Accomodating & allowing 2 employees to work but not a 3rd?

My fiance's place of employment won't let him come back to work right now. He broke his wrist a month ago playing softball OUTSIDE of the work place and had surgery. he now has his cast off stitches out and has a removeable wrist brace. A permanent plate & 7 screws were put in place on his wrist though.

His DR has given human resources TWO notes stating he can return to work.

HR won't let him though. First they said they "Have no work for him to do" even though his boss said he does have work for him to do.

Then they later recanted that and said until he is 100% healed he cannot return. (which, he has a permanent plate & 7 screws in his wrist, it will never be the same and could be a year of recovery give or take.

Turns out, the general managers son works there and is 16 (to work in that dept you have to be 18) and he injured himself off the job playing a sport and was in a sling & they allowed HIM to work still, doing the exact same work my fiance does. (in fact he trained the kid)

Another employee had a broken leg and was using a device to help him get around and they allowed HIM to work.

WHY NOT MY FIANCE???

IS THIS DISCRIMINATION???