1. Describe the biology of skin wound repair.
2. Describe a continuous percutaneous skin suture closure.
3. Describe a continuous dermal skin suture closure.

FOREWORD
If this educational program heightens the surgeon's, resident's, and student's interest in the biology of wound closure and infection, the long years occupied in my search for improved methods of wound management would more than fulfill my expectations. Through the ages, selection of surgical sutures, needles and gloves has been an important consideration for surgeons. Despite these important historical considerations, some surgeons perceive surgical suture, needle and glove selection more as an art than as a science. For those artisans, the use of methods and materials for suturing and glove selection is usually a matter of habit, guesswork, or tradition. This approach to suturing has contributed to a growing concern that the suture selection as well as knot tying techniques employed by many surgeons are not optimal and that they incorrectly select sutures and use faulty techniques in tying knots, which is the weakest link in a tied surgical suture. When the recommended configuration of a knot ascertained by mechanical performance tests was compared to those used by board-certified general surgeons, only 25% of surgeons used the appropriate knot construction.¹ Of the twenty-five gynecologists, mostly department heads, who were polled about their knot tying technique, most were convinced that they made square knots, even though their knot-tying techniques resulted in slipped knots that became untied.² When a knotted suture fails to perform its functions, the consequences may be disastrous. Massive bleeding may occur when the suture loop surrounding a vessel becomes untied or breaks. Wound dehiscence or incisional hernia may follow knot disruption.

As with any master surgeon, he/she must understand the tools of his/her profession. This linkage between a surgeon and surgical equipment is a closed kinimatic chain in which the surgeon's power is converted into finely coordinated movements that result in wound closure with the least possible scar and without infection. The extensive clinical experience's of the gifted plastic surgeon Kant Lin and trauma surgeon, Dr. William B. Long, were essential ingredients of this empowering continuing education program. Dr. Kant Lin a internationally recognized craniofacial surgeon and Dr. William Long, Medical Director of Trauma Specialists, LLP, have been viewed by many of his colleagues as the Paderewski's of the scalpel who has brilliant results in trauma surgery.

It is my belief that these surgeons have transformed surgical suture and needle selection from a ritual practice to a surgical discipline. Early in my career, surgical selection of sutures and needles was largely based on testimonials and anecdotal experiences of senior surgeons. Today, modern surgeons select sutures and needles on the basis of well-controlled, randomized clinical and experimental trials. Having a keen appreciation of surgical education, they have modeled the format of this manual to be an individualized learning environment. The manual is designed to teach each participant the scientific basis for suture and needle selection as well as to illustrate the appropriate surgical techniques involved in wound repair of skin and abdominal incisions and femoral arteriotomies.

Richard F. Edlich, M.D., Ph.D.
Distinguished Professor Emeritus of Plastic Surgery and
Professor of Biomedical Engineering
Founder of the DeCamp Burn and Wound Healing Center
University of Virginia Health Systems
Editor-in-Chief of the Journal of Long-Term Effects of Medical Implants
Director of Trauma Prevention, Education and Research
Trauma Specialists, LLP, Legacy Emanuel Hospital
Portland, OR

SUTURAL SKIN CLOSURE
All operating room personnel should wear powder-free surgical gloves because the cornstarch glove mold release agent causes tissue injury and serves as a vector for latex allergy.³ Participants sensitized to latex should wear powder-free, latex-free surgical gloves.⁴ Because the Food and Drug Administration permits 2.5% of the sterile surgical gloves to have holes, the operating room personnel should wear sterile surgical double-gloves. Because most surgical glove hole punctures go unnoticed for some time after perforation even with double-gloves, many operating room personnel are now using a double-glove hole puncture indication system.⁵ When the outer glove is punctured, the colored inner glove is exposed to blood and other fluids in the operative procedure. After exposure to fluids, this double-glove puncture indication system develops the appearance of a darker color around the outer glove puncture site, a warning to operating room personnel to the presence of glove puncture of the outer glove. After noting this color change, the operating room personnel must remove all surgical gloves, wash hands and don a new double-glove puncture indication system. 6 Following needle stick injury of operating personnel, postexposure prophylaxis is mandatory.

