Surgical implants corrosion

Pitting and stress corrosion cracking, although usually associated with stainless steels in chloride media, have not been observed on recovered surgical implants. Implants often exhibit cracks and surface pitting, but these are most likely the result of improper manufacture rather than corrosion . 

One of the most serious corrosion problems associated with type 316 stainless steel is its susceptibility to crevice corrosion. The incidence and extent of this type of corrosion in surgical implants was stressed by Scales eta/. who reported the presence of crevice corrosion in 24% of type 316L bone plates and screws examined after removal from patients. This record however compared favourably with the presence of crevice corrosion in 51 % of 18-8 stainless plates, demonstrating the superiority of the molybdenum-containing grade. 

Intercrystalline corrosion was a serious problem with the austenitic stainless steels early in their development since carbon contents then were relatively high, e.g. En58J contained up to 0.12type stainless steel contained up to 0.08 Vo C. The problem in relation to surgical implants has been reported by Scales eta/. and as a result of this and several other reports the British, American and International Standards specified the use of a 316S12 type austenitic stainless steel which contains 0.03 Vo C max. The use of the lower carbon content stainless steels as specified in the various standards has now eliminated the problem of sensitisation of implants. If manufacturers do use the 0.08% C versions they have to be very careful with the forging temperatures or anneal the prostheses afterwards. 

Greene, N. D., Corrosion of Surgical Implant Alloys A Few Basic Ideas , in Corrosion and Degradation of Implant Materials, Second Symposium, (Eds) A. C. Fraker and C. D. Griflin, 5-10 ASTM Publication STP 859, Philadelphia (1985)... 

Hughes, A. N., Jordan, B. A. and Orman, S., The Corrosion Fatigue Properties of Surgical Implant Materials. Third Progress Report — May 1973 , Engineering in Medicine, 7, 135-141 (1978)... 

Revie, R. W. and Greene, N. D., Corrosion Behaviour of Surgical Implant Materials 1 Effects of Sterilisation , Corrosion Science, 9, 755-761 (1969)... 

Syrett, B. C. and Wing, S S., An Electrochemical Investigation of Fretting Corrosion of Surgical Implant Materials , Corrosion, 34, 379-386 (1978)... 

Solar R. J., Pollack, S. R. and Korostoffe, E., In-vitro Corrosion Testing of Titanium Surgical Implant Alloys An Approach to Understanding Titanium Release from Implants , Journal of Biomedical Materials Research, 13, 217-250 (1979)... 

Method for total immersion corrosion test for tank-type aircraft maintenance chemicals Method for total immersion corrosion test for aircraft maintenance chemicals Practice for assessment of compatibility of bio-materials (non-porous) for surgical implants with respect to effect of materials in muscle and bone... 

The test method ASTM F7464 covers the determination of the resistance to either pitting or crevice corrosion of passive metals and alloys from which surgical implants are produced. The resistance of surgical implants to localized corrosion is carried out in dilute sodium chloride solution under specific conditions of potentiodynamic test method. Typical transient decay curves under potentiostatic polarization should monitor susceptibility to localized corrosion. Alloys are ranked in terms of the critical potential for pitting, the higher (more noble) this potential, the more resistant is to passive film breakdown and to localized corrosion. (Sprowls)14... 

Titanium metal is lightweight and has high strength thus, it is used in aircraft and other structures where cost is not a major factor. It also resists corrosion, making it especially useful in surgical implants and prostheses. Titanium fibers are used as an asbestos substitute. Titanium s most widely used compound, titanium dioxide, is used as a white pigment in paints and plastics and as a food additive to whiten flour, dairy products, and candies. It is also used in cosmetics and sunscreen formulations. 

Corrosion of metallic surgical implant materials used in orthopedic, cardiovascular, and dental devices resulting in the release of metal ions to tissues, and degradation of the physical properties of polymeric implant materials due to interactions with tissue fluids and/or blood... 

The important forms of titanium are its dioxide, the tetrachloride compounds, and the metal. The metal and its alloys are used in applications such as the space industry, tubings and surgical implants or prostheses, where strength, lightness and resistance to corrosion are desirable. Titanium additions to chromium-nickel steel are transformed during production into titanium carbide inclusions with increased strength. Titanium tetrachloride is an intermediate in titanium production, and is used by the military for generating smokescreens. 

F746-87, Standard test method for pitting or crevice corrosion of metallic surgical implant materials. Annual Book of ASTM Standards, ASTM International, Philadelphia, Pa., 2000, p. 203, Vol. 13.01. 

Fraker, A.C., Ruff, A.W., Sung, P. von Orden, A.C. and Speck, K.M. (1983) Surface Preparation and Corrosion Behaviour of Titanium Alloys for Surgical Implants, in Titanium Alloys in Surgical Implants, (eds H.A. Cuckey and F. Kubli), ASTM STP 796, pp. 206-219. 

In an attempt to reduce the release of potentially harmful metal ions from Co-Cr-Mo surgical implants, a thin coating of TiN has been applied via physical vapour deposition (PVD) (Wisbey et al., 1987). In vitro corrosion performance has been investigated using electrochemical techniques. The release of Co and Cr ions is reduced by the presence of the TiN coating. Data concerning this study are shown in Figure 9.13. 

Steineman, S.G. (1985) Corrosion of Titanium and Titanium Alloys For Surgical Implant, in Lutergering, G., Swicker, U., Bunk, W. (eds). Titanium, Science, and Technology, Volume 2, DG fiir Metal. e.V. Oberuresel, Berlin, 1373-1379. 

---