3.21 Surgery Basics - Wildpro

3.21 Surgery Basics
Lesa Longley MA BVM&S DZooMed (Mammalian) MRCVS. Reviewed, Steve Unwin
Introduction
The veterinary clinician may be called upon to perform surgery on animals in their care.
This section is a basic introduction to surgery, in particular suture materials and
patterns. Clinicians should take every opportunity to practice these techniques. For
example, taking the opportunity to practice surgical approaches when conducting a post
mortem.
Reasons for surgery
Trauma
This is often due to con-specific aggression within groups of primates, but in rescue
centres may also be anthropogenic (for example traps or bullet wounds).
Reproductive
This usually relates to contraception – such as implants in females and vasectomy or
castration in males. Caesareans may also be performed.
Dentistry
This may be minor—such as descaling calculus—or more involved—such as tooth
extraction or root canal fillings.
Suture material & pattern selection
Various types of suture are available. Consideration should be given to the
requirements of the material, i.e. the purpose of utilizing it.
Absorbable vs. non-absorbable
Advantages of absorbable suture material include breakdown by the body and thereby
no foreign body is left. The main disadvantage is a variation in the period of wound
support.
Examples of absorbable suture material: catgut, poliglecaprone 25 (MonocrylÇ),
polyglactin 910 (VicrylÇ), and polydioxanone (PDSÇ). Short-term wound support is
provided by catgut, MonocrylÇ or Vicryl RapideÇ; medium term support by VicrylÇ,
DexonÇ or BiosynÇ; and long-term support by PDSÇ or MaxonÇ.
Non-absorbable suture material provides permanent support to wounds. However,
foreign material is left in the body and a suture sinus or extrusion of suture may occur.
Examples of nonabsorbable materials: silk (MersilkÇ), nylon (EthilonÇ, NurolonÇ),
polypropylene (ProleneÇ), and stainless steel.

Monofilament vs. multifilament
There are many advantages to monofilament suture material – it has a smooth surface,
low friction means less drag and less tissue trauma, no bacteria may be harboured, and
there is no capillarity (i.e. no ‘wicking’ effect). However handling and knotting are more
difficult than multifilament material, burial of sutures ends and knots can also be
problematic with monofilament, and it is more prone to stretching.
Multifilament material tends to be stronger, and is soft and pliable with good handling.
Bacteria may be harboured within multifilament suture, it is inclined to wicking (which
allows bacteria to migrate into deeper tissues), and tissue trauma may result due to
‘drag’ from the material and a cutting effect.
Biological vs. synthetic
Biological suture materials have excellent handling and knotting capabilities, are
economical, and are absorbed by hydrolysis. They are absorbed by enzymatic action,
may cause tissue reactions, and have an unpredictable rate of absorption.
Synthetic materials resemble natural substances, but have predictable absorption and
are strong.
Packaging
Foil pack. In general—though not always—suture in these packs has a swaged-on
needle.
Reel – the suture material is stored in a preservative such as alcohol. An assistant
removes the cap and pulls the end of the suture material, allowing the surgeon to grasp
a sterile region. Pull the suture upwards—ensuring not to touch the non-sterile edges of
the cap—before cutting the required length. Use a sterile needle to attach the suture.
Absorbable sutures
Catgut
This is obtained from sheep intestinal submucosa or cattle intestinal serosa. It is
absorbed by phagocytosis and enzymatic degradation, and there is a large
inflammatory response. The rate of absorption depends on the site and wound
conditions.
Catgut loses tensile strength rapidly and unpredictably. Chromic gut is better than
plain gut – chromic gut has reduced inflammation associated and an extended
tensile strength (50% by 14 days, 0% by 28 days). Catgut has a tendency to swell and
weaken when wet. It is also weakened by knotting, but ties good ligatures (you
shouldn’t need to use a surgeon’s knot). There is some controversy over the use of
catgut due to the risk of TSE (transmissible spongiform encephalopathy). Only use
for ligating.

Poliglecaprone 25 (MonocrylÇ)
This is a synthetic monofilament suture that is absorbed by hydrolysis. It is virtually
memory free (i.e. doesn’t return to its previous shape after deformation) – meaning
that it handles well and knots securely. This material has the highest tensile strength
of any monofilament absorbable suture – with 60% retained at 7 days, 30% at 14
days, and gone by 90-120 days.
Polyglactin 910 (VicrylÇ, Vicryl RapideÇ)
This is a braided synthetic absorbable suture. It is coated to reduce tissue drag and
improve knotting characteristics. It is absorbed by hydrolysis and therefore has a
predictable loss of tensile strength – 55% retained at 14 days, 40% at 21 days, 10% at
28 days, and gone by 56-70 days.
The initial tensile strength of Vicryl RapideÇ is 70% that of VicrylÇ; Vicryl RapideÇ
retains 50% at 5 days, 0% at 14 days, and is gone by 42 days. It is usually used in
skin (e.g. intradermal sutures), mucosa (where healing is rapid), or for fractious
animals (again using intradermal skin sutures).
Polyglycolic acid (DexonÇ, Dexon IIÇ, SafilÇ)
This is a braided synthetic multifilament polymer—usually coated—with high tissue
drag and poor knot security. It is broken down by hydrolysis, the products of which
are bacteriostatic in vivo – with 67% strength retained at 7 days, 35% at 21 days, and
gone by 60-90 days.
Polydioxanone (PDSÇ, PDSIIÇ)
This suture material is a monofilament synthetic polymer. It has low tissue drag.
Degradation is by hydrolysis, but at a slow rate to provide extended wound support
– 75% is retained at 14 days, 50% at 28 days, 25% at 42 days, and gone by 180 days. It
is useful for slowly healing tissues such as tendon and fascia.
Polyglyconate (MaxonÇ)
This synthetic monofilament has similar properties to PDSÇ.
PanacrylÇ
This braided synthetic absorbable suture retains 80% tensile strength at 3 months
and 60% at 6 months. Thus it provides extended wound support.
Non-absorbable sutures – these are often used for repair of tendons or hernias
Silk (MersilkÇ, SilkamÇ)
This braided multifilament is usually coated to decrease capillarity. Ultimately it is
absorbed, but extremely slowly – no tensile strength remains at 12 months. There is
significant tissue reaction. Silk has nice handling characteristics but poor knot
security. Its main use is for ligatures, but it should never be used in the presence of
infection or contamination. Silk is not recommended for use in sanctuaries for these
reasons.

