Articular cartilage wear characterization with a particle sizing and counting analyzer.

Quantitative measurements of cartilage wear have been challenging, with no method having yet emerged as a standard. This study tested the hypothesis that latest-generation particle analyzers are capable of detecting cartilage wear debris generated during in vitro loading experiments that last 24 h or less, by producing measurable content significantly above background noise levels otherwise undetectable through standard biochemical assays. Immature bovine cartilage disks (4 mm diameter, 1.3 mm thick) were tested against glass using reciprocal sliding under unconfined compression creep for 24 h. Control groups were used to assess various sources of contamination. Results demonstrated that cartilage samples subjected to frictional loading produced particulate volume significantly higher than background noise and contamination levels at all tested time points (1, 2, 6, and 24 h, p < 0.042). The particle counter was able to detect very small levels of wear (less than 0.02% of the tissue sample by volume), whereas no significant differences were observed in biochemical assays for collagen or glycosaminoglycans among any of the groups or time points. These findings confirm that latest-generation particle analyzers are capable of detecting very low wear levels in cartilage experiments conducted over a period no greater than 24 h.

Effect of glutaraldehyde fixation on the frictional response of immature bovine articular cartilage explants.

This study examined functional properties and biocompatibility of glutaraldehyde-fixed bovine articular cartilage over several weeks of incubation at body temperature to investigate its potential use as a resurfacing material in joint arthroplasty. In the first experiment, treated cartilage disks were fixed using 0.02, 0.20 and 0.60% glutaraldehyde for 24h then incubated, along with an untreated control group, in saline for up to 28d at 37°C. Both the equilibrium compressive and tensile moduli increased nearly twofold in treated samples compared to day 0 control, and remained at that level from day 1 to 28; the equilibrium friction coefficient against glass rose nearly twofold immediately after fixation (day 1) but returned to control values after day 7. Live explants co-cultured with fixed explants showed no quantitative difference in cell viability over 28d. In general, no significant differences were observed between 0.20 and 0.60% groups, so 0.20% was deemed sufficient for complete fixation. In the second experiment, cartilage-on-cartilage frictional measurements were performed under a migrating contact configuration. In the treated group, one explant was fixed using 0.20% glutaraldehyde while the apposing explant was left untreated; in the control group both explants were left untreated. From day 1 to 28, the treated group exhibited either no significant difference or slightly lower friction coefficient than the untreated group. These results suggest that a properly titrated glutaraldehyde treatment can reproduce the desired functional properties of native articular cartilage and maintain these properties for at least 28d at body temperature.