What is Bone Quality and how does it Impact Bone Strength?
In our prior posts we discussed the importance of bone fragility and the tremendous burden this problem represents for patients and society. We also touched on the DXA scanner; what it can and cannot tell us about skeletal health. In this post we discuss the importance of Bone Quality as a measure of tissue properties, and its contribution to the overall problem of fragility fracture.
So what is bone quality? To scientists and medical professionals, quality refers to properties of the bone material itself, devoid of considerations of gross structure or amount. This is analogous to the way structural engineers view the underlying properties of materials such as concrete or metallic alloys, and as such, an independent consideration in assessing the overall strength of a structure. For example, one could construct an object from high tensile steel or aluminum, but in doing so would expect differences in weight and strength to result. In a similar fashion, the quality of our boney tissue is an independent risk factor for fragility fracture. Fracture resistance depends not just on the amount of bone in one’s skeleton, but on the quality of that bone as well.
Human bone is a complex composite structure, comprised of both organic and inorganic components. The principal organic component is a protein called collagen. Ubiquitous in human hair, skin, and ligaments, collagen is one of the key building blocks of the human body. The collagen undergoes mineralization with inorganic components, the majority of which is calcium phosphate. This explains the utility of the X-ray based scanners to measure the amount of bone comprising the skeleton, as these mineral elements are potent absorbers of X-ray beams. The mineralized collagen fibrils are held in place by other proteins, present in much smaller amounts, which function like a biological glue. The overall quality of the tissue, the ability of bone to absorb energy and resist fracture, is dependent on the organization of these varied materials into an efficient composite structure.
In efforts to determine the influence of tissue quality on the strength of our skeletal structure, scientists have investigated human bone with a variety of high-tech tools, including ultra-high resolution CT scanners, spectroscopy and others. Yet, while each of these approaches yields important insights, all are essentially static images. None gives an indication of the ability of bone to respond to mechanical forces in real time.
Active Life has introduced an entirely new technology, reference point indentation (RPI), as a means of assessing the bone in a truly novel way. RPI is like a magic finger, measuring with micron level accuracy how the bone material responds to modest mechanical forces. Using this unique approach, RPI can determine the bone’s resistance to forces which, on a larger scale, lead to mechanical failure and fracture. Reference point indentation technology has captured the attention of researchers at the nation’s top academic centers, who are now using it to assess the intrinsic material properties of bone in a variety of disease states. Conditions from Type 2 Diabetes to Stress Fractures are being found to involve alterations in the material properties of bone; the quality of the tissue itself, rather than a decrease in amount, as a cause of skeletal weakness. This knowledge increases physician’s understanding of the basis of skeletal problems, opening the door to treatments tailored to address them.
In our next installment we discuss some of the research showing that Active Life Scientific’s RPI instruments can measure the quality of bone, and some of the specific health conditions where it provides new and exciting insights.