By: Dan Ladizinsky, MD, CEO, SUTUREGARD Medical, Retired Board Certification in General Surgery, Plastic Surgery, with Certificate of Added Qualifications in Surgery of the Hand, Former Fellow of the American College of Surgeons.
By: Dan Ladizinsky, MD, CEO, SUTUREGARD Medical, Retired Board Certification in General Surgery, Plastic Surgery, with Certificate of Added Qualifications in Surgery of the Hand, Former Fellow of the American College of Surgeons.
Let’s back up a bit and make sure we understand what undermining is and does. Undermining is a surgical technique that mechanically lifts/separates the skin and superficial subcutaneous fat as one layer, up and away from its underlying soft tissues. Undermining can be done in a superficial or deep subcutaneous plane and may include part or all the subcutaneous fat and fascia down to the muscular fascia.
How is undermining done? Most typically the surgeon will use a blunt tipped instrument in a spreading motion that is either parallel or perpendicular to the plane of the skin. I always preferred the perpendicular plane. Why? During undermining, the surgeon often will encounter perforator vessels that are coursing up from the muscular fascia or from septae between the muscles to supply the overlying skin with blood flow. Parallel plane spreading motions are much more likely to sever perforators than are perpendicular motions. Both motions loosen/free the skin from its underlying attachments to allow advancement.
Why are perforators important? The human integument is supplied by 442 +/- 121 perforator vessels originating from underlying tissues and penetrating the skin (1). Each perforator supplies an overlying area of skin called an angiosome. Knowledge and respect of these perforators/angiosomes allows surgeons to move/advance skin without damaging the underlying blood supply that keeps the skin viable.
It is crucial to understand that there is regional variation in how dependent the skin is on these individual perforators. For example, an ankle/foot perforator supplies on the average 68 sq cm. A face perforator supplies on the average of 19 sq cm (1). This means that a perforator injury to the foot ankle can jeopardize a large area that might not be supported by collateral flow from an adjacent angiosomes. There is much less risk when a perforator is injured in the face.
Avoidance of perforator injury is a big reason to limit undermining. This will maximally preserve blood flow to the skin and contribute to successful healing. If undermining is to be done, avoiding sweeps parallel to the skin will reduce the chance of perforator injury. Intraoperative doppler can detect perforator presence by auscultation. These areas can be avoided when undermining is necessary.
Are there alternatives to undermining? Twice as much skin can be advanced by stress relaxation than by undermining (2). Stress relaxation lengthens skin through applied force causing collagen parallelization and fiber lengthening and can be accomplished quickly and safely with a device such as the SUTUREGARD ISR Device. Advancement of skin without undermining also avoids creation of a potential cavity that can fill with blood (hematoma) which can cause infection and/or necrosis.
A final point involves procedural coding. New rules governing wound closure CPT codes have been developed to reduce the overly frequent use of the complex closure codes. In the past “extensive undermining” would justify the use of this more expensive code. Now the new codes are much more specific about degree of undermining that must be done/documented to warrant reimbursement at the complex level. Use of a suture retention bridge, like the SUTUREGARD ISR Device, to assist in the closure allows correct valid use of the complex code.
In summary, consider avoiding/limiting undermining to reduce perforator injury which can increase the risk of hematoma or skin necrosis, especially on the lower extremity, where large areas of skin are dependent on single perforators. Stress relaxation is an alternate method that can gain considerable skin for advancement closures. Use of a suture retention bridge for achieving stress relaxation is fast and gentle and will justify the correct use of complex closure codes.
1Morris, S et al. The Anatomic Basis for Perforator Flaps. Clin Plas Surg 37(4), 553-570, 2010
2 Melis, P etal Tension decrease during skin stretching in undermined versus not undermined skin: an experimental study in piglets. Plast Reconstr Surg. 2001 Apr 15;107(5):1201-5; discussion 1206-7.