Sutures are strands of material used to approximate tissue during wound healing. They consist of needles and suture material. Needles are traditionally made of stainless steel alloys while suture material can be natural (silk, catgut) or synthetic (polypropylene, polyglycolic acid). Sutures are classified based on absorbability, fiber construction (monofilament, multifilament), and origin (natural, synthetic). Key properties include tensile strength, absorption rate, and tissue reaction. The ideal suture elicits minimal reaction while maintaining strength for adequate healing. Future development focuses on antimicrobial and rapidly absorbing sutures.

1. Sutures

2. 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. Needle
2. Suture material

3. 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

4. The Needle…
Source: Suture Technical Specifications, Demetech (http://www.demetech.us/suture-specs.php)

5. Classifying Suture Material…
Natural
Origin
Synthetic
Absorbable
Sutures Absorption
Nonabsorbabl
e
Multifilament
Fiber
construction
Monofilament
Source: Ratner et al. 2004

6. Classifying Suture Material…
Vicryl Silk
Synthetic, Absorbable Natural, non-absorbable

7. Classifying Suture Material…
Fiber construction
Source: Suture Technical Specifications, Demetech (http://www.demetech.us/suture-specs.php)

8. Classifying Suture Material…
Suture Types Generic Structure Classification Representative
Product/Brand
Catgut Collagen from animal Natural, absorbable, twisted Surgical Gut,
intestines multifilament (mono.) Chromic Gut
Silk Fibroin from silkworm Natural, non-absorbable, Perma-Head,
Bombyx mori braid multifilament Softsilk
Polypropylene Isotactic crystalline Synthetic, non-absorbable, Prolene, Surgipro
stereoisomer of PP monofilament
Polyamide Nylon 6 and nylon 6,6 Synthetic, non-absorbable, Ethilon, Dermalon
monofilament
Stainless steel 316L (low carbon) stainless Metal, non-absorbable, Ethisteel, Flexon
steel alloy mono and multifilament
Polyglycolic acid/ 90% PGA, 10% PLA Synthetic, absorbable, Vicryl, Vicryl
Polylactic acid braided multifilament Rapide
Polydioxanone Polyester p-dioxanone Synthetic, absorbable, PDS II
monofilament
Polyglycolic acid/ Copolymer of glycolic acid Synthetic, absorbable, Maxon
Polytrimethylene and trimethylene carbonate monofilament
carbonate
Source: Ratner et al. 2004

9. 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

10. Properties of Suture Material…
Properties
Physical Handling Biological
Knot-tie down, First Tissue
Tensile Strength,
throw hold, Tissue reaction, Absorptio
Dimension, Knot-
drag, Package n, Biocompatibility,
pull strength, Knot
memory, Tensile strength
security, Stiffness
Suppleness loss
• All standards, test procedures and product specifications are set by U.S.
Pharmacopeia (U.S.P.)

11. 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: Collagen: USP Synthetic: Collagen:
Diameter Diameter Diameter Diameter
(mm) (mm) (mm) (mm)
11-0 0.01 – 0.019 3-0 0.2 – 0.249 0.3 – 0.349
10-0 0.02 – 0.029 2-0 0.3 – 0.349 0.35 – 0.399
9-0 0.03 – 0.039 0.04 – 0.049 0 0.35 – 0.399 0.4 – 0.499
8-0 0.04 – 0.049 0.05 – 0.069 1 0.4 – 0.499 0.5 – 0.599
7-0 0.05 – 0.069 0.07 – 0.099 2 0.5 – 0.599 0.6 – 0.699
6-0 0.07 – 0.099 0.1 – 0.149 3 0.6 – 0.699 0.7 – 0.799
4 0.8 – 0.899
5-0 0.1 – 0.149 0.15 – 0.199
5 0.70 – 0.799
4-0 0.15 – 0.199 0.2 – 0.249
Source: US Pharmacopeia (http://www.pharmacopeia.cn/v29240/usp29nf24s0_m80190.html)

12. 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* USP Synthetic Collagen*
11-0 3-0 17.4 12.2
10-0 0.24 2-0 26.3 19.6
9-0 0.49 0 38.2 27.2
8-0 0.69 0.44 1 49.8 37.3
7-0 1.37 0.69 2 62.3 44.2
6-0 2.45 1.76 3 71.5 57.8
5-0 6.67 3.73
4 68.6
4-0 9.32 7.55
*Based on limit on average minimum
Source: US Pharmacopeia (http://www.pharmacopeia.cn/v29240/usp29nf24s0_m80190.html)

13. Properties: Tensile Strength Loss…
• The loss of tensile strength as a function of time (Ratner et al.
2004)
Source: Ratner et al. 2004

14. Properties: Absorption…
• Enzymatic and/pr hydrolytic breakdown of a strand followed
by elimination (Ratner et al. 2004)
Source: Ratner et al. 2004

15. 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)
PE
PET
PET
PGA/PLLA
Source: Najibi et al. 2001

16. Properties: In summary…
• Knot security: Force that a knot can withstand before slipping or untying
(Ratner et al. 2004)
Suture Types Knot pull Knot Handling Tissue In vivo strength
strength security reactivity loss
Catgut Poor Poor (plain) Fair High 7-10 days (plain),
Fair 21-28 days
(chromic) (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

17. Wound Healing…
Usually clean,
Primary Intention uninfected, surgical
wound
Wound healing
Cell or tissue loss
more extensive due to
Secondary Intention
injury, malignancy or
infection
Source: Dunn 2007

18. Interaction with Biological System + Host Reaction
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

19. Interaction with Biological System + Host Reaction
Grades of Tissue Reaction
(Source: Postlethwait et al. 1975)
GlOD, Gut 10 days, G19D, Gut 19 days, GIl Y, Gut 11 years,
gastroenterostomy. subcuitaneotus. vaginal cuff closure.
Essentially no Absorption beginning, No absorption or
mainly by monocytes. reaction.
reaction.
Serrations at edges and
one cleft in suture.

20. 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

21. Interaction with Biological System + Host Reaction
Let’s Recap on the Biological Properties
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
Source: Ratner et al. 2004

22. 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

23. 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:
INNOVATION
• Vicryl Plus (contains triclosan or 5-
chloro-2-(2,4-dichlorophenoxy)phenol) PROSPECT
• More commercialized non-suture products DEMAND
like tissue sealant made of fibrin glue
Source: Ratner et al. 2004

24. References
1. 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