The appropriate depth for undermining varies by body area.
"As dermatologic surgeons continue to increase the volume of cancers we're treating, and hence the volume of flaps and grafts we're performing, our standards and expertise are improving immensely," says Roberta Sengelmann, M.D., assistant professor of dermatology and otolaryngology and director of the Center for Dermatologic and Cosmetic Surgery at Washington University School of Medicine here.
When it comes to 3 cm and smaller defects of the head and neck, Dr. Sengelmann says, "We repair more of those than any other group (of physicians) nationally," although this hasn't always been the case.
To achieve these goals, Dr. Sengelmann says, "Always perform the simplest repair to get the job done. It's never appropriate to use a flap or graft when a primary closure will give as nice a cosmetic outcome, because the complication rate for flaps and grafts is higher, without offering any perceivable benefits."
When second intention wound healing and simple repair are not appropriate for wound closure, Dr. Sengelmann says, "Flaps are my next line of defense. These include advancement, transposition, rotation and pedicle flaps."
In working with flaps, she says that as much as possible, she likes to use adjacent skin from the same cosmetic subunit. Advantages of this approach include camouflaging scars and achieving the most elegant tissue match between donor and recipient sites, Dr. Sengelmann explains.
"Always undermine flaps adequately and at the appropriate plane," she says. "For example, nasal flaps should be undermined over cartilage at the distal nose" to help ensure adequate blood supply.
The appropriate depth for undermining varies by body area, Dr. Sengelmann notes.
"On the scalp, it's under galea. On the cheek, it's the mid-fat. On the extremities of an average-sized person, it would be over fascia," she explains.
Additionally, Dr. Sengelmann recommends undermining the flap's recipient site to allow secondary movement or the proper amount of "give" for the flap.
"This prevents the risk of pincushioning," she says.
This problem, also known as the trapdoor appearance, seems to occur more frequently when flaps are moved into place without undermining of the adjacent tissue, Dr. Sengelmann says.
Another principle that's helpful in preventing pincushioning is to make absolutely certain that all tissue planes are reapproximated so that muscle is resutured to muscle, then dermis to dermis and epidermis to epidermis, she says.
As for skin grafts, Dr. Sengelmann says she uses these only when patients possess a very limited tissue reservoir of adjacent skin.
"If the patient has a wound on the side of the nose," she explains, "I will try to borrow skin from the side of the nose to fill it" unless the defect is too large and the capacity for tissue movement in the same cosmetic unit or subunit is too small. Dr. Sengelmann says the only other circumstance in which she will use a skin graft is when a patient chooses one over a flap repair.