The term "decubito" simply means "the position of the body as it lies in bed". My guess is that since the patient in question has had a mastectomy previously, we are talking about delayed reconstruction, where a flat expander is inserted and filled with liquid over time to stretch the tissue.

Just a guess on my part though!!

"If a large amount of skin is removed during mastectomy or you're having the staged approach to implant reconstruction (delayed-immediate reconstruction), your plastic surgeon places a tissue expander between the skin and chest muscle after your breast surgeon has removed the breast tissue. A tissue expander is an implant that’s more like a balloon. It stretches the skin to make room for the final implant."

See this link for details:
http://www.breastcancer.org/treatment/surgery/reconstruction...