Fracture failure mechanisms in patients with osteogenesis imperfecta.

This investigation examines the failure mechanism of bone from patients with osteogenesis imperfecta (OI). Mechanical testing and ultrastructural analysis of surgically obtained bone specimens, from patients with OI and from approximately age matched normal controls, were performed. Small rectangular bone samples (1.0 mm X 1.2 mm X 15 mm) with a prismatic cross section were put under three-point bending to determine the work to fracture. Furthermore, the fracture surface was observed with scanning electron microscopy (SEM). The SEM observation of partially dissected lamellae was also performed to determine the collagen organization of the bone. The OI bone has a consistently lower work to fracture and reduced collagen organization than the normal controls. The fracture surface of the OI bone is rough and exhibits a "pull-out" type of morphology, as opposed to the smoother fracture surface of the controls. This study shows that a relatively simple mechanical test utilizing a small amount of bone can differentiate between a diseased state (OI) and a normal state of bone.