SUTURE MATERIALS

The word wound is described as any tissue that has been damaged by surgical or traumatic means. Surgical wounds are an incision is an intentional cut through intact tissue for the purpose of exposing underlying structures. Wounds include deep and superficial structures. Closure of a surgical wound or other wound is performed after necessary hemostasis has been achieved. Methods of wound closure include sutures, staples, clips, tapes, and glues.

Suture materials are used to approximate tissues (bring tissue edges together by suture or other means) while healing takes place and to ligate (tie) blood vessels or tubal structures. If the material is tied to occlude the lumen, it is called a ligature.

In surgery, suture can refer to a length of suturing thread or a suture thread and needle combination. Packages of suture material are simply called “sutures.” Suture material is made from synthesized chemicals, animal protein, metal, and natural fibers.

SUTURE

• Sutures, commonly called stitches, are sterile, surgical threads that are used to repair cuts (lacerations). They also are used to close incisions from surgery.
• A suture is a medical device that is use to hold skin, internal organs, blood vessels and all other tissues of the human body together, after they have been severed by injury, incision or surgery. Tissues are held together until enough healing occurs to withstand stress without mechanical support.
• The time takes for a tissue to no longer require support from sutures will vary depending on tissue type:
• Days: Muscle, subcutaneous tissue or skin
• Weeks to Months: Fascia or tendon
• Months to Never: Vascular prosthesis
• It is worth noting that regardless of suture composition, the body will react to any suture as a foreign body, producing a foreign body reaction to varying degrees.

PROPERTIES AND CHARACTERISTICS OF SUTURES

It contributes to the selection and application of a suture. The following terms relate to the properties of suture:

• Physical characteristics: The physical structure of the suture and its size.
• Structure of suture: Structurally, sutures are broadly divided into three categories:
• Monofilament: A single continuous fiber made of a polymer chemical made by extrusion and stretching the material.
• Multifilament: Many filaments that together form one strand of suture. Further divided into two types:
• Twisted: Multiple fibers are twisted in the same direction.
• Braided: Multiple fibers are intertwined.
• Composite: A core strand of one suture material is jacketed with another of a different type.
• Suture Size: The size of the suture is based on the diameter of a single strand. it contributes to strength of the suture.
• The USP numbering suture’s size system
• USP numbering system indicates the suture’s size biased on outside diameter of suture.
• Suture Sized according to diameter with “0” as reference size.
• Numbers alone indicate progressively larger sutures (“1”, “2”, etc.)
• Numbers followed by a “0” indicate progressively smaller sutures (“2-0”, “4-0”, etc.)
• Suture ranges in size from 11-0 (thinnest) to 5 (thickest).

Smaller ß-------------------------------------àLarger

.....”3-0”...”2-0”...”1-0”...”0”...”1”...”2”...”3”.....

• Suture outer diameter is the same for same size regardless of the material. For example, size 2-0 silk suture has the same diameter as size 2-0 nylon suture.
• Selection of a particular size is based mainly on the type of tissue and the load or tension that will be placed on the sutures.
• Brown and Sharp (B & S) sizing system-
• Stainless steel suture historically has used the B & S sizing system rather than USP sizes.
• These numbers begin with size 38/40 gauge (the thinnest) up to 18 gauge (the thickest).
• Stainless steel now is sized according to USP standards.

B & S gauge (no.)	40	35	32	30	28	26	25	24	23	22	20
USP size	6-0	5-0	4-0	3-0	2-0	0	1	2	3	4	5

