Comparison of in vitro techniques to controllably decrease bone mineral density of cancellous bone for biomechanical compressive testing

It is not surprising that an orthopedic device used with poorly mineralized bone can have lower mechanical fixation strength than the same device with well-mineralized bone. As new devices are being designed and tested, it is important to develop a controllable technique to decrease the bone mineral density of bone in vitro, so the fixation strength of the devices can be better modeled. Several different bone demineralization techniques have been established, but some use caustic chemicals and comparisons of their rates of demineralization have not been performed. In this study, a total of 120 cancellous bone cores were excised from ovine vertebra, scanned using a pico dual energy X-ray absorptiometry system to determine bone mineral density, then placed into one of five solutions (0.9% saline, 0.5 M hydrochloric acid, 0.5 M ethylenediaminetetraacetic acid, 0.5 M formic acid, and 5% acetic acid). For each solution, 12 time periods ranging from 0 to 144 h were investigated. After demineralization, all cores were rescanned and biomechanically loaded in compression to failure. Based on the rate of demineralization, the ease of use, the availability, and the correlation with the compressive bone strength, it was determined that the 5% acetic acid was the optimal demineralization solution to controllably decrease the bone mineral density of cancellous bone.