Spatially-resolved slow dynamics of strains due to residual stresses in cartilaginous implants visualized by phase-sensitive optical coherence tomography

Laser-assisted relaxation of internal stresses can be used to stabilize the new shape of cartilaginous implants. The ability of cartilage tissue to experience irreversible deformation under certain conditions, as well as to restore its original configuration after external mechanical stress, is studied in near real time using a new method of optical coherent elastography (OCE), developed to visualize slow deformation. The OCE technique allows one to monitor the efficiency of laser-induced stress relaxation at 1–2 minute intervals using 2D subsurface strain mapping. It has been shown that the redistribution of the interstitial fluid due to the applied load is an important factor for the mechanism of "shape memory" of the cartilage. Deviations in the behavior of cartilage from the usual elastic properties of homogeneous materials, such as subsurface dilatation opposing the applied load, are identified and analyzed.