The World Federation One Stop Fiqh

Ruling 1054

With regard to someone who can sit but cannot make his forehead touch the ground, if he can bend forward to the extent that it can be commonly called sajdah, he must bend forward to that extent and place the turbah (or something else on which it is permitted to perform sajdah) on an object in order to raise it, and then he must place his forehead on it. However, he must place his palms, knees, and toes on the ground in the usual manner if possible.