Sutures are the stitches that doctors, and especially surgeons, use to hold skin, internal organs, blood vessels and all other tissues of the human body together, after they have been severed by injury or surgery. They must be strong (so they do not break), non-toxic and hypoallergenic (to avoid adverse reactions in the body), and flexible (so they can be tied and knotted easily). In addition, they must lack the so called "wick effect", which means that sutures must not allow fluids to penetrate the body through them from outside, which could easily cause infections.
Sutures are the stitches used to hold together the skin and internal organs that have been damaged by injury or surgery.
Sutures are designed to help the body heal by closely opposing two sides of a wound to minimize scar formation or to prevent leaking blood, like in vessels. Sutures have to comply with several regulations and guidelines such as United States Pharmacopeia , Europian pharmacopeia  and the FDA , etc. to ensure they meet the necessary requirements.

United States Pharmacopeia
The United States Pharmacopeia classification system was established in 1937 for standardization and comparison of suture materials, corresponding to metric measures. The 3 classes of sutures are collagen, synthetic absorbable, and nonabsorbable. Size refers to the diameter of the suture strand and is denoted as zeroes. The more zeroes characterizing a suture size, the smaller the resultant strand diameter (eg, 4-0 is larger than 5-0). The smaller the suture, the less tensile strength of the strand.

United States Pharmacopeia classification
•  Class I - Silk or synthetic fibers of monofilament, twisted, or braided construction
•  Class II - Cotton or linen fibers or coated natural or synthetic fibers in which the coating contributes to suture thickness without adding strength
•  Class III - Metal wire of monofilament or multifilament construction
 
Sutures are probably the largest group of devices implanted in humans, few devices have been made of so many different materials. By definition, a suture is a thread that either approximates and maintains tissues until the natural healing process has provided a sufficient level of wound strength or compresses blood vessels in order to stop bleeding.
 
The United States Pharmacopeia (USP)is the official compendium for the suture industry. It sets standards and guidelines for suture manufacture.
These monographs have the force of law, established the standards by which legal acceptability of Sutures is judged, and are the final reference in cases of compliment and dispute concerning properties covered by them.
 
The United States Pharmacopeiadetermines the procedure and parameters for standard suture test. Sutures are tested immediately after removal from their sterile packages without drying or conditioning. Diameters of sutures are measured using a gauge of the dead-weight type with a presser-foot 12.7 +/- 0.02mm in diameter. The diameter of each strand is measured at three points corresponding roughly to one-fourth, one-half, and three-fourths of the strand length.
 
For knot pull breaking strength, the suture is tied with a surgeon's knot with one turn around a flexible rubber tubing of 6.5 mm inside diameter and 1.6 mm wall thickness. The suture is then attached to a suitable testing machine and tested at a rate such that the specimen breaks in less than twenty seconds. In all strength tests, it is important to keep in mind that the breaking strength retention of absorbable and nonabsorbable sutures should be considered separately because the strength retention of the absorbable sutures will be quite different than that of the nonabsorbable suture.
 
Also, needle attachments tests are done in a similar manner to the knot pull breaking strength tests. SMB measures knot pull strength and needle etachment load on Universal Ultra Test Machine with microprocessor Digital Advanced Force Gauge.
 
Nonabsorbable Surgical Suture
 
Nonabsorbable Surgical Sutures is a flexible strand of material that is suitably resistant to the action of living mammalian tissue. It may be in either monofilament or multifilament form. If it is a multifilament strand, the individual filaments may be combined by spinning, twisting, braiding or any combination thereof. It may be either sterile or nonsterile. Its diameter and tensile strength correspond to the size designation indicated on the label, within the limits prescribed herein. It maybe modified with respect to body or texture, or to reduce capillarity and may be suitably bleached. It may be impregnated or treated with a suitable coating, softening, or antimicrobial agent.
Nonabsorbable Surgical Suture is classed and typed as follows.
 
Class[I] Suture is composed of silk or synthetic fibers of monofilaments, twisted, or braided construction where the coating, if any, does not significantly affect thickness (e.g., braided silk, polyester, or nylon; monofilament nylon or polypropylene).
Class[II] Suture is composed of cotton or linen fibers or coated -natural or synthetic fibers where the coating significantly affects thickness but does not contribute significantly to strength (e.g., virgin silk sutures).
Class[III] Suture is composed of monofilament or multifilament metal wire.

Natural Suture Materials

Natural sutures are made from natural materials such as collagen derived from the gastrointestinal track of animals, woven cotton, raw silk, linen, or steel. Because of the material, tissue reaction is often greater with natural sutures, especially those that are absorbable (e.g. Catgut). Coating agents are often used to help reduce tissue reactivity and to help reduce friction.

