Effect of hydration on the frequency-dependent viscoelastic properties of articular cartilage

Abstract

The aim of this study was to determine the effect of tissue hydration on the frequency-dependant viscoelastic properties of articular cartilage. Such changes were determined at frequencies associated with normal (1-10 Hz) and impulsive/traumatic (90 Hz) heel-strike times. Cartilage on bone samples, obtained from bovine humeral heads, was tested when hypo-hydrated and hyper-hydrated using dynamic mechanical analysis. Dynamic mechanical analysis was performed at a range of frequencies between 1 and 90 Hz. Hypo-hydration increased the stiffness of cartilage as compared to hyper-hydrated cartilage; this increase was greater at higher frequencies. The storage modulus and stiffness increased in hypo-hydrated cartilage as compared to hyper-hydrated cartilage. However, the loss modulus and stiffness increased when cartilage was hypo-hydrated as compared to hyper-hydrated, but these increases were not frequency dependent. An impulsive heel-strike time may result in a greater increase of stiffness in hypo-hydrated cartilage, compared with hyper-hydrated cartilage. However, the ratio of storage to loss stiffness was greater for hyper-hydrated cartilage, thereby, reducing the tissue's ability to dissipate energy and increasing the likelihood of cartilage rupture.

Effect of the variation of loading frequency on surface failure of bovine articular cartilage

“…Crack length was found to increase with increasing loading frequency; this increase was also found to be greater at higher maximum loads. An increase in cartilage damage with increasing the loading frequency was predicted in previous studies 12,14,28 . This prediction was made because of the change in viscoelastic properties of articular cartilage with frequency.…”

“…Significant increase in crack length with frequency in peak stresses which resembles peak stresses acting on cartilage during light and moderate activities shows the important role of loading frequency in the initiation and propagation of damage on the surface of articular cartilage in this study. Other studies 12,13,28 have reported that the ability of cartilage to store and dissipate energy is altered with loading frequency. This may change the stress transfer to the underlying bone which leads to bone stiffening and ultimately failure of articular cartilage 13 .…”

“…This study has investigated the dependency of surface damage on loading frequency. Frequencies of 1, 10 and 100 Hz were used as they correspond to normal gait, above healthy gait heelstrikes and similar to traumatic heel-strike rates, respectively 1e14, 20,28 . The results show that repetitive mechanical loading of articular cartilage causes damage in the form of crack and fissures to its surface.…”

Systemic Hydration: Relating Science to Clinical Practice in Vocal Health

“…Investigations into the biomechanical properties of soft tissues have supported this notion, with behaviour linked with extracellular matrix (ECM) hydration both in vivo and in vitro (39). The viscoelastic properties of articular cartilage for example, have been shown to alter depending on hydration, with reduced ability to dissipate energy and resultant increased likelihood of rupture in a hyperhydrated state (as in osteoarthritis) (40). At the cellular level, the properties of elastin have shown significant stiffening with dehydration, resulting in reduced fatigue resistance to cyclic loading particularly at high frequency (39).…”

Studies in Fat Grafting

“…The bouncing corresponds to elastic behavior on a short time scale, while the flattening corresponds to viscous flow on a long time scale. Along with fat, a myriad of other biological tissues are viscoelastic, including cartilage, ligaments, tendons, and muscle (13–15). …”