Computational Simulation of Adolescent Idiopathic Scoliosis in the Spine

Adolescent Idiopathic Scoliosis (AIS) is a condition marked by an abnormal curvature of the spine. This study aims to model AIS using computational techniques to analyze varying bone densities within vertebrae under different muscle paralysis conditions. The aim is to investigate how unilateral muscle paralysis affects bone density and to model conditions similar to AIS. A three-dimensional model of the L2 vertebra was created using Mimics and 3-matic software for segmentation and meshing. The model was imported into ABAQUS for further integration and assignment of properties. The bone remodeling algorithm was applied over 12 months, simulating the intact scoliosis (IS) condition. Loading conditions specific to IS were applied, and three scenarios of muscle paralysis were modeled: longissimus pars thoracic (LGPT) muscle paralysis, multifidus lumborum (MFL) muscle paralysis, and both muscles’ paralysis. The current study found variable bone density and Young’s modulus distributions for cancellous and cortical bones in the AIS model. Trabecular bone density varied between 0.297 and $0.317 \mathrm{~g} / \mathrm{cm}^{3}$, with Young’s modulus ranging from 99.61 to 115.83 MPa. Cortical bone density ranged from 1.466 to 1.665 $\mathrm{g} / \mathrm{cm}^{3}$, while Young’s modulus was between 11,794 and 16,110 MPa. The highest von Mises stress was observed in the cortical bone, particularly in the concave region, which is under higher compression in AIS patients than healthy spines. The results of this study support Frost’s mechanostat theory, suggesting that uneven loading leads to higher bone density on the concave side of scoliotic vertebrae. The study demonstrates the feasibility of using computational models to simulate AIS and highlights the significance of muscle conditions on bone remodeling and stress distribution in vertebrae.