Chapter 5.1: The Simple Interrupted Suture

This is the standard benchmark suture used for closure and epidermal approximation. It may be used alone in the context of small wounds under minimal to no tension, such as those formed by either a small bunch biopsy or a traumatic laceration. It is also frequently 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.

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. Simple interrupted sutures may be placed with the goal of: (1) accomplishing epidermal approximation in a wound under moderate tension, such as a laceration or punch biopsy, or (2) fine-tuning the epidermal approximation of a wound where the tension has already been shifted deep utilizing a deeper dermal or fascial suturing technique.

On the face and eyelids a 6-0 or 7-0 monofilament suture may be utilized for epidermal approximation. When the goal of simple interrupted suture placement is solely epidermal approximation, this suture material may be used on the extremities as well. Otherwise, 5-0 monofilament suture material can be used if there is minimal tension, and 4-0 monofilament suture may be 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, particularly in the context of a multimodality approach, for example when mattress sutures are placed in the center of the wound to maximize tension relief and eversion, and simple interrupted sutures are placed at the lateral edges of the wound to minimize dog-ear formation.

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 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 5-1A, 5-1B, 5-1C, 5-1D).

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. The final cross-sectional appearance of the needle’s course should be a flask-like shape, wider at the base than at the surface.

The simple interrupted suture may also be used layered over the top of another suture in order to fine-tune epidermal approximation. For example, if a vertical mattress suture was placed to facilitate eversion, occasionally the wound edges may not be fully approximated. A small simple interrupted suture, placed at the point where the wound edges are farthest apart, may be used to solve this problem and effect accurate approximation of the wound edges.

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.

With any suturing technique, knowledge of the relevant anatomy is critical. When placing a simple interrupted 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.

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 an interrupted 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. Some studies have also demonstrated an increased rate of dehiscence when utilizing interrupted sutures alone without underlying dermal tension-relieving sutures, highlighting that this technique should be used either for wounds under minimal tension or in concert with deeper tension-relieving sutures.