The incident I would like to briefly talk about is the abnormal corrosion-wear of β-Ti alloy TMZF (Ti-12Mo-6Zr-2Fe) in one model of Stryker’s early hip implants that was recalled in 2011. In this case, Stryker used an innovative TMZF alloy in the stem segment of their implant instead of the Ti-6Al-4V (Ti64) alloy which was popular at the time. While all hip implants degrade over a period time due to metal on metal abrasion, it was found that the TMZF alloy was degrading twice as fast and creating excessive metal shavings localized around the implant. These shavings both caused irritation to the site and compromised the integrity of the implant compounding the issue. After research was done to investigate this issue, it was found that the TMZF and Ti64 both had similar wear in dry conditions, however, in simulated bodily fluid, hydroxyapatite particles greatly accelerated the wear on TMZF due to its intrinsically poor strain hardening capacity. This result meant that under abrasive conditions from the hydroxyapatite particles, the Ti64 would be able to withstand the abrasion more effectively than TMZF which would have microscopic pieces ‘chip off’ due to its brittle material property. In the end, Stryker took full responsibility for the defect and offered corrective surgery and financial compensation to all those affected over the past decade by the defective hip implant. In addition, I believe that the FDA’s job is to perform its due diligence by mandating clinical trials, however, they cannot be held responsible (like the manufactures should be) for any defective product if the defect was not initially visible in research/ report.

http://www.sciencedirect.com/science/article/pii/S1742706116303245