• Tensile strength: The amount of tension a length of suture can withstand before breaking. i.e. the amount of force needed to break the suture.
• Knot strength: The amount of force a knot can withstand before slipping or breaking. This is related to friction and plasticity. Knot strength are influenced by many factors, such as:
• Type of knot
• Biological environment – body fluid, infection etc.
• Uniformity of suture diameter.
• Memory (recoil): The ability of a suture to return or maintain its original shape or configuration after it is removed from the package. This is related to diameter, plasticity, and elasticity.
• Plasticity: The ability to withstand bending and crimping without breaking and to maintain the new shape after it is made. This applies to knot tying and the suture’s tendency to untie, or to maintain the configuration of the knot.
• Compliance or pliability: A measure of the ease of handling, softness in the hand, and flat knotting. It makes the suture material easier to manipulate. The knots lie flat and remain secure (called tie-down). Silk suture has traditionally been considered the gold standard of all suture materials for its pliability, tight knots, and ease of use.
• Absorption quality: Absorption describes how the suture reacts in the presence of body tissue, its resistance to breakdown (degradation of the material by the lysosomal action of enzymes), and absorption into the body. Absorbable, protein-based suture is attacked by enzyme- releasing lysosomes that digest the suture. Absorbable synthetic sutures are degraded by hydrolysis. All sutures, except stainless steel, can degrade if infection is present.
• Bioactivity: The body’s response to suture i.e. immune system reacts to suture as foreign material. It depends on the chemical structure of the suture material and the condition of the patient. Sutures that cause little or no bioactivity are said to be highly inert, causing little or no inflammation. Stainless steel and titanium sutures are the most inert of all materials; natural fiber and protein-based sutures cause the most tissue reaction.
• Composition: The chemical, molecular, or elemental makeup and origin of the substance used to manufacture the suture.
• Wicking or Capillary Action- Sutures made of multifilament strands absorb moisture and hold body fluids is called wicking or capillary action. Suture with low capillarity is preferred in surgery when the risk of infection is high. If bacteria are present, suture materials with high capillarity are able to retain and spread infection by means of the suture fibers. Some multifilament suture is coated with a chemical polymer to reduce tissue drag and wicking.

THE IDEAL SUTURE

• The ideal suture should allow the healing tissue to recover sufficiently to keep the wound closed together once they are removed or absorbed.
• Other characteristics are –
• This should produce minimal tissue reaction.
• It should be smooth (minimal tissue drags).
• It should have maximum tensile strength.
• Ease of handling - minimum memory.
• It should have good knot security.
• The performance of material should be consistent and predictable.
• It should be cost effectiveness.
• It can be used for any tissue.
• It should be unfriendly to bacteria.
• It should not tear the tissue

CLASSIFICATION

             There are many kinds of sutures, with different properties suitable for various uses. Sutures can be classified into two groups: absorbable sutures and non-absorbable sutures and then further by their chemical makeup of the suture material i.e. Natural and Synthetic

Absorbable Suture

• Absorbable sutures are the sterile strands prepared from collagen derived of healthy mammals or from a synthetic polymer. They are capable of being absorbed by living mammalian tissue i.e. do not act as a foreign body. The sutures break down by reacting with water in tissue fluids or they are digested by enzyme activity and assimilated by the tissues during the healing process but may be treated to modify resistance to absorption. Absorbable sutures provide temporary wound support until the wound heals well enough to withstand normal stress.
• Examples: Plain gut/catgut, chromic catgut/ chromic gut, Vicryl, Monocryl, Maxon, Dexon and PDS (poly-di-oxa-none) etc.

Non-absorbable Suture

• Non-absorbable Suture are strands of natural or synthetic material that effectively resist enzymatic digestion or absorption in living tissue. They act as a foreign body and may require removal (when used for skin) but some may remain left in the body. During the healing process, suture mass becomes encapsulated and may remain for years in tissues without producing any ill effects. Non-absorbable Suture are used only when long term support is required.
• Examples: Surgical silk, Surgical Cotton, nylon, prolene, Mersilene, Novafil, Dacron, stainless steel etc.

Natural Suture

• Natural sutures are of biological origin, which may be made from the collagen of mammalian intestines or from synthetic collagen (polymers). Traditionally, they are more inflammatory than synthetic materials. Tissue response and suture antigenicity lead to inflammatory reactions, especially with natural materials.
• Examples: Catgut, Chromic catgut, Surgical silk, Surgical Cotton etc.

Synthetic Sutures

• Synthetic sutures are made of artificial/Synthetic polymers. They do not cause intense inflammatory reaction.
• Examples: Vicryl, Monocryl, Maxon, Dexon, PDS (poly-di-oxa-none), nylon, prolene, Mersilene, Dacron, Stainless Steel etc.

