Sutures and staples by Genesis Albarran

PRACTICAL PROCEDURES

Sutures and staples

The characteristics of an ideal suture material

W E G Thomas • • • • • • • • • • • •

Following any operative procedure, careful approximation of the tissues will allow healing to occur, as long as there is no tension and a good blood supply. The method for the approximation of the tissue edges varies depending on the site and tissue concerned, but the mainstay of such approximation for centuries has been the suture. Other methods have now become available such as Steristrips, tissue glue, clips and staples, but the suture in its many forms and characteristics remains the predominant method for wound closure.

it with the needle holder or forceps. Such damage can predispose towards fracture of the suture. Multifilament sutures, or braided materials, are rougher on the tissues and have a surface area of several thousand times that of monofilament sutures, resulting in capillary action and the potential for the interstices of the braided material to become colonized with bacteria. However, such sutures are easy to handle and have good knotting qualities.

Sutures There is no such product as the ideal suture. Surgeons have sought to define certain characteristics that are highly desirable (Figure 1) but no suture material fulfils all these criteria. Furthermore, certain procedures place specific requirements upon suture material (e.g. vascular anastomoses require a smooth, non-absorbable suture material, while gastric anastomoses require an absorbable material). For absorbable sutures, the length of time needed for wound support varies in different tissues (e.g. subcutaneous tissues or muscular aponeuroses). Therefore, in closing any wound the surgeon needs to define clearly the requirements for closure, bearing in mind the tissues involved, and then to select the suture material and method of suturing that will most effectively achieve the desired objective.

Strength: the strength of a suture depends on its thickness, the material of which it is made, and its behaviour in the tissues. Manufacturers classify suture diameter in tenths of a millimetre. It is important to recognize that losing tensile strength and mass absorption are two separate events, in that a suture may support the wound for only a few days but it may remain as a foreign body for a much longer period. The ideal suture that disappears completely as soon as its work is done does not yet exist. Even for non-absorbable sutures, strength is not always constant. Although these materials do not absorb, those of biological origin, such as silk, lose strength without initially showing any change in the mass of the suture, and even fragment over time. However, other non-absorbable materials, especially those of synthetic origin, never lose tensile strength and do not change in mass in the tissues. These materials are particularly useful where permanency is required, such as for vascular anastomosis.

Suture materials For any suture material, its physical nature, strength, tensile behaviour, absorbability and biological behaviour must be considered. Physical nature: suture material can be monofilament or multifilament. A monofilament suture such as polypropylene (prolene) is smooth and slides well in the tissues, but requires very careful knotting techniques. Furthermore, it can be easily damaged by gripping

Tensile behaviour: some suture materials display plastic characteristics while others may be more elastic. Deformability and flexibility are important for ease of handling, while many of the synthetic materials demonstrate ‘memory’, whereby they curl up in the pattern in which they were packaged. A sharp but gentle pull on the material helps to remove some of the curl. More memory results in less knot security. Thus, knotting also plays a role in a suture’s tensile strength and it is important to note that most sutures lose 50% of their strength at the knot.

W E G Thomas is Consultant Surgeon and Clinical Director of Surgery at the Royal Hallamshire Hospital, Sheffield, UK. He qualified from St George’s Hospital, London, and trained in Cambridge and Bristol. His main clinical interests are hepatobiliary-pancreatic surgery and endocrine surgery. He is currently a member of the Council of the Royal College of Surgeons and Chairman of Education. He is a past member of the Court of Examiners and Surgical Skills Tutor of the Royal College of Surgeons and is also a past member of the Intercollegiate Panel of Examiners for the Specialty Board of General Surgery for the FRCS.

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Easy to handle Secure knotting Predictable tensile strength and performance Sterile Should not shrink in the tissues Pulls through tissues easily Non-electrolytic Non-capillary Non-allergenic Non-carcinogenic Does not promote tissue reaction or infection Inexpensive

Absorbability: suture materials tend to be either absorbable or non-absorbable. Absorbable sutures provide temporary wound support over a period of time, but this period depends on the nature of the material. Man-made non-absorbable sutures tend to

PRACTICAL PROCEDURES

maintain their strength indefinitely, but natural protein materials like silk, although officially classified as non-absorbable, lose most of their tensile strength in about one year, fragment and usually cannot be found after 2–3 years.

sues (Figure 2). All sutures should be placed at right angles to the wound, the same distance apart and each suture should reach into the depth of the wound. Continuous sutures: these should be inserted in an identical manner to interrupted sutures but, after tying the first suture, the rest of the sutures are inserted in a continuous manner until the far end of the wound is reached when the suture material should then be knotted. In order to maintain constant tension along the wound, it is vital to have an assistant who will ‘follow’ the suture keeping it at the correct tension at all times. If this does not occur then there is a danger either of ‘purse-stringing’ the suture (by using too short a suture), or of leaving the suture line too lax. There is more danger of the former than of the latter. Postoperative oedema will often take up any slack.

Biological behaviour: the biological behaviour of a suture in tissues depends on the origin of the raw materials. Man-made or synthetic materials are more predictable, elicit minimal tissue reaction and tend to be inert, which is an important noncarcinogenic property. Biological or natural sutures tend to produce a much greater tissue reaction and can cause local irritation and even rejection. The handling of the suture material by the body also varies, with absorption taking place by proteolysis (enzymic activity) for substances like catgut (no longer in clinical use), and by hydrolysis for materials like glycolide and lactide. Such activity is rendered more unpredictable in the presence of infection, urine or faeces.

