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Sutures
Briefly…
Definition of suture:1. A strand of material that is used to approximate tissues or to ligate blood
vessels during the wound-healing period (Ratner et al. 2004).2. A stitch or row of stitches holding together the edges of a wound or
surgical incision (Oxford Dictionary).
Tools:1. Needle2. Suture material
The Needle…• Traditionally used stainless steel alloys 300 and 420• Modern needle uses 455 for superior properties (Ratner et.al. 2004)
Chemical Composition 420 300 455
Fe Majority Majority 73%
C < 0.15% < 0.08% < 0.05%
Cr 12 – 14% 17.5 – 20% 11.8%
Ni 8 – 11% 8.5%
Cu, Nb, Ti 2, 2, 1.1 %
Mn < 1% < 2% < 0.5%
Si < 1% < 1% < 0.5%
P < 0.04% < 0.045% < 0.004%
S > 0.03% < 0.03 % < 0.03%
Density (kg/m3) 7750 8000 7800
Elastic Modulus (Gpa) 200 193 200
Specific Heat (J/kg.K) 460 500 N/A
Tensile Strength (Mpa) 655 205 965
Source: Azom.com
The Needle…
Source: Suture Technical Specifications, Demetech (http://www.demetech.us/suture-specs.php)
Classifying Suture Material…
Sutures
Origin
Natural
Synthetic
Absorption
Absorbable
Nonabsorbable
Fiber construction
Multifilament
Monofilament
Source: Ratner et al. 2004
SilkNatural, non-absorbable
VicrylSynthetic, Absorbable
Classifying Suture Material…
Classifying Suture Material…
Fiber construction
Source: Suture Technical Specifications, Demetech (http://www.demetech.us/suture-specs.php)
Classifying Suture Material…Suture Types Generic Structure Classification Representative
Product/BrandCatgut Collagen from animal
intestinesNatural, absorbable, twisted multifilament (mono.)
Surgical Gut, Chromic Gut
Silk Fibroin from silkworm Bombyx mori
Natural, non-absorbable, braid multifilament
Perma-Head, Softsilk
Polypropylene Isotactic crystalline stereoisomer of PP
Synthetic, non-absorbable, monofilament
Prolene, Surgipro
Polyamide Nylon 6 and nylon 6,6 Synthetic, non-absorbable, monofilament
Ethilon, Dermalon
Stainless steel 316L (low carbon) stainless steel alloy
Metal, non-absorbable, mono and multifilament
Ethisteel, Flexon
Polyglycolic acid/ Polylactic acid
90% PGA, 10% PLA Synthetic, absorbable, braided multifilament
Vicryl, Vicryl Rapide
Polydioxanone Polyester p-dioxanone Synthetic, absorbable, monofilament
PDS II
Polyglycolic acid/ Polytrimethylene carbonate
Copolymer of glycolic acid and trimethylene carbonate
Synthetic, absorbable, monofilament
Maxon
Source: Ratner et al. 2004
A Truly, Ideal Suture Material?
Does Not Exist, BUT…
Sterile, highly uniform tensile strength, predictable performance, non-capillary, non-allergic, easy to
handle, minimal tissue reaction, absorbed completely
Properties of Suture Material…
Properties
Physical
Tensile Strength, Dimension, Knot-pull
strength, Knot security, Stiffness
Handling
Knot-tie down, First throw hold, Tissue
drag, Package memory, Suppleness
Biological
Tissue reaction, Absorption,
Biocompatibility, Tensile strength loss
• All standards, test procedures and product specifications are set by U.S. Pharmacopeia (U.S.P.)
