[Swelling observation and modulus extraction of cartilage based on transient ultrasonic]

Subtle changes in structure or composition can lead to degeneration of articular cartilage such as in osteoarthritis, so it is significant to study the materials attribute of the degenerating articular cartilage. A new transient ultrasonic technique was introduced into this study for measuring the swelling effects of the degenerated cartilage. The swelling-induced strain was calculated based on the measurement result, and then the uniaxial module of the articular cartilag was extracted using Narmoneva's triphasic model. The ultrasonic observation showed that the strains induced by the nonuniform swelling are depth-dependent, and the strains are small in the deep zone and big in the middle and surface zones. The uniaxial modulus also revealed that the cartilage in the deep zone (E1 = 12.20) is harder than that in surface zone (E2 = 0.15). These results suggest that the transient ultrasound technique accompanied by triphasic model provides a quantitative means to study the degeneration of articular cartilage.