Effect of Surface Roughness on Friction of CoCrMo-on-UHMWPE Bearing in Total Hip Arthroplasty Under Lubrication of Bovine Serum Albumin

The study aims to examine the effect of surface roughness as well as lubricant and normal load on frictional response of CoCrMo-on-UHMWPE bearing using a custom friction-measuring device. A cylindrical CoCrMo pin with surface roughness of 0.25 mu m was prepared. Ten UHMWPE discs with different surface roughness of 2.5 and 0.25 mu m were machined. BSA at concentration of 25 mg/ml was prepared by dissolving in PBS. A custom pin-on-disc friction-measuring device was designed to measure the coefficient of friction (mu). The normal loads were varied in two values of 4 and 16 N at sliding velocity of 28 mm/s. The mean mu values were taken in 3600 s. Results demonstrated that BSA 25 mg/ml improved the frictional properties between CoCrMo-on-UHMWPE bearing (p < 0.0001) and the mu values were increase with the increase of the surface roughness as well as with the increase of the normal loads (p < 0.0001). These results suggest that BSA plays an important role in improving the lubricating ability of CoCrMo-on-UHMWPE bearing and the frictional response between CoCrMo-on-UHMWPE depend on the surface roughness as well as the normal load.