Indentation testing of human cartilage: Sensitivity to articular surface degeneration

Abstract

Objective. To determine, for clinical indentation testing of human articular cartilage, the effects of aging and degeneration on indentation stiffness and traditional indices of cartilage degeneration; the relationship between indentation stiffness and indices of degeneration; and the sensitivity and specificity of indentation stiffness to cartilage degeneration.Methods. Results. Indentation stiffness, India ink staining, and the histopathology score each varied markedly between normal-sample and degenerate-sample groups but varied relatively little between normal samples obtained from different age groups. A decrease in indentation stiffness (softening) correlated with a decrease in the reflectance score and an increase in the overall histopathology score, especially the surface irregularity component of the histopathology score. Receiver operating characteristic analysis suggested that the indentation testing could accurately detect cartilage degeneration as indicated by macroscopic appearance, India ink staining, and histopathology score.Conclusion. The indentation stiffness of the normal to mildly degenerate samples tested in this study was sensitive to mild degeneration at the articular surface and was insensitive to changes associated with normal aging or to slight variations in cartilage thickness. This suggests that indentation testing may be a useful clinical tool for the evaluation of early-stage degenerative changes in articular cartilage.Short-duration indentation testing is being considered as a diagnostic tool for assessing the biomechanical properties of human cartilage (1-6). In the laboratory setting, indentation tests of long duration have been performed routinely on human or animal tissue as an end point (post mortem) method of evaluation (7-13). In the clinical setting, however, such traditional laboratory tests are not practical because of the long duration of the test and the large size of the test apparatus. Short-duration indentation testing, performed using an arthroscopic probe, may be useful and appropriate in the clinical setting.A short-duration indentation test of articular cartilage in adult humans may be affected by both degenerative changes and normal age-associated changes in the cartilage. Although several biomechanics studies have analyzed human articular cartilage using a rapid indentation test (2,(4)(5)(6)12,(14)(15)(16)(17), and others have examined the relationships between short-duration indentation stiffness and traditional measures of cartilage degeneration (5,14,17,18), the effects of normal aging and mild cartilage degeneration remain to be established. The establishment of baseline indentation measurements for articular cartilage in the setting of normal aging would be useful to help interpret an indentation test result in the clinical setting. Determination of the

Spatially‐localized correlation of dGEMRIC‐measured GAG distribution and mechanical stiffness in the human tibial plateau

“…Furthermore, in two of the three tibial plateaus, when the average [GAG] was computed over the full thickness, the correlation between [GAG] and indentation stiffness was eliminated. This result may help explain two previous studies in which mechanical properties were found not to correlate well with GAG, studies which involved full thickness GAG analyses in human knee articular surfaces exhibiting natural variation in cartilage integrity where one would expect the potential for considerable local spatial heterogeneity [5,16]. While the MRI and indentation studies here yielded high overall correlations between [GAG] and load response, clearly other factors must be considered.…”

“…Abundant ex-vivo studies have shown that the load-bearing capacity of cartilage is dependent on the glycosaminoglycan (GAG) content. The structure-function relationship between GAG composition and mechanical properties has been observed in numerous studies examining normal, diseased, and experimentally-manipulated cartilages from humans and other species [1, 2,15,19,20,[22][23][24][25]30,37,411, although in some studies the relationship was not as clear [5,16]. Taken together, these past studies indicate a generally strong correspondence between bulk tissue GAG and mechanical properties, with most of the studies involving homogeneous normal cartilage samples or homogeneously-degraded cartilage samples, and all depended on bulk assays to provide the biochemical correlate.…”

Intrinsic fluorescence and mechanical testing of articular cartilage in human patients with osteoarthritis

“…In prior work by Bae et al, human cartilage plugs were analyzed by India ink staining and video image analysis to obtain a light reflectance score, with the 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 purpose of characterizing this degeneration [10]. In these experiments, it was observed that India ink particles do not enter into healthy cartilage, but can be entrapped in irregular surfaces and will adhere to fibrillated cartilage.…”

Non‐enzymatic cross‐linking of collagen type II fibrils is tuned via osmolality switch

“…Depending on the intensity of the cross‐linking, that is, ageing, the color of cartilage undergoes alterations from white (normal cartilage) to brown (cross‐linked cartilage) 16. To quantify possible color changes as an indication of the cross‐linking following incubation with l ‐threose, samples were placed side‐by‐side and digital images from the cartilage surface were captured from above (Samsung Galaxy S6, 12 Megapixels) at the same time during the day.…”