Harri Foster Davies
An Introductory Guide to Suture Types
Classification of a suture may depend on the needle or the suture thread. Below
is a diagram of suture packaging, demonstrating the variety of specifications:
Suture Thread Length
Needle size and
The ideal needle:
Sterile; high-quality stainless steel; stable in the grasp of
a needle holder; able to carry suture material through tissue
with minimal trauma; as slim as possible without compromising
strength; sharp enough to penetrate tissue with minimal
resistance; rigid enough to resist bending but not break.
1. Needle Size
The needle size describes the distance along the edge of the needle. This
typically varies anywhere from 4 mm right up to 90 mm. A smaller needle is more
suitable for delicate/thin/small tissues.
2. Needle Curvature
Harri Foster Davies
The needle curvature describes how tightly the needle curves. Common
• Straight – designed to be used by hand; mostly used for
skin closure or microsurgical procedures.
• Half-curved (ski) – used in laparoscopic surgery.
• 1/4 circle - a shallow curve and is used on easilyaccessible
convex surfaces, for instance, in ophthalmic
and microsurgical procedures.
• 3/8 circle – the most commonly needle curvature; easy to
manipulate in large/superficial wounds.
• 1/2 circle – suitable for confined locations.
• 5/8 circle – ideal for deep confined holes.
3. Needle Body and Points
Needles either have round bodies or triangular-shaped bodies.
• Round-bodied needles pierce and spread tissues with minimal cutting. They have
either sharp (taper-point) or blunt points.
o Taper-point - used in easily-penetrated tissues (e.g. abdominal viscera).
o Blunt - used to dissect through friable tissues (e.g. liver, kidney).
• Needles with triangular-shaped bodies are referred to as “cutting” needles.
They are used to penetrate tough tissues. They are either ‘conventional’ or
o “Conventional” cutting needles have the cutting edge on the inside arc of
the needle and are useful for skin and sternum.
o “Reverse” cutting needles have their cutting edge on the outside arc of
the needle and are ideal for tough tissue like skin, tendon sheath, or
oral mucosa. Reverse cutting needles have a reduced risk of tearing
through tissues compared to conventional cutting needles since tension is
not in the same vector as the cutting edge. These types of needles are
typically used in ophthalmic and cosmetic surgery, where minimal trauma is
The ideal suture:
Sterile; small as possible whilst providing high, uniform
tensile strength; consistent uniform diameter; appropriate
pliability; provides knot security; low bioreactivity.
The choice of suture material is based on the balance of certain
characteristics. Such characteristics can be grouped into 4 categories:
Physical, Handling, Biocompatibility, and Biodegradation.
• Physical characteristics include size (diameter), number of filaments,
tensile strength, elastic modulus, bending stiffness, stress relaxation, and
coefficient of friction.
• Handling characteristics include pliability, packaging memory, knot tiedown,
knot slippage, and tissue drag.
• Biocompatibility characteristics include inflammation, wound infection risk,
thrombus formation risk, carcinogenicity, and allergenicity.
Harri Foster Davies
• Biodegradation characteristics include absorbability, as well as the
biocompatibility of any breakdown products.
1. Suture Size
There are two classification systems: USP (United States Pharmacopeia) and the
European system. The USP grading is calculated using not only diameter, but
also tensile strength and knot security. The European system uses only the
diameter of the suture in millimetres.
As suture material is a foreign substance, it will cause inflammation. This
tissue reaction will continue until the suture material is absorbed or
encapsulated by fibroblasts. The smaller the suture diameter, the less the
tissue reaction due to decreased presence of foreign material. However, the
smaller the diameter, the weaker the tensile strength. As a general rule, the
smallest suture material that properly holds tissues should be used.
2. Suture Filaments
Suture strands can either be monofilament, braided, or twisted.
• Monofilament sutures are formed from one strand. They have a lower infection
risk and create less drag when passing through tissues. However, they have a
lower ease of handling and knot strength. They can also crimp easily,
resulting in weak spots that lessen tensile strength.
• Multi-filament sutures are comprised of several strands braided or twisted
together. They provide increased tensile strength and pliability but also
increase drag within tissues. Multi-filamentous sutures can be coated with
materials that lessen the drag and make knots easier to slide into place
(but this then results in poor knot security).
3. Suture Material
Suture material can be classified as absorbable or non-absorbable.
Types of absorbable suture include:
• Gut – a natural monofilament suture. Often used for internal soft tissue.
The body has a strong reaction to this suture material which often results
in encapsulation. Not commonly used outside gynaecological surgery.
• Polydioxanone (PDS) – a synthetic monofilament suture. Used for many types
of soft tissue wound repair (such as abdominal closures) as well as for
paediatric cardiac procedures.
• Poliglecaprone (Monocryl) – a synthetic monofilament suture. General use in
soft tissue repair. Most commonly used to discretely close skin.
• Polyglactin (Vicryl) – a synthetic braided multi-filament suture. Good for
repairing hand or facial wounds.
The absorbability of a suture is determined by the material it is made from and
the number of strands that comprise that suture. Natural suture will be
degraded by enzymes whilst synthetic suture will be degraded through hydrolysis
(i.e. water gradually penetrates the suture filaments, causing breakdown of the
suture’s polymer chain).
Types of non-absorbable suture include:
• Silk – a natural braided suture.
Harri Foster Davies
• Nylon (Ethilon) – a natural monofilament suture.
• Polypropylene (Prolene) – a synthetic monofilament suture.
• Stainless steel wires.
Non-absorbable sutures will retain their tensile strength for >60 days. They
are grouped into 3 classes: Class 1 (silk, nylon, and polypropylene); Class 2
(cotton and linen); Class 3 (metallic). Class 1 and 3 are the most popular as
class 2 is prone to infection and contamination. Non-absorbable sutures are
eventually encapsulated by fibroblasts.
Having read this brief guide, it may seem like there are thousands of potential
combinations of needles and sutures. However, it is important to remember that
most surgeons typically just find a few sutures that they prefer to work with
and stick with these (unless a particular procedure specifically asks for a
different suture/needle type). You will also find your preferences as you gain