Chapter 3: Suture Materials, Knot Tying, and Postoperative Care

A wide variety of suture materials are available, all with variable handling characteristics, tissue reactivity, absorption characteristics, and costs. While much attention is paid to suture material, the needle may be as or more important than the suture material itself in promoting an ideal surgical outcome. Needles vary by manufacturer and even by suture material, and utilizing the most appropriate needle for the task is critical. Even the most accomplished surgeon will perform in a less-than-ideal fashion if their instruments or needle choices are flawed.

Most needles used for skin and soft tissue reconstruction are 3/8 circle in diameter, and most needles used for skin and soft tissue reconstructions are reverse cutting in nature (Figure 3-1). There are, however, important exceptions to this rule. For example, a semicircular P-2 needle may be used for narrow closures, such as those sometimes encountered on the nose, and a cutting needle, with the sharp edge on the inside of the curve, may be useful for nasal reconstruction where the thin atrophic dermis may be cut by the superficially coursing outside of the needle.

The two largest manufacturers of suture material used in cutaneous surgery are Ethicon and Covidien. While suture size is governed by USP guidelines (the larger the number of zeros, the smaller the suture), needle size and configuration is largely proprietary. Thus, the surgeon must be comfortable understanding the various needle sizes and configurations of the various manufacturers. Suture material packaging does include a cross-sectional image of the needle, permitting some comparison between companies. Of note, Covidien does not (except on its website) refer to any of its needles as reverse cutting; instead, they label cutting needles as conventional cutting and reverse cutting needles as cutting (Table 3-1). These distinctions are important when choosing suture, though many suture type and needle combinations are only available with a finite number of permutations. Since cutting and reverse cutting needles have a triangular tip, the orientation of the cutting end is indicated by whether the triangle on the box is pointing up (cutting) or down (reverse cutting).

The material used to make the needles themselves also varies considerably between manufacturers, as proprietary alloys are used to maximize strength and durability. While Ethicon and Covidien products are used most often in skin and soft tissue reconstruction, many other reputable companies manufacture suture material, and individual preferences may vary widely (Table 3-2).

Any monofilament suture, including absorbable sutures, may be used for transepidermal suture placement. Thus, utilizing a monofilament absorbable suture may permit the use of a single suture pack for both buried and epidermal sutures.

Many suture characteristics are commonly discussed, including handling, memory, pliability, knot security, tissue reactivity, and others. There are subtle differences between the handling characteristics of different suture materials, most modern options fall well within the realm of utility, so that while the handling of silk, for example, is clearly superior to the handling of nylon, even nylon handles very well. Similarly, certain materials, such as catgut, may be highly reactive, though the more frequently used formulations, such as chromic gut and fast-absorbing gut, do not lead to enough inflammation to make a marked clinical difference in most situations. For the most part, monofilament sutures lead to less tissue drag, and therefore are useful with running techniques, while braided sutures provide excellent handling and knot security, and are therefore useful for interrupted buried sutures. With improvements in materials, the distinction between outcomes now likely relates more to suturing technique than to choice in suture materials.

Vicryl (polyglactin 910)

Vicryl is one of the most frequently used suture materials in skin and soft tissue reconstruction. It is a braided, coated suture material that retains its strength for approximately 3 weeks and is completely absorbed in less than 3 months. It has excellent handling characteristics and only mild tissue reactivity. Recently a faster-absorbing variation, VicrylRapide, was developed, which loses its strength entirely in less than 2 weeks and may be seen as an alternative to fast-absorbing gut suture when suture removal is not desired. An antibacterial-coated variation is now also available in the market.

Polysorb (glycolide/lactide copolymer)

This is a braided absorbable suture, similar to Vicryl. It provides similar handling and knot security while ostensibly providing slightly improved initial tensile strength when compared with Vicryl. Its absorption characteristics are also similar to Vicryl. Velosorb Fast has also been developed as an alternative to VicrylRapide.

Monocryl (poliglecaprone)

Monocryl, often seen as a monofilament alternative to Vicryl, is another popular suture material choice. It is more expensive than Vicryl, has excellent handling characteristics for a monofilament suture, and loses its strength in less than 1 month, though complete absorption takes 3-4 months. As with Vicryl, an antibacterial option is also now available.

Maxon (polyglyconate)

Maxon is a long-lasting monofilament absorbable suture; while it loses some strength already after 3 weeks, it takes 6 months or more for the suture material to be entirely absorbed, making this a good choice when long-term strength retention may be helpful. It has good handling characteristics, though the slow absorption times should be taken into account if dyed suture material is used, as the suture may be visible if placed in a running subcuticular pattern.

