are needed to clarify its mechanical behaviour. A study of the evolution of the design of dynamic thoracic implants was carried out and such implants were biomechanically tested. Furthermore, finite element analyses were carried out to obtain a simple and reliable model to predict the implant behaviour, considering a rib and its costal cartilage. In the models, the stiffness and stress distribution along the implant and the bone showed that the reconstructions exhibited adequate mechanical behaviour. One of the designs provided a flexibility that closely matched the native model and the maximum stress values did not exceed the 30% of the yield strength of Ti-6Al-4V. The implants strength was demonstrated to be sufficient under tested conditions.