Micromechanical behavior of cortical bone as inferred from laser speckle data

We investigated the micromechanical behavior of porcine femoral cortical bone using a novel, nondestructive, noncontacting, laser-based strain measurement technique. The technique is based upon the well-known concept of tracking translating laser speckle with a linear array CCD camera, but employs a unique data-processing scheme based upon a two-dimensional frequency transform of the data. The method proved to be successful in evaluating strain rates in the bone samples. Measured strain rates ranged between 4.61 and 23.84 micro epsilon/s. Total strains recorded were between 3.7 and 19.1 micro epsilon. Estimated Young's moduli averaged 9.01 +/- 3.93 GPa, which, considering the extremely slow strain rates, is an acceptable value for porcine cortical bone. General advantages of the technique include high sensitivity, insensitivity to zero-mean noise sources, compact design, and the fact that it is truly noncontact. A brief discussion of possible error sources within the method is also given.