Surface damage of bovine articular cartilage-off-bone: the effect of variations in underlying substrate and frequency

Abstract

BackgroundChanges in bone mineral density have been implicated with the onset of osteoarthritis, but its role in inducing failure of articular cartilage mechanically is unclear. This study aimed to determine the effect of substrate density, as the underlying bone, on the surface damage of cartilage-off-bone, at frequencies associated with gait, and above.MethodsBovine articular cartilage samples were tested off-bone to assess induced damage with an indenter under a compressive sinusoidal load range of 5–50 N at frequencies of 1, 10 and 50 Hz, corresponding to normal and above normal gait respectively, for up to 10,000 cycles. Cartilage samples were tested on four underlying substrates with densities of 0.1556, 0.3222, 0.5667 and 0.6000 g/cm3. India ink was applied to identify damage as cracks, measured across their length using ImageJ software. Linear regression was performed to identify if statistical significance existed between substrate density, and surface damage of articular cartilage-off-bone, at all three frequencies investigated (p < 0.05).ResultsSurface damage significantly increased (p < 0.05) with substrate density at 10 Hz of applied frequency. Crack length at this frequency reached the maximum of 10.95 ± 9.12 mm (mean ± standard deviation), across all four substrates tested. Frequencies applied at 1 and 50 Hz failed to show a significant increase (p > 0.05) in surface damage with an increase in substrate density, at which the maximum mean crack length were 3.01 ± 3.41 mm and 5.65 ± 6.54 mm, respectively. Crack formation at all frequencies tended to form at the periphery of the cartilage specimen, with multiple straight-line cracking observed at 10 Hz, in comparison to single straight-line configurations produced at 1 and 50 Hz.ConclusionsThe effect of substrate density on the surface damage of articular cartilage-off-bone is multi-factorial, with an above-normal gait frequency. At 1 Hz cartilage damage is not associated with substrate density, however at 10 Hz, it is. This study has implications on the effects of the factors that contribute to the onset of osteoarthritis.

Frequency dependent viscoelastic properties of porcine brain tissue

“…Four half porcine brains under 8 months old were obtained from a supplier (Dissect, Kings Heath, Birmingham, UK). Following arrival in the laboratory the samples were wrapped in tissue paper soaked in Ringer's solution (Oxoid Ltd, Basingstoke, UK) and then stored at -40C in a freezer in double heat-sealed plastic bags [30,31]. From previous studies, such freezing treatment does not change the mechanical properties of biological tissues [32].…”

In Vitro Effects of Bupivacaine on the Viability and Mechanics of Native and Engineered Cartilage Grafts

“…10,23,28 It has also been used as a model to study osteoarthritis pathogenesis. 30,32,34 There are extensive data on the histology and mechanical properties of the tissue. 30,34 Moreover, the large joint size allows for sufficient explant material to perform statistically powered in vitro studies.…”

A technique for measuring the frictional torque of articular cartilage and replacement biomaterials

“…Bovine articular cartilage has been identified as a suitable model for human cartilage [30]. See our previous work on the protocol for storage and identification of suitable cartilage areas for testing [31], [32]. The underlying subchondral bone was used for the secure fixation of the specimen for friction measurements.…”

“…The indenter was designed with a diameter of 5 mm, 7.5 mm in length and with a 0.5 mm chamfered end to prevent damage to the cartilage [31], [35]. The chamfered-polished end ensured a smooth surface for the assessment of the frictional torque.…”

“…The rig was designed with a diameter of 63 mm and a thickness of 13.5 mm. Ringer's solution was used as the lubricant similar to previous cartilage friction work [3], prepared as described previously [31]. For the preservation of the hydration of the tissue during testing, the Ringer's solution was inserted within the test rig [35]- [37].…”