Age- and segment-specific heterogeneity of tensile mechanical behavior in human circle of Willis arteries: A specimen-level in vitro study.

Abstract

Human intracranial artery mechanics are still insufficiently described across the full circle of Willis. We therefore quantified segment- and age-related variation in geometry-normalized tensile behavior using engineering stress- and strain-based descriptors from a common in vitro mechanical testing protocol. The analytical dataset included 643 longitudinal strip specimens from 97 donors after predefined exclusions and removal of two extreme outliers. Specimens were tested under uniaxial tension to failure in the longitudinal (axial) direction. Peak engineering stress, peak engineering strain, and secondary stress-strain curve-shape descriptors were derived where the required geometric metadata were available. Associations were assessed with regressions using donor-clustered robust standard errors. Tensile behavior varied across arterial families. Geometry-normalized tensile descriptors remained heterogeneous across arterial families. Older age was associated with lower peak engineering stress and lower peak strain. Measured specimen geometry was evaluated as metadata and as a covariate context for interpreting stress-based outcomes. Circle of Willis arteries show marked segment-specific heterogeneity under the present uniaxial protocol. The resulting peak and curve-shape stress-strain metrics should be interpreted as comparative engineering descriptors rather than direct constitutive material parameters, but they provide useful segment-specific response bounds for intracranial biomechanical modeling.