About Sutures

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 Pharmacopeia determines 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 detachment load on Universal Ultra Test Machine with microprocessor Digital Advanced Force Gauge.

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.