1. Sutures, staples, and adhesives
Wound Closure
Sutures, staples, and adhesives
Some material taken from

2. Historical Background – Sutures
Use of textiles goes back at least 4000 years
Linen (earliest)
Other
Fe wire, Au, Ag, dried gut, horse hair, strips of hide, bark fibers, silk, and tendon
Up until 1930, catgut and silk
Stainless wire and polymers (nylon, polyester, polypropylene) during and after WW II
1970s Dexron® (polyglycolic acid) and Vicryl® (polyglactic acid) resorbable
Controlled degradation

3. The “Ideal” Suture Material
Universal applicability – only difference in diameter
Limp – easy to handle, no kinks, coiling, twisting, or levitating
Biocompatible
Inert
Strong
Frictionless surface to glide through tissue
High friction for secure knotting
Sterlizable without composition changes
Complete absorption, no residue, after healing is complete – no matter how long it takes

4. Suture Classification
Physical/Mechanical
Handling
Biocompatibility
Biodegradation
Size (diameter)
Number of Filaments
Tensile strength and elongation
Elastic modulus
Bending stiffness
Stress relaxation and creep
Capillarity
Swelling
Coefficient of friction
Pliability
Packaging memory
Knot tie-down
Knot slippage
Tissue drag
Inflammatory reaction
Propensity toward wound infection, thrombi formation, carcinogenicity, and allergy
Tensile breaking strength and mass loss
Biocompatibility of degradation properties

5. Absorbability
Lose 50% of breaking strength within 60 days of implanting
Monofilament, braided, or twisted
Natural or synthetic
Natural – enzymatic attack
Synthetic – hydrolysis
More stable mechanism
Rapidity commonly rated as percentage of breaking strength – breaking strength rate (BSR)
Can be modified in synthetic sutures

6. BSRs for Some Absorbable Sutures
Natural Fiber
Synthetic Fiber
BSR
Monofilament
Poly(glycolide-co-ε-caprolactone) (Monocryl)*
Poly(p-diaxonone) (PDS II)*
Poly(glycolide co-trimethylene carbonate) (Maxon)+ 7 35
Braided
Polyglactin 910 (Vicryl)*
Polyglactin 910 (Vicryl Rapide)*
Polyglycolic acid (Dexon)+ 15 5 12
Twisted
Plain Surgical Gut
Light Surgical Gut
Medium Surgical Gut
Heavy Surgical Gut
BSR = Approximate days after placement when 50% of breaking strength remains. *Ethicon Inc., +Davis & Geck Inc.

7. Nonabsorbable
Retain majority of breaking strength for more than 60 days
Three classes
Class I – silk, monofilament, and sheathed
Class II – cotton and linen
Class III – metallics
Classes I and III most common as Class II are prone to contamination and infection

8. Common Nonabsorbable Sutures
Monofilament
Polypropylene (Prolene* & Surgilene+)
Nylon (Ethilon* & Dermalon+)
Braided
Polyester (Mersilene*)
Silk
Nylon (Surgilon* & Nurolon+)
Braided & Coated
Polyester & Polybuterate (Ethibond*)
Polyester & Silicone (Tichron+)
Polyester & Teflon (Tevdek#)
Silk & Beeswax
Multifilament Sheathed
Multistrand Nylon & Polyethylene Sheath (Supramid$)
*Ethicon Inc., +Davis & Geck Inc., #Deknatel Inc., $S. Jackson Inc.

9. Suture Sizes – Two Systems
United States Pharmacopœia (USP)
Complex relationship between diameter, tensile strength, and knot security
Precise criteria vary with suture class, natural or synthetic, and absorbability
Whole numbers from 5 to 12-0
Allows comparison among different types
European
Diameter in mm
Differences in tensile strength of materials make comparisons difficult
Sutures function best when their strength and tissue strength are similar.