DIFFERENT TYPES OF SUTURE

Surgical Gut/Catgut

• Catgut or surgical gut is a natural absorbable monofilament suture material. It is available in sizes 3 to 6-0.
• This is prepared from either sheep intestinal submucosa or bovine intestinal serosa.   Catgut is commercially supplied as plane or chromic catgut.
• Plain catgut- Plain surgical gut is digested quickly and absorbed by tissues, but this rapid reaction can also cause inflammation. The suture retains tensile strength in the body for 7 to 10 days. Suggested uses are for Ligating superficial blood vessels, Subcutaneous and subcuticular suture.
• Chromic catgut- Chromic gut is treated with chromic salt to resist digestion and absorption and reduces tissue irritation. Chromic gut usually is absorbed in 7 to 21 days. This can also cause inflammation but less than plain gut. Suggested uses for chromic catgut are in the suturing of peritoneum, muscle, fascia, intestinal anastomosis, uterine tubes and vessels and in ophthalmic surgery.
• Both types of gut are rapidly broken down in the presence of infection.

Surgical silk

• Surgical silk is a natural non-absorbable multifilament (braided) suture material. It is available in sizes 5 to 9-0.
• This is an animal product made by the silkworm larva for its cocoon.
• Silk is not a truly nonabsorbable material. It loses much of its tensile strength after about 1 year and usually disappears within 2 years.
• It has weaker tensile strength and knot protection than its synthetic counterparts, and produce greater tissue reaction (but less surgical gut).
• Silk sutures are used dry. They lose tensile strength if wet. Therefore, they should not be moistened before use.
• It is used frequently in the serosa of the gastrointestinal tract and to close fascia in the absence of infection.

Surgical Cotton

• Surgical Cotton is a natural non-absorbable multifilament (braided) suture material. It is available in sizes 1 to 5-0.
• This is made from cotton fibers (natural cellulose fiber).
• Surgical cotton is one of the weakest of the nonabsorbable materials. however, it gains tensile strength when wet (increased 10% by moisture). It should be moistened before it is handed to the surgeon.
• It is rarely used. When left in body tissue, there is much inflammatory tissue reaction.

Vicryl (Polyglactin 910)

• Vicryl is a synthetic, absorbable multifilament (braided) suture material. It is available in sizes 3 to 8-0.
• It is degraded by hydrolysis of the polymer's chemical bonds, and is completely absorbed after approximately 60 days.
• It has moderate relative knot security and minimal tissue reaction. Its losses his tensile strength moderate to rapid compared to other absorbable synthetic materials (lost faster than PDS, Maxon, slower than Monocryl and at a similar rate compared to Dexon).
• This is also available in a coated format; Coated Vicryl (Coated polyglactin 910). It is coated with a mixture of equal parts of calcium stearate and a copolymer of glycolide and lactide (polyglactin 370) to reduce tissue drag (coating provides a nonflaking lubricant for smooth passage through tissue) and precise knot placement. This coating does not affect the absorption rate or tensile strength of the suture.
• Vicryl Rapide is absorbed more rapidly than Vicryl and is designed for fast healing tissues (tensile strength is completely lost at 10-14 days). 

Monocryl (Polyglecaprone 25)

• Monocryl is a synthetic, absorbable monofilament suture material. It is available in sizes 2 to 6-0.
• Prepared from a copolymer of glycolide and epsilon-caprolactone.
• It has excellent knot security and causes minimal tissue reaction. 
• It is the most pliable of the monofilament synthetic sutures. The tensile strength of this is lost rapidly compared to other absorbable synthetic material, but its initial tensile strength is high. It retains approximately 50-60% of its tensile strength in tissue for 7 days, 20-30% up to 14 days and loses all tensile strength by 21 days.
• It is degraded by hydrolysis of the polymer's chemical bonds, and is completely absorbed after approximately 91 to 120 days.
• Because of its strength retention and absorption profiles, it is indicated for use in all types of soft tissue approximations and/or ligations, especially in general, gynecologic, urologic, and plastic surgery, but it is not indicated for use in cardiovascular, neural, or ophthalmic tissues.
• This material has exceptional handling characteristics for a monofilament suture, due to a lack of stiffness and memory. 

Maxon (Polyglyconate)

• Maxon is a synthetic, absorbable monofilament suture material prepared from a copolymer of glycolic acid and trimethylene carbonate. It is available in sizes 2 to 7-0.
• It has relatively good knot security & tensile strength and causes minimal tissue reaction.
• It is indicated for approximation of soft tissue except in cardiovascular, neural, and ophthalmic tissues.
• It is degraded by hydrolysis of the polymer's chemical bonds, and is absorbed after approximately about 60 days and then is complete within 6 months.

