Chapter 2 Antiseptic and Aseptic Surgery

   

2.1  HISTORICAL:

• - Ligatures came into use before sutures.
• - Celsus recommended ligature in the protocol of control of hemorrhage.
• - Gaten in Second Century recommended silk for sutures.
• - Dr. Philip Physick, in 1806, made absorbable suture from kid & buckskin.
• - Lister advocated the chromic acid impregnation of catgut so as to delay its absorption.
• - Twine, flax, strips of cloth were used for ligation around 1890.
• - In 1911, cushing used silver clips in surgery
• - Stainless steel suture were manufactured in 1934.
• - Synthetic sutures were introduced in 1940’s. 

2.2 DEFINITION:

The term suture may refer to either: 

• - material used to close the wound e.g. gut, silk, PDS, PGA etc.
• - method of use e.g. interrupted or matters. 

2.3 IDEAL SUTURE:

Should be:

• - easy to handle
• - high in tensile strength
• - nonreactive in tissues
• - non - capillary
• - absorbed/dissolved after having served its purpose
• - easy to sterilize
• - high in knot security
• - economical

"There is no ideal suture material, it does not exist"

Hence surgeon must choose a suture based on the characteristics of the suture and the wound e.g. where biological process reduce the sulire strength we may need a thicker suture material, or where we need less reaction we may prefer PGA catgut. 

2.4 GENERAL OBSERVATIONS:

• - The most important consideration in suturing is not the strength of the suture material, but the holding power of the tissues to be sutured.
• - The ability of the tissue to hold sutures depend upon the strength (collagen, elastic, or reticular fibril content) of the tissue, direction of suture pull and orientation of fibers, e.g. muscle have little holding power across its fibers and less in direction of its fibers.
• - Of the soft tissues skin and fascia have the greatest suture holding power and fat the least.
• - Knotting decreases the strength of a suture strand 40% to 50%. Functional strength is equal to dry strength minus the loss resulting from knotting and wetting.
• - A tied suture is about 1/3 stronger than the straight, unknotted strand.
• - Functional strength of a suture line increases in direct proportion to the number of sutures, but only to a certain point, i.e. when placed approximately 0.5 cm apart.
• - Co-efficient of friction closely correlates with knot security. It is highest with monofilament steel and reduces in order in gut, Dacron, cotton, nylon & Teflon coated materials.
• - In buried sutures, the suture end should be cut close to the knot, as long ends are irritating, cause additional separation of tissues and act as foreign material.
• - Knots of skin sutures should be placed on one side of the incision to avoid irritation and separation of wound edges.
• - Ends of skin suture are left 1/3 cm long to facilitate removal.
• - Multifilament and plain gut sutures are unsuitable for use in contaminated wounds.
• - Monofilament suture material is superior to multifilament sutures .
• - Steel has great strength and can remain in body indefinitely without causing tissue reaction. Good for use in infected wounds.
• - Interrupted sutures are superior to continuous suture pattern.
• - Weakest point in a suture is at the knot
• - Chemical byproducts of some materials, e.g. nylon, may inhibit bacterial colonization and infection.
• - The diameter of suture strands has been described by USP method (15-0 thru 7), metric method (#2 suture is .2 mm) & Brown & sharp method (for wire gauge). Metric method is more rational.
• - Medium chromic gut, also called Type C with tensile strength half life of 20 days is the most widely used of all suture materials.
• - Suture strength is critical in the early healing period of all surgical wounds.
• - Suture is a non-inert foreign body capable of inducing inflammatory response associated with edema & weakening of surgical closure. Hence suture materials that cause least tissue reaction (polypropylene & stainless steel) are desirable. 

2.5 CLASSIFICATION:

2.5.1 ABSORBABLE SUTURES OF NATURAL ORIGIN:

2.5.1.1 Surgical Gut (catgut)

• - Comprised of formaldehyde treated fat free strips of collagen harvested from submucosa of sheep or serosal layer of cattle small intestine.
• - It is a capillary multifilament suture composed of several plies that are slightly twisted, machine ground and polished to yield a relatively smooth surface and diameter that resembles a monofilament.
• - As autoclaving denatures the proteins with loss of strength, it is sterilized by ionizing radiation.
• - After implantation, loss of tensile strength results from:
  • a). cleaving of molecular bonds by acid hydrolytic and collagenolytic activity and 
  • b). digestion and absorption by proteolytic enzyme in later stages. 
• - Premature absorption is seen when gut is exposed to acidic secretions of stomach, infected environment, highly vascularized tissues & protein depleted patients.
• - Increasing suture diameter has very little influence on time of absorption.
• - Surgical gut is classified by the degree of chromicization. Chromic acid treatment helps to lengthen and standardize absorption time and to reduce the intensity of soft tissue reaction to gut.
• - Four types of gut are available:

Type A - Plain - absorbed in 3-7 days

Type B - Mild chromic - absorbed within 20 days

Type C - Medium chromic - absorbed within 20 days

Type D - Extrachromic - absorbed within 40 days

• - Rate of loss of strength for B, C, and D are 10, and 40 days respectively. Medium chromic, most common in use, loses 88% of its original strength after 7 days and about 67% after 28 days.
• - Advantages of gut are its elasticity, knot security, usage in presence of infection and adsorbability.
• - Disadvantages are its inflammatory response, variable rate of loss of tensile strength, its capillarily and occasional sensitivity reaction. 

