Suturing

Sutures are placed to aid with wound healing following a traumatic laceration or surgical incision and to promote haemostasis. In this article, we will look at the different types of suture classifications, the indications for each type of suture and the common suturing techniques that are used.

Alternative methods of tissue closure

  • Steri-strips
    • Often used in children
  • Skin clips
    • Have similar cosmetic results and similarly low infection rates
    • More expensive than sutures.

Ideal characteristics of a suture

  • Sterile
  • Cheap
  • Inert, i.e. causing minimal reaction to tissues
  • Good handling characteristics
  • Able to tie secure knots
  • Having adequate tensile strength
  • Being resistant to infection

What are the different parts of the suture?

Suture classification

There are various ways in which sutures can be classified.

They can be classified according to its:

  • Source – i.e. the material from which the suture is made (whether it is Natural or Synthetic)
  • Structure – i.e. whether the material is Monofilament or Braided
  • Fate – i.e. whether it is absorbable or non-absorbable
Source of a suture material

Examples of natural suture materials:

  • Silk
  • Steel

Examples of synthetic suture materials include:

  • Nylon (“Ethilon”)
  • Polyester (“Dacron”)
  • Polypropylene (“Prolene”)
  • Polyglactin (“Vicryl”, “Vicryl Rapide”)
  • Polydioxanone (“PDS”)
  • Polyglecaprone 25 (“Monocryl”)
Structure of a suture material

Monofilament:

  • Made of a single strand or filament
  • Very smooth and able to glide easily through tissues
  • Less flexible, and liable to fracture if used inappropriately
  • Can be difficult to handle in comparison to braided sutures
  • Higher risk of suture knots unravelling

Examples of monofilament sutures:

  • Polyglecaprone 25 (Monocryl)
  • Polypropylene (Prolene)
  • Nylon (Ethilon)
  • Polydioxanone (PDS)
  • Silk (can be monofilament or braided)

Braided Sutures:

  • Made of braided multiple strands or filaments
  • Easier to handle
  • Have a larger surface area
  • More flexible and better elasticity
  • Suture knots are less likely to unravel
  • Glides less easily through tissues
  • Greater risk of wound infection

Examples of braided sutures:

  • Polyglactin (Vicryl, Vicryl Rapide)
  • Silk (can be monofilament or braided)
Absorbable vs non-absorbable suture

Absorbable sutures:

  • Broken down by either proteolysis or hydrolysis
  • Rate of absorption depends on the material that is used.
  • Commonly used for deep tissues and for rapidly healing tissues, e.g. oral mucosa.
  • Do not need to be removed.

Examples of absorbable sutures:

  • Polyglactin (Vicryl, Vicryl Rapide)
    • Vicryl resorbs in ~60 days
    • Vicryl Rapide resorbs in ~42 days
  • Polyglecaprone 25 (Monocryl)
    • Resorbs in ~ 100 days
  • Polydioxanone (PDS)
    • Resorbs in ~ 200 days

Non-absorbable sutures:

  • Used for longer term tissue support and approximation.
  • Commonly used for skin closure and for tissues that heal slowly, e.g. vascular anastomoses, closure of abdominal wall, fascia and tendon repair.
  • Removal of these sutures is dependent on the area of the body where the sutures are placed:
    • Head and neck: 5-7 days
    • Abdomen and chest: 7-14 days
    • Feet: 10-14 days
    • Limbs: 5-10 days

Examples of non-absorbable sutures:

  • Nylon (Ethilon)
  • Polypropylene (Prolene)
  • Silk
  • Steel
  • Polyester (Dacron)

Summary of the properties of common sutures

NaturalSyntheticAbsorbableNon-absorbableMonofilamentBraided
Polyglactin (Vicryl)
Polydioxanone (PDS)
Polyglecaprone 25 (Monocryl)
Nylon (Ethilon)
Polypropylene (Prolene)
Silk
Summary of common sutures and their properties

Suture sizes

  • These are calibrated by the United States Pharmacopia (USP) scale.
  • The larger the number designated to a suture, the smaller the diameter of the suture.
  • The diameter of the suture affects the handling properties and the tensile strength of the suture.
    • Smallest diameter suture has the least tensile strength
  • Commonly available sizes and diameters of sutures are:
    • 3 = 0.7mm diameter
    • 2 = 0.6mm
    • 1 = 0.5mm – this size is typically used for abdominal closure
    • 0 = 0.4mm
    • 2/0 = 0.30mm – this size is typically used for bowel anastomoses
    • 3/0 = 0.25mm
    • 4/0 = 0.20mm – this size is typically used for fine vascular anastomoses
    • 5/0 = 0.15mm – this size is typically used for skin closure
    • 6/0 = 0.10mm – this size is typically used for skin closure in the head+neck region
    • 7/0 = 0.07mm
    • 8/0 = 0.05mm

Suture needles

As with the different suture materials, the body of suture needles can also be classified in various ways.

  • The needles can be described as curved or straight.
  • Straight needles can to be used for the closure of easily accessible tissues, e.g. skin.
  • However, curved needles are more commonly used, with a shallower curved needle used for superficial tissues (e.g. 1/4 circle), whilst more deeper tissues tend to require the use of a larger circle arc (e.g. 5/8 circle).

Commonly used needle curvatures are seen below:

The structure of the tip of the needle can also vary according to its point.

The point of the needle can be either sharp or blunt.

Blunt needles:

  • Blunt and round-bodied needles has low tissue penetrance, and therefore, is ideal for mass closure of the abdominal wall and of friable tissue, e.g. blood vessels.
    • Unlike sharp needles, these needles tends to dilates the tissues rather than cut through tissues.
    • This reduces the risk of needle stick injuries.
    • However, this also makes blunt needles more difficult to use than sharp needles.

Sharp needles:

  • Sharp needles are used in situations where tissue leakage needs to be avoided.
  • Sharp needles can also be used in the closure of dense, keratinized tissue, e.g. fascia and tendons
  • Sharp needles can be further subdivided into:
    • Conventional cutting point needles have a sharp point with a triangular cross-section with two opposing cutting edges and a third edge on the inside curvature of the needle.
      • This makes the suture liable to tear through the tissue.
    • Reverse cutting point needles also have a sharp point with a triangular cross-section.
      • However, unlike conventional cutting point needles, these needles had two opposing cutting edges and a third edge on the outer curve of the needle.
      • This makes reverse cutting needles less traumatic than conventional cutting point needles.

All of the above information can be found on the packaging of the suture, as illustrated in an example below (along with the length of the suture):

Suturing techniques

There are various techniques that can be used to place sutures, including:

  • Simple interrupted
  • Continuous
  • Continuous locking
  • Subcuticular continuous
  • Horizontal mattress
  • Vertical mattress

The knots that are placed can be either be tied by hand or using the following instruments:

Suturing guide:

  • When using instruments to place sutures, the suture should be held approximately 1/3 of the distance from the swage of the suture, with the needle tip perpendicular to the handle of the needle holder.
  • The needle should pass from mobile to fixed tissue.
  • The needle should enter the tissue perpendicular to the tissue surface, and 2-3 mm from the wound edge.
  • The needle should pass through the tissue, following the curvature of the needle.
  • The needle should then pass to the other end of the open tissue, ideally at the same distance as which the needle entered the cavity, i.e. 2-3 mm.
  • The needle should also ideally be at the same depth.
  • The suture should not be closed under tension, since there is a risk of necrosis and of tearing of the suture.
  • Sutures should be placed approximately 3-4 mm apart.

An example of a suture placement using instruments can be seen in the clip below:

YouTube player

Edited by: Mudassar Khan (Y4 Medical Student)

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