In vivo corrosion

Buchanan, R. A. and Lemons, J.E. In Vivo Corrosion-Polarisation Behavior of Titanium-base and Cobalt-base Surgical Alloys , Transactions of the Eighth Annual Meeting of the Society for Biomaterials, Orlando, Florida (1982)... 

Gettleman, L., Cocks, F. H., Darmiento, L. A., Levine. P. A., Wright, S. and Nathanson, D. Measurement of In Vivo Corrosion Rates in Baboons and Correlation with In Vitro Tests , Journal of Dental Research, 59, 689-707 (1980)... 

The successful clinical use of titanium and cobalt-chromium alloy combinations has been reported Lucas etal. also investigated this combination using electrochemical studies based on mixed potential and protection potential theories. Verification of these studies was made by direct coupling experiments. The electrochemical studies predicted coupled corrosion potentials of -0.22 V and low coupled corrosion rates of 0.02 ft A/cm. Direct coupling experiments verified these results. The cobalt-titanium interfaces on the implants were macroscopically examined and no instances of extensive corrosion were found. Overall, the in-vitro corrosion studies and the examination of retrieved prostheses predicted no exaggerated in-vivo corrosion due to the coupling of these cobalt and titanium alloys. 

Black J (1988) In vivo corrosion of a cobalt-base alloy and its biological consequences. In Hildebrand HF and Champy M, eds. Biocompatibility of Co-Cr-Ni alloys. NATO-ASI Series 158 A, pp. 83 — 100. Plenum, London-New York... 

Shahgaldi, B. R, Heatley, R W., Dewar, A and Corrin, B. (1995), In vivo corrosion of cobalt-chromium and titanium wear particles, J. Bone Joint Surg. 77B(6) 962-966. 

The biocompatibility of HO2 has been demonstrated by the formation of apatite on Ti02 substrates in simulated body fluids [166-169] (Figure 1.11). As an example, plasma-sprayed Ti02 coatings on Ti alloys have shown promising in vivo corrosion characteristics, and may act as a chemical barrier against the release of metal ions from medical implants [170]. 

J.L. Gilbert, C.A. Buckley, and J.J. Jacobs, In vivo corrosion of modular hip prosthesis components in mixed and similar metal combinations. The effect of crevice, stress, motion, and alloy coupling. Journal of Biomedical Materials Research, 27, 1533-1544 (1993b). 

In this chapter the variables affecting in vivo corrosion, the tests used to assess it, the materials used for implants (and the standards governing them), and various aspects that make the in vivo corrosion environment unique are discussed. Much useful information related to these subjects is found in the Medical and Dental chapter in the "Testing in Industries section. 

The gases dissolved in body fluids also can play an important role in implant alloy corrosion. The most important of these is oxygen, whose partial pressure within the body is widely variable from about 2.67 x 10 to 1.33 x lO" Pa [3]. Sometimes implant surfaces can be in contact with areas of widely different pOj, creating the possibility for differential aeration cells to develop. Carbon dioxide is another gas that can be important for in vivo corrosion, because of its influence on pH. 

An additional unique feature of the in vivo corrosion environment is the existence of bioelectric effects. These are potentials and ionic currents of physiological origin resulting from nerve and muscle activity, heart and brain function, stresses applied to skeletal tissues, etc. Since their magnitudes are small, usually they cannot be expected to have much influence on in vivo corrosion processes. In cases of border-line passivity, however, it is possible that these potentials could polarize portions of implant surfaces sufficiently to exacerbate pitting processes [74]. 

Implant design can alter the corrosion performance of alloys in vivo. A case in point of a device whose complex design has spurred much interest in its corrosion behavior is that of the cardiovascular stent [75,76]. To consider another example, many prosthetic devices and fracture fixation implants are by nature multicomponent or modular. This means they have various pieces that mate together, e.g., screws and screw holes in plates. These locations may be foci of localized corrosion processes such as crevice corrosion or (in the case of relative motion) fretting corrosion or both. Careful design of such components can minimize in vivo corrosion problems. 

Testing in the laboratory allows the many complex variables discussed in the previous section to be investigated individually and in combination with each other. The in vivo corrosion environment is one that is sufficiently aggressive to cause a variety of corrosion phenomena. Therefore, a number of different types of tests have been developed and should be used to assess the in vivo resistance to corrosion of newly developed materials. 

Gil rt, J. L., Buckley, C. A., and Jacobs, J. J., "In Vivo Corrosion of Modular Hip Prosthesis Components in Mixed and Similar Metal Combinations. The Effect of Crevice, Stress, Motion, and Alloy Coupling, Journal of Biomedical Materials Research, Vol. 27, 1993, pp. 1533-1544. 

Witte F, Fisher J, Nellesen J, Crostack H-A, Kaese A, Pisch A et al. (2006), In vitro and in vivo corrosion measurements of magnesium alloys . Biomaterials, 27, 7, 1013-1018. 

Key words degradable metals, biocompatibility, in vivo corrosion, in vitro corrosion, magnesium implant. 

In vivo corrosion of magnesium (Mg) alloys what happens in living tissue ... 

Table 10.3 In vivo corrosion rates (mm/yr) calculated from the volume reduction of the corroding metal implant according to equation 10.6. With kind permission from Elsevier (Witte et a ., 2010).

Witte, F., Kaese, V., Haferkamp, H., Switzer, E., Meyer-Lindenberg, A., Wirth, C. J. Windhagen, H. (2005) In vivo corrosion of four magnesium alloys and the associated bone response. Biomaterials, 26, 3557-63. 

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