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Chapter 9254Fig. 7: Intra-operative pictures of case 2. (a) Condensed bone chips in the scaffold in the condylar neck for lateral pterygoid muscle attachment (red arrow). (b) The implanted fossa component.MetalsA meta-analysis of implant-related metal sensitivity showed that 10% of the general population is allergic to at least one or more alloy components (usually nickel) found in orthopedic implants. In patients with a functioning prosthesis, this number increased to 23%, while for patients with a failing prosthesis, it was as high as 63%.(23) A more recent study reported that nickel, chromium, and cobalt induce allergic skin reactions in 20%, 4%, and 7%, respectively, of the general population in Europe and in 14%, 4%, and 9%, respectively, of the population in the United States.(24) The prevalence of metal sensitivity appears to be rising and is most pronounced in nickel-containing implants.(25) In contrast, only occasional sensitivity has been reported for titanium.(23) In a recent review, only two studies presented strong evidence of sensitization to commercially pure titanium.(26) In contrast to chromium-cobalt particles, titanium-aluminum-vanadium-containing particles of a similar size to those found in the surrounding tissues of failed prostheses in humans showed little toxicity in an in vitro study using rat macrophages, even at high concentrations.(27)These findings result in Ti6Al4V being the preferred titanium alloy in small load-bearing implant applications. Important to remark is that the use of grade 23 Ti6Al4V extra-low interstitial (ELI) is preferred for long-term implants, such as in joint applications. Because of the reduced oxygen, nitrogen, and iron content, this grade shows enhanced biocompatibility Nikolas de Meurechy NW.indd 254 05-06-2024 10:14