Bone Mineral Density (BMD) as determined by DEXA scan has long been used to try and determine fracture risk in osteoporotic populations. However, BMD is a measure of bone structure, not strength, which is a material property. A new study out claims that the BioDent from Active Life Technologies was able to directly measure bone mechanical properties of the tibia in-vivo in women.
The BioDent uses a needle within a hypodermic needle to tap out micron-scale holes in bone. The further the needle goes, using a constant amount of force, the weaker the bone is
Bone tissue mechanical properties are deemed a key component of bone strength but their assessment requires invasive procedures. Here we validate a new instrument, a Reference Point Indentation (RPI) instrument, for measuring these tissue properties in vivo. The RPI instrument performs Bone Microindentation Testing (BMT) by inserting a probe assembly through the skin covering the tibia and, after displacing periosteum, applying 20 indentation cycles at 2 Hz each with a maximum force of 11 N. We assessed 27 women with osteoporosis-related fractures and 8 controls of comparable ages. Measured Total Indentation Distance (46.0 +/- 14 vs. 31.7 +/- 3.3 microns, p = 0.008) and Indentation Distance Increase (18.1 +/- 5.6 vs. 12.3 +/- 2.9 microns, p = 0.008) were significantly greater in fracture patients than in controls. Areas under the Receiver Operating Characteristic, ROC, curve for the two measurements were 93.1% (95% CI: 83.1, 100) and 90.3% (95% CI: 73.2, 100) respectively. Interobserver CV ranged from 8.7 to 15.5% and the procedure was well tolerated. In a separate study of cadaveric human bone samples (N = 5) Crack Growth Toughness and Indentation Distance Increase correlated (r = -0.9036, p = 0.018) and SEM images of cracks induced by indentation and by experimental fractures were similar. We conclude that BMT, by inducing microscopic fractures, directly measures bone mechanical properties at the tissue level. The technique is feasible for use in clinics with good reproducibility. It discriminates precisely between cases with and without fragility fracture and may provide clinicians and researchers with a direct in vivo measurement of bone tissue resistance to fracture.
Abstract in Journal of Bone and Mineral Research: Microindentation for in vivo measurement of bone tissue mechanical properties in humans
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