Evaluation on mechanical diagnosis of osteoarthritic cartilage using Dynamic Optical Coherence Straingraphy (D-OCSA)

Abstract

In this study, we have proposed D-OCSA which is a tomographically micro-visualizing method of mechanical properties estimated from continuous OCT images. This can provide temporal and spatial distribution of strain rate during a stress relaxation test and a dynamic viscoelasticity test. This was experimentally applied to comparatively both normal cartilages and cartilages degenerated by the collagenase enzyme treatment. The temporal attenuation and the sinusoidal variation of strain rate were locally observed to have characteristic viscoelastic behaviors around surface zone. In the former, the attenuation of strain rate was visualized to be lager in the superficial tangential zone than that in the middle zone. In the latter, the phase difference of sinusoidal time-varying strain rate corresponded to the degradation of viscoelasticity. Consequently, it is possible to diagnose the degeneration of the early-grade OA, taking the temporal attenuation of relaxation modulus and spatial gradient of phase delay into consideration.