Chapter 4.9: The Percutaneous Set-Back Dermal Suture

Percutaneous Kantor suture

This technique is designed primarily for the closure of narrow wounds. In anatomic locations such as the scalp and lower leg, there is often insufficient laxity to permit the effective visualization of the undersurface of the undermined wound edge that would be ideal for the placement of set-back dermal sutures.

This technique could theoretically be utilized in other areas, though in practice the standard buried set-back dermal suture should probably be utilized if at all possible to effect better wound-edge approximation.

On the scalp, a 3-0 or 4-0 absorbable suture is probably best, as it allows for robust closure in this area where tension is occasionally moderate to severe. On the lower legs, 3-0 or 4-0 absorbable suture material may be used as well, as this area is sometimes under marked tension. As always, utilizing the smallest gauge suture material that will permit adequate closure under tension is best.

1. If possible, the wound edge is reflected back using surgical forceps or hooks. Adequate visualization of the underside of the dermis is not required.

2. While gently grasping the skin edge, the suture needle is inserted at 90 degrees into the underside of the dermis 2-4 mm distant from the incised wound edge.

3. The first bite is executed by traversing the dermis and piercing directly up through the epidermis, with the needle exiting the epidermis 2-4 mm from the incised wound edge.

4. The needle is then reloaded on the needle driver in a backhand fashion and inserted at 90 degrees just medial to the exit point. The needle exits the undermined surface of the dermis into the undermined space between the undersurface of the dermis and the deeper subcutaneous tissue, medial to its entry point.

5. The needle is then reloaded, again in a backhand fashion, and inserted into the undersurface of the dermis on the contralateral wound edge, 2-4 mm distant from the incised wound edge. Depending on needle size and the breadth of the wound, this step may be combined with the prior step, saving the need to reload the needle. The needle should traverse the dermis and exit through the epidermis 2-4 mm distant from the incised wound edge.

6. The needle is then reloaded in a standard fashion and inserted in the epidermis just lateral to the exit point at 90 degrees, exiting the undersurface of the dermis in the undermined space.

7. The suture material is then tied utilizing an instrument tie (Figures 4-9A, 4-9B, 4-9C, 4-9D, 4-9E, 4-9F, 4-9G, 4-9H, 4-9I, 4-9J, 4-9K).

A central advantage of this approach is its ease of execution; since the suture pierces the epidermis and dermis at a 90-degree angle, 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 other techniques.

This technique is also appropriate in areas where extensive undermining is not possible; since the undersurface of the dermis does not need to be visualized to effectively place the sutures, the throws can be essentially placed blindly.

An important theoretical advantage of this approach over other percutaneous approaches is that no suture material is left between the wound edges. Since even absorbable suture material may represent a physical impediment to wound healing, this is an important benefit that this approach shares with the standard set-back dermal suture technique.

This technique may also be useful when adding additional sutures to an already largely closed wound. In these cases there may not be sufficient room to insert a traditional vertically oriented buried suture, both as the space available to insert the needle driver is limited and the degree of possible wound-edge reflection is limited by the presence of surrounding buried sutures. In these cases, a percutaneous set-back dermal suture can be easily executed.

The percutaneous set-back dermal approach creates significant wound eversion, and the degree of eversion elicited by this approach may be more marked than that seen with the standard set-back dermal suture approach. This pronounced eversion may lead the epidermal portion of the wound edges to separate as the dermis is brought together, as the epidermal edges fail to drape together as they would normally do with the standard set-back dermal technique.

There are two possible approaches to this situation: (1) Superficial running or interrupted sutures may be placed to better approximate the epidermal edges, and (2) The defect could be removed with an inward bevel (as is done with the butterfly suture technique), or the dermis may be incised at an inward bevel after the original defect is created, permitting the epidermal edges to come together gently even in the face of the marked eversion seen with this approach. Many clinicians favor a bilayered approach in general, and therefore placing the epidermal sutures is an easy solution and does not require the degree of preplanning associated with the bevel approach, though a combination of the two solutions may be utilized as well.

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.

Epidermal dimpling will often occur with this approach, since the suture material traverses the epidermis. A small degree of dimpling will resolve with time as the absorbable sutures are gradually resorbed, and patients should be warned that this is a likely occurrence and that it is of no long-term clinical consequence.

Since suture material traverses the epidermis, there is a theoretically greater risk of infection with this technique than with approaches that remain entirely buried on the undersurface of the dermis. Meticulous attention to sterile technique may help mitigate this theoretical risk, and anecdotally infection is seen no more frequently with this approach than with any other closure technique.