These are benefits that cannot be overlooked, and as such, efforts are being focused on further understanding and ultimately on preventing fretting corrosion phenomena at the modular taper interface. Whereas the orthopedic community recognizes MACC at modular interfaces as a concern, it also must be recognized that modularity in joint replacement is an important design feature that allows for placement of the optimum materials in certain locations, may allow for better restoration of anatomy, and may allow for easier revision should an implant fail. Furthermore, in vitro models to understand the performance of tapers in a simulated physiologic situation have been developed, and there are multiple reports linking cyclic loading of head-neck tapers to the generation of corrosion currents in these models. Many efforts have been made to document in vivo evidence of fretting corrosion through retrieval studies aimed at a better understanding of the mechanisms through which it occurs and the conditions that may lead to its initiation. Pending further in vitro and in vivo analyses, this approach may be able to preserve the advantages of modular junctions for surgeons while potentially limiting the downside risks associated with mechanically assisted crevice corrosion.įretting corrosion, or mechanically assisted crevice corrosion (MACC), of modular tapers is a well-documented process by which damage of the implant may lead to corrosion and wear debris that may cause a negative biological response in some patients including increased serum ion levels, pseudotumor formation, aseptic loosening, and others. This novel SRC-PEEK material may offer potential as a thin film gasket material for modular tapers. The SRC-PEEK gaskets in this study demonstrated higher crystallinity and crystalline orientation and improved monotonic tensile properties compared with bulk PEEK with the ability to effectively insulate Ti6Al4V and CoCrMo alloy surfaces and prevent the initiation of fretting corrosion under high contact-stress conditions. Minimal damage was observed on surfaces insulated with SRC-PEEK, whereas control surfaces showed considerable fretting corrosion damage and metal transfer. SRC-PEEK reduced fretting currents compared with metal-on-metal controls by two to three orders of magnitude in both variable load (4.0E−5 ± 3.8E−5 μA versus 2.9E−3 ± 7.1E−4 μA, respectively, p = 0.018) and variable potential (7.5E−6 ± 4.7E−6 μA versus 5.3E−3 ± 1.4E−3 μA, respectively, p = 0.022) fretting corrosion testing. SRC-PEEK showed improved mechanical properties to bulk PEEK (modulus = 5.0 ± 0.3 GPa, 2.8 ± 0.1 GPa, respectively, p < 0.001) and higher crystallinity to bulk PEEK (44.2% ± 3%, 39.5% ± 0.5%, respectively, p = 0.039), but had comparable crystalline orientation as compared with the initial PEEK fibers. SRC specimens were analyzed for traces of alloy transferred to the surface using energy dispersive spectroscopy after pin-on-disk testing. Pins, disks, and SRC samples were imaged for damage (on alloy and SRC surfaces) and evidence of corrosion (on alloy pin and disk surfaces). Fifty-micron cyclic motion at 2.5 Hz was applied to the interface, first over a range of loads (0.5–35 N) while held at −0.05 V versus Ag/AgCl and then over a range of voltages (−0.5 to 0.5 V) at a constant contact stress of 73 ± 19 MPa for SRC-PEEK and 209 ± 41 MPa for metal-on-metal, which were different for each group as a result of changes in true contact area due to variations in modulus between sample groups. SRC-insulated pin-on-disk samples were compared with metal-on-metal control samples in pin-on-disk fretting corrosion experiments using fretting current and fretting mechanics measurements. SRC-PEEK, bulk isotropic PEEK, and the in-house-made PEEK fibers were analyzed for thermal transitions (T g, T m) through differential scanning calorimetry, crystallinity, crystal size, crystalline orientation (Hermanns orientation parameter) through wide-angle x-ray scattering, and modulus, tensile strength, yield stress, and strain to failure through monotonic tensile testing. SRC-PEEK was fabricated by hot compaction of in-house-made PEEK fibers by compacting uniaxial layups at 344☌ under a load of 18,000 N for 10 minutes. The purpose of this study is to characterize a novel material, self-reinforced composite polyetheretherketone (SRC-PEEK) and to evaluate its ability to inhibit fretting corrosion in a pin-on-disk metal-on-metal interface test. Fretting corrosion in medical alloys is a persistent problem, and the need for biomaterials that can effectively suppress mechanically assisted crevice corrosion in modular taper junctions or otherwise insulate metal-on-metal interfaces in mechanically demanding environments is as yet unmet.
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