Well, you can always depend upon this forum to find out all sorts of tidbits of information like this!! I just dug out some old prostheses and weighed them and found that, metal on metal or metal on plastic, they all weigh in at around 250-300gms. The two I weighed were stainless steel and cobalt chrome. Titanium is a very much lighter material but I don't have a specimen in that so can't exactly say what it would weigh.