2.5.1.2 Collagen:

• - Sutures are prepared from bovine flexor tendon as homogeneous extrusion of collagen fibers.
• - Fibers are treated with formaldehyde or chromium salts or both.
• - At present only five sizes for ophthalmic use are being manufactured. 

2.5.1.3 Miscellaneous:

• - Kangaroo tendon, fascia lata, and dura are other absorbable sutures 

2.5.2 ABSORBABLE SUTURES OF SYNTHETIC ORIGIN:

• - Were designed to have a standardized absorption and predictable loss of tensile strength. 

  2.5.2.1 Polyglycolic Acid (PGA):

  • - PGA (Dexon) is a braided suture made from fine filamentous threads extracted from Hydroxyacetic acid.
  • - It is strong, pliable and causes little tissue reaction.
  • - has a consistent rate of hydrolysis and hence predictable loss of tensile strength.
  • - Absorption is minimal until 14 days with complete absorption at 100-120 days.
  • - Hydrolysis of PGA is quicker in alkaline environment, with complete absorption an 6 day in urine and at 3 day in infected urine
  • - Loss of tensile strength is 33% during first 7 days and 80% with in 14 days.

  PGA tends to saw through tissues and is harder to handle than gut.

  2.5.2.2 Polyglactin 910 (vicryl):

  • - A braided co-polymer of glycolic and lactic acid in a ratio of 9:1.
  • - Its physical properties are much the same as PGA except it is more hydrophobic and resistant to hydrolysis.
  • -Coated suture has improved handling characteristics.
  • - Absorption occurs within 40-90 days.
  • - It is stronger than PGA at 35 days post implantation
  • - 50% loss of tensile strength seen at 14 days and 80% at 21 days.
  • - It has excellent size to strength ratio is easy to handle, stable in contaminated wounds and elicits minimal tissue reaction. 

  2.5.2.3 Polydioxanone (PDS)

  • - A Polymer of paradioxanone, available is monofilament suture 
  • - Has greater flexibility than PGA, Polyglactin 910, is extremely strong, incites minimal tissue reaction and is absorbed in a predictable manner.

  PDS retains 74%, 58%, and 41% of its breaking strength at 2, 4, 6 weeks post implantation

2.5.3 NON-ABSORBABLE SUTURES OF NATURAL ORIGIN:

2.5.3.1 Silk

• - Obtained as silk fibers from silk worm cocoon. Fibers are cleaned of waxes and gums, twisted or braided and dyed black.
• - It is coated with wax, silicone, olive oil to reduce its capillary action.
• - Silk is used as a standard to compare the handling of other suture materials.
• - Silk, a foreign protein, is degraded over time and loosen half of its tensile strength by 1 year.
• - It is applicable, easy to handle, with low knot security but high inflammatory response.
• - May not be used to close mucosal layer of hollow viscera or contaminated wounds. 

2.5.4 NON-ABSORBABLE SYNTHETIC SUTURES:

2.5.4.1 Polyamide (nylon):

• - A synthetic amine - containing plastic polymer, available as mono or multifilament suture.
• - Monofilament is relatively stiff, with high degree of memory and low knot security
• - Tensile strength half life is 6 months when it degenerates into amide by products which are potent antibacterials.
• - Can be used in contaminated areas, however not in serous or synovial cavity because ends may cause frictionalirritation. 

2.5.4.2 Polyolefins (polypropylene & polyethylene):

• - Polypropylenes (prolene) suture is a monofilament polymer of propylen, a derivative of propane gas, sterilized with ethylene oxide.
• - Its material properties are very similar to nylon.
• - It is not weakened by tissue enzymes and is least thrombogenic.
• - Its strength, inertness, retention of strength after implantation, minimum tissue reactivity and resistance to bacterial contamination are its main advantages. The disadvantage being slippery handling and memory 

2.5.4.3 Polyesters:

• - It is a braided multifilament suture available as plain or coated with Teflon, Silicone or Polybutylate to decrease, suture drag.
• - It maintains its high tensile strength with no loss post implantation. Hence, is good for slow healing wounds.
• - It has poor handling ability, low knot security and high tissue reactivity (equal to cat gut) 

2.5.4.4 Caprolactum (vetafil or Supramid):

• - A twisted multifilament polyamide suture with a smooth coating dispensed from spools from containers filled with chemical sterilizing solution. Not very sterile when dispense in this manner, hence not to be used for buried sutures. Ethylene oxide or heat sterilization is necessary prior to implantation in deep tissues.
• - It has good tensile strength, poor knot security and variable tissue reactivity. 

