Close in layers | Choose the right material and method | Tension-free, well-apposed edges | Eversion not inversion
- Close in layers: deep absorbable sutures take the tension and obliterate dead space, so the skin layer can be apposed under little or no tension - a tension-free skin closure is the single biggest controllable factor for a good scar and a low complication rate
- Two axes describe every suture: absorbable vs non-absorbable (does it need removing or does it dissolve), and monofilament vs braided (braided handles and knots better but harbours bacteria more easily)
- Aim for everted, well-apposed edges: take equal bites either side, bring dermis to dermis, and evert the edges slightly - inverted or overlapping edges heal as a depressed, weak scar
- Match the method to the wound: precise/high-tension/contaminated wounds favour interrupted sutures; long clean incisions can be closed fast with staples or a subcuticular suture; only clean, low-tension, well-apposed superficial wounds suit glue or strips
- The evidence: for orthopaedic skin closure, large reviews show sutures and staples give broadly similar infection rates, with the main practical trade-offs being closure speed (staples faster) and cost - so technique and tension matter more than the device
- “Knot security on a monofilament needs more throws than a braided suture, because monofilament is slippery - quote this if asked why you add throws
- “A subcuticular (buried intradermal) suture gives the best cosmetic skin result because there are no cross-hatch suture marks, but it relies on the deep layer to hold tension
- “Suture size: the bigger the number, the smaller the suture - 5-0 is finer than 2-0; use the finest suture that will hold the load
- “Take sutures out earlier where cosmesis matters and blood supply is good (face ~5 days) and later where tension and movement are high (over a joint, the back ~10 to 14 days)
Clinical Imaging
Learning and applying suture technique
The deep (fascial/subcutaneous) layer takes the tension and removes dead space; the skin layer is then apposed under minimal tension. A tension-free, well-apposed closure is the most important controllable factor for a good scar and a low rate of dehiscence and infection.
Classify every suture by absorbable vs non-absorbable (dissolves vs needs removal) and monofilament vs braided (single strand, low infection, slippery knots vs multifilament, easy handling, but more bacterial wicking). Knowing where a named suture sits in this grid is a classic viva.
Take equal, generous bites either side, bring dermis to dermis, and evert the edges slightly. Inverted, overlapping, or strangulated edges heal as a weak, depressed scar. Tied too tight, sutures cut out and leave cross-hatch ("railroad") marks.
Interrupted sutures for precision, high tension, or a contaminated wound (one failing stitch does not open the whole wound). Continuous/staples/subcuticular for speed on long clean incisions. Glue or strips only for clean, dry, low-tension, well-apposed superficial wounds.
Memory aids
ABMClassifying Any Suture
Hook:ABM - Absorbable?, Build (mono/braided), Material - and you can describe any suture in a viva.
TEASEPrinciples of a Good Closure
Hook:A good closure should TEASE the edges together - Tension-free, Everted, Apposed, Sterile, Equal bites.
123Choosing the Method
Hook:1-2-3: stitch it, staple it, or stick it - in order of how much control you need.
Overview
Wound closure is how the surgeon brings tissue layers back together at the end of an operation (or after an injury) so the wound can heal by primary intention - clean edges held in apposition until they knit. It sounds simple, but the choices made here directly affect the scar, the risk of wound breakdown, and the risk of infection - and they are favourite basic-science and operative viva material.
There are really three decisions: how to organise the closure (almost always in layers), what to close it with (the suture material, staples, glue or strips), and which technique to use (the specific stitch or device). Underneath all of them sits one principle that the examiner keeps coming back to: the wound should be closed with well-apposed, slightly everted, tension-free edges, because that is what gives a fine, strong scar and protects the healing wound.
For the exam, three threads run through this topic: suture materials (the absorbable-versus-non-absorbable and monofilament-versus-braided grid), suture techniques and the alternatives (interrupted, continuous, mattress, subcuticular, plus staples and glue), and how to choose and apply them well (layers, tension, eversion, and timing of removal). This topic builds directly on wound healing - you are closing the wound so those healing phases can proceed undisturbed.
Principles: Layered, Tension-Free Closure
The first decision is structural: close the wound in layers. Each anatomical layer (fascia, then subcutaneous/deep dermal, then skin) is brought together separately. There are two reasons this matters so much:
- It removes tension from the skin. The strong deep layers are closed first and carry the load, so the skin can be apposed under little or no tension. Skin closed under tension heals as a wide, stretched scar and is much more likely to break down.
