Sutures and Suture Patterns

Question 1

1. Properties of suture in terms of the material.
2. Properties of suture material in terms of its construction.
3. Properties of suture material in terms of persistence (loss of tensile strength).
4. Suture material properties in terms of handling.

Answer 1

1. Natural (aka biological).
   Synthetic.
2. Mono-filament.
   Multi-filament (aka braided).
   (Coated multi-filament).
3. Absorbable – short duration.
   Absorbable – long duration.
   Non-absorbable.
4. Pliability.
   Memory.
   Surface friction (tissue drag).

Question 2

1. Pliability.
2. Memory vs plasticity.
3. Surface friction.

Answer 2

1. i.e. limp vs stiff. – The more pliable, the easier to handle. Silk is most pliable, steel is most stiff. Also refers to how sharp or soft the cut edges are.
2. Tendency to return to its original shape. The more memory, the more difficult to handle. Monofilament has more memory, multifilament has more plasticity.
3. The amount of resistance as suture passes against itself / other surfaces. Can be disadvantageous (tissue drag) or advantageous (knot security).

Question 3

1. What is catgut made of?
   – Why is it disliked?
2. Give another example of a biological suture material.
3. Construction of all natural suture materials.

Answer 3

1. Cow/sheep intestines.
   – Can cause inflammatory reaction with fibrosis.
   – Less initial strength (for a given size).
   – Faster and less predictable loss of tensile strength. - Absorbed by phagocytosis and proteolysis.
2. Silk.
3. Multifilament.

Question 4

1. Construction of synthetic suture materials.
2. Advantages of synthetic suture materials?

Answer 4

1. Monofilament or multifilament.
2. Reduced inflammatory response.
   Higher initial strength (for a given size).
   Slower and more predictable loss of tensile strength – absorbed by hydrolysis.

Question 5

1. Compare monofilament with multifilament.
2. Give example of monofilament.
3. Give example of multifilament.
4. How can the disadvantages of multifilament be reduced?

Answer 5

1. Monofilament provokes less of an inflammatory reaction than multifilament.
   Monofilament has less potential to cause infection than multifilament.
   Monofilament causes less tissue drag than multifilament.
   Monofilament is more difficult to handle and knot (due to increased memory) than multifilament.
   Monofilament has less knot security than multifilament.
   Monofilament can cause more irritation from cut ends than multifilament.
2. Monocryl, PDS.
3. Vicryl.
4. Coating.

Question 6

1. Define tensile strength.
2. Loss of tensile strength.
3. Insufficient tensile strength.
4. Considerations in terms of tensile strength when choosing suture material.

Answer 6

1. How much force something can withstand before pulled apart. Clinically, we describe a suture as having ‘lost its tensile strength’ when it has lost a certain % of its original strength, and is therefore no longer supporting the wound. Varies between suture materials.
2. Does not mean a suture is fully absorbed.
3. Can cause breakage and wound dehiscence.
4. Consider the tissue it will be in and the force it will be under, and how long it needs to have sufficient tensile strength until the tissue has healed and regained its own strength.

Question 7

1. What can reduce the TS of a suture material?

Answer 7

1. Excessive manipulation and use.
   Knotting.
   Wetting.
   Natural absorption in tissues.
   Placement in hostile environment (infected wound or contact with gastric acid).
   Abuse of the material by grasping it with instruments anywhere other than the end.
   Repeated autoclaving.

Question 8

1. Duration of retention of TS by non-absorbable suture material?
2. Give examples of non-absorbable suture material.
3. Duration of retention of tensile strength by absorbable suture material.
4. Duration of retention of TS for absorbable short duration suture material.
5. Give examples of absorbable short duration suture material.
6. Duration of retention of TS for long duration absorbable suture material.
7. Give example of long duration absorbable suture material.

Answer 8

1. > 60 days.
2. Nylon, silk, steel.
3. Degradation and loss of TS within 60 days.
4. <21 days.
5. Monocryl, Vicryl.
6. 21-60 days.
7. PDS.

Question 9

1. Considerations for choosing suture material.

Answer 9

1. Strength of tissue?
   Healing time?
   Any adverse conditions? e.g. infection, inflammation.
   Mechanical properties? e.g. handling, knot security?
   Purpose of suture placement? e.g. close tissues / ligate blood vessel / anchor drain / stay sutures.

