Nonabsorbable Surgical Suture

This article is compiled based on the United States Pharmacopeia (USP) – 2025 Edition

Issued and maintained by the United States Pharmacopeial Convention (USP)

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1 DEFINITION

Nonabsorbable Surgical Suture is a flexible strand of material that is not absorbed in 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 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 may be 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. It may be colored by a color additive approved by the FDA.

Nonabsorbable Surgical Suture is classed and typed as follows. Class I Suture is composed of silk or synthetic fibers of monofilament, 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.

2 SPECIFIC TESTS

[Note-If the Suture is packaged with a fluid, make the required measurements for the first four of the following tests within 2 min after removing it from the fluid.]

2.1 Length

Sample: A length of Suture

Analysis: Lay the Sample out smooth and without tension on a plane surface and determine the length of the Sample.

Acceptance criteria: The length of each strand is NLT 95.0% of the length stated on the label.

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2.1.1 Sutures-Diameter 〈861〉

Sample: 10 strands of Suture

Analysis: Determine the diameter as directed in the chapter.

Acceptance criteria: The average diameter on the 10-strand Sample is within the limits on average diameter (for all 30 measurements) in Table 1 for the size stated on the label. None of the observed individual measurements should be less than or greater than the limits on individual diameter in Table 1.

Table 1. Average Knot-Pull Limits of Various Sizes and Diameters of Sutures

ᵃ The tensile strength of sizes smaller than USP size 8-0 (metric size 0.4) is measured by straight pull. The tensile strength of sizes larger than USP size 2-0 (metric size 3) of monofilament Class III (metallic) Nonabsorbable Surgical Suture is measured by straight pull. Silver wire (silver-coated fabric) meets the tensile strength values of Class I Sutures but is tested in the same manner as Class III Sutures.

ᵇ The limits on knot-pull tensile strength apply to Nonabsorbable Surgical Suture that has been sterilized. For nonsterile Sutures of Class I and Class II, the limits are 25% higher.

ᶜ To convert from N to kg, divide N by 1.0197 and round to one significant figure.

ᵈ USP sizes may not represent all sizes commercially available. For sizes other than those listed in the table, suture manufacturers must generate appropriate diameters and tensile strength data to support use.

2.2 Tensile Strength 〈881〉, Surgical Suture

Sample: NLT 10 strands of Suture

Analysis: Determine the tensile strength of the Sample as directed in the chapter. Average all observations obtained.

Acceptance criteria: The average tensile strength is NLT that set forth in Table 1 for the class and the size stated on the label.

2.2.1 Sutures-Needle Attachment 〈871〉: Suture on which eyeless needles are swaged meets the requirements.

2.2.2 Sterility Tests 〈71〉

Suture that is claimed to be sterile meets the requirements.

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2.3 Extractable Color (if Suture is dyed)

Matching solutions: Prepare by combining the colorimetric solutions (CS) in the proportions indicated in Table 2, and adding water, if necessary, to make 10.0 parts. [See Reagents, Indicators, and Solutions-Solutions, Colorimetric Solutions (CS) for composition.]

Table 2. Matching Solutions

Sample: NLT 250 mg of Suture

Analysis: Place the Sample in a conical flask containing 1.0 mL of water for each 10 mg of the Sample. For microsutures use 2.5 mL of water for each 25 mg of the Sample. Cover the flask with a short-stemmed funnel, heat the contents of the flask at the boiling point for 15 min, cool, and restore the volume by the addition of water, if necessary, to replace that lost by evaporation. Decant the water from the Suture, and compare it with the Matching solution. Where fibrous extraneous material may affect the color, filter the solution before performing the color determination.

Acceptance criteria: Any color present is not more intense than that of the appropriate Matching solution.

3 ADDITIONAL REQUIREMENTS

Packaging and Storage: Preserve nonsterilized Suture in well-closed containers. Preserve sterile Suture dry or in fluid, in containers (packets) so designed that sterility is maintained until the container is opened. A number of such containers may be placed in a box.

Labeling: The label of each individual container (packet) of Suture indicates the material from which the Suture is made, the size, construction, and length of the Suture, whether it is sterile or nonsterile, kind of needle (if a needle is included), number of sutures (if multiple), lot number, and name of the manufacturer or distributor. If removable needles are used, the labeling so indicates. Suture size is designated by the metric size (gauge number) and the corresponding USP size. The label of the box indicates also the address of the manufacturer, packer or distributor, and the composition of any packaging fluids used.