Properties: Size and Dimension• Smallest diameter possible to minimize the amount of
material drawn on tissue• Size ranges from #5 (largest) to #11-0 (smallest)
USP Synthetic: Diameter (mm)
Collagen: Diameter (mm)
11-0 0.01 – 0.019
10-0 0.02 – 0.029
9-0 0.03 – 0.039 0.04 – 0.049
8-0 0.04 – 0.049 0.05 – 0.069
7-0 0.05 – 0.069 0.07 – 0.099
6-0 0.07 – 0.099 0.1 – 0.149
5-0 0.1 – 0.149 0.15 – 0.199
4-0 0.15 – 0.199 0.2 – 0.249
USP Synthetic: Diameter (mm)
Collagen: Diameter (mm)
3-0 0.2 – 0.249 0.3 – 0.349
2-0 0.3 – 0.349 0.35 – 0.399
0 0.35 – 0.399 0.4 – 0.499
1 0.4 – 0.499 0.5 – 0.599
2 0.5 – 0.599 0.6 – 0.699
3 0.6 – 0.699 0.7 – 0.799
4 0.8 – 0.899
5 0.70 – 0.799
Source: US Pharmacopeia (http://www.pharmacopeia.cn/v29240/usp29nf24s0_m80190.html)
Properties: Knot pull tensile strength• Maximum tensile stress that can be applied on the ears of a
knot (Ratner et al. 2004)• The larger the diameter, the higher the knot pull tensile
strentgh
USP Synthetic Collagen*
11-0
10-0 0.24
9-0 0.49
8-0 0.69 0.44
7-0 1.37 0.69
6-0 2.45 1.76
5-0 6.67 3.73
4-0 9.32 7.55
USP Synthetic Collagen*
3-0 17.4 12.2
2-0 26.3 19.6
0 38.2 27.2
1 49.8 37.3
2 62.3 44.2
3 71.5 57.8
4 68.6
*Based on limit on average minimumSource: US Pharmacopeia (http://www.pharmacopeia.cn/v29240/usp29nf24s0_m80190.html)
Properties: Tensile Strength Loss…• The loss of tensile strength as a function of time (Ratner et al.
2004)
Source: Ratner et al. 2004
Properties: Absorption…• Enzymatic and/pr hydrolytic breakdown of a strand followed
by elimination (Ratner et al. 2004)
Source: Ratner et al. 2004
Properties: Strain, Stiffness• Strain: Ratio of the change in length of a material to the initial
unstressed reference length (Helmenstine 2012)• Stiffness: Resistance of an elastic body to deflection or deformation by
an applied force (Engineering Toolbox)
Source: Najibi et al. 2001
PE
PET
PGA/PLLA
PET
Properties: In summary…
Suture Types Knot pull strength
Knot security
Handling Tissue reactivity
In vivo strength loss
Catgut Poor Poor (plain)Fair (chromic)
Fair High 7-10 days (plain), 21-28 days (chromic)
Silk Fair Good Very good High 1 year
Polypropylene Fair Poor Poor Low Indefinite
Polyamide Fair Fair Good Low 1.5 – 2.5% /year
Stainless steel High Good Poor Low Indefinite
PGA/PLLA Good Fair -good Good Low 10 days – 4 weeks
Polydioxanone Fair -good Poor-fair Fair-good Low 10 days – 6 weeks
Source: Ratner et al. 2004
• Knot security: Force that a knot can withstand before slipping or untying (Ratner et al. 2004)
Wound Healing…Wound healing
Primary Intention
Usually clean, uninfected, surgical wound
Secondary Intention
Cell or tissue loss more extensive due to injury, malignancy or infection
Source: Dunn 2007
Tissue Reaction• Immune system considers all suture threads to be foreign bodies• Inflammatory response occurs is similar to any reaction towards
foreign body• Reaction depends on the type of suture, texture, degree of tissue
trauma and length of implantation (Braun & Aesculap t.th)
(Postlethwait et al. 1975):• Catgut >> encourage formation of thin connective tissue, histiocytes
and lymphocytes and cellular infiltrations >> complete absorption leaves
• Silk >> formation of fibrous tissue capsule with variety of giant cells presence, with latter invasion of histiocytes and fibtoblasts
• Nylon >> narrow fibrous tissue zone, least reaction seen
Interaction with Biological System + Host Reaction
(Source: Postlethwait et al. 1975)
Interaction with Biological System + Host Reaction
GIl Y, Gut 11 years, vaginal cuff closure. No absorption or reaction.
