CHAPTER 9 Like pillars and buttresses that strengthen a building, sutures join arteries together and secure their connection. And as exposed brick and beams display the builder’s craftsmanship, sutures display the surgeon’s aesthetic. Smooth, snug approximation of everted endothelium on the artery’s inside is what matters most, but the number, spacing, and regularity of stitches show outwardly in the suture lines like a façade making a statement about the surgeon’s skill, standards, and pride. The needle has a body, a point, and a swage; the latter is the hollowed end that receives the nylon suture (Fig. 9.1). The body is rounded with a tapered tip for atraumatic penetration, although the points are also made with cutting and reverse cutting designs. The body curves in a ⅜ circle, but also comes in ¼, ½, and ⅝ circles. The circle has a radius (mm) and a chord length (mm), which is the distance from the needle’s point to the swage. The diameter of the needle ranges between 50 and 100 μm (Table 9.1). Manufacturers describe the needle with a code combining its diameter and chord length; for example, the BV75-3 needle used for most STA-MCA bypasses has a 75-μm diameter and 3-mm chord length with 10-0 suture (Ethicon US, LLC, Somerville, NJ). Circle and radius are not in the descriptive code, but are printed on the package. Other manufacturers such as Davis & Geck and Xomed have other codes that may or may not incorporate these descriptors. Bypass suture is nonabsorbable, monofilament nylon defined by its size according to the United States Pharmacopeia (USP). USP nomenclature refers to suture diameter that originally ranged from No. 1 to No. 6, but as thinner sutures were manufactured with improved techniques, the range extended to No. 0, No. 00, and so on. A higher number of zeros indicates a smaller suture diameter with lower tensile strength. Neurosurgical bypasses use 10-0 and 9-0 suture, with diameters of 20 and 30 μm, respectively. Associated needle size varies in proportion to the suture, with the 11-0 suture using the smallest BV50-3 needle and the 9-0 suture using a larger BV100-4 needle. The smallest BV50-3 is useful in small pediatric patients with fragile tissues, but size advantages must be weighed against the disadvantages of delicate suture more prone to breaks, particularly with the running suture technique. A 10-0 suture comes with both BV75-3 and BV100-4 needles. The BV100-4 needle is preferred for radial artery and saphenous vein grafts with thick walls requiring greater forces to pass the needle, and stronger 9-0 suture is used for stay sutures that pull together the ends of two arteries separated by a wide gap when tying the first knot. Needle diameter always exceeds suture diameter, producing holes in the arterial walls that are only partially filled by the suture material and that leak around the suture when temporary clips are removed (Fig. 9.2). This bleeding is expected, stops quickly, and is a favorable sign of anastomosis patency. The difference between the needle and suture diameter secures a bite once the needle passes through the wall. A suture loaded on a donor artery will not back out when the donor is mobilized into the field. However, this size discrepancy makes it difficult to undo a bite after it is taken. Backing a needle out will damage the wall, and therefore stitches should be inspected by mobilizing arteries and looking intraluminally before passing the needle all the way through the walls if there are concerns about a suturing error or through-stitch. The needle can be backed out easily if a problem is identified, or advanced if not. Titanium needle drivers are strong, lightweight, and preferred (Fig. 9.3). Curved tips translate wrist rotation into needle rotation with a motion arc that has a larger radius than straight tips. Curved tips also facilitate viewing the needle in deep surgical fields where tangential views down the shaft of the needle driver are obstructed. A curved needle driver brings the needle forward into view and compensates for this angulation of the instrument. Curved needle drivers are less important in shallow surgical fields where hands and instruments lie flat with a good overview of the needle, but curved needle drivers are still preferred. Rounded handles are superior flat handles because the instrument can be rolled between the thumb and index finger to smooth the rotational motion. Knurled handles add friction to the handgrip, and diamond dusting on the inside surface of the tips adds friction to the needle grip. The tips of the needle driver are maximally tapered for a low profile (Lawton micro titanium needle holders, Mizuho America, Inc., Union City, CA). Locking mechanisms are not used because locking and unlocking requires extra movements that interrupt suturing mechanics and might injure the tissues with tweaks of the needle. A bite passes the needle through the arterial wall and transfers it to instruments on the opposite side in four steps: bite, grab, counter-sweep, and reload. The bite is the needle’s penetration through the wall (Fig. 9.4). The needle’s body is held in the needle driver between the one third closest to the swage and the two thirds closest to the needlepoint, which allows more than half of the needle to travel through the wall. The grasp is most stable when the needle and driver are perpendicular. The needle’s point is positioned at the point of penetration on one side of the wall and the microforceps’ tips are positioned on the opposite side of the wall. The driving hand is pronated (palm downward) to face the curve of the needle downward, and the driver is