Influence of synovia constituents on tribological behaviors of articular cartilage

The extremely low friction and minimal wear in natural synovial joints appear to be established by effective lubrication mechanisms based on appropriate combination of articular cartilage and synovial fluid.The complex structure of cartilage composed of collagen and proteoglycan with high water content contributes to high load-carrying capacity as biphasic materials and the various constituents of synovial fluid play important roles in various lubrication mechanisms.However,the detailed differences in functions of the intact and damaged cartilage tissues,and the interaction or synergistic action of synovia constituents with articular cartilage have not yet been clarified.In this study,to examine the roles of synovia constituents and the importance of cartilage surface conditions,the changes in friction were observed in the reciprocating tests of intact and damaged articular cartilage specimens against glass plate lubricated with lubricants containing phospholipid,protein and/or hyaluronic acid as main constituents in synovial fluid.The effectiveness of lubricant constituents and the influence of cartilage surface conditions on friction are discussed.In addition,the protectiveness by synovia constituents for intact articular cartilage surfaces is evaluated.

Biomimetic artificial cartilage:fibre-reinforcement of PVA hydrogel to promote biphasic lubrication mechanism

The fibre-reinforced structure in synovial articular cartilage plays an important role in enhancing the fluid load support in the biphasic lubrication mechanism.Poly(vinyl alcohol)(PVA)hydrogel is a potential biomimetic articular cartilage material.In this study,PVA hydrogel was reinforced with PVA fibres to improve its frictional properties.By computational analysis,the position of the PVA fibre layer was examined with a migrating contact condition to reduce the friction coefficient.To improve the fibre reinforcement,a method for fibre placement was developed to retain the initial strain of the fibre in the hydrogel matrix.The experimental results showed that the fibre-reinforced PVA hydrogel with a surface fibre layer had a low friction coefficient of 0.031 in pure water.The fibre-reinforced PVA hydrogel successfully reduced friction coefficient.

Transitional behaviour between biphasic lubrication and soft elastohydrodynamic lubrication of poly(vinyl alcohol)hydrogel using microelectromechanical system pressure sensor

The soft hydrogel material is expected for a candidate material as biomimetic artificial cartilage with synergisticfunctionalities of adaptive multimode lubrication.In boundary lubrication mode of hydrogel material,the biphasiclubrication mechanism cooperatively exerts its functionality.In hydrodynamic lubrication mode,it is preferable that thelubricating surfaces be impermeable to trap the fluid pressure in contact surfaces,whereas the actual biphasic materiallike a hydrogel is a permeable material with surface porosity.lt is indicated that the interstitial fluid pressurisation inthe permeable biphasic material can contribute to significant fluid load support under lower sliding speed condition.So,the authors examined how the contrary fluid pressure effect appears in the transition from the boundarylubrication mode to soft elastohydrodynamic lubrication mode.In the experiment,a small pressure sensor was utilisedto measure the in-situ fluid pressure in sliding condition.Although the experimental condition of this study wasselective,the result showed a possibility of the negative effect of the biphasic surface,in which the permeable surfacediminished the hydrodynamic fluid pressure.This means that one should manage and enhance the biphasic lubricationabilities in wide operation range when the hydrogel material was used as a load bearing material.

Erratum to: Influence of synovia constituents on tribological behaviors of articular cartilage

Erratum to Friction 1(2):150-162(2013)DOI 10.1007/s40544‐013‐0010‐6 The original version of this article unfortunately contained the incorrect lengend“HA 0.5 wt%+DPPC 0.01 wt%+albumin 1.4 wt%”in Fig.7 on page 155,instead of.

My personal stories and anecdotes with the late Professor Duncan Dowson

1JOHN B.MEDLEY Professor Duncan Dowson had a major influence on my life,both personal and professional.He supervised my PhD,collaborated with me on setting up the Leeds-Waterloo Stu-dent Exchange Program and co-authored academic papers with me.During my PhD studies,he even,indirectly,found me a wife(Judith Dowling)who came from his research group.Duncan always took an interest in my career,my ideas and my life.He was my friend.I have tried,in this short rendition of stories and anecdotes,to convey the essence of my personal interactions with Duncan.