The Use of Finite Element Method Analysis for Modeling Different Osteotomy Patterns and Biomechanical Analysis of Craniosynostosis Correction.

PURPOSE: Several post-processing algorithms for 3D visualization of the skull in craniosynostosis with their specific advantages and disadvantages have been already described. The Finite Element Method (FEM) described herein can also be used to evaluate the efficacy of the cutting patterns with respect to an increase in the projected surface area under assumed uniform loading of the manipulated and cut bone segments. METHODS: The FEM analysis was performed. Starting with the classic cranial osteotomies for bifrontal craniotomy and orbital bandeau a virtually mirroring of the unaffected triangular shaped frontal bone was performed to achieve a cup-shaped sphere of constant thickness of 2.5 mm with a radius of 65 mm. Mechanical properties required for the analysis were Young's modulus of 340 MPa and Poisson's ratio of 0.22. Four different cutting patterns from straight to curved geometries have been projected onto the inner surface of the sphere with a cutting depth set to 2/3rds of the shell thickness. The necessary force for the deformation, the resulting tensions and the volume loss due to the osteotomy pattern were measured. RESULTS: Better outcomes were realized with pattern D. The necessary force was 73.6% smaller than the control group with 66N. Best stress distribution was achieved. Curved cutting patterns led to the highest peak of stress and thus to a higher risk of fracture. Straight bone cuts parallel to the corners or to the thighs of the sphere provided a better distribution of stresses with a small area with high stress. Additionally, also with pattern D a surface increase of 20.7% higher than reference was registered. CONCLUSION: As a proof of concept for different cutting geometries for skull molding in the correction of craniosynostosis, this computational model shows that depending of the cutting pattern different biomechanical behavior is achieved.

Does mechanical stimulation really protect the architecture of trabecular bone? A simulation study.

Although it is beyond doubt that mechanical stimulation is crucial to maintain bone mass, its role in preserving bone architecture is much less clear. Commonly, it is assumed that mechanics helps to conserve the trabecular network since an "accidental" thinning of a trabecula due to a resorption event would result in a local increase of load, thereby activating bone deposition there. However, considering that the thin trabecula is part of a network, it is not evident that load concentration happens locally on the weakened trabecula. The aim of this work was to clarify whether mechanical load has a protective role for preserving the trabecular network during remodeling. Trabecular bone is made dynamic by a remodeling algorithm, which results in a thickening/thinning of trabeculae with high/low strain energy density. Our simulations show that larger deviations from a regular cubic lattice result in a greater loss of trabeculae. Around lost trabeculae, the remaining trabeculae are on average thinner. More generally, thin trabeculae are more likely to have thin trabeculae in their neighborhood. The plausible consideration that a thin trabecula concentrates a higher amount of strain energy within itself is therefore only true when considering a single isolated trabecula. Mechano-regulated remodeling within a network-like architecture leads to local concentrations of thin trabeculae.