Metal On Metal Hip Replacement My Husband Had A Titanium Hip Replacement, Now He Has Been Told That He Has Metal Hitosis & Needs Surgery-why?

My husband had a titanium hip replacement, now he has been told that he has metal hitosis & needs surgery-why? - metal on metal hip replacement

He had surgery two years ago, about 6 months ago I started with hip pain again recently after a visit to the doctor, what a needle is inserted to see if the fluid flows and has the doctor said it was something that rarely happens but then, you should be replaced at the head of his hip surgery and have the metal causes mitosis. They say it's the friction of metal on metal. Could you me more about it. Thank you.