Biology of skin wound repair
From the surgeon's point of view, the rate of gain of strength of the skin wound is a key determinant of many decisions including when the suture can be removed, the level of patient activity, and the selection of the incision. The answers to these questions are found in the results of bioengineering studies of the strength of skin wounds. Even though collagen fibers are evident on the third day after injury, the skin wound has negligible tensile strength.⁷ During the first eight days after closure, the wound is held together by blood vessels crossing the wound, epithelialization, and a fibrinous coagulum. If the percutaneous sutures are removed at this time, the wound may be disrupted easily unless supported by dermal sutures and/or skin closure tapes. Over the next 13 days (8 to 21 days after injury), there is a rapid gain in strength of skin wounds. They continue to gain strength at a relatively rapid and constant rate for four months and at a slower rate for one year. The strength of repaired skin incisions never reaches that of uninjured skin. Adamsons and Kahan⁸ demonstrated that rabbit skin wounds closed with a continuous 4-0 silk suture regained only 40% of the strength of unwounded tissue 120 days after wounding. In the dog, Van Winkle and associates⁹ noted that skin wounds approximated by different percutaneous sutures developed 70% of their normal strength by 120 days. Consequently, the skin wound remains a relatively brittle structure that is capable of absorbing much less energy than normal skin.

The diminished tensile strength of wounded skin as compared with normal skin can be correlated with histologic appearance.¹⁰ The morphologic features of scarred collagen differ distinctly from collagen in unwounded tissue, particularly collagen bundle size. Wound collagen bundles are narrower than normal collagen. Polarized light studies indicate that there is also a more generalized disorganization of the wound collagen. Normal collagen is birefringent, whereas wound collagen is clearly a nonbirefringent material, which indicates a relatively disorganized structure at the molecular or small fibril level. Physical irregularities in fiber shape and "weave" are more readily appreciated by scanning electron microscopic examination. Scanning electron micrographs of a normal collagen fiber show that it is made up of bundles of cross-banded fibrils, characteristically organized into an interlacing network. In the healing wound, the fibers lie in a haphazard pattern. As time passes, the randomly dispersed collagen bundles coalesce to form irregular masses of collagen. Close examination of the wound shows no evidence of the collagen fibril structure. Unfortunately scar collagen appears to be fixed irretrievably in this haphazard arrangement.

Through the years, imaginative biologists have suggested methods to accelerate healing. To date, this avenue of research has resulted in important findings on the repair of dehisced and resutured wounds. Incised wounds allowed to heal for short periods, then dehisced and immediately resutured, developed strength at a significantly faster rate than the primary wound.¹¹ Experiments in animals demonstrated that strength gained in secondary wound healing correlated with the rate of collagen synthesis at the time of dehiscence rather than the collagen content of the wounds.¹² Interestingly excision of the wound edges and reapproximation of the debrided edges eliminated this acceleration of healing.¹³ Such debridement of the wound edges of a dehisced wound is therefore clearly an error in surgical judgment. The benefits of secondary wound healing can be realized in patients requiring surgical intervention soon after the first procedure. Patients with wounds exhibiting gross malapposition of skin edges should be returned immediately to the operating theater to reapproximate these edges. The development of complications, such as ischemia of the wound edges or hematoma, also warrants reexploration of the wound. When performed between the first and fourth week after injury, the secondary wound exhibits a greater breaking strength than the first. This accelerated healing is associated with enhanced resistance of the wound to infection.¹⁴

