Biphasic poroviscoelastic characteristics of proteoglycan-depleted articular cartilage: simulation of degeneration.

This study investigated the biphasic poroviscoelastic properties of normal and proteoglycan-depleted articular cartilage to validate this model for use in the diagnosis of degenerated cartilage. A normal control group, a buffer-treated control group, and a trypsin-treated proteoglycan-depleted experimental group were investigated. Water content and glycosaminoglycan concentration were measured for each group in order to assess the affects of buffer treatment and trypsin treatment on normal articular cartilage. Histological staining with toluidine blue confirmed the depletion of proteoglycan molecules by trypsin treatment. Specimens from each group were tested in unconfined compression, and the biphasic poroviscoelastic model was fit to the data obtained. No significant difference in water content was found between any of the three groups. Glycosaminoglycan concentration was found to be significantly lower in the trypsin-treated group when compared to both the normal and buffer-treated groups, while no difference between normal and buffer-treated specimens was found. Specimens from the normal and buffer-treated groups behaved the same mechanically. Model parameters from these two groups were not statistically different. However, model parameters for the trypsin-treated group were statistically different from those from the other two groups, suggesting that the biphasic poroviscoelastic model may be a powerful diagnostic tool for degenerative articular cartilage.