Answer:
Unlike a graft, a flap has its own blood supply. Although the skin graft is often simpler, there are cases in which a flap is required or may be more desirable. Flaps are usually needed for covering recipient beds that have poor vascularity; reconstructing the full thickness of the eyelids, lips, ears, nose, and cheeks; and padding body prominences (i.e., for bulk and contour). Flaps are also used when it is necessary to operate through the wound at a later date to repair underlying structures. In addition, muscle flaps may provide a functional motor unit or a means of controlling infection in the recipient area.
In an experimental study, Mathes and colleagues12 compared musculocutaneous flaps with “random” flaps to determine the bacterial clearance and oxygen tension of each. Placement of 107 Staphylococcus aureus underneath random flaps in dogs resulted in 100% necrosis of the flaps within 48 hours; however, the musculocutaneous flaps demonstrated long-term survival. Looking at the quantity of viable bacteria placed in wound cylinders under these flaps showed an immediate reduction of bacteria under the musculocutaneous flap. Oxygen tension was measured at the distal end of the random flap and compared to that underneath the muscle of the distal portion of musculocutaneous flap as well as in its subcutaneous area. It was found that the oxygen tension in the distal random flap was significantly less than distal muscular and cutaneous portions of the musculocutaneous flap.