Antimicrobial sutures

Another recent development in wound closure involves the use of sutures coated with antimicrobial substances to reduce the chances of wound infection. While long-term studies are not yet available, preliminary results indicate that these sutures are effective at keeping bacteria out of wounds.

Absorbable and Non Absorbable Sutures

 
Sutures are divided into two kinds - those which are absorbable and will break down harmlessly in the body over time without intervention, and those which are non-absorbable and must be manually removed if they are not left indefinitely. The type of suture used varies on the operation, with a major criteria being the demands of the location and environment:
Sutures to be placed internally would require re-opening if they were to be removed. Sutures which lie on the exterior of the body can be removed within minutes, and without re-opening the wound. As a result, absorbable sutures are often used internally; non-absorbable externally.
Sutures to be placed in a stressful environment, for example the heart (constant pressure and movement) or the bladder (adverse chemical presence) may require specialized or stronger materials to perform their role; usually such sutures are either specially treated, or made of special materials, and are often non-absorbable to reduce the risk of degradation
 
Absorbable Sutures
Absorbable sutures are made of materials which are broken down in tissue after a given period of time, which depending on the material can be from ten days to eight weeks. They are used therefore in many of the internal tissues of the body. In most cases, three weeks is sufficient for the wound to close firmly. The suture is not needed any more, and the fact that it disappears is an advantage, as there is no foreign material left inside the body and no need for the patient to have the sutures removed.
Absorbable sutures were originally made of the intestines of sheep, the so called catgut. The manufacturing process was similar to that of natural musical strings for violins and guitar, and also of natural strings for tennis racquets. The inventor, a 10th century surgeon named al-Zahrawi reportedly discovered the dissolving nature of catgut when his lute's strings were eaten by a monkey. Today, gut sutures are made of specially prepared beef and sheep intestine, and may be untreated (plain gut), tanned with chromium salts to increase their persistence in the body (chromic gut), or heat-treated to give more rapid absorption (fast gut). However, the major part of the absorbable sutures used are now made of synthetic polymer fibers, which may be braided or monofilament; these offer numerous advantages over gut sutures, notably ease of handling, low cost, low tissue reaction, consistent performance and guaranteed non-toxicity. In Europe and Japan, gut sutures have been banned due to concerns over bovine spongiform encephalopathy (mad-cow disease), although the herds from which gut is harvested are certified BSE-free. Each major suture manufacturer has its own proprietary formulations for its brands of synthetic absorbable sutures; various blends of  polyglycolic acid , lactic acid or caprolactone , Polydioxanone , Poliglecaprone are common. Occasionally, absorbable sutures can cause inflammation and be rejected by the body rather than absorbed.

Non Absorbable Sutures

Non-absorbable materials are used to suture tissues requiring long term or permanent support in which the product strength is critical. They tend to be classed in two distinct areas; whether they are monofilament or multifilament and if they are natural or synthetic.Nonabsorbable sutures are made of materials which are not metabolized by the body, and are used therefore either on skin wound closure, where the sutures can be removed after a few weeks, or in some inner tissues in which absorbable sutures are not adequate. This is the case, for example, in the heart and in blood vessels, whose rhythmic movement requires a suture which stays longer than three weeks, to give the wound enough time to close. Other organs, like the bladder, contain fluids which make absorbable sutures disappear in only a few days, too early for the wound to heal. Inflammation caused by the foreign protein in some absorbable sutures can amplify scarring, so if other types of suture are less antigenic (ie, do not provoke as much of an immune response) it would represent a way to reduce scarring.

There are several materials used for nonabsorbable sutures. The most common is a natural fiber, silk, which undergoes a special manufacturing process to make it adequate for its use in surgery. Other nonabsorbable sutures are made of artificial fibers, like polypropylene, polyester , nylon , Polyvinylidene fluoride ( PVDF), polytetrafluoroethylene (PTFE); these may or may not have coatings to enhance their performance characteristics. Finally, stainless steel wires are commonly used in orthopedic surgery and for sternal closure in cardiac surgery.

DAPS TECH Co.  Has a wide range of Absorbable and Non-absorbable sutures to match today's demanding surgical procedures.

Surgical Sutures Needles

Traumatic needles are needles with holes or eyes which are supplied to the hospital separate from their suture thread. The suture must be threaded on site, as is done when sewing at home. Atraumatic needles with sutures comprise an eyeless needle attached to a specific length of suture thread. The suture manufacturer swages the suture thread to the eyeless atraumatic needle at the factory. There are several advantages to having the needle pre-mounted on the suture. The doctor or the nurse does not have to spend time threading the suture on the needle. More important, the suture end of a swaged needle is smaller than the needle body. In traumatic needles with eyes, the thread comes out of the needle's hole on both sides. When passing through the tissues, this type of suture rips the tissue to a certain extent, thus the name traumatic. Nearly all modern sutures feature swaged atraumatic needles.