rolled between the thumb and index finger to align the needle perpendicular to the wall. The bite begins with a faint push and rotation of the wrist and fingers, ensuring that the needle passes perpendicularly through the full thickness of the wall and all of its layers. The interplay between the needle driver and microforceps is like a dance, with one instrument initiating and driving the bite, and the other instrument reacting with counterpressure. The push of the needle through the wall with the driver synchronizes with the push of the wall across the needle with the microforceps. The two actions are equal and opposite, balanced in force and timing. Either one done in isolation might rip or tear delicate tissues. The available two thirds of the needle’s curvature is advanced with a supinating motion of the wrist and finger (palm upward) until the driver meets the wall and microforceps on the other side. This motion consumes little of the hand’s biomechanical range. After the bite, the needle is grabbed with the microforceps. With the spreading technique of presenting arterial wall to the needle’s point, slightly spread tips of the microforceps counter-resist the needle during the bite and lie waiting on either side of the needle as it passes through the wall. Microforceps in this position grab the needle effortlessly with a small squeeze (Fig. 9.5). With other presentation techniques such as straddling or tenting (discussed in Chapter 10), effort is required to move the microforceps into position and grab the needle. The body of the needle is grasped between the one third closest to the needle’s point and the two thirds closest to the swage, thereby protecting the needle’s point. Direct handling dulls the sharp point and compromises subsequent bites. In addition, direct handling may bend the needle’s tapered tip because it is weaker than its body, and bent needles no longer arc atraumatically through delicate tissues. The dance between instruments continues, with the needle driver releasing its hold on the needle and transferring control to the microforceps. These transfers take place on the needle’s body, with at least one instrument in control of the needle and in contact with metal rather than tissue. Full release of the needle, with no instrument hold, frees the needle to shift or escape, even when it penetrates tissue. Hunting for and recapturing lost needles takes time, breaks the suturing rhythm, and may force attention outside the zone. The counter-sweep is next with the now-liberated needle driver. After releasing the needle, the driver swings to the other side of the arterial wall and sweeps the tissue off the back end of the needle, thereby completing the bite. Tissue is pushed backward in a direction opposite to the advancing needle, which releases the tension of the bite and relocates the wall to its original position. The counter-sweep gently finishes the needle’s transmural passage without additional forward pull on the needle that might stretch or slice through the wall. The counter-sweep is applied with a backhanded push with closed tips of the needle driver, following the curve of the needle back to the swage to unfurl the tissues (Fig. 9.6). Meanwhile, the microforceps holds the needle steady with its body curved up and its point lifted high, letting the tissues sweep downhill off the needle. The final step is the reload. With the needle free of arterial tissue and already in the grip of the microforceps, it is easy to reload the needle driver, but the objective is to ready the needle for the next bite. The needle grasp and hand position determine an efficient reload. The needle is grasped on the body between the one third closest to the swage and the two thirds closest to the needle’s point, with the needle perpendicular to the driver. The reload is performed with the hand supinated (palm upward), even though this position may be less comfortable than with the hand pronated (Fig. 9.7). When an upwardly curved needle is reloaded with a supinated hand, subsequent pronation turns the needle’s curve downward and readies the hand to push and rotate into the next bite, without any further maneuvers. In contrast, when an upwardly curved needle is reloaded with a pronated hand, the hand is positioned for the next bite but the needle is facing the wrong direction, and as a result, the needle must be reloaded or the needle driver must be rolled 180 degrees in the fingers. The counter-sweep shortens the arc of the needle’s bite and keeps the needle’s point forward and the body curved upward, which makes the supinated reload easier than if the full arc of the bite had been taken, with the needle’s point backward and the body curved downward. One bite consists of the four-step cycle of biting, grabbing, counter-sweeping, and reloading. Before advancing to the next bite in a run of continuous sutures, slack is pulled through with the driving hand and the loop of suture is guided into position with the microforceps hand. Slack is taken up slowly and deliberately, watching for snags on tissues, temporary clips, corners of the dam, and other suture loops. Some of these snags occur outside the microscope’s magnified view, and trimming suture upfront gets rid of excess length that might catch on these things. Staying at high magnification and keeping the suture within the zone increase efficiency. The microforceps ushers the loop into position, but saves tightening for later after all sutures are placed.
Suturing Technique
Craftsmanship
Anatomy of Sutures
The Needle Driver
Mechanics of a Bite
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