2.5.5 METALLIC SUTURE MATERIALS:

2.5.5.1 Stainless steel Sutures:

• - Monofilament stainless steel, a 816 L (Low Carbon) iron alloy is inert, non corrosive extremely strong and will not support infection.
• - Multifiament steel is easier to handle but is more easily broken if kicked.
• - Knotts should be tied not twisted, and cut close to the knot to prevent tissue irritation
• - It is sold in R & S gauge 40 (smallest) to 10 (Largest) or in USP sizes 10-0 to 7. 

2.5.5.2 Metal clops/Staples/Staplers:

• - Currently used for providing hemostasis, approximate wound edges, anastomosis, ligations etc. 

2.5.6 SUTURE SIZE AND SUTURE MATERIAL SELECTION:

• Skin - 4/0 to 3/0 - Monofilament nylon or polypropylene
• Subcutis - 4/0 to 3/0 - Synthetic absorbable (SA)
• (PGA, RDS, Polyglaclin 910).
• Fascia - 3/0 to 0 - PDS, Nylon, polypropylene
• Skeletal Muscle - 3/0 to 0 - SA
• Cardiac N. - 3/0 to 2/0 - Synthetic non absorbable
• Bronchial - 2/0 to 3.0 - Polypropylene, nylon, PDS Stump
• Tendon - 3/0 to 0 - Synthetic non absorbable
• Blood Vessels
• Ligature - 4/0 - 2/0 - Synthetic nonabsorbable
• Suture - 5/0 - 5/0 - Synthetic nonabsorbable
• Nerve - 0/0 - 5/0 - Synthetic nonabsorbable
• Hollow viscus
• GI - 3/0 . 4/0 - Gut Nylon, PDS, prolene
• Urinary - 3/0 - 4/0 - Gut
• Tract
• Uterus - 3/0 - 4/0 - SA Gut

2.5.7 SUTURE NEEDLES:

Most often suture is made available in sterile single pack with or without needle. The needles when present are swedged on to the thread and are of either cutting or non cutting (taper) type.

Needles are made out of stainless steel and have varying configuration with straight half curved or varying parts of a circle (1/2 or 3/8 of a circle etc).

Taper point needles are around in shape with no edge and are used in parenchymatons organs fat muscles etc.

Cutting point needles have an edge to penetrate dense tissues. They are available in conventional cutting (cutting edge on concave side) reverse cutting (cutting edge on convex side) and taper cutting (cutting point and round shaft)

Tissue Adhesives:

• - Most commonly used are cyanoacrylate which take 2 to 60 seconds to set.
• - Tissue toxicity, granuloma formation, severe wound infections, delayed healing and poor adhesions are some of the problems encountered.
• - Iso-butyle, Hyoctyle, and fluoro-analogues have more potential for clinical use in oral surgery, intestinal anastomosis, corneal ulceration, control of hemorrhage from cut surfaces and skin grafting.

2.5.9 SUTURE REMOVAL:

• - When they have done the job
• - Often removed on 7th post-operative day in wounds closed without tension.

2.6 SUTURE PATTERNS 

2.6.1 Interrupted Sutures:

• a. Simple interrupted
• b. Horizontal mattress
• c. Vertical mattress
• d. Cross mattress
• e. Crushing or Gambee Suture
• f. Everting Suture
• g. Inverting Suture
• h. Halstead 

2.6.2 Continuous Sutures:

• a. Simple continuous
• b. Ford interlocking
• c. Lembert
• d. Connell
• e. Cushing
• f. Parker - Kerr 

2.6.3 Tension Sutures:

• a. Quill Suture
• b. Far - near, near-far Suture
• c. Far - Far, Near - Near
• d. Mayo - Mattress 

2.6.4 Miscellaneous:

• a. Bunnell Suture
• b. Circlage
• c. Nemicirclage

2.7 RECOMMENDED READING:

• Bojrab, M.B.: Current Techniques in Small Animal Surgery, 2nd Edition, lea and Febiger; Philadelphia, Page 3-6, 1983.
• Slater, D.E. editor; Textbook of Small Animal Surgery, W.D. Saunders; Philadelphia page 336-344, 1985.
• Gourley I.M. and Vasseur, P.B. editor: General Small Animal Surgery. Lippincot, J.D; Philadelphia, page 92 - 104, 1985.
• Archibald J. editor: Canine Surgery, 2nd editor. American Veterinary Publications; California, page 35-52, 1974.
• Knecht, C.D et. al: Fundamental Techniques in Veterinary Surgery; B. Saunders, Philadelphia, page 20-87, 1981