It is useful to be familiar with the various types of suture, their uses and their effect on the management of wounds. Generally, a suture may be either absorbable or non-absorbable, and has either a braided, twisted or monofilament structure. New varieties of suture material are constantly being developed.
Types of suture
Absorbable sutures are broken down in the body tissues over a varying number of days either by enzymes or by hydrolysis by the tissue fluid. It is important to differentiate between the times of loss of tensile strength and of disappearance of the material as these are not necessarily the same.
Non-absorbable sutures remain in place for some years unless they are removed.
Braided sutures (where the strands are plaited together) and twisted sutures (where the separate strands are twisted round each other) are very flexible and therefore easy to handle and knot. The knots usually hold and are secure. The disadvantage of these types of suture is that fluid can seep between the strands (capillarity) and microorganisms can get into the interstices of the yarn. Giving rise to long-term infections. Most braided sutures are proofed or coated in an attempt to prevent this.
Monofilament sutures, on the other hand, consist of only one strand of material. They tend to be less flexible and more 'slippery'. They are therefore less easy to handle and knot, and the knots need more throws to be secure. The only nidus provided for infection is within the interstices of a knot.
Examples
*Several of these names are company trade marks and the companies involved are then known.
1 Tying off small arteries and veins near the skin.
2 Stitches in the ureter, urinary tract, or biliary tract (where permanent sutures term a focus for stone formation).
3 Closing off tissue spaces, e.g. subcutaneous space.
4 Occasionally for closing the skin in children, where it is an advantage not to have to remove the stitches.
5 In small bowel anastomosis or stomach mucosal anastomosis (non-absorbable sutures in the stomach can cause long-term ulceration).
The following are different types of absorbable suture.
Catgut. This is made of strands of collagen from the submucous part of sheep or cow intestine which is dried out and sterilized. It is absorbed by cell and tissue proteases. Plain catgut loses its strength in about 3 days. Chromic catgut is catgut soaked in potassium dichromate, which delays its breakdown. It retains its strength for 57 days. Both cause a tissue reaction but this is less with chromic catgut.
Collagen sutures. These consist of pure collagen fibrils from cow flexor tendons. They have a smoother surface and are more homogeneous than catgut. They can either be plain or chromic and cause minimal tissue reaction with good knotting properties. They are absorbed by proteases and are used in ophthalmic surgery.
Other absorbable sutures are synthetic and braided in structure. Their tensile strength lasts for longer than catgut or collagen.
Polyglycolic acid {Dexon, Davis & Geek). This is a homopolymerofglyvcolide and is braided. The material loses 50%
of its effective tensile strength in 20 days but is not absorbe, for between 100 and 120 days.
Polyglactin 910 (Vicryl.Ethicon). This is a synthetic absorbable suture made of a copolymer of lactide and glycolideIt is braided and non-antigenic and causes minimal tissue reaction. It has good knotting properties. It loses 60% of its effective tensile strength in 20 days. The sutures are absorbed by slow hydrolysis in 6090 days.
Polydoixanone (PDS, Ethicon). This is a synthetic monofilament absorbable suture. It is absorbed by hydrolysis and causes minimal tissue reaction. There is very little harbouring of infection. Its loss of tensile strength is slower than other absorbable materials. At 28 days 5060% of its strength remains. It is completely absorbed in about 1
Non-absorbable sutures
Silk. This is a strong, flexible material which handles easily and knots very securely. It is of two main types a braided thread which has a rough surface, and floss silk which is very loosely twisted and allows cellular infiltration and the deposition of collagen. Although classified as non-absorbable, it loses 80% of its tensile strength in 80 days and is absorbed over about 2 years.
It is used for tying off large vessels and to provide a strong suture layer for intestinal and vascular anastomoses.
Dermal suture. This is a suture of twisted silk fibres coated in a non-absorbable layer of tanned gelatin or other protein. It is very strong. It is used to suture skin under tension and the coating prevents cellular infiltration that could interfere with its removal.
Linen and cotton thread. These sutures arc made of twisted flax and cotton fibres. They are similar to silk but not as strong, although cotton fibres gain tensile strength when wet. Like all braided sutures they may become infected and can give rise to persistent sinuses. Their uses are the same as for silk, although the latter has now virtually replaced them.
