Chapter 4.2: The Set-Back Dermal Suture

Kantor suture, set-back suture

This technique is best used in areas under significant tension. The back, shoulders, and thighs are particularly amenable to the set-back technique, though it may be used in almost any location, including the central face and ears. Areas prone to wound inversion, such as the cheek and forehead, may also be well-served utilizing this technique.

Since it is easier to place than a buried vertical mattress suture, this technique may be used by budding surgeons, medical students, and residents as the workhorse technique for deep tension-relieving sutures.

Suture choice is dependent in large part on location, though as this technique is designed to bite the deep dermis and remain buried well below the wound surface, the surgeon may choose to utilize a larger gauge suture than would be used for an equivalently placed buried simple or buried vertical mattress suture. Using a 2-0 absorbable suture on the back with this technique results in only vanishingly rare complications, since the thicker suture remains largely on the underside of the dermis, and suture spitting is an uncommon occurrence. On the extremities, a 3-0 or 4-0 absorbable suture material may be used, and on the face and areas under minimal tension a 5-0 absorbable suture is adequate.

1. The wound edge is reflected back using surgical forceps or hooks. Adequate visualization of the underside of the dermis is required.

2. While reflecting back the dermis, the suture needle is inserted at 90 degrees into the underside of the dermis 2-6 mm distant from the incised wound edge.

3. The first bite is executed by traversing the dermis following the curvature of the needle and allowing the needle to exit closer to the incised wound edge. Care should be taken to remain in the dermis to minimize the risk of epidermal dimpling. The needle does not, however, exit through the incised wound edge, but rather 1-4 mm distant from the incised edge. The size of this first bite is based on the size of the needle, the thickness of the dermis, and the need for and tolerance of eversion.

4. Keeping the loose end of suture between the surgeon and the patient, the dermis on the side of the first bite is released. The tissue on the opposite edge is then reflected back in a similar fashion as on the first side, assuring complete visualization of the underside of the dermis.

5. The second and final bite is executed by inserting the needle into the underside of the dermis 1-6 mm distant from the incised wound edge. Again, this bite should be executed by following the curvature of the needle and avoiding catching the undersurface of the epidermis that could result in epidermal dimpling. It then exits further distal to the wound edge, approximately 2-6 mm distant from the wound edge. This should mirror the first bite taken on the contralateral side of the wound.

6. The suture material is then tied utilizing an instrument tie (Figures 4-2A, 4-2B, 4-2C, 4-2D, 4-2E, 4-2F, 4-2G, 4-2H).

This technique was recently compared with the buried vertical mattress suture in a randomized blinded trial. It was found to be superior to the buried vertical mattress suture in terms of eversion, and cosmetic outcomes were deemed to be better than buried vertical mattress sutures based on both physician and patient assessments.

One of the chief advantages of this technique is its ease of execution; since the suture follows the arc of the needle on the undersurface of the dermis, there is no need to change planes, effect a heart-shaped suture placement, or guarantee that the suture exit point is precisely at the inside edge of the lower dermis, as may be needed with the buried vertical mattress suture.

Accurate suture placement is predicated on having a sufficiently undermined plane, since the entire suture loop lays on the undersurface of the dermis. Therefore, broad undermining is a prerequisite for utilizing this technique, since the first throw of the needle begins 2-6 mm distant from the incised wound edge.

This technique may also be used to minimize dead space when excising a space-occupying lesion such as a cyst or lipoma. In this event, taking the first bite set back even further from the incised wound edge will translate into a larger ridge and will simultaneously minimize the laxity in the central portion of the wound as the dermis is pulled taut so that potential dead space is converted to a hyper-everted wound ridge which will absorb with time.

Finally, a recent study has demonstrated that treating chest keloids with a combination of the set-back suture and postoperative electron beam irradiation led to an almost 98% success rate. The authors posited that the combination of tension reduction across the wound surface coupled with deep suture placement and suture material placement away from the incised wound edge was responsible for this dramatic effect.

The set-back dermal approach creates significant wound eversion, and the degree of eversion elicited by this approach may, depending on how far set back the dermal bite is taken, elicit significantly more wound eversion than even the buried vertical mattress technique.

Patients should be cautioned that they might develop a significant ridge in the immediate postoperative period. Depending on the suture material used and the density of the sutures, this ridge may last from weeks to months. Explaining that the technique is akin to placing a subcutaneous splint may help the patient develop reasonable and realistic expectations and reduce anxiety regarding the immediate postoperative appearance of the wound.

A possible complication of overeversion and an overly broad bite is that the raised ridge may be too large or bulky to be supported by the deep sutures. In this event, the wound edges may paradoxically collapse centrally leading to the appearance of a dramatically raised ridge with a central valley approximately 1 week postoperatively. As the sutures absorb overtime, this will yield a depressed or inverted scar line. This can generally be avoided by not setting back the sutures more than a few millimeters from the wound edge and by placing a sufficient number of sutures so that the body of the ridge may be easily supported.

Epidermal dimpling will occasionally occur where the arc of the suture reaches its apex at the dermal-epidermal junction; on the face and areas with thin dermis this should be assiduously avoided. Similarly, areas with sebaceous skin, such as the nose, require meticulous avoidance of dimpling which has the potential to persist. In truncal areas or those with thick dermis, however, a small degree of dimpling will resolve with time as the absorbable sutures are gradually resorbed.