Quantifying intrinsic stress and structural strength of human clavicles from CT-derived geometry: An analytical framework.

BACKGROUND: Accurate, geometry-aware estimates of intrinsic stress are essential for interpreting clavicle failure experiments and assigning realistic material properties in computational models. To date, literature reports clavicle material parameters based on models or constitutive laws, leaving the complex internal stress distribution of the clavicle under axial loading poorly defined. OBJECTIVE: This article introduces an analytical framework that integrates experimental biomechanical testing with specimen-specific geometry to compute the stress distribution along the clavicle. METHODS: Nine male clavicles (37-56 years) underwent quasi-static uniaxial compression until failure, and specimen-specific geometries were reconstructed from pre-test Computed Tomography. A novel analytical approach was applied by explicitly incorporating clavicle curvature through the barycentric line and an associated Frenet-Serret local frame. This allowed for projection-corrected cross-sectional measures and local second moments of area, and computation of bending moments induced by the offset between the load line and the section centroid. RESULTS: The mean maximum load was Fmax=2545±710N. The estimated peak compressive and tensile stresses were σmax,c=-291.3±51.7MPa and σmax,t=+212.9±46.1MPa, respectively. All specimens failed on the external surface of the second half of the clavicle within the tensile region, consistent with greater compressive than tensile strength under the tested boundary conditions. Importantly, peak force was a poor predictor of tensile strength, whereas stress-based metrics reduced inter-individual variability (coefficients of variation: CVF=27.9% vs. CVC=17.8% and CVT=21.6%). CONCLUSIONS: This article provided the first estimates of tensile/compressive strength-related stress values for the human clavicle. These results support the use of geometry-informed stress, rather than force alone, as an intrinsic descriptor of clavicle mechanical strength and a more reliable basis for calibrating and validating clavicle models.