Polydioxanone (PDS)

Polydioxanone I and II are very long lasting monofilament absorbable sutures. They are useful when long-term strength retention is critical. PDS II was developed as a better-handling alternative to PDS I, which was criticized for its less-than-ideal handling characteristics. It retains strength for an extended period of time, with 50% strength retention at 5 weeks, and may take more than 6 months to absorb.

Biosyn (glycomer 631)

Biosyn is another monofilament absorbable suture. It has very good handling characteristics and outstanding initial tensile strength. It retains its strength for at least 3 weeks and takes up to 4 months to absorb completely. If Biosyn is used for superficial closures, the undyed version may be preferable.

Caprosyn (polyglytone 6211)

Caprosyn is a fast-absorbing monofilament suture, often seen as an alternative to Monocryl. It absorbs completely in 8 weeks, while retaining tensile strength for 7-10 days postoperatively. It is therefore useful in low-tension closures, such as those on the face, where rapid suture material breakdown is an advantage.

Catgut

Plain gut is derived from bovine or sheep intestines, and therefore breaks down by enzymatic degradation, rather than the hydrolysis which breaks down synthetic absorbable sutures. Chromic gut is a longer-lasting version of gut, while fast-absorbing gut is heat treated to speed up absorption. On a practical level, fast-absorbing gut may be useful for closures when transepidermal sutures are desired for wound-edge apposition but where suture removal is impractical or inconvenient. Gut does lead to more tissue reactivity than other absorbable sutures and has a tendency towards breakage after multiple passes through tissue (Table 3-3).

Nylon

This is a frequently used nonabsorbable suture, and provides minimal tissue reactivity coupled with very good handling. While a very good choice for most closures, it does not move through tissue as smoothly as polypropylene, so if buried subcuticular sutures are placed with nonabsorbable suture, the latter would be preferred. Nylon is available either braided or monofilament; the former may confer slightly better handling, though this is outweighed by the ability of monofilament nylon to move easily through tissue.

Polypropylene (Prolene, Surgipro)

This is a minimally reactive suture that has the ability to move smoothly through tissue. It does have a fair amount of memory, and therefore may be slightly more challenging to work with than nylon. Extra throws are often advisable during knot tying as well, though this does represent a good option for nonabsorbable subcuticular suturing.

Novafil (polybutester)

This is a very well-handling suture material that also provides significant elasticity. Though not as widely used as some other materials, it provides excellent pliability. The elasticity may be helpful in areas where significant wound edema is anticipated, as it will accommodate tissue swelling while maintaining wound-edge apposition.

Silk

This is the most highly reactive of the nonabsorbable sutures. It also, however, is the gold standard for suture material handling. Its natural softness makes it useful in closures along the lips, where synthetic suture has a tendency to poke against the delicate tissues. Its reactivity, however, makes it less useful on a daily basis for most other surgical sites.

Most surgical knots in skin and soft tissue reconstruction are tied using an instrument tie. This is generally the fastest approach and also affords the least amount of suture material waste. Hand tying, using either one- or two-handed ties, may be used rarely in cutaneous surgery and reconstruction, and will not be addressed here in detail.

The distinction in knot tying between transepidermal sutures, where pulling suture tight may lead to strangulation, and buried sutures, where the goal of suture placement is developing directly opposed dermal, muscle, or fascial structures, is critical. When tying a deep suture, it is generally desirable to pull the suture strands together as tightly as possible, secured with a stable knot. For transepidermal sutures, since the goal of suture placement is wound-edge apposition, placing the minimal necessary tension across of the surface of the wound is a must; overtightening these sutures will lead directly to strangulation, necrosis, and—at a minimum—track mark formation. Indeed, while dermal suture placement should be performed as tight as possible, transepidermal sutures should be secured with the minimal possible tension, and some additional give may be provided by permitting laxity between the first and second throws of the knot, anticipating tissue edema.

Generally, most surgical knots are tied as square knots, so that the two throws occur in opposite directions, locking the knot in place. Sometimes, a granny knot is desirable, where the first two throws are in the same direction, as this allows the suture material to be cinched down and tightened. It is critical, however, to follow the granny knot with a throw in the opposite direction so that once the knot is in place it is secured and cannot slip.

Each throw refers to one half knot, that is a complete twisting of two strands. Thus, to secure a knot, by definition a minimum of two throws are necessary, and for practical purposes three throws are used for most braided sutures, while four throws are used for some sutures with a higher risk of knot slippage.

After placement of the suture itself, when beginning an instrument tie the leading end of suture must be grasped with the nondominant hand. In order to minimize the risk of needle-stick injury, it is possible to grasp the suture material approximately 6-10 cm from the needle swage between the thumb and index finger of the left hand, allowing the needle to drop down below the hand. Since the needle is hanging freely and is not under tension, there is little chance for a needle stick injury. Excess suture material may be wrapped around the nondominant hand with a gentle turn of the wrist. Some surgeons prefer to hold the needle itself in the nondominant hand.