Continuous percutaneous skin suture closure
Small skin incision whose length is less than five cm are made with a no.15 knife blade. The surgeon uses a reverse cutting edge needle with a subtended arc of 135° for continuous dermal skin closure. Continuous percutaneous suture closure has definite, distinct advantages over interrupted suture closure. First, continuous suture closure can be accomplished more rapidly than interrupted suture closure. This time saving is related to the short time involved in constructing knotted suture loops. For the continuous suture closure, there is one knotted suture at each corner of the wound. In contrast, interrupted suture skin closure requires knot construction for each separate suture loop. Another advantage of the continuous suture is that it accommodates to the developing edema of the wound edges during healing. In contrast, the dimensions of the interrupted suture loop remain unchanged, constricting the edematous tissue within each suture loop. These benefits of the continuous suture skin closure technique must be weighed against one notable disadvantage. Interrupted suture closure permits a more meticulous approximation of the wound edges than continuous suture closure, especially in stellate lacerations with irregular wound edges.

Continuous percutaneous suture closure of the wound can be accomplished by two different techniques. In the first technique, the needle pathway is at a 90° angle to the wound edges and results in a visible suture that crosses the wound edges at a 65° angle (Figure 1). This technique is technically easier to accomplish than one in which the needle pathway is oblique to the wound edge. Consequently, you will be visualizing this first technique for continuous percutaneous suture closure in Figure 1.

In the second technique, the needle pathway is at a 65° angle to the wound edges, so that the visible suture is at a 90° angle to the wound edges rather than at a 65° angle (Figure 2). This oblique passage of the needle is difficult to reliably replicate throughout a long incision.

With either technique, the surgeon starts the continuous percutaneous suture with an interrupted percutaneous suture placed 1 mm from either end of the wound. The needle is passed in a direction toward the surgeon, rather than away from the surgeon. The exit and entrance points of this first interrupted percutaneous suture are 4 mm from the wound edges. After completion of the first percutaneous suture, construct a secure 3-throw square knot and cut the free suture ear 3 mm from the knot. Position the knot so that it lies at a point farthest from you. Holding the fixed suture end parallel to the wound, the needle should be passed through the skin 2 mm from and adjacent to the knot. This needle entrance site is 4 mm from the wound edge and 2 mm from the first interrupted percutaneous suture. Pass the needle beneath the skin at an angle 90° to the incision and exit 4 mm from the wound edge through the skin on the opposite side of the wound.

The next suture then crosses the wound at a 65° angle to the wound to an entrance point 4 mm from the wound edge. Again, the needle is passed beneath the wound at a 90° angle to the wound to continue placement of the suture. The passage of the suture is repeated as described until the wound edges are almost completely approximated by the continuous percutaneous suture, with one remaining needle pass necessary for complete repair. When the surgeon is at a point that is 2 mm from the end of the wound, pass your needle perpendicular to the wound through the skin so that its entrance and exit points are 4 mm from the wound edge. This last needle passage traverses the wound at an angle of 90° to the incision. The continuous percutaneous suture ends as an interrupted percutaneous suture which is accomplished with care to leave a suture loop remaining during suture pull through; this suture loop will be used in knot construction.

Knot construction is accomplished using an instrument tie with the fixed end of the suture and the remaining suture loop. When constructing a secure knot with a suture loop and free suture, we prefer a six-throw square knot with 3 mm ears, rather than a three-throw knot, to ensure knot security.¹⁵ It is advisable to cut the needle from the fixed suture end with surgical scissors before performing the instrument tie.

Continuous dermal skin suture closure
Although continuous dermal wound closure is technically more challenging for the surgeon than interrupted dermal suture closure, it has become an important wound closure technique (Figure 3 A-E). It results in closely approximated wound edges that quickly become impervious to exogenous topical bacterial contamination. The use of a continuous dermal suture, without percutaneous sutures, is an attractive alternative for wound subjected to strong skin tensions, in patients prone to keloid formation, children frightened by suture removal, and those individuals who are unable to contact a health professional for suture removal.

Figure 3 A, B, C, D, E.

