Mastering the use of needles, sutures, and instruments, as well as the technique of knot tying, is the technical foundation of the surgeon's craft. A bewildering array of needles and sutures are available. Some offer distinct advantages in specific situations, while others are simply competitive equivalents. This chapter describes the variety of available needles and sutures, guidelines for their selection and use, and principles and techniques of surgical knot tying.
Characteristics of surgical needles include their attachment to the suture, the shape of the tip, the suture lever in tissue, and the curve of the needle. Surgical needles consist of three structural parts: the point or tip, the body, and the swage or eye. Their specific design depends on their intended surgical use and each variation has merits and disadvantages.
Three types of eye are commonly used in surgery: swaged, controlled release or "pop-off," and open. With a swaged needle, the suture is placed inside the hollowed end of the needle and crimped in place by the manufacturer. This anchors the suture to the needle, and the suture must be cut to free the needle. Because of this security, a swaged needle is ideal for a running suture line and thus is often selected for obstetric applications. The swaged end is flattened to permit a secure grasp by the needle driver. Therefore, during suturing, the swage is ideally grasped rather than the rounder needle body to avoid lateral needle rotation. The diameter of the swaged needle end is larger than that of the rest of the needle and determines the size of the suture tract through tissue (Bennett, 1988).
Controlled-release needles differ from a swaged-on needle in that they allow the surgeon to release or "pop off" the needle with a sharp tug of the needle holder. This saves the time required to cut the suture with scissors. This design is used for interrupted sutures or for vascular pedicle ligation.
Last, the open-eyed needle is fashioned similar to a sewing needle, and suture must be threaded through the eye before use. Open-eyed needles offer the ability to pair a great variety of suture types and needles. Disadvantages include the time needed to thread the eye and its easy unthreading during suturing. Open-eyed needles are rarely used in obstetric surgery.
In cross section, the needle body may be round or ovoid and is tapered gradually to the point. Ovoid needles may be flattened on top and bottom with rounded sides, or flattened on all four sides, producing a square or rectangular body. Some needle bodies also are ribbed longitudinally on the inner curvature to allow them to be securely grasped by the needle holder. For most obstetric surgery, the needle body is round and smooth.