Suture materials

If you bring two soft tissues together and hold them there for about 10 days they will join. Most surgery depends on this. The easiest way to hold them is to sew them. You can use: (1) absorbable sutures which are absorbed by the tissues so that you need not remove them. (2) Non-absorbable ones which you leave indefinitely if they are deep, or remove if they are on the skin.

Absorbable sutures can be plain catgut (from the submucosa of sheep, not cats!), which usually holds its strength for about 10 days. Or catgut can be treated with chromic acid (chromic sutures) which slows its absorption and makes it keep its strength for 20 days. Sepsis speeds the dissolution of catgut, especially plain catgut, so that it may dissolve in 2 or 3 days. You can also use absorbable sutures of synthetic material such as polyglycolic acid (''Dexon').

Catgut is soft and holds knots well, but not so well as a non-absorbable multifilament, such as linen or cotton. If a suture material does not hold knots too well, knots made of it need longer ends. So leave knots in catgut with 5 mm ends, unless you are using it for fine superficial vessels. You can cut linen or cotton 2 mm from the knot.

While catgut is being absorbed it makes a good culture medium and may promote sepsis. So don't use more than is necessary, don't leave the ends of ligatures unnecessarily long and avoid thick No. 2 or 3 catgut. Monofilament sutures, especially fine ones, don't have this risk, which is why so many surgeons like them.

If necessary, you can use almost any suture material almost anywhere, especially on the skin. But, always use use catgut for: (1) The urinary and the biliary tracts because non- absorbable sutures can act as the focus around which a stone can form. (2) The mucosa of the stomach, where a non-absorbable suture may be the site of an ulcer later. (3) The mucosa of the uterus (less important). (4) Sutures close under the skin, where non-absorbable sutures may work their way to the surface.

Plain catgut does not hold its strength for very long, so never use plain catgut for: (1) Tying larger vessels (use linen, cotton or silk). (2) Suturing the gut (use chromic catgut).

One problem with catgut is that it may be of poor quality, and so give way early and perhaps disastrously. This is another reason for using monofilament where you can.

Non-absorbable sutures can be polyamide (''Nylon'), polypropylene (''Prolene'), polyethylene (''Courlene'), linen, cotton, silk, or stainless steel wire. You can use the first three as a single (mono)filament, or as multiple filaments which are braided or twisted together. Whenever we refer loosely to ''monofilament', we mean a non-absorbable suture of nylon, polyethylene, or polypropylene, or a similar synthetic material as a single filament. It is the most useful general purpose suture material. Although non-absorbable sutures remain as permanent foreign bodies, monofilament nylon, polyethylene, and steel are less likely to promote infection than catgut, or multifilament cotton, linen, or silk.

Unfortunately, a single thicker filament makes less reliable knots than a many finer ones braided or twisted together, except for steel wire, which is always used as a single filament, and which knots superbly but is difficult to work with. So, always tie monofilament with a surgeon's knot (4.8).

Apart from the indications for catgut given above, you can use monofilament for almost anything, but silk, cotton, or linen threads, are better than monofilament for tying larger vessels. Braided silk may cause troublesome stitch abscesses. Don't use it immediately under the skin, because it may work its way through to the surface, long after healing is complete. If it does become infected, you may have to remove it piece by piece. Even monofilamant can come to the surface, so keep it well buried, and use catgut close under the skin.

The strength of sutures is measured in two systems. In the old system the finest ones are measured in ''zeros' and the thicker ones are numbered. From finest to thickest the sequence is[md]6/0, 5/0, 4/0, 3/0, 2/0, 0, 1, 2, 3, 4. Although attempts are being made to replace the old system by a metric one from 0 to 8, most surgeons still use the old one. So do we.

Use the thinnest sutures you can[md]they need only be as strong as the tissues they are holding together. You can do most operations with sutures between 3/0 and 1 on the old scale. Only very occasionally will you need sutures which are thicker or thinner than this, except for fine work such as nerve or tendon repairs, and for eye and plastic surgery. If you do need a thicker suture, you can double up a thinner one.

The cost of sutures can significantly increase the cost of an operation. In the industrial world they are now sold in individual disposable packs, which are expensive to make and waste much suture material each time a pack is opened. This, combined with the use of atraumatic needles, means that the needles and sutures for one operation may cost $20. But if you buy monofilament in rolls, and use ordinary needles, the suture materials for a single operation cost almost nothing. Monofilament suture material in packets is 20,000% more expensive than in reels, and with needles swaged on is 30,000% more!

