I say, and with God's success: Whoever has one of his legs cut off from the ankle must wash the place of the cut, and it is not permissible for him to wipe over the remaining sock; because washing the place of the cut is obligatory, and it is not permissible to combine washing and wiping. Moreover, it is a condition for the permissibility of wiping that there remains on each foot from the front of the foot in the sock an amount equal to three fingers of the smallest finger of the hand; this is to ensure the required amount for wiping is present, and here it is not present. Refer to: Nihayat al-Murad, p. 380, and God knows best.