- It obliterates dead space. Closing the layers leaves no pocket under the skin for blood or fluid to collect. A haematoma or seroma in dead space is a culture medium for infection and pushes the wound edges apart.
The second set of principles is about how the edges meet:
- Equal bites either side. Take the same depth and width of tissue on each side so the edges come up level, not stepped.
- Eversion. Aim to evert the edges very slightly (turn them outward) - they then settle flat as they heal. Inverted or overlapping edges heal as a depressed, weak scar with epithelium trapped below.
- Approximate, do not strangulate. Tie just tight enough to bring the edges together. Too tight and the suture cuts off the blood supply at the edge, causing necrosis, cross-hatch marks, and wound problems.
- Atraumatic, aseptic handling. Handle tissue gently, use the fine instruments, and keep the field sterile - crushed or contaminated edges heal badly.
If asked "what makes a good closure?", lead with the principles, not the products: layered, tension-free, dead space obliterated, edges everted and well apposed, gentle aseptic handling. The choice of suture or staple comes second - examiners want to hear that you understand why tension and apposition matter most.
Suture Materials
Every suture can be placed on two axes, and examiners expect you to classify a named suture instantly.
| Property | Option A | Option B |
|---|---|---|
| Fate in tissue | Absorbable - dissolves over weeks (hydrolysis or enzymatic) | Non-absorbable - stays until removed or permanently |
| Structure | Monofilament - single smooth strand, low infection risk, slippery knots | Braided (multifilament) - easy to handle and knot, but wicks bacteria |
| Origin | Natural (silk, catgut) - more tissue reaction | Synthetic - predictable absorption, less reaction |
| Suture (example brand) | Type | Typical use |
|---|---|---|
| Polyglactin 910 (Vicryl) | Absorbable, braided, synthetic | Deep/subcutaneous layers, ties - workhorse buried suture |
| Poliglecaprone (Monocryl) | Absorbable, monofilament, synthetic | Subcuticular skin closure - low reaction, good cosmesis |
| Polydioxanone (PDS) | Absorbable, monofilament, synthetic | Long-lasting deep closure (fascia, tendon repairs) where prolonged strength is needed |
| Nylon (Ethilon) | Non-absorbable, monofilament, synthetic | Interrupted skin sutures - removed later; low infection |
| Polypropylene (Prolene) | Non-absorbable, monofilament, synthetic | Skin and vascular work - inert, slides easily, very low reaction |
| Silk | Non-absorbable, braided, natural | Securing drains/lines - easy to handle but high tissue reaction; rarely for skin now |
A few extra points are worth knowing. Suture size runs the "0" scale: more zeros means a finer suture (5-0 is finer than 2-0), and you use the finest suture that will safely hold the load. Knot security depends on the material - a slippery monofilament needs more throws than a braided suture to hold. And absorbable sutures lose strength before they fully disappear, so the layer must be healed enough to be self-supporting by the time the suture weakens.
Suture Techniques
The same material can be placed in several ways, each with a job it does best.
Simple interrupted - each stitch is placed and tied separately.
- Strengths: precise, allows fine adjustment of each part of the wound, and is the safest in contaminated or high-tension wounds because if one stitch fails the rest hold.
- Trade-off: slower, and leaves more individual knots and suture marks.
- Use it for: irregular wounds, areas of high tension, contaminated wounds, and anywhere you need to "dog-ear" correct as you go.
A clean way to answer "which stitch would you use?" is to tie the choice to the wound: interrupted for tension or contamination, continuous or subcuticular for a long clean incision, mattress when the edges keep inverting or the wound gapes. Always anchor it back to apposition, eversion, and tension.