Never let the lack of suture materials be the reason for not doing an urgent operation. Either use ordinary nylon fishing line, which is exactly the same material as that used for surgical sutures. Or, if necessary, you can use ordinary linen or cotton thread almost anywhere.

SUTURES, polyamide (''Nylon'), or polyethylene (''Courlene'), monofilament, strengths 5/0, 4/0, 3/0, 0 and 1, reels of 1000 metres, preferably each size a different colour (PEA), two reels only of No. 1, one reel only of the other sizes. No. 1 is the most generally useful size. Use 4/0 monofilament as your basic suture material for fine skin sutures.

SUTURES, catgut, plain, 3/0, in boxes of 12, five boxes only. Plain catgut is soft. Use it for suturing the mouth, tongue, and lip.

SUTURES, catgut, chromic, strengths 3/0, 2/0, 0, 1 and 2, boxes of 12, ten boxes only of each strength. This is the most commonly used form of catgut.

SUTURES, catgut, chromic, atraumatic, (a) 2/0 on half circle 30 mm needles, ten boxes only. (b) 2/0 on 5/8 circle 30 mm needles, ten boxes only. (c) 4/0 on 16 mm curved needle, ten boxes only. These sutures have needles swaged on to them. Use them for the gut, the gall-bladder, and the stomach, held in a needle-holder. The smaller needles (c) are for children.

SUTURES, prolene, atraumatic, (a) 4/0 on 16 mm half circle, round-bodied needles, (b) 8/0 on 3 mm 3/8 circle atraumatic needles, two boxes only of each size.

SUTURES, linen, No. 1, five reels only. Use linen for tying vessels. It holds knots well and is stronger than cotton.

SUTURES, nylon or virgin silk, 8/0, one box only. These are for suturing the cornea.

WIRE, monofilament, soft stainless steel, (a) 5/0, (b) 0.35 mm, (c) 1.0 mm, one reel only of each thickness. Surgical wire must be soft and malleable because springy wire is difficult to work with. Autoclave the whole reel. (a) Fine 5/0 wire is cheap, and is excellent for the skin, if you can learn to use it efficiently. (b) 0.35 mm wire is for wiring the teeth (62.10) and for hemicirclage (72.18). (c) Tension 1.0 mm wire in a stirrup and use it for exerting traction (70.12). These wires and the equipment to use them (70.9) are essential. One of the advantages of wire is that, unlike more massive pieces of metal, it does not promote infection, so that you can if necessary put it though infected tissues. You can wire tissues in the presence of sepsis; for example, when you repair a burst abdomen (9.13).

Fasten wire by passing its ends through any convenient tube, such as that from a ball pen, and then grasping the ends and twisting them. Finally, cut the twisted ends of the wire short. This will prevent it from coiling up in an inconvenient way.

WALL BRACKET, stainless steel, to hold rolls of monofilament, as in Fig. 4-5, one only. Fix this to the wall, and pull lengths of monofilament from it. If you cannot get one of these brackets, make it.

REELS, stainless steel, egg shaped (''eggs'), for holding suture material, five only. Wind monofilament into these, autoclave them and cut off the length of suture material you require.

Dr JAMES MUKOLAGE was horrified to find in his village a woman with an abdominal wound from which gut was protruding. He was only recently qualified and had not operated on one of these cases before. He had few facilities, but he managed to find some local anaesthetic solution and some linen thread in the shops. A few instruments from the local health centre were boiled up; he washed the wound thoroughly, and anaesthetized the tissues round it with lignocaine. Fortunately, her gut had only a minor cut in it which was easily repaired. When he had returned her gut to her abdomen he was able to close it with linen thread. She survived. LESSON Improvisation can save lives. Fig. 4-5 BUY MONOFILAMENT IN REELS. A, hang them from a wall bracket, cut lengths of suture material about a metre long and twist them into loose coils (B, and C) or wind them round the empty spools used for disposable sutures. If funds are scarce, avoid the expensive proprietary sutures F, and G. You can also use cotton or linen thread, or colourless fishing line. Match this against surgical monofilament nylon strength for strength. A good strength for abdominal sutures is 5 to 7 kg breaking strength. MONOFILAMENT IS THE MOST USEFUL GENERAL PURPOSE SUTURE MATERIAL TIE IT WITH A SURGEON'S KNOT