Title

AN ELECTROCHEMICAL METHOD TO EVALUATE LOCALIZED CORROSION IN RETRIEVED MODULAR TAPERED ORTHOPEDIC IMPLANTS

Date of Award

December 2016

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Biomedical and Chemical Engineering

Advisor(s)

Jeremy L. Gilbert

Subject Categories

Engineering

Abstract

In most of retrieval cases, severe taper damage and failed implant surgery result in revisions. However, some damage of tapers might not be too severely to be require replacinged the component. Surgeons, however, have no clear means for judging the quality of the corroded interface other than visual inspection. Because of this, it is very critical to have a method to determine the extent and severity of corrosion and fretting damage at the modular junction to minimize the risks to patients and to determine whether a patient needs to have their implant undergo revision surgery for secondary hip replacementremoved during revision surgery.

This study aims to develop an assessment method for new and damaged tapered head and neck junctions to analyze the corrosion state of retrieved taper interfaces of modular hip prostheses. To do this, the relationship between the degree of fretting and corrosion damage of a set of retrieved modular hip prostheses with a range of corrosion damage present, and their associated corrosion behavior of damaged tapersneeds to be established.

It was hypothesized in this study that the retrieved modular hip prostheses would reveal with a range of surface corrosion and fretting damage, particularly corrosion, on the bore-cone tapers and that the said surface damage would exhibit different corrosion characteristics (electrochemical impedance characteristics) depending on the type of designs and taper geometryseverity of corrosion observed. A visual corrosion scoring method (The Goldberg scale) . Moreover, it is also hypothesized that the corrosion behavior of the retrieved tapers is a function of the extent of prior corrosion damage. A visual scoring system, the Goldberg’s 4-point scoring system, is was used to determine any indication of the extent and severity of corrosion based on the extent and severity of surface damage seen at the taper. The taper surfaces were then evaluated using electrochemical impedance methods and a correlation between the results from electrochemical test could be correspond to and the Goldberg’s scale was investigated.

The results of this study establish show that the retrieved modular hip prostheses with a wide range of corrosion damage exhibit surface damage on the bore-cone tapers. Strong evidence of corrosion in for both same-metal and mixed metal tapered modular hip prostheses is presented. Moreover, various types of corrosion such as etching, fretting, pitting, intergranular attack, fracture, and a selective leakage of cobalt exist in vivo in the taper interfaces of modular hip prostheses studied. The results of the electrochemical test showed that the decline exhibited a strong correlation in the constant phase element (CPE) impedance and CPE exponent polarization resistance and interfacial capacitance of most of the samples tested and their Goldberg score. indicates an increase in corrosion. Also, the impedance and phase angle at 0.01 Hz could were different based on the extent of corrosion observed. This was translated into corrosion current from the whole surface. The presence of mechanically assisted crevice corrosion was confirmed based on the tests and observations conducted on the samples. However, the result might be due to

While there were the limitations in this study related to and unstable conditions during some of the experiments, this method was reasonably able to assess the extent of taper damage present. Future studies are necessary to learn more about the damage mechanisms that exist at the head and neck junctions and their effect on the impedance behavior of the damaged surface. The method described may be a possible means for clinical assessment of the extent of corrosion damage present in modular trunnions during revision surgery., this study established that severe corrosion could happen in modular head and neck junctions during in vivo function. Future studies should ensure optimal conditions and the stability of the experiment process to gain a better understanding of the relationship between the corrosion behavior of the retrieved tapers and the extent of prior corrosion damage. Overall, this study develops a new field for retrieval study of modular hip prostheses.

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