Mattress sutures: mattress sutures may be either vertical or horizontal (Figure 3). They may be useful in awkward sites or for ensuring eversion or inversion of a wound edge. They appose the wound edges accurately but should not be tied too tightly. The initial suture is placed as for an interrupted suture, but then the needle should be reversed in the needle holder and either the needle taken back vertical to the previous traverse or horizontal to it, and then ligated.

Suture techniques There are four frequently used suture techniques: interrupted, continuous, mattress and subcuticular. Interrupted sutures: interrupted sutures require that the needle should be inserted at right angles to the tissue, pass through both aspects of the suture line and exit at right angles, taking care not to drag the needle through the tissues but to follow the curve of the needle. As a guide, the distance from the entry point to the edge of the wound should be approximately equal to the thickness of the tissue being sutured, and the distance between successive sutures should be approximately double the thickness of the tis-

Subcuticular sutures: when the wound edges can be approximated easily with no tension, then a subcuticular suture results in a very neat scar. The suture material may be absorbable or non-absorbable, and depending on the material used, the initial fixation at one end of the wound is either by means of beads for

Interrupted suture technique

Mattress sutures

x x x 2x a Vertical mattress suture As a rough guide, the distance between the edge of the wound should be approximately the same as the thickness of the tissues being sutured, and successive sutures should be placed twice this distance apart

b Horizontal mattress suture 2

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PRACTICAL PROCEDURES

Stapling devices These are in wide use, particularly in the gastrointestinal tract. They tend to apply two rows of staples, offset in relation to each other, to produce a sound anastomosis. Many of them also divide the bowel or tissue that has been stapled while other devices merely insert the staples and the tissue has to be divided separately. It is crucial for the surgeon to understand the principles behind each device and to know intimately the mechanism and function of the instrument.

Subcuticular suture

End-to-end anastomoses (EEA): circular stapling devices allow tubes to be joined together, and are in common use in surgery of the oesophagus and low rectum. The detached stapling head/anvil is introduced into one end of the bowel, usually being secured within it by means of a purse-string suture. The body of the device is then inserted into the other end of the bowel, either via the rectum for a low rectal anastomosis, or via an enterotomy for an oesophago-jejunostomy, and the shaft is either extended through a small opening in the bowel wall or is secured by a further pursestring suture. The head/anvil is re-attached to the shaft and the two ends approximated. Once the device is fully closed (shown by the green indicator in the window) the device is fired, and after unwinding three half-turns the stapler is gently withdrawn. It is important to assess the integrity of the anastomosis by examining for completeness the ‘doughnuts’ of tissue excised. It is essential that no extraneous tissue be allowed to become interposed between the two bowel walls on closing the stapler.

non-absorbable sutures or a buried knot for absorbable sutures. Small bites of the subcuticular tissues are taken on alternate sides of the wound (Figure 4) and then pulled gently together and fixed at the far end either by a further crushed bead, or by a ‘Z’ sequence of passes of the needle. Other techniques Steristrips: an alternative to skin sutures are self-adhesive tapes or Steristrips. These cannot be used wherever there is any tension on a wound or significant moisture. However, they are suitable for superficial lacerations of the face and fingers. When using such strips on fingers or toes, it is important to ensure that the digit is not encircled entirely for fear of producing a tourniquet effect.

Transverse anastomoses (TA): these instruments, which come in different sizes, simply provide two rows of staples for a single transverse anastomosis. They are useful for closing bowel ends, and the larger sizes have been used to create gastric tubes, gastric partitioning, etc. One technical point of importance is that the bowel should be divided before the instrument is re-opened after firing, as it is designed with a ridge along which to pass a scalpel to ensure the correct length cuff of bowel remains adjacent to the staple line. In the pelvis it may be helpful to use one with a moveable head (roticulator).

Tissue adhesive: tissue adhesives or ‘glue’ are now available and tend to be based upon a solution of n-butyl-2 cyanoacrylate monomer. When applied to a wound it rapidly polymerizes, forming a firm and adhesive bond. The wound should be clean, dry, and able to be approximated without tension. The wound edges should be approximated accurately beforee applying the adhesive as polymerization is very rapid and mistakes can occur.

Intraluminal anastomoses (IA): these instruments have two limbs which can be detached. Each limb is introduced into a loop of bowel, the limbs re-assembled and the device closed. On firing, two rows of staples are inserted either side of the divided bowel, the division occurring by means of a built-in blade that is activated at the same time as the insertion of staples. Such an instrument may be used in fashioning a gastro-jejunostomy or jejuno-jejunostomy and is used in ileal pouch formation.

Staples Staples tend to be made of stainless steel and thus confer the advantage of high tensile strength with low tissue reaction. These can either be applied individually as for skin closure, or be part of a stapling device that can be used to fashion an anastomosis during either open or laparoscopic surgery.

Other devices: there are other instruments that will staple/ligate and divide blood vessels. Skin closure may be undertaken using hand-held stapling devices rather than by individual insertion of clips or staples by hand. Many intestinal stapling devices are now adapted to be inserted down cannulae during laparoscopic surgery, and although they look very different, the principles of function are identical to the open surgery variety.

Clips Skin clips produce a very neat scar with good wound eversion and a minimal cross-hatching effect. They can be placed faster than suture insertion and have a lower predisposition to infection as they do not penetrate entirely through the wound and do not produce a complete track from one wound edge to the other. However, they can be uncomfortable for the patient and require a special instrument to remove them. Furthermore, they tend to be a more expensive method for wound closure than simple suture techniques.

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