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- Title
Experimental verification of the role of interstitial fluid pressurization in cartilage lubrication
- Authors
Krishnan, Ramaswamy; Kopacz, Monika; Ateshian, Gerard A.
- Abstract
The objective of the current study was to measure the friction coefficient simultaneously with the interstitial fluid load support in bovine articular cartilage, while sliding against glass under a constant load. Ten visually normal 6-mm-diameter cartilage plugs harvested from the humeral head of four bovine shoulder joints (ages 2–4 months) were tested in a custom friction device under reciprocating linear motion (range of translation ±2 mm; sliding velocity 1 mm/s), subjected to a 4.5 N constant load. The frictional coefficient was found to increase with time from a minimum value of <f>μmin=0.010±0.007</f> (mean ± SD) to a maximum value of 0.243 ± 0.044 over a duration ranging from 920 to 19,870 s (median: 4,560 s). The corresponding interstitial fluid load support decreased from a maximum of 88.8 ± 3.8% to 8.7 ± 8.6%. A linear correlation was observed between the frictional coefficient and interstitial fluid load support (<f>r2=0.96±0.03</f>). These results support the hypothesis that the temporal variation of the frictional coefficient correlates negatively with the interstitial fluid load support and that consequently interstitial fluid load support is a primary mechanism regulating the frictional response in articular cartilage. Fitting the experimental data to a previously proposed biphasic boundary lubrication model for cartilage yielded an equilibrium friction coefficient of <f>μeq=0.284±0.044</f>. The fraction of the apparent contact area over which the solid cartilage matrix was in contact with the glass slide was predicted at <f>ϕ=1.7±6.3%</f>, significantly smaller than the solid volume fraction of the tissue, <f>ϕs=13.8±1.8%</f>. The model predictions suggest that mixed lubrication prevailed at the contact interface under the loading conditions employed in this study.
- Subjects
CARTILAGE; EXTRACELLULAR fluid; CONNECTIVE tissues; LIGAMENTS
- Publication
Journal of Orthopaedic Research, 2004, Vol 22, Issue 3, p565
- ISSN
0736-0266
- Publication type
Article
- DOI
10.1016/j.orthres.2003.07.002