Question 10

1. Suture material for skin sutures.
2. Suture material for subcutis.
3. Suture material for fascia.
4. Suture material for muscle.
5. Suture material for viscera.
6. Suture material for tendon.
7. Suture material for vessel ligation.

Answer 10

1. Ext. sutures = non-absorbable multi.
   Intradermal sutures = absorbable short duration monofilament.
2. Absorbable short duration mono/multi.
3. Absorbable long duration / non-absorbable mono.
4. Absorbable long duration / non-absorbable mono.
5. Absorbable short duration mono.
6. Non-absorbable mono.
7. Absorbable short duration. Multi / mono dept on type of knot.

Question 11

1. Suture sizings.
2. What diameter in mm is size 0 usp.
3. What diameter in mm is size 0 usp catgut.

Answer 11

Metric = based on actual size in mm diameter.
e.g. 0.1mm diameter = 1 metric.
e.g. 0.15mm diameter = 1.5 metric.
e.g. 0.3mm diameter = 3 metric.
USP (imperial) = initially thought size 0 was the smallest they could make. But tech improved and they could make smaller diameters so now the smaller to diameter, the more 0s.
e.g. 4-0 smaller in diameter than 2-0.

2. 0.35mm.
3. 0.4mm.

Question 12

1. Choosing an appropriate suture size.
2. Rule of thumb for suture sizes.

Answer 12

1. Choose the smallest size that will provide adequate TS.
   Smaller diameter means:
   - Greater knot security (can tie tighter)
   - Less foreign material (reduces SSI risk).
   - Less tissue trauma.
2. 3 metric/2-0 dogs.
   2 metric/3-0 cats.
   *Reduce by 1 size for delicate tissue or smaller dog.
   *Increase by 1 size for tough tissue or larger dog.

Question 13

1. Swaged needle.
2. Eyed needle.
3. Advantages of swaged needles.
4. Disadvantages of eyed needles.

Answer 13

1. Single use and already attached to suture material.
2. Multi-use and used with suture on the reel.
3. Less tissue trauma – always sharp as single use.
   Less tissue drag – no knot where suture attached to the needle.
   Easier to handle – suture material will not fall off needle prematurely.
4. More tissue trauma – multi-use so becomes blunt.
   More tissue drag – knot where suture attaches to needle.
   Less easy to handle – suture material may fall off needle prematurely.

Question 14

1. Needle shape selection.
2. Needle shapes.

Answer 14

1. Curved in deeper wounds with restricted access e.g. 1/2 circle good for thick muscle layer.
   Progressively straighter as more superficial e.g. 3/8 circle good for intradermal skin sutures.
2. 5/8 circle.
   J shape.
   Compound curve.
   1/2 circle.
   3/8 circle.
   1/4 circle.
   1/2 curved.
   Straight.

Question 15

Types of needle points. – bluntest to sharpest.

Answer 15

Round-bodied.
– Less traumatic IF delicate tissue.
– Use in v delicate tissue e.g. liver.
Taperpoint.
– Less traumatic, but the tip is pointed instead of rounded.
– Use in delicate fibrous tissue e.g. muscle, GIT.
Tapercut.
– More traumatic.
– Use in moderately dense tissue e.g. fascia, skin.
(Reverse) Cutting.
– Most traumatic (sharp) BUT cleaner cut through dense/tough tissue.
– Use in the most dense tissue e.g. fascia, skin.

Question 16

Symbol representation of needle point types.

Answer 16

Round-bodied – circle.
Taper point – Circle with dot in centre.
Taper cut – circle with upside sown triangle or circle with Y.
Cutting – Upright black triangle.
Reverse cutting – Upside down triangle.
*Triangles of cutting/reverse cutting represent the cross-section of the needle and whether the point of the triangle is on the concave or convex edge of the needle.

Question 17

What useful information can be found on the suture pack?

Answer 17

Suture material trade name, proper name and properties.
Suture size.
Needle shape.
Needle point.
Suture length.

Question 18

Define a throw.

Answer 18

When you cross the ends of the suture to form a loop.
For an instrument throw, wrap the suture around the needle holders and pull the ends across each other so that they can cross over.
– Simple throw = wrap suture around the needle holders ONCE.
– Surgeon’s throw = wrap suture around the needle holders TWICE. Done first, then a simple throw on top.

