A commentary on the significance of stresscoat and split-line patterns on bone.

Stresscoat,” a n industrial technique for showing sites of highest tensile strain and failure in machine parts, has been used for similar purposes in intact living and cadaver bones. Stresscoat cracks only arise from tensile struin in the underlying material and always lie transverse to the direction of the strain. Stresscoat and split-line patterns do not represent stress trajectories. A trajectorial diagram can not be drawn for a bone because a bone is a three dimensional porous body composed of heterogeneous anisotropic material. Split-lines show the “grain” of bone and may be related to its vascularity or growth. The mechanical significance of split-lines is