<unk>  is a plastic surgery technique in which a thumb is created from an existing finger. Typically this consists of surgically migrating the index finger to the position of the thumb in patients who are either born without a functional thumb (most common) or in patients who have lost their thumb traumatically and are not amenable to other preferred methods of thumb reconstruction such as toe-to-hand transfers.
During<unk>  the index finger metacarpal bone is cut and the finger is rotated approximately 120 to 160 degrees and replaced at the base of the hand at the usual position of the thumb.  The arteries and veins are left attached.  If nerves and tendons are available from the previous thumb these are attached to provide sensation and movement to the new thumb ("neopollux").  If the thumb is congenitally absent other tendons from the migrated index finger may be shortened and rerouted to provide good movement.
The presence of an opposable thumb is considered important for manipulation of most objects in the physical world.  Children born without thumbs often adapt to the condition very well with few limitations therefore the decision to proceed with<unk>  lies with the child's parents with the recommendation of their surgeon.  Persons who have grown to adulthood with functional thumbs and then lost a thumb find it highly beneficial to have a thumb reconstruction, not only from a functional but from a mental and emotional standpoint.
Another case for<unk>  is where someone is born with a hand which has five fingers, but the radialmost finger is an ordinary finger and not a thumb.
Pollicization
Concoction
Polishing 
Mourning
Hymenorrhaphy
Castration
Canning
Pronation