Why the study?
Does lubricant viscosity affect frictional resistance and lubrication mode in hip prostheses?
Does lubricant viscosity affect frictional resistance and lubrication mode in hip prostheses?
In vivo synovial fluid after total hip replacement has a viscosity < 0.1 Pas, which results in suboptimal mixed lubrication rather than full fluid film lubrication.
Low in vivo viscosity may drive mixed lubrication in hip prostheses; animal data leave open whether viscosity modification improves implant performance.
McKee-Farrar, Charnley and Muller prostheses have been studied in a hip function simulator using a range of silicone fluids as lubricants. Frictional resistance was measured continuously while the joints were subjected to dynamic loading. It was observed that the lubricant viscosity was very important to the mode of lubrication prevailing and that for viscosities in excess of 0.1 Pas, full fluid film lubrication was achieved. At viscosities which were less than this, mixed lubrication resulted These results can be extrapolated to the clinical situation where it was found that after hip surgery for total joint replacement, the synovial fluid produced around the prosthesis had a viscosity which was less than 0.1 Pas, and therefore could not give the most advantageous lubrication in these joints in vivo.
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O’Kelly et al. (1979) studied this question.
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