Chapter 4.17: The Pulley Set-Back Dermal Suture

Pulley Kantor suture, double set-back suture, double set-back dermal suture

This technique is best used in areas under very significant tension. In addition to high-tension wounds in general, areas under marked tension that are prone to wound inversion, such as the back and chest, may be well-served utilizing this technique.

Wounds under marked tension may be challenging to close even with well-placed buried sutures. The pulley set-back dermal suture technique relies on the pulley effect of multiple loops of suture to permit the closure of wounds under even significant tension. In addition, the locking effect of placing a double loop of suture leads the suture material to lock in place after the first throw of the surgical knot, obviating the need for an assistant maintaining the alignment of the wound edges.

Suture choice is dependent in large part on location. Though 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 pulley buried dermal 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, if this pulley approach is needed at all, a 5-0 absorbable suture is adequate. Braided suture tends to lock more definitively than monofilament, though monofilament suture allows for easy pull through when taking advantage of the pulley effect.

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 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. Steps (1) through (5) are then repeated after moving proximally toward the surgeon and taking care to leave the tail of the suture material deep to the loops of suture.

7. The suture material is then tied utilizing an instrument tie.

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 pulley 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 is useful when there is significant tension across the wound, and a single set-back dermal suture may not hold the edges together. As long as undermining has been carried out effectively, utilizing a pulley technique with a thicker gauge suture material should allow for effective closure of all but the tightest wounds.

This technique is also very useful when the surgeon needs the first throw of the knot to securely hold the wound edges together, as this technique is able to effectively lock the suture in position after only a single throw. This obviates the need for an assistant's constant presence in these instances, and permits precise placement of the suture and knot to allow for precise epidermal approximation.

It is critical to keep the suture material deep to the loops of suture when using this technique, as this is the mechanism by which the suture locks in place after the first throw. As long as the surgeon conceptualizes this approach as placing a standard set-back dermal suture followed by a second standard set-back dermal suture closer to the surgeon, this technique can be very simple to learn and is easily reproducible.

As always, the choice of suture material is largely based on the individual surgeon's preference. Braided absorbable suture material has the advantage of locking more reliably than monofilament, though monofilament suture allows for easier pull through and therefore may better facilitate the pulley effect of the double loop of suture material.

In areas under extreme tension, a three-loop variation of this approach is possible as well, allowing for an even more dramatic pulley effect. This benefit must be weighed against the added retained suture material that would be associated with the additional loop.

The pulley 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 pulley 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.

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.

Since pulley sutures leave two loops of suture material in the skin in lieu of one, this may result in an increased risk of foreign-body reaction, suture spitting, or suture-abscess formation. Still, since the bulk of retained suture material is in the knots, rather than in the thrown loops of suture, this theoretical risk may not translate into a real-world problem in most cases.