There are several shapes of surgical needles, including:

  straight

  half curved or ski

  1/4 circle

  3/8 circle

  1/2 circle

  5/8 circle

  compound curve

 

Needles may also be classified by their point geometry; examples include:

taper (needle body is round and tapers smoothly to a point)

cutting (needle body is triangular and has a sharpened cutting edge on the inside)

reverse cutting (cutting edge on the outside)

trocar point or tapercut (needle body is round and tapered, but ends in a small triangular cutting point)

blunt points for sewing friable tissues

side cutting or spatula points (flat on top and bottom with a cutting edge along the front to one side) for eye surgery

Finally, atraumatic needles may be permanently swaged to the suture or may be designed to come off the suture with a sharp straight tug. These "pop-offs" are commonly used for interrupted sutures, where each suture is only passed once and then tied.

Essential suture characteristics

All sutures are manufactured to meet the necessary qualities:

  • Sterility
  • Uniform diameter and size
  • Pliability for ease of handling and knot security
  • Uniform tensile strength by suture type and size
  • Freedom from irritants or impurities that would elicit tissue reaction


U.S.P.
Designation

Collagen
metric diameter
(mm)

Synthetic absorbable
metric diameter
(mm)

Non-absorbable
metric diameter
(mm)

11-0

   

0.01

10-0

0.02

0.02

0.02

9-0

0.03

0.03

0.03

8-0

0.05

0.04

0.04

7-0

0.07

0.05

0.05

6-0

0.1

0.07

0.07

5-0

0.15

0.1

0.1

4-0

0.2

0.15

0.15

3-0

0.3

0.2

0.2

2-0

0.35

0.3

0.3

0

0.4

0.35

0.35

1

0.5

0.4

0.4

2

0.6

0.5

0.5

3

0.7

0.6

0.6

4

0.8

0.6

0.6

5

 

0.7

0.7

6

   

0.8

 

Needle Shape

Point Type

Symbol

Round Bodied

Curved Cutting

Reverse Cutting

Reverse Cutting Prime

Taper Cutting

Reverse Cutting Precision Point

Micro-point Spatula Curved

CSU Spatula

SBR Spatula

 

Needle Curvature

 

Suture Materials

 

Needle Shapes (Curvature)

1/4 CIRCLE

CURVED 3/8 CIRCLE

 

1/2 CIRCLE

5/8 CIRCLE

 

J-SHAPED

SKI (1/2 CIRCLE)

 

STRAIGHT

 

 

 

Daps Tech Co.  has a wide variety of needles suitable for every surgical application nas required.

 

 

Needle Type (Point and Body)

 

Needles having a taper point which gradually tapers to a round body. These needles are designed for soft tissue closure. The flattened body of the needle enables better grip to be obtained with the needle holder.


 

These are conventional cutting needles of triangular cross section but the apex of the triangle on the inside curvature of the needle. These needles are used for cutting through tough tissues. The triangular section is taken along the length of the needle to ensure excellent cutting strength throughout the needle length.


 

Needles have a triangular cross section which are used for cutting through tough tissue. These needles have three cutting edges with apex of triangular cross section on the out side curvature of the needle. The triangular section is taken along the length of the needle to ensure excellent cutting strength through out the needle length.


 

These are newly introduce needles primarily for Cosmetic Surgeries. Their special body designed and their sharper cutting edges enables a better penetration of the muscle layers.


 

Needles of circular cross section but having a Cutting Point. Since the cutting point remains within the original wire diameter of the needle, minimal trauma and good penetration are obtained. the body of the needle is flattened to enable a better grip to be obtained with the needle holder.


 

Needles with circular cross section but having the point with four edges giving excellent penetration. The body of the needle is flattened to enable a better grip to be obtained with the needle holder.


 

Needles with circular cross section but having a Cut Taper point. the cut taper is formed by grinding three short cutting edges on a taper point needle. Since the cut taper remains within the original wire diameter of the needle, minimal trauma and good penetration are obtained.


 

Needles with circular cross section but having a Blunt Point that does not cut through the tissue. The body of the needle is flattened to enable a better grip to be obtained with the needle holder.


 

Needles that are flat on the inside & outside curvature to enable ease of penetration between scleral or corneal tissue. these are used in ophthalmology.


 

These are Squared Bodied needles primarily intended for cardiovascular applications. The square bodied geometry combined with the newly improved 300 series steel alloy significantly improves the bending resistance of these needles. The flattened body of the needle is enable a better grip to be obtained with the needle holder.