Chapter 5.6: The Locking Horizontal Mattress Suture

Modified locking horizontal mattress

This is a modification of the horizontal mattress suture, a frequently used everting technique used for closure and epidermal approximation. 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 also frequently used as a secondary layer to aid in everting the wound edges when the dermis has been closed using a deep suturing technique. This technique may also be used in the context of atrophic skin, as the broader anchoring bites may help limit the tissue tear-through that may be seen with a simple interrupted suture. This locking variation confers two advantages over the traditional horizontal mattress suture: better ease of suture removal and improved wound-edge apposition.

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. Locking horizontal mattress sutures may be placed with the goal of: (1) effecting eversion, or (2) adding an additional layer of closure for wound stability and dead-space minimization.

On the face, a 6-0 or 7-0 monofilament suture may be used, though fast-absorbing gut may be used on the eyelids and ears to obviate the need for suture removal; in these cases, standard horizontal mattress sutures are probably preferable to their locking counterparts. When the goal of the horizontal mattress suture placement is solely to encourage wound-edge eversion, fine-gauge suture material may be used on the extremities as well. Otherwise, 5-0 monofilament suture material is useful if there is minimal tension, and 4-0 monofilament suture maybe 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 the wound 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 passed under the loop of suture material on the contralateral side.

7. 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 (Figures 5-6A, 5-6B, 5-6C, 5-6D, 5-6E, 5-6F).

The locking technique confers two 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 be associated with a small degree of gaping at the center of the horizontal mattress suture. Locking the suture material brings the knot, as well as the two 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.

A modification of this technique has also been described, where instead of passing the needle under the loop of suture, the loop is instead incorporated into the knot, thus increasing economy of motion. For this modification, a loop is left as described previously and all steps are followed through step (5). Then, the end of the suture with needle attached is looped twice around the needle driver and the tip of the needle driver is passed through the loop to grasp the tail of suture. Once the suture tail is pulled, the horizontal mattress suture becomes locked.

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 failing 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.

With any suturing technique, knowledge of the relevant anatomy is critical. When placing a locking horizontal mattress suture it is important to recall that the structures deep to the epidermis may be compromised by the passage of the needle and suture material. For example, the needle may pierce a vessel leading to increased bleeding.

Similarly, particularly if the knot is tied 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. These concerns are more acute with the 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.

The potential to constrict deeper structures may be used to the surgeon’s advantage in the event that a small vessel deep to the incision line is oozing; rather than opening the wound, localizing the source of the bleed, and tying off the individual vessel, it may be possible to simply place a locking horizontal mattress suture incorporating the culprit vessel within its arc, tie it tightly, and thus indirectly ligate the vessel. This should only be used in the event that the offending vessel is relatively small, since otherwise there is a significant risk that this indirect ligation will not be sufficiently resilient. Moreover, tying the suture too tightly may increase the risk of developing track marks or superficial necrosis.

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, 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.