So Many Pieces of String - How to Choose Appropriate Suture Material
World Small Animal Veterinary Association World Congress Proceedings, 2015
A. House, BSc, BVMS, PhD, CertSAS, DECVS
Veterinary Referral Hospital, Melbourne, VIC, Australia

Useful Websites

http://www.ussdgsutures.com/

http://ecatalog.ethicon.com/

The properties and characteristics of suture are described using the following terms:

 Breaking strength: The stress value on the stress-strain curve at which suture acutely fails.

 Capillarity: The degree to which absorbed fluid is transferred along a suture.

 Creep: The tendency of a suture to slowly and permanently deform under constant stress.

 Elasticity: The degree to which a suture will deform under stress or load and return to its original form when the load is removed.

 Fluid absorption: The degree to which a suture will absorb fluid following immersion.

 Knot pull-out strength: The load required to break a suture deformed by a knot.

 Knot strength: The force necessary to cause a knot to slip.

 Memory: The tendency for a suture to return to its original shape after deformation.

 Plasticity: The degree to which a suture will deform without breaking and will maintain its shape after removal of the deforming force.

 Pliability: The ease of handling and the ability to change the shape of suture.

 Stress relaxation: The ability of suture to reduce stress under constant strain.

 Suture pullout value: The weight required to pull a suture loop from tissue. The measured value relates to tissue strength (fat = 0.2 kg, muscle = 1.27 kg, skin = 1.82 kg, fascia = 3.77 kg).

 Tensile strength: Similar to ultimate strength, breaking strength, or yield strength. It is a measure of a suture's ability to resist deformation and breakage and the stress at which deformation (yield strength) or rupture (breaking or ultimate strength) occurs.

Sutures are generally classified as natural or synthetic, monofilament or multifilament and absorbable or nonabsorbable. Monofilament suture consists of a single strand of material. Multifilament suture is a collection of multiple strands. Monofilament suture tends to be less pliable and higher memory which can reduce the handling properties. Additionally monofilaments tend to be susceptible damage from instrumentation which can result in catastrophic damage from crushing. Monofilament suture is typically smooth and hence has lower tissue drag and capillary action.

Multifilament suture is either a braid or twist of smaller strands. Multifilament sutures are generally stronger and more pliable than a monofilament of the same material and size. The surface of multifilament suture is frequently rough and hence has greater tissue drag but frequently improved knot security. Due to the presence of multiple filaments multifilament sutures have greater capillarity and an increased tendency for bacterial colonisation. Many multifilament sutures are treated with a coating to improve suture handling and decrease tissue drag and capillary action; however, these coatings frequently decrease knot security.

Absorbable sutures can be sub-classified into short duration (< 21 days) or long duration (> 21 days). Non-absorbable sutures despite been classified as non-absorbable are frequently susceptible to degradation and can lose tensile strength over time.

There is no single suture that is the ideal suture. The theoretical ideal suture has the following properties:

 Adequate tensile strength

 Minimal tissue reaction

 Inhibits bacterial growth

 Handles easily

 Secure when knotted

 Absorbed after tissue healed

 Non-capillary

 Non-allergenic

 Non-ferromagnetic

 Non-electrolytic

 Non-carcinogenic

 Not corrosive

 Not toxic

 Inexpensive

 Easily sterilised

Common Absorbable Sutures - Short Duration

Catgut

A natural suture made from the small intestinal submucosa of sheep or the intestinal serosa of cattle and is available in plain or chromic forms. Catgut is relatively weak compared with other sutures and has a non-uniform profile which results in non-uniform strength. Catgut incites an inflammatory reaction and is absorbed by an enzymatic process. Consequently the absorption is extremely variable depending on local conditions and extent of inflammation. When exposed to proteolytic enzymes in environments such as the bladder or intestinal tract the loss of tensile strength can be very rapid, within 7 days. Consequently, catgut is an acceptable suture material when a short duration of effect is required, such as ligation of small vessels or suturing of rapidly healing tissues like mucosa. It should not be relied upon for prolonged strength or used in bladder or intestinal surgery.

Monocryl

Monocryl is composed of poliglecaprone 25 which is a rapidly absorbed monofilament co-polymer of ε-caprolactone and glycolide. Monocryl has identical knot performance compared with Vicryl, similar performance to PDS, and lesser performance compared with Maxon. Monocryl has high initial breaking strength, being superior to chronic gut, Vicryl, and PDS. Monocryl loses 70% to 80% of its tensile strength at 1 and 2 weeks. Poliglecaprone 25 is completely absorbed in 90 to 120 days.

Caprosyn

Caprosyn is composed of Polyglytone 6211 which is a rapidly absorbed, monofilament polymer of glycolide, caprolactone, trimethylene carbonate, and lactide. Caprosyn has approximately twice the initial loop strength of chronic gut suture and less tissue drag and knot security than chromic gut. It has no measurable strength after 3 weeks.

