Thursday, June 7, 2007

Suture

It's not "Silver Threads and Golden Needles" used to repair a laceration. Nor is it these lovely threads from my sewing room at home. When I was in medical school (having used a needle and thread since age 5 yr) I often slipped and called suture thread. I thought it was an honest miss-speak as we "threaded" those Keith needles. My superiors (residents and staff) did not, and always corrected me. Suture, not thread, is used to repair lacerations.

Suture varies in characteristic---tensile strength, ease of handling, inflammatory response elicited, contribution to infection, knot security, and re sorption (only in absorbables). Suture may be absorbable or nonabsorbable. It may be monofilament or multistrand (twisted or braided together).

Absorbable--biologically derived:
Plain Catgut is derived from sheep or cattle bowel intima. It's has a tensile strength for only 4-5 days, and wound security is almost gone by 2 weeks. It has a moderate-to-high tissue reactivity. It glides poorly through tissue and requires multiple square knots to prevent the knot from unraveling. It is primarily used when tissue healing is rapid and there is minimal tension on the wound or when suture removal will be difficult (children).
Chromic Catgut has good tensile strength for up to 3 weeks. It is more reactive than catgut, so is most often sued for suturing mucosal surfaces (inside the mouth). There its added strength outweighs the increased tissue inflammation, and the scars are not visible.

Absorbable--Synthetic--Monofilament
Monocryl has excellent pliability for easy handling and tying. It is virtually inert in tissue (minimal to none tissue reactivity). It has predictable adsorption. At 1 week, 50% of the initial strength remains; at 2 weeks, 30% remains; and all the original suture strength is lost by 3 weeks. Absorption is essentially complete in approximately 3 months.
PDS (polydioxanone surgical) keeps its tensile strength longer. At 2 weeks, 75% of the initial strength remains; at 4 weeks, 60% remains; and at 6 weeks, 40% remains. Complete absorption occurs in 6 months. As a monofilament, PDS has less tendency to harbor bacteria. It has some intrinsic stiffness and a prolonged memory which some find difficult to handle during surgery.

Absorbable--Synthetic--Multistrand
Vicryl comes in dyes (purple) and un-dyed (white). It is braided. It has a lubricant coating which gives it excellent handling and smooth tie-down qualities. Its tensile strength retention at 2 weeks is 75% and less than 25% at 4 weeks. Complete absorption is between 2 - 3 months. It has low elasticity which predisposes it to cutting through soft pliable tissue if care is not taken ("approximate, don't strangulate"). It is most appropriate for buried intradermal or deep suturing. If placed too close to the surface of a cutaneous wound, Vicryl may be extruded (or spit) before dissolving completely.
Dexon is know for its excellent tensile and knot strengths. Also for delayed absorption and tissue reactivity when compared to catgut. Its tensile strength at 2 weeks is 20% and at 4 weeks on 5%. Complete adsorption occurs after 3-4 months.
Maxon has the excellent tensile strength retention. At 2 weeks its tensile strength is 80%, at 4 weeks 60%, and at 6 weeks 30%. Complete absorption takes place in 6-7 months.

Nonabsorbable--Natural
Silk is made of natural protein filaments spun by the silkworm, usually black (though can be white), and is braided. Possibly the easiest suture to handle (Isn't that true with silk thread too. And silk thread blends in so beautifully when appliquing!). It has the lowest tensile strength of all the sutures mentioned here. Even though it is classified as nonabsorbable, it losses most of its tensile strength in about 1 year and cannot be detected in tissue after 2 years. It results in more tissue reaction than any other suture material except catgut. Because of its increased tendency toward fluid absorption and capillarity, its use is undesirable in areas prone to infection.

Nonabsorbable--Synthetic
Nylon has a high tensile and minimal tissue reactivity. Its prominent memory is its main disadvantage, making it important to throw 3 plus square knots to hold the stitch in place. Although classified as a nonabsorbable, it partially degraded in vivo (in the body). It has only 90% of its tensile strength at 1 year, and only 70% at 2 years.
Prolene/Surgilene (polypropylene) is extremely inert. It expands when stretched (as with wound swelling postoperatively or injury) and helps prevent strangulation of tissue. It is extremely smooth and knot security requires extra throws (square knots) to compensate.
Ethibond/Mersilene (braided polyester) has greater tensile strength than most synthetic nonabsorbale sutures and has improved handling and knot-security qualities.
Wire sutures are stainless steel (so still no silver thread). They are available in monofilament or multistrand, and are seldom used except in sternal (breast bone) closure or tendon repair.

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