Reciprocating sliding wear behavior of alendronate sodium-loaded UHMWPE under different tribological conditions

The aim of this study is to investigate the tribological behaviors and wear mechanisms of ultra-high molecular weight polyethylene (UHMWPE) loaded with alendronate sodium (ALN), a potential drug to treat osteolysis, under different normal loads and lubrication conditions. A mixture of UHMWPE powder and ALN (1.0 wt.%) solution was dried and hot pressed. The static and dynamic friction coefficients of UHMWPE–ALN were slightly higher than those of UHMWPE except under normal load as 10 N and in 25 v/v % calf serum. The specific wear rates of UHMWPE–ALN and UHMWPE were the lowest in 25 v/v % calf serum compared to those in deionized water or physiological saline. In particular, the specific wear rate of UHMWPE–ALN was lower than that of UHMWPE at 50 N in 25 v/v % calf serum. The main wear mechanisms of UHMWPE and UHMWPE–ALN in deionized water and UHMWPE in physiological saline were abrasive. The main wear mechanism of UHMWPE–ALN in physiological saline was micro-fatigue. In 25 v/v % calf serum, the main wear mechanism of UHMWPE and UHMWPE–ALN was abrasive wear accompanied with plastic deformation. The results of Micro-XRD indicated that the molecular deformation of UHMWPE–ALN and UHMWPE under the lower stress were in the amorphous region but in the crystalline region at the higher stress. These results showed that the wear of UHMWPE–ALN would be reduced under calf serum lubricated, which would be potentially applied to treat osteolysis.