Adriana Esguerra Arce

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The introduction of modular design in total hip arthroplasty has enabled the use of different materials in one single configuration and the adjustment of the prosthesis to the patient's body, and facilitated medical revisions. However, modularity leads to the presence of new interfaces created between pieces in contact, raising the issue of degradation. Tribocorrosion phenomena have been identified as the main degradation mechanism due to the mechanical, chemical, and electrochemical conditions acting on the materials. In addition, conditions inside the human body are unclear, regarding electrochemical settings and the interaction between the electrochemical and mechanical action. This work is focused on the degradation of monopolar hip joint implants made from biomedical alloys such as stainless steel, Ti, and CoCr alloys. Three cases are presented and analyzed in terms of the degradation level along the trunnion length. Surface analysis done on a titanium trunnion showed a significant ploughing on the distal part, compared to what was found for stainless steel and cobalt-chromium alloys, which can produce a stuck in this area. Meanwhile, in the proximal part, wear debris is found, which suggests more movement in the internal part. Although few debris particles were identified in CoCr trunnion, a large amount of material inside the contact was observed. This could be related to the ploughing generated in the distal thread pattern, which allowed the material to come inside and outside the contact.

IMPRENTA UNIV ANTIOQUIA2021

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Fretting corrosion between bone and calcium phosphate-calcium titanate coatings

Adriana Esguerra Arce, Stefano Mischler

Biocompatibility is one of the biggest challenges for biomaterials development. This issue arises in the case of coatings. Calcium phosphate (CP) coatings are currently used to cover femoral stem implants, while calcium titanate (CT) has also been proposed as a coating for biomedical applications due to its good biocompatibility and osteoconductivity. However, its behavior under fretting corrosion conditions, one of the degradation mechanisms of hip joint implants, has not been studied. In this work, tribocorrosion behavior of calcium phosphate - calcium titanate coatings obtained by Radio Frequency (RF) magnetron sputtering onto AISI 304 stainless steel was evaluated. The coatings were deposited in 100%CP-0%CT, 75%CP-25%CT, 50%CP-50%CT, 25%CP-75%CT and 0%CP-100%CT volume proportions. An electrochemical cell integrated with a ball-on-flat reciprocating tribometer was used to investigate the performance of the coatings under fretting conditions against bone in Hank's solution at 37 degrees C. The suitability of three specific coating compositions for the protection of AISI 304 stainless steel, based on their hardness, non-conductive nature and absence of a passive layer, was demonstrated by open circuit potential measurements. It was concluded that 75CP-25CT and 0CP-100CT coatings are potential materials for bone tissue replacement and regeneration.

ELSEVIER SCIENCE SA2018

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Atomic aluminum content (x) effect on fretting-corrosion of Ti1-xAlxN coatings for orthopedic applications

Adriana Esguerra Arce, Stefano Mischler

Normal micro-movements at the bone-implant interface originate fretting-corrosion processes, thus releasing wear debris from the bone and metallic devices and compromising the fixability of the implant. Titanium aluminum nitride (Ti1-xAlxN) coatings have been considered to overcome these drawbacks and the effect of aluminum content on the fretting-corrosion resistance against bone in a simulated body fluid has been studied. Coatings were synthesized by magnetron co-sputtering by varying the power applied to the aluminum target. Morphology and chemical composition were studied by optical profilometry, SEM and XPS. Coatings with x=0.39, 0.47, 0.61 and 0.69 were obtained. Mechanical properties, adherence and corrosion behavior were assessed by nanoindentation, scratch test and potentiodynamic curves, respectively. The fretting-corrosion behavior was assessed at open circuit potential (OCP) using a tribo-electrochemical apparatus, bone-pins as the counterpart and Hank's solution as the simulated body fluid. It was found that the fretting-corrosion against bone in the simulated body fluid can damage the metal and coatings, thereby accelerating wear and increasing the current corrosion densities. Coatings with x=0.39, 0.47 and 0.61 are able to protect 304SS against fretting corrosion. The behavior of wear volume with aluminum content in coatings is related to the corrosion resistance and hardness to elastic modulus ratio. (C) 2016 Elsevier B.V. All rights reserved.

Elsevier Science Sa2016

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