My Grandmother kept hens, and when one became crop bound, she decided to 'operate' - got my mother to hold the hen down, sliced open the skin, emptied the crop (crammed with grass cuttings) and sewed it back with a needle and cotton! This was the 1930s - they were a hardy breed of folk back then. Needless to say, the hen bounced back and lived to a ripe old age. Wouldn't necessarily recommend it to anyone tho!