Bone Diagnostic Instrument
In the forefront of our current research is the development of a an instrument, the Bone Diagnostic Instrument, capable of determining the material properties of bone in a living patient. No diagnostic tool is currently available to probe the material properties in bone of a living patient even though material properties, such as fracture toughness, are known to degrade with aging and disease.. Our basic research has revealed that the molecular level processes involved in bone fracture can be probed with micro-scale testing and our applied research has resulted in 18 preliminary iterations of prototypes designed for use as a diagnostic tool for determination of bone material properties. We are on track to provide the basis for an instrument suitable for clinical trials.
The Bone Diagnostic Instrument, that will measure microscopic materials properties of the bones of living patients with accuracy and ease. Our hypothesis is, and our preliminary results are in agreement, that a measure of microscopic fracture resistance with the Bone Diagnostic Instrument in an individual's bone correlates with their resistance to macroscopic bone fractures, or, stated another way, their overall bone fracture risk. Indentation testing is already well-established as a powerful tool in characterizing mechanical properties of materials. Fundamental research has revealed that bone fractures begin when the organic matrix of the bone, or “glue”, holding mineralized collagen fibrils together fails causing crack propagation. Preliminary results with the Bone Diagnostic Instrument have shown that an individual's susceptibility to this fundamental failure mode can be measured by indentation tests in which bone is forced, on a microscopic scale, into the same types of failure - separation of mineralized collagen fibrils - that is the root event of bone fractures. Preliminary results with the Bone Diagnostic Instrument have also shown that the necessary measurement can be performed on bone that is still covered with soft tissue.
The heart of the Bone Diagnostic Instrument is a probe assembly that can be inserted through the skin of a living patient to measure the fracture properties of bone by creating microscopic fractures in an indentation on the surface of the bone (Figure 1).
Figure 1. Basic operation of the bone diagonstic instrument.
These indented fractured areas are very small: of order of one-thousandth of a cubic millimeter, but give important information about how easy or difficult it is to fracture the bone of an individual.
The Bone Diagnostic Instrument has advanced through eighteen prototypes to date, and its development continues.