What are cells dead and gone when a decubitus ulcer is the result?

Decubitus Ulcer: The usual mechanism of forming a decubitus ulcer is from pressure. However it can also occur from friction by rubbing against something such as a bed sheet, cast, brace, etc., or from prolonged exposure to cold. Any area of tissue that lies just over a bone is much more likely to develop a decubitus ulcer. These areas include the spine, coccyx or tailbone, hips, heels, and elbows, to name a few.