I would surely ask if they can use the other arm. As I understand this, the flap is a section of tissue with skin, muscle, fat, and, most importantly, nerves and blood vessels attatched. This would be stitched into his mouth after removal of whatever they plan to remove....and the circulation would be hooked up to vessels in the neck, to provide circulation to the transplanted tissue. I don't know if they have to use the tissue from the same side as the surgery. I don't really see why they would have to, though there might be a structural reason that it would be desirable. There are several on this forum who have had this procedure and can tell you more. I wish you luck. You will find answers, advice, and support here.