Chapter 5.4: The Running Locking Suture

This is a locking variation of the standard running suture used for epidermal approximation. It may be used alone in the context of small wounds under minimal to no tension, such as those formed by a traumatic laceration. It is generally used as a secondary layer to aid in the approximation of the epidermis when the dermis has been closed using a dermal or other deep suturing technique.

It is used for three central reasons: (1) To aid in hemostasis, (2) To provide improved eversion over the standard running suture, and (3) To provide equal tension across all loops of the running suture.

With all techniques, it is best to use the thinnest suture possible in order to minimize the risk of track marks and foreign-body reactions. Suture choice will depend largely on anatomic location and the goal of suture placement. On the face and eyelids, a 6-0 or 7-0 monofilament suture is useful for epidermal approximation. When the goal of the running locking suture layer is solely epidermal approximation, 6-0 monofilament may be used on the extremities as well. Otherwise, 5-0 monofilament suture material may be used if there is minimal tension, and 4-0 monofilament suture is useful in areas under moderate tension where the goal of suture placement is relieving tension or hemostasis as well as epidermal approximation.

1. The needle is inserted perpendicular to the epidermis, approximately one-half the radius of the needle distant to the wound edge. This will allow the needle to exit the wound on the contralateral side at an equal distance from the wound edge by simply following the curvature of the needle.

2. With a fluid motion of the wrist, the needle is rotated through the dermis, taking the bite wider at the deep margin than at the surface, and the needle tip exits the skin on the contralateral side.

3. The needle body is grasped with surgical forceps in the left hand and pulled upward with the surgical forceps as the body of the needle is released from the needle driver. Alternatively, the needle may be released from the needle driver and the needle driver itself may be used to grasp the needle from the contralateral side of the wound to complete its rotation through its arc, obviating the need for surgical forceps.

4. The suture material is then tied off gently, with care being taken to minimize tension across the epidermis and avoid overly constricting the wound edges. This forms the first anchoring knot for the running line of sutures. The loose tail is trimmed, and the needle is reloaded.

5. Starting proximal to the prior knot relative to the surgeon, steps (1) through (3) are then repeated, but rather than pulling all of the suture material through after completing the throw, a loop of suture is left from the beginning of the throw, and the needle is then passed through the loop of suture, locking the suture in place.

6. Instead of tying a knot, step (5) is then sequentially repeated until the end of the wound is reached.

7. For the final throw at the inferior apex of the wound, the needle is loaded with a backhand technique and inserted into the skin at a 90-degree angle in a mirror image of the other throws, entering just proximal to the exit point relative to the surgeon on the same side of the incision line and exiting on the contralateral side.

8. The suture material is only partly pulled through, leaving a loop of suture material on the side of the incision opposite to the needle.

9. The suture material is then tied to the loop using an instrument tie (Figures 5-4A, 5-4B, 5-4C, 5-4D, 5-4E, 5-4F, 5-4G, 5-4H, 5-4I, 5-4J, 5-4K, 5-4L).

The running-locking technique permits better hemostasis than the standard simple running technique, and therefore it is sometimes used with traumatic lacerations (when a small amount of oozing may be present) or as a secondary layer in repairs on patients who are on aspirin or otherwise may have a small amount of oozing even after placement of deeper sutures. Importantly, the hemostatic effect of the locking should not be used as a replacement for properly tying off deeper vessels or cauterizing small vessels.

This technique also affords improved eversion over the standard simple running suture approach, since the locked edges of suture have an almost horizontal mattress-like effect on the epidermis, leading sometimes to the formation of a ridge along the wound.

Standard simple running sutures may lead to gaping at the central portions of the wound, since the equal tension across each loop in the context of unequal lateral forces over the course of the length of the wound mean that the areas under greatest tension—those in the central wound—may pull laterally while areas under only minimal tension at the apices do not exert a similar effect. This tendency is obviated with the running-locking technique, as the amount of tension across each loop of suture is individually controlled.

An assistant may be helpful in keeping each of the loops under a small degree of tension before the needle and suture material are passed through the loops. This helps with maintaining a uniform degree of tension across the loops of suture and aids in permitting each throw of suture to be easily locked.

As with the simple running suture, it is important to enter the epidermis at 90 degrees, allowing the needle to travel slightly laterally away from the wound edge before fully following the curvature of the needle when utilizing this technique. This will allow for maximal wound eversion and accurate wound-edge approximation.

Care should be taken to avoid skimming the needle superficially beneath the epidermis. This results from failing to enter the skin at a perpendicular angle and following the curvature of the needle. This may result in wound inversion as the tension vector of the shallow bite pulls the wound edges outward and down.

In order to maintain uniformity in the length of the visible running sutures and to allow all of the suture loops to remain parallel, it is important to take uniform bites with each throw of the running locking suture technique. Therefore, each subsequent loop should begin at the same point lateral to the incised wound edge and at a uniform distance closer to the surgeon than the preceding entry point.

As with the simple running technique, it is critical to permit sufficient laxity between the epidermis and the suture material when using this technique in order to minimize the risk of track marks or an exaggerated inflammatory response. Recalling that this technique is designed exclusively for epidermal approximation, and that some postoperative wound edema is expected, will help with conceptualizing the need to keep the throws of suture material loose.

The central drawback of this approach is that, as with all running techniques, the integrity of the entire suture line rests on two knots. Moreover, suture material compromise at any point may lead to a complete loss of the integrity of the line of sutures. Since this technique is designed for low-tension environments, however, and the locked loops of suture may hold in place due to pressure from the skin against the suture, this problem is less pronounced with this technique than with many other running approaches.

In order to avoid wound-edge necrosis, it is important not to be over-zealous with tightening the locking loops of suture. While it may be tempting to pull each loop tight to maximize the hemostatic effect of this approach, this should be avoided. This is particularly important as postoperative edema may lead the sutures to be even tighter after time has passed, increasing the risk of tissue strangulation.

Since all loops of suture are placed in succession, this technique does not permit the same degree of fine-tuning of epidermal approximation as a simple interrupted suture. This must be weighed against the benefit of the increased speed of placement of a line of running locking sutures versus interrupted suture placement, where each throw is secured with its own set of three or more knots.

While this technique may help minimize some of the potential risk of track marks associated with running techniques—the differential pull across different areas of the wound—overly tight throws may actually increase this risk, since the locked loops lead to a secondary row of sure material running parallel to the incision line.

With any suturing technique, knowledge of the relevant anatomy is critical. When placing running locking sutures it is important to recall that the structures deep to the epidermis may be compromised by the passage of the needle and suture material.

Similarly, particularly if the throws are locked relatively tightly, structures deep to the defect may be constricted. This can lead to necrosis due to vascular compromise or even, theoretically, superficial nerve damage; again, this risk may be mitigated by maintaining some laxity in the locked suture throws.

This technique may elicit an increased risk of track marks, necrosis, inflammation, and other complications when compared with techniques that do not entail suture material traversing the scar line, such as buried or subcuticular approaches. Therefore, sutures should be removed as early as possible to minimize these complications, and consideration should be given to adopting other closure techniques in the event that sutures will not be able to be removed in a timely fashion.