Suturing — MRCS Part B Procedural and technical skills

A clean forearm laceration in a young builder. The station is the practical decision about how to close it, the materials, the techniques, and what to tell the patient afterwards.

Choosing the closure

A clean, fresh wound on the extensor forearm with no tension is closed primarily with simple interrupted non-absorbable monofilament sutures, 3-0 or 4-0 nylon or polypropylene on a cutting needle, after infiltration with local anaesthetic, cleaning and a check for foreign bodies and tendon injury. Monofilament drags less and harbours fewer bacteria than braid; non-absorbable material holds its strength for the two weeks the skin needs and is then removed, leaving nothing behind to react. Interrupted sutures let one fail without the whole wound opening and let a single one be removed if infection collects.

Suture sizes

Sutures are sized on the USP scale, in which more zeros mean thinner material: 2-0 is thicker than 3-0, which is thicker than 4-0. Skin on a limb takes 3-0 or 4-0; the face 5-0 or 6-0; fascia 1 or 0; vascular anastomoses 5-0 to 7-0 polypropylene, a non-absorbable monofilament chosen because it is smooth, inert and holds its strength indefinitely. Absorbable sutures are natural (catgut, no longer used in the UK) or synthetic: polyglactin (Vicryl) and polyglycolic acid, braided, lasting three to four weeks; poliglecaprone (Monocryl) and polydioxanone (PDS), monofilaments, the first gone in three weeks and the second lasting six months. A subcuticular closure of a clean wound uses an absorbable monofilament, 4-0 Monocryl, so nothing needs removing and no stitch marks are left; for the best cosmesis on a forearm that is the choice.

Jenkins' rule

For closing the abdominal wall: the suture length should be at least four times the length of the wound, with bites 1 cm deep and 1 cm apart, so the tension is shared along the whole closure and no single bite cuts out. It is the basis of the mass closure of a laparotomy with a looped slowly absorbable suture.

Techniques

Simple interrupted: the needle enters perpendicular to the skin as far from the edge as the wound is deep, passes through the full thickness, comes out at the same distance on the other side, and the knot is tied to one side with the edges everted, not inverted. Vertical mattress: a wide deep bite far from the edges and then a small shallow bite close to them, in the same line, "far-far, near-near"; it everts edges that want to roll in and closes dead space, so it is used over the shin or the back of the hand, or where the skin is thin and lax. Horizontal mattress: a bite across the wound, then a second bite back across it a few millimetres along, so the suture runs parallel to the edge on each side; it spreads tension along the wound and everts, and is used for wounds under tension or for a fragile edge, at the cost of more ischaemia of the skin between the loops. Subcuticular: the deep dermis is picked up with horizontal bites alternating from one side to the other, in the same plane, so the thread runs in the dermis and nothing crosses the surface; buried knots at each end, or a bead or a tape, hold it.

Aftercare and the wound in the picture

Keep it dry for 48 hours, then wash it and pat it dry; no soaking. Look for spreading redness, pus, or fever, and come back if they appear. Sutures out at 10 to 14 days on a limb (5 to 7 on the face), and tape or a scar cream after that; keep it out of the sun for a year. Check tetanus cover. In this man the questions to ask of the photograph are the ones a laceration over the extensor forearm always raises: is there a tendon under the wound and does every finger and the wrist extend against resistance, is the skin edge bruised or crushed in a way that will not survive a tight closure, and is there a hidden foreign body that a radiograph should exclude before the wound is closed.