I had a septoplasty does on my nose a while back. I'm familiar with the term rhinoplasty, but I didn't know the origin of the suffix. I just saw an interesting video on a different kind of -plasty, called a rotationplasty:

http://www.wired.com/playbook/2011/05/little-leaguer-leg-reversal/

So I googled and found: http://www.etymonline.com/index.php?term=-plasty

which says that -plasty derives from the Greek plastos meaning moulded or formed.

http://en.wiktionary.org/wiki/-plasty
says a -plasty is moulding or forming through a surgical procedure.