I tell my residents that no one is born knowing how to place 10-0 nylon sutures, but rather it is a learned skill that requires significant practice to master. It is imperative that time is spent practicing in the wet-lab prior to coming to the operating room for actual surgery.
The development of very small gauge ophthalmic sutures truly revolutionized the field of cataract surgery decades ago. With the move to self-sealing incisions, our use of sutures for routine cataract surgery has become less common, but still important for other ophthalmic surgeries. These tiny sutures, typically 10-0 in size, can be challenging to use given their low tensile strength and the small circular needles.
While the ophthalmologists in practice are already experts in using 10-0 nylon to suture incisions or corneal wounds, it helps to review some of the basic concepts to further hone our techniques. For our ophthalmology residents, learning these basic concepts of suturing is an important part of the foundation of ophthalmic surgical technique.
The sutures typically come with semi-circular needles which create circular paths when they are passed through tissue. There should be no linear pushing with these needles, otherwise they will bend and distort the tissues. Rather, the movement used to pass these sutures is similar to turning a screwdriver in a circular motion. (Figure 1)
Sutures should be placed symmetrically so that an even amount of tissue on either side of the incision is captured by the suture. This results in optimum holding power of the incision, better long term stability, and a lower likelihood of cheese-wiring through the tissues. (Figure 2)
The entry angle of the suture plays a large role in determining the depth of the suture. Since needle creates a circular path, acute angles of less than 90 degrees result in shallow passes, while obtuse angles of more than 90 degrees result in deeper passes. If the needle entry angle is 90 degrees, then the circular path of the needle will result in a depth equal to the radius of curvature of the needle. (Figure 3)
The suture holding power is greatest directly under the suture itself, and this diminishes as you move further away. The resulting forces from the suture result in a diamond-like distribution pattern. (Figure 4)
Shorter sutures distribute their force over a smaller area and therefore more sutures are required to close the incision or wound. This may be helpful in situations where higher strength closure of the wound is required. Sutures that are placed at a more ideal length will provide good holding power at the incision while minimizing the number of sutures required for a given length of incision. Overly long sutures tend to distribute the closure force over too broad an area and as a result they may give less effective holding power for the incision. (Figure 5)
Suture placement in clear corneal incisions should be radial, much like the spokes of a bicycle wheel. The needle should be grasped at about one-third the distance from the swaged end to the point and the needle-holder should be unlocked before passing the suture. When tying nylon monofilament sutures, it is customary to tie interrupted sutures with three knots in a 3-1-1 manner: the first knot should be three throws, and the second and third knots should be one throw. These three knots are placed in alternating directions in order to create square knots. Sutures placed in the cornea can then typically be rotated so that the knots are buried within the corneal stroma, which aids in patient comfort while helping to prevent unraveling of the knots.
Placing a suture with good depth, symmetry, spacing, and length, with the correct tensile forces is an art and an integral part of ophthalmic surgical technique.
for further reading, please see the Ethicon Wound Closure Manual
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