GlOD, Gut 10 days, gastroenterostomy. Essentially no reaction.
G19D, Gut 19 days, subcuitaneotus. Absorption beginning, mainly by monocytes. Serrations at edges and one cleft in suture.
Grades of Tissue Reaction
Interaction with Biological System + Host Reaction
Coated Vicryl Rapid ®, 7 days, presence of multinucleated giant cells between filaments of suture
SEM of Coated Vicryl Rapid ®, Series of absorption occurs (A) implantation (B) 7 days post and (C) 14 days post.
Source: Andrade & Weissman 2005
Suture Types Tissue reactivity In vivo strength loss
Catgut High 7-10 days (plain), 21-28 days (chromic)
Silk High 1 year
Polypropylene Low Indefinite
Polyamide Low 1.5 – 2.5% /year
Stainless steel Low Indefinite
PGA/PLLA Low 10 days – 4 weeks
Polydioxanone Low 10 days – 6 weeks
Let’s Recap on the Biological Properties
Interaction with Biological System + Host Reaction
Source: Ratner et al. 2004
Risks & Side Effects…
1. Suture knot slipping• Inability of the suture to retain until wound healing complete• Common in absorbable suture
2. Re-infection• Site for microbial growth causing re-infection• the need for suture with antimicrobial activity
3. Failure of wound healing• Improper suturing technique does not allow collagen formation
Future Development• Limited to products that can demonstrate a
performance benefit due to cost-constrained market
• Continue development of multifilament braid coatings to provide the best suture possible
• Need to have an ideal absorbable suture should only degrades rapidly following loss of tensile strength
• Development of more suture with antimicrobial properties:• Vicryl Plus (contains triclosan or 5-
chloro-2-(2,4-dichlorophenoxy)phenol)• More commercialized non-suture products
like tissue sealant made of fibrin glue
INNOVATION
PROSPECT
DEMAND
Source: Ratner et al. 2004
References1. Andrade, M.G.S. & Weissman, R. 2005. Tissue Reaction and Surface Morphology of
Absorbable Sutures after In Vivo Exposure. Journal of Material Science: Material Medicine 17:949-961.
2. Braun & Aesculap. 2006. Suture Glossary.http://www.themonofilamentadvantage.com/documents/Training/Glossary_Sutures_neu.pdf
3. Chrimax. 2001. Non-absrobable Materials: Reaction in Tissue. http://www.chirmax.cz/chirmax_multi/index.php?stranka_id=21&jazyk=3j
4. Dunn, D.L. 2007. Wound Closure Manual. Johnson & Johnson. http://surgery.uthscsa.edu/pediatric/training/woundclosuremanual.pdf
5. Engineering Toolbox. 2012. Stiffness. http://www.engineeringtoolbox.com/stiffness-d_1396.html
6. Helmenstine, A.M. 2012. Strain. About.com Chemistry. http://chemistry.about.com/od/engineeringglossary/g/strain-definition.htm
7. Najibi, S., Banglmeier, R., Matta, J.M. & Tannast, M. 2001. Material Properties of Common Suture Materials in Orthopaedic Surgery. The Iowa Orthopaedic Journal 30:84-88.
8. Postlethwait, R.W., Willigan, D.A. & Ulin, A.W. 1975. Human Tissue Reaction to Sutures. Annals of Surgery 181(2):144-150
9. Ratner, B.D., Hoffman, A.S., Schoen, F.J. & Lemons, J.E. 2004. Surface Properties and Surface Characterization of Materials. Biomaterial Science: An Introduction to Material in Medicine. 2nd Edition. San Diego: Elsevier
10. Salhan, S & Dass, A. 2012. Textbook of Gynecology. New Delhi: Jaypee Brothers Medical.11. US Pharmacopeia. http://www.pharmacopeia.cn/v29240/usp29nf24s0_m80190.html