Chapter 5.14: The Double Locking Horizontal Mattress Suture

Double loop mattress suture

This is a modification of the locking horizontal mattress suture, which adds an extra one-half horizontal mattress suture and then is locked through each of the resultant loops. As with many interrupted techniques, it may be used alone for wounds under minimal tension, such as those formed by a small punch biopsy or a traumatic laceration. It is useful in cleft palate repair, and may be used as a transepidermal suture when deeper structures have already been closed. This technique may also be used in the context of atrophic skin, as the broader anchoring bites may help limit tissue tear-through that may be seen with a simple interrupted suture. The double locking variation confers three advantages over the traditional horizontal mattress suture: (1) better ease of suture removal, (2) improved wound-edge apposition, and (3) improved strength under tension.

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, though this technique is rarely used, a 6-0 or 7-0 monofilament suture may be used; in these cases, standard horizontal mattress sutures are probably preferable to their locking counterparts. Elsewhere, 5-0 monofilament suture material may be used if there is minimal tension, and 4-0 monofilament suture is used in areas under moderate tension where the goal of suture placement is relieving tension as well as epidermal approximation. In select high-tension areas, 3-0 monofilament suture may be utilized as well.

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, with care being taken to avoid grasping the needle tip, which can be easily dulled by repetitive friction against the surgical forceps. It is gently grasped 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 needle is then reloaded in a backhand fashion and inserted at 90 degrees perpendicular to the epidermis proximal (relative to the surgeon) to its exit point on the same side of the incision line as the exit point. Importantly, a loop of suture material is left protruding from where the needle exited on the prior throw to where it enters on this throw.

5. The needle is rotated through its arc, exiting on the right side of the wound (relative to the surgeon) in a mirror image of steps (2) and (3).

6. The needle is then reloaded in a standard fashion, and inserted perpendicular to the epidermis proximal (relative to the surgeon) to its exit point on the same side of the incision line as the exit point. Again, a loop of suture material is left protruding from where the needle exited on the prior throw to where it enters on this throw.

7. The needle is rotated through its arc, exiting on the left side of the wound (relative to the surgeon).

8. The needle driver is then passed through the first loop and the tail of the suture material is then grasped and gently pulled through the loop, temporarily locking it in place. The tail of the suture material is then released.

9. The needle driver is then passed through the second loop of suture material, and the needle is grasped with the needle driver and gently pulled through the loop, similarly locking it into place. At this point, both the leading and trailing strands of suture material are on the same side of the incision line.

10. The suture material is then tied off gently (Figures 5-14A, 5-14B, 5-14C, 5-14D, 5-14E, 5-14F, 5-14G, 5-14H, 5-14I, 5-14J).

This double-locking technique allows for some wound eversion while concomitantly taking advantage of the pulley effect of spreading the wound tension over multiple loops. Its central advantage is the increased strength of this approach over the standard locking horizontal mattress suture, and it is therefore best used in closures under significant tension, such as the back and shoulders, or when a transepidermal approach is desired and no deeper sutures have been placed, such as the closure of punch biopsy sites.

The double-locking technique confers three important advantages over the traditional horizontal mattress suture. First, the standard horizontal mattress suture does not typically permit the same degree of wound-edge apposition as can be accomplished with other transepidermal sutures, since the everting effect of the suture technique may even be associated with a small degree of gaping at the center of the horizontal mattress suture. Double locking the suture material brings the knot, as well as the parallel external rows of suture, to the center of the wound, thus improving wound-edge approximation.

Second, suture removal with the standard horizontal mattress technique may be challenging, particularly if sutures are left in situ for an extended period of time and some of the suture material has been overgrown by the healing epidermis, as the knot may be buried in the context of a ridged everted repair. Bringing the knot, along with the parallel rows of external suture material, centrally with the locking technique allows the knot to be more easily grasped at the time of suture removal.

Finally, the double-locking approach adds a pulley effect, thus increasing the strength of the suture and permitting closure under higher-tension environments. As an added benefit, the double-locking technique incorporates an extra throw of the horizontal mattress suture, meaning that each suture extends further along the wound, thus necessitating fewer knot ties for a given incision length.

As with most transepidermal techniques, 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.

As with the simple interrupted suture, 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 to follow 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.

This technique incorporates three strands of suture crossing the wound, along with a significant amount of suture material resting parallel to the wound, and therefore may be associated with a higher risk of track marks than many other techniques. In addition, the double-locking component and the change in the tension vectors markedly reduce the everting effect of the horizontal mattress technique, thus negating one of the major benefits of this approach.

Additionally, the tension vectors associated with this suture are not uniformly perpendicular to the incision line, theoretically increasing the chances of tissue bunching.

Moreover, structures deep to the defect may be constricted or may be perforated by the multiple passes of suture. This can lead to necrosis due to vascular compromise, bleeding, or even, theoretically, superficial nerve damage. These concerns are more acute with the double locking horizontal mattress suture than with the simple interrupted suture, since the wide arc of the suture material and its horizontal component incorporate more skin and underlying structures, thus increasing the risk of strangulation.

As noted previously, this technique may elicit an increased risk of track marks, necrosis, and other complications when compared with techniques that do not entail suture material traversing the scar line, such as buried or subcuticular approaches. Therefore, this technique is best used when the closure is under significant tension. Regardless, 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.