 In a normal person, the vertebral bodies are composed of a porous structure called trabecular or spongy bone encapsulated within a thin external cap of cortical dense bone. In a person with osteoporosis, the trabeculae that form the central porous bone become thinner and weaker. When this occurs, the vertebral bodies begin to fracture and become deformed. This deformation of the vertebral bodies is classified into three types, according to the shape: wedge, biconcave, and crush. The degree of severity of these deformations is classified as grade A1.1, grade A1.2, or grade A1.3 