Staples, Tissue Adhesive and Adhesive Strips
Sutures are not the only way to close skin, and each alternative has a clear niche.
| Method | Best for | Trade-offs |
|---|---|---|
| Sutures | Almost anything - precise, versatile, high or low tension | Slowest; non-absorbable types need removal; technique-dependent |
| Staples | Long clean incisions (hip, knee, spine approaches) - very fast | Need a remover; cosmesis debated; less precise on curves and irregular edges |
| Tissue adhesive (cyanoacrylate skin glue) | Clean, dry, low-tension, well-apposed superficial wounds | No good on high-tension or gaping wounds, wet/mobile areas, or contaminated wounds |
| Adhesive strips (Steri-Strips) | Reinforcing a closure or very superficial low-tension wounds | Fall off if wet or under tension; not a primary closure for deep wounds |
Staples are popular for long orthopaedic incisions because they are quick and consistent, and they hold the edges without an inflammatory knot in the wound. They still need a remover and the cosmetic result is debated. Tissue adhesive (skin glue) polymerises across apposed edges to form a flexible water-resistant film; it is fast and needs no removal, but it is only for clean, dry, low-tension, well-apposed superficial wounds - never inside the wound or on a gaping/high-tension edge. Adhesive strips are best as a supplement (for example over a subcuticular closure) or for the most superficial low-tension wounds.
Cyanoacrylate skin glue must be applied to the skin surface across apposed edges, never down into the wound, and only when the wound is clean, dry, and under little or no tension. Glue used on a high-tension or contaminated wound, or allowed to run into the wound, leads to dehiscence and a foreign-body reaction.
Choosing the Method and Timing Removal
Putting it together, the choice flows from the wound and the patient:
Tension (high tension favours interrupted sutures or mattress sutures), contamination (interrupted, and consider delayed closure), location and mobility (over a joint needs stronger, longer-lasting closure), and how superficial and well-apposed the edges are (clean superficial wounds suit glue or strips).
Cosmetic priority (subcuticular or fine interrupted), ability to return for removal (absorbable or glue avoids a second visit), blood supply (poor perfusion needs gentler, longer-retained closure), and cost and speed (staples are fast and cheap for long incisions).
Timing of suture removal balances scar quality against wound strength. Take them out earlier where the blood supply is good and cosmesis matters, and later where tension and movement are high:
| Site | Approximate removal | Why |
|---|---|---|
| Face / neck | About 5 days | Excellent blood supply, cosmesis matters, low tension |
| Scalp / upper limb | About 7 to 10 days | Moderate tension and blood supply |
| Lower limb / over a joint / back | About 10 to 14 days | High tension and movement, slower to gain strength |
Remember the wound is at its weakest in the first week (from wound healing), so removing sutures too early risks dehiscence, while leaving them too long causes cross-hatch scarring. The site-based removal times above are the practical compromise.
Clinical Relevance
Wound closure is the last step of almost every orthopaedic operation, and it is one of the few parts of the case entirely under the surgeon's control. A poorly closed wound - under tension, with dead space, with inverted edges - can undo an otherwise excellent operation by breaking down or becoming infected, which around a joint replacement or fracture fixation can be catastrophic. In trauma, the choice to close primarily, leave open for delayed closure, or close with interrupted sutures over a contaminated wound is a daily judgement. In elective surgery, the choice between staples, a subcuticular suture, or glue affects speed, cost, and the scar the patient lives with. In the basic-science and operative viva, classifying suture materials, naming the techniques, and explaining the principles of a good closure are classic, examinable, high-yield material - and they all reduce to the same idea: bring the layers together, take the tension off the skin, and appose the edges cleanly.
Evidence: Sutures, Staples and Principles
Sutures vs Staples for Skin Closure After Orthopaedic Surgery (Meta-Analysis)
- Systematic review and meta-analysis of 13 studies comparing sutures versus staples for orthopaedic skin closure in adults
- No significant difference in surgical site infection between sutures and staples (cumulative relative risk 1.06)
- No difference in infection in hip or knee surgery analysed separately
- Except for closure time, no significant difference in secondary outcomes (inflammation, dehiscence, pain, length of stay)
Sutures vs Staples for Surgical Wounds (Meta-Analysis of RCTs, Non-Orthopaedic)
- Meta-analysis of 20 randomised controlled trials (2111 patients) comparing sutures and staples, excluding orthopaedic operations
- Staples were faster to apply (mean ~5.6 minutes less per wound)
- Wound infections were fewer with sutures than staples in this non-orthopaedic group (odds ratio 2.06 favouring sutures)
- Staples were associated with more pain in several studies; cosmetic result and satisfaction were mostly similar
Surgical Strategies to Promote Cutaneous Healing (Review of Closure Principles)
- Reviews how surgical principles - suture material, suture technique and timing - shape wound healing and the final scar
- Choosing the appropriate material, technique and timing creates optimal conditions for healing
- Wounds are classified by contamination (clean, clean-contaminated, contaminated, infected) which guides the closure decision
- Debridement of necrotic/non-viable tissue and aseptic technique are central to achieving successful closure
Exam Viva Scenarios
Practise clinical reasoning and management decisions out loud
“The examiner hands you a few suture packets and asks you to classify sutures and explain how you would choose one for closing a knee replacement wound.”
