Median time to first infection. Moderate optimism

[TwoStep]

Implants are said to last 10 years on average. Let’s say the time to failure follows an exponential distribution, then the rate of failure is λ=0.1 per year. When it fails we need a revision. According to [1] the probability of an infection is 10% for a revision surgery. So the rate of having a failure and getting an infection in the revision surgery is λ=0.1*0.1, that is, 1% per year. Then median time to first infection is (ln 2)/λ ~69 years. I think that’s cause for some optimism.

If the rate of infections increases with each surgery as suggested by another paper then none of this holds. On the other hand if you believe in self-reported infection rates from the popular doctors then the numbers will look better.

[1] https://www.ncbi.nlm.nih.gov/pmc/articl ... po=78.5714

[westerntown]

Thanks for making an expression for us. And I agree there is quite some optimism in these numbers