Got a brand new metal knee.
Its only half a knee (called an Oxford) and is much harder to "install".
They opened me up, clamped a jig to upper and lower halves then routed out a notch.
Then used a 90 degree drill guided by a different jig to bore a hole straight up the middle of the notched out half.
Then bonded (glued) the the top and bottom halves.
Surgeons are like tool and die makers sometimes.
check it out
http://www.biomet.com/patients/oxfordAnimationVideoPopup.cfm