Decubitus ulcers generally form when the weight of a persons body presses the skin against the firm surface of a bed or wheelchair for an extended period of time, according to Harvard Health Publications. The pressure cuts off the blood supply to the skin, injuring it and forming sores.
Decubitus ulcers, or bedsores, commonly occur on people in hospitals and nursing homes, notes Harvard Health Publications. For people confined to a bed, decubitus ulcers typically develop on the hips, spine, lower back and tailbone. They may also appear on the shoulder blades, elbows and heels. For people who use a wheelchair, ulcers generally appear on the buttocks and bottom of the feet.