Sutures

Question 1

Suture

Answer 1

• a strand of material that is used to ligate blood vessels or approximate tissue

Question 2

History of sutures/needles

Answer 2

• traced back centuries
• Egyptians documented using silk, cotton, horsehair, and animal tendons/intestines
• needles have similar long history that has led to evolved designs
• absorbable sutures introduced in the early 1970’s

Question 3

What is the suture device composed of?

Answer 3

1) the suture strand
2) the surgical needle
3) the packaging material used to protect both of these

Question 4

Suture packaging

Answer 4

• non-absorbable sutures are placed in Tyvek packaging
• absorbable sutures are packed in sealed foil (Hermetic seal) to maintain a sterile, gas/moisture resistant barrier

Question 5

Suture Needle

Answer 5

• supplied attached to the suture material, either through crimping to the end of the strand or using adhesive
• different needle points: tapered (for tissues easy to penetrate like blood vessels), conventional cutting (penetrating tough tissue like skin), reverse cutting (reduced risk of cutting through tissue, eye surgery)
• inert (stainless steel), slim and strong, sharp, balance of rigidness and ductility, and corrosion resistant

Question 6

Suture materials

Answer 6

• natural, synthetic, and metallic
• suture size from 7 (largest) to 11-0 (smallest)
• most are between 6 and 2
• size 0 and smaller, the number of 0s in description increases as the diameter decreases (00 = 2-0)
• use lowest size possible that still supports the wound, minimizing trauma and mass of foreign material left in the body

Question 7

Synthetic suture fabrication

Answer 7

• melt extruded or gel spun for fiber formation, then oriented (extrudate is heated and drawn to reduce fiber size and align chains)
• mono- or braided multifilament
• heat treated to anneal the material, then surface coated to increase lubricity, reduce capillarity (??), and maybe add antimicrobial agents

Question 8

Monofilament vs. Braided multifilament

Answer 8

• monofilament strands exhibit lower tissue drag
• multifilament have more compliance and physical resilience to damage (but can also have void spaces that harbor bacteria)

Question 9

Absorbable Natural Suture Material

Answer 9

• surgical gut sutures derived from bovine intestines, based on collagen (formaldehyde treated, ground/polished, if treated with chromium salts increases functionality from 1-2 weeks to 2-3 weeks)
• tend to fray at tie points, can be inconsistent in performance
• long history of use and less costly

Question 10

Non-adsorbable natural suture materials

Answer 10

• silk: protein fiber derived from silkworm cocoon, braided to make thread and coated, not absorbable but does degrade
• cotton: composed of cellulose, twisted multifilament with wax coating, not as strong and not absorbable

Question 11

Non-adsorbable synthetic suture materials

Answer 11

• polyester: PET (most common) and PBT, extruded multifilament fiber that is braided and coated
• nylon: nylon 6 and 6,6 (slightly softer) are used with similar mechanical properties, either braided or monofilament, lose strength due to hydrolysis
• polypropylene: isotactic for crystallization, low immune response, good for monofilament but hard to tie
• UHMWP: very strong, crystalline, can use smaller diameters, gel spinning, inherent lubricity can cause creep/slippage
• stainless steel: surgical procedures, very strong but prone to kinks

Question 12

Absorbable synthetic suture materials

Answer 12

• polymerized from hard/soft segment monomers
• hard: PG, PL, p-dioxane are major constituents
• soft: TMC, CI, PEG are minor constituents alter material properties
• degrade by hydrolysis via ester groups
• rate of degrading: glycolide > dioxane > lactide-based
• PEG imparts degree of swellability

Question 13

Coatings

Answer 13

• primary purpose is to reduce tissue drag/prevent fraying
• fill void spaces and can carry antimicrobial agents
• silicone/PTFE based for non-adsorbable sutures
• polyurethanes, PEG, caprolactone, lactide/glycolide copolymers for absorbable sutures
• alternatives to sutures include staples, tapes, clips, sealants/adhesives