Cartilage Assessment Requires a Surface Characterization Protocol: Roughness, Friction, and Function

Abstract

The surface of articular cartilage is integral to smooth, low-friction joint articulation. However, the majority of cartilage literature rarely includes measurements of surface characteristics and function. This may, in part, be due to a shortage of or unfamiliarity with fast, nondestructive, and, preferably, noncontact methods that can be applied to large cartilage surfaces for evaluating cartilage surface characteristics. A comprehensive methodology for characterizing cartilage surfaces is useful in determining changes in tissue function, as for example, in cases where the quality of cartilage grafts needs to be assessed. With cartilage storage conditions being an area of ongoing and active research, this study used interferometry and tribology methods as efficient and nondestructive ways of evaluating changes in cartilage surface topography, roughness, and coefficient of friction (CoF) resulting from various storage temperatures and durations. Standard, destructive testing for bulk mechanical and biochemical properties, as well as immunohistochemistry, were also performed. For the first time, interferometry was used to show cartilage topographical anisotropy through an anterior-posterior striated pattern in the same direction as joint articulation. Another novel observation enabled by tribology was frictional anisotropy, illustrated by a 53% increase in CoF in the medial-lateral direction compared to the anterior-posterior direction. Of the storage conditions examined, 37°C, 4°C, -20°C, and -80°C for 1 day, 1 week, and 1 month, a 49% decrease in CoF was observed at 1 week in -80°C. Interestingly, prolonged storage at 37°C resulted in up to an 83% increase in the compressive aggregate modulus by 1 month, with a corresponding increase in the glycosaminoglycan (GAG) bulk content. This study illustrates the differential effects of storage conditions on cartilage: freezing tends to target surface properties, while nonfreezing storage impacts the tissue bulk. These data show that a bulk-only analysis of cartilage function is not sufficient or representative. The nondestructive surface characterization assays described here enable improvement in cartilage functionality assessment by considering both surface and bulk cartilage properties; this methodology may thus provide a new angle to explore in future cartilage research and tissue engineering endeavors.

Yucatan Minipig Knee Meniscus Regional Biomechanics and Biochemical Structure Support its Suitability as a Large Animal Model for Translational Research

“…It should be noted that values in the present study were obtained using an LC-MS method, which has been shown to be more precise and accurate than HPLC fluorescence detection methods ( Milićević et al, 2010 ; Wang et al, 2012 ; Bandeira et al, 2013 ; Bielajew et al, 2020 , 2021 ). Pyridinoline crosslink content, for example, has been quantified using LC-MS techniques in bovine articular cartilage, showing crosslink levels of 0.12% of total dry weight, which were on par with values recorded in this study ( Espinosa et al, 2021a ). The posterior region of the medial meniscus contained significantly fewer crosslinks normalized to collagen content compared to the central region ( Figure 6G ), which may contribute to the low radial tensile stiffness in the posterior region.…”

Vibrometry as a noncontact alternative to dynamic and viscoelastic mechanical testing in cartilage

“…This represents a 93% reduction in time. Lastly, we do not expect changes in tissue properties arising from enzymatic degradation or the freeze-thaw cycle in this work given that the joint remained closed prior to testing, cartilage cells are known to very metabolically inactive [66], and that refrigeration is the standard way of storing cartilage tissue [67]. However, this might not be the case when working with large samples, where properties can be affected by testing times; thus, groups working with large tissues and/or requiring a fast turnover will find this decrease in time of utmost importance.…”

A Tribological Comparison of Facet Joint, Sacroiliac Joint, and Knee Cartilage in the Yucatan Minipig

“…The friction coefficients for knee cartilage reported here are comparable to those found in the literature under similar testing conditions. 10,39 To the best of our knowledge, these data do not exist for the facet and SI joints. The friction coefficients from the present study may correlate to the greater range of motion (ROM) required in the knee than in either the facet or SI joints.…”