1. The leading end of suture material is grasped between the thumb and index finger of the left hand, approximately 6 cm from the needle swage. The needle driver is brought between the leading and trailing strands of suture, and the leading end of suture is wrapped twice around the needle driver. This should be done by moving the needle driver around the suture, not moving the suture material around the needle driver, as this will permit better precision and economy of movement.

2. The needle driver then grasps the trailing end of suture material.

3. The hands are pulled in opposite directions, perpendicular to the incised wound edge, so that the right hand moves to the left (where the leading end of suture began) and the left hand moves to the right (where the trailing end of suture began). This should form a surgeon’s knot that will be resistant to slippage.

4. The trailing end of suture is released by the needle driver, and the needle driver is then brought from the inside, between the two end of suture, and the leading end of suture is wrapped once around the needle driver.

5. The needle driver grasps the trailing edge of suture, and the hands again move in opposite directions, so that now the right hand moves to the right and the left hand moves to the left. The knot is now locked.

6. For the third (and often final) throw, steps (1) through (3) are then repeated, except that now the suture is wrapped only once around the needle driver. Additional throws may be placed if needed (Figures 3-2, 3-3, 3-4, 3-5, 3-6, 3-7, 3-8, 3-9, 3-10, 3-11).

1. The leading end of suture material is grasped between the thumb and index finger of the left hand, approximately 6 cm from the needle swage. The needle driver is brought between the leading and trailing strands of suture, and the leading end of suture is wrapped twice around the needle driver. This should be done by moving the needle driver around the suture, not moving the suture material around the needle driver, as this will permit better precision and economy of movement.

2. The needle driver then grasps the trailing end of suture material.

3. The hands are pulled in opposite directions, parallel to the incised wound edge, so that the right hand moves in the direction of where the leading end of suture began, and the left hand moves in the direction of where the trailing end of suture began. This should form a surgeon’s knot that will be resistant to slippage.

4. The trailing end of suture is released by the needle driver, and the needle driver is then brought from the inside, between the two ends of suture, and the leading end of suture is wrapped once around the needle driver.

5. The hands again move in opposite directions parallel to the wound, so that the right hand moves in the direction of where the leading strand began and the left hand moves in the direction of where the trailing strand began. The knot is now locked.

6. For the third (and often final) throw, steps (1) through (3) are then repeated, except that now the suture is wrapped only once around the needle driver. Additional throws may be placed if needed (Figures 3-12, 3-13, 3-14, 3-15, 3-16, 3-17, 3-18, 3-19).

Absorbable suture material is generally trimmed either at the knot (for braided suture material) or with a 1-2 mm tail of suture, for monofilament suture material. Nonabsorbable sutures are generally left with a 3-6 mm tail, depending on surgeon preference, suture material size, and the anatomic location.

When tying knots with nonabsorbable suture, if there is only minimal tension across the surface of the wound it is sometimes desirable to leave a gap between the initial surgeon’s knot and the square knot. To execute this maneuver, the first throw is placed as a surgeon’s knot. The next throw is not tightened to lock the surgeon’s knot, but rather leaves 1-2 mm of space between the surgeon’s knot throw and the subsequent throws. This allows for some give so that tissue edema does not cause the suture material to overly constrict the wound edges.

After suturing a wound, the surgeon must decide on the most appropriate dressing. In general, wounds heal best in a moist environment, and therefore an occlusive film dressing is often appropriate. Such dressings are also helpful in providing a protectant film over the nascent wound in order to minimize the risk of bacterial colonization. Film dressings are usually adequate for most surgical wounds, since these wounds are generally not highly exudative, as the wound margins have already been adequately approximated. Dressings can usually be left in place for at least 48 hours, and leaving a film dressing in place for a week or more is often a reasonable choice for many wounds, as this also improves the convenience for the patient.

Adhesive strips are sometimes used to help with wound-edge approximation. That said, the degree of gain achieved by adding adhesive strips to an already well-sutured wound is minimal, and these strips may sometimes become covered in serous fluid or serve as a magnet for bacterial colonization.

Suture removal timing remains more of an art than a science. In general, the sooner sutures are removed, the better. Since nonabsorbable sutures generally should not be holding significant tension across the wound, and ideally are used for fine-tuning wound-edge approximation only, they may be removed as early as 5 days postoperatively. In the rare even that these sutures are carrying significant tension, sutures may be left in place for 7-14 days or even longer, though patients should be warned of the high risk of leaving significant track marks.