Orbital stress analysis--Part I: Simulation of orbital deformation following blunt injury by finite element analysis method.

PURPOSE The purpose of this study was to develop a 3-dimensional finite element model (FEM) of the human orbit, housing the globe, to predict orbital deformation in subjects following a blunt injury. MATERIALS AND METHODS A FEM of the human orbit including the eye, fatty tissues, and extraocular muscles was constructed. Simulations were performed with a computer using the finite element software NISA (EMRC, Troy, MI). The orbit was subjected to a blunt injury of a 0.5 kg missile with 30 m/s velocity. The FEM was then used to predict principal and shear stresses/strains at each node position. RESULTS Two types of orbital deformation were predicted during different impact simulations: a) horizontal distortion and b) rotational distortion. Stress values ranged from 112.12 to 262.3 MPa for the maximum principal stress, from -226.8 to -552.1 MPa for the minimum principal stress, and from 111.3 to 343.3 MPa for the maximum shear stress. CONCLUSION This is the first finite element study that demonstrates different and concurrent patterns of orbital deformation in subjects following a blunt injury. FEM is a powerful and invaluable tool to study the multifaceted phenomenon of orbital deformation.

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