Vicryl

Vicryl is composed of a multifilament braided copolymer of 90% glycolide and 10% L-lactide and is coated with calcium stearate and polyglactic acid to improve its handling characteristics. Vicryl loses approximately 50% of its tensile strength between 2–3 weeks. Vicryl RapideTM is an irradiated form with very rapid absorption characteristics with 50% tensile strength loss by 5 days and no measurable strength after 14 days. Vicryl is similar to Dexon in terms of mechanical and absorption characteristics.

Polysorb

Polysorb is composed of a multifilament lactomer (glycolide/lactide). When compared to Dexon and Vicryl which have essentially the same indications, Polysorb had the highest linear tensile strength but also the fastest loss of function following tissue implantation. Polysorb had the best knotting characteristics compared to Dexon and Vicryl.

Dexon

The composition of Dexon is a braided homopolymer of glycolic acid and is available in a coated or uncoated form. Dexon loses approximately 50% of its strength between 2 to 3 weeks. When tested against Vicryl, Mersilene, silk, nylon and Prolene, Dexon has the highest breaking stress. Uncoated Dexon has a greater knot security compared with Vicryl.

Common Absorbable Sutures - Long Duration

PDS

PDS is composed of polydioxanone an uncoated, monofilament suture. Absorption of PDS is significantly prolonged with approximately 50% of its initial tensile strength remaining at 5 to 6 weeks. PDS is similar to Maxon in terms of absorption and strength, but it has better handling and less memory.

Biosyn

Biosyn is composed of glycomer 631, a monofilament absorbable composed of glycolide, dioxanone, and trimethylene carbonate. Biosyn is relatively rapidly absorbed with approximately 50% loss of tensile strength at 2 to 3 weeks and is completely absorbed at 90 to 110 days. When compared with Vicryl, Biosyn is stronger and has greater knot security.

Maxon

The composition of Maxon is a co-polymer of glycolic acid and trimethylene carbonate monofilament. Maxon has greater memory compared with PDS which gives it poor handling characteristics. Maxon retains approximately 50% of its tensile strength after 4 to 5 weeks. Maxon has excellent knot performance.

Common Non-Absorbable Sutures

Polypropylene

Polypropylene is a monofilament polyolefin suture. Polypropylene is very strong but has less knot strength when compared with sutures such as PDS. Polypropylene has good handling characteristics and is very resistant to degradation.

Nylon

Nylon is a monofilament polyamide-based suture. Nylon is second to polypropylene in strength. Despite classification as a non-absorbable suture, nylon is susceptible to degradation.

In reality no single suture fulfils all these criteria in every circumstance. Below is a summary of the commonly available sutures and their properties.

Suture

Characteristics

Absorption rate

Tensile strength

Handling and knot security

Catgut

Absorbable monofilament

Rapid and variable (within 2 to 14 days)

Poor

Good handling, poor knot security

Monocryl/Caprosyn

Absorbable monofilament

Rapid (within 14 days)

High

Excellent

Vicryl/Polysorb/Dexon

Absorbable braided

Medium (approx. 3–4 weeks)

Moderate

Excellent handling, moderate knot security

PDS/Biosyn/Maxon

Absorbable monofilament

Slow (at least 6 weeks)

High

Poor - Biosyn better than PDS. Maxon - poor handling, excellent knot properties

Nylon/Prolene

Non-absorbable monofilament

  

High

Poor

Needles

Needles may be straight, curved, or a combination. In most circumstances straight needles are used closer to the surface of the body and curved needles are used within cavities. Suture needle points are classified as blunt, taper, or cutting. Blunt needles are used in friable tissue but have little use in most tissues. Taper needles have a fine point that pierces and spreads tissue during needle passage and are indicated for gastrointestinal organs, fat, the urinary bladder, and muscle. Tapercut needles are a combination of a taper and a cutting needle. Tapercut needles have a reverse cutting point and an oval body, allowing greater ease of needle penetration with less risk of inadvertent tissue cutting or fraying during needle passage.

Cutting needles are indicated in tough or fibrous tissue such as skin, periosteum, and fascia. Standard cutting needles are triangular and have the cutting surface on the concave surface of the needle with the cutting edge parallel to the incision. This configuration can result in a larger than ideal suture hole. Reverse-cutting needles have the cutting surface on the convex surface, resulting in a triangular needle hole with a flat edge parallel to the incision. This design should have less risk of inadvertent needle hole elongation during needle passage and consequently less risk of suture pull-through.

  

Speaker Information
(click the speaker's name to view other papers and abstracts submitted by this speaker)

A. House, BSc, BVMS, PhD, Cert SAS, DECVS
Veterinary Referral Hospital
Melbourne, VIC, Australia


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