Based on the assumption that bone breaks where it is weakest, so that the fracture surface represents the weakest area locally, a fractographic study was made of a series of accidental and experimental fractures of human long bones.

The architecture of the fracture surfaces as a whole, and of the local morphology of the fractured microstructure, was examined. This led to a classification of the fractographic features observed. Several quantitative characteristics of the experimental fracture surfaces were explored, including the number (n₀), volume fraction (p₀), and average cross-sectional area (A₀) of the osteons. These parameters were compared with the same data for cross-sections of the bone beneath the fracture surfaces. The results show a short-range fluctuation in the microstructural constitution of the diaphysis close to the fracture surface, with lower values of n₀, p₀ and A₀ and at the fracture surface.