10. Examples of Suture Sizes for Use in Pet Animals
Suture Sizes/Use
Examples of Suture Sizes for Use in Pet Animals
1 - 2
Microvascular
Corneal
Ophthalmic
Neural
Vascular
Skin & Subcutis
Bowel
Bladder
Abdominal Fascia
Stomach
Hernia
Rib Retention
Cutaneous Stents
Increase or decrease abdominal fascia and retention sutures appropriately based on weight & suture pattern

11. Tensile Strength of Sutures
Dependent upon
Material
Size/diameter
Condition
Wet
Dry
Knotted
Absorption of bodily fluids
Hydrophobic
Hydrophilic
“Abuse”
Heat history – “re-autoclaving”

12. Knot Strength vs. Tensile Strength
Strength of a knotted suture generally significantly less than strength of a straight yarn (~ 50%)
Knotting induces stresses in the suture due to bending and twisting
As knotted suture pulled compressive stress develops increasing residual stress and lowering overall strength values

13. Sizes and Breaking Strengths of Dry 2-0 and 3-0 Sutures
Straight Pull
Knotted Pull
Dia. inches
No. 3-0
No. 2-0
3-0
2-0
lbs.
psi.
Surgical Gut Dexon Vicryl PDS II Maxon
Silk Cotton Polypropylene Nylon Polyester

14. Coating Materials Facilitate handling Nonabsorbable coatings
Ease of passing through tissue
Ease in sliding knots down
But can result in poor knot security
Nonabsorbable coatings
Beeswax
Silicone
Paraffin wax
Poly(tetrafluoroethylene)
Absorbable
Must be absorbable like the suture
Water soluble
Water insoluble – break down by hydrolysis

15. Problems Associated with Surgical Sutures
Time-consuming nature of secure knot tying
Need for knot security under all conditions with all sutures
Risk of suture breakage during surgery
Loss of control due to needle slippage or rotation within the needle holder
Postsurgical slippage of the knotted suture
Early or pathologically induced degradation of absorbable suture

16. Ligating Clips
Essentially “clips” to replace sutures when occluding (closing) the lumen (central canal) of a vessel or tubular organ
Blood vessels
Gynecological & urological (GU) procedures
Metallic or polymeric
Requirements
Nontoxic and biocompatible
Absence of allergic and immunogenic effects
Tolerated by wide range of tissue types
High strength and low solubility
Finite longevity
Secure

17. Metallic Clips First – Cushing neurosurgery clip, 1910
Ag wire formed in the shape of a “U” and closed around blood vessel
Tantulum (1940)
Tubule ligation
Others
Co-Cr
Titanium
Stainless Steel
“Memory metal” – Ni-Ti alloy
Desirable properties in metallic clips
High strength
Malleability & ductility – can make fine wire
Capacity for work-hardening
Corrosion resistance
Some problems
Allergic reaction
Radio-opaque – can cause problems with CT, X-ray, and MRI examinations

18. Polymeric Clips Absorbable and non-absorbable Viscoelastic Creep
Stress-relaxation

19. Surgical Stapling Introduced in the late 1970s
Used widely in human and veterinary medicine
Gynecological
Cardiovascular
Gastrointestinal
Esophageal
Pulmonary
Staples originally stainless but now Ti and polymeric used
Polymeric – 2 parts
“U”-shaped fastener
Figure “8” retainer

20. Surgical Staples
Staple
Staple Gun
Staple Remover

21. Staples & Clips vs. Sutures
Speed
Convenience
Reduced infection rate
Lower cost
If done properly, no cosmetic difference

22. Tissue Adhesives Sterilizable Easy in preparation
Before Curing
After Curing
Sterilizable
Easy in preparation
Viscous liquid or liquid possible for spray
Nontoxic
Rapidly curable under wet physiological conditions (pH 7.3, 37°C, 1 atm)
Reasonable cost
Strongly bondable to tissues
Biostable union until wound healing
Tough and pliable
Resorbable after wound healing
Nontoxic
Nonobstructive to wound healing or promoting wound healing

23. Natural Tissue – Fibrin Glue
First reported in 1940
Mimics blood clot – major component fibrin network
Excellent tissue adhesive but insufficient in amount for larger wounds
Nontoxic if human protein sources are used to obtain fibrin

24. Synthetic Systems: Poly-Alkyl-2-Cyanoacrylates
Discovered in 1951
“Crazy Glue”
H2C=C―CO2―R CN
R = alkyl group
CH3 (methyl)
H3CCH2 (ethyl)
Release small amount of formaldehyde when curing
amount lessens with length of alkyl chain

25. Characteristics of Currently Available Adhesive Systems
Fibrin Glue
Cyanoacrylate
Handling
Excellent
Poor
Set time
Medium
Short
Tissue bonding
Good
Pliability
Toxicity
Low
Resorbability
Cell infiltration

26. Other Experimental Systems
Gelatin-based adhesives
Mimic coagulation but without fibrin
Polyurethane (-HNOCO-) based adhesives
Capped with isocyanate to rapidly gel upon exposure to water
More flexible than current cyanoacrylate adhesives
Collagen-based adhesives