New insights into fretting corrosion products from modular total hip replacement revision

摘要

Introduction: Adverse tissue reaction (pseudotumor formation) associated with corrosion products generated from modular interfaces is one major reason for modular total hip replacements (THR) revision. Particularly, the fretting corrosion products from interface between femoral head and stem neck (head-neck junction) become a growing concern among the medical community because of its potential link to pseudotumor formation in MoP (metal-on-polyethylene articulation) system • the most majority of implants used today. Unfortunately, the nature of fretting corrosion products remains inconclusive. Since cellular response varies according to composition and shape of paniculate materials, understanding the nature of these fretting products is essential for identifying the major stimuli trigging pseudotumor formation. The purpose of this study is to identify the nature of fretting corrosion products in modular interface, periprosthetic tissues and synovial fluid from modular THR revision using various advanced techniques including synchrotron radiation. These results will be used to explain the in-vivo development of fretting corrosion products and assist developing proper in-vitro cell culture model on investigation of pseudotumor formation. Materials and Methods: 7 MoP and 4 MoM implants along with periprosthetic tissues and synovial fluids were concerted from patients with pseudotumor following university ethics approval. Corrosion particles located at head-neck junction of the implant, synovial fluids as well as periprosthetic tissue were analyzed. Results and Discussion: Fretting corrosion products at head-neck junction are mainly dusters of nanosized crystals consisting of Cr (Ⅲ) and Mo (Ⅵ). These corrosion product exhibited typical crystalline patterns under X-ray diffraction at interplanar distances of 2.46,2.19,1.69 and 1.43A. This unknown diffraction feature is different from Cr_2O_3, which was widely reported in literature. This structural feacture could be used to identify fretting corrosion products between Co-26Cr-6Mo alloy and Ti-6Al-4V alloy in the future. Corrosion product formed at head-neck interface started to change its nature from the opening site of the interface. Some corrosion products located at the opening site of the interface presented relatively higher P and lower Mo in contrast to major corrosion products found inside the junction. Corrosion products at tissue and synovial fluid shared similar properties in terms of composition and crystal structure with those at opening site of the interface. It strongly supported the in-vivo migration pathway of corrosion particles from modular interface to the opening site, synovial fluid and then periprosthetic tissue. These results further strengthened the possible link of fretting corrosion products at modular interface with adverse local tissue reaction. Another interesting result is the widespread existence of Mo in the fretting-corrosion products. Mo only takes up around 6 wt% in the CoCrMo alloy and some Laboratory studies indicated the presence of Mo oxide in the passive film of the CoCrMo. However, limited studies have been reported on the Mo of fretting corrosion products in retrieved modular implants. The role of Mo in adverse tissue reaction is unknown and needs further investigation in in-vitro cell culture experiments.