Biomechanical Elucidation of Temporal Bone Fracture Mechanisms Using Finite Element Analysis: Identification of Stress-Concentration Sites and Crack Propagation Simulation Under Static Loading.

HYPOTHESIS: To investigate the relationship between the contact site and fracture patterns under static loading using finite element analysis (FEA).

BACKGROUND

Although temporal bone fractures often lead to critical otologic complications, such as hearing loss and facial palsy, their mechanisms are not well understood.

METHODS

Two types of cranial models were developed: a "Simplified model" (S-model) using geometric approximations, and a "Precise model" (P-model) reconstructed from head CT images of a 40-year-old male. Static structural analysis was performed, and static loads were applied to the vertex, left temporal, and occipital regions. First, fracture initiation was estimated from the first principal shear stress, and then fracture propagation paths were predicted from the distribution of the vectors for the first principal stress distribution.

RESULTS

S and P-models showed similar stress distribution patterns with some differences; thus, we used the S-model for general mechanical analysis and P-model for anatomically detailed evaluation. Under some loadings, high-stress concentrations were observed at both the contact site and temporal squama. Temporal loading induced stress distributions roughly similar to longitudinal fractures along the petrous ridge. Occipital loading resulted in stress concentration around the foramen magnum, suggesting a correlation with transverse fracture patterns.

CONCLUSIONS

As an initial simulation effort, the results partially reproduced the clinical correlation between contact site and fracture orientation (longitudinal vs. transverse) under static analysis conditions. This mechanical approach provides a theoretical basis for predicting internal injuries from external trauma. Future refinements incorporating dynamic loading and internal structures are necessary to enhance diagnostic accuracy in emergency situations.