Framework: I classify every suture on two main axes - absorbable versus non-absorbable, and monofilament versus braided - and I also note natural versus synthetic.
Absorbable vs non-absorbable: Absorbable sutures (such as Vicryl, Monocryl, PDS) dissolve over weeks and are ideal for buried layers; non-absorbable sutures (nylon, Prolene, silk) stay until removed and are used for skin or where lasting strength is needed.
Monofilament vs braided: Monofilament is a single smooth strand with a low infection risk but slippery knots that need more throws; braided handles and knots well but can wick bacteria.
Choosing for a knee: I close in layers - an absorbable braided suture such as Vicryl for the deep capsule and subcutaneous layer to take the tension and remove dead space, then the skin closed either with a subcuticular absorbable monofilament such as Monocryl for cosmesis, or with staples for speed. The key is a tension-free, well-apposed skin closure.
“A junior shows you a sutured wound with inverted, gaping edges that is under obvious tension. The examiner asks what is wrong and how a wound should be closed properly.”
Problems I can see: The skin is closed under tension, the edges are inverted rather than everted, and the wound is gaping - all of which predispose to a poor, depressed scar and to dehiscence or infection.
Principle 1 - close in layers: The deep fascial and subcutaneous layers should be closed first with absorbable sutures to take the tension off the skin and obliterate dead space, so no haematoma or seroma collects.
Principle 2 - apposition and eversion: I take equal bites either side, bring dermis to dermis, and evert the edges slightly so they settle flat. Inverted edges trap epithelium and heal as a pit.
Principle 3 - approximate, do not strangulate: I tie just tight enough to bring edges together; over-tight sutures cut off the edge blood supply and leave cross-hatch marks and necrosis.
Principle 4 - asepsis and gentle handling: Sterile technique, atraumatic handling, debride non-viable tissue, and choose the right method and material for the wound. Here I would take it down, close the deep layer to relieve tension, and re-appose the skin with everting interrupted or mattress sutures.
Principles First
- Close in layers - deep layer takes the tension, removes dead space
- Tension-free, well-apposed skin - the biggest controllable factor
- Evert the edges, equal bites, dermis to dermis
- Approximate not strangulate; aseptic, atraumatic handling
Classifying Sutures
- Absorbable (Vicryl, Monocryl, PDS) vs non-absorbable (nylon, Prolene, silk)
- Monofilament (low infection, slippery - more throws) vs braided (handles well, wicks bacteria)
- Size: more zeros = finer (5-0 finer than 2-0)
- Use the finest suture that holds the load
Techniques
- Interrupted: precise, high tension, contaminated wounds
- Continuous: fast, even tension, long clean incisions
- Mattress (vertical/horizontal): eversion and gaping/fragile edges
- Subcuticular: best cosmesis, relies on the deep layer
Alternatives and Timing
- Staples: fast for long incisions; similar infection to sutures in orthopaedics
- Glue/strips: clean, dry, low-tension superficial wounds only
- Removal: face ~5 days, limb ~7-10, over joint/back ~10-14
- Wound weakest in week 1 - do not remove too early
Guidelines, Registries and Global Practice
- Surgical site infection (SSI) guidance worldwide (for example WHO global SSI guidelines and NICE in the UK) frames closure as part of infection prevention: aseptic technique, gentle tissue handling, obliteration of dead space, and avoidance of tension all protect the healing wound. No major guideline mandates one skin-closure device over another for routine clean wounds.
- Sutures versus staples in orthopaedics is broadly a wash for infection in the best evidence; practice varies by surgeon, unit, and incision type, with staples favoured for speed on long approaches (hip, knee, spine) and subcuticular sutures or glue favoured where cosmesis or no-return-for-removal matters.
- Tissue adhesives and adhesive strips are widely endorsed for clean, low-tension, well-apposed superficial wounds, and as a supplement to a deeper closure - never as the sole closure of a high-tension or contaminated wound.
- Across all settings the principle is constant: closure quality depends far more on sound technique - layered, tension-free, everted, aseptic - than on the particular suture, staple, or glue chosen.