Theoretical assessment of an intramedullary condylar component versus screw fixation for the condylar component of a hemiarthroplasty alloplastic TMJ replacement system.

Virtual design gives flexibility to explore constructive solutions or structures. It enables analysis that would often be impossible even if expensive real prototypes were available. Simulations using finite element models allow access to the stress and strain tensor or to the deformation tensor within an implant or a tissue which is impossible experimentally, even in vitro. This study is based on two numerical models of temporomandibular joint (TMJ) implants, comparing two bone-implant connections: an external connection performed with surgical screws (commercial model) and an internal connection carried out by penetration into the intramedullary space. The finite element models were constructed based on a cadaveric mandible and considering the five principal muscles in action. Strain distributions into the surrounding bone tissue are analysed and in both models they show significant differences at the external surface of the mandible in displacements. However, while the intramedullary fixation increases strains in the cancellous tissue, the study shows that strain distribution is mainly influenced by the number and distribution of screws in commercial solution.