Rheological behavior of an artificial synovial fluid – influence of temperature, shear rate and pressure

Rothammer, Benedict; Marian, Max; Rummel, Florian; Schroeder, Stefan; Uhler, Maximilian; Kretzer, Jan Philippe; Tremmel, Stephan; Wartzack, Sandro

doi:10.1016/j.jmbbm.2020.104278

Cited by 23 publications

(21 citation statements)

References 54 publications

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“…For a protein concentration of 20 g/L at a temperature of 37 • C a density of 1.0044 g/cm 3 was found. This is in very good agreement with the observations of Rothammer et al, who found a density of 1.0037 g/cm 3 at this setting point [33].…”

Section: Discussionsupporting

confidence: 93%

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Rheologic Behavior of Bovine Calf Serum

et al. 2021

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Recent studies have illuminated the rheological behavior of synovial fluid and the role of protein and hyaluronan (HA). However, with respect to artificial joint replacement in standardized wear simulations, bovine serum is used as fluid test medium. Little is known about the rheological characteristics of bovine serum, which are needed for precise tribological investigations. The steady shear viscosity η of bovine calf serum is determined for protein concentrations used in standardized wear simulations depending on shear rate γ˙ and temperature T. Additionally, the density of the serum is determined for both protein concentrations. The results show shear thinning behavior of bovine calf serum with a nearly Newtonian behavior in the range of high shear rates. Within the range of high shear rates, mean viscosities of η = 0.82–0.88 mPa·s were found for protein concentrations of 20 g/L and mean viscosities of η = 0.88–0.94 mPa·s for 30 g/L, decreasing with temperature. Densities of 1.004–1.005 g/cm3 and 1.007–1.008 g/cm3 were found for 20 and 30 g/L protein concentrations, respectively.

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Section: Discussionsupporting

confidence: 93%

“…With the zero-shear viscosity η 0 , the infinite shear viscosity η ∞ , the Cross time constant C and the Cross rate constant m. The four Cross constants were fitted following the rheological models suggested in literature for bovine serum [33] and human synovial fluid [27,28].…”

Section: Cross Modelmentioning

confidence: 99%

Rheologic Behavior of Bovine Calf Serum

et al. 2021

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“…The latter can play a crucial role for synovial joint tribology [ 68 , 71 ] and rheology [ 108 ] but was no constituent of the lubricant used in this study. However, the poor fluid film formation with predominantly mixed and boundary lubrication was a result of the low viscosity, which was in the range of human joints affected by inflammatory disease [ 77 ], and can be interpreted as a kind of worst-case scenario that the coatings had to withstand. Ultimately, it should be noted that UHMWPE is increasingly being replaced by HXLPE [ 9 ].…”

Section: Discussionmentioning

confidence: 99%

“…For an anti-microbiological function and to reduce calcium phosphate layers on the material surfaces, 1.85 g/L sodium azide (NaN 3 ) as well as 5.85 g/L ethylenediaminetetraacetate (EDTA) were added. Since the fluid substantially influences the tribological performance, a detailed characterization of the respective rheological properties and the suitability for mimicking human SF was already shown and discussed in [ 77 ]. The fluid was pre-cooled to 4 °C and subsequently deep-frozen at −20 °C.…”

Section: Methodsmentioning

confidence: 99%

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Amorphous Carbon Coatings for Total Knee Replacements—Part II: Tribological Behavior

et al. 2021

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Diamond-like carbon coatings may decrease implant wear, therefore, they are helping to reduce aseptic loosening and increase service life of total knee arthroplasties (TKAs). This two-part study addresses the development of such coatings for ultrahigh molecular weight polyethylene (UHMWPE) tibial inlays as well as cobalt-chromium-molybdenum (CoCr) and titanium (Ti64) alloy femoral components. While the deposition of a pure (a-C:H) and tungsten-doped hydrogen-containing amorphous carbon coating (a-C:H:W) as well as the detailed characterization of mechanical and adhesion properties were the subject of Part I, the tribological behavior is studied in Part II. Pin-on-disk tests are performed under artificial synovial fluid lubrication. Numerical elastohydrodynamic lubrication modeling is used to show the representability of contact conditions for TKAs and to assess the influence of coatings on lubrication conditions. The wear behavior is characterized by means of light and laser scanning microscopy, Raman spectroscopy, scanning electron microscopy and particle analyses. Although the coating leads to an increase in friction due to the considerably higher roughness, especially the UHMWPE wear is significantly reduced up to a factor of 49% (CoCr) and 77% (Ti64). Thereby, the coating shows continuous wear and no sudden failure or spallation of larger wear particles. This demonstrated the great potential of amorphous carbon coatings for knee replacements.

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Wear Mechanism of Superhard Tetrahedral Amorphous Carbon (ta‐C) Coatings for Biomedical Applications

Rothammer

Schwendner

Bartz

et al. 2023

Adv Materials Inter

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Tetrahedral amorphous carbon (ta‐C) coatings have the potential to protect biomedical implants from wear and increase their service life. This study elucidates the biocompatibility, mechanical properties, adhesion, and wear resistance of ta‐C coatings fabricated by physical vapor deposition on cobalt‐chromium‐molybdenum (CoCr) and titanium (Ti64) alloys as well as ultrahigh molecular weight polyethylene (UHMWPE). Satisfactory cytocompatibility is verified using contact angle and surface tension measurements as well as indirect and direct cell testing. Scratch testing demonstrates excellent adhesion to the substrates and as confirmed by nanoindentation, the coatings represent an up to 13‐fold and 182‐fold increase in hardness on the hard and soft materials. In metal pin‐on‐UHMWPE disk sliding experiments under simulated body fluid lubrication, the wear rates of the disk are reduced by 48% (against CoCr) and 73% (against Ti64) while the pin wear rates are reduced by factors of 20 (CoCr) and 116 (Ti64) compared to uncoated pairings. From optical and laser scanning microscopy, Raman measurements, and particle analyses, it is shown that the underlying substrates remain well protected. Nonetheless, focused ion beam scanning electron microscopy revealed coating process‐related and thermally driven subductions as well as tribologically induced near‐surface fatigue, which can potentially constitute critical wear mechanisms.

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Rheological behavior of an artificial synovial fluid – influence of temperature, shear rate and pressure

Cited by 23 publications

References 54 publications

Rheologic Behavior of Bovine Calf Serum

Rheologic Behavior of Bovine Calf Serum

Amorphous Carbon Coatings for Total Knee Replacements—Part II: Tribological Behavior

Wear Mechanism of Superhard Tetrahedral Amorphous Carbon (ta‐C) Coatings for Biomedical Applications

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