Jacquie,
Pretty much the same train of thought about bio vs. mechanical and buying time for the future...but in my case childbitembered h was not a consideration (grin).
just remembered that you were quite gadgety and On-X seemed a given, but have heard that On-X requires specialized surgeon skills.
If it makes you feel any better in a meeting with surgeon a few days before op, he mentioned to me, that if he were me, the bovine option would likely be his 1st choice
for me,, yep must of been out of mgna in my 21mm size at time of surgery or something (smile)...but I will be sure to ask why when i see him, yet to be scheduled by his secretary
fever must be some minor infection, so hopefullythey can get you back in range, are you using cold compress on forehead for relief in meantime?