Monofilament absorbable synthetic sutures, whose tensile strength remains for at least 28 days, are ideally suited for continuous dermal suture because they do not have to be removed. In contrast, the nonabsorbable dermal continuous suture has to exit percutaneously from the ends of the wound and must surface every 3cm through the skin, along the length of the continuous suture, to facilitate removal. The 4-0 monofilament synthetic absorbable suture is attached to the laser-drilled hole of the reverse cutting edge needle.

Placement of a continuous dermal suture can be facilitated by first approximating the midportion of the wound with an interrupted synthetic absorbable suture. This suture serves to align accurately the divided edges of the wound as well as to restore the configuration of the wound edges before suture closure.

The continuous dermal suture is begun as an interrupted anchoring dermal suture by passing the needle in an upward direction, through the subcutaneous tissue and exiting through the reticular dermis at the apex of the wound (Figure 3 A). A secure five-throw square knot is constructed to secure the suture.

After cutting the one ear attached to the free suture end, the fixed suture end with attached needle is used for the continuous dermal skin closure. The next stitch is passed horizontally from the end of the wound through the superficial papillary dermis. After exiting the dermis, the position of the next bite is identified by pulling the suture across at right angles to the wound (Figure 3 B). Accurate needle placement is assured by slight back-tracking of each bite. By keeping each bite of the continuous dermal closure small, less than 3mm, you can avoid puckering of the skin edges after closure, and subsequent malapposition of the wound edges. During passage of the needle, the skin is stabilized by the tissue forceps. As the small horizontal bites are taken, gentle constant traction of the fixed suture brings the wound edges together.

At a point one bite from the end of the wound, a small horizontal bite is passed toward the end of the wound. The suture before this corner stitch is withheld, forming a loop for the free end of the suture that will be used in constructing the knot. After passing the suture horizontally through a small bite of dermis in the opposite wound edge, the fixed suture end and the long loop of the free suture end are used to construct a secure six-throw square knot.¹⁵

It is important to note that the knot may not remain buried in the subcutaneous tissue using this technique. Consequently, some surgeons cut only the suture loop flush with the knot. They then bury the knot by passing the fixed end of the suture attached to the needle proximal to the knot at the apex of the wound at the level of the subcutaneous tissue, exiting through the skin approximately 5 mm from the end of the wound (Figure 3 C). As the surgeon exerts tension on the fixed suture end after needle passage through the skin, this movement inverts the knot into the subcutaneous tissue. While maintaining tension on the fixed suture end, the suture is cut (arrow) flush with the skin (Figure 3 D). The cut suture disappears from the surgeon's view, retracting into the subcutaneous tissues (Figure 3 E). It is important to note the exact technique of suture passage that is required for knot inversion. If the fixed suture end with its attached needle is passed distal to the knot at the apex of the wound, this maneuver will serve to evert the knot into the wound. In the human, the skin edges are then approximated by percutaneous tape closure to ensure a meticulous approximation of the wound edges.

CONCLUSION
Your success in achieving optimal wound closure using sutures and their attached needles will depend on several factors. First, you must have all of the appropriate sutures and attached needles that are necessary to achieve wound closure. Inadequate instruments will defeat the efforts of even the master surgeon. Second, mastery of surgical skills using sutures and needles requires repetitive practice. Surgeons who do not have adequate psychomotor skills will not achieve an excellent result even with the finest sutures and their attached needles. Third, select the most appropriate sutures with their attached needles based on the biology of wound repair and infection and the biomechanics of sutures and needles. Finally, you must always use a double glove hole indication system that accurately detects holes in the gloves. In the event of a needle stick exposure during surgery, operating personnel must follow carefully the postexposure prophylaxis plan against blood borne deadly viral infections outlined in this course. As you perfect your surgical discipline, share this information with your colleagues and encourage them to participate in this training program. In addition, we encourage each of you to evaluate carefully the clinical results of your wound closure with sutures and strive to devise new and improved techniques that are based on scientific investigations rather than testimonials.

References

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