Dynamic viscoelastic characterisation of human osteochondral tissue: understanding the effect of the cartilage-bone interface

Abstract

BackgroundDespite it being known that subchondral bone affects the viscoelasticity of cartilage, there has been little research into the mechanical properties of osteochondral tissue as a whole system. This study aims to unearth new knowledge concerning the dynamic behaviour of human subchondral bone and how energy is transferred through the cartilage-bone interface.MethodsDynamic mechanical analysis was used to determine the frequency-dependent (1–90 Hz) viscoelastic properties of the osteochondral unit (cartilage-bone system) as well as isolated cartilage and bone specimens extracted from human femoral heads obtained from patients undergoing total hip replacement surgery, with a mean age of 78 years (N = 5, n = 22). Bone mineral density (BMD) was also determined for samples using micro-computed tomography as a marker of tissue health.ResultsCartilage storage and loss moduli along with bone storage modulus were found to increase logarithmically (p < 0.05) with frequency. The mean cartilage storage modulus was 34.4 ± 3.35 MPa and loss modulus was 6.17 ± 0.48 MPa (mean ± standard deviation). In contrast, bone loss modulus decreased logarithmically between 1 and 90 Hz (p < 0.05). The storage stiffness of the cartilage-bone-core was found to be frequency-dependent with a mean value of 1016 ± 54.0 N.mm− 1, while the loss stiffness was determined to be frequency-independent at 78.84 ± 2.48 N.mm− 1. Notably, a statistically significant (p < 0.05) linear correlation was found between the total energy dissipated from the isolated cartilage specimens, and the BMD of the isolated bone specimens at all frequencies except at 90 Hz (p = 0.09).ConclusionsThe viscoelastic properties of the cartilage-bone core were significantly different to the tissues in isolation (p < 0.05). Results from this study demonstrate that the functionality of these tissues arises because they operate as a unit. This is evidenced through the link between cartilage energy dissipated and bone BMD. The results may provide insights into the functionality of the osteochondral unit, which may offer further understanding of disease progression, such as osteoarthritis (OA). Furthermore, the results emphasise the importance of studying human tissue, as bovine models do not always display the same trends.

Identification of an Ultrathin Osteochondral Interface Tissue with Specific Nanostructure at the Human Knee Joint

“…An exponential increment profile of tissue stiffness at the interface was validated by FEA results to facilitate efficient force transfer and reduce stress concentrations to avoid tissue failure. The excellent force transfer properties of the interface tissue may be ascribed to the energy absorption and dissipation mechanism of the specific structures and compositions. ,, The nanoscale heterogeneity of HAp may facilitate force transfer by energy dissipation at the interface . The soft biomolecules like titin at the interface were crucial in dissipating energy through large deformation and viscoelastic properties. , These soft biomolecules also have extraordinary energy-absorbing capabilities via local deformation to favor force transfer of the interface tissues .…”

High-performance bilayer composites for the replacement of osteochondral defects

“…This behavioral pattern of the same-application materials and the differences between the two types is consistent with the stress-relaxation properties of OC tissues. 84,85 The viscoelastic properties of a biomimetic material should match those of the replaced tissue to avoid the accumulation of residual stress, either in the implant or in the adjacent tissue, and do not compromise the successful restoration of the damaged site. Wang et al 86 found that an agarose gel grafted into an OC defect recovered faster than the neighboring cartilage after removing the applied load, causing a build-up of residual stress at the implant-tissue interface.…”

“…This behavioral pattern of the same-application materials and the differences between the two types is consistent with the stressrelaxation properties of OC tissues. 84,85 The viscoelastic properties of a biomimetic material should match those of the replaced tissue to avoid the accumulation of residual stress, either in the implant or in the adjacent tissue, and do not compromise the successful restoration of the damaged site.…”

Analysis of hydration and subchondral bone density on the viscoelastic properties of bovine articular cartilage

“…Cartilage exhibits frequency-dependent viscoelastic behaviour [15,16]. Viscoelasticity can be characterised through a storage and loss modulus [17][18][19], or via storage and loss stiffness for a structure [20,21].…”