Density is not the sole measure that protects bones on the one hand or predisposes them to fracture on the other. As Dr. Susan Love, clinical professor of surgery at the University of California, Los Angeles, reminded us recently, “…bone density is only one aspect of bone health. It just happens to be the one we can measure.”
Quantifiable or otherwise, additional physical qualities that bones possess include their size, shape, and architecture. Bone architecture can be defined as the pattern of trabeculae (partitions) in the bone and associated structures. Along with density, these aspects of bones govern the ability to sustain the loads to which we subject the bones. Just as architects and engineers must design buildings to code to safely sustain environmental forces, Mother Nature has spent millennia perfecting her design specs for our bones.
What all designers understand is that form follows function. The theory of bone architecture that defines how bone in a healthy body will adapt to loads is known as Wolff’s law, and was developed over 100 years ago by the German bone anatomist and surgeon, Julius Wolff. This law states, “Every change in the form and the function of a bone, or in its function alone, is followed by certain definite changes in its internal architecture and secondary alterations in its external conformation.”
This simply means that the architecture of bone directly relates to its function. The bones in our extremities, for example, must support most of our weight and carry heavy loads, so they are longer, harder, and denser than those that must frequently expand and contract, like our rib cages do with our breathing, and our spines, which are articulated and pliant.
For more on the demographics of bone fracture, check out bone specialist Dr. Susan Ott’s graphs, which show the rates of fracture for different bone types, geographic regions, different races, and both genders across the lifespan.
Please click here for information on types of fractures — what different kinds of bone fractures can happen?.