How to choose a suture thread?

The needle:

The needles are made of stainless steel, they are made up of a tip and a body. There are needles with a round, triangular, lanceolate (or diamond) or mixed (tapercut) section: triangular tip and round body.

The round section allows you to puncture the tissues without tearing them while the triangular section includes 3 sharp edges, these triangular edges can cause tearing of the tissues when pulling the flap when the stitch is closed. This type of needle will be reserved for thick fabrics.

Needle body:

Along with the tip, the body is the other part of a needle. It can have different shapes (triangular, round, etc.); each of these shapes responds to a use.

The body of the needle is the part which is gripped by the needle holder according to the 1/3 – 2/3 rule for good stability and grip.

There are a very large number of curvature/body/tip associations to be able to adapt to all tissues and all surgeries.

Each type of needle body corresponds to a letter and a pictogram :

CodeShapePictogramSTriangularRRoundLDiamond / Lanceolate /

Needles with a triangular body are generally used to pass through hard tissues such as skin, needles with a round body are most often used for suturing soft tissues. As for needles with a lanceolate body, also called spatulate, they are very often used in ophthalmology.

Needle tip:

The tip is, with the body, one of the constituent elements of a surgical needle.

It can have different geometries (round, triangular, diamond, foam, etc.); each of these shapes has an impact on the tissues it passes through and therefore a particular indication which takes into account the nature of the tissue to be sutured.

TipsCharacteristicsExamples of useRoundNon-sharpVisceral surgeryTriangularPenetratingSkin/cutaneous sutureDiamondSharp on 4 sidesCalcified and sclerotic tissuesFoamAtraumaticParenchymal tissuesFine point : Fine tipReverse cutting: Reverse cutSoft cut: Soft cutPrecision point: Precision tipTaper point: Conical tipConventional cutting: Conventional cutting

Curvature of the needle:

Curvature is one of the needle characteristics. There are straight needles and curved needles.

Straight needles can be used without a needle holder; they are most often used for superficial planes.

The curvature is expressed as an 8th of a circle; for example 5/8th or 3/8th, the 4/8th corresponding to a semi-circle and 2/8th to the quarter of a circle (1/4).

In practice, the deeper the plane, the more curved the needle must be.

Diameter of the thread:

We speak of diameter (or gauge) for both the needle and the thread. The diameter is expressed differently depending on the reference pharmacopoeia.

The decimal classification from the European Pharmacopoeia (EP for European Pharmacopoeia) is used as a reference to define the gauge of the wires (from 0.1 to 10). Example: a decimal 2 corresponds to a thread of 0.20 to 0.29mm in diameter.

But it is the American Pharmacopoeia (USP for US Pharmacopoeia) which is the most used: the caliber varies from 12/0 to 4 from the thinnest to the thickest and depending on the origin of the suture and its resorption profile.

There is an equivalence between these two standards:

USPEP / DecimalWire gauge in mm12-00.010.001 - 0.00911-00.10.010 - 0.01910-00.20.020 - 0.0299-00.30.030 - 0.0398-00.40.040 - 0.0497-00.50.050 - 0.0696-00.70.070 - 0.0995-010.10 - 0.1494-01.50.15 - 0.1993-020.20 - 0.2492.50.25 - 0.2992-0*30.30 - 0.34903.50.35 - 0.399140.40 - 0.499250.50 - 0.5993+460.60 - 0.699570.70 - 0.799680.80 - 0.899790.90 - 0.9998101.00 - 1.0999111.10 - 1.19910121.20 - 1.299

• USP 2/0 = 0.30 to 0.339 mm

Wire length:

It varies from 20 to 120 cm depending on the materials and their use. The most common length is 70 cm.

Monofilaments vs. braids:

The suture material can be composed of a single filament (monofilament) or several filaments (multifilaments or braids).

Monofilaments have attractive qualities, such as strength, low tissue entrainment and low propensity to promote infection.

It is accepted that the incidence infection rate is significantly lower with monofilament compared to braid. Monofilaments constitute surgical progress because their structure facilitates intra-tissue passage and eliminates the phenomenon of capillarity.

The advantages of monofilaments are summarized in the table below:

CharacteristicsAdvantagesBenefitsSmooth and regular surfaceExcellent intratissue passageMinimum tissue traumaAcapillarityNo wicking effect Prevents the propagation of infection Applicable stitchesLess risk of post-operative infection Better healing Saving time Uniform distribution of the tension force on the incisionElasticityBetter knot holdingSuture safety

Compared to monofilaments, braids are more likely to cause infections by capillarity, because the interstices between the fibers can facilitate the propagation of pathogenic elements along of the fiber and therefore directly in the location of the installation. The braids have a relatively rough surface which causes a “saw effect” when the thread passes through the tissues.

Absorbable vs. non-absorbable

Once implanted, the suture material can remain in the body or, on the contrary, degrade. This distinction in behavior classifies sutures into two categories: non-absorbable sutures and absorbable sutures.

Non-absorbable sutures are permanently present in the body; they offer long-term support; if used on a superficial level (skin or mucous membrane = Ex: episiotomy), they will require removal.

Absorbable sutures disappear in the more or less long term; the degradation profile depends on the chemical composition of the threads. We are talking about sutures that are absorbable in the short term (~50 days), medium term (60 to 90 days), long term (180 to 210 days) or very long term (390 days). The degradation mechanism varies depending on the origin of the material constituting the suture. For resorbable synthetic threads, this is a hydrolysis reaction which guarantees homogeneous, regular and predictable degradation; it generates physiological metabolites (degradation products).

Resorption is also called “mass loss”.

Resorbable synthetic monofilament threads:

Polydioxanone:

They have a very smooth surface, good elasticity and excellent tolerance. Resorption occurs in approximately 210 days.

Polyglyconate, Glycolide Trimethylene Carbonate (GTMC):

Resorption occurs between 180 and 270 days, with loss of 60% of its resistance at 21 days.

Poliglecaprone 25:

It is characterized by great flexibility, a certain elasticity. Resorption takes place between 90 and 120 days (hydrolysis).

Glycomer 631:

It is characterized by great handling.

Non-absorbable synthetic monofilament threads:

Polypropylene:

Unalterable, good tolerance.

Polyamide (nylon):

Good tolerance and flexibility.

Polybutester:

It elongates under traction initially, then its elasticity ceases until rupture.

Stainless steel:

Source:

ABC of sutures - ligatures (published brochure by the B.Braun laboratory)