Nylon (EthilonÇ, NeurolonÇ, DermalonÇ)
This is usually monofilament, but multifilament nylon is available. This has a high
tensile strength – losing 10-20% per year. Nylon has a high ‘memory’, resulting in
poor handling and knot security. Its main use is for skin sutures (which have to be
removed after healing has occurred).
Polypropylene (ProleneÇ, PremileneÇ, FluorofilÇ)
This is a monofilament polymer. High memory and poor handling mean that good
knots are difficult to tie, but with careful tying strands flatten at the knot to enhance
holding. This material is virtually inert in tissues, and is used in meshes to repair
large tissue defects.
Stainless steel
This may be either monofilament or braided. It has high tensile strength and good
knot security. However it has poor handling characteristics and breaks if subjected
to cyclic loading (i.e. repeated stresses). The main uses for stainless steel are in
orthopaedic surgery, and as haemostatic clips and skin staples.
Suture selection
Sutures are no longer needed when a wound reaches maximal strength. Use
non-absorbable materials or those with extended absorption for tissues that heal
slowly, such as tendon.
Foreign bodies in potentially contaminated tissues may convert contamination to
infection. Therefore use monofilament or absorbable suture in potentially
contaminated tissues.
Where cosmetic results are important, close and prolonged apposition of wounds
and avoidance of irritants will produce the best result. Use the smallest inert
monofilament suture. Close subcuticularly where possible. Topical skin glue
may be useful.
Use rapidly absorbed sutures in the urinary and biliary tracts, or else you risk the
suture becoming a nidus for stone formation.
Suture size is recorded as either Metric (Eur.Ph.) or Imperial gauge (USP). Metric
measurements are in tenths of a mm, from 0.1 to 10. Imperial measurements range from
11/0 to 6 (although catgut is different!) For orthopaedic wire, the measurement is a B&S
wire gauge, in mm.
Choose the smallest size of suture for the natural strength of the tissue. Reinforce with
retention sutures if there may be sudden strains on the suture line post-operatively.
Surgical needles come in a variety of sizes, shapes and types. The needle should pass
through the tissue without excessive force and with minimal disruption of tissue
architecture. Swaged needles—that produce less tissue trauma but are more
expensive—are preferred to closed eye needles—that require threading and pull a
double strand of suture through the tissue. Curved needles are easier to use with
instruments.

Needle shapes: Conventional cutting needles have the apex of the edges on the inside
curvature. Reverse cutting needles have the apex of the edges on the outside curvature.
Taper point needles separate tissue but do not cut. **PHOTOS
Ligatures must be secure! Avoid granny knots and half-hitch or tumbled knots, which
will slip. (See references)
Simple knot
Square knot – one hand or two hands
Surgeon’s or friction knot
Deep tie – ensure this is a square knot
Ligation around a haemostatic clamp
Instrument tie
Transfixing ligature
Suture patterns (see references)
Interrupted
- Simple interrupted
- Cruciate
- Horizontal or vertical mattress: this is a tension-relieving pattern
Continuous
- Simple continuous: including intradermal pattern (finishing with a
surgeon’s or Aberdeen knot)
- Intradermal
For interrupted patterns, 4 throws should be used on knots. For continuous patterns,
use 5 throws at the start and 6 at the end (as the end knot tends to be less secure and
therefore needs an extra throw).
Surgical instruments **PICTURES
As basics for suturing, you need scissors, forceps and needle holders. Other instruments
are required for more involved surgery – for example haemostatic clamps, Allis tissue
forceps, dental elevators, retractors, and towel clamps.
Common procedures
Trauma
E.g. digit/tail amputations after fighting, attack wounds, trap or gunshot wounds.
Not all fight wounds require surgery, and many will be infected so primary closure
will not be possible.
Primate wounds usually heal rapidly, even particularly severe fight wounds. In
many cases, surgical intervention is not necessary – and may even be
contraindicated if infection is present (as wound dehiscence is likely). Veterinary
experience will determine when surgery is required and when it is not.
Reproductive
E.g. Contraceptive implant, caesarean section, castration, vasectomy

NB It is important to use an intradermal pattern in the skin of primates to prevent
self-trauma post-operatively.
Dental
E.g. Extractions
Further information
Fossum, T.W. (2006) Small Animal Surgery, 3 rd Edn. Mosby
Niles, J. & Williams J. (1999) Suture materials and patterns. In Practice. 21 (6): 308–320
http://www.ethicon.com/ - Suture materials
http://www.animalcare.co.uk/Instruments-Equipment/default.aspx - Surgical
instruments
http://cal.vet.upenn.edu/projects/surgery/5000.htm (provides suture pattern videos
for practice)