Investigation On The Wear And Tribocorrosion Of Metal-on-polymer Total Hip Prostheses

Charnley’s metal-on-polyethylene(M-o-P)total hip replacement(THR)is widely regarded as the gold standard for the end-stage arthritis treatment.However,due to the cyclic loading,the wear and fretting corrosion of the modular hip prosthesis are critical engineering issues that can limit the lifetime of THR.Therefore,the study of the evolution mechanism of wear and biotribocorrosion of the hip prosthesis has indispensable significance in solving the above engineering problems.However,there are still technical difficulties in studying the corrosion behavior of hip prostheses in a physiological environment,while studies of different influencing factors under simulated human gait activities are even rarer.Based on this,this paper established a method to assess the wear and corrosion behavior of hip prosthesis,elucidates the relationship between the state of the lubricating medium,differences in metal corrosion sources,differences in femoral head materials,differences in prosthesis design and the performance of hip prostheses.The main work of the full paper are as follows.(1)The biotribocorrosion of metal-on-polymer(M-o-P)hip prosthesis under long-term gait has been investigated.It revealed that the damage of the M-o-P hip prosthesis under walking gait was the result of the interaction between wear and corrosion.The taper/trunnion interface was the main metallic corrosion source of the M-o-P hip prosthesis.The study of several influencing factors,such as equipment downtime,deionized water rinsing,and protein status in serum,showed that the formation and disruption of the adsorbed protein layer was the main reason for the cyclic change of corrosion behaviors in M-o-P hip prosthesis.The tribolayer was observed on the worn area of the taper/trunnion interface,which is mainly composed of graphitized carbon.In addition,both the tribolayer and adsorbed protein layer can inhibit corrosion by isolating the metal surface from the serum solution.(2)The femoral head material has a significant effect on the biotribocorrosion of the taper/trunnion of M-o-P total hip prosthesis.It was shown that the corrosion resistance of the three femoral head prostheses was in a descending order of Ceramic,Oxidized Zirconium and Cobalt-chromium-molybdenum.The inductively coupled plasma mass spectrometry(ICP-MS)technique was used to quantify the metal ion concentrations in the serum solution of the three femoral head prostheses,and it was found that the damage at the taper/trunnion interface of all three materials was of the ‘wear-dominated’ type.The wear and corrosion type of M-o-P hip prosthesis changed from ‘wear-corrosion’ to ‘wear-dominated’ when the ball head diameter was increased from 28 mm to 36 mm,indicating that the contribution of increasing the ball head diameter to the fretting wear at the taper/trunnion interface was higher than that of fretting corrosion.The results of Raman spectroscopy revealed that the femoral head material was related to the formation of the tribolayer at the taper/trunnion interface.(3)The wear and corrosion of the dual-mobility hip prosthesis(dual-mobility cup)was investigated using an established test method.The wear results showed that the volumetric wear rate of the dual-mobility cup was 37.9% higher than that of the conventional hip joint.Electrochemical and ICP-MS results showed that both the metal liner-metal cup interface and the taper/trunnion interface of the dual-mobility joint were the important metallic sources of corrosion.Compared with the damage mechanism of the conventional joint,the taper/trunnion interface in the dual-mobility joint showed a ‘wear-corrosion’ damage mechanism,while the ‘wear-dominated’ damage occurred on the metal liner-cup interface.(4)Both simulation and experimental results showed that the wear of the polyethylene liner of the dual-mobility cup was greater than that of the conventional joint,which was attributed to the additional bearing surface of the dual-mobility cup.By comparing the contact mechanics and electrochemical results at the taper-trunnion interface of conventional and dual-mobility joints,it was found that the contact mechanics and wear prediction results at the taper/trunnion interface of dual-mobility cup were equivalent to those of conventional joints,and therefore the additional articulation design of the dual mobility cup is the main reason for the difference in corrosion behavior between the two kinds of hip prostheses.This paper built an electrochemical test platform for wear and corrosion behavior of M-o-P hip prostheses,which provides strong support for the pre-clinical assessment of wear and corrosion behavior of hip prostheses,and benefit for the doctors to make surgical plans.This study provided data support and theoretical reference for the ultimate realization of reducing fretting corrosion at the metal interface and enhancing the life-time of hip prostheses.