avascular necrosis thank you moose that is what he had, research is your best friend and you seem to already be on track with that, and like I said others I have over the years talked too about such operations, all had the hesitation before but all were glad after wards, even my friend John, he had a rough re-coop, but can walk better now and get about better, he too is glad he had the replacement surgery. i hope and pray for it to be a huge success, if this is the path you choose, your not immune to a moosesize hug coming back at you are ya