Two-dimensional strain fields on the cross-section of the bovine humeral head under contact loading

Abstract

The objective of this study was to provide a detailed experimental assessment of the two-dimensional cartilage strain distribution on the cross-section of immature and mature bovine humeral heads subjected to contact loading at a relatively rapid physiological loading rate. Six immature and six mature humeral head specimens were loaded against glass and strains were measured at the end of a 5 s loading ramp on the textured articular cross-section using digital image correlation analysis. The primary findings indicate that elevated tensile and compressive strains occur near the articular surface, around the center of the contact region. Few qualitative or quantitative differences were observed between mature and immature joints. Under an average contact stress of ~1.7 MPa, the peak compressive strains averaged −0.131 ± 0.048, which was significantly less than the relative change in cartilage thickness, −0.104 ± 0.032 (p < 0.05). The peak tensile strains were significantly smaller in magnitude, at 0.0325 ± 0.013. These experimental findings differ from a previous finite element analysis of articular contact, which predicted peak strains at the cartilage-bone interface even when accounting for the porous-hydrated nature of the tissue, its depth-dependent inhomogeneity, and the disparity between its tensile and compressive properties. These experimental results yield new insights into the local mechanical environment of the tissue and cells, and suggest that further refinements are needed in the modeling of contacting articular layers.

Meniscus and cartilage exhibit distinct intra-tissue strain distributions under unconfined compression

“…Consistent with previous findings in articular cartilage[14–18], the local strain in articular cartilage decreased with depth from the tibial surface, indicating a depth-increasing compressive modulus. The relatively compliant surface layer in cartilage has been proposed to play a role in enhancing joint congruity[14].…”

“…This progressive increase in compressive modulus with depth has been observed consistently in articular cartilage from different joints, species and ages[14–19]. These techniques have been extended to examine cartilage mechanics in a variety of other situations, including strain fields surrounding indenters[20] and cartilage defects[21, 22], relationships between macroscopic strain and chondron deformation[23], compression of cross-sections of intact joints[18, 24], and shear properties under static, dynamic and sliding conditions[25–28]. In contrast, few studies have similarly focused on the details of fibrocartilage tissue mechanics.…”

Fatigue strength of bovine articular cartilage-on-bone under three-point bending: the effect of loading frequency

“…This location was selected because it has a flat surface and is in the centre of the contact region of the joint. Articular cartilage located in this position has been shown to undergo maximum deformation in the humeral head [26]. …”

Time and dose-dependent effects of chondroitinase ABC on growth of engineered cartilage

“…Under physiological loading, cartilage experiences both high compressive strains (10-15 %) and tensile strains (~6 %) in the superficial layer, which results as the two articulating surfaces contact one another (Canal et al ., 2008; Chahine et al ., 2004; Guterl et al ., 2009; Miller and Morgan, 2010; Zhang et al ., 2005). In native cartilage, these large tensile strains are supported predominantly through the tissue’s dense fibrillar collagen network.…”

“…Increasing the collagen content of engineered cartilage has been correlated with improvements in tensile mechanical properties (Kelly et al ., 2013; Natoli et al ., 2009b). Therefore, it is likely that ensuring engineered tissues can withstand the physiologic loading conditions will require recapitulating the native tissue’s collagen architecture and composition (Adeeb et al ., 2004; Canal et al ., 2008; Chahine et al ., 2004; Guterl et al ., 2009). …”