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Thoracoscopic surgery has usually been limited by 2-dimensional vision and the limited space between ribs—problems that have been only partially overcome by the use of robotics. One of the technical challenges of any minimally invasive surgical approach is tying an intracorporeal knot. For the thoracoscopic surgeon, we describe an easier technique of knot-tying that involves using a right-angled dissector. The technique enables ambidextrous performance and is particularly useful for ligating major pulmonary vessels that might be too small to be stapled or too confined for the admission and maneuvering of a stapling device. Rotating the thumb-dials accordingly enables one to vary the configuration of the knots to create slip or reef knots.
The technique is easy to learn and does not require any complicated devices. It is easily adapted to create even more complex constructs, such as a double surgeon's knot. This technique has special advantages in areas of limited domain and in situations that require very narrow angles of instrument manipulation, particularly in thoracoscopic-assisted procedures.
The last decade has seen significant advances in the development of instrumentation for thoracoscopic and robotic surgery. There is no question that most practitioners of minimally invasive surgery rely heavily on special instruments to accomplish a variety of operative maneuvers. An aspect that remains technically challenging is the tying of intracorporeal knots.1
Tying a secure knot is a basic yet vital component of any surgeon's skill set, but intracorporeal knot-tying for endoscopic and thoracoscopic procedures has always been a technical challenge. Several methods and tools have been used to overcome this problem: devices specifically developed to tie intracorporeal knots; special knot pushers to cinch extracorporeal knots; sutureless techniques, such as using clips or tissue-sealing devices (harmonic scalpels, bipolar coagulators); suture-assist devices; and even modified suture materials intended to make endoscopic knot-tying easier.2–6 An axiom in surgery is that the availability of too many options for application to the same problem means that nothing works best. Clearly, the availability of so many devices and techniques indicates the complex nature of the seemingly simple task of tying a knot.
A novel technique of tying an endoscopic intracorporeal knot with a right-angled dissector has been described previously.7 The technique has several advantages and uses the axial spin of the instrument to accomplish a crucial step in the knot-tying maneuver—creating a loop. Although the technique can be used to create reef or slip knots, it cannot be used to tie more advanced knots, such as surgeon's knots. In addition, when this technique is used to ligate delicate pulmonary vessels, undue tension applied while the knots are cinched can exert unnecessary shear force on the delicate pulmonary vessels, increasing the chances of intraoperative bleeding.
The key to success in endoscopic ligation, we believe, is the ability to tie a secure knot with only minimal manipulation of and dissection around the pulmonary vessels, which are typically quite fragile. Although endoscopic staplers have proved advantageous in most circumstances, the medium to small pulmonary arterial branches do not lend themselves to good hemostatic purchase with the staple line because of their small diameter. Hence, conventional knot ligatures must be used before these vessels are divided. This requires the use of a secure knot with a low likelihood of “slipping,” such as the surgeon's knot. We have devised a novel technique for tying more advanced knots, such as the surgeon's knot, with an endoscopic right-angled dissector by taking advantage of this device's axial spin. This instrument was chosen because it provides easy maneuverability and requires only minimal dissection around delicate vessels—just enough to pass the suture around—as opposed to stapling devices, which require that the entire anvil be passed behind the vessel to be divided.
The surgeon's knot is essentially a 2 × 1 configuration knot, which means that the 1st throw requires making 2 loops before the strands are pulled apart to gain tissue approximation. Thus, the 1st hitch consists of 2 twists—essentially a double overhand knot—and the 2nd hitch is a single overhand knot. The double loop provides more friction between the suture material and holds better than a single loop. However, forming the 2 loops for the 1st throw of the knot is a little more challenging than performing conventional single throws. Creating an intracorporeal double loop by the conventional method of knot-tying is even trickier and requires a lot of practice, especially for trainees.8 Our technique circumvents the problem of translating a 2-dimensional image on a monitor screen to the real-time, 3-dimensional movement that occurs while one is attempting to create suture loops to configure a knot. The technique we describe uses a right-angled Mixter dissector (Microline Surgical Inc.; Beverly, Mass).
After the suture is passed through or around the vessel to be divided, the armed side of the suture is grasped with the needle driver about 3 to 4 inches from the point where the suture exits the tissue. The knuckle (heel) of the working tips (rather than the tips themselves) of a right-angled dissector is used to grasp the armed end of the suture (Fig. 1). The suture is grasped so that the free ends of the tips are oriented toward the attached needle (Fig. 2A). Grasping the suture in the opposite manner (Fig. 2B) would make it impossible to drag the bight of the suture through the loops. After the suture is grasped with the knuckle of the instrument tips, the shaft of the instrument is spun twice around its axis to create 2 loops on the shaft while the entire instrument is advanced slightly into the body cavity so that the loops form a spiral-worm (Fig. 3). Care must be taken to allow laxity of the suture so that the loops are not tightly wound around the shaft or the working tips, which can make it difficult to open the working end of the instrument and can prevent the loops from sliding onto the bight. The tips of the dissector are slowly opened to release the armed end of the suture and are then advanced and turned (as needed) to grasp and pull the bight end of the suture through the loops (Fig. 4). The knot is tightened by pulling the strands in opposite directions (Fig. 5). The subsequent single throws can then be placed by using the same technique, by using another technique with the same dissector that has been described elsewhere,7 or by using any other technique with which the surgeon is comfortable. The same technique can be used to create even more complex knot constructs, such as 2 × 2 configurations, as needed. Reef (square) knots are tied by simply alternating the direction of the spinning shaft in a clockwise or counterclockwise direction, accordingly.
Because this technique avoids all the cumbersome and complex 3-dimensional movements that would otherwise be necessary, it does not require hours of practice, as other techniques do. Anyone who is versed in simple endoscopic maneuvers can easily use this technique to throw a knot. Knots can be placed even with longer sutures, whereas conventional techniques require the surgeon to shorten the sutures to comfortable lengths before tying. The knot can easily be tied with a 5-or 10-mm right-angled dissector; we prefer the 10-mm dissector because it provides better stability of the loops while the knots are being tied. Another advantage of this technique is that each step enables ambidextrous performance. Most surgeons who perform minimally invasive procedures can easily spin the shaft of any endoscopic instrument with the nondominant hand, which offers a significant advantage when tying knots in confined spaces—particularly the thorax, the esophageal hiatus, and the pelvis. Operating in such locations can be a challenge, because the knots can be tied only in a certain direction via particular laparoscopic/thoracoscopic ports that may be accessible only to the surgeon's nondominant hand.
A potential disadvantage of our technique is the fact that the suture is grasped by the instrument, which can weaken monofilament suture materials such as Prolene because of potential fracture at the point of contact. However, monofilament sutures are not used very often in endoscopic surgery.
To make knot-tying easier, one should allow enough suture length between the grasping point of the instrument and the tissues to avoid accidentally pulling the suture through. Unnecessary traction on the suture should be avoided, or else one can inadvertently pull the entire suture out before the knot can be tied. The loops should be wrapped loosely around the shaft; if they are too tight, we suggest unwinding the suture by twisting the shaft in the opposite direction and starting again.
Stephen N. Palmer, PhD, ELS, contributed to the editing of this manuscript.
Address for reprints: Raja R. Gopaldas, MD, Division of Cardiovascular Surgery, University of Missouri-Columbia, One Hospital Drive, Suite MA312, Columbia, MO 65212.