Nylon. Nylon is a polyamide polymer and sutures can either be multi-filament (braided) or monofilament. The most commonly used is a monofilament nylon which is extremely strong; and inert in the tissues, although it does degrade very slowly at about 15% per year. knots can be unreliable unless tied with a double 'surgeon's knot'
Nylon sutures are used for the following.
1 Stitching the skin. The minimal tissue reaction causes less scarring.
2 Closure of the abdominal muscles. A double monofilament nylon suture provides very good immediate wound strength.
3 Ophthalmology and microsurgery. At 11/0 it is the smallest suture made.
Polypropylene' (Prolene.',Ethicon). This is a synthetic polymer of polypropylene extruded into a monofilament suture. It is strong and inert causing minimal tissue reaction (it is the most permanent, non-absorbable suture) and it looks like nylon. It is, however, more flexible and has better knotting properties. It has a slippery surface and slides through the tissues well.
Prolene is popular for closure of the skin, particularly for subcuticular sutures. It is widely used in arterial surgery and some surgeons use it for large bowel anastomosis and bile-duct surgery.
Polyesterfibre suture (Merseline, Ethicon). This is a braided, multi-filament suture of polyester, another synthetic polymer. It is strong and well tolerated in the tissues.
Another type (Ethibond,Ethicon) is braided polyester coated with polybutylate a surgical lubricant. This travels yen smooth through the tissues and knots securely. It is \en inert with good tensile strength maintained over a long period. It is used in cardiovascular surgery for vessel anastoStainless steel wire. This
Surgeon's knot.
n material is popular with a fewsurgeons. It is difficult to use but is extremely strong and on-reactive. Over a period of years it does fragment and therefore lose its tensile strength.
Some surgeons use stainless steel wire for closing the abdominal muscles. It is also used in orthopaedic surgery to wire bones together and in thoracic surgeon for rejoining the sternum.
Sizes of sutures
Suture size is expressed on the scale given in Table below. Sizes of sutures
Size
Metric scale (mm x 10)
Diameter
(mm)
4
6.0
0.6i
3
5 .5
0.55
2
5.0
0.5
1
4.n
0.4
0
3.5
0.35
2/0
3.0
0,3
3/0
11 11111111
2.0
0.2
4/0
'II k'K.1
1.5
0.15
5/0
1.0
0.1
6/0
0.75
0.0 7 5
7/0
0.5
0.05
8/0
0.4
0.04
9/0
0.3
0.03
10/0
0.2
0.2
These sizes only apply to synthetic materials. Natural collagen tends to be slightly larger. Size 0 silk is used for tying of arteries of about 5 mm in diameter. Size 6/0 is a very fine suture used in arterial surgeon'. Size 10/0 is only just visible to the naked eve and is used in micro-vascular surgeon.
Suture removal
The time of suture removal depends on the site of the incision and the general state of the patient.
1 Head and neck. Wounds in the head and neck heal rapid. A cosmetic result is also needed and therefore early suture removal is an advantage. Sutures in this area are generally removed within 3.'' days, e.g. thyroid scar 3 days. face scar 4 days.
2 Abdomen and thorax.Transverse or oblique incisions 5-7 days.Vertical incisions 710 days.
3 In patients who are cachectic, i.e. those with carcinomatosis, on steroid therapy. with severe infection, or with hepatic or renal failure, the tissue healing can he delayed and therefore the sutures must he left longer (1014 days or longer).
Curved
Straight
Eyed
Atraumatic
Round -bodied
Taper-cut
With cutting edge
Small used with needle holders Large hand needles
Suture material must be threaded through the eve
The suture material is built into the end of the needle and the needle puncture therefore causes only a minimally larger hole than the suture itself
The needle has a round shape and is only sharp at its tip. Used for suturing the peritoneum, fat, bowel, liver, etc.
