Tattooing numb area of old necrosis site, is it safe?

Tattooing the area should be safe at this point; however, you may be better off having the scar revised. After several years, there is often enough skin elasticity to remove relatively wide scars from skin necrosis. Good luck!

Thanks for your question.  Being 2 years out from surgery you should be perfectly fine to proceed with a tattoo of the scar(s) as long as the area is 100% healed.  Make sure you tell the tattoo artist that you have some numbness in that area so that he or she does not cause any injury.  I would not expect a tattoo to cause skin death again.  Your tattoo artist will actually have the most experience with this, so be sure to explain everything in full before you proceed, but it is safe from a Plastic Surgery perspective.  Best wishes!