Dexon (Polyglycolic Acid)

• Dexon is a synthetic, absorbable multifilament (braided) suture material.
• It is available in sizes 2 to 6-0.
• It has relatively moderate knot security and causes minimal tissue reaction. 
• The loss of tensile strength of this synthetic material is moderate to rapid compared to other absorbable synthetic material.
• Dexon is available as coated with surfactant Poloxamer 188 (Dexon II/ Dexon Plus) and uncoated (Dexon S) materials. 
• It is degraded by hydrolysis of the polymer's chemical bonds, and is completely absorbed after approximately 30 to 90 days.

Polydioxanone (PDS)

• PDS is a synthetic, absorbable monofilament suture material.
• It is available in sizes 2 to 9-0.
• It has good knot security and causes minimal tissue reaction.
• The tensile strength is retained longer than the other absorbable synthetic materials.
• PDS is degraded by hydrolysis of the polymer's chemical bonds, and is completely absorbed after approximately 180 days.

Nylon

• Nylon (Polyamide) suture is a synthetic, nonabsorbable suture material available in a monofilament and multifilament (braided); coated or uncoated form.
• It was the first synthetic suture material available (1940) and is still widely used.
• The most outstanding feature of nylon is that is causes little or no tissue reaction and passes very easily through delicate tissues of the eye or blood vessels.
• Nylon has a very high tensile strength but it loses his tensile strength over time.
• Nylon suture is noted as having a high degree of elasticity, which can be useful in edematous tissue and in skin closure. 

Prolene (Polypropylene)

• Prolene is a synthetic, nonabsorbable monofilament suture material that is available in sizes 5 to 8-0.
• It possesses good tensile strength and excellent knot security (due to plastic deformation during tying) and may also be steam sterilized.
• It is often favored for cardiovascular surgeries because it has reduced thrombogenic potential.

Mersilene (Polyester)

• Mersilene is a synthetic, nonabsorbable multifilament (braided) suture material that is available in various sizes (5 to 11-0) as well as plain (Mersilene) and coated (Ethibond) forms.
• The plain Mersilene suture material has significant tissue drag, coating reduces this drag but also knot security.
• Mersilene suture material has excellent initial and prolonged tensile strength.
• it elicits more tissue reaction as compared to other synthetic nonabsorbable sutures and has poor knot security.
• Mersilene is often used to stabilize unstable joints because it is strong and non-elastic.

Dacron

• Dacron is a Synthetic non-absorbable multifilament (braided) suture material made from polyester fibers.
• It is available in two forms uncoated and coated fibers and in sizes 2 to 10-0.
• It has excellent tensile strength & knot security and causes minimal tissue reaction. 
• Used in soft tissue approximation and ligation; especially useful in respiratory tract and some cardio vascular procedures.

Stainless Steel

• Stainless steel is the most commonly used nonabsorbable metallic suture, usually composed of a 316L alloy stainless steel. 
• It is the strongest of all suture materials. It has no significant inflammatory properties. It is available in monofilament and twisted form and in various sizes (7 to 10-0).
• It is the most inert and strong and it has the best knot security. 
• Stainless steel suture is difficult to handle, it can easily cut tissue and can weaken if bent inappropriately. 
• It is widely used in the approximation of bone in orthopedic surgery and in infected wounds due to its strength and inertness.\

SURGICAL NEEDLES

• Surgical needle is a medical device used to stitch tissues with sutures, made of high-quality steel alloy or titanium.
• The ideal surgical needle would have the following characteristics:
• It is made of high-quality stainless steel
• It is strong enough so that does not break easily
• It is rigid enough to prevent excessive bending
• It is flexible enough to prevent breaking if bent
• It is stable in the grasp of the needle holder
• It is sharp enough to penetrate tissue with minimal resistance
• It has the smallest diameter possible and approximately same diameter as the suture, to minimize trauma in passage through tissue
• It is sterile and corrosion-resistant to prevent introduction of microorganisms or foreign materials into the wound

BASIC COMPONENTS/ PARTS OF SURGICAL NEEDLE

• All surgical needles have three basic components: the point, the body (or shaft), and the eye (or swaged). They are classified according to these three components.