The needle also has a round shape but is sharpened on several sides towards the rip, giving it cutting properties. This type of needle is useful for passage through tough tissues where it is important to keep the needle track size
to a minimum
These are flattened and 'sword-like' and cut through the tissues as they are passed. They can he used on tough fibrous tissue (e.g. breast) or the skin, hut may cause haemorrhage by cutting neighbouring blood vessels
Needles
Needles are either curved or straight; eyed or traumatic; round-bodied, taper-cut or with a cutting -J
Drains
Drains are put in by the surgeon to allow any fluid or air collecting at the operation site or in (he wound to drain to the surface while allowing the main wound to heal. Fluids to be drained include blood, pus, urine, faeces, bile or Lymph. Drains may be:
1 superficial, i.e. in the wound;
2 deep:
(a) intraperitoneal, e.g. covering an intestinal anastomosis,
(b) in a hollow organ or duct, e.g. a T-tube in the bile duct,
(c) in an abnormal channel, e.g. a fistula,
(d) to drain a deep cavity, e.g. an abscess or haematoma In addition drains may be:
1 open, i.e. draining into a dressing or bag open to the air:
2 closed, i.e. draining into a sterilized air-right tube and container. The drainage system may be:
(a) on tree drainage, e.g. drainage of ascites by gravity;
(b) on suction, e.g. Redivac drains:
(c) controlled by a one-way valve, e.g. an underwater sea! or chest drains .
Types of drains and their uses
Open drains
(Corrugated rubber drainRubber causes a tissue reaction and the drain track caused by this material persists longer than when inert materials arc used. The drain is fixed by a suture at the end of the wound and a safety pin must he placed through the end to prevent the drain slipping inwards. Corrugated rubber drains can be used either for the wound or for deep drainage.
Yates' drain. This is a corrugated drain made of a series of capillary tubes joined side to side. It is generally made of polyethylene which is less reactive than rubber. The drain site, therefore, tends to close more quickly once the drain has been removed. Its uses are similar to corrugated rubber drains and it is secured as described above.
Penrose drain. This is a drain fashioned out of thin-walled rubber tubing and a gauze wick is threaded through the centre of the tube. Fluid can then either drain down the track once the tube is removed or through the centre whilst it is in place.
Closed drains
Redivac drainThis is a fine tube. with many holes at the end, which is attached to an evacuated glass bottle providing suction. It is used to drain blood beneath the skin, e.g. after mastectomy or thyroidectomy, or from deep spaces, e.g. around a vascular anastomosis.
'Shirlry' wound drainage. This is a suction drain with an intake tube supplying air to the bottom of the main tube. This allows continuous suction and the flow of air prevents the tube getting blocked.
Yates drain
Redivac drain
Silastic tube drum. Silastic is a polymeric silicone and incites little tissue inflammation. Once this type of drain is removed, therefore, the track closes rapidly. A Silastic tube drain can be used to provide closed drainage to deep anastomoses, e.g. of the bowel
Red rubber tube drain. This causes an intense tissue reaction and fibrosis. The track will, therefore, persist for some time after the drain is removed. This feature can be useful for drainage of chronic abscess cavities such as an empyema or hepatic abscess.
. Deep closed drainage of a colonic anastomosis.
T-lube drains. After bile duct surgery a T-tube is inserted in the bile duct, which allows bile to drain while the sphincter of Oddi is in spasm . Once this relaxes the bile can drain normally down the common bile duct into the duodenum. T-tubes are made of a variety of materials and surgeons van in the design they prefer.
A T-tube allows bile to drain if the sphincter of Oddi is in spasm.
Removal of drains
A drain is removed as soon as it is no longer required. Hence it is necessary to know the purpose for which it was inserted and you should ascertain this from the surgeon at the time of operation. The following are general guidelines:
1 Drains put in to cover perioperative bleeding and haematoma formation, can come out after 24 48 hours.
2 Drains put in to cover serous collections can come out after 35 days.
3 Where a drain has been put in because the wound may later become infected, it should be left for 1-5 days.
4 Drains put in to cover intestinal anastomoses should not be removed until after 57 days.
5 A T-tube can be removed after 6 10 days. Before this is done, a T-tube cholangiogram must be performed to make sure that there is distal patency in the common bile duct. Some surgeons clamp the T-tube for 24 hours before it is removed.
