Nonabsorbable Surgical Suture
» Nonabsorbable Surgical Suture 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 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.
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 non-sterile, 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.
note—If the Suture is packaged with a fluid, make the required measurements for the first four of the following tests within 2 minutes after removing it from the fluid.
Length— Determine the length of Suture while the strand is laid out smooth, without tension, on a plane surface: the length of the strand is not less than 95.0% of the length stated on the label.
Diameter— Determine the diameter of 10 strands of Suture as directed under Sutures—Diameter 861. The average diameter of the strands being measured is within the tolerances prescribed in the accompanying table for the size stated on the label. In the case of braided or twisted Suture, none of the observed diameters is less than the midpoint of the range for the next smaller size or is greater than the midpoint of the range for the next larger size.
Tensile strength— Determine the tensile strength on not fewer than 10 strands of Suture as directed for Surgical Sutures under Tensile Strength 881. Average all observations obtained: the average tensile strength is not less than that set forth in the accompanying table for the class and the size stated on the label.
Needle attachment— Suture on which eyeless needles are swaged meets the requirements under Sutures—Needle 871.
Sterility 71: Suture that is claimed to be sterile meets the requirements.
Extractable color (if Suture is dyed)— Proceed as directed in the test for Extractable color under Absorbable Surgical Suture, but instead of allowing to stand at 37 ± 0.5 for 24 hours, cover the flask with a short-stemmed funnel, heat the contents of the flask at the boiling point for 15 minutes, cool, and restore the volume by the addition of water, if necessary, to replace that lost by evaporation.
Average Knot-Pull Limits of Various Sizes and Diameters of Sutures
Limits on
Limits on Average Knot-Pull
(except where otherwise
specified)a Tensile Strength (in kgf)b
Limits on Average Knot-Pull
(except where otherwise
specified)a Tensile Strength (in N)b
USP Size Metric Size (gauge no.) Min. Max. Class I
Class II
Class III
Class I
Class II
Class III
12-0 0.01 0.001 0.009 0.001a 0.002a 0.01a 0.02a
11-0 0.1 0.010 0.019 0.006a 0.005a 0.02a 0.06a 0.05a 0.20a
10-0 0.2 0.020 0.029 0.019a 0.014a 0.06a 0.194a 0.14a 0.59a
9-0 0.3 0.030 0.039 0.043a 0.029a 0.07a 0.424a 0.28a 0.68a
8-0 0.4 0.040 0.049 0.06 0.04 0.11 0.59 0.39 1.08
7-0 0.5 0.050 0.069 0.11 0.06 0.16 1.08 0.59 1.57
6-0 0.7 0.070 0.099 0.20 0.11 0.27 1.96 1.08 2.65
5-0 1 0.10 0.149 0.40 0.23 0.54 3.92 2.26 5.30
4-0 1.5 0.15 0.199 0.60 0.46 0.82 5.88 4.51 8.04
3-0 2 0.20 0.249 0.96 0.66 1.36 9.41 6.47 13.3
2-0 3 0.30 0.339 1.44 1.02 1.80 14.1 10.0 17.6
0 3.5 0.35 0.399 2.16 1.45 3.40a 21.2 14.2 33.3a
1 4 0.40 0.499 2.72 1.81 4.76a 26.7 17.8 46.7a
2 5 0.50 0.599 3.52 2.54 5.90a 34.5 24.9 57.8a
3 and 4 6 0.60 0.699 4.88 3.68 9.11a 47.8 36.1 89.3a
5 7 0.70 0.799 6.16 11.4a 60.4 112a
6 8 0.80 0.899 7.28 13.6a 71.4 133a
7 9 0.90 0.999 9.04 15.9a 88.6 156a
8 10 1.00 1.099 18.2a 178a
9 11 1.100 1.199 20.5a 201a
10 12 1.200 1.299 22.8a 224a
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 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.
Auxiliary Information— Please check for your question in the FAQs before contacting USP.
Topic/Question Contact Expert Committee
Monograph Radhakrishna S Tirumalai, Ph.D.
Senior Scientist
(GTMDB05) General Toxicology and Medical Device Biocompatibility
71 Radhakrishna S Tirumalai, Ph.D.
Senior Scientist
(MSA05) Microbiology and Sterility Assurance
USP32–NF27 Page 3646