POINT OF THE NEEDLE

Points of surgical needles are honed to the configuration and sharpness desired for specific types of tissues. Many different types of needle points are available. However, they all are variations of the three basic types:

• Cutting point
• Tapered point
• Blunt point

Cutting point

The cutting needle has a cutting edge along its shaft. Cutting needles are preferred when tissue is difficult to penetrate like fibrous connective tissue, such as the skin, joint capsule, and tendon. Two opposing cutting edges form a triangular configuration with a third edge on the body of the needle. Cutting edge make a slight cut in tissue as they penetrate.

• Conventional Cutting Needles - A needle with the cutting edge on the inside of the curve is called a conventional cutting needle.

• Reverse-Cutting Needles - A needle with the cutting edge on the outside or lower edge of the curve is called a reverse cutting needle.

• Side-Cutting Needles - A needle with the angulated cutting edges are on the sides and relatively flat on the top and bottom is called a Side-Cutting needle. Primarily Used in ophthalmic surgery.

Tapered Point

• The tapered needle has a round shaft without a cutting edge that tapers to a sharp point. It punctures tissue, making an opening for the body of the needle to follow, rather than cut it. These needles are primary used for suturing soft tissue, such as muscle, subcutaneous fat, peritoneum, dura, and gastrointestinal, genitourinary, biliary, and vascular tissue.

Blunt Point

• The blunt needle is a round shaft with a blunt tip. It pushes tissue aside as it moves through it. It does not puncture the tissue, but rather slides between tissue fibers. It is the least traumatic and safest needle point. The blunt needle traditionally has been used only for suturing friable tissues and organs that are soft and spongy, such as the liver, spleen, and kidneys.

BODY OF THE NEEDLE

• The shaft or body of the needle is located between the suture strand and the point. The body of the needle may be round, oval, flat, or triangular. It varies in wire gauge, length, shape, and finish. The nature and location of tissue to be sutured influence the selection of needles with these variable features. Typically, the heavier the tissue, the heavier the body. Length is determined by the depth of the “bite” of the tissue to be sutured. The shape of the body may be straight (Keith needle), ¼ circle, ⅜circle, ½ circle, or ⅝ circle.

EYE OF THE NEEDLE

The eye is the segment of the needle where the suture strand is attached. Surgical needles are classified as

• Closed Eye Needles
• French Eye Needles
• Swaged/Atraumatic Needles

Closed-eyed needles

• It may have round or square holes and are loaded by inserting the end of the suture material through the hole. The eyed needle allows the use of a wide variety of sutures with a wide variety of needles. The eyed needle causes more tissue damage than the eyeless (swaged) needle because the suture strand is not continuous with the needle.

French-eyed needle

• It is loaded by pulling the taut strand into a V-shaped area just above the eye. This type of needle is loaded more quickly than a closed-eyed needle, but still results in more tissue damage than the eyeless needle.

Swaged/atraumatic needles

• Needles that are manufactured with suture strands inserted into one end are referred to as eyeless or swaged needles. These needles are continuous with the suture strand, and the hole created in the tissue by the needle should be completely filled by the suture strand when suturing.

SELECTION OF SUTURES AND NEEDLES

The choice of suture is often a matter of opinion, but wide variety of factors that must be considered while choosing suture material. These are –

1. Type of Procedure
2. Type of Tissue
3. Condition of The Patient’s tissue - factors modifying the condition of tissue are -
• Age of the patient
• Weight of the patient
• Metabolic factors
• Carbohydrates
• Proteins
• Vitamins
• Dehydration
• Vascularization
• Thickness of tissue at a given time
• Edema or induration (hardening and thickening of tissue)
• Incision relative to fiber direction
• Amount of devitalized tissue within wound
• Radiation therapy
4. Nature of The Disease Process - disease processes affecting suture choice are-
• Diabetes mellitus
• Immune system diseases
• Pituitary gland dysfunction
• Localized infection
• Systemic infection
5. Surgeon’s Preference
6. Suture Availability
7. Cost

PACKAGING OF SUTURE

• Every suture packet provides clear product identification through color coding, bold graphics, and descriptive symbols.
• The most important information that the nurses should learn to identify the box is suture size (USP and metric) and material and the type and size of needle.
• Other important information displayed on the suture box includes:
• Surgical application
• Product code number
• Suture length and color
• Metric diameter equivalent of suture size and length
• Shape and quantity of needles.
• Needle point geometry
• Lot number
• Expiration date

Fig. Sample suture packet

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