One for whom it is difficult to place his forehead on the ground

Question:
If it is difficult for a person to place his forehead on the ground, does he place his hands and is that sufficient, or is it necessary for the forehead to touch the place of prostration?

Answer:
Prostration is performed with the forehead, and the hands follow the forehead. So if a person is unable to prostrate with his forehead, he does not place his hands. Prostration is not with the hands, but rather with the forehead, as far as possible. If it is not possible, he indicates the prostration with his head and does not place his hands.