Structural analysis of the intervertebral discs adjacent to an interbody fusion using multibody dynamics and finite element cosimulation

Abstract

This work describes a methodology for the dynamic and structural analysis of complex (bio)mechanical systems that joins both multibody dynamics and finite element domains, in a synergetic way, through a cosimulation procedure that takes benefit of the advantages of each numerical formulation. To accomplish this goal, a cosimulation module is developed based on the gluing algorithm X-X, which is the key element responsible for the management of the information flux between the two software packages (each using its own mathematical formulation and code). The X-X algorithm uses for each cosimulated structure multiple pairs of reference points whose kinematics are solved by the multibody module and prescribed, as initial data, to the finite element counterpart. The finite element module, by its turn, solves the structural problem imposed by the prescribed kinematics, calculates the resulting generalized loads applied over the reference points and return these loads back to the multibody module that uses them to solve the dynamic problem and to calculate new reference kinematics to prescribe to the finite element module in the next time step. The proposed method is applied to study the cervical spine dynamics in a pathologic situation in which an intersomatic fusion is simulated to confirm its potential advantages. Taking into account the proposed simulation scenario, a cervical spine multibody model that includes the rigid vertebrae, the facet joints’ and spinous processes’ contacts, ligaments and the finite element models of the intervertebral discs, and their surrogates is developed. The proposed model is simulated for extension in a forward dynamics perspective.