**4. Surgical wound closure options and impact on healing**

While there are different approaches to the closure of surgical incisions, the goals of all are to (1) facilitate the natural healing process leading to restoration of tissue function, (2) supply exogenous strength until tissue strength is restored by the endogenous healing process, and (3) avoid potential complications through appropriate closure technique and choice of closure approach [7]. Hence, clinicians closing wounds are concerned about the wound closure strength provided by the device they select, with not interfering with endogenous wound healing and ideally avoiding or minimizing complications [7]. Apposition of tissue edges by a wound closure device is maintained until the endogenous healing process restores enough wound tensile strength such that the wound becomes self-supporting [7]. The duration of time that a wound is completely dependent on the closure device for its initial holding strength is often referred to as the "critical wound healing period" [20]. The critical wound healing period is longer or shorter depending on the tissue type as well as on an individual patient's healing ability based on their health status as described earlier [20].

Surgeons have several types of wound closure devices/materials to choose from when closing a surgical incision. There is no single wound closure choice that is ideal for all situations, the physician must decide which material is best suited to a particular wound and situation based on their knowledge and experience [21]. Surgeons may choose to close the tissue layers that have been separated by the incision in two general ways; en masse (e.g., using a single closure material and technique to close multiple tissue layers at once) or layer by layer (e.g., making specific wound closure choices of material and technique for different tissue layers) [21]. There are differing opinions on closing specific tissue layers separately versus en masse. For example, some surgeons question the need of separately closing the subcutaneous fat layer because it has little tensile strength due to its composition, which is mostly water, whereas others believe it is necessary to place at least a few sutures in a thick layer of subcutaneous fat to prevent dead space, where tissue fluids can accumulate to create seromas or hematomas which can delay healing and potentiate infection [7].

Regarding the tissue layers, there are multiple types of devices for skin (epidermal) closure including sutures, staples, and topical skin adhesives. For the tissue layers below the epidermis—dermis, subcutaneous fat, fascia, muscle—sutures are still the only option for wound closure [7].

#### **4.1 Sutures for wound closure**

#### *4.1.1 Suture technique and impact on healing*

A suture is any strand of material attached to a surgical needle designed to carry that material through tissue with minimal trauma to approximate two opposing tissue edges [7]. Regardless of the type of suture material selected, an important aspect of their use is how they are deployed by the surgeon. Suturing techniques require considerable skill by surgeons and affect wound closure outcomes. The method of where the suture enters and exits the tissue, the distance between throws, the distance from the wound edges, the suture length to wound length ratio, the way knots are performed, etc. are all aspects of suture technique [22]. Frequently used suturing techniques for tissue approximation include, but are not limited to simple interrupted, continuous (also referred as a running), mattress (horizontal or vertical), and subcuticular (interrupted or continuous) [22].

Suturing technique alone can have an impact on wound closure success [22]. For example, the European Hernia Society undertook a systematic review of the literature to establish guidelines for the optimal wound closure technique for elective midline incisions of the abdominal wall with the goal of decreasing the occurrence of the surgical wound complications of both burst abdomen and incisional hernia [23]. These guidelines were intended for all surgeons performing abdominal incisions in any type of surgery including visceral, gynecological, aortic vascular, urological, or orthopedic, and for both open and laparoscopic approaches [23]. Their final recommendations regarding the optimal suture technique included using a continuous suturing in a single layer aponeurotic closure technique without separate closure of the peritoneum [23]. Further, a small bites technique (stitches placed 5 mm apart and 5–8 mm from the wound edges) with a suture to wound length (SL/WL) ratio of at least 4/1 was recommended [23]. They went on to make specific recommendations also regarding the optimal suture material and suggested the use of slowly absorbable monofilament suture when using this closure technique [23].