Question 19

Define a knot.

Answer 19

At least 2 throws, tied on top of each other.
– Square knot = 2 x simple throws.
– Surgeon’s know = surgeon’s throw, then a simple throw on top.
*Once knot tied, extra simple throws added on top to lock it down. Number varies dept. on suture pattern / materal.

Question 20

1. Define ligature.
2. Define appositional tension.
3. Friction.

Answer 20

1. When a knot is tied around a vessel, and pulled tightly to occlude the vessel.
2. When you are suturing tissues closed and you make your suture tight enough so that the two tissue edges are touching, but not so tight that you occlude blood vessels.
3. If tying a ligature, or bringing together tissue edges that are under tension, need friction to help you. Friction can come from the type of suture material or the type of knot used.

Question 21

1. What type of knot is considered bad?
   – why?
   – where can it be useful?

Answer 21

1. Granny knot / slip knot.
   – Fails to maintain tension evenly on both strands.
   – To close under tension but must be converted back to square knot and lock with more throws.

Question 22

1. What types of knots are appropriate for ligating blood vessels?
2. What is an Aberdeen knot used for?

Answer 22

1. Modified miller’s
   Surgeon’s.
   Transfixing.
2. Finishing off a suture pattern.

Question 23

1. What does knot security depend on?
2. When should knot security be assessed? – why?

Answer 23

1. Suture material properties.
   - pliability.
   - memory.
   - Surface tension.
   - diameter.
   Type of knot used.
   Placing the correct number of throws.
2. Assess knot security when wet.
   – catgut has good knot security when dry but starts to untie when wet.

Question 24

1. Types of interrupted suture pattern.
2. Types of continuous suture pattern.

Answer 24

1. Simple interrupted.
   Cruciate.
   Vertical mattress.
   Horizontal mattress.
2. Simple continuous.
   Intra-dermal.
   Ford interlocking.
   Utrecht / crushing / Lembert.
   Purse string.

Question 25

1. Types of appositional suture pattern.
2. Types of inverting suture pattern.
3. Types of everting suture pattern.

Answer 25

1. Simple interrupted / continuous.
   Intradermal.
   Cruciate.
   Ford interlocking.
2. Connell / Crushing.
   Lembert.
   Utrecht.
   Purse string.
3. Horizontal mattress.
   Vertical mattress.
   Near-far pattern.

Question 26

1. Advantages of interrupted suture patterns.
2. Disadvantages of interrupted suture patterns.

Answer 26

1. Failure of one knot does not affect entire suture line.
   Allows precise adjustment of tension at each point.
2. Tension not distributed evenly along the entire incision so lower holding power against stress.
   Increased surgical time.
   Increased suture material.

Question 27

1. Disadvantages of continuous suture patterns.
2. Advantages of continuous suture patterns.

Answer 27

1.Failure of one knot may cause failure of entire suture line.
Does not allow adjustment of tension at each point.

2. Tension evenly distributed along entire incision so greater holding power against stress.
   Decreased surgery time.
   Decreased suture material.

Question 28

What do appositional suture patterns do?

Answer 28

Bring the tissue edges into close approximation, with tissue edges in the same position as prior to the incision.

Question 29

What do inverted suture patterns do?

Answer 29

Turn the edge into itself away from the surgeon i.e. into the lumen.
Traditionally used to close hollow viscera. For a better, more water-tight closure.

Question 30

What do everted suture patterns do?

Answer 30

Turn tissue edges up and outwards towards the surgeon and away from the lumen.
Tension relieving.

Question 31

1. Advantages of staples.
2. Disadvantages of staples.

Answer 31

1. Quicker to place.
   Cheaper?
   Doesn’t increase risk of delayed healing, infection or poor wound cosmesis if used correctly.
2. Slightly everts skin edges.
   Tend to rotate in very mobile areas or thin skin e.g. cats.
   Should not be placed in wound under tension.

Question 32

Where would staples be used internally?
Benefits of internal staples.

Answer 32

Lung or liver lobe biopsies.
Splenectomy.
GI anastomoses.

Benefits – quicker, decreased tissue handling and trauma.