Stephanie,
 
Please, ask for the exact NAMES of the conditions!  PLEASE!  Without
those nothing is known and the info is virtually useless.  But once you
send along those exact terms from the vets you will help many ferret
people know a great deal more, and when there is more data from the
x-rays and such that will help even further.
 
These look like polydactyly and syndactyly combined.
 
Actual complete feet BILATERALLY makes no sense to me for several very
reasonable  reasons rooted in developmental biology, genetics, and foot
structure.  (Besides, they are far enough down in the photos that they
are BELOW the metatarsals for the most part so more likely polydactyly
(extra toes -- and these can be in quite a large number) with partial
tissue sheaths from syndactyly).  (Like with the way that  similar one
with two bilateral human feet was in photos compared to the photos of
this ferret.)  Ferrets for their rear feet largely walk on the toes
rather than also on more proximal part of the foot (in comparison to
humans) and the ankle forms that extra joint which looks like a backward
pointing knee.  Toe walking and the use of the backward facing joint from
the ankle is taken to an extreme in some other animals like ungulates
(cows, deer, etc) and perrisodactyls (Like horses) which walk on the tip
of some toes and the toes and nail/claw have specialized into bones like
the canon bone and into hooves.
 
Thanks for letting us all know that it is not a terrible case of
keratosis (which when horribly bad HAS actually confused people into
thinking that there were extra toes or extra partial feet).  Keratoses
can have a genetic vulnerability aspect, a sun exposure aspect,
nutritional inputs, and other unknown causes.
[Posted in FML issue 4622]