Image-based strength assessment of bone.

A patient's bone status is commonly assessed by radiologic methods. Although the desired information concentrates on the probability of future fractures, the radiologic density is widely used as a surrogate for bone strength. There have been attempts to develop new parameters that have a closer relationship with bone strength, but the investigators tend to use a linear relationship between measured density and their strength-related parameter. We briefly discuss the background of mechanical deformation as it relates to bone and point out some of the basic principles involved in the assessment of strength. We then show that the relevant connection between strength and density makes use of the elastic modulus, which relates to density in a power law with an exponent of close to 2. We suggest modifications of some of the widely used strength-related parameter expressions that follow the theory more closely and will, thus, have the potential to better reflect the patient's bone status.